DRAWBAR COUPLER

Abstract: A drawbar coupler for work vehicle has a drawbar (10) with a removable stud (18) mounted on its end such that it can engage an implement hitch. A main bracket (20) is mounted on the drawbar between the stud (18) and the work vehicle. A lockable strap (16) pivoted on the main bracket is pivotal between an engaged position close to the top of the stud (18) and a disengaged position remote from the top of the stud to allow the implement hitch access to and from the stud. The strap is lockable in at least the engaged position by a locking pin (40). The stud and strap are interchangeable to allow the coupler to be used with other implement hitches.

Description: The present invention relates to couplers for use with pickup drawbars on work vehicles. Most farm, industrial and other work vehicles are provided with a drawbar for towing implements, trailers and the like. Such drawbars usually are able to swing somewhat from side to side and sometimes are longitudinally adjustable as well, e.g. as taught in US-A-3795415. Pickup drawbars which are vertically movable under power sometimes are provided where the implements to be towed are heavy anough that it is difficult to manually lift the implement tongue onto the drawbar. Such pickup drawbars may be straight, as taught in US-A-3791456 but often are provided with a hook end, as taught in US-A-3863955. Whatever the drawbar structure, some coupling mechanism must be provided to attach the implement to the drawbar. There is a wide variety of such mechanisms, the most common of which is a simple drop pin. With such a structure, either the drawbar is provided with two flanges which extend over a ring ended implement tongue or the implement tongue is provided with two flanges which extend over a flat drawbar. A pin then is dropped through holes in the drawbar and implement tongue, and held in place by a cotter pin or spring, as shown in US-A-4008905, or by some sort of horizontally pivotal plate, as shown in US-A-3794357. US-A-1145026 teaches a further alternative using a spring biased hook rather than a pin. With any of these constructions, excess clearance around the pin or hook allows some degree of movement or "slop" between the implement tongue and the drawbar. Sometimes, as when a PTO shaft is to be connected between a tractor and an implement, this slop must be avoided. A ball coupler of some form then typically is used. The most common ball couplers provide a ball on the drawbar and a mechanism on the implement tongue to hold the ball. Pivotal movement of the implement tongue around the ball still can occur, but longitudinal movement between the drawbar and the implement tongue is prevented. US-A-3827724, US-A-4008906 and US-A-4434996 provide examples of such ball hitches. In all three of these references, a clamp mechanism of some form is provided to hold the implement tongue on the ball. Alternatively, the implement tongue can be provided with a captured ball hitch, in which a ball is movably captured within a ring hitch. A hole is provided through the ball, and the hitch can be attached to a drawbar by putting a pin through the hole, as shown in U.S. Patent Specification US-A-4008905. Each of the aforementioned coupling techniques has certain disadvantages. Drop in pins and spring-biased hooks do not work well with a pickup drawbar since the implement tongue can simply slide off the drawbar before the pin or hook is dropped in place. A pre-mounted pin such as shown by US-A 4008905 overcomes this problem, but has the remaining problem that a high amount of stress is placed on the cotter pin if the angle between the work vehicle and the implement is such that the implement tongue is lifted upwards from the drawbar. Finally, the clamp mechanisms used with conventional ball couplers typically have a relatively high number of parts, increasing their complexity. U.S. Patent Specification US-A-4448439 describes a drawbar coupler in accordance with the introductory part of claim 1 in which the means for locking the strap in the engaged position comprise a nut screwed onto a threaded upper end of the stud. The present invention is characterized by the locking means comprising a pin rotatably mounted in the main bracket, the pin having a locking surface selectively engageable with at least one corresponding surface on the strap to hold the strap in at least the engaged position and allowing the strap to pivot when the locking surface is disengaged from the corresponding surface. In the preferred embodiment, a pin or stud is mounted at one end of the drawbar. A bracket is mounted on the drawbar between the stud and the vehicle, with a top strap pivotally mounted in the main bracket. The top strap can pivot between a position engaging the top of the stud and a position spaced away therefrom (preferably swung all the way back against the drawbar) so that an implement tongue can readily be placed on the stud. The strap can be locked into the closed position on top of the stud and preferably also into a fully open position. With this construction, the pickup drawbar can be raised under the implement tongue until the stud engages the implement hitch. Once fully engaged, the top strap can be closed over the top of the stud and locked in place, thereby preventing the implement tongue from rising off the stud. Preferably, the stud and top strap are interchangeable with other studs and top straps, so that the stud and top strap combination best for any particular implement can be provided. For similar reasons, the coupler preferably is provided on a longitudinally extendible drawbar. The top strap preferably is mounted in the bracket by a removable pivot pin. It is locked and unlocked by a rotatable pin which can selectively engage or disengage locking surfaces formed in the top strap. When in the locked position, a handle on the