US2638392A - Piston - Google Patents

Description

May 12, 1953 J. P. Bu'rTl-:RFIELD 2,638,392

PIs'roN FiledDec. 15, 1950 2 Sheets-Sheet 2 if i Hai/WQ HM,

#rra/valira' Patented May 12,

PIs'roN John P. Butterfield, Grosse Pointe Woods, Mich., assignor to' Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Applieetm December 15, 1950, serial No. 201,032

15 claims. (o1. 309-10) This invention relates to internal combustion engines of the double acting type and is primarily concerned with the pistons used in such engines and the piston mounted slideway means employed` to connectv the pistons ofrsuch engines to the associated engine crankshaft. This invention represents an improvement on the piston construction disclosed in my co-pending application, Serial No. 133,926 led December 19, 1949.

In the double acting type of engine a doubleended piston is vusually employed for reciprocatory movement in each engine cylinder bore, such engines being arranged to provide a cornbustion chamber at each end of each cylinder bore for cooperation with each end of the double-ended piston mounted therein. Engines of this general type are known in the art vand einploy a crankshaft whichusually extends through and is generally connected to the double-ended piston by Ameans other than a connecting rod such as is employed in the more conventional type of internal combustion engine. For a more detailed description of this particular type of engine, see the copending applications of A. G. Herreshoff, Serial No. 16,801, filed Marchl `24, 1948, now PatentNo. 2,613,651, issued October 14, 1952 and Serial No. 84,081 filed March 29, 1949, now Patent No. 2,581,326 issued January 1, 1952, the applications of John P. Butterfield,

all led March 24, 1948, Serial No. 16,645, now

Patent No. 2,610,615 issued September 16, 1952, Serial No. 16,646, now PatentNo. 2,595,761, issued May 6, 1952; Serial No. 16,647, now Patent No. 2,571,198 issued October 16, 1951; Serial No. 16,648, now Patent No. 2,603,538 issued July 15, 1952; Serial No. 16,649 now Patent No. 2,614,009 issued October 14, 1952, and Serial No. 16,650 and Serial No. 133,926, filed December 19, 1949, and the application of A. J. Slemmons, Serial No.

80,729, filed March 10, 1949, now Patent No. 2,588,666 issued March 4, 1952. l

The double acting type of engine offers many advantages over the more conventional types of engines but certain difficulties in thev manufacture, assembly and operation of such, an engine have heretofore been deemed to be of such a bothersome or supposedly insurmountable character as to discourage the use of this type of engine.

One of the difficulties experienced with the double-acting type of engine has been in providing a practicable operating, connection between the pistons and engine crankshaft which connections .must providel a meansfor` controlling the clearances between the connected pistons and crankshaft and also provide a means for distributing the bearing loads more or less uniformly lover the surfaces of the piston slideways that lare slidably engaged by the crankshaft bearing ock.

It is a primary object of this invention to provide an internal slideway type of piston having a structural arrangement that permits accurate control of the temperature variable Working clearances between the elements slidably engaged with the piston.

It is a further object of this invention to provide a piston construction wherein the piston skirt and the portions of the piston head connected thereto are connected bya strut member that effectively controls the thermal expansion of the piston during engine operation and also provides a means for controlling the bearing block slideway stress distribution. It is another object of this invention to provide a composite double-ended, internal slideway type of piston formed in such a manner and formed from such materials that the thermal expansion and contraction as Well as the working clearances betweenv the associated elements may be accurately controlled.

It is another object of this invention to provide a piston construction with 'an interiorly disposed slideway adapted to be slidably engaged by a crankshaft bearing block wherein the slidep way and support therefor are formed in a manner adapted to distribute .the bearing block loads more or less uniformly over the bearing block engaged surfaces of the slideway to thereby reduce the unit pressures on these engaged parts during engine operation.

