Patent ID: 6981854

Claim:
A small piston pump comprising in combination, A) housing having a bore therein with a pair of spaced opposed ends and having a sleeve in said bore adjacent one end of said bore, 1) said one end of said bore having an inlet opening therein and having a slit valve overlying said inlet opening and controlling the flow of fluid therethrough, B) said sleeve having a periphery thereabout spaced from said housing bore and having an axially extending bore therein and having a pair of axially opposed ends with one of said ends being disposed adjacent said slit valve whereby to receive fluid into said sleeve bore flowing into said housing through said slit valve, and the other of said sleeve ends being axially spaced from said one end and engaging and being supportingly carried by said housing within said bore thereof, C) said sleeve having a radial passageway therein adjacent said one end thereof which leads from the sleeve bore to the periphery of said sleeve and said sleeve carrying an annular elastic valve member overlying said radial passageway, D) second passage means in one of said bore and sleeve for conducting fluid from the area of the periphery of said sleeve to the area of said housing bore past the engagement of said sleeve and said housing, E) an elongated piston with a first end thereof disposed in said sleeve and sealing and slidingly supported thereby and having a second end axially spaced from said first end and slidingly and sealingly engaging said housing within the bore thereof, said engagement being disposed axially beyond said second passage means, F) and an outflow opening from said housing disposed between said second passage means and said second end of said piston, and G) means operatively connected to said piston and projecting from said housing for reciprocating said piston.