US1790664A

US1790664A - Whstthbop

Info

Publication number: US1790664A
Authority: US
Publication date: 1931-02-03
Anticipated expiration: 1948-02-03

Description

Filed Feb. 15. 1929 INVNTOR YATTORNEY Patented Feb. 3, 1931 UNITED STATES wnflzrnnor's. neuron, or NEW Yoan, N.. s.

COMPOSITE PISTQN appliquanniea February 15, 192s. serial no. 340,067.

The invention relates to pistons and more especially to that class of pistons wherein the head and skirt are composed of different materials, such pistons being commonly termed composite pistons.

The Yobject of the invention is to rovide such com osite piston which is particularly adapted or use in internal combustion engines and which, moreover, thou h of great strengtlrand rigidity, will be o minimum weight and operate at low temperature and will not be subject to overheatin A further object ofthe inventlon resides' in the provision of a piston structure of this type such that the piston as a whole will retain its shape under the various conditions of temperaturev and physical loading to which it is subected in, operation and in which no internal un mmetrical stresses will A develop as a result t ereof.

A still further object of the invention isV to design the members composing said piston of shapes to allow of ready' and cheap manufacture and assembly thereof into a 2li corlxzilplet'eapiston.

- ereto orez it has been the practice to form composite istons by bolting, rivetin or casting toget er a sklrt portion, as v0 cast iron or steel,' to a head portion .of aluminum alloy or other light metal of high thermal conductivity.. However, failure has usually resulted fattlie joint between the two metals due to the wide difference in their respective rates stresses produced in thel structure under changeset temperature have-also produced distortions in t ese istons which are particularly objectionablb--in desi of piston whose-parts are not' diametrica lysymmetri` cal, or wherein castin strains occur during theproce'ss of fabrication.

-In Athe novel piston; forming the subject \matter vof the present invention, these objectionable features are eliminated; and a novel manner of forming joints between the metal parts having different coeliicients ,of expansion provides for the various parts to retain their proper shapeV irrespectivelof the temperature changes involved.

-507 This is attained by yproyiding a skirt, as

veloped the novel composite piston.

of expansion 5 and' the .highA of sheet metal, with an inturned flange at its extreme outer end, which liange jointly 'supports an annular ring-.groove member within which is frictionallyheld a head of material different from thatV composing tl1e 56 ring member, for example, aluminum, and the diameter of which head normally exceeds the diameter of said ring-groove member to an extent such that ade uate holding friction will prevail between t e two members at the lowest operating temperature and such that, furthermore, no pressures are deat the highest operating temperature which will exceed the yield points of the two materials. The arrangement there by is such that the softer metal will not be in contactwith wearing surfaces and the will thus have maximum operating e. The nature of the invention, however, willbest be understood when described inconnection with the accompanying drawings, in which: f

Fig. 1 is alongitudinal section through' Fig. 2 is a transverse vertlcal section taken on the line 2`-2, Fig. 1 of the drawings 'with the piston head removed and before the groovesl are cut in the ring therefor.

Fig. 3 is ahorizontal section taken on the line 3-4-3', Fi 1 of the drawings.

Figs. 4 an 5 arevertical sections of dif- -ferent t es of heads, the tapershown in Fig 5 belng on a. greatly exaggeratedscale.

Fig. dis a perspective view of an integral prist pin boss and supporting bridge thereor.

Fi 7 .is a vertical section through a skirt mem er with modiied form of wrist pin support; and Fig. 8 is a vertical section thereof-taken on the line 8-8, Fig. 7.

Referring tothe drawings, 10 designates the skirt member of the piston which is preferably formed as a sheet steeLdrawn cup and is characterized by -a deep inturned flange 11 `at itsextreme outer or head end. Diametrically disposed

openings

12 and 13, moreover, are formed in the Mrt-member, the same having thev lips 14 and 15 toaccommodate wristpin bosses'16 and 17 respectively. The 100 inner ends of these bosses are supported by, or preferably formed integrally with, triangular shaped bridges 18, the outer faces of which are arranged to contact with the inner face of the iange 1 1 and are rigidly attached to said fiangc as by spot welding, brazing'or soldering the same thereto. These bridge members are arranged parallel to each other, as shown, preferably in chords of the cylindrical skirt member, The inner end of the skirt member may, also, be provided with the inturned iange 19 to stiften the same at this point, as well as to provide a pilot for subsequent machining operations.

