US1628864A - Machine for generating gears - Google Patents

Description

- 1,628 864 Ma? 17,192? 'N. TRBoJEv|c|-| yMACHINE FOR GENEATING GEARS Filed May '7, 1923 5 Sheets-Sheet i ww @Hoz 14u30 May i7, 1927.

N. TRBOJEVICH MACHINE Foa GENERATING GEARs -5 Sheets-Sheet 2 Filed May 1925 l'xfmdc Inra-luft @zug WM AMM/#mmm 17 192 May 7 N. TRBoJEvlcH yMACHINE FOR GENERATING GEARS' Filed May '7, 1923 5 Sheets-Sheet V3 I alm. P .m +de .a afm n .He .ma ab MSM May 17, 1927.

TRBoqEvlcH `Mamma Fon GENERA'rI/N'G GEARs Filed May v. 1925 5 sheets-.sheet 4 mw /wJ/fm MM Veoznelfv May 17, 1927.

N. TRBOJEVICH MACHINE FOR GENERATING GEARS Filed May '7.,1925 5' Sheets-Sheet 5 y I n a N alma? helical tooth type, may be produced by the' Patented May 17, 1927.

'UNETED STATES-fl lenses PATENT orifice.y i.

'NIROLA TRnoJEvIoH, or DETROIT, anonieme, .assrGNoR TO anunciav women ROCHESTER, NEW YORK, A CORPORATION or' NEW YORK.

Madama FOR GnNERaTrNe sans.

Application l'ed Hay 7, 1923, Serial No. 637,372, and in Canada April 19,v 1923.

The invention relates to hobbing of spiral bevel gears, and in particular to a hobbing machine embodying my novel method of ear generating, which method was describe at some length in my Patent Numbers 1,465,149, 1,465,150 and 1,465,151, issued August 14, 1923. i

In the drawings g Figure-1-5 and 7-8 aregeometrical diagrams illustrating the theory of the process ofBgenerating,

lgure 6 1s an elevati-on of a tapered hob en a 'n a s iral bevel ear, Fiilur'f) ig the plan iew of the bobbing machine the hob spindle and work spindle being shown in a common plane for. clearer illustration of the mechanism.

Figure 10 is the sectional view of the' feed spindle on the line 10-10 of Figure 9,

Figure 11 is a front elevation of the hob and feed spindles, the hob axis being swivelled about the axes 50.

Figure 1 2 is a rear end view of the machine, l

Figure 13 and Figure 14 show the neces sary adjustments of the pitch cone apeXes in the common tangent plane.

In order fully to understand the operation and the specific `features of this Amachine it is necessary briey to .recapitulate the basic principles of my method of ear cutting.

It is a well known fact t at the common spur gears whether of the straight or the bobbing process. From theoretical consid erations, it may be stated that the onliy)7 terion determining the possibility of ho a gear of any description is whether or no said gear meshes with a worm. vBecause if it does, the. gear may be `gtheoretically) hobbed, first, by makin a stee helical cutter an exact counterpart o the worm, second, by bringing said cutter in a tangential relation with the gear blank and by rotating both elements in a timed relation, and third, by imparting a relative'feedmovement, or a movement of translation to the cutter'.

The above named criterion i, e., the meeh- `ing of the gear with a worm, needs further explanation. Generally speaking there are possible two kinds of meshing or engagement between two gears, the rolling engagement when the pitch surfaces roll on each other bin without sliding and the axes arek co-planar, and the sliding engagement when the pitch surfaces slide and the axes are non intersecting and non parallel. The two kinds of engagement may also be distinguished by the relatlon of'4 their respective developments in the commontangent plane'. In the first case (the rolling engagement), both gears of hobbing only the sliding engagement is of interest.

This rinciple is illustrated in the rigs. 1 4. 1g.- 1 shows two spur gears- B1 and B2 in mesh, while their development in the .common tangent plane T is the rack B in Fig. 1". In' Fig.' 2 two helical gears C an D mesh with sliding engagement, and their respective developments C and D are shown in Fi 2". Fig. 3 shows two bevel ears E1 an E2 in a rolling contact, said evel gears having. the common development (or crown'gear) E Fig. 3. A bevel worm drive,(my discovery) is shown in Fig. 4, Thetapered Worm F meshes with a spiral bevel gear G with a sliding contact. In den velopment (Fig. 4") the lmaginary crown gears F and G yare distinct and are super osed in such a manner that their base circ es e and 0'.- touch and the common generators g coincide. Itis to be noted that in all four types of engagement the gen-- a mathematical dlscoveryj t at there isa certain family of spirals which if used as 'longitudinaltooth curves produce a system of bevel gears capable of meshing together in a dual fashion, namely with intersecting axes (a rolling engagement) as shown in Fig. 3l and Fig. 3a and with axes nonintersecting and nonarallel and slidin action as Ashown in igs. 4 and 4a. aid

s iials form the-family of general, or moditied involutes o fcircle and include the common involute of circle together ywith its iccv ' and the labridged involutes, and the Archi- .medean spiral.

modified involute. An important property. of these curves is that if any number of involutes e and any number of its derivatives" f are drawn from the same evolute d, the

L normals n, n2 etc. of the corresponding points when p=o the curve reduces to a' common' A1 A2 etc. will always pass through the same point A of the evolute.

Referrin of circle, t eyall can be expressed bythe following mathematical equation where a and p are constants and ip is a parametric angla In particular a is equal to-the C base radius while 7; is the modilicationas shown in'Fig.' 5. Themodiid involute as defined by the above equations has two spe-l cial cases, one of which is important as it makes this invention practicable. First,

involute of a circle. Second, when a-l-po the curve reduces to an'Archimedean spiral, that is to a spiral ofconstant lead. This latter property is the important one, because We are now able to include a tapered hob of constant pitch (an Archimedean spiral in development) in this system of spiral bevel gearing'.

According to the geometric laws governingv this system of gearing two bevel gears will mesh in an apex to apex position (Fig. 3 and Fig. 39) if both a and are'respectively the same, forboth deve opments. They will mesh withV a'sliding action as shown in Figs.`4 and 4a if the values of a are different while the modifications are-the same inabsolute value for both. The last case may be still further subdivided. If p is of the same design (either positive or negative) for both developments F G (Fig. 4a) the base circles c and c" touch internally; If the si of p is positive for one and negative for t e othersaid base circles touch each .now to the modified involutes subnormal. Furthermore, if the 'base circles of the generated gear and of the hob touch i' each other vexternally in development, the produced curves will have a positive modiii- `cation, that is, they will beextended involutes. They will be abridged involutcs" if said base circles touch internally. In my method I prefer to generate extended involuteS, as inthat combination the teeth of the hob fmove in an opposite ,direction to the rotation of the blank which is a desirable Acondition in milling. rFigure 6 shows a tapered hob-H of constant pitch, in engage-v nary' spur hob except that it is tapered. It

is provided with a number of axial gashes h and the remaining teeth j are relieved by a movement of a relieving tool in an axial plane, and perpendicularly to the side ofthe cone. The cone angle is preferably 30 (as shown), as that angle'is about themostA satisfactory for ordinary commercial purposes. For the same reason, the pressure angle is selected as 20." It. will be understood that if the same cone angle is selected for all hobs, the construction of the hobbing machine-is simplilied, as the tool head of the machine may be built to accommodate that particular cone angle.

