GB1600845A

GB1600845A - Coupling member

Info

Publication number: GB1600845A
Application number: GB16835/78A
Authority: GB
Original assignee: C Van der Lely NV
Current assignee: C Van der Lely NV
Priority date: 1977-05-04
Filing date: 1978-04-27
Publication date: 1981-10-21
Also published as: NL7704893A; DE2819008A1; GB1600846A; NL187222B; NL184348B; FR2389312B1; FR2389312A1; IT7823025A0; NL187222C; IT1096075B; NL184348C; NL8802486A

Description

(54) IMPROVEMENTS IN OR RELATING TO A COUPLING MEMBER (71) We, C. VAN DER LELY N.V., of 10, Weverskade, Maasland, The Netherlands, a Dutch Limited Liability Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a coupling member.

According to the present invention there is provided a coupling member comprising a first coupling portion which is constructed as a hydraulic cylinder and a second coupling portion which is constructed as a piston which is slidable within the cylinder and from which extends a piston rod projecting from the cylinder, a transfer duct being provided, which extends externally of the cylinder and which includes a pressure relief valve which is responsive to pressure generated in the cylinder by a load applied to the coupling member, the transfer duct, when the pressure relief valve is open, providing communication between the portions of the interior of the cylinder on the two sides of the piston, whereby the coupling member remains substantially rigid under load until the loads exceeds a predetermined value, when the pressure relief valve opens to allow the first portion and the second portion to move relatively to one another, a by-pass conduit being provided which bypasses the pressure relief valve the by-pass conduit being closed in normal operation by a blocking member but, when open, providing communication between the said portions of the cylinder to permit initial adjustment of the relative positions of the piston and the cylinder.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a side elevation of part of a tractor having a three-point lifting device which supports an implement; Figure 2 is a side elevation of a coupling member of the three-point lifting device; Figure 3 is an enlarged longitudinal sectional view of the coupling member shown in Figure 2; Figure 4 is a sectional view taken on the lines IV-IV in Figure 2; and Figure 5 is a sectional view taken on the lines V-V in Figure 4.

Figure 1 shows the rear part of a tractor 1 which is provided with a three-point lifting device 2. The lifting device 2 comprises two adjacent lower lifting arms 3, which can be turned together with respect to the tractor frame in a manner not shown by the hydraulic system of the tractor. The lifting device 2 also comprises a coupling member in the form of a top rod 4, which is mounted pivotably at the front, with respect to the intended direction of operative travel of the tractor 1, indicated by an arrow A, about a horizontal pivotal shaft 5 fastened to the tractor frame and extending transversely of the direction A. The top rod 4, like each of the two lower lifting arms, is provided at the rear with a coupling point for connection to an agricultural implement to secure the implement to the tractor 1. In the embodiment shown in Figure 1 the lifting device 2 has attached to it a harrow 6 having a plurality of soil working members in the form of rotors 7 which are provided with tines and are driven by means of an auxiliary shaft 9. which is connected with the power take-off shaft 8 of the tractor. The harrow 6 is provided with a trestle 10, which has the shape of an inverted V or U, as viewed in the direction A, the top rod 4 being connected near the top of the trestle 10 and the lower lifting arms 3 being connected at the two lower ends.

The top rod 4 is shown in detail in Figures 2 to 5. The top rod 4 comprises a locking device having a cylinder 11 in which a piston 12 is axially movable. This piston 12 is mounted on a piston rod 13, which projects only from the rear end of the cylinder 11, with respect to the direction A (Figure 2).

The cylinder 11 constitutes a first coupling portion and the piston rod 13 a second coupling portion of the locking device. The cylinder 11 has at the front an end portion 14 which is provided with a fastening member in the form of an eyelet 15, in which a bearing 16 is arranged for engagement with the pivotal shaft 5. The piston rod 13 is provided at its end away from the piston 12 with a fastening member in the form of an eyelet 17 in which a bearing 18 is fitted. The bearing 18 receives a rod which extends substantially parallel to the pivotal shaft 5 and is part of the topmost connecting point of the trestle 10.

