US2379359A - Piston - Google Patents

Description

June 26, 1945. E. w. KETTERING Filed Jan. 9, 1943 2 Sheets-Sheet 1 oco.o

Ek QN Sk h4 u Patented June '26, 1945 PISTON Eugene W. Kettering, Hinsdale, lll., assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application January 9, 194s, serial Ns. 471,s21 (cl. aos-19) A 23 Claims. Many of the outstanding defects or pistons of the type usually found in internal combustion engines are basically attributable to the location of the bearings for the piston pins on the skirts of the pistons. This location of the bearings for the piston pins entails transmission of loads from one to the other. of the crowns and the connecting rods through the skirts of the pistons and distortion of the skirts in the zones through which the loads are transmitted unless in these zones the skirts are made so thick that there is danger of transmission to the zones in which the piston rings are located of enough heat to carbonize lubricating oil and stick the piston rings.

The non-symmetrical construction, which the location of the bearings for the piston pins on the skirt of the pistons entails imparts to the pistons dierent expansion characteristics in different directions. These dierent expansion characteristics in .different directions, in turn, aggravate the stresseswhich arise in the pistons when their temperatures are raised or lowered, makes it necessary to increase the clearances between the pistons and the cylinders in order to obviate seizing of the pistons when the engines are hot, which results in rocking of the pistons in the cylinders, blow-by, and oil pumping, and also results in uneven wear of the pistons at different points in their circumferences.

The fixed position, diametrically, of the bearings for the piston pins, which the location of them on the skirts of the pistons also entails, gives rise to the tendency to concentrate the wear on the pistons and promotes the tendency to concentrate the wear on the cylinders on the sides at right angles to the axes of the piston pin bearings, and this and the uneven wear which results from the dierent expansion characteristics in different directions and the 'hammering which results from rocking aggravate each other and the other defects which have been mentioned.

All of the mentioned defects, which reduce the efficiency and shorten the lives of the engines `in which the pistons are installed, are exaggerated in the cases of the pistons of two-stroke cycle engines because these pistons operatel at higher temperatures than do the pistons of fourstroke cycle engines.

This invention has to do with pistons, particularly with pistons for two-stroke cycle engines, although certain and, it may be, most features of it are applicable to pistons for four-stroke cycle engines.

The principal object of the invention is to provide pistons which are so constructed and in which the piston pins are so mounted that the defects mentioned above are obviated.'

To improve further in the respects mentioned,

lpistons in which are incorporated the features of my invention referred to above, I preferably construct the pistons so as Vto provide for internal cooling by a liquid, particularly the lubricating oil of the engine in which the pistons are lnstalled.` I

Another object of the invention is to improve pistons, particularly pistons in which are incorporated the features of my invention first referred to above, in respect to internal cooling by a liquid, particularly the lubricating oil of the engine in which the pistons are installed.

Still another object of the invention is to improve pistons, particularly pistons in which are incorporated the features of my invention referred to above, in' respect to lubrication of the pistonpins.

For a better understanding of the nature and lobjects of this invention reference is made to the following specification and accompanying drawings in which are described and illustrated the preferred embodiments of Amy invention.

In the accompanying drawings: Figure 1 is an axial section at a right angl to the axis of the piston pin through a piston in which is embodied my invention and the upper end of its connecting rod.

Figure 2 is, in the main, an axial section through the piston and connecting rod in the plane of the axis of the piston pin looking in the direction indicated by the arrows 2--2 in Figure 1 but with parts in advance of the plane in elevation with parts broken away.

Figure 3 is a section through the piston at, aA

right angle to its axis at the level indicated by the line 3 3 of Figure 1.

Figure 4 is an axial section through the piston taken as indicated by the line 4-4 of Figure 3 with the connecting rod, pistonpin and piston pin bushings removed and the ends of the piston broken away.

Figure 5 is a View similar to Figure 2 of another 'piston in which is embodied my invention and the upper end of its connecting rod.

