US1588060A - Method of and apparatus for generating tapered gears - Google Patents

Description

June 8,1926. 1,588,060

0. G. SIMMONS METHOD OF AND APPARATUS FOR GENERATING TAPERED GEARS I Filed Jan. 5, 1922 4 Sheets-Sheet 1 I N VEN TOR;

Macaw ATTORNEY.

June 8 1926. 1,588,060

' O GFSMMONS METHOD OF AND APPARATUS FOR GENERATING TAPERED GEARS Filed Jan. 5, 1922 v 4 Sheets-Sheet 2 #89 r A 17 pg 39 Z 60 2 BY $5 fl A TTORNEY.

:32 O I r o Sly mam.

June 8 1926.

O. G. SIMMONS METHOD OF AND APPARATUS FOR GENERATING TAPERED GEARS 1922 4 Sheets-Sheet 5 Filed Jan. 5.

INVENTOR.

ZZZMG 1 A TTORNE Y.

June 8 1926. 1,588,060

0. G. SIMMONS METHOD OF AND APPARATUS FOR GENERATING TAFEREPD GEARS Filed Jan. 5. 1922' 4 Sheets-Sheet 4 ATTOIIRNEY.

Patented June 8, 1926.

UNITED STATES OLIVER G. SIMMONS, OF PHILADELPHIA,

PENNSYLVANIA, ASSIGNOR TO SIM IONS METHOD-HOB COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

METHOD OF AND APPARATUS FOR GENERATING T Application filed January 5, 1922. .Serial No. 527,176.

-My invention relates to a method of and apparatusfor enerating, upon the molding principle, as distinguished from forming tapered, as distinguished from bevel, spur and helical spur gears and racks, or cutters or other articles resembling gears;

In accordance with the broad aspect of my invention, the cutter which generates teeth in the gear, rack or other blank moves, during the act of tooth cutting or genera-- tion while moving across the face of the blank, toward or away from the axis of the blank at any suitable rate with respect to the speed of traverse of the blank by the cutter. The rate of movement of the cutter toward or away from the axis of the blank may be uniform throughout the traverse of the blank by the cutter, in which case a gear or rack of constant or uniform taper results; or such rate of movement may be nonuniform or vary as the cutter proceeds across theblank, in which case the resultant gear or rack may have portions having different tapers, may have a portion which is tapered joining a portion which is not tapered, or the rate of motion mayso vary as'to produce a curvilinear-outline in the periphery of the finished gear or rack.

In accordance with a further specifie aspect of my invention, and that herein specifically disclosed, the cutter is a hob or bobbing cutter whose teeth are helically disposedand continuously rotated while traversing the continuously rotating blank in. a direction in general longitudinally of the axis of the blank, the hob simultaneously moving toward or away from the axis of the blank at suitable rate to produce thetaper effects as aforesaid. The longitudinal movement of the blank with respect to the hob may be in a direction longitudinally of the axis of rotation of the blank or may be in a direction at an angle to the axis of rotation of the blank corresponding with the angle of taper of the finishedgear.

My invention resides in the method of and apparatus for producing tapered spur or helical gears having generated teeth, and resides also in tapered helical spur or tapered spur gears having generated teeth.

For an understanding of my method, for an illustration of some of the forms my apparatus may take, and for an illustration of the gears and the like produced by my method and apparatus, reference is. to be -hto the accompanying drawings, in W 1c Fig. 1 is a skeletonized view in perspective of a hobbing machine embodying my inven- Eion and utilizable in practicing my invenion.

Fig. 2 is a plan view of such a hobbing machine.

Fig. 3 is a fragmentary end elevational view of part of the gearing of the a paratus shown in Figs. 1 and 2 and constituting a povel attachment for practicing my inven- Fig. 4 is a fragmentary side elevational view of the same gearing and additional parts.

Fig. 5 is a fragmentary diagrammatic view illustrating the movements 'of hob and blank:

I Fig. 6 is a fragmentary diagrammatic view illustrating a modification of the relative movements of hob and blank.

