US1758193A

US1758193A - Machine for generating gears

Info

Publication number: US1758193A
Application number: US233118A
Authority: US
Inventors: Ernest C Head
Original assignee: Gleason Works
Current assignee: Gleason Works
Priority date: 1927-11-14
Filing date: 1927-11-14
Publication date: 1930-05-13
Anticipated expiration: 1947-05-13

Description

May 13, 1930. E. c. HEAD 1,758,193

MACHINE FOR GENERATING GEARS Original Filed Nov. 14, 1927 4 Sheets-Sheet 1 INVENTOR May 13, 1930. E. c. HEAD 1,758,193

MACHINE FOR GENERATING GEARS Original Filed Nov. 14, 1927 4 Sheets-Sheet 2 INVENTOR Ema-st Cfflad ATTOR Y May 13, 1930. E. c. HEAD ,7 8,193

MACHINE FOR GENERATING GEARS Original Filed Nov. 14, 1927 4 Sheets-Sheet 3 INVENTOR t Gilead ATToRNEYZ May 13, 1930. E c, HEAD 1,758,193

MACHINE FOR GENERATING GEARS Original Filed Nov. 14, 1927 4 Sheets-Sheet 4 IMHI llll INVENTOR Ernest GHaad Patented May 13, 1930 ERNEST C. HEAD, '05? ROCHESTER, NEW YQRK, ASSIGFNOR TO GLEASON WORKS, 025 R QCHES'EER, HE? YQRK, -A CORPORATION OF YORK MACHINE F03. GENERATING GEARS Application filed November 14, 1527, Serial No. 233,118.

The present invention relates to a machine for producing gears and particrrlarly to a machine for -ge'nenati ng bevel gears in a continuous indexing "or bobbing process. Among the objects of this invention are to provide a machine which will be fully automatic and which will be much faster in op erotic-n than machines heretofore construc't eel for the same purpose.

Other objects of the invention Will be apparent hereinafter from the specification, when read in conjunction with the accompa nying drawings, the novel features being ointed out in the claims appended hereto. 5 Inthe drawings:

Figure 1 is a side elevation of a machine constructed according to one embodiment of my invention;

Figure 2 is a plan View, partly in section, of this machine;

Figure 3 is an end elevation of the machine lookii'ig from the right of Figure 1;

Figure 4 is a View partly in end elevation from the left of Figure 1 and partly in sec- 'tion on the line 4-4 e f Figure 1;

Figure 5 is a view, partly in section, on a somewhat enlarged scale showing a detail of the fast and slow feed drive mechanism and the clutch controlling the operation of i the same;

Figure 6 is a section on the line .-6 of Fig-me 5;

l igr-lre 7 is aside elevation of the cam governing the feed and withdrawing movements :1 of the blank carrier and of the mechanism for shitting the speed control clutch;

Figure 8 is a section on the line 8 8 of Figure 7; c

Figure 9 is a section on the line 9 -9 of Figure 7.; and

Figure :10 isa diagrammatic View showing the-general arrangement ofthe gearing controlling the operation of the various parts of the machine.

The present invention relates, in particular, tomachmes'for generating tapered gears in continnouscutting or bobbing process. In a machine of this character the tool and blank ere rolled relatively to each other While a continuous indexing rotation is imparted Renewed Seiiterlabcr 17, 1929.

to the blank, a predetermined timed relation being maintained between the toolmechanism and blank during the rolling movement.

In a machine of this character the blank is completely out during the roll of the machine in one direction. The machine is returned to initial or starting position prepara tory to cutting a new gear, by reversing the llirection 'of'th-e rolling movement. For convenience, throughout this application, the rolling movement during which cutting takes place will be referred to as the rolling gen vrating motion and the rolling movement d uring which the parts are returned to starting position will be referred to "as the rolling-return movement. It will be understood that these rolling n'iovements may be imparted wholly to the blank,- Wholly to the tool or in part to the blank and in part to the tool.

A machine of this character has the advantage that all of the teeth of the blank are operated upon simultaneously with the consequence that any Wear of the tool is distributed equally over all the teeth and that there is no danger of overheating the bianlr at any one point, as is possible when the teeth are completely generated successively. With a bobbing machine, moreover, complicated indexing mechanisms are avoided, the blank being indexed by a simple continuous rotary movement timed up with the tool movement.

Since the continuous relative rolling generating movement is coordinated with the continuous indexing movement of the blank, a motion is produced between the tool and blank corresponding exactly to that of a gear, as a crown gear, represented by the tool rolling continuously With-tire gear to be cut. The relative rolling generating motion has, therefore, been used in the past-to move the tool into and out of full depth cutting engagement with the blank, in addition to generating the profiles of the teeth of the blank. This has meant that a sufiiciently long rolling generating movement has been provided heretofore between the tool and blank to move the tool and blank into and out of engagement and to generate the teeth. With this arrangement, however, the tool is doing no cutting at the beginning and at the end of the roll, the roll being employed at these times simply to move the tool and blank into and out of engagement. The purpose of the present invention is to make this excessively long rolling action unnecessary and thereby speed up the operation of the machine. To this end, in a machine constructed according to the preferred embodiment of this invention, the blank is positively fed into the tool during the first part of the rolling generating motion and is positively withdrawn relative to the tool by a bodily movement during the last part of the rolling generating motion. In other words, instead of'using a long rolling motion to feed the tool into the blank, to generate the teeth and to withdraw the tool from the blank, the blank is moved bodily relative to the tool during the first and last parts of the rolling generating movement to feed the tool and blank into engagement and to withdraw them from engagement, respectively.

By the new method ofoperation, the actual rolling movement required is considerably lessened andithe speed of the machine is accordingly increased.

In order to further reduce the time required for the operation of the machine, a two speed drive is provided, by means of which the operation of the machine can be speeded up before and after the cutting operation, which necessarily takes place at a relatively slow speed, so that at the beginning and during the last part of the rolling generating movement during the relative feed and withdrawing motions, respectively, the machine can be operated at a relatively fast speed.

