Title of Invention	"CRANE AND CONTROL METHOD THEREOF"
Abstract	A crane is disclosed which can be continuously operated in the case when a part of its motor control unit breaks down. The crane includes a plurality of first motors 47A, 47B, 47C, 47D, a plurality of first motor control units 59A, 59B, 59C, 59D that control the outputs of the first motors 47A, 47B, 47C, 47D by respectively controlling the power supplied thereto, a second motor 75, and a second motor control unit 87 that controls the output of the second motor 75 by controlling the power supplied thereto; wherein, it is possible to control whether or not to supply the power from a specified one 47D of the first motor control units to the second motor 75.

Title of Invention

"CRANE AND CONTROL METHOD THEREOF"

Abstract

A crane is disclosed which can be continuously operated in the case when a part of its motor control unit breaks down. The crane includes a plurality of first motors 47A, 47B, 47C, 47D, a plurality of first motor control units 59A, 59B, 59C, 59D that control the outputs of the first motors 47A, 47B, 47C, 47D by respectively controlling the power supplied thereto, a second motor 75, and a second motor control unit 87 that controls the output of the second motor 75 by controlling the power supplied thereto; wherein, it is possible to control whether or not to supply the power from a specified one 47D of the first motor control units to the second motor 75.

Full Text	BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to a crane, and more specifically, to a ladle crane used for conveying a ladle and a control method thereof. 2. DESCRIPTION OF RELATED ART In ironmaking plants and/or steelmaking plants, traditionally, molten steel is contained in a ladle and conveyed using a ladle crane. For example, molten steel is poured into a ladle from an electric furnace or the like, conveyed using a ladle crane to a converter or the like, and then poured into the converter. The ladle crane conveys the ladle that is lifted using a main winching device, and tilts the ladle by raising a lower part of the ladle with an auxiliary winching device to pour the molten steel into the converter or the like (see, for example, Japanese Unexamined Patent Application No. Heill-268881). In a known example of a ladle crane, a main winching device that performs lifting and lowering of a ladle consists of two pairs of a motor and a motor control unit. There has been, however, a problem in that when, for example, one of the motor control units breaks down, the ladle crane ceases to be operatable because the remaining pair of a motor and a motor control unit is only capable of either lifting or lowering the ladle. On the other hand, an auxiliary winching device consists of a pair of a motor and a motor control unit, the pair of a motor and a motor control unit undertaking tilting and the like of the ladle. There has also been a problem in that when, for example, the motor control unit of the auxiliary winching device breaks down, the operation of the ladle crane has to be stopped. The auxiliary winching device is mounted on an auxiliary trolley and laterally moved by a pair of a motor and a motor control unit disposed on the auxiliary trolley for lateral movement thereof. There has been, therefore, another problem in that when, for example, the motor control unit for the lateral movement breaks down, the operation of the ladle crane has to be stopped. BRIEF SUMMARY OF THE INVENTION The present invention has been made to address the above problems with the object to provide a crane and a control method thereof such that even if a motor control unit of the crane should break down, the crane will be able to be continuously operated. In order to attain the above object, the present invention provides the following means. A crane according to a first aspect of the invention is characterized by including a plurality of first motors, a plurality of first motor control units that control the outputs of the first motors by respectively controlling the power supplied to the first motors, a second motor, and a second motor control unit that controls the output of the second motor by controlling the power supplied to the second motor; wherein a specified one of the first motor control units can selectively control whether to supply the power to the second motor or to suspend it. According to the first aspect of the invention, even if, for example, the second motor control unit should break down, the crane will be continuously operated since the power for driving the second motor is supplied from the specified one of the first motor control units. Namely, in the case when the power supply from the second motor control unit is interrupted, the second motor is driven by the power supplied from the specified one of the first motor control units and therefore the crane can be continuously operated. The first motor, which has been supplied with the power from the specified one of the first motor control units, may stop or lose its output when the power supply is switched to the second motor; however, the remaining plurality of first motors enable the crane to be continuously operated. While the second motor control unit is in working order, the specified one of the first motor control units suspends to supply the power to the second motor and keeps to supply the power to the specified one of the first motors. Therefore, compared with the case that a backup motor control unit is used only for supplying power to the second motor, the second motor can be securely supplied with power because the specified first motor control unit has been consistently used. In the first aspect of the invention described above, it is desired that the specified first motor control unit has a larger electrical capacity for controlling a motor than the second motor control unit. According to the above arrangement, since the specified first motor control unit has a larger electrical capacity than the second motor control unit, the power required for driving the second motor can be surely supplied to secure the operation of the crane when the second motor control unit breaks down. In the first aspect of the invention described above, the crane is preferably equipped with a pair of main hooks for hanging a load and an auxiliary hook for controlling the attitude of the load; wherein, the main hooks are lifted and lowered by the plurality of first motors and the auxiliary hook is lifted and lowered by the second motor. According to the above arrangement, even if, for example, the second motor control unit should break down, the second motor will be continuously driven and consequently the lifting and lowering of the auxiliary hook will be continuously performed; namely, the operation of the crane can be continued. Furthermore, compared with the case that a backup motor control unit is used only for supplying power to the second motor, the operation of the auxiliary hook can be secured, since the specified first motor control unit has supplied power to one of the first motors while the second motor control unit has been in working order. In the first aspect of the invention described above, it is desired that, while the second motor is supplied with power from the specified first motor control unit, the main hooks and the load are lifted and lowered by the other first motors which are supplied with power from the first motor control units different from the specified first motor control unit. According to the above arrangement, even if, for example, the second motor control unit should break down, lifting and lowering of the main hooks and the load will be performed by ones of the first motors other than the specified one and therefore the operation of the crane will be continued. Specifically, in the case when the second motor control unit breaks down, the second motor is supplied with power from the specified one of the first motor control units; as the result, the first motor which has been supplied with power from the specified first motor control unit may lose its output or come to a stop. In this case, lifting and lowering of the main hooks and the load are undertaken by other first motors than the specified one, and also lifting and lowering of the auxiliary hook are performed by the second motor, which allows the crane to be continuously operated. In the first aspect of the invention described above, it is desired that a main trolley having the first motors installed thereon is disposed so as to be movable in predetermined directions, and an auxiliary trolley having the second motor installed thereon is disposed so as to be movable in predetermined directions; wherein, the main trolley is moved by the plurality of first motors and the auxiliary trolley is moved by the second motor. According to this arrangement, even if, for example, the second motor control unit should break down, the second motor will be continuously driven and the auxiliary trolley will be continuously moved; namely, the operation of the crane can be continued. While the second motor control unit is in working order, the specified one of first motor control units supplies the power to the specified one of the first motors; therefore, compared with the case that a backup motor control unit is used only for supplying power to the second motor, driving of the auxiliary trolley can be secured. In the first aspect of the invention described above, it is desired that, while the second motor is supplied with power from the specified first motor control unit, the main trolley is driven by the remaining first motors supplied with power from other first motor control units than the specified one. According to the above arrangement, even if, for example, the second motor control unit should break down, the main trolley will be moved by other first motors than the specified one and therefore the operation of the crane will be continued. Specifically, when the second motor control unit breaks down, the second motor is supplied with power from the specified one of the first motor control units; as the result, the first motor which has been supplied with power from the specified first motor control unit may lose its output or come to a stop. In this case, the main trolley is moved by other first motors than the specified one, and also the auxiliary trolley is moved by the second motor, which allows the crane to be continuously operated. In the first aspect of the invention described above, it is desired that an inverter apparatus is employed for each of the first motor control units and the second motor control unit, and an inverter motor driven by the inverter apparatus is employed as each of the first motors and the second motor. According to this arrangement, the outputs of the first motors and the second motor can be easily controlled by employing the inverter apparatus for the first motor control units and the second motor control unit, and also by employing the inverter motor as the first motors and the second motor. A crane control method according to a second aspect of the invention is characterized by that the outputs of the plurality of first motors are controlled by respectively controlling the power supplied from the plurality of first motor control units, the output of the second motor is controlled by controlling the power supplied from the second motor control unit, and, when the second motor control unit breaks down, the second motor is supplied with power from the specified one of the first motor control units. According to the second aspect of the invention, even if the second motor control unit should break down, the operation of the crane will be continued since the second motor is supplied with power from the specified one of the first motor control units. Namely, when the power supply from the second motor control unit is interrupted, the second motor continues to be driven and the operation of the crane can be continued, because the power supply to the second motor is covered by the specified one of the first motor control units. The first motor which has been supplied with power from the specified one of the first motor control units may stop or lose its output when the power supply is switched to the second motor; however, the remaining first motors enable the crane to be continuously operated. The crane and the control method thereof according to the present invention enable the crane to be continuously operated even in the case when some part of the motor control units breaks down since the second motor can be supplied with power from the specified one of first motor control units. