GB1253411A - Regulating devices for hydraulic power lifts of tractors - Google Patents

Abstract

1,253,411. Tractor power lift. KLOCKNERHUMBOLDT-DEUTZ A.G. 9 Jan., 1969 [9 Jan., 1968], No. 1299/69. Heading A1P. A regulating device for the hydraulic power lift of a tractor comprises a ganging spring 24 for sensing the working resistance of a semimounted plough, a valve spool 28 being moved by the linkage 27 via an intermediate lever 18 pivoted to the cylinder 5 at 17 and to an increment lever 20 at 19. Under an increase of working resistance the increment lever 20 is turned anti-clockwise which moves the spool valve towards the "lift" position whereupon the pump 29 delivers hydraulic fluid under pressure through the non-return valve 35 to the ram 34. The lift shaft 1 and lift arms 2 are rotated anticlockwise which, through the cam 3, moves the piston 6 to the right-hand side whereupon hydraulic fluid is forced through the conduit 14 and throttle 15 from one side of the cylinder to the other. Under a sudden increase in working resistance. The valve 28 is moved into the "lift" position and the resulting fast operation of the lift arms moves the piston 6 quickly and as hydraulic fluid cannot flow sufficiently quickly through the throttle 15 the cylinder 5 moves, tensioning the compression spring 11. The pivot 17 is thus moved to the right and via the levers 18, 26 and the linkage 27 the valve spool is thrown into "neutral". The spring 11 then forces the cylinder back to its original position. If during this time the working resistance has not been reduced the pivot 19 will be shifted towards the left hand side (compared with Fig. 1) and thus the return motion of the pivot 17, i.e. the anticlockwise rotation of the lever 18 causes the valve spool to be moved to the "lift" position. The process described above thus repeats itself until the working resistance reaches the desired value. Under a sudden reduction of working resistance the valve spool is moved to the "lower" position and the corresponding but reverse process to that described above occurs, i.e. the lift shaft 1 and lift arm 2 is intermittently lowered until the required working resistance is regained. Under gradual changes in working resistance the pump supplies fluid to the ram slowly and the piston 6 moves slowly in the cylinder 5 which remains in the position shown in Fig. 1 as fluid can flow sufficiently quickly through the throttle 15. The motion of the lift arms 2 is thus continuous.