US2724306A - Automatic spiraling machine for making electrical resistors - Google Patents

Description

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illn- Nov. 22, 1955 Filed April 14, 1952 V. A. WCODELL AUTOMATIC SPIRALING MACHINE FOR MAKING ELECTRICAL RESISTORS Nov. 22, 1 955 Filed April 14, 1952 INVLNIUR. Mc far f5'. ,f4/00de# Nov. 22, 1955 v. A. WOODELI. 2,724,306

AUTOMATIC SPIRALING MACHINE FOR MAKING ELECTRICAL RESISTORS 3 Sheets-Sheet 3 Filed April 14, 1952 l 1N VEN TOR. V/aar 4. M0027/ BY M IQORNEK 2,724,306 Patented Nov. 22, 1955 AUTGMATIC SPIRALING MACHINE FOR MAKIN ELECTRICAL RESISTORS Application April 14, 1952, Serial No. 282,101 z Claims. (C1. io-11.46)

`This invention relates to machines for cutting a spiral groove in articles, and has for` its primary object the provision of apparatus for automatically feeding the articles to be grooved, advancing the same toward a holder, `reciprocating the holder while the same is rotated and while the article is held in engagement with a rotatable cutter, and thereupon releasing the grooved article, all `without operator attention so long as the machine is supplied with the material and is operating properly. t

The` machine of the present invention is adapted particularly for use in forming a spiral groove in an outermost carbon coating forming a part of an electrical resistor for the purpose of determining the resistance value p thereof, all depending upon the amount of material removed in the grooving process;

Grooving machines much in the nature of a lathe have heretofore been provided, but for the most part, such machines required an operator to handle each and every resistor rendering the same time-consuming and making it necessary to utilize the time of a workman.

It is accordingly the most important object of the present invention to render a lathe-like grooving machine entirely automatic except only for maintaining a constant supply of resistors to be grooved and removing the completely grooved resistors therefrom by means of a suitable collection pan.

Another important object hereof is to provide a grooving machine that includes a lathe-like construction wherein a carriage is reciprocated and is provided with a resistor-holding means that rotates with respect to the carriage and to render the machine operable to groove a resistor during reciprocable movement in each direction. l

Other objects include the way in which a chuck-like holding means for the resistors is automatically released at each end of its path of travel; the way in which a resistor for grooving is advanced vto the releasable chuck means at each end of its path of travel; the way in `which the carriage and therefore, the holder thereon,

is swung toward and away from the continuously rotating `cutter wheel; the manner of limiting the extent of reciprocable movement of the carriage; and the way in which the machine is rendered immobile in the event of `failure of any of the primary control means therefor.`

` Other objects will be made clear or become apparent as the following specification progresses, reference being had to the drawings, wherein: I

Figure l is a `fragmentary top plan view of an automatic spiraling machine for making electrical resistors forming the subject matter of the present invention.

Fig. 2 is an end elevational view thereof, parts being broken` away and in section for clearness. p

Fig. `3 is a fragmentary, detailed, cross-sectional view taken on line III-lll of Fig. l.

Fig. -4 is an enlarged, fragmentary, cross-sectional view taken on line IV-IV of Fig. l,

Fig. 5 is an enlarged, fragmentary, detailed crosssectional view taken on line V-V of Fig. l.

Fig. 6 is a detailed, cross-sectional view taken on line VI--VI of Fig. 1.

Fig. 7 is a vertical, cross-sectional View `illustrating `the type of feeder used with the machine shown in Figs.

l and 2; and

Fig. 8 is a schematic wiring diagram showing the electrical components of the machine and the manner of intercoupling the same.

Resistors 10, shown in Figs. l, 2, 4 and 7 of the drawings, are advanced to a suitable feeder such as shown in Fig. 7 and broadly designated by the numeral 12 through the medium of automatic sorting and feeding mechanism not shown, and having an outlet tube 14. A pair of spaced-apart, horizontal plates 16 and 18, receive tubes 14 and 20 in offset relationship.

A reciprocable plunger 22 is provided with a vertical opening 24 for receiving resistors 10 one at a time from the tube 14, advancing the same along the plate 18 and nally depositing such resistor 10 from the opening 24 into the tube 20 and thence into a hopper 26, the lowermost end of the hopper 26 being also illustrated in Figs. l, 2 andS of the drawings.

