US2879361A - Resistor - Google Patents

Description

March 24, 1959 A. HAYNMAN 2,879,361

- RESISTOR Filed Oct. 3, 1956 Fig.

5O INVENTOR.

ALEXANDRE HAYNMAN fimaji J WM United States Patent Ofiice "2,879,361 Patented .Mar. 24, 1959 RESISTOR Alexandre Haynman, Copenhagen-Vanlose, Denmark, assignor to International Resistance Company, Philadelphia, Pa., a corporation of Delaware Application October 3, 1956, Serial No. 613,746 11 Claims. (Cl. 201-63) My invention relates to the construction of an electrical resistor and more the resistor.

In general, electrical resistors comprise a coreof an electrical insulating material, such as 'a. ceramic or plastic, a resistance material either in the form of a metal wire helically wound along the surface of the core, or a film of a resistance material such as carbon or a metal coated on the surface of the core, terminals of an electrically conducting metal attached to the end portions of the resistance material, sometimes additional terminals atparticularly to a termination for t tached to the resistance material at various points intermediate its end portions, and a protective insulating coat- .ing covering the resistance material. The construction of the terminals and the method of attaching them to the resistance material have presented many problems in the manufacture of such resistors.

In the wire wound type resistor, the terminals are usually soldered, welded or brazed to the resistance wire to provide a good electrical connection therebetween. However, prior to soldering or welding, it is a common practice to tie the resistance wire to the terminal or to a lug or projection on the terminal to maintain the resistance wire tightly wound on the core during the soldering or welding operation. This tie-on operation is both difiicult and time consuming and therefore an expensive operation. Other problems arise from the fact that it is generally the resistance wire and the terminal on or along the surface of the core so that it is only necessary to provide the protective coating on the wound surface of the core. Since the terminals are of a much heavier material than the resistance wire, they will bulge through the protective coating unless the coating is .made unnecessarily thicker. Also, to prevent cracking of the protective coating during operation of the resistor, it is necessary that the thermal coefficient of expansion of the coating material be substantially the same as that of the resistance wire and the terminals. It is difiicult enough to match the coefiicient of expansion of two different materials such as that of the protective coating and the wire, but it is even more difiicult to also match that of the material of the terminals. Some wire wound resistors include additional terminals attached to the resistance wire .be-

. tweenthe end terminals to permit the obtaining of various resistance values from the single component, 'For problems prevail but there is the additional problem of designing the additional terminals and the method of attaching them to the resistance wire so that the terminals do not short out too many turns of the wire and so that the terminals do not interfere with the winding of the :-wire on the core member.

desirable to provide theconnection between such components not only do the previously discussed or by wires inserted into central holes in the ends of the core and connected to the film by an electrically conducting cement or solder. The first two types of termi= nals raise the problem of bulges in the protective coating while the third type requires additional protective coating material around the ends of the core. The same problems arise with the film type resistor as with the wire wound resistor in providing additional intermediate terminals.

It istherefore the object of my invention to provide a resistor construction wherein the resistance material is simply and easily connected to any desired number of terminals. Another object of my invention is to provide a wire wound resistor wherein the resistance wire is antomatically connected to the terminals during the winding of the resistor. It is a further object of my invention to provide a resistor construction wherein the terminals can be easily and simply connected to. the .resistance material at any point therealong. It is still a further object of my invention to provide a resistor construction in which the terminals and their connections to the resistance material are below the surface of the core member. Other objects of the invention will in part be obvious and will in .part appear hereinafter. I

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.

accompanying drawing in which:

Figure 1 is a side elevation view of the core element for the resistor of my invention; I

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

Figure 3 is a side elevation view of a wire wound resistor made in accordance with my invention;

Figure 4 is an enlarged sectional view of the wire wound resistor taken along line 44 of Figure 3;

Figure 5 is a side elevation view of a film type resistor made in accordance with my invention including a modification of the terminal arrangement;

Figure 6 is an enlarged sectional view of the film type resistor taken along line 6-6 of Figure 5;

Figure 7 is a side elevation view showing another modification of the terminal arrangement;

Figure 8 is a side elevation view showing still another modification of the terminal arrangement;

fication of the core element; and

Figure 10 is a perspective view of a portion of another modification of the core element including a modification of the terminal.

Referring to the drawing in which like numerals identify similar parts throughout, Figures 1 and 2 show an elongated core member 10 of my invention made, of an electrical insulating material such as a plastic or ceramic which core can be used to make either a wire wound or film type resistor. The core 10 is shown to be substantially elliptical in transverse cross section (Fig. '2) and provided with a central longitudinally extending hole 12 which may be used in mounting the resistor. The core 10 also has a pair of small diameter holes 14 and 16 extending longitudinally therethrough just beneath the outer surface 18 thereof. The holes 14 and 16 are preferably located in the sharply rounded corners of the ellipitical core for reasons which will be obvious later. A pair of longitudinally spaced transverse slots corners. Slot 20 extends to hole 14 while slot 22 in the opposite corner extends to hole 16.

