Title of Invention	"A LIFTING CLAMP"
Abstract	The invention relates to a lifting clamp (1) for mounting in a housing of an electrical appliance, e.g. a circuit breaker, comprising a rectangular frame (14) and a rectangular box (15), the upper section (150) of said box being arranged between the upper section (140) and the lower section (141) of the frame (14), enabling the box (15) to be held in the frame (14) in a displaceable manner. Said lifting clamp also comprises a clamping screw (16) which is guided through an opening (142) incorporated in the upper section (140) of the frame in a freely rotatable manner, and which engages in a screw thread (152) incorporated in the upper section (150) of the box (15). Said box (15) is held in the frame (14) against a resistance in a displaceable manner.

Title of Invention

"A LIFTING CLAMP"

Abstract

The invention relates to a lifting clamp (1) for mounting in a housing of an electrical appliance, e.g. a circuit breaker, comprising a rectangular frame (14) and a rectangular box (15), the upper section (150) of said box being arranged between the upper section (140) and the lower section (141) of the frame (14), enabling the box (15) to be held in the frame (14) in a displaceable manner. Said lifting clamp also comprises a clamping screw (16) which is guided through an opening (142) incorporated in the upper section (140) of the frame in a freely rotatable manner, and which engages in a screw thread (152) incorporated in the upper section (150) of the box (15). Said box (15) is held in the frame (14) against a resistance in a displaceable manner.

