US1413939A - Resistance unit for electric heaters and regulating resistances - Google Patents

Description

- W. SCHULZ. RESISTANCE UNIT FOR ELECTRIC HEATERS AND REGULATING RESISTANCES.

APPLICATION man JUNE 11. 1916.

1,911 3,939. v Patented Apr. 25, 1922.

UNITED STATES PATENT OFFICE.

WILLY SCHULZ, OF FRANKFORI-ON-THE-MAIN, GERMANY, ASSIGNOR TO PROME- THEUS, FABRIK-ELEKTRISCHER KOCK- & HEIZAPPARATE, GESELLSCI-IAFT MIT BESCHRANKTER HAFTUN G, CF FRANKFORT-ON THEMAIN, GERMANY.

RESISTANCE UNIT FOR ELECTRIC HEATERS AND REGULATING RESISTANCES.

Specification of Letters Patent. i Patgnted Apr, 25, 1922, Application filed June 17, 1916. Serial No. 104,266.

(GEANTED UNDER THE IlROVISIONS OF THE ACT OF MARCH 3, 1921,41 STAT. In, 1313-) To all whomit may concern:

. Be it known that I, VVVILLY, SoHULz, a subject of the German Emperor, and a resident of Frankfort-on-the-Main, Germany, have invented certain new and useful Improvements in a Resistance Unit for Electric Heaters and Regulating Resistances, of which the following is a specification.

In the construction of electric heating a'pparatus including resistance and regulating units the means employed for supporting or securing the resistance material in position is of the greatest importance.

'Such' resistance units are commonly formed of coils of round wire, metal tape or tubes and are only secured toa support at their ends. The eli'ect of blows or jars to which such apparatus is necessarily subjected causes such oscillation of the coils that the members thereof frequently contact, producing short circuits and shunts, especially when the coils are expanded or extended by the heat due to the passing of current therethrough. This is particularly .true when the units are made of thin metal such as required. for obtaining a high-ohmage.

With a view of overcoming this trouble, it has been proposed to wind the resistance material upon cores or bodies of insulating material of various forms and in some instances provided with grooves to receive the wire or tape. However, even with such constructions the expansion of the metal is often sufficient to produce such deflection of the members of the coil as to cause contact and resulting short circuiting.

If the members of the coils are separated to such an extent thatundesirable contact between them is avoided the device must neces arily be so large as to render itunsuitable for many uses.

Various other expedients have been tried to avoid the hereinbefore noted objections. For example, the resistance material has been embedded in enamel or secured to its support by such a substance or cement. The.

difference 1n expansion of the materials results in loosening the connection between the resistance material and its support and therefore such an arrangement is not satisfactory.

By the present invention, the objections incident to prior constructions are overcome and a simple, compact, resistance unit is provided in which the danger of short circuiting due to expansion of the coils is entirely obviated. 1

In the accompanying drawing;

Figure 1 is an elevation of the lower end of an embodiment of the invention;

Figure 2 is a horizontal sectional view on the line IIII of Figure" 1; i

Figure 3 isfa similar view, some' o fithe parts being on an enlarged scale, showing elements. j a

Referr ng to the drawing, the resistance conductonl 1s a flat band or strip which is the preliminary assembling jolt the several 2 bent back and forth. into column form, the

members of each section of such conductor extending between clampingdevices shown as bars that extend longitudinally of the resistance column and of U-shape in cross section. 7

The clamping bars 2 are insulated from the adjacent surface of the coil 1 by any suitable means, as for example, strips of mica 3; andbetween' the inner faces of the coil sections are arranged strips 4: of asbestos or other insulating material. c

In forming the coil the metal band 1 is wound about two yieldingpins or guides 5 and after the parts 2, 3 and 4 are properly assembled the members of each section of the conductor are drawn toward each other by the action of suitable screws on the clamping bars until such members are held in close contact with the compressed or compacted insulating strips 4.

The terminal coils or members of the resistance coil are provided with suitable means for connecting them with the line wires of an electric circuit. Figure 2 shows two different forms of terminal connection, namely, a tubular connector 8 and a threaded bolt S provided with suitable nuts. A's shown these terminal connections may be mounted on a block 7 of insulating material attached to one of the clamping bars 2.

The terminal of the coil remote from the block 7 may be electrically connected with one of the connectors 8, 8 by a conductor 9 which is positioned between the asbestos as preferred.

that can be connected in series or parallel By this arrangement a con ductor of certain size and resistance may be employed for currents of different voltage. For example, the two halves of a coil may be connected in parallel for a 110 volt current or in series for 220 volts.

The form of the clamping bars 2 is of considerable importance. The ribs or walls oi? the channel bars being directed outward act to carry the heat away so thatportions ot' the coil not directly exposed to the air may be kept suitably 0001.

A resistance unit constructed in accordance with the invention may be readily immersed in an oil bath to heat it or provide an explosion-proof, oil cooled apparatus.

Having thus described the invention What is claimed is:

1. A resistance unit comprising a resistance conductor bent back and forth into column form, strips oi insulating material Within and extending throughout the length of said column, and means engaging both members of each section of the conductor and compressing the insulating means between them.

2. A resistance unit comprising a resistance conductor bent bacl: and forth into column lorm, strips of insulating .i'i'iaterial. within and extending longitudinally of said column, clamping bars arranged exteriorly oi the column and insulated therefrom, and means connecting the clamping bars adapted to cause the members of each section of the conductor to compress the intermediate strips of insulating material.

' 3. A resistance unit comprising a resistance conductor bent back and forth into column form, strips of asbestos extending longitudinally of the column between the members of each section oi? the conductor, clamping bars arranged exterior-1y ol': the column and extending parallel to said asbestos strips, means insulating the bars from the conductor. and means connecting said bars and acting to cause them to compress the conductor and intermediate asbestos strips.

in testimony Whereoi I affix my signature in presence of two Witnesses.

\VILLY SCHULZ.

lVitnesses ERWIN Drrrnn, CARL GRUND.

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