Reciprocable movement is imparted tot the plunger portion 22 of the feeder 12 through the medium of an air valve that is magnetically operated by means of a solenoid 28 (see Fig. 8). During descent of the resistors 10 in the hopper 26, they turn from a vertical position to a horizontal position as shown in Figs. l and 2 of the drawings. Resistors 10 gravitate into an elongated receiver 30 capable of receiving several resistors 10 in stacked relationship. The receiver 30 is mounted on one end of an elongated, inclined support 32 that underlies and slidably receives a reciprocable plate 34. Plate 34 is notched as at 36 to receive the resistors 10 one at a time from the tubular receiver 30.

An air valve 38 mounted on the support 32 is connected with the plate 34 to reciprocate the latter, valve 38 being operated by means of a solenoid 40 (see Fig. 8). It is noted in Fig. 5 of the drawings that the reciprocable plate 34 is T-shaped in cross-section and releasably held for free sliding movement on the support 32 by means of a pair of L-shaped strips 42, the latter serving to support the tubular receiver 30.

A carriage broadly designated by the numeral 44, is provided with an elongated bar 46 mounted within an elongated, horizontal track 48 for longitudinal reciprocation within a vertical plane intersecting the inclined, reciprocable path of travel of the plate 34. The track 48 is in turn carried by a bed 50 that has a U-shaped extension 52 provided with a horizontal bight 54 in spaced,`

parallelism to the path of travel of the carriage 44. Bight 54 receives a roller 56 mounted on a bracket 58 depending from the support 32.

A second U-shaped extension 60, is mounted on the bar` 46 of carriage 44 for reciprocation therewith and has a horizontal bight 62 spaced above and inwardly of the bight 54 of extension 52. A bracket 64 rigidly interconnects the support 32 and the bight 62 of extension 60.

The bar 46 of the carriage 44 has a plurality of upm standing lugs 66 that receive a shaft 68 overlying the bar `46 in parallelism with the longitudinal axis of the latter for swingably receiving a plurality of upstanding arms 70 and movable toward and away from a rotatable cutter disc 72. Disc 72 is rotatably mounted on a bracket 74 extending upwardly from the bed S0. A pulley 76 on the shaft of cutter disc 72 is coupled with an electric motor or other suitable prime mover 78 by means of a continuous belt 80, the motor 78 (see also Fig. 8) being likewise mounted on the bed 50.

A reversible electrical motor 82 (Fig. 8) is operably coupled with a shaft 84 to rotate the latter and to reciprocate the carriage 44 in any well known manner and since such coupling has heretofore been used in lathes generally, the same has not been herein shown in detail. A ksecond shaft 86 cooperates with the shaft 84 and, like the latter, is rotatably carried by the arms 70 at the uppermost end of the latter.

Holding means for the resistors takes the form of opposed, spaced chucks 88 and 90 on the proximal ends of shaft 84 and 86 respectively. The shaft 86 is reciprocable within its supporting arm 70 and is yieldably held biased toward the chuck 88 by means of a spring 92 coiled thereabout between a collar 94 on the shaft 86 and the proximal arm 70 (see Fig. 4). Cavites 96 and 98 are formed in the ends of chucks 88 and 90 respectively to receive the resistor 10, there being a small plate 100 within the cavity 98 of chuck 90 and a small ball 102 between plate 100 and the proximal end of shaft 86, plate 100 and ball 102 both being loosely disposed in the cavity 98.

An inclined deflector plate 104 carried by the arms 70 beneath the chucks 88 and 90, receive groove'd resistors 10 after release thereof by reciprocation of shaft 86 in one direction, suchl finished resistors gravitating to a receptacle not shown beneath bed 50, the latter being cutaway as shown in Fig. l, to clear the gravitating resistors 10.

Movement of the shaft 86 on its longitudinal axis against the action of spring 92 to release a resistor 10 from beneath chucks 88 and 90, is accomplished by means of an air valve 106 carried by the extension 60 at one end thereof. The air valve 106 is actuated by means of the solenoid 28 (see Fig. 8). The air valve 106 has a reciprocable plunger 108 disposed to swing an L-shaped artn 110 (see Fig. 3), pivotally carried as at 112 by an L-shaped bracket 114 secured to the extension 60. The arrn 110 extends into overlying relationship to the shaft 86 on one side of a disc 116. Disc 116 is integrally connected with a second disc 118 in spaced parallelism to disc 116 and both of the discs 116-118 are joined rigidly to the shaft 86. One of the arms 70 that includes a bearing forV the shaft 86, has an adjustable screw 120 that is held in an adjusted position by locknut 122. The screw 120 extends between a pair of substantially wedge-shaped, spaced-apart stops 124 that are adjustable toward and away from each other and suitably mounted on the bed 50.