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIG. 1 is a plan view illustrating the structure of a ladle crane according to an embodiment of the present invention. FIG. 2 is a side view illustrating the structure of the main girder and the main trolley illustrated in FIG. 1. FIG. 3 is a layout plan illustrating the structure of the ladle crane illustrated in FIG. 1. FIG. 4 is a block diagram illustrating the electric circuit used for the travel motors illustrated in FIG. 3. FIG. 5 is a sectional view illustrating the structure of the main trolley, auxiliary trolley, and electric cabinet illustrated in FIG. 1. FIG. 6 is a block diagram illustrating the electric circuit used for the main winching device and auxiliary winching device illustrated in FIG. 1. FIG. 7 is a block diagram illustrating the electric circuit used for the main lateral moving motors and auxiliary lateral moving motor illustrated in FIG. 1. FIG. 8 is a partial sectional view illustrating the structure of the auxiliary trolley illustrated in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION A ladle crane according to an embodiment of the present invention will now be described with reference to the drawings, FIGS. 1 to 8. FIG. 1 is a plan view illustrating the structure of a ladle crane according to this embodiment. As shown in FIG. 1, the ladle crane (crane) 1 includes end ties 3, main girders 5, auxiliary girders 7, a main trolley 9 and an auxiliary trolley 11. FIG. 2 is a side view illustrating the structure of the main girder and the main trolley illustrated in FIG. 1. The end ties 3 are a pair of members extended along travel rails 17 mounted on travel beams 15, as shown in Fig. 2, the end ties 3 being equipped with travel units 19 that travel on the travel rails 17. Furthermore, as shown in FIG. 1, the main girders 5 and the auxiliary girders 7 are attached to the end ties 3 . FIG. 3 is a layout plan illustrating the structure of the ladle crane illustrated in FIG. 1. The travel units 19 are disposed between the travel rails 17 and the end ties 3, as shown in FIG. 2, and allow the ladle crane 1 to travel along the travel rails 17. An example of this embodiment, in which four travel units 19 are installed at ends of the end ties 3, will now be described. The travel units 19 are equipped with travel motors 21A, 21B, travel motors 21C, 21D, travel motors 21E, 21 F and travel motors 21G, 21H as shown in FIG. 3 to allow the ladle crane 1 to travel along the travel rails 17. It is noted that the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H can be selected from, but not limited to, known inverter-controlled motors. FIG. 4 is a block diagram illustrating the electric circuit used for the travel motors illustrated in FIG. 3. As shown in FIG. 4, the travel motors 21A, 21B are supplied with power from an travel inverter apparatus 23A; similarly the travel motors 21C, 21D are supplied with power from a travel inverter apparatus 23C, the travel motors 21E, 21F are supplied with power from a travel inverter apparatus 23E, and the travel motors 21G, 21H are supplied with power from a travel inverter apparatus 23G. These travel inverter apparatuses 23A, 23C, 23E, 23G are supplied with AC power from the outside. It is noted that the travel inverter apparatuses 23A, 23C, 23E, 23G may control the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H by applying variable-voltage variable-frequency control to the power supplied thereto, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like. As shown in FIG. 1, the main girders 5 are a pair of beam-shaped members disposed so as to join the pair of end ties 3, and the main trolley 9 is mounted on the main girders 5 so as to be movable. The main girders 5 are disposed outside the auxiliary girders 7 (described later) so as to be substantially orthogonal to the end ties 3. On the top of the main girders 5 (the side toward the viewer in FIG. 1), a pair of main lateral moving rails 27 are disposed so as to extend along the main girders 5, and to the side of one of the main girders 5 (the lower side of the drawing in FIG. 1), an electric cabinet 29 is installed in which a main winching inverter apparatus 59 (described later) and the like are contained. The main lateral moving rails 27 are provided for guiding the main trolley 9 mounted thereon along a direction substantially orthogonal to the travel rails 17 (hereinafter referred to as "lateral direction"). FIG. 5 is a sectional view illustrating the structure of the main trolley, auxiliary trolley, and electric cabinet illustrated in FIG. 1. As shown in FIG. 5, the electric cabinet 29 is a box-shaped member disposed at a position facing the side of the main girder 5 (the left side of FIG. 5). On the top of the electric cabinet 29 (the upper side of FIG. 5), fixing members 33 fixed to a support member 31, which extends from the main girder 5, are disposed and connection members 35 engaged with the hook (not shown) of the crane are also disposed. A thermal barrier member 37 is provided underneath the electric cabinet 29 (the lower side of FIG. 5) and also underneath the main girder 5. The electric cabinet 29 can be attached to or detached from the support member 31 by connecting the fixing members 33 to or by disconnecting it from the support member 31. In the inside of the electric cabinet 29, four main winching inverter apparatuses 59A, 59B, 59C, 59D, an auxiliary winching inverter apparatus 87 (see FIG. 6), two main lateral moving inverter apparatuses 67A, 67B, an auxiliary lateral moving inverter apparatus 95 (see FIG. 7), and four travel inverter apparatuses 23A, 23C, 23E, 23G, (see FIG. 4) are disposed. The main winching inverter apparatuses 59A, 59B, 59C, 59D and the like are electrically connected to a main winching motor 47A (described later) or the like while the electric cabinet 29 is mounted to the support member 31. As shown in FIG. 1, the auxiliary girders 7 are, similar to the main girders 5, a pair of beam-shaped members disposed so as to join the pair of end ties 3, and the auxiliary trolley 11 is mounted on the auxiliary girders 7 so as to be movable. The auxiliary girders 7 are disposed inside the main girders 5 so as to be substantially orthogonal to the end ties 3. On the auxiliary girders 7 a pair of auxiliary lateral moving rails 39 are disposed, the auxiliary lateral moving rails 39 being provided to guide the auxiliary trolley 11 mounted thereon in the lateral direction. As shown in Fig. 3, the main trolley 9 is equipped with a main winching device 43 for lifting and lowering a ladle (a hung load) 41 (see FIG. 5), and main lateral moving motors (first motors) 45A, 45B allowing the main trolley 9 to laterally move. The main winching device 43 includes the main winching motors (first motors) 47A, 47b, 47C, 47D, main speed-reducing members 49A, 49B, 49C, main winching drums 51A, 51B, and, as shown in FIG. 5, main hanging sheaves 53, a hanging beam 55, and main hooks 57. The main winching motors 47A, 47B and the main winching motors 47C, 47D are separately disposed at one end and another end of the main trolley 9 as shown in FIG. 3. The rotational power of the main winching motors 47A, 47B, 47C, 47D are transmitted to the main winching drums 51A, 51B via the main speed-reducing members 49A, 49B, 49C. The main winching motors 47A, 47B, 47C, 47D are chosen so that any three of the four motors have together an output power capable of lifting and lowering the main hooks 57 and the ladle 41 containing molten steel. It is noted that the main winching motors 47A, 47B, 47C, 47D can be selected from, but not limited to, known inverter-controlled motors. FIG. 6 is a block diagram illustrating the electric circuit used for the main winching device and auxiliary winching device illustrated in FIG. 1. The main winching motors 47A, 47B, 47C, 47D are respectively supplied with AC power, as shown in FIG. 6, from the main winching inverter apparatuses (first motor control units) 59A, 59B, 59C and the main winching inverter apparatus (specified first motor control unit) 59D, the main winching inverter apparatus 59A, 59B, 59C, 59D being supplied with AC power from the outside. There is an auxiliary winching line switch 61 connected to the line between the main winching inverter apparatus 59D and the main winching motor 47D, the auxiliary winching line switch 61 enabling or disabling supply of AC power from main winching inverter apparatus 59D to an auxiliary winching motor 75. The capacity of each of the main winching inverter apparatuses 59A, 59B, 59C, 59D is specified so as to be larger than that of the auxiliary winching inverter apparatus 87 described later. As examples of the capacity, 500 kW is given for each of the main winching inverter apparatuses 59A, 59B, 59C, 59D, and 250 kW for the auxiliary winching inverter apparatus 87, but the capacity is not limited to these. It is noted that the main winching inverter apparatuses 59A, 59B, 59C, 59D may control the main winching motors 47A, 47B, 47C, 47D by applying variable-voltage variable-frequency control to the power supplied thereto, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like. The main speed-reducing member 49A is disposed between the main winching motors 47A, 47B so as to combine the rotational power of the main winching motors 47A, 47B and transmit the combined power to the main speed-reducing member 49C. The main speed-reducing member 49B is disposed between the main winching motors 47C, 47D so as to combine the rotational power of the main winching motors 47C, 47D and transmit the combined power to the main speed-reducing member 49C. The main speed-reducing member 49C is disposed so as to transmit the rotational power input from both the main speed-reducing member 49A and the main speed-reducing member 49B to the main winching drums 51A, 51B. It is noted that the main speed-reducing members 49A, 49B, 49C can be selected from, but not limited to, known speed reducers capable of transmitting rotational power. For example, a combination of three speed-reducing members can be used as described in this embodiment, or one speed-reducing member may be used to transmit the rotational power from the main winching motors 47A, 47B, 47C, 47D to the main winching drums 51A, 51B; the power transmitting arrangement is not limited to this. The main winching drums 51A, 51B are each cylindrical or column-shaped members that are disposed so as to be rotatable around the center axis thereof and to be substantially parallel to the lateral direction. As shown in FIG. 5, a main wire rope 63 for lifting and lowering the main hook 57 is wound around each of the main winching drums 51A, 51B. The main wire ropes 63 are wound when the main winching drums 51A, 51B are