US1847947A - Piston - Google Patents

Description

F. JARDINE March 1, 1932.

PISTON I Filed Oct. 15, 1928 fig] Patented Mar. 1, 1932 UNITED I STATES FRANK JARDINE, F CLEVELAND, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE COMPANY, OF CLEVELAND, OHIO, A. CORPORATION? OF OHIO, AS

CLEVELAND 'rnus'r 'rnusrnn PATENT OFFICE PISTON Application filed October 15, 1928. Serial No. 312,429.

7 I This invention relates to pistonsand is .particularly applicable to pistons made of aluminum, its alloys and other hght materials, and adapted to be used in internal combustion motors and the like.

Aluminum and .like materials have been used in pistons in internal combustion motors and possess many desirable characteristics, such aslightness in weight and high heat- -10 conductivity. However, when'pistons of such materials are used in the ordinary cast iron cylinders of internalcombustion motors these pistons, due to the bigh-coeflicientof expansion of material thereof, must befitted with a large clearance when cold, in order that the pistons will not stick when hot, a'nd this large clearance permits slapping of the piston the motoris-being "heatwhen cold, as while edup. v v

An object of the present invention is to provide a piston which may be made of ma.-

terial having a high-coeflicient of expansionand which may be fitted with a large clear: ancein a cylinder having a low-coefficient of expansion, so that the piston may expand freely and naturally without sticking when on the line I'I'-II of Fig. 1;

Fig. 3 is a bottom plan viewof a piston; 'and F ig. 4 is a cross sectional view taken on the line IV1V of Fig. 2, the upper half of the figure indicating the parts in their relative positions when hot and the lower half indicating these parts in the positions they 00- cupy when cold.

' The piston shown comprises a hea d having a flat top 1 surrounded b a depending marginal flange 2 provided with piston ring grooves 3. A cylindrical skirt 4 is formed integrally with its head "and connected thereto at both sides as illustrated at 5, the skirt being provided on its inner surface with wrist pin bosses 6, these bosses being connected to the head and flange 2 as by re-enforcing webs 7. The portions of the skirt intermediate the wrist pin bosses and constitutingthe bearin faces of the piston are separated from the hea by slits or air gaps 8, while between the hearing faces the sides of the skirt are integrally joined with a depending flange of the head.

The skirt is first ground round and then the sides of the skirt for an extent ofabout sixty degrees to each side of the wrist pin V axis are relieved by being ground eccen-.

trio to the axis of the piston, The purpose of the relief or'eccentric grinding of the sides of the piston is as follows:

If the skirt-were made" circular and fitted with suificient clearance in the piston it would, when the piston is cold, sla within the cylinder or cock out of line,

waging itself orthe cylinder wall. If, however the piston were caused to move sidewise of the cylinder; along the wrist pin axis, it would bear upon one element of the cylinder wall, 7

skidding'around on the curved wall of the cylinder. However, a bearing along only one element ofthe cylinder skirt would not suificiently positively retain the piston with its axis parallel that of'the cylinder and would permit the same to cock out of line almost-as if it were free from all of the walls thereof. 'If', however, a bearing on two spaced elements of the walls of the skirt is provided, the piston is quite positively maintained with its axis parallel that of the cylengaging the diametrically opposite side by following an arcuate path bearing upon the side of the cylinder wall in the direction of the wrist pin axis, and will at all times be maintained against cocking out of line.

The means for causing the piston to move along the wrist pin axis comprises a ring 9 of steel or other material having a co-eflicient of expansion lower than that of the material of the piston and preferably substantially the same as that of the walls of the cylinder in which the piston operates.

This ring is situated in a groove 10 in the exterior surface of depending flange 2 positioned between the lowermost piston ring groove and the .next piston ring groove thereabove. A portion of the ring 11 is inwardly offset and this portion issurrounded by the metal of the depending flange 2, the offset being over one of the wrist pin bosses 6. The dimensions of the ring are such that it will seat within the groove when the piston is heated to its maximum operating temperature, with the exterior of the ring face flush with the exterior of the depending flange 2. Obviously when the piston cools, the aluminum or the like of which it is composed, having the greater co-efiicient of expansion, shrinks more rapidly than does the ring, and the ring, due to its being held'by the 1mbedded portion 11, is caused to project from the opposite side of flange 2. This projection of the ring, as it remains at substantially the same size as the-interior of the cylinder, causes the piston to be translated along the piston pin axis to the left in Fig. 4

maintaining its side, at which the imbedded' portion of the ring is, closely adjacent and in contact with the side of the cylinder, so

that the skirt thereof will bear upon two ele-" ments of the cylinder wall along which it may slide as thrust is transferred from one bearing face to the other. 4 1

Of course, when the piston has become heated to operating temperature, it fits the cylinder with very little clearance so that slap is impossible, while its contact with the side of the cylinder wall prevents such slap while the engine is being heated up.