Fig. 7 illustrates in plan view a modified construction of a bobbing machine having the'movements indicated 'in Fig. .5 and corresponding in general with Figs. 1 and 2.

Fig. 8 illustrates in plan view a modified construction of hobbing machine for producing the movements of Fig. 6.

Fig. 9 illustrates the, tooth contours at opposite end faces of the tapered gear.

Fig. 10 is a sectional view, partly in elevation, illustrating my in intermeshing relation.

Fig. 11 is a view, partly in section, illustrating my helical tapered gears in meshing relation. v i

Fig. 12 is a sectional view of a multi-tooth cutter in accordance with my invention.

Fig. 13 is an elevation of the left face of the cutter of-Fi 12.

, Fig. 14 is an e evation of the right face of the cutter of Fig. 12.-

Figs. 15 and 16'show modified forms of guide bar which may replace the cutter guide bar shown in Fig. 7. i

Referring to Figs. 1 to 4 inclusive, there is illustrated, by way of one example merelof numerous hobb'ing machines, a Lees-Brad nor hobbing machine which may readily be modified for purposes of my invention. The primary driving shaft is indicated at 1 and is rotated by pulley 2 fast thereon, by belt,

APERED GEARS.

tapered spur gears not shown, the loose pulley 3 simply running idly when the belt is shifted thereto when the shaft 1 is to be stopped. The shaft 1 drivesthe shaft 4 through the gears 5 and 6. Secured upon the shaft 4 is the bevel gear 7 meshing with and driving the bevel gear 8 splined upon the shaft 9, which in turn drives the bevel gear 10 meshing with and driving the bevel gear 11 which drives the shaft 12 which drives the arbor 13 through the gears'14 and 15. Upon the arbor or shaft 13 is secured the hob or hobbing cutter H whose teeth are disposed in helical sequence. The shaft 12, arbor 13 and gears 14 and 15 are supported by or within the cutter head 16, which is supported upon and rotatable with respect to the cutter head support 17 about the axis of the shaft 9-, the bevel gear 11 rolling upon bevel gear 10 during such adjustment, which is utilized for tilting the axis of the arbor or shaft 13 from true vertical position, in the direction of the arrow 18, through a small angle corresponding with the an le of the helix of the hob teeth, as well un erstood in-hobbing machine practice.

Upon the shaft 4 isv a pinion 19 which drives the gear 20 with respect to which the longitudinally movable shaft 21 is splined. The shaft 21 is supported by and has a hearing in the carriage 22, which is movable in the direction of the arrow 23, that is, movable at right ang es to the longitudinal axis of the shaft 9, upon the base A. The shaft 21, driven by gear 20, drives the-pinion 24 which drives the gear 25 through the intermediate gears 26, 27 carried by a bracket 28 swingable about the axis of the shaft 29 upon which the gear 25 is secured; the bracket 28 may be clamped in the operative position shown or in inoperative position by the Y clamping screw 30 extending through a slot in the arm 31 on the bracket 28, the screw 30 being threaded into a portion of the carriage 22. The shaft 29 drives the spiral gear 32, which "in turn drives the spiral gear 33 securedupon the shaft 34 which in turn drives the worm 35 meshing with the worm gear 36 secured upon the work spindle or shaft 37. The work or blank to be operated upon by the hob H is indicated at B and is mounted upon the shaft 37 as an arbor, Fig. 1, or generally upon an arbor 38, Fig. 2,

which is co-axial with and driven with the shaft37, the arbor 38 being supported at its far end in an outboard supporting memloose upon shaft 46, but coupled thereto by the coupling 47 operated by the fever 48. The shaft 46 drives the gear 49, which drives the gear 50 secured to the pinion 51 which drives the pinion 52 which drives the aforesaid gear 43, gear 50 and pinions 51 and 52 having bearings on members adjustable longitudinally in slots in the bracket member 53. The bracket 53 is clamped to a portion of the carriage 22.