Figure 7 ,shows the supeiI-posiedgtangent:

of a spiral plane developments J and bevel gear of ythe extended involute type, and of an Archimedean spiral hob, respectively. Said ligure shows. graphically that if this method .of gear generating is to be theoretically correct it is necessary that the pitch cone apex of thehob be placed at K,

and that of the gearv at L, and the distance K L be made equal to a-I-.pthe sum of the f base radii of the gear and the hob. Thel rack generator g is always perpendicular 'toy the apex distance L K at the point K, consequently it maintains its parallel relation to;

the parent involute generator,v g passing n through the pomt of tangeicy M 'of the i v base circles c1 and 02. The point M lies on the evolutes (base circles) to bothy systemsl and is therefore'analogous to `thepoint A shown in Figure f5. mathematically that the lines NlM, NZM, N .,M, are common normalsto the systems lof curves H and J at-the points N1, N2 and N3. Therefore, there is a complete tangency between4 the `corresponding tooth curves, and that tangency is maintained when the two developments H and J are rotated about their respective centers K and L at such a ratio that the two base circles c, and o, roll It is easily proved on each other without slipping. In that .case4 the points N, and N2 etc. of the rack generator g will have a linear translation equal to the circumferential velocity of said base circle c, and o, in the direction indicated by the arrow. It will be noticed" by inspecting said Figure 7, that while there is a complete tangency of the curvesl H and- J' along thegenerator g there is. also what might be termed a .secondaryA interference and` crossing of said curves further away. That interference, however, is only apparent, and would take place only ifboth the gear and the hob were plane developments, that is. crown gears. But in the present method of gear cutting the hob is always pinion Shaped,

and the coneangle and the pressure angle of the hob arealways so selected thaty secondary interference does not occur even if crown gears are being cut.

` From the preceding outline of the theory of engagement between the hob and the gear',

i va bobbing-,machine mayl be designed.

The-.characteristic 'feature of any hobbing machine embodying this invention is that it possesses three mam axes or spindles, two of which are intersecting while the third is inI a skew position (non-intersecting and nonparallel') with respect to either. In particular,- Fig'. 8, sh'owsxthe relativepositions of said-three axes; the feed, the gear, and the vhob axes. The diagram is self-explanatory as far as'it goes. In addition, it should be remembered that in order to generate correct gears, the pitch con`e apexesof the hob and the gear must be at the points Q and P respectively. Furthermore, either thel hob axis, or the gear axis,'must be rigidly attached to the feed axis. In my preferred construction, the hobY axis is so attached. Hence. when the feed axis is rotated in a direction as indicated by the arrow it carries the hob axis with it vtoward thegear axis.

' Therefore, the hob performs a planet-ary` motion, and its apex describes the modified base circle in the tangent plane. As it was formerly stated, the gear blank always rotates against the hob when extended involutes are generated. It is also vpossible to select the direction of the feed in such a manner that the large en'd of the hob always enters the blank first. This is of considerable practical importance, as then the large end of the hob performs the largest part of the work of the metal removing, thus rendering a tapered 'hob even more efficientv in thatrespect than the ordinary spur hob.

vFigure 9 to Figure 12 show the various r views of a typical hobbing machine embodying this principle of 'gear generating. n

The general organization of such a ma- A chine includes three spindles rotatable in a timedrelation together with means for adi justment of their relative positions with respect to the tangent plane] To this a compensatinggear or differential may be added to facilitate the proper timing of said three shafts; -The last named mechanism is not absolutely necessary for the correct operation of this machine as it is possible to connect three shafts with only two sets of change gears in any desired and positive ratio. VThe addition of the compensating gear, however, permits of engaging or disengaging the feed spindle at any instant,

and 'as often as it maybe desired without disturbing the proper meshing ofthe hob and the blank.

It will be noted that the above is nothing but Va 'most general type 'of the ordinary bobbing machine. In other wordsathe common hobbing machine is but' a special case of this machine, adapted to cut spur gears, that is, modified involute gears of infinite base radius, infinite modification and zero cone angle. In that case, thehob also must have an infinite modi ation, or polar subnormal, from which it ollowsthat the cone angle of the hob must be zero, that is, a spur hob of constant pitch is used. In my method, the feed is along a circular arc drawn from the apex of the gear. This feature translated into the well known spur system means that the feed of the hob is along a straight line, that is,I a lcircular arc havin-g` an infinite radius. The analogy may be .carried still further and goes to prove that my invention' consists `of broadening and generalizing the principle of ordinary gear hobbing ini'such a manner as to include the 4bevel gears also. Thus, according to this theory all hobable gears are lproduced by a hob of constant pitch and mesh with' a rack center distance, on the end of-the shaft 27. y

Thus, by increasing the number of teeth in the first change gear 25, and'bycorrespondingly reducing that number -in the gear 26,

the speed` of the whole machine-may be in.. v -creased relatively to the angular` velocit of the driving pulley 20. The transverse s aft 27 is mounted in two suitablel bearings 28 and 29` cast integral with the bracket 30, which bracket also carries the bearing 31 holding "the bevel gear 32, the function of vwhich gear will be explained later. on.y 4On the shaft 27 two mitre gears 33 and 34, held together with a s lined sleeve 35, are placed, and may be shi ted longitudinally and senov curely held in any such longitudinal position, thus permitting the mitre 36 to be driven either by the gear 33 or by the gear 34. In that manner the direction of the rotation of the entire machine may be reversed.

The cutter drive and adjustment.

The mitre 36 is keyed to the end of the shaft 37. One end of said shaft is housed in the bearing 38 while the other end is splined and engages the-corresponding sleeve of the gear 39. Said gear is housed in, and carried by the feed cylinder, cradle, head, face plate, or barrel 40, and remains in engagement with the shaft 37 when said cylinder is either moved lengthwise orrotated. From the sun Iear 39 the rotation is transmitted to the p anet idler 4l and the planet gear 42, both carried in the rearwall of the said cylinder 40. The pinion shaft 43 is also housed in the cylinder 40 and has two gears keyed thereto,.the planet gear- 42 and the bevel pinion 44. The last named pinion mates. with the spindle bevel gear 45, slidably mounted on the cutter spindle 46 to the end of which the hob or cutter 47 t is securely mounted. The manner of mounting of the hoben the spindle 46 may be vaccomplished in many various ways. Inl

my preferred construction, the hob has a tapered hole, and a threaded shank or boss near the large end (Fig. 6) into which bossa wide keyway or slot is cut. A corresponding hob arbor having a tapered shank snugly fits into the front end of the spindle 46 and the hob is drawn tightlyagainstthe same arbor by means of a threaded ring 48, while the hob arbor is drawn into the spindle by means of a suitable draw bolt.

