US1910866A - Resistor - Google Patents

Description

May 23, 1933. A. N. VAN NOSTRAND ,910,866

RESISTOR Filed March 25, 1930 2 Sheets-Sheet l @vwenboz ow w U Wm 45 35 341.): 5m

May 23, 1933. A. N. VAN NOSTRAND 1,910,866

RESISTOR Filed March 25, 1930 I 2 Sheets-Sheet 2 glnbewtoz Gum/"04f ,45 vention;

Patented May 23, 1933 UNITED STATES PATENT I OFFICE ARLEIGH N. VAN NOSTRAND, OF FIAN 'HASSE'L NEW YORK, ASSIGNOR TO TELAU'IO- GRAPH CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF VIRGINIA RESISTOR Application filed March 25, 1930. Serial No. 438,664.

This invention relates to aresistor. The invention is intended generally to provide a resistor in the form'of a unit, of simple,

compact and durable construction,-a.nd of reliable and dependable operation.

- The resistor to which the invention relates is of a type which comprises a 'core of insulating material, a resistance wire wound on tional, showing vertlcal mountin g of a pluralsaid core from end to end, and a metallic ter- .Qminal cap surrounding each end of the core and wire and connected electrically to the wire end. 1 e f It i one object of the invention to develop a construction which provides good firm electrical connections and contacts between the wire endsand caps.

1 Another object is to introduce a resistor which has a large, rapid heat madiating surface for dissipating the heat generated in 2 service.

A-further object oftheinvention is to restrict contact of the resistance wire with air, to reduce and minimize oxidation and deteriorating effects due thereto.

Another object is-to produce a construction to facilitate obtaining an exact resistance for the resistor in manufacture.

.Other objects are to make provision for permitting vertical panel mounting of the 3 resistor and series mounting of resistor units and to produce practical structure for obtaining themountings of resistors and connections to the resistors. I

With these general objects in view, the invention consists 'n the features'fcombinations,

arrangements and detailsof construction which will first be described in connection With the accompanying drawings and then more particularly pointed out in the appended claims.

In the drawings: I

Figure 1 is an end view of a resistor constructed in accordance with the present in- Figure 2 is a longitudinal elevational view, partly in section, of the resistor; i

Figure 3 is an interior, partly sectional view, showing different strata of the resistor;

Figure 4 is an elevational View, partly in resistor.

The resistor selected to illustratethe in Figure 7 is an elevational view, partly sec ity of resistors in series;

Figure 8 is a similar view, illustrating atap connection and F igure 9 is a sectional-elevational view of a screw threaded form of mounting for the vention comprises a core 10 which is of electrically. insulating, heat-resisting material, suchas porcelain. As here shown, the insulating core is turned to a cylinder in shape and is provided with an axial hole 11 for .mounting in certain cases. Around the core a resistance wire 12 of any approved composition is spun and wound helically from one endof the core to .the other.

The wire is advantageously of relatively small diameter and the convolutions are spaced close together over the lengthof thecore. In this embodiment, the surface of the core is smooth butit might be provided with helical or other grooves to accommodate the wire. Surrounding each end of the core and wire is a terminal cap 13 of metal, suchas aluminum, which engages the wire end and is connected electrically thereto. 1

Provision is made for restricting contact with air, minimizing oxidation and deteriorating effects due thereto. This is advantageously accomplished by surrounding the wire with a sheet of flexible insulating material, such as clear mica. In this example, the wire is first cemented to thecore after being wound thereon. To this end, a cementitious substance 14, such as a mixture of lacquer'and pipe clay, may be distributed over the wire convolutions and against the core surfaces.

, The cement also serves to insulate adjacent convolutionsof resistance wire. The sheet of mica-15 is' now wrapped around the wire 1n-a few layersand directly above the wire.

The mica extends longitudinally and axially of the resistor and terminates just short of the wire ends to leave said ends uncovered to be engaged directly by the caps, said mica preventing contact of resistance wire with terminal caps throughout the mica length.

