US2671705A - Oil-control piston ring - Google Patents

Description

March 1954 c. F. ENGELHARDT 1,705

OIL-CONTROL PISTON RING Filed Nov. 1, 1 951 3 Sheets-Sheet 1 /5 20 Fly. 2. /z4, [ll f I 13 f 2 l *25 I3 20 fif f f 25- 30 l6 l5 25 2O l8 l7 l2. 15 My. 5 -52 4. 7L,

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Z0 I 7 I 22 INVENTOR. CARL F ENGEL HARDT ATTORNEY c. F. ENGELHARDT OIL-CONTROL PISTON RING March 9, 1954 5 Sheets-Sheet 2 Filed NOV. 1, 1951 INVENTOR. (4R! 1-. ENGELHARDT ATTORNEY March 1954 c. F. ENGELHARDT 2, 7 ,7

OIL-CONTROL PISTON RING Filed Nov. 1, 1951 5 Sheets-Sheet 5 Fiy. I9. 0 (J7 4-0 1 1:9.

INVENTOR. CARL F. ENGELHARDT fiiu/mga/ Patented Mar. 9, 1954 UNITED STATES PATENT OFFICE 2,671,705 OIL-CONTROL Piston itiNG Carl F. Engelhardt, Yeadon, Pa., assignof to" Wil'-' kening Manufacturing ('Jorxipany,= Philadelphia; 9a., a corporation of Delaware Application Novemlier 1, 1951, serial No. 254,309

9 Claims.-

The present invention relates to certain new and useful improvements in piston-rings, of the self eizpanding type and it relates more particmany to segmented flexible oil-control pistonrings adapted for use in internal combustion engines.

An object of the invention is to provide a simple, inexpensive and effioie'nt seinex anding oil-cohtrol piston rin'g for use in internal combustion engines, capable of conforming to any out-ofroundness of cylinder and which will be durable arid comparatively easy to manufacture. Still another object of the invention is a more efiective oil control ring formed of one or more strips of sheet steel or other suitable sheet-metal, formed, bent and folded to provide a pair of relatively thin annular cylinder-contacting flanges and oil-passages therebetwe'en.

Other objects and advantages of the present invention will appear from the following specification and accompanying drawings.

Broadly the invention comprehends a segmerited self expanding, resilient piston-ring havmg a generally continuous, axially corrugated band spaced substantially inwardly from the outermost periphery of the piston-ring and having cylinder-contacting segment extending directly radially outwardly from the upper and lower terminals or loops of successive corrugations, the adjoining radial marginal portions of adjacent cylinder-contacting segments overlapping each other" with the overlapping surfaces generally contiguous to each other and with the circumferential extent of the over"- lapped marginal portions substantially less than the portions of the cylinder contacting segments which are not overlapped.

The invention further comprehends a self-expanding, resilient piston-ring composed of a pair of intermeshed ring-elements each of which is providedwith the corrugated band and the radially outwardly extending cylinder-contacting segments thereon. as outlined above, and the corrugated band of one ring-element is spaced radially inwardly (from the outermost periphery of the piston-ring) at a greater distance than the corrugated band of the other ring-element and the two corrugated. bands are arranged concentrically and within the other and generally eontigiioiis to each other, with the closed ends of the loops in one band adjacent the open end of the loops in the other band, and with the cylindercontaeting segments or extensions on the closed ends of the loops" of the radially imierniost corrugated hand extending flirough the open ends 2 of the loops of the radially outermost corrugated band;

Any suitahle sheet ihetal, such as sheet steel and the like m be used to form the ring of the present invention. v

For the purpose of illustrating the invention, there are shown in the accompanying drawings erms thereof which are at present preferred. although it is to be understood that the various instrumentalities or which the invention consists an he variously arranged and organized and that the inventiori is not limited to the preeise arrangements and organizations of the instrumentalities as herein shown and described.

Figure 1 represents a perspective view of a, selfexpanding piston-ring formed of a single strip of sheet metal, constituting one embodiment of the present inventioh.

Figure 2 represents a fragmentary top plan view of the ring-dement of Figure 1, in its flat cohdition prior to corrugation. I

Figure 3'- rpifeent's' an edge or side elevational View of Figiire 2 Figure 4 represents an outer side elevational view of the piston ring of Figure 1.

