GB879790A - Improvements in or relating to hydraulic valves - Google Patents

Abstract

879,790. Tractor power lift mechanisms. FORD MOTOR CO. Ltd. Aug. 2, 1960 [Aug. 13, 1959], No. 26681/60. Class 79(1). A tractor has a pair of double acting hydraulic cylinders connected respectively to left and right hand implement sections controlled by a handle which has movement in two angularly disposed paths; movement in one path operating a remote cylinder control valve and movement in the other, preferably orthogonal path, operating a distributer or selector valve. As shown in Fig. 1 right hand cylinder 19 operates right hand :implement section 20 through a link-work and is controlled by hydraulic lines from control valve 15 and selector valve 16. These valves are bolted as a unit to a cover of the tractor centre housing, preferably connected to hydraulic pressure and return lines in the housing by bolts 35 having internal passages. A valve operating lever 62 (Figs. 4 and 5) is pivoted on a horizontal pin 77 to lever 66 which pivots on a vertical spindle 67 in a 'bearing member 69 bolted to the tractor housing. Horizontal and vertical notches in the end of the lever 66 engage end 73 and pin 72 of a lever 64 which is pivoted at pin 65 and engages one enn of spool 40 of the cylinder control valve. This valve is preferably of the type which automatically returns to the neutral position when the piston has completed its stroke. Horizontal movement of the lever 62 controls the position of spool 40 and hence the control valve action and cylinder movement. A spherical ball 75 on lever 62 is received in a socket 79 of a lever 80 pivoted on pin 81 and engaging spool 46 of the distributer valve 16. Movement of spool 46 and hence the distributer valve action is controlled by vertical movement of lever 62. Figs. 7, 8, 9 (not shown) show diagrammatically the connections between the distributer valve and cylinders for the different modes of operation. To give more rapid operation of the cylinders they are arranged in series when operating together (Fig. 8) but, when raising the implement sections by supplying fluid from valve 16 to the left hand cylinder, because of the volume displaced by the piston rod, the left hand piston will complete its stroke before the other one has done so. To allow the second piston to finish its stroke a shuttle valve is fitted to the left hand piston which opens when a stem portion contacts the end of the cylinder allowing flow through the shuttle piston. The valve also operates when the implements are lowered. Specification 688,073 is referred to.