US2800376A - Reciprocable plunger packing - Google Patents

Description

July 23, 1957 R. J. TRAUPMANN ETAL 2,800,376

RECIPROCABLE PLUNGER PACKING Filed April 6, 1955 C7 INVENTORS A 7' TORA/E/S.

RECIPRQCABLE PLUNGER PACKING Raymond J. Traupmann, Wauwatosa, and Harold I.

' Southerwick, Whitefish Bay, Wis., assignors to Blackhawk Mfg. (30., West Aiiis, Wis., a corporation of Wasconsin Application April 6, 1955, Serial No. 499,693

1 Claim. (01.309-34) The present invention relatesgenerally to improvements in the art of sealing relatively movable elements against leakage of fluid under pressure past coacting surfaces thereof, and relates more specifically to improvements in the construction and functioning of packings for plungers, pistons or rods reciprocable within the bores of cylinders or the like subjected to fluid pressure.

The primary object of this invention is to provide an improved reciprocable plunger'packing which is simple and durable in structure and highly eflicient in operation.

It has long been customary to utilize flexible cup packings for sealing the peripheries of plungers which are movable along cylinder bores and are subjected to fluids such as gas or liquid, against possible leakage of such fluid past the plunger. These cup packings may be formed of leather, nylon or other flexible and rather homogeneous materials, and each packing ordinarily comprises a plane rear wall adapted to be firmly clamped against a flat end surface of the plunger, and which is connected by an annular heel with one end of a cylindrical bore engaging flange having a continuous lip of angular shape at its free end. In such a plunger packing it is occasional practice to provide some kind of expander such as an internal spring ring'forassisting the fluid pressure in forcing the cup flange into engagement with the cylinder'bore, but none of these prior packing assemblages have proven satisfactory especially when operating with fluid such as oil under high pressure.

' It has been found that cup packings of the above type usually fail and wear out along an annular zone of the flange just beyond the heel bend. When the annular heel of the cup is forced into snug engagement with the cylider bore by means of a local expander as in the prior assemblages, the lip tends to pull away from the bore surface thus permitting the fluid pressure onfthe internal and external surfaces of the annular flange to substantially equalize so that the packing promptly fails to provide an eflective lip seal. The fluid under pressure then forms an annular wedge extending toward the intimate contact zone near the heel of the cup and causes rapid wear on thisheel with resultant failure at such zone, and this destructive actionis especially pronounced when operating with oil under high pressure.

"It is therefore an important .object of the present invention to provide a packing assemblage which eflectively eliminates such rapid failure in cup type packings by providing means for maintaining the lip in intimate contact with the cylinder bore while preventing excessive contact pressure adjacent to the heel of the cup.

Another important object of this invention is to provide simple but efiicient instrumentalities for insuring uniform sealing contact between an annular cup packing flange and the bore of a cylinder with which the packing cooperates, throughout an extended portion of the external surface of the flange remote'frorn the heel and attaching wall of the cup. 7

- A further important object of the inventionis toprovide an improved plunger packing of the flexible cup 2,800,376 Patented July 23, 1957 type having a resilient annular expander cooperable with the interior of the sealing flange of the cup so as to eflectively distribute wear and to eliminate localized wear failures on the flange sealing surface, thus insuring long life for the packing.

Still another important object of our invention, is to provide an insoluble fluid grommet of controlled large viscosity, for a flexible annular cup packing, which under the normal laws of fluid mechanics operating within itself but influenced by the cylinder fluid pressure, behaves in a manner to automatically distribute the applied force so as to produce the most effective sealing under all conditions.

An additional important object of the present invention is to provide an improved plunger packing unit especially adapted for effective operation with oil or relatively thin fluid under high pressure, and in which the various parts are conveniently accessible for inspection, removal and assembly.

These and other more specific objects and advantages of the invention will be apparent from the following description from which it may be noted that the gist of the improvement is the provision of a fluid pressure distortable resilient ring or grommet adapted to be snugly confined within and to coact with the sealing flange of a flexible cup packing in a manner whereby the sealing pressure is most eifectively applied to and distributed along the flange of the cup while the outward pressure of the heel is minimized.

A clear conception of the features constituting the present improvement, and of the construction and functioning of a typical embodiment of the invention, may be had by referring to the drawing accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various views.

