claim is: 1. The method of cutting longitudinally curved 45 tooth gears which comprises rotating a face @mill, which has a plurality of blades arranged part-way around its periphery only, in opemtive relation with a coiitinuously rotating gear blank, wMIe.' prodticing a back and forth movement of transla- 50- tion between the cutter and blank in time with the cutter ro@tation. 2. -The method of cutting a longitudinally curved tooth gear wwcll comprises employing a face mill, which has a plurality @of blades ar- 55 raliged around its periphery in c)@ne or more grgups with a space between the last blade of one group ap-d the first blade o-f another, and rota+,ing said cutter continuously iii engagement with a continuously rotating gear blank while producing a 60 back and forth movement of translation between the cutter and gear blank, said translatbry move-- melit being in timed relation Vilh the gear blank rotatiorn wbile a group of blades a7ce passing through a togth spa;ce of the gear blank, and op- 65 6rating to return the cutter to initial position while a blankspace of the cutter is abrea@st of the ge,,r blank3. The method of cutt'mg longitudinally curved 70 tooth gears whir-h comprises employing -a face mill, whigh has a plurality of blades arranged part-way around its periphery only, and rotating sadd cutter continuously in operative, relation with a continuously rotating gear blahk while pro- 75 wheel 30 and viorm 3', 'Ln time vp-'th the cam and @ In the preceding description, the osbillatory and

2,006,750' ducing a back and forth movement of trawl.ation between the cutter and blank so timed that during each revolution of the cutter, one completi@ eycle@of the tramlatory motion occurs. 5 4. The met-hod of cutting longitudiwmy curved, t4D6th gears which comprises@ employing a face mill, which has a plurality of blades arranged around its periphery in one or more grotips with a@blank, 'bet the last and first blades pace ween 10 of the group or groiips, and rotating sead cutter continuously in engagement with a continuously iotating gear- blank while produr,mg a relative@ translatory@ movement between the cutter and blank aboitt an axis angularly disposed to the 10 @axis of the blank, said trainslator@r mortion being timed tc) @the blaxik rotation while a: group of blades of the cutter are passing through a tooth space of the blank and acting to return the cutter to initial position While a blankspace of the cut20 ter. is abrea-ct of the gear blank. 5. In a ma-chine f(yr produe'mg gears, a rotatable work support, a rotary face mill cutter, a c-arrier on wh,'@ch one of -said parts is mounted, said cutter hai7ing a plurality of blades arranged in one 25. or mo@re groups aro-und its periphery with a blank@ space between the last and first blades of the group Gr groups, means for rotating the cutter@ and work support continuously on@ their respeetive axes, and mealns for impafting a back and 30 forth movement of traaislation to the carrier so timed that during movement of the carrier iii,one. direction, a group of blades of the cutter:is passing through a tooth space of the gear blank and the 6pposite during movement of carrier in the 35 direction, a blank s-pace of the cutter is abreast of tla@e geax blank, 6. In a mach'me for producing gears, a rotatable work support, a rotary face mill cutter, an oscillatory cradle upon vihieh one of said parts is 40 mounted,,,caid cutter having a plurality of blades arranged in bne 6.r more groups around its periphery with a blank space between the last and first blades of the group or groul@s, means for rotating said cutter and work suppgrt continuou.@l@ on their respective axes, a@ld@means for imparting 45 an oscillatory movement to the dradle so: timed that durir@g@movement@ of the Gradle in one dir6cti6n, a@ group of blades of the @cutter is passing@ through a tooth space-of the blahkl and during 50, movement of the cradle in the, opposite directioin, a bla , nk space of the cutter is abreast of'the ge@Eir bl%nk. 7. The method of producing a- longitudinall[y curved tooth gear @ which comprises actuating a 55- cutting tool,tg move the tool in a longitudinally curved path acro,--s the face of a continuously rotati-P-9 gear blank and then return the t,ool. to cutting position, and slmwtaneously- imparting C,o a back and forth. movement of. translation