US2720806A - Machine for forming pistons of elliptical cross section - Google Patents

Description

5 Sheets-Sheet 1 NvEzN-roh Stewart- CATIQQQELM.

Oct. 18, 1955 G. D. STEWART MACHINE FOR FORMING PISTONS OF' ELLIPTICAL CROSS SECTION Filed Feb. 3, 1949 Guben.- D

Oct. 18, 1955 G, n. STEWART MACHINE FOR FORMING PISTONS OF ELLIPTICAL CROSS SECTION 5 Sheets-Sheet 2 Filed Feb. 3, 1949 havana-rok Stewart M, /'mar auf Gilbert :D

clamav/- Oct. 18, 1955 G. D. STEWART MACHINE FOR FORMING PISTONS OF ELLIPTICAL CROSS SECTION 5 Sheets-Sheet 3 Filed Feb. 3, 1949 NVE-NTO@ (Silber-t D. Stewart" .A, MMM ,f a/ga dH-romvsyf Oct. 18, 1955 G. D. STEWART 2,720,805

MACHINE FOR FORMING PISTONS OF ELLIPTICAL CROSS SECTION Filed Feb. 5, 1949 5 Sheets-Sheet 4 I' IEE? 69 NVELNTQY2`- Gilbert D. tewqr-U (Artemisa/f Oct. 18, 1955 G. D. STEWART MACHINE FOR F'ORMING PISTONS OF' ELLIPTICAL CROSS SECTION 5 Sheets-Sheet 5 Filed Feb. 3, 1949 kmr n fl.

n D. SQLLJOLY'A 'fw W155i# United States Patent O masse MACHENE FR FRMING PSTONS 0F ELLHTCAL CRSS SECTION Gilbert D. Stewart, Detroit, Mich., assigner to Ex-Ceil-O Corporation, Detroit, Mich., a corporation or' Michigan Application February 3, 1949, Serial No. 74,418

4 Claims. (Cl. 82-24?) The present invention pertains to machines for forming internal combustion engine pistons of special shape and, more specifically, to a novel and improved machine of the general character disclosed in United States Patent No. 2,121,934 issued June 28, 1938, to Ira l. Snader et al.

The pistons of modern internal combustion engines such as those used in aircraft must be designed for operation at high temperature, pressure and speed. Due to the unequal distribution of metal in the piston walls resulting from the formation of wrist pin bosses, such pistons normally tend to expand unevenly. Thus, a piston which is perfectly round when subjected to room temperature will tend to assume a distorted, out-of-round shape when subjected to the substantial operating temperature of the engine within which it may be used. To oset this tendency, engine designers have called for pistons having slightly distorted initial shapes but which, when heated to operating temperature wthin the engine, will then assume the optimum shape for best perfomance. Designers have also found that a satisfactory way to achieve this result is to fasten each piston with a cross section approximating that of an ellipse having a minor axis slightly smaller than theV normal diameter of the piston and with such axis lying generally parallel to the axis of the wrist pin bosses.

Accordingly, the general aim of the invention is to provide a novel and improved machine for turning pistons of the character set forth so as to impart a predetermined elliptical shape thereto.

Another object is to provide a machine of the foregoing type adapted to fashion pistons of generally elliptical cross section and which will have a predetermined longitudinal taper or are.

A further object is to provide a machine of the above character which will be susceptible of simple, rapid adjustment and high production operation.

Other objects and advantages will become apparent as the following detailed description proceeds, taken in connection with the accompanying drawings, wherein:

Figure l is a fragmentary front elevation of an illustrative machine embodying the invention, such machine being in condition to start an operating cycle.

Fig. 2 is' a slightly exaggerated diagrammatical view illustrating the nature of the cut taken on a round work piece by the machine of Fig. l.

Fig. 3 is a view similar to Fig. l but with a portion of the supporting bridge broken away and the machine near the end of its operating cycle.

Fig. 4 is a slightly exaggerated diagrammatical View illustrating the axial are on a piston produced by the action of the machine shown in Fig. 1.

Fig. 5 is a fragmentary plan view of the machine in the condition illustrated in Fig. l.

Fig. 6 is an enlarged fragmentary vertical sectional view taken longitudinally through the tool holder and a portion of the spindle assembly.

Fig. 7 is a transverse sectional view through the tool holder taken in the plane of the line 7-7 in Fig. 6.

Fig. 8 is an end elevation of the tool holder taken in the plane of the line 8 8 in Fig. 6.