In hobbing machines as heretofore constructed, it has been usual to reverse the machine at the end of the rolling generating movement by hand and throw in a fast speed return drive. It is one of the purposes of the present invention, also, to provide means for automatically operating the reverse mechanism. This mechanism is so coordinated with the mechanism controlling the speed of the machine that the direction of roll is reversed at predetermined points in the cycle and the rolling return movement is at a faster speed than the rolling generating movement during cutting.

In the preferred embodiment of this invention, the speed control mechanism is made adjustable relative to the mechanism controlling the direction of the rolling and continuous indexing motions and to the mechanism producing the relative feed and withdrawing motions. By this arrangement, the speed control mechanism may be adjusted to speed up or slow down the operation of the machine at any predetermined points in the cycle as may be deemed best in practise.

The invention is herein-disclosed in con nection with a machine for bobbing spirai or longitudinally curved tooth bevel gears with a taper hob. It will be understood, however, that the invention is not limited to machines employing this form of tool but may be used in connection with bobbing machines employing other forms of tools, as planing tools, face-mill hobbing cutters or cylindrical hobs and that, moreover, the invention may be used in connection with the cutting of other forms of gears as, for instance, hypoid gears.

In the machine illustrated, the rotary taper hob is mounted upon a carrier or cradle which rotates in one direction during the rolling generating movement and in the opposite direction during the rolling return movement. The gear blank is mounted upon a support or spindle and is given a combined generating and indexing rotation during the movement of the cradle in either direction. The blank spindle is mounted on a table which is movable to feed the blank'into'cutting contact with the'tool and to withdrawit' from engagement after the gear has been completely generated. a

The motions of the cradle and blank spindle are governed from a continuously operating driving shaft which rotates a reversible driven shaft through suitable reversingmcchanism. A two speeddrive is provided so that the driving shaft may be rotated selectively at a relatively fast speedior a relatively slow speed. By this arrangement, a rotary motion may be imparted to the crad'leand blank support alternately in opposite directions and at either a relatively fast or a relatively slow speed. I

The feeding and withdrawing motions of the blank support are'effected by a cam which rotates continuously in one direction. The reversing mechanism is, also, controlled by a cam which rotates continuously in one direction. The two cams are preferably mounted on the same shaft and this cam shaft carries preferably, also, thedevice controlling the speed drive of the driving shaft above referred to. The speed control device is preferably made adjustable relative to the two cams and the cams and speed control are preferably so coordinated that the blank is fed toward the hob partly during the last part of the rolling return movement and partly during the first part of the rolling generating movement, during which time the machine will be operated at a relatively liigl' speed, that the machine will be driven at a relatively slow speed during cutting and that the blank will be withdrawn from engagement with the hob partly-during the last part of the rolling generating motion and partly during the first part of the rolling return movement. The reversing mechanism which controls the direction of the roll is actuated automatically to permit of such a cycle. The cam which controls the feed and withdrawi motions of the work table is pre' :ahly d1" continuously in one direction from the driving shaft, whereby by a suitable ad ustn'ient of the devices controlling the speed of the driving shaft, it will be possible to use the same cam to produce the feed and withdrawal movements at dili'erent times in the cycle of operation of the machine as may be desired in cutting chill-rent pears.

Referring now to the drawn gs: l indicates the base or frame of the in. bed or frame is provided with pays on which are guided the tracks 11 of the cradle 12 on which the tool nicchanisn'i is mounted. The bed or frame serves as a support, also,

for the Work carrier or table 14. The tool,

which in the mechanism illustrated is a per hob H is mounted upon a spindle 1o journaled in a tool carrier 16 (Fig. Preferably, the hob is supported at its outer end by a tailstock 17 carried by a bracket 18 which is adjustable on the tool carrier 16 to permit of supporting hobs of different lengths. For the sake of clearne-ss in illustration the tailstock has been omitted in Figure 1. The angular adjustment of the tool carrier 16 i clfectcd about the axis of a vertical shaft 2) (Fig. 1) and is for the purpose of poll ing the hob in the proper tangential relation to the blank. The carrier 16 may be secured in any adjusted position by means of the bolt 21 (F 2) which engages in a curved slot formed in the slide 22 concentric with the axis of the shaft 20.

The tool carrier 16 is supported on the swiveling head 19 which is angular-1y adjustable about the axis of the shaft 53 (Fig. 2) to permit adjusting the hob to cut gears of either right or left hand. The head 19 can be secured in any adjusted position, as by means of Tbolts (not shown), on the slide which is horizontally adjustable upon a vertical slide 23 and which may be secured in any adjusted position by means of the bolts 24. The vertical slide 23 is vertically adjustable upon the upright or standard 243 and this upright or standard 26 is in turn horizontally adjustable upon the cradle 12 in a direction at right angles to the direction of adjustment of the slide The bolts 27 serve to hold the vertical slide 23 in adjusted position, while the bolts 28 serve to secure standard or upright 26 in any position of adjustinent upon the cradle. The various adjustments described, which may be effected by hand or in any usual or suitable manner are for the purpose of positioning the hob H in proper relation to the gear blank to be cut. The work carrier or table 14 is angularly adjustable upon the bed or frame 10 for positioning the blank in the correct tango-stial relation to the hob. This adjustment can be ell'ected by rotating a pinion (not shown) carried by the blank carrier in engagement with a rack member 30 (Figs. 2 and This is a usual adjustment in bevel gear cutting machines. The blank carrier or table can be secured in any adjusted position to the rack member 30 by means of bolts which engage in a T-sl-ot 31 formed in this member. Slidably adjustable on the swinging base or WOI'k table 14 is the work head column 33 which is movable on the base or table 14 in a horizontal direction to permit adjusting the cone apex of the blank to the correct position. lrlounted for vertical adjustment upon the work head column 33 is the work head 35 in which the blank spindle 36 is journaled. The "ertical adjustment of the work head permits of positioning the blank spindle with the axis of the blank either intersecting the a 's of the cradle or otiset therefrom any desired amount. The work head column 33 may be secureo in any adjusted position on the work table 14 by means of the bolts 37 and the work head 35 can be secured in any adjusted position upon the column by means of the bolts 38. The various adjustments of the blank spindle may be effected by hand or in any usual or suitable manner.