' The piston shown in Figures 1 to 4 of the drawings includes a body l0 and a piston pin carrier Il.v The body includes a concave crown l2 and a cylindrical skirt I3 which depends from' the crown. On the underside of the 'crown there are formed coaxially with the body of the piston circular reinforcing and heat dissipating ribs it.

The wall of the skirt is of uniform thickness throughout its circumference at all points in its length but there are on the inside of the skirt at its lower end and a short distance below its upper end protuberant bands I6 and I5 which increase the thickness of its wall in these zones and between these bands an annular rib I1. In outwardly opening annular grooves in the skirt opposite the bands I5 and I6 are installed split compression and oil control rings I6 and I9.

Within the body of the piston just below the band I5 there is an annular foot 20 which is coaxial with the body but spaced radiallyfrom the wall of the skirt. The foot `is connected to the crown in the region of the outermost of the ribs Il and to the skirt in the region of the lower edge of the band I5 by eight similar vertically and eight similar diagonally upwardly extending equicircumferentially spaced struts 2I and 22.

The body I0, foot 20 and struts 2| and 22 are, aSl

of the band I6 of the skirt is finished to provide a cylindrical lateral bearing surface coaxial with the body of the piston for the lbwer end of the pin carrier.

The pin carrier I I is, as the drawings indicate, a one-piece casting, preferably of steel, shaped generally like a frusto-conlcal shell. Its length is somewhat greater than the distance from the end face of the rabbet 23 in the foot 20 to the band I6 of the skirt and it tapers from a diameter slightly less than the internal diameter of the band I6 at its lower end to a. diameter slightly less than the diameter of the cylindrical face of the rabbet 23 at its upper end. On the upper end of the carrier there is formed an annular inwardly projecting lip 24 to increase its end bearing at that end to a value equal to that of the end face of the rabbet 23. At points diametrically opposite each other there are formed on the side wall of the carrier piston pin bosses 25 with alined bores 26 in them. Across the interior of the carrier at a sulllcient distance above the bosses 25 to clear the extremity of a connecting rod oscillatorily connected to the carrier by a piston pin installed in the bores 26 in the bosses 25 but below the lip 2l on the upper end of the carrier extends a partition 21 shaped generally like a segment of a cylinder coaxial with the bores 26. The partition 21 with the portions of the side wall of the carrier which extend upwardly beyond it define an upwardly open chamber 28 which at its perimeter increases in depth from points directly above the axis of the bores 26 to points at a right angle thereto.

The upper end of the carrier II is finished to provide a cylindrical lateral bearing surface coaxial with the carrier and an end bearing surface at a. right angle thereto. The lower end of the carrier is finished to-provide a cylindrical lateral bearing surface coaxial with the carrier. The carrier is preferably electroplated with cadmium or some other suitable metal to improve the bearing qualities of its bearing surfaces.

The small end of the connecting rod 29 through which extends a bore in which is fixed a case hardened steel sleeve 30 is disposed within the interior of the pin carrier II below the partition .in the band I6.

21 and is connected to the pin carrier by the plston pin 3l which extends through the bores 23 in vthe piston pin bosses 25 and the sleeve 3l. The piston pin 3I is journalled in bushings 32 pressed into the bores 26 in the bosses 25 and in a bushing 33 which is free to rotate in the sleeve 30 and is retained in place therein by retainer rings 34 and split snap rings 35 which hold them in place. In the inner surfaces of the bushings 32 there are formed lubricant grooves 36 which extend from end to end of the bushings and in both inner and outer surfaces of the bushing 33 there are formed lubricant grooves 31 which extend from end t0 end of the bushing.

As the drawings show the pin carrier II is disposed within the body of the piston with itsupper end in the rabbet in the foot 20 and an anti-friction washer 38, preferably of sintered bronze, between its end bearing surfaces and the corresponding bearing surface of the rabbet and its lower end extending well into the band I6 of the skirt. It is held in this position by a plane split snap ringl 39, preferably of cast iron. disposed in an annular groove in the band I6 below it. The rib I1 on the interior of the skirt I3 is located so that it will be at the'level of the axis of the plston pin 3l when the pin carrier is installed in the body of the piston and serves' to limit endwise movement of the piston pin.

