US2064079A

US2064079A - Commutator finishing machine

Info

Publication number: US2064079A
Application number: US29855A
Authority: US
Inventors: Lora E Poole
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1935-07-05
Filing date: 1935-07-05
Publication date: 1936-12-15
Anticipated expiration: 1953-12-15

Description

Dec. 15, 1936. L, E, POOLE 2,064,079.

' COMMUTA'I'OR FINISHING MAG H INE Filed July 5, 1935 7 Sheets-Sheet l w r-% fi ATTORNEY p Dec. 15, 1936.

1.; E POOLE COMMUTATOR FINISHING MACHINE Filed July 5, 1935 7 Sheets-Sheet 2 OR M M"% TTORNEY J 1 Y L. E. POOLE COMMUTATOR FINISHING MACHINE Dec. 15, 1936.

"Filed July-5, 195 5 7 Sheets-Sheet 3 ATTORNEYL Dec. 15, 1936. E. POOLE COMMUTATOR FINISHING MACHINE 7 Sheets-Shet 4 Filed July 5, 1935 INVENTOR BY ATTORNEYl Dec. 15, 1936. POOLE COMMUTATOR FINISHING MACHINE 7 Sheets- Sheet 5 Filed July 5,-- 1935 w &

v wk

INVENTOR ,4 ATToRNEw Dec. 15,1936. L E- H 2,064,079.

" COMMUTATOR FINISHING MACHINE 'F iled July 5, 1955 .7 Sheets-Sheet '7 INVENTOR ATTORNEYt ciently to compensate in fresh strip material that Patented Dec. 15, 1936 corn vm'mroa rmrsnmc MACHINE Lora E. Poole, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of 'Delaware Application July 5, weasel-m No. 29,855

16 Claims.

This invention relates to commutator finishin machines and more particularly to a machine performing successive finishing operations on the commutator of an armature assembly.

It is one of the objects of the present invention successively to turn the polygonal commutator of an armature assembly into cylindrical shape and to smoothen the comparatively, rough periphery of the turned commutator in order to obtain good electrical contact between the commutator and a brush riding thereon and to reduce the wear of the latter to a minimum. This object is accomplished by turning the polygonal circumference of the commutator into cylindrical shape and thereafter stretching an abrasive strip such as emery paper partly around tator.

It is another object of the present invention automatically to advance the abrasive strip willamount of abrasive which is persistently .worn off during smoothening operations.

It is another object of the present. invention to provide for relative movement between the abrasive strip and the spinning co'mmutatorlonitudinally of the latter not onlyto exhaust the A abrasive but also toprevent the occurrence' of annular ridges which are so conspicuous on cylindrical surfaces abraded by mere relative rotation between said surface and the abrasive.

Further objects and advantages of the present invention will be apparent fromthe following descripticn, referenceibeing had to the accompanying. drawings wherein a preferred embodiment of the present invention is clearly shown. e

In the drawings:

Fig. l-is a perspective view of a machne em-.

bodying the present invention Fig. 2""is another perspective view of the machine, viewed from the rear thereof.

Fig. 3 is a fragmentary rear elevation of the machine. Fig. 4 is a fragmentary plan viewof the machine.

however, certain parts being shown in a different position of operation.

Fig. 9 is a section taken on the line 99 of Fig. 7.

Fig. 10 is an enlarged fragmentary section taken on the line ilk-I ll of Fig. 3.

Fig. 11 is a fragmentary section taken on the line ll-II of Fig. 10.

Fig. 12 is a section taken on the line I2-l2 of Fig. 10.

"Fig. 13 is a fragmentary section taken on the line l3l3 of Fig. 10.

Fig. 17 is a cam chart representing the movement of certain structure of the machine.