Figures 3 and 4 show the wire Wound resistor of my invention which comprises the core 10, shown in Figures 1 and 2, having a pair of wire terminal members 24 and 26 of an electrically conducting metal inserted-into holes '14 and 16 respectively until they cross slots 20 and '22 respectively. The terminal members 24 and 26 are preferably secured in the holes 14 and 16 by a friction fit. A resistance wire 28 is helically wound on the core surface 18 substantially from end to end'thereof. Where the resistance Wire winding 28 passes each of the slots 20 and 22, one or more turns of the wire extend in the slot across and preferably in contact with the portion of the terminal members 24 and 26 exposed at the bottom of the slots to provide an electrical connection therebetween (Figure 4). To ensure-the electrical connection between the resistance wire 28 and the terminals 24 and 26 and to secure the winding on the core 10, the resistance wire 28 is soldered at 30 to each of the terminals 24 and 26 within the slots 20 and 22. The protective insulating covering (not shown) can then be coated over the core surface 18 and the resistance winding 28. Since the "connections between the resistance wire 28 and theter- " minals 24 and 26 are in the slots 20 and 22, there are no projections above the winding to bulge through the protective coating. Also, since the terminals are not exposed along the core surface, there is no problem of matching the coeflicient of expansion of the covering to that of the terminals'to prevent cracking of the covering.

Figures 5 and 6 show the film type resistor of my invention in which the core element 10 is coated with a film 32 of an electrical resistance material. The mate- 'rial may be carbon 'or a metal havingthedesired resistance characteristics which is applied on'the core by'any "desired method such as painting or spraying or deposited thereon by either pyrolytic deposition or evaporation in avac'uum. The film '32 extends into slots 20 and 22 to cover the bottom surfaces thereof as shown in Figure 6, "or'the sides of the slots, or all the surfaces thereof. Terminal 24a extends into hole 14 from one end of core 10 until it crosses slot 20 and terminal 26a extends into hole 16 from the other end of core 10 until'it crosses slot 16. By having slots "20 and 22 extend to the bottom of holes 14 and 16 respectively and inserting the -terminals 24a and 26a after resistance film 32 is applied to core 10, the terminals will automatically contact the film when they are inserted to provide the electrical connection therebetween. trical conducting material maybe applied in the slots between "the terminals and the film to ensure the electrical connection therebetween (Figure 6). .A protective coating (not shown) may then 'be applied around the resistor.

Although the Wire wound resistor "shown :in Figures '3 and 4 "has both terminals extending "from the :sarne end of the core 10, it niay have the terminals extending from opposite ends of the core in the same manner as the film type resistor shown in Figures 5 and 6. Likewise the film type resistor may have both terminals extending from the same end thereof instead of'from opposite ends as shown. Figure '7 shows-another terminal arrangement which can be used for :either the wire wound or film type resistor in which both " slots 20b and 22b are across the same corner of core 10 and extend to hole 14. Terminals 24b and 26b extend into hole l /from opposite ends'of core liluntil they cross the closest slot. Care must be taken in inserting'the terminals 24b and 26b so that their inner ends, 25b and 27b respectively, do

not contact each other and thereby shot out the unit.

This may be prevented by inserting the terminals by means of an apparatus which automatically limits the dist'ance each terminal is inserted or by providing tW'o sepa- -r'ate blind end holes extending from opposite ends of the-core instead of the single through hole.

However, a cement 34 of an elec- Y This method of attaching the terminals to the J'resistance material is particularly advantageous when it is desired to provide the resistor with additional terminals tapped into the resistance material intermediate the end terminals. Figure 8 shows such an arrangement in which the resistor comprises a core having a pair of terminal members 240 and 260 extending from one end thereof and connected to the resistance material in slots 20c and 220 respectively in the same manner previously described. A third transverse slot 36 is provided in the core surface 18c intermediate slots 20c and 22c, and a third terminal 38 extends through the core 14) and across the third slot 36 where it is likewise connected to the resistance material. .Care must be taken that the end 39 of terminal 38 does not contact the end 250 of terminal 240. When used in a wire wound resistor as the resistance wire is helically wound on the core 10 at least one turn thereof will automatically extend into slot 36 and across and in contact with terminal 38. Thus there is provided an intermediate terminal which is easily and simply connected to the resistance material Without substantially affecting the resistance value of the unit or in the case of the wire wound type without interfering with the winding of the wire on the core. Any number of additional terminals may be provided by inserting the terminals into both ends of the core and by spacing the terminals around the circumference of the core. The location of the transverse slot which exposes the terminal to the resistance material determines the resistance value tapped ofi by the terminals.