FigureB represents an inner side elevational view of the ring shown in Figure 1.

Figure 6 represents a top plan view of the ring of Figure 1-.

Figure '7' represents a cross-'s'eetion taken along the line L4 of Figure 4.

Figure 8 represents a perspective View of a riiodified piston-ring composed of two corrugated annular ring-elements.

Figure 9 represents a fragmentary top plan new of one of the ring elements of the embodiment shown in Figure 8 (namely, the ring elemerit which has the outer of the two corrugated hands shown in its flat condition, prior to corrug'atiori. V

Figure 10 represents an outer side elevational or edge view of Figure 9.

Figure 11 represents a fragmentary top plan view of the other of the ring elements of the embodiments shown in Figure 8 (namely, the ring element having the inner of the two corrugated bands), shown in its flat condition, prior to corrugation.

Figure 12 represents an outside elevatiorial or edge view of Figure 1-1.

Figure 13 represents an outer side elevational view of the piston ring of Figure 8.

Figure 14 represents an inner side elevational view of the pistoii ring of- Figure 8*.

Figure 15 represents a cross-sectional view on line Iii-I of Figure 13.

Figure 16 represents a fragmentary top plan view of the piston ring of Figure 8, on a slightly larger scale, and showing the gap in the ring.

Figure 17 represents a perspective View of still another modified embodiment of the piston ring of the present invention, composed of two corrugated annular ring elements.

Figure 18 represents a fragmentary top plan view of one of the two ring elements of the piston ring of Figure 17 (namely, the one which has the outer of the two corrugated bands), shown in a fiat condition, prior to corrugation.

Figure 19 represents a front side elevational or edge view of the fiat ring element of Figure 18.

Figure 20 represents a top elevational view of the other of the two ring elements of the piston ring of Figure 1'7 (namely, the one which has the inner of the two corrugated bands), shown in a fiat condition, prior to corrugation.

Figure 21 represents an outer side elevational or edge view of the flat ring element of Figure 20.

Figure 22 represents a fragmentary outer side elevational view of the ring of Figure 17.

Figure 23 represents a section on line 23-23 of Figure 22.

Figure 24 represents a fragmentary top plan view of the piston ring of Figure 17 on a somewhat larger scale, showing the gap.

In the embodiment shown in Figures 1 to 7, the ring is constructed from a single piece of sheet metal such as spring sheet steel or other suitable material, which is first stamped, out out or otherwise formed generally to the shape indicated in Figures 2 and 3. As shown in these figures, the material from which the ring is made is formed with a relatively narrow band I I from which project at regular intervals horizontal cylinder-contacting segments generally identified by the number I2. Each of these cylinder-contacting segments is composed of a relatively narrow or reduced portion or leg I3 and the outer cylinder-land-bearing section I4, which together form the generally T-shaped portions I2.

The outer circumferential edges of sections I4 are first cut (and later ground) on the radius of the cylinder to be fitted. One radial marginal portion (the right side as shown in Figures 2 and 3) of each of the sections I4 is bent (along lines It or 8) to form an off-set portion (I5 or H) which is in a plane parallel to and offset from the main portion of each T-shaped section I4. Alternate sections I4 have this olf-set portion I5 projecting upwardly while remaining alternate off-set portions I! are extended downwardly, as indicated in Figure 3.

The generally fiat blank element shown in Figures 2 and 3 is then corrugated and the radial marginal portions of the segments I4 overlapped as shown in Figures 4 and 5, and then coiled into a circular form and cut to a single circle or convolution to form the ring shown in Figures 1 and 5. The upwardly ofi-set portions I 5 on alternate segments I4 overlap the unbent marginal portions 20 of alternate segments I4, to form the continuous segmented and generally gap-less lower cylinder-contacting flange or edge 2i of the piston-ring, while the downwardly off-set marginal portions IT on the remaining alternate segments I4 overlap the unbent marginal portions 22 of such alternate segments I4 to form the similar upper cylinder-contacting flange or edge 23 of the piston-ring.

