GB2172082A

GB2172082A - Tractor linkage stabiliser

Info

Publication number: GB2172082A
Application number: GB08603438A
Authority: GB
Inventors: Jurgen Vollmer; Paul Herchenbach; Hermann Rugen
Original assignee: GKN Walterscheid GmbH
Current assignee: Walterscheid GmbH
Priority date: 1985-02-15
Filing date: 1986-02-12
Publication date: 1986-09-10
Also published as: JPS61187702A; DE3505243A1; IT8505262A0; IT1210143B; AT393431B; IT8507154V0; ATA305685A; DE3505243C2; GB8603438D0; JPH0449366B2; FR2577376A1; FR2577376B1; GB2172082B

Abstract

A lateral stabiliser connected between a lower link arm of the three-point implement attachment linkage of an agricultural tractor and the tractor comprises a telescopic assembly having outer connection points 60 and 66. An inner shaft 36 is telescopically received within an outer tube 32, 34 and is biased to a neutral position by means of a compression spring 38 which remains in compression in its neutral position. Telescopic extension or retraction of the shaft and tube relative to one another is resisted by the compression spring which, always being under compression, imparts a high return load to the neutral position even upon small relative movements between the shaft and tube. Spring 38 acts on thrust washers 44, 46 which abut against stops 42, 48 on the shaft and 50, 52 on the tube, as appropriate. The device can be locked, as by pin 56 or by spring-loaded arms (Figs. 5 to 7), and the shaft and tube can act to some extent as piston and cylinder to effect a degree of pneumatic damping. Belleville washers (Fig. 8) can also provide damping on excessive displacement. <IMAGE>

Description

SPECIFICATION Tractor linkage stabiliser This invention relates to a lateral stabiliser for a lower link arm of a three-point implement attachment link of an agricultural tractor, such a stabiliser being connectable between such a lower link arm and the tractor and comprising a telescopic damper assembly.

Lateral stabilisers of this general type are known as described for example in German patent specification 3129537 which describes a stabiliser having a spring bias intended to effect a return of a lower linkage arm to a predetermined position.

It is an object of the present invention to provide an improved construction of lateral stabiliser and, in accordance with the invention, there is provided a lateral stabiliser for a lower link arm of a three-point implement attachment linkage of an agricultural tractor, said stabiliser being connectable between a said lower link arm and the tractor and comprising two members telescopically assembled together, the outer ends of one of said members being connectable respectively to a said lower link arm and to the tractor, the inner ends of said members being telescopically slidable one within the other; a coil compression spring being arranged at the inner end of said members around the inner one of said members and within the outer one of said members, said spring abutting at its ends against stops associated with ssid inner and outer members to bias said members to a neutral position relative to one another with the spring in compression in said neutral position, the spring being placed under further compression upon either inward or outward movement of said members relative to one another.

Said stops may comrpise a pair of stops extending radially outwardly of the inner one of said members between which the spring is maintained in its compressed condition and a pair of stops extending radially inwardly of the outer one of said members each engageable respectively by one of said stops on the inner member. Each of said radially outwardly extending stops on the inner member is preferably so engageable with one of said radially inwardly extending stops on the outer member as to support the inner member coaxially within the outer member. A thrust washer may be mounted on the inner member at each end of the compression spring between the ends of the spring and the respective radially outwardly extending stops.One of the radially outwardly extending stops on the inner member may comprise a fixed stop thereon and a sleeve thereon abuttable against said fixed stop, said sleeve supporting the inner member coaxially within the outer member; the inner member being slidable inwardly of the outer member through said sleeve against the bias of the compression spring with the sleeve engaged with a said one of the radially inwardly extending stops on the outer member.

The other of said radially outwardly extending stops on the inner member may comprise a fixed stop thereon whilst the radially inwardly extending stops on the outer member comprise fixed stops thereon.

Means may be provided within the outer member for damping the rate of movement of the inner and outer members relative to one another and said damping means may comprise a deformable element mounted about the inner member and located between a collar on the inner member and a radially inwardly extending stop on the outer member. Alternatively, or additionally, said damping means may be provided by the pneumatic piston and cylinder effect between the inner and outer members upon relative movement therebetween.

Selectively engageable securing means may be provided on the stabiliser for selectively preventing or permitting relative movement between the inner and outer members, such relative movement being preventable by said securing means when the inner and outer members are in their said neutral position.

Said securing means may comprise a pin selectively insertable through aligned bores extending transversely of the inner and outer members or, alternatively, said securing means may comprise spring biased arms mounted on the outer member selectively engageable with an annular groove on the inner member.

Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawings wherein Figure 1 is a diagrammatic side view of a three-point implement attachment linkage at the rear of a tractor having a lateral stabiliser in accordance with the invention connected between the tractor and each of the two lower link arms, Figure 2 is a diagrammatic plan view of the three-point attachment linkage and lateral stabilisers of Figure 1, Figure 3 is a side cross sectional view through a lateral stabiliser constructed in accordance with the invention, Figure 4 is a side cross sectional view through an alternative embodiment of lateral stabiliser constructed in accordance with the invention, Figure 5 is a-side cross sectional view of a further alternative embodiment of lateral stabiliser constructed in accordance with the invention having securing means in the form of spring biased arms for locking the stabiliser in its neutral position, Figures 6 and 7 are transverse cross sectional views showing the locking arms of Figure 5 in their engaged and disengaged positions respectively, and Figure 8 is a scrap side cross sectional view of the stabiliser of Figure 1 with the addition of damping means within the outer member.

Referring to Figures 1 and 2 of the drawings there is shown a conventional three-point implement attachment linkage mounted at the rear of an agricultural tractor having a power take off shaft 10. Diagrammatically, in Figure 1, there is shown the tractor transmission casing 12, a tractor rear axle 14, two lower link arms 16 and 18 and one upper link arm 20. Each of the upper and lower link arms is pivotally mounted at the rear of the transmission casing 12 of the tractor with each of the lower link arms 16 and 18 being mounted for multi-directional pivotal movement. Each such lower link arm is raisable and lowerable in the vertical plane by means of a lever 21 conveniently hydraulically powered from the tractor.

The rearmost outboard end of each arm 16, 18, 20 is provided with a respective coupling hook 22, 24, 26 for attachment to respective connecting pins of an implement to be towed by the tractor.

Lateral stabilisers 28 and 30 constructed in accordance with the invention are connected one between each lower link arm 16, 18 and the tractor as shown in Figure 2. The forward end of each stabiliser 28, 30 is pivotally mounted on the tractor on the same lateral axis A as the pivotal mounting points of the lower link arms 16, 18 on the tractor. The rearward end of each lateral stabiliser is pivotally mounted to a lower link arm at a point intermediate the ends of the arm.

One of the lateral stabilisers in accordance with the invention is shown in more detail in Figure 3 wherein the stabiliser will be seen to comprise two members telescopically assembled together. An outer one of said members is of tubular form comprising a pair of partially overlapped coaxial tubes 32, 34 welded together whilst the inner one of such members comprises either a solid or tubular shaft 36 telescopicaly and coaxially received within the outer member.

In accordance with the invention a coil compression spring 38 is arranged at the inboard ends of said members around the shaft 36 and within the tube 32 with the spring 38 abutting at its ends against stops so as to bias the members to a neutral position relative to one another with the spring in compression in such neutral position. The innermost end of the shaft 36 is provided with a fixed radially outwardly extending stop 40 against which abuts a sleeve 42 freely mounted about the shaft 36 and being of only slightly smaller external diameter than the inner diameter of the tube 34 so as to support the inner end of the shaft 36 coaxially relative to the tube 34.

The adjacent end of the coil compression spring bears against a thrust washer 44 disposed between said spring end and that end of the sleeve 42 remote from the fixed stop 40.

The other end of the coil compression spring 38 bears against a further thrust washer 46 located between said end and a further fixed stop on the shaft 36 comprising a radially outwardly extending shoulder 48 thereon.

The tube 32 is provided with radially inwardly extending fixed stops comprising a first stop defined by the inner end 50 of the overlapped tube 34 and a sleeve 52 fixedly secured in position at the innermost end of the tube 32. The internal diameter of such sleeve 52 is only slightly greater than the external diameter of the enlarged diameter part 54 of the shaft 36 whereby said shaft is further coaxially supported within the tube 32.

Thus, in the neutral position shown in Figure 3, the coil compression spring 38 is retained in compression by means of the one thrust washer 46 bearing against the one radially inwardly extending stop comprised by the sleeve 52 and the other thrust washer 44 bearing against the other fixed stop provided by the overlapped end 50 of the tube 34.

Also shown in Figure 3 is a selectively engageable securing pin 56 insertable through aligned bores in the inner and outer members whereby the stabiliser may be locked when in its neutral position to prevent relative movement between the inner and outer members thereof. This locking of the stabilisers is necessary when a tractor is towing an implement on a road whereas, when the implement is being towed for use in an agricultural environment, the locking pin 56 will be removed thereby permitting the inner and outer members of the stabiliser to move telescopically relative to one another either inwardly or outwardly.

