US2801140A - Piston packing - Google Patents

Description

July 30, 1957 F. P. KRETZER 2,801,140

PISTON PACKING Filed Jan. 12, 1955 2 Sheets-Sheet 1 2, Z fl a f PM.

INVENTOR. fled P Wefzer July 30, 1957 F. P, KRETZER 2,801,140

PIISTON PACKING Filed Jan. 12, 1955 2 Sheets- Shat 2 Fm. FM.

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IN V EN TOR. Fed P We)? 6/" BYQMQ QM United States atent PISTON PACKIN G Fred P. Kretzer, Gainesville, Tex., assignor to The National Supply Company, Pittsburgh, Pa., a corporation of Pennsylvania Application January 12, 1955, Serial No. 481,335

Claims. (Cl. 30923) This invention relates to packing members for pistons of the type used in pumps for the circulation of flushing fluid in oil well drilling apparatus. The primary object of the invention is to provide a piston packing having increased service life.

' It has been known that packing members comprising flexible rubber elements, suitably backed to limit their movement during operation, give fairly satisfactory service in double acting pumps of the kind usually known as slush pumps. These pumps are called upon to circulate either a water-base or oil-base mud or flushing fluid into a well being drilled, for the purpose of removing the cuttings from the vicinity of the drilling bit. The circulated mud may be quite viscous and may contain abrasive particles that cut and wear the pump packing. Obviously it is necessary to shut down the pump for the purpose of changing the packing rubbers and the expense of this operation should be avoided as long as possible. Packing constructed in accordance with the present invention has been found to have greatly increased life over known and competitive equipment.

An important object of the invention is the provision of a packing that will provide successive seals against leakage axially of the pump cylinder, sealing being obtained by spaced packing elements which are distorted by cooperation with the walls of the pump cylinder, being larger in diameter than the cylinder in which the pump piston operates.

Other objects and advantages of the invention will become apparent from the following specification, reference being had to the accompanying drawings, in which- Fig. l is a central vertical sectional view of a pump piston packed in accordance with the present invention;

Fig 2 is a fragmentary sectional view of a piston packing inserted as it is formed when in a cylinder, the cylinder being shown only diagrammatically;

Fig. 3 is a fragmentary sectional view of a modified form of the invention;

Fig. 4 is a fragmentary sectional view of another modification in which juxtaposed packing ring surfaces are formed only incidentally to axial compression;

Fig. 5 is a fragmentary sectional view of another modification somewhat similar to the form shown in Fig. 4, and;

Fig. 6 is a fragmentary sectional view of another modification in which the divergent packing ring surfaces of the other forms of the invention have been replaced by spaced parallel surfaces.

Referring to the drawings, and particularly to Fig.- 1,

10 designates a piston rod having the conventional tapered end over which a piston body 11 is received and retained by a suitable nut 12. The body 11 comprises an axial hub 13 and an intermediate or central flange 14 which takes the axial load on the piston when the device is in use. Adjacent its ends the hub 13 is provided with annular grooves 15 for the reception of snap rings 16 which hold the several packing elements in assembled relation. Ob-

- 2 viously any suitable retaining means could be used for this purpose.

Since the pump piston shown is intended to be doubleacting so that pressure is developed by each end alternately, the packing elements are duplicated on each side of the center of the piston. Adjacent the central flange 14 is an annular disk 17 of impregnated fabric which is trimmed peripherally to have a running fit in the bore of the cylinder and which is shaped to lie closely around the hub 13 although it would not of itself provide a pressure tight seal on the interior surface adjacent the hub.

On the outer side of each of the fabric disks 17 is an inner rubber ring member 18. The word rubber used herein includes compositions whose principal ingredient is a natural or synthetic elastomer mixed with suitable fillers, hardening agents, plasticizers and other compounding ingredients. The inner ring 18 has one of its radial surfaces mating with the fabric disk, While its opposite surface is formed first in a radial plane as at 18 and then in the form of an intersecting cone 18 The periphery of the ring is flared outwardly either conically or in an arc of large radius from a small diameter coinciding substantially with the diameter of the fabric ring. The intersection of the peripheral surface and the conical surface 18 forms a sharp lip 18.

A second or outer rubber ring member 19 is provided on each end of the piston. On its inner side each of the rings 19 is formed with a radial plane surface 19 coinciding with and in close juxtaposition to the surface 18 of the inner ring. Radially outward of the juxtaposed plane surface is a conical surface 19 formed at a greater angle of divergence from the radial plane than its opposing surface 18 so that a conical void 20 remains between the packing rings 18 and 19. At its periphery the outer ring 19 is also conical from a base diameter again sub stantially equal to, but preferably less than, the diameter of the fabric disk 17 and extending outward to form a sharp lip 19. If the flared periphery of the outer ring is started from a base diameter less than the diameter of the cylinder in which the piston operates, a small void 21 will remain behind this ring and in front of the inner ring during operation.

