GB2076624A - Improvements in towbar linkages primarily for towing agricultural implements - Google Patents

Abstract

A towbar linkage for towing a pair of large, heavy, agricultural implements such as ballast rollers consists of leading (14) and trailing (16) towbar sections one end of each of which is articulated about a generally upright axis to a static intermediate section (18) adapted to be rigidly secured to the frame of the front implement at or near one side thereof. The free end of each of the leading and trailing sections has an appropriate coupling of conventional design for connection to the tractor hitch or to the normal towbar of the rear implement respectively. Each of the leading and trailing sections is locked in either of two alternative working positions by a strut pivoted thereto at one end and anchored to the frame of the front implement by a removable cotter. In the transport position, the two implements are aligned with the tractor in tandem; in the working position the front implement is offset from the tractor to one side by half its width and the rear implement is offset to the other side by half its width, the change-over being effected without the necessity of unhitching and manhandling either implement. <IMAGE>

Description

SPECIFICATION Improvements in towbar linkages primarily for towing agricultural implements This invention relates to towbar linkages for towing two units of mobile equipment. It is primarily designed for towing agricultural implements such as, for example, rollers or seed drills. Such implements (which term will be used hereinafter for convenience to define any mobile toward unit) are frequently of a width measured at right angles to the direction of towing which is the maximum permissible for passage through gateways or other access openings, or on the public highway. Yet such width is often narrow in the context of economic working in a field. For example, when rolling a field, the number of traverses by the tractor can be halved if the overall effective roller width is doubled. Hitherto, however, it has not been possible to tow two 8-ft.

rollers abreast or in echelon, the latter formation effectively simulating the abreast formation in terms of performance on the ground. It has been possible to tow an 8-ft. roller followed by two 4-ft.

rollers, one on either side of the 8-ft. roller in echelon, by hitching each small roller to the end of a respective one of a pair of booms pivotally mounted on the back transverse member of the 8-ft. roller frame and adapted to be swung laterally outwards so as to project beyond the adjacent end of the roller by 2 feet, and to be locked in this position. For transport of the implements to or from the field, the booms are swung inboard so that the two 4-ft. rollers follow as a pair abreast in tandem behind the 8-ft. roller.

This arrangement has two main drawbacks.

First, in order to change from the transport to the working formation, it is necessary to unhitch each of the small rollers, extend the booms, manoeuvre each small roller individually into a position in which its towbar registers with the towbar hitch at the free end of the respective boom, and recouple the small roller. Even on a relatively hard, level smooth field, it is very difficult for one man to manhandle a 4-ft. roller. This means that usually the two small rollers must be separately towed into position by the tractor, and this calls for considerable skill and takes a relatively long time.

The reverse operation, after the field has been rolled, also requires skill in lining up all three rollers and hitching them together for transport.

Secondly, a singte 4-ft. roller weighs more than half the weight of an 8-ft. roller so that rolling of the field is uneven.

Similarly, in respect of other implements such as seed drills, there are problems of repositioning a pair of implements between a "line astern" or tandem transport formation and a working echelon formation. For the purposes of the present specification, the echelon formation is one in which the rear implement is displaced from its transport position by substantially its own width.

When the implements are being towed in the tandem transport formation, the pull of the tractor is exerted through the centre of gravity of each implement, whose towbar is located accordingly.

This ensures accurate following by each implement of the path of the tractor without yawing. But when the implements are in their working echelon formation, the pull of the tractor must be exerted along a median axis between the normal towing axes of the individual implements, this median axis passing through the effective centre of gravity of the two implements regarded as a unitary system. For practical purposes, the median axis can be regarded as lying mid-way between the individual normal towing axes of the separate implements.

In order that a common towbar linkage can achieve the transition between the transport tandem formation and the working echelon formation, the point of coupling of the front implement to the tractor hitch must be displaced sideways by substantially half the width of the implement, and the point of coupling of the rear implement to the front implement hitch must be displaced sideways in the same direction by substantially the full width of the rear implement.

The present invention aims at meeting this requirement in a simple and effective way requiring a minimum of time and physical effort by an operator such as a tractor driver.

According to the present invention, a towbar linkage for towing a plurality of implements in alternative formations has a leading and a trailing movable towbar section articulated at their adjacent ends to each other or to a common intermediate section. The point or points of articulation is or are adapted to be fixed to the frame of the front implement at or near one side thereof and permit angular displacement of the respective movable sections in a generaliy horizontal plane.Means is provided for selectively locking each movable section in either a transport position in which its free end, which carries the appropriate towing hitch coupling component, is substantially coincident with the normal towing axis of the front implement or a working position in which the free end of the leading section is coincident with the median axis and the free end of the trailing section is located substantially the same distance on the other side of the median axis as it is on the one side thereof when in its transport position.

Preferably, the means for locking a movable towbar section in position consists of a strut pivotally attached at one end to the section and engageable with a releasable locking device adapted to be mounted on the frame of the front implement.

