US1762598A - Art of and mold for casting piston rings - Google Patents

Description

June 10, 1930..

M. o. TEETOR 62,598

ART OF AND MOLD FOR CASTING PISTON RINGS Filed Aug. 12, 1927 2 Sheets-Sheet 1 Patented June 10, 1930 UNITED STATES PATENT OFFICE MACY O. TEETOR, OF HAGEBSTOWN, INDIANA, ASSIGNOR TO THE PERFECT CIRCLE COM- PANY, OF HAGERSTOWN, INDIANA, A CORPORATION OF INDIANA ART OF AND MOLD FOR CA STIN G PISTON RINGS Application filed August 12, 1927. Serial No. 212,387.

This invention relates to improved piston rings and to the art of and mold for casting the same.

It is now common practice to make piston rings by casting them separately and then machining and finishing them. Each ring cavity in the mold forms a continuous unbroken circle and when the molten metal is poured into the gate it passes through an opening or runner into the ring cavity, there divides into two'streams which flow around opposite sides of the ring cavity and meets at the back of the ring cavity opposite the runner. Opposite the gate, an enlarged off-set recess is connected to the mold cavit by a narrow. opening to form a riser which is also known as a button or a bleeder. After the casting has been removed from the mold, the runner and riser are removed, the ring is rough machined, then cut or slotted to provide the usual joint or gap in the ring, and finally finished. I find that many rings cast by this method have some serious defects resulting in a large number of rejected rings which are scrapped. In some instances the stream of molten metal flowing around one side of the ring cavity travels faster than that flowing around the other side of the ring cavity, and it passes the opening to the riser and as some of the metal of the stream then enters the riser,

the end of the stream which has passed the opening to the riser slows down with the result that it remains in contact with a small portion of the sand mold and is cooled more. Then the advancing end of the slower stream on the opposite side meets it. When this condition exists the hot metal of the slower stream meets the cool end of the faster stream and the meeting ends of the two streams are not together, if the metal has cooled to an extreme degree or, if the metal has suflicient heat to permit the ends of 'the two streams to mix and unite, the metal at the place of properly joined and united joinder will cool quicker than the rest of ture at this lace, and this has a tendency to keep the carbon in the combined state, which causes hardness. The end of the faster stream or the spot of joinder becomes harder than the rest of the ring due to the formation of what are known as double carbides resulting from the cooling of the end of the faster stream. Obviously, at this point the ring would be brittle, the hard spot would be diflicult to machine and the machine and finishing tools would be quickly dulled. The riser is used to enhance the chances of the meeting of the two streams adjacent the opening to the riser, allowing the chilled metal, if there is any formed, to flow into the riser. The useof the riser in this old method, however, causes the ring to anneal adjacent the riser, the annealing being the result of the heat stored in the larger mass forming the riser. This annealing takes place at a point opposite the runner and the gap is usually cut in the, finished ring adjacent the place where the runner was attached and at this point the ring naturally bends or flexes the greatest amount when in use in an engine, because the greatest leverage is exerted at that po nt. The annealing at this point makes the r1ng weaker and impairs the resiliency of the ring and prevents the ring from exerting a uniform pressure throughout its periphery against the walls of the cylinder. Further, when the ring casting cools 1t shrinks and warps out of the plane of the F111 because of its unbroken solid structure an the prolonged hot spots caused by the runner and the riser. This necessitates a straightening operation and greater thickness of the ring casting so that it can be finished to the exact 'dimension and so that the faces of the ring fective, because of the loose sand or slag in the iron being caught or embodied in the castings. Usually the dirt or foreign particles, being lighter than the iron, are pushed along ahead of the molten streams, and it will be evident that it is quite unlikely that these foreign particles will be deposited in the riser particularly when the end of one of the streams passes the opening to the riser. Y