During the operation of the machine, the hob is rotated continuously on its axis being driven from the motor 40 1, 2 and 10) through the bevel gears 41, 42, the spur gears 43, 44, the shaft the miter gears 46. 47, the miter gears 48, 49, the swinging shaft 50, the miter gears 51, 52, the shaft 53, the miter gear 54 which has a splined connection with said shaft, the miter gear 55 meshing therewith, the speed change gears 57, 58 and 59 the bevel pinion 60 and the bevel gear 61 which is secured to the spindle 15 to which the hob arbor is secured.

The blank is rotated continuously on its axis in timed relation with the hob rotation. This continuous rotary movement acts to contini'ous y index the blank during cutting s0 that all the teeth of the blank are completed simultaneously. The continuous rotation is etlected from the shaft 45 through the

gears

65, 66 and 67 (Figs. 1. 2 and 10), the bevel gee. rs (l8 and 69, the shaft 70, the miter gears 71 and 72, the shaft 73. the differential gears 74 connecting this shaft with the shaft 75. the shaft 75 (see also Fig. the miter gears '76 and 77, the vertical shaft 78, the miter gears 79 and 80, the diagonal shaft 8i, the miter gears 82 and 83, the horizontal telescoplug shaft 84, which is journale-tl in the work table 14 and in a bracket 85 secured to the work head column 33, the index change gears 87, 88 and 89, the shaft- 90 which is journaled in the work head 35. the miter gears 91 and 92, the worm shaft 94 journaled in the work head, the worm 95 secured to said shaft and the worm wheel 96 which meshes therewith and is secured to the blank spindle 36.

For the purpose of generating the teeth profiles of the gear to be cut a relative rolling motion is imparted between the hob and blank. This relative rolling motion is ef fected in the machine illustrated by rotating the cradle on its axis and simultaneously imparting to the blank a rotary motion which combined with the cradle movement produces a relative movement between the hob and blank corresponding to that of a gear rolling on the basic gear represented by the hob. The mechanism for producing the rotary motion of the cradle and the generating rotation of the blank will now be described. Mounted upon the shaft 15 already referred to is a miter gear which meshes with a miter gear 101 upon a shaft 102 which is journaled in the base or frame of the machine. This shaft 102 carries adjacent its outer end a spur gear 103 which meshes with a spur gear 101 that is secured to a shaft 105 which is also journaled in the base or frame of the machine. The shaft 105 is adapted to drive a shaft 106 at either a relatively fast or a relatively slow speed. The fast speed drive is effected through the spur gears 108, 109 and 110. The slow speed drixe is effected through the

bevel gears

111 and 112, the worm shaft 113 which is journaled in the frame of the machine, the worm 114 and the worm wheel 115 which meshes with the worm and is driven thereby. The spur gear and the worm wheel. are both rotatably mounted upon the shaft 106 and may be selectively and alternately connected with the shaft 106 by means of the slidable clutch member 118 which has a splined connection with the shaft 106 and which is provided with clutch teeth at either end adapted to engage selectively the clutch teeth formed upon the adjacent ends of the sleeves of the

gears

110 and 115. As will be obvious, by engagement of the clutch member 118 with the gear 110 or the gear 115 the shaft 106 may be driven either at a relatively fast or a relatively slow speed.

The shaft 106 drives a reversible shaft 120 through a reversing mechanism which may he of any usual or suitable character. The reversing mechanism illustrated is described in the U. 9. patent to Gleason et al., No. 1,203.608, November 7, 1916 and reference may be had to that patent for a more rom plete description of the mechanism herein shown. Suflice it to say that the shaft 120 may be driven from the shaft 106 in one direction or the other. alternately, through the spur gears 121 and 122 or through the spur gear 124. the idler 125 and the spur gear 126.

The reversible shaft 120 carries adjacent its outer end a spur gear 127 which meshes with a spur gear 128 that is secured to a shaft 129 which is journaled in the frame or base. of the machine. The shaft 129 carries two bevel gears 130 and 131. The beve gear 131 meshes with a bevel gear 132 upon a trait;- verse worm shaft 133. This worm shaft 13 is journaled in the base or frame of the ma chine and carries a worm 134 that meshes with and drives a worm wheel segment 135 which is secured to the cradle 12. By the means just described a rotary motion is imparted to the cradle in either direction depending upon the direction of rotation of the reversible shaft 120 and at a relatively slow or a relatively fast speed depending upon the position of the clutch member 118.

The bevel gear 130 already referred to meshes with a bevel gear 137 on a shaft 138 which carries adjacent its outer end a spur gear 133. The spur gear 139 drives through the spur gears 110, 141, and 112, the spur gear 1413 which is secured to the housing 115 of the differential gears 74. The differential acts to combine the continuous indexing motion with the generating motion and impart these combined motions through the shaft 75 and the gearing already described to the worm wheel 96 and the blank spindle.

From what has been said, it will be seen that the generating motion may be imparted to the cradle and to the blank spindle in either direction and at either a fast or a slow speed. The means governing the speed of the driving shaft 106, the means for controlling the reversin g mechanism and the means governing the feed and withdrawing motions of the blank table will now be described.

Mounted on the driving shaft 106 adjacent one end is a spur gear which drives through the idler 151 and the gear 152, the worm shaft 154 which is journaled in the frame of the machine. This worm shaft 15-1 carries a worm 155 which meshes with and drives a worm wheel 156 upon a cam shaft 157 that is journaled in the frame.

Mounted on the cam shaft 157 are two

cams

160 and 161. The cam 160 controls the reversing mechanism through the lever 162 and slide 163 which is operated by this lever to operatively engage the gear 122 or the gear 126 with the reversible shaft 120. The lever 162 is pivoted on a bracket arm 16% which is secured to the frame of the machine and carries intermediate its end a roller 165 which travels in the cam slot formed in the face of the cam member 160.

