Multiple piston pump apparatus

Claim 1

A pump apparatus comprising: a. a multiple piston pump including casing means defining at least two pump cylinders, a pump piston slidable in each pump cylinder and defining a motive chamber therein, eccentric means for cylically reciprocating the pistons in successive preselected phase relation, fluid supply means including inlet passage means and inlet valve means operative to open to supply fluid to the motive chambers during the intake stroke of each piston, fluid discharge valve means operative to open to allow delivery of fluid from each motive chamber to the respective fluid discharge passage means during the discharge stroke of each piston, fluid delivery passage means adapted to supply fluiD to a utilization device and communicating with the fluid discharge passage means associated with at least two of said motive chambers to receive fluid therefrom, a first pressure relief passage means communicating with said fluid supply means and with a first of said fluid discharge passage means associated with a first of said motive chambers, b. a first valve means controlling flow between said first discharge passage means and said first relief passage means and said delivery passage means, said first valve means including a relief valve seat intermediate said first discharge passage means and said first relief passage means and facing in the direction of fluid flow to the first relief passage means, a relief valve member having means yieldably biasing the same toward a seated position against said relief valve seat and responsive to a first preselected fluid pressure in said first discharge passage means to unseat for flow through the relief passage means, said first valve means also including a delivery valve seat intermediate said first discharge passage means and said delivery passage means and facing in the direction of fluid flow to the delivery passage means, a delivery valve member cooperable with said delivery valve seat and operable when seated to block return flow from the delivery passage means to said first discharge passage means, and means operatively interconnecting said delivery valve member and said relief valve member for holding said relief valve member in an unseated position when said delivery valve member is seated to thereby unload said first motive chamber, and c. at least one other valve means operative when the fluid pressure in a second of said passage means reaches a pressure substantially higher than said first preselected fluid pressure for passing fluid from the second discharge passage means back to said supply means.