US2076543A - Process of making piston rings - Google Patents

Description

April 13, 1937. T. A. BOWERS PROCESS OF MAKING PISTON RINGS Filed Dec. 12, 1935 5 Sheets-Sheet l 2777 warrior {:9 affar'irgy April 13,1937. T. A. BOWERS v I 4 PROCESS OF MAKING PISTON RINGS Filed Dec. 12, 1955 5 Sheets-Sheet 2 April 13, 1937. T. A. BOWERS I PROCESS OF MAKING PISTON RINGS Filed Dec. 12, 1935 3 Sheets-Sheet 5 Patented Apr. 13, 1937 PROCESS OF MAKING PISTON RINGS Thomas A. Bowers, Boston, Mass., assignor to Flexion, Inc., Boston, Mass, a corporation of Massachusetts Application December 12, 1935, Serial No. 54,152

11 Claims.

My present invention relates to a method of making packing and more particularly to a method of fabricating piston packing rings froma ribbon or sheet material.

5 Attempts have been made to provide a flexible and circumferentially compressible packing ring for pistons by methods which consist generally of reversely bending and compacting a length of metal ribbon into a substantially cirl cular body, and flattening the saidbody at the points of bending to form top and bottom sides of a piston ring. Such methods have in general been proven to result in a ring which will not withstand the normal amount of wear en- 15 countered in piston use. I have discovered that one of the reasons, among others, for ring failtire is breaking, which commonly occurs at the points of bending or bends, as these points may be termed, and is largely due to that step 20 of flattening referred to above which necessarily thins the ribbon material at the .bendsand creates a weakened structure at those points where greater wearing strength is required.

The present invention discloses a method hav- 25 ing several new features, one of-which is the step of treating the ribbon materialwhereby such thinning and consequent weakened bend structure are eliminated and proportionately greater bend. thickness and strength are pro- 30 vided.

The present application is a continuation in part of my co-pending applications, Ser. Nos. 34,193, 21,183, 733,472 and 733,243.

The principal object of my invention is there- 35 fore an improved process of making packing rings- Another object is a continuous process of forming flexible piston rings from a metal ribbon.

Another object is a process of the character described for effecting strengthened ring structure at the points of bending.

Still another object is a process as described in which preforming of the ribbon stock before a bending occurs.

And still another object is a process of circumferentially reducing an annular body of reversely bent metal ribbon to effect proportion- 50 ate changes in said body. 4

And still another object is a process of treating metal ribbon to form a pistonring wherein an increased number of interstices per unit length of material is attained, a locking means 55 for the ends of the ring is elected, certain (or. 29-15mm hardening operations are performed and the width of the ring is increased.

Other objects and novel features comprising the construction and operation of my invention will appear as the description of the same progresses. 1

In the drawings illustrating the preferredembodiment of my invention,

Fig. 1 is a perspective view showing a length of metal ribbon as used in my improved process.

Fig. 2 is a view showing in side elevation a length of the ribbon material, shown in Fig. 1, reverselybent as the first step in the process of forming a piston ring.-

Fig. 3 is 'a view showing in side elevation-a length of the material being passed through forging dies which form the material with boxshaped crown portions.

Fig. 4 is aplan view diagrammatically indicating a closing step in which a pair of rolls go frictionally compact the material against ares'istance. I

Fig. 5 is an enlarged elevational. view showing a length of the compacted. forged material.

Fig. 6 is a plan view of a ring of material formed in a furtherstep from material similar to that shown in Fig. 5.

Fig. 7 is a reduced cross sectional view diagrammatically indicating a tapered die structure with the ring of material illustrated in Fig.

6 having been inserted in the die preparatory to being passed through the die.

Fig. 8 is a plan view of a finished ring as formed by the die illustrated in Fig. '7 and fur.- ther indicating the formation of a lock for the ends of the ring as effected by the die of Fig. 7.

Fig. 9 is an end elevatibn taken on the line 9-9 of Fig. 8. Y Fig, 10 is a modified plan view of material similar to that shown at the right hand side of Fig. 3, the material differing in that it is wedge-shaped or keystoned in its lateral dimension throughout.

, Fig. 11 is a broken-line showing, in side elevation, of reversely folded material in a compacted state upon which has been superimposed, in full lines, a similar view -of preformed material in a compacted state.

