Patent GB-747674-A (GB)
Title: Improvements in or relating to tractor-implement combinations
Inventor: HULL CHARLES HARTLEY
IPC: A01B63/114
Filed: 1953-05-26
Abstract: 747,674. Tractor power lift mechanisms. BROWN TRACTORS (ENGINEERING), Ltd., D. May 25, 1954 [May 26, 1953], No. 14553/53. Classes 79 (1) and 79 (3). In a tractor hydraulic power lift mechanism d having a ram h<SP>1</SP> in a cylinder h supplied by a continuously-discharging pump f, means are provided whereby, when an implement e connected to the tractor a is in its desired soil-working position, liquid from the pump f can be applied to the ram h<SP>1</SP> so that the implement e is not lifted but the downward force on the tractor rear wheels is increased. As shown in Fig. 4, the tractor a has a weight of 3000 units and the implement e 600 units, and the invention aims at achieving ground thrusts of 733, 2667 and 200 units at the front and rear wheels of the tractor and at the implement, respectively, with the object of increasing the tractive effort of the tractor by transferring part of the implement weight to the traction wheels. In the arrangement shown in Fig. 5 a conduit f <SP>1</SP> having a non-return valve g connects the pump f to the cylinder h and the ram h<SP>1</SP> is connected by linkage i, j to an implement-carrying lower link k. The conduit f has connections f<SP>2</SP>, f<SP>3</SP>, f<SP>5</SP> to a by-pass valve m, a drop valve p and a weight transfer valve r respectively, the connection f<SP>3</SP> including a restriction f<SP>4</SP> and the valves being spring closed. The valves are linked to a control lever n and control return flow of liquid to the source for the pump f. In the position shown in Fig. 5 the valves are closed and the implement is raised; with the lever n in position n<SP>1</SP> the valve m is opened connecting the pump delivery to source whereby the implement is maintained raised; with the lever n in position n<SP>2</SP> the valve p is opened allowing liquid on the cylinder side of the non-return valve to return to source where by the implement is lowered; on the loss of requisite adhesion of the tractor wheels the lever n is moved from position n<SP>2</SP> to position n<SP>3</SP> determined by an adjustable stop n<SP>4</SP> and the valves m, p remain spring closed, but the valve r can be opened by hydraulic pressure against the action of the valve spring r<SP>5</SP> which is determinably weaker than the spring m<SP>4</SP> holding the valve m closed. In another arrangement, Fig. 6, the valves m, p are as in the previous arrangement and are controlled by lever n, and the valve r, which is associated with a valve member r<SP>11</SP> controlled by an adjustable spring r<SP>13</SP>, can be opened against the action of a spring r<SP>e</SP> through linkage s<SP>2</SP>, s<SP>3</SP> by a hand lever s carrying a link s<SP>1</SP> having a pin and slot connection with lever n. In a further arrangement, Fig. 7, liquid from the pump enters a valve bore t<SP>1</SP> through conduit f<SP>1</SP>, the bore having a return port t<SP>9</SP> and ports t<SP>5</SP>, t<SP>6</SP> leading to the hydraulic cylinder, and the port t<SP>5</SP> being associated with the non-return valve m. The bore t<SP>1</SP> houses a valve member t carrying a spring-urged piston v and operated through a linkage n<SP>7</SP> by lever n.