US2563982A - Hobbing machine - Google Patents

Description

Aug. 14, 1951 Filed April 1; 1947 H. C. WARNER HOBBING MACHINE 8 Sheets-Sheet 1 M/VENTOR. 13. M

Aug. 14, 1951 H. c. WARNER 2,563,982

HOBBING MACHINE Filed April 1, 1947 s Sheets-Sheet 2 INVENTOR c. WARNER 2,563,982

HOBBING MACHINE 8 Sheets-Sheet 5 Aug. 14, 1951 7 Filed April 1, 1947 INVENTOR W dfl wav WIT? Aug. 14, 1951 H. c. WARNER HOBBING MACHINE 8 Sheets-Sheet 4 Filed April 1, 1947 l/VVE/VTOR. MGM/mm, /T

JTG-S Aug. 14, 1951 v H. c. WARNER 2,563,982

' HOBBING MACHINE Filed April 1, 1947 s Sheets-Sheet 5 BYMCZJJMMI/ 4, 1951 H. c. WARNER 2,563,982

HOBBING MACHINE Filed April 1, 1947 8 Sheets-Sheet 6 EYE-10 INVENTOR.

4, 1951 H. c. WARNER 2,563,982

HOBBING MACHINE Filed April 1, 1947 8 Sheets-Sheet 7 H. C. WARNER HOBBING MACHINE Aug. 14, 1951 8 Sheets-sheaf 8 Filed April 1, 1947 lNVE/VTOR. I

patented Aug. 14,

Homer C. Warner, Gleveland, Ghio, a q i or to The LeesBradner ,Compa'ny Gleveland bhio, a

corporation of: Ohio Application April 1947i serial Ive-teeth 3' Claims.

My invention relates' to hobbing machines and relates: more particularly to a"- never and admir tageo'us driving: mechanism for the op'erativeele ments thereof which may he r-ea ly and simply so setup as: to adapt said'rnachin for the precisely controlled ho'bhi ng generation of helical gears or the like; which are thereby eauseeto respond toprescribed? specifications.

Hobbing; machines heretofore have been prb= vi'ded withtran'smi'ssien gearing wherein a lead dilierentiak gear set is emnloyed to var y'the' speed of rotation at the work spindle according;- to" the rate: of relative: feed movement of the hob and work: blank; spindles: to effect cutting of gear teeth having a desired helical lead.

similarlead difierentiali gearing: has commonly been interposed between the index" gearing and the work spindle; but s1icharrangements: have beerri subject to the objections or requiring bur densome time consumings calculations" in order to: determine the required? gearratio between driving and driven lead? and other gears to 0011* dition the transmission oi the machine for 6t fecting cutting; of the desired number of gear teeth having-s the desired: lead; and again" aftera first gear on asset-of mating gears has-been then cut; it is repeatedly necessary to repeat the calculations order to" condition said: transmission for. the ciitting: for each: relatively niat'ingi gear having difiere'nt' numbers; of teeth;

Moreoven; as a result of such calculations; those skilled'fim the art and familiar with these present day machines can only decide upon a ratio between said" lead gears that merely approhimates the: required lead for the=gean to be out. Therefore: to' cut a gearblank' to produce a gear adapted to mate with a given helical gear; the ultimate result istoo largely dependent upon theskill or possibly good luck of the calcik latbr.

In themechanisin ohmyi'nvention, Idesignediy place the lead differential gearing: inadvarice of the index gears, and by virtue thereof, I have found. it possible to greatlyreduce the otherwise: required calculations" and: much ofthe mechanical changes in the mechanism set-up;- for eife'cting thehobbing: of a helical gear accordingto required specifications, and thereafter, to greatly; simplify" and: reduce the set-up'worlc for producing: sets of relatively mating gears hav ing, relatively different numbers of teeth includiing elimination of the ordinarily required:- calculations;

An: obj ect oi my invention therefore: .is to aftordvgreatersimplicity ln-the nature'of the pre 2 liminary set 'up otahobbme machine to adapt it for the cutting of helical gears of desired sped-'- .Anotlier object of the present invention is 1 therefore to provide" a mechanism of the fore going character which is readily set up for the hobbin'gof helical gears" without requiring time consuming oalculationsa= Another object of my invention is to provide a novel and; improved arrangement of driving: elemen-ts of a: finishing machine whereby the same may" be successively expeditiously and properly set up for the generation ot helical gear teeth of widely different specifications.

Another objectvofi my invention is to substantially reduce and fior avoid-the previously required time: previously spent in wbrleing out laborious calculationsand/or making reference to various pr e=prepared chartsn incidental to the setting up of a bobbing: ma'chine in'z such manner that the rotat'iQnai-"rate of the blank will be' so' relatively timed relative to the hob" and: work blank feed movement in a direction parallel to' the axis of the work blank whereby any helical gear having teeth -ha vlng a prescribed lead angle may be accurately byr' the-hobbing machine.

Another object of my invention is to reduce and simplify calculation and set-up" work for hobbing rrelatively mating gears to cause them to have prescribed different numbers of teeth;

Another-- object of my invention is to achieve setting up of the transmission mechanism for a bobbing machine to condition said machine for the; cutting of helical gears responding to prescribed. numbers of: teeth and/0r lead of said teeth by an improved method.