Fig. 12 is a view similar to Fig. 11 and showing the relative size of the reversely folded mate- 5o rial when thinned-by flattening to form crowns as compared with thepreformed material.

Fig. 13 is a diagrammatic elevational view indicating a preforming step as effected by a pair 1 reciprocating dies and illustrating the preformed material in cross section as reacted upon by the dies. n

Fig. 14 is a plan view illustrating the material after it has passed through the preforming step of Fig. 13.

Fig. 15 is an elevational view and illustrates a step of reversely bending the material, formed in Fig. 13, by rotating toothed members which effect the bending midway of the thicker'portions of the preformed stock.

Fig. 16 isan enlarged side elevation of a length of material formed by the step illustrated in Fig. 15 and as compacted by a step similar to that illustrated in Fig. 4.

Fig. 17 is a view similar to Fig. 'I diagrammatically indicating incross section a tapered die with a ring of material formed from material like that shown in Fig. 16, inserted therein.

Fig. 18 is a perspective view showing a finished ring as formed by the step illustrated in Fig. 17, the ring being similar to .the finished ring of Fig. 8.

Fig. 19 is. a side elevational view of a pair of rolling dies fragmentarily shown and indicating the first step in another modified method of preforming a piston ring material, the ribbon stock beingindicated in cross section.

F G. 20 is a view similar to Fig. 19 and illustrating a second step in which the dies have been somewhat deepened and the material has been thinned and slightly bent in a reverse manner.

Fig. 21 is a similar view and illustrates a further die step. i I

Fig. 22 is another similar view illustrating a still further die step.

Fig; 23 is a sirnilar view and illustrates a final step with the preformed ribbon material fully shaped and ready for compacting.

Fig. 24 is a view in perspective of a length of the 40 ring material preformed by the steps illustrated in Figs. 19-23 inclusive and passed through a compacting step. v

Fig. 25 is a plan view of a completed ring formed from passing a ring of material similar to that illustrated in Fig. 24 through a tapered die similar to that shown in Figs. '7 and 17.

Fig. 26 is a view showing in side elevation a length of unpreformed ribbon stock reversely folded and compacted as the first and second steps in another modified method of forming a piston ring.

Fig. 27 is a plan view of a ring indicating a furtherstep of shaping a length of material, similar to that shown in Fig. 26, into an annular body.

Fig. 28 is a view showing in cross section a tapered die with a ring of material, similar to that illustrated in Fig. 27, inserted therein.

Fig. 29 is a plan view of a ring which has been passed through a number of dies similar to that 0 illustrated in Fig, 28 with each succeeding die being smaller and the ring becoming correspondingly reduced in diameter.

Fig. 30 is a view showing, in cross section, a die similar to and smaller than the die illustrated in Fig. 28; and having a ring of material similar to that shown in Fig. 29 mounted therein.

Fig. 31 is a plan view of a finished ring formed by thismultiple die method.

Fig. 32 is a view showing in side elevation a portion of a ring similar to that illustrated in Fig. 27.

Fig. 33 is another similar side elevation and illustrates the ring portion after treatment by a die similar to that illustrated in Fig. 28.

Fig. 34 is still another similar side elevation 75 further illustrating the changing proportions of the ring portion as formed by a smaller die similar to that shown in Fig.30.

Fig. 35 is a side elevation showing the ring portion in its finally formed state.

Fig. 36 is a plan view of a length of ribbon stock used similar to that shown in Fig. 1.

I Fig, 37 is a plan view of a portion ofa ring resulting from folding such stock and treating it in a die similar to that shown in Fig. 28.

Fig. 38 is a similar plan view showing the effect of further die steps, and

Fig. 39 is a similar plan view of a portion of a J completed ring similar to that illustrated in Fig.

