US1219629A - Method of forming electrical heat units. - Google Patents

Description

R. W. DAVENPORT. METHOD OF FORIVHNG ELECTRICAL HEAT UNITS. APPLICATION FILED APR.8.1Q15.

1 ,21 9,629. Patented Mar. 20, 1917.

UNITED STATES PATENT OFFICE.

RANSOM W. DAVENPORT, OF DETROIT, MICHIGAN, ASSIGNOR TO DETROIT STOVE WORKS 0F DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

METHOD OF FORMING ELECTRICAL HEAT UNITS.

Specification of Letters Patent Patented Mar. 20, 1917.

Griglnal application filed February 13, 1914, Serial No. 818,469. Divided and this application filed April 8,

To all whom it may concern:

Be it known that I, Ri-xNsoM V. DAVEN- ron'r, a citizen of the United States of America, residing at Detroit, in the county of Jayne and State or Michigan, have invent ed certain new and useful Improvements in Methods of Forming Flectrical Heating Units, of which the following is a specification, reference being bad therein to the 1C- companying drawings The invention relates to the method. of forming electrical heating units of the embedded. resistor type, and it is the object of the invention to facilitate the embedding of the resistor, and also to obtain a construction in which there is good thermal conduction from the resistor on. one sic e and thermal insulation upon the opposite side. It is a further object to obtain. a constructi n in which the convelutions of the resistor are but slightly separated from each other, to concentrate the heat development without any danger of short circuiting between convolntions,

An electrical heating unit of the embedded resistor type is disclosed in. my earlier application, Serial No. 818,469, filed Feb. 13, 1914:, the present application being a division thereof.

In the drawings:

Figure 'l is an elevation showing the method of coiling the resistor;

Fi 9 is a perspective View oi the coiled resistor;

Fig. 3 is a section showing the manner of engaging the resistorwith the heat-insulating body;

Fig. 4 is a similar View showing the spat?- ing member removed; and

Fig. is a cross section through the completed unit. I

In the first step oi my improved method 0.5 forming heating" units, the resistor A, which is pre'leral'ily in the form of a flat ribbon, is placed adjacent to a destruetible strip or ribbon C, such as string, cord, twine, e c., and is then bent or fashioned to have adjacent contacting portions. As specifically shown in Fig. 1, the bending is in a volute form, the convolutions of the re sister being: separated by the. parallel conrelations of the destructible strip. After the ceiling the convolutions are held from separation by suitable means such as binding Serial No. 20,611.

strips D, and are preferably dipped in some adhesive, such as shellac.

The second step is the covering of the coil with a plastic material, which preferably a material of relatively low thermal conductivity, an example of this material being infusorial silica with clay added for plasticity. The destructible strip is preferably slightly less in width than the resistor, and therefore the. plastic material will slightly enter in between the resistor convolutions to obtain a binding effect thereon.

The third step is the removal of the destructible strip, preferably by combustion, after which the ashes are cleared away, prefcrably by blowing. This leaves the spaced conrolutions of the resistor, which are held by the slight embedding 0t tl eir edges in the insulating material.

The next step is in filling the interstices or spaces between the resistor coni'olutions with a plastic material of relatively good thermal coii(liicti\-'it y, an example of this material being calcined bauxite or aluminum oxid with clay added for plasticity, and tli material is extended a sullicient depth to form theheat distributing body.

The unit when completed as described will have the maximum portion of the surface of the resistor convolutions in contact with a good heat-conducting material. which will rapidly conduct the heat into the distributing body. At the same time the h mt insulating body, which is upon the opposite side of the resistor, will prevent loss of h at \in this direction, and as both or" the bodies are united to each other, the resistor will be completely embedded and thoroughly insulated electrically.

The destructible spacer strip which is wound between the resistor cmivolutions is preferably a round cord, which will leave. sulticient space at the edge of the resistor for binding engagement of the plastic material.

lVhat I claim as my invention is:-

l. The method of forming electrical heatinn elements, comprisinc the placing oi a resistor strip and av strip formed of destructible material adjacent to each other, bending said strips to form adjacent con tacting portions, placing plistic' material on one side in binding contact with the resistor, and destroying the destructible element.

2. The method of forming electrical heating elements, comprising the placing of a resistor ribbon and a destructible strip in parallelism, bending said parallel strips to form contacting adjacent portions, covering an area, placing plastic material of an electrically insulating character on one side in binding contact with the edges of the resistor, and destroying The method of forming electrical heatinc elements. comprising coiling an electrical resisto' and a parallel spacing strip to cover an area. placing plastic material on one side of said area into binding contact with the edge of the resistor, and removing the spacing strip.

4. The method of forming electrical heatin;- elements, comprising windin c together into a volute coil a length of resistor and an adjacent length of destructible strip, cement ion a plate of insulating material to one lace of said \olute coil iirbiliding contact with the edge of the resistor, and in burning out said destructiblc strip.

5. The method of forming electrical heating elements, comprising winding together a resistor and a parallel destructible spacer strip to term a close coil, cementing a plate of insulating material upon one side 01 said coil. destro \'ing the spacer strip and removing the same, and filling the spaces vacated by said dcstructible strip with an electrically insulating refractory material.

(3. The method 01 forming electrical heating elements, comprising the winding together ot a resistor ribbon and a destructible spacer strip to form a close coil, cementing a plastic material of low thermal conductivity upon one side of said coil, destroying said spacing strip, and placing; a plastic material of relatively high thermal conductivity upon the opposite side of the coil and filling; the interstices between the convolutions.

7. The method of forming electrical heating elements, comprising the winding of a resistor and a destructible spacing strip into a volute coil, coating one side of this coil with a plastic material, destroying the spacthe destructible strip.

ing strip and removing the same from the conyolutions of the resistor, and coating the opposite side of said resistor with a plastic material. 5:

8. The method of forming electrical heating units, comprising the winding of a resistor element and a parallel dcstrnctible spacing strip into a yolute coil, binding the convolutions together to temporarily hold the same in fixed relation, placing a plastic material on one side of the coil and forcing the same sufficiently into engagement with the cmn'olutions of the resistor to bind the same in fixed relation, destroying the spacjug strip and removing" the same from between the resistor convolutions, and filling the space. between said convolutions and upon the opposite face of the coil with a plastic material.

9. The method of forming electrical heating elements, comprising the winding; of a resistor ribbon and a parallel strip of destructiblc material into a rolute coil, coating;- one side of said coil with a plastic material of low thermoconductivity and forcing the same sutliciently in engagement with the convolntions of the resistor to bind the same, destroying the spacing strip and removing it from between the resistor convolutions, and filling the space between said convolntions and upon the opposite side of the coil with a plastic material of relatively high theri'no-condnctivity.

10. The method of forming electrical heating elements. comprising the winding of a resistor and a spacing strip into a volnte coil, coating one side of this coil with a plastic material, removing the strip from between the convolutions of the resistor, and

filling the interstices between the convohr tions with an electrical-insulating, heatconducting material.

In testimony whereof I r 1n presence of two witnesses.

RANSOM lV. DAVENPORT. Witnesses lVM. J. BELKNAP, JAMES P. BARRY.

\' my signature

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