rotated in a rotating direction, and unwound when the main winching drums 51A, 51B are rotated in another rotating direction. Both of the main wire ropes 63 are simultaneously wound or unwound as the main winching drums 51A, 51B rotate. The main wire ropes 63 extend from the main winching drums 51A, 51B toward main hook-side sheaves 54 to be wound thereon and also on main hanging sheaves 53; one end of each of the main wire ropes 63 is fixed to the hanging beam 55. Each of the main hanging sheaves 53 is a cylindrical or column-shaped member that is disposed under the main trolley 9 so as to be rotatable around its center axis substantially parallel to the lateral direction. Each of the main hook-side sheaves 54 is a cylindrical-shaped or column-shaped member that is disposed at one end of the hanging beam 55 so as to be rotatable around its center axis substantially parallel to the lateral direction. The main hooks 57 provided for hooking respective shafts 41a of the ladle 41 are disposed at both ends of the hanging beam 55 as shown in FIG. 5. Each of the main hooks 57 is attached to the hanging beam 55 by using a pin 65 so as to be rotatable around the center axis of the pin 65. As shown in FIG. 3, the main lateral moving motor 45A is disposed at one end of the main trolley 9 and the main lateral moving motor 45B is disposed at another end of the main trolley 9. The rotational power generated by the main lateral moving motors 45A, 45B is transmitted to the main lateral moving members 9A of the main trolley 9 as shown in FIG. 2. It is noted that the main lateral moving motors 45A, 45B can be selected from, but not limited to, known inverter-controlled motors. FIG. 7 is a block diagram illustrating the electric circuit used for the main lateral traveling motors and auxiliary lateral traveling motor illustrated in FIG. 1. The main lateral moving motors 45A, 45B are supplied with power from the main lateral moving inverter apparatus 67A (first motor control unit) and the main lateral moving inverter apparatus 67B (specified first motor control unit), respectively, the main lateral moving inverter apparatuses 67A, 67B being supplied with AC power from the outside. There is an auxiliary lateral moving line switch 69 connected to the line between the main lateral moving inverter apparatus 67B and the main lateral moving motor 45B, the auxiliary lateral moving line switch 69 enabling or disabling supply of AC power from the main lateral moving inverter apparatus 67B to an auxiliary lateral moving motor 73. The capacity of each of the main lateral moving inverter apparatuses 67A, 67B is specified so as to be larger than that of the auxiliary lateral moving inverter apparatus 95 described later. As examples of the capacity, 45 kW is given for each of the main lateral moving inverter apparatuses 67A, 67B and 15 kW for the auxiliary lateral moving inverter apparatus 95, but the capacity is not limited to these examples. It is noted that the main lateral moving inverter apparatuses 67A, 67B may control the main lateral moving motors 45A, 45B, respectively, by applying variable-voltage variable-frequency control to supplied power, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like. FIG. 8 is a partial sectional view illustrating the structure of the auxiliary trolley illustrated in FIG. 1. The auxiliary trolley 11 is equipped, as shown in FIG. 3, with an auxiliary winching device 71 that controls the tilt of the ladle 41 (see FIG. 5), and the auxiliary lateral moving motor (second motor) 73 allowing the auxiliary trolley 11 to laterally move. The auxiliary winching device 71 includes the auxiliary winching motor (second motor) 75, an auxiliary winching speed-reducing member 77, an auxiliary winching drum 79 and, as shown in FIG. 8, an auxiliary trolley-side sheave 81, an auxiliary hook-side sheave 83, and an auxiliary hook 85. The auxiliary winching motor 75 is mounted on one end of auxiliary trolley 11 as shown in FIG. 3. The rotational power from the auxiliary winching motor 75 is transmitted to the auxiliary winching drum 79 via the auxiliary winching speed-reducing member 77. It is noted that the auxiliary winching motor 75 can be selected from, but not limited to, known inverter-controlled motors. As shown in FIG. 6, the auxiliary winching motor 75 is supplied with power from the auxiliary winching inverter apparatus (second motor control unit) 87, which is supplied with AC power from the outside. It is noted that the auxiliary winching inverter apparatus 87 may control the auxiliary winching motor 75 by applying variable-voltage variable-frequency control to supplied power, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like. The auxiliary winching speed-reducing member 77 is disposed so as to transmit the rotational power from the auxiliary winching motor 75 to the auxiliary winching drum 79. It is noted that the auxiliary winching speed-reducing member 77 can be selected from, but not limited to, known speed reducers. The auxiliary winching drum 79 is a cylindrical or column-shaped member that is disposed so as to be rotatable around the center axis thereof and to be substantially perpendicular to the lateral direction. An auxiliary wire rope 89 for lifting and lowering the auxiliary hook 85 is wound around the auxiliary winching drum 79. The auxiliary wire rope 89 is wound when the auxiliary winching drum 79 is rotated in a rotating direction, and unwound when the auxiliary winching drum 79 is rotated in another rotating direction. The auxiliary wire rope 89 extends from the auxiliary winching drum 79 toward the auxiliary hook-side sheave 83 to be wound on the auxiliary hook-side sheave 83 and the auxiliary trolley-side sheave 81; one end of the auxiliary wire rope 89 is fixed to the auxiliary trolley 11. The auxiliary trolley-side sheave 81 is a cylindrical or column-shaped member that is disposed between the auxiliary winching motor 75 and the auxiliary winching drum 79 on the auxiliary trolley 11 so as to be rotatable around its center axis substantially perpendicular to the lateral direction. The auxiliary hook-side sheave 83 is a cylindrical or column-shaped member that is disposed in an auxiliary hook block 91 for the auxiliary hook 85 so as to be rotatable around its center axis substantially perpendicular to the lateral direction. The auxiliary hook 85 disposed in the auxiliary hook block 91 as shown in FIG. 8 is a hook that is connected to the tilting bracket 41b provided on a sidewall of the ladle 41. The auxiliary lateral moving motor 73 is disposed at another end of auxiliary trolley 11 as shown in FIG. 3. The rotational power generated by the auxiliary lateral moving motor 73 is transmitted to auxiliary lateral moving members 93 as shown in FIG. 8. It is noted that the auxiliary lateral moving motor 73 can be selected from, but not limited to, known inverter-controlled motors. The auxiliary lateral moving motor 73 is supplied with power from the auxiliary lateral moving inverter apparatus (second motor control unit) 95, the auxiliary lateral moving inverter apparatus 95 being supplied with AC power from the outside. It is noted that the auxiliary lateral moving inverter apparatus 95 may control the auxiliary lateral moving motor 73 by applying variable-voltage variable-frequency control, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like. Now, the way of conveying the ladle 41 using the ladle crane 1 constituted as described above will be explained. In order to convey the ladle 41, the ladle crane 1 is made to travel along the travel rails 17, and the main trolley 9 is also moved in lateral direction so that the main hooks 57 are located at a position above the ladle 41 as shown in FIG. 2. Upon locating the main trolley 9 at a position above the ladle 41, the main hooks 57 are lowered to hook the shafts 41a of the ladle 41, and then lifted together with the ladle 41 by the main winching device 43 to a higher level. When the main hooks 57 are lifted, as shown in FIG. 6, the main winching motors 47A, 47B, 47C, 47D of the main winching device 43 are supplied with AC power from the main winching inverter apparatus 59A, 59B, 59C, 59D. The rotational power generated by the main winching motors 47A, 47B, 47C, 47D are transmitted to the main winching drums 51A, 51B via the main speed-reducing members 49A, 49B and the main speed-reducing member 49C, which results in rotating the main winching drums 51A, 51B. As the main winching drums 51A, 51B rotates, the main wire ropes 63 are wound thereon and the main hooks 57 hanging the ladle 41 is lifted upward. At that time, the auxiliary winching line switch 61 is off and all the AC power from the main winching inverter apparatus 59D is supplied to the main winching motor 47D. The respective main winching motors 47A, 47B, 47C, 47D are driven at a same output, and the main winching motors 47A, 47B, 47C, 47D as well as the main winching inverter apparatus 59A, 59B 59C 59D are operated with a margin. After being hung up, the ladle 41 is conveyed to, for example, near a converter or the like by the ladle crane 1 traveling along the travel rails 17 and also by the main trolley 9 moving in lateral direction. When the ladle crane 1 travels, as shown in FIG. 4, the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H are supplied with AC power from the travel inverter apparatuses 23A, 23C, 23E, 23G. The rotational power generated by the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H is transmitted to the travel units 19; thereby the ladle crane 1 is made to travel along the travel rails 17 until the ladle 41 comes near the converter or the like. At that time, the travel inverter apparatuses 23A, 23C, 23E, 23G supply the respective travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H with controlled AC power to generate the same output. When any of the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H breaks down, power supply to the broken travel motor may be interrupted by a switch provided for that purpose; then the ladle crane 1 is moved by the remaining travel motors along the travel rails 17. As shown in FIG. 7, the main lateral moving motors 45A, 45B of the main trolley 9 are supplied with AC power from the main lateral moving inverter apparatuses 67A, 67B. The rotational power generated by the main lateral moving motors 45A, 45B is transmitted to main lateral moving members 9A, and the main trolley 9 is laterally moved along the main girders 5 until the ladle 41 comes near the converter or the like. At that time, the auxiliary lateral moving line switch 69 is in an off position and all the AC power provided from the main lateral moving inverter apparatus 67B is supplied to the main lateral moving motor 45B. After that, the ladle 41 is tilted by the auxiliary winching device 71 to pour the molten steel in the ladle into the converter or the like. When the ladle 41 is tilted by the auxiliary winching device 71, the auxiliary hook 85 is first lowered and the auxiliary trolley 11 is laterally moved to a position where the auxiliary hook 85 is allowed to hook the tilting bracket of the ladle 41. When the auxiliary trolley 11 is moved, as shown in FIG. 7, the auxiliary lateral moving motor 73 of the auxiliary trolley 11 is supplied with AC power from the auxiliary lateral moving inverter apparatus 95. The rotational power generated by the auxiliary lateral moving motor 73 is transmitted to the auxiliary lateral moving member 93, and the auxiliary trolley 11 is laterally moved along the main girders 5 to the position where the auxiliary hook 85 is allowed to hook the tilting bracket of the ladle 41. At that time, the auxiliary lateral moving line switch 69 