Patent ID: 8021128
Filing Date: 2011-09-20
Classification: B01D,F04B

Abstract:
1. A fluid pump and motor unit comprising: a pump body having formed therein a piston rod axially reciprocal in a pumping stroke direction and a return stroke direction and having a distal end portion extending through a passageway in said pump body and into said cylinder, said distal end portion having a piston disposed within said cylinder and separating said first and second flow paths; said piston being slideably connected to said distal end portion and being free to move axially relative to said piston rod between said distal rod stop and said proximal rod stop, said piston being engageable by said proximal rod stop and drivable by said piston rod in the pumping stroke direction to pump a first fluid flow through said first flow path, and engageable by said distal rod stop and drivable by said piston rod in the return stroke direction within said cylinder, said piston also being at least partially drivable by a second fluid flow through said second flow path, a first pair of associated valves respectively disposed in an upstream part of said first flow path and a downstream part of second flow path, a second pair of associated valves respectively disposed in a downstream part of said first flow path and an upstream part of second flow path, and means normally biasing the valves toward their flow path closing positions; and piston stop means for limiting piston travel in at least one stroke direction within said cylinder to at least one of the following two positions;