The pin carrier is installed in the body of the piston by inserting it into it through its lower end and then springing the ring 39 into its groove The pin carrier and the body can, of course, be disassembled upon removal of the ring 39. This makes it possible, upon removal vof the cylinder head of the engine, to remove the body of the piston from the cylinder without disassembling the connecting rod from the crankshaft. It also makes it possible to remove the connecting rod and pin carrier from the engine through the crankcase without removing the body of the piston from the cylinder or removing the cylinder head. The piston pin 3l and the connecting rod 29 are assembled with the pin carrier before it is installed in the body of the piston and may be disassembled from it after the pin carrier is removed from the body. There is. consequently, no occasion for providing in the skirt I3 openings through which the piston pin may be inserted into and withdrawn from its bearings in the pin carrier and connecting rod.

The t of the pin carrier II in the body I3 of the piston, both lengthwise and radially, while not loose, is such that the body may rotate freely on the carrier. While I do not consider the values critical, I mention by way of example, that in pistons in which the pin carrier was approximately six inches (6") in diameter at its upper end, seven and one-half inches (7l/2) in diameter at its lower end and six inches (6") long total clearances of five to seven thousandths of an inch (0.005'f-0.007) on the diameters and one to seven thousandths of an inch (0.001"-0.007") on the length were found satisfactory.

The space confined by the pin carrier II and the crown I2 and skirt I3 of the body I3 of the piston accommodates lubricating oil to cool the piston and lubricate the bearings of the pin carrier I I and the piston pin 3l. To provide for the vintroduction and escape of lubricating oil into and from this space there are provided in the wall of the pin carrier, which in the regions in which they are located is formed to accommodate them, bores 40 and 4I which extend through the pin carrier parallel to its axis from its lower end to of the bores 4I and 4| is disposed on one side of and as near as practicable to the bore 26 in one of the piston pin bosses and the other on the opposite side of and as near as practicable to the bore 25 in' the other of the piston pin bosses. The lbore 4i through which the oil escapes from the space'ls a plain cylindrical bore and the bore 40 through which oil is introduced into the space is like it except that its lower end is chamiered to facilitate thea introduction of oil\ into it. .Through the pin carrier there also extends upwardly and radially with respect to it. from a point just above the upper end of the bore 40 into the chamber 42l at its perimeter at a point above the lowest level of its bottom a bore 42 whose axis intersects the axis of the bore 40. To direct oil from the bore 40 into the bore 42 and. thence, into the chamber 28, there is formed on the pin carrier a baille 42 which extends from the upper side of the bore 42 over the upper cud of the bore 40.

The body. the foot' and 'the struts which connect the foot to the body ofrthe piston shown in Figures l to 4 may be formed, instead of in one piece, of several pieces suitably secured together.

above the chamber and onto the struts 2l (or 53)- and, through the openings between the struts,

.onto the band i5 of the skirt and the portion of the crown between the skirt andthe struts. The chamber 28 is, of course, in the interest of uniformity and adequacy of cooling, made of sufiicient capacity to hold enough oil to drench the In Figure 5 of the drawings there is shown an example of a piston of this type.

'I'he piston shown in Figure 5 includes a crown ASii, a skirt 5I, a foot 52 and seven struts 53 formed separately of steel and secured together by welding, as indicated at 54, 55 and 56, in the same relation as are the corresponding elements of the piston shown in Figures l to 4. To facilitate han'- dling of the struts 53 and assembly of them with the crown 50 and foot 52, the Struts 53 are, preferably, as shown in the drawings, formed as parts of a one-piece element of ring-like form. The struts 52, of course, correspond to the vertically disposed struts 2l but there are in the piston shown in Figure 5 no struts which correspond to the diagonally disposed struts 22 of the piston shown in Figures l to 4. Except in the indicated respects, the piston shown inv Figure 5 is like that shown in Figures 1 to 4.

