US1759108A - Method of making piston-ring patterns - Google Patents

Description

Mayv20, 1930. H. SEGRAVES 1 l(759,108

METHOD OF MAKING PISTON RING PATTERNS Filed Sept. 16. 1926 2 Sheets-Sheet 1 gmnntoo May 20, 1930. H. s. GRAVES I METHOD of MAKING PISTON RING PATTERNS Filed Sept. 16, 1926 2 Sheets-Sheet 2 Pym Patented May 20, 1930 UNITED STATES PATENT OFFICE HARRY S. GRA VES, OF DETROIT, MICHIGAN; ETHEL S. GRAVES ADMINISTRATRI X OF SAID HARRY S. GRAVES, DECEASED METHOD OF MAKING- PISTONRING PATTERNS Application filed September 16, 1926. Serial No. 135,801.

In the manufacture of piston rings for internal combustion-engines, pumps and other apparatus wherein pistons are provided with various kinds of packing rings, engageable with a cylinder wall, it is essential that such rings be round and have a predetermined force so as to exert a predetermined pressure against the wall of the cylinder for packing purposes. In quantity production of the piston rings there are given dimensions and known qualifications to be incorporated in the cast rings, so the preparation of patterns used for casting the rings is of utmost importance. Obviously, if the pattern is not correct the ring will not meet the specific re quirements, therefore the size and shape of the pattern are very essential. In addition to this the'co-efiicient of expansion and contraction of a ring for a predetermined use is known, also the wall pressure expected from such ring, so in preparing a pattern for a cast ring dimensions are used which will eventually result in a ring of such size and configuration that it will exert a desired wall pressure under predetermined operating'conditions.

This invention has special reference to the preparation of one or more patterns for the production of cast piston rings, which will possess the requisite degree of resiliency. A pattern is prepared which is tested for all requirements so that when a ring is cast it will possess inherent qualifications. This will expedite production of piston rings in large quantities and insure a product that is as perfeet as can be obtained under quantity production. I

In the preparation of a piston ring pattern in accordance with this invention a method is involved which will now be described by aid of the drawings, wherein V Figure 1 represents a print or chart of a piston ring of desired size;

Fig. 2 shows views of a ring made in accordance wit-h the print shown in Fig. 1;

Fig. 3 shows a device for subjecting the ring of Fig. 2 to a force equivalent to a redetermined wall pressure, so that the ring will be expanded to approximately a configuration under such wall pressure;

Fig. 6 is a plan of a profile machine by which two or more master pattern templets' may be produced;

F 7 is a cross sectional View of the same;

Flg. 8 shows views of a completed master pattern templet;

Fig. 9 shows views of a perfect master ring pattern;

Fig. 10 shows views of the master ring pattern supported by the master pattern templet, and

Fig. 11 shows master pattern rings an ranged and held so that cast rings may be produced uniformly.

In the drawing, the reference numeral 1 denotes a chart, print or Working drawing showing a plan in elevation of a split piston ring which has a width B, a thickness C, and an external diameter A. From this-working drawing a split ring 2 is made having the dimensions A, B and C of the working drawmg.

The split ring 2 is placedon an expander or testing device 3, comprising a stationary post 4, a scale 5, an adjustable anchorage 6 for one end of the scale, and a ring engaging member 7 at the opposite end of the scale.

The scale 5 may be of the graduated spring tension type and is adapted to exert a pull on the ring 4 to expand the ring to a desired wall pressure, that is, to stress the ring to a configuration that it would assume if exerting a predetermined pressure against the wall of a cylinder. The ring is placed on the device over the post 4' with the split or gap 8 a right angle to the minor axis which intersects the split or gap 8.

A master templet 9 is now prepared, as shown in Fig. A and the master templet has a major axis 10 corresponding to the internal major axis of the expanded ring shown in Fig. 3. A minor axis 11 is also laid out on the master templet corresponding to the internal minor axis of the expanded ring and there may be other axes 12 corresponding to other internal axes of the expanded ring so that the periphery of the master templet will be an exact reproduction of the inner periphery of the expanded ring shown in Fig. 3. To test this master templet it may be placed on the post 13 carried by the holder 14 of a conventional form of micrometer 15 and by rotating the master templet 9 the micrometer can be observed to ascertain if the periphery of the master templet is correct.

Having produced such a master templet it is placed on the arbor 16 of a profile machine shown in Figs. 6 and 7. The arbor 16 has a worm and gear drive 17 from a hand wheel 18 or any suitable source of power may be employed for revolving the master templet equipped arbor. The profile machine includes a carriage 19, preferably spring pressed so that a guide roller 20 of the carriage will at all times bear against the master templet 9 mounted on one end of the arbor 16. On the opposite end of the arbor 16 are mounted two or more blank master pattern templets 21 which in embryo form approach as near as possible the circumferential configuration ot the master templet. One of these master pattern templets is shown in Fig. 8 and it may be laid out with different axes 22 with the major axis represented by w and the minor axis by 3 so that the quantity zr+y will represent the mean diameter.

