Hydraulics - Seafish

39
Radial Piston Pumps
Radial piston pumps have their pistons arranged in a cylinder
block in star formation and there are two main forms of this type
of pump.
Cylinder block
centreline
Reaction Centreline
Ring
Outlet Port (2)
Pintle
Case
Inlet Port (2)
Cylinder
block
rotation
Pistons
Cylinder block
Figure 48.
Reaction
Ring
The first form which is shown in Figure 48 has its pistons
mounted in a cylinder block which rotates round a central shaft.
The centreline for the cylinder block is arranged slightly 'offcentre'
or eccentric to the reaction ring and casing.
As the cylinder block rotates the outer ends of the pistons keep in
contact with the reaction ring and this causes them to move in
and out in their cylinders.
As each piston moves out, oil is drawn in from the inlet ports and
as the ring pushes each piston in, oil is delivered to the outlet
ports. The pressure line is coupled to the outlet ports and the
return line to the inlet ports. The capacity of the pump is deter
mined by the number of pistons, their diameter and the speed at
which the pump is rotated.
Figure 48 shows a pump with a fixed reaction ring. In some types
the reaction ring can be moved sideways and this will alter the
output of the pump.
The second form of radial piston pump is shown in Figure 49. In
this form the cylinder block is stationary and the pistons are
operated by a central eccentric on the shaft.
Seafish Open Learning