Fig. 9 is a fragmentary vertical sectional view taken through the machine of Fig. 1 and detailing the spindle actuating yoke.

Fig. l0 is an enlarged fragmentary horizontal sectional view taken in the plane of the line 10-10 of Fig. 9.

While the invention is susceptible of various modiications and alternative constructions, a preferred embodiment has been shown in the drawings and will be described below in considerable detail. It should be understood, however, that there is no intention to the invention to the specic form disclosed, but on the contrary, the intention is to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more specifically to the drawings, the invention is there exempliiied in the form of an illustrative turning machine in which it finds particular but by no means exclusive utility. The machine 20 comprises a base 21 having appropriate Ways thereon to support and guide a work holding table 22, which in the present instance is longitudinally movable therealong. Rigidly xed to the table 22 in any suitable manner is a work support 24 having adjacent its upper end an arm 25 extending longitudinally of the machine 20. The arm 25 has incorporated therein suitable detachable clamping means for securing thereto a hollow cylindrical work piece in the form of a rough machined piston P, the details of such clamping means being unimportant for present purposes. Mounted in overlyn'ng and straddling relation upon the base 21 is a bridge or saddle 26. The latter, while movable relative tothe table 22 and work support 24, may or may not be movable with respect to the base 21. The bridge 26 serves as a support for a tool head 28 and an electric driving motor 29 which transmits power to the tool head via belt 38 and pulleys 31, 32.

The tool head 28 of the machine 20 (Figs. l and 3) comprises a stationary body 33 which rotatably supports therein a tubular spindle 34 journalled in spaced apart bearings indicated diagrammatically at 35 and 36, respectively. The pulley 32 is drivingly connected to the left hand end of the spindle 34 (Fig. 10) as by means of a key 37 and a set screw 38. The end of the spindle 34 remote from the pulley 32 is of somewhat larger diameter than the opposite end portion andaterminates in an annular face plate 40. The latter has a tapered central socket 41 extending into the diametrically enlarged portion of the spindle 34. The socket 41 is adapted to snugly receive a hollow tapered shank 42 integral with a generally cup-shaped tool holder 43 which is drivingly mounted on the face plate 40. The opening of the tool holder 43 is of suitable size and depth to receive the work piece P as the latter is machined. In the present instance,` the tool holder 43 carries a single point cutting tool 44 mounted so as to project in a radial inward direction. The tool 44 may be adjustably secured in various radial positions, within relatively narrow limits, by means of adjusting screw 45 and locking plug 46.

Provision is made for moving the tool 44 in the proper v path to dene an elliptical cross section in the work piece P. This is accomplished preferably by mounting the tool head 28 with the longitudinal axis of its spindle lying in a vertical plane passing through the longitudinal axis of the work supporting arm 25 and work piece P, but skewed at a slight angle with regard to the latter axis. With the tool head thus mounted, the cutting tool 44 is caused Vto' move in an orbital path, the plane V(of which is inclined at a slight angle' to the axis of the arm 25'and the work piece P. This orbital path, although above, the bridge 26 has associated therewith a wedge broc/k 47 :-(.Fig.; having a ila-t upper surface 48 sloping downwardly in thedirection of the work holding table. 212.' Mountedat spaced' apart points along. the. surface 48 are a pair of cleats or abutments 49 secured in place as by cap; screws 50.( The underside of the bodyv 33. is fashionedvv with( a planev surface VLV which` Vabut's the surfacev 48, the surface. SL-being interruptedv by a pair of transverse groovesV 52.whieh house the cleats l49. To

permit. limited adjustment of the tool head 28. upon the wedge block 47, the grooves 52 are made substantially wider than thel cleats49; Set screws. 53 carried. by'. the body 33 and adjustable from the exterior; thereof serve toclampit tothe'cleats 49.

Y Means is provided for automatically regulating the Ysize ofthe cross section generated in the work piece P as the latter advances axially relative to the cuttingrtool 44'.l This is accomplished in theV machine 20 by the use of means for progressively changing=.the radial position Y' of the cutting tool 44A during its: period of engagement VWith the work piece P. Referring. more specifically to Figs. 3, 6,7 and 8, it will be perceived'that a tool carry-V ing arnr- 54 is pivotally secured'to the tool holder 43 as by means of a pin 55 located close tothe tool 44.