The spaced-apart legs I3 extend generally at a right angle to the band II and directly outwardly therefrom, and are separated by more or less rectangular openings 24, from which extend the radial slots 25 formed between the cylinder-land-bearing segments I4. The slots 25 are preferably wider at their inner ends than at their outer ends, so that when the band II is corrugated and the ring is formed into a circle, the side-edges 26 of the segments I4 will be on generally radial lines, as indicated in Figure 6. A single gap 54 is formed in the circle.

The dimensions of the segments I 4 and the distance between them are such that when the ring is in its final circular form and compressed in a cylinder, the overlapped marginal portions of the sections I4 have a circumferential extent which is less than, and preferably substantially less than the non-overlapped portions of the sections.

A flexible ring is thus provided with continuous upper and lower cylinder-contacting edges 2| and 23 which seal, scrape and control the oil on the cylinder-wall, with oil-drainage orifices or openings 21 formed by the axial loops, through which the excess oil removed from the cylinderwall is drained back into the crank-case (through drain-holes extending from ring-receiving groove of piston to the interior of piston) The ring is compressible circumferentially by flexing and stressing the legs of the U-shaped loops I9 of the axially corrugated band II. The ring will tend to have a uniformly distributed radially outward expanding force, when circumferentially and radially compressed into the cylinder-wall, with its ends and 56 abutting each other. This outward radial expansion of the ring, against the confining cylinder-wall, will be generally uniform at all points in the circumference. The ring will also conform to nonuniform or worn or out-of-round portions of the cylinder-wall, thus more effectively controlling the oil and reducing blow-by.

In the modified embodiment of the piston-ring of the present invention, shown in Figures 8 to 16, the ring is composed of two intermeshed ringelements, the flat blank of which are shown separately in Figures 9 and 11. The two ringelements together form a piston-ring with a pair of spaced-apart segmented but generally continuous oil-control cylinder-contacting flanges.

The flat blank of one of the ring-elements of this modification is illustrated in Figure 9, prior to corrugation. This ring-element is similar to that of Figure 2, and is provided with a narrow band 3!! from which the cylinder-contacting segments 3i project directly outwardly. The segments 3| are composed of outer portions 32 connected to the band by relatively short legs 33. The band 30, the legs 33 and the cylinder-contasting segments 32 form relatively narrow more Or less rectangular openings 34 and the relatively wide inwardly tapering slots 35. The radial marginal portions of each of the portions 32, are off-set (by bending) in the same direction, and

-' these off-set portions (36 and 37) are parallel to the main or intervening portions of 32. The portions 35 on alternate elements 32 are offset upwardly while the portions 31 on the remaining elements 32 are off-set downwardly, as is shown particularly in Figure 10. The cylindercontacting edges 38 of the segments 32 also are out or stamped to the shape of portions of a circle and are finally ground to a circle after the ring-element or ring is fully formed.

The flat blank of the second ring-element of modified form or oil=coiitrol ring is illustrated in Figures 11 and 12. As indicated in- Figure 1 1, a fiat sheet or suitable metal, such as a spring sheet-steer, is stamped or cut to the configuration she '11 in this fi to provide a narrow band 46 having cylinder-contacting segments 42 forming parts of the r 'shaped sections 43 connected to the band by relatively long legs 44, thus forming the relatively large rectangular opening 45" and the wedge shaped slots 4'6. Ihe fishe ies sections 43' are fiat,- without any on set marginal portions; a; is illustrated in Figure 12. The outer circurnrerential edges of these r-shaeed sections 43 are also cut or stamped along portions of a circle of the compressed radiu's oi the pistomring, which edges are ground on radius.

Each of the two ring-elements illustrated in Figures 9' and 11, respectively, is then corrugated in a manner similar to that assented in consection was the or Figures 1 to B; so that the pol tion of the bands and 45 betweenthe regs 33 and M, respecti'i ely, fi-r'n' lJ-sha'p'e'd loops in the reshectiveb orally continuous cor ushered loops, which are alternately seen at opposite sides.