Both rings 18 and 19 are thus larger in diameter than the working cylinder in which the pump piston operates so that they are distorted by insertion in the cylinder.

In the form of the invention so far described, a conically dished backing plate thereof so that the ring is free to flex during reciprocation of the piston. As above noted the several rings and plate are held against axial displacement by a snap ring 16.

Fig. 2 shows the piston in its cylinder and indicates the normal displacement of the periphery of the packing rings 13 and 19 by insertion in the cylinder. It will be noted that the elastomeric material of the inner ring 18 has been forced into the void 20, substantially filling the same. The volume of the void 20 is made substantially equal to or slightly greater than the volume of the material in the flared peripheral portion of the ring 18.

The outer ring 19 is distorted also in the direction of the axis of the piston, but in the preferred form, the small. void 21 remains open behind this ring. It is accepted practice that a piston of the type with which the present invention is concerned should be coated with a lubricant prior to installation in the cylinder to prevent burning and galling of the rubber rings during the initial strokes of the pump. Void 21 provides a reservoir for this initial lubrication, the lubricant being forced out as the piston the cylinder is filled with the fluid being pumped. Thus,

Patented July 30, 1957 22 bears against the outer surface. 'of the outer ring 19 but terminates short of the periphery I plate.

:void 21, acting as a reservoir, provides for amore positive lubrication of the piston lips during this critical time.

During operation of the pump, lip 19 will wipe fluid fromthe cylinder wallwhichwill collect in void,;21i; lf;-

due to operating conditions such as poor suction, the liner;

wallis dry during part of the stroke, then the fluid, colwill protect the piston lips. a A, s V s In the preferred form of the invention thefouter, ring. 13 would be made of a somewhat softer material than the inner ring 18. The'outerring '19 wears somewhat'faster than! the;inner ring 1 8, but dueto thecons'truction of the lected in yoid 21 will provide a film of lubrication; which.

pistonand thefunctions of the outer ring; this Wear-isnot detrimental. The outer ;ring;. 1-9 ha s two. functions, depending-upon the operating'conditions and, the degree to which the lip-is worn. [Afteran initial periodof ,use the outer ring acts primarily 'as a wiper ring, protecting the sealing lip of the inner ring lS from the damaging effects of-sandgrains; and grit entrained in the .fluid being pumped; Initially the outer ring acts as a sealing member in fconjunction'with the inner sealing. ring 18," but as the lip 19? wears. in service itmay pass a'limitedquantity of fluid and thereafter acts as a wiper ring.

'Insealingbetweena piston and cylinder of this type, two factors must be considered. 'The'sealing material mustbe flexible enough to pro vide a tight seal to resist abrasion andjyet enough to. resist extrusion. Heretofore,

pistons have had to sacrifice one for the other. In'the piston'of, the present invention, the" inner sealing ring 18 is enough-to resist extrusiombut would abrade easily. The outer sealing ring19 is made flexible enough to seal and resist abrasic'grn, buft w ould extrude easily. In con- 7 junction with each other, the outer ring seals and protects. the inner-ring from ,abrasion, whilefthe inner ring closes the clearanceto protect the outer ring frjomextrusion'.

'llhe form of the retainer or backing plate 22 may be varied depending'on the forces working against it. In some instances it may be desirable to replace the conically dished plate shown in Figs. 1 and 2 with a plate of the 7 form shown in Fig. 3. As thereshown the plate comprises a radial portion 30 against which a snap ring 31 is disposed, and a conical portion 32 extending from the radial portion. I Thefront surface of the outer sealing ring 1 9is molded to conform to the shape of the retainer In the form of the invention shown in Fig. 4, the radial plane surfaces 18* and 19 have been substantially eliminated'by molding the adjacent surfaces of the sealing rings 18 and 19 as plane conical surfaces 40 and 41 with slightly diiferent angles of divergence. A conical void 42 is thus established between the sealing rings, with the juxtaposed ormeeting surfaces of the rings being limited. to a small area near the hub which is established by squeezing the rings together during installation. Ob-

V viously it is not possible to maintain a complete separawithouthaving theparts loose on the hub.

Fig. shows a modification which includes the variations of Figs. 3 and 4. It will be seen that a retainer plate 50' shaped with a radial portion 51 and a conical portion 52 is provided: The void 53 between the sealing rings tion of the sealing rings from the periphery to the hub 64 which is of uniform width from top to bottom when the rings are relaxed. This void is, of course, partially filled by rubber displaced from the inner ring 18 when the piston is inserted in its cylinder, but is of sufficient extent to act as a reservoir for lubricant, while the juxtaposed surfaces 60 and 61 prevent flow of fluid along the hub.