Referring to the drawings,.the reference numeral 20 designates the bed' of a conventional lathe having longitudinal guide-ways 22 on which a transport 24 is slidable. *Longitudinally adjustably mounted at one end of the lathe bed 20 is a taihstock 26 and mounted on the other end thereof is an electric motor 28 which supports and drives a centrifugally operated chuck 30, adapted togrip one end of the shaft 32 of an I armature assembly 34, the other end of said armature shaft 32 is journaled in the tail-stock 26. The transport 24 is provided with guideways 36 supportinga slide 38 for movement at right angles to the direction of movement of the transport 24. Mountedon this slide 38 is a tool 40 for turning the polygonal circumference of the commutator 42 ofthe armature 34 into cylindrical shape, and a device including a supply ofv abrasive, preferably emery paper 44, for smoothening the turned periphery of the commutator. Suitably journaled in bearing brackets 46 at the rear of the machine is a shaft 48, carrying cams I for moving the transport '24 as well as the slide 38. The cam shaft 48 is driven by means of an electric motor '50 which is mounted in any suit able manner on the rear of the machine. A manually enga'geable clutch 52 is provided and adapted to cause or interrupt driving connection.

between motor 50 and cam shaft 48. The clutch 52 is automatically disengaged after a completed turning and smoothening operation of the machine. Such automatic disengagement' of the clutch causes immediate braking'of .the chuck driving motor 28 and subsequent stoppin g there-.-

.of as will be described later.

With sole reference to Fig. 4 the operation of the machine is briefly as follows:

After proper mounting of an armature the transport 24 is caused to move to the left, whereby the tool 40 moves longitudinally of the .com-

, .rotor shaft 18.

mutator 42 while in cutting engagement therewith. Immediately upon arrival of tool 48in the dot-and-dash position,'the transport 24 returns into the full line position whileremaining in cutting engagement with the commutator. Thereafter and while the transport 24 remains in the full line position, the slide 38 is caused to move in the direction of arrow 68, whereby the abrasive material 44 approaches the turned commutator periphery and is subsequently stretched around part of said periphery in the manner shown in dot-and-dash lines in Fig. 10. The

transport 24 is then moved slightly to the left as shown in Fig. 4, sufficiently to contact the abrasive material with the entire length of the commutator. As soon as the abrasive strip reaches the left margin of the commutator, the transport 24 immediately reverses its direction of movement and returns to the full-line position, however with the abrasive strip still stretched around part of the commutator periphery. Thereafter, the slide 88 moves in the direction of arrow 62 into the full-line position, in which the tool 48 is in longitudinal cutting alignment with the commutator of a new armature to be deposited in the machine. This ends a complete cycle of opera'tion of the machine.

Chuck and tail stock Referring particularly to Figs. 1, 2 and 7 to 9 inclusive, the rotor shaft 18 of the electric motor.

28 supports and drives the centrifugally operated chuck 88 as will be presently described. Mounted by means of a key 16 to one end of the rotor shaft- 18 which extends beyond the motor 28 is a frame 14. Slidable in this hollow rotor shaft 18 is a sleeve 18 which is connected to a draw bar 88 by means of a nut 82. Interposed between a shoulder 84 of said sleeve and a retainer 86. secured at 88 to frame 14, is a compressed spring 88 which normally urges sleeve 18 and therewith drawbar 88 to the right as shown in Fig. 7. Pivotally mounted at 82 in opposite recesses 84 of frame 14 are levers 86 which carry weights 88, having arcuate slots I88 concentric 0f the pivot axes 82, through which pins I82 extend which are secured to the frame 14. The levers 86 are also provided with lugs I84 which extend through opposite slots I86 of the rotor shaft 18 and engage sleeve 18. Upon rotation of the rotor shaft 18, the weights 88 fly outwardly by centrifugal force, causing the lugs I84 of the weight carrying levers 86 to move sleeve 18.and therewith drawbar 88 to the left as shown in Fig. 8, i. e. against the compression of spring 88. After the rotor of the electric motor again comes to rest, spring 88 expands under its own compression, thereby causing the weights 88 to move into the position shown in Fig. 7 through intermediation of sleeve 18 and levers 86, as can be readily understood. The hollow rotor shaft 18 is at one end internally tapered and receives therein ato provide gripping jaws H8. This chuck H6 is:

threadedly connected at I28 with an enlarged portion I22 of drawbar 88, slidable in the hollow It can now be understood that while the rotor shaft 18 is at rest, the chuck H5 able tail stock 26. Since this tail stock does not form part of the present invention, no detailed description thereof is deemed necessary, it being sufficient to understand that manipulation of a hand lever I26 about an axis I28 into either one of two positions will cause movement of the tail' stock spindle I24 into either the full-line or the dot-and-dash position shown in Fig. '1. To remove an armature from the tail stock and the chuck, the tail stock spindle I24 is withdrawn into the dot-and-dash position, and to deposit a new armature, the shaft 82 thereof is introduced into the chuck H6 and the tail stock spindle moved into the full line position in Fi 7. To insure that a shoulder I88 of the armature shaft 82 is in abutment with the tail; stock spindle, a plunger I82 in the enlarged portion I22 of drawbar 88 is normally urged by means of a compression spring I84 to the right as viewed in Fig. 7, engaging the adjacent end of the armature shaft and thus shifting the same to the right until suchabutment occurs. Movement of plunger I32 is limited by means of an oblong slot I86 in said plunger and a pin I88, carried by the enlarged portion I22 of drawbar 88.

Turning tool tool "block I48 may be adjusted longitudinally of the armature shaft and locked in adjusted position by tightening nut I64. Locatedin an aperture I56 of said tool block is the cutting tool 48 which is secured therein in adjusted position by means of .a clamping screw I58. Slide 88 is provided with lug I68 through which extends a screw I62, threaded into the tool slide I42 and provided with a collar I64. A shoulder I66 of screw I62 and the collar I64 straddle the lug I68, preventing longitudinal movement of the screw relative to the lug but permitting free rotation of said screw which isprovided with a square head I68 for the application of a wrench or other suitable tool,

thereby to adjust the position of the tool slide I42 on the guideways I48. It can now be understood that thecutting tool 48 can be adjusted longitudinally of and parallel to an armature in the machine.

.. dma devic e Referring more particularly to Figs. 3 to 5 inclusive, and 10 to 13 inclusive, there are two parallel upright frames I18 mountedat I12 to" the slide 88. Tie rods "I maintain the frames I18 in spaced parallelism. .Mounted in bushings I14 of the frames I1Ilv are two parallel feed rolls I16. Cooperating with these feed rolls I16 are extend through suitable bores of the retainer blocks I90. 'One of the frames I10 pivotally supports at I96 a comparatively heavy lever I98, the forked portion 200 of which straddles a pivotally mounted roll 202. Extending from lever I98 is a pin 204 which in the lowermost position of roll 202 rests on top of one of theframe's I10 as best shown in Fig. 5. Pivotally mounted at 206 to the same frame I 10 which carries lever I98 are two guide rolls 208 which are parallel to the feed rolls I16, I18 and also to the weight roll 202. A- suitable reel 2| is pivotally mounted at 2I2 to one of the frames I and contains a supply of abrasive strip material 44 such as emery paper of a selected grade. A strip 44a, of emery paper is intially guided around the various rolls just described bydrawing a strip of emery paper from the supply on the reel and feeding the same between the first pair of cooperating feeding rolls I16, I18, then around the weight roll 202 and over the guide rolls 208 and finally between the second pair of feed rolls I16, I18. Upon the earlier mentioned approach of the abrading device to the commutator, the strip portion 44b between the guide rolls 208 is caused to embrace part of the periphery of the commutator and the resulting stretching of the abrasive strip between the first pair of cooperating feed rolls I16, I18. and the nearest guide roll 208 causes the weight roll 202 as well as the lever I98 to be raised from the position shown in Fig. 10 in which'the pin 204 of said lever I98 rests on one of the frames I10. It can therefore be understood that upon engagement of the abrasive strip portion 44b with a commutator periphery, the weight roll 202 tightens the entire strip portion situated to the left of both pairs of feed rolls I16, I 18 in Fig. 10. It can'likewise be understood that while the strip portion 44b is out of engagement with a commutator, the weight roll 202 is ineffective because the pin 204 of lever I98 then rests on top of one of the frames I10 and. the strip 2I4 rather loosely embraces part of the periphery of said weight roll.