Other objects of my invention and theinventi'o'n itself will Become cleaf'f to those skilled in the art by" reference to the drawings hereof which" ill'iist' a waneamen mechanism for hobbi'ngl machm which isaf preferred embodirhe r inventitn; and by reference to the specification related td the Said df'awifigs whereof:

Fig: 1 1s anaem a-diagram or the mechanism of iny ihveiitidihapbl'i'cable to "hobbina machine; f amewtaken-in a plaheiht'e he the a xes of" a hob drive gear and'woi'lr'siiin'd e- Fig} 3 15- a s'etlbii geaemeenanism w and output rel'atiii di thereon. v

' Fig 4': is arviewtalsen trans ersely of the were spindle: showing 3'; pair" 6f Helical mating} power lead dinjerent'iai plane or the input and driven shafts 3 output gears comprising a driving helical gear secured to the work spindle, the view also comprising a relatively parallel section taken through a driving power input worm and a fragment of a relatively driven gear secured to said spindle;

Figs. 5 and 6 are, respectively, elevational views of a hobbing machine, the first showing an end elevational view of the lead gears of the mechanism in side elevational view, and the second showing the index change gearing, the feed change gearing thereof in side elevational view;

Fig. '7 is a schematic perspective view of a portion of th lead differential mechanism of Fig. 3;

Figs. 8 and 9 are views illustratin an assembly of transmission mechanism comprising a rapid traverse differential gear unit and lead screw and differential gearing driving means, Fig. 8 being a perspective view of some of the parts shown in Fig. 9 which is largely a diametrical section of the apparatus of Fig. 8 and affording a showing of certain power drive elements related to the apparatus of Fig. 8;

Fig. 10 is a view of the rapid traverse mechanism largely taken on a diametrical line of section of the driving and brake mechanism thereof; and

Fig. 11 is a view of gearing associated with a pair of shafts, said gearing being shown in diametrical section with the shafts shown in side elevation.

Referring now t the various figures of drawings, in all of which like parts are designated by like reference characters, the said drawings are illustrative of a transmission mechanism which is a preferred embodiment of my invention, said mechanism being adapted to caus th hob and work spindles of a, hobbin machine to be rotated at suitable rotational rates, and to cause a relative feeding movement between the spindles in a direction parallel to the spindle axis, whereby said machine may be adapted for the hobbing of helical gears having prescribed specifications, particularly with reference to the number of teeth and the lead of said teeth of any helical gear to be cut.

Certain of the drawings show the said mechanism as applied to a hobbing machine wherein the relative feeding movement between the spindles is of the nature of that disclosed in the prior patent to H. C. Warner etal. No. 2,075,489, dated March 30, 1937, wherein the feed movement is imparted to the head carrying the hob, but it will be apparent to those skilled in the art to which my invention appertains that my invention is readily applicable to hobbing machines wherein the feed movement is imparted to the work spindle, and in fact, to all hobbing machines wherein there is imparted to either or both hob and work spindles a relatively feeding movement in parallelism to the axis of the work blank.

Referring primarily to the diagram of Fig. 1 with explanatory reference to the other drawings, the transmission mechanism disclosed therein is a preferred embodiment of my invention.

The said illustrated embodiment of my invention, is here disclosed as being applied to a vertical type differential hobbing machine, of either single spindle or multiple spindle rotary types.

While the mechanical drawings of Figs. 2-10 are more particularly relied upon to show details of preferred mechanical construction relating to the transmission mechanism of my invention, certain of said drawings sufficiently show the same as applied to well known elements of a typical vertical type hobbing machine, that the operation and operative results of said mechanism of my invention will be readily understood.

Although it will be understood that hobbing machines, of the type referred to, commonly are provided with a suitable preliminary adjustment mechanism whereby the hob spindle 88 may, by a rapid traverse movement initially bring th hob spindle into full depth in position with respect to a work blank carried by a work spindle S, and whereby subsequently, the hob spindle may be withdrawn to the restored or out position, the hob spindle being usually movable in a substantially rectilinear path, preferably by electrical power means, in any usual manner, the present drawings do not essay to show all such mechanical details of such ancillary mechanism nor the electrical controlling means therefor which may be of any well known type, the present invention being related only to the mechanism for effecting operative relative feed movements of said hob and work spindles, and to the preliminary "setup of said mechanism to cause the hob to so cut gear blanks as to generate helical gears of prescribed specifications.

The sequence of movements of the hob head when the hobbing mechanism is set up to hob a gear comprises first an actuation of the rapid traverse motor 60, including actuation of the lead screw l5, to effect quick return of the hob slide to the starting position, then with the rapid traverse motor T shut off and its shaft braked by a brake 6I6la, the main drive motor and the in-out motor (not shown) is started whereby the feed is engaged and the hob OH is brought into the proper depth, whereupon the in-out motor is stopped and its shaft likewise then automatically braked, but the main transmission driving motor M which was preferably started at the same time continues to run to drive the transmission mechanism disclosed herein, including the lead screw [5, to feed the rotating hob across the face of the rotating work blank, which is thereby operated upon.