Provision is made for obtaining good firm contacts between the wire ends and caps. To this end, circumferential grooves 16 are provided in the core surfaces, one near each end. A plurality of turns of wire 17 are laid in each groove and partly fill the groove. These turns are connected electrically to the respective ends of the resistance Wire. It is possible to make the turns of a cheaper wire and splice same to the resistance wire. It has been found cheaper and more advantageous, however, to make the turns of resistance wire, that is, to bring the ends of the resistance wire out in a suitable manner and wrap and. lay them in the grooves, thus eliminating need for splicing. Some 25 or 30 turns of resistance wire may be wound in each groove. It will be noted that these turns are in parallel contact with each other and do not function as resistance but simply form a relatively massive end electric terminal for contact with the inspun cap. During assembly, the extreme wire ends are inserted in holes 18 in the core. As here shown, these holes extend obliquely from the grooves to the core endsand the wire ends can be conveniently inserted and temporarily fastened therein in process .of assembly. The metal of the caps is crimped or spun circumferentially and inwardly in the form of annular indentations 19 which project into the grooves and firmly engage the turns within throughout the circumferential area thereof. Good contacts are thus made between the caps and the wire ends, the caps securely held in place and a tight unit formed.

In the illustrated embodiment, provision is made for varying the resistance so as to obtain an exact resistance value. In the practice of the invention according to what is now deemed to be the best advantage, such variation in resistance is achieved by varying the effective length of resistance wire without changin the core size or the wire size or spacing. 0 this end, as here shown, a groove 21 is placed in the core surface at each end of the core and extends diagonally and into the respective circumferential groove. The respective wire end is laid in the diagonal groove (Fig. 3) and the length of the helical resistance windings is determined by said grooves and the wire ends terminated therein at points giving the required exact resistance, the wire ends being brought out in the diagonal grooves somewhat sharply to the circumferential grooves.

. The invention provides for dissipating rapidly the heat generated by the resistance wire in service. To this end, the resistor is equipped with a large, rapid heat-radiating surface. As here shown, the metallic terminal caps 13 are elongated axially and incase the resistor like sleeves. The caps are tightly spun againstthe mica, thus sealing the wire in an air tight container. Each cap extends axially nearly one-half the length of the core but a small space 20 is left between the adjacent cap ends. This space is just sufficient to insure against short-circuit therethrough. Radiation of heat is throu h the mica to the metallic incasing caps. 11 addition to roviding a large, rapid heat'radiating sur ace over practically the entire peripheral area of the resistor, the sleeve-like caps present large contact areas, if such are desired.

The resistor may be mounted horizontally in the usual manner between two spring terminal clips which engage respectively the end caps of the resistor. This form of resistor also lends itself very readily to vertical mounting and to vertical mounting of two or more resistors in series whereby very little panel space is occupied. In such vertical mounting, the central bore of the resistor is utilized for reception of a supporting bolt and the resistor is mounted on the bolt.

In one practical exemplification of such vertical mounting, one end of the resistor is seated in a cup-shaped metallic washer 22 or socket-device abutting against the panel 23 (Figs. 4 and 5) and the resistor and washer are clamped tightly against the panel by bolt 24. As here shown, a washer 25 is placed beneath head 26 of the bolt and engages one end of the resistor, the bolt passing through the central bore of the resistor and throu h a hole 27 in the cup washer and a hole 28 in t e panel and having a nut 29 threaded on the end projecting from the opposite side of the panel. The nut is tightened on *the bolt to draw the resistor and cup washer tightly against the panel and to hold them rigidly in position. The bolt through washer 25 makes electrical connection with one terminalcap of the resistor and the cup washer engages the other terminal cap. As here shown, a washer 30 is positioned beneath the nut 29 and a wire 31 soldered or otherwise connected to the said washer. The cup washer has an extending lug 32 (Fi 6) to which a wire 33 is soldered or join This latter wire passes through an aperture 34 in the panel so that the wires are behind the panel relative to the resistor. The electric circuit is from wire 31, washer 30, bolt 24, washer 25 to one terminal cap of the resistor, then through the resistance wire to the other terminal cap, cup washer 22 to wire 33. Considerable clearances are left between the bolt and the cup washer and abutting terminal cap end to prevent short-circuit between these parts. To augment the rigidity of the mounting and the firmness of the electrical connecbolt. In such case, the resistors are stackedv one upon the other (Fig. 7) around the same bolt and are clamped together with abutting terminal caps of adjacent resistors firmly engaging. A relatively strong spring washer 36 may advantageously be placed beneath the resistor stack and in the cupwasher to keep tension on the whole assembly.