is in the off position and all the AC power provided from the auxiliary lateral moving inverter apparatus 95 is supplied to the auxiliary lateral moving motor 73. As the auxiliary hook 85 hooking the tilting bracket of the ladle 41 is lifted by the auxiliary winching device 71, the ladle 41 is tilted. When the auxiliary hook 85 is lifted, as shown in FIG. 6, the auxiliary winching motor 75 of the auxiliary winching device 71 is supplied with AC power from the auxiliary winching inverter apparatus 87. The rotational power generated by the auxiliary winching motor 75 is transmitted to the auxiliary winching drum 79 via the auxiliary winching speed-reducing member 77. As the auxiliary winching drum 79 is rotated by the transmitted rotational power, the auxiliary wire rope 89 is wound there around and the auxiliary hook 85 hooking the tilting bracket is lifted upward; since the ladle 41 is turned around the shafts 41a, the molten steel is poured from the ladle 41 into the converter or the like. Here, a features of this embodiment, i.e., the operating method of the ladle crane 1 in the case when the auxiliary winching inverter apparatus 87 or the auxiliary lateral moving inverter apparatus 95 breaks down will be described. In the first case when the auxiliary winching inverter apparatus 87 breaks down, as shown in FIG. 6, the auxiliary winching line switch 61 is made ON to supply AC power from the main winching inverter apparatus 59D to the auxiliary winching motor 75. The auxiliary winching motor 75 that is supplied with AC power generates rotational power, by which lifting and lowering of the auxiliary hook 85 can be performed and the operation of the ladle crane 1 can be continued. On the other hand, the supply of AC power to the main winching motor 47D is interrupted and the output of the main winching motor 47 becomes zero. Then, the main winching inverter apparatuses 59A, 59B, 59C control the power supplied to the main winching motors 47A, 47B, 47C so as to maximize their outputs; thereby the main winching device 43 is enabled to continue lifting and lowering of the main hooks 57 and ladle 41. In the case when two of the four main winching motors 47A, 47B, 47C, 47D, for example, the main winching motors 47C, 47D fail, the remaining two main winching motors 47A, 47B undertake lowering of the main hooks 57 and ladle 41, but other operations of the ladle crane 1 are interrupted. When the main hooks 57 and ladle 41 are lowered, the outputs of the main winching motors 47A, 47B are maximized to safely lower the main hooks 57 and ladle 41. It is not possible to continue lifting of the main hooks 57 and ladle 41 because of insufficient output power from the two main winching motors 47A, 47B. Next, the case when the auxiliary lateral moving inverter apparatus 95 breaks down will be described. When the auxiliary lateral moving inverter apparatus 95 breaks down, as shown in FIG. 7, the auxiliary lateral moving line switch 69 is made ON to supply AC power from the main lateral moving inverter apparatus 67B to the auxiliary lateral moving motor 73. The auxiliary lateral moving motor 73 that is supplied with the AC power generates rotational power, by which lateral movement of the auxiliary trolley 11 can be performed and the operation of the ladle crane 1 can be continued. On the other hand, the supply of AC power to the main lateral moving motor 45B is interrupted and the output of the main lateral moving motor 45B becomes zero. Lateral movement of the main trolley 9, however, can be continued although the speed of movement is decreased since the main trolley 9 is driven only by the main lateral moving motor 45A. It is noted that a failure of the auxiliary winching inverter apparatus 87 or the auxiliary lateral moving inverter apparatus 95 may be detected by an self-diagnostic apparatus provided in the auxiliary winching device 71, or by regular inspections executed by an operator; it is not limited to any one method. The actuation of the auxiliary winching line switch 61 and the auxiliary lateral moving line switch 69 is preferably executed by an operator, because the operator can realize the failure of the auxiliary winching inverter apparatus 87 or the auxiliary lateral moving inverter apparatus 95, and surely take an action of repair, replacement, or the like for the failed auxiliary winching inverter apparatus 87 or auxiliary lateral moving inverter apparatus 95. According to this arrangement, even if the auxiliary winching device 87 should break down, the auxiliary winching motor 75 will be continuously driven, so it is possible to continue lifting and lowering of the auxiliary hook. Namely, the operation of ladle crane 1 can be continued. While the auxiliary winching inverter apparatus 87 does not fail, AC power is supplied from the main winching inverter apparatus 59D not to the auxiliary winching motor 75 but to the main winching motor 47D. That is, since the main winching inverter apparatus 59D is consistently used, power supply to the auxiliary winching motor 75 in the case when the auxiliary winching inverter apparatus 87 breaks down can be assured, compared with a method using a spare motor control unit just when the auxiliary winching inverter apparatus 87 fails. According to the ladle crane 1 of this embodiment, even if the auxiliary winching inverter apparatus 87 should break down, the remaining main winching motors 47A, 47B, 47C will perform lifting and lowering of the ladle 41 and main hooks 57, and therefore the operation of the ladle crane 1 can be continued. Specifically, in the case when the auxiliary winching inverter apparatus 87 breaks down, the auxiliary winching motor 75 is supplied with AC power from the main winching inverter apparatus 59D, and the main winching motor 47D that has been supplied with AC power from the main winching inverter apparatus 59D stops. In this condition, since the remaining main winching motors 47A, 47B, 47C perform lifting and lowering of the ladle 41 and main hooks 57 as well as the auxiliary winching motor 75 performs lifting and lowering of the auxiliary hook 85, the operation of the ladle crane I can be continued. The main winching inverter apparatus 59D can surely supply the auxiliary winching motor 75 with the power required for continuing the operation of the ladle crane 1 when the auxiliary winching inverter apparatus 87 breaks down, since the capacity of the main winching inverter apparatus 59D is larger than that of the auxiliary winching inverter apparatus 87. According to the ladle crane 1 of this embodiment, even if the auxiliary lateral moving inverter apparatus 95 should break down, the auxiliary lateral moving motor 73 will be continuously driven, so lateral movement of the auxiliary trolley 11 can be continuously performed. Namely, the operation of ladle crane 1 can be continued. While the auxiliary lateral moving inverter apparatus 95 does not fail, AC power is supplied from the main lateral moving inverter apparatus 67B to the main lateral moving motor 45B. That is, since the main lateral moving inverter apparatus 67B is consistently used, the operation of the auxiliary trolley 11 in the case when the auxiliary lateral moving inverter apparatus 95 breaks down can be assured, compared with a method using a spare motor control unit just when the auxiliary lateral moving inverter apparatus 95 fails. According to the ladle crane 1 of this embodiment, even if the auxiliary lateral moving inverter apparatus 95 should break down, the main trolley 9 will be laterally moved by the remaining one main lateral moving motor 45A, so the operation of the auxiliary trolley 11 can be continuously performed. Specifically, in the case when the auxiliary lateral moving inverter apparatus 95 breaks down, the auxiliary lateral moving motor 73 is supplied with AC power from the main lateral moving inverter apparatus 67B, and the main lateral moving motor 45B that has been supplied with AC power from the main lateral moving inverter apparatus 67B stops. In this condition, since movement of the main trolley 9 is performed by the remaining one main lateral moving motor 45A as well as lateral movement of the auxiliary trolley 11 is performed by the auxiliary lateral moving motor 73, the operation of the ladle crane 1 can be continued. The main lateral moving inverter apparatus 67B can surely supply the auxiliary lateral moving motor 73 with the power required for continuing the operation of the ladle crane 1 when the auxiliary lateral moving inverter apparatus 95 breaks down, since the capacity of the main lateral moving inverter apparatus 67B is larger than that of the auxiliary lateral moving inverter apparatus 95. We claim, 1. A crane (1) comprising: a plurality of first motors(47A,47B,47C,47D); a plurality of first motor control units(59A,59B,59C,59D) , each corresponding to one of the first motors, that control the output of the corresponding first motors(47A,47B,47C,47D) by controlling the power supplied to the corresponding first motors; a second motor(75); and a second motor control unit (87)that control the output of the second motor(75) by controlling the power supplied to the second motor, wherein it is possible to control whether or not the power is supplied from a specified one of the first motor control units(67A) to the second motor (75). 2. The crane as claimed in Claim 1, wherein the specified first motor control unit has an electric capacity for controlling a motor larger than the electric capacity of the second motor. 3. The crane as claimed in Claim 1 or 2,wherein a pair of main hooks from which a load can be hung, the pair of main hooks being lifted and lowered by the plurality of first motors; and an auxiliary hook that controls the attitude of the load, the auxiliary hook being lifted and lowered by the second motor. 4. The crane as claimed in Claim 3, wherein when the second motor is supplied with power from the specified first motor control unit, the hooks and the load are lifted and lowered by the first motors that are supplied with power from ones of the first motor control units other 5. The crane as claimed in any one of Claims 1 to 4, wherein a main trolley having the first motors installed thereon, the main trolley being disposed so as to be movable in predetermined directions; and an auxiliary trolley having the second motor installed thereon, the auxiliary trolley being disposed so as to be movable in predetermined directions, wherein the main trolley is moved by the first motors, and the auxiliary trolley is moved by the second motor. 6. The crane as claimed in Claim 5, wherein when the second motor is supplied with power from the specified first motor control unit, the main trolley is moved by the first motors that are supplied with power from the ones of the first motor control units other than the specified first motor control unit. 7. The crane as claimed in any one of Claims 1 to 6, wherein each of the first motor control units and second motor control unit comprises an inverter apparatus and the first motors and the second motor are inverter motors driven by the inverter apparatuses. 8. A method of controlling a crane, wherein the outputs of a plurality of first motors are controlled by controlling the power supplied from a corresponding plurality of first motor control units, each of the first motor control units corresponding to one of the first motors, the output of a second motor is controlled by controlling the power supplied from a second motor control unit, and the second motor is supplied with power from a specified first motor control unit when the second motor specified first motor control unit when the second motor control unit breaks down.