Further objects yand advantages of my invention reside in the novel combination and arrangement of vpartshereinafter described and disclosed in the .accompanying drawings in which: f

Fig. 1 isla transverse vsectional elevational view through a double acting engine cylinder block structure showing Vacrankshaft connected by a bearing block to a slideway of a piston embodying my invention;

Fig. 2 is a sectional plan elevation of the structure shown in Fig. 1, the view being taken as indicated by the reference line 2-2 of Fig. 1;

Fig. 3 is an enlarged side elevational view of the piston structure shown in Figs. 1 and 2;

Fig. 4-is a fragmentary sectional elevational view of one head portion of the piston shown in Fig. 3, the View being taken along the line 4-4 -efri'a s;

Fig. 5 is a sectional elevational view of one head portion of the piston shown in Figs. l-4, the View being taken along the reference line 5--5 of Fig. 3; and

Figs. 6, 7 and 8 are side, plan and end elevational views respectively of the strut member that is imbedded in the .piston headsof. a piston' embodying this invention.

In general, the engine utilizing pistons of the type embodying this invention comprises a cylin der block structure A formed of component o'r complementary half portions I and II having, planar face contact in a plane I2-.-I2iwhich is vertical for the illustrated positioning of the engine in Fig. l. Each portion ci'` the cylinder block structure A is formed with a half-part of a cylinder I3 of substantially uniformediameter extending between the opposite side faces I4 oi the block structure A. Each exposed end of the cylinder I3 is closed by a cylinder head i5 providing a combustion chamber It'. Suitable intake and exhaust valves (not shown) control inlet of the fuel mixture tothe combustionchambers I6 and discharge ofthe exi-faustA` gas from said combustion chambers. Combustion chamber fuel ignition means such as the spark plu-gs I1 are provided althoughothertypes ofA fuel ignition may be used.A

The cylinder block portions IIJk and II 'are broughit together andthe :cylinder heads i" maintained in their illustrated assembled-posh tions by a plurality of through bolt assemblies i9 which extendthrough the block portions and cylinder heads. For an engine loi the circulating liquid cooled type, asr illustrated, the cylinder heads I5 and blockportionsfl, I Igareprovi-ded with cored intercommunicating coolant passages 34.

Reciprocating within the typical illustrated cylinder I3 is a piston structurehavingf'a head portion 35 at each en'd'the'reof arranged Vto cooperate with the combustion chambers t6 fof the cylinder heads I5. The, piston structure'B carries a set of rings 36 adjacent leach of-'its head portions 35 and the oppositely disposed'pis'tonhead portions 35 are connected` together Yby 'an intermediate slotted, tube-like, `skirt structure 31 herein illustratedjas comprisingVV cylindrical end portions connected, by a plurality 'of circumfe'r` entially spaced piers or tie-portionsV 318. The y piston skirt portion 31 isconnectedjto't'he associated -head portions 435 at apair of fdametrically disposed locations by screw or boltconne'ctions 1I that are more fully Vdescribed below.

The skirt portion 31 Yof piston structure Bi's provided with two pairs ,oi 'diametrically disposed, axially extending openings or slots 45jand '46, respectively, which slots are bouruied.ciir'iiiin-er--y entially of the piston by the piers 38.` 'The slots 45 are adapted to receive the crankshaft "22 -a'nd to accommodate reciprocation 'of the piston structure B relative to the crankshaft 22. Crankshaft 22 is rotatable 'about its airis 40 on. its journal portions 41"that Yare mounted inbe'ar... ings 48 carried by Semi-cylindrical b'earin-g.openings 49 formed in 'the 'opposed inner ac'es vofthe cylinder block .portions IIJ andfl'l. The slots 45, which 'are crcumferentially 'rotated ninety degrees from the slots 45,(see Figs. l andv '3). are adapted to receive the endpo-rtions of the internal, transversely extending-,'-lfopposed,` piston slideways 5I that depend from each piston head inner surface.

Associated with each; cylinder;l andyitsfcone tained piston structure is a cylindrical 'crankpin portion 23 of the crankshaft 22. Each crankpin portion 23 is connected to an adjacent pair of crankshaft journal portions 41 by the obliquely extending crankshaft web portions 24. The crankpin 23 and the oblique connecting web portions 24 are continuously disposed within the hollow chamber formed interiorly of `piston skirt structure y31 intermediate the heads 35 of the double-ended piston B.