" The arm 54 runs generally parallela to the axis of the tool holder 43,. terminating in a bifurcated endA portion comprising spaced apart knuckles 56. A biasing spring 518 tends to urgeV the bifurcated end ofthe arm 54v toward anextreme radial outwardposition which corresponds to the extreme. radial inward position of the' cutting tool 44. The radial position; of the Varm 54 and the tool Y44 is governed' bymerans of a slide 59 housedwithin a transverse bore 60 in the tool head and adapted to recipro-f cate within narrow limitsl along-the. bore 60. Adjacent oneend thereof, the slide 59Y is formed with. a pair of diametrically Vopposed notches 61Y which receive the.V knuckles 56 of the tool carrying arm 54. To counter` balance the weight of' the arm 54, a'portion of the tool Y holder wall diametrically opposite the arm 54 is thickened as'y at 62.

For the `purpose of coordinating the radial position of Y the tool 44 andthe armv 54 with the relative bodily movement between.v the work support and the tool holder 43, a simple' yet highly Veffective arrangement is utilized.

7 Briefly, such arrangement comprises displaceable. means carried by the bridge 26 and adapted,rwhen actuated'. by the approaching work support 24, to rock the tool. carry- Y ingarm 54 Yand the tool 44 into the desired radial position. In the present instance, the bridge-.26 carries a linkage comprisinga control ybar 63, a rockable yoke 61,

andr aniactuating shaft 65 Vrotatable with the spindle 34VV butaxifa'lly slidable within'rthe, same. The bar 63 is. dis-- posed longitudinally ofthe machine 20, being. slidably supported. withina bore in the wedge block 47 by means of a pair of spacedV apart guide bushings 66. VThe latter serve: to maintain the bar. 63 inA alinement withk a bumper Y' 67` on the worksupp'ort 24, the bumper being adapted to accost thefree end of the-'bar 63 during the machining of the Work piece P. Y

The ro'ckable V yoke 64 (Figs. l, 3, 9 and I0) which Y translates the axial movement of the control bar 63 into movement ofthe actuating shafty 65, is provided with a pairrof bushings 68'; whichy Vengage a corresponding pairof fixed supporting trunnions 69, the latter being mounted on the bridge or saddle 26 as by means of suitable brackets. The depending end of the yoke 64 terminates in a Vpair of spaced apart bosses 70, each having an inwardly projecting pivot pin 71 threadedly secured thereto. `The pins 71 engage an enlarged abutment member 72 rigidly fixed to the control barV 63. The member 72 is provided with a pair of vertical slots 73 ofsuitable size to receive the inner ends4 of the pins 71 and to permit movement of the latter along the slots 73. The upstanding Vend of the yoke 64 also terminates in a'pai'r of spaced apart bosses.

74, each of the latter carrying an inwardly projecting pivot pin 75. having a slide block 76 journalled thereon. The

blocks 76 are arranged for coaction with a Yrelatively large and substantially rectangular abutment member 78 mounted on the shaft 65 adjacent the spindle driving pul- Vley 32. The member 78 is formed Withra relatively wide vertical groove 79fon-1either-side thereof togslidably receive theblocks 76. l

lrrordet to eliminate excessivewear which. might `other-'Vv j Y wise occurin the parts'connecting the Vyoke 64. andthe.V rotating actuating shaft 65, thev abutment member ,'18 is journalled on the shaft 65 as by means of a pair .of axially spaced bearings 80.. Theflatter arefmounted onda portionof the shaft 65 of reduced diameter and are locked. against axial movement. relative; thereto. by means of. a,l washer 81,A sleeve 82,. washer 84, and retainer bossi 85. The, bearings.. 80 are4 protected against the entry of chips` Y and other foreign material by means of end caps 86 rigf Y idly attached to= the member 78.

For theY purpose of effecting reciprocatory movementof the slide 591m response. to axial movement of the actuating shaft 65, the end of the latter adjacent the toolv holder Y '43l has a cam portion 88 integraltherewith (Figs..6 and 8).

The cam portionf. 88 is slotted longitudinally over a sub-V stantial portion of itslength so as .to dene a pair of laterally spaced camiingers 89 which straddle central portion 9020i the slide.. Each. of the fingers 89'is formed.

with a relatively flat. guide surface 91running substan tiall-yy parallel tof the'axis of the shaft 65 and. a; cam sur'- face` 92 having a moderate curvature along itsf length..

