US1944934A - Piston - Google Patents

Description

Jam., E@ H9340 F. JARDHNE L944p934 PISTON Filed Aug. 6, 1928 NVE TOR :QW F/b/mavs Patented Jan. 30, 1934 UNITED STATES PATENT OFFICE PIs'roN tion of Ohio Application August 6, 1928. Serial No. 297,594

2 Claims.

This invention relates to pistons fofr internal combustion engines or the like, and more particularly to pistons made of some material having a high coeicient of expansion such as aluminum, or aluminum alloys, to be used in a cylinder having a relatively low coeflicient of expansion, such ascast-iron.

It is well known that such pistons possess many desirable qualities, such as lightness, high heat conductivity, and the like, but since the coeiiicient of expansion due to heat of such materials diier from that of the cylinders in which they operate, difficulties and disadvantages are encountered at various temperatures. For example, pistons that will not slap when cold will stick when hot and l5 vice versa.

The principal object of the present invention is to provide a piston made of, aluminum, aluminum alloy or the like, which can be fitted with a very small clearance when installed in a castiron cylinder, and which clearance will be substantially maintained throughout the temperature ranges met in practice without slapping, binding, or scoring of the cylinder, or undue wear on the piston itself.

This invention is an improvement in the type of piston claimed inthe co-pending application of Jardine and Cooper, Serial No. 174,202, led March 10, 1927, which is a division of Jardine and Cooper, Serial No. 79,800, iiled January 7, 1926; and also embodies the subject in my copending application, Serial No. 47,214, filed July 31, 1925.

Other objects will hereinafter appear.

The invention will be better understood from the description of one practical embodiment thereof illustrated in the accompanying drawing in which Figure 1 is aside elevation of a piston embodying the invention Figure 2 is a central sectional View taken on the line II-II of Figure 1 i Figure 3 is a sectional central view of the same piston taken on the line III-III of Figure 2;

and I f Figure 4 is a bottom plan view partly in section taken on the line IV-IV of Figure 2.-

The piston is shown as having a head composed of a top 1 and depending ange 2, grooved as at 3 for the reception of the usual piston rings. From the ange of the cylinder head, at

each side of the piston, depends a wrist pin boss supporting ange or wall 4, carrying a wrist pin boss 5 and reinforced by two parallel internal webs 6 between the wall and the cylinder head,

and also by a central external web or rib 7 and two substantially triangular angularly disposed ribs 8.

Below the wrist pin boss, the wall is stiffened by two downwardly extending parallel webs 9, the webs depending below the wall and extending outardly to join the bottom parts of the piston skirt.

The skirt comprises two bearing faces 10 intermediate the boss carrying walls, and below the same the skirt is rendered substantially continuous by the strap-like portions 11, separated beneath the wrist pin axis by splits l2, which allow, by closing, for the peripheral expansion of the skirt. The depending webs 9 beneath each boss carrying wall connect with the strap-like portions 11, one lying on each side of the split l12. All the parts above described are formed of aluminum, aluminum alloy, or the like, and are conveniently cast integrally.

Two expansion control members A and B are provided to control the expansion of the piston skirt across the bearing faces. These are shown as comprising upper and lower horizontal members 13 and 14 connected by integral end members 15. The members 13 and 14 are embedded in the boss carrying walls and are provided on their edges adjacent the wrist pin bearing-with curvedoutwardly flanged edges 16 and 17, and on their opposite edges with outwardly struck tongues 18 and 19, the anges and tongues serving to securely key and lock the horizontal members to the boss carrying walls to prevent any sliding therein. The horizontal members are bent slightly inwardly as they leave the boss carrying walls and the vertical ends are disposed at an 90 angle as shown at 20, so as to be securely keyed i and deeply embedded in ribs 21 cast thereabout and integral with the bearing faces of the piston.

The control members are formed of steel or similar material which expands at a rate much 95 lower than that of the aluminum and near that of the cylinder in which the piston is intended to operate. This therefore limits the rate at which skirt can expand to substantially the rate at which the cylinder expands.