`The pistons `shown in the drawings and hereinbefore described were designed for'installation in two-stroke cycle internal combustion engines with nozzles in their crankcases alined with the bores 40 in the pin carriers il and connected -to the lubricating systems of the engines so that when the engines are operating streams of lubrieating oil are continuously squirted. from the nozzles into the bores. The oilsquirted in'to the bore 40 is deected by the baille 43 into the bore 42 and, thence, into the chamber 28. The hiatus at the junction of the bores 40 and 42 permits oil which drains from the chamber 2l through the bore 42 to flow into the space between the side wall of the pin carrier and the skirt of the piston instead of into the bore 40 and thus obviates interference by oil draining from the chamber 28 through Ithe .bore 42 with introduction of further oil into the chamber. Location 0f the inner end of the bore 42 at a point above the lowest `level lof the bottom of the chamber 28 insures that the volume of oil in the chamberfwill never be reduced below a fixed value by drainage through the bore 42.

tarily held against it by inertia; In any event, f

immediately or after a moment, the oil which has been dashed out of the chamber '28 drops. or tlows down the skirt I3 or the struts 2l (or 53) or splashes or is dashed by inertia back into the chamber or into the space between the side wall of the pin carrier and the skirt. .'Ifo reach the last mentioned spacegthe oil, in the case ot the piston shown in Figures 1 to 4, passes through the spaces between the skirtand the "foot 2li`and the struts 22 or flows over the struts 22 or, in the case of the piston shown in Figure 5, passes through the space between the skirt and the foot 52. In this way the space between the side wall ofy the pin carrier and the skirt is kept filled with oilup to the level 4of the upper end of the bore 4i through ,Y which the excess escapes into the crankcase of the engine. v

Of course, upon deceleration of the piston in the direction toward whichthe chamber 2l faces or acceleration of the piston in the opposite direction, the oil in the'space between the side wall of the pin carrier and the skirt is also dashed upwardly by inertia. Besides moving about in the space conned by the pin carrier and the body have been mentioned the oil in this space drops, and nows and is dashed and splashed and welters around more or less at random, The total result of all this movement and the continuous replacement with cooler oil of the oil heated by contact with the interior of the piston is to efficiently and uniformly cool the whole of the piston. 'I'he eiiciency and uniformity of the cooling, particularly of the crown, is augmented by conducting the oil introduced through the bore into the chamber and dashing it therefrom onto the crown, instead of squirting it directly onto the crown, since the former results in more general and. even application' of the oil to the crown.

Side thrust is transmitted from one to the other of the connecting-rods and the skirts ofthe pistons shown in the drawings through the pin carriers and their lateral bearings on the bands yIl; of the skirts and the feet 20 and 52. In 4the case of the piston shown in Figure 5, the portion of the side thrust transmitted through the lateral bearing ofthe pin carrier on the foot 52 is transmitted from one to the other of the footand the skirt through the vertically disposed struts 53 and the crown 50. In the case of the piston shown in Figures 1 to 4, the portion of the side thrust trans- Upon deceleration of the'piston inthe direc.

tion toward which the chamber 28 faces or ac `celeration of the piston in the opposite directionlv the oil in the chamber 28 is Adashed by inertialL onto the portion of the crown i2 (or lli) directly` mitted through the lateral bearing of the pin carrier on the foot 20 is transmitted from one to the other of the foot and the skirt, partly through the vertically disposed struts 2l and the crown I2,

but mainly through the diagonally disposed struts Loadsare transmitted from one to theother of the connecting rods and the crowns of the pistons,

notthroughthe skirts of the pistons, but through Consequently, the

'of the piston in the particular manners which as the cylinders.

safely without distortion theA portion of the side thrust transmitted to them through vthe crowns o! Y sion rings arelocated, to the end of reducing the amountof heat transmitted from the crowns to the bands through these zones, without danger of distortion ofthe skirts -in these zones. Thisand the cooling. of the bands i5 in whichthe compression ringsare locatedt by the oil splashed on them Aminimizes danger of these bands attaining a suillciently high temperature to carbonize lubricating oil and stick the rings.

