US2200609A - Piston ring forming apparatus - Google Patents

Description

E. R. WEEK, JR

PISTON RING FORMING APPARATUS May 14, 1940.

Filed March 12, 1937 Patented May 14, 1940 UNHTED STATES PATENT OFFICE Edmund R. Week,

In, Oakland, Calif.

Application March 12, 1937, Serial No. 130,545

5 Claims.

I The invention relates to apparatus for formmg and manufacturing piston rings. This applicationis a continuation-in-part of my co-penda. ing applications, Serial Numbers 742,033 and 742,220, filed August 30, 1934, and August 31, 1934, respectively.

Piston rings of internal combustion engines may be divided roughly into two classes, the single one piece type and the multiple piece type.

The former belongs to a class comprising a single annular ring, as of cast iron or the like, which is mounted in a ring groove in the piston and serves by its own resilience to expand outwardly from the ring groove into sealing engagement with the cylinder wall. This type of ring by reason of its simplicity and relative cheapness has found a very wide usage in internal combustion engines. However, as may be understood, a single piece ring must have the dual qualities of resilience so as to firmly urge the ring against the cylinder wall and in addition have a proper bearing surface against the cylinder walls for procuring a smooth and uninterrupted seal. As

, may be also understood, these qualities of resilionce and bearing surface are not necessarily or normally found together in a single metal and accordingly a plurality of members having specially selected metals to accomplish separately I the functions of resilience and cylinder engagerings have been found to function remarkably well and at a considerably higher efficiency than the first mentioned type. Especially is this true at higher engine speeds where the relatively poor resilience of the one piece ring is incapable of preventing an excessively high blow-by of products from the combustion chamber of the cylinder into the crank case.

While the multiple piece, spring type of ring is capable of affording these and many other important advantages over the simple one piece ring first mentioned, the multiple piece ring ordinarily involves in its construction the use of relatively small cylinder engaging rings and the construction of these small rings to withstand the high pressures and temperatures obtaining in This type of ring makes the cylinder has been a source of weakness in these rings. At first attempts were made to cast or machine these relatively small rings from cast iron, but they were found much too brittle to give lasting service and would, after a relatively short period of use, be broken. Attempts followed the use of cast iron in the field of bronze but it was found that when this substance was cast the same was substantially as brittle as: the cast iron and relatively unusable. Also, when the bronze rings were drawn r extruded they were much too soft, were quickly mutilated, and consumed by oxidation and disintegration.

Applicant has found through exhaustive tests extending over a protracted period of experimentation that these small cylinder engaging rings of the multiple piece type should be as substantially as hard as the cylinder wall that they engage, or if there is any difference in hardness that it should be on the softer side, preferably not exceeding from to points on the Rockwell B scale. It has been demonstrated that if these small rings are materially harder than the cylinder side walls, they will have an abrasive action thereon tending to scratch and deform the cylinder. On the other hand, if such rings are materially softer than the cylinder wall, they permit the embedding and seating of particles of dust and other foreign substances which in turn have an abrasive action on the cylinder side wall. Furthermore, it has been found that coordinated with the aforesaid hardness: the rings must be of maximum toughness so as to resist wear and deformation. Also, these small rings should be of low resilience and relatively flexible so that substantially the total resilience of the ring will reside in the body ring and the smaller rings will be uniformly pressed outwardly by the body ring into close conformity with the cylinder walls. In addition, the rings should have a substantially different fineness of surface grain structure and texture than the cylinder walls so as to aiford a low coefficient of friction therebetween.

In satisfying the above conditions, attempts have been made to use materials such as steel in one form or another, but while the hardness of the ring was thus obtained, the other desired characteristics did not follow. Tempered high carbon steels in most instances were too hard, too abrasive and much too stifi and resilient. Annealed steels proved too soft, became mutilated and of little use. In accordance with my invention, however, and as a principal object thereof, I have provided for the use of materials such as steel in the construction of these small rings by initially selecting a certain hardness and carbon or other alloy content and then processing and working the metal in a way as to retain and increase its hardness to approximately that of the cylinder side wall with which it is used, to greatly increase its toughness, to introduce a necessary degree of pliancy and to maintain its resilience low.

Another object of the invention is to provide an apparatus for causing the desired fabrication of the metal as aforesaid simultaneously with and by the same operations involved in fabricating the ring structure and thereby not only to greatly simplify the manufacture of the ring but also utilize the changing molecular arrangement involved in the fabrication of the steel to effect a greatly improved construction in the cylinder engaging edge and the free ends of the ring.