Referring more in detail to the drawings, ID in dicates a length of ribbon or sheet material from which my improved piston ring is fabricated. I may make use of any suitable material although I prefer a steel ribbon which may be of varying thickness and width. It will be understood that when this ribbon is reversely folded and compacted upon itself, interstices or minute openings occur between the adjacent bent portions. It has been found that certain characteristics, as flexibility and circumferenial compressibility, of the ring are greatly improved upon increasing the number of such interstices for a given ring size. Increase in the number of interstices for a given ring size may beobtained by preparing an oversize-ring and reducing it in diameter, or by using a thinner ribbon stock. With respect to the latter practice, there may be used a steel ribbon stock having a thickness of .015 inch and a width of inch. A thinner or thicker ribbon may be used and I may further desire to employ a keystone shaped ribbon. By this is meant a ribbon which is uniformly thickeralong one edge than the other. The ribbon material l0 may be formed into a piston ring by the present method with several modifications being practiced, if desired, as illustrated in the drawings. In general the ribbon material either in its normal state or a preformed state is reversely bent and compacted into a circular body which is reacted upon in a die or dies to form a finished packing or piston ring. The annular body as shown has the reversely bent portion occurring in a vertical plane and this relation is preserved in the finished ring. These portions are generally referred to throughout the specification as webs. The points of bending of the material comprise the top and bottom of the circular body. Theseportions are generally referred to in the specification as the bends or crowns. The top and bottom sides of a ring completely finished comprise a plurality of these crowns compacted together and they may be referred to collectively as the land surfaces of the ring.

One of the chiefsources of failure of rings of this general character, as shown by long and exhaustive experimentation, occurs in the crown structure of the ring. An important point in the present process is the specific treatment, relating to these crowns, and more particularly to the formation of a relative crown thickness greater than that obtainable by prior methods and pref erably equal to or greater than the thickness of an adjacent web portion.

In my improved process there are in general two methods by which such a result may be effected, the first comprising roughly the preparation of a ribbon blank having relatively thickened preformed crown proportions, as described,

substantially embodied therein, and the second comprising the gradual treatment of unpreformed reversely bent ribbon to effect, by steps,

the desired proportions in an annular body of the material.

In the drawings, Figs. 1-8 inclusive indicate 5 a method of preforming a ribbon blank and compacting the same to form a finished ring. This is illustrative of the first classification just cited.

Figs. 13-18 inclusive indicate a modified method of preforming a ribbon blank, reversely bending the same and compacting the same to form a finished ring. This is also illustrative of the first classification.

Figs. 19-25 inclusive indicate another modified method of forming a ribbon blank which combines preforming, reversely bending and compacting the material to form the finished ring. This is also illustrative of the first classification.

Figs.26-39 inclusive indicate a method of treating a ring of unpreformed reversely bent ribbon, in a series of dies which act to form the relatively thick crown and relatively thin web structure in successive steps. This is illustrative of the second classification.

These various modifications are all merely illustrative of the general method of my invention, which comprises so thinning the web portions of the ring that the minimum vertical thickness of the crown portions becomes relatively greater in comparison with the thickness of adjacent web portions measured in the direction of the circumference of the finished ring. The methods herein shown and described are believed to be fully representative of such procedure.

Taking these operations up in the order set forth by the drawings and with reference first to Figs. 1-8 inclusive, in Fig. 1, l indicates in perspective view a broken length of the metal ribbon stock already described.

The first step consists in passing the ribbon 40 I0 through a pair of complementary rotating dies, not shown, to obtain the reversely bent material H as illustratedin Fig. 2. The reversely bent material comprises webs l2 and bends or crowns IS. The bending action occurs along 45 sharp V edges l4 formed by these dies and extending transversely across the ribbon. The ribbon stock may be wound on a spool and delivered therefrom to the forming dies with any desired length being treated or a continuous action being maintained.

The next step comprises passing the reversely bent stock through a pair of rotary complementary forging dies 15 and I6 which have been frag- -mentarily illustrated in Fig. 3. This step results 55 in the formation of a material'with preformed crowns l3 and webs l2. The dies comprise openings ll alternately occurring with tooth portions 18. When one of the openings H is in a dead center position with respect to an opposite tooth 50 portion l8, the distance between the sides of opposed teeth I8 is less than the thickness of the ribbon stock whereby metal is flowed forming a structure as shown emerging at the right hand side of Fig. 3. An important point in this step 7 is the relative change in proportions of the crowns l3 and the webs l2. The crown now appears with a fiat top l3 and the vertical thickness of such a crown from the fiat top to the tip of the V point of bending may be equal to or greater than the thickness of an adjoining web l2.

