US1891914A - Alloy piston - Google Patents

Description

Dec. 27, 1932. C R BUTLER 1,891,914

ALLOY PISTON Filed March 13, 1929 s sheets-Sheet 1 Z* 1' Z .2. 45 I? 1 2a .55 fa Dec.27,1932. R BUTLER gL89L914 ALLOY PI. STON Filed March 15, 1929 6 sheets-sheet 2 Dec. 27, 1932. c, R. BUTLER 11,891,914

ALLOY PIsToN Filed March 13. 1929 6 Sheets-Sheet 5 Dc; 27, 1932. c. R. BUTLER 1,891,914

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ALLOY PIsToN Filed March 15. 1929 6 Sheets-Sheet 6 Il?. 2.9. fa d (5H/6255 /Q 5ans@ Patented Dec. 27, 1932 PATENT OFFICE CHARLES R. BUTLER, OF INDIANAPQLIS, INDIANA Application led March 13,-1929. Serial No. 346,517.

My invention relates to light-metal pistons for internal combustion engines, with an effective expansion control of such pistons.

It is the object of my invention to make a sturdy light-weight piston, as of aluminum alloy or other light-weight metal having a large co-eilicient of thermal expansion, with substantially full circumferential skirt-bearing at least in the zone between the pistonpin bosses andthe piston-ring belt and desirably also at or near the open end of the piston, and to produce an effective control of the expansion and contraction of the piston skirt, especially in that zone, so that it is more nearly equal to that of iron or' steel; to reduce the internal stresses in the piston due to changes in temperature; towree from the piston-pin bosses the controlled skirt portions d1rectly over such bosses, so that there may be relative movement between such portions and the bosses Without the production of excessive bending stresses; to provide good heat conductivity between various parts of the piston so that the heat may be conducted away from the piston head even though not directly to the controlled zone of the piston skirt lyingbetween the piston-pin bosses and f the piston-ring belt; to provide for adequate transfer of heat from the piston to the cylinder; to reduce pounding and breakage, by so controlling the expansion and contraction of the piston that it fits closely within the cylinder at all temperaturesl through substantially the entire circumference in the zone between the piston-pin bosses and the piston-ring belt; to provide effective sealing against leakage of gas or oil, while yet,` permitting good lubrication; and to accomplish these results in a piston low in manufacturing cost and amply rugged to withstand the terrific loads to which pistons of heavy duty engines are subjected..

In carrying outmy invention, I desirably make the piston as a whole of light metal, such as aluminum or aluminum alloy, and separate the head and piston-ring belt from the lower skirt portion or guiding'portion by a circumferential slot so that stresses'l willl not be transmitted from one to the other at or near the periphery of the p'ston;andpro vide carrying struts which connect the piston-pin bosses to the piston head, desirably at points on the latter fairly remote from the periphery thereof; and carry the skirt or guiding portion of the piston from the pistonpin bosses; and provide one or more endless steel bands, which are located in the piston skirt or guiding portion below such circumferential slot and at least one of which is located between said slot and the transverse plane of the piston-pin bosses; and slit longitudinall the light-metal portions of the skirt above tlie piston-pin bosses, and desirably at or nearv the longitudinal plane of such bosses, while permitting the endless steel band e5 or bands to cross said longitudinal slits and complete'the mechanical continuity of the skirt; and separate from the piston-pin bosses theskirt portions in the neighborhood of the aforesaid longitudinal slits s0 that those skirt 7o portions may serve as guides without material distortion from the piston-pin bosses; and in some forms of my invention provide other longitudinally extending breaks in the lightmetal portion of the piston skirt from the open end thereof up to or beyond the pistonpin bosses, or even to the said circumferential slot,- but desirably at locations angularly spaced from theflongitudinal plane of the piston pin.

The accompanying drawings illustrate my invention, and show six of the many forms it may take. One form is shown on Sheet 1, Figs. 1 to'5 inclusive; another form on Sheet 2. Figs. 6 to 10 inclusive; a third form on 85 Sheet 3, Figs. 11 to 15 inclusive; a fourth form on Sheet 4, Figs. 16 to 21 inclusive; a fifth form on Sheet 5, Figs. 22 to 27 inelusive; a sixth form on Sheet 6, Figs. 28 to 31 inclusive; and a modification of the Vferroust metal control members also on 32 and 33.

