US Patent 7794212 Multi-piston pump/compressor

A pump/compressor that utilizes a wedge at a fixed angle to operate the pump's pistons at a fixed stroke. Alternatively the wedge can be moved axially to increase or decrease the clearance volume. Variable fluid flow at any clearance volume is achieved by rotating the wedge with respect to the port plate thereby changing the timing of the pistons with respect to the fixed port plate which changes the timing of the intake and output cycles. This results in a portion of the intake charge being breathed back into the intake port and a portion of the output charge being breathed back from the outlet port. This causes the pistons to not take in a full charge from the inlet port and to not pump out a full charge into the outlet port. Thus, fluid flow is varied. The design results in a smaller pump as the wedge is supported by the pump housing rather than a mechanical linkage required of prior adjustable angle swashplate designs.