At the end away from the end portion 14, the cylinder 11 has an end portion 19, which is fitted to the end of the cylinder 11 by means of a screwthread 20 (Fig. 3). The end portion 19 has a bore 21 in which the piston rod 13 is slidable. The centreline 21A of the bore 21 coincides with the centreline of the cylinder 11. The bore 21 has, at each end, seals 22 surrounding the piston rod 13.

The end portion 19 also has a cylindrical recess 23, the centreline of which also coincides with the centreline of the cylinder 11.

The cylindrical surface of the recess 23 constitutes an extension of the screwthread 20 on the end portion 19 surrounding the cylinder 11. The end wall of the recess 23 extends perpendicular to the centreline of the bore 21 and is located at a short distance behind the end face of the cylinder 11 to provide a space 24. The space 24 communicates with the space 11A provided between the inner surface of the cylinder 11 and the outer surface of the piston rod 13.

The cylindrical outer surface of the end portion 19 has a tapped bore 25. The bore 25 is extended in the direction towards the centreline 21A by a bore 26 which is disposed so that the centrelines of the bores 25 and 26 coincide and are perpendicular to the centreline 21A of the bore 21. The bore 26 communicates through a bore 27 with the space 24; t le bore 27 is coaxial with the bores 25, and 26. The bore 26 communicates through a bore 28, which is parallel to the bore 21, with a conduit 29. The conduit 29 is also parallel to the centreline 21A and is in liquid-tight engagement with the end portion 19 by virtue of coupling pieces 30. The conduit 29 is connected at the end away from the end portion 19 with the end portion 14 by coupling pieces 31 so that the interior of the conduit 29 communicates with a bore 32 in the end portion 14, which is also parallel to the centreline 21A. The bore 32 opens out in a bore 33, which is perpendicular to the centreline 21A, this bore 33 communicating with a portion 1 1B of the interior of the cylinder 11.

The bore 25 receives a guide member 34 having an external screwthread co-operating with the screwthread in the bore 25. The guide member 34 has an uninterrupted tapped hole 35. The hole 35 receives a set screw 36, the stem of which has an external screwthread co-operating with the screwthread of the hole 35. The set screw 38 has a conical end 37 which, over its whole circumference, is in contact with the transitional area between the bores 26 and 27, at least in the position shown, these bores being thus separated from one another. The set screw 36 has an adjusting knob 38.

The end portion 19 also has a bore 39, which is perpendicular to the centreline 21A and is inclined by an acute angle to the planes containing the centrelines of the bores 21 and 28 (Figures 3 and 4). The bore 39 opens out at one end into the bore 28 (Figure 3). Some distance from the bore 28, the bore 39 opens into a bore 40, the centreline of which is parallel to the centreline 21A (Figure 5). The bore 40 opens out, at its end furthest from the end portion 14, in a bore 41, which is coaxial with the bore 40 but is a few times larger in diameter than the bore 40. The bore 41 opens out at the end face of the end portion 19 facing away from the end portion 14.

The cylindrical surface of the bore 41 has a screw-thread 42 over part of its length, which receives a guide member 43 with an external screwthread over part of its length, which co-operates with the thread 42. The guide member 43 also has an internal screwthread receiving an adjusting member 44. The part of the adjusting member 44 facing the bore 40 has a hollow cylindrical part 45, the interior of which communicates with the interior of the bore 41. The interior of the cylindrical part 45 is closed at its end away from the bore 40 by an adjusting knob 46.

The adjusting knob 46 has a dial from which to read the setting of the limit value of the fluid pressure or force at which a valve 49 opens.

The interior of the part 45 accommodates a compression spring 47 which at one end bears on the inner side of the adjusting knob 46 and at the other end surrounds a stem 48 of the adjustable pressure limiting valve 49.

