US1809377A - Method of and machine for relieving cutters - Google Patents

Description

June 9, 1931. J. EDGAR 1,809,377

METHOD OF AND MACHINE FOR RELIEVING GUTTERS Filed July 9, 1928 8 Sheets-Sheet 1 0) as QJ Inventor B 07727 .Enggaz June Q 1931.. J. EDGAR I 1,809,377-

METHOD OF AND MACHINE FOR RELIEVING CUTTERS Filed July 9, 1928 8 Sheets-Sheet 2 Inventor John Edgar ways June 1931- J. EDGAR 1,809,377

METHOD OF AND MACHINE FOR RELIEVING CUTTERS Filed July 9, 1928 8 Sheets-Sheet s Inventor B- John Edgar W ,umm

Y Jlttys June 9, 1931. Y J. EDGAR 1,809,377

METHOD OF AND MACHINE FOR RELIEVING CUTTERS Filed July 9. 1928 8 Sheets-Sheet 6 Inveniar John Edgar y W film June 9, 1931. J. EDGAR METHOD OF AND MACHINE FOR RELIEVING CUTTERS Filed Jul 9, 1928 8 Sheets-Sheet 7 r w mw t u n 1 m Ill/ .allvzlllllii June 9, 1931. -J. EDGAR 1,809377 METHOD OF AND MACHINE FOR RELIEVING CUTTEHS Filed July 9, 1928 8 Sheets-Sheet B INVENTOR EY John Edgar ATTORNEYS nc point in the contour Patented June 9, 1931.

w s EDGAR; o em e simmers lsma 1 BAR ER-c mer ome s, 9

Q FGR i m-Nate a CQREOR-ATION on initiators I l I Mn'rnon or Annivrncnmn ron'nnmnvinecnrpnnas Application filed July 9,

present invenie sharpened repeatedly without altering the effective cutting contour. I 1

On standard spiral gashed hobs, difierent points along the teeth do not lie in radial planes due to the fact that the teeth are identical to the teeth on straight gashed hobs, but are turned at a helical angle. lhis condition causes part of the contour to lie below an axial plane and the remainder to lie above said plane, there being only one that is in a radial plane. gashed hobs are used to f standard spiral produce spline shafts having relatively wide flutes, the sides of the flutes will not be per ll l-.. 2.5 its are specified for the hob, andthe latter is formed by a cut and try method until one part of the tooth, for example the top, is near the maximum limit, while the other part of the tooth, for example the root, is near the minimum limit. renders it difiicult to obtainaccurate work from spiral gashed hobs, itbeing especially noticeable i hobbing spline shafts where the spacing betweenthe teeth of the hob is large An important object of the present inv nt t r e, re s the nre isioe} f a m h f nd 1 37 1 1 1 f em esand. relieving the teeth of spiral gashed hobs by a molding-generating process in whicha regenerated tool is used.

Another important object resides 'in the'; provision of a new and improved spiral gashed hob in which the teeth have a generated ii'orm so that all points in successive and adjacent edges are formed helical lines, about the'circumference and when unwrapped from cylindrical position OlltQ' a plane are identical in shape to a. form gen:

hare In ordinary practice, certain lim-i I This condition ed in a, p a e from a predetermined ee 1928. Serial No. 291,161. Y

A further object of the invention resides in the provision of a new and improved ma chine of the foregoingcharacter which t ie e n pe at on wh h is relatively simple and inexpensivein construction, and which is adjustable to adapt it to holes of many different forms-and sizes.

Another ohjectoi the invention resides in the provision of a methodloi forming and relieving spiral gashed hobs, such as spline shaft hobs, in which aregenerated lathe tool having a. cutting facelinclined, at the same angleas the hobygashes, is caused to have a series of relative cyclic movements with a revolving hob blank, each movement mp ng a u tin roke a d a w re u IQ Q ng u inally o th -b1an ,.i causeclto have a relative relievingmovement once for each tooth transversely of the blank, 7 is caused to have a gradual infeed ng move-v,

ri lati t blank (l ing c ess ve 5.1 mom ie nti o e end of h oo in a horizontal i l p an threuah the bl 1 cu ng o h ire ldep h, i th n ca se A further object I resides. in. thenprovision in a machineof'the foregoing character :of

novel means forefiectin'g a positive and accurate reversal in'e'ac'h cycle of movements so as to insure proper'timing of themove ing parts;v a sun other objects reside in the provision a machine of the above "character of novel means for advancing the relieving reciprocation'sto compensate forthe inclination of the teeth, and for advancing the traverse of the tool along the blank tocompensate for the:

lead of the contour, during the vertical feed; I

ing movement.

Further ObJQCl3$ and advantages be,

come apparent asthe descriptionprcceeds.

' n th c omp nyme drawi gs wh ei I have illustrated the preferred embodiment of my invention:

Figure 1 is a plan view of the machine, certain parts being shown in horizontal sec tion.

Fig. 2 isa fragmentary front view of the machine. i

Fig. 3 is a fragmentary rear view of the machine.

Fig. 4 is a left end view of the machine as viewed in Fig. 2.

Fig. 5 is a fragmentary sectional view taken along line 5-5 of Fig. 2.

Fig. 6 is an enlarged sectional view of the main clutch mechanism taken along line 6-6 of Fig. 3.

Fig. 7 is a fragmentary vertical sectional view of a differential mechanism at the rear of the machine, taken along line 7-7 of Fig. 5.

Fig. 8 is a fragmentary sectional View taken along line 88 of Fig. 3.

