US2553296A

US2553296A - Piston

Info

Publication number: US2553296A
Application number: US48003A
Authority: US
Inventors: James W Brown
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-09-07
Filing date: 1948-09-07
Publication date: 1951-05-15
Anticipated expiration: 1968-05-15

Description

J. W. BROWN May 15, 1951 PISTON Filed Sept. 7, 1948 Fla? Patented May 15, 1951 YUNVFED S TATIES Il'ieA'lErPJ T O FFIC E PISTON James W.'-.Br0wn, Oakland, Calif.

'Application September 7, 1948, Serial No.48;003

7 Claims. .1

Thisinven'tion relates itofa f piston '.'cons'tructi'on of the type `,used fin reciprocating .engines '.of the internal 'combustion class. It is #conventional practice 'to allow for lpiston expansion fin such rengines'fby g'rinding 'the pistons ito :substantially :smaller size than theibor'efof-thefcylinders willich tney fare 'to dit, and then 5to 'employ 1 compression frings to maintain .a substantially lgas:tight seal between feachpiston and' itsflcylinder.

Tin v"the ease 4v'of what lare called fcameground Ypiston-s, the piston iis fovaI Tin shape having its major dimensions alcngfalinelatfarightiangleito A"tlfiefcent'er of ktl'ieaiiis fo'f the wrlist pin .".so `that 'Pits 't Within 'the cylinder iis l'closest foppo'site fthe rends ff `said "lineand ithe tendencyfof the lfpistcn to meek on theaiisfo'f .the'iwrisltpin `and 'cock ithe :sharp *edges df fthe compression rings into fenlgagement with 'the cylinder walls `lis minimized. `However, it isnecess'ary even infsuchconstructions itoy allow fa minimum oi 20005 linch fclearance "betweenthe :cylinder and the piston'atftheplaces 'just described and lt'o allow forexpans'ion 'ofthe piston with respect lto :lits cylinder by :allowing greater Eclearance between :these iplace's, :so 'ithat :as the ipiston fexpands 'itmay `be deformed from its foriginal :oval .fsnape Ito ra tmoreinearly .freund Esh'ape.

In the :case of vround-grcun pistons which are `truly `round. Ain shape, much larger -minimum clearances between the pistons and cylinders must .-b'e fallowed fatwall :points in :order fto :permit expansion of reach ipistonwrelatve ito its-cylinder, and thetendency of therpistontto -rockion the :axis -of the fwristpin Iandncock -the fsharpt-edges .of rthe Ycompression vrings finto v.engagement with .the icylinder 'Walls is `'even #greater than iin the case of icamgroundpistons.

In .either case, `theamount of .such Acocking is suicient to produce ,greater v.wear of the .cylinader rwalls in the areas generally opposite 4the yends of a -line drawn `at `a right/.angle gto .the .center .of .theax'is Aof .the wristip-ingso that each cylinder Wears -unequall-y and =compression is gradually decreased,

It is 'thepr'incipal .objecto'f the present'inven- 'Jtion to makeposs'ible a substantiallyv closer "fitting Yf the piston structures Within the cylinders of internal ccmbustion engines, withoutrisk of'seiz- "ure occurring 'by 'reason o'f 'expansion 'of the ,piston's relative"totheircylinders 'By thusfdecreasing the clearance between piston 'and cylinder, "the Acooking tendency referred *to labove `is V'decreased to thepeintof substantial elimination, and 'the v'resulting wear "of "the Jcylinder walls fin `the 'areas mentioned '-is not substantially greater l2 than in` any other 'area adjacent the piston, -even Where oil rings, or even lightcom-pression rings are Iused althoughfcompression rings of .the Ausual type are unnecessary `with theipiston` of the present invention.

A further and important .objectof `.the-invention kis to make possible fa .closer nfit `of cylinder and piston in the area of the piston lying. generally above Ythe axis of ytl'ie-wrist..pin,ithereby still further decreasing .the .co.cking tendenc7 Y.previously mentioned.

.LA .still kfurther and Very .important .object `of the invention .is to ,provide a piston construction which will have substantially as close 'a 't Within the -cylinder lwhen cold as it lhas at operating temperatures, therebygleatly reducing the cylinder .xvearincidentfto cold starting; which Wear is very great in .conventional lconstructions 'in which `clearances `of the order previously men- Aaccessory oil ring is employed.

In the pref-erred'embodiments offthevinvention the 'piston structure .consists-essentially of three lprincipal parts.

The fouter body, or sleeve lil, preferably of Vcast iron,.is formed with acircurn- .ferential internal vgroove -|YI. .Inside vthe -upper portionof sleeve l) there -is .a ^thineilexible steel ring .or band I2 brazed or other-wise ,secured arc-und its upper edge to theinnermargin ofthe sleeve ld, Vas. at i3, witnits .lower edgeat about .the center of groove Internally of these there'is the innerpiston ,bodyiandhead M which Ain .the embodiment illustrated 4is 'equal in vertical dimension tothe outer Sleeve'ili. The inner bcdy /Z is an .aluminum alloy pressure die casting which is preferably 'cast into the sleeve iii 'and ring l2 to complete the piston. Tlie'aluminurn alloy is preferably `cast intothe sleeve and rins in"moltenstate and inthe process of casting some of the metal is for'cedinto'groove H andinto'intimate contact with both side'softheY lower 'edge or the flexible -steelfring -I72,asat l5; and as it cools and shrinks it will vform 'an aire'tight 'seal with the ring. However, the inner body may be machined to the same dimensions it would have if so cast, and an air-tight seal with the ring I2 effected by any desired means. The annular lug I6 produced by now of the metal into groove II effectively locks the cast iron sleeve I against vertical movement with respect to the aluminum piston body I 4. In the construction of Figures l and 2, as well as in the modifications of Figures 3 and 4, to be referred to, the aluminum'alloy cast in molten state will contact the inner surfaces of sleeve I0 and ring I2, as illustrated by Figure 1. As the casting cools and contracts, it will shrink away from sleeve I0 as illustrated by Figure 2 and the elements of the assembly will assume substantially the relation there shown, the lower end of the flexible steel ring I2 being drawn away from sleeve Ill with lug I while preserving an air-tight seal at the joint.

same manner as in the first construction described.