A laterally extending arm 126 on the arm 70 for shaft 86 has an adjustable counterweight 128 tending to swing the interconnected arms 70 and therefore, the chucks 88 and 90 as well as resistor 10 carried thereby, away from the cutter wheel 72. A safety switch 130 (see also Fig. 8), has a pair of resiliently mounted contacts disposed between the discs 116 and 118 as shown in Fig. l.

The machine is also provided with an additional pair of safety switches 132 and 134 (see Fig. 8), disposed within the helix adjusting means forming a part of the interconnection between three-phase motor 82 and the carriage 44, as well as the shaft 84. In this connection, bymeans of a feed screw, an adjustable lever, and a suitable train of gears not herein illustrated, the pitch of the spiral groove to be formed in the resistors 10, may be selected and it is within such mechanism that the safety switches 132 and 134 are disposed. The chucks 88 and 90 and the resistor 10 held thereby, are moved toward the cutter wheel 72 against the action of counterweight 128 by means of a spring 158, after deenergization lof solenoid 136 (Fig. 8), and its attendant air valve, not shown. A pair of limit switches 138 and 140 (Fig. 8)', are provided with reciprocable, spring-loaded actuatingvplu-ngers 142 and 144 respectively (Fig. 1), in turn provided with rollers 146 and 148 respectively. Rollers 146 and 148 ride along a. plate 150 mounted on the carriage 44 for reciprocation therewith. Plate 150 is pro- 4 vided with a pair of elongated projections 152 and 154 for the rollers 146 and 148 respectively.

Bed 50 is provided with mounting means 156 for one end of spring 158 that has its opposite end pivotally connected with an extension 160 on the bearing arm 70 for shaft 84, spring 158 thereby tending to hold the resistor 10 between chucks 88 and 90 biased toward the cuter wheel 72. The tension of spring 158 is varied in one di rection of reciprocable travel of the carriage 44 by means of a swingable dog 162 (see Fig. 6), that is moved into engagement with the spring 158 by means of an extension 164 on the carriage 44 and within notch 166 ofdog 162. Electrical components in addition to those hereinabove set forth, are illustrated in Fig. 8 of the drawings.

A source of energy not shown, is provided for a power transformer broadly designated by the numeral 168 having secondary windings `170, 172 and 174 (see Fig. 8). A :nain manual switch broadly designated by the numeral 176, is provided with three switch arms 178, 180 and 182, ganged together for simultaneous operation. A single switch 184 controls the cutting wheel motor 78. A timing motor 186 is provided with cams 188, 190, 192 and 194 on its shaft 196 for switches 1.98, 200, 202 and 204 respectively. The switches 280 and 202 are normally open as illustrated in Fig. 8 of the drawings; switch 198 is opened during travel of the carriage 44 in one direction and closed as the carriage 44 reciprocates in the opposite direction; and switch 204 is always closed with respect to one of its two stationary contacts 206 and 208. Switches 138 and 140 are closed when the plungers 142 and 144 thereof are forced away from the plate 150 by the corresponding extension 152 or 154 as the case may be.

The electrical circuit shown in Fig. 8 of the drawings includes additionally an auxiliary transformer broadly designated by the numeral 210 and having a primary winding 212 and a secondary winding 214. Four relays, broadly designated by the numerals 216, 218, 220 and 222 are provided with coils 224, 226, 228 and 230 re-` spectively. Relay 216 is provided with three normally open setsof contacts 232, 234 and 236. Relay 218 has a pair of doubley pole, double throw switches 238 and 240. Relay 220 has a single set of normally closed contacts 242. Relay 222 has two sets of contacts 244 and 246' that are normally closed. Motor 82 is provided with a brake 248 for its drive shaft 250, brake 248 being normally biased against the shaft 250 by spring 252 and a solenoid 254 being provided to release the brake 248 against the action of spring 252.

When the machine is initially placed in operation, switch 184 is closed and remains closed to continuously energize the motor 78 and thereby rotate the cutter wheel 72 through the following circuit:

From secondary of transformer 168, through lines 256, 258 and 260, .motor 78, line 262, closed switch 154 andlines 264 and 266, to secondary 170.

