Reciprocating piston pump

A pump system comprising:

• a housing defining a first internal volume and a second internal volume;
• a first piston positioned to separate the first internal volume into a first chamber and a second chamber;
• a second piston positioned to separate the second internal volume into a third chamber and a fourth chamber, wherein the first chamber and the third chamber are configured to receive a first fluid from a gas spring at a low pressure, and the second chamber and the fourth chamber are configured to receive a second fluid from a second fluid source;
• a directional control valve (DCV) repositionable between (a) a first position where the DCV is configured to fluidly couple the second chamber to a reservoir and (b) a second position where the DCV is configured to fluidly couple the fourth chamber to the reservoir;
• and
• a relief valve configured to supply the second fluid through an orifice to move the DCV between the first position and the second position in response to a pressure at a point between the relief valve and the orifice reaching a preset shift pressure.

A pump system comprising:

• a housing defining a first internal volume and a second internal volume;
• a first piston positioned to separate the first internal volume into a first chamber and a second chamber;
• a second piston positioned to separate the second internal volume into a third chamber and a fourth chamber, wherein the first chamber and the third chamber are configured to receive a first fluid from a gas spring at a low pressure, and the second chamber and the fourth chamber are configured to receive a second fluid from a second fluid source;
• a directional control valve (DCV) fluidly coupled to the second chamber and the fourth chamber;
• a relief valve fluidly coupled to the DCV via a control line and the second chamber via a sensing line;
• and
• an orifice positioned along the sensing line,
• wherein the relief valve is configured to reposition the DCV in response to a pressure at a point between the relief valve and the orifice reaching a shift pressure, and wherein the orifice is positioned to cause a delay in a flow of a fluid along the sensing line, such that a pressure within the second chamber exceeds the shift pressure when the pressure at the point between the relief valve and the orifice reaches the shift pressure.