To obtain a tap connection, a washer like cup washer 22 ma be interposed between adjacent resistors {Fig 8) and ta Wire'37 soldered to the lug of said cup was er.

of mountw. .for the resistor. In this embodiment, 1; e resistor is adapted to be applied to a conventional screw socket comprising an internally threaded shell contact 40 mounted against an insulating base 41 and having a central contact 42 insulated from,

said shell, as by an insulating washer 43. An electrical conductor 44 is connected to said central contact and another conductor 45 tosaid socket shell through rivet 46'.

The means for applying the resistor to the socket,.as here shown, include a tubular metallic shell 46 having an open end with rolled outside and inside threads 47 and a flanged or closed end 48. I The resistor is inserted in the shell and the threads 47 of the latter then screwed tightly into the socket. One cap terminal 13a of the resistor is thus clam firmly against the center contact and the other cap terminal 13b is firmly engaged by the shell.

To prevent the shell from, engaging the lower terminal 13a and thus short-clrcuiting the resistor, an insulating spacer 49 is inserted between the shell and terminal cap. As here shown, the spacer is an externally threaded fibre ferrule which screws inside the shell. The threads may be'cut or rolled and the inside surface may or may not show corrugations. I

It may be desirable to provide the shell with openings for allowing air circulation and preventing overheating. Such openings may be designed in various ways.

What is claimed is:

1. A resistor comprising an insulating core having a peripheral resistance-wire supporting-surface arranged to receive a plurality of convolutions of the resistance wire and having a groove near each end, each groove extending spirally along said supporting surface from the respective end of the said supporting-surface toward the longitudinal center of the said surface, whereby various lengths of resistance-wire may be used on any core and each terminal end of such wire may be brought out through the corresponding groove, and a resistancewire wound on the said supporting-surface of the core and having terminal portions laid in said grooves.

2. A- resistor comprising an insulating core having a circumferential groove near each end, a resistance wire wound on said core, each end of the wire being laid in the respective end groove in a plurality of turns of bare wire, a metallic cap for eachend of the core, each cap surrounding its respective end of the core and wire and being crimped circumferentially and inwardly into conductive contact with the turns in the respective end groove, and means for insulating each cap from the resistance wire except at its crimped portion. Figure 9 illustrates a screw threaded form 3. A resistor comprising an insulating core having a circumferential groove near each end, a resistance wire wound on said core, each end of the wire being laid in the respective end groove in a plurality of contacting turns of bare wire and its extreme end caught in a hole in the core extending obliquely from the groove, and a pair of metallic caps, each surrounding its respective end of the core and wire and crimped circumferentially and inwardly into conductive contact with-the turns in-the respective end groove.

4. A resistor comprising an insulating core, a resistance wire wound on said core from end to end and having its end portions bare, a sheet of flexible insulating material wrapped aroundthe wire and extending longitudinally and terminating just short of the ends of the wire to leave said ends un- 1 ing turns of bare wire laid in each groove,

said turns being connected electrically to the resistance wire, and a metallic end cap for each end of the core, each cap surrounding its respective groove and being crimped circumferentially and inwardly into conduc-' tive contact with the turns therein.

6. A resistor comprising an insulating core, a resistance wire wound on said core from end to end and having its ends bare, and a metallic cap for each end of the core, each cap surrounding its respective end of the core and wire and being indented inwardly near its outer end into engagement with the respective bare wire end and out of contact with the resistance wire except at its tial groove near each end, a resistance wire indented portion, each cap extending axial- 1y nearly one-half the length of the core to rovide a large radiating surface, the space etween caps bein just suflicient to insure against short-circuit therethrough.

7. A resistor comprising an insulating core having an axial hole and a circumferenwound on said core its turns bein spaced apart, each end of the wire being are and laid in the respective end groove in a plurality of turns, a cementitious substance distributed over the wire and between the turns thereof, a sheet of flexible insulating material wrapped around the wire between the grooves and terminating just short of the grooves, and a metallic ca for each end of the core, each cap surroun ing its respective end of the core, wire and insulating material and being crimped circumferentially and in-,

Wardly into contact with the bare turns of wire in the respective end groove, each cap extending axially nearly one-half the lengt of the core to provide a large radiating surface, the space between caps being just sufficient to insure against short-circuit therethrough.

In testimony whereof, I have hereunto set my hand.

ARLEIGH N. VAN NOSTRAND.

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