- Fig. 1 is a top or end view of a ram assemblage embodying a cylinder and a plunger provided with the improved packing confined within the clyinder bore;

Fig. 2 is a central longitudinal section through a fragment of the cylinder and through a portion of the sealing end of the plunger of the assemblage shown in Fig. 1, illustrating the shapes of the flexible packing cup and of the resilient pressure distributing grommet before these elements are inserted within the cylinder bore;

Fig. 3 is a similar central longitudinal and fragmentary section through the same packing assemblage, but illustrating the shapes of the flexible and resilient plunger sealing elements, after the plunger has been initially inserted within the cylinder bore but before fluid pres sure is applied; and

Fig. 4 is still another similar central longitudinal and fragmentary section through the same packing unit, butshowing the shapes of the flexible and distortable ele-" .improved plunger, packing assemblage disclosed therein comprises in general a cylindrical by way of illustration, plunger follower 6 snugly embracing an integral screw threaded extension 7 at one end of a motion transmitting plunger rod 8, and which is movable by liquid 9 under pressure along the bore 10 of a cylinder 11; a flexible cup packing having an approximately plane end wall 12 coacting with the end face of the plunger follower 6 remote from the plunger rod 8, this wall being integrally connected to one end of an annular bore engaging flange 13: by a heel 14 while theopposite end of thisuflange is provided with a bore engaging lip 15;. and a resilient expansion grommet 16 having one end clampingly engageable with the cup. wall 12 while its opposite end coacts with a packing retainer 17 secured to the threaded rod extension 7 by a nut 18, the grommet having an inner surface 19 which snugly embraces the retainer 17 and also having an outer peripheral surface 20 which likewise engages the inner bounding surface of the cup flange 13.

The ram plunger may be of any desired length but the follower 6 should be of such diameter that its peripheral surface will have only a sliding fit within the cylinder bore 10, and the central bore of the follower 6 should snugly engage the rod extension 7 and may be sealed against leakage by an O-ring 22 confined within a V- groove 23 in the plunger and which coacts with the extension 6.. The follower 6 is also provided with an annular groove 24 for receiving a portion of the cup wall 12 when the cup packing is subjected to fluid pressure. The cylinder 11 may also be of any suitable length and diameter, and should be provided with the usual end head for producing a fluid confining displacement chamber in advance of the plunger 6 and the packing elements, and for introducing the pressure liquid 9 to such chamber during normal operation.

The flexible cup packing may be formed of leather, nylon, or any other suitable packing material, of sufficient pliability so that when subjected to fluid pressure, some material of the end wall 12 will flow into the groove 24 of the follower 6 and will thus provide a ridge which prevents enlargement of the diameter of the heel 14. The central opening in the end wall 12 of the cup packing should also snugly engage the central tubular portion of the follower or retainer 17, and this retainer may be formed of metal and should be snugly fitted upon the rod extension 7, preferably being provided with some means such as holes 25 for the relief of entrapped air when hydraulic installations are not initially bled of air. Such air, because of its lesser viscosity relative to the liquid, tends to enter between the grommet surface 19 and the adjacent retainer surface thus causing the grommet 16 to expand and increase the friction between the cup flange 13 and the cylinder wall and resulting in difiiculty in retraction of the plunger. The annular flange 13 01. the,

cup packing should also be biased outwardly as indicated in Fig. 2.

The resilient grommet 16 ispreferably formed of readily distortable but incompressible material such as solid rubber, and the flat end surface of'this grommet ring which clampingly engages the end Wall 12 of the flexible cup packing should be connected to the outer grommet bounding surface 29 by a surface having sufficientlylarge curvature so that it will be free from contact with the interior of the cup packing heel 14 at all times. The grommet 16 should also be of such thickness measured along the central axis of the ram, so that when the retainer 17 is initially clamped firmly against the follower 6 with the aid of the clamping nut 18, the central portion of the grommet will be snugly confined between the enlarged end of the retainer 17 and the endwall 12 of the cup packing, as in Figs. 2 and 3.

It is important that the various parts of the improved packing assemblage be accurately formed and cooperabl'e as hereinabove described in order to obtain best results, and when the packing elements have been applied and attached to the plunger follower 6, the sealing assemblage and its plunger and rod may be-initially introduced into the cylinder bore 10=as shown in Fig. 2, with the cylinder head removed. The annular flange 13 of the cup packing and the grommet 16 will then be expanded to the fullest extent, but the flexibility of the cup flange and of the grommet ring will permit the assemblage to be readily completely inserted longitudinally within the cylinder 11 as illustrated in Fig. 3.

