(57) A variable displacement piston pump (10) includÂing a plurality of axially aligned
pumping cylinders (24) with a driven drive shaft (16) extending there between having
a tiltable swash plate (30) disposed on one end of the drive shaft (16) for operating
the pumping cylinders, and a reaction thrust plate (38) on the other end of the drive
shaft (16), for providing reaction force in the drive shaft (16) opposite that provided
by the swash plate (30). The pumping cylinders (24) feed a common manifold (52). A
check valve (50) is disposed between each cylinder (24) and the common manifold (52)
to ensure one way flow. Check valve (50) between cylinders (24) and the common manifold
(52) also reduces pressure pulsations during pumping. The thrust plate (38) is formed
with a centrifugal impeller opening (62) formed therein through which incoming fluid
flows and its pressure is increased. A dummy piston (28) is provided in each cylinder
(24) opposite the active pumping piston (26). The active piston (26) and the dummy
piston (34) each include an opening there through which is exposed during an intake
stroke so that fluid is admitted into both ends of the cylinder (24). After the intake
stroke, the openings in both pistons (26, 28) are sealed and pumping action occurs.
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