In order to compensate in fresh strip material that amount of abrasive which is worn off during smoothening operations, the feed rolls I16, I18 are intermittently indexed, thereby drawing fresh strip material from the supply and exhausted strip material away from the guide rolls 208 aswill be presently described. Each pair of cooperating feed rolls I16, I18 is provided with meshing, identical gears 2I6. The gears 2I6 of the feed rolls I 16 are both in mesh with another gear 2I8 which is mounted on a stub shaft 220, journaled in suitable sleeves222 of the frames I10 and carrying at one end a. ratchet disc 224 with which cooperates a pawl 226, normally urged into engagement with the ratchet disc by a spring urged plunger 228, carried by ,an arm 230 which is suitably journaled at 232 to'the stub shaft 220. It has been already explained that the slide 38 has a definite motion at right angles to the armature in order to approach and withdraw the strip portion 44b to andfrom a commutator periphery. This motion is utilized for the indexing of the feed rolls I16, I 18 as will be presently explained. Mounted by screws 234 to the transport 24 is a bracket 236, having two spaced lugs 238, receiving set screws 240a and 24017 which are in alignment with the pawl carrying arm 230. The set screw 2400. is so adjusted that during the latter part of approaching movement of the abrading device to the commutator, the arm 230 strikes said set screw 240a and is thereby slightly rotated counterclockwise, resulting in a jumping by the pawl-226 of one or more teeth of the ratchet disc 224. There is sufiicient friction in the journal support of arm 230 to maintainthe latter in the position assumed after such slight counterclockwise rotaticn. During the latter part of retraction of the abrading device into the position shown in Fig. 5, arm 230 strikes the other set screw 2401) and is thereby rotated clockwise untilsaid abrading device comes to rest in most retracted position. Such clockwise rotation of arm 230 results in an indexing of the ratchet disc 224 by the pawl 226 and may amount to the angular distance between two or more consecutive ratchet teeth, depending upon the adjustment of set screw 24%. However, the indexing of the ratchet disc 224 can under no circumstances exceed the amount of counterclockwise rotation of arm 230 as caused by set screw 249a as-can be readily understood. Rotation of the ratchet disc 224 is transmitted to both pairs of cooperating feed mils I16, I18 through intermediation of stub shaft other suitable tool to rotate said stub shaft and thereby the feed rolls I16, I18 in the proper direction.

Movement of transport and slide As already mentioned, a cam shaft 48 is mounted in the rear of the machine and carries certain cams for moving the transport as well as the slide. groove 260 in a drum 262 which is mounted on shaft 48. Cooperating with this cam groove 260 is an anti-friction roller 264 (see also Fig. 5) which is carried by a bracket 266, mounted by bolts 268 to the transport 24 which is retained on plates 210. Motion of the transport 24 for one complete cycle of operation of the machine is caused by-one revolution of cam drum 262. I In One of these cams is in the form of a cam the guide ways 22 of the lathe bed by means of gib,

order to prevent a backing up of the cam drum" after one complete revolution thereof, i. c; after disengagement of the earlier mentioned clutch 52, a pawl 212, pivotally mounted at 213 to the lathe 'bed, is adapted to engage the shoulder 214 of an arcuate plate 216 whichis angularly adjustably mounted on the cam drum 262. Since the cam drum rotates normally clockwise as viewed in Fig. 5, it can be understood that the pawl 212 does not interfere with the normal rotation of said cam drum but merely prevents counterclockwise rotation thereof after one complete revolution in normal direction. Also mounted on shaft 48 is a disc cam 218 which cooperates with an antifriction roller 288 of an arm 282, pivotally mounted at 284 to a lug 288 of one of the bearing brackets 48. As best shown in Fig. 5, the other end of arm 282 is part-cylindrical and received in a socket 281, provided by an angle 288 which is secured to slide 38 by screws 288. The transport 24 includes a transverse tie 282 on which the slide 38 is movable in the earlier mentioned guideways 38. Extending over the greater length of said tie 292 is a bore 296 against the bottom 298 of which bears a compressed spring 388, the-other end of which bears against a pin 382, carried by slide 38 and extending through a slot 384 in said tie into the bore 288 (see Fig. 6). This compression spring 282 normally urges slide 38 to the left as viewed in Fig. 5, thereby retaining roller 288 of arm 282 in permanent engagement with the cam disc 218. It can be understood from all the foregoing that the slide 38 is positively moved to the right as viewed in Fig. 5 by the cam disc 218, and