Fig. 9 is a fragmentary sectional view of a differential mechanism at the front of the machine, taken along line 9-9 of Fig. 1.

Fig. 10 is a transverse vertical sectional View taken along line 10 -10 of Fig. 1.

Fig. 11 is a view similar to Fig. 10, but showing the lathe tool withdrawn from the hob blank.

Fig.12 is a fragmentary sectional .view through a lathe tool and a work blank, diagrammatic in character, and showing the tooth generation of the spiral thread.

- Fig. 13 is a plan view of one form of a spline shaft hob adapted to beformed on t e machine, and a lathe tool for forming and relieving the hob, the hob and lathe tool be ing shown in s aced relation.

- ig. 14 is a ragment'ary perspective view ofthe hob and the lathe tool atthe start of the generating operation.

Fig. 15 is a view similar to Fig. 14, but showing the position of the lathe tool at an intermediate stage of the generating operation. i

Fig. 16 is a view similar to Fig. 14, but showing the lathe tool at the end of the generating operation. V

Fig. 17 is a diagrammatic view taken end- Wise of the hob blank illustrating the generating action resulting from elevating the of the blank.

lathe tool through the horizontal axial plane While the invention is susceptible of variousflmodifications and alternative construe-V tions, I have shown in the drawings. and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intendv to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring to the'exemplary embodiment hob 20. The hob is formed with a plurality of equally spaced and longitudinally inclined flutes or gushes 20 defining a plurality of generally longitudinal blades 20 and with a single spiral groove 20 intersecting the gashes 2O at a large lead to define a thread of a plurality of hob teeth 20 It will be understood that While but single thread is shown, the hob may be formed with any desired number of threads, i. e., may be a single or a multiple thread hob. The entire contour of the hob is formed in a molding generating process to be more fully describedflhereinafter, and hence all points along the contour are correctly formed and relieved.

A lathe tool 21, having the desired form, is provided for cutting the hob blank. In the present instance the lathe tool 21 has a distorted contour comprising a section 21' adapted to form the groove 20 and a section 21 adapted to form the top of thehob teeth 20 The upper face of the tool 21 is inclined longitudinally of the hob at an angle corresponding to that of the gashes 20*. It will be understood that the hob blank may be roughed in a preliminary operation before being accurately formed and relieved in the present machine, or may be formed completely in one machine operation as illustrated herein.

Briefly stated, the operation comprises rotating the work blank 20 at a predetermined speed in a given direction, reciprocating the lathe tool 21 laterally of the blank once for each tooth to relieve the latter, traversing the lathe tool in a cutting stroke longitudinally of the work blank and in timed relation to the rotation thereof to generate the hob thread 20 separating the lathe tool and the work blank laterally of the latter after the completion of the cutting stroke and reversing the direction of rotation of the work blank and the direction of traverse of the lathe tool to return the latter in a free return stroke to its initial position, feeding the lathe tool into the work blank and repeating the foregoing cycle until the lathe tool is cutting the blank to the desired depth, then discontinuing the infeed of the lathe tool but continuing the foregoing cycle, gradually elevating the lathe tool to generate the desired contour during the last mentioned cycles, and advancing the relieving reciprocations and the rate of traverse of the lathe tool relative to the rotation of the Work blank during each cutting stroke so as to compensate for the inclination of the gashes 20 'and the spiral lead of the hob thread 20 In the preferred embodiment, the machine comprises a closed base 22 upon which the on pivot pins 89 and within the slots 88 are two clutch fingers 90 having rounded ends 91. The ends of the key members 87 are cut away, as shown at 92 to provide cam surfaces for engaging the rounded ends 91. Rounded lugs 93 on the fingers 90 project into the notches 74 to key the sleeve 75 to the sleeve 71. A pair of arcuate shoes 94 respectively engage opposite sides of the groove 86 and are pivotally mounted on spaced arms 95 and 96 of a clutch yoke 97. The latter is pivotally mounted on'a pin 98 for swinging movement on a bracket 99 rigidly secured to the end bracket 54. To provide means for actuating the clutch 59, a lever 100 is secured 'to the pivot pin 98, and the free end of the lever is connected through a link 101 (see Fig. 2) to a hand lever 102 pivotally mounted at one end on a supporting stem 103.

The cutting mechanism 7 The cutting mechanism (see Figs. 1, 10

' and 11) comprises a. main carriage '104 mounted for reciprocation on longitudinal ways 105 and 106 on the upper side edges of the base 22. The front edge of'the carriage 104 is formed with an inwardly inclined depending fiange 107 engaging a plate 108 on the underside of the way 105. The rear edge of the carriage 104 is formed with a depending flange 109 secured on the way 106 by means of a gib plate 110. The carriage 104 is provided with an extension 111 having a threaded lug 112 (see Fig. 2) on its underside and freely disposed in a channel 113 formed in the upper surface of the base 22. An adjusting or feed screw 114 engages the lug 112, and, upon rotation in opposite directions, is adapted to feed the carriage in opposite directions longitudinally of the work blank 20.

I To provide means for feeding the carriage 104 manually, one end of the feed screw 114 is provided with a bevel gear .115 meshing with a bevel gear 116 on a shaft 117. The latter is journa led in a suitable bearing 118 formed on a bracket 119 secured to one end of the base 22, and is provided with a squared end 120.