Since the bodies, the feet and the struts which join the feet to the bodies of the pistons shown in the drawings are symmetrical with respect to all planes within which the axes of the bodies lie and the bodies are not xed to the pin carriers, the bodies of the pistons will expand uniformly in all directions radially and the stresses which arise in the first mentioned elements when the temperatures of the pistons are raised or lowered are minimized. The uniformity of expansion of the bodies of the pistons in all directions radially and the minimization of the stresses which arise in the bodies, the feet and the struts of the pistons when the temperatures of the pistons are raised or lowered, of course, makes it possible to fit the pistons in the cylinders with less clearance without incurring danger of seizing when the pistons are hot, with the advantageshereinbefore indicated, and lengthens the lives of the pistons. The properties mentioned are, of course, augmented by the efficient and uniform cooling of the pistons.

When the pistons shown in the drawings and hereinbefore described are installed in an inter- 'nal combustion engine and the engine is operating the bodies of the pistons rotate about their axes on the pin carriers under the influence of a force to which the pistons are inherently subjected as aresult of operation of the engine. To what this force is attributable I have not ascertained but it has been suggested that it is attributable to the unavoidable minute lateral play of the pistons in the cylinders. However .this may be, the rotation has the very desirable effect of eliminating the tendency to concentrate the wear on two sides of the pistons and reducing the tendency of the cylinders to wear out of round since it naturally results in uniformizing the wear of the pistons at all points in their-circumferences and maintaining them of the same shape Also, particularly in engines whose cylinders are not vertically disposed, the rotation has the further very desirable effect of promoting uniformity of cooling of the pistons by the oil introduced into their interiors.

The upper end and lateral bearings of the pin carriers are kept thoroughly lubricated by the oil which drops and iiows and is dashed and splashed and welters around inA the spaces confined by the pin carriers and the bodies of the pistons. The lower lateral bearings of the pin carriers, the bearings of the piston pins and the bearings of the bushings 33 on the sleeves 30 are kept thoroughly lubricated by seepage of oil from the supplies in the spaces between the side walls of tre carriers and the skirt. In the cases of the bearings of the piston pins and the bearings of the bushings 33 on-the sleeves 33, the seepage is through the oil grooves in the surfaces of the bushings 32 and, thence, to the oil grooves in the surfaces of the bushings 33. However, to insure that the mentioned bearings will be adequately lubricated until suilicient oil reaches them from the supplies inthe 'spaces confined by the pin carriers and the bodiesf the pistons. I consider it desirable to lubricatef these bearings thoroughly before the pistons are installed in an engine.

Offhand, the rings 39 may appearcinadequate to hold the pin carriers in the pistons. But when it is considered that in two-stroke cycle internal combustion engines the load transmitted from one to the other of the pistons and the connecting rods isv always compressive, it will be seen that there is actually no need for anything to hold the piston carriers in the pistons while the engines are operating normally. And further, it has been found that the rings 33 are adequate to hold the pin carriers -in the pistons evenwhen the pistons seize badly in the cylinders.

I claim:

1. In a piston, a body, and means for transmitting motion from one to the other of the body and a connecting rod including an element on which the connecting rod may oscillate with respect to the body, and a member interposed between the element and the body but not fixed with respect to the body.

2. In a machine, a piston which includes a body, and means for transmitting motion from' one to the other of the body and a crank includ-I ing a rod with respect to which 'the body is rotatable under the influence of a force to which it is inherently subjected as a result of operation of the machine.

3. In a piston, a body, and means for transmitting motion from one to the othe'r of the body and a connecting rod including an element on which the connecting rod may oscillate with respect to the body, and a member with respect to which the body is rotatable interposed between the element and the body.

4. In a piston, a body which is substantiallyl symmetrical with respect to all planes within which its axis lies and within which there is an end bearing surface which faces away from its crown and a cylindrical lateral bearing surface coaxial with the body, and means for transmitting motion from one to the other of the body and a connecting rodincluding a member which is disposed within the body and on which there are end and cylindrical lateral bearing surfaces disposed opposite the corresponding bearing surfaces on the body so that the body may rotate with respect to the member.