Full Text	1 A LIFTING CLAMP The invention relates to a lifting clamp for mounting in a housing of an electric apparatus such as a circuit-breaker, comprising a rectangular frame and a rectangular box whose upper section is arranged between the upper section and the lower section of the frame, enabling the box to be held in the frame in a displaceable manner, and further comprising a clamping screw which is guided through a breakthrough incorporated in the upper section of the frame in a freely rotatable manner and which engages in a screw thread incorporated in the upper section of the box, with the box being held in the frame against a resistance in a displaceable manner. Electric lines can be clamped in such lifting clamps at two places, namely between the lower sections of the frame and the box (lower receiving space) and between the upper section of the frame and the head of the clamping screw (upper receiving space). When the clamping screw is rotated in the opening direction, the box is moved downwardly at first and thus the lower receiving space is opened. Only when the box has reached its lowermost position in which it comes to rest on a housing part will the clamping screw be displaced upwardly in the further progressing opening movement and thus the upper opening space will be opened. When tightening the clamping screw it needs to be rotated at first to such an extent until the lower box section comes to rest on the lower frame section. Only then will the rotating movement of the clamping screw in the close direction be converted into a clamping contact of the screw head on the upper section of the frame or on an electric conductor situated between said upper section and the screw head. When only the upper receiving space is used, it is necessary to turn the clamping screw to a very high extent in order to open this space or to clamp an electric conductor in said space, as a result of which the amount of time required for connecting electric conductors to the lifting clamp is very high. Such a terminal with clamping boxes is known from EP 0 168 596 A for example. Such a lifting clamp is also known from EP 0 905 839 A. Lifting clamps are also known in which a resistance is provided against which one of the clamping boxes could be displaced in order to thus reduce the time needed for connecting 2 electric lines to the clamping terminals. In DE 195 13 281 A, DE 2 107 218 A and EP i 028 489 A connection terminals or lifting clamps are known in which the resistance against which a box is held displaceably in the frame is realized by a spring. Such a resistance is produced in EP 0 280 672 A by friction of the box on parts of the housing. The disadvantageous aspect in this state of the art is that the resistance against which the box is displaceable in the frame could be overcome inadvertently und thus the lower receiving space could be opened at an early stage. It is the object of the present invention to avoid this disadvantage and to provide a lifting clamp of the kind mentioned above in which on turning the clamping; screw in the opening direction the receiving space situated between the upper frame section and the screw head is opened, but the lower receiving space remains closed for the time being. The lower receiving space is only to be opened by performing special measures such as the exertion of a higher force on the screw in order to thus securely prevent any inadvertent displacement of the box. This is achieved in accordance with the invention by a shearing pin which is fastened to the housing, is preferably arranged in an integral manner with the housing and is connected with the box in a positive manner. If during the rotation of the clamping screw no large force is exerted, i.e. not more force than is mandatory for rotating a screw, said resistance at first prevents a displacement of the box. The opening movement of the screw is converted entirely into a lift-off of the screw head from the upper frame section, i.e. into an opening of the upper receiving space. This allows inserting a terminal lug of a busbar system into the upper receiving room even after a minor rotation of the clamping screw and reliably clamping the same by a slight rotation of the clamping screw in the closing direction. When overcoming the resistance (e.g. by exerting a pressure on the clamping screw), the resistance can be overcome, the box is displaced downwardly and thus the lower receiving space can be opened. Any displacement of the box relative to the frame is prevented especially through the shearing pin, thus preventing any inadvertent displacement of the box in an especially secure way. A displacement of the box and thus an opening of the lower receiving space can still occur after the shearing of the shearing pin. 3'. It would also be possible that the resistance is formed by a spring situated below the box, e.g. a helical spring, which pretensions the box in the direction towards the frame. The force of a spring decreases over time and in the case of frequent compression only very slightly, and even less than the frictional forces prevailing between two components resting on each other in a frictional manner in the case of frequent frictional movements. This realization variant of the resistance thus offers the advantage of a longer service life as compared with those based on friction between two components. The resistance could also be formed by friction of the lug on parts of the housing. It is advantageous in this case too that for forming the resistance only components are used which are present anyway and thus separate components can be avoided as well as the technical effort in conjunction with their production and mounting. According to a preferred embodiment of the invention, a lug can be provided which is fixed to the box and which extends from the lower section of the box away into the space situated below the box and parallel to the plane of opening in the housing situated adjacent to the lifting clamp. The section of the opening situated below the lower box section is thus covered off, as a result of which any inadvertent insertion of conductors into the lower box section is prevented. In the case of a first concrete possibility for realizing the invention it may be provided that the resistance is formed by friction of the box on the frame and/or parts of the housing. This embodiment is simple in the respect that no components are required in addition to the existing components of box, frame and housing and thus the technical effort for producing and installing such special components is avoided. The invention further relates to a lifting clamp for mounting in a housing of an electric 3a apparatus such as a circuit-breaker, comprising a rectangular frame and a rectangular box whose upper section is arranged between the upper section and the lower section of the frame, enabling the box to be held in the frame (14) in a displaceable manner, and further comprising a clamping screw which is guided through a breakthrough incorporated in the upper section of the frame in a freely rotatable manner and which engages in a screw thread incorporated in the upper section of the box, and further a lug which is fixed to the box and extends away from the lower section of the box to the space situated below the box and extends parallel to the plane of an opening situated adjacent to the lifting clamp. Such lifting clamps with lugs or seal covers are known from EP 0 559 585 A and USL5.5.80.285 A for example. The disadvantageous aspect in EP 0 559 585 A is that the bracket shown there is arranged in an integral manner with the metallic box and thus does not offer an electrically insulating protection. US 5 580 285 A on the other hand shows a removable seal cover. This seal cover is merely fastened to the box with a small hook, so that the resulting small connecting surface does not offer any secure connection. The further object of the invention is connecting a lug for covering the lower receiving space with the box. This is achieved in accordance with the invention that a small plate is shaped on the lugs which extends parallel to the lower box section, by means of which the lug is connected with the box. The section of the opening situated below the lower box section is thus covered, thus preventing any inadvertent insertion of conductors below the lower box section. The small plate thus allows a contact over a relatively large surface area with the box and thus ensures a secure connection. In this connection it may further be provided that a small mounting plate is shaped on the small plate which extends normal to the same as well as the lug and which is fixedly joined to a side wall of the box. In a further embodiment of the invention it may be provided in this connection that a pin is shaped on the mounting plate which engages in a breakthrough incorporated in the side wall of the box. 3b In this way the box can be fixed in a very simple manner on the mounting plate which entails a low amount of technical effort, namely by merely placing the box on the mounting plate. In this connection it may further be provided that a breakthrough is incorporated in the mounting plate in which the shearing pin engages which is fixed to the h&using. As a result of this arrangement of the shearing pin, it can fulfill, in addition to its main function of providing a resistance against a displacement of the box, the auxiliary function of the holding of the mounting plate, small plate and lug in the housing. When installing the components of the switch in the housing, the mounting plate, small plate and lug can be inserted into the lower shell in a mechanical manner. The invention is now explained in closer detail by reference to the accompanying drawings showing preferable embodiments, wherein: Fig. 1 shows a top view of a circuit-breaker with removed upper shell and equipped with the lifting clamps 1 in accordance with the invention ; Fig. 2 shows the lower shell of the circuit-breaker equipped with merely the lifting clamp 1 according to fig. 1 in a oblique view, with the second lifting clamp 1 being shown lying outside of the lower shell; Fig. 3 shows a top view of a lower shell of the circuit-breaker according to fig. 1 which is merely equipped with the right lifting clamp 1, with a lug 24 being provided which can be fixed to box 15 of the lifting clamp 1 in the region of the left lifting clamp ; Fig. 4 shows the representation of fig. 3 in an oblique view; Fig. 5 shows a top view of lifting clamp 1 in accordance with the invention which is mounted in a housing, with the resistance against which the box 15 of clamp 1 is dssplaceable formed by a screw pressure spring 32 ; 4 Fig. 6 shows the representation of fig. 5, with a shearing pin 33 being provided which is shaped on the inner wall of the housing instead of the screw pressure spring 32 for the purpose of realizing the resistance. 