US 3181876 A
Description (OCR text may contain errors)
y 4, 1965 M. D. FELT 3,1s1,876
PISTON CUP Filed May 22, 1963 FIG. 3
IN VENTOR MAURICE .FELT BY WM@ H A ORNEY United States Patent O 3,18L876 PISTON CUP Nani-ice D. Feit, Murray, Utah, assignor to Paehing Supply Company, Salt Lake City, Utah, a Corporation of Utah Filed May 22, 1963, Ser. Ne. %2,273 3 Claims. (Cl. 277-212) The present invention relates to piston sealing means suitable for use in hydraulic and pneumatic applications, and, more particularly, to a new and improved piston cup readily mountable to a piston Construction and which, by its unique Construction will have an unusually long life, exhibit optimum scaling properties, preclude undesired seal distortion, seal blowout, and general seal failure during operation, and which further may be easily and satisfactorily installed even through forces of compression thereon, due to mounting, may vary widely.
Accordingly, an object of the present invention is to provide a new and improved piston cup useable principally in pneumatic and hydraulic context.
A further object of the invention is to provide a new and improved piston cup which is suitably reinforced at its base to deter outward radial flow of the pisten cup material in the presence of high pressure imposition due either to operation contexts or to seal mounting.
A further object of the invention is to provide a new and improved piston cup which can be easily fabricated in a manner so as not to require conventional, expensive, laminate processes.
A further object of the invention is to provide a method of manufacturng the piston cup of the present invention, this with the choice of particular materials constituting the piston cup which will be most advantageous in obtaining low friction, high pressure seals for pistons.
A further object of the invention is to provide a piston cup wherein conventional mounting techniques may be employed in such a manner that the torque loading of the compression mount of the piston cup seal does not lie within a critical range, thereby insuring that, though high torque mounts may indeed be used, ow of the material or" the cup to the outer rim or flange thereof will be precluded, thereby preserving the inherent strength of the piston cup.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings in which:
FIGURE 1 is a top plan of a piston cup as conternplated by the present invention in a preferred embodiment thereof.
FIGURE 2 is a sectional View taken along the line 2-2 in FIGURE 1.
FIGURE 3 is an enlarged, fragmentary, sectional detail, taken along the line 3-3 in FIGURE 2 indicating the composite structure of the piston cup base in the present invention.
FIGURE 4 is a vertical section of a negative mold which may be used in practicing the method of manufacture employed in the present invention to produce the piston cups thereof; 'FIGURE 4, in particular, illustrates the initial deposit of a liquid mixture onto the upper surface of the mold.
FIGUR-E S is similar to FIGURE 4 but illustrates initial placement of a web material, preferably a cloth Web, over the initial layer of the liquid layer previously deposited onto the bottom of the mold.
FGURE 6 is similar to FIGURES 4 and 5, but illustrates, in addition, that after the web material has been placed, a supplemental pouring or deposit of the castable liquid substance is introduced into the negative mold and the positive mold positioned thereover so as to form the complete, piston-cup part.
-FIGURE 7 is an enlarged fragmentary wertical section of a cylinder construction enploying a reciprocating piston rod and piston which utilizes the piston cup of the present invention.
In FIGURE 1 piston cup lt? includes base 11 and peripheral fiange or lip 1@ integral therewith. The base ll is provided with aperture means 13 which is suitable for mounting purposes and which, generally, will be coaxially disposed about a portion of the pisten rod utilized in the mounting of the piston cup.