Means is provided for driving the feed screw 114 so as to feed the carriage 104 in predetermined relation to the rotation of the 'work blank 20. This means (see Figs. 1, 2, 4

and 9) preferably comprises a gear 121 on the work spindle 44 within the bracket 40, and meshing at one side with a gear 122 on a shaft 123. The latter is suitably journaled in a bearing 124 formed in the bracket 40 and a bearing 125 formed in a bracket 126 at the left end of'the base 22, and at its outer end is connected through suitable speed change gears 127128 129130 131 to ashort shaft 132. The speed change gears 128 to inclusive are adjustably mounted on a segment arm 133 .which is pivotally mounted on the bracket 126 for adjustment about the shaft 132 and which is adapted to be clamped in any position of adjustment by means of a suitable clamp bolt 134 extending through and adapted to engage an arcuate slot 135.

The shaft 132 (see Fig. 9) is journaled in a bearing 136 formed in the bracket 126, and extends into an inner housing 137 of a differential mechanism 138. The inner housing 137 has a hub 139 rotatably disposed in the inner end of the bearing 136, and is disposed in an outer housing 140 to which the bracket 126 is secured. The outer housing 140 is rigidly secured to the base 22 by any suitable means such as bolts 141 (see Fig. 2). The inner end of the shaft 132 is provided with a bevel gear 142 in mesh at opposite sides with two bevel gears 143-144 pivotally mounted in the peripheral wall of the inner housing 137 The bevel gears 143144 mesh with a bevel gear 145 on the end of the feed screw 114 journaled in a bearing 146 in the right end of the housing 140. The shaft 132 thus is adapted to drive the feed screw 114 through the housing 137.

Mounted in dovetailed guideways 147 (see Fig. 2) on the carriage 104 for reciprocation laterally of the base 22 is a back-01f or relieving slide 148. This slide is provided with transverse ways 149 supporting a side relief slide 150. Mounted for adjustment in transverse ways 151 on the slide is a tool slide 152. Any suitable means may be provided for adjusting the slide 150, and in the present instance an adjusting screw 153 having threaded engagement with the tool slide 152 is provided. The front end of the screw 153 is rotatably journaled in an upstanding lug 154 formed on the front edge of the side relief slide 150. Mounted on the outer end of the screw 153 is a suitable hand wheel 155 and a micrometer sleeve 156;

The tool slide 152 is formed with vertical ways 157 in which a tool holder 158 is mounted for a vertical feed. To this end, the holder 158 is formed with a lug 159 in which is journaled a nut 160 having threaded engagement with an upstanding feed screw 161 journaled in the slide 152. The holder 158 is formed with a seat 162 to the undersideof which the lathe tool 21 is adapted to be secured by means of bolts 163.

The relieving and free return mechanism Means is provided for reciprocating the lathe tool 21 laterally of the hob blank 20 and l in timed relation to the rotation thereof so as to properly relieve the hobteeth 20 This means (see Figs. 10 and 11) comprises a compression coil spring 164 tending to hold the cutting tool 21 out of engagement with the hob. The spring 164 is positioned in a bore 165 formed in the backing-01f slide 148, and extending from the front edge thereof to a central vertical bore 166 also formed in the slide. The front end of the bore 165 eloaed.

by a threaded plug 167 which is held in ad j usted position by a llOCk nut 51618, and which serves as an abutment for the front end of the spring. The inner end oi'lthe 164 is secured formed on a stud 170 rigidly carriage The rear ei id of the backing-.ofi slide 1l8-is formed integralvwith a rearward and up vvjardl inclined extension 171 havin a air secured to the of spaced 172l73 in which a stub shaft.

17%]: issupported. Pivotally mounted intermediate its ends onthe stub shaft 17% is a cam lever 175,. v .pairofhardened cam followers 176-l77 are removebly secured respectively to the upper and 1 33781 ends of the cam lever 175. i

Seeurel b t carriage 10s atopposite sides ofthecarn lever 17 5 are a pair of spaced uprights 1781 179. in the present instance, these uprightsare secured in position by means of bolts 180, the heads of which engage a T-slot 181 formcd in the rear edge of the carriagelO. The uprights 17 8-17 9 are formed respectively with upper alined bearings 182--183 and lower alined bearings 184-185.

A lower cam shaft 186 is journaled in the lower a lined ,bearin gs 18 1-185, and supports rotary cam ;187 adapted to coact with the cam follower The cam 187 hasa spiral working face 187 terminating abruptly at 187*, and is adapted uponlrotation in a clockwise direction as viewed in Figs. 10 and 11,

- .to oscillate the lever 17 5 about the point of [this end, the shaft 186 is keyed for rotary l'novement in a spline sleeve 190 (see 3) which telescopes with and is sp lined for relative axial movement to a stub shaft 191. The

' latter is journaled in a hub 192 of aidiilereningv 193.

tie-l casing 193 (see Fig. 7), and is provided with a bevel gear 194; in the casing. The hub 192 is journaled in a bearinghub 195 formed in a gear casing 196 rigid with a bracket 197 suitably secured to the rear side of the base 22. The bevel gear 194; meshes at opposite sides with two bevel gears 198-199which are, rotatably mounted on studs 2QO,201 fixed in opposite sides of the diilerentialcas- The bevel gears 198+199v mesh with a bevel geer202 which is rotatable on a shaft 208 and which is formedgintegral with a drive plate 294. The drive plate forms partof afratehet mechanism 205 tofa spring anchor l69'whi'ch is adjustably mounted on the (se ig I n 1 whi i perativ ly 91 nect edt'o the shaft 203 for rotating the shaft coi'interclofiky ise direction as view d in 5'; ut .ilithl o posite irection The ratchet nechianisin 205 comprises a lietchet Whi h-P efe a y i ir l hlei rm 24 g, end ewe i th L l-ri e Pis e M i t l fleng i l nlb 2 7L 5 w pd ill p J Y suita l "scr w bolts 208 he ratchet 206 is" rotatably' disposed within fi hell ylin ie eus ri g2q hi h i keyed to the shaft 203 a d one end of which is 63M y h-W l 96 2 l h l $1 6 he 20. b many su abl t m;

