Piston pumps are durable, fairly
simple devices. The basic piston pump is made up of a piston, a chamber, and a
pair of valves. The pump operates by driving down into the chamber, thereby
compressing the media inside in
a hand pump this is usually air. Once the pressure of the air exceeds that of
the outlet valve spring, the compressed media is sent through the open outlet
valve. When the piston is drawn back up, it opens the inlet valve and closes
the outlet valve, thereby utilizing suction to draw in additional media for
compression.
Piston pumps are a type of reciprocating pump, which are positive-displacement
pumps that can use a piston, plunger or diaphragm to displace fluids. The input
and output valves in a piston pump are check valves; this term is used to
describe devices that limit flow in a system to one direction. Piston pumps can
be driven manually or automatically, and there are a number of devices that can
be used to drive the piston. A common piston pump design is the rotary piston
pump, which uses a rotating shaft or wheel to drive the piston. The rotating
component is attached to an intermediary shaft at a point away from its center,
and this shaft is attached to the piston. As the rotating component turns, it
drives the shaft and piston down and then pulls it back up.
A large portion of piston pumps are axial. Axial piston pumps use multiple
cylinders grouped around a main axis. The pistons within each cylinder are
attached to a swash plate, which is attached to a rotating shaft. The swash plate
is also known as a cam or wobble plate. As the shaft turns, the angle of the
swash plate changes, which drives the pistons in and out of their respective
cylinders. Radial piston pumps are used less frequently, but are preferred for
certain applications; both radial and axial pumps are available as fixed or
variable displacement pumps.
Although fairly expensive, piston pumps are among the most efficient pump
types. They have an exceptional pressure rating (as high as 10,000 psi), but
their design makes them quite susceptible to contaminants. They provide an
excellent solution for many high-pressure hydraulic oil pumping applications.