The valve 49 has a conical end 50, which in normal operation is in contact with the transitional area between the bores 40 and 41, which are thus separated from one another.

The bore 41 communicates through a bore 51 with the space 24 (Figure 5).

From Figure 3 it will be appreciated that the end portion 9 has a bore 52, which is coaxial with the bore 27. The bore 52 opens out into the interior of a reservoir 53 on the top of the end portion 19. In the reservoir 53 there is a piston 54 which is a close fit in the inner wall of the reservoir 53. The piston 54 has a guide rod 55, which projects from the reservoir through an opening in a cover 56.

Between the inner surface of the cover 56 and the top surface of the piston 54 there is a light compression spring 57. The cover 56 has an opening 58 for providing communication between the space between the inner surface of the cover 56 and the top surface of the piston 54 with the open air.

Hydraulic fluid fills the hydraulic circuit including the spaces 1 1A and 11B in the cylinder 11 on both sides of the piston 12, the space 24, the bore 27, part of the bore 26, the bore 28, the conduit 29, the bores 32 and 33, the bores 39, 40, 41, 51, 52 and the space in the reservoir 53 below the piston 54. The bores 27, 26, 28 constitute a by-pass or parallel communication with respect to the bores 39, 40, 41 and 51.

In normal operation the eyelet 15 of the top rod 4 is engaged by the pivotal shaft 5 secured to the tractor frame and the eyelet 17 is engaged by a rod secured to the upper junction of the trestle 10 of the agricultural implement attached to the tractor. In normal operation the set screw 36 prevents communication between the bores 27 and 28 (this is the position shown in Figure 3). The compression spring (Figure 5) presses the conical end 50 of the valve 49 into the entry of the bore 40. The force with which the valve 49 is pressed into the bore 40 can be adjusted by turning the adjustment knob 46, which then moves axially with respect to the guide member 43 owing to the threaded connection between said two parts.

From the position shown in Figure 2 of the piston 12 with respect to the cylinder 11, the piston 12 and the piston rod 13 can be pushed towards the end portion 14 by overload resulting from a force exerted in operation on the implement, and this force can be such that a locking device and an overload safety device are desirable. The top rod 4 described above comprises such a device. If the piston 12 is pushed towards the end portion 14 with a force approaching the adjusted overload value, the fluid pressure in the space 11B between the piston 12 and the end portion 14 will reach a given high value as will the fluid pressure in the byres 33, 32,the conduit 29, the bore 28 and the bores 39 and 40. If the adjusted overload limit value is reached, the fluid pressure will lift the valve 49 against the set pressure of the spring 47 and the fluid can then flow from the bore 40 through the space 41 and the bore 51 into the space 11A around the piston rod 13 on the other side of the piston 12 from the space 1 1B, so that unlocking occurs. Since the volume of the space inside the cylinder 11 occupied by the piston 12 and the piston rod 13 increases when the piston 12 moves towards the end portion 14 (since the piston rod 13 projects only from one end of the cylinder 11), a quantity of hydraulic fluid corresponding to the volume of the extra length of the piston rod 13 has to be discharged. When the valve 49 is lifted in the event of overload a portion of the hydraulic fluid will flow through the conduit 52 towards the reservoir 53, which will move the piston 54 towards the cover 56 against the relatively light pressure of the spring 57. The piston 54 is provided to prevent the hydraulic fluid in the reservoir 53 from absorbing air or forming bubbles. The construction described thus prevents the occurence of excessive forces in the top rod of the lifting device and hence in other structural parts of the agricultural implement and the tractor. It is of great advantage that unlocking of the locking device can be achieved solely by the operational force exerted on the implement 7 and is independnet of the hydraulic system of the tractor.