The cam member 161 governs the feed and withdrawing movements of the swinging base or work table 14. The work table is angularly adjusted on and secured to the rack member 30 and this rack member 30 may be oscillated about the axis of the vertical shaft 78 under actuation of the cam 161 to feed the blank into and withdraw it from engagement with the hob. The cam 161 is connected to the rack member 30 through instrumentalities similar to those shown in Patent No. 1,203,608 above referred to. These instrumentalities comprise generally a swinging arm connected to the rack member and carrying a roller 172 which engages in the peripheral cam groove of the cam member 1 61.

Secured to one face of the cam member 161 are apair of

logs

173 and 174. These lugs are adjustable about the axis of the cam and may he seemed in any adjusted position by means of bolts 175 and 17 6 which engage in a: circular T-slot formed in the front face of the cam coaxial with the axis of the cam shaft. .l ournaled i-n-the frame and extending parallel to the (am shaft 157 is a rock shaft 180 (Figs. 2 and S). This rock shaft carries a segment 181 which meshes with a segment 182 rotatably mounted upon a stud 183 which is secured in a bracket 185 that is fastened to the frame. Secured to the segment 181 is an arm 186 that carries a roller 187. Secured to the segment 182 is an arm 188 that carries a roller 189. The roller 189 carried by the I arm 188 is engaged by the lug 173. while the roller 187 carried by the arm 186 is engaged by the lug 174 during the rotation of the cam shaft 157. The arm 188 is bent laterally at one end and the lug 174 is cut away, as shown in Figures 8 and 9, so that the roller 189 and arm 188 will clear the lug 174 during the rotation of the cam 161. From the arrangement described, it will be seen that as the cam rotates the

lugs

173 and 174. will alternately engage the

rollers

189 and 187 thus alternately rocking the

arms

186 and 188 to rock the shaft 180 alternately in opposite directions through the

gear'segments

181 and 182.

Secured to the rock shaft 180 at its outer end is an arm 190 which is connected by a link 191 1, 5 and (3) with an arm 192 which is osci-llatablo upon a stud 193 that is mounted in the frame. The arm 192 carries a pin 195 which travels in an elongated slot 196 in the arm 197 of the yoke member 198. The yoke member 198 is osci-llatable on the stud 193 and is-connected to the clutch member 118 in the usual manner. The arm 192 furcated to receive the link 191 and a roller 199 which is mounted upon the pin 195. Mounted: in a socket in the base is spring pressed plunger 200, the head of which is of truncated V-shape. This plunger 200 enthe roller 199.

VVhen the shaft 180 is rocked the arm 192 is oscillated in one or the other direction about the stud 193 causing the roller 199 to ride on ihe plunger 209 and the pin 195 to travel in the slot 198 of the yoke member 198. When the pin has passed neutral position in travel-- ing in the slot 196 from left to right or right to left the plunger 200 will give it a quick thrust which will throw the arm 197 of the yoke member about the stud 193 and shift the clutch member 118 to disengage the slow or fast feed drive, as the case may be, and en- ;rag'e the other drive.

The operation of the machine will be obvio'us" the preceding description but may be briefly summed up here. The upright 26 is adjusted on the cradle 12, the vertical slide 23 is adjusted on the standard 26, the head 19 is swivelled about the axis of the shaft 53 and the tool carrier 16 is angularly adj usted' about the axis of the vertical shaft to secure the desired offset of the hob axis from the axis of the cradle and to bring the hob apex into the correct position. By a proper angular adjustment of the head 19, it is possible to position the hob for cutting right or left hand spiralteeth, as may be desired. The horizontal slide 22 is adjusted on the vertical slide 23 to bring the hob into the correct tangential plane. The work table or swi'ging base 14* is adjusted on the rackmember to bring the blank into correct tangential relation with the'hob, thework head column 33 is adjusted uponthe base or table 14 to bring the cone apex of the blank into the correct position; and the work head is adjusted vertically upon the column 38120 position the blank axis in any desired offset relation to the axis of the cradle or with the blank axis intersecting the axis of the cradle. The lugs 173 and 1744' (Fig. 7) are also adjusted upon the earn 161 to actuate the cl-ntch shifting mechanism to change the speed of the machine at the desired points in the cycle of'operation. The motor may then be started. The hob is rotated continuously on its axis through the gearing already described. Simultaneously the blank given a combine'l indexing and generating rotation and the cradle is rotated in one or other d-iI'ectioi-r upon its axis. The cam shaft 157 is driven continuously in the same direction through the gearing described and the earn 160 will operate the reverse mechanism at the desired points in the cycle. while the can 181 will swing the base or table 14 to feed the blind: positively into the hob or withdraw' it from engagement with the hob;

Means is preferably provided for stopping the machine automatically on the rolling: re turn movement when the machine has reached the starting position. In the machine iliu's trim-ted. this automatic stopping. mechanism comprises a do; 205 (Fig. 4) carried by the oral l le whit-h is adapter lto cnga ge a eta 1, wheel 208 which is rotatably mmlnl'cl P Hill fraene. The dog 295 is so constructed as to pass idly over the star wheel during move-- ment. of the cradle on one direction and to en gage and rotate the star wheel through the angle of one tooth on the return roll of the cradle. The rotation oft h'e star wheel under actuation of the dog brings a tooth of the star wheel into engagement with the switch 307, disengaging the switch and stopping the liifit fil a fiil the machine. The star wheel 206 resiliently held against movement except when actuated by the dog 205 by a spring pressed plunger 208 which is housed in the frame. The machine is thus stopped automatically at a predetermined point on the return roll of the cradle. \Vhen the motor is started, then, the machine will complete the return rolling movement, the reverse mechanism will be operated, the cradle and blank will be rolled in the opposite direction for cutting and after the blank has been cut, the machine will be again reversed and the parts returned to initial or starting position when the machine will be automatically stopped by the ircclmliisiii ju t described.