5 The circuit-breaker shown in fig. 1 comprises two screw terminals 1 which are arranged as so-called "lifting clamps" and by means of which conductor wires and the comb-like terminal lugs of busbar systems can be connected to the circuit-breaker. The circuit-breaker further comprises an overload triggering element 2 as well as a short-circuit triggering device 3, and further a switch mechanism 4 which can move the movable contact 5 from a closed position in which the movable contact 5 rests on the fixed contact 8 to the opened position as shown in fig. 1. The current to be monitored flows in this circuit-breaker starting from the right screw terminal 1 at first through the overload triggering element 2, reaches the movable contact 5 via a movable stranded conductor 6 and the switching bridge 7, and thereafter via the fixed contact 8 to the short-circuit triggering element 3 and finally the second terminal 1. The switching mechanism 4 can be actuated both by the short-circuit triggering element 3 as well as by the overload triggering element 2. The short-circuit triggering element 3 is formed in the known manner by a magnet coil with a movable armature, which armature will impact on the switching bridge 7 of the switching mechanism 4 in the case of a respectively high short-circuit current. The overload triggering element 1 consists of a bimetal strip which is heated by the current to be monitored. The first end 21 of the bimetal strip is fixed to the housing of the circuit-breaker. The second end 22 is held in a freely movable way. The bending of the same caused by the heating of the bimetal therefore leads to a movement of the second end 22 in the direction of the arrow 23. In the case of a sufficiently strong heating the free end 22 of the bimetal strip comes into contact with the bracket 9 acting upon the jack rest 36 during said movement, entrains the same in the direction of movement and thus initiates the response of the switching mechanisrn 4. The switching bridge 7 is pretensioned by means of a spring 10 in the direction towards the opened position of the movable contact 5. The illustrated slight deflections of the jack rest 36 by the armature of the short-circuit triggering element 3 or by the overload triggering element 2 via the bracket 9 are amplified by means of said spring 10 for the purpose of the complete pivoting of the switching bridge 7 into the opened position of the movable contact 5. 6 An outwardly accessible lever 11 which can be manually activated is provided for switching on the circuit-breaker, i.e, for pivoting back the contact support 7 to the closed position of the movable contact 5. The housing of the circuit-breaker is designed in the known manner in two parts, consisting of the lower shell 12 shown in the figures and an upper shell which is not shown in the drawings, but which is mirror-like in its design with respect to the lower shell 12. The present invention relates to the lifting clamps 1 and is not limited to the use of said lifting clamps 1 in circuit-breakers. The drawings show a circuit-breaker or the lower shell 12 of such a circuit-breaker merely for the reason that this is an especially preferred field of application for the lifting clamp 1. Apart from that, it can be used in electric devices of any type, i.e. miniature circuit breakers, discharge disconnectors, staircase lighting timers, etc. The lifting clamp 1 in accordance with the invention comprises a frame 14 like previously known screw terminals of this type, which frame - in the position as shown in fig. 1 - is rectangular. It usually consists of an integral copper strip which is bent off three times by 90°. Said frame 14 is held immovably in the housing, which can be achieved for example by clamping between shaped parts fixed to the inner wall of the lower shell. The second main component of a lifting clamp I is the box 15 which is also provided with a frame-like arrangement (also see fig. 2). Box 15 is rotated by 90° relative to the frame 14 and is suspended in the same, i.e. the upper section 150 of the box 15 is situated between the upper section 140 and the lower section 141 of the frame 14. Box 15 is thus displaceably guided in the frame 14. The third main component of the lifting clamp is the clamping screw 16. The upper section 140 of the frame 14 comprises a breakthrough 142 through which the clamping screw 16 is guided in a freely rotatable manner. A thread 152 is incorporated in the upper section 150 of the box 15, in which the clamping screw 16 engages. When the clamping screw 16 is rotated in the closing direction (i.e. clockwise when the clamping screw 16 is configured as a right helix), the box 15 is lifted, i.e. it is moved in the direction towards the upper frame section 140. This displacement is produced for the reason that the clamping screw 16 comes to rest with its end on the base side on the lower frame section 141 or with its head 160 on the upper frame section 140. Any further 7 progressing screwing of the clamping screw 16 into the box thread 152 can thus not lead to any downward displacement of the clamping screw 16, but only to a lifting of box 15. When the clamping screw 16 is turned in the opening direction (i.e. counter-clockwise in the case that the clamping screw 16 is arranged as a right helix), the box 15 is lowered, i.e. it is moved in the direction towards the lower frame section 141. Such a lifting clamp 1 comprises two places where electric lines can be clamped. On the one hand, feed lines can be introduced into the space 17 situated between the lower frame section 141 and the lower box section 152 and on the other hand in the space 18 situated between the upper frame section 140 and the screw head 160 (cf. fig. 2). When tightening the clamping screw 16, both the lower sections 141 and 151 of the frame 14 and the box 15 are pushed towards each other and also the screw head 16 against the upper frame section 140. The conductors introduced into the spaces 17 and 18 are thus clamped. Conductor wires are usually inserted into the space 17 situated between the lower frame section 141 and the lower box section 151 and a terminal lug of a busbar system is inserted in the space 18 between the upper frame section 140 and the screw head 16. In order to keep these two spaces 17, 18 accessible for the insertion of said electric conductors, openings 19 and 20 are provided in the housing at the level of said spaces 17, 18. In connection with the insertion of a conductor wire in the lower space 17 there is the problem (especially when the terminal is not opened widely enough, i.e. the lower section 150 of box 15 is too close to the lower section 141 of the frame 14) that although said wire is guided through the opening 19, it is erroneously placed not in the space 17 but below the box 15. A proper clamping of this wire is then no longer possible. In order to prevent such erroneous insertion of the conductor wire, a lug 24 is fixed to the box 15 which extends in a normal manner with respect to the lower section 152 of the box 15 and extends away from the same, i.e. in the space situated below the box 15. This lug 24 thus extends parallel to the plane of opening 19 and is arranged directly adjacent to the same. As a result of its connection with the box 15, the lug 24 is jointly displaced with the box 15 and thus covers the section of opening 19 which is situated below the box 15. A wire pushed through said opening 19 can thus only be inserted into the space 17 situated between the lower frame 8 section 151 and the lower box section 141. An erroneous insertion of a wire below box 15 as described above is reliably prevented. The lug 24 can be provided with a random constructional configuration: It could be designed in an integral way with the box 15, such that it is bent from the same conductive sheet metal strip as said box 15. It can also be a component which is separate from box 15 and is rigidly connected with box 15 (e.g. it is welded or glued to the same). It can be formed from an insulating material such as plastic, which offers the additional advantage that the lug 24 can be touched without any hazard even in the case that its terminal is live, which would be the case for example when a live conductor is already connected to the other terminal. In the embodiment as shown in figs. 1 to 4, a small plate 25 is shaped on the lug 24, which small plate extends parallel to the lower box section 151 and through which the lug 24 is connected to box 15. The small plate 25 can be glued or welded together for example with the lower box section 151. According to the embodiment of figs. 1 to 4, the connection between the small plate 25 and the lower box section 151 is achieved by a mounting plate 26 which is shaped on the small plate 25 and extends in a normal manner both with respect to said plate 25 as well as the lug 24. Said mounting plate 26 is rigidly connected with a side wall of the box 15, which could be realized again by a gluing or welding of said two parts. A preferably used variant which is therefore also shown in figs, 1 to 4 for fixing the mounting plate 26 to box 15 provides a pin 27 which is shaped on the mounting plate 26. A breakthrough 28 is incorporated