The shaft 54is mounted in bearings carried bythe base A of the machine (not by carriage 22), and there issplined thereon for rotating the same the gear 55, which may be driven by shaft 46 through a suitable train of gearing carried by the bracket 53, in which case .the bracket 53 is in another of its positions to which it may be adjusted, and

when the gear.55 is driven from the shaft ries a worm 56 driving the worm gear 57 loosely journalled on the transversely extending shaft 58, but capable of being coupled to the shaft 58 for rotating the same by the coupling 59, one of whose members is secured to the hand wheel 60 splined upon the shaft 58. At its other end the shaft 58 is provided with a lead screw 61engaging in the nut 62 secured to the cutter head support 17, whereby upon rotation of the shaft 58 the support 17 and the cutter head 16 and the hob H are moved arallel to the .hafts 58 and 9 upon the gui e structure 63 n the base A of the machine upon which the carriage 22 is, also movable, but in a direction at right angles to the direction of movement of the member 17.

The slrafts and gearing, from shaft 21 to pinion .52, all have bearings upon and move longitudinally in the direction of the arrow same time is fed in the direction of the arrow 23 past the hob, producin an ordinary spur gear which is not tapere that is, is of the same diameter at the peripheries of its opposite end faces. Or by similar movements, but with a suitably diflerent speed of rotation of the shaft'37 as may be procured by different indexing gears 26 and 27, and by a suitable definite speed of longitudinal movement of the work B in the direction of the arrow 23, procured by suitable definite feed gears in the train between the shafts 46 and 42, a helical gear will be produced upon the blank B, but of the same diameter at its opposite end faces.

Or by disconnecting the lead screw 42, in

which case the carriage 22 will not befed longitudinally, and coupling the shaft 54 the hob' H'fandithe work work 'B' 's fed longitudin teeth.

principle,

to thshaijtae H will fe'd ma W ar However, r05 purposes. of y produeetapered spur heliic tinuously atlsuitable relatijv of assumes, as 1n-th described; but, in addition,

toward theshaft 37 and we practice above be hob-H" is fed nal movement of of the" arrow 23, wherebg helical gear produce h ile the carriage22 i's heiiig' fed forward ously with my invention,

movement of the carriage 22 as procured by the simultaneously rotating lead screw. 42.

That is to say, in accordance with my inven-' tion, I produce tapered helical or spur gears with generated teeth by simultaneously em? effected bylead screws 42 and 58. This additional-simultaneous op.-1. ,V v d' K s-tire hjo bfI-I and work' Bj rotatepandthe ploying the feeds eration of the lead screw 58 is accomplishe by providing carriage 22 by connecting the bracket 64 through the link 65, which at its one end is pivoted to the bra'cket53 at 66 and which is pivoted at its other end upon a" bolt67 g the, link 65 to the bracket 64 slot 68 in; et 64. Upon members secured to the securing engagement of the bolt in the brac bracket 64 and adjustable tosuitable posig tions in the, aforesaid slot '68 are pinions or" ears 69 and 7 Q meshing with ea'chjother' and ousl at suitable rate fed intothe blank or, wor I B to roduce a tapered gear or the like whose teet are generated on the molding as distinguished from formed. In the example just described, the hob H, while 1 the work or blank B from its due to'longitudiit is traversing one end face to theother,

.t u ea a a into the blank and producei in iition, to'

p at a fsuitablef rate compared; with the speed of lb'ngitudi-Q the work thedirection shea ssp 2g n d.

an additional bracketl64 piv oted and slidable longitudinally u on the" shaft 54,-the bracket 64 being carrie by the 'underjstood that it may comprise a e shaft 46' drives the lead screw 58 at' it drivesthele'ad ,screw 42.