When the machine is arranged with a standard in-out mechanism, suitable adjustable stops of well known character are adjustably set, one of such stops adapted to cause the hob to be brought into full depth position with just sufficient clearance so that the hob 0H will not engage the work blank when in the full depth position, and another stop should be adjustably set so that it will be actuated as soon as generation of the gear teeth on the blank has been completed to effect restoration of the hob to a 7 normal inoperative position to. permit reloading of the work spindle S with a new blank.

Portions of horizontal slideways carried by the hob head carriage I-I--H upon which the mount 55 for the hob head 50 is adapted to slide horizontally, are shown at 6|, and portions of a pair of vertical guides for the carriage H--H which supports the hob head 50, are shown at 62.

The carriage H--H is movable only in vertical directions by virtue of timed rotational movement given a lead screw 15 which is anchored at its lower driven end to a stationary portion of the mechanism frame K, Fig. 2, to prevent longitudinal movements of the screw, the threaded upper end being meshed with an internally threaded bore of an element of said carriage, which is thus moved vertically responsive to rotational movement of the screw.

The carriage being movable vertically on slideways 62 and the hob head '50 being movable attache horiaontaliy on slideways 6' 1 eii said carriage; to accommodatesuchmovenients hehohdrive shaft 30" comprises upper and lower relatively interlocked and relatively reciprocabl'e splined upper and lower verticalsections to permit up" and down movement of thecarriage; similarly, the horizontal shaft 31 likewise comprisesrelatively longitudinally extensible relatively splined sections to permit continuous driving or the hob" spindle by a gear 6 secured; to" the upper sectionof. the shaft 38'' through the' relativelymeshed gear in turnanixed toth'e laterally immovable section of the shaft. 3|, said spindle being carrij'ed by andm'ovable: with" thehob head; during lateral input adjustment movements of said hob head".

The hob'head. 5t oarryiiig'the spindle 8B is also carried by a rotatably' adjustable support whereby the hob may manuauy be pread'justed todispose its axis at the'proper angle relative tothe vertical" axis of the w'ork'spirrdle s" in order to set the hellcall'y arranged series of hob teeth at the proper operating? angle to" the work blank spindle S.

The section of the shaft 31" which is laterally movable with the head 50",: together with the relatively meshed gears 3-4", as'well'as the relatively meshed gears 2 and l are all fixedly journalled in. the hob head whereas the relatively meshed gears 5 and 6, together with the driving sectionof the splined shaft 3T are an journalled on the solely vertically. movable carriage IIH as distinguished. from thel'aterally movable carriage-supportedhob head' 50.-

.With the foregoing. explanation of common generally known portions of a vertical hobbi'ng machine. the diagram of Fig.1 sufficiently. discloses my improved transmission mechanism. in a preferred embodiment. andits application. to such vertical type bobbing. machine is shown in Figs. 5 and 6. Referring now more particularly to-Fig. l but withraccompanying referenceto the other drawings, for a description of the operative elements of my improved transmission mechanism. and to show'their cooperative relationship;the-work and hob-spindles S and 88-are bothshown as rotatabl-y. driven from a main drive shaft 32, which, dur ing operation of the bobbing machine, is. driven by a motor M, the'pulleys and P,- andbelt 64, or. in. any other suitable manner at any desirable rotational" speed.

While herein, the shaft-.32 is conveniently designated as the'main' drive shaft, it will. be understood that the shaft 30 or. other primary driving shaftor shafts may, in other embodiments be more properly terme.d:the main drive shaft; .Fig. 1 shows an alternative arrangement where a motor M is adapted to drive" the shaft 30 in any suitaJoleway, thus replacing the. motor M,. the broken.- away portion of the shaft. 30 as designated at B being here intended to indicate that in. the present portion of" the description. the motor rather than the motor M is the driving motor.

ut: 3*; through tiiegear pair ee -34. Tothe ends of said input shaft are secured the gear 3'4 and a di fierenti-al driving gear 36 ofthe differential mechanism L which is providedwith a difi'erential driven gear" 3-1 which is disposed axial alignment with'said gear 36 and issecured to" a differentia-l outputshaft 23; which drives the set of index change gears A-B-c the driving index gear A being also securedto the The drivingand driven gears= 36= and 3 1 are: axialiy interspaced adi-fierentialcasing 2-2 towhich a worm wheel 211- is rigidly aiiix'ed, and on'e or more pairs of relatively intermeshed' diff'erenti'al pinions 40' and' 4 1 each separatelyjour-- nale'd on shafts secured to the casing 2-2, are adapted tocommunibate driving motion from the-gear' 36 to the gear 31; each or the pini'ons Ml being meshed with the gear 36 and each of the pinion's M beihg intermeshedboth with the: pinion "Fahd the gear'3 I l The set of index gears may be variously arranged; but inthe formshow-n in Fig; 6 comprises a" driving gear secured to the differential ou-t-' Put shaft 23 and a driven gear'C, there being one ormoreihtermediateindexgearsBinterposed-between and in' serial relation with the gears A and- 6' whereby the gear. G is driven by thegear' A through the intermediat'e gears fie The output indexgear C is secured to a shaft $3 to whose other end a worm pinion Msafiixed; said' worm pinion being meshed with a worm wheel I!) rigidly secured to the work spindle S whereby the spindle maybe rotated at: an appropriate" rotational rate'by the worm pinion 9. The spindle Sbeing rotated, ahelical-gear H aifixed to thespindle S drives a relatively meshed mating helical gear [2' which, being afiixed to a shaft 4 4; rotates said shaft to whose other end the driving feed gear D of feed gears D-EF"is secured; reference being here made to the right hand sideof Fig. 6*fora showing of an appropriate-set of said feed gears, the gear F being the drivengear and" the gear E; in any appropriate number, transmittingdriving-motion to the output feed gear'F; The output feed gear F'is secured to a shaft the other end ofwhich: having aflixedi thereto the driving gear 49- of a rapid traverse: differential mechanism T comprising. a frame 46 to which is secured a worm'. gear 48:- which, during cutting feed movements of the hob;.is maintained non.- rotatable in-a manner later: described;

