Cyclic hydraulic pump improvements

摘要

A two stage pump has coaxial first and second stage reciprocating pumps with the second stage piston reciprocably driven by the first stage piston. Multiple sets of first and second stage pumps are provided, and the second stage pistons can be returned by supercharge pressure, a loose connection between the first and second stage pistons, or a spring. An accumulator which is charged on a compression stroke and discharged on an intake stroke may also be provided in communication with a pumping chamber to improve the efficiency of a pump.