The force transmitting connection between each piston structure B and the crankshaft 2?. Acomprises the internal, opposed, slideways or bearing block guides 5I that are carried by the free 'ends of the ilanges 54 and 5E that depend from the inner side or face of each piston head portion 35. slideways 5I slidably receive therebetween a bearing block D operatively carried by and rotatably mounted on the crankshaft crankpin 23.' The connected parts 5I, D and 23 are so constructed and arranged as to provide a sliding,- rockable bearing connection between the piston structure B and the 'crankshaft crankpin 23.

The spaced apart, opposed, piston lhead carried, bearing block 'slideway portions 5i are pref*- erably cast as portions of the piston heads 35 as will be more fully explained in the Vsubsequent description. Slideways iii are'con'nected tol the4 heads 35 bythe depending piston head flanges or webs til and 55. The webs tft are aligned with and sweep into the associated guideway portions ti in a manner that'supports the slideways 5i as more or'less rigid parts of the piston headstructures 35. The webs 55 are disposed at right angles to lthe webs 54 and provide additional support'ior the slidewaysi; By the arrangement shown the slideway portions 5I are thus spaced from eachother in a direction yaxially-of the piston structure and present opposed, arcuately-shaped bearing surfaces 53 facing each other. Each slideWa-y bea-ring surface Eidis a portion of a cylindrical `suriace which is adapted to slidably and rockably engage a mating cylindrically formed bearing surface on the icrankshaft bearing biockD. Bearing block D may be oany Iof the forms specically described in the aforementioned A. J. Slemmonsapplication Serial No. 80,729, now Patent No. 2,588,666 issued March 4, 1952. As Will beseen from Figs. 1 and V3 the slideways 5I extend transversely through thepiston, the opposite ends of the slideways 5I beingopen and disconnected from the piston skirt portion 31, that is directly supported by a head Web'54.v Each piston head web portion 513 extends the-full length of the associated slideway 5Iy and is flared out (seeliigs. 2' and 4) at its inner end lto cover the full width of the slideway 5I.Y As itis practically essential to arrange the slideway supporting web portion of a double ended piston se that it extends along and is aligned-with the ycentral portion 'iaisee Fig. 4) of the slideway 5l, ithasbeen found that in conventional constructions of this type, using solid, centrally arranged, slideway supporting, web portions 54, the solid webs provide the slidewaysl with 'a relativelyKV high `'stress concentrationV and a maximum :rigidity along the central portion 59a.l (-seeFig. 4) of the bearing surface 5B while` vthe vedgevor side portions v58h of the slideway bearing surfaces 58, which are somewhat flexiblerela-tive tothe portions 58a, are very lightly stressed du-ringengine operation. Whena solid web member is, used toA support theslideway 5I-itghasbeen, found 'that the in'- creased.: rigidity.` and relatively high, noir-unistorm, strimssgeeneenttaton .fanless me viwifthsof v.theloeating.1..surface :5B durinegengine Iover. ion Vvhas .a;.;.tsndenoy..tounnecessarily increase; ear along the .central .portions 5.8 '.ofthe-slideways and to even cause the sldably -engageghearng .5

atleet., @andthe slideways '5.1 .-...toselzeagnl cause rgglje desti f high, t `tion .-inereased.; .1.1.0.1. ons eof .the slideways .tenanee ...the 4.loefse.ssart'. le

. .-loloek,..el.ement .D .and the `walls .of .t spande, hosted?. n onal ...el on ,constrnetionso the .typefneliemfsenexely.

e wisten heads..

toallno.. @.Svndfto )lleattached sults infbotne .ial

.dialnet eaflltnerneiesnnsionof the ni. on

. 3.5. ness-itt 3l. .axialfthermelexpa vv.of eadsat .senses the. opp

ine .pressures on .the .beer-ins. .snrfaeesfoffthe .expansion `of .ne piston heads 35 C @ses :to enlarge .and r uoe the Aolea ness vJezetween 1.1.S9f .the rcylmtelrs .l.3 Amaltnermal .expansion ztheeeds en .lt and .thereby .op

antisense ts'setnsr .sns this ne.

beating bleek D. .Blame .leal L .the needs 1.35

the sides ofV .the :piston .5B and the.