preferably'itis providedwith atsingle peripheral tooth 210. "Piyotally mount a pi 211 'e .r'ese 2 he P lhere wall of the housing2jQ9 is a ratchet p 1 213 adeiit fl 't l ngths e oo h 10 "T e ea the mov endo t pawl 2131 1.1016 he t y s y i cl- 8 89 191 1 w t the riphery of the ratchi 20,6. 'f T Shaft 5 jbur eled in b arin 216 formed in the bearing brsclgethg and carries gear'217' shits .quter'en'dfwhic operetively connected through speed .Q gears 21,8 21'9 to a gear' ;220 on thee end of the drive shaft 49. f The gears 219 are adjustably mountedon a' bracket 221. embracing the hearing 53. and adjustable ebout the Ta xis of the :Slltlfil; The w ng a m braCk Q h a slq 'edaiicjuse 2221ad-i te t mumps 'inefiy go tio of adju ment by" .me i spf bjolt The a 188 is dapted ,pos ie lle b k ngf slide'lii8 .sQe ehii kth ;1 t9 tool 21in operative relation to the hob lan k 20 during each cutting stroke, andiiiin'opera-tive relation thereto during each free return stroke. cam 1.88 is substantially circular in form" to provide a -large arciiate cam surface 224. The end "of surface terminates abruptly 7 in a notch 225 the peripheny of the cam' 11.88, the ;lead sile of notch smogthlyappr'oaches jsaidfsur face. Movement of the c m :suriace 22s into engagement with the ic iii iQlIOWQr 176 Will oscillate, the cam lever the cam follower. 177 asa fulcrum to move the The icamshaft .189 is splined 188, one ;is jgurnaledl'in .a s'uitabl bearing 226 .iormed in the bearing br 51 The free endfoflthe shaftT remt re y c nfided ina e-1 ed on spri g 2' secured in th r ce 212' ses'es slide 1 18 rearwarelly.against'jthefo rce of the spring l64lt0 bring the tool 21 intooperative' mechanism 227, not disclosed in detail but similar in construction to the ratchet mechanism'205, to a gear 228 on a shaft 229 which is suitably journaled in a bearing 230 in the bracket 54. The gear 228 is connected through reduction gears 23l232 to an idler gear 233 freelyrotatable on the shaft 49, and meshing with the gear 121. The gears 231 and 232 are adjustably mounted on a supporting arm 234 on the bracket 51. It will desired. This means (see Figs. 1 and 2) comprises a bracket 235 secured to the right end of the slide 148 and defining a lateral notch or guideway 236. A lever 237 is pivoted at one end in the bracket 235, and carries a roller 238 at one side of its pivot engaging the guideway 236. The lever 23? is ormed with a longitudinal guideway 239 which is engaged by astud 240 adapted to be adjustably mounted in a block 241 on the carriage 104. When the stud 240 is clamped in position on the block 241, reciprocation of the slide 148 will pivot the lever 237 about a fixed pivot, thereby causing the roller 238 to reciprocate the slide 150. The rectangular relieving components result in an oblique relief which is desirable when certain portions of the cutter contour are close to radial.

"The control mechanism Means is provided for automatically reversing the clutch 59 at opposite ends of the traverse of the cutting tool 21. With the clutch in one position, i. e., to the right as viewed in Fig. 6, the hob 20 will be rotated'downwardly against the lathe tool 21, the carriage 104 will be fed slowly in a cutting traverse'to the left as viewed in Fig. 1, and the cams 187188 will be rotated. WVith the clutch in the opposite position, the Work blank will be rotated in the opposite direction, the carrage 104 will be moved rapidly in a. return traverse, and the cams 187-188 will be inoperative, the cam 188 being positioned as shown in Fig. 11 to provide clearance between the lathe tool and the hob.

The clutch reversing mechanism (see Figs. 1 to 5) comprises a rocker shaft 242 suitably j ournaled in a bracket 243. extending up from the bracket 54. The forward end. of the rocker shaft. carries a crank arm 244 having a pin 245 engaging in a notch 246 formed in an arm247 on the clutch lever 100. As

.. the crank arm 244 is moved intoeither extreme position, it serves to oscillate the lever 100 to reverse the clutch. Secured intermediate its ends to the rear end of the rocker shaft 242 is a lever 248 having-outwardly projecting pins 249-250 at opposite ends. Rotatably secured on the rear end of the rockor shaft is a weight arm 251 on the free end of which a weight 252 is adjustably secured.

Means is provided for lifting the weight over dead vertical to cause the arm in the falling of the weight to strike one or the other of the pins 249-250 to reverse the clutch. Preferably this means comprises a spiral gear 253 rotatably mounted on the rocker shaft 242 and meshing with a spiral gear 254 on the shaft 229.

Formed on the rear face of the spiral gear 253 concentrically about the rocker shaft 242 is a ring 255. Two suitably spaced lugs 256257 are formed on the end of the ring, and abutment screws 258259 are threaded therethrough for alternately engaging the wei ht'arm 251 and lifting the latter over dead vertical upon rotation of the gear 253 in opposite directions.