The adjustment of the hob apex with respect to the tangent plane will best be understood from Fig. 9 and Fig. 11. The front end of the feed cylinder is machined to a plane exactly perpendicular to the axis o f said cylinder and therefore parallel to thetangent plane Y-Y of the machine. A swivelable cutter base 49 is mounted on said front end of the cylinder 40 and may be swiveled about the pivot 50, concentric with the pinion 44. The upper surface of said base is machined to a way 49a including exactly the same angle with the front end of the cylinder 4() as the cone angle of t-hehob to be used (in our casel 30 degrees). Therefore, when the cutter head proper 5l is mounted on the said top slide of the buse' 49, the hob 47 is always either tangent, or parallel to the plane YwY irrespective of the angular adjustment about the pivot 50 or the longitudinal adjustment in the inclined plane- The angular adjustment is effected by releasing the bolts 52 and swiveling the base to a predetermined angle from the center line of the machine either to the right (as shown), when right hand gears are generated or to the left-for left hand gears, and then tightening the bolts 52 against the corresponding T slots 53. As the distance of the pivot 50 from the center line of the machine is a constant of the machine, and thereby known, theangle 'to which the base 49 is to be swiveled to suit any particular modified base radius (a-l-p) may be easily determined by calculation, as it will be understood.

The longitudinal adjustment is accomplished first by releasing the bolts used for clamping the cutter head 51 `to the base 49 and the spindle 46 to the bevel gear 45 by moving the head 51 in its slide by means of anl accurately cut screw '54 and the graduated dial 55 until the apex of the hob falls into its proper position, the point .of tangency ofthe cutter axis with the base circle, and by clamping the head and the-spindle in that position. It is to be noted that during saidlongitudinal adjustment the bevel gear '45 does not move longitudinally with the cutter head 51 but stays in engagement with its mating pinion 44.

There is one more adjustment necessary, namely to regulate the depthv of the cut, or,

to bring the pitch cone of the hob 47 in tandirectly bolted tothe feed spindle 40 but it it to house the corresponding three drive screws 58. On the outer ends of said three screws, three planetary gears 59 arekeyed, said gears being constantly in mesh with the sun gear 60, mounted on a shank 61 integral and concentric with the worm gear 56.

The sun gear 60 is preferably made integral with the bevel gear 62, the latter engaging the bevel pinion 63. Said pinion is keyed to a shaft which is housed in the bearing 64, and carries on its other extremity a handwheel 65 keyed thereto. The other ends of the screws 58 are threaded and engage the corresponding internally threaded bosses 66 of the cylinder 40. Three check nuts 67 serve to clamp said screws to the `body of the cylinder 40.

The worm gear 56 is housed in the upper and lower ring castings 68, and 69, the walls of which are accurately machined on the inside to hold the worm gear 56 in position, and also to act as thrust bearings for the same. In order to make an adjustment lfor the depth of cut, the check nuts 67 are `has three equally spaced bearings 57 built in made, the check nuts 67 are tightened, and the hob is ready for cutting of the gear.

The feed mechanism. Mitre 32 is driventby the mitre 71 keyed 'to the shaft 37. Said mitre 32 is keyed-to a shaft '72 housed in two suitable bearings 31 and 73. Shaft 7 2 is inclined to the central plane'of the ,machine to an an 'le of about 45 degrees and carries the beve pinion 74 keyed to its tlower end. Bevel gear 75, on the shaftv 76, engages said pinion 74 and transmits the rotation to the wrm 77 mounted on said shaft 76, and also to the worm gear 78. The shaft 79, carrying the last ynamed worm gear, is mounted in the bearing 80 andit carries on itsouter end the first feed change' gear 81. Change gears "82 and 83 are mounted on a swing sector (not shown) and the last gear 83 engages the driven change gear 84, mounted on the hand wheel shaft 85. Said shaft is -mounted in the bearings 86 and 87 and in the bearings 88 and 89 underneath the main worm to the shaft 85, or disengaged, as desired, by

` se, se, and e4 an .means of a hand o erated clutch (not .shown "rotate Thus the fee cylinder 40 may be at any desired rate by power, by the feed chan e gears 81, again, it may e operated by hand through the hand 'wheel 91.

.The deferment The first, differential change gear 90 engages the change gear 92 from which the properly selecting :rotation is transmitted through change gears 93 and 94, the shaft 95 housed in the beari-n 96, to a worm of comparatively large iameter and. small angle of thread 97. Said Worm 97 fengages the gear 98, and thereby controls the rotation of the first differential sun gear 99 and is rotatable with respect to the shaft 76. The differential spider 101 is keyed to the end of the shaft 76v and kept there in position by means of a thrust collar 102. In said spider 101 four bearings are formed to permit of mounting there of the planet pinion shafts 103, carrying two sets of planet pinions keyed on their respective ends, namely, the pinions 104, en-

' gaging with the sun ear 99,'and the pinions 105, engaging with t e driven sun gear 106.

The action of the `di'erential gear employed in this'machine is fully analogous 'to that employed in' same of the ordinary gear hobbing machines designed for cutting of helical spur gears.l The object is, as already stated, to impart to the gear blank the sum (or the difference) of two rotations s'imul-i4 taneously, first, tov keep the gear blankfin; timed relation when the Vhob i-s rotated aboutv its own axis, and second, to maintain saidtimed relation when the hob is bodily translated in the tangent plane, to producethe feed. These two elements of rotationmust be, naturally, compounded correctly and con;A tinuously at every instant during` the process of gear cutting, and the arrangement as -shown in Fig. 9 `and Fig. 11 accomplishes that purpose. If the (p -lley 20 is heldfast, and the feed gear 84 isengaged, the spider 101 will remain stationary when the hand wheel 91 is v 'F operated. Through the changegears 90, 92, 93, 94, the woun 97, the worm gear 98, the sleeves 100, the sun gear 99, the differential pinions 104 and 105, and the drive sun gear 106 a rotationis imparted to the shaft 107 and thence to the blank. Again through the worm 70 and the gear 56 the feed spindle 40 is simultaneously rotated which imparts a movement of translation to the hob 47 as previously described. By a y'proper selection of the differential change gears to 94 this element can be compensated for, therefore.

lRegarding the selection' of the last named inder 40 is rotated, it ma be considered that thetangent plane Y is carried with it, that is, rotates with it. Hence, the ear blank should be rotated as if -its-were rol ng with said tangent vlanewithout slipping. However, when said) cylinder 40 isl rotated, the hob 47 also will slightly rotate on its axis even if the pulley. i's held' fast due to the fact that the sungear 39 is stationary and the drive gears 41, 42,44, and 45,2"receive a rotation owing to their planetary position with respect to said gear 39. Thus, the

(imaginary) rotation of the tangent plane Y-Y' is slighty different from that ofv the. cylinder (the i lconditions about one er cent) and for close work this must be ta en into consideration los iference is under ordinary when a calculation for change gears is made.