Preferably the

lugs

173 and 174 will be so adjusted on the cam 161 that when the machine is started the driving shaft 106 will be operated at a fast speed, that during this fast speed movement and during the last part of the return roll and the first part of the rolling generating movement, the blank will be fed into engagement with the hob, that after the blank has been fed into the proper depth the speed clutch 118 will be shift-ed and the machine operated at a relatively slow speed for cutting, that after the cutting operation has been completed the slow speed drive will be disengaged and the fast speed drive again brown in, that during the last part of the rolling generating movement the now completed gear will be partly withdrawn from engagement with the hob, that this withdrawing motion will be completed on the return roll and that the return roll will be at the relatively fast speed also.

Vvhile the invention has been described in connection with a particular embodiment, it is to be understood that the invention is capable of various further modifications and uses without departing from its scope and that this application is intended to cover any adaptations, uses or embodiments of the invention followin in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practise in the gear art and as may be applied to the essential features hereinbeforc set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

l. in a gear generating machine, a blank mpport. a tool mechanism, means for ettccting a continuous relative rollil'ig generating movement of the tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means for imparting a continuous rotary motion to the blank during the rolling movement in either direction, and means acting automatically to impart a relative depthwise l'ccd movement between the tool and blank during the first part of said rolling generating movement to move the tool and blank into engagement.

:2. In a generating machine, a blank support, a tool mechanism, means for etlecting a continuous relative rolling generating movement of tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means for producing a continuous rotary movement of the blank during the rolling motion in either direction, and means acting automatically to effect a positive relative withdrawing movement between tool and blank during the latter part of said rolling generating movement.

3. In a gear generating machine, a blank support, a toool mechanism, means for efiecting a continuous relative rolling generating movement of tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means for producing a continuous rotary motion of the blank during the rolling movement in either direction, and means acting automati cally to effect a positive movement of tool and blank into and out of engagement during the first and latter parts of said rolling generating movement, respectively.

-1. In a gear generating machine, a blank support, a tool mechanism, means for eflecting a continuous relative rolling generating movement of tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means for imparting a continuous rotary motion to the blank during the rolling movement in either direction, and means acting automatically to commence a relative depthwise feed movement between tool and blank during said rolling return movement and to complete said feed movement during the first part of said rolling generating movement.

5. In a gear generating machine, a blank support, a tool mechanism, means for effect ing a continuous relative rolling generating movement of tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means for imparting a continuous rotary motion to the blank during the. rolling movement in either direction, and means acting automatically to commence a positive relative withdrawing movement between tool and blank during the latter part of said rolling generating motion and to complete said relative withdrawing movement during the first part of said rolling return motion.

6. lo a gear generating machine, a blank support, a tool mechanism, means for effecting a continuous relative rolling generating movement of tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means tor imparting a continuous rotary motion to the blank during the rolling movement in either direction, and means acting automatically to complete a relative dept-hwise feed movement between tool and blank and to commence a positive relative withdrawing drive being); operable movement between: tool and blank during the first and latter parts of said rolling gem crating movement, res ectively.

T. In a gear generating machine, a blank si-urp'ort, a tool mechanism, means for effecting: a continuous relative rolling generating n-iovement of tool and blank in one direction and a continuous relative rolling return movement in the oppositediroctiommeans for imparting a continuous rotary motion to the blank during the rolling movement in either direction, and means acting automatically to commence a relative depthwise feed movement between tool and blank during the rolling: return movement and to complete said feed: movement during the first part of said rollling generating movement, and to commence a: positive relative withdrawing movement between tool and blank during the latter part 01? said rolling generating movement and to complete said relative Withdrawing movement during: the first part of said roll ing return motion.

8. In a gear generating machine, a blank support, a tool mechanism, means for effecting a continuous relative rolling generating movement of tool and blank in one direction and a continuous relative rolling return movement in the opposite direction, means for imparting a continuous rotary motion to the blank during; the rolling movement in either direction, a slow speed drive and a fast speed drive a'i'lapted to alternately ac tuat-e said first named means, said slow speed during" cutting and means acting automatically to disengage the slow speed drive and to engage the fast speed drive after the cutting operation has been completed to client the return movement at a relatively llast speed.

9. In a gear generating machine, a blank support. a tool. mechanism for cil'ccting a cont-inumis relative rolling generating movement of tool and blank in one direii'ion and a continuous relative rolling: return movement in the opposite direction. means for producing: a. continuous ratauv motion of the blankduring the rolling movement in either direction. a relatively slow speed and a rclatively fast speed drive for alternately drivin said first named mechanism. and means a uioimitically controlling said drives to ope:- ate said mechanism in a relatively fast speed during the first part of said rolling! generating motion, While the tool and blank are out of engagement. and to operate said mcchanism at a relatively slow speed during: the cutting operation.

10. In a gear generating machine. a blank support, a tool, mechanism for effecting a continuous relative rolling generating movement of tool and blank in one direction and a. continuous relative rolling return movement of tool and blank in the opposite direction means for efi'ecting acontinuous ro- *ary motion of the blank during the rolling movement in either direction, a: slow spent-l and a fast speed drive for alternately driving said first named mechanism, and means automatically controlling said drives to operate said mechanism at a relatively fast speed during the first and last parts of said relative rolling generating movement, While the tool and blank are being moved into and out of engagement, and to operate said mechanism at a relatively slow speed during the cutting operation.

11. In a gear generating machine, a blank support, a tool. mechanism for reflecting a relative rolling generating movement be tween the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction. means acting autoi-i-latically to impart a relative depthwise feed movement between the tool and blank during. the first part of said rolling generating movement to move the tool and. blank into engagement. and means for actuating said first named mechanism at a relatively fast speed durin said feed movement and at a relatively slow speed during the actual cutting. operation.