Full Text

BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to a crane, and more specifically, to a ladle crane used for conveying a ladle and a control method thereof.
2. DESCRIPTION OF RELATED ART
In ironmaking plants and/or steelmaking plants, traditionally, molten steel is contained in a ladle and conveyed using a ladle crane. For example, molten steel is poured into a ladle from an electric furnace or the like, conveyed using a ladle crane to a converter or the like, and then poured into the converter. The ladle crane conveys the ladle that is lifted using a main winching device, and tilts the ladle by raising a lower part of the ladle with an auxiliary winching device to pour the molten steel into the converter or the like (see, for example, Japanese Unexamined Patent Application No. Heill-268881).
In a known example of a ladle crane, a main winching device that performs lifting and lowering of a ladle consists of two pairs of a motor and a motor control unit. There has been, however, a problem in that when, for example, one of the motor control units breaks down, the ladle crane ceases to be

operatable because the remaining pair of a motor and a motor control unit is only capable of either lifting or lowering the ladle.
On the other hand, an auxiliary winching device consists of a pair of a motor and a motor control unit, the pair of a motor and a motor control unit undertaking tilting and the like of the ladle. There has also been a problem in that when, for example, the motor control unit of the auxiliary winching device breaks down, the operation of the ladle crane has to be stopped. The auxiliary winching device is mounted on an auxiliary trolley and laterally moved by a pair of a motor and a motor control unit disposed on the auxiliary trolley for lateral movement thereof. There has been, therefore, another problem in that when, for example, the motor control unit for the lateral movement breaks down, the operation of the ladle crane has to be stopped.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to address the above problems with the object to provide a crane and a control method thereof such that even if a motor control unit of the crane should break down, the crane will be able to be continuously operated.
In order to attain the above object, the present invention provides the following means. A crane according to

a first aspect of the invention is characterized by including a plurality of first motors, a plurality of first motor control units that control the outputs of the first motors by respectively controlling the power supplied to the first motors, a second motor, and a second motor control unit that controls the output of the second motor by controlling the power supplied to the second motor; wherein a specified one of the first motor control units can selectively control whether to supply the power to the second motor or to suspend it.
According to the first aspect of the invention, even if, for example, the second motor control unit should break down, the crane will be continuously operated since the power for driving the second motor is supplied from the specified one of the first motor control units. Namely, in the case when the power supply from the second motor control unit is interrupted, the second motor is driven by the power supplied from the specified one of the first motor control units and therefore the crane can be continuously operated. The first motor, which has been supplied with the power from the specified one of the first motor control units, may stop or lose its output when the power supply is switched to the second motor; however, the remaining plurality of first motors enable the crane to be continuously operated.
While the second motor control unit is in working order, the specified one of the first motor control units suspends to

supply the power to the second motor and keeps to supply the power to the specified one of the first motors. Therefore, compared with the case that a backup motor control unit is used only for supplying power to the second motor, the second motor can be securely supplied with power because the specified first motor control unit has been consistently used.
In the first aspect of the invention described above, it is desired that the specified first motor control unit has a larger electrical capacity for controlling a motor than the second motor control unit.
According to the above arrangement, since the specified first motor control unit has a larger electrical capacity than the second motor control unit, the power required for driving the second motor can be surely supplied to secure the operation of the crane when the second motor control unit breaks down.
In the first aspect of the invention described above, the crane is preferably equipped with a pair of main hooks for hanging a load and an auxiliary hook for controlling the attitude of the load; wherein, the main hooks are lifted and lowered by the plurality of first motors and the auxiliary hook is lifted and lowered by the second motor.
According to the above arrangement, even if, for example, the second motor control unit should break down, the second motor will be continuously driven and consequently the lifting

and lowering of the auxiliary hook will be continuously performed; namely, the operation of the crane can be continued. Furthermore, compared with the case that a backup motor control unit is used only for supplying power to the second motor, the operation of the auxiliary hook can be secured, since the specified first motor control unit has supplied power to one of the first motors while the second motor control unit has been in working order.
In the first aspect of the invention described above, it is desired that, while the second motor is supplied with power from the specified first motor control unit, the main hooks and the load are lifted and lowered by the other first motors which are supplied with power from the first motor control units different from the specified first motor control unit.
According to the above arrangement, even if, for example, the second motor control unit should break down, lifting and lowering of the main hooks and the load will be performed by ones of the first motors other than the specified one and therefore the operation of the crane will be continued. Specifically, in the case when the second motor control unit breaks down, the second motor is supplied with power from the specified one of the first motor control units; as the result, the first motor which has been supplied with power from the specified first motor control unit may lose its output or come to a stop. In this case, lifting and lowering of the main

hooks and the load are undertaken by other first motors than the specified one, and also lifting and lowering of the auxiliary hook are performed by the second motor, which allows the crane to be continuously operated.
In the first aspect of the invention described above, it is desired that a main trolley having the first motors installed thereon is disposed so as to be movable in predetermined directions, and an auxiliary trolley having the second motor installed thereon is disposed so as to be movable in predetermined directions; wherein, the main trolley is moved by the plurality of first motors and the auxiliary trolley is moved by the second motor.
According to this arrangement, even if, for example, the second motor control unit should break down, the second motor will be continuously driven and the auxiliary trolley will be continuously moved; namely, the operation of the crane can be continued. While the second motor control unit is in working order, the specified one of first motor control units supplies the power to the specified one of the first motors; therefore, compared with the case that a backup motor control unit is used only for supplying power to the second motor, driving of the auxiliary trolley can be secured.
In the first aspect of the invention described above, it is desired that, while the second motor is supplied with power from the specified first motor control unit, the main trolley

is driven by the remaining first motors supplied with power from other first motor control units than the specified one.
According to the above arrangement, even if, for example, the second motor control unit should break down, the main trolley will be moved by other first motors than the specified one and therefore the operation of the crane will be continued. Specifically, when the second motor control unit breaks down, the second motor is supplied with power from the specified one of the first motor control units; as the result, the first motor which has been supplied with power from the specified first motor control unit may lose its output or come to a stop. In this case, the main trolley is moved by other first motors than the specified one, and also the auxiliary trolley is moved by the second motor, which allows the crane to be continuously operated.
In the first aspect of the invention described above, it is desired that an inverter apparatus is employed for each of the first motor control units and the second motor control unit, and an inverter motor driven by the inverter apparatus is employed as each of the first motors and the second motor.
According to this arrangement, the outputs of the first motors and the second motor can be easily controlled by employing the inverter apparatus for the first motor control units and the second motor control unit, and also by employing the inverter motor as the first motors and the second motor.

A crane control method according to a second aspect of the invention is characterized by that the outputs of the plurality of first motors are controlled by respectively controlling the power supplied from the plurality of first motor control units, the output of the second motor is controlled by controlling the power supplied from the second motor control unit, and, when the second motor control unit breaks down, the second motor is supplied with power from the specified one of the first motor control units.
According to the second aspect of the invention, even if the second motor control unit should break down, the operation of the crane will be continued since the second motor is supplied with power from the specified one of the first motor control units. Namely, when the power supply from the second motor control unit is interrupted, the second motor continues to be driven and the operation of the crane can be continued, because the power supply to the second motor is covered by the specified one of the first motor control units. The first motor which has been supplied with power from the specified one of the first motor control units may stop or lose its output when the power supply is switched to the second motor; however, the remaining first motors enable the crane to be continuously operated.
The crane and the control method thereof according to the present invention enable the crane to be continuously operated

even in the case when some part of the motor control units breaks down since the second motor can be supplied with power from the specified one of first motor control units.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a plan view illustrating the structure of a ladle crane according to an embodiment of the present invention.
FIG. 2 is a side view illustrating the structure of the main girder and the main trolley illustrated in FIG. 1.
FIG. 3 is a layout plan illustrating the structure of the ladle crane illustrated in FIG. 1.
FIG. 4 is a block diagram illustrating the electric circuit used for the travel motors illustrated in FIG. 3.
FIG. 5 is a sectional view illustrating the structure of the main trolley, auxiliary trolley, and electric cabinet illustrated in FIG. 1.
FIG. 6 is a block diagram illustrating the electric circuit used for the main winching device and auxiliary winching device illustrated in FIG. 1.
FIG. 7 is a block diagram illustrating the electric circuit used for the main lateral moving motors and auxiliary lateral moving motor illustrated in FIG. 1.
FIG. 8 is a partial sectional view illustrating the structure of the auxiliary trolley illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION
A ladle crane according to an embodiment of the present invention will now be described with reference to the drawings, FIGS. 1 to 8. FIG. 1 is a plan view illustrating the structure of a ladle crane according to this embodiment. As shown in FIG. 1, the ladle crane (crane) 1 includes end ties 3, main girders 5, auxiliary girders 7, a main trolley 9 and an auxiliary trolley 11.
FIG. 2 is a side view illustrating the structure of the main girder and the main trolley illustrated in FIG. 1. The end ties 3 are a pair of members extended along travel rails 17 mounted on travel beams 15, as shown in Fig. 2, the end ties 3 being equipped with travel units 19 that travel on the travel rails 17. Furthermore, as shown in FIG. 1, the main girders 5 and the auxiliary girders 7 are attached to the end ties 3 .
FIG. 3 is a layout plan illustrating the structure of the ladle crane illustrated in FIG. 1. The travel units 19 are disposed between the travel rails 17 and the end ties 3, as shown in FIG. 2, and allow the ladle crane 1 to travel along the travel rails 17. An example of this embodiment, in which four travel units 19 are installed at ends of the end ties 3, will now be described. The travel units 19 are equipped with travel motors 21A, 21B, travel motors 21C, 21D, travel motors