In these drawings, Fig. 1 is a longitudinal section through one type of piston embodying my invention, the section being taken on the line 1-1 of Figs. 2, 3, and 4, in the longitudinal plane of the piston pin; Fig. 2 isa section on the line 2f-2 of Fig. 1, and also substantially on the lines 2-2 of Figs. l3 and 5; Fig. 3 is a transverse section sub- 100 sheet 6, Figs.

stantially on the lines 3-3 of Figs. 1 and 2; Fig. 4 is an elevation of the piston of Figs. 1 and 2, viewed in the same position as Fig. 2; and Fig. 5 is a transverse section substantially on the line 5-5 of Figs. 1 and 2: Figs. 6, 7, 8, 9, and 10 are views corresponding generally to Figs. 1, 2, 3, 4, and 5 respectively, but of a somewhat different specific embodiment of my invention, the sections on which Figs. 6,7, 8, .and 10 are taken being indicated by the lines 6 6, 7--7, 8 8, and 10-10 on others of those figures; Figs. 11 to 15 inclusive are also views generally correspondirig to Figs. 1 to 5 inclusive respectively, but of a third specific form of my invention, the sections on which Figs. 11,12, 13,

and 15 are taken being indicated by the lines 11--11, 12-12, 13-13, and 15-15 on others of those figures; Figs. 16, 17, 19, and 2 0 are views generally corresponding to Figs. 1, 2 and 4, 3, and 5 respectively, but of a fourth specific embodiment of my invention, and Figs. 18 and 21 are an elevation and a bottom view respectively of the same piston, the various sections of which Figs. 16. the right half of 17, 19, and 20 are taken being indicated by the lines 16-16, 17-17, 19-19, kand 20-20 on others of those figures; Figs. 23, 23, 24, and 26 are views corresponding generally to Figs. 1, 2 and 4, 3, and 5 respectively, but of a fifth specific embodiment of'my invention, the sections on which Figs. 22, the right half of 23, 24, and 26 are taken being indicated by correspondingly numbered section lines on the other figures; Fig. 25 is a transverse section on the line 25-25 of Figure 23; and Fig. 27 is a perspective view of a steel strut which is shown by way of example in this fifth embodiment of my invention; Figs. 28, 29, 30, and 31 are views corresponding generally to Figs. 22, 23, 24, and 27, but showing a sixth embodiment of my invention, the sections of which Figs. 28, 29, and 30 are taken being indicated by correspondingly numbered section lines on others of those figures: and Figs. 32 and 33 are views corresponding generally to Figs. 29 and 30 respectively,`but with a pair of overlapping arcuate strips each Ianchored at its end instead of the continuous control bands of the other figures.

In all these forms of my piston. thereis a piston head 2O having a depending pistonring-belt 21 provided with piston-ring grooves 22 for the usual piston rings; pistonpin bosses 23 which are located below the piston head and its ringbclt,`and which. co-operate with the usual piston pin, either directly or with suitable interposed bushings 24, such bushings being shown in the first form of my invention.(Figs. 1 to 5) by way of example.'

although they may be used or omitted with any form of my invention; carrying struts 25 which extend from the piston-pin bosses at or near their inner ends to the head 20, desirably to join the latter in regions spaced inward from the periphery of the head and from the ring belt, as in the first three and the preferred forms of my invention, so that such regions are intermediate regions between the center and the periphery of the head, a1- though in some instances these struts or webs may also extend to and join the ring belt, as in the remaining forms which I have illustrated of my invention; and a guiding or in weight and has certain desirable bearingmctal and heat-conducting characteristics. In addition, all the parts 20, 21, 23, 25, and 26 are desirably made as a single homogeneous casting, for ruggedness of construction and for high heat-conducting capacity.

