GB1225112A - - Google Patents

Abstract

1,225,112. Hydrostatic transmissions. DOWTY HYDRAULIC UNITS Ltd. 17 July, 1968 [21 July, 1967], No. 33693/67. Heading F2C. A hydrostatic power transmission has a swash plate pump with a block 21 and a tilting plate 31 which drives a tilting head motor 55. The pump block 21 is driven from a flywheel 3, shafts 4, 5 and gear-wheels 8, 11, whilst a power take-off shaft 19, housed within a shaft 13 splined to the pump block, is driven by gears 9, 12. The swash plate 31 is supported in semicylindrical trunnions 32 and is tilted by a servo piston and cylinder 33, 34. Hydraulic fluid passes to the motor through a valve plate 39 and a pair of passages of which only 44 is shown. The motor comprises a drive shaft and flange 52, 54 and a tilting head 55 which is slidable on arcuate lands 48. A universal joint 79 connects the cylinder block 66 to the drive shaft for rotation therewith. The head is tilted by a servo piston and cylinder 92, 93 and bell-crank linkages. Control is by manually operated levers and valves which supply either high or low pressure fluid to the servo cylinders. Fig. 6 shows a second embodiment in which the pistons of the motor are attached to the drive flange 54 by slippers 115 and ball joints 61. The pistons 64 substantially enclose the rods 62 thereby restricting the articulation thereof. The block is located on the flange 54 by a ball-and-socket 118, 119. The swash plate may be rotated rather than the cylinder block of the pump in both embodiments and the angle of the swash plate may be fixed. Control is then effected by an unloading valve. The tilting head of the motor may be supported by a yoke and trunnions instead of by arcuate hands.