72, 71,69, 70 and their lishing my" reward-means dfifi amma'tically'illustrated"inFig. 5. whe

it f will'jlbe iinderstoodithat the llOlJH, while rotat ng Kin" suitable direction, that indicated by the ar ow h, and while tl ie'wo k B s rotatin'gfin the' direction of the an; iaiidf s (fed'glongitudinallyi in"the 1 difreit on of: the arrow 23, is simultaneously in-fp i i 'r i ibn. sa a-r wa- 1. i"

Referring'toFigi 7,there is 'show'n modified means for feedingthehob Had-- blank B or its shaft 37 simultaneously withmovement of the work B in the direotion 'of the arrow 23, without recourse} screw h s is accomplishe'd to the lead ivotin at 73, to the carriage 22, the" gui e iner'n 'e'rf74,whichmaybe clamped in" any suitable o'sition by/the bolts 75,'thread'- ed' intomeni' er 22,"andexteiidin through slotsl76in the ends of the member Y 4, a suitable index scale 77 being provided for indicating suitableo'r desired taper angles. The member 74 has I the longitudinally extending slot or channel 78, in which engages a" roller or slide 79 secured by the-pivot bolt 80 withe arm1 jsecured to the cutter head supi port 17.

row '23 by j the carriage 22, the guide member 74 111", wfsthe arm 81 "and thereiore the ment "emanates snags-22mins a red:- tio o the arrow23, isfed 1 I w nd r B 1o fo 1" example,

ber 17 and hob H'toward the right, in the direction of arrow 7: toward the; axis of ear." v1

Gears of different 'tapers'jare produced by adjus 'lng tlieY member 741 to different pqsitionstij; "Q I. i While the s t"78"is shown as straight, it

series of straight portions disposed atdif-j curved slot of 'anyform as indicated at 78"; iii-Fig. l6, in which latter case the outline rotationof thejwork B, producing a tapered;

' llU ferent' angles with respect to each other, as] "shown at/Z8 in FigLf 15, or it may be a? 1 15 curved. When the f idal, spheroidal, ellipsoidal or other gear having generated tapered spur or helical tapered spur teeth adapted to me'shfwith the teeth of alike gear 'whose'faxi'siis parallel. .Whileini 'theforegoing arrangements the movement of hob H has been atKrightangles tQl he axis of. rotation of thefwork B, thatis, at "right angles to the axis of the shaft 37, for produclng the taper effect,

it will be understood that anyother equivalent arrangement may be employed,

For example, as indicated diagrammatically in Fig. 6, the axis of the' work B, that is, the shaft 37, may be set at such angle to thearrow 23, which indicates the direction of movement of the carriage 22, as to correspond with the angle of. taper desired in the finished gear. In this case the hob II is not fed in the direction of the arrow 71, (or the reverse), but tapering of the gear is nevertheless obtained because the axis of the work B, that is, the shaft 37, is set at a suitable angle, but nevertheless moved .in the direction of the arrow 23, and not An arrangement for producing this type of relative movement between hob and work .isindicated in Fig 8. The hob H is, as before, driven by the shaft 1. In this case,

of the arrow 23. The housing 82 is moved upon its pivot 83 to adjust the shaft 37 to proper angle with respectto the arrow 23, and the housing 82 is clamped in such position to the carriage 22. A scale 84 upon the carriage 22 co-acting with an index 85 on the housing 82 serves for adjusting the housing 82 to proper angle. The shaft .37 is driven by the gear wheel 20. through the shaft 21 through a universal joint 86, and the shaft '21 drives the gear 24 through a similar universal joint 87. The-bracket 28 in this case is carried b the housing 82, and supports the interme iate gears 26 and 27, the latter driving the gear 25 upon the shaft 29 carnied by the housing 82 and driving the spiral gear 32 which drives the spiral gear 33 secured upon the shaft 34 which drives the worm 35 which drives the worm gear 36 secured upon the shaft 37.

The globoidal gear 88 is secured upon the shaft 37 and drives the gear 89 which,

through the coupling 47, drives the shaft 46. The gear49, coupling 47 and the shaft 46 are mounted upon the carriage 22, which is moved in the direction of the arrow 23 by the lead screw 42 driven from the shaft 46 through a-suitable train of gears carried by the adjustable bracket 53 mounted upon the carriage 22.