While the invention has beendisclosed in conjunction with certain specific modifications, it should be expressly.

understood that it is capable of numerous other modifications and changes Within the scope of theap'peuded claims.

WhatIcIaimis: 1. In a pump pistonforpumping viscous abrasive bearing liquids the combination of, a piston body having a radial load carrying flange, and packing material on each side of said flange comprising, an inner deformable ring bearing against the outer face of said outer ring member.

is a deep conical space formed by adjacent conical surfaces 54 and 55 ofthe sealing rings, with the juxtaposed surfacesioftliesealingrings being formed by' forcing the ringsto'gether during aissemblyand during insertion of the piston in its working cylinder.

f In the forms so far described the voidfbetween the sealing rings has been formed by diverging surfaces. Fig. 6 showsa modification of -the invention in which the facing surfaces of the sealing rings are notdiverg'ent, but parallel, at leastin the relaxed state. In that modification therings 18 and 19; are provided with radial. juxtaposed surfaces and 61 of differ'ingradial' extent. Parallel conical surfaces 62 and 63 extend to the periphery of the rings from the respective radial surfaces to form a void 2. In a pump piston for pumping 'viscous abrasive bearing liquids the combination of, a piston body having a radial load carrying flange, and packing material onfv each side of said flange comprising, an inner. deformable ring member. having a peripheral surface that is conical with respect to the axis ofth'e piston' and having its minimum diameter substantially equal to 'the diameter of'the working cylinder in which the piston operates, an outer deformable ring member having a lip portion larger in diameter than the working cylinder in which the piston operates, said inner and outer ring members having juxtaposed surfaces and having surfaces extending radially away from said juxtaposed surfaces to form. a void between said members, thevolume of said void being at least equal to the volume of material displaced in said inner ring member by insertion of the piston in the Working cylinder, and a retaining member bearing against the outer face of said outer ring member.

3. In a pump piston for pumping viscous abrasive bearing liquids the combination of, a piston body having a radial load carrying flange, and packing material on each side of said flange comprising, an inner deformable ring member having a peripheral surface that is conical with respect to the axis of the piston and having its minimum diameter substantially equal to the diameter of the working cylinder in which the piston operates, an

outer deformable ring member having a lip portion larger in diameter tharithe working cylinder in which the piston operates, said inner'and outer ring membershaving justaposed surfaces .and having diverging surfaces extending radially away from said juxtaposed surfaces to form'a void between said members, the volume of said void being at least equal to the volume of ma-:

teri'al displaced in said inner ring member by insertion of the piston in the'w'orking cylinder, and. a retaining member'bearing against the outer face of said outer ring member. s

4. In' a pump piston for pumping viscous abrasive bearing liquids the combination of, a piston body having I a radial load carrying flange, and packing material on I each side of said flange comprising aninner deformable ring member having a peripheral surface that is conical with respect to the axis of the piston and having its minimum diameter substantially equal to the diameter of the working cylinder in which the piston operates, an outer deformable ring member larger in diameter than the eylifider in which the piston operates and hav ing its largest diameter terminating in a sharp wiping lip, said inner and outer ring members having juxtaposed surfaces and having diverging surfaces extending radially away from said juxtaposed surfaces to form a void between said members, the volume of said void being at least equal to the volume of material displaced in said inner ring member by insertion of the piston in the working cylinder, and a retaining member bearing against the outer face of said outer ring member.

5. In a pump piston for pumping viscous abrasive bearing liquids the combination of, a piston body having a radial load carrying flange, and packing material on each side of said flange comprising an inner deformable ring member having a peripheral surface that is conical with respect to the axis of the piston and having its minimum diameter substantially equal to the diameter of the working cylinder in which the piston operates, an outer deformable ring member having a conical peripheral surface the maximum diameter of which is larger than the diameter of the cylinder in which the piston operates to form a lubricant reservoir behind said maximum diameter, said inner and outer ring members having juxtaposed surfaces and having diverging surfaces extending radially away from said juxtaposed surfaces to form a void between said members, the volume of said void being at least equal to the volume of material displaced in said inner ring member by insertion of the piston in the working cylinder, and a retaining member bearing against the outer face of said outer ring member.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,054 Sharp et al Mar. 24, 1942 1,844,236 Armentrout Feb. 9, 1932 1,992,967 Roy Mar. 5, 1935 2,284,340 Nuckles May 26, 1942 2,417,840 Rodgers et a1. Mar. 25, 1947 2,431,653 Volpin Nov. 25, 1947 FOREIGN PATENTS 564,999 France Jan. 16, 1924

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