A reciprocating piston motor, motor-pump assembly and method for driving a pump. The piston motor includes a pressure medium housing, comprising a first pressure medium chamber having a first pressure medium piston, a second pressure medium chamber having a second pressure medium piston, and a pressure medium control system. The pressure medium control system includes a pressure medium inlet and outlet that are operatively connected to the pressure medium housing. The pressure medium control system is configured to move the pressure medium pistons. A coupling system is provided that is configured to combine the driving forces generated by the first and second pressure medium pistons for driving a fluid pump.

A reciprocating piston motor, motor-pump assembly and method for driving a pump. The piston motor includes a pressure medium housing, comprising a first pressure medium chamber having a first pressure medium piston, a second pressure medium chamber having a second pressure medium piston, and a pressure medium control system. The pressure medium control system includes a pressure medium inlet and outlet that are operatively connected to the pressure medium housing. The pressure medium control system is configured to move the pressure medium pistons. A coupling system is provided that is configured to combine the driving forces generated by the first and second pressure medium pistons for driving a fluid pump.