US2679441A

US2679441A - Piston

Info

Publication number: US2679441A
Application number: US177724A
Authority: US
Inventors: Crawford K Stillwagon
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-08-04
Filing date: 1950-08-04
Publication date: 1954-05-25
Anticipated expiration: 1971-05-25

Description

May 1954 c. K. STILLWAGON 2,679,441

PISTON Filed Aug- 4 1950 4 Sheets-Sheet l CRAWFO/QD K 57744 W460 IN V EN T OR.

A TTORN E Y6 y 1954 c. K. STILLWAGON PISTON 4 Sheets-Sheet 2 Filed Aug. 4, 1950 BY X CRAW OEO 577Mk/46' W INVENTOR.

ATTO/PAEYJ y 1954 c. K. STILLWAGON 2,679,441

PISTON Filed Aug. 4, 1950 4 Sheets-Sheet 5 CRAWFOQfl K. $7744 WJGO'Y IN VEN TOR.

y 1954 I c. K. STILLWAGON 2,679,441

PISTON Filed Aug. 4, 1950 4 Sheets-Sheet 4 CRJIV/ORO 6775(116460/7 INVENTOR.

wwyxw Patented May 25, 1954 OFFICE PISTON Crawford K. Stillwagon, Houston,

Tex.

Application August 4, 1950, Serial No. 177,724

18 Claims.

This invention relates to improvements in pistons and refers more particularly to pistons used in heavy duty pumps and the construction of the piston which makes for simplicity, economy of manufacture, long life, and ready replaceability of the seal elements.

In heavy duty pumps for circulating drilling mud, cement, boiler feed fuel, acids and the like, the abrasive or corrosive character of the fluids pumped frequently result in relatively rapid wear of the seal elements of the piston. Also in such pumps frequently pressures ranging upwardly to 12,000 lbs. per square inch are encountered and these high pressures accelerate wear of piston seal elements.

Heretofore attempts have been made to design pistons having replaceable rubbers but all such prior attempts have been complicated by utilizing a large number of parts. The large number of parts have been objectional from the stand point of the difiiculty of assembling the pistons, the large number of parts which must be kept in inventory and the high cost of fabrication of the various number of parts, the metal ones of which each require machining operations.

An object of this invention is to provide a durable two-piece heavy duty piston.

Another object is to provide a durable heavy duty piston fabricated in two parts in which the seal means are carried by one of the parts which is replaceable.

A further object is to provide a piston having a body part and a core on which are molded the seal elements, the arrangement being such that one of the seal elements provides a seal between the core and body part.

Still another object is to provide a two-piece piston wherein the seal means are carried by one piece which is adaptable for use on either a tapered end type piston rod or a universal rod.

A still further object is to provide a heavy duty piston which may be fabricated with a minimum number of machining operations.

Yet another object is to provide a piston having a replaceable core which carries the seal elements, the construction being such that the replaceable core may be changed without removing the piston rod from the pump.

Yet a further object is to provide a two-piece piston wherein a seal element may be compressed between the two body parts and the piston rod to seal between the body parts and between the rod and the body parts.

Even another object is to provide a two-piece piston wherein one of the pieces may be formed with a closed end nut to threadedly receive and cover the end of a piston rod upon which the piston is to be mounted.

An even further object is to provide a piston 2 having a minimum number of metal to metal seating parts.

Other and further objects of the invention will appear as the descrption proceeds.

In the accompanying drawings forming a part of the instant specification, and wherein like reference numerals are used to indicate like parts in the various views:

Fig. 1 is a side elevational view, partially in section, illustrating a piston embodying this invention and shown mounted upon the taper end of a piston rod;

Fig. 2 is an exploded view illustrating the various parts of the piston shown in Fig. 1;

Fig. 3 is a fragmentary plan view of an annular wire mesh piece which may be forcing the seal material of the seal elements of the piston shown;

Fig. 4 is a view similar to Fig. 1 but illustrates a modified piston embodying the invention;

5 is a side elevational view partially in section illustrating a piston constituting another modification of the invention; and

Fig. 6 is a view illustrating a modification of the piston shown in Fig. 5.