be-, tween the tool and blank, the forwgrd rndtion Of tianslation beihg at@ the same rate as @ the blank rdtation, dun'ng cutting, and the returii motion taking pl"e while the tool is clear of the blank, 6ry so that, by- reas'on of- the continuous. rotation of the blank,: the tool will enter a different tooth: space of the blank each time it cuts. 8. In 9. machine for producing lohgitudinally@ curved 'tooth gears, a work support, a fice iiiill rutter h9lviiii: @@ plurality of arruately arranged @,5 biades extending part-way around its periphery only with a gap between the last a@nd@th6 first blades which is of greater angular extent than the distance between successive blades, means;f6r rotating the cutter and meam for producing a 10@ relative movement between the cutter and w6rk@. su-pport while the gap in the cutt6r is abreast of the vrork to cause the blades of the cutter to: enter a different tooth space of the blank on @ach revolution of the cutter. 15 9. The method of cutting longitudinally curved togth gears which comprises rotating a face mill gear r-utteri which has a plurality of axcuately arranged blades,extending part-way around its periphery only so that there@is a gap between the@ 20, last and first blades of the cutt6r whic,h is of gfciater angular extent than the distance betwei6n successive blades, in Gperative relation with a geg@r blank and effecting a relative movement bet*een the cutter and blank wliile the gap in the cutt@-r, 25.@: is abreast of the blank to cause the blades of the cutter to enter La different tooth space of the blank on@@each revolution of thff cutter. 10. The method of producing a longitudinally curved tooth gear which comprises actuating @a 30 cutting tool to@ move it in a longitudinally curved path across the face of @ a continuously rotat-. ing gear blank and then return the tbol to.@cutting p6siti on and slmultaneously Imparting a relative -oscillating movement to the tool @and 35 blank about an axis angularly disposed to the axig' of the blank, the forward, motion of oscillation being timed to the blank rotation during@ cutting and the return motion of oscillatioii taking place while the tool is clear of tbe blank so that 40, by reason of the eontinuous rotation of the blilnk the tool enters a different -tooth space of the blank each time it cuts. 11. The method of cutting a longituldinally curved toeth geax which comprises employing a 45 face-mifl gear cutter having a Pliir@ity of bmes arranged thereon in an are concentric, with@ the cutter axis with at least tmo suceessivd blades spaced for suemsive engagement with cori@esponding side tooth surfaces of different teeth of 50@ a blank, each of said blades being so @elieved that all points in a top cutting edge Gf the blade are at the same radial distance from the axis of the cutter, and rotating said @ cutter cgntinuously in one direction in.operative relation with a geax 55@ b, ank while rotating the blank continuously in one direction and simultaneously producing a relative to a I nd ffo mcvtion of translation b@tween the cutter and blank wliich@ is timed to the blank rotation during pa.%We of bmes across the face 60 of,the blank and in which the return motion occurs while the space between blades, wmch are. arranged to:engage suecessive te e , is abri@ast of the blank B. E. SHLESINGER 65

Patented July 2, 1935 2,0,0'6,7 0 UN@ITED STATES PATENT OFFICE 2,00@6,750 METHOD AND APPARATUS FOR,CUTTING GEA.RS Bernard Edivard Sb-les'@nger, Irondequo@.t, N. Y., @,ssignor to Gleason Work@, R6chester, N. Y., corporation of Neiv York AppHeat,,-on Mar@h 10, 1933, Serial No. 660,281, The present invention, relates to methods and apparatus for cutting longitudinally curved to6th gears and particularly to a metho(i and apparatus for cutting longitudinally curved- toothZ tapered gears, such as spiral bevel and hypoid gears, ivith a tool of the face-mill type. Longitudinally curved tooth gears can be cut with recipr(>cating tools or with fo@ce mills-. F-or production work, the face-mill-i-s the tool usual10 ly _Irnployed and the method of cutting is an intermittent indexing process. The cutter has a plurality of equi-spaced, at-lnularly arra . nged cutting blades. It is alternatel y fed into - and withdrawn fro-rii engagenient with the blank. 