The'principal object of my invention is to provide a new and improved process or method of and mold for casting individual piston rings which will be free from the above mentioned defects, existing in piston rings cast by prior methods. My invention consists, in general, in providing a mold with a broken ring cavity having a transverse Wall or partition and enlarged cavities adjacent the ends of the ring cavity, the transverse wall or partition. being employed to form a gap 111 the ring casting, and more particularly I preferably provide my improved mold with a gate or runner, near one end of the ring cavity, broken by the transverse wall, and a riser or risers at the other end of the ring cavity, so that the molten metal preferably flows in but one direction and a ring casting free from defects is formed. Thus there'are not two streams of metal to be fused together and no hard spots are formed in the ring. The ring anneals more at its free ends due to the runner and the riser. This is desirable as the annealing makes the iron softer at the ends of the ring and the transverse finish cutting'of the ends of the ring at the gap much easier to perform. The soft iron atxthese points is not detrimental to the ring because less resiliency is necessary at the ends of the ring than throughout the rest of the ring. lVhen the casting cools it may shrink circumferentially and hence does not warp out of its plane or distort from the true shape of the pattern, making it easier to machine and finish. It will also be obvious that in pouring the metal into this type of mold it is not, so essential that the molds be setting perfectly horizontal, as is the case in the old method described above. I have also practically eliminated by the use of my invention ring castings which are defective due to the slag in the iron or loose sand in the mold cavities, as the foreign particles in the ring cavity and 7 those forced into this cavity from the head or runner, are pushed alon ahead of the single stream and lodged in the riser or' risers at the end of the ring cavity or in.

the very end of this cavity, and if-at the latter fiplace it does no harm as this end is out o in finishing the gap. Some of the dirt or foreign particles, such as slag or sand, or dirt coming from the head are collected in a pocket in the runner.

I will explaln my lnventlon more fully by reference to the accompanying drawings, showing a preferred form of embodiment thereof, and in which Figure 1 is a bottom plan view of half of the upper part of a mold embodying my invention;

Fig. 2 is a cross-section through part of the mold as on the line 22 of Fig. 1;

Fig. 3 is a cross-section through part of the mold as on the line 33 of Fig. 1; and

Fig. 4 is a perspective view of one of the ring castings showing part of therunner and the riser attached.

The sand mold comprises two parts, an upper part 5 consisting of a cope 5 filled with sand, and a lower part 6, consisting of a drag 6 filled with sand, the cavities being formed in the upper part by a suitable pattern in the usual manner. In Fig. 1, I have illustrated one half of the upper part of a mold which is adapted for simultaneously forming six ring castings, though it will be understood that a mold may have one or any number of cavities as may be desired. Each ring cavity 8 forms a continuous circular chamber except for the small break or sold wall 9 of sand. A central opening or head 10 is formed in the upper part of the mold and it is connected by horizontal passages or runners 11 each opening into one end of the circular ring cavity 8. Pairs of deep recesses 12 are formed in the upper part of the mold, the recesses of each pair being adjacent the other end of their respective ring cavity 8, and the recesses 12 being connected to the ring cavity by small openings 13.

When the molten iron is poured through the central opening 10 of the mold, it flows through the runners into the ring cavities 8. A stream of metal enters one end of each ring cavity, encircles the cax'ity and the advance end of the stream passes through the openings 13 and rises in the recesses 12.

Thus a ring casting, such as shown in Fig. 4, is formed in each cavity. The arm or gate 15 formed by the runner 11, isintegral with one end of the ring casting and the risers 16, formed by the cavities 12, are integral with the ot er end. I preferably em loy two recesses 12 adjacent one end of eac ring cavity, though one may be used if desired. I find, however, that when only one is used the corner of the end of the ring opposite the one recess is often slightly harder than the adjacent portionof the rmg.

stream, and as there are not two streams of metalwhich meet, hard spots do not form in the casting. The portion of the ring casting opposite the gap 17 does not anneal when the casting cools and therefore it loses none of its reslllency. There is a slight annealing.

