US2797290A - Spiralling apparatus - Google Patents

Description

June 25, 1957 w. F. EBLING, JR 2,797,290

SPIRALLING, APPARATUS Y Filed Sept. 26', 1956 4 IO I6 68 g 30 it:

'l/l/l/l/l III/l I INVENTOR. WILLIAM F. EBLING JR.

AWMJ. QM

ATTORNEY United States Patent@ SPIRALLING APPARATUS William F. Ebling, Jr., Springfield, Pa., assignor to International Resistance Company, Philadelphia, Pa.

Application September 26, 1956, Serial No. 612,318

12 Claims. (Cl. 219-19) This invention relates to apparatus for spiralling electrical resistors.

In the manufacture of film type electrical resistors which comprise an insulating core, usually of glass or ceramic, coated with a film of resistance material, such as carbon or a metal, it is the practice to spiral the individual units to increase the resistance value thereof to a desired value. Spiralling a resistor comprises cutting a helical groove in the resistance film to increase the path length of the film. Previously, spiralling was accomplished by translating and rotating the resistance unit across a rotating cutting wheel such as shown in Patent No. 2,405,485, to E. E. Barkstorm et al., issued August 6, 1946, orby sand blasting the groove in the film as shown in Patent No. 2,743,554 to E. G. Dailey et al., issued May 1, 1956.

In patent application Serial No. 385,066, filed October 9, 1953, by Sidney J. Stein et al., there is disclosed a method of making film type electrical resistors by coating the resistance material film on a single continuous length glass or ceramic rod or tube filament of small diameter. After being coated, the filament is cut into the individual resistance elements. It is desirable to spiral the coated filament preferably while still a single continuous length since it is very difficult to handle the small'individual resistance elements. However, the nature of the filament raises many problems which make spiralling by the well-known techniques previously described, either impracticable or substantially impossible. Because the filament is a single continuous length it cannot be rotated as is done in spiralling individual resistance elements but the spiralling apparatus must be rotated about the filament. Also, since the small diameter glass filament is fragile, care must be taken not to apply too much pressure thereto or to further weaken the filament during the spiralling. It is practically impossible to rotate a cutter wheel around the filament at speeds necessary for fine spiralling and at the same time maintain sufiicient contact on the filament to cut away the film and yet not break the filament. This is made even more difficult by the fact that, to ensure cutting com pletely through the film it is necessary to cut slightly into the filament which weakens the filament, Although there is no problem in rotating a small sand blast nozzle around the filament, ditficulties arise in feeding the sand laden stream to the rotating nozzle without damaging the apparatus by sand entering the bearings and like parts. Spiralling by a sand blast also weakens the filament since the blast must cut into the filament to ensure removal of the film.

However, it has been found that, when a sufficient electric current is passed between the film on the filament and an electrode contacting the film, an electric arc is formed which removes the film beneath the electrode without damaging the filament core. The electrode can be easily rotated around the filament at the necessary speeds to provide apparatus for spiralling the continuous length coated filament.

It is therefore an object of this invention to provide an apparatus for spiralling a continuous length coated filament. It is a further object of this invention to provide an apparatus for spiralling a fragile continuous length coated filament without damaging the filament. Another object of this invention is to provide an apparatus for electric arc spiralling a continuous length coated filament.

The invention accordingly comprises the features of construction, combinations of elements and arrangement of parts, which will be exemplified in the constructions hereinafter set forth and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

Figure 1 is a partially sectioned view of a spiralling apparatus of this invention;

Figure 2 is an end view of the apparatus shown in Figure 1;

Figure 3 is a side view, partially sectioned, of a modification of the apparatus; and

Figure 4 is an end view of the modification shown in Figure 3.