Rotary motion is communicated. fromthe. input gear-49m the differential. driven gear 'Ifl'through one or more pairs of differential pinions, each pair comprising relatively-intermeshed pinions 53 and 54 which, in-- turn, are respectively. meshed with the: gear 49 and? H1. Each. of the differential pinions 53 and; 54 arev separately journaled onshafts such as 9! anchoredto the differential casing 46 and preferably the" driving. ratio. between the gears 53 and 54 is a 1 to. 1 ratio. The driven gear 10' is secured. on the end of a shaft 5! to which is also afiixe'd a bevelled gear H and a worm pinion [3, said gear andpini'on, as also the worm gear 48, being respectively longitudinally inter'spaced along'th'eshaft 5|.

Rotational movement imparted to the shaft 5| communicated to thewo'rm" pinion It causes said pinion to drive the worm gear Mwhich is rigidly afflxed' to the lower end of the lead" screw l5 whereby the leadscrew f5 is give'n a rotary movem'e'nt to verticallymove' the hob'" carriage tocause thereqnired feed movement of the hobspinclletB aaeaesa while moving transversely across the periphery of the work blank placed on the work spindle S, and in a direction parallel to the axis of said work spindle.

It will be apparent that the bevelled gear I! secured to and rotated with the shaft at all times rotates in a definitelytimed relation with respect to the driven lead screw l5 and therefore is effective to communicate a compensatory rotational movement to the element 22 of the lead differential mechanism L, which is proportional to the rate of feed movement of the carriage H-H and therefore of the hob OH.

The worm gear 2 secured to the hub of the differential frame 22 is driven by the relatively meshed worm 2 l secured to a shaft 64, to the other end of which the gear 19 is affixed and is, in turn, driven through an idler gear 89 by a gear l8 secured to a shaft 63, to the other end of which a lead gear G is aflixed. The gear G is adapted to be driven through one or more idler gears H by a gear J secured to one end of a shaft 62 which carries a bevelled gear 16, in mesh with, and driven by the bevelled gear H, which is secured to the aforesaid shaft 5 i.

In the exemplary operations hereinafter set forth, the set of gears |8--89l9 when having a 1 to 1 ratio are relatively unimportant since the shaft 63 could be substituted for the shaft 64 as a carrier for the worm 2|, and are only shown since they have been incorporated, as a matter of convenience, in a Lees-Bradner type of hobbing machine.

Similarly, the gears 3334 could similarly and for like reason be omitted, these being preferably of a l to 1 ratio and the shaft 32 could be extended to include the input shaft element 35 of the differential mechanism L. It will be noted that the differential mechanism L and T are quite similar, the latter being merely employed to effect a rapid vertical traverse movement of the hob OH, achieved by a rapid rotation of the lead screw I5, at times prior to and subsequent to a gear teeth generating feed movement of the hob.

Having described the operation of the transmission mechanism of my invention with omission of specific description relating to the rapid traverse mechanism, reference will now be had to various of the figures of drawing showing typical arrangements of the index gearing, the feed gearing, the lead gears and the differential mechanisms L and T, and also showing other of the parts referred to in the foregoin narrative.

The differential mechanisms L and T are quite similar in construction and Fig. 7 is therefore applicable to both said mechanisms, being a schematic view of driving and driven axially aligned gears, such as the gears 36 and 31 of the mechanism L and the differential pinions, one pair of which are shown at 40 and 4|, the latter being relatively intermeshed and respectively meshed with said gears 36 and 31, the relatively supporting pinion shafts indicated at 40' and 4| being anchored in the manner schematically shown in Fig. l as in the frame 22 of the mechanism L.

Figs. 8 and 9 which illustrate the differential mechanism T, also afford a showing of the like construction employed in the mechanism L. The rotatable frame 22 of mechanism L corresponds to that shown at 46 in Figs. 8 and 9, and the shaft 5| is shown as having secured thereto in longitudinally spaced relation the bevelled gear I! and worm pinion l3, above referred to, and the shaft 8 45 is shown as provided with a gear spindle" 45' to which is secured the output feed gear'F.