15: During the per,@@ods of. feed, a to6th surface of a pair of tooth surfaces of the @ blank ar c e Om pletely cut and during the periods of withdrawal, the blank is indexed. The cutting operation is. completed when fhE@, blank has been indexed 20 through one revolution. At differe@,it times, efforts have been made to cut longitudinally- curved tooth gears with face mills in a continuous indexing,process. A contil'itious indexing process offers theoretically sev-, 25 eral advantages Tool-wear and the heat generated by the fr',--ction of cutting-are distributed evenly over all the teeth of the blank, for all the teeth are being operated on.simultaneously, and t,heoretically be-tter toot'n-spacing should result, 3o.; Moreover, '@he time lost through iiidexing and indexing w;@thdrawals is el,.' M4hate-d. While r6cipro@,ating i tools have. been employed successf,,illy in a coritini)ous indexin@. pi@ocess where provi,-Ion has been made to compehsate for the 35@ variable motion of. the too.1 u-,der Acttation of the crank, no satisfactory method has heretofore been devised.folcLit@ting,longitiidj--ially curved tooth gears with a face-,-jaill in a continuous indexing process. The diff,@e-alb-y I has been to secure 40 a satisfactory form of cutting tobl. In a --onti-illious ir@dexing process,: thd blank is rotating contiiiuolsly and it rotates away fr6m one side of a cutting blade and into the other side of that blade e!,s the blade moves across the 45 face of. the blank. T'nis caiises the cutting clearance or ar-gle between the sides of the blade and the tooth @urfac6s beiiig cut thereby, to change contiilliolisly as the cutting blade moves across th6 fac6 of the blar-k Hence, W.Lth an Y 50@ previously known continuous indexing'process, a standard foce mill c'iitter could not be ernploy6d. Various other forins of face-r,qill cutters *Iilch have 'oeen suggested, have not -p@oved @- practi-bal. Thus, cutters have -been made with blad6s whose 55 rearendshavebeenoffsetwithreferenceto'cheir (Cl. 90--I) cuttin g edges so as to secure the proper cutting Qlear ance, cutters have been made with blades @imil ar to stail-dard cutting blades but of higher pressu re, angle, elu-c. Iii the type of cutter first mei,4i 6hed, the blodes must be adjusted radially 5 after sl@a@,rpe-,iing and as,against the standard face mill cutter in wwch nb adjustment bf the I)lade s is r6quired, this has donstititted a decisive disadv antage. In the second -type of cutter raenti oned, there is too much clea@ance on one 10, side of the blade and g6ars of standard pressure ongle cannrt be produced. Other objections apply toother t3@pes of c6ntintious index, g cutters @n aiid so the continuous indexing process has never come into comriaercial use., 15 Tne primary purpose 6f the present invention is, to prov@de a,gear cuttii@g process which possesses all the adi7ar@tag6s of the continuous ind6x!n g process- so far a@'a@ccuracy of toouh spacing, distribution of tool wear.and of the fric- 20 t--Idpal heat of ciitting are concerned alnd in which a practical- form of' face-r-qill can be er@iployed, The itive.,ition is also applicable, however, to the cuttin g of gears with a reciprocating tool where th& tobl is swung in a curved path to pr6duce 25 the lenkthwise tooth shape. Afdce-riaill cuttiiig,-tobl made for use in the Prescnt inethod.has blades 6f exactly the same 'typo as are used in tiie standdrd face mill gear cutte@ of tl-te intermittent indexirig process. The 30 on Y difference is 'Lhat the blades are arranged oill@ paft-way. ar6und the ci7L cumference of the cuttlr. If a single se@ies of blades are employed, the@6 is a relatively l@rge space between the first and last blades of the series, while if the blades 35 are arranged in more than one series, there is a much' larger spa--e between the last blade 6f each qeri6s and the first blade of the next series than there is b6tween adjacent blades of a, series. The. invention will be des.,ribed particularly in 40 coni@ection with the cutting of gears with a, faceim'll. In this case, both the cutter and blank are roteled continuously in engagement and @imultaneously.a to and fro motl@on of translation is impaited between them. While a series of blades 45 of the cutter are passu-ig through. a, t6oth space of the blalik, the motion of translation is in one direction. When the blank-space between.two series of blades or betweei -i the first and last blades of the cutter is adjacent the gear blank, the 50 mg@tion of translation is in the opposite direction. While the s@ries 6f blades are passing through the tooth s@6eb 6f the blank the.. inotion of translation acts 'to comdensate -for or counteract the rotary m6tion of the blank and maintaiii a uni- 55