that this slide is moved to the left by the compression spring 388 under the control of cam disc 218.

The cam shaft 48 is driven by the earlier mentioned electric motor 58 in a manner to be described presently. This motor 58 -is provided with any suitable reduction gearing 3I8, the slow shaft of which carries a small pinion 3|2 which is in permanent mesh with a larger gear 3, mounted on a stub shaft 318 which is in axial alignment with cam shaft 48 and suitably journaled in a bearing bracket 48a on the lathe bed. Motor. 58 is preferably continuously driven, wherefore the stub shaft 318 is also continuously driven. Mounted on this stub shaft 318 is the driving half of the earlier mentioned clutch 52,

carries a hand lever 328 for manipulation of said.

shaft and clutch. Also mounted on shaft 328 is an arm 338, carrying an anti-friction roller 332 which is adapted to cooperate with the periphery 334' of a disc-like extension 338 of the driven clutch half 338. Roller: 332 is normally urged into engagement with the disc periphery 334-by .means of a tension spring 348 which, as

shown in Figs. 1 and 4, is secured to an arm 342, which is in turn mounted on shaft 328 near the hand lever 328. The disc periphery 334 is provided with a sole detent 344 into .which the cam roller 332 will drop and cause disengagement of the clutch 52 at the end of one complete revolution of the cam shaft 48. To start a new revolution of said cam shaft, the operator of the machine manipulates handle 328 against the tension of spring 348, thereby causing withdrawal of cam roller 332 fromthe detent 334 and engagement of the clutch as can be readily understood. With the start of the cam shaft on a new revolution, the detent in the disc periphery 334 moves out of alignment with cam roller 332. After such disalignment of the detent 334, the operator may release handle 328 because the cam roller now rides on the periphery 334 and thus maintains the clutch in engagement until after one complete revolution of (mm shaft 48 the detent 3'44 realigns with the cam roller 332 and permits disengagement of the clutch.- Hence, the operator merely has to engage the clutch 52 and pay no attention whatever to the disengagement thereof, thus enabling him to closely inspect finished armatures without haste. 1

stoppage of chuck driving motor' I In the present instance the chuck driving motor 28 is preferably a three phase motor, de-

riving its power source from any suitable sup ply, indicated by the power lines 358 in Figs. 14 to 16 inclusive. A conventional switch 352 is so connected between the motor and the power lines as to reverse the phase order and to open the motor circuit. In Fig. 14 theswitch 352 is shown in a position in which the motor 28 I0- tates the chuck in the proper direction for performing a turning and abrading operation upon the commutator of an armature. Fig. 15 shows the switch 352 in reversing position, causing a braking action on the motor 28 and a subsequent momentary reversal of the motor. Fig. 16 discloses the switch 352' in open position. Therefore, Fig. 16 shows the motor circuit while the machine is at rest. As best shown in Figs. '1 and 14, the rotor shaft 18 of motor 28 carries a'small pulley 358 which by a suitable belt 358' drives a larger-pulley 388. Rotatable together with pulley 388 coaxially thereof is a disc 382 which is partly embaced by a band 384 of any suitable friction material. This friction band is secured to the opposite endsof a lever 388 which is pivotally mounted at 388 and carries a contact 318 and a stop 312. Cooperating with stop 312 is a stationary stop314, and cooperating with contact 318 is a stationary contact 318. Lever 388',

contacts

318, 318 and stops 312, 314 may conveniently be termeda switch 381. Contact 318 is connected by a lead 311 to one contact 318 of any conventional switch 318, having another contact 388 and a shiftable arm 382, carrying a contact 384 which may be engaged with either