The mounting of the diiferential spindles, such as those at 40' and 4| on the differential frame 22, is relied upon to communicate the increment of speed variation to be imparted to the gear 31 and the shaft 23 by the effect of rotation of the worm pinion 2| by'motion derived from the haft 5|, as described, since the rotational rate imparted to the gear 31is at a rate which is the algebraic sum of the rotational rate of the input gear 36 plus the rotational rate imparted by the worm 2| to the frame 22.

The action is similar with respect to the acceleration of rate of rotation imparted to the shaft 5| carryin the gear 1!] by rotation of the frame 46 of the differential mechanism T by the driving effect of the worm 55 on the gear 48.

Fig. 5 illustrates the lead gears GHJ. the intermediate lead gear H being interposed between and meshed with said gears G and J. It may be said that the gearing illustrated in Figs. 5 and 6 is in forms which are typical in change gearing commonly employed in hobbing machines and other forms of change gearing may be substituted for the forms herein shown by the drawings which merely illustrate my present preference in this respect as to the form of change gearing which may be conveniently employed in the Lees-Bradner machine in which my invention is shown as embodied.

It may be here stated as is obvious that the diagrammatic view of Fig. 1 illustrates parts in variously differing spaced relationship and to different scales than actually are employed in the mechanism of my invention, and for a proper understanding of relative sizes of parts shown on different of the drawings reference should be had to the mechanical drawings of Figs. 2-11 inclusive and as these may be modified by this specification and particularly by the gear ratios set forth elsewhere herein.

Brief reference is now made to certain of the mechanical drawings, of which Fig. 5 illustrates the set of lead gears GH-J which are disposed in an outwardly facing compartment LC of a housing forming part of the stationary frame of the hobbing machine, the cover plate for said housing having been removed to thereby expose to view said lead ears.

It may be said that the terminal lead gears G and J are preferably on fixed centers whereas the intermediate gear H is adapted for lateral adjustment to vary the radial distance between the axis of the gear H and the axes of the gears G and J according to variations in the sizes of gears G and J and sometimes possibly of the gear or gears H, as may be desired, and to meet the requirements of practice.

Fig. 6 similarly shows from left to right a set of index gears and a set of feed gears, the arrangement being similar in each case and each set of said gears comprises a pair of intermediate relatively intermeshed gears respectively shown at B and E. These intermediate gears may in practice be but a single gear or any convenient plurality of gears, the essential requirement being to secure necessary gear ratios as between the terminal index gears A and C and the terminal feed ears D and F.

Figs. 5 and 6 also show the essential elements of the hob carriage I-I-H, the hob head 50 and the hob spindle 88, the latter carryin a hob, in the usual manner.

Fig. 10 illustrates the driving elements of the :9 ,rapid traverse mechanism comprising motor 50 having a double endedshaft "5,9 (to which at one end a brake .drum 61a is aifixe'd and disposed ,in operative relation tobrake s'hoedevices, the latter normally holding the drum Glaand the motor shaft 59 immovable.

.Automatically operable "means, indicated at .61, .of a well'known type, are adapted to retract the brake shoes to release the brake concurrently with the starting of the motor .60. To the :other :end of the shaft .59, 1a bevelled gear 58 is affixed, being meshed with avsecon'd bevelled gear 5.! ,se cured to a shaft 56 to which issecured .a worm ,pinion 55 meshing with the worm gear "48 which, -.in turn, as bests'hownFigs. 1 and 9, is secured to the hub 4.6 of the frame 16 of the differential mechanism.

.As previously stated, the rapid traverse mechanism is, during hob cutting Derations, inoperati-ve and therefore the brake comprising the drums am and the brake shoes .61 maintains the differential frame 46 non-rotatable by-the locking effect of the non-reversible worm gearin -55.

Whenever, during theoperation of the hobbing machine, the .rapid traverse mechanism is opera- .tive,-it is adapted tospeed up the rotational rate of the shaft and thereby the lead screw 15 by the driving eefieet of the .relativelyrapidly rotating worm 55-on the worm ,gear 48 added rotational speed is effected regardless-of any con- :current rotary movement imparted to the differentialgear 49 by the feedgear F.

By virtue of that feature of my invention whereby the disposition of the lead differential -mechanism L in advance .of the index gearing AB--C whereby the index gearing is driven through the differentialmechanism L at all times, Iachieve the resulting --simplification of the preliminary set up for the transmission gearing for of helicalgears comprising typical practical'driv aing ratios :for the index change gearing, the feed changergearingsand the ;lead change gearing, =are mow" set iforth together "with on'e {practical typical Name of the lead screw pitch whereby advantages "in readily ascertaining sand effecting the "correct set up ffori'hobbmg helical gears of varying speciiiioations may'ibe'achieved.

Index years The ratioof the serially rlated.,g'ear sets 1-4,

"34, 56, "1-48, 33-34, 36 31, and that comprising the worm and wheel -9-.TIJ determines therindex constant, and therefore the number .of teeth which the hob will out on the peripheral surfaceof the work blank carried bythe. spindle S.

