US2556281A - Electric stove - Google Patents

Description

m R. 2, mm 5 6 .y E vm/UM m R 2 fm N T M E \l vl/d. .I f wm. Kw, ns oc. Km@v .CF Le El m u EL June l2, 1951 Patented June 12, 1951 ELECTRIC STOVE J an Kotk, Prague, Czechoslovakia Application February 28, 1948, Serial No. 11,880 In Czechoslovakia November 22, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires November 22, 1966 2 Claims. (Cl. 219-34) This invention relates to electrically heated furnaces of a kind in which heat is accumulated in a block of fire-bricks provided with air ducts through which air flows into the interior of the furnace and from there into the room to be heated. This known arrangement hasthe disadvantage that comparatively hot air, of up to about 400 C., enters the room through a relatively large number of holes in the cover of the furnace so that the room is heated principally through air circulation. This type of heating is unhygienic due to the burning of the dust in the stove and the stirring-up of dust in the room, and also uneconomical since the temperature in the room is unsuitably stratified, that is the temperature is substantially higher at the ceiling than near the floor, Where the heat is in fact mostly required. Furthermore the bulk of the re block, in this system, is nothing like so well utilised as its refractory properties would allow, because the high temperature of the mass results in the air emerging from the furnace into the room being at too high a temperature.

The object of the present invention is to overcome these disadvantages and with this object in view the casing around the block of fire-bricks which is preferably made of metal, is completely closed, an air clearance on the one hand, and a layer of insulating mass on the other hand, being arranged between said casing and the block of nre-bricks. The heating elements are cylindrical and are freely housed in horizontal transverse ducts in the lire-brick block, for example three elements may be arranged one above the others. These ducts are connected with one another by vertical air channels which open at the upper and at the lower side of the block of nre-bricks into air spaces between the said block and the external casing.

In order that the invention may be more clearly understood one particular embodiment thereof will now be described, by way of example, with reference to the accompanying drawings wherein:

Figure l is a vertical longitudinal section through the stove on the line I-I of Figure 2, which is a vertical cross section on the line II-lI of Figure 1.

In the embodiment shown the stove comprises a block of lire-bricks I, which is supported in known manner by means of suitable supports 2 on a base plate 3, and which is surrounded by a heat-insulating layer 4 and moreover by a suitable casing of sheet metal 5, an air space 5 being arranged between the latter and the insulating layer 4.

According to the invention the block of rebricks I is provided with horizontal transverse ducts 1 of substantially circular cross-section but having a transversely corrugated surface so that in the interior of these ducts there are rounded annular ribs 'I'. In these ducts 'l cylindrical electrical heating elements 8 are substantially freely housed, resting on the said rounded ribs, as shown in Figure l, where free crescent-shaped spaces remain between the upper portion of the surface of the heating elements and the edges of the annular ribs.

These ducts 1 are connected with one another in appropriate groups by vertical air-flow channels 9 which open at the upper and lower ends into the air space I0 between the block of rebricks and the insulating layer 4 and into the air space above the base plate 2 in the sheet metal casing 5.

In the upper wall of the insulating cover 4 of the block of fire-bricks I there is an opening II with a controllable slide I2, which can be operated by a hand lever I3 and a small hand wheel I4, in order either to close the said opening or to open it partly or fully, and thereby to control the circulation of air through the vertical channels 9 around the heating elements 8.

These heating elements are conductively connected with one another by a terminal rail or bar I5, and since they are freely housed in the horizontal transverse ducts, they can be easily removed and replaced.

As the heating elements 8 are freely housed in the horizontal transverse ducts 'I of the block of nre-bricks I, in the manufacture of this stove neither particular accuracy nor the action of dilatation of the dilerent materials has to be taken into account so that the manufacture is simple and inexpensive. By the annular corrugation of the openings for the heating elements 8 in the block of fire-bricks I a substantial increase of surface area is obtained whereby the temperature of the heating element is steadily lowered and also the heat delivery from the block of nre-bricks is more ecient than would be the case if the heating elements tted tightly in the block of nre-bricks.

