Priming pump

Claim 1

A PUMP HAVING: AN AXIALLY MOVABLE PISTON WITHIN A CYLINDER, THE DIAMETER OF SAID PISTON BEING SUBSTANTIALLY LESS THAN THE DIAMETER OF SAID CYLINDER TO PERMIT THE FLOW OF LIQUID BETWEEN THE WALLS OF SAID PISTON AND SAID CYLINDER; AN ANNULAR GROOVE OF GENERALLY RECTANGULAR CROSSSECTION AND OF PREDETERMINED DEPTH AND WIDTH AROUND SAID PISTON; A LIQUID TRANSFER CHAMBER EXTENDING FROM THE BOTTOM SURFACE OF SAID GROOVE THROUGH SAID PISTON INTO AN OUTLET CHAMBER DEFINED BY SAID PISTON, THE WALL SURFACES OF SAID CYLINDER AND BY THE END OF SAID CYLINDER HOUSING A LIQUID OUTLET; AND AN ANNULAR, RESILIENT SEALING ELEMENT OF GENERALLY SQUARE CROSS-SECTION POSITIONED IN SAID GROOVE; SAID ELEMENT HAVING INNER, OUTER AND SIDE SURFACES AND SAID ELEMENT BEING NARROWER THAN SAID GROOVE AND HAVING A GREATER INNER DIAMETER THAN THE INNER DIAMETER OF SAID GROOVE AND BEING IN CONTACTING RELATION WITH SAID CYLINDER WALL SURFACES AND SAID INNER SURFACE OF SAID ELEMENT BEING ARCHED AWAY FROM THE INNER SURFACE OF SAID GROOVE PROVIDING AT LEAST ONE THIN RELATIVELY FLEXIBLE SEALING LIP ADJACENT THE SIDE SURFACE OF SAID GROOVE OPPOSITE SAID OUTLET CHAMBER.