21E, 21 F and travel motors 21G, 21H as shown in FIG. 3 to allow the ladle crane 1 to travel along the travel rails 17.
It is noted that the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H can be selected from, but not limited to, known inverter-controlled motors.
FIG. 4 is a block diagram illustrating the electric circuit used for the travel motors illustrated in FIG. 3. As shown in FIG. 4, the travel motors 21A, 21B are supplied with power from an travel inverter apparatus 23A; similarly the travel motors 21C, 21D are supplied with power from a travel inverter apparatus 23C, the travel motors 21E, 21F are supplied with power from a travel inverter apparatus 23E, and the travel motors 21G, 21H are supplied with power from a travel inverter apparatus 23G. These travel inverter apparatuses 23A, 23C, 23E, 23G are supplied with AC power from the outside.
It is noted that the travel inverter apparatuses 23A, 23C, 23E, 23G may control the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H by applying variable-voltage variable-frequency control to the power supplied thereto, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like.
As shown in FIG. 1, the main girders 5 are a pair of

beam-shaped members disposed so as to join the pair of end ties 3, and the main trolley 9 is mounted on the main girders 5 so as to be movable. The main girders 5 are disposed outside the auxiliary girders 7 (described later) so as to be substantially orthogonal to the end ties 3. On the top of the main girders 5 (the side toward the viewer in FIG. 1), a pair of main lateral moving rails 27 are disposed so as to extend along the main girders 5, and to the side of one of the main girders 5 (the lower side of the drawing in FIG. 1), an electric cabinet 29 is installed in which a main winching inverter apparatus 59 (described later) and the like are contained. The main lateral moving rails 27 are provided for guiding the main trolley 9 mounted thereon along a direction substantially orthogonal to the travel rails 17 (hereinafter referred to as "lateral direction").
FIG. 5 is a sectional view illustrating the structure of the main trolley, auxiliary trolley, and electric cabinet illustrated in FIG. 1. As shown in FIG. 5, the electric cabinet 29 is a box-shaped member disposed at a position facing the side of the main girder 5 (the left side of FIG. 5). On the top of the electric cabinet 29 (the upper side of FIG. 5), fixing members 33 fixed to a support member 31, which extends from the main girder 5, are disposed and connection members 35 engaged with the hook (not shown) of the crane are also disposed. A thermal barrier member 37 is provided

underneath the electric cabinet 29 (the lower side of FIG. 5) and also underneath the main girder 5. The electric cabinet 29 can be attached to or detached from the support member 31 by connecting the fixing members 33 to or by disconnecting it from the support member 31. In the inside of the electric cabinet 29, four main winching inverter apparatuses 59A, 59B, 59C, 59D, an auxiliary winching inverter apparatus 87 (see FIG. 6), two main lateral moving inverter apparatuses 67A, 67B, an auxiliary lateral moving inverter apparatus 95 (see FIG. 7), and four travel inverter apparatuses 23A, 23C, 23E, 23G, (see FIG. 4) are disposed. The main winching inverter apparatuses 59A, 59B, 59C, 59D and the like are electrically connected to a main winching motor 47A (described later) or the like while the electric cabinet 29 is mounted to the support member 31.
As shown in FIG. 1, the auxiliary girders 7 are, similar to the main girders 5, a pair of beam-shaped members disposed so as to join the pair of end ties 3, and the auxiliary trolley 11 is mounted on the auxiliary girders 7 so as to be movable. The auxiliary girders 7 are disposed inside the main girders 5 so as to be substantially orthogonal to the end ties 3. On the auxiliary girders 7 a pair of auxiliary lateral moving rails 39 are disposed, the auxiliary lateral moving rails 39 being provided to guide the auxiliary trolley 11 mounted thereon in the lateral direction.

As shown in Fig. 3, the main trolley 9 is equipped with a main winching device 43 for lifting and lowering a ladle (a hung load) 41 (see FIG. 5), and main lateral moving motors (first motors) 45A, 45B allowing the main trolley 9 to laterally move. The main winching device 43 includes the main winching motors (first motors) 47A, 47b, 47C, 47D, main speed-reducing members 49A, 49B, 49C, main winching drums 51A, 51B, and, as shown in FIG. 5, main hanging sheaves 53, a hanging beam 55, and main hooks 57.
The main winching motors 47A, 47B and the main winching motors 47C, 47D are separately disposed at one end and another end of the main trolley 9 as shown in FIG. 3. The rotational power of the main winching motors 47A, 47B, 47C, 47D are transmitted to the main winching drums 51A, 51B via the main speed-reducing members 49A, 49B, 49C. The main winching motors 47A, 47B, 47C, 47D are chosen so that any three of the four motors have together an output power capable of lifting and lowering the main hooks 57 and the ladle 41 containing molten steel. It is noted that the main winching motors 47A, 47B, 47C, 47D can be selected from, but not limited to, known inverter-controlled motors.
FIG. 6 is a block diagram illustrating the electric circuit used for the main winching device and auxiliary winching device illustrated in FIG. 1. The main winching motors 47A, 47B, 47C, 47D are respectively supplied with AC

power, as shown in FIG. 6, from the main winching inverter apparatuses (first motor control units) 59A, 59B, 59C and the main winching inverter apparatus (specified first motor control unit) 59D, the main winching inverter apparatus 59A, 59B, 59C, 59D being supplied with AC power from the outside. There is an auxiliary winching line switch 61 connected to the line between the main winching inverter apparatus 59D and the main winching motor 47D, the auxiliary winching line switch 61 enabling or disabling supply of AC power from main winching inverter apparatus 59D to an auxiliary winching motor 75. The capacity of each of the main winching inverter apparatuses 59A, 59B, 59C, 59D is specified so as to be larger than that of the auxiliary winching inverter apparatus 87 described later. As examples of the capacity, 500 kW is given for each of the main winching inverter apparatuses 59A, 59B, 59C, 59D, and 250 kW for the auxiliary winching inverter apparatus 87, but the capacity is not limited to these.
It is noted that the main winching inverter apparatuses 59A, 59B, 59C, 59D may control the main winching motors 47A, 47B, 47C, 47D by applying variable-voltage variable-frequency control to the power supplied thereto, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like.

The main speed-reducing member 49A is disposed between the main winching motors 47A, 47B so as to combine the rotational power of the main winching motors 47A, 47B and transmit the combined power to the main speed-reducing member 49C. The main speed-reducing member 49B is disposed between the main winching motors 47C, 47D so as to combine the rotational power of the main winching motors 47C, 47D and transmit the combined power to the main speed-reducing member 49C. The main speed-reducing member 49C is disposed so as to transmit the rotational power input from both the main speed-reducing member 49A and the main speed-reducing member 49B to the main winching drums 51A, 51B. It is noted that the main speed-reducing members 49A, 49B, 49C can be selected from, but not limited to, known speed reducers capable of transmitting rotational power. For example, a combination of three speed-reducing members can be used as described in this embodiment, or one speed-reducing member may be used to transmit the rotational power from the main winching motors 47A, 47B, 47C, 47D to the main winching drums 51A, 51B; the power transmitting arrangement is not limited to this.
The main winching drums 51A, 51B are each cylindrical or column-shaped members that are disposed so as to be rotatable around the center axis thereof and to be substantially parallel to the lateral direction. As shown in FIG. 5, a main wire rope 63 for lifting and lowering the main hook 57 is

wound around each of the main winching drums 51A, 51B. The main wire ropes 63 are wound when the main winching drums 51A, 51B are rotated in a rotating direction, and unwound when the main winching drums 51A, 51B are rotated in another rotating direction. Both of the main wire ropes 63 are simultaneously wound or unwound as the main winching drums 51A, 51B rotate.
The main wire ropes 63 extend from the main winching drums 51A, 51B toward main hook-side sheaves 54 to be wound thereon and also on main hanging sheaves 53; one end of each of the main wire ropes 63 is fixed to the hanging beam 55. Each of the main hanging sheaves 53 is a cylindrical or column-shaped member that is disposed under the main trolley 9 so as to be rotatable around its center axis substantially parallel to the lateral direction. Each of the main hook-side sheaves 54 is a cylindrical-shaped or column-shaped member that is disposed at one end of the hanging beam 55 so as to be rotatable around its center axis substantially parallel to the lateral direction.
The main hooks 57 provided for hooking respective shafts 41a of the ladle 41 are disposed at both ends of the hanging beam 55 as shown in FIG. 5. Each of the main hooks 57 is attached to the hanging beam 55 by using a pin 65 so as to be rotatable around the center axis of the pin 65.
As shown in FIG. 3, the main lateral moving motor 45A is disposed at one end of the main trolley 9 and the main lateral

moving motor 45B is disposed at another end of the main trolley 9. The rotational power generated by the main lateral moving motors 45A, 45B is transmitted to the main lateral moving members 9A of the main trolley 9 as shown in FIG. 2. It is noted that the main lateral moving motors 45A, 45B can be selected from, but not limited to, known inverter-controlled motors.
FIG. 7 is a block diagram illustrating the electric circuit used for the main lateral traveling motors and auxiliary lateral traveling motor illustrated in FIG. 1. The main lateral moving motors 45A, 45B are supplied with power from the main lateral moving inverter apparatus 67A (first motor control unit) and the main lateral moving inverter apparatus 67B (specified first motor control unit), respectively, the main lateral moving inverter apparatuses 67A, 67B being supplied with AC power from the outside. There is an auxiliary lateral moving line switch 69 connected to the line between the main lateral moving inverter apparatus 67B and the main lateral moving motor 45B, the auxiliary lateral moving line switch 69 enabling or disabling supply of AC power from the main lateral moving inverter apparatus 67B to an auxiliary lateral moving motor 73. The capacity of each of the main lateral moving inverter apparatuses 67A, 67B is specified so as to be larger than that of the auxiliary lateral moving inverter apparatus 95 described later. As

examples of the capacity, 45 kW is given for each of the main lateral moving inverter apparatuses 67A, 67B and 15 kW for the auxiliary lateral moving inverter apparatus 95, but the capacity is not limited to these examples.
It is noted that the main lateral moving inverter apparatuses 67A, 67B may control the main lateral moving motors 45A, 45B, respectively, by applying variable-voltage variable-frequency control to supplied power, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like.
FIG. 8 is a partial sectional view illustrating the structure of the auxiliary trolley illustrated in FIG. 1. The auxiliary trolley 11 is equipped, as shown in FIG. 3, with an auxiliary winching device 71 that controls the tilt of the ladle 41 (see FIG. 5), and the auxiliary lateral moving motor (second motor) 73 allowing the auxiliary trolley 11 to laterally move. The auxiliary winching device 71 includes the auxiliary winching motor (second motor) 75, an auxiliary winching speed-reducing member 77, an auxiliary winching drum 79 and, as shown in FIG. 8, an auxiliary trolley-side sheave 81, an auxiliary hook-side sheave 83, and an auxiliary hook 85.
The auxiliary winching motor 75 is mounted on one end of