In general, the piston of this invention comprises a body of rigid material made up in two parts which, upon assembly of the'piston, have metal to metal seating surfaces. One of the body parts has secured thereto the piston seal elements and is fabricated to be readily replaceable when the piston seal elements become worn or otherwise damaged in use. The other body part, as it does not carry any of the seal elements, usually need not be replaced, but may be used with successive body parts or cores which carry the seal elements. The piston parts may be held in assembly upon a piston rod by the usual nut and the arrangement is such that this nut may actually be formed upon one of the body parts and have a closed end for covering the end of the piston rod.

Referring to the drawings in detail, and more particularly Figs. 1 and 2, the invention is described as it is applicable to a tapered end piston rod. The end of a tapered end piston rod is shown at 5. Such piston rods are conventional, well known equipment, representing one type of rod in common use in slushpumps, cement pumps and the like, particularly where very high pressures are to be developed. The end of the rod is threaded at 5a to receive a threaded member, as nut 6, for securing the piston in assembled position upon the rod.

The piston body is made up in two parts including a tapered part 7 and a flanged part 8. The tapered portion of part 1 corresponds to the taper of the rod end 5. The part I preferably should have sufiicient length to substantially cover the tapered end of rod 5 so that the taper of the rod employed for reinterminates adjacent the end of member I as indicated by the line designated by the numeral 9.

The maximum diameter of the member or part 1 is considerably less than the overall diameter of the piston but is great enough to provide a shoulder H] which overlaps the axially extending flange or extension l l formed on the body part 8. The shoulder Hi and the flange H provide annular parts or portions carried by the body mem bers in which a portion of one of the seal elements [2 is disposed so as to seal between the two body parts.

The body part I may have portion l3 which mates in a socket Hi formed in part 8. This is especially desirable in short pistons as shown in Figs. 1, 2, and 4, because it makes it possible for part I to properly fit the taper of the rod end and still meet the other requirements of the piston. The socket i4 is deep enough to provide a space between a shoulder l5 and the end of member '1'. Thus, two faces which oppose each other are provided, between which the seal means it may be disposed. This seal means It is adapted to be expanded radially so as to seal between the rod 5, the body part i, and the body part 8 when the two body parts are mated so as to seat the shoulders I! and (8, formed upon the body parts i and 8. This is another real advantage of the mated construction.

In the embodiment shown, the body part it is held upon the rod 5 by means of a not 6 threaded to the end of the rod.

The body part 8 is the core part of a seal unit for upon it are securely mounted the seal elements l2 and I9. Preferably, these seal elements are molded directly on the body part a so as to be well bonded thereto, and the flange ll may have a series of openings circumferentially spaced there-about through which a portion of the seal element It extends. These openings are shown at Ila. The seal elements may be fabricated of suitable sealing material such as rubber, synthetic rubber, plastics, oil resistant rubber, freeze resistant rubber or the like. The seal means may have imbedded therein adjacent the out-turned flange or annular member 8a of the body, a plurality of stiffener elements which may be wire, fabric or the like. Preferably, wire mesh screens are utilized for this purpose. Bronze screens are preferred, as they are softer than the cylinder walls of pumps and will not scratch them and the seal elements bond nicely to them. This type of stiffener is preferred because it has been found that they expand when the seal elements are under pressure and provide a stiffener to back up the main body of the seal elements immediately adjacent flange 8a to prevent its extrusion between the flange and the wall of the cylinder.

The seal elements constitute seal means which are adapted to seal in each direction as the piston is reciprocated in use. The seal material is rigidly backed up by the out-turned member or flange 8a regardless of the side of the piston upon which the pressure builds up.

These elements 22 and [5% may be of the lip type as shown in the drawings or of any other suitable type. The lip type elements have substantially cylindrical portions adjacent their lip extremities as shown at I: and led. The diameters of these cylindrical portions are such as to provide an initial seal against the wall of the cylinder. Element i2 is provided with a cylindrical surface l2b which covers extension. H and is adapted to sealingly receive a corresponding cylindrical sura reduced diameter When surfaces 11 and I8 are seated by tightening nut B the portion element l2 between shoulder in and extension H is placed under pressure to form a seal and any excess seal material may flow from between body I and extension H through parts l la and between shoulder l8 and the end of extension H.

As an expedient in the molding of the seal unit, the flange 8a may be formed with a peripheral groove 8b so that any surplus molding material may be forced into the groove during the molding process. This insures a complete filling of the mold cavity so that the elements l2 and I9 will be full fashioned, filled out seal elements. This leaves a deposit of seal'material 2| within the groove.