In a further closing step, Fig. 4 indicates diagrammatically in plan view a pair of friction wheels which are adjusted a distance apart such 75 that they will grip a length of material similar to that illustrated at the right hand side of Fig. 3 and compact the webs and crowns together against a resistance. The friction wheels may grip the material at the alternately occurring crowns I3 or at the edges of the webs and crowns, the former being preferable. The resistance may comprise any suitable holding mechanism and in the present instance I have employed a pair of presser feet 2! which pass the material after it has become firmly compacted upon itself. The presser feet 2| are disposed against a channel base, not shown, which partly supports the material while it is being compacted. The presser feet 2| are also laterally adjustable so that the gripping force they will exert on material passing therebetween may be increased or decreased, depending on the amount of force found necessary to completely compact "the material. Fig. 5 shows a length of compacted material in side elevation and greatly enlarged. The material ll may be compacted into a circular body or ring 22, as is illustrated in Fig. 6, by using a curved compacting or holding mechanism similar to members 2| with the only difierence that these sides are curved, or a. length of the straight compact ed material may be given the circular formation when placed in a die in a later die step.

An intermediate step may be performed at this point for the purpose, if desired, of effecting locking means for the ends of the ring. This comprises cutting or impressing a slot 23 or other form of opening in one or the other of the ends of the ring 22. formation of the ring and the resulting locking structure will be later discussed in company with the finished ring characteristics.

The final step in this process has been diagrammatically indicated in Fig. 7 in which an oversize ring of compacted material similar to that shown in Fig. 6 is passed through a tapered die. Fig. 7 shows in cross section a die, generally denoted by the numeral 24, which comprises an annular tapered sleeve portion 25 in which is slidably located a core 26 which is provided around its top portion with means for receiving the ring of material 22. Upon the ring 22 and adjacent the core 26 is looked a punch member 27 by means of a threaded bolt 28. The action of the die is to pass ring 22 through a decreasing diameter whereby the ring is circumferentially reduced to a given ring size with the webs becoming thinned and the ring growing in height and width, and a polishing action being effected. These characteristics are somewhat illustrated in the finished ring shown in Fig. 8 and the detail Figures 11 and 12. Fig. 8 also illustrates the complete locking structure which may result from the intermediate step briefly referred to above. By the action of the die, metal will be flowed from the opposite end of the ring to take the shape of the slot or opening 23 and will comprise a key portion 29. Any type of opening and corresponding key portion may be formed although a vertical slot is considered more suitable since such a lock will prevent any radial displacement of the ends of the ring with respect to one another. Vertical displacement'is largely prevented by the piston groove in which the ring is located, although suitable locking means for such displacement may be provided.

While the die step is cited as the final step in the process there may sometimes occur certain small inaccuracies and roughness in the finished ring and when this occurs it may be desirable to perform certain minor flashing or grinding op- This step is not essential to the erations to provide polish and smoother finish. Such steps have not been illustrated, as conventional grinding apparatus is employed when this is done. One means of performing such grinding would, for example, comprise applying the ring to the fiat side of a grindstone-and then revers ing the ring so that both top and bottom land surfaces would be equally treated by the fiat side of the grindstone.

Fig. 10 shows in plan view a preformed material very similar to the material formed by the dies of Fig. 3. Such a material is formed by keystoning the portions I1 and i8 of the forming dies l5 and 16. By this is meant giving these portions a transverse wedge shape. Attention is again directed to the new step of forming a crown having a vertical thickness greater than that obtainable by processes heretofore proposed, preferably equal to or greater than the thickness of an adja cent web portion. Figs. 11 and 12 show a comparison of the two types of materials and the result of flattening a plain reversely bent material in which the crown thickness from the tip of an interstice to the flattened top is less than the thickness of an adjacent web portion, whereas the reverse is true with a preformed crown.

Referring to the modified forging process illustrated in Figs. 13-18 inclusive, Fig. 13 illustrates a first step in which a ribbon material similar to that shown in Fig. 1 and already discussed, is employed. A pair of reciprocating dies 30 and 30a receive a length of the ribbon l8 and form a blank 3| indicated in cross section, with crowns 32.

The action of these dies will be to effect a thinning and widening of the metal ribbon as illustrated in Fig. 14. A second step comprises reversely bending the blank 3| by passing it through a pair of rotary dies 33 and 34 which are similar to the dies described and illustrated in Fig. 3 and are designed to perform the bending at predetermined points located midway of the crowns 32.

Fig. 16 is a sideelevation of compacted material similar to that formed by the step illustrated in Fig. 15 and is intended to be illustrative .of a

compacting step as well, where a closing mechanism, similar to that described and illustrated in Fig. 4, has been used.

