Patent ID: 6877966

Claim:
A rotary sliding vane pump, comprising: (a) a housing containing a bore forming an interior wall, an inlet port, and an outlet port; (b) a pumping apparatus rotatably mounted within the bore, the pumping apparatus comprising a rotor having a plurality of circumferentially spaced, radially extending slots formed therein, an equal number of vanes of a predetermined length slideably positioned within the slots; (c) a drive attachment coupled to the pumping apparatus to rotationally drive the rotor in the bore thereby urging the vanes radially outwardly and into engagement with the interior wall to form at least one pumping chamber; (d) one or more leakage ports formed at a position in the pumping apparatus so as to allow leakage of air in the one or more pumping chambers through the one or more leakage ports after a predetermined amount of vane length wears, said predetermined amount of vane length being chosen such that a substantial amount of vane length remains for continued operation of said pump, and wherein said leakage does not substantially reduce the performance of said pump, wherein the one or more leakage ports are formed as an enlarged section at an open end of at least one of said slots, wherein the enlarged section extends inwardly in the slots to a point where after a predetermined amount of vane length wear occurs, an open passage is formed between the at least one pumping chamber and an adjacent pumping chamber; and (e) means for displaying decreasing efficiency of the rotary vane pump as air leaks from the at least one pumping chamber.