After the two ring-elements have been so corifiigated they are ihterifieshed as is shown in Figures 13 to 1 5-, with the corrugated band M radially inwardly or contiguous to orrugated hafid 30, with the closed ends or the loops in hat-id 40 adjacent the open ends or the loops of the hand 30. The radial 1egs 44 on the band it extend. radially through the open ends of the loops or the corrugated band so and the radially extending segments 42 (it the corrugated hand 4B overlap" the ou set outer sin-faces or" radially extending" segments 32 of the co ugates '30; thus formin generally continuous and generally gap-less oil sealing scraping and controllin cylinder-contacting flanges or edges 41 of the piston-ring.

The dimensions of the T-shaped sections E i and 43 and the imensions or the slots and 4'6 and of the oft-set marginal portions 36 and 3'! of the segments 32' are such that the marg'inzl' portions of adjacent T-shaped cylindercen'tacting' segments 31 and 43 overlap each other in the manner generally indicated in Fig ure 13, with the overlapped marginal portions having a circumferential extent less (and preferably substantially less) than the non-overlapped portions of these segments. The radial extent of the legs 44 of the T sh'aped segments t3 are suchthat when the cuter edge of the corrugated band is in contact with the inner edge of the corrugated band 3!), the outer on curnferential edges of the T--shaped segments 13 extend outwardly just as far as the outer circumferentialedges of segments 3!, so that the outer circumferential edges of both segments SI and 43 will bear against the cylinder-wall with generally equal outward radial pressure when the ring is compressed threwithin. As shown particularly in Figure 16, the marginal sideeriges 39 and 28 of the T-shaped segments 3! and ii-l, respectively, are generally radially disposed.

The flexible segmented oil-control ring thus formed with radial oil-drainage openings 2?, wherein no open axial gap is left between segments at the outer periphery of the ring, thus reducing if not indeed eliminating blow-by between segments.

In the embodiment shown in Figures 8 to 16, inclusive (as well as in the embodiment shown in Figures 1? to 24, inclusive) any given or desired amount or outward radial cylinder contactin'g pressure between the pair of flanges and the cylinder wall- (or the unit pressure) can be achieved with less flexing or stressing of the convolutions or loops or the inner corrugated ring-expanding band or hands than is the case with the form of construction shown in Figures 1 to '1 inclusive.

Instead of the offset portions on the T-shaped segments of Figure 9, the T-sh'aped segments of Figure 11 may be appropriately offset. Instead oi the relationship shown in Figure 13, the T- shaped segments 43 may be disposed interiorly of the" T-shaped segments 31.

Another modified embodiment of the present invention is shown in Figures 18 to 24, inclusive. This modification also comprises two ring-elements in which the segments are intermeshed so as to reinforce ea'ch other and to close the gaps between segments of the cylinder-contacting flanges.

One ring-element is shown in Figures 18 and 19 and the other ring-element is shown in Figures- 20 and 21.

The ring element shown in Figures 18 and 19 is similar to that shown in Figure 9, but with the cylinder-contacting flange segments 32 of somewhat greate'd circumferential extent, and is likewise provided with a relatively narrow band 36 having at regular intervals the integral legs 33 which carry the segments 32. The outer radial cylinder-contacting edges of the segments 32 are cut or stamped with their outer edges as parts or a circle of the radius of the piston ring when compressed in the cylinder. Likewise,- the side-edges 3!! are onlines generally corresponding to the radius of the ring when confined in the cylinder. Ihis ring-element is also provided with the relatively narrow generally rectangular openings 34 and the relatively wide inwardly tapered slots 35. The segments 32 however are not provided with ofiset marginal portions (see Figure 19').

The second ring-element of this modification, shown in Figures 20 and 21, is generally similar to the ring -element shown in Figures 11 and 12 but with the cylinder-contacting flange segments 5'! thereof being smaller circuniferentially. The integral cylinder 'contacting segments 5! instead of being r shaped as in Figure 11 are generally straight, with the outer circumferential edges thereof also parts or the aforesaid circle, and with the side e'dge's thereof on lines generally corresponding to radii of the ring.

The two ring elem'ents shown in Figures 18 to 21 are corrugated in the same manner as de-- scribed in connection with Figures 2, 9 and 11, after which they formed into a circle and are intermeshed in the manner described in connection with the modification of Figures 8 to 16, so that the corrugated band 423 i disposed radially inwardly of and contiguous to corrugated band 30 with the closed ends of the loops in band 40 adjacent the open ends of the loops in band 30. The cylinder-contacting segments 5! onthe band All extend through the open ends of the loops in the band 36 and the outer end portions of segments 5i overlap the interior surfaces of the segments 32 ofthe band 38,- and bridge the gaps therebetween to form generally continuous sideflanges having oil sealing, scraping and controlling edges.

