US2051546A - Piston - Google Patents

Description

G. W. CRlST Aug. 18, 1936.

PISTON 7 Filed March 5, 1934 INVENTOR.

Patented Aug. 18, 1936 PISTON George W. Crist, Detroit, Mich, assignor to The I Cleveland Graphite Bronze Company, Cleveland, Ohio, a corporation of Ohio Application March 5, 1934, Serial No. 714,015

7 Claims.

'- The present invention, relating as indicated to pistons, is more particularly directed to a new and improved composite piston formed of separately manufactured head and skirt portions of differ- 5 ent materials. The principal object of the invention is the provision of a light, simple, inexpensive piston which will combine the advantages of the wearing qualities of such metals as iron and steel inthe skirt and the light weight and heatconducting properties of such metals as aluminum, magnesium and the like in, the head portion',-and one in which the head and skirt may be manufactured in separate units at low cost and then readily "assembled together. 15 To the accomplishment of the foregoing and relatedends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims; the annexed drawing and the following description setting forth 20 in detail certain structure embodying the invention, such disclosed means constituting, however, but one of various forms in which the principle of the invention may be used. I

In said annexed drawing: 7

Fig. 1 is a longitudinal central section through one form of my improved piston; Fig. 2 is a similar sectionillustrating a modified form; Fig. 3 is a central section on the plane 3-3 in Fig. 2; and Fig. 4 is a plan view of my improved piston.

My improved piston consists, as shown in Fig. 1, of a relatively'heavy cast or forged head portion consisting of an annulus or ring I, in which are ormed ring-receiving grooves or slots 2, 3 and 4 and a central member 5 mounted within the ring Land provided with a depending portion 6, on which are mounted the bosses I provided with aligned openings 8 for the piston pin. The bosscarrying member 5 may either be in the form shown in Fig. 1 or that shown in Fig. 2. In the L former an extension I0 is provided from the upper portion of the boss-carrying member 6, which is then threaded and secured in the threaded ring I I. In the construction shown in Fig. 2, the member is engaged within the ring by press-fitting 5 or by expanding the ring I while contracting the member 5, that is by the dry ice method, or any other suitable method, and after assembly the member 5 may be upset slightly, as indicatedat the point II, to secure and look over the upper D edgeoftheringl. I

The members I and 5 arepreferably formed of a metal of high conductivity and light weight,

such as aluminum, magnesium, or alloys of these or similar metals, and such metals ordinarily have 5 a considerably higher rate of expansion under temperature increases than metals such as cast iron or steel. 0n the other hand, the wearing qualities of light-weight metals are not equal to those of iron or steel, and because of the expansion an allowance must be made for this in the 5 initial dimensions of the head of the piston when formed out of a light-weight metal, which frequently produces noise and slap in the motor until the piston has become warmed up.

Various methods have. been suggested for the 10 manufacture of pistons of light weight metals for compensating for the undesirable expansion of they metal and for maintaining a relatively uniform flt between piston and cylinder and a substantially uniform diameter of the piston. None of these 15,

methods, however, avoidsthe objection of the lack of good-wearing quality in light-weight metal and all lead to increased expense. and complexity in the manufacture of pistons. I

In my improved piston I avoid these disadvantages by forming the head and piston pin bosses of a light-weight metal to reduce the reciprocating forces and secure good heat conductivity but I employ a relatively thin sleeve I5 of cast iron or cast steel for the skirt portion of the piston, and since the piston'laosses are supported from the head I am enabled to make this sleeve of uniform, and thin section. The absence of any large masses of metal secured to the sleeve avoids the unequal expansion and distortion which is inevitable when piston pin bosses are formed integrally with the skirt of a piston; and hence my thin skirt of uniform wall section is enabled to give very much more satisfactory service than one of metal in which the expansion is effected by such elements as the piston pin bosses which are usually secured thereto.