Closing of the main switch 176 energizes the coil 224 of relay 216 through the following circuit:

From'secondary 174, through line 266, switch 182, lines 268, 270 and 272, coil 224, line 274, switch varm 204, stationary Contact 208, line 276, closed switch 140,

lines 278 and 280, closed contacts 244 of relay 222, linesV 282 and 284, closed switch and line 286, to secondary 174.

Energization of the coilv 224 of relay 216 closes switches 232, 234 and 236, releasing brake 248, energizing motor 82 and deenergizing `motor 186. Solenoid 254 is energized to release brake 248 through the following circuit:

From secondary 170 through lines 256, 288 and 290, solenoid 254, lines 292, 294 and 296, closed switch 234, lines 298. andv 284, closed switch 180 and line 286 to transformer 168.

Motor 82 is energized for rotation in one direction through the following circuit:

l From secondary 172 of transformer 168, through line 300, closed switch 178, lines 302 and 304, closed switch 232, line 306, motor 82, lines 308 and 310, switches 238 and 240, lines 312, 314 and 296 to closed switch 234, lines 316 and318 to closed switch 236, lines 298 and 284, toelosed switch 180, lines 320, 270 and 268 to closed switch 182 and lines 266 and 286, to transformer 168.

Energizationof coil 224 of relay 216 also energizes coil `228 of relay 220 to open the contacts 242, through the `following circuit: i* From secondary 170 of transformer 168, through lines 256, 258, 322 and 324, coil 228,` lines 326, 294 and 296, closed contacts 234 of relay 216, lines 298 and 284, closed switch 180 and line 286 to transformer 168.

Opening of the contacts 242 of `relay 220.deenergizes the following circuit for timing motor 186:

From secondary 170 of transformer 168, through lines 256,288, 328 and 330, motor 186, lines 332 and`334, contacts 242 when closed, line 336, `closed contacts 246 of relay 222, lines 338 and 302, closed switch 178 and line 300 to secondary 17 0.

. `6 From secondary 214 of transformer 210, through lines 354 and 356, closed switch 198, line 358, coil 226 of relay 218 and lines 360 and 362, to secondary wiring It is seen that while the carriage 44 was moving from the left to theright (viewing Fig. l), switch 198 was closed and coil 218 thereby energized to hold the switches 238 and 240 in one of their two positions. Deenergiza- Assuming that a resistor 10 has been positioned between the chucks 88 and 90 and releasably heldtherein by the bias of spring 92, release of the brake 248 and energization of motor 82, causes the carriage 44 and all parts mounted thereon to move in one direction, namely, from the left to the right, viewing Fig. 1 of the drawings. The aforementioned air valve coupled with the arms 70 toswing the same away from the cutter wheel 72 and operated by the solenoid 136, is also released by deenergization of the solenoid 136 and the resistor 10 between the chucks 88 and 90 moves into engagement with the cutter wheel 72. `The energization of relay 220 to open contacts 242, deenergizes the solenoid 136 by virtue of its parallel coupling in the above traced circuit for motor 186.

It is to be noted in Fig.` 8 that solenoid 136 is` coupled with lines 328 and 330 by means of a line 340 and with lines 332 and 334 by a line 342. As soon as the carriage 44 moves a predetermined distance to the right, viewing Fig. l, the roller 146 moves off of the extension 152 and commences riding on the plate 150. Plunger 142 moves toward the plate `150 by virtue of its being spring-loaded, thereby closing the switch 138 (see Fig. 8) readying the same forthe return travel of carriage 44. Carriage 44 continues to move to the right, viewing Fig. 1, until the switch 140 is opened by virtue of roller 148 moving onto the extension 154.

As above set forth, the circuit for relay 216, i. e. the coil 224thereof, includes the switch 140. Accordingly, opening of the` latter deenergizes coil 224, opening switches 232, 234 and 236. This immediately deenergizes the motor 82 to stop further movement of the carriage to the right, viewing Fig. 1, and to` discontinue the rotation of the resistor 10 held between the chucks 88 and 90. Deenergization of relay 216 also deenergizes thesolenoid 254, causing the brake 248 to be appliedto the shaft 250 and assuring an immediate stopping of motor 82. Deenergization of the relay 216 also deenergizes coil 228 of relay 220, whereupon the switch 242 closes, thereby making the circuits above traced through the timing motor 186 and through the solenoid 136. Energization of the solenoid 136 immediately causes operation of its associated air valve, which in turn operates to swing the carriage 44 against the action of spring 158, fully removing the grooved resistor 10 from engagement with the cutter wheel 72.