In this modification also, the overlapped marginal portions of the segments have a circumferential extent which is less (and preferably substantially less) than the non-overlapped portions of these segments.

In the modification shown in Figures 17 to 24 the segments in each of the spaced parallel cylinder-contacting flanges of the ring may have one of the marginal overlapping portions thereof offset in relation to the margins of adjoining segments, with the non-oflset portions disposed in such offset portion.

If desired, the segments may be disposed exteriorly of the segments 3|.

In each of the embodiments of the present invention, the narrow outer circumferential edges of the pair of cylinder-contacting flanges are also ground to a true circle (corresponding to the cylinder in which the ring is to operate), and, if desired, the outer side-surfaces of the flanges may also be ground parallel, so as to present ground surfaces to the sides of the ring-receiving groove of the piston.

The oil-control rings of the present invention are to be used in the lower ring-receiving groove or grooves of the piston with oil-drain holes extendin from the inner part of the ring-receiving groove to the interior of the piston.

In each of the embodiments of the present invention th flange-forming segments extend directly radially outwardly from the closed ends of the loops or convolutions of the corrugated ringexpanding band or hands, and bridge what otherwise would be a gap between adjacent segments at the outermost peripheries or at the cylindercontaoting zones of the flanges. Thus, each segment becomes a part of the cylinder-contacting flange on the same side of the piston-ring as that of the closed end of the loop of the corrugated band which carries the segment. By reason of this construction the segments are comparatively shorter and less subject to axial flexing and breakage than would be the case if the segments forming the flange on one side of the ring were connected to the corrugated band at the other side of the ring and were thus made to cross axially from one side of the ring to the other between the outer periphery of the ring and .the point at which the segment is connected to the band.

Instead of having the cylinder-contacting portions (I4, 32 and 42) symmetrical in relation to the legs (I3, 33 and 44) which carry them, the cylinder-contacting portions or segments may be disposed asymmetrically in relation to said legs, with the laterally longer side of such cylindercontacting portions overlapping the adjacent segment, with their overlapping marginal portions between such adjacent segment and the side-wall of the ring-receiving groove, and so as to be supported against axial flexing.

The present invention may be embodied in other specific forms without departing from the spirit or ssential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

Having described my invention, I claim as new and desire to protect by Letters Patent:

1. A segmented self-expanding resilient sheetsteel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and self-expanding inner portion intervening and connecting said flanges, said inner portion of said piston-ring comprising a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, a cylinder-contacting flange-segment integral with and extending directly radially outwardly from each of the closed ends of each of said loops to form said sideflanges and having generally radial side edges, one set of alternate flange-segments forming one side-flange and the other set of alternate flangesegments forming the other side-flange, relatively small marginal portions of the generally radial sides of adjacent flange-segments in each flange overlapping each other at the periphery of such flange and for some distance inwardly therefrom, the overlapped portions of said flangesegments being of substantially less circumferential extent than that of the non-overlapped portions thereof.

2. A segmented self-expanding resilient sheetsteel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and self-expanding inner portion intervening and connecting said flanges, said inner portion of said piston-ring comprising a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, and a cylindercontacting flange-segment extending radially outwardly from each of the closed ends of each of said loops to form said side-flanges and having generally radial side edges, one set of alternate flange-segments forming one side-flange and the other set of alternate flange-segments forming the other side-flange, and marginal portions of the generally radial sides of adjacent flange-segments in each side-flange overlapping each other at the outer periphery of such sideflange and for some distance inwardly therefrom.

3. A segmented self-expanding resilient sheetsteel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and self-expanding inner portion interventing and connecting said flanges, said inner portion of said pistonring comprising a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, and a cylinder-contacting flange-segment extending radially outwardly from each of the closed ends of each of said loops to form said side-flanges and having generally radial side edges, one set of alternate flange-segments forming one sideflange and the other set of alternate flange-segments forming the other side-flange, and marginal portions of the generally radial sides of adjacent flange-segments in each side-flange overlapping each other at the outer periphery of such-flange and for some distance inwardly therefrom, one of said marginal portions of each pair of overlapping marginal portions being offset inwardly by an amount approximately equal to the thickness of the other overlapping portion and such other overlapping portion being disposed within such offset.