A practical embodiment of the present invention will now be described, purely by way of illustration thereof, with reference to the accompanying drawings in which: Figure 1 is a plan view of two agricultural rollers coupled in tandem formation for transport by a towbar linkage according to the invention; Figure 2 is a plan view similar to Figure 1 of the rollers coupled by the linkage in echelon formation for working; Figures 3-5 are line diagrams of the towbar linkage of Figures 1 and 2 in three successive positions from the transport position (Figure 3) to the working position (Figure 5); and Figure 6 is a side elevation of the front roller and towbar linkage.

Referring first to Figures 1 and 2, a towbar linkage according to the invention for towing two agricultural rollers 10, 12 in alternative transport (Figure 1) and working (Figure 2) formations consists of a leading movable towbar section 14 and a trailing movable towbar section 1 6. Each movable towbar section 14, 1 6 is articulated, as described below, to a common intermediate static section 18 in such a way that it can be angularly displaced in a generally horizontal plane between transport and working positions.Each roller 10, 12 has its own normal towbar 20, 22 respectively which is permanently fixed to the associated roller frame 11, 1 3, and the intermediate static towbar section 1 8 is adapted to be bolted or welded to one side of the frame 11.

The design of the section 1 8 is tailored to suit the particular design characteristics of the particular implement to whose frame it is to be attached. As seen in Figure 6, the intermediate static section 18 is carried on pillars 19 to clear the rim of the roller 10. When a different implement is being towed, the section 1 8 may be differently designed.

It is also (geometrically) possible to dispense with the section 1 8 altogether if the design of the towed implement allows for the articulation points 24, 26 at each end of the section to be coalesced.

Each end of the intermediate static section carries, as noted above, upright pivot bolts or the like 24, 26 about which the movable leading and trailing sections 14, 1 6 can be swung laterally as required. The movable towbar sections 14, 1 6 are of specific lengths which are related to the operating functions of the implements 10, 12. In the case of the rollers 10, 12, when working on a field it is desirable that in straight-ahead travel there should be a slight overlap of the paths traversed by them, as indicated at win Figure 2.

On the other hand, if the rollers are substituted by, say, seed drills, no such overlap is desirable. In fact, a positive gap equal to the pitch of the drills is necessary to avoid duplication of seeding. Thus, in displacing the rear implement laterally from the transport tandem formation (Figure 1) to the working echelon formation (Figure 2), the magnitude of such lateral displacement is dependent on the functions of the machine, and the minimum iength of the movable towbars 14, 1 6 will depend on the towed implements, and on the location of the intermediate fixed section 18.

In Figures 1 and 2, this location is inboard of the left-hand end of the drum of the front roller 10 by 2 W. For zero overlap, it would preferably be immediately above the left-hand end of the drum of the roller 10, while for a positive gap is would preferably be half the gap beyond the left-hand end of the drum of the roller. Such an arrangement simplifies the design of the linkage insofar as the median axis M-M in the working formation (Figure 2) coincides with the axis of the fixed section 1 8 through the points of articulation 24, 26 of the leading and trailing sections 14, 1 6, respectively.Such an arrangement also means that the leading section 14 is coaxial with the median axis M-M in the working position while the trailing section 16 has a length equal to the distance between the normal towing axis T-T through the towbar 20 and the axis of the fixed section 18, both as shown in Figure 2.

However, it is to be understood that the section 18 can be laterally located in any one of a range of positions relative to the front implement without detriment to the choice of magnitude of lateral displacements of the rear implement. For example, if the axis of the section 1 8 through the articulation points 24, 26 is at the left-hand end of the frame 1 the trailing towbar section 1 6 will be longer so that its free end 1 7 can lie on the normal towing axis T-T of the towbar 20 in the transport formation. In the working formation, however, it will be locked at an angle other than 900 to the axis of the fixed section 1 8 through the articulation points 24, 26 so that its free end can engage the normal towbar 22 of the rear implement in the same position.Similarly, the leading towbar section 14 will be locked at such angle to the axis of the fixed section 1 8 that its free end 1 5 lies on the median axis M-M in the working formation.

Each movable towbar section 14, 1 6 is locked in the required position by a strut 28, 30 respectively. One end of each strut is pivotally connected to the respective towbar section at 29, 31 , while the other end is engageable with the frame 11 (or a part which is rigid therewith) by a selective locking element. Thus, the leading strut 28 slides in a sleeve or muff 32 (from which it is rendered non-releasable by a stop 27) pivotally mounted on the normal towbar 20, both the sleeve 32 and the strut 28 being drilied to receive a conventional cotter pin 34 when either of the holes 36, 38 in the strut register with the coaxial holes in the sleeve 32.The other end of the trailing section strut 30 is normally permanently slidably engaged in a longitudinal channel in the intermediate fixed section 18, and is similarly lockable to the fixed section 1 8 by a cotter pin 40 which, when as shown the trailing towbar section 1 6 must be swung through 1 800 between the transport and working positions, enters the same hole in the fixed section 1 8 in both locking positions.

