Pump Piston

Abstract

A single-acting pump having an elastomeric and synthetic fabric piston seal ring and means to supply fluid to the piston to cool and clean the piston and cylinder.

Description

SUMMARY

This invention relates to pump pistons for use in mud or slush pumps used in connection with petroleum well drilling apparatus, pipeline, mining and related industries, and particularly to a piston having an elastomeric seal ring including synthetic material fabric and fluid means for washing, cooling and lubricating the piston and the wall of the cylinder or liner in which it operates.

In double-acting pumps, the piston is flooded on both sides, as is the liner, with the fluid being pumped, whereas, in a single-acting pump, only the working face of the piston is so flooded so that on the back stroke of the piston abrasive substances may be on the liner, and the wall thereof may be relatively dry, which can result in abrasive wear on the piston, seal ring and liner wall, and which may result in excessive heating of these parts particularly in modern high speed pumps.

It is an object of this invention to provide a new and improved piston for a single-acting pump, which piston employs an elastomeric seal ring having synthetic material fabric which has a relatively low operating temperature limit but which gives superior results over other piston seals when supplied with the new and improved fluid circulating system of the invention.

My invention has other objects and advantages some of which, with the foregoing, will be set forth in the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is fragmentary sectional view of a single-acting pump showing the piston in operating position in a liner.

FIG. 2 is an enlarged view, partly in axial section, of the pump and piston shown in FIG. 1.

FIG. 3 is an enlarged view, partly in axial section, showing another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a pump piston cylinder assembly is shown comprising a single-acting piston 10 carried by a piston rod 11 and adapted for reciprocation within a cylinder or liner 12. The piston 10 includes a piston head 13 having an axially extending cylindrical portion 14 and a radially extending annular flange 15. The piston rod 11 has a reduced threaded end 16 and an annular flange 17. The piston head 13 is mounted on the threaded end 16 and a nut 18 secures the piston head 13 against the annular flange 17.

A seal ring 20 is placed on the cylindrical portion 14 against the flange 15, and an annular spacer 21, which is contoured to fit the working face of the seal ring 20, is placed against the ring 20. The seal 20 and spacer 21 are secured on the piston head 13 by means of a split retaining ring 22 or other suitable means. The piston rod 11 may have wrench flats 23 thereon to hold the rod with a wrench while the nut 18 is being applied to or removed from the rod. The rod 11 has a flange 24 which is adapted to be connected to a power source which is shown generally at 25. The piston head 13 has a groove 26 into which is disposed a seal ring 27 to effect sealing between the end 16, the head 13 and the flange 17.

The seal ring 20 may comprise generally an elastomeric material such as Buna-N or, other suitable material, having molded therein a fabric 26 which may comprise a regular weave or square woven nylon fabric or other suitable synthetic material.

The periphery of flange 15 when new has a small diametral clearance with the wall of the liner 12 of preferably about two and one-half thousandths to about seven and one-half thousandths of an inch. The flange 15 has an annular groove 28 in its periphery. A radially extending hole 29 is drilled inwardly from the bottom of the groove 28. Another hole 30 is provided in flange 15 to intersect hole 29 and thereby establish communication with the annular groove 28. A tube 31 is secured in the hole 30. Seal means 31a is provided between the wall of the hole 30 and the tube 31. The tube 31 may be secured to the piston rod 11 by means of clamps 32. A flexible conduit 33 is connected at one end to the tube 31 and connected at its other end to a pressure source of fluid, which may be water or other suitable fluid. As can be seen in FIG. 1, the flexible conduit permits the piston to be moved from its rearward position, as shown, to a forward position, moving a distance indicated at 34.

Another embodiment of the invention is shown in FIG. 3, which is similar to that shown in FIGS. 1 and 2, except that fluid supply in this embodiment is carried through flexible conduit 40 which is threadedly secured into piston rod 41, communicating with passageways 42 and 43. The flange 44 of piston head 45 has passageways 46 communicating with passageway 43 and an annular groove 47 in the periphery of flange 44.

In operation, fluid in sufficient volume under ample pressure is forced between the piston flange and cylinder to form a continuous film of fluid behind the piston. This fluid film cools, cleans and lubricates the seal ring and cylinder and helps to prevent air and foreign material from being drawn into the working chamber by the piston on its back stroke.

The fluid forced through the small clearance between the piston flange and cylinder is more efficient, more uniformly distributed, and less fluid is required than an open spray system which directs a stream of liquid onto the back side of the piston.

The fabric 26, which is preferably nylon or the like molded into the seal ring 20, is much superior to the cotton fabrics previously used in such pump piston seals because it has higher tensile strength, a lower coefficient of friction and a good ability to stretch before breaking. Such a seal will have greatly increased field performance if it can be kept sufficiently cool in operation. Nylon or the like is much more heat sensitive than cotton fabric, but its other properties, as above mentioned, make such a nylon-reinforced seal very desirable especially for use in modern high speed pumps. With the cooling arrangement of my invention, such seal has been proven to be superior in actual field use.

While the embodiments of the invention as herein disclosed constitute preferred forms, it is to be understood that other forms may be adopted within the scope of the appended claims.

Claims

What is claimed is:

1. In a pump having a cylinder,

a single acting piston operative in said cylinder,

said single acting piston including an axially extending cylindrical portion terminating in an enlarged radially extending annular flange portion, said cylindrical portion having an external diameter considerably less than the internal diameter of said cylinder and said annular flange portion having a diameter commensurate with the internal diameter of said cylinder,

a single elastomeric sealing ring positioned upon the cylindrical portion of said piston in abutting engagement with said annular flange portion.

a member carried by said cylindrical portion and engaging said sealing ring to retain same in engagement with said flange, readily releasable means clamping said member and sealing ring upon said cylindrical portion of said piston,

said sealing ring having a sliding engagement with the inner surface of said cylinder,

said annular flange portion having a circumferential fluid passageway provided in the peripheral surface thereof,

said annular flange portion having fluid passageways communicating with said circumferential fluid passageway to conduct a fluid to the inner surface of said cylinder proximate said sealing ring and flange portion to form a continuous film of fluid behind said piston for cooling and cleaning the cylinder and sealing ring.