US1721325A - Piston packing - Google Patents

Description

w. G. WILEKDN PISTON PACKING July 16, 1929.

Filed Jan. 25, 1926 3 Sheets-Shem l A ITO/(NE July 16, 1929. G ,wu' soN 1.721,:525

PISTON PACKING Filed Jan. 25, 1926 3 Sheets-Sheet L l N l 751V TOR.

BY X/W G. WILSON mm jufly H6, Wag

' PISTON PACKING Fild Jan. 25, 1926 5 Sheets-Sheet 5 eY Z ,lflllillll"IHIIJIIIIIIIIII 1557/ I'I l/ I INVENTOR. .M/ /e Q. (14/00 Patented July 16, 1929.

. UNITED. STATES PATENT OFFICE.

WYLIE G WILSON, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO WILSON RINGS COMPANY, :OF JERSEY CITY, NEW JERSEY, A CORPORATION OF EW JERSEY.

PISTON PACKING.

the ring into relatively-close conformity with the cylinder wall. 7, Such rings are generally made with a normal exterior diameter, somewhat larger than the cylinder bore and upon introduction into the cylinder are contracted and slipped into place, so that their inherent resiliency will cause them to press against said wall.

In a ring of this character, it is absolutely essential in order to compensate for expansion and contraction of the ring under vary- .ing changes in temperature, to provide more or less clearance at the gap and it has long been recognized that no matter how well the ring is fitted some leakage must occur at this point, as well as through the ring groove of greater pressurethan at-other points, thereby causing unequal wear on both the ringand the cylinder wall. It is largely because of the leakage to which I have referred that a pluralit-y of such rings are generally employed, so that the pressure which may leak past the first ring will be partially retained by the next and so on. Thus. in a piston having three rings, all three are in practice essential,

to hold compression and if these rings are not properly fitted or are unduly worn, even three of them will not properly hold such compression.

The foregoing practice is common in internal combustion engines In some of the other arts where pistons and cylinders cooperate, as in pumps, pliable packing of leather, rubber 'and analogous materials has been extensively used. These materials are, however, permanently deformable and they soon become so permanently distorted as a result of wear,

7 physical deterioration or other causes that they can no longer perform their intended functions. In all prior art structures e1nploying either meta-l piston rings or a flexible packing, frequent inspection and repairs, at very considerable annoyance and expense, are necessary in order to maintain the assembly in a condition to preclude serious leakage of compression.

\Vith. these considerations in mind, the primary object of the present invention is to provide a piston and ring assembly capable of functioningthroughoutlong periods of use or inactivity in the promotion of a tight seal between the piston and the cylinder wall, so as to hold pressure or compressioh and without that detrimental leakage which so quickly developsin spite of the best prior practiee' Speaking generally, the assembly of this in vention embodies as one element of the construction. a piston ring of unbroken, i. c., unsplit, hollow frusto conical form, and in the preferred embodiment of the invention, the ring is of composite frusto couical scction- That is to say, it preferably embodies two frusto conical sections which intersect one another at substantially midway of their height, so as to form a ring section which is substantially cruciform or X shape.

I have discovered that a ring thus formed will function with remarkable efficiency in the formation of a tightseal against leakagt of pressure between the ring and the. cylindei wall and the base of the ring groove, when such ring is constructed from materials which, .for the purpose of this invention are termed obdu'rate materials. By this term is meant materials which are bendable, but not easily bent, compressible, but not easily coi'i'ipressed. elastic, but not easily deformed. As examples of obdurate materials, I may mention, with excluding others, iron, steel, hard alloys (such as bronze), glass, ceramic materials, hard rubber and wood. These materials are in pronounced contradistinction to those, which may be termed non-obdurate, such as leather, asbestos, soft rubber, soft metals, etc.

I have discovered that when an unbroken hollow frusto conical section of obdurate material is placed under axial compression which tends to flatten it, that the outer pe riphery of the frusto conical section will tend to expand cross axially and its inner periph ery will tend to cross axially contract to bring both of said peripheries into engagement with suitable cooperating seats or abutments.

By hollow frusto conical section, I mean a frusto conical section which is hollowed out to provide a frusto conical shell and by axial compression, I mean pressure exerted upon the element in a direction coaxial withor parallel to its axis, whereby its altitude is diminished and the peripheral diameter of the base increased.

lVhat has been said with reference to the peripheral expansion and contraction of a simple frusto conical section is also found to be present in composite sections and this is particularly true in sections wherein two hollow frusto conical sections are formed into a unitary structure in such manner that the sections intersect one another and producea substantially cruciform cross section. \Vhen a ring thus formed is axially compressed, each frusto conical section will be expanded at its outer periphery, while each inner periphery will be simultaneously contracted.