The carrying struts 25 from the two piston-pin bosses to the head may be entirely separate from eachother, as for instance in the forms of my invention shown in Figs. 6 to 15 inclusive; but for heavy work I prefer to interconnect them by a pair of webs 27 which extend from the h ead downward toward the piston-pin bosses in planes'transverse to the struts 25, as shown in Figs. 1 to 5, so that the struts 25 and Webs 27 together form a box-strut. This smakes for great strength and ruggedness, and is especially desirable for pistons in heavy duty engines.

In all forms of my invention, the upper edge of the skirt or guiding ortion 26 is separated yfrom the lower end o? the ring-belt 21 by a circumferential groove or slot 30; which may be either cut straight in, as for in- IOLl stance in Figs. l to`5 inclusive, or cut in conically, as in Figs. 6 to'15 inclusive, and which if desired may communieatewith one of Vthe piston-ringgrooves 22 usually the lowest one,

as in Figs. 1 to 5 inclusive, or may be slightly i substantially parallel to each other, and to the pistonjaxis, as ,in the form of piston shown in Figs; 1 to 5 inclusive; or they may be inclined with respect to each other an/d to the piston axis.l as inthe forms of my invention shown in Figs. 6 to 10 and 11 to 15. These struts join the piston-pin bosses at or fairly near the inner ends of the latter, so that the struts are spaced inward from that portion of the piston skirt which liesbetwen the circumferential slot 30 and the piston-pin bosses, to leaye a space 31 between such struts and that portion of the piston skirt.

The piston skirt 26 may yextend for substantially the fullcirc'umference of the7 piston its asseoir' my invention, however, the pislon shirt extends for substantially the compl-eee eircomerence in a zone lying hetwee the sirens-.1.4 erential slot 30 .end the transverse plane of the piston-pin boes, save eertsin slits which will shortly describedn That is, whether the shirt below the igiene the pis- 'ein bosses extends for the complete eirr-ence or is merely e peir of siippers, the plane o'i the esten-pin bosses it ezitends snhstnn'tielly the nli eircnniier ence, for the slits rei-erred to, so that there it 'will iorin -snbstentielly complete snide for the piston throughout s cir-enroy renee, not only in the nien-e of the but else in the longitudinal piene of 'n if 'ion pin so that roeiiingij oi the pis on piston rings Win i will zfiso forni e sul here ere ons or i i enioedded in the -nieiei or piston l 1 y slnr'z. Tney are desirelolrly endless steel rings, as molested in eli `orrns shown of insentieri sere that shown in Figs. 552 end There is least one sneh stesi control band 35 in 'the zone just referred to, between the eireurnerentiai slot 3@ and the transverse piene of the piston-pin bosses. This control band may be ot any suitable cross-section, either rectangular or round, as shown in the serions views f the drawings'. It may be oiE any suitable iron or steel composition, to control the ex ansion oi the piston skirt in its plone; so t' at it may be either ordinary iron or steel, or it may be of some ferrous-metal alioy (such as a nickel-steel alloy of which inver is one example) which has a oo-eicient oi thermal expansion less than that of cast iron or steel if in the design of the piston that lower co-ei'cient of thermal expansion is desired, Ordinarily l prefer that this control hand have a greater co-eicient of thermal expension than has inver, because the co-eii-l cient of thermal ex ansion of invar is ordinarily too small or producing the best results; but invar may be used if desired. While I have shown only one ferrous-metal control band in the zone between the circumerential slot and the piston-pin bosses, as that is suicient to illustrate my invention, such invention is not at 'all limited to the use of only a single control band in that general location. But my invention does contemplate the use of atleast one control bend in that generell loeetion, 'whether or not more thonone control hand is used in that location, and Whether or not a control band or bends ore else used in other locations now to he described.

