US2139271A - Piston - Google Patents

Description

Dem. 6, 1933. JARDINE 2,139,271

PISTON Filed July 51,' 1925 Patented Dec 6, 1938 UNITED. STATES PISTON Frank Jardine, Cleveland, Ohio, assignor, by mesne assignments, to The Cleveland Trust Company, Cleveland, Ohio, a corporation of Ohio, trustee Application July 31, 1925, Serial No. 47,214 .16 Claims. (01. 309-13) This invention relates to pistons for internal combustion engines, particularly pistons composed of metal having a coeflicient of expansion greater than that of iron.

By my invention I am enabled to construct a piston which may be characterized as being light in weight, having ample strength at all temperatures, having substantially the same rate and amount of expansion and contraction in its skirt as of the cylinder in which it operates, having very low frictional resistance and correspondingly high efficiency, being comparably free from the accumulation of dense carbon deposits and pre-ignition troubles, having a substantially uni form bearing over the entire length and breadth of the bearing portions at all temperatures, having little or no tendency to collapse and increase the original clearance, having relatively very wide or circumferentially extended bearing portions,

and being capable of operating with an ex-- tremely small amount of actual wear as compared with similar pistons of the prior art. Moreover, by my invention I have been enabled to construct a piston having decreased rates and amounts of expansion and contraction at the lateral edges of the bearing faces as compared with the corresponding rates and amounts intermediate these edges.

In the drawing accompanying this application and forming a part of this specification:

Fig. 1 is a side elevation of one form of piston embodying my invention;

Fig. 2 is a vertical section taken on line 2--2 of Fig. 1; I

Fig. 3 is an open end view of the piston shown in Fig. 1;

Figs. 4 and 5 are respectively top plan and side elevational views of the insert employed in the piston shown in Figs. 1 to 3, inclusive; and

Fig. 6 is an open end view of a modified form of piston embodying my invention.

Referring to Figs. 1 to 3, inclusive, the piston there shown comprises a head I and a skirt 2. The head I consists of a disc-like cross wall 3 and a depending peripheral ring flange 4, from opposite sides of which depend boss carrying webs 5, which webs are, for convenience, here considered as constituting parts of the skirt 2.

. These chordal webs 5, which are disposed inwardly of the outer circumference of the piston skirt, may be supported by ribs 6 integral with l. The bearing or thrust walls or portions of the skirt 2 or cylinder bearing portions consist of substantially similar, oppositely disposed, semicylindrical members 8, flexibly joined together below the bosses, as by a resilient or flexible arch 9, and preferably cut away from just below the bosses 6 to the upper -ends of the portions ti so as to expose thebosses B and webs 5. The walls 8 are spaced apart at their upper ends from the ring flange 4, as by an air gap ll. Each wall 8 is flexibly connected to the webs 5 by flexible or resilient webs or arches II] which unite with the walls 8 along their longitudinal sides or edges. It will be seen that each bearing wall 8 is so connected to the other parts of the piston that -it may move relative to the webs 5 and the other bearing wall 8, simply by a flexing action of the arches 9 and webs ill.

Means is provided at the upper ends of portions 8 for changing and controlling the normal action of the skirt. The means comprises a band or ring [2 having two opposite flattened sides lie, the intervening parts being curved on substantially the same radius as the bearing portions 8 of the skirt. This ring [2 is preferably embedded in the upper ends of member 8 adjacent to the air gap H, with the flattened sides l2a. being disposed adjacent to, and conforming in general shape to the configuration of the outer surface of webs 5. The flattened sides l2a conveniently, but need not necessarily, lie in contact with the outside surface of these webs 5, and extend through the ribs 1 whenever such ribs are present. These flattened sides constitute connectors, plates, or struts between the opposed thrust faces and function as web flexing means for the webs ID in the embodiment illustrated. It will be understood that the band l2 may be conveniently formed in the piston by suitably supporting the band in a piston mold and casting the metal of the piston thereabout.

This band or ring I2 is preferably composed of iron or steel, although it may consist of any suitable material having a coefiicient of expansion substantially the same as that of the engine cylinder in which the piston is to operate. The remaining material of the piston is preferably a light metal or alloy, for example aluminum ormagnesium alloys.