4. A segmented self-expanding resilient sheetsteel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and self-expand ing inner portion intervening and connecting said flanges, said inner portion of said piston-ring comprising a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, and a cylindercontacting fiange=segment extending radially outwardly from each of the closed end of each of said loops to form said side-flanges and having generally radial side edges, one set of alternate flange-segments forming one side-flange and the other .set of alternate flange-segments forming the other sideefiange, and marginal portions of the generally radial sides of adjacent flange-segments in each side-flange overlapping each other at the outer periphery of such sideflange and for some distance inwardly therefrom, one of said marginal portions of each pair of overlapping marginal portions being offset in wardly by an amount approximately equal to the thickness of the other overlapping portion and such other overlapping portion being disposed within such ofiset, the overlapped portions of said flange-segments being of substantially less circumferential extent than that of the non-overlapped portions thereof.

.5. A segmente lf-expan ing r silient h e s eel p n-rin havin a pai of e m nted cylinder-c n act n s lan es and an inte ven ing circumierentially compressible and self-exp n i r p ion inte ven n an connecting said flanges, said inner portion of said pistonring comprising a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, a cylinder-contacting flangeesegnient extending directly radially outwardly from each of the closed ends of each of said loops to form said side-flanges, one set of alternate flange-segments forming one side-flange and. the other set of alternate flangesegments forming the other side-flange, and marginal portions of the sides of adjacent flangesegments of each flange overlapping each other.

6. A segmented sel-f expa nding resilient sheet-,- steel piston-=ring having a pair of segmented cylinder-contacting side-flanges and an intervening circl n ferentially commiessi'ble and self-expanding portion intervening said flanges, said pistonring comprising two nested and intermeshed ring-elements each having a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, the corrugated band of one ring-element forming an inner circumferentially compressible intervening connection between one set of alternate segments in each of said side-flanges and the corrugated band of the other ring-element forming an inner circumferentially compressible intervening connection between the other set of alternate segments in the other of said side-flanges, said two corrugated bands being disposed concentrically in relation to and one Within the other, with the open ends of the loops of one corrugated band being generally in radial alignment with the closed ends of the loops of the other corrugated band, a cylinder-contacting flange-segment integral with and extending radially outwardly from each of the closed ends of each of the loops of the two corrugated bands to form said sidefianges and having generally radial side-edges, alternate flange-segments extending from and carried by each corrugated band forming parts of opposite side-flanges, and one set of alternate flange-segments of each side-flange extending from and being formed integrally with one corrugated band and the other set of alternate flange-segments of each side-flange extending from and being formed integrally with the other corrugated band, the flange-segments of the innor corrugated band extending through the open ends of the loops of the outer corrugated band, all flange-segments, of each flange, extending to 1c the outer periphery of the ring and having cylinder-contacting edge portions, and marginal portions of the generally radial sides of the adjacent flange-segments overlapping each other at the periphery of .such flanges and for some distance inwardly therefrom.

7. A segmented self-expanding resilient sheet.- steel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and selfexpanding portion intervening said flanges, said piston-ring comprising two nested and inter, meshed ring-elements each having a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, the corrugated band of one ring.- elernent forming an innner circumferentially compressible intervening connection between one set of alternate segments in each of said sidefianges and the corrugated band of the other ring-element forming an inner circumferentially compressible intervening connection between the other set of alternate segments in each of said side flanges, said two corrugated bands being disposed concentrically in relation to and one withthe other, with the open ends of the loops of one corrugated band being generally in radial alignment with the closed ends of the loops of the other corrugated band, a cylinder-contacting flange-segment integral with and extending radially outwardly from each of the closed ends of each of the loops of the two corrugated bands to form said side-flanges and having generally radial side-edges, alternate flange-segments exending from and carried by each corrugated band forming parts of opposite side-flanges, and one set of alternate flange-segments of each sidefiange extending from and being formed integrally with one corrugated band and the other set of alternate flange-segments of each sideflange extending from and being formed integrally with the other corrugated band; the flange-segments of the inner corrugated band extending through the open ends of the loops of the outer corrugated band, all flange-segments, of each flange, extending to the outer periphery of the ring and having cylinder-contacting edge portions, relatively small marginal portions of the generally radial sides of the adjacent flangesegments overlapping each other at the periphery of such flanges and for some distance inwardly therefrom, the overlapped portion of such flangesegment being of substantially less circumferential extent than that of the non-overlapping portions thereof.