5. In a piston, a body which is substantially symmetrical ,with respect to all planes within which its axis lies and within which there is at a distance from its crown a cylindrical lateral bearing surface coaxial with the body, a member within the body which is disposed between its crown and the mentioned bearing surface and is substantially symmetrical and joined to the body substantially symmetrically with respect to all planes within which the axis ofthe body lies and on which there is an end bearing-surface y which faces awayfrom the crown and a.cylin drical lateral bearing surface coaxial with the body, means for transmitting motion from one to the other of the body and a connecting rod including a member which is disposed within the body and on which there are end and cylindrical lateral bearing surfaces disposed opposite the corresponding bearing surfaces on the body and the first specified member so that the body may rotate with respect to the second specified memchamber-closed at its end most distant from v ber under the influence of a force to which it is inherently subjected as a result of operation of the piston, and means to retain the second specified member within the bodydisposed at the end of the second specified member most ldistant from the crown but movable to a position in which the second specified member may be removed from the body.

6. In a piston, a body which includes a crown and a skirt, a chamber within the body opposite the center of the crown with an open side which faces the crown and through which cooling liquid may be dashed from the chamber onto the center of the crown by inertia as a result of deceleration of the piston in the direction toward which the chamber faces orlacceleration of the piston in the opposite direction, and a passage through which cooling liquid may be introduced into the chamber without first striking the crown.

7. In a piston, a body which includes a crown and a skirt, a chamber Withinv the body with an open side which faces the crown and through which cooling liquid may be dashed from the chamber onto the crown by inertia as a result of deceleration of the piston in the. direction toward which the chamber faces or acceleration of the piston in the opposite direction, a passage through which cooling liquid may be introduced into the chamber including a section into which cooling liquid may be squirted and a section through which cooling liquid may pass from the first mentioned section into the chamber, and a hiatus in the passage at the junction of the sections through which cooling liquid which drains from, the chamber into the'second men- -tioned section of the passage may escape therefrom to obviate interference of it with introduction of further cooling liquid into the chamber. 8. In a piston, a body which includes a crown and a skirt, a member with an opening through it disposed within and crosswise of the body and fixed with respect to the body withspaces between it and the crown and the skirt, a, member through which and the first specified member motion is transmitted from one to the other of the body and a connecting rod disposed within the body, a. chamber in the second speced member with an open side which faces the crown and registers with the opening in the first specified member and through which and the opening in the first specified member cooling liquid may be dashed from the chamber onto the crown by inertia as a result of deceleration of the piston in the direction toward which the open side of the chamber faces or acceleration o f the piston in the opposite direction, a passage through which cooling liquid may be introduced into the chamber and drained therefrom without interfering with the introduction of further cooling liquid into the chamber including a section which extends lengthwise through the second specified member from its end which is most distant from the crown to a point nearer the region in which the chamber is located and into which cooling liquid may be squirted and a section which extends laterally through the second speciiied member into the chamber from a point beyond the last mentioned end of the first mentioned section, and means for deilecting cooling liquid squirted out of the last mentioned end of the first mentioned section into the second mentioned section and, thence, into the chamber.

9. In a piston, a body winch includes a crown and a skirt, a member with piston pin bearings in it disposed within the body with an annular the crown'into which open the piston pin bearings between it and the skirt, grooves which ex-l bearings in it disposed within the body with anA annular chamber closed at its end most distant from the crown into which open the piston pin bearings between it and the skirt,- a connecting rod with apiston pin bearing invit, a piston pin journalled in the bearings in the member and the connecting rod, grooves in the surfaces of the bearings which extend from ends to ends of the bearings, and a passage through which lubricant may be introduced into the chamber and, thence, successively, into the grooves in the bearings in the member and the grooves inthe bearing in the connecting rod. l

