Dynamic seal arrangement for impeller pump

Claim 1

In a pump including a rotatable shaft, an impeller on said shaft to pressurize fluid during rotation of said shaft, a pump housing defining a seal cavity surrounding the shaft, means sealing said shaft and housing against fluid leakage therebetween during said pumping operation and when said shaft is not rotating said means comprising, in combination, an expeller rotatable with said shaft to evacuate fluid from the seal cavity during pump operation, thereby eliminating the need for a fluid tight seal between said housing and said shaft during said pumping operation, a dynamic seal arrangement for providing a seal between said pump housing and said shaft when said shaft is not rotating, said seal arrangement comprising: (a) an axially movable primary seal ring adapted to be disposed annularly about said shaft and secured in fluid tight relation to one of said shaft and said housing, said primary seal ring defining a radial seal face; (b) a stationary mating seal ring adapted to be disposed annularly about said shaft and secured in fluid tight relation to the other of said shaft and said housing, said mating seal ring defining a radial seal face adapted for sealing contact with said radial seal face of said primary seal ring; wherein one of said radial faces of one said seal ring defines a smooth surface and the radial seal face of said other seal ring defines a surface having a plurality of spiral grooves therein, said faces being exposed to the fluid within the pump at one circumferential periphery and to the atmosphere external to the pump at the opposite circumferential periphery, said grooves extending from said circumferential periphery exposed to atmosphere external to the pump radially partially toward the other circumferential periphery thereof and terminating to define on said surface of said radial face, between said grooves and said circumferential periphery, exposed to atmosphere external to the pump a sealing dam adapted to sealingly engage said smooth radial face of said other of said seal rings; biasing means urging said axially movable ring toward said stationary mating seal ring to cause said dam to engage said radial face of said other ring when said pump shaft is not rotating; said grooves pumping atmosphere between said faces when said pump shaft is rotating at operational speed at a pressure to separate said radial faces of said seal rings.