Referring to the drawing, in which like numerals identify similar parts throughout, Figures 1 and 2 show a spiralling apparatus comprising a bearing sleeve 16 mounted on a support 12. A sleeve 14 is rotatably supported in bearing 10 and has a radially extending flange 16 at one end abutting against an end of the bearing. If desired, flange 16 may be a separate collar brazed or welded to sleeve 14 or secured thereon by a set screw. The other end of sleeve 14 extends beyond bearing 10 and a pulley 18 is secured thereon by a set screw 20. Pulley l8 abuts against the other end of bearing 10 to prevent lateral movement of sleeve 14. A pin 22 of electrically conducting material projects from flange 16 and an electrode 24 is mounted on the pin 22 and eX- tends substantially radially across the open end of sleeve 14. The electrode 24 is a substantially resilient wire of an electrically conducting material which will withstand high temperatures, maintain spring tension and resist abrasion, such as tungsten, and is shaped to have substantially point contact wtih the coating on the filament. A guide sleeve 26 having an inner diameter slightly larger than that of the filament 32 to be spiralled is mounted centrally in the entrance end of sleeve 14 by a ring 28 of an insulating material. Rotation of sleeve 14 and thereby electrode 24 is provided by motor 2?, preferably a variable speed type, connected by drive pulley 30 and endless belt 31 to pulley 18. A D. C. electrical current is provided between the electrode 24 and coated filament 32 from a variable source 34 which is connected to the electrode 24 through a spring contact 36 which has one end mounted on an insulator 38 on the bearing 10 and the other end slidably engaging fiange 16. The current source 34 is connected to the filament 32 through a mercury block 44 which is mounted in alignment with the entrance end of the sleeve 14 and through which the filament passes. Tnstead of the mercury block, a rolling wheel or other type of contact may be used.

In operation, the continuous length coated filament 32 is fed in the direction of arrow 42 through the mercury block 40, past the electrode 24 and through guide sleeve 26. To permit the filament to pass, the end of the electrode 24 must be bent back as shown in Figure 2 so that the electrode through its own resiliency is urged and held against the filament. Motor 29 is then started to rotate electrode 24 around the filament. The D. C. current source 34-is then turned on to pass sufiicient current between electrode 24 and the filament 32 to form an arc. The are removes the portion of the coating from the filament 32 directly beneath the electrode and, since the electrode is rotating around the filament as the filament moves thereacross, the coating' will be removed in the form of a helical path 43. The pitch of the helical path can be varied so as to obtain a desired resistance per unit length of the filament by varying the speed of rotation of the electrode24. Thus the filament is quickly and easily spiralled and with only the coating being removed by the are so that the glass filament is not damaged or weakened. h

The wire electrode 24 has a disadvantage which arises because the wire electrode 24 slides over the surface of the filament 32 causing it to wear. This not only shortens the useful life of the electrode but also widens the area of contact between the electrode and the filament and thereby widens the path of the removed coating. Thus, as the electrode wears, the resistance per unit length will change for a given set pitch. Figures 3 and 4 show a modification of the electrode which overcomes this disadvantage. This electrode comprises a substantially triangular cage 44 having two straight sides 44a and 4411 at right angles to each other and the third side 440 being arcuate (Figure 4). Each of the straight sides 44a and 44b has a slot 46 therein extending from the junction of the two sides (Figure 3). Extending across the edges of sides 44a and 44b at their junction are a pair of parallel bearingplates 48 (Figure 4). A shaft 50 has end bearing pins 52 rotatably supported in holes in bearing plates 48 and an electrode wheel 54 fitting in slots 46 is mounted on shaft 50. The electrode wheel 54 is made of a hard, electrically conducting material which will withstand high temperatures such as tungsten carbide and has a pointed outer edge 54a (Figure 3). Cage 44 has another pair of parallel bearing plates 56 extending across the edges of side 44a and 440 at their junction. A headed hinge pin 58 extends through holes in the bearing plates 56 and is threaded into flange 56 (Figure 3). p The cage 44 pivots on hinge pin 58 between its head 58a and a collar 60 threaded on the pin which prevent the cage from moving from side to side. A threaded rod 62 projects substantially radially from side 44c of the cage 44 and a weight 64 is threaded on the rod (Figure 3). A U- shaped spring 66 has the end of one leg 66a clamped on hinge pin 58 between collar 60 and a nut 68 and the end of the other leg 66b fitting in a U-shaped bracket 70 secured to side 44a of the cage 44. Spring leg 66b is under tension so that it tends to pivot cage 44about hinge pin 58 and thereby urge electrode wheel 54 toward the filament 32. The sides of bracket70 prevent spring leg 66b from sliding off cage side 44a. A stop pin 72 (Figure 4) extends from flange 16 adjacent cage side 44c and across the outside surface thereof so as to limit the pivotal movement of cage 44 caused by the action of spring 66. g

