US2926976A - Pistons and sealing elements therefor - Google Patents

Description

March 1, 1960 H. E. BOWERMAN ETAL 2,926,975

PISTONS AND SEALING ELEMENTS THEREFOR Filed 001:. 15, 1956 -& WI/4 HULIE E. BOWERMAN JOHN E. M! LLER, JOHN W. JACOBY ATTY.

United States Patent PISTONS AND SEALING ELEMENTS THEREFOR Hnlie E. Bowerman, Arlington, and John E. Miller and John W. Jacoby, Dallas, Tex., assignors to United States Steel Corporation, a corporation of New Jersey Application October 15, 1956, Serial No. 616,021 4 Claims. Cl. 309-23 This invention relates to pump pistons of the type commonly used to circulate the drilling mud or medium in boring holes in the earth, such as for oil wells. Salient features of the invention include a sealing member of rubber or rubber-like material having bonded to its face a metallic or other rigid retaining ring, a fabric support at the lower or base portion of the rubber-like section and a rigid base ring below, or partially below, the fabrlc section, the whole being molded or otherwise bonded into a unitary structure.

We are aware that pistons have been proposed heretofore in which fabric sections have been provided in support of the lower or base portion of the rubber seallng member; however, the mud pressures on the face of the piston worked downwardly thereof and behind the fabric which forced it outwardly against the cylinder walls where it prematurely was worn away and especially on the back or idle stroke the plies of the fabric dragged or scrubbed against the walls of the cylinder whereby the 'plies of the fabric were separated and the intended support was first weakened and then soon destroyed. Moreover, the resultant jetting action of the fluid medium acting on the underside of the fabric soon disintegrates and destroys the fabric sections. In a preferred form of our invention we provide a novel means of securing the fabric section against this outward and destructive movement as will be made clear later in this specification. We also provide the base ring with larger diameter than the flange of the piston hub so that a piston hub of one size may accommodate various sizes of piston seal elements to be mounted thereon. Other novel features of the invention will appear in the following description together with the accompanying drawings in which:

Figure I is a section of a preferred form of our piston mounted on a hub;

Figure 11 is a section of a modified form of piston shown in Figure I;

Figure III is a modified form of the part of a piston shown enclosed in dotted line circle of Figure I, in a pump cylinder and distorted by operating pressures.

Figure IV is a modification of the section shown in Figure III.

In the several figures like references indicate similar parts wherein 5 is a piston hub having a flanged central portion 6 and portions 7 extending therefrom whereupon opposed piston members 8 may be mounted. We have shown only one extended portion 7 since the opposite of such portion would be identical. A central aperture 9 passes through hub 5 whereby the latter may be mount ed and secured to a conventional pump rod, not shown. The rubber or sealing portion 10 of our piston member 8 is provided with lips 11 for engagement with the cylinder walls of the pump and normally will be slightly larger in relaxed dimensions than the inside diameter of the pump cylinder, while fabric section 12 will preferably be of slightly less diameter than the pump cylinder. The base ring 13 will also be of less diameter than the pump cylinder but will overhang the flange 6 of the hub as shown in Figures I and IV and more pronouncedly in Figure III. Retaining ring 14 is provided with an opening slightly larger than extended portion '7 of the hub and with an outside diameter substantially less than the outside diameter of rubber sealing portion 10 which arrangement permits the sealing lip 11 to freely flex and function as the pump strokes. Portion 7 of the hub is provided with groove 15 adapted to receive snap ring 16 whereby to secure the piston and hub assembly in operative relation.

In a preferred form of the invention shown in Figures I, II and III, the base ring 13 is provided with a larger inside diameter than the extended portion 7 of the hub into which portions 17 of fabric 12 will be depressed by the pressures used in the process of molding and vulcanizing our piston member. The sections of fabric will have been duly impregnated with rubber and the base. ring and the retaining ring duly prepared to receive and be cemented to the rubber and fabric by well-known methods before the whole is molded and bonded into the unitary structure.

It will thus be seen that the portion 17 of the fabric extends downwardly into and about the inside diameter of the base ring 13 whereby the movement of the fabric section outwardly under the influence of pressure on the face of the piston is greatly restricted or prevented. The fabric overhang at 17 will further act to prevent fluid which may move downwardly about hub projection 7 inside the piston member from passing outwardly between the rubber impregnated fabric 12 and base ring 13 or from separating these parts, or from having a tendency to do so, while the piston is stroking in the pump cylinder. The fabric section is effectively mechanically prevented or locked against outward movement by the base ring.

It will be noted that a groove or cup 18 is provided in the face of the rubber portion 10 of our piston shown in Figure I whereby to effect the more ready movement of sealing lip 11 outwardly under fluid pressure to maintain seating contact with the pump cylinder under low pres sure operation, Whereas, for higher pressures, this cup or groove may be omitted as shown in Figure II.

