Патент USA US2110345код для вставки
March 8, 1938. R. R. TEETOR ~ ` f " 2,110,345 PIsToN Filed July 3l, 1954 2Q ' S22 '24 23 1 Patented Mar. 8, 1,938 ' - Í - ' i UNITED STATES PATENT >OFFICE 2,110,345 rrs'roN Ralph R. Teetor, Hagerstown, In ., assignor Ato The Perfect Circle Company, Hagerstown, Ind., a corporation of Indiana Application July 31, 1934, Serial No. 737,800 6 Claims. (Cl. 309-13) This inventionr relates to pistons for internal of the piston while Vthe piston is being rotated. combustion engines and the like. The skirt after the sizing operation and while the The principal object of my invention is to provide a piston so constructed that the desired 5 clearances between the skirt and cylinder Wall at right angles to the piston pin may be maintained throughout the operating range of the engine. I provide> a piston of aluminum alloy or the like which is simple in structure and cheap to manu- piston head is hot is round or cylindrical. Upon cooling of the piston, the head shrinks more than the skirt and the hangers, being connected rigidly 5 and directly to the top of the' skirt, pull in the portions of the skirt in line with the pin bosses so that the skirt becomes elliptical with the major axis at right angles to the axis of the pin bosses. 10 facture, while at the same timefthe piston is free from the objectionable> defects present in the slotted skirt type of aluminum pistons now on the Using this cooled’piston as a pattern, I form a 10 cam to be used in a machine which will form turn or grind the skirts of `other pistons in pro market. `_ The above and further objects of my invention _15 will appear more fully from the following description, reference being had to the accompanyin'g drawing in which: i Fig. 1 is a vertical sectional view through `a piston embodying the preferred form of my in20 vention; Fig. 2 is a vertical sectional view through the piston, the section being at 90° -to that of Fig. 1; Fig. 3 is a cross sectional view through the piston, taken~ on line 3-3 of Fig. 1;_ and n 25 Figs. 4 and 5 are plan and side views, respec- duction to the desired elliptical form. With the piston in the cylinder, when _the en gine is cold there is the correct clearance between l5 the cylinder wall and the bearing surfaces of the piston skirt which are midway between the piston pin bosses. As the engine becomes heated in operation, the piston head is heated to a much higher temperature than the skirt with the result 2o that the head tends to expand twice‘as muchas the skirt or thereabout. The expansion of the head separates the hangers and thus increases the diameter of the top of the skirt in the plane of the axis of the pin bosses, the hangers being 25 tively, of one of the cross struts. ' Thepistoncomprises ahead I6 separated from the skirt I1 by the slot I8. 'I'he skirt is provided with piston pin bosses I8 and the head, 30 upper portion of the skirt and the bosses are connected together by integral hangers or webs 20. 'I‘he piston is formed of the usual aluminum alloy or the like. Near the bottom of the skirt are two cross _struts 22, formed of metal known as Invar, or fsb Gil _ steel or some other suitable metal having a lesser coemcient of expansionthan the head and skirt. As illustrated in Figs. 4 and 5, one form o! each strut may be L-shaped in cross section and have 40 inclined end ears 23 provided with apertures 24'. As best shown in Fig. 3, the end portions of the struts‘ including the apertured ears 23 are embedded in thickened portions 25 of the skirt. In.` casting the piston, above described, the 45 cross struts are mounted in arnold and the piston is then cast so that the ends of the struts are embodied in the thickened portions of the piston skirt. In order to impart to the skirt the desired elliptical or out of round shape or form, I pref50 erably take a piston after it has been cast, heat the head _to approximately the temperature to which the head would be heated under normal operating conditions in an engine and then while the piston is in this heated condition size it by 55 a tool brought into engagement with the skirt inflexible and connected directly to the upper portion of the skirt. In other words the expan sion of the head tends to change the upper por tion of the skirt from its elliptical form to one approaching a round form by increasing the 30 diameter in the plane of the pin bosses so that it approaches the diameter at right angles thereto. 