|Title of Invention||
"A HYDRAULIC DISTRIBUTOR AND LIFTER WITH CONTROLLED POSITION AND EFFORT FOR AGRICULTURAL TRACTORS AND MACHINES"
|Abstract||A distributor for a hydraulic lifter with controlled position and effort for agricultural tractors and machines comprises a compact body with at least one inlet duct for a pressurized fluid, at least one discharge duct, and at least one duct for supplying a hydraulic lifting cylinder of the lifter arms. Differential-valve means are formed in the distributor body for selectively directing the fluid input to the discharge duct directly or to the cylinder-supply duct. The position of further, shuttle-valve means is controlled by a shaft movable between a central or neutral position and two end positions for filling and for discharge, respectively. The shaft also controls the selective opening of a discharge valve for selectively putting the differential valve means into communication with a delivery-fluid pressure or with a discharge-fluid pressure and advancing or retracting the hydraulic cylinder or keeping it in a fixed position. The distributor is housed in the casing of a lifter which comprises linkages for regulating controlled-position and controlled-effort operation. The linkages are controlled by the angular positions adopted by two concentric shafts controlled by respective control levers.|
|Full Text||The present invention relates to a hydraulic distributor and lifter with controlled position and effort for agricultural tractors and machines. In particular, the lifter and the distributor associated therewith are intended to be used for regulating and controlling the movement of a three-point coupling which is mounted on the agricultural tractor or machine, and to which a tool is connected for working or preparing the soil.
Lifters of various types for three-point couplings and distributors of various types for controlling their movement are known. A particular known distributor comprises a substantially cylindrical and compact body in which there are various valve elements of primary importance amongst which is a distributing slide-valve the slider of which is operated by the levers of the lifter and which permits, alternatively, modulation of a certain flow-rate of pressurized fluid towards an actuator cylinder, or discharge of a certain quantity of fluid therefrom. Lifters are usually connected to the pressurized-oil distribution system which is provided on the agricultural machine for other services.
The object of the present invention is to provide a distributor and a lifter which are formed integrally with one another, which are simple and inexpensive to produce, easy to fit and compact, and which permit very accurate regulation of the effort and of the position of the tool connected to the three-point coupling.
To achieve the objects indicated above, the subject of the
invention is a distributor and a lifter the innovative characteristics of which are defined in the appended claims.
The distributor formed in accordance with the present invention is easy to fit on the respective lifter by virtue of its limited size. A further advantage of the invention consists of ease of maintenance and of control of the full functional capacity of the distributor. Further characteristics and advantages will become clear from the description of a preferred embodiment which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which:
Figure 1 is a perspective view of the rear portion of a tractor having a three-point coupling connected to a lifter according to the present invention,
Figure 2 is a hydraulic diagram of a lifter and of a distributor according to the present invention,
Figures 3, 4 and 5 are schematic longitudinal sections of a distributor according to the present invention in three different operative configurations,
Figure 6 is a detailed longitudinal section of the distributor of Figures 3, 4 and 5, and
Figures 7 and 8 are longitudinal sections of a lifter of the present invention in two different operative configurations.
With reference now to Figure 1, a three-point coupling for a tractor comprises two lower arms 1 and a third-point arm 2 which together are intended to support a tool carried or partially carried by the tractor. The lower arms 1 are
supported by lifting rods 3 connected to lifting levers 4 projecting laterally from the casing 5 of a lifter 6. The third-point arm 2 is articulated to the casing of the lifter 6 directly.
With reference now to Figure 2, a hydraulic supply circuit for the lifter 6 and, in particular, for a distributor 15 of the lifter 6, comprises a hydraulic pump 10 the flow-rate of which depends upon the rate of revolution of an engine 11. Upstream and downstream of the pump 10 there are two filters 12 for filtering the oil coming from a tank 13. The hydraulic circuit supplies, in cascade, an auxiliary distributor, generally indicated 14, for moving auxiliary tools, which does not fall within the scope of the present invention and will not therefore be described in detail. Downstream of the auxiliary distributor 14, the hydraulic circuit supplies a lifter, generally indicated 15, comprising a cylinder 16 for operating the lifting levers 4 (see Figure 1) and hence the lower arms of the three-point coupling. The cylinder 16 is regulated by the functioning of the distributor 15 which is described below.