Primary 212 of transformer 210, is energized upon closing of the switch 176 through the following circuit:

From secondary 170 of transformer 168, through lines 256, 258, 322, 344 and 346, primary winding 212, lines 348, 350, 352 and 268, switch 182 andline 266 to secondary 170.

Operation of motor 186 actuates the cam 188 to open switch 198, thereby deenergizing coil 226 of relay 218 whose circuit is traced as follows:

tion of the -c`oil 226 causes the switches 238 and 240 to move downwardly, viewing Fig. 8, and when the relay 216 is again energized, the motor 82 operates in the reverse direction from that above traced, through the following circuit:

From secondary 170 through line 300, switch 178, lines 302and 304, closed contacts 232, line 306, motor 82, lines 308 and 310, switches 238 and 240, lines 364 and 366, line 318 to switch 236, lines 314 and 296 to switch 234, lines 320, 270 and 268, to switch 182, lines 298 and 284, to switch 180 and lines 2661 and 286, to transformer 168. Thereupon the cam 190 moves to a` position closing switch 200 by operation of motor 186 to energize the solenoid 28, through the following circuit:

From secondary 170 of transformer 168, through lines 256, 258, 322, 344, 368 and 370, solenoid 28, line 372, switch200, lines 374, 352 and 268, switch 182 and line 266, to secondary 170.

Such energization of solenoid 28 supplies air to the valve 106 (Fig. l) to move plunger 108 thereof against the arm 110. Swinging of the arm 110 against the disc 116 retracts the shaft 86 and therefore, the chuck 90 against the action of spring 92, permitting gravitational movement of the grooved resistor 10 to the deector` plate 104, and thenceto a receptacle therebelow. ,En ergization of the solenoid 28 also operates the plunger 22 (Fig. 7) to feed a resistor 10 into the tube 20 and thence into the hopper 26 where it gravitates into the receiver 30. While the solenoid 28 is energized, the cam 192 moves toa position closing the switch 202, thereby energizing the solenoid 40 through the following circuit:

From secondary of transformer 168, through lines `25,6, 258, 322, 344, 368 and 376, solenoid] 40, line 378, switch 202, lines 380, 350, 352 and 268, switch 182 and line 266 to secondary 170.

Energization of the solenoid 40 supplies air to the valve 38, thereby causing the plate 34 to shift upwardly along the support 32, carrying therewith a resistor 10 within the notch 36 for reception by the chucks 88 and 90. Before the solenoid 40 is deenergized, the cam 190 moves to a position opening the switch 200, deenergizing the solenoid 28, which not only retracts the plunger 22 (Fig. 7) so that it will receive another resistor il() in its opening 24 from the tube 14, but releases the plunger 108 of valve 106, thereby releasing the arm 110 (Fig. 3)V

and causing the chuck 90 to move by the action of spring 92 to engagement with a resistor 10 being held in position by the reciprocable plate 34. Thereupon the cam 192 moves to a position `opening switch 202 and deen- Secondary 170, through line 266, switch 182, lines i 268, 270 and 272, coil 224, line 274, switch 204, stationary contact 206, line 382, closed switch 138, lines 384 and 280, switch 244 of relay 222, lines 282 and 284, switch and line 286 to transformer 168.

The operations above described are repeated in reverse order as the chucks 88 and `90 move from the right to the left and thus to the position illustrated in Fig. 1

yof the drawings. It is thus seen that during a complete cycle of reciprocation of the carriage 44, two resistors 10 are grooved spirally and discharged to a receptacle below deilector 104. v

The adjustable vstops 124-124 in the path oftravel of the screw 126 operate to move the resistor 10 away from the cutter wheel 72. Accordingly, the solenoid 136 and its associated air valve is utilized to `swing the arms "Z0 still further and thereby positively clear the cutter wheel 72 for replacement of resistors between the chucks 88 and 90.

In the event the machine fails to deliver a resistor 10 between the chucks 88 and 90, release of the air valve 106 will cause the disc 118 to close the contacts of switch 130 by the action of spring 92, see Figs. 1 and 8. VSuch action energizes coil 230 of relay 222 and a bell 386 (Fig. 8) through the following circuit: n

From secondary winding 214 of transformer 210 through lines 354, 33S and 390, closed switch 130, lines 392, 39,4 and 396, coil 230, and lines 393, 4511) and 362 to secondary winding 214.

