Double-action proportioning pump
AssigneeExtracorporeal Medical Systems, Inc.
InventorStephen Mason Meginniss, III
Life of this patent
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Abstract
In a blood dialysis system a proportioning pump accurately mixes precise quantities of water and concentrate. A double-acting piston assembly is disposed in a stepped cylinder which has proximity sensing switches at both ends thereof. These are operated as the piston assembly reaches the end of its stroke in each direction. The switches alternate a bistable solenoid valve system which directs pressurized water to opposite sides of a large central piston, thus causing the piston assembly to reciprocate. Small pistons, attached on opposite sides of the large piston, move in small pump chambers, with check valves. The small pistons pump concentrate in a precise ratio to the volume of water driving the large piston.
Claims5
A fluid pressure driven pump comprising:
- a double-acting piston means including a center cylinder, and a pair of end cylinders disposed on either side of said center cylinder, a center piston and end pistons each operated by said center piston, said end cylinders being extensions of said center cylinder with no exposed moving parts between said cylinders,
- switch means operated by said piston means,
- solenoid operated valve means alternately connecting opposite chambers of said center cylinder with a source of first fluid under pressure and an outlet of said valve means,
- valve means alternately connecting said end cylinders to a source of second fluid and to an outlet of said valve means, said switch means being connected to operate said solenoid operated valve means between alternate states as said piston means reciprocates within said cylinder,
- seals around the periphery of each end piston, said seals engaging said end cylinders to provide the only separation between said first fluid in said center cylinder and said second fluid in said end cylinders, and
- a cup seal around the periphery of said center cylinder, said cup seal being formed from a circular piece of compliant, durable rubber-like material which is deformed so that the outer periphery thereof bears against the inner surface of said center cylinder.
Dependencies are inferred from the claim text.