in the side wall of the box in which the pin 27 engages, thus producing a positive fastening of the mounting plate 26 and thus the lug 24 to box 15. As already explained, the lifting clamp 1 comprises two places, namely the spaces 17 and 18, for clamping electric conductors. Conductor wires are usually inserted into the lower space 17 and terminal lugs of a busbar system are inserted into the upper space 18. It is usually the case that only one type of conductor is connected to one and the same terminal, i.e. either a terminal lug of a busbar system or a conductor wire. 9 When opening the clamp, the clamping screw 16 is not only rotated with the screwdriver used for this purpose, but also pressed downwardly. This leads to the consequence in lifting clamps which comprise the constructional features discussed up to this point that the screw head 16 is always pressed against the upper frame section 141 and the rotation of the clamping screw 16 is merely converted into a downward displacement of the box 15., i.e. into an opening of the space 17. Only when the box 15 has been displaced entirely downwardly and comes to rest in this position on the housing part 29 underneath the same there will not be any further downward displacement of the box 15. An opening movement of the clamping screw 16 which is then still performed is converted into an upward displacement of the clamping screw 16, as a result of which the screw head 160 is lifted off from the upper frame section 140 and the upper space 18 is opened. When turning the clamping screw 16 in the closing direction, the space 18 is closed first, then the box 15 is lilted until its lower section 152 comes to rest on the lower section 141 of the frame 14 and only after continued rotation of the clamping screw 16 in the closing direction will the screw head 160 be pressed in a clamping manner against the upper frame section 140. This manner of function ensures that when merely a terminal lug of a busbar system is to be connected to lifting clamp 1, the clamping screw 16 is fully opened at first and then needs to be closed completely again after the insertion of the terminal lug in space 18. In accordance with the invention it is provided for to remedy this circumstance which leads to a time-consuming mounting process that the box 15 of the clamping terminal 1 is not held freely in the frame 14, but is held in a manner displaceable against a resistance. This resistance can be realized in many ways: Thus, the box 15 can rest in a frictional way on the frame 14 or on parts of the housing. The thus provided static friction between the box 15 and the frame 14 or the housing parts at first prevents the discussed displacement of the box 15 relative to the frame 14, as a result of which the clamping screw 16 migrates during the rotation in the opening direction out of the box 15 and frame 14 and during the rotation in the closing direction into box 15 and frame 14. The (frictional) resistance is dimensioned in such a way that it can be overcome, e.g. by exerting a pressure on the screw head 160. This allows that the lower space 17 can be opened immediately on turning the clamping screw 16 (if desired). 10 In the embodiment of the housing as shown in fig. 1, a rib 30 is situated above the screw head } 60 into which a bore 31 is incorporated- Said bore 31 which is used for guiding through the screw driver necessary for rotating the clamping screw 16 has a lower diameter than the head 160 of the clamping screw 16. During the upward migration of the clamping screw 16 which occurs during the rotation in the opening direction when a pressure is not exerted simultaneously on the clamping screw 16, the screw head 160 comes to rest on the rib 30. When the clamping screw 16 is continued to be rotated in the opening direction, the box 15 is pressed downwardly (because the clamping screw 16 is unable to migrate upwardly anymore). The resistance is thus overcome and the box 15 is displaced downwardly. As shown in fig. 5, the resistance can be realized by means of a spring 32 which pretensions the box 15 in the direction towards frame 14. Said spring 32 can be formed for this purpose by a leaf spring or (as shown explicitly in fig. 5) by a screw pressure spring which is situated below the box 15 and rests with one end on housing part 29 and with the other end (by using small plate 25 if provided) on the lower section 151 of box 15. Several variants of realizing the resistance can be present simultaneously, e.g. the box 15 can be frictionally held both on the frame 14 as well as the housing or a spring 32 can be present additionally for frictionally bearing the box 15 on frame 14. As is shown by these explanations of the function of the resistance, such components required for its realization can be provided Independent from a lug 24t i.e. even in cases when such a lug 24 is missing. If there is such a lug 24, the resistance can be realized by frictional bearing of said lug 24 in housing 12. The common aspect in the discussed possibilities for realizing the resistance is that they exert this resistance continually, i.e. this resistance is not relevantly changed by displacements of the box 15. In a preferred embodiment of the invention a shearing pin 33 is provided which is fastened in the housing. The shearing pin 33 is connected with the box 15 in a form-fitting manner when it is located in the position as shown in fig. 1 and fig. 6. This can be achieved in such a way that the 11 shearing pin 33 engages in a breakthrough incorporated in the side wall of the box or by an arrangement of the shearing pin 33 slightly below the lower box section 151, as shown in fig. 6. When turning the clamping screw 16 in the opening direction, the shearing pin 33 at first prevents any displacement of the box 15. The rotational movement is exclusively converted into an upward migration of the clamping screw 16. If a sufficiently large pressure force extending in the longitudinal direction is exerted on the clamping screw 16 (e.g. by an impact on the clamping screw 16 or during the further turning of the clamping screw 16 when its head 160 already rests on the rib 30), the shearing pin 33 is shorn off and the box 15 can now be displaced in an entirely free manner. In this variant for realizing the resistance it is exerted only temporarily, namely prior to the shearing of the shearing pin 33. Only the space IS is opened or closed in the case of intact shearing pin 33, so that the terminal lug of a busbar system can be connected to lifting clamp 1 with a low amount of screwing work. Such a shearing pin 33 is also provided in the preferred embodiment as shown in closer detail in the drawings I to 4f which shearing pin is connected with the box 15 merely in an indirect way: As already explained above, a lug 24 is provided in this embodiment on which a small plate 25 shaped with which the mounting plate 26 is formed in an integral way. Said mounting plate 26 is displaceably held in a rectangular guide groove 34 incorporated in the housing in a direction parallel to the dire,c.tion-of-displacement of the box 15. In order to join the mounting plate 26 to the box 15, a pin 2? is provided which is shaped on the mounting plate 26 and which engages in a breakthrough 28 incorporated in a side wall of the box./JT The shearing pin 33 is shaped on the floor of said guide groove 34. The mounting plate 26 comprises a breakthrough 35 in which the shearing pin 33 engages (see fig. 2,3). The shearing pin 33 is connected with the box 15 in an indirect way, namely by using the mountmgjplate 26 and the pin 27. To ensure that a pressure force exerted on the clamping screw 16 will actually only cause a . shearing of the shearing pin 33 but not of pin 27, the shearing resistance of said pin 27 is dimensioned in a respectively higher way than that of the shearing pin 33. 12 The shearing pin 33 assumes a secondary function in this embodiment in such a way that it holds the mounting plate 26, or in combination with the same the lug 24, during the mounting of the switch at the correct position (i.e. during the insertion of the individual components into the lower shell of the housing). The mounting plate 26 with shaped plates 25 and lugs 24 can thus be inserted mechanically into the lower shell. Frame 14 and box 15 of the lifting clamps 1 can be placed with ease on the mounting plate 26. 13 WE CLAIM: 1. A lifting clamp (1) for mounting in a housing of an electric apparatus such as a circuit-breaker, comprising a rectangular frame (14) and a rectangular box (15) whose upper section (150) is arranged between the upper section (140) and the lower section (141) of the frame (14), enabling the box (15) to be held in the frame (14) in a displaceable manner, and having a clamping screw (16) which is guided through a breakthrough (142) incorporated in the upper section (140) of the frame in a freely rotatable manner and which engages in a screw thread (152) incorporated in the upper section (150) of the box (15), with the box (15) being held in the frame (14) against a resistance in a displaceable manner, characterised in that the resistance is formed by a shearing pin (33) which is fastened to the housing, is preferably arranged integrally with the housing and is connected with the box (15) in a positive manner. The invention relates to a lifting clamp (1) for mounting in a housing of an electrical appliance, e.g. a circuit breaker, comprising a rectangular frame (14) and a rectangular box (15), the upper section (150) of said box being arranged between the upper section (140) and the lower section (141) of the frame (14), enabling the box (15) to be held in the frame (14) in a displaceable manner. Said lifting clamp also comprises a clamping screw (16) which is guided through an opening (142) incorporated in the upper section (140) of the frame in a freely rotatable manner, and which engages in a screw thread (152) incorporated in the upper section (150) of the box (15). Said box (15) is held in the frame (14) against a resistance in a displaceable manner.