Similarly, Fig. 17 is intended to be illustrative of a final die step similar to that described in connection with Fig. 7, with Fig. 18 illustrating a finally completed ring 36 similar in all major characteristics to ring 22 already described in detail.

Referring to the further modified process illustrated in Figs. 19-25 inclusive, Fig. 19 illustrates the first step in which the same ribbon material 10 is utilized. The ribbon is passed through a pair of rolling dies 36 and 31 which are provided with scalloped surfaces 38. These scalloped surfaces form the ribbon III with corresponding formations 40 occurring at regularly spaced intervals.

Fig. 20 illustrates a second step in which a second pair of dies 4| and 42 having a more sharply defined scallop formation 43 treat the material to deepen the shoulders 44, thin the intervening portions and slightly bend the material.

Fig. 21 illustrates a third step in which a third pair of dies 45 and 46 treat the material to effect an increased shoulder formation 41 with pronounced reverse bending and further thinning of the intervening portions taking place.

Fig. 22 illustrates still another die step in which a fourth pair of dies 48 and 49 react simiby dies similar to those shown in Figs. 19-23 inelusive, which has been compacted in a step similar to that indicated in Fig. 4 and passed through a die step similar to that illustrated in Figs. 7 and 17.

Fig. 25 shows the finished ring 55 formed by this process, and being similar to the two previous rings 22 and 36.

Referring to the second classification illustrated in Figs. 2639 inclusive which sets forth a method of forming a piston ring from an unpreformed ribbon, Fig. 26 illustrates a first step in this process comprising reversely bending a length of the material to form bends 56 and webs 51.

A second step comprising the shaping of a.

ring 58 of such reversely bent material is illustrated by Fig. 27. It will be noted that the ring 58 is formed considerably oversize. For example, in forming a 3% inch diameter finished ring by the present process, ring 58 may be approximately 8 inches in diameter and it may comprise approximately 1450 interstices. process there may be a slight annealing given to the ring of material although it is not cited as necessary. This would be done by heating the ring to a suitable temperature and allowing it to cool slowly.

The third step in the process comprises passing ring 58 through a series of dies, such as die 59 of Fig. 28, similar in construction to those shown in Figs. 7 and 1'7. The size of the die may be such that for the 8 inch diameter ring used, there may be a reduction in diameter of the ring in the first die step of inch and approximately this decrease will occur in each succeeding step, although this exact figure need not be adhered to. Fig. 29 is intended to show in an exaggerated manner such a decrease in size of the ring.

Fig. 30 is illustrative of a number. of such die steps. For example, the ring may be passed through twenty of these die steps, in dies of successively decreasing diameters, before being finally completed as shown in Fig. 31, although a greater or less number of such die steps may be utilized. The passage of the rings from one die step to another may be performed as a continuous process by a suitable operation such as a Geneva movement. As stated in regard to the previous methods, there may be a simple grinding or polishing operation to finish the land surfaces of the ring although this is not cited as a necessary step in the process.

Figs. 32-35 inclusive illustrate diagrammatically the change in proportions effected in the ring during the die steps. It will be noted that the ring grows in height with the webs and crowns being thinned circumferentially of the ring and the proportionate difference between the vertical crown thickness and the circumferential web thickness being constantly increased. Also the crowns are entirely flattened. In some cases it would be possible to effect a flattening action with a die although it is not considered that this is preferable. Figs. 36-39 inclusive further indicate in development the circumferential thinning of the crowns and the widening of the whole ring.

Considerable emphasis has been laid upon cer- At this point in the '30 the ring, it is pointed out that these improve merits overcome definitely established problems and are of definite advantage in a packing ring.

Flexible piston rings, in use, are constantly moving or flexing radially. In so far as prior methods have resulted in thinning the crowns vertically relative to the thickness of the con- 1 necting webs measured in a direction circumferentially of the ring, a serious weakness in the finished ring has resulted. The radial flexing of the ring results in stresses and strains in the ribbon material, which tend to cause a break at the weakest point. The relatively inflexible crown portions are less adapted to absorb these strains than the relatively flexible connecting web portions. Thus my method of making a ring 01' relatively increased vertical crown thickness increases the strength of the finished product at the crucial point and results in a greatly improved ring. I prefer to form the crown portion with a minimum vertical thickness equal to, or even greater than, the thickness of adjacent web portions. It will be obvious, however, that the advantages of my process will be inherent in the finished ring to the extent that the relative crown thickness is increased over that obtainable by prior methods, whether or not full advantage is taken ofthis feature.