The controlling of expansion of the skirt is further effected in the following manner. As will be noted the boss carrying Walls are quite rigidlybraced to the piston head and, therefore, these walls move outwardly substantially at therate of expansion of the head. As the bearing faces of the skirt are separated from the head and so remain cooler in operation the distance between the two ribs 21 on either skirt does not vary at as great a rate as the distance between 1m,

the boss carrying walls, and the control members are, therefore, when the piston becomes heated, bowed outwardly at their centers. This deformation tends to pull their ends toward each other and further limit the expansion of the skirt. This expansion is also partially controlled by the webs 9 which are relatively rigid in the direction of the wrist pin axis, but relatively flexible in the direction transverse thereto. This causes the lower portion of the skirt, which is the most remote from the cylinder head, consequently cooler, to increase at a greater rate than would be the case if it were connected by the controlmembers alone, and so compensate for the difference in temperature. f

The skirt may be relieved throughout the lower strap-like portions, so that expansion in the direction of the wrist pin axis does not cause the same to bind upon the cylinder walls, the expansion in the direction normal thereto being compensated therefor by the exure of webs and the closure of splits 12.

From the above it will be seen that by properly choosing material for the control members and proportioning the same and the other parts of the piston, the expansion of the skirt may be rendered substantially that of the cylinder in which it operates and that-the disadvantages lattendant differences of expansion between the ment of myl invention in some particularity, ob-

viously many variations and modifications thereof will readily occur to those skilled in the art to which this appertains anfLI do not, therefore, limit myself to the precise details shown and described but claim as my invention all embodiments thereof coming within the scope of the subjoined claims.

l. A piston composed of aluminum alloy and comprising a head having a depending cylindrical ring flange, opposed boss carrying piers integral with and depending from said ring flange, bracing webs integral with saidv piers, the inner side of said ring flange and the under side of said head rendering said piers substantially, rigid with respect to said head, in the line of the wrist pin axis, a pair of skirt sections separated from each other and from said ring flange, each of said skirt sections being spaced from said piers and beirigformed with arcuate extensions below said piers extending toward corresponding extensions of the vother skirt sectionv and separated thereposed of a materialA having a lower co-etilcient of expansion than the material of the piston, each of said control vmembers having its centraly portion embedded in one of said piers and its ends embedded in the spaced edges of said skirt sections above said arcuate extensions, each of said control members being bowed outwardly at its center and arranged in such a manner as to transmit forces to said skirt sections substantially all of which are directed inwardly of the adjacent outer surface of said skirt sections upon expansion of said head and consequent separation of said piers tending to move the ends of said control members closer together, to preventany decrease in the curvature of said skirt sections upon the flexure and spreading of saidarcuate extensions resulting from the separation of said piers.

2. A piston composed of aluminum alloy and comprising a head having a depending cylindrical ring flange, opposed boss carrying piers integral with and depending from said ring flange, bracing webs integral with said piers, the inner side of said ring flange, and the under side of s said head, rendering said piers substantially rigid with respect to said head in the line of the wrist pin axis, a pair of skirt sections separated from each other and from said ring liange, each of said skirt sections being spaced from said piers and being formed with arcuate extensions below said piers extending toward corresponding extensions of the other skirt section and separated therefrom by a slot, a pair of columns integral with each of said piers and extending downwardly and outwardly from the wrist pin boss carried by said pier and integral with the adjacent arcuate extensions of said skirt sections, said columns being relatively rigid in the direction of the wrist pin axis and relatively flexible at right angles thereto, said arcuate extensions being relieved to permit the same to be spread apart by said piers upon expansion of the head without binding in the cylinder, and a pair of control t members composed of a material having a lower co-eilicient of expansion than the material of the piston, each of said control members consisting of a pair of spaced horizontal straps connected at their ends by vertical portions and each of said horizontal straps having its central portion embedded in a pier and bowed outwardly at its central portion, one of the straps of each control member being disposed above and one being disposed below the wrist pin axis, the ends of said control members being embedded in the spaced edges of said skirt sections, said control members arranged in such a manner as telg( transmit forces to said skirt sections substantially all of which are directed inwardly of the adjacent outer surfaces of said skirt sections on expansion of said head and consequent separation of said piers tending to move the ends of said 35 control members closer together, to prevent any decrease in the curvature of said skirt sections upon the flexure and spreading of said arcuate extensions resulting from separation of said piers.

FRANK A JARDINE;

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