In operation, the sleeve 14 and flange 16 are rotated in the direction of arrow 74 (Figure 4) which through centrifugal force causes contact wheel 54 to be thrown away from the filament 32. Rod 62 and weight 64 are so located that the centrifugal force thereon throws them in the opposite direction so as to counterbalance wheel 54. The weight 64 is positioned on the rod 62 so that the countcrbalancing is just suflicient to cause wheel 54 to just contact the filament 32. The Weight 64 is adjustable along rod 62 to enable adjustment for various diameter filaments. The tension in spring ('6' is just sufficient to hold electrode wheel 54 against the filament during starting and stopping of rotation. As the wheel 54 is rotated around filament 32 the contact therebetween causes the wheel to rotate about its own axis so that the wheel actually rolls around the filament 32. Therefore, since the wheel does not slide over the filament, there is very little wear on the wheel.v Further more, the wheel 54 is not damaged by the heat of the electric are formed between it and the filament since only a small portion of the circumference of the wheel is subjected to the are at any one time so that the heat is conducted away by the rest of the wheel and this portion merely passes through the are so that it is cooled for a longer time than it is heated by the are.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statemerits of the scope of the'invention which, as a matter oflanguage, might be said to fall therebetween.

Having decribed my invention, what I claim as new and desire to secure by Letters Patent isi 1. Apparatus for forming a spiral path in the coated surface of an elongated longitiidinall'y moving filament comprising the combination of an electrode, means for rotating said electrode about said filament and in contact with the coating thereon and ineans for forming an electric arc between said electrode and the coating on said filament for removal of the portion of coating contacted by said electrode.

2. The combination as set forth in claim 1 in which the electrode comprises a resilient wire of an electrical conducting material which will withstand high temperatures and said wire extends across the path of said filament to contact the filament under its own resiliency.

3. The combination as set forth in claim 1 in which the electrode comprises 'a wheel of an electrically conducting material which is mounted for rotation about its own axis as well as for rotation about the filament.

4. Apparatus for spiralling a continuous length filament coated with an electrical resistance material comprising the combination of a sleeve, means rotatably supporting said sleeve, means for rotating said sleeve, an electrode mounted on one end of said sleeve and extending across the entrance end of the bore thereof to contact said filament and means for providing an electrical are between said electrode and said filament.

5. The combination as set forth in claim 4 in which the means for providing the electrical arc comprises an electrical contact in alignment with the entrance end of the sleeve and adapted to engage the filament and a source of electric current connected between said contact and the electrode.

6. Apparatus for spiralling a continuous length filament coated with an electrical resistance material comprising the combination of a sleeve, means rotatably supporting said sleeve, means for rotating said sleeve, a hinge pin extending from the end of said sleeve, a substantially triangular cage pivotally mounted on said pin in one corner thereof, an electrode wheel of an electrical conducting material rotatably mounted, in another corner of said cage, means for urging said wheel against the filament and means for providing an electric are between said wheel and the filament.

7. Apparatus for spiralling a continuous length filament coated with an electrical resistance material comprising the combination of a sleeve, means rotatably supporting said sleeve, means for rotating said sleeve, a hinge pin extending from the end of said sleeve, a substantially triangular cage having two sides thereof at right angles to each other, said cage being pivotally mounted on said hinge pin in one of the acute angle corners thereof, an electrode wheel of 'an electrical conthe filament and means for providing an electric are between said wheel and the filament.

8. The combination as set forth in claim 7 in which the means for urging the Wheel against the filament includes a rod extending from the side of the cage opposite the right angled corner and a weight mounted on said rod.

9. The combination as set forth in claim 8 in which the means for urging the wheel against the filament also includes a spring mounted on said hinge pin and engaging a side of said cage.

10. Apparatus for spiralling a continuous length filament coated with an electrical resistance material comprising the combination of a sleeve, means rotatably supporting said sleeve, means for rotating said sleeve, a hinge pin extending from the end of said sleeve, a substantially triangular cage having two sides thereof at right angles to each other, a slot in each of said sides extending from the junction thereof and a bearing plate extending along each edge of said sides at the junction thereof, said cage being pivotally mounted on said hinge pin in one of the acute angle corners thereof, a shaft rotatably mounted between said bearing plates, an electrode wheel of an electrical conducting material on said shaft and extending through the slots in said sides, means for urging said wheel against the filament and means for providing an electric are between said wheel and the filament.

11. The combination as set forth in claim 10 in which the third side of said cage is arcuate, and the means for urging the wheel against the filament includes a rod extending from said third side and a weight mounted on said rod.

12. The combination as set forth in claim 11 in which the means for urging the wheel against the filament further includes a spring mounted on the hinge pin and engaging one of said two sides.

References Cited in the file of this patent UNITED STATES PATENTS

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