In detail, a pressurized-oil delivery duct 17 reaches the distributor 15 from which a duct 18 for supplying the cylinder 16 emerges. A plurality of discharge ducts 19 convey the discharged oil towards a collection tank 20 which communicates with or corresponds to the tank 13. Inside the distributor 15, the delivery duct 17 communicates with a calibrated safety valve 21. The delivery duct 17 also communicates with a differential valve 22 which permits or stops the flow of the oil from the pump 10 towards the discharge 19 in accordance with the operating conditions described further below.
The delivery duct 17 also communicates with a calibrated check valve 23 downstream of which the supply duct 18 for the cylinder 16 opens; also branching out from the duct 18 are ducts for connection to a pressure-relief valve 24 which protects the cylinder 16 from any excessive pressures, and to a valve 25 for regulating the discharge of the cylinder 16 and hence the downward movement of the arms of the three-point coupling. Downstream of the valve 25 there is a discharge valve 26 for the cylinder 16.
The distributor 15 is operated in order to fill and discharge the cylinder 16 by a shuttle valve 27 controlled by a control shaft 28. The position of the shuttle valve 27 also determines the position of the discharge valve 26, by means of a coupling rod 29. The shuttle valve 27 puts a regulation chamber 30 of the differential valve 22 selectively into communication with the discharge 19 or with the delivery 17.
The members of the distributor 15 described above with
reference to the hydraulic diagram of Figure 2 are preferably
grouped in a single compact body, shown schematically in
Figures 3 to 5 and in greater detail in Figure 6. In these
drawings, the members corresponding to the symbols of the
hydraulic diagram of Figure 2 are indicated by the same
The distributor 15 is arranged to bring about three distinct modes of operation shown in Figures 3 to 5, respectively: a neutral stage, a filling stage, and a discharge stage. These stages are set by the position adopted by the control shaft 28, this position being selected from a central or neutral position N, a retracted or filling position C, and a projecting, discharge position S.
In the neutral stage, shown in Figure 3, the distributor 15 holds the load applied to the lifting arms in a certain position, keeping the cylinder 16 in a predetermined locked position, and allows the oil coming from the pump 10 to flow out freely to the discharge 19. At this stage, the control shaft 28 is in the central position N so that the regulation chamber 30 of the differential valve 22 is subject to the discharge pressure.
The pressure of the oil arriving from the pump 10 can thus open the differential valve 22 so that the oil can flow out freely to the tank 20 through one of the discharge ducts 19. However, the oil contained in the cylinder 16 cannot flow out to the discharge because it is retained by the check valve 23 and by the discharge valve 26. The oil retained in the cylinder 16 keeps the latter in the desired position, unless the load applied to the cylinder 16 by means of the lower arm of the three-point coupling causes an excessive increase in the pressure in the cylinder 16 and consequent intervention of the pressure-relief valve 24.
When the lower arm of the three-point coupling is to be lifted, it is necessary to supply pressurized oil from the pump 10 to the cylinder 16 through the supply duct 18. In order to do this, as shown in Figure 4, the control shaft 28 is moved to the filling position C. The oil coming from the pump 10 enters from the delivery duct 17 and passes through the shuttle valve 27 into the regulation chamber 30, closing the differential valve 22. The oil coming from the pump 10 is thus forced to pass through the check valve 23 to reach the cylinder 16 through the supply duct 18, extending the cylinder 16 and consequently lifting the lower arms of the three-point coupling. The pressure in the circuit also affects the pressure-relief valve 24 and the safety valve 21
which control the pressure of the oil at the input to the distributor 15.