Tous in .addition to a control hand in the zone just described, there may be one or :more lower control bands 35, also o' suitable ferrous metal, located in the zone between the transverse plane or" the piston-pin bosses ond 'the open end of the cylinder. rEhese are esgeeeialiy desirable in the full-skirt type of piston, such es shown in Figs. l to i0 in- 'cinsiveg elthongh not essential to many forms of my invention, and thus not shown in the forms oi my invention ilnstreted in Figs. li to inclusive. 'lhst is, the lower control bend is `not necessary to my present invention, :although frequently desirable, lout upper control bend 35 is essential to it. The shirt 26 is carried from the piston-pin bosses IThis carrying of the sltirt from *eisten-pin bosses is such that the shirt ons which lie between the transverse one the piston-pin bosses and the ring,y end the neighborhood othe longitndinei I iene of the bosses, are free from di- .ichnient to such bosses. To end, the shirt may be attached to the piston-loin bosses in various ways. it may be directly continuons with the lower portions or the outer ends o1? the piston-pin bosses 23, es in the 'forms shown in Figs. i to 5 inclusive and 6 to l@ inclnsive; with suitable strengthening webs interconnecting it to the bosses at and below the plane of the piston-pin axis ir desired; such sstronsverse Webs 40 which extend from the piston-pin bosses ont to the shirt as illustrated in Fig. 2, 3, and d and lie slightly below the transverse plane o the piston pin, or transverse webs 4l and oblique webs 42 which lie in and below such trans; verse plane as illustrated in Figs. 7, 8, and l0. These constructions are suitable or the full-skirt type of piston. If the skirt is of the slipper type below the transverse plane of the piston pin, it may be supported from the bosses by transverse carrylng Webs i3 which lie wholly or at least largely below the transverse plane of the piston-pinaxis, Y

as is illustrated in Figs. l1 to 15. The webs 43 are symmetrical with respect to the longitudinal plane of the piston pin. lf desired, however, there may be such webs 43* and 43 which are unsymmetrical with respect to such plane, as is illustrated in Figs. l? and 20, the webs 43 extendin from the open end of the piston up to and yond the' transverse plane of the piston pin, While the webs 43 do not extend so high. The webs 43* join the bosses to the thrust face which takes the side thrust `on the explosion stroke of the engine, and are made to extend higher than do the webs 43" so that they may be better able to do so. In the arrangement shown in ranged, as in all the forms of my invention Figs. 22 to 33, the webs 44 which interconnect the skirt segments to the piston-pin bosses do not extend so high as the vaxis of such bosses, save where they join such bosses on the underside thereof.

In any case, the portion of the skirt 26 in the zone between the circumferential slot 30 and the transverse plane of the piston pin extends for substantially the entire circumference, has embedded in it a control band 35, and in the regions which lie over or `near the ends of such bosses is free from direct attachment to the bosses so that some relative movement between those' regions and the bosses is permitted.

The skirt portion which lies in this zone is provided with slits 45, which extend longitudinally of the piston and which are crossed by the control band 35 to complete the mechanical circumferential continuity of the skirt'structure in spite of those slits. These slits 45 are thus only in the alulninum. Usually, and desirably, the slits 45 are located directly above the ends of the piston-pin bosses, as shown in all the forms illustrated of my invention save that in Figs. 16 to 21 inclusive; but in that form they are shown as angularly shifted from that location toward each other on one side of the longitudinal plane of the piston pin, usually but not always the side opposite that which is the thrust side of the explosion stroke. I prefer the symmetrical arrangement shown in the other figures, with the slits 45 substantially in the longitudinal plane of the piston-pin axis; but the nnsymmetrical arrangement shown in Figs. 16 to 21 inclusive, especially if combined with the unsymmetrical arrangement of the webs 43 and 43", has certain advantages, especially when the side thrust is heavy.

By reason of the slits 45, the skirt portion above the region around each end of the piston pin comprises one or two aluminum fingers 46. lf the slits 45 are symmetrically arshown except that in Figs. 16 to 21 inclusive, there are two such fingers 46, which project toward each other substantially free from any immediate connection to the piston-pin bosses: and these fingers are joined, and the gap between them spanned, by the endless steel control band 35 which extends completely around the piston and in doing so projects from the end of each projecting finger 46 across the intervening gap formed by the slit 45 and into the finger 46 on the other side of such gap. lf' the slits 45 are arranged unsynunetrically. as in the arrangement shown in Figs. 16 to 21, there may be only one such finger 46 over each piston-pin boss, which finger extends from the thrust face on one side (the left as shown in Fig. 17) over the piston-pin boss to the slit 45, here shown arranged at the edge of the thrust `face on the otller side (the right side as shown in Fig. 1