In operation the piston, when assembled upon the rod 5, functions substantially as any other conventional tapered end type piston. It has been found to have a long life in use and the stiffener elements 20 have particularly added to the life of the seal elements immediately adjacent to the flange 8a where the pistons are used under high pressure. Where the elements 20 are duck, nylon, or the like they do little good but wire mesh has been found very desirable where the additional expense is warranted.

The arrangement of the piston parts is such that the seal unit including the body part 8- and the two seal elements may be readily removed without the necessity of removing the piston rod 5 from the pump. The nut 6 is backed off first and then the piston rod is reciprocated in a direction which would correspond to an upward movement as viewed in Fig. l, and this withdraws the body part I from the body part 8. Thus, considrable force is readily available to break the parts loose in the event they are stuck together or that the seal element 12 has become bonded to the body part 1. When the worn seal assembly has been removed, a new unit is placed over the rod end with the body part of the new unit matin with the part i of the old piston assembly. A nut E is then secured to the rod end to complete face on part i.

the assembly. This results not only in a saving of time heretofore necessitated in connection with the removal of the piston rod, but also the arrangement is such that the actual installation of the new seal unit upon the rod results in a saving of time as compared with the earlier and conventional practice.

The construction. of the piston is such that only two parts need be replaced, that is, the seal means l6 and the unitary assembly of the replaceable unit and the seal means 16 may in many instances be dispensed with.

One of the seal elements, namely l2, actually provides the seal between the cooperating parts of body members 1 and 8 so as to seal between these body parts. The seal means l5 also seals between these parts so that no foreign material which might be corrosive and tend to stick the mating joint between the body parts is able to get between the mating surfaces. In addition, the seal means It provides an effective seal between the member '1 and the rod end 5 to prevent washing of fluid therebetween which might have a cutting action.

It will be noted particularly Fig. l,

by reference to the drawing, that the only metal contacts between parts of the installed piston are the contact of body part 1 upon the rod, the contact between shoulder l1 and iii of the two body parts and the contact between nut 6 and the body part8. This has reduced the number of metal to metal seats subject to erosion by fluid washing therebetween over any replaceable rubber type piston heretofore available. Furthermore, the seal I6 and.

of fluid washing between these contacting parts. This is one of the advantages inherent with the two-piece construction with the core 8 having pistons heretofore available machining operations Thus this construction lends to economical fabrication.

The modification shown in Fig. 4 is the same as that shown in the preceding figures with the exception of the removable body part which is itself readily parts Ifl8a, H181),

nut 22 may be threaded to abut against the end tapered end rods too, is mounted on the rod sufficient to provide them with seat surfaces 2! 7 and U8.

The body part 208 has at its end remote from part 201, an annular tapered seal surface 208a adapted to be contacted by the tapered surface 220 on the abutment part 22! carried by the rod end. Surface 208a preferably is grooved at 2418b to receive an O-ring 222 to perfect the seal between the surfaces 208a and 220. Thus the seal is completed between the universal rod end and the body parts and between the body parts themselves, by the one O-ring 222 and that portion of the seal element 212 which resides between extension 2! l and the encircled portion of body 201.

The body part 281 has an internal thread so that it is threaded directly to the universal end and provides its own nut. This nut may be closed replace the old body part 201.

The modification of Fig. 6 is similar in all parts 30-6 and 3931, but it is to the part 39'! and nut 306 may be used in lieu of the body part 207 shown in Fig. 5

From the foregoing, it will be seen that this invention is one well adapted to attain all of not in a limiting The invention having been described, what is claimed is:

1. A piston comprising a body made up of two parts with a continuous passage therethrough, two-way resilient seal means molded operating and one of the seal portion disposed between the annular body portions when the piston is assembled to seal between the body parts.

2. The piston of claim 1 wherein the body part t which the seal means are not molded has a a taperinteriorly' of; the passage therethrough' to fit a tapered end piston rod.

3. The piston of claim 1 which is adapted for use upon a universal rod wherein the body part carrying the seal means has a tapered seal surface surrounding the passage therethrough at its end which isremote from the other body part.

4. The piston of claim, 1 wherein the body parts have closely mating portions, said seating shoulders on the body parts limiting the degree of mating, and confronting annular faces on the mating portions, said faces extending transverse- 1y of the longitudinal axis of the body and terminating interiorly of the passage to provide a seal receiving space.