If, on the other hand, the lower arm of the three-point coupling is to be lowered, the oil contained in the cylinder 16 is made to flow out to the discharge 19, together with the oil coming form the pump 10, as shown in Figure 5. If the control shaft 28 is moved to the discharge position S, the regulation chamber 30 of the differential valve 22 is put into communication with the discharge; the oil coming from the pump 10 through the delivery duct 17 can thus pass through the differential valve 22 and can pass directly into the discharge tank 20. At the same time, the oil contained in the cylinder 16 flows out through the supply duct 18, through the regulation valve 25 which has moved down and, finally, through the discharge valve 26 which is opened by the rod 29 controlled by the movement of the shaft 28. The oil coming from the cylinder 16 thus flows out freely to the tank 20, bringing about lowering of the lifting arms and of the respective tool connected thereto. During the discharge stage, the speed of downward movement of the tool fitted on the lifting arms can be regulated by means of a downward-movement regulation knob 31. For moving on the road with tools connected to the lifter, the discharge of the cylinder 16, and hence the lowering of the lower arms, can be stopped completely in a predetermined position by tightening the knob 31 fully so as to close the regulation valve 25 completely.
The distributor 15 described above is incorporated in the lifter 6 the internal regulation members of which are shown schematically in Figures 7 and 8. For simplicity of illustration, the members essential for controlled-position operation of the lifter are indicated in Figure 7 whereas the members essential for controlled-effort operation of the
lifter are indicated in Figure 8. In detail, the control shaft 28 of the distributor 15 projects into the casing 5 and is operated by a rod 40 carried by a transmission lever 41 connected by means of a shock-absorber 42 to an arm 43 of a rocker 44. The distributor preferably has a compact cartridge-like shape with the shaft 28 projecting from the end and can thus easily be fitted and removed for replacement or maintenance.
The transmission lever 41 is also connected to a tie rod 45 having a travel-limit stop 46 the function of which will become clearer from the following. A second arm 47 of the rocker 44 interacts with a position roller 48 carried by a crank 49 fixed to a shaft 50. The position roller 48 can also interact, as will be explained below, with a position cam 51 which has a step 66 arranged facing the second arm 47 of the rocker 44, and from which an orientation lever 52 projects and is articulated to a link 53 articulated to a crank 67 fixed to the lifting levers 4 projecting from the casing of the lifter 6.
An effort shaft 54 (see Figure 8) is also mounted movably and coaxially on the shaft 50 and a crank 55 fixed firmly thereto is connected to a tie rod 56 which carries at its end a roller 57 for cooperating, as will be described further below, with a shank 58 of the rocker 44 and with an effort cam 59. The effort cam 59 is mounted for rotating on the casing 5 and is controlled by an effort crank 60 operated by a tie rod 61 connected to a pivoting plate 62 for the connection of the third-point arm. The controlled-position, controlled-effort, or combined controlled-position and controlled-effort operation of the lifter is set by the positions of a pair of control levers 63, 64 which regulate the position of the tool relative to the ground and the
effort which the tool exerts on the ground, respectively, in order to achieve the fullest operating characteristics of the three-point coupling, by methods known in the agricultural field.
During controlled-position operation of the lifter 6, the effort-control lever 64, which controls the angular position of the effort shaft 54 to which the tie-rod 56 is connected, is positioned against a lower stop of a guide sector 65 so as to move the roller 57 completely away from the effort cam 59, as shown in Figure 7. The effort-control members do not thus affect the controlled-position operation of the lifter 6. The lower arms are lifted by upward movement of the position-control lever 63 which controls the angular position of the shaft 50. The crank 49 fixed to the shaft 50 rotates clockwise, causing the roller 48 to pass over the step 66 of the position cam 51, thus bringing about clockwise pivoting of the rocker 44 which transmits an anticlockwise pivoting movement to the transmission lever 41, by means of the shock-absorber 42, urging the shaft 28 of the distributor 15 towards the filling position C. The cylinder 16, which is connected to the lifting levers 4 in known manner (which is therefore not shown in the drawings), consequently brings about lifting of the lower arms of the three-point coupling. During the lifting movement of the arms, the link 53 is moved anticlockwise so as to bring about a clockwise counter-rotation of the position cam 51. When the roller 48 passes over the crest 66 of the position cam 51, it can return to the retracted position shown in Figure 7 and thus allows the rocker 44 to pivot anticlockwise. This anticlockwise pivoting of the rocker 44 is transmitted to the shock-absorber 42 which brings about a clockwise pivoting movement of the transmission lever 41 so as to allow the shaft 28 of the distributor 15 to return to the neutral position N and
thus to stop the movement of the lower arms. During the lowering of the lower arms, the movement of the linkages takes place in the opposite direction to that indicated above. The position of the arms, both during lifting and during lowering, corresponds to a predetermined position of the position-control lever 63 on the sector 65.