The modification of Figure 4 differs from that of Figures l and 2 only in the provision of a ring groove Il in the outer sleeve l0 d-esigned to receive an oil ring I8. In this construction the cast iron sleeve I0 is thickened at the groove location to provide the required ring seat, as shown,

forming an annular protuberance I9 on the inner surface of the sleeve. This serves as an addition al lock between the aluminum inner piston It and the sleeve I B. After the aluminum piston is cast, as before described, circumferential oil drain apertures 20 preferably are provided as by drilling through the bottom of groove Il and the skirt of piston I4 as shown.

As well known to the art, the head of a piston is subjected to the highest heat and will expand against the cylinder wall under conditions producing high heat and contract away under conditions of low heat and is, therefore, the most troublesome part of a piston. With the piston of the present invention, the head is poured into the cast iron sleeve in a molten state. As it cools it shrinks away from the sleeve which is in contact with the cylinder wall. Under operating conditions the aluminum piston and head will never become as hot as when it was formed and so can never expand to a degree where it would put pressure on the cast iron sleeve and force it against the cylinder wall. The cast outer sleeve will, therefore, tend to run at an equal temperature to the cast iron cylinder wall and if any eX- pansion or contraction takes place in the cylinder wall, it will be practically constant with that of the cast iron piston sleeve. Hence, when the cast sleeve of the piston herein disclosed is either lapped into a cylinder or ground to equivalent dimensions there will be a constant fit under operating conditions between the cylinder and piston. Furthermore, use of aluminum for the inner body and head of the piston will result in a considerable reduction in weight with a consequent gain in engine efficiency.

Utilizing pistons embodying the present invention it has been found possible to employ round ground piston constructions in which, in a one cylinder, one and three quarter inch bore, air--r cooled, four cycle engine, a clearance of only .0002 of an inch was maintained between the piston sleeves and the cylinder walls, and completely successful ioperation was demonstrated by an extended test.

It will be evident from the above disclosure that a simplified and highly efficient piston construction has been provided by this invention and that further modifications of the structures disclosed could be made without departure from the scope of the invention as defined in the claims.

What is claimed is:

1. In a piston for reciprocating engines, an outer cast iron sleeve formed with a circumferential groove in its inner surface, an integral aluminum body and head co-extensive with said sleeve and fitted within the sleeve with an integral circumferential lug projecting into said groove, and a continuous flexible steel band positioned between the sleeve and body adjacent the upper ends thereof and having its opposite edges sealed to the sleeve and body respectively.

2. In a piston for reciprocating engines, an outer cast iron sleeve, an inner aluminum head and bodyV co-eXtensive with said sleeve fitted within the sleeve, interlocking elements between the sleeve and body for preventing relative movement longitudinally, and a continuous exible steel band positioned between the sleeve and body and having its opposite edges sealed to the sleeve and body respectively.

3. In a piston for reciprocating engines, an outer cast iron sleeve, an inner aluminum head and body fitted within said sleeve, interlocking elements between the sleeve and body for preventing relative movement longitudinally, and a. continuous flexible steel band positioned between the sleeve and body and having its opposite edges sealed to the sleeve and body respectively.

4. In a piston for reciprocating engines, an outer cylinder engaging sleeve, an inner body forming the piston head fitted within said sleeve and formed of an alloy having a higher coeflicient of expansion than the sleeve, means on the sleeve and'body for preventing relative longitudinal movement, and a continuous flexible metal band having its opposite edges in sealed union with the sleeve and inner body respectively.

5. In a piston for reciprocating engines, an outer cylinder engaging sleeve, an inner body of aluminum alloy, forming the piston head, cast within said sleeve, interlocking means between the sleeve and body for preventing relative longitudinal movement, and a continuous flexible metal seal uniting the sleeve and body.

6. In a piston for reciprocating engines, an outer cast iron sleeve formed with a circumferential groove in its inner surface, a second circumferential groove formed on the outer surface of the sleeve below the location of the internal groove and provided with oil drainage apertures in its base, an inner aluminum head and body fitted within said sleeve and formed with a projecting portion engaged in said internal groove, a flexible metal band positioned between the sleeve and body adjacent the upper ends thereof and havingfits upper edge sealed to the upper edge of the sleeve and its lower edge sealed to the body at the portion thereof project- .ing into the internal groove, and an oil ring seated in the external circumferential groove.

'7. In a piston for reciprocating engines, an

5 6 outer cylinder-engaging sleeve, an inner body REFERENCES CITED forming the piston head tted within said sleeve The following references are of record in the and formed of an alloy having a higher coefme of this patent: cient of expansion than the sleeve, means on the sleeve and body for preventing relative longi- UNITED STATES PATENTS tudinal movement, and a relatively thin elon- Number Name Date gate metal band having its opposite edges in 1,733,422 Mertz Oct. 29, 1929 sealed union with the sleeve and inner body 1,916,978 Harper, Jr July 4, 1933 respectively. 2,390,586 Hastings Dec. 11, 1945 JAMES W. BROWN. i0 FOREIGN PATENTS Number Country Date 338,707 Great Britain Nov. 27, 1930