US1257106A

US1257106A - Electric heating device.

Info

Publication number: US1257106A
Application number: US85260314A
Authority: US
Inventors: Leon F Parkhurst
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1914-07-23
Filing date: 1914-07-23
Publication date: 1918-02-19
Anticipated expiration: 1935-02-19

Description

L. F. PARKHURSY.

ELECTRIC HEATING DEVlCE.

APPLICATION man JULY 23,1914.

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MOT/s155555' ffm/5570A. BYwK/Ug, /g ff/5A TTURNEK kUNITED STATES PATENT OFFICE.

LEON F. PARKHURST, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GEERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATING DEVICE.

Specification of Letters Patent. Patented Feb. 19, 1918.

Application led July 23, 1914. Serial No. 852,603.

To all whom t may concern:

Be it known that I, LEON F. PARKHURsT, a citizen of the United States, residing at Pittsiield, county of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Electric Heating Devices, of which the following is a specification.

My invention has reference to the manufacture of electric resistance heating units, and more particularly to such as are provided with a flat heating surface and which may either be used independently as a stove or heater, or in conjunction with other heat ing apparatus. In devices of this character, it is, of course, necessary that the resistance member should he thoroughly insulated from the metallic parts of the heating device, and at the same ztime it is highly desirable that it should be in intimate thermal relation with the supporting metal plate in order that the thermal drop between the resistance inember and the heating surface may not be so reat as to require the heating element to e run at a temperature under which it rapidly deteriorates in order to produce the desired temperature at the working surface.

' In one of its aspects, my invention has for its object the provision of a novel structure for securing the heating unit in intimate thermal relation with the plate and the method of producing this structure. My invention also provides simple and elicient means for largely restricting the amount of heat that is conducted from the working portion of the plate to the edges thereof and from thence to the support for the plate, thereby greatly decreasing the losses and adding to the eiiiciency of the device.

Another object of my invention is the provision of a heating device of the character indicated, which issimple, compact and eiii cient in operation.

Other novel features of my invention will be apparent from the description and will be fully pointed out in the claims.

For a fuller understanding of my'invention, reference may be had to the accompanying drawing, in which Figure 1 is a vertical section of a heating device embodying my invention, and Fig. 2 is a sectional view showing more in detail the structure of the heating unit and of the parts by which the same is secured to the top plate.

Referring now to the drawings, l is a continuous freely exposed metallic flat top plate which may conveniently be made of sheet steel the surface of which is prefer* ably treated by any known process to prevent corrosion, and is provided with a corrugation 2 which will ordinarily be annular in form. The heating unit A is preferably formed of a resistance element 3 surrounded by insulation Ll which is in turn inclosed in a continuous metallic sheath 5. The unit may be made by sii/aging or otherwise working down an ingot in a manner nonT well understood in the art. W'hile the unit may be secured-directly to the top plate, I prefer iirst to place the same between two

perforated plates

6 and 7 of a size to be received within the annular corrugation 2. The plate l is now inverted and the

plates

6 and 7, with the heating unit A arranged between the same, preferably in the form of a helical coil, are placed within its pan-shaped center, brazing material is placed upon the whole, and the parts thus assembled are placed in a suitable furnace when the brazing material will melt and flow through the openings of the

plates

6 and 7 and between the coils of the unit A, thereby firmly inclosing the plates with the heating unit against the top plate and affording a good heat conducting path between the unit and the top plate. The brazing material, solidified in the openings of the

plates

6 and 7 and between the coils of the heating unit, is indicated by the reference numeral 8. The brazing material also runs between the plate 6 and the plate 1 so that a thin lm is formed between these plates and the structure comprising the

perforated plates

6 and 7 and the heating unit A are welded or alloyed to the top plate l at every point. While the heating unit may be secured directly to the top plate, I find in practice that the brazing operation which I usually utilize in securing the unit to the plate is apt tovresult in the warping of the top plate due to .thediiierence in the coeiiicients of expansion between the top plate and the brazing material. The construction which I have above described leaves the top plate perfectly flat, as it will be seen that the brazing material touches the top plate only at separated points, and, since the plat-es G and 7 are made of a metal having substantially the same coefficient of eX- pansion as the top plate, it is obvious that screws 19.

the expansion of the plates with the heating1 unit and the brazing material secured thereto as a whole will be substantially the same as that of the top plate, and the top plate will remain dat throughout the process of manufacture.

