US1050912A - Electric resistance. - Google Patents

Description

F. BULLING.

ELECTRIC RESISTANCE.

APPLIOATION FILED JUNE 20, 1912.

1,050,912, I Patented Jan.21, 1913.

"UNITED STATES PATENT OFFICE.

rnninmcmiaonmue, OF FRANKFORT-ON-THE-MAIN, GERMANY.

ELECTRIC RESISTANCE.

I type of electric resistances,especially used for heating purposes, in which a conductor formed by a metal wire or band is arranged on a sheet of insulating material capable of withstanding high temperatures. Such resistances have, however, the drawback, that A, it becomes the conductor at the points where it is bent or folded is very liable to burn out and that further its different portions are easily displaced, thus coming in contact and forming short circuits. In order to avoid these difficulties I employ clamps, which are clasped about the bending points of the conductor, so that they protect the latter against burning out and secure it on the insulating sheet. Such clamps may further be employed for greatly facilitating the building up of such electric resistances, which contain a metal band, especially if it is stamped out in zigzag form.

Further improvements will be readily understood from the following specification and the accompanying drawing, in which- Figures 1 and 2, 3 and 4, three constructional forms each side view respectively.

In the first example (Figs. 1, 2) the conductor is a wire A wound around a sheet B of suitable insulating material, for instance mica. If a current flows through the wire hot and its strength lessens. Also the sheet B is heated and tries to stretch itself. Thus partly by the heating of the wire in top and A, partly bythe stretching of the sheet B, the

employed as the bending" polnts of the conductor are'sub- 'jected to a heavy 'mechanical stress, so that they very easily break ortear, if they are This is now done by the clamps C, which are clasped about the and the edges of the insulating sheet. The

clamps further prevent the single pieces of the wire A from becoming displaced. In-

stead of a wire, a metal band could alse be conductor and wound around the sheet B.

In the second example (Figs. 3, 4) the Specification of Letters Patent.

lating sheet length is to be left 5 and 6 show which were, however, bending points of the wire.

Patented Jan. 21,1913.

Application filed June 20, 1912. Serial- No. 704,873.

conductor is a thin metal. band A, which is cut into pieces. The clamps C not only mechanically secure these pieces on the insu- B, but form also their electric connections. This construction has the further advantage, that it is not necessary to first fold a comparatively long metal band before it is secured on the insulating sheet.

If the ohmic value of resistances with a metal band as conductor is to be high, without decreasing its thickness too much, the band is usually stamped out in zig-zag form, as shown in Fig. 5. Such a band can, however, not be wound around an insulating sheet without certain precautions, as otherwise the drawbacks set out above would result. On the other hand, if such stamped out bands are arranged only on one side of an insulating sheet, great diiticulties are encountered in the process of making them, viz: The length of the different pieces must be in accord. with the respective purposes, and at both ends of such a piece, a certain Thus the mode of stamping such bands is very complicated, as the stamping machines, which work automatically and also automatically feed or transport the band, are to be regulated for different lengths. All these dii'liculties are easily overcome by again employing the clamps C (Figs. 5, 6). Now it is possible to stamp out or to slit the band for its whole length without interruptions, and to cut it afterward into pieces of the requisite length. These pieces are arranged on one or both sides of the insulating sheet B and are secured by the clamps C, which also form the electric connections between the ends of the single band pieces, The special advantage of this construction is to be easily recognized from Figs. 5, 6 which show a heating resistance for a fiat iron, such as is used for ironing clothes and 'the like. For such a resistance there were previously employed three diflerent lengths of a band stamped out in zig-zag form, the ends of not slotted, while acthe stamped out cording to my invention slots can extend over the whole length of the band.

I In the first example (Figs. 1, 2) the conductor could also be arranged on one side of the insulating sheet, and in the other examples (Figs. 3-6) it could be arranged on both sides of it. In the first example the without stamped slots.

heat developed radiates from-both sides, and in the other forms only from one side of the resistance.

All the constructions are still. to be provided veying the current and cover. These elements are, however, not specified and illustrated, as they do not form parts of my invention and could be constructed in any known or special manner.

I claim: v v

1. In an electric heating resistance the combination of a thininsulating sheet of refractory niateral, a thin, flexible metal conductor arranged to form a plurality of windings extending between opposite edges of said sheet, and clamps of sheet metal clasped about the ends of each of said windings and the edges of the sheet, substantially as and for the purpose described.

2. In an electric heating resistance the combination of a thin insulating sheet of refractory material, a'thin, flexible'metal conductor arranged to form a plurality of windshown and described with means for conwith an insulatlng ings consisting of separated pieces extending between opposite edges of said sheet, and clamps of sheet metal clasped about the ends of each of said pieces and the edges of the sheet, substantially as and for the purpose described.

3. In an electric heating resistance the 'metal clasped about the ends of each of said pieces and the edges of the sheet, substan- I tially as and for the purpose described.

In testimony whereof I aflix my signature 1n presence of two witnesses.

FRIEDRICH BGLLING.

Witnesses:

JEAN GRUND, CARL GRUND.

Images