The mechanism causes simultaneous rotation of the hob H and work B and movement of the work B in "the direction of the arrow 23 while its axis or shaft 37 is inclined as shown. In thisway, as hereinbefore described, taperedhelical or spur gears with generated teeth are produced.

Thetapered spur gears produced in accordance with this invention have unusual characteristics, among which are the following. As indicated in Fig. 9, the circumfervolute curves,

ential width of the tip or point .90 of a gear tooth is narrowerthan the qircumferential width 91 ofthe tip or poiht of the same tooth at the opposite face of the gear where the gear has lesserexternal diameter,- while the breadth of the tooth as measured between its sides 92, 92 at the end. or face of great diameter is greater than the breadth or thickness of the tooth between its faces 93,93 at the end or face of smaller diameter. 'As indicated in Fig. 9, the sides of the gear teeth are represented by inthough'it is to be understood that my invention is not limited in these respects. In the example illustrated, the involute curve 92 is the same as the involute curve 93, but the curve 92 is longer than the curve 93, the curve 92 corresponding with the curve 93, but having additional Y length as occasioned-by the greater diameter of the that where the gear face is represented by the curve 93. The teeth taper as togtheir thickness from one face of the gear-to the other, but nevertheless have true-generated surfaces. Similarly, the surfaces of the spaces between the teeth complementarily taper and are truly generated surfaces. The pitch circle changes in diameter from one face of the gear to the other, the circle 94 representing the pitch circle for the tooth at that end of the gear of smaller diameter, while the line 95 represents the pitch circle for the tooth at opposite end of the gear. Inasmuch as the thickness of all the hob teeth is the same at their pitch line, and since the hob is in effect moved toward the axis of the'blank in accordance with m described rnethod, the diameter of the pitc circle of the teeth of the gear increases from one face of the gear tothe opposite face of the gear. 94 and 95? represent the root circles for the teeth at opposite faces or ends of the gear, the root circle diminishing in diameter from that end of the gear of larger diameter to the opposite end. The height or depth of the tooth is constantifrom one end or face of the gear to the other, in that the depth or height 94 of the tooth at that end of the gear of smaller diameter is equalto the depth or height 95 of the same tooth at that end of the gear of greater diameter.

The diameter of the root circle and the height or depth of the tooth in every plane from end face to end face of the gear are such that when the gear is in proper meshing position with a complemental tapered gear of the same characteristics, there is clearance between the top of the tooth and the root of the tooth of the complemental gear, that is, the teeth of one of the gears of a pair will not strike or engage the roots of the teeth of the complemental gear. This clearance is indicated in Figs. 9 and 10; and this matter of clearance and avoidance of gear at the opposite end fromincluding low pressure-angles, as degrees and less. The characteristic of constancy other, while it. is characteristic of my 'tapered gear that the; diametral or circular pitch of the teeth is constant from one end ace of the gear to: the other.

When a pair of such tapered gears are brou 'ht to intermeshing; relation as indica in Figs. 10 and'll, the teeth contact:

with each other throughout their lengths:

or throughout that part of their lengths whichv overlap .lon tudinally of their axes.

of rotation. Furt ermore, these lines of contact are parallel to their axes of rotation, the line of contact between a pair of teeth shifting from near the tip of-one and the root of the other to the root of the one and the top of the other as they roll upon each other, but the line of contact aways remaining. parallel .to their axes of rotation, in the, case of both spur and helical spur ta ere'd gears with generated teeth. When t e sides of the teeth are involute curves, the teeth of the different tapered gears truly roll upon eachother and maintain contact with each. other from end "to end along lines which are parallel to their axes of rotation. 7