Referring now to the piston shown in Fig. 6, it will be understood that this piston is similar in many respects to the piston shown in Figs. 1 to 3, inclusive. The bearing walls ll are connected to the webs l5 which carry bosses ID, by resilient or flexible webs 22 which unite with the portions l1 along their longitudinal side edges. Arche l8 correspond to arches 8 in Figs. 1 to 3. A band or ring 23, substantially like the band l2 shown in Figs. 1 to 3 but differing slightly in configuration therefrom to conform to the difierent location of the webs l5 as contrasted with webs 5, is embedded in the walls I1 near the upper end thereof and corresponding to the general location of ring l2 in walls 8 of the piston of Figs. 1 to 3, the curved portion of the ring 28 being cast into the bearing walls H, while the flattened sides 23a of the ring 23 lie spaced apart from the outer surface of the webs l5.

In this construction the ring I! is attached to the walls I! adjacent to their side edges as contrasted with the construction in Figs. 1 to 3 Where the ring I: joins the walls 8 at some little distance from their lateral edges.

The piston shown by Figs. 1 to 3, or by Fig. 6, operates in substantially the same manner. My theory of the operation of only the former will therefore be described. The piston I is fitted into a cylinder with a clearance of substantially onethousandths inch per inch of cylinder diameter. As the piston becomes heated in operation the head expands radially outward carrying with it the bosses 6 and boss carrying walls 5 and band 12. The band I! tends thereupon to bend in its sides I2a and to exert inward movement on its curved sides which are in walls 8. The bearing walls 8 tend at the same time to increase their diametrical and circumferential dimensions, and since the coefficient of expansion of the light- .weight metal, such as aluminum or magnesium alloys, is greater than that of iron, which composes the ordinary engine cylinder, the clearance between the piston skirt and the cylinder walls tends to diminish. The ring l2, however, expands at substantially the same rate as the cylinder wall and acts to prevent such a change of diametrical and circumferential dimension of the bearing portions 8 and ll of the skirt. It is, of course, impossible to prevent the expansion of the light metal in accordance with its coefficient of expansion but the change in these aforesaid dimensions is more or less closely controlled by the ring I! acting in conjunction with the flexible arches or webs 9 and I0. Since these flexible arches or webs can be distorted more easily, due to their configuration and size, than v the band i2 can be stretched or compressed. the

expansion and contraction of the bearing walls 8 results partly in distortion of the webs or arches 9 and III, with changes in dimensions of the bearing walls approximately in accordance with the rates and amounts of expansion or contraction of the bands. These members 8 are illustrated as shaped like culverts or Chinese bridges and are best made substantially uniform in thickness and resiliency throughout the span so that the bending is substantially uniformly distributed throughout the bridge. The webs Ill thus act in the nature of expansion joints between the webs 5 and bearing walls 8 to absorb the diametrical expansion and contraction across the walls 8 in excess of that of the ring l2. The circumferential expansion of the parts 01' the bearing walls 8 lying between the opposite sides I20. 01'- the bands I! is resisted by these flattened sides In and together with the control of transverse expansion of the skirt results in a slight distortion of these walls from their original truly circular shape. This distortion consists of a slight bowing out of the bearing walls between the sides In, as is indicated by a trifle greater wear or heavier bearing on the surfaces of the bearing walls intermediate the flattened sides of the ring and by a slight retraction or restrained expansion of the edges of the bearing portions opposite the Junction of the webs In as is indicated by slightly less wear or lighter bearing at such points. This action and movement of the bearing walls is different from the normal action and movement of a similar piston without the ring I! and in which the greatest bearing force or heaviest bearing is localized opposite the junction of webs ID with bearing portions 8. By reason of the control of the movements of the upper ends of the bearing walls by the ring, these walls tend to bear at all times on the cylinder wall with substantially the same force. Furthermore, since the greater tendency to diametrical expansion or contraction of the bearing walls is at the upper ends thereof and since the flexible arches 9 are provided to accommodate diametrical changes in the lower ends of the bearing walls, it will be obvious that I have provided a piston in which the bearing walls not only bear throughout their substantial longitudinal and circumferential extent on the cylinder walls with uniform force, but in which the bearing walls move under the forces of contraction and expansion substantially parallel to the cylinder walls. It will also be obvious to those skilled in the art that I have provided a piston construction in which the bearing walls have been extended relatively far in a circumferential direction and in which the unit bearing force is not concentrated at any one part of the bearing Walls.

Pistons embodying my invention have shown an amount of wear on the bearing surfaces measured in fractions of thousandths of an inch after many thousand miles of travel, which is several hundred per cent less than the wear found in pistons of the prior art composed of similar material and tested under substantially the same conditions.

Having thus described my invention, what I desire to secure by Letters Patent is defined in what is claimed.

