US2097049A - Light alloy piston - Google Patents

Description

Oct. 26, 1937. K. s'rEmR' LIGHT ALLOY PISTON Filed June 10, 1935 Patented Oct. 26, 1937 UNITED STATES 2,097,049 men-r ALLOY PISTON Karl Steiner, Heilbronn, Germany, assignor to American Lnrgi Corporation, New York, N. Y.,

a corporation of New York Application June 10, 1935, Serial No. 25,746

. In Germany July 25, 1934 2 Claims. (Cl. sue-i1) The present invention relates to light alloy pistons and more particularly to pistons of the type in which the effects of heat expansion are reduced or compensated for.

5 Heretofore, a great number of various piston structures has beensuggested toicompensate for the heat expansion of light alloy pistons. It has been proposed to eliminate this diiliculty by separating the piston head from the piston sleeve la and using a light metal, for example aluminum, for the head and a heavy metal for the sleeve. However. the combination of these two metals having widely different properties did not solve the outstanding problem'and, as a matter of is fact, has presented new difficulties. It has been 4 also proposed to cast steel strips having a low coeflicient of expansion integral with the piston skirt or sleeve but neither did this method provide a satisfactory structure. It has been attempted to dispense with a direct connection between the piston sleeve and the piston head by providing a. transversal slot between the same.

and relying only on rib-like reinforcements for the connection of the piston head to the piston pin bosses. In a structure of this character the greater heat expansion of the piston head was.

utilized to expand the piston sleeve in the direction of the piston pin and thereby to approximately maintain the distance. of k the bearing surfaces of the sleeve constant at all temperatures. In some pistons of this type the piston sleeve consisted only of two slipper sections which have been connected by means of narrow ribs 5 to the piston pin bosses. In some cases the slipper sections have been extended up to underneath the piston pin bosses where they have been mparatedby means ,of a slot. All these structures although providing compensation forthe heat expansion to a certain extent, .had the serious inconvenience that they have provided openings of relatively large surface on the piston sleeve which not only considerably weakened the structure but at the same time also respective bearing surfaces which remains constant and substantially unaffected by changes in the temperature of the piston.

It is another object of the present invention to provide an improved light alloy piston which is compensated for changes in the distance between the slipper sections and which may beinserted into a cylinder with a minimum of clearance.

It is a further object of the invention to provide a light alloy piston which has a substantially unbroken sleeve surface and for this reason great mechanical strength and good wearing qualities. p

The invention also contemplates to provide a light alloy piston which is simple in structure and easy and inexpensive in manufacture.

Other and further-objects and advantages of the invention will appear from the following description taken in conjunction with the accompanying drawing in which,

Fig. 1 illustrates a. longitudinal sectional view of the piston embodying the principles of the present invention;

Fig. 2 depicts a cross-sectional view of the piston illustrated in Fig. 1 and taken online A-A of Fig. 1;

Fig. 3 shows a longitudinal sectional view of a modified embodiment of the present invention.

Broadly stated, according to the principles of my invention I provide a closed and somewhat resilient piston'sleeve or skirt having a substantially oval cross-section. I also provide a pair ofslipper sections which are arranged on the said skirt diametrically opposite to each other and are connected thereto by means of a narrow rib extending along the full length of the piston skirt. The piston skirt proper is separated from 'the piston head by means of the conventional transversal slot extending around most of the circumference of the head and is connected to the head only by means of the two conventional supports or ribs joining the piston head to the piston pin bosses which are integral with the piston sleeve.

The invention will now be. more fully explained to those skilled in the art in conjunction with the accompanying drawing.

Referring more particularly to Figs. 1 and 2 of the drawing, a piston head I is separated from the bearing surfaces 1 of the piston-sleeve 6 by means of a conventional transversal slot 2. The

- only connection between piston pin bosses 5 and.

piston head I is established {bymeans of supports, or piers, 4. Integrally supported by-supsleeve 6 which in contrast to prior structures has a closed cross-section of oval character and is closed also underneath the piston pin bosses The thrust faces of piston sleeve or skirt 6 each' piston skirt or the associated slipper sections. The

expansion of the head will be transmitted to the sleeve by means of the two supports 4 whereby the distance between the two piston pin bosses 5 will increase, The increased distance between the pin bosses will tend to draw by means of the sleeve 6 also the slipper sections 1 inwardly, by approximately the same amount as they have been expanded by the effect of the heat. In this manner the slipper sections will maintain a substantially constant distance between their bearing surfaces at all operating temperatures and will not .be distorted in shape. a v

As illustrated in Fig. 3, in some cases I prefer to provide a pair of inclined supports, or piers, 9 passing over into-parallel supports Hi to connect the piston pin bosses with the bottom of the pis-' I ton head. instead of the straight supports 4' shown in Fig. 1. In view of the fact that this piston is practically identical with the one depicted in Figs. 1 and 2, its structure and operation will be readily understood without any further explanaover prior light alloy pistons. The piston skirt or sleeve is completely smooth, has no slots opening up thesleeve and by means of the narrow ribs 8 supports the slipper sections along the full length thereof. -This makes possible to obtain great safe;

ty of operation and increased mechanical strength unattainable heretofore.

, A further important advantage of my improved piston is that the part of .the cylinder sleeve or skirt providing the connection between slipper sections and'piston pin bosses is convex towards the outside. This not only Permits utilization of the heat expansion of the piston head to stronger expand the piston skirt in the direction of the piston pin and thereby toforce the slipper sectionslinwards by means of the connecting ribs but at the same time also provides a resilient sup- 2,097,049 ports or piers, 4 is arranged a resilient piston templated. The two very narrow and deep slots between the slipper section and the piston skirt provide the necessary clearance for the purposes of this resilient displacement.

It will be also appreciated that the piston ac cording the present invention is extremely simple in construction and easy and inexpensive in manufacture. In most cases I prefer to cast a piston blank in which the slipper sections are integral with'the piston skirt or sleeve and the grooves separating same from each other are subsequently provided, for example, by means of milling. Likewise, I prefer to extend the piston skirt in the blank up to the first piston ringgroove, so that the transversal slot 2 is provided when the grooves are made. In contrast to prior pistons this considerably simplifies the core necessary for the casting. K v

The improved piston according to the present invention permits considerable reduction of the clearance between the cylinder wall and the piston surface. For example, a conventional piston of 10 centimeters in diameter made of an aluminum-silicon alloy having a heat expansion coeificient of 21 10' necessitated the provision of a clearance of 0.10'to 0.15 mm. whereas my improved piston made of the same alloy and having bodiments thereof, many variations and modifications are possible and will suggest themselves to those skilled in the art without departing from the principles of the invention. All of these variations and modifications are to be considered as being withinthe true spirit and scope of my invention as described in the present specification and as defined in the appended claims.

I claim:

1. A piston comprising a head and depending skirt of generally oval cross section, the said skirt being provided with bosses interiorly thereof, the said bosses being connected to the head by depending piers, the said skirt being disconnected fromthe head by two oppositely disposed slots circumferentially extending between said piers, and each of the thrust .faces of said skirt com prising a web and a slipper section, the said slipper sections being connected to said web by an elongated vertical rib.

2. A piston comprising a head, a skirt of generally oval cross-section depending from said head, said skirt being provided with bosses interiorly thereof,.a pair of converging piers for each of said bosses depending from said head and connected to said bosses, the said skirt being disconnected from the head by two oppositely disposed slots circumferentially extending between said piers, and each of the thrust faces of said skirt comprising a web and a slipper section, the

said slipper sections being connected to said web by an elongated vertical rib.

1 STEINER.

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