"Assuming a l to 1 (ratio for the .index gears -.A--.C, .and that the drivingratio-ofgearsl to 2 and .3 to '4 were 6 to .1, that of gears .5-6 and L -Brand .33--.34, 36-41 were 1 to 1,-rand that the 1 driving ratio between the worm 9 .and the gear .HJ whichissecured to the Work spindle S, i554 to 1, them, 'upon .operation of the machine-it .is obwwvious that the hob 30H will out ,9 teeth on the blanbcarriedby the .workispindl'e S.

1:0, !Ihe index gear iormul'a could then be set forth "Where N .is the number of teeth which the operator desires to have-tout on the periphery of the work blank, the ratio of 11/6 being the driving ratio of the index gears comprising the gears A and. C.

Feed years The ratio of the serially related {gear sets 14-12,, .I 3l 4, '49-"lll, and the pitch "of the lead screw l5 determines the travel or Lfeed of the hob for .each single rotation iof, the 'Work spindle S which vcarries the workblank.

Therefore, assuming a 11 to 1 driving ratio between the feed gears D and a ratio "between the ,gear .H which is secured to 'theworkspindle, to gear [2,, ef '3 .1102, and that the ratio between the ,gears 11.3 ,and ill "is ,2 to .15, and with the (pitch vof the feeding lead screw 15 being one-half inch, then,.insuch.a case, a 1 to .1 driving ratio of gears and D will achieve a dec'imally expressed ghjob feed of A00" for each complete rotation of the work spindle S, and of the work blank rotating therewith.

Thus, 'by providing a gear at F, having teeth, the set-up operator may readily predeter- :mine that the hobzfeed shall be equal to any-multiple of .5001" which maybe required, "by merely substituting a ,gearD having such a number of teeth as 'will -.1corresp0nd .in number 'to the number of thousandths Koran inch), of hob feeding movement required.

The determination of the setup for "achieving .a desired .feed' movement of the hop OH, is thus determinable without calculations or reference to charts, and with the exercise of little ,mathema'tioalsk ill.

Lead-gearing Thepitch of thesc'rew =l-5 as well as the respec- "tive ratios of "the gear sets l 3-l'4, l 6l1, G--J,

F 'l 8' l:9, 20-21 the ratio between the differential ge'ar casing 22 to the "shaft 23, and *ratio of gear sets A-C "and 9-I0, is determinative of the amount, of hob advance for each single rotation "of the *wo'rkand therefore-determines the lead of the gear teeth formed in the blank by cutting :actiOII'dfthG h'db teethj For example, in a typical and pra'dtical setmp, and assuming the aforesaid pitch of lead screw pitch being equalto /z flet the following gear ratios be assumed asexisting in the above gear sets, whose ratios have not above 'been 'set forth, "towit:

Ratio of gearing l3l4 being 2 to 15, that of l6l'| being 5 :to 8,-lthat of l8-,I9 being 1 to 1, that of 2 il 2l' bing 8 to 1, and "that of 22-23 .beingZtml. 7

Then, also assuming, as aforesaid, that the ,ratioof :A =9 5 equa s 37 (see under"Index gears"), and that the ratio of the gear .set ,9-.l,0 equals 1 to. 5.4, then .foreach single {rotation of the work spindle and lwork blank; the lead expressed in inches ,is equal to the product of N multiplied by G, dividedby J, or N XQZJ. '1

This value, expressed in terms of inches of :lead, ,found as the ,productobtained by imultitainable from the above and foregoing listed ratio values, as follows:

a a 1 a i i .2 i" 1 92 1 18 2 the result being expressed in inches, and being multiplied by the ratio G/J for the gear set G--J, an ultimate product of which being reduced to numerical values, expresses the lead value in inches, therefore the equation GzJ: :lead:N expresses the relationship which is controlling.

It is to be noted therefore that the driving ratio of lead change gears G and J, is thus made equal to the lead for each tooth of the gear to be cut and from the foregoing, it is apparent that having first calculated the ratio of the gear set comprising gears G and J, these same change gears G and J are used without any substitution of either, when the hobbing machine is subsequently employed to cut any and all gears which are relatively mating with a first helical gear for which the gear ratio G/J has been ascertained. The above advantage is achieved as a result of the positioning of the set of lead differential gears between the hob drive and the index change gears.

When cutting all other mating helical gears, it is therefore only necessary to employ the predetermined gears G and J and then, as previously related, to so choose the index driven gear C that such a gear C will have the proper number of teeth in the helical gears to suit the number of teeth in the helical gears to be cut.

The following typical examples will show the practical application of the above described methods, the first being for a specified helical gear, and the second being for a relatively mating helical gear having a different number of teeth whose lead value is also different.

The above result is achieved in the mechanism described while still permitting changing of the feed drive gear D at any time to vary the amount of speed required for cutting blanks of different materials.

For the first example, and while retaining the aforesaid assumed values of gear ratios, for hobbing a helical gear having teeth having a lead of 32":

Therefore, gear A should be provided with 36 teeth, and the gear C should be provided with 80 teeth.

. the gear C.

