US1655838A - Electrical heater element - Google Patents

Description

"Jan; 11),1'928. "1,655,838

E. c. LACKLAND ELECTRICAL HEATER ELEMENT Filed May 7, 1924 -3 these objections and in additionwill be in- Patented J... 10, 1928.-

UNITED STATES 1,655,838 PAITEN-TOFFICE.

EDGAR C. LACKLAND, OF NEW HAVEN, CONNEGTICU'JL ASSIGNOR TO ROCKBESTOS PRODUCTS CORPORATION, OF

NEW HAVEN, CONNECTICUT.

Application filed Kay 7, 1924. Serial No. 711,568.

This invention relates generally to the construction of heater elements for use in-electrical heating devices.

In the manufacture of electrical heating 5 pads in the prior art it has been the practice to wind a bare conductor on a flexible support of insulating material and to arrange the element thus produced in a convoluted formation in order to obtain the necessary length of resistance wire in a given space,

and then to enclose the heater element between ads of material having a suitable insulating quality. It has been known also to wind the resistance wire together with a yarn formed of cotton or other suitable material and to place this element within the heating pad to be formed. It has been found that the heating element formed in the latter manner is open to' the objection that a sharp bend produced in the element tends to force the resistance wire out of its protective position in contact with the yarn so that the wire is then exposed and does not move back into its protective position when the bend is removed from the conductor. This gives rise to a possibility of short circuiting the conductor or of setting fire to the material forming the pad. In either type of con struction referred to the insulation is not satisfactory and leads to the making of an inferior product. v

It is an object of the present invention to provide a heater element for thegeneral urpose referred to which will be free rom expensive to-manufacture and will rovide in other ways an article su erior to t e article produced in prior met ods of manufacture.

The invention includes the production of\ a heater element which forms either the weft or the warp element of a loosely woven fabric, the heater element consisting of a resistancewire so wound or wrapped in a specially formed asbestos roving that the I wire is permanently situated at substantially the axial center of the insulating wind-' ing orcasing provided. By this construction a heater element is formed in which no to amount of bending can force the wire from its protected position at the center of the insulatin casing. The other element of the weave, tjat is, the warp or weft yarn is formed by a yarn produced by twi stingas- I bestos roving threads of thesametypeu'sed provided for the heater element but the use of resistance wire in the form of an element of the woven fabric produces a relatively pliable structure which particularly facilitates the use of the heater element in heating pads such as are used for therapeutic purposes. The fabric formed in this manner is preferably of an open mesh character which, as will be seen, adds to the pliability desired and also enhanced the insulating qualities of the structure.

It is possible to produce a multiple heating effect by the use of two resistance wires woven together in the fabric from the same shuttle. Preferably in such a case the two elements would be. colored differently so as J to distinguish them apart in the assembly of the device.

In the drawings, in which a preferred embodiment of the invention has been selected'for illustration, I

Figure 1 is a view in a more or less diagrammatic form of a heater element made in accordance with the invention,

enlarged scale of Figure 2 is a view on ana resistance wire element used in the production of the device shown in Figure 1.

Figure 3 is a view similar to Figure 1 showing a modified form of the invention.

Referring to the drawings for a more detailed description of the invention, Figure 1 shows an open mesh fabric formed with a weft thread 10 consisting of a suitably insulated resistance wire and of a series of warp threads 11 formed of insulating material similar'to and substantially the same sizeas is provided by the weft "thread ele- 'ment 10. It will be noted that the fabric thus formed is of an open mesh character wound on areinforcing or carrier thread 14 and then'wound ln-relatively close c011s on I the wire 12. By this structural arrangement a yarn is formed having excellent heating and electrical insulating qualities of asbestos fibers and with the tensilestrength provided by'the 'reinforcing thread which makes it trude orbreak through the insulation when thefabric is sharply bent.

' to form ayarn. In a preferred construction Thwarp threads 11' of the structure are preferably formed of yarn members formed .of the same material'used in insulating the resistance wire. Preferably two thread reinforcing asbestos rovlngs are twisted together of the heater element two rovings of this character are used in provldlng the lnsulating winding for the wire so that the warp elements and the weft element are of the same general character and diameter thereby forming a fabric of a uniform character. It

' will be seen that the fabric thus formed has an open mesh formation, the effect of which is to produce a relatively spaced apart re-' lation between the stretches of the weft element 10 forming the heater element. In this I way a' doubly efiective insulation of the weftfelement stretches from each other is obtained. i

, In'a modified form of the invention shown in Figure 3 of the drawing a double heater element 10 is provided formed of a pair of resistance wires wound as in Figure Q'and' woven into the fabric from the same shuttle reel.

to permit of an identification in forming the connections to the source of current. This ing values since the separate resistance wires Preferably the two elements are col-' 'ored differently'or otherwise distinguished have different resistance capacities thereby providing a combination of three heat pro ducing values. 7

WhllG I have described my'invention with particular reference to a heating pad, ,itwill be readily understood that the same is not limited thereto butmay be used in various other electrical heater devices in which the characteristics of the invention maybe useful, and thus while I have described a preferred embodiment of my invention, it will "be readily. understood that the same is not to be limited to all the details shown but is consisting-of thread reinforced asbestos rovings helically wound about the wire, and the other elements comprise yarns formed of asbestos rovings twisted together.

'2. A heating element for electrical heater devices comprising an open mesh woven fabric in which one element comprises a resistance wire having an insulating casing consisting of asbestos rovings helically wound about the Wire, and the other elements comprise yarns formed of thread reinforced asbestos rovings .twisted together.

3. A heating element for electricalheater devices comprising an open mesh woven fabno in which the weft element comprlses a resistance wire havlng an insulatmg casing consisting of thread reinforced asbestos rovingsihelically wound about the wire, and the Warp elements comprise yarnsformed of thread reinforced asbestos rovings twisted 5 together. arrangement provides a combination of heat EDGAR o. LAGKLAND,

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