locking pin will hold the pivot pin in place, preventing removal thereof. The stud preferably extends through a hole in the drawbar and is held in place by a keyhole slot in a plate underneath the drawbar. The present invention will be described in greater detail with reference to the following figures, in which like reference numerals indicate like elements. Figure 1 is a perspective view of a first embodiment of the coupler according to the present invention connected to a ring hitch, Figure 2 is a cross section taken along line 2-2 of Figure 1 of the first embodiment in its closed position, Figure 3 is a cross section taken along line 2-2 of Figure 1 of the first embodiment in its open position, Figure 4 is a bottom plan view of the first embodiment in its locked position, Figure 5 is a view analogous to Figure 2 for an alternative embodiment of the coupler according to the present invention. Referring to Figure 1, a drawbar 10 of a tractor or other work vehicle has a coupler 12 mounted thereon. A ring hitch 14 of an implement, not shown, is connected thereto. A top strap 16 holds the ring hitch 14 on a stud 18 of the coupler 12. The top strap 16 is pivotally mounted in a main bracket 20 mounted to the drawbar 10. The top strap 16 can be locked and unlocked by movement of the handle 22. Referring to Figs. 2 and 3, in which the implement hitch has been omitted for clarity, it can be seen that the main bracket is mounted to the tractor drawbar 10 by bolts 24, 26 and nuts 28, 30. Top strap 16 is pivotally mounted in the main bracket by a removable pivot pin 32. A hole 34 is provided in top strap 16 to receive the top end of stud 18 when the top strap 16 is in its closed position, shown in Fig. 2. The top strap 16 further is provided with locking depressions 36, 38 which selectively interact with locking pin 40 to hold the top strap in either its fully closed or its fully open position, as shown in Figs. 2 and 3, respectively. Locking pin 40 is substantially crescent shaped, at least over the portion thereof adjacent to the top strap 16. Locking pin 40 is connected to and rotatable by handle 22. When the locking pin 40 and handle 22 are in the position shown in Fig. 2, with the outer surface of locking pin 40 engaged with one of the locking depressions 36, 38, the top strap 16 is prevented from pivoting. When the locking pin 40 and handle 22 are rotated to the position shown in Fig. 3, i.e., so that the concave portion of crescent shaped locking pin 40 is facing the top strap 16, the top strap 16 can pivot. Thus, rotation of the handle 22 and locking pin 40 selectively locks the top strap in its fully closed or fully opened positions, or allows rotation thereof. If desired, it would be possible to add additional locking depressions to the surface of the top strap 16 to hold it in any other position. In addition, a device such as pin 41 (best seen in Fig. 1) preferably is provided to prevent the handle 22 from moving past the unlocked position. As best seen in Figs. 1 and 4, pivot pin 32 is provided with a flange 33 at the end thereof on the side of the handle 22. When the handle 22 is in the locked position, the flange 33 will prevent removal of the pivot pin 32. A locking bracket 42 is provided to frictionally hold the handle 22 in its locked position. Referring again to Figs. 2 and 3, the stud 18 extends through a hole 44 formed in the tractor drawbar 10. The stud has a groove 46 formed in the base thereof which interacts with a keyhole slot 48 (best seen in Fig. 4) in bottom plate 50 to hold the stud in place. The bottom plate 50 in turn is held in place by the rearmost bolt and nut 24, 28 mounting the main bracket 20. The spacings between the drawbar 10, ring hitch 14, top strap 16 and stud 18 in this first embodiment are designed to provide a substantial amount of clearance therebetween, so that sufficient play between the drawbar and ring hitch will be allowed. Such clearances are undesirable in some instances, for example, with a captured ball hitch. Fig. 5 illustrates a second embodiment of the present invention using a different stud 18′ and different top strap 16′ sized to hold a captured ball hitch 14′. These new elements 16′, 18′ are substituted easily for the prior elements 16, 18, while leaving all the other elements intact. In particular, to substitute the top strap 16′, the handle 22 is rotated to the unlocked position, the pin 32 removed, the top strap 16 removed and replaced with the top strap 16′, and the pin 32 replaced. To replace the stud 18, the bolt and nut 24, 28 are removed, the plate 50 slid to allow removal of the stud 18 through the keyhole slot 48 and hole 44 in the drawbar 10, new stud 18′ is substituted therefor, the plate 50 is slid back and the bolt and nut 24, 28 replaced. The thus modified coupler is designed to provide minimal clearance between the drawbar 10, captured ball hitch 14′, top strap 16′ and stud 18′. As is readily apparent, other top strap and stud combinations can easily be provided for other hitch sizes and types, with the result that the coupler according to the present invention is readily and easily modifiable for use with a large variety of implement hitches. Various modifications to the embodiments described would readily be apparent to one of ordinary skill in the art. For example, alternative locking mechanisms for the top strap and alternative mechanisms for holding the stud in the drawbar could be provided. In addition, while it has been indicated that the coupler is best used on a longitudinally extendible pickup drawbar, it could be used even on a fixed, non-extendible drawbar. Further, the locking pin could be D-shaped rather than crescent shaped. Accordingly, while the present invention has been described with reference to particular embodiments, it is not intended to be limited thereby, but only by the following claims.

