US2643316A - Resistance unit - Google Patents

Description

June 23, 1953 F. A. GLASSOW RESISTANCE UNIT Filed Oct. 11, 1951 IN V EN TOR.

I Tran/O BY Mm,

I w ATTORNEY Patentecl June 23, 1953 RESISTANCE UNIT Franklyn A. Glassow, Rockford, 111., assignor to Barber-Colman Company, Rockford, 111., a cr-= poration of Illinois Application October 11, 1951, Serial No. 250,927

1 Claim. (o1. eon-6e) I This invention relates to resistance units of the type used in measuring and control circuits and comprising one wire whose resistance varies with ambient temperature changes and another wire serving as a heater to alter the temperature of the first wire.

The general object is to provide a resistance unit of the above character which is much more sensitive than prior units, which is extremely rugged in construction when made of fine wire, and which is simple and economical to construct.

A more detailed object is to provide a unit of the above character in which each wire is disposed in intimate side by side heat exchanging contact with the other wire throughout the lengths of the two wires.

Another object is to form each wire into a helix with each turn of one wire lying in the channel formed between the adjacent turns of the other wire.

The invention also resides in the novel manner of supporting the two helical coils and in binding the same to their support.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a perspective view of a tube incorporating the novel compound resistance of the present invention, the envelope being broken away to show the manner in which the resistance is mounted.

Fig. 2 is an enlarged sectional view taken along the line 22 of Fig. 1.

Fig. 3 is an enlarged fragmentary perspective view of the compound resistance.

Fig. 4 is a magnified sectional view taken alone the line 44 of Fig. 3.

The improved resistance unit shown in the drawings and indicated by the numeral l0 comprises generally a temperature sensitive Wire H and a heater wire l2 both of substantial length and mounted on a common support (3 having insulated terminals I4 thereon connected to the four ends of the wires. To provide large surface areas, the wires are very fine, being only a few thousandths of an inch in diameter. At least one and preferably both of the wires are cov ered by a coating 2| of electrical insulating enamel or varnish which is also very thin, for example, .00015 of an inch and is a relatively good heat conductor. The heater element 12 may be a so-called nichrome alloy while the wire I i may be composed of metal sold under the trade name of Balco and having a resistance which changes appreciably with variations in ambient temperature.

For purposes to appear later, the support 53 is of special construction comprising a plurality of angularly spaced radially disposed plates l5 rigid with each other and upstanding from the terminal base it. If desired, the support with the resistance unit it thereon may be enclosed by a casing ll also mounted on the base it.

To provide for extremely rapid heat transfer between the two wire elements i! and i2, the invention contemplates arranging the two wires on the support it in side by side contacting relation substantially throughout their lengths with each part of one wire disposed in a groove or channel [8 formed between two portions of the other wire. To this end, each of the wires is wound helically around the support so that the adjacent turns of the coil form the groove for receiving the other wire. Herein, the adjacent turns are spaced apart axially just far enough to receive the other wire, the channel l8 thus being defined by the opposed sides of the wires of adjacent turns. In the double helix thus formed, the adjacent surfaces of the two wires are separated from each other only by the enamel coatings 2i and, as a consequence, are disposed close together and in intimate heat exchanging relation throughout the full length of the coil.

Arrangement of the two wires in this manner is facilitated by laying the wires side by side and in contact with each other and holding the same under tension while they are being wound around the support 13. In such winding, the Wires bend around the outer rounded edges of the plates 15, but such bending is not sufficient to break the enamel coatings. At opposite ends of the multiple turn helix thus formed, the end portions H and 12 of the two wires are separated and bent inwardly across the faces of the plates l5 and then threaded through holes 19 in the plates. Finally, the free ends of the wires are bared and soldered to buttons 29 which may be joined to the corresponding terminals 14 by conductors 22 extended along the plates and into the base it. With such an arrangement, the two wires contact each other along their entire lengths and the resistance of the temperature sensitive wire i l responds quickly to heat emitted by the heater wire 12 meeting the need in control circuits of high sensitivity.

To anchorthe wires II and I2 firmly on the support and to further facilitate the exchange of heat between them, a coating 23 (Fig. 4) covers both sides of the double helical coil. This coating may best be applied in liquid form and may comprise enamel, silicone varnish, or the like. Each turn of the heater wire is thus secured firmly to the two adjacent turns of the temperature responsive wire forming a unitary relatively rigid tubular structure which is locked firmly onto the support 13. The wires are thereby prevented from slipping on the support l3 and the intimate association of the wires is maintained during handling and usage of the device. The angular spacing of the plates leaves both sides of the double helical coil exposed enabling the latter to be coated on both sides. It will be observed that the coating 23 extends into the crevices between the wires only up to the points at which the insulating coatings 2! of the two wires contact each other without separating the wires. As a result, the distance between the wires is kept at a minimum as determined by the thickness of the insulating coatings 21. Since the enamel used for the additional coating 23 is a good heat conductor, it also serves to transfer heat from the heater wire l2 to the temperature sensitive wire I I increasing the sensitivity of the latter to temperature changes caused by the heater wire.

It will be apparent that a resistance unit of the above construction is extremely sensitive to the temperature changes effected by the heater wire l2. By winding the two wires II and [2 in intimate heat exchanging relation throughout their lengths with each turn of the heater wire closely associated with two turns of the temperature sensitive wire, the resistance of the latter will be changed quickly in response to a change in the temperature of the heater wire resulting from a variation in the flow of current therethrough. The angularly spaced plates I5 0f the support 13 permit both sides of the double helical coil to receive a coating 23 to bind the turns of the wires together and to provide better heat transfer between the wires.

I claim as my invention:

The combination of, a heater wire, a second wire whose resistance varies with ambient temperature changes, at least one of said wires comprising a metallic conductor surrounded by a thin coating of electrical insulation thereon, and a support, said wires being wound helically around said support and lying side by side in mechanical contact substantially throughout their lengths to permit the rapid transfer of heat from each part of said heater Wire to the two adjacent parts of said second wire.

FRANKLYN A. GLASSOW.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,841,332 Kranz Jan. 12, 1932 1,902,427 Sawyer Mar. 21 1933 2,031,480 Hamada Feb. 18, 1936 2,359,278 Allan et al. Oct. 3, 1944

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