Piston pump and seal ring

A single-stoke pump comprising:

• a working cylinder having a working fluid inlet, a working fluid outlet, and a throat;
• a pump cylinder having an inlet end and an outlet end, wherein the inlet end is attached to the throat;
• a reservoir fluidly connected to the pump cylinder and configured to store a pumped fluid and to provide the pumped fluid to the pump cylinder;
• an outlet valve connected to the outlet end of the pump cylinder;
• and
• a piston disposed within the working fluid cylinder and extending into the pump cylinder through the throat, wherein the piston comprises:
• a piston head disposed within the working fluid cylinder;
• a pump rod extending from the piston head through the throat and into the pump cylinder, wherein the pump rod comprises:
• a first portion attached to the piston head and extending through the throat and into the pump cylinder and having a first diameter;
• a second portion extending from the first portion into the pump chamber and having a second diameter, wherein the second diameter is smaller than the first diameter;
• a retaining device connected to a distal end of the pump rod;
• and
• a seal ring extending about the second portion of the pump rod and disposed within the pump cylinder, wherein the seal ring comprises:
• a body extending between a first end and a second end;
• and
• a bore extending through the body between the first end and the second end;
• wherein a bore diameter of the bore is less than the first diameter and greater than the second diameter;
• wherein the pump cylinder defines a pump chamber extending between the seal ring and the outlet valve, wherein a volume of the pump chamber decreases as the piston proceeds through a forward stroke and increases as the piston proceeds through a return stroke;
• and
• wherein the seal ring is configured to be movable between a first position in which the seal ring sealingly engages a portion of the pump rod at a transition between the first diameter of the first portion to the second diameter of the second portion during the forward stroke to prevent fluid within pump cylinder from flowing around seal ring during the forward stroke, and a second position in which the seal ring is disengaged from the pump rod during the return stroke such that a refill flow path is opened through the bore to allow the pumped fluid from the reservoir to flow into the pump chamber.

A method of pumping with a single-stroke pump having a pump cylinder connected to a working fluid cylinder, a reservoir connected to the pump cylinder to provide fluid to the pump cylinder for pumping, an outlet valve connected to an outlet end of the pump cylinder, and a piston disposed partially within the working fluid cylinder and extending through a throat of the working fluid cylinder into the pump cylinder, the method comprising:

• driving a pump rod of the piston, using a piston head disposed in the working fluid cylinder, into a forward stroke through the pump cylinder, wherein the pump rod includes a first portion attached to the piston head disposed in the working fluid cylinder, the first portion extending through the throat and into the pump cylinder, and the first portion having a first diameter, and wherein the pump rod includes a second portion extending from the first portion into the pump chamber, the second portion having a second diameter, wherein the second diameter is smaller than the first diameter;
• forcing fluid out of the pump cylinder during the forward stroke using a seal ring, wherein the seal ring includes a body extending between a first end and a second end and a bore though the body between the first end and the second end extends about the pump rod and provides a fluid tight seal between the pump rod and the pump cylinder;
• the seal ring being disposed about the second portion and engaging and sealing against a portion of the pump rod at a transition between the first diameter of the first portion to the second diameter of the second portion during the forward stroke, and wherein a bore diameter of a bore through the seal ring is less than the first diameter and greater than the second diameter;
• and
• driving the pump rod in a return stroke in which the seal ring shifts to a second position abutting a retaining member and opening a flow path through the bore of the seal ring and through which fluid flows from a reservoir and into the pump cylinder defined between the seal ring and the outlet valve.