effect at the ends of the ring, due to the greater mass of the gate 15 and risers 16, but this is not objectionable, and in fact, is advantageous, as, the ends of the ring are somewhat softer than the rest of the ring and can be easily cut by the usual cutting tool. Also,

when the ring casting cools it is ermitted,

dueto the gap 17, to shrink circumferentially without the creation of any strains or stresses so that the casting does not warp out of shape nor out of its plane, thus enablin the casting to be easily machined and finished with the minimum amount of removal of metal and minimum machining and finishing operations. The rings being accurately formed, the operation of cutting the ends of the ring at the gap is more easily performed alflfd the correct amount of metal is always out o v i It will also be evident that any dirt or foreign matter carried along by the molten stream of metal in the ring cavity is pushed around the ring cavity ahead of the end of the stream and the dirt is collected in the recesses 12 or deposited at the very end of the ring which is later cut oil". I also form a pocket 19 in each runner 11 to collect dirt, such as loose sand, coming from the head or runner, and also slag in the iron, the dirt or slag rising in the pocket because they are lighter than the iron. The texture and hardness of the ring may also be controlled by varying the size, location and shape of the risers. For example, if it is desirable to have a softer ring the risers may be made larger, as the more metal that flows through the ring cavity the softer the ring. Further risers may be formed by recesses at different points around the ring cavity, thus controlling, as desired, variations in hardness and texture at different points or on the inside and outside of the ring.

It will now be evident that by employing my improved mold and method individual piston ring castings are formed free of the many serious defects which develop in rings cast by theabove described method,'now generally in use, and other methods. I have found from actual practice that a very large percentage of ring castings made by the method now generally in use are so defective that they are scrapped, whereas when employing my method and mold, the percentage of rejections is remarkably low.

\Vhile I have shown the preferred form of embodiment of my invention, it will be apparent that various changes, such as variations in size, shape and location of the runners and risers, may be made without departing from the spirit and scope of'my invention as defined in the claims which follow.

I claim:

1. The method of forming piston ring castings in a mold, which consists in form- 7 ing a circular ring cavity with a break forming the gap in the ring casting, a recess at one end of the ring cavity, and a runner adjacent the other end of the ring cavity, and pouring the molten metal which flows from the runner around the ring cavity into the recess.

2. The method of forming piston ring castings of iron in a sand mold, which consists'in forming a ring cavity with a break forming the gap in the ring casting and a large opening at one end of the ring cavity connected to the end of the ring cavlty by a narrow throat, and a runner adjacent the other end of the ring cavity, and pouring the molten metal which flows from the run ner around the ring cavity in but one direction and into the recess.

3. The method of forming piston ring castings of iron in a sand mold, which consists in forming a circular ring cavity with a break forming the gap in the ring casting, two recesses at one end of the ring cavity and on opposite sides of said end, and a runner adjacent the other end of the ring cavity, and pouring the molten metal which flows from the runner around the cavity into said recesses.

4. The method of forming piston ring castings of iron in a sand mold, which consists in forming a circular ring cavity with a break forming the gap in the ring casting, two recesses at one end of the ring cavity and a runner adjacent the other end of the ring cavity, at least one of said recesses beingslightly curved or' inclined away from said runner, and pouring the molten metal which flows from the runner around the ring cavity into said recesses.

5. A mold for forming individual piston ring castings, having a circular ring cavity with a break to form the gap in the piston ring, a runner opening into one end of the ring cavity and a depression for forming a riser at the other end of the ring cavity.

6. A mold for forming individual piston ring castings, having a circular ring cavity with a break to form the gap in the ring, casting and a recess at each end of the ring cavity to form a projection on the ring casting.

7. A mold for forming individual piston ring castings of iron, having a circular ring cavity with a break to form the gap in the ring casting, a runner opening into one end of the ring cavity and depressions on opposite sides of the other end of the ring cavity for forming risers.

8. A sand mold for forming individual piston ring castings of iron, having a circular ring cavity with a break to form the gap in the ring casting, a runner opening into one end of the ring cavity and depressions on opposite sides of the other end of the ring cavity for forming risers, the depression outside of the ring cavity being inclined away from the runner openlng.

9. The method of casting piston rings in a sand mold which consists in forming a 7 piston ring casting of iron With a gap and a gate adjacent one side of the gap, and at least one riser adjacent the other side of the gap, the molten metal being poured through the runner forming the gate that it has a uni-directional flow from the runner through the ring cavity to the enlargement forming the riser, and then removing the gate and riser from the ring.

In testimony whereof, I have subscribed my name.

MACY O. TEETOR.

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