Full Text

1
A LIFTING CLAMP
The invention relates to a lifting clamp for mounting in a housing of an electric apparatus such as a circuit-breaker, comprising a rectangular frame and a rectangular box whose upper section is arranged between the upper section and the lower section of the frame, enabling the box to be held in the frame in a displaceable manner, and further comprising a clamping screw which is guided through a breakthrough incorporated in the upper section of the frame in a freely rotatable manner and which engages in a screw thread incorporated in the upper section of the box, with the box being held in the frame against a resistance in a displaceable manner.
Electric lines can be clamped in such lifting clamps at two places, namely between the lower sections of the frame and the box (lower receiving space) and between the upper section of the frame and the head of the clamping screw (upper receiving space). When the clamping screw is rotated in the opening direction, the box is moved downwardly at first and thus the lower receiving space is opened. Only when the box has reached its lowermost position in which it comes to rest on a housing part will the clamping screw be displaced upwardly in the further progressing opening movement and thus the upper opening space will be opened. When tightening the clamping screw it needs to be rotated at first to such an extent until the lower box section comes to rest on the lower frame section. Only then will the rotating movement of the clamping screw in the close direction be converted into a clamping contact of the screw head on the upper section of the frame or on an electric conductor situated between said upper section and the screw head.
When only the upper receiving space is used, it is necessary to turn the clamping screw to a very high extent in order to open this space or to clamp an electric conductor in said space, as a result of which the amount of time required for connecting electric conductors to the lifting clamp is very high. Such a terminal with clamping boxes is known from EP 0 168 596 A for example. Such a lifting clamp is also known from EP 0 905 839 A.
Lifting clamps are also known in which a resistance is provided against which one of the clamping boxes could be displaced in order to thus reduce the time needed for connecting

2
electric lines to the clamping terminals. In DE 195 13 281 A, DE 2 107 218 A and EP i 028 489 A connection terminals or lifting clamps are known in which the resistance against which a box is held displaceably in the frame is realized by a spring. Such a resistance is produced in EP 0 280 672 A by friction of the box on parts of the housing.
The disadvantageous aspect in this state of the art is that the resistance against which the box is displaceable in the frame could be overcome inadvertently und thus the lower receiving space could be opened at an early stage.
It is the object of the present invention to avoid this disadvantage and to provide a lifting clamp of the kind mentioned above in which on turning the clamping; screw in the opening direction the receiving space situated between the upper frame section and the screw head is opened, but the lower receiving space remains closed for the time being. The lower receiving space is only to be opened by performing special measures such as the exertion of a higher force on the screw in order to thus securely prevent any inadvertent displacement of the box.
This is achieved in accordance with the invention by a shearing pin which is fastened to the housing, is preferably arranged in an integral manner with the housing and is connected with the box in a positive manner.
If during the rotation of the clamping screw no large force is exerted, i.e. not more force than is mandatory for rotating a screw, said resistance at first prevents a displacement of the box. The opening movement of the screw is converted entirely into a lift-off of the screw head from the upper frame section, i.e. into an opening of the upper receiving space. This allows inserting a terminal lug of a busbar system into the upper receiving room even after a minor rotation of the clamping screw and reliably clamping the same by a slight rotation of the clamping screw in the closing direction.
When overcoming the resistance (e.g. by exerting a pressure on the clamping screw), the resistance can be overcome, the box is displaced downwardly and thus the lower receiving space can be opened. Any displacement of the box relative to the frame is prevented especially through the shearing pin, thus preventing any inadvertent displacement of the box in an especially secure way. A displacement of the box and thus an opening of the lower receiving space can still occur after the shearing of the shearing pin.

3'.
It would also be possible that the resistance is formed by a spring situated below the box, e.g. a helical spring, which pretensions the box in the direction towards the frame.
The force of a spring decreases over time and in the case of frequent compression only very slightly, and even less than the frictional forces prevailing between two components resting on each other in a frictional manner in the case of frequent frictional movements. This realization variant of the resistance thus offers the advantage of a longer service life as compared with those based on friction between two components.
The resistance could also be formed by friction of the lug on parts of the housing. It is advantageous in this case too that for forming the resistance only components are used which are present anyway and thus separate components can be avoided as well as the technical effort in conjunction with their production and mounting.
According to a preferred embodiment of the invention, a lug can be provided which is fixed to the box and which extends from the lower section of the box away into the space situated below the box and parallel to the plane of opening in the housing situated adjacent to the lifting clamp.
The section of the opening situated below the lower box section is thus covered off, as a result of which any inadvertent insertion of conductors into the lower box section is prevented.
In the case of a first concrete possibility for realizing the invention it may be provided that the resistance is formed by friction of the box on the frame and/or parts of the housing.
This embodiment is simple in the respect that no components are required in addition to the existing components of box, frame and housing and thus the technical effort for producing and installing such special components is avoided.
The invention further relates to a lifting clamp for mounting in a housing of an electric

3a
apparatus such as a circuit-breaker, comprising a rectangular frame and a rectangular box whose upper section is arranged between the upper section and the lower section of the frame, enabling the box to be held in the frame (14) in a displaceable manner, and further comprising a clamping screw which is guided through a breakthrough incorporated in the upper section of the frame in a freely rotatable manner and which engages in a screw thread incorporated in the upper section of the box, and further a lug which is fixed to the box and extends away from the lower section of the box to the space situated below the box and extends parallel to the plane of an opening situated adjacent to the lifting clamp.
Such lifting clamps with lugs or seal covers are known from EP 0 559 585 A and USL5.5.80.285 A for example. The disadvantageous aspect in EP 0 559 585 A is that the bracket shown there is arranged in an integral manner with the metallic box and thus does not offer an electrically insulating protection. US 5 580 285 A on the other hand shows a removable seal cover. This seal cover is merely fastened to the box with a small hook, so that the resulting small connecting surface does not offer any secure connection.
The further object of the invention is connecting a lug for covering the lower receiving space with the box.
This is achieved in accordance with the invention that a small plate is shaped on the lugs which extends parallel to the lower box section, by means of which the lug is connected with the box. The section of the opening situated below the lower box section is thus covered, thus preventing any inadvertent insertion of conductors below the lower box section. The small plate thus allows a contact over a relatively large surface area with the box and thus ensures a secure connection.
In this connection it may further be provided that a small mounting plate is shaped on the small plate which extends normal to the same as well as the lug and which is fixedly joined to a side wall of the box.
In a further embodiment of the invention it may be provided in this connection that a pin is shaped on the mounting plate which engages in a breakthrough incorporated in the side wall of the box.