2,006 750 form angle of clearance between the cutting blades and gear blank as the blades move across the face of the blank, while, during the return translatory movement, the continued rotation of the blank operates to index the blank so that when the first blade of the next series or the first blade of the cutter rotates into position to out it will enter a new tooth space of the blank. No new equipment is required to manufacture 10 the blades of the face-miu cutter used in, the present invention. They are of standard form and they do not require adjustment eter sharpening. The present iiivention has the advantage over the lnterrnittent indexing process that no 15 periodic movement of withdrawal between the cutter and blank are required for indexing, the indexing mechanism itself can be eliminated, and, as above indicated, all of the tooth spaces of the blank are operated on simultaneously. 20 In the drawing: Figure@ 1 is a view illustrating diagrammatically the principal constructional features of one possible foiin of machine for cutting gears with a face-mill according to the present invention, Figures 2, 3 and 4 are side elevational views illustrating . diagrammatically three: successive steps in the cutting of ;a gear with th6 face-miu; and Mgures 5, 6 and 7 are end views of the cutter and blank, corresponding, respectively, to Flgures 2, 3 and 4. IO designates the cutting tool. This is provided *Ith a plurality of circularlya@ranged cutting blades I I which- are Identical with the blades ofa standard face nu'll gear cutter of @the intermit tent indexing t s ype uch as shown, for instance, in the patent to James E. Gleason No. 1,236,834 of ' @August 14, 1917. Instead of being arranged all @ the way around the 40, head, as, i@@ the case 'm the tool of the Gleason patent, the blades of the cutter 10 are arranged only part vay around the T)eriphe of the cutter ;ry head.. There is a relatively large blank space between -the last and first blades, 13 and 12, respec45@, tively, of the cutter. The blades between the blades 12 and, 13 are equally spaced from one another and there is no restriction as to their number as @long as the necessary ciitting clearance Is provided bet@veen successive blades. The gear blank to be cut is designated at 15. In Mgure 1 practically all the teeth of the blank h,ave @been cut@ but the other figures show the blank at the beginning of the cutting operation. In,the cutting operation, the cutter and blank 55- are brought into engagement and rotated continuously on@.their respective axes 10 and 17. Simultaneously there is a relative movement of t,o and fro translation produced between the cutter and the blank. This t6 and fro motion is 60 timed t(> the rotation of the cutter and, dui-ing cutting, to the rotation of the blank. P6r any taper,ed,gear, the translatory niovement will be abbui, aii axis angularly disposed to the axis of the blahk and for a spiral bevel gear, the axis 65 ab6ut which the translatory movement takes place will ordinarily intersect the blank axis in the.blaliik apex, that is, the transiatory movement will be an angular movement about the blank apex. This is th6 case shown in the draw'mg, 70 where the gear 15 being cut ls a spiral bevel gear and the axis 18 about which the translatory movement takes place intersects the axis 17 of the blahk iln the blank apex. Figures 2 and 5 show- the cutter IO beginning to 75 cut in the flrst togtb space 20 of the blank. The flrst blade 12 of the cutter is just taking its cut. The cutter is rotating in the direction indicated by the arrow 2 1, while the blank is rotating in the direction indicated by the arrow 22. The cutter and blank continue to rotate in these 5 respective directions throughout the whole of the cutting operation. As the cutter rotates on from the @p6sition s hown in Mgures 2.and 5, moving the blades, which follow the blade 12, @ through the blank, the cutter is swung relative to the blank 10 about the axis i 8 and in the direction indicated by the arrow 23. The mte of