Thus, referring back in particular to Figure 2, it will be apparent that, in use, when a towed implement sways relative to the tractor one of the stabilisers will be telescopically contracted and, at the same time, the other stabiliser will be telescopically extended. Such contraction or extension is accommodated, but resisted, by further compression of the coil spring 38 as will be apparent from an examination of Figure 3. Thus, upon contraction of the stabiliser, the one thrust washer 44 remains in abutment against the stop provided by the overlapped end 50 of the tube 34 whilst the other thrust washer 46 is carried inwardly by the shoulder 48 on the shaft 36 to compress the spring 38. Conversely, upon extension of the stabiliser, the one thrust washer 46 remains abutted against the stop provided by the sleeve 52 whilst the fixed stop 40 at the innermost end of the shaft 36 causes the adjacent sleeve 42 and thrust washer 44 to compress the spring 38.

It will be appreciated that, for any given implement to be towed, the lateral spacing between the coupling hooks 22, 24 at the ends of the lower link arms 16, 1i8 is predetermined by the size of the implement and it is thus necessary that the overall length of each stabiliser 28, 30 must be adjustable to its neutral position. To enable this adjustment to be made, one end connection 60 of the stabiliser is provided as a threaded shaft 62 engaging within a cooperating threaded end of the tube 34 and is lockable in position by a lock nut 64. It will of course be appreciated that either the outer end 66 of the shaft 36 may be connected to a link arm and the outer end 60 of the outer member to the tractor or vice versa.

A modified form of stabiliser in accordance with the invention is illustrated in Figure 4 wherein like reference numerals refer to like parts hereinbefore described. In this embodiment the outer member is provided as a single tube 33 radially inwardly deformed intermediate its ends to provide a fixed radially inwardly extending stop 39. This stop 39 is in lieu of the fixed stop 50 provided by the overlapped end of the tube 34 of the Figure 3 embodiment. Also in this Figure 4 embodiment, the thrust washer 44 is not provided and the adjacent end of the compression spring 38 bears directly upon the sleeve 42.

Also, as will be seen from Figure 4, the stop sleeve 52 is retained against movement axially outwardly of the tube 33 by a clamping ring 53. Otherwise the contracting and extending telescopic action of the stabiliser is identical with the action described with respect to the embodiment of Figure 3.

In Figure 4, provision is made for a wider range of adjustment of the overall length of the stabiliser by providing a further locking pin 70 engageable through aligned through bores provided in the outer tube 33 and an inner tube 72 slidably mounted therein at the outer end of the outer tube 33. As illustrated, a single through bore is provided in the inner tube 72 and two through bores are provided in the outer tube 33 whereby two selective positions are provided.

Furthermore, the end connection 60 of the outer tube 33 is provided as a threaded shaft engageable 62 within a threaded bushing 74 itself in screw threaded engagement within the inner tube 72. The bushing 74 is rotatable, upon release of a locknut 76, to enable fine axial adjustment of the overall length of the stabiliser to be accomplished whilst the stabiliser is in situ connected between a lower link arm and the tractor. The internal and external threads of the bushing 74 are preferably of different pitch and also preferably of opposite hand.

A still further embodiment of stabiliser in accordance with the invention is illustrated in Figure 5 wherein like reference numerals refer to like parts hereinbefore described. In this embodiment, the arrangement of radially inwardly and radially outwardly extending stops and thrust washers are substantially the same as those described with reference to Figure 3 and the contraction and extension telescopic action of the stabiliser is the same as that described in the Figure 3 embodiment.

However, in the Figure 5 embodiment, the locking means for locking the stabiliser in its neutral position comprises a pair of spring loaded arms 80, 82 mounted within a housing 84 carried on the outer tube 32 with each arm being selectively engageable within an annular groove 86 provided on the larger diameter part 54 of the shaft 36.

The locking arms 80, 82 are shown in more detail in Figures 6 and 7 from which it will be seen that each such arm is of arcuate form pivotally mounted at one end thereof within the housing 84 and being biased radially inwardly towards the annular grooves 86 in the shaft part 54 by means of compression springs 88 acting between the housing and the arms. A headed pin 90 extends outwardly of the housing 84 through the centre of each compression spring 88 and such pins act as indicators in order that the tractor operative can readily visually observe if the locking arms 80, 82 are in their locked or unlocked positions relative to the shaft 36.

Adjacent the pivotally mounted ends of the locking arms 80, 82 are provided respective cam surfaces engageable by cooperating surfaces 91, 92 on an operating lever 94 extending out of the housing 84. Such lever is conveniently attached by means of a cable 96 or the like (shown diagrammatically in Figure 1) whereby the locking and unlocking action of the stabiliser when in its neutral position may be actuated remotely by the tractor operative from his driving seat by altering the length of the cable. Alternatively, the locking and unlocking action may be actuated automatically upon lowering or raising the arms 16, 18 by the hydraulically powered lever 21; a fixed length of chain 97 or the like (see Figure 1) being connected between the lever 94 and the tractor.