However, with the embryo master pattern templets 21 on the arbor 16, these embryo templets may have the peripheries thereof brought into engagement with the grinding wheel or instrumentality 23 which will produce a periphery on the patterns corresponding to that of the master templet 9, thus insuring accuracy in the reproduction of the master pattern templets.

Having obtained master pattern templets, one of which may be used in one part of a plant, while the other is used elsewhere, a perfectly round master ring pattern 24 is made with an interior diameter approximate to the quantity T This ring pattern is resilient enough to be placed over the master pattern templet, as shown in Fig. 10 and if desired the side wall of the ring pattern may be notched or provided with some demarcation 25 which will indicate the location of the split or gap to be eventually provided in the finished product. With the ring pattern 24:

perfectly fitting the master pattern templet, which it must do, the ring pattern is now laid on a pattern board or support 26 and suitably secured thereto, as at 27, so that it becomes an immovable pattern fixture. After being attached to the board or support 26 the master pattern templet 21 can be removed and used in stretching other ring patterns for mounting on the board or support 26, as clearly shown in Fig. 11, thus producing the gang or multiple ring pattern that may be used for easting a plurality of rings.

As a result of producing master patterns in accordance with this method, I have a ring pattern of a ring which has been subjected to all conditions and tested to meet the requirements of the cast ring on a piston in a cylinder. Rough dimensions have been obtained from the working drawing and an embryo ring expanded for wall pressure. With the ring under such predetermined pressure, dimensions, have been obtained for the preparation of a master templet and the templet has been used to produce correspondingly shaped master pattern templets over which perfectly formed rings may be stretched and held to such shape to be used as ring patterns for casting rings. After the rings are cast it is only necessary to split or gap the same and this dimension having been ascertained from the embryo ring 2, under pressure as in Fig. 3, the requisite amount of ma terial can be removed from the cast rings, at the proper places, to permit of said rings contracting to perfect roundness. Since the embryo ring can be made of any desired dimension it is obvious that allowance may be made for expansion and contraction, the embryo ring being made oversize so that the master templet and master pattern templet are actually oversize and thus take care of shrinkage due to the cooling of cast rings. In making these allowances and using the proper amount of material in an embryo ring it is possible to produce a ring by casting that will be perfectly round. It made oversize, the ring may be mounted on a mandrel and its periphery turned down to perfect size without the metal being subjected to stresses and strains that would tend to produce a ring out-of-round.

In other words, there is a body of metal of such configuration as to be perfectly round when turned into a piston ring by my method.

What I claim is 1. A method of making a piston ring pattern, which consists in providing a split ring of the desired final circumferences expanding said split ring for wall pressure, making a master pattern templet with dimensions corresponding to the expanded split ring, fitting a perfectly round ring over the master pattern templet, and fixing the pattern ring to hold its configuration when the master pattern templet is removed.

2. A method of making a piston ring pattern, which method consists in providing a templet, having a periphery approximating the internal dimensions'of a ring under Wall pressure condition, making a pattern from said templet, fitting a ring over said pattern, and then fixing the ring so that the pattern may be removed with the shape of the pattern ring maintained for molding purposes.

3. A method of making distorted piston ring patterns from a chart giving dimensions of a perfectly circular ring, said method consisting in making the ring according to said dimensions, expanding the ring to place the same under tension corresponding to a desired Wall pressure, producing a templet having external dimensions corresponding to the internal dimensions of the expanded ring, fitting a perfectly round ring pattern on said templet, and fixing said ring pattern so that the templet may be removed from the ring and used as a pattern in a mold.

4. A method of making a piston ring pattern consisting in providing a templet pattern having a periphery approximating the internal dimensions of a ring under Wall pressure conditions, fitting a ring over said pattern, and then fixing the ring as fitted so that the pattern may be removed With the shape of the ring maintained for molding purposes.

5. A method of making tensioned piston rings according to given dimensions, consisting in expanding a ring of such dimensions to place the same under tension corresponding to a desired Wall pressure, and making a reproduction of said expanded ring.

6. A method of making tensioned piston rings according to given dimensions, consisting in expanding a ring of such dimensions to place the same under tension corresponding 49 to a desired Wall pressure, producing a templet having external dimensions corresponding to the internal dimensions of said expanded ring, producing a ring having internal dimensions equal to' the external dimensions of said templet, and reducing the last named ring to the dimensions of the first named ring.

In testimony whereof I aflix my signature.

HARRY s. GRAVES.

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