Prior pistons have been provided with fabric porting sections bonded to the base of the rubber but without bond to the rigid piston flange or supporting ring, and without the extension of the fabric downwardly inside of and in mechanical as well as bonded engagement by the fabric with the base ring as in our structure.

in pistons where the fabric support is bonded only to the rubber, the fluids under pressure expand the lower plies of the fabric outwardly where they are pinched or sheared off between the rigid piston member and the pump liner. Deterioration is aggravated by erosion of the fabric by the fluids in motion in the area between the unprotected lower fabric plies and the piston flange, leading to separation and outward displacement, and resulting in premature exhaustion and failure of the parts; whereas, in our structure this is prevented by the turning downward of the lower plies of fabric into locking engagement with the inside diameter of the base ring and by also being bonded to the base ring. A pattern of outward distortion of the fabric section of my piston is indicated in Figure Ill at 12a wherein it will be noted that the lower ply of the supporting fabric distorts outwardly but little, While succeeding upper plies distort outwardly progressively as the strength of the rubber and fabric otter resistance thereto, until plies of the fabric are brought to bear against the cylinder 'Walls 12b, effectively eliminating subjection of the fabric section to shearing wear stresses, thus providing an effective long-wearing bridge or support for the rubber above the fabric, which has also been distorted outwardly into contact with the cylinder.

By observing the drawing of the present invention it will be seen that the resilient portion of the piston seal is proportioned so as to provide a sturdy member wherein pressuresapplied at the Working face end of the seal are distributed directly to the areas of contact between the piston hub 7 and the inner periphery of the rubber seal so as to prevent leakage of fluids between the hub and the seal. This proportioning as shown in the drawing can be conveniently expressed by stating that in any radial plane, such as the plane of the drawing which includes the axis of the seal, lines drawn through the seal member from the inner periphery of the base ring to the outer periphery of the sealing lip intersect rubber at all points along their lengths. in other Words, there is a direct path through the rubber itself by which pressure forces on the face of the seal can be transferred to tighten the engagement of the seal on the piston hub, and this direct path is not obstructed by intervening metal reinforcements or by air spaces such as might result if, for example, the groove 18 were made excessively deep.

'While we have described preferred forms of our invention, other modifications will readily occur to those skilled in the art and all such as fall within the appended claims are meant to be included herein.

What we claim is:

l. A piston seal member comprising an annular rubber sealing portion having a central axis and having a sealing lip at the face end of said rubber portion; radial fabric reinforcements embedded in and bonded to said rubber portion at the end thereof opposite said face end, the rubber portion having an axial bore extending therethrough; a rigid retaining ring at the face end of the rubber portion and extending from the bore outwardly toward said sealing lip, the retaining ring being bonded to the rubber and embedded therein substantially flush with the face end; and a rigid base ring bonded to the fabric reinforced end of the member and extending outwardly coextensively therewith, the inner periphery of the base ring being of greater diameter than said bore, and the rubber portion being shaped such that the distance between the retaining ring and the base ring is substantially equal to the thickness of the rubber portion from the bore to the outer periphery of the seal member and so that lines drawn in radial planes through the seal member from the inner periphery of the base ring to the outer periphery of the sealing lip intersect rubber at all points along their lengths.

2. In a seal member as set forth in claim 1, said rubber portion having an annular axially extending groove in its face end between said sealing lip and said retaining ring and spaced from both, the groove extending into the rubber portion to a depth short of intersecting said drawn lines.

3. In combination, a piston hub having an axially disposed seal-receiving portion and having a radially disposed fiange forming a shoulder on said seal-receiving portion; and a piston seal member comprising an annular rubber sealing portion having a central axis and having a sealing lip at the face end of said rubber portion; radial fabric reinforcements embedded in and bonded to said rubber portion at the end thereof opposite said face end, the rubber portion having an axial bore extending therethrough; a rigid retaining ring at the face end of the rubber portion and extending from the bore outwardly toward said sealing lip, the retaining ring being bonded to the rubber and embedded therein substantially flush with the face end; and a rigid base ring bonded to the fabric reinforced end of the member and extending outwardly co-extensively therewith, the inner peripheryof the base ring being of greater diameter than said bore, and the rubber portion being shaped such that the distance between the retaining ring and thebase ring is substantially equal to the thickness of the rubber portion from the bore to the outer periphery of the seal member and so that lines drawn in radial planes through the seal member from the inner periphery of the base ring to the outer periphery of thesealing lip intersect rubber at all points along their lengths.

4. In a combination as set forth in claim 3, said rubber portion having an annular axially extending groove in its face and between said sealing lip and said retaining ring and spaced from both, the groove extending into the rubber portion to a depth short of intersecting said drawn lines.

References Cited in the file of this patent UNITED STATES PATENTS 2,306,838 Volpin Dec. 29, 1942 I 2,317,122 Volpin Apr. 20, 1943 2,574,299 Sterrett Nov. 6, 1951 2,677,581 Taylor May 4, 1954 2,808,302 Bowerman Oct. '1, 1957

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