auxiliary trolley 11 as shown in FIG. 3. The rotational power from the auxiliary winching motor 75 is transmitted to the auxiliary winching drum 79 via the auxiliary winching speed-reducing member 77. It is noted that the auxiliary winching motor 75 can be selected from, but not limited to, known inverter-controlled motors.
As shown in FIG. 6, the auxiliary winching motor 75 is supplied with power from the auxiliary winching inverter apparatus (second motor control unit) 87, which is supplied with AC power from the outside. It is noted that the auxiliary winching inverter apparatus 87 may control the auxiliary winching motor 75 by applying variable-voltage variable-frequency control to supplied power, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like.
The auxiliary winching speed-reducing member 77 is disposed so as to transmit the rotational power from the auxiliary winching motor 75 to the auxiliary winching drum 79. It is noted that the auxiliary winching speed-reducing member 77 can be selected from, but not limited to, known speed reducers.
The auxiliary winching drum 79 is a cylindrical or column-shaped member that is disposed so as to be rotatable

around the center axis thereof and to be substantially perpendicular to the lateral direction. An auxiliary wire rope 89 for lifting and lowering the auxiliary hook 85 is wound around the auxiliary winching drum 79. The auxiliary wire rope 89 is wound when the auxiliary winching drum 79 is rotated in a rotating direction, and unwound when the auxiliary winching drum 79 is rotated in another rotating direction.
The auxiliary wire rope 89 extends from the auxiliary winching drum 79 toward the auxiliary hook-side sheave 83 to be wound on the auxiliary hook-side sheave 83 and the auxiliary trolley-side sheave 81; one end of the auxiliary wire rope 89 is fixed to the auxiliary trolley 11. The auxiliary trolley-side sheave 81 is a cylindrical or column-shaped member that is disposed between the auxiliary winching motor 75 and the auxiliary winching drum 79 on the auxiliary trolley 11 so as to be rotatable around its center axis substantially perpendicular to the lateral direction. The auxiliary hook-side sheave 83 is a cylindrical or column-shaped member that is disposed in an auxiliary hook block 91 for the auxiliary hook 85 so as to be rotatable around its center axis substantially perpendicular to the lateral direction. The auxiliary hook 85 disposed in the auxiliary hook block 91 as shown in FIG. 8 is a hook that is connected to the tilting bracket 41b provided on a sidewall of the ladle

41.
The auxiliary lateral moving motor 73 is disposed at another end of auxiliary trolley 11 as shown in FIG. 3. The rotational power generated by the auxiliary lateral moving motor 73 is transmitted to auxiliary lateral moving members 93 as shown in FIG. 8. It is noted that the auxiliary lateral moving motor 73 can be selected from, but not limited to, known inverter-controlled motors.
The auxiliary lateral moving motor 73 is supplied with power from the auxiliary lateral moving inverter apparatus (second motor control unit) 95, the auxiliary lateral moving inverter apparatus 95 being supplied with AC power from the outside. It is noted that the auxiliary lateral moving inverter apparatus 95 may control the auxiliary lateral moving motor 73 by applying variable-voltage variable-frequency control, or by applying other control modes including, but not limited to, constant-voltage constant-frequency control, variable-voltage constant-frequency control, constant-voltage variable-frequency control, or the like.
Now, the way of conveying the ladle 41 using the ladle crane 1 constituted as described above will be explained. In order to convey the ladle 41, the ladle crane 1 is made to travel along the travel rails 17, and the main trolley 9 is also moved in lateral direction so that the main hooks 57 are located at a position above the ladle 41 as shown in FIG. 2.

Upon locating the main trolley 9 at a position above the ladle 41, the main hooks 57 are lowered to hook the shafts 41a of the ladle 41, and then lifted together with the ladle 41 by the main winching device 43 to a higher level. When the main hooks 57 are lifted, as shown in FIG. 6, the main winching motors 47A, 47B, 47C, 47D of the main winching device 43 are supplied with AC power from the main winching inverter apparatus 59A, 59B, 59C, 59D. The rotational power generated by the main winching motors 47A, 47B, 47C, 47D are transmitted to the main winching drums 51A, 51B via the main speed-reducing members 49A, 49B and the main speed-reducing member 49C, which results in rotating the main winching drums 51A, 51B. As the main winching drums 51A, 51B rotates, the main wire ropes 63 are wound thereon and the main hooks 57 hanging the ladle 41 is lifted upward.
At that time, the auxiliary winching line switch 61 is off and all the AC power from the main winching inverter apparatus 59D is supplied to the main winching motor 47D. The respective main winching motors 47A, 47B, 47C, 47D are driven at a same output, and the main winching motors 47A, 47B, 47C, 47D as well as the main winching inverter apparatus 59A, 59B 59C 59D are operated with a margin.
After being hung up, the ladle 41 is conveyed to, for example, near a converter or the like by the ladle crane 1 traveling along the travel rails 17 and also by the main

trolley 9 moving in lateral direction. When the ladle crane 1 travels, as shown in FIG. 4, the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H are supplied with AC power from the travel inverter apparatuses 23A, 23C, 23E, 23G. The rotational power generated by the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H is transmitted to the travel units 19; thereby the ladle crane 1 is made to travel along the travel rails 17 until the ladle 41 comes near the converter or the like.
At that time, the travel inverter apparatuses 23A, 23C, 23E, 23G supply the respective travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H with controlled AC power to generate the same output. When any of the travel motors 21A, 21B, 21C, 21D, 21E, 21F, 21G, 21H breaks down, power supply to the broken travel motor may be interrupted by a switch provided for that purpose; then the ladle crane 1 is moved by the remaining travel motors along the travel rails 17.
As shown in FIG. 7, the main lateral moving motors 45A, 45B of the main trolley 9 are supplied with AC power from the main lateral moving inverter apparatuses 67A, 67B. The rotational power generated by the main lateral moving motors 45A, 45B is transmitted to main lateral moving members 9A, and the main trolley 9 is laterally moved along the main girders 5 until the ladle 41 comes near the converter or the like. At that time, the auxiliary lateral moving line switch 69 is in

an off position and all the AC power provided from the main lateral moving inverter apparatus 67B is supplied to the main lateral moving motor 45B.
After that, the ladle 41 is tilted by the auxiliary winching device 71 to pour the molten steel in the ladle into the converter or the like. When the ladle 41 is tilted by the auxiliary winching device 71, the auxiliary hook 85 is first lowered and the auxiliary trolley 11 is laterally moved to a position where the auxiliary hook 85 is allowed to hook the tilting bracket of the ladle 41. When the auxiliary trolley 11 is moved, as shown in FIG. 7, the auxiliary lateral moving motor 73 of the auxiliary trolley 11 is supplied with AC power from the auxiliary lateral moving inverter apparatus 95. The rotational power generated by the auxiliary lateral moving motor 73 is transmitted to the auxiliary lateral moving member 93, and the auxiliary trolley 11 is laterally moved along the main girders 5 to the position where the auxiliary hook 85 is allowed to hook the tilting bracket of the ladle 41. At that time, the auxiliary lateral moving line switch 69 is in the off position and all the AC power provided from the auxiliary lateral moving inverter apparatus 95 is supplied to the auxiliary lateral moving motor 73.
As the auxiliary hook 85 hooking the tilting bracket of the ladle 41 is lifted by the auxiliary winching device 71, the ladle 41 is tilted. When the auxiliary hook 85 is lifted,

as shown in FIG. 6, the auxiliary winching motor 75 of the auxiliary winching device 71 is supplied with AC power from the auxiliary winching inverter apparatus 87. The rotational power generated by the auxiliary winching motor 75 is transmitted to the auxiliary winching drum 79 via the auxiliary winching speed-reducing member 77. As the auxiliary winching drum 79 is rotated by the transmitted rotational power, the auxiliary wire rope 89 is wound there around and the auxiliary hook 85 hooking the tilting bracket is lifted upward; since the ladle 41 is turned around the shafts 41a, the molten steel is poured from the ladle 41 into the converter or the like.
Here, a features of this embodiment, i.e., the operating method of the ladle crane 1 in the case when the auxiliary winching inverter apparatus 87 or the auxiliary lateral moving inverter apparatus 95 breaks down will be described. In the first case when the auxiliary winching inverter apparatus 87 breaks down, as shown in FIG. 6, the auxiliary winching line switch 61 is made ON to supply AC power from the main winching inverter apparatus 59D to the auxiliary winching motor 75. The auxiliary winching motor 75 that is supplied with AC power generates rotational power, by which lifting and lowering of the auxiliary hook 85 can be performed and the operation of the ladle crane 1 can be continued.
On the other hand, the supply of AC power to the main

winching motor 47D is interrupted and the output of the main winching motor 47 becomes zero. Then, the main winching inverter apparatuses 59A, 59B, 59C control the power supplied to the main winching motors 47A, 47B, 47C so as to maximize their outputs; thereby the main winching device 43 is enabled to continue lifting and lowering of the main hooks 57 and ladle 41.
In the case when two of the four main winching motors 47A, 47B, 47C, 47D, for example, the main winching motors 47C, 47D fail, the remaining two main winching motors 47A, 47B undertake lowering of the main hooks 57 and ladle 41, but other operations of the ladle crane 1 are interrupted. When the main hooks 57 and ladle 41 are lowered, the outputs of the main winching motors 47A, 47B are maximized to safely lower the main hooks 57 and ladle 41. It is not possible to continue lifting of the main hooks 57 and ladle 41 because of insufficient output power from the two main winching motors 47A, 47B.
Next, the case when the auxiliary lateral moving inverter apparatus 95 breaks down will be described. When the auxiliary lateral moving inverter apparatus 95 breaks down, as shown in FIG. 7, the auxiliary lateral moving line switch 69 is made ON to supply AC power from the main lateral moving inverter apparatus 67B to the auxiliary lateral moving motor 73. The auxiliary lateral moving motor 73 that is supplied