3b
In this way the box can be fixed in a very simple manner on the mounting plate which entails a low amount of technical effort, namely by merely placing the box on the mounting plate.
In this connection it may further be provided that a breakthrough is incorporated in the mounting plate in which the shearing pin engages which is fixed to the h&using.
As a result of this arrangement of the shearing pin, it can fulfill, in addition to its main function of providing a resistance against a displacement of the box, the auxiliary function of the holding of the mounting plate, small plate and lug in the housing. When installing the components of the switch in the housing, the mounting plate, small plate and lug can be inserted into the lower shell in a mechanical manner.
The invention is now explained in closer detail by reference to the accompanying drawings showing preferable embodiments, wherein:
Fig. 1 shows a top view of a circuit-breaker with removed upper shell and equipped with the lifting clamps 1 in accordance with the invention ;
Fig. 2 shows the lower shell of the circuit-breaker equipped with merely the lifting clamp 1 according to fig. 1 in a oblique view, with the second lifting clamp 1 being shown lying outside of the lower shell;
Fig. 3 shows a top view of a lower shell of the circuit-breaker according to fig. 1 which is merely equipped with the right lifting clamp 1, with a lug 24 being provided which can be fixed to box 15 of the lifting clamp 1 in the region of the left lifting clamp ;
Fig. 4 shows the representation of fig. 3 in an oblique view;
Fig. 5 shows a top view of lifting clamp 1 in accordance with the invention which is mounted in a housing, with the resistance against which the box 15 of clamp 1 is dssplaceable formed by a screw pressure spring 32 ;

4
Fig. 6 shows the representation of fig. 5, with a shearing pin 33 being provided which is shaped on the inner wall of the housing instead of the screw pressure spring 32 for the purpose of realizing the resistance.

5
The circuit-breaker shown in fig. 1 comprises two screw terminals 1 which are arranged as so-called "lifting clamps" and by means of which conductor wires and the comb-like terminal lugs of busbar systems can be connected to the circuit-breaker.
The circuit-breaker further comprises an overload triggering element 2 as well as a short-circuit triggering device 3, and further a switch mechanism 4 which can move the movable contact 5 from a closed position in which the movable contact 5 rests on the fixed contact 8 to the opened position as shown in fig. 1.
The current to be monitored flows in this circuit-breaker starting from the right screw terminal 1 at first through the overload triggering element 2, reaches the movable contact 5 via a movable stranded conductor 6 and the switching bridge 7, and thereafter via the fixed contact 8 to the short-circuit triggering element 3 and finally the second terminal 1.
The switching mechanism 4 can be actuated both by the short-circuit triggering element 3 as well as by the overload triggering element 2. The short-circuit triggering element 3 is formed in the known manner by a magnet coil with a movable armature, which armature will impact on the switching bridge 7 of the switching mechanism 4 in the case of a respectively high short-circuit current.
The overload triggering element 1 consists of a bimetal strip which is heated by the current to be monitored. The first end 21 of the bimetal strip is fixed to the housing of the circuit-breaker. The second end 22 is held in a freely movable way. The bending of the same caused by the heating of the bimetal therefore leads to a movement of the second end 22 in the direction of the arrow 23. In the case of a sufficiently strong heating the free end 22 of the bimetal strip comes into contact with the bracket 9 acting upon the jack rest 36 during said movement, entrains the same in the direction of movement and thus initiates the response of the switching mechanisrn 4.
The switching bridge 7 is pretensioned by means of a spring 10 in the direction towards the opened position of the movable contact 5. The illustrated slight deflections of the jack rest 36 by the armature of the short-circuit triggering element 3 or by the overload triggering element 2 via the bracket 9 are amplified by means of said spring 10 for the purpose of the complete pivoting of the switching bridge 7 into the opened position of the movable contact 5.

6
An outwardly accessible lever 11 which can be manually activated is provided for switching on the circuit-breaker, i.e, for pivoting back the contact support 7 to the closed position of the movable contact 5.
The housing of the circuit-breaker is designed in the known manner in two parts, consisting of the lower shell 12 shown in the figures and an upper shell which is not shown in the drawings, but which is mirror-like in its design with respect to the lower shell 12.
The present invention relates to the lifting clamps 1 and is not limited to the use of said lifting clamps 1 in circuit-breakers. The drawings show a circuit-breaker or the lower shell 12 of such a circuit-breaker merely for the reason that this is an especially preferred field of application for the lifting clamp 1. Apart from that, it can be used in electric devices of any type, i.e. miniature circuit breakers, discharge disconnectors, staircase lighting timers, etc.
The lifting clamp 1 in accordance with the invention comprises a frame 14 like previously known screw terminals of this type, which frame - in the position as shown in fig. 1 - is rectangular. It usually consists of an integral copper strip which is bent off three times by 90°. Said frame 14 is held immovably in the housing, which can be achieved for example by clamping between shaped parts fixed to the inner wall of the lower shell.
The second main component of a lifting clamp I is the box 15 which is also provided with a frame-like arrangement (also see fig. 2). Box 15 is rotated by 90° relative to the frame 14 and is suspended in the same, i.e. the upper section 150 of the box 15 is situated between the upper section 140 and the lower section 141 of the frame 14. Box 15 is thus displaceably guided in the frame 14.
The third main component of the lifting clamp is the clamping screw 16. The upper section 140 of the frame 14 comprises a breakthrough 142 through which the clamping screw 16 is guided in a freely rotatable manner. A thread 152 is incorporated in the upper section 150 of the box 15, in which the clamping screw 16 engages. When the clamping screw 16 is rotated in the closing direction (i.e. clockwise when the clamping screw 16 is configured as a right helix), the box 15 is lifted, i.e. it is moved in the direction towards the upper frame section 140. This displacement is produced for the reason that the clamping screw 16 comes to rest with its end on the base side on the lower frame section 141 or with its head 160 on the upper frame section 140. Any further