.of theslnrt .3.1 will tend. y,tn-111 er-.ences between :the slieeway surface v .ing Plesk. .D- .'.Likewises 'pension of the skirt'l l .closetv to the. wal-.leef the. .ttloeshtfto be .obviens I.. .fplenstionthet .itis .neces aisle *.elearanee. between Ithe eating. Plesk hde- .nays Atl and the .hearing .bleek D and .also .bek.tft/een the sides of thepstonz. .andthe eylniel -l .to compensate for the yal-leus '.thexmal .ions .that .soeur .in .the pistons-B nnne 60.

.oneration- Also, .in the usuel femme-sneed Vpist snoonsaeawn theses@ .s1 is sssnsetsdts the.. sten :n eds '35 varene the eoxnplete @erinnern of .the .mston- This provides. a y-ready -nathtot heat .flow from .the .heads 35 tothefskrt .fandftends -to increase both diametrcal ...as *..well .as N.axial ...thermal expansion of the skirtv portion :31. .Asthe `.piston heads :.35 valte usually `of Valuminumor similar material vof v.high ithermaL-conductvty,Y. While the skirt -31 Yis usually ofsteel ora-sim lar low-.thermal conductvltymaterial, t-.canbe seen that --skrt 31 may lelongate A and.A .ex-pand at one `rate while the` heads 351 will expand Land elongate ata differenterate. yThis u'stflf-utthen areonneoteittheshirt; no. 1930, along two .xelatively posed, nenpneral finortlons .clearance .or 1'.nS.n.1. tane thetpston .Band 'ts slda yeneaeedi.

vThe sneeiflctype.otonneetionbetween he. pisbed-inteonnectinnfwlth,th construction embodying .-.thi.s .,ineention..

-.sl.on Lo1? .t tion 31..

13,5 .so that ,it oxmsethe hack v:leone of .and A.ex- -;.tends :centrally alone thefslideway .supporting webjl- .fti'nti comprises ...e plate-like body ifrll'fa portion of .the bore lnthetubular. Joer 1.6.3. flfowever, .sturing the .nal machining oft-the 4piston -B the lhere. ,3.1 is .drilledto nemove anyheadmateral .thattmight be lodged .therethe -fsldeway rbearing surfaces M58. f of lthis relatively limited V`contact 4area between ...ztlseseontrel th ...and

soreness esenz nts ome .stuemof :F.es.; een.. 5 ds 5 sten ion 3:1 y.;.th.e..strut ,.hort, sdametrleally ...dis-

.. and -rthattnere isa that the piston;

headsf .andthe skirt of. the `piston neriphersf. .:Snoh arrangement rnaterial.l.yeednoesithe heatalowatoand 1 -.r re aoenratessontxo of henlearanoesfnetween ents.

tonsfheads-and :the skirt A.nca/.e1 pistonhead Figs.. .6, ,-7 .and ...8 ...dsolose A.a `.strut fmember .$0

.1 that -ris integrally l.cast in. each .piston .head .:3-5.

The strut ...member .56.0 serves .a vdual.) functonpf 4met provdinefa more orrless Aunitolnn,stir-.ess .concentration across .thebearing surfaces f5.6 :of

the slideways 5| and secondly provdne ameans yfor aceultately .eontrollng .the y:thenrnal .expanhe ypiston heads 3.5; .and -pistonskir-.t 'norof @in *.extendng, enlaleei ...anchor headmnortion .-1.62

.formed .along Athe 'fupnersportlon theneof and an Y enlarged, tubular, 1. longitudinally extending, `tormation 613 `formeel along theylowerfpottion thereof. Theupperanohor portonrz? Yisfiormetl vr.with .a .plurality of .slots .64 v.that fproyde a ...degree y.of

lexl-a1itt'in .the...anchor head. .62 .so .thatthermal .expansion ,of 'the .piston VV.will-.not leause. .cracking '.ofA the piston head :35. vThe slots-Bielsa fill-,with

head. material v.during the .head `.casting process .so as .to` securely .anchor .the stnutfgi .in the-head material e The body portion 6l .anglthetllbular v,lower .portion .6;3, are .v each -vnlwrled...with a series `of holes $5 .and Strespectvely, whehholes .'.ll

