Page 133 - Fluid Power Engineering

Hydraulic Pumps 107

FIGURE 4.18 Typical design of an axial piston pump with a rotating swash
plate (wobble plate).

reliably at such high pressures. The construction and operation of
a radial piston pump with an eccentric cam ring are illustrated by
Fig. 4.19. This example shows a variable displacement pump, where
the pistons are arranged radially in the cylinder block. They are held
in contact with the inner surface of a cam ring by means of a retainer
ring and slipper pads. The pistons and slipper pads are connected to
each other by means of ball-and-socket joints. The stroke of pistons
and consequently the pump geometric volume are controlled by
adjusting the eccentricity of the cam ring (stroke ring) by means of two
control pistons. The cylinder block is rotated by the driving shaft. Dur-
ing the suction stroke, the pistons’ motion is governed by the retainer
ring, while during the delivery stroke the pistons are displaced by the

FIGURE 4.19 Radial piston pump with an eccentric cam ring. (Gotz, 1984, courtesy
of Bosch Rexroth AG.)