Claims: 1. A drawbar coupler for a work vehicle comprising, a drawbar (10) mounted on the work vehicle, a stud (18) mounted on the drawbar, a main bracket (20) mounted on the drawbar (10) between the work vehicle and the stud (18), a strap (16) pivotally coupled to the main bracket (20), the strap being pivotal between an engaged position in close proximity to an end portion of the stud (18) and a disengaged position remote from the said end of the stud, and means (40) for selectively locking the strap in the engaged position, characterized by the locking means comprising a pin (40) rotatably mounted in the main bracket (20), the pin having a locking surface selectively engageable with at least one corresponding surface (36, 38) on the strap (16) to hold the strap in at least the engaged position and allowing the strap to pivot when the locking surface is disengaged from the corresponding surface (36, 38). 2. A coupler according to claim 1, characterized in that at least a portion of the pin (40) is substantially crescent shaped in cross-section, a convex surface of said crescent serving as said locking surface. 3. A coupler according to claim 2, characterized in that the corresponding surfaces (36, 38) comprise at least one depression formed in an outer surface of the strap (16), the depressions substantially matching the convex surface of the crescent shaped portion of the pin (40). 4. A coupler according to claim 2, characterized in that a concave surface of the crescent shaped portion of the pin (40) will not engage the strap (16) when the concave surface is adjacent to the strap, thereby allowing the strap to pivot. 5. A coupler according to claim 1, characterized in that the locking surface is selectively engaged with and disengaged from the corresponding surfaces (36, 38) by rotating the pin (40). 6. A coupler according to claim 1, characterized by a handle (22) attached to the pin (40) for rotating the pin, and a handle bracket (42) mounted to the main bracket (20) releasably holding the handle (22) in a position such that the locking surface of the pin (40) is engaged with one of the corresponding surfaces (36, 38) of the strap (16). 7. A coupler according to claim 6, characterized in that the strap (16) is removably mounted to the main bracket (20) by a removable pivot pin (32), the handle (22) being engageable with the pivot pin to prevent removal of the pivot pin (32) from the main bracket (20) when the handle (22) is held in the handle bracket (42). 8. A coupler according to any of claims 1 to 6, characterized in that the strap (16) is removably mounted on the main bracket (20) and the stud (18) is removably mounted on the drawbar (10). 9. A coupler according to claim 8, characterized by a hole (44) formed in an end of the drawbar in which the stud (18) is removably mounted, and a plate (50) removably mounted on the drawbar and having a keyhole slot (48) for releasably holding the stud (18) in the hole (44). 10. A coupler according to claim 8, characterized by a second strap and a second stud selectively mountable to the drawbar (10) in place of the first strap and the first stud, the first strap and the first stud being suitably sized to couple with a first type of hitch and the second strap and the second stud being suitably sized to couple with a second type of hitch. 11. A coupler according to any of claims 1 to 10, characterized in that the drawbar (10) is a pickup drawbar selectively extendible to a plurality of distances from the work vehicle. 12. A coupler according to any of claims 1 to 11, characterized in that the strap (16) has a hole (34) formed therein near an end thereof, the stud (18) being received by the hole when the strap is in the engaged position. 13. A coupler according to any of claims 1 to 12, characterized in that the strap (16) rests substantially parallel to the drawbar (10) between the main bracket (20) and the drawbar when the strap is locked in the disengaged position.

Inventors: JACOBSON, EARL CARL, MYERS, THOMAS WILMER
Applicants: DEERE & COMPANY
Application year: 1988
Main classification: B60D1
IPC codes: B60D1