During controlled-effort operation of the lifter 6, the position-control lever 63 is brought against the lower stop on the sector 65, as shown in Figure 8. The crank 49 thus reaches the end position of its anticlockwise rotation. In this position, the roller 48 moves down completely from the inclined plane of the position cam 51 on the left-hand side of the crest 66, permitting anticlockwise pivoting of the rocker 44 and clockwise pivoting of the transmission lever 41. This brings about movement of the shaft 28 of the distributor 15 which is brought to the discharge position S. The position levers do not thus affect the operation of the controlled-effort lifter.
Positioning of the effort-control lever 64 against the upper stop of the sector 65 brings about a clockwise rotation of the effort shaft 54 (see Figure 8) , the angular position of which is determined by the position of the effort-control lever 64. The crank 55 fixed to the shaft 54 reaches the end position of its clockwise rotation and moves the roller 57, by means of the tie rod 56, so that the roller 57 reacts against the effort cam 59, causing the rocker 44 to pivot clockwise and, by means of the shock-absorber 42, to pivot the transmission lever 41 anticlockwise, thus bringing the shaft 28 of the distributor 15 to the filling position C, resulting in lifting of the lower arms.
The arms stop only when the piston 16 comes into contact with
the travel-limit pin 46 which pivots the lever 41 clockwise by means of the tie rod 45, compressing the spring of the shock-absorber 42 and thus leaving the shaft 28 free to move to the neutral position N. If the effort-control lever 64 is moved downwards from the upper end position, the crank 55 rotates anticlockwise and, by means of the tie-rod 56, causes the roller 57 to run along the rocker 44 until the roller 57 passes over the top of the effort cam 59, thus permitting anticlockwise pivoting of the rocker 44. This pivoting allows the shaft 28 of the distributor 15 to move towards the neutral position N. Continued downward movement of the lever 64 causes the shaft 28 to move towards the discharge position S and the arms consequently to be lowered. Given the configuration of the internal linkages of the lifter and, in particular of the effort cam 59, during the initial portion of the return travel of the effort-control lever 64 from the upper position, a corresponding lowering of the lower arms of the three-point coupling does not yet occur.
A pulling force on the tool connected to the three-point coupling, for example, due to more compact soil, brings about, in known manner, a compression force on the third-point arm and hence a clockwise pivoting of the third-point coupling 62. This pivoting exerts a compression force on the tie-rod 61 which brings about a clockwise rotation of the crank 60 and hence of the effort cam 59 connected thereto. When the inclined plane of the effort cam 59 meets the roller 57, the rocker 44 is pivoted clockwise so that the transmission lever 41 moves the shaft 28 of the distributor 15 to the neutral position N, by means of the shock-absorber 42, stopping the movement of the lower arms of the three-point coupling.
As the pulling force increases, the effort cam 59 moves the
roller 57 further, adding to the movement described above. The shaft 28 of the distributor 15 is thus moved from the neutral position N to the filling position C, resulting in lifting of the arms. When the pulling force on the tool decreases, the shaft 28 returns to the neutral position N or the filling position C, causing lowering of the lower arms by the above-described operation of the lifting linkages performed in reverse.