A further object of the invention is to provide an apparatus for forming on rings of the character described minute annular beads extending around the cylinder engaging wall and which serve to provide almost from the very outset a proper seating of the ring against the cylinder wall.

Still another object of the invention is to provide an apparatus of the character described which will in a single advance movement of a die completely form a ring of the character above set forth.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Referring to said drawing:

Figure 1 is a cross sectional view of a multiple piece type ring in the forming of which the apparatus of the present invention is particularly used. the ring being here shown operatively positioned in the ring and cylinder.

Figure 2 is a side view of the bending and rolling device used in connection with the present invention.

Figure 3 is a plan view of a ring loop as placed in the die for forming by the die.

Figure 4 is a side elevation of one part of a die constructed in accordance with the present invention.

Figure 5 is a sectional elevation view of a cooperating part of the die.

Figure 6 is a transverse sectional view of a part of the die member illustrated in Figure 4 and is taken substantially on the plane of line 66 of Figure 4.

Figure '7 is an enlarged fragmentary sectional view of opposed ring connecting surfaces of the die.

Figure 8 is a fragmentary plan view of a part of the ring formed by the die.

Figure 9 is a transverse sectional view of the ring illustrated in Figure 8 and is taken substantially on the plane of line 99 of Figure 8.

The piston ring shown in Figure l of the drawing is illustrative of a multiple piece type ring referred to in the foregoing. The ring here shown is of an improved form which has been more fully described and claimed in my co-pending applications aforesaid and includes a resilient body or main ring II which carries one or more side cylinder engaging rings l2. The body ring by reason of its appreciable size and inclusion of resilience is not of critical construction from a strength and wearing standpoint as are the smaller side rings l2. It is with these side rings that the present invention is primarily concerned and in the making of these small rings strong, durable, and possessive of other desirable characteristics hereinbefore mentioned. However, as will be understood, the apparatus of the present invention may be used for makin other piston rings of a different character.

As here shown, the side cylinder engaging rings are of substantially square or rectangular cross section and for simplicity in the construction of these rings. I prefer to use a steel wire l3 which is commercially square and of cross sectional dimensions somewhat larger than the finished dimensions of the ring. In accordance with the present invention, I select a drawn annealed steel wire of 50 to 65 point hardness of the Rockwell B scale and which has about 1 per cent carbon content. This wire at the outset is too soft for immediate use as a piston ring but when treated and formed by the apparatus of the present invention the metal is hardened to approximately the hardness of the cylinder wall and is worked to increase its toughness.

The wire is first fed into a bending and rolling machine M which is of conventional design including an enlarged and grooved roller it which cooperates at its circumference with smaller wire confining and bending rollers 21. The wire is delivered from the rollers in a helical formation and is cut into single unit coils l8. Preferably in cutting the coils, the free ends 29 thereof are arranged, with the radially outer edges 2| thereof cut diagonally ahead of the inner edges 22. Also, will be understood the bending of the normally straight wire into a circular formation will cause by relative crowding and expansion of the material respectively at the inner and outer circumferential, axially extending, sides with a corresponding increase and decrease of the axially extending dimensions of such sides. This has the effect of distorting the cross-sectional shape of the ring as indicated roughly in dotted lines in Figure 9 from which shape the ring is cut and pressed into a sharply defined square by means of the die and as shown in full lines of Figure 9.

The loops !8 when cut as above, are ready for working and forming into the final product. Such operations are arranged, in accordance with my invention to be effected by a single die 23 and by a single advance movement of the die. The latter, as here shown, consists of male and female sections 24 and 26 which are arranged for interengaged positioning for forming and working the ring therebetween. The female member is of stationary construction and includes a base support 21 having a recess 28 for the receipt of a removable annular die block 29 and is formed centrally therethrough with a guide bore 3!. Formed in the block and opening jointly to the top and inner surface thereof is an annular ring seat 32 for receipt of the loop l8 and is arranged to cooperate with the male section to compress and form the ring therebetween.