The operation of the linkage can best be followed by reference to Figures 3-5 of the drawings. In all Figures, the normal towing axis of the front implement is shown at T-T and the median axis at M-M. The leading and trailing towbar sections 14, 1 6 are moved independently but in harmony - i.e. there is no automatic connection between the two which ensures that both move in synchronism; but both must be moved to their other positions -- to working (Figure 5) from transport (Figure 3) and vice versa - in the same operation.In Figure 3, the leading section 14 is inclined to the normal towing axis T-T at an angle which places the free end 1 5 on the axis just ahead of the mounting 21 on the normal towbar 20 for the towing hitch component (not shown). The trailing section 1 6 is swung inboard to lie close against the rear member of the front roller frame 11 so that its free end 17 also lies on the towing axis T--T. Both free ends 1 5, 1 7 of the respective movable sections 14, 1 6 are defined by the appropriate towing hitch elements for connection, respectively, to the tractor and the rear implement towbar 22 respectively. The leading section 14 is locked by engagement of the cotter pin 34 in the registering hole 38 in the strut 28 and those in the muff 32.

The leading towbar section thus offers a triangulated linkage for transmission of the tractor pull to the front implement. Similarly, the trailing towbar section 1 6 is locked in position by the strut 30 and the cotter pin 40 to present a second triangulated linkage for transmission of the tractor pull to the rear implement..

On arrival at the site to be treated by the implements 10, 1 2, the driver stops the tractor and pulls out both cotter pins 34, 40. He then drives forward, preferably on a left steering lock.

This causes both the leading and trailing towbar sections 14, 1 6 to swing about their respective articulation points 24, 26 towards the mutually aligned position shown in Figure 4, the two implements 1 0, 12 slewing relative to the tractor and each other until at least the leading section 14 achieves its working position as shown in Figure 4. The driver stops again and inserts the cotter pin 34 through the muff 32 and the hole 36 in the strut 28. A new pattern of leading triangulated towing linkage 14, 28 is now established.

The driver again moves forward far enough to ensure that the trailing towbar section 1 5 swings beyond its position of mutual alignment in Figure 4, and when a sufficient angle between the section 1 6 and the common axis of the leading and intermediate sections 14, 1 8 (coincident with the median axis M-M for the linkage illustrated) has been achieved, he reverses (on opposite steering lock) until the trailing section 1 6 reaches its working position shown in Figure 5. At this point, the strut 30 has moved "over-centre" (Figure 4) - where the sliding captive end which receives the cotter pin 40 travels as far as the articulation point 26 - and then slid back to its starting position (Figure 3).The cotter pin 40 is reinserted and the implements 10, 12 are now locked in the working echelon formation.

To resume the transport tandem formation, the above sequence of operations is reversed, and the linkage relocked in the positions shown in Figure 3. Throughout the changes from one formation to another, no manual effort has been involved in repositioning the implements nor in the precise alignment of coacting hitch components since the couplings at 1 5, 1 7 are not released at any stage. The invention thus provides a system which facilitates rapid and effortless handling of heavy or bulky implements which are required to travel in either a transport or a working formation.

It will be understood that certain detail modifications are possible to the linkage which is described above and illustrated as one practical example. Thus, in the transport formation, a supplementary lock may be provided to anchor the coupling 17 directly to the frame 11. It is also possible to make provision for a third implement to be towed by duplicating the towbar section 1 6 and strut 30 on the frame 13 of the implement 12, and at the same time making provision for the leading towbar section 14 to swing about its pivot 24 through the same angle to the left of the axis M-M as the angle between them in the transport formation. Suitable modification of the strut assembly 28... 32 will, of course, be required.

Other forms of locking arrangement for the struts 28, 30 may be adopted if preferred.

Claims (6)

1. A towbar linkage for towing two implements in alternative formations comprising leading and trailing towbar sections articulated together or to a common static intermediate section for angular displacement in a generally horizontal plane, the point or points or articulation being adapted to be fixed to the frame of the front implement at or near one side thereof, and means for selectively locking each movable towbar section either in a transport towing position, in which its free end lies substantially on the normal towing axis of the front implement, or in a working position in which the leading towbar section lies along a median towing axis between the normal towing axes of the implements when in echelon formation and the free end of the trailing towbar section lies at the same distance from the median axis on the side thereof opposite to its transport position.

2. A towing linkage according to claim 1 wherein the means for locking each of the leading and trailing sections in their alternative operative positions comprises a rigid strut pivotally connected at one end to the respective towbar section and at the other end engageable with a releasable locking device adapted to be mounted on the frame of the first towed implement.

3. A towbar linkage according to claim 2 wherein each releasable locking device includes a cotter pin which can be withdrawn to free the respective strut for displacement of the associated towbar section and is replaceable when the section is in its next alternative position.

4. A towbar linkage according to claim 2 or 3 wherein the points at which the strut of the trailing towbar section is locked to the frame of the front implement are coincident for both working positions.

5. A towbar linkage according to claim 4 wherein the means for detachably anchoring the strut of the trailing section to the central section comprises a member adapted to slide lengthwise of the central section and be selectively locked in either of the two working positions of the trailing towbar section.

6. A towbar linkage substantially as hereinbefore described with reference to the accompanying drawings.