US1749147A - Process of piston-ring casting - Google Patents

Description

PROCESS or PISTON RING CASTING Filed March 5', 1929- k \mmfior 3% Thurloo lflficm A WW4 3,

85 "Q1 W I Gimme/15 ner core of the casting which has not yet sufficient heat to hold the casting against Patented Mar. 4, 1930 PATENT OFFICE THURLOW E. MOFALL, OF SPARTA, MICHIGAN PROCESS OF PTSTON-RING CASTING Application filed March 5, 1929. Serial No. 344,375.

This invention relates to a process of piston ring casting In the manufacture'ofpiston rings'it has become the usual practice to cast individual ring castings from which piston rings are manufactured as distinguished from the previous method of casting a sleeve or pot casting as it was called from which a number of rings were cut. The piston ring produced from an individual ring casting is far supe rior to those produced from the pot casting.

It has within the last few years become more and more the practice to manufacture piston rings for internal combustion engines of less dimension between the upper'and lower flat sides of the ring, the great ma ority of piston rings now used being one-eighth of an inch or less between the upper and lower flat sides thereof. It is also becoming very common that part of the rings at least around a cylinder in an internal combustion engine are sawed through from "their outer curved to their inner curved sides to provide slots through the rings for the passage of excess 011 1 scraped from the walls of the cylinder through said slots in the ring grooves in the piston and thence through drainage openings tothe interior of the piston.

With the decrease in size of the rings d1fficulties have arisen in individually casting the piston ring castings for such small sizes, due primarily to the fact that the molten iron entering the mold and contacting with the. sides of the mold rapidly cools and forms a hard and rigid shell around the 1n-' .solidified as rapidly as theouter shell, and holds the core in a compressed state so as to prevent the usual separation of carbon from the the molten iron which occurs in most iron casting. The molten iron as it comes from a cupola furnace is a'chemical mlxture'of iron with relatively small percentages of carbon. When it is poured into a mold ofsufliclent size so that the body of iron in the mold has caused by sueh'separation, the casting consisting ofiron and free carbon which permeates the casting throughout. But where the body of metal is small, as in individual piston ring castings from which piston rings have a face of one-eighth inch or less are made, the practically immediate solidifying of the outer shell of the casting while the core thereof is still in a fluid state prevents the necessary expansion of such core, whereby the iron and the carbon are held in chemical combination with the production of core which is very hard, in fact, maybe as hard as chilled cast iron. I

The core thus produced is not of uniform cross section and does not ordinarily extend entirely around the ring and-in fact, may occur only at one point for a short length or at a number of points spaced from each other in the circumference of the ring; and all piston ring castings even of this smaller size may not have the interior hard spots described.

But enough of the piston ring castings will be so affected that when oil passage slots are sawed through the castings it results in a greatdestruction of the saws used and in the spoiling of a large percentage of piston rings due to the damage to the saws which are blunted and dulled when striking one of the interior hard spots in the piston ring castings cast individually and in which the face of the ring is approximately one-eighth of an inch or less.

It is a primary object and purpose of the present invention to provide a process of piswhereby slotted rings as described may be readily produced in the small dimension rings now required without danger of detriment to the tools used to cut the slots and without waste of castings or waste of partial 1y machined castings caused by the dulling and blunting of the saws.

An understanding of the invention for the attainment of the ends described may be had from the following description, reference being hadto the accompayning drawing, in

which,

I, sizes of the or less face.

Fig. 1 is a perspective view of thefinished piston ring such'as is required for internal combustion engines with oil slots out therethrough, a part of the ring, at one side being removed for clearness of disclosure.

Fig. 2 is a fragmentary enlarged section through an individual casting for piston rings illustrating the central hard spot which is likely to occur in the castings for the small piston rings of one-eighth inch Fig. 3 is a similar fragmentary enlarged section through the casting which I have produced to-eliminate said hard spots at the core of. the casing, and y Fig. 4 is a fragmentary enlarged section showing the casting in F1g. 3 divided midway between its .upper and lower sides to provide two like uniform individual ring from each of which a piston ring may be made, the figure also illustrating oil slots cutthrough each ring.

around the circumference of the ring. The

' casting produced from thepattern in accordance with my invention, is indicated at 3 inFig. 3, and as it has twice the body of metal in the casting over that shown in Fig. 2, there is sufficient heat to obviate the possibility of an immediate and quick hardening of a surrounding shell around the inner core,

as at 2 in Fig. 2, and the metal in the casting shown in Fig. 3 is of uniform properties and includes no interior hard spotsconsisting of chemically combined iron and carbon.

the ring.

The casting shown in Fig. 3 is divided between its upper and lower sides, as at 4 in Fig. 4, making two rings 5 each of which may be finished to provide a piston ring and through each of which the oil drainage slots 6 maybe readily out without danger of striking hard spots as the saws are passed from The process which I have described, while simple, has completely solved the problems and troubles encountered. in making oil drainage ringsof the small sizes required in internal combustion engines. This process, so far as I now know, is more or less limited the outer curved to the inner curved sides of of valuei'n rings having a face of five-thirtysecondths or three-sixteenths inch. When the ring is less than one-eighth inch face, or the distance between its upper and lower flat sides, the process is not so useful because the cutting of slots through rings of such small dimensions between the upper and lower flat sides thereof is impractical and it makes little or no difference whether there are hard spots in the interior of a ring through which slots are not to be cut.

' Making a casting for piston rings so as to produce more than two piston .rings is no part of my invention. It then becomes a pot casting subject to all of the deficiencies and disadvantages thereof in which the rings are not uniform in quality and properties,

while a ring casting which is divided mid way between its two flat sides produces two rings completely uniform in all of their qualities and characteristics.

The invention is defined in the appendedclaims and is to be considered comprehensive of all forms coming within the scope thereof.

I claim:

. -1. The method of providing ring castings v for piston rings having a face of approximately one eighth inch, which consists in forming a pattern having a face of approxi mately one-fourth of an inch plus allowance for machining and shrinkage, casting from said pattern, and dividing the casting producedinto two equal parts by cutting the casting circumferentially midway between its opposite fiat sides.

for piston rings having a face of one-eighth of an inch or less, which consists in providing a pattern having twice the face dimension of the rings which are to be produced plus allowances for machining and shrinkage, casting from said pattern and dividing the casting produced by cutting the same circumferentially midway between the opposed flat sides thereof.

3. The method of providing ring castings for piston'rings which consists in providing a pattern having twice the face dimension of the rings which are to be'produced plus allowances for machining and shrinkage, casting from said pattern and dividing the casting produced by cutting the same circumferentially midway between the opposed flat sides thereof.

In testimony ture.

in'practice to the production of rings having 7 approximately a one-eighth inch face, though whereof I afiix my signa- THURLOW E. McFALL.

2. The method of providing ring castings

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