An ideal piston ring construction thereby results from this arrangement for the reason that if the ring is positioned in an adjustable ring groove and axially compressed, by-contraction, of the wall of said groove, the inner peripheries of the two sections will firmly engage with the base of the ring groove, while the outer peripheral edges of said sections may be brought into very nice sliding adjustment with respect to the cylinder wall. In this manner leakage back of the ring is absolutely precluded and the sliding engagement with the cylinder wall can be so nicely adjusted as to produce, in practice, a leak proof ring without undue friction.

Attention is particularly directed to the factthat the stressing of the ring must be within its elastic limit otherwise that nice adjustment to which I have referred would be impossible. For the best results, the ring, when in sealing condition, must be under internal stresses and thus in substantially balanced condition with respect-to the compres sion forces acting upon it, so as to properly conform with the coacting surfaces of the piston and cylinder to form the elticient seal to which I have referred. 'If the materialused in the manufacture of the ring is not obdurate. or if the ring is compressed beyond its elastic limit, the efticient functioning of the ring cannot be obtained. In practice, the ring should tend to resume (i. e. tend to spring back to) its normal unsealingform when the sealing stresses are relieved.

The term elastic limit, as employed in the specification and claims, is so employed to designate that quality or characteristic of the frusto conical form of obdurate material' employed, which, when compressed within predetermined limits, and then react-ion.

lieved from such compression, will cause the section to-return to approximately its original form and size. In accordance with this invention, it is intended that such con1pression shall be within and notbeyond the tendency of said frusto conical section to return to its original form and size. That is to say, it is intended that the degree of axial pressure employed shall not be sufficient to=break down and destroy the resilient orreactive quality of the frusto conical form herein described. On the contrary, it is the purpose in practising this invention that the degree of compression employed shall be limited to a degree where such reactive characteristic of the frusto conical form will not be seriously affected. For a better understanding of the operation of the frusto conical form of this invention, it is suggested that itfunctions like a. toggle. This analogy is, of course, not absolute, but when considered in that light, it may be helpful to a clearer conception of the operation of the invention. \Vhen force is applied to the elbow of a togglc, a greater force is exerted at the ends of the toggle links, and this force increases in proportion as the axial dimension of the toggle, relative to the distance between the ends of the links, becomes less and less.

The ring of the present'invention may be considered as functioning like a multiplicity of toggles; that is to say, there is a togglelike action in each diametric plane of each frusto conical element of the construction, and,'obviously, there is an infinite number of toggles. When the sealing element is compressed axially, the dimensions of each element and the proportion of the obduratc material of which it is composed, bring about, within the element, the steadily increasing functional characteristics incident to toggle This action results in a cross axial or radial movement of the ring until its outer and inner peripheries are forced into the desired tight sealing engagement with the cooperating seats.

The ring is so dimensioned and proportioned. and the seal is effected in the manner described before the elastic limit of the ring is reached. Accordingly. upon release of the stresses incident to producing the seal, the

element tends to autogenously, i. e., automaticall y, return to its unstressed, unsealing form. To utilize the ring of the character described, it is of course essential that the piston be constructed to embody means for placing the ring under axial compression requisite to produce the seal and while the specific structural details of the piston may vary within wide limits withoutdeparting from the invention, I lind it practical to provide a piston having a ring groove, the. axial dimension of which is adjustable, so that after the ring is positioiied in the groove in an unstressed condition, the axial dimension of said groove may be deereasedto place the ring under axial compression to effect the seal in the manner described.

It therefore follows that. in an assembly en'ihodying this invention. the. seal between the ring and the piston and between the ring and the cylinder all is effected by stressing a sealing member of hollow frusto conical form (preferably composite 'hollow frusto conical form) of obdurate material, within its elastic limit, by adjustment of the dimension of the ring groove, and that the seal is maintained as long as the. ring'is thus stressed.

It has been found in practice that in the operation of this device the grinding of the ring to a perfectly true lit may be dispensed with, thus accomplishing material economy in the operation of devices of this nature. It has been found that the structures here pre sented are such that even though in their primary manufacture they may not be axially coincident with relation each to the other, or of true complementary shape. yet in their conjoint operation they will adjust themselves to such irregularities and compensate for the' same by reason of the material from which they are manufactured, together with the particular form employed in their construction.

Features of the invention, other than those specified. will be apparent from the hereinafter detaileddescription and claims, when read in' conjunction with the accompanying drawings.