` In order to, examine the second element of rotation vtransmitted by 'the differential mechanism, we again disengag'e the feed gear 84, butnow hold the .handwheel 91 fast, and rotate the pulley 20. In that case the-sun gear 99 remains stationary and the differential mechanism acts as if it were an Ordinar lspeed reducing e -icyclic gear.- The shaft 6 being keyed to t e spider 101 rotates the same, and due to the fact. that Ythe sun gear 99 is stationary, and has a`different number of teeth from the driven sun i rotation described above are imparted to the differential simultaneously, ,they will not interfere with each other, but will4 be correctly and continuously compounded at every instant andthe shaft 107 will alwa. s

receive the sum or the difference, as t e case may be, of the two rotations.

Tw lwork dri/ve adjustment.

The arrangement forholding` and adjusting the ,blank in this machine is designed along well established lines found in the majorit of the bevel gear cutting machines. The on y' novelty will be found in 'the increased range of angular adjustability of the work arbor.- While in ordinary. bevel gear cutters that range is usually 90, in,

, this `case the range is 180 that is half a circle. By the virtue of this increased ad- ]ustability it is possible to generate inthis machine commercial ears of all sizes withn in the range of machine, right or left hand, in such V-a manner that first, the hob always cuts on the upward swing of the feed cylinder; second the lar e end of the hob always enters rst, an third the blank always rotates in Athe opposite direction (against the cut ofthe hob). The observation of these practical requirements in the desi n of this machine have greatly added to t e utility of this method. i

The shaft 107 carrying on one, end .the

i. driven vdifferential sun gear 106, and the mitre `108 on the other, is housed in `two bearings 109 and `110. A cross shaft 111 carrying the mitres 112 and 113 on opposite ends, brings the rotation to the apex or center of the machine. A short vertical shaft carrying two mitres 114, transmits said rotation through the mitre 115, and the swingingshaft 116 to the index change gear 117. From there another change gear 118, keyed to the end of the splined shaft 119, is driven, thus impartin the rotation tothe .final drive pinion slidaly mounted on the shaft 119 (not seen in Fig. 9) the final drive gears 120 and 120a and the'work spindle 121.

' The blank to be cut 122 is mounted in the customary way on the-face plate=123, and is drawn tightly against the same by means of the drawbolt 124. The work spindle 121 is mounted in two bearings 125 and 126 integrally cast with the upper work slide 127.

The lower work slide 128 may be swungl about the apex ofthe machine on the semicircular Atable 129, the latter being provided with a number of circular T slots 130. The upper portion of the slide 128 is formed to a rectangular way, the axis or center line of which is always in a vertical plane'passing through the apex of the machine, and

the upper work slide 127 is fitted carefully sition the work spindle is brought to, its

axis is always'co-planar with the feed axis,v

and intersects the tangent plane Y--Y at the apex of the machine.

From this description theadjustment of I the` gear blank willbe understood. The

lower slide is swiveled on the semicircular apron' ,129 until the pitch coneof 4the blank is lparallel to the tangentplane Y-Y. In that position the lower slide isclamped against the T vslots 130, with suitable bolts and nuts. Then the .longitudinal adjustment of the cutter spindle is effected, that is, the pitch cone of the blank isbrought into tangency with the planel Y-Y., A train of suitable index changev gears is selected, and the blank is ready to be cut. I

What I claim as my invention is z" 1. In a gear hobbing machine, the combination of a work spindle and a hob spindle having their axes non-intersecting and nonparallel, a feed spindle for rotating one of ence a said spindles about an axis intersecting the axis of said work spindle and in acute angular relation to the axis of said hobspindle, and means for rotating said 'three spindles to maintain a predetermined timed relation between said hob and work spindles.

2. In al gear hobbing machine, the combination of a work spindle and a hob spindle having their axes non-intersecting and nonparallel, means for rotating said spindles in predetermined timed relation, means for rotatively feeding one of said spindles about an axis intersecting the axis of the work spindle and in acute angular relation to the axis of the hob spindle, and compensating means for maintaining said timed rotation during therotation ofsaid feeding means.

3. In a gear hobbing machine, the. combination of a work spindle, and a hob spindle having their axes non-intersecting and non-parallel, a feed spindle for rotating one of said spindles about an axis intersecting the axis of said work spindle and. in acute angular relation'to the axis of said hob spinhaving their axes` intersecting in. a common plane, a hob spindle mounted on saidfeed spindle having its axis at an t.acute angle with a plane perpendicular with said'l feed axis and non-intersecting' and non-parallel with the-axis of said Work andfeed spindles,`

and means for rotating said three spindles in a predetermined timed relation.

5. In a gear bobbing machine, the com bination of a work spindle and 'a feed spindle-having their axes intersecting in -a common plane, .a hob spindle mounted on said feed spindle having its axis at an acute angle` vvith a plane perpendicular to said feed axis and non-intersecting and non-parallel with the axis of said work spindle, means for rotating said Work spindle and hob spindle= =in a predetermined. timed relation, means spindle.

for rotating said feed spindle, and compensating means for maintaining said-.timed l the axis of said work spindle and in acute angular relation to the axis of said hobk spindle, means foradjusting the hob spindle in a plane transverse-tothe axis of said feed spindle, means for adjusting said Work spinldle in an axial plane relative to said feed axis, and means for rotating said three spin- .dles to maintain a predetermined timed relation between said hob and Work spindles.l

7. In a gear bobbing machine, the combination vv-ith a feed spindle, and a work spindle having their .axes'intersecting ina common plane, means -for adjusting said Work spindle about the point of intersection of said axes, a hob spindle mounted on said feed spindle and having its axis in a plane at an acute angle to said feed axis, a tapered hob on said spindle, means for adjusting said hob spindle to' set the apex of said hob a predetermined distance from said feed axis, means for rotating said hob spindle and Work spindle in a predetermined timed relation, means for .rotating said feed spindle, and compensating means for maintaining said timed relation during the rotation of said feedv spindle. v

8. In a gear bobbing machine, the combination with a Work spindle and a feedk spindle having their axes intersecting'in a common plane, means for adjusting said work, spindle about the point of intersection of said axes, a hob spindle mounted' on said feed spindle and l'i'aving its vaxis in a plane at an acute angle to said feed axis, means for rotatively adjusting said hob spindle in its plane to set'the axis thereof a predetermined distance froln said feed axis, means hobbing machine, the comi.

for adjustingi hob spindle longitudinally ofthe axis of said feed spindle, means for rotating said hob spindle and work spindle in a predetermined timed relation, means for rotating said feed spindle', and' compensating means for `maintaining said time relation durinlg the rotation of said-'feed spindle.

9. n a gear hobbingjmachine, the combination of a Work spindle and a feed spindle having their axes intersecting in acommon plane, a hob spindle mounted on said feed spindle having its axis in aplane at an acute angleto said feed axis, means vfor rotating said hob spindle and work spindle in a predetermined timed relation, means for rotatively adjusting said hob spindle in its plane to set the axis thereof a predetermined dlstance' from said feed axis, means for rotatively adjusting said work spindle, and

means for rotating saidthree spindles to maintain a predetermined timed relation between said hob and work spindles.