Referring to Fig. 10, G and Gr are tapered spur gears with generated teeth in accordance with my invention. They are secured or keyed to their respective shafts S and S with'the face of large diameter of the gear G and the face of small diameter of the ar G? adjacent each other. On the shaft 1 may be rovided a shoulder 96, between which an ,the gear Gr are'disposed the shim washers 97' of ual or varyin thicknesses. On the shaft is a threade portion 98 upon which is threaded a nut 99 holding the gear (3r against'the shims 97 and locked by the lock nut 100. By choos-. ing or varying the total thickness of the shims 97 the gear G? is shifted-longitudinally of the axis of shaft S of the gear G and so. the pla or back lash between the teeth of gears fir and G may be made anything suitable or desirable, and may be entirely eliminated. And as the gears wear after use,the. play or.back' lash between their teeth maybe reduced or eliminated from time to time by removing. one or more shims 97. Similarly, when the distances be-' tween the centers of shafts S and S vaI'y, the back lash may be reduced or eliminated by ad ustm the gears to suitabl'e positions longitudinaly of their shafts or either of.

them. v

By way of example, it may be stated that the effective distance between the centers of a pair of these tapered gears may be varied one unit of length for ten units of length of adjustment of one of the gears lon 'tudinally of its axis if the taper angle we each gear, Figs. 10 and 11', is approximately two degrees and fifty-one minutes.

The dotted' line 101, parallel ,to the axis of the gears G, G indicates the line of contact between teeth, as above referred to. i

In Fig. 11 the gears G and G* are shown as tapered helical spur gears, the back lash or play between whose teeth may besimilarly adjusted by adjusting one of the gears, as G, longitudinally ofits shaft.

In producing tapered gears, either spur or helical, as above described, the gear blank may be cylindrical or of other suitable form. Or, and preferably, it is conical, the pitch of the cone corresponding substantially with the taper of the finished gear. And as a matter of convenience, my tapered gears correspond as to diameter of blank, addendum, pitch, base and root circles,-mid-way between their end faceswith. the corresponding diameters of standard non-tapering gears.

.While I have hereinbefore referred to the production of tapered spur cars, it will be understood that kindred evices may be similarly produced. g i For example, as indicated in Figs. 12, 13

and 14, a multi-tooth circular cutter (utilizable for various purposes, as for example, generation of threads in a blank rotating on an axis substantially at right angles to the axis of rotation of the cutter) =may' be similarly produced by a hob, as'H, by mounting the cutter blank upon the shaft 37, Figs. 1, 7 and,8, or mandrel 38, Fig. 2, in the position occupied by the blank B. The cutter Owill then have generated in it teeth t which, for cutting purposes, however, have a relatively great taper, as for example, a taper angle a of twent de s, more or less, as may be require T e surfaces of the teeth and the spaces between them are generated by the hob which simultaneously tapers the teeth. The blank before cutting by the hob may be conical, the angle a being predetermined in turning up the blank. Or the blank maybe cylindrical and the hob will generate the tapering surfaces milling process heretofore commonly employed. Furthermore, by my method of producing a cutter, its teeth are generated and are of correct shape and contour, as dlstinguished from the teeth produced by milling, which are only approximately correct in dimensions and contour. It will be understood that the cutter produced as above described has substantially the same characteristics as a tapered spur gear formed bythe present methods and having the same taper. A cutter so formed will mesh with a like cutter or with a gear formed with-the same taper.

,These facts are true of my cutters produced by hobbing as above described, or when produced by reciprocating a multitooth cutter (Fellows) or a single cutter or element across the face of the. cutter blank and simultaneously moving the cutter toward the axis of the blank.

It will be understood that while I have hereinbefore described the method of producing the gears by hobbing, it will be understood that tapered gears with generated teethmay also be formed by reciprocating a multi-tooth cutter (Fellows) or a. single cutter tooth or element across the face of the blank in a direction inclined to the axis of the blank to produce the taper effect.

The gears in accordance with my invention are not bevel gears, but are true tapered gears with generated teeth.

