US Patent 9777721 Hydraulic drive system for a pulseless positive displacement pump

A drive system for a pump includes a first housing defining an internal pressure chamber, a working fluid disposed within and charging the internal pressure chamber, a second housing having a first and second pumping chambers and an aperture through an end of the second housing, a reciprocating member slidably disposed between the first pumping chamber and the second pumping chamber, a pull housing integral with the reciprocating member and projecting through the aperture, a first sealing member disposed around a circumference of the reciprocating member, a second sealing member disposed around a circumference of the aperture, the pull housing defining a pull chamber, a pull disposed within the pull chamber, and a fluid displacement member coupled to the pull.