10. In a gear hobbing machine, the combination ofv a feed spindle longitudinally adjustable to providejfor the depth of cut 'and' rotatable about its axis to provide the feed.

motion, a hob spindle carried by said feed spindle having its axis intersecting'a certain plane perpendicular to the feed axis, means for axially adjusting said hob spindle, an axially adjustable work spindle having4 its axis intersecting said feed axis, said Workspindle being laterally adjustable with respect to said plane, a tapered hob upon said hob spindle having a cone angle such that 1t may be adjusted to a position tangent to said plane, sald hob being provided With cutter Ateeth arranged in an Archimed'ean spiral, means for vadjusting said hob spindle to set the. apex of said hob a' predetermined fdistance from said feed axis,'means for rotating said hob spindle and said Work spindle to maintaina predetermined timed relation, and means for rotating said feed spindle to advance the hob across the Work `upon said4 work spindle. i

11. In a gear bobbing machine,'the combination of a work spindle and a hob spindle. having their axes non-intersecting and nonparallel, a rotary spiral hob mounted upon said hob spindle. said hob being provided with cutting teeth of the modified involute type, means for rotating said spindles 'in lll) such a manner that said hobl and the Workl v upon said work spindle are tangent to a common plane on opposite sides thereof. 12. In a gear bobbing machine, the combination of a pair of spindles, a rotary spiral hob mounted upon one of said spindles, a gear blank mounted on the other of said spindles, means for adjusting said spindles' in acute angular relation such that said hob and said blank are tangent to a common plane on opposite sides thereof, and means for rotating said spindles in a timed relation and means for moving one of said spindles about an axis lying in the same plane as the other spindle.

13. In a gear bobbing machine, the combination of a work spindle, a hob spindle, a tapered hob of themodiiied involute type mounted upon said hob spindle, means for adjustin said spindles in such a manner that the ob and work are tangent to a common planeon opposite sides'thereof, means for rotating said spindles in a timed relation, and means for feeding said hob into said blank. j

1&In a gear hobbing machine, the combination of a work s indle, a hob spindle, a tapered hob mounte upon said hob spindle, means for adjusting said spindles in an acute angular relation to eachother and to a plane tangent to the hob and the work, means for adjusting the distance between the corresponding points of intersection of said hob spindle and Work spindle axes with said tangent plane, means for rotating said spindles in timed relation, and means for feeding the hob into the blank.

15. In a gear hobbin machine, the combination of a work spin le, a hob spindle, a blank mounted on said work-spindle, a hob mounted on said hob s indle, said hob having cutting teeth of t e modified involute type, the member mounted upon one of said spindles beingA of conical form, and means for adjusting said spindles into acute angular relation such that said hob and said blank are tangent to a common plane upon opposite sidesthereof, means for rotating said spindles in a timed relation, andmeans for feedingsai'd liob into said blank.

16. In a gear hobbing machine, the combination of a .work spindle, a hob spindle, a tapered hob of the modified involutel type mounted upon said hob spindle, a bevel gear blank mounted on said Work spindle, means for adjusting said spindles in an acute angular relation to each other and to a plane tangent to said tapered hob and saidvconical. blank, means for adjusting the distance between the corresponding points ofv intersection of said hob spindle and Work spindle axes with said tangent plane, means for rotating said spindles in a timed relation, and means for feeding said hob into said blank.

17. In a gear hobbing machine, the combination of a work'spindle and a hob spindle, a blank mounted on said work spindle, a hob mounted on said hob spindle, said hob having cutting teeth arranged in acurve, -the development of which is a modified involute of a circle, means for adjusting said spindles such that said hob and said blank are tangent to a common plane upon opposite sides thereof, means for adjusting the distance between the respective points of intersection with the tangent plane of the hob spindle and Work spindle axes, means for rotating said spindles in timed relation, and means for feeding said hob into said blank.

18. In a gear hobbin machine, the combination of a work spin le anda hob spindle, a hob mounted. upon said hob spindle, a blank mounted upon said work spindle, said hob and said blank being tangent to a common'plane upon the opposite sides thereof, and said hob spindle and said Work spindle beinglarranged in acute angular relation to each other and to the common tangent plane, means for rotating said spindles in a timed relation, and means for simultaneously feeding the hob relative to the blank to increase the depth of cut.

19. In a gear bobbing machine, the combination of a pair of spindles arranged in acute angular relation to each other, a hob upon one spindle having cutting 'teeth arranged in a curve, which in development is a modified involute of a circle, a blank mounted upon the other of said spindles, one of said members upon said spindles being of conical form and arranged tangent to a plane which is tangent also'to said other member, means for rotating said spindles in timed relation, and means for feeding the hob relative to said blank. Y

20. In a gear cutting machine, a blank support, a hob support, a hob having its cutting portions arranged in a spiral of Archimedes mounted on said support, means for-positioning the hob and blank supports so thatlthe axis of the hob is spaced from the calculated base circle of the gear by a distance equal to the polar subnormalof the' hob, means for rotating the hob and blank in timed relation and means for si- `multaneously imparting anadditional relative movementv between hob i and blank about the apex of the blank.

21. In a ear cutting machine, a blank sup-v me es, mounted on said support, means for positioning the hob and blank supports so that the axis of the hob is spaced from the calculated base circle of the gear to be cut, by a distance equal to the polar subnormal of the hob, and means for rotating the hob and blank in timed relation.

22. In a machine for producing vgears from conical gear blanks, a blank support, a hob support, means for positioning the hob and blank supports so that the pitch surfaces of hob and blank are tangent to a common plane with t-he axis of-the hob projected into the tangent plane perpendicular to a line connecting the hob and gear apexes and means for rotating the hob and blank in timed relation.'

23. In a gear cutting machine, a blank support, a hob'support, a hob, the normals to whose thread at the pitch surface in development intersect in a single point, mounted on said hob support, means for positioning the hob -and blank supportsso that the point of intersection of the hob normals will'lie on the imaginary base circle of the gear to be cut and means for-rotating the hob and blank in timed relation.

24. In a gear cutting machine, a blank support, a hob support, Vmeans for position- ,ing the hob and blank supportsothat normals to the hob' threads and the teeth to be produced Aon the blank along a line l ing in the pitchsur'faces of both hob and b ank in developmentintersect in a single int, and means for rotating the'hob and lank in timed relation. l l

25. In a machine for bobbing gears whose teeth are curved longitudinally along spirals Aof the modified-involute t pe, a ,blank .support, a hob support, a 'ho of themodied. vinvolute type mounted thereon, means for positioning the hob and blank support so that in development the base circles from .which the longitudinal curvature of hob thread and blank teeth are derived are tangent and meansl for rotating the hob and blank in timed relation.

