Pump for fluent, and especially heavy and abrasive materials

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 having 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 generally cup-shaped end closure rigid with said opposite end of the cylinder chamber, and said cup-shaped closure 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 having a wall diameter which is larger than the diameter of the piston perimeter so that there is a 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; check valved means for receiving pumped material from said extension chamber; a rigid annular rib between said cylinder chamber and said extension chamber and having a radially inner annular rib surface which extends to a smaller diameter than the diameters of the cylinder chamber wall and the extension chamber wall but is of a substantially larger diameter than the piston perimeter diameter, said rib defining a port through which the piston moves freely and in substantial annularly spaced gap relation 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 to a position wherein the piston projects partially through said rib; and a combination valving, sealing and wiping elastic ring engaged with said rib and having an annular portion projecting radially inwardly beyond said inner annular surface of the rib to a substantially smaller diameter than the diameter of the piston perimeter; said projecting annular portion of the elastic ring extending across said gap and being engaged by the piston during the forward stroke through said rib into said extension chamber, and the piston perimeter elastically expanding the radially inwardly projecting portion of the elastic ring into a tensioned sealing and wiping annular gripping engagement with the piston perimeter and maintaining pumping pressure in said extension chamber against leakage past said rib and the piston during said forward stroke of the piston and the extension chamber; said rib providing a rigid annular portion between said cylinder chamber and the elastic ring serving as a backup barrier for the elastic ring to prevent backward extrusion of the ring into the cylinder chamber due to pumping pressure in said extension chamber; said piston producing a suction effect and developing a negative pressure in said extension chamber during the return stroke of the piston; said piston completely withdrawing from the elastic ring at the end of said return stroke so that material can flow from said cylinder chamber past said piston and through said rib and said elastic ring into said extension chamber in response to said negative pressure; said projecting annular portion of the elastic ring 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 including said rib remaining at all times substantially spaced from the piston perimeter.