. .with the .head mate1fial..during .the piston-.heed nesting .oneness .to :provide .another means .for Vsecurely .head 135. YHead materalfthat lowsthroughfthe anchoring the strut .member ...6.0 .in :the

holes ...6.6 ,in the .lower tubular member 3 ...may

in. .non .each emi-.of `the .stent body portion t6 I, there is .formed-.a transyexsely extending, Ywinelke, flange .6.8, Flangesz provide an. i-mproved .means for connecting the 4'piston l.hl-satis::t5 to Athe l:the.flanees 5.8 .ofastrut .-5,0 are .theonly'portions .of the piston yheafl.e5...thatare.in aotualznontaet with thepston .skirt fell. ftneneiore the .flow .of

'heat Vfrom .thefheaes :3.5 to the .sk-.ift :31 .isma- Iterially A.reduced from .f that. occurring .with L .601.1-

of a. 4Widthtl'latis .no greater than thewldth of As ya result is` only. l@..minor .heat snow from thepistonzlheads 35 to the piston skirt 31. Furthermore as the strut 6I is preferably formed from the same low thermal conductivity material as the piston skirt 31, such 'as steel or the like, the heat flow to the piston skirt from the piston head in this i are used the strut flanges 68 and the adjacent t portions of the piston head 35 are bored and threaded to receive the threaded shanks of the screws 1|. The piston skirt 31 is also bored to provide a shoulder formation 12 against which i the heads of the screws 1l may bear. The screws 12 originally have a head formation 13 (see Fig.

5) with an intermediate necked portion 14. As the screws 12 are threaded into the tapped bores in the strut iianges 68 and into the heads 35,

'sufficient torque is applied to the heads 13 to twist oif the heads 13 outwardly of the necked portions 14 and the remaining portions of the screw heads 13 that thereafter project outwardly beyond the skirt 31 are then cut off during nal machining of the piston B.

y From the above description of the strut member 60 and its arrangement in the piston structure B, it is thought to be obvious that the tubular bore 61 of the strut lower portion 63 provides the necessary flexibility in the slideway supporting web 54 to more or less uniformlydistribute the bearing block stresses across the full width of the slideway surfaces 58 as more fully explained in my co-pending application `Serial No. 133,926, led December. 19, 1949. Furthermore, strut member 6D provides a means for controlling the heat flow from the piston heads 35 to both the piston skirt 31 and the piston slideways 5i. Not only is the heat flow from the heads 35 controlled but the resulting thermal expansion of the piston B is controlled and in this manner the required clearances between the several elements slidably engaged with the piston may be reduced without danger of parts seizure. Accordingly, quieter and more eiiicient engineoperation results from the use of pistons embodying this invention. By using the steel strut members B to connect the aluminum piston heads 35 Lto the steel piston skirt 31, it will be notedthat a complete ring of similar material, steel in this case, is utilized toconnect and more or less insulate the heated piston heads 35 from the' slidable, steel, crankshaft bearing block D. This arrangement thus provides a connection between the crankshaft throw 23 and the piston B that is substantially of the same material and thus the thermal expansions and contractions of these connected elements are of the same degree and working clearances between these engaged elements may be most accurately controlled. It is thought that the arrangement disclosed is such that heat that is applied to the piston heads 35 will cause thermal expansion of the aluminum heads 35 in an axial direction that will be outwardly from rather than inwardly towards the slideways I and thus the operating clearances between the slideways 5| of the piston B and the bearing v block D will be practically unaffected during engine operation. The only contact between the aluminum piston heads 35 and the steel bearing block D is at the portions 35a of the piston heads located between the slideway surfaces 58 and 8 the steel strut 60 acts as a heat dam -between the heads 35 and the portions 35a the heat transferred to the portions 35a is negligible and thus the working clearances are unaffected.