The electrical bell 386 is coupled in parallel with the last mentioned circuit by means of lines 402 and 404, the latter joining lines 394 vand 396. Opening of the contacts 244 and 246 within the circuits for coil 224 of relay 216 and within the circuits for motor 186, and solenoid 136 respectively, causes a complete shut-down of the machine With the exception only of the continuously rotating cutter wheel 72. Coupling of the safety switches 132 and 134 in the manner illustrated in Fig. 8 of the drawings, causes the same safety action and operation of alarm 386 when a mechanical defect takes place in the mechanism for` rotating the shafts 84 and 86 and causing reciprocation of the carriage 44V through the action of motor 82.

Sincerres'istors 10 rotate in one direction when the carriage 44 moves to the left, viewing Fig. 1, and in the opposite direction when the carriage moves to the right, there will be a tendency of variance in pressure between the resistor being spirally grooved and the cutter 72. Accordingly, when the carriage 44 moves in one direction, the extension 164 engages the dog 162 to swing the same against the spring 158, increasing the tension thereof and thereby increasing the bias of the resistor 10 being cut upon the peripheral cutting edge of wheel 72.

Having thus describedvthe invention what is claimed as new and desired to be secured by Letters Patent is:

1. In a machine for automatically forming spiral grooves in electrical resistors, said machine having a rotatable cutter disc, the improvement including a carriage reciprocable relative to the disc; a pair of spaced shafts rotatable on aligned axles parallel with the path of travel of the carriage and the axis of rotation of the disc, said shafts having chuck means adapted to receive a resistor therebetween, one of the shafts being longitudinally shiftable for releasing the chuck means when the one shaft is shifted away from the other shaft; resilient means yieldably biasing said one shaft toward lsaid other shaft; a support for the shafts swingably mounted on the carriage for reciprocation therewith and for movement of the resistor held by the chuck means into and out of cutting engagement with the periphery of said disc; a reversible `prime mover operably coupled with said otherV shaft for reciprocating the carriage and for rotating the shafts in one direction when the carriage moves in one direction and in the opposite direction when the carriage moves in the opposite direction;means mounted on the carriage for reciprocation therewith and connected with the support for swinging the same toward the disc; spaced, stationary elements engageable `alternately with the support at each end of the vpath of travel of the carriage for swinging the support away fromthe disc; and means mounted on the carriage for reciprocation therewith and operably coupled with said one shaft for shifting the same away from the other shaft against the action of said resilient means when the support is swung away from the disc to release the chuck means at each end of said path of travel of the carriage.

A2. ln a machine for automatically forming `spiral grooves in electrical resistors, said machine having a rotatable cutter disc `and a feeder adapted to discharge the resistors singly, the improvement including `a carriage reciprocable relative to the disc; a pair ofspaced shafts rotatable on aligned axles parallel with the path of travel of the carriage and the axis of rotation of the disc, said shafts having chuck means adapted to receive a resistor therebetween, one ofthe shafts being longitudinally shiftable for releasing the chuck means when the one shaft is shifted away from the other shaft; resilient means yield-V ably biasing said one shaft toward said kother shaft; a support for the shafts swingably mounted on the carriage for reciprocation therewith and for movement of the resistor held by the chuck means into and out of cutting engagement with the periphery of said disc; a reversible prime mover operably coupled with said other shaft for reciprocating the carriage and for rotating the shafts in one direction when the carriage moves in one directionand in the opposite direction when the carriage moves in the opposite direction; means mounted on the carriage for reciprocation therewith and connected with the support for swinging the same toward the disc; spaced, stationary elements engageable alternately with the support at each end of the path of travel of the carriage fon swinging the support away from the disc; means mounted on the carriage for reciprocation therewith and operably coupled with said one shaft for shifting thesame away from the other shaft against the action of said resilient means when the support is swung away from the disc` to release the chuck means at each end of said pathl of travel of the carriage; .and a device mounted on the carriage for reciprocation therewith and reciprocable toward and away from said chuck means for advancing a resistorfrom the feeder to the chuck means when the latter is released.

References Cited in the file of this patent UNITED STATES PATENTS Muller July 30, 1918V

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