The accompanying drawings illustrate one practical embodimentof the inventiom'but the construction therein shown is to be understood as illustrative, only, and not as defining.

the limits of the invention.

Figure l is an end view of a piston and piston ring asscmblyembodying the present invention.

Figure 2 is a section on the line 22 of Fi rurel; and, r

Figures 3, 4 and 5, respectively. show a .piston ring of the character illustrated in Figure 2 1n radial cross section; these views show said ring in plan, elevation and radial cross section.

Figure 6 is a vertical section ofa modified construction. in that a frusto-conical element. is shown. instead of a cruciform construction.

Figure 7 is a. vertical section, partly in elevation, of said f usto-conical form.

Referring to the drawings, the several pa rts are indicated by numerals and letters, like numerals and letters referring to like parts.

1 .is a cylinder diagrammatieally illustrated. 2 is a piston and 3 a. piston rod. These elements may cooperate as part of any kind of an'engine assemblage or in any form of valve or pump in which such devices may be appropriately used. and in this sense they are employed in the description and claims of this application,

The details of construction are as follows:

A piston rod 3 is'reduced in diameter at 4 to form a shoulder, and hub as 5 and again re-. duced as at. 6 to provide a screw thremhrd sec tion on which is run the conventional nut 7. 8 is the periphery of the cylindrical piston 2.

piston. while 12 and 13 are cylindricalsurfaces having each an axis common with the axis of the piston. 14 is a disk having a. central aperture 15. 16 is a hub adapted to lit loosely into the aperture 15 ofthe disk 14. Said disk 14 is stepped forming the surfaces 17 and 18. which are in plancs' pcrpcmlicular to the. axis of the piston. while 19 is a cylindrical surface. 20 represents a plurality of scre.w-thrcadcd depressions in one section of the piston 2. while/21 represents a plurality of screws adapted to pass through suitable apertures in the disk 14 and enter said screw holes. 22 are set screws adapted to be mount- 'ed in suitable screw threaded apertures in the disk 14 and bear upon the surface 11 to lock the disk in 'tinaladjustment when the screws 21 have accomplished.their purpose.

'lhe-ringiexhibited in- Figxures 3, 4 and 5, and particularly designated by the numeral 23, has the characteristicsheretofore more The physical construction of such a ring is preferably as follow. ,Tt-is provided-with eight faces, two of which, as 24 and 25. and 29 and 30. are in planes perpendicular to the axis of the ring and hence parallel to each other. one being the top surface and the other the bottom. It is also provided with two peripheral surfaces 2'? and 28 which are in the lines of a common c linder, and two internal faces 31 and 32 which in like manner are in the lines of a common cylinder said cylinders having a common axis. It is also provided with annular grooves or depressions 26. 33, 34 and 35 r The device is assembled as follows: The lower half of the cylinder 2 is run on the shaft 5 resting on the shoulder t. The nut. 7 is then screwed 'down so as to look the section 2 to the shaft 5. A ring such as exhibited in Figures 3, 4; and 5, and designated generally till lift) as za is then cylinder wall generally as dropped into the peripheral aperture formed between'the" piston and the This'ap'erture is designated 36. Thedis'k '14 is then run on 7 to thefhub 16 and the bolts 21, of which there "are preferably three, I

are screweddown. It

is desirable that the pressure exercised by these screws be uniformly appliedbetween the sections f the piston 2- and 1%, and as s lt-hpressure 1s applied'it w ll cause the ring 23 to'e'xpand radially to the axis of the ring,-

' thus causing the internal surfaces of the ring ill and 32 to bear on the internal cylindrical surfaces 12 and 19, whereas the peripheral I surfaces 2T and 28 will be forced radially,

into engagement with the cylinder wall 9.

In other words there will'be a simultane- .ous expansion of the outer periphery of said ring and a contraction of the inner periphery resulting in cross-axial movement of the inner periphery in engagement with the inner face of said peripheral aperture of the piston, and a corresponding axial movement of the outer periphery into engagement with the cyl inder wall.

By this operation the inner peripheries of the ring are caused to form an elastic fluid tight joint with the inner periphery of said peripheral aperture of the piston, while the outer peripheries of'the ring are expanded to bear with an elastic sliding engagement but fluid tight fit upon the cylinder wall. In the form of the invention shown there are eight sealing surfaces presented by the ring to the walls of the peripheral aperture of the piston and the wall of the cylinder; hence an eflieient seal is accomplished.

Inasmuch as the ring, when axially compressed to form a seal, is stressed within its elastic. limit, its structure is such as to permit itto yield to slight irregularities 'in the cylinder wall, so that at all times said sealing relation is maintained.