The finger or fingers 46 may lie directly over the outer ends of thepiston-pin bosses, as in the second, third, fourth, fifth, and sixth forms of my invention, shown in Figs. 6 to 33 inclusive, in which case there may be a fairly wide slot 47 open to the outside of the piston skirt between the upper portion of the outer end of-each pistonin boss and the lower edges of the finger or ngers 46. This slot is crescent-shaped in the second and third forms of my invention, shown in Figs. 6 to 15 inclusive, in the third form of my invention extending downward to -form the side edges of the lower parts of the thrust faces ofthe piston skirt. In the fourth form of my invention, shown in Figs. 16 to 21 inclusive, such sloti47 is like that in the third form on the side toward one thrust face, usually the one which takes the thrust on the explosion stroke, though on the other side the upper edge of the slot extends horizontally alongthe under side ofthe finger 46 to the slit 45. In the fifth and sixth forms of my invention, shown in Figs. 22 to 33 inclusive, thefingers 46 are shown flat on their under sides, and spring only from the topmost parts of the .thrust portions of the skirt; so that the slot 47 between the bosses 23 and such fingers 46 is apparently not in the shape of a crescent, although effectively it is still crescent-shaped. Thus in all of these forms of my invention, there is in effect a crescent-shaped separation 4T which separates the outer ends of the bosses 23 from the finger or fingers 46 which overlie such outer ends.

However, especially if the length of the piston is limited, the fingers 46 may lie radially outward beyond the outer ends of the upper parts of the piston-pin bosses, and at about the same height as such upper parts, instead of directly overlying the bosses. This is the situation in the form of my invention shown in Figs. 1 to 5 inclusive. In this case, the fingers 46, which lie radially beyond the outer ends of the upper ortions of the pistonpin bosses, are separat from such upper portions of such outer ends by vertically extending slots 48, which lie just inside of the fingers 46. The slots 48 have the same general function as the generally crescent-shaped slots 47. It is usually in such cases as this that I may provide the bushings 24, although they are not necessary even here, so that if they are provided the slot 48 may not extend completely to the bearing surface of the piston pin. Any relative movement between the fingers 46 and the piston-pin bosses 23 in this construction will be by relative movement of the fingers toward and from the ends of the bosses. or along the bushings 24 if they are provided. To facilitate this, a slight clearance may be provided around the outer ends of the bushings 24, although only a microwave slots 50 in the molding operation, and also the slits 45 and slots 47 but usually form the circumferential slot 30 by a machining operation subsequent to molding.

In operation, heat which is produced in the piston head by the explosions is transmitted by the carrying struts 25 to the piston-pin bosses, and thence to the piston skirt, whence it may be dissipated to the cylinder and the cooling water.

In this operation, there are different rises in temperature in the different parts of the piston. The piston head naturally gets the hottest. This produces expansion, which is substantially the same in all directions, and

which is an expansion with the co-eliicient of thermal expansion ofl the aluminum or aluminum alloy or other light metal used. The expansion of the head as it is heated causes the carrying struts 25 to be separated somewhat, thus tending to carry the piston-pin bosses 23 slightly radially outward. The amount of such separation of the bosses 23 depends upon a number of factors, notably on the deflection of such struts and the distance they are spaced apart where they join the piston head. The use of the webs 27 tends to prevent such deflection of the struts 25, by reason of the strength of the box-strut which the carrying struts 25 and the webs 27 together form. The closer together the upper ends of the carrying struts 25 are placed, the less the forcing apart of the piston-pin bosses will be by reason of the expansion of the head; because of the reduction in the intervening distance between them at the head where aluminum-expansion mainly occurs.

