High pressure piston pump and wiper, sealing, valving structure

Claim 1

A pump for fluent materials and especially suitable for moving heavy fluent and abrasive materials, comprising: a housing member providing a hollow cylinder chamber receptive of material to be pumped and having an axially extending chamber wall and opposite ends; a piston within and shorter than the cylinder chamber and having its perimeter of smaller diameter than and in limited spaced gap relation to said wall so that material can flow through the gap; a closure at one end of the cylinder chamber and means for guiding a piston rod of the piston for axial forward and return strokes of the piston relative to the opposite end of the cylinder chamber; means for driving the piston rod and thereby the piston in said forward and return strokes; a closure member and means securing the closure member to said housing member in closing relation to said opposite end of the cylinder chamber, and said closure member having a blind end chamber which forms a forward extension from the cylinder chamber and into which the piston extends a limited distance in the forward stroke of the piston, said blind end extension chamber being of a diameter which is larger than the diameter of the piston perimeter so that there is a limited spaced gap relation between the piston perimeter and said extension chamber when the piston extends into said extension chamber; means for introducing into said cylinder chamber material to be pumped, and check valved means for receiving pumped material from said extension chamber; a rigid annular ring plate clamped between said housing member and said closure member and having an inner annular rib portion which extends to a smaller diameter than the diameters of the cylinder chamber wall and the extension chamber wall but to a larger diameter than the piston perimeter diameter, said rib portion defining a port through which the piston moves freely in a forward stroke from a position wherein the forward end of the piston is entirely within the cylinder chamber and clear of said rib portion; and a combination valving, sealing and wiping elastic ring comprising a normally substantially flat elastic annular element fixedly clamped between said ring plate and said closure member and having an annular portion projecting radially inwardly beyond said rib portion to a substantially smaller diameter than the diameter of the piston perimeter, said elastic ring being engaged by the piston during the forward stroke through said rib portion and the piston elastically expanding the radially inwardly projecting portion of the elastic element into a tensioned sealing and wiping annular lip extending forwardly on the piston perimeter and maintaining pumping pressure in said blind end chamber against leakage past said rib flange during said forward stroke of the piston; said rib portion serving as a backup for the elastic ring to prevent backward extrusion of the ring past the rib portion due to pumping pressure in said blind end chamber; said piston producing a suction effect and developing a negative pressure in said extension chamber during the return stroke of the piston whereby said lip expands and relieves its grip on the piston perimeter and diminishes the power load required to withdraw the piston from the lip during the return stroke; said piston completely withdrawing from the elastic ring in said return stroke so that material can flow from said cylindr chamber past said piston and through said rib portion and said elastic ring into said blind end chamber in response to said negative pressure; said lip providing the only surface in the pump with which the perimeter of the piston engages at any time and all other surfaces within the pump remaining at all times spaced from the piston perimeter.