Means is provided for throwing the clutch 59 into neutral at the end of each stroke of thecarriage 104. This means comprises a rotary cam 260 having offset abutments 26l262 spaced about its periphery and adapted upon'rotation of the shaft 229 in opposite directions to engage and move a pin 263, projecting from the yoke arm 96, in opposite directions. Preferably, the cam 260 has a limited rotational lost motion connection with the shaft 229 through a pin 264 and slot 265 and is weighted to assume a predetermined position after each actuation of the clutch. By reason of this construction, the cam 260 need not turn a complete revolution with the shaft.

At the end of each cutting stroke, the abutment 262 will engage the pin 263 to open the clutch. Simultaneously, the weight 252 will have been carried over dead vertical by the abutment screw 258 so that the weight will fall, thereby closing the clutch in a direction to institute the free return traverse. At the end of each free return stroke, the abutment 261 will engage the pin 263 to open the clutch, and the weight 252 will have been carried over dead vertical by the abutment screw 259 so thatit will fall to close the clutch in the opposite direction to institute the next cutting stroke.

Tool feeding mechanism Means is provided for gradually elevating the lathe tool 21, during successive cutting cycles and after the latter has been fed into the blank to the desired depth so as to cause the effective cutting point of the tool in a horizontal axial plane through the blank to shift across the blank, thereby forming a correct and properly relieved generated contour throughout the length of each blade 20". This means comprises a suitable drive for rotating the vertical feed screw 161. To this end, a worm 264 (see. Figs. 7 and 8) is secured for rotation with the drive plate 2042. The worm 26 i meshes with a worm Wheel 265 freely rotatable on a shaft 266 journaled on a bearing 267 on the bracket 19:7. The front face of the worm wheel 265 is formed with suitable clutch teeth 268 adapted to react with similar clutch teeth 269 on a clutch member 270 ,splined' to the forward end of the shaft. The clutch member "270 is formed furcated shifting yoke 2T2 is rotatably splined. The yoke 272 is connected to the rear end of a shifting rod 273 which is slid,- ably disposed in a pair ofspaced lugs 274 formed on the headstock bracket 4L0, and which, is operatively connected at its front end to the depending arm of a clutch lever 2T5 pivotally mounted on a pin 275 supported in the bracket 40. v

Secured-to the rear end of theshaft 266 is a gear 276 which is connected through an intermediate speed change gear 277 to a gear 278 mounted on a shaft 279 journaled in the gear casing .196. The intermediate gear 277 is mounted on a carrier arm 280 pivotally secured on the bearing267 for adjustment about the axis of the shaft266, and adapted to'be secured in adjusted position by means of a clamp bolt 281 engaging an arcuate slottedsarm 282 thereon. V

The shaft 279 is connected through spur gears 28-3284= to a transverse shaft 285 extending to the front of the machine. Connected .to the frontend of the transverse shaft 289 iourna'led inasuitable casing 290 secured to the front of the base 22. v A spiral gea-r291 on the shaft 289 meshes with a spiral gear 292 on a feed shaft 293 extending longitudinally of the machine. The right end of the feed shaft 293--is connected "through the flexible connection 294 to a shaft 295 which is journaled in andextends slidably through pair 10f spaced bearings 296 formed n a .tool slide 152; Splined' to the shaft295 isfagear 297 meshing with agear298 on a short shaft 299 journaled in the tool slide 152; The shaft 299 is provided with a suitableworm "300 which is operatively connected to the "lower end of the feed screw 161, through a chain of gears '301302303-suitablyarranged in a recess 304s1nthe undersideofithetool slide.

Compensating mechanisms As thelathe tool 21 is fed upwardly through the horizontal axialnplane :of the blank, the effective point on the cutting con:

tour, .cuttingsto ma-ximiun depth, gradually shifts fromright to left. Due to the inclination of each blade 20, the cutting edge there-- of advances as the out to depth progresses along the blank. To compensate for-the lead of the blades so that the effective cutting point on the lathe tool will meet each blade in a horizontal axial plane through the blank,

means, designated for convenience as the relief compensating mechanism, is provided for advancing the relieving reciprocations in timed relation to the elevation of the tool. Preferably,=the relief compensating mechanism comprises suitable gearing for driving the differential casing. 193 To this end,

Due to the lead of the contour of the hole blank, an additional compensating move- 1 ment is provided. To this end, means designated for convenience as the generating (30,111,- pensating mechanism is prov ded-for accelcrating the feed of the lathe tool21alongthe hob blank in timed relation tothe vertical feed.

The generating compensating ,mechanism ,(see Figs. 1, 2, 1,5 and 19,) preferably coni- ;prises a driving connection between the feed shaft 293 and the inner differentialpasing 137. To this end, a spiral gear 307 is secured 'on theilleft end .of the feed shaft 293, and meshes with a spiral gear 308 on a shaft309 journaled in a bearing 310 formed on the differential casing 140. Theouter endofzthe shaft 309*,has :agear :311 which is connected through intermediate speed change gears -312-313 to a gear 31 i mountedona shaft 315 journaled in abearing 316 formed in the differential casing 140. The intermediate speed change gears -312f313 are adjust-ably mounted on a swing arm bracket 317 which is-mounted on :thezbearing 310 for pivotal adjustmentabout-the axis of the shaft 309, and which has a slotted arcuate arm 318 adapted .to be clamped indifferent positions of adjustment-bya suitableclamp bolt 319. The shaft 1315 (see Figs. '5 and 9) hasa worm 320 meshing with a worm wheel 321 preferablyformed integral with thedifferential casing137. It

will beevident that as'the lathe tool21 is elevated, the -differential-casing 137 will be given a movement in addition ;to that imparted from the shaft'132, thereby accelerating the feed of 1thecarriage104tocompensate nection with the operation.