7
progressing screwing of the clamping screw 16 into the box thread 152 can thus not lead to any downward displacement of the clamping screw 16, but only to a lifting of box 15.
When the clamping screw 16 is turned in the opening direction (i.e. counter-clockwise in the case that the clamping screw 16 is arranged as a right helix), the box 15 is lowered, i.e. it is moved in the direction towards the lower frame section 141.
Such a lifting clamp 1 comprises two places where electric lines can be clamped. On the one hand, feed lines can be introduced into the space 17 situated between the lower frame section 141 and the lower box section 152 and on the other hand in the space 18 situated between the upper frame section 140 and the screw head 160 (cf. fig. 2). When tightening the clamping screw
16, both the lower sections 141 and 151 of the frame 14 and the box 15 are pushed towards each
other and also the screw head 16 against the upper frame section 140. The conductors introduced
into the spaces 17 and 18 are thus clamped.
Conductor wires are usually inserted into the space 17 situated between the lower frame section 141 and the lower box section 151 and a terminal lug of a busbar system is inserted in the space 18 between the upper frame section 140 and the screw head 16. In order to keep these two spaces
17, 18 accessible for the insertion of said electric conductors, openings 19 and 20 are provided in
the housing at the level of said spaces 17, 18.
In connection with the insertion of a conductor wire in the lower space 17 there is the problem (especially when the terminal is not opened widely enough, i.e. the lower section 150 of box 15 is too close to the lower section 141 of the frame 14) that although said wire is guided through the opening 19, it is erroneously placed not in the space 17 but below the box 15. A proper clamping of this wire is then no longer possible.
In order to prevent such erroneous insertion of the conductor wire, a lug 24 is fixed to the box 15 which extends in a normal manner with respect to the lower section 152 of the box 15 and extends away from the same, i.e. in the space situated below the box 15. This lug 24 thus extends parallel to the plane of opening 19 and is arranged directly adjacent to the same.
As a result of its connection with the box 15, the lug 24 is jointly displaced with the box 15 and thus covers the section of opening 19 which is situated below the box 15. A wire pushed through said opening 19 can thus only be inserted into the space 17 situated between the lower frame

8
section 151 and the lower box section 141. An erroneous insertion of a wire below box 15 as described above is reliably prevented.
The lug 24 can be provided with a random constructional configuration: It could be designed in an integral way with the box 15, such that it is bent from the same conductive sheet metal strip as said box 15. It can also be a component which is separate from box 15 and is rigidly connected with box 15 (e.g. it is welded or glued to the same). It can be formed from an insulating material such as plastic, which offers the additional advantage that the lug 24 can be touched without any hazard even in the case that its terminal is live, which would be the case for example when a live conductor is already connected to the other terminal.
In the embodiment as shown in figs. 1 to 4, a small plate 25 is shaped on the lug 24, which small plate extends parallel to the lower box section 151 and through which the lug 24 is connected to box 15. The small plate 25 can be glued or welded together for example with the lower box section 151.
According to the embodiment of figs. 1 to 4, the connection between the small plate 25 and the lower box section 151 is achieved by a mounting plate 26 which is shaped on the small plate 25 and extends in a normal manner both with respect to said plate 25 as well as the lug 24. Said mounting plate 26 is rigidly connected with a side wall of the box 15, which could be realized again by a gluing or welding of said two parts.
A preferably used variant which is therefore also shown in figs, 1 to 4 for fixing the mounting plate 26 to box 15 provides a pin 27 which is shaped on the mounting plate 26. A breakthrough 28 is incorporated in the side wall of the box in which the pin 27 engages, thus producing a positive fastening of the mounting plate 26 and thus the lug 24 to box 15.
As already explained, the lifting clamp 1 comprises two places, namely the spaces 17 and 18, for clamping electric conductors. Conductor wires are usually inserted into the lower space 17 and terminal lugs of a busbar system are inserted into the upper space 18.
It is usually the case that only one type of conductor is connected to one and the same terminal, i.e. either a terminal lug of a busbar system or a conductor wire.

9
When opening the clamp, the clamping screw 16 is not only rotated with the screwdriver used for this purpose, but also pressed downwardly. This leads to the consequence in lifting clamps which comprise the constructional features discussed up to this point that the screw head 16 is always pressed against the upper frame section 141 and the rotation of the clamping screw 16 is merely converted into a downward displacement of the box 15., i.e. into an opening of the space 17. Only when the box 15 has been displaced entirely downwardly and comes to rest in this position on the housing part 29 underneath the same there will not be any further downward displacement of the box 15. An opening movement of the clamping screw 16 which is then still performed is converted into an upward displacement of the clamping screw 16, as a result of which the screw head 160 is lifted off from the upper frame section 140 and the upper space 18 is opened.
When turning the clamping screw 16 in the closing direction, the space 18 is closed first, then the box 15 is lilted until its lower section 152 comes to rest on the lower section 141 of the frame 14 and only after continued rotation of the clamping screw 16 in the closing direction will the screw head 160 be pressed in a clamping manner against the upper frame section 140.
This manner of function ensures that when merely a terminal lug of a busbar system is to be connected to lifting clamp 1, the clamping screw 16 is fully opened at first and then needs to be closed completely again after the insertion of the terminal lug in space 18.
In accordance with the invention it is provided for to remedy this circumstance which leads to a time-consuming mounting process that the box 15 of the clamping terminal 1 is not held freely in the frame 14, but is held in a manner displaceable against a resistance. This resistance can be realized in many ways:
Thus, the box 15 can rest in a frictional way on the frame 14 or on parts of the housing. The thus provided static friction between the box 15 and the frame 14 or the housing parts at first prevents the discussed displacement of the box 15 relative to the frame 14, as a result of which the clamping screw 16 migrates during the rotation in the opening direction out of the box 15 and frame 14 and during the rotation in the closing direction into box 15 and frame 14. The (frictional) resistance is dimensioned in such a way that it can be overcome, e.g. by exerting a pressure on the screw head 160. This allows that the lower space 17 can be opened immediately on turning the clamping screw 16 (if desired).