l1. In a piston, a body which includes a crown and a skirt and is substantially symmetrical with respect to all planes within which its axis lies, an annular member which is substantially symmetrical with respect to all planes within which z its axis lies disposed within the body substantially coaxially therewith and with spaces between it and the crown and skirt and joined to the body substantially symmetrically with respect to all planes within which the axis of the body lies, an end bearing surface which faces away from the crown on the annular member, cylindrical lateral bearing surfaces on the annular member and the skirt farther distant from the crown than the annular member, means for transmitting motion from one to the other of the body and a connecting rod including a member which is disposed within the body and on which there are end and cylindrical lateral bearing surfaces disposed oppositethe corresponding bearing surfaces on the annular member and the skirt so that the body may rotate with respect y to the second specified member under the influence of a force to which it is inherently subjected as a result of operation of the piston, a chamber in the second specified member with an open side which faces the crown and registers with the opening in the annular member and through which and the opening through the annular member lubricant may be dashed onto the crown by inertia as a result of deceleration of the piston in the direction in which the open side of the chamber faces or acceleration of the piston in the opposite direction, a passage through which lubricant may be introduced into the chamber and supplied to the mentioned bearing surfaces and drained from the chamber without interfering with the introduction of further cooly ing liquid into the chamber including a section winch extends lengthwise through the 'second specfied member from its end which is most distant from the crown to a point nearer the region in which the chamber is located and into which cooling liquid may be squirted `and ra section which extends laterally through the second specied member into the chamber from a point beyond the last mentioned end of the first mentioned section, means for deflecting cooling liq uid squirted out of the last mentioned end of the 'v first mentioned section into the second mentioned section and, thence, into the chamber. and means to retain the second specified member within the body disposed at the end of thesecond specified 'member most distant from thev crown but movting motion from one to the other of the body' and a connecting rod including an element on which the connecting rod may oscillate with respect to the body, a, member with respect to which the body is rotatable interposed between the element and the body, and a passage through which lubricantmay be introduced into the body to cool the piston and lubricate the bearings on which the body is rotatable with respect to the member and the connecting rod oscillates with respect to the body.

13. In a machine, a piston which includes a body which includes a crown and a skirt and is substantially symmetrical with respect to all planes within which its axis lies, an annular member which is substantially symmetrical with respect to all planes within which its axisAlies disposed within the body coaxially therewith and with spaces between it and the crown and the skirt and joined to the body substantially symmetrically with respect to all planes within which the axis of the lbody lies, an end bearing surface on the annular member which faces away from the crown, cylindrical lateral bearing surfaces on the annular member and the skirt farther distant from the crown than the annular member, means for transmitting motion from one to the other of the body and a crank including a member with piston pin .bearings in .it disposed within the body with an annular chamber closed at its end most distant from the crown into which open the piston pin bearings between it and the skirt, a chamber in the second specified member with an open side which faces the crown and registers with the opening through the annular member and through which andthe opening through the annular member lubricant may be dashed onto the crown by inertia as a result of deceleration of the piston in the direction in which the open side of the chamber faces or acceleration of the piston in the opposite direction, end and cylindrical lateral bearing surfaces on the second specified member disposed opposite the corresponding .bearing surfaces on the annular member and the skirt so that the body may rotate with respect to the second specified member under the influence of a. force to which it is inherently subjected as a result of operation of the machine, a connecting rod with a piston pin bearing in it, a piston pin journalled in the bearings in the second specified member and the connecting rod, grooves in the surfaces of the bearings, a passage through which lubricant may be introduced into the second mentioned chamber and, thence, supplied to the rst mentioned chamber and the mentioned bearing surfaces and drained from the second mentioned chamber without interfering with the introduction of further lubricant into it including a section which extends lengthwise through the second specified member from its end which is most distantfrom the crown to apoint nearer the region in which the second mentioned chamber is located and into which lubricant may be squirted and a section y which extends laterally through the second specined member into the second mentioned chamber from a, point beyond the last mentioned end of the first mentioned section, means for deflecting lubricant squirted out of the last mentioned end of the rst mentioned section into the second mentioned section and, thence, into the secondmentioned chamber, and means to retain the second specified member within the body disposed at the end of the second specified member most distant from the crown but movable to a position in which the second specified member may be removed from the body. l