In Figs. 1, 2, and 3 my improved skirt is shown as consisting of a tubular element 15 of thin uniform wall section and having two spaced in- 40 wardly extending flanges I6 at its upper end, the spacing between the flanges being'suflicient to permit this sleeve to be slipped over the piston pin bosses I, which fit snugly between the ends of the flanges in the assembly of the skirt in the head. Each of thev flanges I6 is provided with ribs I8, against the radially outer faces of which the lower inner surface IQ of thering I engages, while the ring I rests upon the flanges I5. These ribs I8 serve as a pilot for insuring concentric 5c and accurate assembly of the ring I and sleeve I5. Permanent assembly of the ring I, member 5 and sleeve I5 brings these elements into the arrangement illustrated in Fig.. 1, where the sleeve is firmly secured between the members I and 5 is that radially outward expansion of the ring I,

it is intended. The sleeve is of uniform diameter throughout its length,

except for the portion adjacent its upper end and this portion is of slightly smaller diameter, which should be approximately the initial diameter of the ring I. One of the important advantages of the construction described pulls this ring away from the piloting lip 20 on the sleeve and no distorting pressure is exerted on the sleeve by this expansion, as is the case in some composite piston constructions which have been constructed.

My improved piston construction provides a piston having the advantages as to wear and life of a cast iron piston, the heat conductivity of an aluminum piston and the light weight of an aluminum piston of the best design. Another, and still more important advantage, is that the construction permits all of the parts to be manufactured in presses or hammers, avoiding the expense and the, loss occasioned by the manufacture of such articles in foundries even with the best type of mold equipment. 'The ring I and the central member 5 can both be drop-forged out of forging alloys of aluminum and/or magnesium or similar metals, while the sleeve or skirt l5 can be drawn out of sheet stock, and all of these operations are today relatively fast and inexpensive and are capable of producing articles in which the metal is extremely uniform in character and in which relatively accurate dimensions can be closely maintained.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly .point out and distinct ly claim as my invention:

1. In a piston, the combination of a head consisting of a ring provided with piston ring grooves, a central head member proper having an upper portion extending through said head and to substantially the upper edge thereof, said member having piston pin bosses depending therefrom, and a skirt of uniform wall section having a transversely extending portion, said transversely extending portion being in engagement withsaid ring and head member.

2. ma piston, the combination of a head consisting of a ring provided with piston ring grooves and a central head member proper having an upper portion, extending through said head and to substantially the upper edge thereof, said memher having piston pin bosses depending therefrom, and a skirt of uniform wall section having at its upper end a transversely extending portion, said transversely extending portion being in engagement with said ring and head member.

3.-In a piston, the combination of a ring provided with piston pin grooves, wardly projecting flanges engaging against the bottom of said ring and means'adapted to concentrically align said skirt to said ring, a head member engaged within said ring, said member clamping said flanges on said skirt between it and said ring, and piston pin bosses carried on said head member.

4. In a piston, the combination of a head consisting of a light metal ring provided with piston ring grooves and a. head member proper also of light metal having an upper through said ring and to substantially the upper edge thereof, said member having piston pin bosses integrally secured thereto, said ring and member having transversely disposed cooperating surfaces, and a skirt of heavy metal having flanges extending between said opposed surfaces on said ring and member and being adapted for engagement therebetween upon assembly of said member and ring.

5. In a piston the combination of a ring provided with piston pin grooves, a skirt having inwardly projecting flanges in engagement with the bottom, of said ring and terminating in ribs concentric with said ring and having their radially outer surfaces inengagement with the ring, and a head member secured to said ring and having surfaces thereof in engagement with said flanges so as to clamp the flanges between it and the ring, the radially inner surfaces of said "ribs being spaced from said head member to permit expansion of the head member.

6. In a piston, the combination of a ring provided with piston pingrooves, a skirt having inwardly projecting flanges in engagement with the bottom of said ring and terminating in ribs conportion extending a skirt having incentric with the ring, and a head member secured surfaces thereof in engagement with said flanges so as to clamp the flanges between it and the ring.

GEORGE W. CRIS'I.

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