US2387995A - Heating element and method of production - Google Patents

Description

Oct. 30, 1945. A. .1. HUCK f 2,387,995

HEATING ELEMENT AND METHOD OF PRODUCTON Filed March l, 1944 INVENTOR. /l/f A067( Patented Oct. 30, 1945 HEATING ELEMENT AND METHOD OF PRODUCTION Alfred J. Huck, St. Louis, Mo., assignor to Knapp- Monarch Company, St. Louis, Mo., a corporation of Missouri Application March 1, 1944, Serial No. 524,550

7 Claims. (Cl. 201-67) My present invention relates to a heating element which can be formed in a relatively flattened shape and thereby particularly adapted for heating pads or the like, and to a method of producing such heating element.

One object of the invention is to provide a heating element of simple, durable and inexpensive construction which is flattened in cross section as distinguished. from the usual round heating element, my element accordingly reducing the over-all thickness of a heating pad or the like and minimizing the ridges on the padnormally present where round heating elements are used.

Another object is to provide a heating element which is elliptical in cross section and a method of making it which comprises the steps of forming the heating element of such materials that it can be flattened without danger of short-circuiting the turns of the resistance coil and the flattening of the element gives it the desired elliptical shape and minimizes its final thickness.

With these and other objects in View, my invention consists in the construction, arrangement and combination of the various parts of the heating element and in the steps of the method for forming it whereby the objects contemplated are obtained as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawing wherein:

Figure 1 is a plan View of my heating element sewed to a backing sheet for the purpose of forming the inner portion of a heating pad or the like.

Figure 2 is an enlarged elevation of the heating element showing parts of the ends broken off to illustrate the various components of the element.

Figure 3 is an enlarged cross sectional View of the heating element after it is assembled.

Figure 4 is a side elevation o-f the heating element showing it being attened between a pair of rollers.

Figure 5 is a sectional view similar to Figure 3 showing the cross section after ilattening; and

Figure 6 is a longitudinal sectional view through the heating element on the line 6 6 of Figure 5, part of the ligure being unsectioned to more clearly show the construction.

On the accompanying drawing I have used the reference character H to indicate in general a heating element. A core therefor is shown at I and may be formed of asbestos bers or other suitable insulating and heat-resisting material which is flexible and of a deformable nature. Wound around the core I0 is a resistance wire I2 of suitable size for the wattage with which it is to be energized. lIhe resistance wire I2 is wound tightly on the core Ill so as to press into its surface as shown in Figure 6.

After the resistance wire is wound on the core, a plurality of asbestos threads Ill are wound on the core and resistance coil to form a cover therearound. The threads I4 likewise are flexible and deformable. Finally a plurality of linen or cotton threads I6 are wound on the cover I4 and in the opposite direction to its winding for the purpose of retaining the elements I0, I2 and I4 assembled so that a complete heating element is thereby provided, which can be handled for subsequent steps of the method herein disclosed` without electrically exposing any portion of the resistance coil.

In Figure 3 I illustrate the cross section of the heating element after it is formed in accordance with the foregoing method and the neXt step in the method is to flatten the heating element to the shape shown in Figure 5. This may be done between the dies of a press or by merely passing the heating element between a pair of rollers I8 and 20 (see Fig. 4).

The rollers are suitably driven and are properly spaced to secure the desired degree of flattening. The heating element is fed to the rollers, as at the left side of Figure 4, and comes out at the right side flattened as illustrated at Figure 5.

The flattening process does not in any way harm the heating element as the members I0, I4 and I6 thereof are all readily deformable and the wire I2, of course, can be readily bent from circular shape to elliptical shape. The wire tends to stay in this shape and adjacent coils of the wire, I iind, are not short-circuited with relation to each other but remain substantially equally spaced as originally wound The resultant structure, however, is a well attened heating element as shown in Figure 5 having about half the thickness of the one shown in Figure 3. Subsequently the heating element may be sewed to a backing sheet 22, bythe usual heating element sewing machine which sews across the element with threads indicated at 23, the backing sheet 22 preferably being a woven asbestos cloth.

Figure 6 illustrates how the cover I4 is tightly wound on the coil I2 and nally the threadsJb` tightly wound around the cover so as to bite into the cover and effectively hold the parts of the heating element assembled. The resulting structure, after flattening, makes it possible to form a heating pad or the like of considerably less thickness than at present and one in which the ridges formed by the heating element are much less conspicuous to the touch and more comfortable against the body when the heating pad is in use.

Some changes may be made in the construction and arrangement of the parts of my heating element and the method of producing it may be varied to some extent without departing from the real spirit and purpose of my invention. Accordingly it is my intention to cover by my claims any modified forms of structure'or use of mechanical equivalents or equivalent methods which may be reasonably included Within their scope Without however sacrificing any of the advantages of the invention.

I caim as my invention and desire to secure by United States Letters Patent:

1. A heating element for a heating pad or the like comprising a flexible core of asbestos, elliptical in cross section, a coil of resistance wire Wound tightly therearound, said coil being elliptical in cross section and helically elliptical in form, a cover of flexible asbestos Wound around said coiled Wire and core and a Winding of thread around said cover in the opposite direction to retain said core, coil and cover assembled.

2. A heating element for heating pads or the like comprising a exiblecore of insulation, a coil of resistance Wire wound therearound, a cover of exible insulation wound around said coiled Wire and core, and a Winding of thread around said cover to retain said core, coil and cover assembled, said core, coil and cover being elliptical in cross section and said coil being helically elliptical.

3. In a heating element of the kind disclosed, a flexible core, a helical coil of resistance Wire Wound thereon, a exible cover around said coiled Wire and core, said core, coil and cover being e1- liptical in cross section.

4. In a heating element of the kind disclosed, a exible core, a coil of resistance Wire wound thereon, a flexible cover around said coiled Wire and core, said core, coil and cover being flattened in cross section with said coil and retaining its helical form secured flatwise toa backing sheet.

5. A method of producing a heating element comprising the steps of Winding a resistance wire helically around a flexible deformable core, winding a exible deformable cover around said resistance Wire, Winding threads around said cover to retain the foregoing elements assembled, at-

tening the assembly between rollers to decrease the thickness of the assembly and retain said resistance wire in helical form, and sewing the flattened heating element assembly on a supporting sheet for use in a heating pad or the like.

6. A method of producing a heating element for a heating pad or the like comprising the steps of helically winding a resistance Wire around a flexible vdeformable core, Winding a flexible de- ALFRED J. HUCK.

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