942mm 91 J N *5 40 and the gears G and J, having 64 and 40 teeth, respectively, will be left in place for the cutti g Lead gears,

of the above and all relatively mating gears, with respect to the helical gear for which the setup of the above first example was employed.

The above simple calculation clearly shows that for cutting mating helical gears, it is only necessary to substitute for the previous index gear C having teeth, an index gear C having 25 teeth, in order to cut the desired helical gear having a different number of teeth, 25 instead of 20, and a different lead value of 40" instead of 32".

Therefore, for all relatively mating helical gears, the lead is always in direct proportion to the respective numbers of teeth in such mating gears, the only change necessary to cut any such mating helical gear being to provide an index gear C whose number of teeth corresponds to the number of teeth desired in the mating helical gear, and in such case, it is unnecessary to alter the originally employed lead gear ratio of the first example, which is maintained constant for the hobbing of all relatively mating gears.

The simplified set-up of the mechanism for the cutting of helical gears is to be distinguished from the nature of set-up required in prior differential hobbing machine transmissions wherein the position of the index gears is in advance of the position of the lead differential in the line of drive from the point of the power takeofi for driving the hob which leads to the driving worm for the work spindle, and wherein the rates of rotation of said index gears would be unaffected by the imposition of the increment of driving motion variation communicated to the lead differential element corresponding to the differential casing element 22, by any means such as the present worm gearing 2 |20.

With such a prior arrangement, it would be necessary, when cutting helical gears having different numbers of teeth, to first change the index gear C, and also to change the lead gears G-J, and in such case, changing the index gears for the number of teeth being cut, does not automatically effect any change in the value of lead as in my improved mechanism, as shown by the above recited examples.

It will be noted that with my improved mechanism, the lead gears J-G are the same for all mating helical gears being out, which makes for accurate matching of leads.

In the above described prior art arrangement of differential mechanism and index gearing, the lead gears JG must be different for helical gears having different numbers of teeth, and as a result, two sets of calculations are required. In calculating these gears, the best that can usuallv be done, by those skilled in the art, is to find gear ratios that approximate the leads required. Therefore, the approximate matching of leads in such cases, is dependent upon the skill, or possibly good luck of the calculator.

From the foregoing, it will be clear to those skilled in the art that my invention is in like manner as readily applicable to hobbing ma chines wherein relative hob and work blank traversing motion in a direction parallel to the work spindle is effected by longitudinal movement of the work spindle instead of by the aforesaid herein described relatively parallel movement of the hob, and in any such application, the only difference from the embodiment of my invention herein described resides in the different arrangement of the machine whereby, for instance, the feed lead screw I5 is adapted to communicate a longitudinal feeding movement to the work spindle, while the rotating hob spindle is relar 13 tively stationary in properly adflus'ted depth position.

It will be understood that rotary motion at a rate proportional to the rate of relative hob and "Work spindle relative feed movement to compensatorily rotate the frame -'22 of the differential mechanism L may be derived otherwise than from the shaft through such means as the relatively meshed gears l6 and F! and, for instance, rotation of the shaft 62 may be "alforded "by meshing the teeth of -a gear secured to said shaft with the teeth of a rack carried by the hob marriage or other movable element which isrnovfa'ble at a rate which is proportional to -the'rateof and the operative drive between the feed gearF i and the shaft 51 is "substantially inflexible, then the drive to such 'a shaft as indicated herein at '62 might be taken from the feed gear For from "any other element of the drive wherein suitable provision is ma'deto ensure that the shaft 62 may "be driven at a rate proportional to the rate of relative feed movement as between the "hob and work spindles.

The difierential mechanism T affords an advantage over prior-constru'ctions which commonly ii-nyolve the necessity of operating clutches :between the gear F and the feed mechanism ,comprising any element equivalent to the feed screw IS in order "to drive such feed mechanism at a relatively rapid rate.

The present transmission mechanism -.afi?ords a eneansof ensuring that allirelative feeding or-opposite retracting movements as between thehob and work spindles may be eifected while still ensuring that the hob teeth are moved in such manner with respect to the helical teeth previously cut on the gear blank will not cause damage to said gear teeth. In other words, said hob teeth during such traversing movement will track in the helical cut of the work blank previously generated, assuming, of course, that the transmission mechanism is still operative by power delivered to the power input shaft 32.

Again, while the transmission mechanism of my invention is being driven should the portion of the shaft 5|, which is disposed between the gear l1 and the differential mechanism T be taken away and a hand crank applied to the portion thereof remaining which carries the gear I! and the worm l3, turning of said remaining portion of the shaft 5! to achieve feeding movements of the hob carriage HI-l'. by rotation of the screw l 5 at any desired rate of crank turning will be sufficient to afford correct operational movements of the hob and work spindles, the compensating drive through the lead gears to turn the lead differential frame 22 in any such case being operative to effect proper relative feed movements of the work and hob spindles.

Although, I have herein emphasized the advantages accruing through the positioning of the differential mechanism L in the transmission mechanism of my invention, attention is directed to the fact that I believe the method of and apparatus for communicating the rapid traverse movement from a rapid traverse motor as 60 to such means as the shaft 5| to also be novel and to involve invention.