12. In a gear generating machine, srmport, a tool, mechanism for elft'ectingr a relative rolling generating movement. between the tool and blank in one direction and a relative rel-ing return movement in the on posi-te direction, means for simultaneously producing, continuous rotary motion of the blank during the rolling movement in either direction. means acting automatically to etlrcfi a positive relative Withdrawing movement between tool and blank during the lat ter partof said rolling generating movement. and means for a tuating saidfirst "d mechanism. at relatively slow speed or: the cutting operation and at a relatively test speed during the relative Withd an xvi no; movement.

i l. in a gear generating: machine. a. ilank support. a tool. mechanism for cfiecting: a r lative roiling generating movement between the tool and blank in one direction and a re ative rolling return m vement in the opposite direction, means for sinmltaneously r-rmlucingr a continuou rotary motion of the laul; durim the rolling: movement in either d 'ection. means acting automatically to oflw-t a positive movement. of tool and blank into and out oi engagement during the first and latter parts of said rolling generating. movement, and means for actuating said first named mechanism at a relatively slow speed during cutting and at a relatively fast speed during the movement of the tool and blank into and out of engagement.

1% In a gear generating. machinist;

a blank IUD support, a tool, mechanism for effecting a relative rolling generating movement betvreen the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commence a positive relative Withdrawing movement of tool and blank during the latter part of the rolling generating motion and to complete said relative Withdrawing motion during the first part of said rolling return movement, and means for automatically actuating said first named mechanism at a relatively slow speed during cutting and at a relatively fast speed during said relative withdrawing motion and said rolling return movement.

15. In a gear cutting machine, a blank support, a tool. mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commence a relative Withdrawing movement between tool and blank and to complete a relative depthwise feeding movement of tool and blank at the latter and first parts of said relative rolling generating movements, respectively, and means for automatically actuating said first named mechanism at a relatively fast speed during said Withdrawing and feed motions and at a relatively slow speed during cutting.

16. In a gear generating machine. a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneousl producing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commence a positive relative depthwise feed motion between the tool and blank during the latter part of said rolling return movement and to complete said relative feed movement during the first part of the rolling generating motion and means for automatically actuating said first named mechanism at a relatively fast speed during said feed movement and at a relatively slovv speed during cutting.

17. In a gear generating machine, a blank support. a tool, mechanism for etfecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commerce a positive relative Withdrawing movement between the tool and blank during the latter part of said rolling generating motion, to complete said Withdrawing movement during the first part of the rolling return motion. to commence a relative feeding movement during the latter part of the rolling return motion, and to complete said feeding movement during the first part of the rolling generating motion, and means for automatically actuating said first named mechanism at a relatively fast speed during said Withdrawing and feed movements and throughout said rolling return movement and for actuating said mechanism at a relatively slow speed during the cutting operation.

18. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, driving means for actuating said mechanism alternately at a relatively fast speed and a relatively slow speed. means for automatically effecting a positive relative Withdrawing and a positive relative feed movement between the tool and blank and adjustable means for automatically controlling said driving means to actuate said first named mechanism alternately at fast and slow speeds at predetermined points in the cycle of operation of the machine.

19. In a gear generating machine, a blank support, a tool, mechanism for ettecting a relative rolling generating movement betvveen the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling n'iovement in either direction, driving means for actuating said first named mechanism at a relatively fast speed and at a relatively slow speed, means for automatically reversing the direction of the relative rolling movement, and adjustable means for controlling sail driving means to actuate said mechanism at fast and slow speeds alternately at predetermined points in the cycle of operation of the machine.

.30. in a gear genera ting machine. a blank support, a tool. mechanism for etlecting a r tire rolling generating movement betzvi en the tool and blank in one direction and a rclai ive rolling return movement in the 0pposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means for e fe ting positive relative vc'thdravving and feed movements between tool and blank, means for automatically reversing the direction of the relative rolling movement, and means, adjustable relative to the reversing mechanism and the mechanism for effecting withdrawing and feed movements of tool and blank, for automatically controlling the driving means to alternately actuate said first named mechanism at slow and fast speeds at predetermined points in the cycle of operation of the machine.

21. In a gear generating machine, a blank support, a tool, mechanism for effecting a relatively rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the op posite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, reversing mechanism for automatically controlling the direction of operation of the first named mechanism, driving means for actuating said first named mechanism at a relatively slow speed and at a relatively fast speed, and means for automatically controlling said driving means to effect the rolling generating movement at a relatively slow speed during cutting and the rolling return movement at a relatively fast speed.

22. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the 0pposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, reversing mechanism for controlling the direction of operation of the first named mechanism, gearing for automatically driving said first named mechanism at a relatively fast speed and at a relatively slow speed, means for automatically controlling said gearing to actuate the first named mechanism at a relatively slow speed during cutting and at a relatively fast speed during the rolling return movement, and means for automatically stopping the machine when it has returned to starting position.

In a machine for generating gears, a blank support, a tool, mechanism for imparting a relative rolling movement between the tool and blank in opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the roll in either direction, the cutting operation taking place during the rolling movement in one direction and the parts being returned to starting position during the rolling movement in the opposite direction, and means for driving said mechanism at a relatively slow speed during cutting and at a relatively fast speed during the return movement.

In a machine for generating gears, a blank support, a tool. mechanism for impartng a relative rolling movement between the tool and blank in opposite directions, means for simultaneously producing a continuous rotary movement of the blank during the roll in either direction, the cutting operation taking place during the rolling movement in one direction and the parts being returned to starting position during the rolling movement in the opposite direction, reversing mechanism for automatically controlling the direction of the relative rolling movement, and means for driving said first named mechanism at a slow speed during cutting and at a relatively fast speed during the return movement.

In a merhine for generating gears, a blank support, a tool support, one of which is movable toward and from the other, a tool mounted on d tool support, a movable cradle upon which one of said supports is mounted, a (ll shalt t ning continuously in one (h i shaft operatively connected with the r through reversll'lOQlllIl e driven shaft roe directions, gearsaid ersible shaft with the means for simulsupport and cradle, taneously imparting to the blank a continuous indexing motion, gearing for rotating the driving shaft at a relatively slow speed and at blank a relatively fast speed and means for automatically controlling the operative engage ment of said last named gearing with said driving shaft.