The separation of the bosses 23 is also opposed by the upper control band 35, and by the lower control band 36 if it is present. However, the upper control band 35 permits some such expansion, for the piston-pin bosses may move outward slightly, while the tingers 46 do not move outward so far, if at all, .on account of the fact that the fingers 46 are free from direct attachment to the piston-pin bosses and are held by the steel control band 35 from moving out more than that control band permits. In consequence, as the piston increases in temperature, both the space 31 and the slits 45 tend to narrow somewhat, as indeed do the slots 50 also ,When the lower control band 36 is used.

The narrowingV of the slits 45 and of the slots 50 is due to the diierential expansion of the control bands 35 and 36 on the one hand and the aluminum alloy directly embedding them on the other hand, such control bands serving as tracks on which the aluminum slides circumferentially in such differential expansion. The narrowing of the space 31 is due to the restraint against outward expansion exercised by the control band 35 on the vfingers 46 as the piston-pin bosses 23 are forced apart by the expansion of the head. Such relative movement is permitted by the fact that the fingers 46 and the upper portions of the bosses 23 are separate from each other, so that any bending which may be incident to such narrowing of the space 3l is so slight that it is not detrimental.

Because of these interactions of parts, the fingers 46 co-operate with the rest of the piston skirt to form an effective cross-head to guide the piston smoothly. The fingers 46 serve as firm supports for the piston in the neighborhood just above the regions at the end of the piston pin, for they are located between the ring-belt and the piston-pin axis where they are most effective in doing this. These fingers 46 eHectually prevent chattering of the piston against thecylinder wall in the line of the piston pin, and thereby reduce the wear on the piston rings and on the head section, and serve to hold the head section properly in place.

I claim as my invention:

l. A composite piston, comprising a piston head and piston-ring belt, piston-pin bosses, carrying struts interconnecting said head and said piston-pin bosses, a piston skirt carried from said piston-pin bosses, said skirt having portions which lextend and lie between the bosses and the head, and which fill substantially the entire space between said parts, and which portions are spaced from said carrying struts and are free from direct attachment to the upper sides of the piston-pin bosses and are provided with slits extending lengthwise of the piston, and a circumferentially extending control bandof differentmetal from the aforesaid parts of the piston and embedded in the metal of the skirt between the ring belt and the transverse plane of the piston-pin axis and extending across said slits, said ring belt and said skirt being separated by a circumferential slot.

2. A composite piston, comprising a head having a depending piston-ring belt, pistonpin bosses, carrying struts interconnecting said head and said'piston-pin bosses and joining the latter neartheir inner ends, a skirt having thrust portions supported from said piston-pin bosses, saidthrust portions havin projecting fingers vextending circum'fere tially of the piston in between and substantially filling the spaces between-said pistonring belt and the upper parts of the pistonpin bosses, each finger extending toward and almost but not quite to a cooperating finger projecting from the other thrust portion so that a gap is left between each two fingers which project toward each other, said fingers lying in the transverse plane of the piston between the ring belt and the piston-pin axis and being free from direct attachment to the` upper parts of the piston-pin bosses, and a circumferentially exterding control band of different metal from the skirt and fingers but embedded therein and spanning said gaps between the adjacent ends of the fingers, said ring belt and said skirt and fingers being separated by a circumferential slot.

3. A composite piston, comprising a' head 5 having a depending piston-ring belt, pistonpin bosses, carrying struts interconnecting said head and said piston-pin bosses, a skirt having thrust portions supported from said piston-pin bosses, said thrust portions having projecting fingers extending circumferentially of the piston in between and substantially filling the spaces bftween said pistonring belt and the upper parts of the pistonpin bosses, each finger extending` toward and 15 almost but not quite to a cooperating finger projecting from the other thrust portion so that a gap is left between each two fingers which project toward each other, said fingers lying in the transverse plane of the piston be- 29 tween the ring belt and the piston-pin axis and being free from direct attachment to the upper parts of the piston-pin bosses, and a circumferentially extending control band of different metal from the skirt and fingers 25 but embedded therein and spanning said gaps between the adjacent ends of the fingers, said ring belt and said skirt and fingers being separated by a circumferential slot.

In witness whereof, I have hereunto set my 30 hand at Indianapolis, Indiana, this 9th day of March, A. D. one thousand nine hundred and twenty-nine.

CHARLES R. BUTLER.

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