An axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a cylinder block. This cylinder block is driven to rotate about its axis of symmetry by an integral shaft that is, more or less, aligned with the pumping pistons. The group of cylinders, usually containing an odd number, is called a cylinder block. The pistons within each cylinder are attached to a swashplate. The swashplate is also known as a cam or wobble plate and attaches to a rotating shaft. As the shaft turns, the angle of the swashplate changes, which drives the pistons in and out of their respective cylinders.
Since the swashplate is at an angle to the axis of rotation, the pistons must reciprocate axially as they orbit around the cylinder block axis. The axial motion of the pistons is sinusoidal. As a piston rises, it moves toward the valve plate. At this point in the rotation, the fluid trapped between the buried end of the piston and the valve plate is expelled to the pump's discharge port through one of the valve plate's semi-circular ports. As the piston moves back toward the valve plate, the fluid is pushed through the discharge port of the valve plate. Fixed displacement axial piston pumps have a constant geometric displacement and convey a constant flow rate depending on the rotation speed.
In an axial piston pump, the pistons and cylinder rotate around the center, longitudinal axis. The pistons and shoes move in and out of the cylinder because they are sliding upon a stationary, variable angle, swash block. As the pistons rotate, they alternate between being connected to an inlet port and an outlet port.
Axial piston pumps can contain most of the necessary circuit controls intrinsically by controlling the swash-plate angle, to regulate flow and pressure. They are very reliable and can allow the rest of the hydraulic system to which they’re attached to be very simple and inexpensive. For example, in some industrial reverse osmosis applications:
Feedwater (low pressure)
Feedwater (high pressure)
Energy Recovery Device