In order to set the position of an attached implement with respect to the tractor, the desired position of the piston rod 13 with respect to the cylinder 11 can be adjusted by screwing out the set screw 36. This provides communication between the bores 27 and 28 establishing a direct communication between the spaces 11A and 11B on the two sides of the piston 12. The piston rod 13 can then be moved manually, or by actuating the lifting device 2, into the desired position relative to the cylinder 11. After this setting the set screw 36 is tightened again so that the communication between the bores 27 and 28 is interrupted and the top rod can again respond only via the valve 49 to an overload limit value adjusted by the adjusting knob 46.

The coupling member described can be used not only as a top rod as described above, but also as other kinds of coupling rods establishing a connection between an agricultural implement and a tractor, for example, as the lower lifting arms 3. It can also be applied to machinery other than agricultural machinery. It should be noted that the operating direction of the top rod 4 described with reference to the Figures may be inverted when the force applied by the main load is directed to the rear from the pivotal shaft 5.

WHAT WE CLAIM IS:- 1. A coupling member comprising a first coupling portion which is constructed as a hydraulic cylinder and a second coupling portion which is constructed as a piston which is slidable within the cylinder and from which extends a piston rod projecting from the cylinder, a transfer duct being provided, which extends externally of the cylinder and which includes a pressure relief valve which is responsive to pressure generated in the cylinder by a load applied to the coupling member, the transfer duct, when the pressure relief valve is open, providing communication between the portions of the interior of the cylinder on the two sides of the piston, whereby the coupling member remains substantially rigid under load until the load exceeds a predetermined value, when the pressure relief valve opens to allow the first portion and the second portion to move relatively to one another, a by-pass conduit being provided which by-passes the pressure relief valve, the by-pass conduit being closed in normal operation by a blocking member but, when open, providing communication between the said portions of the cylinder to

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. space 24, the bore 27, part of the bore 26, the bore 28, the conduit 29, the bores 32 and 33, the bores 39, 40, 41, 51, 52 and the space in the reservoir 53 below the piston 54. The bores 27, 26, 28 constitute a by-pass or parallel communication with respect to the bores 39, 40, 41 and 51. In normal operation the eyelet 15 of the top rod 4 is engaged by the pivotal shaft 5 secured to the tractor frame and the eyelet 17 is engaged by a rod secured to the upper junction of the trestle 10 of the agricultural implement attached to the tractor. In normal operation the set screw 36 prevents communication between the bores 27 and 28 (this is the position shown in Figure 3). The compression spring (Figure 5) presses the conical end 50 of the valve 49 into the entry of the bore 40. The force with which the valve 49 is pressed into the bore 40 can be adjusted by turning the adjustment knob 46, which then moves axially with respect to the guide member 43 owing to the threaded connection between said two parts. From the position shown in Figure 2 of the piston 12 with respect to the cylinder 11, the piston 12 and the piston rod 13 can be pushed towards the end portion 14 by overload resulting from a force exerted in operation on the implement, and this force can be such that a locking device and an overload safety device are desirable. The top rod 4 described above comprises such a device. If the piston 12 is pushed towards the end portion 14 with a force approaching the adjusted overload value, the fluid pressure in the space 11B between the piston 12 and the end portion 14 will reach a given high value as will the fluid pressure in the byres 33, 32,the conduit 29, the bore 28 and the bores 39 and 40. If the adjusted overload limit value is reached, the fluid pressure will lift the valve 49 against the set pressure of the spring 47 and the fluid can then flow from the bore 40 through the space 41 and the bore 51 into the space 11A around the piston rod 13 on the other side of the piston 12 from the space 1 1B, so that unlocking occurs. Since the volume of the space inside the cylinder 11 occupied by the piston 12 and the piston rod 13 increases when the piston 12 moves towards the end portion 14 (since the piston rod 13 projects only from one end of the cylinder 11), a quantity of hydraulic fluid corresponding to the volume of the extra length of the piston rod 13 has to be discharged. When the valve 49 is lifted in the event of overload a portion of the hydraulic fluid will flow through the conduit 52 towards the reservoir 53, which will move the piston 54 towards the cover 56 against the relatively light pressure of the spring 57. The piston 54 is provided to prevent the hydraulic fluid in the reservoir 53 from absorbing air or forming bubbles. The construction described thus prevents the occurence of excessive forces in the top rod of the lifting device and hence in other structural parts of the agricultural implement and the tractor. It is of great advantage that unlocking of the locking device can be achieved solely by the operational force exerted on the implement 7 and is independnet of the hydraulic system of the tractor. In order to set the position of an attached implement with respect to the tractor, the desired position of the piston rod 13 with respect to the cylinder 11 can be adjusted by screwing out the set screw 36. This provides communication between the bores 27 and 28 establishing a direct communication between the spaces 11A and 11B on the two sides of the piston 12. The piston rod 13 can then be moved manually, or by actuating the lifting device 2, into the desired position relative to the cylinder 11. After this setting the set screw 36 is tightened again so that the communication between the bores 27 and 28 is interrupted and the top rod can again respond only via the valve 49 to an overload limit value adjusted by the adjusting knob 46. The coupling member described can be used not only as a top rod as described above, but also as other kinds of coupling rods establishing a connection between an agricultural implement and a tractor, for example, as the lower lifting arms 3. It can also be applied to machinery other than agricultural machinery. It should be noted that the operating direction of the top rod 4 described with reference to the Figures may be inverted when the force applied by the main load is directed to the rear from the pivotal shaft 5. WHAT WE CLAIM IS:-