Having above described the apparatus involving transmission mechanism in a particular embodiment, 1am aware that the said invention may be embodied in widely varying embodiments and "that invention vmaysbe applied :to hobb'ing machines ofvarying constructions from that herein shownand described, and that the specific constructions-f the various instrumenta'lities :such as the d iffierential mechanisms L and T may be also widely varied :and may be replaced by equivalent structures adapted for the intended herein described purposes.

I claim:

1. In a differential type hobbing machine of the type adapted for the generation :of helical gear teeth the combination :with motor means, of a work spindle, *a ho'b spindle and means for relatively feeding one of :said spindles with re- 'spect to the other a direction parallel to the axis of the work spindle, and a pair of relatively parallel 'drives from said motor means, each for respectively transmitting power for rotating a different one of said spindles, each at a rate which is in relatively timed relation to the rate of rotation :of the other, said work spindle and said feeding means being driven responsive to rotary movement transmitted over afirst'of said drives to said Work spindle, a lead difierential mechanism and a 'set of index gears serially so disposed in said'first drive that-said index gearing is driven by rotary movement communicated thereto by said 'll'l8Ch2LnlSm,1an'd"S2iid'WOIk spindle and .said feeding means are each rotated by Totary movementidelivered to eachfrom said index gearing, said mechanism comprising a pair of relatively driving and driven gears and rotatable .means adapted when rotated "to vary the rota- 't'ionall rate of .sa'id driven gear by an amount equal to the algebraic :sum of the rotational rates of said driving 'gear and of said rotatable means and transmission means for communicating rotary movement to said rotatable means, said transmission means being actuated by an element of the drive for effecting said spindle feed movement, and a set of lead gears serially interposed in the line of drive including said transmission means and said rotatable means.

2. In a differential type hobbing machine of the type adapted for the generation of helical gear teeth the combination with common motor means for transmitting rotary motion over relatively branched drives of a Work spindle and a hob spindle respectively driven by rotary movement communicated from said motor means over a different one of said drives, feeding means actuatable by rotary motion transmitted over the Work spindle drive and adapted to effect feed movement to one of said spindles with respect to the other in a direction parallel to the axis of the work spindle, lead differential gearing and a set of index gears so relatively serially disposed in said work spindle drive in advance of said work spindle as to dispose said lead clifierential gearing in advance of said index gears, and whereby the output gear of said index gears is adapted to transmit rotary motion to said work spindle and to said feeding means, a set of feed change gears interposed in theline of drive be tween said index output gear and said feeding means, said differential gearing comprising a pair of relatively driving and driven gears and rotatable means adapted when rotated to vary the rotational rate of said driven gear by an amount equal to the algebraic sum of the rotational rates of said driving gear and of said rotatable means, and transmission means for communicating rotary movement from said output feed gear to said rotatable means, and a set of lead change gears interposed in said transmission means, the output one of said feed gears having 100 teeth, and the driving ratio of said feed gears being equal to the quotient obtained by dividing the number oi teeth in the input feed gear by the number of teeth in the output gear thereof, and the rotational driving ratio of said motor means and the gearing ratios and the rate of relative feed movement between said spindles in the line of drive to said work spindle and to said feeding means including said feed gears being such as to drive said feeding means at a rate of inch (0.100") for each complete rotation of said work spindle, when the input and output feed ear rotational rates are equal, whereby the provision of an input feed change gear having any lesser number of teeth than 100 teeth is adapted to efiect a rate of drive for said feeding means equal to one hundred thousandths of an inch (.001") multiplied by the above quotient, expressed in thousandths of an inch.

3. A hobbing machine of the type adapted for the generation of helical gear teeth, the combination with driving motor means, a work and a hob spindle, feed means comprising a rotary driving element for communicating a relative feed movement between said spindles in a direction parallel to the axis of the work spindle, and a pair of transmission drives in relatively parallel relation both receiving power from said means adapted to rotate said spindles in relatively timed relation, a lead differential gear mechanism, a set of index change gears, and work spindle driving gearing in respectively successive driving relation in a first of said drives, and hob spindle driving gearing disposed in a second of said drives, a set of feed change gears, means for transmitting rotary motion respectively successively through said mechanism, said index gears, said feed gears, to said rotatable element of said feed means, said mechanism comprising speed compensating means for varying the rates of rotation of said index gears and of said work spindle at a rate commensurable to the rotational rate of said feed means element, and a rapid traverse differential gearing means interposed between said index gears and said feed means element, said differential means comprising a pair of relatively driving and driven gears, rotatable means adapted when rotated to vary the rotational rate of said driven gear to a rate equal tothe algebraic sum of the rotational rates of said driving gear and of said rotatable means, a rapid traverse motor and gear for driving said rotatable means at an accelerated rapid traverse rate, and means associated with said rapid traverse transmission means adapted when said traverse motor is deenergized during relatively slow feeding movements of said spindles to prevent rotation of said rapid traverse rotatable means to normally adapt said differential means i'or the transmission of relatively slow rotary -motion from said feed output gear to said feed means element.

HOMER C. WARNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,364,932 Warner et a1 Dec. 12, 1944 2,374,254 Zimmerman Apr. 24, 1945

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