These ears have numerous applications, among w ich are the following:

They may be employed as the timing gears of: an internal combustion engine formin a driving'train between the crank shaft 0 the engine and the cam shaft thereof. Generally three gears are. comprised in such a train, and the middle of the three may be mounted upon a shaft, as S, whereby it' may be adjusted longitudinally ofsuch shaft for reducing the back lash between itself and the two outer gears, or if desired, two. or all of the three gears may be so lon 'tudinally adjustable upon their shafts. or this purpose, generally the tapered helical gears may be employed.

Both tapered spur and helical gears may also be employed as those of the transmission of an automobile intervening between the motor or engine and the rear or driving axle. v

hese tapered gears are also of use in rinting presses for preventing lost motion ween elements which should always'remain in perfectly definite relation with respect to each other. For example, in multicolor presses, by employing these tapered gears which eliminate play or'ba ck lash, perfect register of the different applications of color is obtainable. Furthe more, in cylinder printing presses slight scill'ation or variation from uniformity of rotation of the printing cylinder may likewise be eliminated.

Thistype of gear is also of value in machine tools, includinghobbing machinesof the character herein described, wherein it is desirable to prevent variations from constancy of ratios of speeds of rotation of the various parts, and these gears are therefore in such machine tools conduciv'e'to greater accuracy in the product of those tools.

In my spur and helical tapered spur gears hereinbefore described, the pressure angle varies in magnitude from one end face of the gear to the other. At a portion of the gear of greater diameter the pressure angle is greater than the pressure angle at-a part of the gear of smaller diameter. In a gear of a single taper, as in Figs. 10 and 1-1, the pressure angle mid-way between its end faces may be made equal to the pressure angle of a standard gear of diameter corresponding with the'diameter of thetapered gear mid-way between its end faces. Considering two intermeshing tapered gears, as in Figs. 10 and 11, the effective pressure angle of the contact between theteeth of the two gears of a pair remains constant from one end face to the other of the gears, anl this, I believe, accounts for the fact that the pitch line of contact between teeth of the pair of gears is substantially parallel to their axes of rotation, the complemental pressure angles of the contacting teeth of the two gears at a given distance between end faces -of the gears co-acting as an effectivepressure angle for the two gears which is constant throughout the length of the contacting teeth. Y

Tapered spur helical gears formed in accordance with the method of the present application have the advantage that the lateral thrustbetween two meshing gears due to the taper of the gears and the lateral thrust between the gears due to the helical disposition of the teeth are in opposite directions so that one tends to counterbalance the other. In fact by properly proportioning the helix angle of the teeth and thetaper of the gears, the lateral thrusts may be'made.

to counterbalance each other so that when the two intermeshing tapered helical gears are driven under load,-the lateral thrust is eliminated. If the driven gear be mounted to slide longitudinally of its shaft it may be shifted while it is being driven under load in either direction by the application of a very slight pressure thereto.

It will be understood with respect to the appended claims that for the sake of brevity the term taper includes not only single ion . of the teeth therein, while moving longitudinally of the tapers. as indicated in Figs. 10 ,and' 11, but several'dilferent tapers and curved tapers as well. I What I claim is: u

. 1. The method of prodncingtapered.spur, or tapered helical spur gears, cutters and the like having a constant circular pitch, which comprises cutting a blank by a cutter to generate a tooth, by simultaneously producing relative movement between cutter and blank with respect to each other to cause the generating action of the cutter to take place at different distances from. the axis of the blank and causing the cutter to cut the top surface of the tooth parallel to the root surface thereof in passing from end to end of the blank.

