Fluid driven reciprocating pump

A fluid driven reciprocating pump comprising a housing and a reciprocating assembly, wherein:

• the housing and the reciprocating assembly define first and second working fluid chambers;
• the housing defines a working fluid inlet passage through which a working fluid is introduced under pressure, a working fluid outlet passage through which the working fluid is exhausted, and a valve surface which interacts with the reciprocating assembly;
• the reciprocating assembly includes a valve member, a control valve actuator, and a reciprocating rod;
• the valve member slidably moves against the valve surface between a first position, wherein the first working fluid chamber communicates with the working fluid inlet passage and the second working fluid chamber communicates with the working fluid exhaust passage, and a second position, wherein the first working fluid chamber communicates with the working fluid outlet passage and the second working fluid chamber communicates with the working fluid inlet passage;
• the reciprocating rod member moves in response to the alternate introduction and exhaustion of the working fluid into and out of the first and second working fluid chambers, respectively;
• and
• the control valve actuator switches the valve member between the first and second positions in response to the movement of the reciprocating rod member and also urges the valve member toward the valve surface to form a fluid-tight seal as the valve member moves between the first and second position between the valve member and the valve surface.