US1857254A - Method of producing rings - Google Patents

Description

y 0, 932. A. w. MORTON 1,857,254

METHOD OF PRODUCING RINGS Filed 061'. 10, 1928 7 ga A 3114mm we? 9x? 11mm Patented May 10, 1932 UNITED STATES PATENT OFFICE ALLEN W. MORTON, OF BALTIMORE, MARYLAND, ASSIGNOR TO THE AMERICAN HKMMERED PISTON RING COMPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND METHODv OF PRODUCING RINGS Application filed October 10, 1928. Serial No. 311,572.

This invention relates to the production of thin finished annuli and will be found particularly useful in connection with the manufacture of piston rings. The invention will be discussed as applied to the manufacture of'piston rings for the purpose of illustrating its valuable features, but it is not strictly limited in its utility to that field.

The modern mehod of producing piston rings is to caste ring blank and then grind the two plane surfaces of the blank. A cast blank is never absolutely flat, partly from imperfections in molding and partly from cooling strains in the casting. It follows that if the rings are ground between opposed plane grinding disks, as isthe common practice with small rings, or, if they are mounted on magnetic chucks, as is the common practice with larger rings, the rings will be slight ly deflected during the grinding operation and waves or irregularities will persist in the finished product.

The present application discloses a. blank,

preferably acast blank, for piston rings, so formed that when the blank contacts the plane grinding surface at least one surface of the blank grinds away so rapidly that'it conforms to the grinding surface without straining or deforming the ring.

Broadly considered this blank is available for use in various grinding processes in which its peculiar characteristics are of value. It develops especial utility and value in the case of relatively small rings which are rough ground between opposed grinding disks hav-- ing plane grinding surfaces, as will hereinafter be set forth in detail.

The invention will be explained in connection with the accompanying drawings, in which,

Fig. 1 is a plan view of a ring blank look ing from the top or cope side.

Fig. 2 is a section on the line 2-2 of Fig.1,

faces 13 and 14 which will be cylindrical surfaces in the finished ring, but which in the blank are slightly conical to give the necessary draft to the pattern so that the pat tern may be removed from the mold. The other surface 15, which in the finished ring will be a plane surface, is, according to the present invention, not plane in the blank but is slightly conical. The inclination need not be great, and in rings of 3 to 4 inches diameter the difference in thickness is of the order of 0.009 of an inch to 0.010 of an inch.

It is exaggerated in Fig. 2 to make it visible.

The description of the surface 15 as conical is precisely descriptive of the preferred form shown in Fig. 2 and of the alternative form shown in Fig. 4. The term is intended, however, to be broad enough to include forms such as that shown in Fig. 3 in which there are two conical surfaces 15 and 15" which meet to form a ridge which extends annularlv around the ring.

Considering the forms shown in Figs. 2, 3 and 4. it will be apparent that in the annulus these forms .oifer ridges which will enter into line contact with a plane surface and that such plane surface will be parallel or approximately parallel with the plane of the finished surface of the ring.

While I prefer surfaces having the conical characteristics just described, some advantages of the invention can be secured with other forms. and to make clear the general range of equivalents, sdgfar asthe broad aspects of the invention are concerned, there is illustrated in Fig. 5 a cross section having a fiat face 15 with a marginal rib 15f. Similarly in Fig. 6 there is a flat face 155b0unded by'a conical rim 15.

The departures from prior artrepresented by the various forms shown in Figs 2 to 6 inclusive, can be readily appreciated by a comparison with the section shown in Fig. 7 which is representative of the prior art.

Generally stated, rings formed according to the present invention offer initially to a plane grinding surface a narrow annular area which may be quickly ground away andwhich positions the ring in proper relation to the This advantage may be grinding surface. availed of in many processes, but the best knownmode of availing of it consists in feeding rings formed as described between two opposed grinding disks E21 and 22, which, when the disks are concentric, as shown in Figs. 8 and 9, are rotated in opposite directions, Disk grinders with offset axes are known and may be successfully used. The faces of the disks are plane and parallel with each other, except that they have a slight bell mouth, indicated at 23, which facilitates the entrance of the ring between them. This bell mouth may be produced by dressing the wheels, but they need not be so dressed as they tend to assume this form as the result of wear.

The rings are supported between guide bars 2 1 and pass between the disks in the direction of the arrow in Fig. 9. In Figs. 8 and 9 the rings are indicated by the reference numeral 25, and in Fig. 9 several successive rings are shown passing in series between the disks.

The rings issuing from between the disks are rough ground and will be found to be flat or plane with their faces accurately parallel, within remarkably close limits.

An additional advantage is secured by making the side 15 of the ring, that is the one which has the bevel or rib, the top or cope side of the casting. Ithas been found that far more metal is removed by the grinding operation from this side of the ring than is removed from the plane side 12. For example, if the grinding operation removes 0.020 of an inch, approximately 0.015 of an inch will be removed from the beveled side 15 and 0.005 of an inch from the plane side 12. The advantage of making the bevel side 15 the cope or upper side of the casting will now be readily apparent, since practically all sand spots or other casting imperfections will be found in the upper or cope side and hence are removed to a greater degree than is usual. This greatly reduces the percentage of rejections for easting imperfections.

The rough ground rings produced according to this method are found to vary as to the dimensions of any one ring not to exceed 0.00025 of an inch where a variation of 0.001 of an inch is common with prior practices. As between different rings of a given lotit is practicable to hold the variation within 0.0005 of an inch whereas with prior practices variations of 0.003 of an inch are by.no means unusual.

Another marked advantage of the process is that the heating effect of the grinding operation on the rings is much less. According to prior practices it was not unusual to have the rings leave the grinder red hot and quite common for the rings to be discolored to a dark straw or even to a blue color. Rings ground according to the present invention sho no heat discoloration whatever and leave the grinder at a relatively low temperature. This is a very important point, because distortion of the rings often resulted from heating alone. The elimination of heating therefore is conducive to a better finished product.

The production of rings with truly parallel plane surfaces top and bottom is a result long sought unsuccessfully in the piston ring art. The ring must fit the sides of the groove closely or there will be serious leakage and wear. But if a ring which is warped or out of plane and in which the sides of the ring are out of parallel, be closely fitted in the groove, it is certain to become groove-bound and inefficient. The importance of the pres ent invention resides in its simplicity and in the fact that it is applicable to commercial grinding methods carried out on disk rind ers having opposed plane surfaces. over, it is immaterial so far as this process is concerned whether the grinder be of the type in which the axes ofthe two disks are concentric or of the type in which the axes are ore ofiset, both types being extensively used in piston ring manufacture.

What is claimed is,-

1. The method of producing annuli with opposed parallel surfaces, which consistsin forming an annular blank of substantially uniform section throughout its. circumference, in which the surfaces intended to be made parallel in the finished annulus are out of parallel with each other by a substantial angle, in such manner that at least one of said faces offers a line contact with a plane surface substantially parallel with the desired plane of finish, and grinding said blank between opposed grinding elements.

2. The method of producing annuli with opposed plane parallel surfaces, which consists in forming an annular blank having one substantially plane surface and an opposedslightly conical surface, and grinding the blank between opposed grinding elements having plane parallel grinding surfaces.

3. The method of producing annuli with opposed plane parallel surfaces, which consists in forming an annular blank having onesists in casting an annular blank having one N W. MORTON.

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