'Freely journalled on centralI portion .90 of the slide 59' .and adapted. to shift the latter through coaction with each..

of the cam surfaces. 92V isv av Vpair of follower rollersg 94.

Freelyv journalled on pfin;95.v fixed tothe tool head 435 and` adaptedtobear against. the guide surfaces91 is. a pair of reaction rollers 96. The latter are disposed in strad- Y dling relation withzthe: central portion ofy the slide, such portion beingformed with an oblong slot 98. to effect clear'- ance with: the pin, 95 which doesV not move with the slide..

With the arrangementtthus farrdescribed, the bumper 6710i the work support would engage the controlbar l63 only when moving to the left; as viewed=in Figs. 1 and 3l Thus, in order to1 position. the'. bar 63 accurately' When-theV worksupport 24 is moving in the opposite direction, some sort of. loading or biasing device must be utilized. IntheY f present. instance, suchdevice happens to bea fluid actuator v99fmounted on thebridge 26 and. connected with the Y. end of the control har 63 adjacent the yokeY 64. With this construction, when the` work support 24 moves tothe right (asviewed-in Figsj. l'and 3), the actuator99 causes the. Y Y' endV of the control bar 63 to remain in; engagement.

the bumper 67. Such actionV continuesV until adjustable stop j10`0 on the bar 63r accosts guide bushing V66'of'tl'1e I Wedge block 47.

. To protect thejmachine 20 against Vabnormai'movement Y of certain parts and also to facilitate the setting up ofan automaticV operating cycle, a plurality of limit switches and stops may be employed. Thus there is fixed to the workY holding table 22 a dog bar 102v (WFig. l)rwhich5earriesV a. stop dog 104 and various other. control dogs. (not shown).

Rigidly securedto the base 21 in .position to. be actuated 'Y by the dog 104 when the table 22 reaches its extreme. right hand Y'position (as viewedin Fig. l) is a klimit switch plunger 105.- The latter, when` actuated, serves to arrest thetable 22 against further rightward movement.

For the purpose of actuatingan appropriate control when the tool 44 has reached either extreme of its radial movement, there is operatively associated with the yokeL 64 a pair of limit switches 106, 108. The switch 106 is arranged for actuation when the tool 44 has reached its extreme radial inward position. .Under such circum-4 stances, the machine is in the condition indicated in Fig. 1 and the yoke 64 is inclined away from the work piece. To enable the yoke to trip the switch 106, the former is provided with a leg 109 having an adjustable tip 110 adapted to engage a roller 111 carried by a tripping arm 112 on the switch 106. When the tool 44 reaches its extreme radial outward position, as indicated in Fig. 3, the yoke 64 inclines toward the work piece and an extension 114 on the former accosts roller 115 and tripping arm 116 on the limit switch 108.

While the operation of the machine 20 will doubtless be readily apparent to those skilled in the art, a brief rsum thereof might be appropriate at this point. Assume first that the machine is in the condition of Fig. l with a work piece P secured skirt-Erst to the arm 25 and the cutting tool 44 at its extreme radial inward position. Upon initiation of the operating cycle, the tool head 28 is brought up to speed and the work holding table 22 slides toward the bridge 26. This brings the head end portion of the work piece into Contact with the tool 44 without causing engagement of the control bar 63 by the bumper 67. With further movement of the table 22 toward the bridge 26, the entire ring belt of the work piece P is given an elliptical cross section which is substantially constant axially of the work piece P. As the tool 44 commences to machine the skirt portion of the work piece adjacent the ring belt, the bumper 67 accosts the end of the control bar 63 and causes the latter to move leftward (as viewed in Figs. l and 3) toward its retracted position. Such action produces a proportional movement of the yoke 64, the actuating shaft 65, the cam arms S9, the slide 59, the tool carrying arm 54, and nally, the cutting tool 44. With continued movement of the tabel 22 toward the bridge 26, the tool 44 is caused to move progressively outward and travels in an orbit of ever increasing diameter. This causes the tool 44 to deiine in the work piece P a substantially elliptical cross section of gradually increasing area toward the skirted end of the work piece, thus producing the ared skirt indicated in Fig. 4. After the work piece P has been completely machined, it is permitted to overrun the tool 44 by a slight amount. By reason of the increasing steepness of the cam surfaces 92 as the extreme radial outward position of the tool 44 is approached, such action is suicient to move the tool clear of the periphery of the work piece and thus avoid an undesirable tool dragout line when the work piece is withdrawn from the tool holder.