contact

318, 388. Contact 388 is connected by a lead 388 to the forward winding 388 of a solenoid 388, having a reverse winding 382 and a core 384 which may be actuated by either winding and is drivingly connected to the switch 352 by means indicated at 388. The reverse winding 382 is connected to contact 318 by a'lead 388, and both

windings

388, 382 are connected to one of the power lines 358 by a lead 488. The conductive switch'arm 382 is connected to another power line 358 by a lead 482. The switch arm 382 is linked at 484 to the arm 342 on shaft 328 (see also Fig. 1). Therefore, upon engagement of clutch 52 by manipulation of handle 328 in the earlier explained manner, the switch arm 382 is shifted from the position shown in Fig. 16 to that shown in Fig. 14, thereby closing the forward energizing circuit of the solenoid 388 through intermediation of lead 488, forward winding 388, lead 388, the engaged

contacts

388 and 384, switch arm 382 and lead 482. Such energization of the solenoid causes a shifting of the switch 352 from the open position in Fig. 16 to that shown in Fig. 14, in which the motor 28 is energized for forward rotation. Immediately after the motor 28 starts to rotate forwardly. lever 388 is rotated from the position shown in Fig. 16 to that shown in Fig. 14 in which contact 318 engagescontact 318. This is accomplished due to the frictional engagement of band 384 with the disc 382 which is driven by motor 28 in the earlier explained manner. 0! course, 7

after the

contacts

310, 316 are in engagement with each other, the band 364 will merely slide on the disc 362, thereby frictionally maintaining the contacts in engagement. These

contacts

310, 316 form part of the reverse energizing circuit of the solenoid 390, but fall short of closing the same because the

contacts

384 and 318, forming also part of said reverse circuit are as yet open. Hence, during one complete revolution of the cam shaft 46 during which a turning and abrading operation take place, the forward energizingcircuit of the solenoid is kept closed due to the link connection 404 between the switch arm 382 and the arm 342 on shaft 326. As already explained, the clutch 52 is automatically disengaged after one complete revolution of cam shaft 48, and such clutch disengagement is accompanied by a slight rocking of shaft 326 and am 342 in such direction that the link 404 is shifted in the direction of arrow 420 in Fig. 14. Such shifting of link 404 results in a switching of arm 382 from the position shown in Fig. 14 to that shown in Fig. 15, in which contact 384 engages contact 318 and closes the reverse energizing circuit of the solenoid 390. Consequently the core 394 and the switch 352 are then shifted from the position shown in Fig. 14 to that shown in Fig. 15, resulting in a braking action on the motor 28 and subsequent momentary reversal of the same. starts to rotate in the reverse direction, disc 362 rocks the lever 366 from the position shown in Fig. 15 to that shown in Fig. 16 due to frictional engagement of said disc with the band 364. Such rocking of lever 366 naturally results in immediate disengagement of

contacts

310, 316 and consequent opening of the reverse energizing circuit of the solenoid 380. Th solenoid core 394 is connected to two tension springs 422 which normally tend to maintain said core in the balanced position shown in Fig. 16 in which the switch 352 is in open position. The

switches

352, 319 and 361 may be conveniently housed in

suitable boxes

500, 502, and 504,- respectively,

which are mounted in any suitable'manner. on

lever 328, thereby engaging clutch 52 and thus causing one revolution of shaft 48 and the cams carried thereby.' Such manipulation, of hand lever 328 by the operator also starts the chuck driving motor 28. While the machine is at rest, the transport 24 and slide 38 assume 'theposition shown in Fig. 4. Immediately after shaft 48 starts on its one revolution, the cam drum 262 causes movement of transport 24 such that the cutting tool 40 moves into the dot-and-dash position shown in Fig. 4, and then immediately returns to the full line position shown in that figure. During such movement of the transport 24, represented by the lines m-b and bc in the chart, the polygonal circumference of the com- 'mutator 42 is turned into cylindrical shape. It