The male section of the die is arranged for mounting in a press and comprises a guide portion 33, a skirt 34 surrounding and longitudinally spaced from the portion 33 and an annular shoulder abutment 36 surrounding an end of the skirt, the portion 33. skirt and abutment being substantially concentrically arranged and adapted for movement into the guide bore 3|, the recess 28, and the seat 32 respectively of the female die section. In accordance with the present arrangement the stock from which the ring is made somewhat wider in radial thickness than the finished ring, as indicated by the dotted lines in Figures 3 and 9. On the other hand, the base or end Wall 39 of the seat 32 is of a width corresponding to the finished radial thickness of the ring with the result that when the loop I8 is first placed in the seat 32 an inner portion 20 of the loop will overlie the inner circumferential surfaces of the die block 29 and overhang the wall 30 ofthe seat. Thus, on lowering of the die section 26 the end wall of the skirt 34 is brought into engagement with the inner portion 20 of the ring loop and shears this portion from the remainder of the ring. The skirt 34 is provided with a longitudinal peripheral recess which extends from the end 35 to the shoulder 36 and leaves at the portion 2!] of the loop an in- Wardly projecting lug which is arranged to engage in a suitable opening (not shown) in the body ring I l for preventing relative rotation between the body and side rings.

The skirt 34 is formed with a small downwardly convergent taper (in the present case about 4 v degrees) which is effective to engage the inner periphery of the loop and expand the same against the outer peripheral wall 31 of the ring seat 32. Preferably the taper is confined to the lower portion 34 of the skirt, whereas the portion 34 of the skirt adjacent the shoulder 36 and opposite the side wall 31 in the final position of the die is formed parallel to the surface 31 and at right angles to the shoulder 36 so that the final form of the ring will be perfectly square and prior to the final forming of the ring the same is sub jected to a considerable radial compression or swedging between the tapered side 34' and the seat side 31. However, in certain types of rings it is desirable to form the inner and outer peripheral surfaces thereof in an inclined relation so as to produce a turning out of the ring against the cylinder Wall and in the formation of such rings it may be desirable to extend the taper of the skirt substantially completely to the shoulder I 36 so as to affect the final shape of the ring.

During this radial compression or swedging of the ring the same is free to expand circumferentially and also to expand axially between the die surface 30 and 36 which, during the swedging operation are spaced by a considerable distance. At the end of the swedging operation, that is, after the tapered portion34' has passed the seat side 30, the shoulder 36 is brought sharply against the top surface of the ring and the ring is compressed by the opposed surfaces 30 and 36 of the ring enclosure under a tremendous axial pressure corresponding to an axial force of approximately 40 to 60 tons for the average size automotive ring. During this compression the ring is held against radial expansion by the opposed sides 34" and 37 of the ring enclosure and, as the result the material of the ring is forced to fiow in a circumferential direction towards the free ends of the ring. Preferably, in order that the outer cylinder engaging side 39 of the ring may have the top edge thereof sharply defined, the base or end wall 30 of the ring seat is formed with a rise or upstanding annular shoulder 4! adjacent the wall 31 for depressing and sharply defining the outer edge of the ring top surface 42. This extra depression of the outer portion of the ring has further and very important ad-, vantages in the forming of the ring, in that the extra circumferential flow of material caused by this depression produces a greater proportionate fiow of material at the outer surface of the ring than at the inner surface thereof, and thereby causes a greater circumferential advancement of the outer edges 2! of the free ends of the ring than of the inner edges 22 with the result that the ring will be progressively curved inwardly from the normal circumference thereof towards the free ends of the ring and the latter will be drawn well within the circumference of the ring. This feature is of particular advantage since these outer edges are sharply defined and have been a source of nuisance in the past in that they required either filing down or rounding on to prevent their digging into and scratching the cylinder wall. In accordance with the present invention, however, and as above explained, these ends are automatically withdrawn from the circumference of the ring as indicated in Figure 7 and are thus removed from immediate contact with the cylinder wall,

The flow of material circumferentially has an additional effect on the ring in that it changes the texture of the outer cylinder engaging surface thereof. Since there is a relative shearing of material caused by the different degrees of material flow aforesaid, it Will be understood that the tendency of such flow is to elongate the metal fibers in the direction of shear. This has the eifect of changing the rather granular structure of the original steel wire into a vastly tougher, denser and fibrous or grain structure which in addition, since it contrasts with the surface texture of the cast cylinder wall, affords a low coefiicient of friction between the cylinder wall and the piston ring.

As an important feature of my invention, the ring is set, during the compressions aforesaid, to a diameter closely corresponding to that of the cylinder with which the ring is to be used. In this manner any required expansion or contraction of the ring to constantly engage the cylinder wall will be but slight from its set diameter and will not be materially resisted by the ring. Thus as will be clear, the ring will be free for expansion against the cylinder wall by the body ring and will as readily be retractable to conform to minor variations in cylinder bore diameter. This setting is effected by raising the stress on the ring to a point above its elastic limit, so that the same will retain the shape imparted to it by the die. of the ring fibers is productive of a certain degree of flexibility which permits the latter to more closely follow any variations in the cylinder.