The wrist pin bosses may be formed, also, with independent screw bosses 20 as indicated in Figs. 7 and 8, orthey may be constructed integrally with the corresponding bridges as hereinbefore described; and this latter construction is especially desirable inI .designs wherein a wrist pin turns in its wrist pins boss,. :in which case, they are designed to receive bushings 21.

:Carried by the said flange 11 and rigidly secured thereto, as by welding, is a thickwalled steel head ring or annular ring-groove member 25 provided vwith piston ring grooves 26 and cylindrically bored through; and the same is designed to retain the head 27 of the piston. This is in the natureof a symmetrically-formed 'block of aluminum alloy, or other light metal, and its outer diameter is normally larger than the inside diameter of the ringf'25, being pressedor shrunk in place therein so that its inner face 28 is in contact with or'4 seats upon the .outer face of the. flange 1 1.

The minimum amount by which the diameter of said head 27'exceeds the diameter of the bore of ring 25 is such as to produce adequate holding friction at the lowest temperature offoperation and that no pressures are developed at the highest operating temperatures which will exceed the yielding points of the two materials; and the amount of which excess will, of course, be determined by the nature..of the alloy employed.

As the temperature of the assembled piston head rises in operation, the portion 27 will tend to expand more than its surrounding steel ring member 25 and thus pressure between the contacting surface is increased. The op'eraticn temperature of head 27 at its inner ed, however, will be lower than at its outer end, which is exposed to the highest temperature, because of Vheat dissipation through the successive piston rings (not shown) and retained by the grooves 26. To secure a more even distribution of the pressure (temperature) throughout the length of a joint as well as to maintain high total wall friction at the said joint without the development of excessive pressure at thevhotter end of the head 27, said head may beof taper form, being of `greater diameter at its inner end,- as indicated in Fig. 5, and assembled ting parts, it offers less total restriction than y the loose,contact surfaces of piston rings and their grooves whereby a large partof the' heat entering the head is dissipated to the cooler cylinder wall in which the piston operates. `1

In operation, the loads are transmitted to the wrist pin bosses at their outer ends through the wall ofthe skirt member and at their inner ends through the bridges 18 as a 'lol result of the contact with the liange 11. This arrangement constitutes stiff straight-line compression and strong tension members so that loads due to the gas -pressure within the cylinder in which the piston operates, or due to'inertia, will not tend to distort the structure nor change the roundness of the skirt member, nor willit cause misalignment of the wrist pin boss center lines. This allows of making pistons of sections of minimum thickness and with consequent decrease in weight of such pistons.

Also, changes in temperature in operation do not ,cause distortion or change in the roundness of the head 27 and the peripheral ring lands 26 in the surrounding ring-groove member 25 which are symmetrical and tend to expand with a uniform increase in diamter. Actually, the shape of the head in conjunction with the Harige 11 effects control ofthe shape or roundness of the head end of the piston assembly, which portion is that subjected to the greatest temperature changes. Furthermore, due to the fact that the bridges 18 are attached tothe stiff control flange 11,

or to the skirt. wall only adjacent thereto, which may be effected at the portions 28 and at a point above the center lines of said bosses, they have no restrictive effect upon the natural diametrical expansion or contraction of the skirt wall due to changes in temperature of this part.

Moreover, the said bridges 18 are comparatively weak in a direction to restrict movement of the skirt in a radial direction, whereby the said skirt is substantially free to cxand or contract and tends to do so symmetrically so that'it may be closely fitted to a surrounding cylinder. The inertia load tending to force the head 27 outwardly from its surrounding ring-groove member 25. is

adequately restricted by the 'frictional resistance offered as a result of the iit'between the two parts, as aforesaid; and with respect to any tendency of thesame to be forced inwardly into the skirt, vthe flange 11 upon which it seats provides an adequate abutment.

The design of the novel piston provides for a minimum quantity of the higher cost aluminum alloy which is utilized therein only where its heat-conducting property is most useful while the remaining portions of the piston may be constructed ofa materials requiring greater strength and resistance to wear and which are also less expensive. Furthermore, all of the component parts of the piston lend themselves to rapid and i nexpensive manufacture; but it nis understood that while the preferred materials only have been set forth, other materials may be utilized and the form of the design changed without departing from the scope of the invention.