I am aware that the structure shown in the drawings may be modified as will be apparent to those skilled in the art in adapting the in-- vention to use in the difi'erent arts, wherein pistons and cylinders cooperate and in some cases it may be desirable to provide the piston with more than one ring. For these reason the invention is to be understood as not limited to the specific showing of the drawings, but is rather to be considered as broad 1y novel asv is commensurate with the apended claims.

The degree of press'ure exercised by said screws 21'will determine the nature of the fit of the piston within the cylinder walls, and such fit may be made to conform to the par ticular usage to which the apparatus is-to be applied. In the event of wear incident to the operation of the pistonwithinathe cylinder, this can be taken up by tightening the screws 31, or if for any reason-it becomes desirable lultl'flOVC the piston, it is only necessary to re- [I lease said screws 2l'and the resilient or elastic quality of said obdurate ring will cause the same to retract, thus releasing the ring from contact with the wall of the cylinder.

It is desirable that when the appropriate relation is established between the cylinder and said ring by the screws 21, such relation should be permanently fixed. Provision is made for such fixing'or locking by the operation of the set screws 22 bearing upon the surface 11. \Vith the operation of these screws the relation ofthe sections of the cylinder 2 and LL will be permanently established and, vice versa, when it isdesired to release said setting.

It will be understood from what has previously been stated in" this specification that it is desirable in the operation of this device that, in the exercise of axial compression on the ring 23, such pressure should be limited so that it will not exceed the elastic limit of the ring. So long as said compression is within such elastic limit the ring will retract from its compressed condition when relieved of such axial pressure, and thus release the compression of the ring against the wallsof the cylinder for the purpose of accomplishing a suitable packing or seal.

In this application the packing ring is illustrated as a composite frusto-conical section embodying two frusto-conical sections intersecting one another substantially midway of their height so as to form a ring section which is substantially cruciform or of X-sh'ape in radial section. -This is regarded as the preferred form of construction but it is not intended to limit the case to that particular form of construction, as satisfactory results can be obtained by frusto-conical ring of obdurate material, as distinguished from the compound structure wherein two frusto-hollow cones are comhined to form the radial section of X or cruciform shape.

a is a frusto-conical element having faces I) and 0 parallel with its axis and faces e and f perpendicular to such axis. In other respects said frusto-cone is similar to the cruciform construction herein described as regards the material of which itis constructed, and the operation thereof.

Claims:

1. In a cylinder and piston assembly, :1 cylinder and a piston, said piston being provided with a peripheral aperture adapted to receive a piston ring, a piston ring'mounted within said aperture, such ring being de of obdurate material and integral, the form thereof corresponding to two hollow frusto-cones intersecting to produce a cruciform or X radial cross section. with means to exercise axial pressure on said ring to expand the same within its elastic limit between the wall of said aperture adjacent the axis of the piston and the cylinder wall.

the employment of one 2. In a cylinder and piston assembly, a cylinder and piston, said piston'being divided in a plane perpendicular to its axls, into two relatively movable sections to form a peripheral aperture between such sections, such aperture being adapted to receive a piston ring, and means to move such sections axially of said piston with relation each to the other to decrease or increase the axial diameter of said aperture, a piston ring mounted within said radial aperture, the same beingmade ofobdurate material and integral, the form thereof corresponding to two hollow frusto cones intersecting to produce cruciform or X 111-.

dial cross section so that with the axial contraction of said aperture, said ring will be expanded within its elastic limit with rel'av t-ion to its \seat within said aperture and the aperture between such sections, such aperture 7 having parallel walls in planes perpendicular to the axis of the piston and cylindrical wall adjacent the axis of-the piston, said aperture adaptedto receive a'piston ring, andmeans to move such sectlons, ax allyof said piston with relation eachto the-other, to decrease or ncrease the anal dimension of sald 2 aperture, a piston ring mounted within said radial aperture, the'same being of obdurate material and integral, theform thereof correspondingto two hollow frusto cones intersectin'g to produce a -cruciform or X radial cross section, the external and internal faces "of said ring corresponding to parallelc'ylin- Y I 40' planes perpendicular to the'axis of said-ring,

ders, whereas the remaining. faces are in sothat with the axial contraction of saidaperture said ring willbe expanded within its elastic limit between the cylindrical wall of said apertureadjacent the axisof the piston and the cylinder wall and, vice-versa, when relieved of such compression, saidring will" contract.

Signed byline at Jersey City, .N. this I day of J anuary, 1 926. wrrna e. w on;

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