FIGURES 2 and 3 illustrate in cross section the construction of piston cup 10. It will be noted that the base 11 of piston cup i@ includes, embedded theren, a reinforcing web means i@ which is preferably disc-configured and concentric with the aperture i&
As to materials, the 'einforcing web means 14 preferably comprises cotton (luck, canvas, nylon or dacron cloth, or other material. Forty-two ounce cotton duck cloth has been used with much success. The body of the piston cup is shown to comprise a castable plastic material. In this area of discussion it is important to point out that while, conceivably, there may be some other liquid plastic which could perhaps perform the purpose of providing a lowfriction, high pressure piston seal, the inventor has discovered that a highly desirable composition of matter which can be used in this regard is his composition comprising a castable, liquid polyurethane, with granular tetrauorethylene resin and granular molybdenum disulfide being employed as additives and held in suspension therein. See the inventofs copending application referenced below. Preferably, and as is common practice in curing polyurethane, a suitable curative such as caster oil, water, a substance going under the trade name Moca, or other curative is added to the polyurethane preparatory to molding. The inclusion of a suitable curative is well established in making cast or molded, polyurethane parts. As the inventor's copending application, Serial No. 262,183, filed March 1, &963, and entitled composition of 'Matter Suitable for Machinery Packings and the Like" points out, it is preferred that the particle size of the tetrafiuorethylene resin be of from 4 to 10 microns, with the particle size of the molybdenum disulfide being in a range of from 1 to 4 microns. As to amount, it is preferred that to every 100 parts by weight of the castable liquid polyurethane, that an amount of tetrafiuorethylene resin be added within the range of 2 /2 to 10 parts by weight, with an amount of of molybdenum disulde being within a range of from 1 to 10 parts by weight. In the above regard, the complete disclosure of the above referenced copending patent application is entirely corporated herein by way of reference, and the material suggested is highly preferred in the practice of this invention.
lt will be noted with reference to FIGURE 2 that while the peripheral ange 12 is laterally or transversely dis-- posed with reference to base ll., somewhat greater than a degree relationship is enjoyed between the peripheral fiange 12 and base ll. Where the nominal diameter of the piston cup (see dimension ND in FIGURE 2) is nominally equivalent to or slightly less in dimension (as shown) than the cylinder bore, of diameter B, within which the pisten cup is to be employed, then the outwardly fiared character of the piston cup, which is resilient at flange 12, in desirably being greater in ultimate diameter than the diameter of the cylinder bore, will accomplish a scaling function of a self-loading type. This is particularly true in the case of employing the composition of matter suggested, since considerable resilience as to flange contour is enjoyed and may properly be taken advantage m of. In FIGURE 2, accordingly, the dimension B suggests the nominal diameter of the cylinder bore within which the piston cup is to be used.
FIGURES 4, 5, and 6 illustrate the progressive steps in the method of forming the piston cup of the present invention. FIGURE 4 suggests that, as to making the piston cup of the present invention, a negative mold 15 be first provided. This mold will also generally include a positioning pin 16. Upon the provision of the appropriate negative mold, a quantity of the liquid mixture comprising the liquified castable polyurethane, having tetrafluorethylene and molybdenum disuifide additives in amounts as above rcferenced, is introduced as a layer 17 over the bottom surface 18 of mold 15.
The next step will be to provide and to place a reinforcing web means 14 over the layer 17. Subsequently, an additional amount 19 of the polyurethane mixture is poured into the mold and the positive mold 26 positioned over positioning pin 16, with suitable pressure and heat being applied the two mold sections so that the part may be suitably forme-d and cured, as desired. It is to be noted in PIGURE 6 that by the above unique manufacturing process the piston cup of the present invention may be fabricated. As explained in the aforementioned patent application above referenced, the molybdenum disulfide and tetrafluorethylene additives in the polyurcthane mixture serve to create a low-friction part, and the polyurethane imparts suflicient strength, high abrasion resistance, and flexibility to the part that a long-lasting, high pressure seal may be obtained. It must be observed at this point that the invention is suitable not only for pneumatic and hydraulic work, but may also be used in other contexts such as vacuum work, for example.
FIGURE 7 illustrates a representative installation of the piston cup 10. Piston rod 21 is provided with a shoulder at 22 against which is seated piston 23. The piston 23 includes an interior bore 24 and a shouldered recess 25 which accommodates a sealing O-ring 26. Turned down portion 27 of piston rod 21 in FIGURE 7 is threaded at 23 to accommodate nut 29 which is torque loaded against Washer 39. Disposed between Washer 30 and piston 23 is the piston cup 10 of the present invention.