It is to be ,-noted, also, that in composite pistons madeA according to the construction hereinbefore set forth and within the limits of fits stated, the joints between the two metals composing the head of said piston are entirely permanent and loosene'ss will 'not develop as a result of the many changes of temperature involved in the operation of these pistons. This feature is a particular improvement upon the type of joints heretofore proposed in composite pistons, which gradually loosen and break down due to the failure of mechanical fastening, to the developing of stresses above the yield points of the materials, to limitation of the particularv alloy employed, to the heat treatment of, and the fits possible when aluminum alloys are cast into'or around the harder metal.

I claim:

l. A composite piston comprising a skirt of sheet metal having an inturnedflange at its `outer end and provided with openings in the wall, wrist pin supporting means within said skirt embodying tubular members fitting the respective openings and depending bridge elements carrying the same and attached to the said flange, an annular ring-groove member secured to said flange, and a head of material different from that comprising the ringgroove member, solely held frictionally thereby against outward movement relative thereto and seating on said flange.

2. A composite piston comprising a skirt member having an inturned flange at its outer end, an annular ring-groove member attached to said flange, and a head of material different from that comprising the ring-groove member, solely held frictionally thereby against outward movement relatively thereto and seated on said flange.

3. A composite piston comprising a skirt member having an inturned flange at its outer end, an annular ring-groove member attached to said flange, and a head of material different from that comprising the ring-groove member, solely held frictionally therebj7 against outward movement relatively thereto and seated on said flange, the diameter of said head with respect to the diameter of said ari-- nular ring-groove member being such that adequate holding friction prevails between the two members at the lowest operating temperature and no pressures are developed at the highest operating temperature exceeding the yield points of the two materials.

4. A composite piston comprising a skirt member having an inturned flange at its outer end, a ring-groove member having a cylindrical bore and attached `to said flange, and a head when cold being in the form of a truncated cone and of material different from the annular ring-groove member and solely held frietionally thereby against outward movement relatively thereto.

5. A composite piston comprising an annular ring-groove member, a head of material different from that composing the' ringgroove member and solely held frictionally thereby against outward movement relatively thereto, and a skirt member having an inturned flange at its extreme outer end jointly supporting the said ring-groove member and the said head.

6. In a piston, an upright tubular skirt provided at its upper end with an inturned skirt flange and provided at some distance below the said flange with diametrieally opposed and coaxial apertures,`and two journal supports spaced along the axis of the said .perforation; each journal support comprising an upright plate extending at right angles to the said axis, a tubular portion integral with the plate and socketed in one of the said aperf. tures, and two horizontal plate flanges underhanging and secured to spacedportions of the skirt flange, the saidtubular portion and the two plate flanges extending respectively in opposite directions from the upright plate supported at both ends by the said flange.

7. In a piston, an upright tubular-skirt pro# vided at its upper end with an inturned skirt Harige and provided at some distancebelow the said flange with diametrieally opposed and coaxial apertures, and two journal supports spaced along the axis of the said perforation; each journal support' comprising an upright plate extending at right angles to the said axis and a'tubular portion integral with the plate and socketed in one of the said apertures, each plate having at each end of its upper portion two plate flanges respectively secured to the said skirt flange and to a por 'tion of the skirt adjacent to the skirt flange.

8. In a piston, a tubular skirt provided at its upper end with an inturned radial skirt flange and also provided with diametrieally opposed tubular journaling formatioins formed from the skirt, the journaling formations having a common axis intersecting the axis of the skirt; two journaling tubes each shorter than one-half the bore of the skirt and each having its outer end socketed in one of the journaling formations; vand two tube upright and 'latplatechordate to the skirt and provided at its entire periphery with :L

` supports each fast upon the inner end of one of the-tubes; each tube support comprising an plate flange extending transversely of the said plate,.the plate flange including two upper l portions respectively underhanging and secured to two circumferentially spaced parts of the skirt flangeR the plate flanges and the tubes` having theisame temperature coei cient's of elxpansion as the skirt, and the plate flange includingupper and lmver medial por-- tions bowed to extend relatively near to the .inner-end of the tube.

In testimony whereof I ailix my Signature,

y WINTHROP Sr HORTON.