The control slide I2 on the upper surface of the insulating layer 4 on the opening II is linked up at the free end of the control lever I3 so as to be freely tiltable and adjustable in height in such a manner that its correct function in the adjusted position is not affected even when the height of the block of fire-brick with the insulating layer 4 is altered through changes of dilata- 3 tion although this diiference of level of these upper surfaces may amount to several centimeters.

A furnace according to the invention has the following advantages:

1. The air flowing through the ducts in the block of fire-bricks does not penetrate into the room, but transfers the heat to the external casing which is turn transmits the heat to the room, mostly by radiation and only to a small extent by convection. The temperature is thus evenly distributed over the room, and since vthe highest temperature of the external casing amounts to about 100 C., no unhygienic distillation of the dust takes place and there is no detrimental circulation of the air in the room.

2. The block of lire-bricks is heat-insulated at its surface whereby the full bulk of the block can be fully utilised, for the block of fire-bricks is heated by electrical heating elements and the highest temperature is naturally at the region of the source of heat. Thus since the surface of the block of fire-bricks is heat-insulated, a high temperature is obtained in all parts of the block, the withdrawal of heat from the block occurring at the region where its temperature is the highest that is through the air ducts passing around of the block of fire-bricks while there is an opening which can be closed by means of a slide. If this opening is closed, the flow of the air through the block of fire-bricks is prevented and thereby the delivery of heat to the external casing is cut-off. Since the surface of the block is heatinsulated, the issue of heat from the furnace is small with the slide closed which is the basic condition for the correct function of the furnace in order to make it accumulate heat in the stove during the night. In day time when the heat is to be delivered by the stove and when the current is switched off from the stove, the slide is opened, and the air flowing through the air ducts transfers the heat to the outer casing. Since the whole block is heated throughout by the aid of the insulating layer, the accumulated heat sufiices for the whole day.

3. The horizontal arrangement of the heating elements allows their being easily exchanged after removal of the rear wall of the external casing.

4. The surface of the horizontal ducts in the block of lire-bricks into which the heating elef ments are inserted is corrugated thereby ensuring that the air ducts are not completely closed by the inserted heating element, the surface being at the same time increased by means of which the block takes over the heat from the heating element; also the heat transfer by the air flowing through the ducts is more efficient.

What I claim and desire to secure by Letters Patent is:

1. An electric heat accumulating furnace, comprising in combination, a block of fire-brick material having a plurality of groups of substantially horizontal passages therein, the passages of each group having annular grooves therein and being connected with each other through a substantially vertical duct, heat insulating material mounted on the sides and the major top surface of said block, a metal casing closed completely and surrounding said block while being spaced .therefrom so as to dene therewith and with said heat insulating material an air chamber surrounding said block, cylindrical electric heating elements arranged in said horizontal passages for heating said block, each of said heating elements having a diameter less than the diameter of the respective horizontal passage housing the same so as to leave a crescent-shaped passage between the upper surface of said heating elements and the adjacent surface of the respective passages and means operable from the outside of said casing for selectively controlling the flow of air from said passages.

2. An electric heat accumulating furnace, comprising in combination, a block of fire-brick material having a plurality of groups of substantially horizontal passages therein, said passages being grooved so as to form ribs extending through said passages with the ridges of said ribs defining a cylindrical space, the grooved portions of each group of passages being interconnected by means of substantially vertical ducts, a plurality of substantially cylindrical electric heating elements respectively located in the respective cylindrical portion of each passage as'defined by said ridges, said heating elements resting on said ridges and having a materially smaller diameter than said cylindrical space so as to leave a crescent-shaped channel between the upper surface of said heating elements and the adjacent surface of the passages housing said elements, insulating material surrounding the major portion of said block, a casing with heat conducting metal surfaces spaced from and surrounding said insulating material, and means for selectively establishing or interrupting communication between said air chamber and said ducts.

JAN KOTK.

REFERENCES CITED The following references are of record in the le of this patent:

FOREIGN PATENTS Number Country Date 77,336 Switzerland Sept. 2, 1918 79,901 Switzerland Jan. 16, 1919 81,873 Switzerland Aug. l, 1919 85,357 Switzerland Oct. l, 1920 577,916 Great Britain June 5, 1948

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