the swinging movement, as the blades cross the blank, is equal to the speed of rotation of the blank so that as each blade of the cutter crosses the face of the :15 blank the cutter and blank roU together. The result is that there is a uniform cutting clearance maintained during cutting between the blades and the side or sides of the tooth or teeth being cut thereby. @ When the last blade 1.3 of 20 the cutter has passed through the tooth space 20 of the blank, as is shown In Mgure 3, the cuttei will@ have been swiing in its translatory move-ment aboiit the axis 18 through an angle a an I d the axis 16 of the cutter will have been carried to 26 the positiqn.16, The blank-spacip of the cutter is now abreast of the gear blank as clearly sbown in Mgures 3 and 6. The cutter and gear blank continue to rotate in the' direciion of the arrows 21 and, 22 re- 30 spectively, but, as soon as the lilst blade 13 of the cutter has cleared the,blank, th6 translit6lu motion is rever I sed and the cutter is swun back about the axis IO to retiim it to Its initlea @posit risi tory. tion. The return ra a moveme iit of the 35 cutter is indicated by the arrow 24 in Mgure 3@ The continued;.rotation of the gear bla'nk 'dur-ing the time that the blank-space of the @cutt, er Is o be t During the return swing of the ctitt,@r about:"the 40@axis 18, the cutter w.ill be carried @back @@td Its initial position corresponding to that 4of Flig'ure, 2 and when the blade 12 agitin 66mrnences to cut the gear blarik wiD bave rotated far enough, as shown In Mgures 4 and[ 7-, so that the blade @ f 2 45" will enter a new tooth space 25 of the gear blank. Ai this moment, the swinging movement of the cutter will again be reversed @o that as the blades of the cutter once more pass across the blank, the swinging movement will again be in the direc- 50 tion of the arrow 23. Fiom th6 preceding description, it will be see that there Is @ complete oscillation of the cutter about the axis 18 for each r evolutidn of the cutter IC and that on each revolution of the @cutter, the r)5: blade& operate -in 9, new tooth si)ace of the blank.. When-the blank.bas made a c lete@ te-4olution OMP I the cutter will hav6 niade a series of cuts on each tooth of the,,blank corresponding in,numb6r to the number.of blades in the cutter. 60 'After a cl4t around on all the tooth-spaces of the. blank, the tool will be fed into. the' blank so that on the next cut around, it will remove further stock. The feed may be effected by a step-cam, for instance, or, if the tooth' rofiles 65 p of -the blank are b in e g generated, the feed may be effected by a step-by-step actuation of the generating mechanism after each revolution . of the blank. @ Flgure 1 illustrates diagramn2atically bow a70 si)iral gear, cutti ng machine might be built or modified to practice the present invention. The cutter 10 is joumaled in a rotary cradle 30 and may be adjustable thereon in the usual manner to produce the correct spiral angle and pressure 75: periphery of the, cutter. abreast of it causes the gear bl ank t udexed.@

angle on the teeth of. the bl-ank. These adjust--@ ments have not been shown for reasons of simplification. The cradle is motmted in a full-citcular bearing in the frame 31 of the machine. @ It is oscillated to impart the reqLiired translatory movement to the cutter by reciprocation: of a worm 32 which nieshes with a wormwheel 33 that is secured to the cradle. ,Thewo,-m32isreci-D,@ocatedby.acam33. TI-Lis 10 produces a -n oscillatory motiori. of the cutter about the axis of the cradle co,rresponding to the translatory motion abo,,i6 the axis I 8.already described. The cam 33 will be d--riven in time with the cutter rota,tion throu-gh aiiy suitable mecha-nlsm, the 15 cam making one revo@lutio@n for each revolution of the cutter @,.hown. If the blades of the cutter are arranged in inore than one series, then a cam of the type shown -tvould be, geal:ed to the cutter to mak(@ a nui-nber of revolutions during each revo20 lution of the cutter equal toi t.,le numbe,, of -ceries of blades in the cutter. The gear to be cut is secured to the @vork spindle 35 of the machine wl'li-ch is rotated by the worm 25 cutter rotations. When the ca-.n is so formed as to provide a quick-rettun mo ('ion of the cradle, the blades can be arranged around the greater portion of the periphery of the cutter, as sho@@vft. Were the cam 30 made so tl-,at the retui:n mGtio-Ti was at the same rate as tl,.e forward motibn, the blades would have to be arra.