WVhile I have described the illustrated embodiment of my invention in some particularity, obviously many variations and modifications thereof will readily occur to those skilled in the art to which this appertains and I do not, therefore, limit myself to theprecise details shown and described, but claim as my invention all embodiments thereof coming within the scope of the subjoined claims.

I claim: 7

1. In an aluminum alloy piston a skirt having concentric bearing faces, the skirt being relieved between the bearing faces, and means comprising a ring relatively immovable at one point with respect to the piston for trans lating the piston along its wrist pin axis to maintain one side thereof in contact with the wall of the cylinder 'in-which it operates.

2. In an aluminum alloy piston, a skirt having concentric bearing faces, wrist pm bosses intermediate the bearing faces, a portion of the. skirtintermediate the bearingtion of the skirt intermediate the bearing faces being eccentric to said faces and within the cylinder in which the surface of said faces lie, and means integral with said piston bearing' upon the wall of the cylinder in which the piston operates at one side thereof to move the piston against theopposite side of said cylinder wall when cool.

4. In an aluminum alloy .piston, means for causing the piston to move along its wrist pin axis comprising an extensible member of a co-etlicient of expansion lower than that of the material of the piston and adapted to bear upon the cylinder walls in which the piston operates in the direction of said wrist pin axis, the member being anchored at a point in alignment with the wrist pin axis to the metal of the piston.

5. In an aluminum alloy piston, a ring of a material of lower co-eflicient of expansion than the aluminum alloy and positioned in a "groove in the cylindrical surface of the piston, the ring being of such size that its outer surface is flush with that of the piston when. both materials are at' operating temperature, 7 and an anchorage between one side of the ring and the piston intermediate the bearing faces of the piston.

6. In an aluminum ,pis'ton, having a head and two thrust faces, a ring of material having lower coefficient of expansion than the aluminum in a peripheral groove in the head, an inwardly' bent portion of the ring imbedded within the material of the piston intermediate the thrust faces.

7. In an aluminum piston, a skirt having concentric bearing faces and relieved at its sides therebetween, a ring seated at operating temperature within a peripheral groove in the piston head, an anchorage between said ring and head in the plane of one wrist pin boss, the ring being extensible beyond its groove opposite said anchorage to move the piston in the direction of the wrist lpin axis when expanding or shrinking.

8. An internal combustion engine piston includin a head, wrist pin bosses, and a skirt, said skirt including opposed thrust faces arranged to fit an engine cylinder when cold with substantially normal clearance,

the sides of said skirt intermediate said thrust faces having substantially greater.

clearance from the cylinder when cold and arranged to approach normal clearance under increased temperatures, and means for maintaining one of said sides in normal clea-rance relation to the cylinder when cold, whereby both of said thrust faces and one intermediate side are in normal clearance relation to the cylinder throughout the range of operating temperature.

9. A piston for an engine cylinder, comprising a relatively highly expansive body portion, a bearing ring in the head thereof having a relatively low co-efficient of thermal expansion and rigidly secured at one side to said body portion to hold the same against bodily movement relative to said body portion and. closely fittin the wall of said cylinder, whereby said bo y portion may expand and contract independently of said ring.

10. A piston for an engine cylinder, comprising a relatively high expansive body por- V groove rigidly secured at one side to said body portlon and closely fitting the wall of said cylinder, thereby permitting expansion and contraction of said 'body portion independently of said bearing ring.

11. A piston for an engine cylinder, comprising a relatively highly expansive body portion, a bearing ring groove in the head thereof, a bearin ring having a relatively low co-eflicient 0 thermal expansion eccen-. 'trically positioned within and rigidly secured at one side of the piston to the bottom of said groove to holdthe, same against bodily move ment relative to said piston body portion, said ring having relatively small mechanical clearance with the cylinder wall, whereby said bod portion may'expand and contract indepen ently of said bearing ring. a

In testimony whereof I hereunto afiix my signature this 6th davof October, 1928.

a FRANK JARDINE.

tion, a bearing ring groove in the head thereof, a bearing ring having a relatively low coeflicient of thermal expansion within said

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