with a peripheral; groove 271 in whichga bi- "(see {Fig 7) a worm 395 is provided 1on the In setting up the machine for a given work blank, for example a. hob with a right hand thread, the lathe tool 21 is adjusted vertically to position the highest point of the contour, designated as 322 (see Fig. 14), at or below a horizontal, axial plane through the work blank 20, and is positioned at the right end of the blank to start a cutting stroke toward the left. The face of the lathe tool 21 is inclined at the same angle as the flutes 20, and hence the entire cutting contour of the'tool will be below the horizontal, axial plane as indicated at a in Fig. 17. Due to the natural curvature of the Work blank, the point in the cutting contour of the tool 21 inthe axial horizontal plane, as indicated at Z) in Fig. 17 will cut to maximum depth, and other points of the contour above and below this plane at any time during the operation will recede from the cutter.

The'clutch 59 is now actuated by means of the lever 102 to startthe machine. In the operation, the cutter blank 20 is rotated forwardly at a predetermined speed, and the cam 187 gives the lathe tool 21 a relieving reciprocation in timed relation to the rotation of the blank so as to generate a spiral relief for each tooth. This relief may be radial or inclined depending upon whether or not the side relief mechanism is used.

The lathe tool 21 is given a cutting traverse to the left along the work blank in timed relation to the rotation of the latter to generate the lead of the hob contour,i. e., the groove 20 and the thread 20. During the cutting traverse, the cam 188 is rotated slowly, but without influencing the position of the lathe tool.

The position of the parts is illustrated in Fig. 10; At the endof the cutting traverse, the cam 188 causes a separation of the blank and the tool, and the cam 260 accurately stops the foregoing operations by opening the clutch 59. The weight arm 251 then falls to reverse the clutch 59 to institute a free return movement for the lathe tool 21. During this v free return movement the cams 187188- are idle, and the rotation of the blank is reversed. The position of the parts is illustrated in Fig. 11. At the end of the free return movement, th

. cam 260 again accurately opens the clutch 59, and the weight arm 251 again reverses the clutch, thereby actuating the cam 188 to return the lathe tool 21 into cutting engagement with the blank, and instituting a repetition of the foregoing cycle of operations.

At periodic times, preferably before the cutting stroke, the lathe tool 21 is given an incremental feed into the work. In the present instance, this feed is effected manually,

but it is obvious that it may be effected in any suitable manner. When the lathe tool 21 has been fed into the blank to the desired depth, the infeed is discontinued. At this time, the

point 322 on the contour of the lathe tool is cutting to full depth and is properly relieving one point on the hob contour.

The generating operation is now instituted by actuating the lever 275 to close the clutch 268-269, thereby instituting a vertical feed for the lathe tool 21, a compensating movement for the relieving cam 187, and a compensating movement for the lathe tool longitudinally of the blank. The repeating cycle of movements is not affected and continues as before, it being understood that the vertical feed supplants the infeed.

During the generating operation, the lathe tool 21 thus is fed slowly in an upward direction to move the cutting contour of the tool through the horizontal axial plane of the blank. In the course of this feed, consecutive points along the cutting contour of the lathe tool will move successively into this plane, and then rise above the same as indicated at 0 in Fig. 17. As a result, the cut to'depth proceeds along the contour of the blankl the cut to depth proceeds, the

relieving reciprocations are accelerated so that successive points along the inclined cut ting contour of the hob will accurately meet the corresponding points on the lathe tool the latter are elevated successively into the horizontal axial-plane of the hob, and

the cutting stroke of the tool is gradually advanced to compensate for the lead of the contour.

The hob thus is formed and relieved in a'molding-generating operation, and when completed has a generated contour as shown in Fig. 12. The inclined cutting edges of the cutter or hob are so formed that like points in successive and adjacent edges are formed in helical lines about the circumferversely of the cutter 'axis to back off the teeth, I'

means for relatively moving the cutter and tool tangentially of the cutter at the cutting point, and means for varying the action of said first mentioned means to compensate for the inclination of the faces and for relatively adjusting the cutter and the tool longitudinally of the cutter to compensate for the lead of the contour. r

2. A machine for relieving cutters having cutting faces longitudinally inclined to the Q.

axis of the cutter and having a contour with a peripheral lead, comprising, in combination, cutter rotating mechanism, a tool having a cutting face longitudinally inclinedto the aXis of the cutter and having a cutting edge adapted to cut the desired contour, means for relatively moving the cutter and; tool transversely of said axis during the passage of each tooth through the cutting plane,

means for passing the tool edge progressively through the cutting plane to transfer the point of operation on the cutter along saidv edge, and means for relatively adjusting said cutter and said tool longitudinally of;

said cutter to compensate for the lead of the cutter contour.

3. A machine for forming and relieving a workblank having generally longitudinal spiral gashes and a helical contour comprising, in combination, means for rotating the blank, a cutting tool having an inclined cutting face with a contour adapted-to cut; a predetermined contour, means for effecting a relative traverse vbetween the blank .and said tool longitudinally of the-blank, means for effecting a relative relieving reciprocation between the blank and said tool-once for each tooth, means for effecting a tangential feed between the blank and said tool to move the cutting: edge of said tool.--throughathecut-.

ting plane, means for accelerating the relieving reciprocation, and", meansfor relatively adjusting the position of said tool longitudinally of the blank.