with the AC power generates rotational power, by which lateral movement of the auxiliary trolley 11 can be performed and the operation of the ladle crane 1 can be continued.
On the other hand, the supply of AC power to the main lateral moving motor 45B is interrupted and the output of the main lateral moving motor 45B becomes zero. Lateral movement of the main trolley 9, however, can be continued although the speed of movement is decreased since the main trolley 9 is driven only by the main lateral moving motor 45A.
It is noted that a failure of the auxiliary winching inverter apparatus 87 or the auxiliary lateral moving inverter apparatus 95 may be detected by an self-diagnostic apparatus provided in the auxiliary winching device 71, or by regular inspections executed by an operator; it is not limited to any one method. The actuation of the auxiliary winching line switch 61 and the auxiliary lateral moving line switch 69 is preferably executed by an operator, because the operator can realize the failure of the auxiliary winching inverter apparatus 87 or the auxiliary lateral moving inverter apparatus 95, and surely take an action of repair, replacement, or the like for the failed auxiliary winching inverter apparatus 87 or auxiliary lateral moving inverter apparatus 95.
According to this arrangement, even if the auxiliary winching device 87 should break down, the auxiliary winching

motor 75 will be continuously driven, so it is possible to continue lifting and lowering of the auxiliary hook. Namely, the operation of ladle crane 1 can be continued. While the auxiliary winching inverter apparatus 87 does not fail, AC power is supplied from the main winching inverter apparatus 59D not to the auxiliary winching motor 75 but to the main winching motor 47D. That is, since the main winching inverter apparatus 59D is consistently used, power supply to the auxiliary winching motor 75 in the case when the auxiliary winching inverter apparatus 87 breaks down can be assured, compared with a method using a spare motor control unit just when the auxiliary winching inverter apparatus 87 fails.
According to the ladle crane 1 of this embodiment, even if the auxiliary winching inverter apparatus 87 should break down, the remaining main winching motors 47A, 47B, 47C will perform lifting and lowering of the ladle 41 and main hooks 57, and therefore the operation of the ladle crane 1 can be continued. Specifically, in the case when the auxiliary winching inverter apparatus 87 breaks down, the auxiliary winching motor 75 is supplied with AC power from the main winching inverter apparatus 59D, and the main winching motor 47D that has been supplied with AC power from the main winching inverter apparatus 59D stops. In this condition, since the remaining main winching motors 47A, 47B, 47C perform lifting and lowering of the ladle 41 and main hooks 57 as well

as the auxiliary winching motor 75 performs lifting and lowering of the auxiliary hook 85, the operation of the ladle crane I can be continued.
The main winching inverter apparatus 59D can surely supply the auxiliary winching motor 75 with the power required for continuing the operation of the ladle crane 1 when the auxiliary winching inverter apparatus 87 breaks down, since the capacity of the main winching inverter apparatus 59D is larger than that of the auxiliary winching inverter apparatus 87.
According to the ladle crane 1 of this embodiment, even if the auxiliary lateral moving inverter apparatus 95 should break down, the auxiliary lateral moving motor 73 will be continuously driven, so lateral movement of the auxiliary trolley 11 can be continuously performed. Namely, the operation of ladle crane 1 can be continued. While the auxiliary lateral moving inverter apparatus 95 does not fail, AC power is supplied from the main lateral moving inverter apparatus 67B to the main lateral moving motor 45B. That is, since the main lateral moving inverter apparatus 67B is consistently used, the operation of the auxiliary trolley 11 in the case when the auxiliary lateral moving inverter apparatus 95 breaks down can be assured, compared with a method using a spare motor control unit just when the auxiliary lateral moving inverter apparatus 95 fails.

According to the ladle crane 1 of this embodiment, even if the auxiliary lateral moving inverter apparatus 95 should break down, the main trolley 9 will be laterally moved by the remaining one main lateral moving motor 45A, so the operation of the auxiliary trolley 11 can be continuously performed. Specifically, in the case when the auxiliary lateral moving inverter apparatus 95 breaks down, the auxiliary lateral moving motor 73 is supplied with AC power from the main lateral moving inverter apparatus 67B, and the main lateral moving motor 45B that has been supplied with AC power from the main lateral moving inverter apparatus 67B stops. In this condition, since movement of the main trolley 9 is performed by the remaining one main lateral moving motor 45A as well as lateral movement of the auxiliary trolley 11 is performed by the auxiliary lateral moving motor 73, the operation of the ladle crane 1 can be continued.
The main lateral moving inverter apparatus 67B can surely supply the auxiliary lateral moving motor 73 with the power required for continuing the operation of the ladle crane 1 when the auxiliary lateral moving inverter apparatus 95 breaks down, since the capacity of the main lateral moving inverter apparatus 67B is larger than that of the auxiliary lateral moving inverter apparatus 95.

We claim,
1. A crane (1) comprising:
a plurality of first motors(47A,47B,47C,47D);
a plurality of first motor control units(59A,59B,59C,59D) , each corresponding to one of the first motors, that control the output of the corresponding first motors(47A,47B,47C,47D) by controlling the power supplied to the corresponding first motors;
a second motor(75); and
a second motor control unit (87)that control the output of the second motor(75) by controlling the power supplied to the second motor,
wherein it is possible to control whether or not the power is supplied from a specified one of the first motor control units(67A) to the second motor (75).
2. The crane as claimed in Claim 1,
wherein the specified first motor control unit has an electric capacity for controlling a motor larger than the electric capacity of the second motor.
3. The crane as claimed in Claim 1 or 2,wherein a pair
of main hooks from which a load can be hung, the pair of main
hooks being lifted and lowered by the plurality of first
motors; and
an auxiliary hook that controls the attitude of the load, the auxiliary hook being lifted and lowered by the second motor.
4. The crane as claimed in Claim 3,
wherein when the second motor is supplied with power from the specified first motor control unit, the hooks and the load are lifted and lowered by the first motors that are supplied with power from ones of the first motor control units other
5. The crane as claimed in any one of Claims 1 to 4,
wherein a main trolley having the first motors installed
thereon, the main trolley being disposed so as to be movable
in predetermined directions; and
an auxiliary trolley having the second motor installed thereon, the auxiliary trolley being disposed so as to be movable in predetermined directions,
wherein the main trolley is moved by the first motors, and the auxiliary trolley is moved by the second motor.
6. The crane as claimed in Claim 5,
wherein when the second motor is supplied with power from the specified first motor control unit, the main trolley is moved by the first motors that are supplied with power from the ones of the first motor control units other than the specified first motor control unit.
7. The crane as claimed in any one of Claims 1 to 6,
wherein each of the first motor control units and second
motor control unit comprises an inverter apparatus and the first motors and the second motor are inverter motors driven by the inverter apparatuses.
8. A method of controlling a crane,
wherein the outputs of a plurality of first motors are controlled by controlling the power supplied from a corresponding plurality of first motor control units, each of the first motor control units corresponding to one of the first motors, the output of a second motor is controlled by controlling the power supplied from a second motor control unit, and the second motor is supplied with power from a specified first motor control unit when the second motor
specified first motor control unit when the second motor control unit breaks down.

Documents:

187-DEL-2007-Abstract-(04-08-2011).pdf

187-del-2007-abstract.pdf

187-DEL-2007-Claims-(04-08-2011).pdf

187-del-2007-claims.pdf

187-DEL-2007-Correspondence Others-(04-08-2011).pdf

187-del-2007-Correspondence-Others (20-11-2009).pdf

187-DEL-2007-Correspondence-Others-(25-01-2011).pdf

187-del-2007-correspondence-others-1.pdf

187-DEL-2007-Correspondence-Others.pdf

187-del-2007-description (complete).pdf

187-DEL-2007-Drawings-(04-08-2011).pdf

187-del-2007-drawings.pdf

187-DEL-2007-Form-1.pdf

187-del-2007-form-18.pdf

187-del-2007-form-2.pdf

187-DEL-2007-Form-26.pdf

187-del-2007-Form-3 (20-11-2009).pdf

187-DEL-2007-Form-3-(04-08-2011).pdf

187-DEL-2007-Form-3-(25-01-2011).pdf

187-DEL-2007-Form-3.pdf

187-del-2007-form-5.pdf

187-DEL-2007-Petition-137-(04-08-2011).pdf

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Patent Number

255707

Indian Patent Application Number

187/DEL/2007

PG Journal Number

12/2013

Publication Date

22-Mar-2013

Grant Date

18-Mar-2013

Date of Filing

31-Jan-2007

Name of Patentee

MITSUBISHI HEAVY INDUSTRIES , LTD.

Applicant Address

16-5 KONAN 2-CHOME,MINATO-KU, TOKYO 108-8215, JAPAN

Inventors:

#	Inventor's Name	Inventor's Address
1	TOSHIHIKO SAKAMOTO	C/O HIROSHIMA MACHINERY WORKS, MITSUBISHI HEAVY INDUSTRIES, LTD., 6-22 KAN-ON-SHIN-MACHI 4-CHOME, NISHI-KU, HIROSHIMA, HIROSHIMA-KEN 733-8553, JAPAN

PCT International Classification Number

B66C 13/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2006-211910	2006-08-03	Japan