My novel process is adapted to the production of a relatively wide piston ring and obviates difflculties heretofore encountered in attempts to produce a ring of this wide type, such as difliculties L0 in assembly and the occurrence of sticking. The flexibility of the ring produced by my process obviates any difiiculty in assembly, whereas a cast iron ring is limited to a ring width which provides an inside ring diameter which can suc- 5 cessfully be sprung over the head of a piston without distortion taking place. If a broad ring in sections, of cast iron, is used, such broadness tends to create sticking of the ring with consequent failure of seal. My ring is installed in a 0 circumierentially compressed state and. there always will be present some flexing to offset sticking. However, the flexing force may be increased by increasing the number of interstices and also by imparting further springiness to the 5 metal while in its reversely bent state by the plurality of die treatments. v

The use of the broad ring necessitates a deeper piston groove and this provides a better seal since "blow-by must pass around a greater distance i in back of the ring. The wall pressure exerted by the ring produced by my process is greater and more uniform than that which can be obtained from a cast iron seal and with the elimination of blow-by through the gap at the ends of the ring by locking these ends together an outstandingly better seal results.

It is to be understood that I may vary the types of material used, the exact proportions cited and the sequence of steps set forth within wide limits while still adhering to the opiginal spirit of the invention.

Having thus described my invention, what I claim is:

1. In a process for forming from a strip of packing ring material, a packing ring in which said strip isreversely bent and presents flat crown portions, and web portions connecting said crown portions, the step which comprises thinning the web forming portions and decreasing the thickness of said portions, relative to the thickness of the crown portions vertically of the ring.

2. In aprocess for forming from astrip of packing ring material, a packing ring inwhich.

said strip is reversely bent and presents crown portions and web portions connecting said crown portions, the step which comprises thinning the web-forming portions of said strip by applying thereto, in a direction circumferentially of the finished ring, a pressure, and simultaneously applying a lesser pressure to said strip in a. direc-' tion vertically of the plane of the finished ring,

whereby the vertical thickness 01. the crown portions is increased relatively to the circumferen- "tial thickness of the webportions in the finished ring.

3. In a process for forming from a strip of packing ring material, a packing ring in which said strip is reversely bent and presents flat crown portions and web portions connecting said crown portions, the step which comprises thinning the web-forming portions of said strip packing ring material, a packing ring in which" said strip is reversely bent and presents crown portions and web portions connecting said crown portions, the step which comprises thinning the web forming portions and decreasing the thickness of said portions relative to the thickness of the crown portions vertically of the ring, and simultaneously increasing the width 01' the ring radially.

5. In a process for forming from a strip of piston ring material, a piston ring in which said strip is reversely bent and presents flat crown portions, and web portions connecting said crown portions, the step which comprises thinning the web-portions to such an extent that the crown portions in the finished ring have a minimum vertical thickness equal to, or greater than, the thickness of adjoining web portions.

6. In a process of forming a piston ring, said process comprising reversely bending a strip of piston ring material and compacting said reverse- 1y bent material to form a piston ring in which saidstrip presents crown portions and connecting web portions, the step which comprises thinning the web-forming portions of said strip whereby in the finished ring the crown portions have a vertical thickness at least equal to the circumferential thickness of an adjacent web portion.

7. In a process of forming a piston ring, said process comprising reversely bending a strip of piston ring material and compacting said re versely bent material to form a piston ring in which said strip presents crown portions and connecting web portions, the step which comprises whereby in the finished ring the thickness of the thinning the web-forming portions of said strip prise vertically disposed webs and bends, compacting the webs together to comprise a substantially circular body, successively decreasing the circumferenceof said circular body whereby said 5 bends are formed into flat topped crowns having a vertical thickness equal to or greater than the thickness of an adjacent web portion.

9. A process of forming piston ring material comprising reversely bending a metal ribbon.

10 closing. the bent portions upon one another and in circular position, passing the material thus shaped through a tapered structure and decreasing the circumference of the circle of material and compacting and shaping same.

15 10. In a process for forming from a strip of packing ring material, a packing ring in which said strip is reversely bent and presents crown portions and web portions connecting said crown portions, the steps which comprise forming in the strip a series of alternate relatively thin webforming portionsand relatively thick crown- -1orming portions, reversely bending the material THOMAS A. BOWERB.

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