26. In a machine for generating gears, a blank support, a tool support, one of which is movable from and toward the other, a tool mounted on the tool support, a movable carrier upon which one of said supports is mounted, a driving shaft turning continu ously in one direction, a driven shaft operatively connected with said driving shaft through reversing mechanism whereby the driven shaft rotates alternately in opposite directions, gearing connecting said reversible shaft with the blank support and cradle, means for simultaneously imparting to the blank a continuous indexing motion, gearing for rotating the driving shaft at a relatively fast speed and at a relatively slow speed, means for automatically controlling the operative engagement of said last named gearing with said driving shaft and means for automatically effecting relative withdrawing and feed movements between the tool and blank at predetermined points in the cycle of operation of the machine.

27. In a machine for generating gears, a blank support, a tool support, one of which is movable toward and from the other, a tool mounted on the tool support, a movable era dle upon which one of said supports is mounted, a driving shaft turning continuously in one direction, a driven shaft operatively connected therewith tl'irough reversing mechanism whereby the driven shaft rotates alternately in opposite directions, gearing connecting said reversible shaft with the blank support and cradle, means for simultaneously imparting to the blank a continuous indexing motion, gearing for rotating the driving shaft alternately at a relatively fast speed and at a relatively slow speed, a cam shaft driven from said driving shaft, a cam mounted thereon for effecting a relative movement of tool and blank toward and from each other, means on said cam shaft for actuating said reversing mechanism, and means adjustably mounted on said cam shaft for controlling the operative engagement of said speed gearing with said driving shaft.

28. In a machine for generating gears, a blank support, a tool support, one of which is movable toward and from the other, a tool mounted on the tool support, a movable era dle upon which one of said supports is mounted, a train of gearing for imparting rotary movement to the blank support and cradle comprising a drive shaft, a driven shaft operatively connected therewith through reversing mechanism whereby the driven shaft rotates alternately in opposite directions, and means connecting said reversible shaft with the blank support and cradle, means for simultaneously imparting to the blank a continuous indexing motion, gearing for alternately driving one element of said train at a relatively slow speed and at a relatively fast speed, a clutch mechanism controlling alternate connection of said speed gearing with said element, a cam shaft driven from said driving shaft, a cam, mounted thereon, for effecting a relative movement between the tool and blank toward and from each other, means on said cam shaft for operating said reversing mechanism, and a member adjustably mounted on said cam shaft for shifting said clutch.

29. In a machine for generating gears, a blank support, a tool support, one of which is movable toward and from the other, a tool mounted on said tool support, a movable cradle upon which one of said supports is mounted, a train of gearing for imparting rotary movement to the cradle and blank support comprising a drive shaft, a driven shaft operatively connected therewith through reversing mechanism whereby the driven shaft rotates alternately in opposite directions and means operatively connecting said reversible shaft with the blank support and cradle, means for simultaneously imparting to the blank a continuous indexing motion, gearing for driving one element of said train alternately at a relatively slow speed and at a relatively fast speed, a clutch mechanism controlling, the alternate connection of said speed gearing, with said element a cam shaft driven from said driving shaft, a cam mounted thereon for effecting a relative movement between the tool and blank toward and from each other, means on said cam shaft for operating said reversing mechanism and means for shifting said clutch mechanism comprising a pair of lugs adjustably mounted on said cam, a pair of rocking arms one of which is adapted to be engaged by one of said lugs and the other of which is adapted to be engaged by the other of said lugs during the rotation of said cam, each of said arms being provided with a toothed segmental portion adapted to mesh with the similar portion on the other arm, a roe shaft to which one of said arms is secured, and means ac tuated by movement of said rock shaft for shifting said clutch mechanism.

Lit). In a gear gen-Eating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank, 11 s for simultaneously imparting a cont nuous rotary motion to the drive nnranw ac". ing said first blank named r echanism at a relatively fast speed and at a relatively speed, means for alternately connecting the fast and slow speed drives with said mechanism to actuate the same and means adjustable to control the operation of sai hat named means to predetermine the of engagement of the fast and slow speed drives during the generating movement.

31. In a gear general, support, a tool, me relative rolling genen the tool and blank relative roiling rot: posite direction,

infi'cli'leil l in the 0pmeans simultaneously producing a continuors ioisiry motion of the blank during the rolinr movement in either direction, drive means for actuating said mechanisn'i at a relatively fast speed and at a relatively slow speed, means for alternately connecting the fast and slow speed drives with said fir t named mechanism to actuate the same and means po table to control the operation of said las; named means to predetermine the time ellfi' nent of the fast and slow speed drives during the cycle of the n'iach nc.

operation of In :1 ear gg'eimratin inaa'shine, a blank fecting a (v C: support. a tool, niecl ill for cl relative rolling 5;? i '5 movement between the tool and blank, means it simultaneously imparting: a continuous nerat rotary motion to the blank, means for el cting a relative deptlr wise feeding nioven'ient between the tonl and blank dnrin g the first part of said generating motion and means for actna said generating mechani ein at a relatively f st speerl during; the feed motion and at a relatively slow speed thereafter while the gear is being cut.

In a gear generating support, a tool, neeha machine, a blank in for effecting a relative rolling '-'enera-;ii.=g movement be- Kl tween the tool and liilank, means for simultanecusly impartin. a c nuous rotary motion to the blank, means for producing a positive relative withdrawing movement between the tool and blank after the tooth surfaces of the blank have been completely generated and means for actuating said generating mechanism at a relatively slow speed during cutting and at a relatively fast speed during said withdrawing movement.

34. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling i'i'iovei'n'ent between the tool and blank, means for simultaneously imparting a continuous rotary motion to the blank, means for producing a relative depthwise feeding movement between the tocl and blank during the first part of said rolling movement and for effecting a relative withdrawal move ment between the tool and blank during the last part of said rolling movement and means tor actuating said rolling mechanism at a relatively fast speed during the feed and withdrawing movements and at a relatively slow speed during actual cutting.

