81 F.2d 206 (5th Cir. 1936), 7707, Texas Rubber & Specialty Corp. v. D. & M. Mach. Works

Docket Nº:7707.
Citation:81 F.2d 206, 28 U.S.P.Q. 180
Case Date:January 22, 1936
Court:United States Courts of Appeals, Court of Appeals for the Fifth Circuit

Page 206

81 F.2d 206 (5th Cir. 1936)

28 U.S.P.Q. 180



D. & M. MACHINE WORKS et al.

No. 7707.

United States Court of Appeals, Fifth Circuit.

January 22, 1936

Rehearing Denied February 26, 1936.

Page 207

Jesse R. Stone and Lester B. Clark, both of Houston, Texas., for appellants.

J. Vincent Martin and E. A. Berry, both of Houston, Tex., for appellees.

Before FOSTER and SIBLEY, Circuit Judges, and DAWKINS, District Judge.

SIBLEY, Circuit Judge.

A decree was rendered upholding patent No. 1,718,474 issued June 25, 1929, to John W. McQuaid, for a piston for slush pumps, adjudging infringement by a similar piston made and sold by Texas Rubber & Specialty Company and H. W. Millmine, and awarding injunction and a reference to take an account. This appeal contests the validity of the patent and denies infringement.

During the past two decades oil wells have been drilled to depths sometimes exceeding two miles by the use of hollow drill stems through which very soft mud called 'slush' is continuously pumped, passing out below the drill head or auger and carrying the materials cut by the drill head up around the outside of the drill stem to the surface, where the coarser particles are taken out by sedimentation and the slush is used again. Pressures on the pumps of several hundred pounds to the square inch are reached. The slush carries considerable abrasive material which tends to cut out the liners of the pump and destroy the packing of the piston. The present patent presents a piston of rubber molded over a rigid (metal) skeleton composed of a central core or hub, through which the piston rod passes and to which it is secured by nuts, with a flange extending radially from the core nearly to the walls of the pump liner, there being rings and grooves on core and flange into which the rubber is formed and vulcanized to securely hold it. The rubber at the working end of the piston is built up into a ring which protrudes beyond the face of the piston and is made a little larger than the bore of the liner so as to press tightly against it, the rubber behind the ring fitting more loosely. The pistons are usually for double acting pumps so that there is such a protruding ring on each end, the portion of the piston between the two rings being out of contact with the liner. The body of the piston is hard rubber, but the protruding rings are more pliable, so that the liquid in front of the piston in its work stroke presses the ring firmly against the liner, preventing leakage and especially preventing abrasive particles from getting between the piston and the liner to the destruction of both. The rings are not feather-edged, but have an ogee section giving them a greater stiffness and stability. The metal pistons...

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