2. The method of producing tapered spur, or taperedhelical spur gears, cutters and the like having aconstant circular pitch, which consists in generating a tooth in a blank by av cutter whose distance fromthe axis of the blank varies while generating the tooth and causing the cutter to cutthe top surface of the tooth parallel tothe root surface thereof in passing from end to end of the blank. I I

' 3. The method of producing tapered spur, or tapered helical spur gears, cutters and the like having a constant circular pitch, which comprises simultaneously rotating :1 hobbing cutter and a blank to generate teeth blank, and simultaneously varying the distance between the bobbing cutter and the axis of the blank and causing the cutter in generating the teeth to cut the top, surfaces parallel to the root surfaces thereof. J k

4. The method of producing tapered spur, or tapered helical spur gears, cutters and the like having a constant circular pitch, which comprises rotating 3. bobbing cutter and a blank in tooth-generating engagement with each other. and varying the distance of the bobbing cutter from the axis of the blank as the bobbing cutter proceeds loi'igitudinally of the blank and causing the cutter in generating the teeth to cut the top surfaces of the teeth parallel to the root surfaces thereof.

5. The method of producing tapered spur. or tapered helical spur gears, cutters and the like having helical or inclined teeth and having a constant circular pitch, which comprises cutting in a blank generated helical or inclined teeth: by n'iovement of the cutter longitudinally of the blank at an angle to the axis thereof, and simultaneously varying the distance between the cutter and the axis of the blank and causing the cutter to cut the top surfaces of the teeth parallelto the root surfaces thereof.

6. The method of producing tapered spur, or tapered helical spur gears, cutters and the like having'helical or inclined teeth and having a constant circular pitch, which coniprises rotatuig a-hobbing cutter and a blank,

.1n engagement with each other to cut in the blank by movement longitudinally thereof generated teeth, the relative speeds -of rotation of hobbing'cutter and blank being such as to cause said teeth tobe inclined with respect'to the axis of thefjblank, and simultaneously varying the distance between said hobbing cutter and the axis of'the blank and causing the cutter in generating the teeth to cut the top surfaces of the teeth parallel to the root surfaces thereof. v jj 7. The method of producingtapered spur,

or tapered helical spur-gears, cutters and the likehaving helical cit-inclined teeth and having 'a circularfpitch, which comprises '51- multaneously rotating a bobbing cutter and a blank to generate helical or. inclined teeth therein while moving longitudinally f of the blank, and simultaneously varying the distance between: the; hobbing cutter and the axis of the blank and causing the cutterto cut the top surfaces of the teethparallelto the root surfaces thereofg" 8 Apparatus for producing tapered spur,

or tapered helical-spur gears, cutters and the 1ike, having a constant circularpitch, com-' prising means for supporting a blank, a cuttcr, means for moving said cutter longitudinally of the blank. for producin'ga tooth.

therein, and means for simultaneously vary:

ing the distance between the cutter and the axis of the blank. I v I 9. Apparatus for producing tapered spur, or tapered helical spur gears, cutters or the like having helical or inclined teeth and. having a constant circular pitch, comprising means for supporting a blank, a cutter,

means for causing movement of said cutter longitudinally andcircumferentially of said blank for producing a tooth therein, and means for simultaneously varying the dis- 10. A hobbing machine for producing tapered spur, or tapered'helical spur gears having a constant circular pitch comprising means for rotating a hobbing cutter, means for rotating a blank, and means for producing motion whereby the bobbing cutter traverses the blank while varying in distance from the axis of the blank,

11. A bobbing machine tapered spur, or tapered helical spur gears having a constant circular pitch comprising means for rotating a bobbing cutter, means forrotating a blank, means for causing the tance between thecutter and the axis of the for producing 190 bobbing cutter to traverse the blank longitudinally thereof, and means for simultaneously moving the bobbing cutter toward the axis of the blank.

12. A bobbing machinecomprising a base,

a cutter head movable transversely on said base, a hobbing cutter carried bysaid cutter head, a carriage movable longitudinally on said base atright angles to the transverse movement of said cutter head, a blank carried by said carriage, driving connections for rotating said blank and hobbing cutter at predetermined speeds, means for feeding said carriage longitudinally, and means for simultaneously moving said cutter head In testimony whereof I have hereunto affixed my signaturethis 3rd day of January,

OLIVER G. SIMMONS.

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