In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously produca continuous rotary motion or" the blank uring the rolling movement in either direction, means for imparting a IQlHlJlXfi depthwise teed movement between tool and blank during the first part of said rolling generat- Eng movement to move the tool and blank into engagement, means for driving the first named mechanism at a relatively fast speed and at a relatively slow speed, means shiftable to operatively connect either of said drives xvi h said mechanism, and means adjustable to control the operation of said last named means predetermine the time of engagement of the fast and slow speed (lTlXQS during the cycle of operation of the machine.

36. In a gear generating machine, a blank support, a tool, mechanism for effecting a rel-- ativc rolling generating movement between the tool and blank in one direction and a rela tive rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means for imparting a relative withdrawing movement during the latter part of said rolling generating movement, means for driving the first named mechanism at a relatively fast speed and at a relatively slow speed, means shiftable to operatively connect either of said drives with said mechanism and means adjustable to control the operation of said last named means to predetermine the time of engagement of the fast and slow speed drives during the cycle of operation of the machine.

37. In a gear generating machine, a blank support, a tool, mechanism for eflecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement between the tool and blank in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commence a relative depthwise feed movement between the tool and blank during said rolling return movement and to complete said feed movement during the first part of said rolling generating movement, means for driving the first named mechanism at a relatively fast speed and at a relatively slow speed, means shiftable to operatively connect either of said drives with said mechanism and means adjustable to control the operation of said last named means to predetermine the time of engagement of the fast and slow speed drives during the cycle of operation of the machine.

38. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously prodncing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commence a positive relative withdrawing movement between the tool and blank during the latter part of said rolling generating motion and to complete said relative withdrawing movement during the first part of said rolling return motion, means for driving the first named mechanism at a relatively fast speed and at a relatively slow speed, means shiftable to operativcly connect either of said drives with said mechanism and means adjustable to control the operation of the last named means to predetermine the time of engagement of the fast and slow speed drives during the cycle of operation of the machine.

39. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either diree tion, means acting automatically to complete a relative depthwise feed movement between tool and blank and to commence a positive relative withdrawing movement between tool and blank during the first and latter parts of said rolling generating movement, respectively, means for driving the first named mechanism at a relatively fast speed and at a relatively slow speed, means shiftable to operativelly connect either of said drives with said mechanism and means adjustable to control the operation of the last named means to predetermine the time of engagement of the fast and slow speed drives during the cycle of operation of the machine.

40. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means for simultaneously producing a continuous rotary motion of the blank during the rolling movement in either direction, means acting automatically to commence a positive relative withdrawing movement between the tool and blank during the latter part of said rolling generating motion, to complete said withdrawing movement during the first part of the rolling return motion, to commence a relative feeding movement during the latter part of the rolling return motion, and to complete said feeding movement during the first part of the rolling generating motion, means for driving the first named mechanism at a relatively fast speed. and at a relatively slow speed, means shiftable to operatively connect either of said drives with said mechanism and means adjustable to control the operation of said last named means to predetermine the time of engagement of the fast and slow speed drives during the cycle of operation of the machine.

41. In a machine for generating gears, 21 blank support, a tool support, one of which is movable toward and from the other, a tool mounted on the tool support, a movable cradle upon which one of said supports is mounted, a train of gearing for imparting a rotary movement to the blank support and for actuating a: 1 cradle, compri "Lug a drive I :1 d1 \en sha t operatgvi averted with the drive shaft thru reversing mechanism whereby the driven shaft rotates alternately in opposite directions and means connecting said reversible shaft with the blank support and cradle, means for simultaneously imparting to the blank a continuous indexing rotation, gearing for driving one element of said train at a relatively fast speed and at a relatively slow speed, means for actuating the reversing mechanism at predetermined points in the cycle of operation of the machine, means for effecting a relative movement between the tool and blank support toward and from each other at predetermined points in the cycle of operation of the machine, means shiftable to operatively connect either of said speed drives with said element, and means adjustable to control the operation of the last named means to predetermine the time of engagement of the fast and slow speed drives during the cycle of operation of the machine.

l2. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement of the tool and blank in one direction and a relative rolling return movement in the opposite direction, means acting automatically to impart a relative depthwise feed movement between the tool and blank during the first part of said rolling generating movement to move the tool and blank into engagement and means for actuating said first named mechanism at a relatively fast speed during the feed movement and at a relatively slow speed during actual cutting and again at a relatively fast speed during the rolling return movement.

43. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movementbetween tool and blank in one direction and a relative rolling return movement in the opposite direction, means acting automatically to impart a relative withdrawing movement between the tool and blank during the latter part of said rolling generating movement and means for actuating the first named mechanism at a relatively slow speed during cutting and at a relatively fast speed during withdrawal and during the rolling return movement.

44;. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between tool and blank in one direction and a relative rolling return movement in the opposite direction, means acting automatically to commence a positive relative withdrawing movement between the tool and blank during the latter part of said rolling generating motion, to complete said withdrawing movement during the first part of the rolling return motion, to commence a relative feeding movement during the latter part of the rolling return motion and to complete said feeding movement during the first part of the rolling generating motion, and means for actuating said first named mechanism at a relatively fast speed during the feed and withdrawing motions and during said rolling return movement and at a relatively slow speed during actual cutting.

45. In a gear generating machine, a blank support, a tool, mechanism for effecting a relative rolling generating movement between the tool and blank in one direction and a relative rolling return movement in the opposite direction, means acting automatically to commence a positive relative withdrawing movement between the tool and blank during the latter part of said rolling generating motion, to complete said withdrawing movement during the first part of the rolling return motion, to commence a relative feeding movement during the latter part of the rolling return motion and to complete said feeding movement during the first part of the rolling generating motion, and means for actuating the first named mechanism at a relatively fast