26. In a gear cutting machine, ablank support, a hob support, a hob, the normals to whose threads along a generatrix of its pitch surface intersect in a point, mounted on said hob support, means for positioning .the hob and blank'v so that in development the hob apex, the blank apex, and thepoint of intersection of the normals, all .lie in the same straight line, and means for rotating the bob and blanks in timed relation.

27. In a gear'cutting machine, a blank support, a hob support, a taper hob mounted on the hob support, means for positioning the hob and blank supports so that the` pitch lines of hob and blank, in development, are tangent along a .straight contact line between the pitch .surfaces ot hob and blank, and means for rotating the hob and blank in timed relation.-

28. lIn a gear cutting machine, avrotatable blank spindle, a`hob spindle, a taper hob mounted on said spindle, a supporting head, a hob carrier pivotally mounted .on said supporting head and having an outer face inclined with reference tothe supporting head at an angle equal to the cone angle of the hob, supporting means for the hob spindle siidably mounted on said hob carrior, means for positioning the hob and blank so that their pitch surfaces are tangent to` a common plane and means :for rotating the heb and blank in timed relation.

22. In. a gear cutting machine a rotatable blank spindle, a supporting bead angularly movable about an axis passmgthrough the et blank b said blank l. :il

"spindle, a 'drive shaft extending through said head and parallel to said head axls,

a cutter base mounted on said head and pivotable about said drive shaft, a hob spindle rotatable on said cutter base, means for operatively connecting the hob spindle with the drive shaft, and means for rotating the drive shaft, supporting head, and blank spindle in timed relation.

curved teeth of said basiccrownl gear, sub- V stantially as set forth.

31. In a machine' of the class described,

the combination of a. rotary blank support,

va head an ularly movable' about an axis extending t rough the apex of a blank carried by said su port, a rotary hob adapted to engage said lank having its rotary axis 'olset from the axis 'of said head, a member carrying saidhob mounted upon the aforel said angularly movable head, and means for adjusting said member to vary the degree of offset of hob axis and head axis, -Substantially as set forth. ,l

32. In a machine for hobblngbevel gears,

a hob support, a taper hob mounted on the.

support, a blank support, means for positioning the hob support so that the axis of the hob extends diagonally across the face of the blank, means for rotating the hob and blank supports in timed relation and means for imparting an additional relative rolling movement between thehob and blank supports.

33'. In a machin mounted on said support, a blank support, means for rotating hob and blank supports in timed relation and means for imparting v an additional relative lmovement between the hob and blank ,supports in the manner of a relative intermeshing rotation between a crown gear and the gear to be out.

34. In a machine for cutting curved tooth bevel gears'a rotatable blank support, a tool carrier, a rotary hob mounted thereon, means for positioning the blank support and tool carrier relatively to one another so that the pitch suriaces oil the hob and blank are tangent to a common plane means for rotat-s ing the hob and blank supports in timed relation and means for imparting an additional relative movement between the heb lll) e for hobbing bevel gears, i a hob support,- a hob of constant lead tating a conical blank carried thereby, a

face late rotatable about an axis -intersecting t e axis of said shaft, a second shaft carried by said face plate, a hob cutter carv ried by said second shaft, means for rotating said face plate adapted. to carry the hob cutter into changed position with respect to the blank, and means comprising a differential mechanism for rotating the hob cutter in continuously operative timed relation to the rotation of the blank as the angular p0- sition of the second shaft is changed by the rotation of the face plate.

36. A gear cutting machine, comprising a shaft, means for driving said shaft for rotating a conical blank carried thereby, a face plate rotatable Aabout an axis intersecting the axis of said shaft, a-second shaft vcarried by said face plate and adjustable longitudinally thereon, a hob cutter carried by said second shaft, means for rotating said face plate adapted to carry the V"hob cutter into changed position with respect to the blank and means comprising a differential mechanism for rotating the hob cutter in continuously operative timed relation to the rotation of the blank as the angular position of the second shaft is changed by the rot-ation of the face plate.l

37. A gear cutting machine, co-mprising a 'r shaft adjustable by a swinging movement in a plane about an axis at right angles to.

said plane, means for driving saidshaft in its adjusted position Jfor rotating a conical blank carried thereby, a face plate rotatable about an axis lying in said first named plane, a second shaft carried by said face plate and adjustable longitudinally thereon, a hob cutter carried by said second shaft, means for rotating said face plate adapted to carry the hob cutter into changed position With respect tothe blank, and means comprising a differential mechanism for rotating said second shaft and said hob cutter in continuously operative timed relation to the rotation of the blank as the angular position of 4the second shaft is changed by the rotation of the face plate. j

'38. The method of cutting spiral bevel gears which comprises rotating a conical blank, swinging a hob cutter circumferentially across the conical face of the blank, applying power to the hob cutter through a uniformly operating driving mechanism for rotating the hob cutter, and applying power additionally to the hob cutter through a differentially operating driving mechanism whereby the rotation of the hob cutter is kept in continuously operative timed relation to the rotation of the blank.

39. In a machine tor producing longitudinally curved teeth on the side face of a4 ear blank, a hob support, a hob of constant pitch rotatably mounted thereon, a blank support, and means for rotating the hob and blank in timed relation.'

40. In a machine for producing longitudinally curved teeth on the side face of a gear blank, a hob support, a taper hob of constant pitch rotatably mounted thereon, a, blank support, and means -for rotating the hob andl blank in timed relation. l

41. In a machine for producing longitudinally curved'teeth on the side face of a gear blank, a hob support, a taper hob rotatably mounted on said support,.a blank support, means for adjusting the hob 'support so that the axis of the hob extends diagonally across the face of thev blank in offset relation to the blank apex, and means for rotating the 8 1 hob and blank in timed relation.

42. Ina machine for producing longitudinally curved teeth on the side face of a gear blank, a blank support, a hob support, a hob of constant pitch mounted on said hob support, means for adjusting the hob support. to position the hob soth-at its axisextends diagonally across the face of the blank 'in offset relation to the blank apex, and means for rotating the hob and blank in timed relation.

43. In a machine for producing longtudiynally curved teeth on the side face of a gear blank, a blank support, a hob support, a` taper hob of constant pitch rotatably mounted thereon, means for adjusting the hob support to position the hob with its axis extending diagonally across the face of the gear blank in oi'set relation to the blank apex.;

and means for rotating the hob and blank in timed relation.

44. In a machine for producing gears, the combination of means 'for supporting a tapered gear blank, a hob of constant pitch, means for rotating the hob and blank in intermeshing timed relation, and means for feeding the hob and blank relatively to each other.

45. In a machine for producing gears, the combination of means for supporting a tapered gear blank, a taper hob of constant pitch, means for rotating the hob and blank in intermeshing timed relation, and means for feeding the hob and blank relatively to each other.