14. A piston comprising, in combination.' a body having a head -portion and a circular skirt, means including a plurality of symmetrically sped struts adjoining the head portion and providing a rbearing concentric with the skirt, said skirt having an inner lbearing surface concentric with the outer surface of the skirt, a carrier disposed within the body and rotatably supported therein by4 said bearing and `bearing surface, said carrier being spaced from the skirt intermediate the bearing surfaces and having therein a piston pin bearing, Iand means holding the carrier in place with respect to the body.

15. ,A piston comprising, in combination, a body having a head portion and a circular skirt, means including a plurality of struts adjoining the head portion and spaced radially inwardly and symmetrically with respect to the skirt providing an inner support element, said skirt having relatively thin walls which are substantially symmetrical with respect to planes passing through the axis thereof, 'a bearing surface on the inside of the skirt near the end thereof opposite said inner support element, and a carrier located by and supported between said support element and bearing surface and being spaced from the skirt exceptat said Ibearing surface, said carrier having a piston pin fbearing therein.

16. In a piston adapted for reciprocating movement in a machine, the combination comprising a body having a head portion and a skirt -which are both substantially symmetrical with respect to planes through the longitudinal axis of the skirt, and means within the body rotatably supporting the body and upon which said body rotates during reciprocation, said means providing a trap for cooling liquid adjacent and facing the inner surface of the head portion from which cooling liquid is dashed onto the head portion during deceleration of the piston in one direction of motion or acceleration of motion in the opposite direction.

17. In a piston adapted for reciprocating movement in a machine, the combination comprising, a body having crown and skirt portions, sym- ,metrically disposed cooling ribs on the inner surpin bearing therein, said 4body and carrier having l cooperating circular .bearing surfacesthrough which the body is carried by the carrier and upon which the body is rotatable with relative freedom with respect to the carrier about the axis of the skirt, and means holding the carrier in place with respect to the body.

1 9. In a machine and in combination with a connecting rod and a cooperating piston pin, a piston comprising, in combination. a circular piston may which is simstantmuy symmetrical with respect to the central axis thereof, means within the body providing a pistonv pin bearing, and means connecting'said means and body in a manner such that the b`ody rotates about its central axis under the influence of force to which it is subjected as a result of operation of ,the machine.

20. In a machine and in combination with" a connecting rod and a cooperating piston pin, a piston comprising, in combination, a body having skirt and crown portions, said skirt portion having an open end opposite the crown portion, a carrier within the body having a piston pin bearing therein, means near and slpported from the crown portion of the body providing a bearing concentric with the skirt Vportion and having plane and cylindrical surfaces, said skirt portion having an inner bearing surface near the open end thereof, said carrier having bearing surfaces f with respect to the first mentioned struts forl -additionally supporting said support element, said skirt having relatively thin walls which are substantially symmetrical with respect to planes passing through the axis thereof, abearing surface on the inside of the skirt near the end thereof opposite said inner support element, and a carrier located by and supported between said support element and bearing surface and being spaced from the skirt, except at said bearing surface, said carrier having a, piston pin bearing therein.

22. In a piston,a :body which includes a crown and a skirt, a member disposed Within the body with a chamber in it with an open side which faces the crown and through which cooling liquid may be dashed from the chamber ontothe crown by inertia as a result of deceleration of the piston in the direction toward which the chamber faces or acceleration of the piston in the opposite direction, a passage through which cooling liquid may be introduced into the chamber, and an annular ,space between the member and the body into which cooling liquid passes from the crown.

23. In a piston, a body which includes a crown` opening in the annular member and through which and the opening through the annular member cooling liquid may be dashed onto the crown by inertia -as a result of deceleration of the piston in the direction in which the open side of the chamber faces or acceleration of the piston in the opposite direction, Iand a passage through which cooling liquid may be introduced into the chamb'er. Y

EUGENE W. `KE'FIERING'.

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