Naturally, the lifter can be controlled in a manner such as to display combined controlled-position and controlled-effort operation. In order to use the lifter in this condition, the position control lever 63 must be moved upwards until the maximum working depth of the tool engaged on the three-point coupling is achieved. The minimum working depth desired must then be set by operation of the effort-control lever 64, by raising it from the lower position on the sector 65 so that the roller 57, reacting on the effort cam 59, brings the shaft 28 of the distributor 15 to the lifting position C and brings about a further upward movement of the lifting arms. Because of the position previously established by the position-control lever 63, the rocker 44, the roller 48, and the position cam 51 prevent the shaft 28 from being brought to the lowering position S and the lower arms of the three-point coupling cannot therefore be lowered, even when the pulling force on the third-point 62 tends to decrease, exerting a pulling force on the tie-rod 61. This condition does not prevent the lifter from operating with controlled effort when, if the soil is more compact, the pulling force on the third-point arm tends to increase, exerting a compression force on the tie-rod 61. Combined position control and effort control thus limits downwardly the depth variations which take place in controlled-effort use ensuring the desired maximum working depth.
Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated, without thereby departing from the scope of the present invention.
1. A distributor for a hydraulic lifter with controlled
position and effort for agricultural tractors and machines,
comprising a compact body with at least one inlet duct for a
pressurized fluid, at least one discharge duct, and at least
one duct for supplying a hydraulic cylinder for lifting the
arms of the lifter, differential -valve means being formed in
the body for selectively directing the fluid input to the
discharge duct directly or to the cylinder- supply duct, the
position of shuttle-valve means being controlled by a shaft
movable between a central or neutral position and two end
positions for filling and for discharge, respectively, the
shaft also controlling the selective opening of a discharge
valve for selectively putting the differential -valve means
into communication with a delivery-fluid pressure or with a
discharge-fluid pressure, and advancing or retracting the
hydraulic cylinder or keeping it in a fixed position.
2. A distributor according to Claim 1, in which the
differential valve means comprise a chamber communicating
with the shuttle valve.
3. A distributor according to Claim 1, further comprising an
pressure-relief valve communicating with the supply duct of
the hydraulic cylinder in order to protect the latter from
excessive fluid pressures.
4. A distributor according to Claim 1, further comprising a
discharge-regulation valve interposed between the discharge
valve and a check valve communicating with the delivery duct,
the discharge-regulation valve comprising a choke variable to
the extent of complete closure for the fine regulation of the
rate of retraction of the hydraulic cylinder and for the
complete stoppage thereof during the discharge stage.
5. A distributor according to Claim 4, comprising a knob for
controlling the discharge-regulation valve.
6. A lifter for a three-point coupling of an agricultural
tractor comprising a casing in which a distributor according
to any one of the preceding claims is housed, the lifter
comprising linkages for regulating controlled-position and
controlled-effort operation, the linkages being controlled by
the angular positions adopted by two concentric shafts
controlled by respective control levers.
7. A lifter according to Claim 6, comprising first and second
cam means for regulating the controlled-position and
controlled-effort operation of the lifter, respectively.
8. A lifter according to Claim 7, comprising first and second
roller means interacting with the first and second cam means,
respectively, the roller means being mounted on respective
lever means coupled to one and to the other of the concentric
control shafts, respectively.
9. A lifter according to Claim 8, comprising reaction lever
means connected to the levers for lifting the lower arms and
to the third-point arm of a three-point coupling,
respectively, the reaction lever means interacting with the
cam means in order to return the shaft of the distributor to
the central, neutral position when the predetermined position
and/or effort set by means of the control levers are reached.
10. A distributor for a hydraulic lifter with controlled
position and effort for agricultural tractors and machines,
substantially as hereinbefore described with reference to the
11. A lifter for a three-point coupling of an agricultural
tractor, substantially as hereinbefore described with reference
to the accompanying drawings.
|Indian Patent Application Number||3672/DEL/1998|
|PG Journal Number||04/2008|
|Date of Filing||07-Dec-1998|
|Name of Patentee||MITA OLEODINAMICA S.P.A.|
|Applicant Address||VIA CARLO CIPOLIA, 12, 37039 TREGNAGO (VERONA), ITALY.|
|PCT International Classification Number||F15B 13/04|
|PCT International Application Number||N/A|
|PCT International Filing date|