After the follower 6 and the packing assemblage have been thus fully inserted, the cylinder head should be applied and liquid such as oil under pressure may be admitted to the sealed plunger displacement chamber, as depicted in Fig. 4. The admitted pressure liquid 9 will then distort the resilient grommet 16 as shown, to cause its face which is exposed directly to the fluid pressure to be forced inwardly thereby expanding the periphery of the grommet outwardly and simultaneously forcing its peripheral bounding surface 20 against the flexible sealing flange 13 of the cup packing throughout its major length from the lip 15 to a zone in relatively close proximity to the heel 14. The heel 14 ofthe cup packing will not however be forced outwardly by the grommet 16 because of the curvature of the grommet surface adjacent to this heel, but the remainder of the external flange surface including the lip 15 will be forced into sealing contact with the cylinder bore 10.

In the drawing, the horizontal lines applied to the cup packing lip 15 in- Fig. 3, represent the approximate area of greatest contact between the sealing flange 13 of the cup packing after the packing assemblage has been initially inserted but before the fluid pressure has been applied. The corresponding horizontal lines in Fig. 4, illustrate the increased and uniform area of contact produced when the fluid pressure has been applied, and these representations have been based upon actual observances through av transparent cylinder 11 and when, utilizing darkened liquid 9. While very slight contact between the, heel 14 and the cylinder bore 10 is effected when the fluid pressure is applied, the grommet 16 upon being distorted by the application of fluid pressure not only produces extended sealing contact along the major portion of the flange 13 but also firmly presses the'li-p 15 into engagement with the cylinder bore, and whenever the fluid pressure;isreleased the packing elements promptly reassumethe position and formationshown in Fig. 3.

From the foregoing detailed description it will be apparent that the present invention in fact provides a plunger packing which is highly effective and positively eliminates rapid wear at the heel 14 of the cup packing by maintaining the lip 15 and the major portion of the flange, 13 in uniform sealing engagementwith the cylinder bore 10 'while relieving the heel from outward pressure whenever the packing is in action. The formation of the resilient and distortable grommet 16 and the manner in which it is caused. to cooperate with the follower 6 and retainer 17 and. with the flexible cup packing, are important factors inobtaining the desired results, and actual tests} have prov'en that, the life of such flexible cup packings can be vastly prolonged with the aid of, suchgrommets 16. y

it has. been found that this improved packing assemblage provides effective sealing under both low and high pressure application, and the ridge formed on the cup flange 12 by the groove 24 positively maintains the heel 14 of the packing cup out of contact with the cylinder wall at all times. The improved packing also effectively prevents, the entry of pressure fluid between the lip 15 and thebore 10 by forming the grommet 16 so that it will constantly maintain contact with this lip 15 and will increase the outward pressure, thereon as the applied fluid pressure increases, and the improved packing may obviously; be applied to rams of various. sizes and for diverse uses.

Itjshould be" understood that it is not desired to limit this invention to the exact details of construction and operation of the rec'i'procable plunger packing herein specifically'shown and described for various modifications within the scope of the appended claim may occur to per'sonsskilledin the art.

We claim:

In combination, a cylinder having a bore, a plunger of less diameter than said bore reciprocable within said cylinder, a flexible cup packing having a supporting end wall integrally united by an annular heel with one end of an annular flange the opposite free end of which is provided with an annular bore contacting lip, a resilient and distortable solid rubber grommet of thickness measured axially of said plunger substantially equal to the length of said packing flange and having one end engag ing said cup supporting end wall and also having a peripheral surface snugly engaging said cup flange near said lip but being constantly spaced from said heel at the junction between said packing wall and flange engaging surfaces, and a retainer carried by said plunger and being cooperable with the opposite end of said grommet to clamp the latter against said cup wall and said wall against the plunger, said cup heel being of less external diameter than said plunger and constantly spaced from said cylinder bore and said grommet being distorta'ble by fluid pressure applied to said retainer engaged grommet end to expand said cup lip and the adjacent portion of said flange but not said heel into sealing contact with said cylinder bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,157 Wayne Apr. 17, 1934 2,658,809 Schultz Nov. 10, 1953 2,666,659 Audernar Jan. 19, 1954 2,701,172 Koester Feb. 1, 1955 2,708,573 Rovoldt May 17, 1955 FOREIGN PATENTS 544,910 Great Britain May 1, 1940 646,249 Great Britain Nov. '15, 1950

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