'I'his tends to decrease the latter diameter. At the same time, however, the aluminum of the skirt expands circumferentially due to the heat, 35 so that -while the expansion of the head may tend to reduce the major axis which is at right angles to the pin bosses, yet the inherent expan sion of the skirt slightly more than compensates for this with the result that the desired clear- 40 ance at the top of the skirt bearing faces is main tained. In other words, the distance between the bearing, faces increases slightly as the diam eter oi' theengine cylinder increases. The struts 22 also perform the function of 45 maintaining this desired clearance at the bottom of the bearing faces. After the piston is cast the aluminum cools so, of course, the struts are al- _ ways in compression and they tend4 to maintain the diameter of the lower ends of the bearing 50 faces about the same when'the piston is cold as . when it is hot. As the skirt becomes heated dur ing operation of the engine, the aluminum ex pands circumferentially but the expansion nec essarily takes place for the most part- on the 55 2 Y . k2,110,345 minor axisof the skirt. This may tend to flatten 'out the bottom portions of the bearing faces be tween the ends of the struts but this tendency is slightly more than compensated for by the circumferential~ expansion ci’ the skirt, so'that as the diameter of the engine cylinder increases, t y , to tend to satten out during thermarerpshsinnf of the piston skirt, said struts each being so shaped and constructed that they are iniiexibie and are of such length that they are held under constant compression by said skirt, the force of i compression being suiiiciently‘great it will not be‘released by the thermal expamion of said bearing faces increasesand the correct clearance skirt during operation in an engine. ` between the cylinder wallvand these portions oi?v the bearing faces is maintained. It will thus beseen -thai; the diameter‘of the'KV 'the distance between the bottom portions of the , piston> skirt from top to bottom is'properly con . trolled during the operating range oi' the engine so that the desired clearance between the bearing faces and cylinderwallis maintained throughout therebetweenv extending substantially through out the circumference of the piston, H bosses integral with the skirt and on the minor axis of the latter, hangers integral with the head their length, thediameter of the skirt in line with ' and upper- portionl ot the skirt, the hangers the pin bosses being permitted vto change without >in_g inflexible so that the expansion of the I.. 4impairing the emciency of the engine. and with I.) upon beingiheated in anengine tends to out danger of scoring and the like. the upper portion of the skirt fromI its elliptical It is understood that my invention is not lim vform to one approaching a round form, ited to the details of construction shown and that struts having a lower coemcient of expansion other forms may be used without departing i’romV than said skirt and arranged parallel to the the scope. of my invention. major axis of the’skirt in the lower portion of I claim: - „ > ~- _ l.’1n~a piston'V formed of metal having‘a high coeiiicient `of expansion, ahead.. a continuous skirt of elliptical form'in rcross-section from one „ end thereof to the other, the upperedge of said ' skirt being separated from said headby a slot ex tending substantiaily throughout the circum ferenceof the piston. rlgid'hangers connecting the skirt, the struts _ having their ends imbedded' with the skirt and being of such length that they are held under constant compression by the skirt so that the circumferential expansion ofthe skirt upon becoming heated in an engine tends to change the lower portion ofthe skirt from its ` elliptical 'form to one'approaching a round form. the length of the major axis remaining substan l'together said head and the upper end of said tially constant.> ' ` t t A skirt, piston 1 pin bosses on skirt and on the 4. In a piston formed of metal having a high minoraxis o'f the ellipse of saidskirt, and a pair -of struts eachformed of a material _having a' coemcient of expansion, `al. head. a continuous walled skirt having an“` elliptical cross-sectional much'lower'ccemcient of expansion than Vsaid shape with the bearing face portions on the skirt and disposed within said" skirt- belo'w. Said ~ major axis, bosses'on the minor. axis pin bosses‘and parallel to the major axis of the. ofthe ellipsepisto?fpin oi' the skirt, and two spaced ellipse of said skirt with their ends Vembedded in struts having-a lower coemeient `ofgexmimicn» l jthewalirof-said skirt'at points substantially than said skirt and’dlsposed within 'said‘ lkii't spaced apart.v said vstruts eachbeingsoshaped». 