Although the core 10 is shown'to be elliptical in transverse cross-section, it may be of any shape desired. For example; Figure 9 shows a core 40 circular in cross-sec tion "having a central mounting hole 42, terminals 43 fitting into a'plurality of longitudinally extending terminal holes 44 spaced circnmferentially around and slightly beneath 'the'surface thereof and atransverse slot 45 extending to one of the holes 44. Figure 10 shows asubstantially rectangular core 46 with rounded corners having a central mounting hole 48 and a longitudinally extending terminal hole '50 located in each corner thereof. Terminal holes 50 are rectangular to receive fiat strip terminals 52. The flat terminals 52 can be used instead of the round wire terminals in any of the modifications previously described. A transverse slot 54 extends to one of the terminals 52. Cores having a configuration pro- "viding sharply rounded corners are preferred since they permit shorter transverse slots and in the wire Wound type resistor ensure proper contact of the terminal by the resistance wire as the wire extends around the corner.

"Itwill'thus 'be'seen that the objects set forth above, "amongthose made apparent from the preceding description, 'are'efliciently attained and, since certain changes "may 'be made in the'above constructions without departingfrom 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 longitudinally from one end and slightly beneath the "surface thereof, a transverse slot in the surface of said core :extending 'toisaid hole, a terminal withinisaid .hole and extending across said slot, and resistance material on the surface of said core and extending in saidzslot to electrically .contact said-terminal.

2. -'1'he combination .as set forth in claim .1 in which said resistance material comprises a wire helically wound on the.surface of said core with aportion thereof .ex-

tending in said slot across and in electrical contact with said terminal.

3. The combination as set forth in claim 1 in which said resistance material comprises a film coating the surface of said core and at least one surface of said slot.

4. A resistor comprising the combination of a core of electrical insulation material having a hole extending longitudinally from end to end thereof and slightly beneath the surface thereof, a pair of longitudinally spaced transverse slots in the surface of said core extending to said hole, a pair of spaced apart terminals in said hole, one of said terminals extending across one of said slots and the other terminal extending across the other slot, a resistance material on the surface of said core and extending in said slots to electrically contact said terminals.

5. A resistor comprising the combination of a core of electrical insulation material having a pair of spaced apart longitudinally extending holes therein slightly below the surface thereof, a pair of longitudinally spaced transverse slots in the surface of said core, one of said slots extending to one of said holes and the other slot extending to the other hole, a terminal in each of said holes extending across the slots, a resistance material on the surface of said core and extending in said slots to electrically contact said terminals.

6. The combination as set forth in claim 5 in which the holes both extend from one end of said core and the terminals project from said holes beyond said end.

7. The combination as set forth in claim 5 in which the holes extend from opposite ends of said core and the terminals project from said holes beyond said ends.

8. A resistor comprising the combination of a core of electrical insulating material having a transverse crosssection providing at least one longitudinally extending sharply rounded corner, a longitudinally extending hole in said core slightly below the surface of said corner, a transverse slot in the surface of said core across said corner and extending to said hole, a terminal in said hole and extending across said slot, a resistance wire helically wound on the surface of said core with a portion of said wire extending in said slot across and in contact with said terminal.

9. A resistor comprising the combination of a core of an electrical insulating material having a transverse cross-section providing at least two longitudinally extending sharply rounded corners, a pair of longitudinally extending holes in said core, one of said holes being slightly below the surface on one of said corners and the other hole being slightly below the surface of the other corner, separate transverse slots extending across the surface of each corner to the hole therebeneath, a terminal in each of said holes and extending across the slot, and a resistance wire helically wound on the surface of said core with portions of said wire extending in said slots and in contact with said terminals.

10. The combination as set forth in claim 9 in which the cross-section of said core is substantially elliptical.

11. The combination as set forth in claim 9 in which the cross-section of said core is substantially polygonal.

References Cited in the file of this patent UNITED STATES PATENTS 1,256,599 Schoop Feb. 19, 1918 1,525,831 Steiner et al. Feb. 10, 1925 1,642,223 Boker Sept. 13, 1927 1,963,755 Mead June 19, 1934 1,976,514 Pugh Oct. 9, 1934 2,008,288 Malone July 16, 1935 2,030,460 Morton Feb. 11, 1936 2,527,026 Mucher Oct. 24, 1950

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