follows from the chart that the reciprocation of the transport 24 takes place during approximately 205 [revolution of the cam drum 262. Simultaneously with the arrival of the transport in the position shown in Fig. 4, the-slide 38 is However, as soon as the-motor 26' moved in the direction of arrow 60 in Fig. 4 by the cam disc 218on shaft 48, until the abrasive strip portion 44b partly embraces the turned periphery'of the commutator'42 in the manner disclosed in dot-and-dash lines in Fig. 10. Such movement of the slide 38 is represented in the chart by theline de and takes place during approximately 50 further revolution of the cam shaft 48. While the abrasive strip portion 44b. is progressing around part of the commutator periphery, the cam drum 262 causes slight move: ment of the transport 24 to the left as 'viewed in Fig. 4 in order to contact the abrasive strip with the entire length of the commutator periphery; Such movement of the transport is represented by the line ,f-g in the chart. Immediately after the abrasive strip portion 44!) reaches the left margin of the commutator as viewed in Fig. 4, the transport 24 returns into the position shown in that figure with the abrasive strip portion still in' engagement with the commutator periphery.- The return movement of the transport is represented in the'chart by the line gh. Somewhat prior to the return of the transportinto the position shown in Fig. 4, slide 38 starts to move in the direction of arrow 62 in Fig. 4 as represented by the line 13-10 in the chart. Of course the abrasive strip is still in engagement with the commutatorperiphery when the transport returns into the position shown in Fig. 4, but by that time embraces a smaller portion of the commutator periphery as can be readily understood. As soon as the slide 38 has returned into the position shown in Fig.4, the one revolution clutch 52 is automatically disengaged, and such disengagement of the clutch is responsible for an immediate braking action on the chuck driving motor 28 and subsequent momentary reversal thereof. As soon as the motor 28 is at rest, the centrifugally operated chuck releases the armature shaft and the operator may then remove the finished armature from the machine and deposit a newarmature' therein. Having this done, the operator again manipulates hand-lever 328, starting the machine on a new cycle of operation.

While the embodiment of the present invention as herein disclosed, constitutes a preferred combination of a support for an armature including a commutator; a transport movable longitudinally of the armature; a slide movable on the transport laterally of the armature; two tools mounted on the slide on opposite sides of the armature; means for moving the slide relative to the transport to cause engagement or separation between either tool and the commutator; and means for reciprocating the transport, said means being operated in such timed relation with the slide moving means asjto reciprocate the transport through different distances during engagement of the different tools with the commutator.

2. In a machine of the character described, the

combination of a. support for an armature, said support including a rotary chuck for driving the armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly ing means; an electric motor driving the chuck;

connecting the rotary means with the power drivmeans closing the motor circuit upon clutch engagement and reversing and subsequently stopping the motor upon clutch disengagement.

4. In a machine of the character described, the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly connecting the rotary means with the power driving means;

a multi-phase motor for rotating the armature;

and means closing the motor circuit upon clutch engagement and reversing the phase order to reverse the motor upon ciutch disengagement.

5. In a machine of the character described, the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly connectin the rotary means with the power driving means; a multi-phase motor for rotating the armature; and means closing the motor circuit upon clutch engagement and changing the phase order to reverse the motor and subsequently opening the reverse motor circuit upon clutch disengagement.

6. In a machine of the character described, the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly connecting the rotary means with the power driving means; a multi-phase motor for rotating the armature; a normally open switch for closing the motor circuit and for changing the phase order to reverse the motor; means for maintaining the switch closed during clutch engagement; and means shifting the switch into phase changing position and subsequently releasing the switch upon clutch disengagement.

7. In a machine of the character described, the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly connecting the rotary means with the power driving means; a multi-phase motor for rotating the armature; a normally open switch for closing the motor circuit and for changing the phase order to reverse the motor; means closing the switch upon clutch engagement and maintaining the switch closed during such clutch engagement; and means shifting the switch into phase changing position and subsequently releasing the switch upon clutch disengagement.