10
In the embodiment of the housing as shown in fig. 1, a rib 30 is situated above the screw head } 60 into which a bore 31 is incorporated- Said bore 31 which is used for guiding through the screw driver necessary for rotating the clamping screw 16 has a lower diameter than the head 160 of the clamping screw 16.
During the upward migration of the clamping screw 16 which occurs during the rotation in the opening direction when a pressure is not exerted simultaneously on the clamping screw 16, the screw head 160 comes to rest on the rib 30. When the clamping screw 16 is continued to be rotated in the opening direction, the box 15 is pressed downwardly (because the clamping screw 16 is unable to migrate upwardly anymore). The resistance is thus overcome and the box 15 is displaced downwardly.
As shown in fig. 5, the resistance can be realized by means of a spring 32 which pretensions the box 15 in the direction towards frame 14. Said spring 32 can be formed for this purpose by a leaf spring or (as shown explicitly in fig. 5) by a screw pressure spring which is situated below the box 15 and rests with one end on housing part 29 and with the other end (by using small plate 25 if provided) on the lower section 151 of box 15.
Several variants of realizing the resistance can be present simultaneously, e.g. the box 15 can be frictionally held both on the frame 14 as well as the housing or a spring 32 can be present additionally for frictionally bearing the box 15 on frame 14.
As is shown by these explanations of the function of the resistance, such components required for its realization can be provided Independent from a lug 24t i.e. even in cases when such a lug 24 is missing. If there is such a lug 24, the resistance can be realized by frictional bearing of said lug 24 in housing 12.
The common aspect in the discussed possibilities for realizing the resistance is that they exert this resistance continually, i.e. this resistance is not relevantly changed by displacements of the box 15.
In a preferred embodiment of the invention a shearing pin 33 is provided which is fastened in the housing. The shearing pin 33 is connected with the box 15 in a form-fitting manner when it is located in the position as shown in fig. 1 and fig. 6. This can be achieved in such a way that the

11
shearing pin 33 engages in a breakthrough incorporated in the side wall of the box or by an arrangement of the shearing pin 33 slightly below the lower box section 151, as shown in fig. 6.
When turning the clamping screw 16 in the opening direction, the shearing pin 33 at first prevents any displacement of the box 15. The rotational movement is exclusively converted into an upward migration of the clamping screw 16. If a sufficiently large pressure force extending in the longitudinal direction is exerted on the clamping screw 16 (e.g. by an impact on the clamping screw 16 or during the further turning of the clamping screw 16 when its head 160 already rests on the rib 30), the shearing pin 33 is shorn off and the box 15 can now be displaced in an entirely free manner.
In this variant for realizing the resistance it is exerted only temporarily, namely prior to the shearing of the shearing pin 33.
Only the space IS is opened or closed in the case of intact shearing pin 33, so that the terminal lug of a busbar system can be connected to lifting clamp 1 with a low amount of screwing work.
Such a shearing pin 33 is also provided in the preferred embodiment as shown in closer detail in the drawings I to 4f which shearing pin is connected with the box 15 merely in an indirect way:
As already explained above, a lug 24 is provided in this embodiment on which a small plate 25 shaped with which the mounting plate 26 is formed in an integral way. Said mounting plate 26 is displaceably held in a rectangular guide groove 34 incorporated in the housing in a direction parallel to the dire,c.tion-of-displacement of the box 15. In order to join the mounting plate 26 to the box 15, a pin 2? is provided which is shaped on the mounting plate 26 and which engages in a breakthrough 28 incorporated in a side wall of the box./JT
The shearing pin 33 is shaped on the floor of said guide groove 34. The mounting plate 26 comprises a breakthrough 35 in which the shearing pin 33 engages (see fig. 2,3). The shearing pin 33 is connected with the box 15 in an indirect way, namely by using the mountmgjplate 26 and the pin 27.
To ensure that a pressure force exerted on the clamping screw 16 will actually only cause a . shearing of the shearing pin 33 but not of pin 27, the shearing resistance of said pin 27 is dimensioned in a respectively higher way than that of the shearing pin 33.

12
The shearing pin 33 assumes a secondary function in this embodiment in such a way that it holds the mounting plate 26, or in combination with the same the lug 24, during the mounting of the switch at the correct position (i.e. during the insertion of the individual components into the lower shell of the housing). The mounting plate 26 with shaped plates 25 and lugs 24 can thus be inserted mechanically into the lower shell. Frame 14 and box 15 of the lifting clamps 1 can be placed with ease on the mounting plate 26.

13 WE CLAIM:
1. A lifting clamp (1) for mounting in a housing of an electric apparatus such as a circuit-breaker, comprising a rectangular frame (14) and a rectangular box (15) whose upper section (150) is arranged between the upper section (140) and the lower section (141) of the frame (14), enabling the box (15) to be held in the frame (14) in a displaceable manner, and having a clamping screw (16) which is guided through a breakthrough (142) incorporated in the upper section (140) of the frame in a freely rotatable manner and which engages in a screw thread (152) incorporated in the upper section (150) of the box (15), with the box (15) being held in the frame (14) against a resistance in a displaceable manner, characterised in that the resistance is formed by a shearing pin (33) which is fastened to the housing, is preferably arranged integrally with the housing and is connected with the box (15) in a positive manner.
The invention relates to a lifting clamp (1) for mounting in a housing of an electrical appliance, e.g. a circuit breaker, comprising a rectangular frame (14) and a rectangular box (15), the upper section (150) of said box being arranged between the upper section (140) and the lower section (141) of the frame (14), enabling the box (15) to be held in the frame (14) in a displaceable manner. Said lifting clamp also comprises a clamping screw (16) which is guided through an opening (142) incorporated in the upper section (140) of the frame in a freely rotatable manner, and which engages in a screw thread (152) incorporated in the upper section (150) of the box (15). Said box (15) is held in the frame (14) against a resistance in a displaceable manner.

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Patent Number

210104

Indian Patent Application Number

01158/KOLNP/2003

PG Journal Number

38/2007

Publication Date

21-Sep-2007

Grant Date

18-Sep-2007

Date of Filing

11-Sep-2003

Name of Patentee

MOELLER GEBAUDEAUTOMATION KG

Applicant Address

EUGENIA 1, A-3943 SCHREMS,AUSTRIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SCHUH GERHARD	WAGNER-SCHONKIRCH-STRASSE 31, A-2232,DEUTSCH,WAGRAM,AUSTRIA

PCT International Classification Number

H02 H

PCT International Application Number

PCT/AT02/00085

PCT International Filing date

2002-03-15

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	A 444/2001	2001-03-20	Austria