Patent GB-536882-A (GB)
Title: Improvements in or relating to hitch means for connecting trailers to tractive vehicles
IPC: B60D1/14
Filed: 1939-11-25
Abstract: 536,882. Vehicle couplings ; tip-wagons. FERGUSON, H. G. Nov. 25, 1939, No. 30783. [Classes 103 (v) and 108 (i)] A coupling for connecting a two-wheeled trailer to a tractor vehicle comprises links connected to the rear of the tractor and so directed as to transfer part of the weight of the trailer on to the tractor forward of the actual connections of the links to the tractor. A tipping vehicle hydraulically operated from the tractor is described. An agricultural tractor is shown such as described in Specification 510,352, [Group XXXI], adapted for a three-link connection to an agricultural implement and comprising a pair of lower links 5 universally pivoted at 5a to the rear axle casing 1 and a bell-crank 6 pivoted at 6a to the casing and to a spring-urged rod 7 that controls the depth-regulating means of the implement. These means comprise a hydraulic ram adapted to raise and lower the links 5 through cranks 9 and links 10. For connecting a trailer, there is substituted for the upper link of the implement connection, a link 14 of adjustable length connected to a lever 18 pivoted to the lever 6 and bearing on the casing 1. The provision of the lever 18 relieves the rod 7 of thrust. The link 14 is universally jointed at 20 to a post 23 adjustable in length and secured to the trailer underframe 28. The links 5 are connected to a cross-bar 12 pivoted to the frame 28 by a vertical pin passing through one of the holes 12a. A pair of links 11 pivoted to the casing 1 and bar 12 prevent lateral swinging of the links. The link 14 is so arranged that its axis passes in front of but preferably close to the axis of the rear tractor wheels and so transfers the unbalanced trailer weight to the rear and front wheels, thus increasing the grip of the rear wheels and by counteracting the lifting effect on the front wheels due to the driving torque, improves the steering action. The links 5 which are preferably horizontal with the plane thereof passing below the rear axle and above the front axle, mainly transmit the tractive pull and are also under tension due to the unbalanced trailer weight. The inclination of the link 14 may be adjusted to vary the distribution of the trailer weight by adjusting the length of the link and of the post 23 and the trim of the trailer can be altered by adjustment of either of these members. The weight on the rear wheels may be increased, particularly to counteract the reduction of weight thereon when the tractor is reversed, by operating the implement lifting mechanism which produces an upward pull on the links 10 as described in Specification 510,352, [Group XXXI]. The trailer shown is a tip-wagon comprising a body 32 pivoted at 34 on the triangular underframe 28 and tipped by a three-part ram 40 having a T-head pivoted at 43 to the frame. The head 43 is connected by pipe 46 to the engine driven pump disposed in the casing 1, by which the implement depth regulating ram is operated. In a modification, Fig. 9, the links 5 converge to a point at or near the tractor front axle as described in Specification 320,084, [Class 103 (v)], and the cross-bar 12 is connected by pins 48 movable in slots 47 in a clevis 20a secured to the trailer. The centre of curvature of each slot is at the other pin when that pin is in engagement with the forward end of its slot. When the tractor is steered, the links 5 swing laterally to an extent limited by the check chains 49 and if the turn is sharper, the trailer can assume a greater angle with respect to the tractor by pivoting about one of the pins 48. In a further modification suitable for higher speed traction, for example, for connecting a caravan to an automobile, an upper link is arranged as previously described and a pair of horizontal links are arranged to converge to the centre of the tractor rear axle, when the vehicles are in alignment. All the links are universally pivoted to the vehicle and are shown directly connected to the trailer, the bar 22 and post 13 being dispensed with in this case. Lateral drag on the tractor steering wheels such as is exerted with the usual draw-bar connected at the rear of the rear axle is thus avoided. Specifications 470,069 and 470,087, [both in Group XXXI], also are referred to.