-,iged only half ivay around the cutter and the remaining half of the cutter would be blank. -ie gear I 5 @are to@ be 35' If the too'@,h surfaces o'L tl generated, the genera@.ing motion can be produced by imparting prefe.-casbl@y a stel,3- by-stop rotation to the worm 32. For this pi-irpose, t-he shaft:33, to wh,@ch the wortn is secuzed may be splined, as 40' ind@eat-cd at '@9 and on the spl-ined portion of the shaft there -,imy I)e mounted a worm wheel 40. This worm wheel may be T'Otated by a vvo= 41 and the worrr- may be rol@-ated intermittently, that is, after each revolution of the bia-nk, by any 45 swta,.blei me@-hanism. Rotation of the worm shaft 38 and worm 32 through the mechanism just described will impart a rota-,:y movement to the worm @vheel 33 and ergdle 1,1 which will combine with the osp-illatory motio.,i --eceived from the cam, 50 33 and will produce the generatiiig action through the timed rotation of th-- vior'@c. The splinin@ of the shaft 38 permits of -its rotation without interference ivith its reciprocation. While the r-radle 3,1 must swing ba@,k and fo-rth 55 once for each revolution of the cutter if there are only one seri.es of blades in the culter @.nd more often if there are a plurali-@Y of series of blades in the cutter, the a-mount of i-ts swing is much less thaii the amouT-l@L, of s,@7iiig of the cradle iT-l a 60 mafhine operating according to the intermi:Ltent indexing process. In the in@LeiTnittent @indexing process, the cutter rota;,' es a ve-ry @large @num-ber, of tirnes in generating a tool@h space, but t7-rie swirg of the cradle dur:ing the cu@tter rotation Is 65 through an angle large enoi)gl-i to roll out the tooth profile and usually is through several circular pitches of the blank. In the present invention, the cradle will be sv7ung t-hrough less than one circular pitch. Therefore, ivhile there are fewer 70 blades in a cutter used in the present inliention than in a cutter employed in an intermittent indexing operation, the cradle can be swung back and fotth faster iil the present invention tban in an intern-iittent indexing process and one fac75 tor compensates for the other so that the metnod 3@ of the present invention need not be slower than an interrnittent indexing process. - By spaci-ng the blades of th-- cutter far enough apart it would,be possible to swing the cradle back and forth betweenL the operation of success-ive blades or successive pairs of blades., Thus, si)ccessive. blades or successive a the cutter could be made to enter successive tooth spaces of the blank as the cutter and blank rotate, together.:, Going a step further, then, it will be 10 seen that instead of using a rotating motion -to carry t7ne cutting blades across t@-ie fa,.e of a gear,, blark; a reciproeotirg motion in a longi.tudinay curved patl-i miglit be emioloyed instead and a single tool used. In this case, the cradle would jr,@ have a to and fro motion with eacli reciprocation of 't,-@ie! tool and the 'iool would cul@ on successive cutting strokes in successive tooth slots of the bl@ank. During the non-cutting or return strokes of the tool, the to,-@l ivould be swung cl6ar of the 20,: blank, as in the usual practi-ce, and it would be diiri-ng these return strokes that the cradle ixiould be returned to ir.Litial position. -f.eed motiotis have been described as being im- 26: parbed to the cu'6ter. It will be. read,:Iy understood, however, tl--Iat they migb-t be irqparted instead to the,work. The. inventibn has been descri-bed in cornection with tl-ie cutting of spiral bevel gears but it 30@ will be readily understoc-d that it is applicable also. to t'iie cutting of splir, and poid gears. In ge7iera,', i-t may be said that the present applica-: tion is, ir-tended to cover &,iy adaptations, u8es, or embodiments of the inventibn fglloiving, in 3b general, the principles of tl-ie invention and inGluding such departures fror4i the present disclosure as come v7ithin knovin or customary practic@.- in the gear art and as may be applied, to the essential features hereinbefore set forth and as 40 fall within the gcope of the inve-@ition or the limits of the appended claa'ms Having thus described niy invention, what I