46. In a machine for producing gears, a hob support, a taper hob rotatably mounted thereon, a blank spindle adapted to carry a tapered gear blank, a cradle on which the hob support is mounted, rotatable about an axis Which lies in the same plane With the rotary axis of the blank spindle, and means for positioning the hob in definite odset relation to said plane. -1

47. In a machine for producing gears, a hob support, a hob of constant rotatably mounted on said hob support, a rotat' i able blank spindle adapted to carry a tapered rotatab gear blank, a cradle, on which the hob support is' mounted, rotatable abouty an axis which lies in the same plane with the rotary axis of the blank spindle and means for positioning the hob in de' ite offset relation to said plane.

48.. In a machine'for producing gears, a hob su port, a ta er hob of constant pitch ily mounte onsaid hob, support, a

rotatable bla-nk spindlel adapted to carry a tapered gear blank, a. cradle, on which the hob support is mounted', rotatable about` an axis which lies in the same' plane with the rotary axis of the blank spindle, and means A for positioning the hob in definite offset re- `lation to said plane. 4:9. In a machine for producing gears, a rotatable blank spindle adapted to carry a tapered gear blank, a hobIsupport, a taper hob rotatably mounted thereon, means or rotating the blank spindle, means for rotat` ing the hob, and means for simultaneously moving the hob and blank relatively to Ieac 'l other about an axis which liesfat an angle to the rotary aXs 4of the hob.

50. In a machine for producing gears, a

I rotatable` blank spindle adapted to carry. a

tapered gear blank, a hob support, -a taper hob of constant pitch rotatably mounted thereon, means. for rotating the blank spindle, means for rotating the hob, and' means for simultaneously moving Kthe hob andblank relatively to eachother about an'axis which lies at an algle vto the rotary axis of the hob.

5l.1 In a machine Afor producing gears, a

, rotatable blank spindle adapted to carry a tapered gear blank, a hob support, a hob of constant pitch rotatably mounted thereon,

means for rotating the blank spindle, means for rotating the hob', and means for simultaneously moving the hob and blank relatively to each other about an axis which lies at an angle tothe rotary axis of the'hob.

52. In a machine for producing gears, a hob support, a taper hob rotatably mounted on said support, a blank support, means for rotating the hob and blank in intermeshing 54C. In a machine for producing gears, a

hob support, a taper hob of constant pitch rotatably mounted thereon, a blank support,

means ror rotating the hob and blank in intermeshing timed relation, and means for simultaneously imparting a relative rolling movement between the hob and Ablank supn 55. In a machine for producing gears, a hob support, a 'tapervhob rotatably'mounted thereon, a blank support adapted to carry a tapered gear blank, means for rotating the hob and -blank in intermeshing timed 7 relation', and means for simultaneously imparting a relative rolling movement between the hobA and blank supports in the manner of agearv -meshing with a crown gear.

56. In a Vmachine -for producing gears, a hob support, a taper hob of constant pitch rotatably mounted thereon, a blank support adapted to carry a tapered gearl blank, means for rotating the hob and blank in intermeshing timed relation, and means for simultaneously imparting a relative-rolling v motion between the hob and blank supports in the manner of a gear meshing with a Acrowngear. Y l

57. In a machine `for producing gears by relative movement of: tool and blank in the manner of relative intermeshing rotation between a crown gear and the gear to be cut, in combination, a blank support, a tool support, a taper hob rotatably mounted on the hob support, means for positioning the tool and blank support-relatively to each other so that the apex of thev blank lies at the center of the imaginary crown gears, means for positioning the hob support and blank support, so that the hob and blank are tangent to a common plane with-the hob axis offset from the center of said imaginary i crown gear,means for rotating the hob and blank in intermeshing timed relation, and

-means for simultaneously imparting' a relative rolling movement between the hob and blank supports above at an axis passing through the center of said imaginary crown gear.

58. In a machine for producing gears by a relative movement 'of tool and blank inthe manner of relative intermeshing rotation between 'a crown gear and a gear to be cut, in combination, a blank support, a hob support, ahob of constant pitch rotatably mounted on said hob support, lmeansfor positioning the blank and hob supports relatively to each other so that the apexot the blank lies at the center of the imaginary crown gear means for positioning the hob.

i and blank supports so that the hob and blank are tangent to a common plane with the hob axis offset from the center of said imaginary crown gear, means for rotating the hob blank in intermeshing timed relation, and means orsimultaneously imparting a rela tive rolling movement between the heb and blank supports about an axis passing through the center oit said imaginary crown t 59. In a machine tor producing .e

a relative movement of tool and blank in the manner of relative intermeshing rotation between a crown gear arida gear `to be cut, in combination, a blank support, a hob support, a taper hob of constant pitch rotatably mounted on said hob support, means for positioning the hob and blank supports relatively to each other sov that the apex .of the blank lies 'at the center of the imaginary crown gear, means for positioning the hob and blank supports softhat the hob and blank are tangent to a common plane with the axis of the hob oilset from the center of said imaginary crown gear, means for rotating the hob and blank 'supports in in. termeshing timed relation vand means for simultaneously imparting a relative rolling movement between the hob and blank supports about an axis passing through the center of said imaginary crown'gear.

60. In a machine for producing gears, a blank support, a taper hob, means for rotating the hob and blank in intermeshing timed relation and means for' simultaneously moving the hob about the apex of the blank at a constant radial distance therefrom.

61. In a machine for producing gears, a blank support, a yhob of constant pitch, means for rotating the hob and blank in intermeshing timed relation, and means --for simultaneously moving the hob about the apex' of the blank at aA constant radial distance therefrom. y

62. In a machine for producing gears, a blank support, a taper hob of constant pitch, means for rotating the hob and blank in intermeshing timed relation and means for simultaneously moving the hob about the apex of the blank at a constant radial distance therefrom.

63. In a machine yfor producing gears, a rotary blank support adapted to carry a tapered gear blank, a hob. support, a worm hob rotatably mounted on said hob support, a cradle upon which one of said supports is mounted, means for rotating the hob and blank in intermeshing timed relation, means for simultaneously rotating the cradle on its axis and compensating means for' maintaining the timed relation of the hob and blank rotation during the movement of said cradle.

64. In a machine for producing gears, a rotary vblank support adapted to carry a 'y tapered gear blank, a hob support, a taper hob rotatably mounted thereon, a rotatable cradle upon which one of said supports is mounted,` means for rotating the hob and blank in intermeshing timed relation, means for simultaneously rotating the cradle on its axis, and compensating means for maintaining tlie timed relation ot' the hob and blank rotation during the movement of said cradle.

65. In a machine for producing gears, a rotary blank support adapted to carry a tapered gear blank, a hob support, a hob of constant pitch rotatably mounted thereon, a rotatable cradle vupon which one of said supports is mounted, means for rotating the hob and blank in intermeshing timed relation,-

means for simultaneously rotating the cradle on its axis, and compensating means for maintaining the timed relation of-hob and blank rotation during the movement of said cradle.

66. In a machine for producing gears, a rotary blank support adapted to carry` a tapered gear blank, a hob support, a taper hob of constant pitch rotatably mounted thereon, a rotatable cradle uponwhich one of said supports is mounted, means for rotating the hob and blank in intermeshing timed relation, means for simultaneously rotating the cradle on its axis, and compensating means for maintaining the timed relation of hob and blank rotation during the movement of said cradle.