l claim as my invention:

l. In a machine for forming pistons of elliptical cross section gradually increasing in area axially thereof, the combination comprising a base, a work support adapted to clamp a work piece with its axis extending along said base, a tool head, means for mounting said work support and said tool head for relative bodily movement along said base, a spindle journalled in said tool head for rotation about an axis intersecting the axis of the work piece and fixed with respect thereto but skewed with respect to the direction of said relative bodily movement, a tool holder rotatable with said spindle, a cutting tool carried by said tool holder and mounted for radial shifting movement therein, cam and follower means for shifting said cutting tool radially without changing the angle between the axes of said spindle and the work piece, and a motion transmitting linkage interposed between said work support and said cutting tool, said linkage being disposed in position to actuate said cam and follower means and thereby effect a progressive change in the radial position of said cutting tool as an incident to said relative bodily movement between said work support and said tool head.

2. In a machine for forming. axially flared pistons of elliptical cross section from generally cylindrical Work pieces, the combination comprising a base, a bridge disposed in overlying and straddling relation with said base, a work holding table mounted on said base for longitudinal sliding movement relative to said bridge, a work support on said table adapted to hold a work piece with its axis extending in the direction of said relative longitudinal sliding movement, a supporting block on said bridge, a tool head fixed to said supporting block and having an axis adapted to intersect the axis of the work piece at a relatively small acute angle, a hollow spindle journalled in said tool head and terminating in a face plate, a generally cup-shaped tool holder mounted in abutment with said face plate and bodily rotatable therewith, a tool carrying arm rockably mounted in said tool holder, a slide in said tool holder adapted to rock said tool carrying arm into various radial positions, a control bar slidably mounted in said supporting block and disposed for abutting engagement with said work support, an actuating shaft housed within said hollow spindle, cam means fixed to said actuating shaft for positioning said slide in response to axial movement of said shaft, and a rockable yoke pivotally mounted on said bridge and adapted to transmit axial motion from said control bar to said actuating shaft.

3. In a machine for forming axially ared pistons of elliptical cross section from generally cylindrical Work pieces, the combination comprising a base, a hollow spindle and a Work holding table mounted on said base for longitudinal sliding movement relative to each other, said spindle being rotatable about an axis skewed with regard to said longitudinal sliding movement, a work support fixed to said table adapted to clamp a work piece with its axis extending in the direction of said relative longitudinal sliding movement and intersecting the axis of said spindle, a bumper on said work support, a tool holder mounted for bodily rotation with said spindle, a tool carrying arm pivotally secured to said tool holder for radial movement relative thereto, a slide in said tool holder adapted to rock said tool carrying arm into Various radial positions, a reciprocable control bar disposed for engagement with said bumper on said work support, loading means for urging said control bar toward said bumper, an actuating shaft housed within said hollow spindle and rotatable therewith but axially movable therein, cam means xed to said actuating shaft for positioning said slide in response to axial movement of said shaft, and a rockable yoke adapted to transmit axial motion from said control bar to said actuating shaft.

4. In a machine for forming pistons of variable cross section, the combination comprising a base, a work support mounted for longitudinal movement on the base, a supporting block associated with the base, a tool head on the supporting block, a cup-shaped tool holder mounted in the tool head, said holder having a thickened wall portion running axially thereof, a tool carrying arm rockably mounted in said tool holder and located diametrically opposite said thickened wall portion, a cutting tool xed to said arm, a reciprocable slide mounted in said tool holder and adapted to rock said arm radially, follower means on said slide, cam means adapted to coact with said follower means to effect radial adjustment of said cam and said cutting tool, a control bar mounted in the supporting block and disposed for abutting engagement with the work support and connecting linkage between the control bar and the reciprocable slide and the tool holder, whereby relative movement between the work support and the supporting block will effect a radial adjustment of the cutting tool.

(References on following page) References Cited inthe He of this patent UNITED VSTATES Pfsljlabrlgs I WhitneyY Feb.x 26, 1889 Se:ott. Sept. 26, 1911 5` Banta Nov. 3, 191.4

Gosper 'Aug 2 1927 VStrindberg July 31., 1928 8 YVSnaid'cl' June 28, 1938 'Gest Nov. 11, 1941 YLmr Dec. 2, 1947 Y Staat Sept. 1'2, 1950 -Eatn Apr. 15, 1952 FOREIGN PATENTS.

Germat1y. Sept. 27, V1938

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