The heating unit il i is provided with free ends 9 bent at richt 'i o angles to the plane or the top plate and preferably having the ends of the resistance conductors bared at 10.. These terminals are preferably formed larger than the resistance conductor and may be made in accordance with the method. described in a patent issued to lll. Whitney April 14th, 191e, lilo. 1,093,512.

have here shown three different terminals in order that different degrees of heat may be produced. Any desired number of terminals may, of course, be used.

il; second imperforate plate 13 is bent upwardly at A, reilered downwardly at 15 and engages the inner edge of the downwardly turned portion 12 of the top plate, and the two are secured together as by welding, the flanges of the two plates thus constituting a support for the device, which may be received in an opening in the top of a and allows of small heat conduction into said range top. et the same time the main portion of the plate 13 is spaced from the top plate to form a chamber' forthe reception of a heat insulating material. rlhis plate is provided with an opening 16 through which a terminal block 17 passes. This bloclr is provided with a iiange 18 by which the same is secured to the bottom plate and to an annular ring 2O located within the bottom plate 13 by means of rlhe terminals 10 of the resistance unit are joined to outer terminals 21 by means of conductors 22, which may be brazed or otherwise secured to the terminals 9. When the parts thus far described have been assembled, the insulating material 23, which is preferably in powdered form and which may be of a composition disclosed in Patents 1,072,413 and 1,072,414, which were issued to "Walter Arthur, Septomber 9, 1918, is dusted into the space between the heating unit and the bottom plate through the terminal block. rlhe space within the terminal block surrounding the terminals 9 of the sheathed wire and the conductors 22 is then lled with any suitable material, such as cement, and the bottom of the terminal block is then closed by a separate section 25 secured to the main portion of the terminal block by screws 24.,

rl`he corrugation formed in the top plate not only serves the purpose of forming a dish when the top plate is inverted and thus confines the brazing material to the parts where the same is utilized, but a more important feature and a permanent advantage range. rlhis support is of limited area the corrugation is that it interposes a space of high thermal resistance between the heating unit and the edge of the top plate and the stove, and it thus serves to greatly reduce 'the heat losses. Furthermore, this corrugation strengthens t-he top plate, and the groove formed thereby acts as a receptacle for the reception of any naaterial that may boil over from a vessel lo cated on the heating unit and thereby tends to prevent it from ruiming between the heating device and the stove top and eventually reaching the electric connections.

ln accordance with t-he provisions of the patent statutes, l have described the principle of operation of my invention, together with the apparatus which l now consider to represent the best embodiment thereof; but l desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

llhat l claim as new and desire to secure by Letters Patent of the United States, is

l. ln an electric heater comprising a substantially flat freely exposed top plate of good heat conducting material, a supporting' edge for said plate, a heating unit mounted in close thermal relation to said plate and means for reducing the flow of heat from the unit to the supporting edge comprising a corrugation between the heated surface and the edge.

Q. An electric heater comprising a sub stantially fiat freely exposed top plate of good heat conducting material, a supporting edge for said plate, a heating unit mounted in close thermal relation to said plate and means for reducing the flow of heat from the unit to the supporting edge comprising a bend in the plate below the heated surface and between it and the edge.

8. The method of making a heating device comprising a continuous metallic plate and a sheathed resistance heating unit which consists in forming a continuous corrugation upon the plate, and brazing the heating unit to the plate within the portion embraced by the corrugation.

rihe method of making a heating unit in which a continuous metallic plate, two perforated metallic plates and an insulated heating unit are utilized in its formation, which consists in assembling upon the continuous plate the perforated plates with the heating unit between and then causing brazing material to flow into the openings of the perforated plates and around the heating unit thereby anchoring the continuous plate, the perforated plate and the heating unit together.

5. The method of making a heating unit in which a continuous metallic plate, two perforated metallic plates and an insulated heating unit are utilized in its formation,

ISG

which consists in forming a continuous corrugation on the continuous plate, inverting the same, assembling the perforated plates with the heating unit therebetween upon the continuous plate within the portion of the plate embraced by the corrugation and causing brazing material to flow into the openings of the perforated plates and around the heating unit.

6. In an electric heater, an envelop comprising upper and lower spaced metallic plates having their edges brought into engagement, secured together and bent downwardly to form an extension for supporting the unit.

7. 4An electric hot plate comprising a substantially fiat upper metallic plate and a lower metallic plate having their edges brought into engagement, secured together and bent downwardly to form an extension for supporting the hot plate, said extension being located above the bottom of the plate, and an electric heating element supported by said upper plate.

8. An electric hot plate comprising a substantially flat upper metallic plate and a lower metallic plate having their edges brought into engagement secured together and bent downwardly to form an extension for supporting the upper plate, said eXtension being located above the bottom of the plate, an electric heating element comprising sheathed wire associated with said upper plate, the terminals of the wire being brought downwardly through the bottom plate.

9. In an electric heater, an envelop comprising a substantially fiat top plate and a lower plate having its edges secured to said top plate, a heating unit intimately secured to the. under side of said top plate, the top plate being provided with an annular depression surrounding said heating unit, and a powdered heat insulating material lling the space between the two plates.

10. A heating device comprising an envelop formed of spaced metallic plates hav ing their edges secured together, an insulated resistance heating unit inclosed within a continuous metallic sheath which is secured to the under side of the top plate, a terminal block secured to the other plate and a thermal insulating material filling the space between the two plates.

In witness whereof, I have hereunto set my hand this 21st day of July. 1914-.

LEON F. PARKHURST. Witnesses: y

A. R. NUGENT, A. E. CoLvrN.