US2713110A

US2713110A - Electric kiln

Info

Publication number: US2713110A
Application number: US407859A
Authority: US
Inventors: Arthur H Edgerton
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-02-03
Filing date: 1954-02-03
Publication date: 1955-07-12
Anticipated expiration: 1972-07-12

Description

nite States Patent Office ELECTRIC KILN Arthur H. Edgerton, Rocky River, Ohio Application February 3, 1954, Serial No. 407,859 7 Claims. (Cl. 219-35) This invention relates broadly to electric kilns and more specifically to kilns for firing vitreous enamel on small metallic parts such asworks of art and industrial parts.

One of the objects of the'invention is to provide a transparent hood or dome defining a firing chamber for a kiln to accommodate theobservation of the work as the glaze matures therein.

Another object of the'invention is to provide a portable kiln adapted to complement a kit containing an assortment of tools, glazing materials and findings.

Another object of the invention is to provide a work supporting stand or so-called trivet to facilitate the suspension of the Work in spaced relation with the heating element while both sides of the work are being fired.

Further objects of the invention reside in the provision of a kiln which is light in weight, durable of structure, economical of manufacture, and efficient of operation.

Other objects and advantages more or less ancillary to the foregoing, and the manner in which all the various objects are realized, will appear in the following description, which considered in connection with the accompanying drawings, sets forth the preferred embodiment of the invention.

In the drawings:

Fig. l is a vertical sectional view through the improved kiln.

Fig. 2 is a plan view thereof.

Fig. 3 is a plan view of a tool for lifting the dome off the heating unit.

Fig. 4 is a side elevational view of the work supporting stand; and

Fig. 5 is a plan view thereof.

Referring first to Fig. 1, the kiln comprises a base preferably drawn from sheet metal stock to form a tubular body having a concave top 11, an opening 12 therein for reception of an electric heating element 13 and legs 14 in the lower open end of the body to facilitate the dissipation of heat. coil 15 of resistance wire mounted in the conventional manner in spiral groove in a plate 16 of refractory material. The top of the heating element is flush with edges of the wall defining the opening 12 and the base thereof is supported on a crossbar 17 welded or otherwise secured to the side wall of the base. The coil 15 is coupled through

lines

18 and 19 to an electrical plug 20 of usual form which is bolted to the cross bar 17 and arranged to protrude through an opening in the side wall of the base 10.

The work pieces may be held either by a stainless steel wire screen (not shown) laid upon the upper face of the heating element or by a stand or so-called trivet 22 adapted to rest upon the ceramic plate 16 or top plate 11 superjacent the electric coil 15. The trivet preferably comprises a cruciform wire frame embodying a pair of base rails 24 flattened in the central portions 25 thereof and welded together in normal relation to each other. The wires forming the base rails are bent vertically upwardly at equidistant points, then downwardly and inwardly in The heating element embodies a helical gconvergent relation with the centers 25 of the base rails 24. The height of the vertical arms is equal and the free ends of the downwardly inclined arms terminate in contigeous relation with each other slightly above the bonded center 25.

The dome 26 which forms the firing chamber of the kiln is molded as an integral unit from clear, transparent, heatresisting glass of the character sold commercially under the trade name Pyrex. The base of the dome is contoured for intimate engagement with the concave face 11 of the top of the kiln, and is preferably formed with bead- 27 around the outer marginal edge thereof. The dome is formed with a shouldered knob 28 in the center of the top thereof anda tool such as the fork 29 illustrated in Fig. 3 may be provided to'facilitate the removal of the dome after a firing operation.

In operation the work pieces arecoated with comminutecl glaze in the well known manner, then placed upon either the screen planchet or trivet 22. The dome is next placed in position on the face 11 of thetop of the kiln and the electric current turned on. As the glaze matures, the operator may observe the characteristic changes therein; first the deep grey or black appearance of the enamel coating, irrespective the original color thereof; next the curdled effect as fusion occurs; next the sheen about the marginal edges of the work, and finally the shiny appearance of the entire surface of the work as the glaze reaches its flow point. When the latter occurs, the operator may either turn off the electric current or remove the dome and lift the trivet or planchet as the case may be.

The glazing material melts at approximately 1500 36., and although the glass from which the dome is made softens, at a somewhat lower temperature during the manufacture thereof, it will be recognized that the ambient air will prevent the dome from reaching a temperature which will have any deleterious effect thereon or cause any deformation or injury thereto. Since the improved kiln affords visual inspection of the work throughout the firing operation, the craftsman may remove the piece from the kiln or turn off the heating element at the critical stage of fusion, thus avoiding over-firing, which generally produces blackened areas about the edges of the work, dots throughout the surface thereof where the glaze burns out, or irregular lumpy surface where the enamel crawls.

Although the foregoing description is necessarily of a detailed character, in order that the invention may be completely set forth, it is to be understood that the specific terminology is not intended to be restrictive or confining, and that various rearrangements of parts and modifications of detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

What is claimed is:

1. A kiln for fusing vitreous enamels comprising a base having a disc shaped top provided with a central opening, an electric heating element in said opening capable of fusing vitreous enamels in the range of 1300 F. to 1600 F. and a transparent cover composed of glass having a softening temperature of approximately 1300 F., said cover having an end wall and a depending annular wall of a greater diameter than the heating element and engaging the upper surface of said top near its outer edge and preventing free access of air to the interior of the cover, the height of the annular wall of said cover being approximately as great as the radius of the mouth of the cover whereby currents of air sweeping the outer periphery of the cover will maintain solidity of the glass cover.

2. A kiln for fusing vitreous enamels comprising a base having a disc shaped top provided with a central opening, a flat electric heating element in said opening capable of fusing vitreous enamels in the range of 1300 F to 1600 F. and a transparent cover composed of glass Patented July 12, 1955 having a softening temperature of approximately 1300 B, said cover having an end wall and a depending annular wall of a greater diameter than the heating element and engaging the upper surface of said top near its outer edge and'preventing free access of air to the interior of the cover, the height of the annular wall of said cover being approximately as great as the radius of the heating element whereby currents of air sweeping the outer periphery of the cover will maintain solidity of the glass cover.

3. A kiln for fusing vitreous enamels comprising a base having a disc shaped top provided with a central opening, an electric heating element in said opening capable of fusing vitreous enamels in the range of 1300 to 1600" F. and a transparent cover composed of glass having a softening temperature of approximately 1300 F., said cover having an end Wall and-a depending annular wall of a greater diameter than the heating element and engaging the upper surface of said top near its outer edge and preventing free access of air to the interior of the cover, the height of the annular wall of said cover being approximately as great as the radius of the mouth of the cover whereby currents of air sweeping the outer periphery of the cover will maintain solidity of the glass cover and whereby the vitrifaction of vitreous enamels melting from 1300 F. to 1600 F. may be observed during the heating operation and removed from the kiln by lifting the cover therefrom when the vitreous enamels attain a shiny smooth appearance.

4. A kiln of the type as set forth in claim 1 including a marginal rim portion on said disc shaped top of a height greater than the central portion of the top for properly positioning said cover thereon.

5. A kiln of the type as defined in and by claim 1 including a work holder removably supported on said heating element.

6. A kiln of the type as defined in and by claim 1 including lifting means detachably connected to said cover for the removal thereof from the kiln.

7, A kiln of the type as defined in and by claim 1 including heat insulating means in said base of the kiln.

References (Iited in the file of this patent UNITED STATES PATENTS