I claim:

1. A piston comprising a head portion and an encircling,r depending, skirt portion, a web depending from the inner surface of said head portion, a bearing block slideway supported from the free end of said web and arranged to extend vtransversely of said skirt portion but disconnected therefrom, said web having a bore extending therethrough in a direction longitudinally of and 'adjacent the slideway, said web hav- 15 thereof connected to said skirt portion and proing relatively limited portions adjacent each end viding'the only contact between said head and said skirt portion. i

2. A piston comprising a head portion and an encircling, depending, skirt portion, a web depending from the inner surface of said head portion, a bearing block slideway supported from the free end of said web and arranged to extend transversely of said skirt portion but disconnected therefrom, said web having a bore extending therethrough in a direction longitudinally of and adjacent the slideway, said web having portions adjacent each end thereof connected to said skirt portion and providing the only contact between said head and said skirt portions, said web end portions extending along the periphery of the skirt portion for distances no greater than the width of said slideway.

3. A piston comprising a head portion and an encircling, depending, skirt portion, a web depending from the inner surface of said head portion, a bearing block slideway supported from the free end of said web and arranged to extend transversely of said skirt portion but disconnected therefrom, said web having a bore extending therethrough in a direction longitudinally of and adjacent the slideway, said web having portions adjacent each end thereof connected to said skirt portion and providing the only contact between said head and said skirt portions, said web l end portions extending along the periphery of the skirt portion for distances no greater than the width of said slideway, and said bore in said web being located in alignment with the central portion of said slideway and in alignment with the path of force transmission between said head portion and said slideway.

4. A piston comprising a head portion and an encircling, depending, skirt portion, a web depending from the inner face of said head portion so as to extend longitudinally of the piston, a

y bearing block slideway supported from the free end of said web and arranged to extend transversely of said skirt portion but disconnected therefrom, said web having enlarged portions adjacent each side thereof extending concentrically within and connected to said skirt portion and A vproviding the only contact between said head and the inner ends 63 of the struts 60. However, as u. porting, a bearing blockslideway that includes a 9, bearing surface arranged't'o extend transversely of and to be disconnected from the piston skirt portion, the opposed bearing block slideways being arranged in alignment with but spaced from each other, each web element including an vopening that extends longitudinally of the associated slideway in a region ladjacent thereto to provide means to increase the ilexibility of the longitudinally extending central portion ofthe associated slideway, each end of eachweb portion having circumferentially extending portions connected to the adjacent piston skirt portion and providing the only connection between the piston head portions and the piston skirt portion. ,u

6. A double ended piston comprising a pair of spaced, opposed., shaped, head portions, an intermediately disposed head encircling, hollow, substantially cylindrically shaped, skirt portion, arelatively narrow web portion depending from the inner surface of each head portion extending longitudinally of the piston, a relatively wide bearing block slideway supported by the inwardly disposed free end of each web portion, each slideway including a bearing surface that extends transversely of the piston skirt portion, the connection of each web portion to the associated slideway being in alignment with the longitudinally extending central portion of each slideway, an opening extending through each web portion in a direction lengthwise of the slideway in alignment with the connection of the web portion to the slideway, and portions on the opposite ends of each web portion connected to relatively small, diametrically opposed, portions of the piston skirt portion to provide the only connection between the piston skirt portion and the piston head portions.

7. A double ended piston comprising a pair of spaced, opposed, substantially cylindrically shaped, head portions, an intermediately disposed, head encircling, hollow, substantially cylindrically shaped, skirt portion, a relatively narrow web portion depending from the inner surface of each head portion extending longitudinally of the piston, a relatively wide bearing block slideway supported by the inwardly disposed free end of each web portion, each slideway including a bearing surface that extends transversely of the piston skirt portion, the connection of each web portion to the associated slideway being in alignment with the longitudinally extending central portion of each slideway, and portions on the opposite ends of each web portion connected to relatively small, diametrically opposed, portions of the piston skirt portion to provide the only connection between the piston skirt portion and the piston head portions.

