US1396813A - Electric air-heater - Google Patents

Description

0. A. COLBY.

ELECTRIC AIR HEATER.

APPLICATION FILED APII. 4, ISIIEI.

Patented Nov. 15, 19216 Fly. 2.

INVENTOR O I W A. [0/15 I ATTORNEY p be heated UNITED STATES PATENT orrica.

ORA A. COLBY, OF IRWIN, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC A: MANUFACTURING COMPANY, A CORPORATION 01 PENNSYLVANIA.

ELECTRIC AIR-HEATER.

Specification 01' Letters Patent.

Patented Nov. 15, 1921.

To all whom z'tmay concern:

Be it known that I, ORA A. Comer, a citizen of the United States, and a resident of Irwin, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Im rovement in Electric Alr- Heaters, of which the following is a spec1- fication.

My invention relates to electric heating and particularly to electric air heaters.

One object of my invention is to provide an electric air heater of simple and rugged design in which the heater units are composed of rods of solid conduct1ng mater1a1.

Another object of my invention is to provide an electric air heater using solid carbonaceous material that has a negative temperature-resistance coefficient, for the resistance units, so arranged that no external current-regulating means will be requlred.

The resistance materials usually employed in electric heaters have a positive temperature-resistance coefficient, and are, therefore, self-regulating in regard to the amount of current traversing the resistor. When carbonaceous material, which has a negativetemperature-resistance coefficient, is used, the resistance of the material tends to decrease as its temperature increases until it may become incandescent and lose its original selfsustaining form. I have found that, by properly proportioning the resistance units and by providing additional radiatin surface therefor, it is possible to use car ona ceous material for resistors and to operate the same at a reasonably low temperature that will permit of using such heaters in ordinary rooms.

In practising my invention, I provide a suitable metal frame forsupporting a number of rods of solid carbonaceous material which may be traversed by the current and thereby. These rods have a greater cross sectional area in the end portions that in the body portions, so that the end portions will have a less energy loss than the body portions and will, therefore, operate at a lower temperature. I provide suitable clamping members which serve as connectors and also help radiate the heat from the end portions of the resistance rods.

In the single drawing, Figure 1 is a front view of an air heater embodying my invention, and Fig. 2 is an end view thereof.

Fig. 3 is a side elevation of a plurality of resistance rods of one type embodying my invention combined with connecting clamps and supporting means, certain parts being cut away to show details of construction; and Fig. 4 is an end elevation of the same apparatus. Fig. 5 is a side elevation of a modification of the device embodying mysteel, cast iron, or similar suitable material,

the three arts being suitably secured together. S iiitable terminals 13, insulated from one end member 11, are provided to enable connection to be made to an electric supply{ circuit.

eferring to Figs. 3 and 4, a suitabl formed supporting bar 14 is provided with holes 15 in the end portions to enable it to be secured, by means of bolts, (not shown) to the end frames 11. Two end members 16 and a plurality of intermediate members 17 are attached to the supporting bar 14 by means of screws 18, a plate 19, of insulating material, being placed between the members 16 and 17 and the bar 14, and a washer 20, of insulating material, being placed between the head of each screw 18 and the bar 14. The members 16 and 17 serve as conductors of current and also assist in radiating the heat in a manner to be more fully described hereinafter. The end members 16 are adapted for attachment to current conductors (not shown), screws'21 being provided to clamp the ends of the conductors in holes 22 drilled in said end members, the other ends of the current conductors being connected to the terminals 13. Each of-the intermediate members 17 is provided with two holes 23 and the end members 16 with one such hole to receive the ends of resistance rods 24 of substantially U-shape. The end portions of the rods 24 maybe of any desired form, in cross section, they being here shown as of circular cross section. The body portion is, preferably, of substantially of heat in the end portions, thus reducing the operating temperature of these portlons.

The holes 23 are larger than the rods 24, so

.as to provide a s ace in which may be placed 10la' mass 25, of

nely divided granular-conducting material, such as graphite. A

washer 26 is provided to cover the hole 23 and the granular material 25 therein;

Figs. 5, 6 and 7Lshow another embodiment of my invention, using straight resistance rods and suitable clamping members at both ends of the rods. Supporting bars 14 are provided at the top and the bottom of a plurality of straight resistance rods 27. A two-part clamping member 28 of copper, brass, or other similar metal, is provided at the lower end of each of the end rods 27 and is fastened to the bar 14: by means of screws 18, being insulated therefrom by plates 19 of insulating material, placed at each side of the bar 14. A bolt 29 securely clamps the rods 27 in the two-part clamping members 28, substantiall semi-cylindrical recesses 30 being provide in said members to receive the rods 27. Similar two-part clamping members 28 are provided for the intermediate rods 27, each part. having two semicylindricalrecesses 3.0 to receive a corresponding number of rods. The clamping members are so disposed at the top and the bottom of the resistance rods as to connect all of the rods in series, although the clamping members may be arranged to connect a plurality of rods in parallel if the resistance of the rods should make this necessary or desirable. The end clamping members are provided with holes and binding screws, as

. described for the end members 16 in Fig. 3.

The rods 27 are made of solid carbonaceous material and have end portions that are larger in cross section than the body portion in order to reduce the heat generated in the end portions. The clamping members 28 are made relatively large so as to assist in radiating the heat from the end portions of the resistance rods and thus keep the operating temperature relatively low, as compared with the temperature of the body portions. The decrease of the resistance of carbonaceous material at increased temperatures will be counter-acted by the increased radiation of the clamping members, as they conduct heat away from the efid portions of the rods and radiate the same. By these means, the maximum temperature of the resistance rods may be kept within a limit that will allow of long continued use of the same without deterioration of the material, and the temperature of the resistance rods msaem type to be used as-an air heater or as an 1. A resistance unit composed of solid conducting material having an initially negative temperature-resistance coefficient and comprising a bare bod portion and integral end portions, the b0 y portion having a higher resistance and a smaller radiating surface per unit of len h than the integral end portions thereof w ereby a constant resistance of said body portion is maintained at a predetermined temperature.

2. In a resistance unit-of solid conducting material having an initially negative temperature-resistance coefficient, the combination with a bare body portion and integral end portions, the body portion having a higher resistance and a. smaller radiating surface per unit, of length than the end portions, whereby the resistance of said body portion becomes constant at a predetermined temperature and means for conducting the heat away from said end portions and radiating the same.

3. An electrical heating device comprising a frame, a plurality of contact members having openings therein, means for supporting said contact members in spaced relation in said frame, a resistance unit of solid carbonaceous material having a negative temperature-resistance coefficient and having its ends located in the openings in said contact members, and a mass of granular electricalconducting material in said openings interposed between said contact' member and said resistance unit; 1, A V

4:. An electrical heating device comprising an open frame, a plurality of metal contact members having openings therein, means for supporting said contact members in spaced relation in said frame, a resistance unit of solid carbonaceous material of substantially. U-shape, having a negative temperature-resistance coefficient, and having its ends located in the openings in said contact members, a mass of granular electricalconducting material in said openings interposed between said contact member and the end portion of said resistance unit, and a 1919. ORA A. COLBY.

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