8. In a machine of the character described, the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly connecting the rotary means with the power driving means; a muiti-phase motor for rotating the armature; a normally open switch for closing the motor circuit and for changing the phase order to reverse the motor; means for maintaining the switch closed during clutch engagement; and means shifting the switch into phase reversing position upon clutch disengagement, said means being also responsive to reverse rotation of the motor to release the switch.

9. In a machine of the character described.

the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for drivingly connecting the rotary means with the power driving means; a multi-phase motor for rotating the armature; a normally open switch shiftable into motor circuit closing position and into motor reversing position; a solenoid; a forward and a reverse circuit for energizing the solenoid, the forward circuit for shifting the solenoid core into motor circuit closing position and the reverse circuit for shifting the core into motor reversing position;

another switch for selecting the forward or redriving means; a clutch for drivingly connecting the rotary means with the power driving means a multi-phase motor for rotating the armature; a normally open switch shiftable into motor circuit closing position and into motor reversing position; a solenoid; a forward and a reverse circuit for energizing the solenoid, the forward circuit for shifting the solenoid core into motor circuit closing position and the reverse circuit for shifting drawn into motor reversing position; another switch shiftable to close either forward or reverse circuit, said switch being linked with the clutch to be shifted thereby; and means responsive to reverse running of the motor for opening the reverse circuit.

11. In a machine of the character described, the combination of a support for an armature; a tool; rotary means for operating the tool; power driving means; a clutch for 'drivingiy connecting the rotary means with the power driving means;

cuit for energizing the solenoid, .the forward circuit for shifting the solenoid core into motor circuit closing position and the reverse circuit for shifting the core into motor reversing position;

another switch shiftable to close either forward or reverse circuit, said switch being linked with the clutch to be shifted thereby; and a third switch in series with said reverse circuit, said switch being yieldingly closed during forward running of the motor andopened upon reverse running of. the motor.

12. In a machine of the character described, the combination of a device holding the ends of a strip of abrasive sheet material stationary, said device including two spaced rolls over which the strip is guided and said strip being of such length as to be loose though guided over said rolls;

and yielding strip tensioning means eng lnz a.

thereby substantially uniformly tensioning the 1 entire strip even though a work piece is forced tioned rolls and deflects said strip portion.

14. In a. machine of the character described;;

the combination of a device 'for moving and directing a portion of a supply of abrasive sheet material into a certain disposition, said device including two identical pairs of cooperating feed rolls yieldingly engaging the beginning and end of said portion which is of such length as to be loose between the pairs of feed rolls; means for simultaneously rotating at least one ofeach pair of 'feed rolls such that one pair thereof draws a length of material from the supply and feeds it toward the other pair of feed rolls and said other pair withdraws the same length of material away from said one pair of feed rolls; and means yieldingly tensioning the material portion between the pairs of feed rolls.

15. In a machine of the character described, the combination of a device for moving and directing a portion ofa supply of abrasive sheet material into a certain disposition, said device including two spaced guide rolls over which said portion ispassed and two identical pairs of cooperating feed rolls yieldingly engaging the beginning and end of said portion which is of such length as to be loose though passing over the guide rolls; means for simultaneously rotating at least one of each pair of feed rolls such that one pair thereof draws a length of material from the supply and feeds it toward the guide rolls and said'other pair of feed rolls withdraws the same length of material away from the guide rolls; a. pivotally supported lever; a roller carried by the lever remote from its pivot support, said roller resting by gravity on apart of the material portionother than that between the guide rolls,

thereby substantially uniformly tensioning the entire portion even though a workpiece is forced against the material between the guide rolls and deflects said material.

16. In a machine of the character described, the combination of a support for an armature including a commutator; a first carrier; a second carrier mounted on the first carrier ior'movement laterally of the armature two tools mounted on the second carrier on opposite sides of the armature; mechanism for moving the second carrier relative to the first carrier to cause'engagementor separation between either tool and the commutator; and means for causing relative re-- ciprocation between the support and first carrier ni'sm as to cause relative reciprocation through different distances during engagement of the dirferent tools with the commutator.

LORA -E. POOLE.