4. A; machine for forming,'andrelieving a work blank having generallyilongitudinaL spiral gashes and a helical contour comprising, in combination, a cutting toolhaving a contour adapted to cut a predetermined contourandhaving an inclined face adapted to engage the blank in an axial cutting plane,

means for effecting a series of relative trav-. erse movements between said tool: and the blank longitudinally of the latter, meansfor effecting a relative relieving-reciprocationbetween said tool and'the blank, means forefi'ecting a relative iinfeed between said tool and the blank in said axial-plane, and means for effecting a relative tangential feed between said tool and the blankto move differ-- ent points along the cutting contour of; the

tool through said axial plane;

5. A machine for forming. and relieving a work blank, having generally longitudinal spiral gashes and a helical contour'compristour and having an inclined face adapted-t0 engage the blank. in an axial cutting plane, means for effecting a series ofv relativetraverse movements between said tool and the blank longitudinally of the latter, means'for effecting a relative relieving reciprocation between said tool and the blank, means fol" effecting a relative infeed between SillClitOOl mg, in combination, acutting tool having, a contour adapted to cuta predetermined con-- "traverse movements between the blank and.

andthe blank in said axial plane, means for effecting a relative tangential feed between said tool and the blank to move different points along the cutting contourv of the tool through said axial plane, and. means for varying the relieving, reciprocation :to com-.

pensate forthe inclination of the blades during" the tangential feed.

6 ..A machine for forming and relieving a work blank having generally. longitudinalv spiral gashcs and a helical contour comprising', in combination, a cutting tool having a contouradapted to cut a predetermined contour and having an inclined face adapted to engage the blank in an axialcutting plane,

, means for effecting a series of relative traverse movements between said: tool and the blank longitudinally of t'he'latter, means for effecting a relative relieving reciprocationbetween said tool and the blank, meansfor effecting arelative infeed between said tool i andthe blank insaid axialplane,ineans for efiecting a relative tangential feed between saidtool and the blank to move different points along the cutting cont-our of the tool through said axial plane, means for varying the relievingreciprocation to compensate for the inclination of the blades d'uring thetangential feed,.and'.means for effecting a relativeadjustment of said tool axially of the blank to' compensate forthelead of the contour during the tangential feed.

7. 'A'inachine for forming and relieving, a

'worjk blank having generally longitudina-l'spiand; said tool longitudinally of the blank,

means for separating the-tool and the blank during each traverse movement in one direction, means for effecting a relative infee'd between the tooland the blanln'and means for effecting a relative tangential feedbetween the tool and the blank to transfer the final point of "operation on the blank along the edge ofsaid tool. c r f 8. A machine for forming and relieving a work blank havinggenerally longitudinal spiral gashes and having a helical thread;

intersecting said gashes, comprising, in com- 1 bination, means forv rotating the workblank, c

a cut-ting'tool having a cuttingv face inclined substantially thesame as said gashes, means for efiecting a relative relieving reciprocation between the blankand said tool in timed relation to the rotation of the blank, means for effecting a continuous c-vcle'of relative said tool longitudinally of the blank, means for separating the tool and the blank during each traverse movement in one direction, means for effecting a relative infeed between the tool and the blank, means for effecting a relative tangential feed between the tool and the blank to transfer the final point of operation on the blank along the edge of said tool, and means for varying the timing of the relieving reciprocation to compensate for the inclination of the gashes during the tangential feed.

9. A machine for forming and relieving a work blank having generally longitudinal spiral gashes and having a helical thread intersecting said gashes comprising, in combination, means for rotating the work blank, a cutting tool having a cutting face inclined substantially the same as said gashes, means for effecting a relative relieving reciprocation between the blank and said tool in timed relation to the rotation of the blank, means for effecting a continuous cycle of relative traverse movements between the blank and said tool longitudinally of the blank, means for separating the tool and the blank during each traverse movement in one direction, means for effecting a relative infeed between the tool and the blank, means for effecting a relative tangential feed between the tool and the blank to transfer the final point of operation on the blank along the edge of said tool, means forvarying the timing of the relieving reciprocation to compensate for the inclination of the gashes during the tangential feed, and means for effecting a relativeadjustment of said tool axially of the blank to compensate for the lead of the thread during the tangential feed. V

10. A machine for cutting rotary cutters having generally longitudinal spiral gashes and having a spiral groove intersecting said gashes to define hob teeth comprising, in combination, a main drive shaft, a reversing clutch for said drive shaft, means connected to said shaft for rotating the cutter blank, a

cutting tool, means operatively connected to said shaft for relatively traversing said tool longitudinally of said cutter, a relieving mechanism operatively connected to said shaft for effecting a relative relieving reciprocation between said tool and the cutter laterally of the latter once for each tooth, a separating mechanism operatively connected to said shaft for separating said tool and the cutfor during each traverse in one direction, acam operatively connected to said shaft for periodically opening said clutch, and means for automatically closing said clutchinthe reverse direction from which it was opened.