Also in this Figure 5 embodiment the overall length of the stabiliser may be adjusted in a manner similar to that described with reference to the Figure 3 embodiment wherein one end connection 66 is provided on a threaded shaft 67 which, in the Figure 5 embodiment, is in threaded engagement with a bore in the interior of the shaft part 54.

It will be appreciated from the foregoing description that, in all of the alternative embodiments, the compression spring 38 is maintained under compression even in the neutral position of the inner and outer members relative to one another. Thus even small displacements of the inner and outer members relative to one another in either contraction or extension of the stabiliser will create high return loads imparted by the compression spring 38.

In order to protect the stabiliser against po tential damage which may be caused by excessive contractive or extensive forces applied thereto, damping means are associated with the stabiliser which may be of the form shown in Figure 8.

Referring to Figure 8, a set of deformable metal elements 100 e.g. Belville washers are provided about the inner shaft 36 at each end of the compression spring 38 and a stop collar 102 is loosely mounted about the shaft 36. Upon excessive displacement of the inner member relative to the outer member, this collar 102 will.therefore abut against the Belville washers and progressively compress them to effect the aforesaid damping action.

Alternatively, or in addition to the provision of Belville washers, the damping action may be usefully effected by the pneumatic piston and cylinder effect which occurs in use during reciprocation of the inner member and outer members relative to one another.

Claims

1. A lateral stabiliser for a lower link arm of a three-point implement attachment linkage of an agricultural tractor, said stabiliser being connectable between a said lower link arm and the tractor and comprising two members telescopically assembled together, the outer ends of said members being connectable respectively to a said lower link arm and to the tractor, the inner ends of said members being telescopically slidable one within the other; a coil compression spring being arranged at the inner end of said members around the inner one of said members and within the outer one of said members, said spring abutting at its ends against stops associated with said inner and outer members to bias said members to a neutral position relative to one another with the spring in compression in said neutral position, the spring being placed under further compression upon either inward or outward movement of said members relative to one another.

2. A stabiliser as claimed in Claim 1 wherein said stops comprise a pair of stops extending radially outwardly of the inner one of said members between which the spring is maintained in its compressed condition and a pair of stops extending radially inwardly of the outer one of said members each engageable respectively by one of said stops on the inner member.

3. A stabiliser as claimed in Claim 2 wherein each of said radially outwardly extending stops on the inner member is so engageable with one of said radially inwardly extending stops on the outer member as to support the inner member coaxially within the outer member.

4. A stabiliser as claimed in either one of Claims 2 or 3 wherein a thrust washer is mounted on the inner member at each end of the compression spring between the ends of said spring and the respective radially outwardly extending stops.

5. A stabiliser as claimed in either one of Claims 3 or 4 wherein one of said radially outwardly extending stops on the inner member comprises a fixed stop on the inner member and a sleeve on the inner member abuttable against said fixed stop, said sleeve supporting the inner member coaxially within the outer member; the inner member being slidable inwardly of the outer member through said sleeve against the bias of the compression spring with the sleeve engaged with a said one of the radially inwardly extending stops on the outer member.

6. A stabiliser as claimed in Claim 5 wherein the other of said radially outwardly extending stops on the inner member comprises a fixed stop thereon.

7. A stabiliser as claimed in any one of Claims 3 to 6 wherein the radially inwardly extending stops on the outer member comprise fixed stops thereon.

8. A stabiliser as claimed in any one of the preceding claims wherein means are provided within the outer member for damping the rate of movement of the inner and outer members relative to one another.

9. A stabiliser as claimed in Claim 8 wherein said damping means comprises a deformable element mounted about the inner member and located between a collar of the inner member and a radially inwardly extending stop on the outer member.

10. A stabiliser as claimed in Claim 8 wherein said damping means is provided by the pneumatic piston and cylinder effect between the inner and outer members upon relative movement therebetween.

11. A stabiliser as claimed in any one of the preceding claims wherein selectively engageable securing means are provided thereon for selectively preventing or permitting relative movement between the inner and outer members, such relative movement being preventable by said securing means when the inner and outer members are in their said neutral position.

12. A stabiliser as claimed in Claim 11 wherein said securing means comprises a pin selectively insertable through aligned bores extending transversely of the inner and outer members.

13. A stabiliser as claimed in Claim 11 wherein said securing means comprises spring biased arms mounted on the outer member selectively engageable with an on the inner member. ^

14. A lateral stabiliser for a lower link arm of a 3 point implement attachment linkage of an agricultural tractor constructed and arranged substantially as hereinbefore described with reference to any one of the accompanying drawings.