What is claimed is:

1. A piston comprising a head having depending boss carrying walls, bearing walls separated from the head at their upper ends and connected by distortable means to the boss carrying walls, the said head, boss carrying walls, bearing walls and distortable means being composed of metal having a high coeflicient of expansion, and chordally extending connectors having a low 00- eflicient of expansion as compared therewith extending between said bearing walls on opposite sides of the piston with their ends extending into and embedded in the material of said bearing walls, said connectors limiting the diametrical expansion and contraction across the bearing walls to substantially that of the connectors and causing flexing of the said distortable means as the temperature of the piston is changed.

2. A piston comprising a head, chordal boss carrying webs integral with the head, oppositely disposed bearing walls separated from the head and joined along longitudinal side edges to the said chordal webs by flexible webs, the said head, webs and walls being composed of metal of a relatively high coeflicient of expansion as compared with iron and an iron ring embedded in the upper ends of the said bearing walls of suflicient tensile strength to cause distortion of the said flexible webs when the piston is heated or cooled.

3. Apiston comprising a head, chordal boss below the bosses and joined to the boss carrying.

carrying webs connected to the head, oppositely disposed semi-circular bearing walls separated from the head flexibly connected to each other webs by distortable webs, the said bearing walls being cut away from below the bosses to the upper ends thereof to expose the bosses, boss carrying webs and flexible webs, and an iron ring connected to the bearing walls at their upper ends of sufficient strength to cause distortion of the flexible webs and to limit the changes in diametrical dimensions across the bearing portions to substantially that of iron. under varying temperature conditions.

4. A piston comprising a head, oppositely disposed chordal boss carrying walls connected thereto, oppositely disposed semi-circular bearing walls separated from the head and joined together below the bosses, the said walls being cut away to expose the boss carrying walls, flexible webs joining the longitudinal side edges of the said bearing walls to the boss carrying walls, and a ring cast in the bearing walls near their upper ends and having flattened side portions disposed substantially parallel to the said boss carrying walls, the said ring having a lower coelficient of expansion than that of the metal composing the bearing walls and flexible webs, and having sumcient strength to cause distortion of the flexible webs when the temperature of the piston is increased to operating temperatures.

5. In a piston for an internal combustion en-' gine, the combination of a head and a skirt of material of a relatively high co-efficient of heat expansion, said skirt provided with bearing faces and being separated at the bearing faces from the head, the skirt being circumfere'ntially integral, means of a material of a-lower co-efficient of heat expansion than the material of the skirt regulating the expansion and contraction of the upper part of the skirt and the lower part of the skirt being split to regulate the contraction and expansion of the lower part of the skirt.

' 6. In a piston for an internal combustion engine, the combination of a head and skirt, the skirt being made of a material of relatively high co-efficient of heat expansion, the skirt-being circumferentially integral, means of a material of a lower co-efficient of heat expansion than the material of the skirt regulating the expansion and contraction due to heat of the upper part of the skirt. and the lower part of the skirt being split to regulate the contraction and expansion of the lower part of the skirt.

'7. In a piston for an internal combustion engine, the combination of a head and skirt, the

head being of slightly less over-all diameter than the skirt, piston ring grooves in the periphery of the head, the skirt being provided with bearing faces and the head and skirt being separated from each other at the bearing faces by horizontal slots, piston pin bosses connected integrally with the head and skirt, the skirt being circumferentially integral, means of a lower coefficient of heat expansion than the material of the skirt for regulating the expansion and contraction of the upper part of the skirt, the lower part of the skirt being split to regulate the expansion and contraction due to heat of the lower part of the skirt.

8. In a piston for an internal combustion engine, the combination of a head and skirt made of, material of a relatively high co-eflicient of heat expansion, piston pin bosses in said skirt, said skirt being relieved about said piston pin bosses, the skirt being circumferentially integral and connected integrally to the bosses, integral connections connecting the bosses to the head and forming an integral member comprising the head, skirt and bosses, the skirt being relieved about the bosses but being circumferentially complete, means of a material of a lower co-efllcient of heat expansion than the material of the skirt regulating the expansion and contraction of the upper part of the skirt, said means joining the opposite bearing faces of the skirt and being connected to the bosses, the lower portion of the skirt being split to regulate the contraction and expansion of the lower part of the skirt. I

9. In a piston for an internal combustion engine, the combination of a head and skirt of a material of a relatively high coefficient of heat expansion, means depending from the said head and integral therewith, piston pin bosses supported by said means, the said skirt having opposed bearing surfaces separated from the head, webs uniting the skirt and piston pin bosses and integral with each, said skirt being provided with a relatively narrow split extending downwardly in the lower part of the skirt, circumferential extensions of the skirt subjacent the webs forming an annulus at the base of the piston and chordal struts of a material of a lower coefficient of .heat expansion than that of the head and skirt conmeeting the opposed bearing surfaces of the skirt.