FIGURE 7 represents a conventional installation for piston cups in general. It is known in the art that two deleterious effects accompany such installation when general piston cups are employed. In the first place, overfightening the nut 29 through excessive torque imposed 'thereon will cause the base material of a conventonal piston cup to flow outwardly so as to weaken the cup and distort the seal between the peripheral flange 12 and cylinder wall 31. The reinforcement employed in the present invention in connection with the web means 14 prevents such material flow, radially outwardly which would otherwise carry piston cup material to the peripheral fiange area. Herce, workmen need not be overly careful about the compression loads which are exerted upon the piston cup by the tightening down of nut 29.
A second ground of failure heretofore encountered in 'the case of conventional piston cups is that while the O- ring 26 tends to serve as a seal, extreme hydraulic or pneumatic pressures may tend to work around this seal, to come into the area of aperture 13 of the piston cup and, at this area, to literally blow out the piston cup or at least produce a severe distortion at the scaling areas at the peripheral wall. This the present invention again avoids by use of reinforcing fabric or cloth 14 to prevent and thereby deter such fluid flow of the cup material. It has been proven in practice that the present piston cup stands up under extremely high pressures, both as to torque loading of the nut 29 and as to pneumatic vacuum or hydraulic pressures present at area P. This has been proven to be a very highly advantageous feature in the design of the present piston cup.
Though not all conventional piston cups are self loading, it is apparent that the present one is, owing to the tapered peripheral flange 12 which is seen in FIGURES 7 and 2.
It must be understood that it is not necessary and, in fact, is undesirable for the web 14 to extend into the lange area at 12, for such would substantially increase manufacturing cost and reduce sealing versatility of the piston cup.
It will be understood that the term cast" shall refer not only to conventional casting techniques but also to compression molding processes; compression molding is much the preferred approach in producing piston cups of the present invention, and compression molding has been specifically referred to herein in the discussion of the process of manufacture.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.
1. A piston cup including, in combination, a disc-configured base provided with mounting aperture means; a pe'ipheral fiange integral with, extending laterally from, and circumscribing said base, said base and peripheral flange being integrally cast of a pre-liquified, castable plastic material; and fiat, Washer-configured, reinforcng web means imbedded solely in said base for impeding material flow thereat under pressure imposition,
2. A piston cup including, in combinaton, a disc-configured base provided with mounting aperture means; a peripheral fiange integral with, extending laterally from, and circumscribing said base, said base and peripheral flange being integrally cast of a pre-liquified, castable, low-friction plastic material comprising liquid polyurethane, with gra-muar tetrafiucrethylene rc sin and grnnular molybdenum disulfide disposed in suspension in said polyurethane; and reinforcing cloth web means imbedded in said base for impeding material flow thereat under pressure imposition.
3. A piston cup including, in combination, a diss-configured base provided with mounting aperture means; a peripheral flange integral with, extending laterally from, and circumscribing said base, said base and peripheral fiange being integrally cast of a pre-liquified, castable, lowfriction plastic material comprising liquid polyurethane, with granular tetraluorethylene resin and granular molybdcnum disulfide disposed in suspension in said polyurethane; and reinforcing web means imbedded in said base for impeding material flow thereat under pressure imposition.
References cited by the Examincr UNITED STATES PATENTS 1,273,738 7/18 Christenson 277-212 1,353,522 9/20 Emerson 264-271 X 1,372,760 3/21 Ludenback 277-212 1,520,704 12/24 Farmer 277-212 1,767,936 6/30 McElroy et al. 277-212 2,600,516 6/52 Pielop 277-212 2,637,606 5/53 Pielop 277-212 2,868,575 1/ 59 Hawxhurst 277-229 X 2,948,651 8/60 Waag 264-271 X 2,990,206 1/61 Bagdon 277-229 X 3,020,185 2/62 Moflit et al 277-229 X LEWIS I. LENNY, P''ma'y Exam'ner.
EDWARD V, BENHAM, Examner.