Patent ID: 7607884

Claim:
A centrifugal chopper pump capable of pumping a fluid containing said solid material, said pump comprising: a pump casing having a frontal intake port, a pump outlet in a side thereof and back plate structure forming a central seal chamber extending rearwardly from a central opening formed in a radially extending wall of said back plate structure; a drive shaft extending into said casing and through said central opening from a rear side of said casing, said drive shaft being rotatable about an axis of rotation in a selected direction of rotation; an open impeller mounted on said drive shaft for rotation therewith, said impeller having radially extending vanes each having a leading edge that extends generally radially in relation to said axis of rotation and each having a trailing edge with a substantially open, circumferentially extending gap between adjacent trailing edges of these vanes; at least one cutter mounted in said pump casing, and located in said input port, the leading edges of said vanes rotating closely past said at least one cutter during operation of the pump in order to cut up incoming solid material; and a mechanical seal mechanism comprising a seal cartridge mounted in said seal chamber, said seal mechanism having a rotating component mounted on said drive shaft and a stationary component mounted on said back plate structure, said rotating component including a central sleeve adapted to and sized to be mounted on said drive shaft for rotation therewith, a seal support mounted on said sleeve for rotation therewith and an annular first seat mounted on the seal support, said stationary component comprising an annular flange member having a radially inwardly extending flange, an annular seat housing, an annular second seat mounted on said seat housing adjacent said first seat, and a spring extending between said seat housing and said flange on said flange member and pressing said second seat against said first seat in order to provide a mechanical seal by maintaining a closing pressure sufficient to keep adjacent faces of the first and second seats together, said seal chamber having a circumferentially extending wall extending around at least a forward portion of said seal mechanism and spaced therefrom so as to form an open annular space exposed to the pumped fluid for circulation of a portion of said fluid, wherein during operation of said pump, said seal mechanism effectively seals an annular gap between said drive shaft and said back plate structure while being lubricated and cooled by said portion of said fluid being pumped by the chopper pump.