67. In a machine'for roducing gears, a rotary blank support a apted to carry a tapered gear blank, a hobsupport, a worm hob rotatably mounted thereon, a rotary cradle upon which one of said supports is mounted, means foradjusting said hob support to offset the axis of the hob relative to the axis of said cradle, means for rotating the hob and blank in intermeshing timed relation, means for simultaneously rotating the I cradle on itsaxis, and .compensating means for maintaining the timed relation ofthe hob and blank rotation during the' movement of said cradle.

68. In a machine for roducing gears, a rotary blank sup ort adapted to carry a tapered gear blan a hob support, a taper hob rotatably mounted thereon, a rotary cradle upon whichl one of said supports is mounted, means for adjusting said hob support to offset the axis of said hob relative to the axis of said cradle, means for rotating the hob and blank in intermeshing timed relation, means for simultaneously rotating the cradle on rits axis, and compensating means for maintaining the timed relation of hob and blank rotation during the movement of said cradle.

69. In a machine for producing gears, a rotary blank support adapted to carry a tapered gear blank, a hob support, a hob or constant pitchrotatably mounted thereon, a rotary cradle upon which -one of said supports is mounted, means for adjusting said hob support to oset the axis of the hob relative to the axis of said cradle, means for rotating the hob and blank in intermeshing timed relation, means `for simultaneously pensating means tor maintaining the timed l 2 o' for rotating the hob and i taneously rotating thecradle on its axis,

relation of the hob and blank rotation durin the movement vof said crandle.

I0. In a machine for producing gears, a rotary blank su port adapted to carry a tapered gear bl a hob support, a taper hob of constant pitch rotatabl mounted thereon, a rotary cradle upon w ich one of said supports is mounted, means for ad'ust- 1n hogblrelative to t e axis of the cradle, means blank in intermeshing timed relation, means for simultaneously rotating the cradle .on its axis, and compensating means for maintaining the timed'relation of the hob and blank rotation during the movement of said cradle.

7l. In a machine for producing gears, a rotary blank support/adapted to carry a tapered gear lbla a hob support, a Worm hob rotatably mounted thereon, a rotary cradle, upon which one of said supports is mounted, angularly movable about an axis extending through the apex or the blank, means for rotating the ob and blank in lintermeshing timed relation, means for simultaneouslyrotating the cradle on its axis, and compensating means for maintaining the timed relation of hob and blank rotation during the movement of said cradle.

72. In amachine for producing gears, a

rotary blank sup ort adapted to carry av ta ered gear b l a hob support, a taperv ho rotatably mounted thereon, a rotary cradle, uponwhich one of said supports is mounted, angularly movable about an axis extending through the apex or the blank, means for rotating the ho and blank in intermeshing timed relation, means for simul compensating means for maintaining the 4timed. relation of hob and blank rotation durin the movement of said cradle.

73; a machine for producing gears, -a rotary blank support a apted to carry a tapered gear` blank, a hob support-a hob of constant pitch rotatably mounted thereon, a cradle, upon which one of said supports is mounted, angularly movable about an axis extending through the apex of the blank, means for rotating the hob and blank in intermeshing timed relation, means for simultaneously rotating the cradle on its axis, and compensating .means for v:maintaining the timed relation between'the hob. and blank rotation during the movement of said cradle.

74:. In a machine for producing gears, a-

rotary blank support adapted to carry a tapered gear blank,`a hob support, a taper hob of constant pitch rotatably mountedthereon, a rotary cradle, upon )which one of said supports is mounted, angularly movable about an axis extending through the apex of the blank, means for rotatm the hob and blank inintermeshing time relation,

sai hob support to offset the axis o the means for simultaneously moving the cradle, on its axis, and compensating means :for maintaining the timed relation between the hob and blank rotation during the movement of said cradle.

75. In a'machine for reducing gears, a 'rotary blank 'support a apted to carry a tapered gear blank, a vhob support, a taper hob rotatably mounted thereon, means for adjusting the hob support to offset the hob axis relative to the apex of the blank, and means for adjusting the hob axially to vary its position relative to the cone apex ofthe blank.

.76. In a machine for producing gears, -a rotatable blank support adapted to carr -a tapered gear blank, a tool support, a ob of constant pitch rotatably mounted thereon, means for' adjusting the tool support to offset the axis of the hob relative to the apex of the .blank and means-for adjusting the hob longitudinally of its axis.

77. In a machine for producing gears, a rotatable blank support adapted to. carry a tapered gear blank, a hob support, a taper hob of constant pitch rotatably mounted thereon, means for adjusting the hob sup.

port to olsetthe axis of the hob relative to the a ex of the blankand means for adjust? ing t' e hob longitudinally of its axis.

78. In a machine for producing gears, a

rotatable blank support adapted to carry a tapered gear blank, a rotary cradle, a hob `support pivotally mounted on said cradle for adjustment about an axis offset from the axis of said cradle, and a taper hob rotatably mounted on said hob support.

79. In a machine orproducing gears, a

rotatable blank support adapted to carry a tapered gear blank, a rotary cradle, ahob support pivotally mounted on said cradle for adjustment vabout. an` axis odset from thesupport pivotally mounted on said cradle for v adjustment about an axis offset from the axis' of said cradle, and a taper hob of constant'pitch rotatably mounted on said hob support.

81. In a machine for. producing'gears, a rotatable blanksupport adapted to carry a tapered gear blank, a rotary cradle, a hob support. pivotally mounted on said cradle for ad'ustment about an axis offset from the axis oi said cradle, and a taper hob rotatably mounted on saidv hob supportl and axially adjustable thereon. 82. 'Ina machine for producing gears, a rotatable blank support adapted to carry a tapered gear blank, a rotary cradle, a hob erating drivmg mechanism to rotate a taper hob `and a tapered gear blank on their respective axes, simultaneously imparting a relative rolling movement between the hob and blank, and applying power additionally through a "differentially operatingl drive ing mechanism to one of said bodies to mainv tain the rotation of the hob in continuously operative timed relation to the rotation of the blank.

84. The method of cutting longitudinally curved tooth tapered gears which consists in applying power through a uniformly operating driving mechanism to rotate a hob of constant pitch and a taper gear blank on their respective axes, simultaneously impart' ing a relative rolling movement between the hob and blank and applying power additionally through a differentially operating driving mechanism to one of said bodies to maintain the rotation of the hob in continuously operative timed relation to the rotation of the blank.

85. The method of cutting longitudinally curved tooth tapered gears, which consists in applying power through a uniformly operating drivlng mechanism to rotate a taper hob and avtapered gear blank on their respective axes, simultaneously imparting a relative rolling movement between the hob and blank and applying .power additionally through a differentially operating driving mechanism to o ne of said bodies to maintain the rotation of the hob in continuously operative timed relation to the rotation of the blank.

In testimony whereof I aix m si nature.

N IKOLA TREO ICH.

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