10. In a piston for an internal combustion engine the combination of a head and a substantially cylindrical skirt of a material of a relatively high coefiicient of heat expansion, means depending from the said head and integral therewith, piston bosses in said means, the said skirt being cut away about the bosses and having opposed bearing surfaces separated from the head, an integral connection between the piston pin bosses and the skirt, said skirt being provided skirt and extending across the cut-away portion of the skirt.

11. In a piston for an internal combustion engine, the combination of a head and skirt of a material of a relatively high coefficient of heat expansion, means depending from the said head, piston pin bosses in said means, said skirt being separated from the head, chordal webs of the same material as the head and skirt uniting said skirt with the piston pin bosses, chordal struts of a material of a lower coefficient of heat expansion than that of the head and skirt and separated by an air gap from said chordal webs.

12. In a piston for an internal combustion engine, the combination of a head and a skirt of a material of a relatively high coefficient of heat expansion, said head having integral means depending therefrom, piston. pin bosses in the means, said skirt being separated from the head, chordal webs of the same material as the head and skirt uniting said skirt with the piston bosses,

in said piston, a cylindrical skirt of aluminum alloy separated from the head by horizontal slots and having bearing i'aces opposite each other, portions of said skirt being cut away about the piston pin bosses, connecting means of aluminum alloy connecting said head and bosses and other connecting means connecting said bosses directly to the bearing surfaces of said skirt, said conecting means uniting said head, skirt and bosses into an integral construction of aluminum alloy, means of a lesser co-efllcient of heat expansion than the aluminum alloy connecting the bearing faces and the bosses together and extending across the cut-away portion of the skirt, the lower portion of the skirt being split with a substantially vertical split terminating in the bottom of the skirt.

14. In a piston for an internal combustion engine, the combination of a cylindrical head made of aluminum alloy and provided with ring grooves on its outer surface for piston rings, aluminum alloy piston pin bosses in said piston, a substantially cylindrical aluminum alloy skirt separated from the head by horizontal slots and provided with bearing faces opposite each other, the portions of said skirt adjacent said bosses being cut away, aluminum alloy connecting means connecting said bosses to said head and aluminum alloy connecting means connecting said bearing faces directly with said bosses, means of a lower co-efilcient of heat expansion than aluminum alloy also connecting said bearing faces with said bosses and extending across the cut-away portion of the skirt and separated by an air gap from the second named aluminum alloy connecting means, the lower portion of said skirt being split with a vertical or substantially vertical split terminating at the bottom of the skirt.

15. In a piston for an internal combustion engine, the combination of a head, piston pin bosses, a skirt, means connecting the same into an integral construction, said head, bosses, skirt and interconnecting means being oi. a material of a relatively high co-efllcient of heat expansion, said skirt and head being separated by air gaps, said skirt being provided in the lower portion thereof with a relative narrow slit terminating at the bottom edge of the skirt, said skirt being provided with hearing faces and being cut away about the bosses, means of a lower coefllcient of heat expansion than the material of the said skirt connecting the bearing faces and the bosses together and extending in a horizontal direction or across the cut-away portions of the skirt, means of high co-eilicient of heat expansion material connecting the bosses and the skirt also extending substantially horizontally across the cut-away portions of the skirt.

16. In a piston for an internal combustion engine, the combination of a head, piston pin bosses, a skirt, means connecting the same into anintegral construction, said head, bosses, skirt and interconnecting means being of a material of a relatively high co-eiiicient of heat expansion, said skirt and head being separated by air gaps, said skirt being provided in the lower portion thereof with a relatively narrow slit terminating at the bottom edge of the skirt, said skirt being provided with bearing faces and being cut away about the bosses, means of a lower co-eiiicient of heat expansion than the material of the said skirt-connecting the bearing faces and the bosses together and extending in a horizontal direction across the cut-away portions of the skirt, means of relatively high co-efiicient of heat expansion connecting the bosses and the skirt also extending in a horizontal direction across the cut-away portions of the skirt and separated by air gaps from the connecting means of lower heat expansion co-eflicient material.

FRANK JARDINE.

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