A reciprocating pump for pumping a liquid, the reciprocating pump including:
- an operatively upright first conduit for holding liquid to be pumped, the first conduit having an open upper end and a lower end, the upper end defining a discharge opening through which liquid is discharged from the first conduit under pressure;
- an operatively upright second conduit for holding liquid to be pumped, the second conduit having an open upper end and a lower end, the upper end defining a discharge opening through which liquid is discharged from the second conduit under pressure;
- a valve assembly located at lower end regions of the first and second conduit, the valve assembly comprising:
- a) valve housing defining a first valve chamber and separate second valve chamber which is isolated from the first valve chamber, the first valve chamber being in flow communication with the second conduit and defining a first discharge opening and a first suction opening located in a source of the liquid to be pumped and the second valve chamber being in flow communication with the first conduit and defining a second discharge opening and a second suction opening located in a source of the liquid to be pumped;
- b) a first valve set comprising a first one-way discharge valve in the first discharge opening for permitting flow of the liquid from the first valve chamber into a first cross-over conduit but preventing return flow;
- and a first one-way suction valve in the first suction opening for permitting flow from the source of liquid into the first valve chamber but preventing return flow;
- c) a second valve set comprising a second one-way discharge valve in the second discharge opening for permitting flow of the liquid from the second valve chamber into a second cross-over conduit but preventing return flow;
- and a second one-way suction valve in the second suction opening for permitting flow from the source of liquid into the second valve chamber but preventing return flow;
- d) a first piston displaceably located within the first valve chamber, a side of the piston being acted upon by a column of liquid in the first conduit, the first piston being displaceable between a first blocking position wherein the first piston blocks flow of liquid between the first suction opening and the first discharge opening and a second open position wherein flow between the first suction opening and the first discharge opening is permitted;
- e) a second piston displaceably located within the second valve chamber, a side of the piston being acted upon by a column of liquid in the second conduit, the second piston being displaceable between a first blocking position wherein the second piston blocks flow of liquid between the second suction opening and the second discharge opening and a second open position wherein flow between the second suction opening and the second discharge opening is permitted;
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- f) force transferral means for transferring a force applied to one of the pistons by a column of liquid acting on the piston, to the other piston and thereby a column of liquid abutting the other piston,
- the first cross-over conduit extending between the first discharge opening and the second conduit, providing for flow communication between liquid in the first valve chamber and liquid in the second conduit;
- the second cross-over conduit extending between the second discharge opening and the first conduit, providing for flow communication between liquid in the second valve chamber and liquid in the first conduit;
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- a drive assembly comprising:
- a) a first plunger which is displaceably located within the first conduit at its upper end for exerting a downward pumping force on the liquid in the first conduit;
- b) a second plunger which is displaceably located within the second conduit at its upper end for exerting a downward pumping force on the liquid in the second conduit;
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- c) drive means for driving displacement of the first and second plungers in an alternating reciprocating manner wherein the first plunger is driven downwards thereby exerting a downward pumping force on the liquid in the first conduit while the second plunger is simultaneously displaced upwards so as to permit liquid to be discharged from the upper end of the second conduit and wherein the second plunger is thereafter driven downwards thereby exerting a downward pumping force on the liquid in the second conduit while the first plunger is simultaneously displaced upwards so as to permit liquid to be discharged from the upper end of the first conduit.