GB1187774A - Liquid Pumping Apparatus - Google Patents

Abstract

1,187,774. Hydrostatic transmissions. JOSEPH LUCAS (INDUSTRIES) Ltd. 18 July, 1967 [27 May, 1966], No. 23918/66. Heading F2D. [Also in Division F1] To provide a wide range of liquid flows in an hydrostatic transmission comprising two pumps 12, 13 connected in parallel in closed circuit with a motor 11, the pump 12, e.g., gear type, is of fixed output whereas the pump 13, e.g. variable-angle, over-centre, swash-plate type, is of variable output and reversible, the arrangement being such that the pump 13 is variable from one extreme position in which it discharges at maximum capacity in the same direction as the pump 12 for maximum pumping output to the motor, through an intermediate zero discharge position for pumping output to the motor from the pump 12 only, to the opposite extreme position in which it discharges at maximum capacity in the opposite direction to the pump 12, i.e. it feeds the latter, for minimum pumping output to the motor. Where the pumps are of equal output in opposite directions, minimum pumping output to the motor is zero. The pumps 12, 13 are driven by a prime mover 10 through shafts 14, 15. Liquid losses are replenished from a reservoir 17 through a filter 18. A restriction 16 provides a back pressure for the pump 13, when the latter discharges in the pump 12 direction, so as to provide the positive inlet pressure desirable for swash-plate pumps.