11. A machine for cutting rotary cutters having generally longitudinal spiral gashes and having a spiral groove intersecting said ashesto define hob teeth comprising, in combination, a main drive shaft, a reversing clutch for said drive shaft, means connected to said shaft for rotating the cutter blank, a

cutting tool having a contour adapted to cut the cutter contour and having an inclined cutting face, means operatlvely connected to said shaft for relatively traversing sald tool longitudinally of said cutter, a relieving mechanism operatively connected to said shaft for effecting a relative relieving reciprocation between said tool and the cutter laterally of the latter once for each tooth, a separating mechanism operatively connected to. said shaft for separating said tool and the cutter during each traverse in one direction, means for effecting an infeed of said tool relative to the cutter, means operatively connected to said shaft for effecting a relative 12. A machine for cutting rotary cutters having generally longitudinal spiral gashes and having a spiral groove intersecting said gashes to define hob teeth comprising, in combination, a main drive shaft, a reversing clutch for said drive shaft, means connected to said shaft for rotating the cutter blank, a cutting tool having a contour adapted to cut the cutter contour and having an inclined cutting face, means operatively connected to said shaft for relatively traversing said tool longitudinally of said cutter, a relieving mechanism operatively connected to said shaft for effecting a relative relieving reciprocation between said tool and the cutter laterally of the latter once for each tooth, a separating mechanism operatively connected to said shaft for separating said tool and the cutter during each traverse in one direction, a cam operatively connected to said shaft for periodically opening said clutch, means driven in timed relation to said cam for automatically closing said clutch in the reverse direction from which it was opened, means interposed in the connections between said shaft on one hand and said rehevmg mechanism and said separating mechanism on the other hand for preventing reversal of movement of said mechanisms.

18. A machine of the character described comprising, in combination, a main drive shaft, a reversing clutch for said shaft, a reciprocatory element, means operatively connected to said shaft for driving said element,

a cam operatively connected to said shaft and rotating in timed relation to the movement of said element, said cambeing operative to open said clutch so 'as to stop movement of said element in either direction, a pivotal weight adapted upon movement in opposite directions over dead vertical to close said clutch in opposite directions, and means driven in timed relation to said cam for alternately moving said weighted member across dead vertical immediately prior to opening of said clutch by said cam, said weighted member upon falling serving to throw said clutch in the opposite direction.

14. A machine of the character described comprising, in combination, a main drive shaft, a reversing clutch for said shaft, a reciprocatory element, means operatively connected to said shaft for driving said element, a cam shaft operatively connected to said shaft, a cam on said cam shaft for opening said clutch at predetermined points in the travel of said element, a pivotal weighted member adapted upon movement in opposite directions over dead vertical to fall so as to close said clutch in opposite directions, and means operatively connected to said cam shaft for alternately lifting said weighted member in opposite directions across dead vertical immediately prior to opening of said clutch by said cam.

15. The method of relieving the teeth of a cutter having cutting faces longitudinally inclined to the axis of the cutter and having a contour with a peripheral lead, which consists in backing off said teeth by relative backing off movements between the rotating cut ter and a tool having a cutting face longitudinally inclined to the axis of the cutter, moving the cutting edge of said tool tangentially of the cutter to move the latter through the cutting plane, and'relatively adjusting said tool along the cutter to compensate for the lead of the cutter contour.

'16. The method of relieving the teeth of a cutter having cutting faces longitudinally inclined to the axis of the cutterand having a contour with a peripheral lead, which consists in backing off said teeth by relative backing off movements between the rotating cutter and a tool having a cutting face longitudinally inclined to the axis of the cutter, moving the cutting edge of said tool tangentially of the cutter to move the latter through the cutting plane relatively adjusting said tool along the cutter to compensate for the lead of the cutter contour, and varying the relieving movement of the tool relative to the gutter to compensate for the inclination of the races.

17. The method of forming and relieving a work blank having generally longitudinal spiral gashes and having a helical thread intersecting saidgashes consisting of rotating the work blank, effecting a relative relieving reciprocation between the blank and a tool having an inclined cutting face, effect ing a continuous cycle of relative traverse movements between the blank and said tool longitudinally of the blank, separating the tool and the blank during each traverse movement in one direction, effecting a relative infeed between the tool and theblank, then effecting a relative tangential feed between the tool and the blank to transfer the final point of operation on the cutter along the edge of said tool, varying the relieving movements to compensate for the inclination of the gashes during the tangential feed, and eifecting a relative adjustment of said tool axially of the blank to compensate for'the lead of the thread during the tangential feed. 18. A machine of the character described comprising, in combination, a drive shaft, a reversing clutch for said shaft, a reversible element, means operatively connectedto said shaft for driving said element, a cam shaft operatively connected to said drive shaft, a cam onsaid cam shaft for opening said clutch at predetermined points in the travel of said element, a pivotal member adapted upon movement in opposite directions past dead center to close said clutch in opposite directions, and means operatively connected to said cam shaft for alternately moving'said pivotal member in opposite directions across dead center immediately prior to-opening of said clutch by'said cam, c

19. A machine of the character described comprising, in combination, a drive shaft, a reversing clutch for said shaft, a reversible element having a drive connection with said shaft, means operable at a predetermined point in the travel of said element in each direction to open said clutch, a reversible trip member'adapted upon movement in opposite directions past a predetermined point to close said clutch, and means operable in timed relation with said last mentioned means for alternately moving said trip member in opposite directions past said last menelement having a drive connection with said shaft, means operable at a predetermined point in the travel of said element in each direction to open said "clutch, a pivotalweighted member adapted upon movement in opposite directions over dead vertical tov fall so as to close said clutch selectively in opposite directions, and means operatively connected to said last mentioned means for alternately lifting said weighted member in opposite directions across dead vertical im mediately prior to each opening of the clutch.

In testimony whereof, I' have hereunto affixed my signature.

JOHN EDGAR.

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