8. A segmented self-expanding resilient sheetsteel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and selfexpanding portion intervening said flanges, said piston-ring comprising two nested and intermeshed ring-elements each having a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, the corrugated band of one ringelement forming an inner circumferentially compressible intervening connection between one set of alternate segments in each of said side-flanges and the corrugated band of the other ring-element forming an inner circumferentially compressible intervening connection between the other set of alternate segments in each of said side-fianges, said two corrugated bands being disposed concentrically in relation to and one within the other, with the open ends of the loops of one corrugated band being generally in radial alignment with the closed ends of the loops of the other corrugated band, a cylinder-contacting flange-segment integral with and extending radially outwardly from each of the closed ends of each of the loops of the two corrugated bands to form said side-flanges and having generally radial side edges, alternate flange-segments extending from and carried by each corrugated band forming parts of opposite side-flanges, and one set of alternate flange-segments of each sideflange extending from and being formed integrally with one corrugated band and the other set of alternate flange-segments of each sidefiange extending from and being formed integrally with the other corrugated band; the flange-segments of the inner corrugated band extending through the open ends of the loops of the outer corrugated band, all flange-segments, of each flange, extending to the outer periphery of the ring and having cylinder-contacting circular edge portions, and marginal portions of the generally radial sides of the adjacent flangesegments overlapping each other at the periphery of such flanges and for some distance inwardly therefrom, one of said marginal portions of each pair of overlapping marginal portions being offset inwardly by an amount approximately equal to the thickness of the other overlapping portion and such other overlapping portion being disposed within such offset.

9. A segmented self-expanding resilient sheetsteel piston-ring having a pair of segmented cylinder-contacting side-flanges and an intervening circumferentially compressible and selfexpanding portion intervening said flanges, 'said piston-ring comprising two nested and intermeshed ring-elements each having a relatively narrow axially corrugated band of successive integrally connected loops alternately open at opposite sides, the corrugated band of one ringelement forming an inner circumferentially compressible intervening connection between one set of alternate segments in each of said sideflanges and the corrugated band of the other ring-element forming an inner circumferentially compressible intervening connection between the other set of alternate segments in each of said side-flanges, said two corrugated bands being disposed concentrically in relation to and one within the other, with the open ends of the loops of one corrugated band being generally in radial alignment with the closed ends of the loops of the other corrugated band, a cylinder-contacting flange-segment integral with and extending radially outwardly from each of the closed ends of each of the loops of the two corrugated bands to form said side-flanges and having generally radial side edges, alternate flange-segments extending from and carried by each corrugated band forming parts of opposite side-flanges, and one set of alternate flange-segments of each sideflange extending from and being formed integrally with one corrugated band and the other set of alternate flange-segments of each sideflange extending from and being formed integrally with the other corrugated band; the flange-segments of the inner corrugated band extending through the open ends of the loops of the outer corrugated band, all flange-segments, of each flange, extending to the outer periphery of the ring and having cylinder-contacting circular edge portions, relatively small marginal portions of the generally radial sides of the adjacent flange-segments overlapping each other at the periphery of such flanges and for some distance inwardly therefrom, the overlapped portion of such flange-segment being of substantially less circumferential extent than that of the nonoverlapping portions thereof, one of said marginal portion of each pair of overlapping marginal portions being offset inwardly by an amount approximately equal to the thickness of the other overlapping portion and such other overlapping portion being disposed within such offset.

CARL F. ENGELHARDT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,044,274 Zahodiakin June 16, 1936 2,343,915 Loeb Mar. 14, 1944 2,410,452 Loeb Nov. 5, 1946

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