5. The piston of claim body part adapted to be nearest the end of a piston rod on which the piston is to be installed, has an internally threaded section.

6. The piston of of claim 1 wherein the body part adapted to be nearest the end of a piston rod on which the piston is to be installed, has an internally threaded section to be threaded on the end of a piston rod and has a closed extension to cover a piston rod end.

7. A piston comprising a body having two seating parts with a continuous passage therethrough, an outturned flange on one of the body parts on the flanged part extending longitudinally from both sides of the flange to seal of the piston when reciprocated and extending radially, immediately adjacent said flange, a distance no greater than the external periphery of said flange.

8. The piston of claim 7 wherein the seal means are molded and bonded to said one body part.

9. A piston comprising a body made up of two parts with a continuous passage therethrough, an outturned annular backup member on one or said body parts extending outwardly thereof, resilient seal elements secured to the latter body part on both sides of the backup member and extending outwardly immediately adjacent said backup member no further than the external periphery of said backup member, a flange extend ing longitudinally from one of said body parts in a direction parallel to the axis of said continuous passage and along a portion of the other body part, said flange being outwardly spaced from said portion of said other body part, an outwardly extending shoulder on the other body part facing in a direction toward the end of said flange and spaced therefrom, and an annular portion on one of the seal elements disposed internally of said flange and against the other body part when the piston is assembled to seal between the body parts.

wherein the body part to which the seal means are not molded has a taper interiorly of through to fit a tapered end piston rod.

11. The piston of claim 9 which is adapted for use upon a universal rod wherein the body part carrying the seal means has a tapered seal surface surrounding the passage therethrough at its end which is remote from the other body part.

12. The piston of claim 9 wherein the body parts have closely mating portions, seating shoulders on the body parts limiting the degree of mating, and confronting annular faces on the mating portions, said faces extending transversely of the longitudinal axis of the body and terminating 'interiorly of the passage to provide a seal receiving space.

13. The piston of claim 9 wherein the body part adapted to be nearest the end of a piston rod on which the piston is to be installed, ternally threaded section.

14. The piston of claim 9 wherein the body part adapted to be nearest the end of a piston rod on which the piston is to be installed, has

an internally threaded section to be threaded,

on the end of a piston rod and has a closed extension to cover a piston rod end.

15. The piston of claim 9 wherein a plurality of annularly shaped wire mesh pieces are molded in that portion of the seal elements immediately adjacent the backup member and extending a substantial distance therefrom and normally of about the same outer diameter as the backup member.

16. As a subcombination a replaceable onepiece seal assembly comprising a metal core or body part with a central passage for receiving a piston rod, an annular outturned backup member on the core, seal means bonded to the core providing sea-ling material on both sides of the backup member for scaling in both directions and extending outwardly immediately adjacent the sides of the backup member no further than the periphery of said backup member, the seal material on one side of the flange having an exposed internal cylindrical surface coaxial with and of greater diameter than the passage, a seat surface on the core at the base of the cylindrical surface and extending inwardly of said cylindrical surface.

17. An assembly as in claim 16 wherein an annular extension is formed upon the core coaxial with the passage and cylindrical surface and terminating somewhat short of the termination of the cylindrical surface, and said cylindrical surface of the seal material is disposed internally of the annular extension and extends substantially to the seat surface, and an annular shoulder formed on the seal material extending outwardly from the cylindrical surface sufficiently to at least partly overlap the end of the extension.

18. As a suhcombination a replaceable piston seal assembly adapted for use in conjunction with a piston rod comprising a rigid body member or core with a passage therethrough and intermediate its,

body part, an outturned flange on the core, and resilient piston seal elements molded on and bonded to the core on both sides of the flange and extending outwardly immediately adjacent to the sides of the flange no further than said flange.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,612,038 Miller Dec. 28, 1926 1,813,930 James, Jr. July 14, 1931 2,062,808 Davis Dec. 1, 1936 2,216,291 Caldwell Oct. 1, 1940 2,216,577 Stillwagon Oct. 1, 1940 2,233,030 Pennick Feb, 25, 1941 2,277,501 Murray Mar. 24, 1942 2,287,483 Miller June 23, 1942 2,549,818 Joy Apr. 24, 1951