A further and most important feature of the compression aforesaid lies in the raising of the hardness of the ring metal. As hereinbefore pointed out, it is highly desirable that the hardness of the ring closely approach that of the cylinder side walls. I have found that the average hardness of such side walls is about from to points on the Rockwell B scale. While the original wire had a hardness of but 50 to 65 points, the same is hardened by the compressions aforesaid to approximately 95 points, this being preferable to maintain the ring slightly on the soft side on a balance hardness with the cylinder wall. Preferably a pair of greater surfaces 48 and 45 of the die sections are engaged at the end of movement to limit the size of the annular ring enclosure and to cause a positive and accu- Also this straining jacent the depression 32.

rate end position of male section and relieve the engaged portion of the ring enclosure and to render the rings formed substantially identical within approximately .0025 or less in mass pro duction.

a further important feature of the present apparatus, the same is arranged to form around the circumferential outer side 39 of the ring a plurality of minute annular beads 43 which initially engage the cylinder wall and provide a perfect quick seating of the ring thereagainst and are thereafter quickly worn away to provide a permanent sealed engagement of the ring against the cylinder wall. As here shown, these beads are formed by the provision of a plurality of minute annular recesses M in the side wall 37 of the ring seat so as to allow the flow of material into such recesses during compression of the ring and the formation of the aforesaid beads. The size of both the beads and the recesses has been enlarged in the accompanying drawing and even in the enlarged illustration of the Figure 7, in view of clarity. However, as will be understood, these beads and recesses are 4 extremely small and are scarcely detectible except upon close inspection of the ring. Preferably one of the recesses id is provided directly at the intersection of the wall 3? and the shoulder 4! so as to form a corresponding head on the ring at the upper outer corner immediately ad- In this position the head has an additional action which is of considerable value.

I claim:

1. A member provided with a cylindrical bore and an enlarged seat adjacent an end of the bore for receipt of a generally round unfinished piston ring having a radial ring thickness greater than said seat so as to overlie said bore, a second member having a generally cylindrical portion extendable into said bore and adapted to engage said ring and shear therefrom a portion of said ring overlying said bore, said second member having a longitudinal recess at the periphery thereof to leave an inwardly extending lug on said ring.

2. A member provided with a cylindrical bore and an enlarged seat adjacent an end of the bore for receipt of generally round unfinished piston ring having a radial ring thickness greater than said seat so as to overlie said bore, a second meming a longitudinal recess at the periphery thereof to leave an inwardly extending lug on said ring, the periphery of said second member being provided with a longitudinal taper so as to cause a radial swedging of the ring against the side of said seat.

3. A die for forming a piston ring comprising, a member having a bore and formed with an enlargement at an end thereof defining an annular seat for an unfinished ring, said seat having a transverse end wall and a peripheral side wall for supporting said ring, a second member having a portion movable into said bore in opposed relation to said seat side wall and engageable with the inner side of said ring to confine the same against said seat side wall, and means extending transversely from said portion and movable in the direction of said seat end wall to compress said ring thercagainst, said seat side wall being provided with a small annular recess to form an annular head on the outer side of said ring.

4. A die for forming a piston ring comprising, a member having a bore and formed with an enlargement at an end thereof defining an annular seat for an unfinished ring, said seat having a transverse end wall and a peripheral side wall for supporting said ring, a second member having a portion movable into said bore in opposed relation to said seat side wall and engageable with the inner side of said ring to confine the same against said seat side wall, and means extending transversely from said portion and movable in the direction of said seat end wall to compress said ring ther against, said seat side wall being provided with a plurality of annular recesses to form beads on the outer side of said ring.

5. A die for forming a piston ring comprising, a member having a bore and formed with an enlargement at an end thereof defining an annular seat for an unfinished ring, said seat having a transverse end wall and a peripheral side wall for supporting said ring, a second member having a portion movable into said bore in opposed relation to said seat side Wall and engageable with the inner side of said ring to confine the same against said seat side wall, and means extending transversely from said portion and movable in the direction of said seat end wall to compress said ring thereagainst, said end wall being provided with an upstanding annular shoulder adjacent the outer edge thereof, said seat side wall being provided with an annular recess at the outer edge of said shoulder.

EDMUND R. WEEK, JR.

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