8. A double ended piston comprising spaced apart, opposed, substantially cylindrically shaped, head portions connected by an intermediately disposed, hollow, head encircling, substantially cylindrically shaped, skirt portion, a relatively narrow web portion extending longitudinally of the piston from the inner face of each head portion, each web portion having at its inwardly disposed free end a bearing block slideway that extends transversely of the piston skirt portion, each slideway being aligned with and spaced from the slideway carried by the web of the other head portion, each web portion having an integral, interiorly disposed strut member that extends longitudinally thereof substantially between the outer face of the piston head and the slideway carried thereby, said strut extending transversely of the head web the full distance besubstantially cylindrically tween diametrically opposed portions of the piston skirt and having portions at each end thereof connected to said diametrically opposed portions of the piston skirt, said last mentioned portions of the strut providing the only connection of the piston head to the piston skirt portion.` y

9. A double ended piston comprising spaced apart, opposed, substantially cylindrically shaped, head portions connected by an intermediately disposed', hollow, head encircling, substantially cylindrically shaped, skirt portion, a relatively narrow web portion extending longitudinally of the piston from the -inner face of each head portion,- each web portion having at its inwardly disposed free end a bearing block slideway that extends transversely of the piston skirt portion, each slidewayfbeing aligned with and spaced'from the slideway carried by the web of the other -head portion, each web-vportionhaving an integral, interiorly disposed strut member that extends longitudinally thereof substantially between the outer face of the piston head and the slideway carried thereby, said strut extending transversely of the head web the full distance between d'ametrically opposed portions of the piston skirt and having portions at each end thereof connected to said diametrically. opposed portions of the piston skirt, said last mentioned portions of the strut providing the only connection of the piston head to the piston skirt portion, said strut member having an enlarged portion at the inwardly disposed end thereof with an opening therethrough extending transversely of the head web adjacent the connection of the web to the slideway, said opening being aligned with the longitudinally extending central portion of the slideway.

10.' A piston as set forth in claim 9 wherein the outwardly disposed end of the strut member adjacent the outer face of the associated piston head has an enlarged anchor portion formed thereon.

1l. A piston as set forth in claim 10 wherein the enlarged anchor portion of the strut includes slotted formations extending transversely thereof.

12. A piston as set forth in claim 9 wherein the portions on the strut ends that are connected to the piston skirt comprise wing-like flanges that extend only a limited peripheral distance around the piston skirt.

13. A piston as set forth in claim 9 wherein the strut includes transversely extending apertures that are adapted to receive portions of the piston head material to provide a means for anchoring the strut in the piston head.

14. A piston as set forth in claim 9 wherein there is a second web member extending, longitudinally of the piston from the inner face of each piston head, said second web being arranged at an angle to the first mentioned web and being connected to the associated slideway.

15. A double ended piston comprising spaced apart, opposed, substantially cylindrically shaped, head portions of aluminum or similar high thermal conductivity material connected by an intermediately disposed; hollow, head encircling, substantially cylindrically shaped, skirt portion of steel or similar low thermal conductivity material, a relatively narrow integral web portion extending longitudinally of the piston from the inner face of each head portion, each web portion having at its inwardly disposed free Vend a bearing block slideway that extends transversely of the piston skirt portion, each slideway being aligned with` and; spacedfrom:l the` slidewaya carriedA by theweb of. the other head portiony each web portion having, an;l integra-li; inteirioily dispo-sed strut: member of steel', or, some; similar. 10Wv the-unal, conductivity material; that. extendslongitudinally thereof substantially between` the outer face of. the piston.- hefad a-nclthe-.slideway oamriedthereby, said-g strut? extending, transversely of the head- Web the full distance betweem-` dia'- inrieti'ica-Illy` opposed poittons: ofY the pistonskirt and having enlargecii` portions. atv each end thereof conneotedy to. said diametrieally olzngosed4 portionsof the, piston skirt, said last, mentioned portions of the strut providing-` the-.onlyconnection. ofthe piston head to the piston skintportion, saidstrut 15 2,123489 member having an. enlarged. portionl at the in- Wardly disposed end thereof with an; opening therethroughextending,- transversely of lthe head web adjacent-the connection. ofv `tne-Weh-to the n assooiated-headrportion.

JOHN P. BUTTERFIELD.

Refenences Gitedin the flieof this patent UNITED STATES PATENTS Number Name Date 1,229,540, Spill-man June 12, 19.17 1,494,483 Howe May 2Q, 1924 Schneider: July 12., 19.38

FOREIGN PATENTS' Number Country Date 200,718 GreatBrtain July 19, 1923-

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