1. A coupling member comprising a first coupling portion which is constructed as a hydraulic cylinder and a second coupling portion which is constructed as a piston which is slidable within the cylinder and from which extends a piston rod projecting from the cylinder, a transfer duct being provided, which extends externally of the cylinder and which includes a pressure relief valve which is responsive to pressure generated in the cylinder by a load applied to the coupling member, the transfer duct, when the pressure relief valve is open, providing communication between the portions of the interior of the cylinder on the two sides of the piston, whereby the coupling member remains substantially rigid under load until the load exceeds a predetermined value, when the pressure relief valve opens to allow the first portion and the second portion to move relatively to one another, a by-pass conduit being provided which by-passes the pressure relief valve, the by-pass conduit being closed in normal operation by a blocking member but, when open, providing communication between the said portions of the cylinder to

permit initial adjustment of the relative positions of the piston and the cylinder.

2. A coupling member as claimed in claim 1, in which the pressure relief valve is manually adjustable.

3. A coupling member as claimed in claim 2, in which the pressure relief valve is provided with an adjusting knob for setting a desired limit value.

4. A coupling member as claimed in claim 3, in which the adjusting knob is provided with a dial to provide an indication of the set limit value.

5. A coupling member as claimed in any one of the preceding claims, in which the cylinder communicates with a fluid reservoir.

6. A coupling member as claimed in claim 5, in which the portion of the interior of the cylinder which is occupied by the piston rod is in open communication with the fluid reservoir.

7. A coupling member as claimed in claim 5 or 6, in which the fluid reservoir comprises a piston which is movable upardly against the pressure of a spring.

8. A coupling member as claimed in any one of claims 5 to 7, in which the fluid reservoir has a capacity which is not less than the maximum variation of the internal volume of the cylinder during a stroke of the piston.

9. A coupling member as claimed in any one of the preceding claims, in in which the blocking member comprises a screw.

10. A coupling member as claimed in any one of the preceding claims, which is adapted so that overload causes the ends of the member to approach one another.

11. A coupling member as claimed in any one of the preceding claims, which is adapted for use as a top rod of a lifting device.

12. A coupling member as claimed in claim 11, which is adapted to be returned to the operational state by lifting the lifting device.

13. A coupling member substantially as described herein with reference to and as illustrated in the accompanying drawings.

14. In combination, a tractor and an agricultural implement which are interconnected by a coupling including a coupling member as claimed in any one of the preceding claims.