Patent GB-949677-A (GB)
Title: Auxiliary valve mechanism for the hydraulic systems of tractor power lifts
IPC: F15B13/08
Filed: 1960-05-23
Abstract: 949,677. Tractor power lifts. MASSEY-FERGUSON Inc. May 23, 1960 [May 21, 1959], No. 18046/60. Heading A1P. An auxiliary valve mechanism for a tractor power lift system incorporating laterally disposed lift arrangements and wherein the hydraulic system comprises a main ram, a fluid pump, a main valve regulating the supply of fluid to and from the main ram, is disposed in the supply conduit to the main ram and controls the flow of fluid to an auxiliary ram and to the main ram in conjunction with the main valve. There may be several auxiliary rams and a further auxiliary valve. As shown, the power lift system comprises a main cylinder A and auxiliary cylinders AA. The main cylinder actuates the three point linkage comprising upper arms 31 and lower arms 30 through lift arm 41 and crank 39. The auxiliary cylinders are disposed one on each side of the tractor and each acts upon parallel links 56, to which an implement frame 55 may be attached, through the piston rod, bell crank and tension links. The hydraulic system is supplied with fluid from a sump S by a pump P, the main cylinder being supplied under the control of a main valve V operated manually by lever 45 or through a weight transfer linkage whose effective length is adjustable by a lever 4A, through pipe 43 and passages 65, 66 and 67 in an auxiliary valve assembly. The auxiliary valve assembly for controlling the cylinders AA and the main ram A comprises two parallel bores 70a and 70b in the same horizontal plane and provided with spools 80a and 80b respectively. A second pair of bores 71a and 71b is disposed above the first pair and comprise the two portions L and R. (The suffices a apply to the unit seen in Fig. 3 and b to the other on numerals where the parts correspond, the arrangements being largely identical). The upper and lower bores are connected by the passages 112a and 114a which are always open and 113a which is controlled by a shuttle 108a. The chambers L and R are connected by a passage 100a controlled by a spring loaded valve 105a, the movement of which to the left is limited by an adjustable stop member 115a. The movement of shuttle 108a to the left is induced by fluid pressure in chamber R and by a projection 109a opens the valve 105a. The movements of the valve spools 81a and 81b are controlled by levers 90a and 90b, having spring loaded detents (90a) to give three positions for each lever. The valve assembly receives fluid from the pump via pipe 43 passage 63 and port 64. A discharge 62 to the sump is provided. Connections 102a, 102b and 104a and 104b lead to the auxiliary cylinders and are all used when the cylinders are double acting, under which circumstances the passage 113a is kept closed. For single acting cylinders the connections 104 are removed and the corresponding ports 103 closed by plugs. The non-return valve 105b may be bypassed by passages 117, 118 and 119 controlled by a needle valve 120 (Fig. 9) so that control of the left hand auxiliary cylinder may be transferred to the main valve V. The bores 80a and 80b have interconnecting passages as shown in Fig. 4 and annular chambers 74b, 75b and 77b are connected by a passage 126. The levers 97 are moved to the left (Fig. 3) for "raise" -the valve spool being shifted to the right. A reduced portion 135a, Fig. 11 of each spool is fitted with a sleeve 136a having a flange 137a against which bears a spring 84a. The spool has bores 141a and 142a controlled by a spring loaded ball 144a. When the spool is moved to the right, the spring 84a exerts a returning force counter-balanced by the spring loaded detent 89a. When the pressure of the fluid trips the valve 144a, fluid pressure assists the spring to return the spool to "neutral." To operate the auxiliary rams with the main rams locked, the main valve V is moved to the position "raise" by the lever 44, the manual control lever being moved to the lower end of the position control range. In the "neutral" position of the auxiliary valves, the pressure fluid flows through the passages and chambers 62, 125, 77b, 126, 127, 75a, 133 and 133 to the sump. Both auxiliary valves can be operated simultaneously except when the right hand unit is set for a single acting cylinder and the valve spool is shifted to the "lowering" position. A third valve unit of similar construction, the corresponding parts being numbered with the suffix c, Fig. 12, may be added to the auxiliary valve unit for controlling an additional cylinder, the added unit replacing the cover 131 in which is formed the passage 130. Various methods for operating one or more of the auxiliary cylinders and/or the main cylinder are described. To allow the auxiliary rams to be lowered simultaneously, each valve port 103a, 103b and 103c is formed with a conical seat at its inner end (Figs. 3 and 8). Interposed in each port is a thin flat disc 147a, b and c which has a small central hole and a notched edge to allow unrestricted fluid flow in one direction but upon reversal of the flow, the disc is forced against the fitting 104 and the flow is restricted to the central hole. Specification 839,689 is referred to.