4below and spaced from said-pin and sub and constructed that they are iniiexible and are stantially parallel to the maior bosses axis of said el ~ of such length that they are held under constantl compression by said skirt, the force of compres lipse'. the struts being inflexible and the hearing ` sion. being sutli'ciently great that it will not be ` face'portions between the ends of the struts be ing flexible, whereby said bearing face portions released by; thermal expansion'ot said skirt dur ing operation ln an engine. tend to‘ilatten >out during thermal expansion of \ coeiiiclent 'of expansion, a head, a continuouswalled skirtr having an elliptical cross-sectional `of theskirtincreasess 2. In s piston formed ormetsi having a high'> the piston‘skirt and the V'lengthof the minor axis shapefrom one endto'the otheryop'posed rigid hangers integral with and depending from said "head and integrally connected to the upper end - of said‘skirt von the rminor axis ofthe 'ellipse of the latter, said headbeing` separated from the “ » i f . _ 5. In a plston'fonned oi'i‘metal having a high 4coeiilcient of expansion, a continuous ' walled skirt having. an elliptical cross-sectional shape from one endtto the, other with the face' portions on` the major opposed hangers rig-` idly connecting the upper end of the/skirt to the upper end of said skirt atÍall .points except at head on the Vminor axis of the ellipse of the skirt. ton adjacent .the »lower ends of sait'l'> hangers 'with the'remainder of the upper wall portion of said and two spaced apart struts having 'a 'lower co eiiicient of ‘expansion thanv said 'skirt and di» >said hangers whereby said head is i'reeto expand the skirt ,being separated from the head vbetween .and contract in a uniform manner and without rthe hangers, piston pin `bosses within the' skirt distortion, piston pin bosses formed on said pis~. ' and on the minor axis’of the kellipse of the mrt. " posed Hwithin'said skirt'below and-spaced from kßk‘li'l: ’free and ‘ unrestrained y .whereby expansion and contraction‘movements of said‘head acuate » said pin bosses, and substantially parallel tothe seid 'hangers to-expandzand contract said skirt major axis of said ellipse.'v the struts being inf along the'minor axisïof its el1ipse’to~.produce, ilexible and the. bearing face'portions between uponl expansion, a -substantially circular skirt the ends of the struts being ¿dexible whereby said4 and, upon contraction, an ‘elliptical skirt, ,and a ~ lbearing face portions tend Vto'tiatten out during pair of struts each formed of la material having a. y 'rthermal expansion of ythepiston ùirt and the mulch lower .coeiiicien y,of expansionl than- said length vof the minor axis of the'skirt increases.r 6. A piston comprising "a head,~rigid hangers 70 skirt and disposed within said skirt »below said pin bosses and parallel to themajor axis/of the depending lfrom said ,head` yand carrying pin 70 ellipse of said'skirt with their ends l integrally vskirtv directly connected to bossesaperturedtoreceiveapistonpimanda secured inthe wall of said skirt at points sub, stantially spaced apart whereby the skirt ma' "terial between adjacent ends of said struts is free , bosses,v all formed of a metal saidhaving hangers a high and co efficient of expansion; said head and skirt being is txiailyspacea from each other throughout theirl 75 9,110,345 entire circumference by a circumferentially ex tending air gap and being maintained in such relation by said rigid hangers. the entire exterior surface of said skirt being generally elliptical in contour with the minor axis thereof substantial ly parallel to the axis Iof said pin bosses and the continuity of said skirt being' interrupted only ' 3 by the pin boss aperturea‘and a pair of rigid struts having a lower coemcient. of expansion than that of the metal of said skirt disposed be low and spaced from said pin bosses, the ends of l said struts being embedded in the metal of said 5 skirt. RALPH R. TEETOR.