GB1581127A

GB1581127A - Electrical heating devices

Info

Publication number: GB1581127A
Application number: GB3968875A
Authority: GB
Original assignee: VULCAN REFRACTORIES Ltd
Current assignee: VULCAN REFRACTORIES Ltd
Priority date: 1975-09-27
Filing date: 1975-09-27
Publication date: 1980-12-10

Description

(54) ELECTRICAL HEATING DEVICES (71) We, VULCAN REFRACTORIES LIM ITED, a British Company of Brookhouses Industrial Estate, Cheadle, Stoke-on-Trent, ST10 1PN, Staffordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment :- This invention relates to electrical heating devices of the kind comprising an electrical heating element embedded in a body of refractory ceramic material.

Heating devices of this kind emit long wave infra-red radiation and are useful in particular in industrial applications for warming, drying, curing and like purposes.

An object of the present invention is to provide an improved heating device of the aforesaid kind.

According to the present invention there is provided an infra-red heating device comprising a solid body part of refractory ceramic material and a heating element wholly embedded in such body part with all surfaces thereof in initmate contact with such material, the body part having a corrugated or quasi-corrugated surface thereto defining alternate side-by-side peaks and troughs, and the heating element having successive reaches thereof in register with respective such peaks and so located in relation thereto as at least to extend to that side of a notional plane extending between the bottoms of the troughs immediately adjacent the said respective peaks remote from such peaks.

With this arrangement it is possible to produce a light, strong heating device which is an efficient emitter of long wave infra-red radiation and is capable of heating up and cooling down in a short period of time whilst possessing adequate thermal intertia.

The reduced thickness body portions corresponding to the troughs may all have a common thickness and the body portions corresponding to the peaks and with which the element is in register may also have a common, and different, thickness.

The heating element is most preferably an elongated resistive metal heating element, particularly a coiled wire heating element, and this may be arranged in a number of reaches at least some of which extend parallel to each other. Preferably, the heating elements comprise a single element with electrical connections only at the two ends thereof.

Preferably also, the body incorporating the heating element is of flat or curved plate-like form. In one embodiment the body is a flat plate, which is of square or rectangular or other shape. In an alternative embodiment the body is in the form of a curved plate, preferably of part-cylindrical curvature. In a further embodiment the element is embedded in a circular disc forming the larger diameter end of a hollow frusto-conical body.

In the case of a heating device comprising a flat or curved plate as in the first two preferred embodiments described above, a projection may be provided at that face of the body part remote from the corrugations therein, such projection serving for mounting the device. In addition, the electrical heating element may have connecting wires which have free ends extending through such projection or which are attached to electrical contacts or connectors supported by the projection and by means of which the heating device can be connected to an electrical supply.

In the case of a heating device having a frusto-conical body as mentioned above, the heating element may be connected to an electrical connector, for example, in the form of an electrical lamp-type screw or bayonette connector, at the smaller diameter end of the body. Such connector may be used for connecting the heating device to electrical supply and also for mounting the device.

The element will normally be incorporated in the body so as to give most radiation from one surface of the body and the arrangement of the element and the corrugations will preferably be such as to give a uniform level of radiation across the said surface. The device may have a temperature sensor, such as a thermocouple or other device, arranged on or outwardly of the corrugated surface thereof. Such sensor may have connecting leads which extend through bores in the ceramic body to support the sensor and for use in connecting same to an indicating circuit.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a rear perspective view of one form of a heating device according to the invention; Fig. 2 is a plan view of the front of the device of Fig. 1; Fig. 2A is a diagrammatic plan view of the heating element of the device of Fig. 1; Fig. 3 is a section on the line III--III of Fig. 2; Fig. 4 is a front perspective view of an alternative form of device; Fig. 5 is a sectional view of a still further form of device; and Fig. 6 is a perspective view of a support for use in the manufacture of the heating device of Fig. 1 or Fig. 4.

With reference to Figs. 1 to 3, a heating device comprises a general planar rectangular ceramic body 1 having a coiled resistive wire heating element 2 (Fig. 3) embedded therein.

The body has a smooth flat rear surface 3 and a front surface (as shown in Fig. 2) which has raised portions 4 and troughs 5, the raised portions 4 having the element 2 embedded therein and the troughs 5 lying between the raised portions 4.

The element 2 is of a single length having two free ends and, as can be seen from Fig. 2, comprises six equally spaced longitudinal reaches 6 extending parallel to the longer sides of the body 1, lateral reaches 7 parallel to and adjacent the shorter sides of the body, and a short central reach 8 which extends parallel to the lateral reaches 7 and which is provided for a purpose hereafter to be made apparent. The manner in which the element 2 is arranged is shown diagrammatically in Fig. 2A, and it will be seen that the central linking reach is provided at a free end of the element 2.

In the centre of the rear surface of the body there is a projection 9 which is an integral part of the body 1 and serves for the mounting of the heating device and/or the attachment of a reflector plate (not shown) to the back of the device. In an embodiment shown there are grooves 10 on opposite sides of the projection 9 for engagement with a reflector plate retaining clip.

The free ends of the heating element 2 pass through the projection and terminate in electrical connection tags 11. The exposed portions of the ends are insulated with ceramic sleeve elements 12.

Two parallel bores 13 (Fig. 2) extend completely through the ceramic body 1 and projection 9 and a thermocouple 14 or other temperature sensor (Fig. 3) may be supported at a position in front of the front surface by leads 15 which pass through the bores and terminate in tags 16 (Fig. 1) which are insulated like the ends of the heating element 2.

The heating device so far described may be formed in the following manner: A wet ceramic forming mixture is placed in a first mould part such part being shaped to form the troughs 5 and raised portions 4 of the front face of the body 1. The element 2 is placed on the mixture and a second mould part shaped to form the back face 3 and projection 9 of the body 1 is positioned on the first mould part. Further wet mixture is inserted into the mould through an inlet in that part of the second mould part which is shaped to form the projection 9. The wet mixture isthen allowed to settle, for say 35 minutes, and make intimate contact with all surfaces of the heating element 2.

If bores 13 for a temperature sensor are required these are formed by means of metal tubes inserted into the mixture in the mould.

The moulded body incorporating the heating element 2 is then inserted into an oven to dry the body and glaze the exposed surfaces thereof. In the oven the body is supported on a device 17 as shown in Fig. 6. The projection 9 on the back of the body 1 fits into a groove 18 in the top of the supporting device 17.

With this arrangement it is possible to form a strong yet light heating element which is an efficient emitter of long wave infra-red and which can heat up and cool down quickly whilst possessing sufficient thermal inertia to level out temperature fluctuations in use.

The dimensions of the front surface of the device may be 47/," by 23/8" and the thickness may be 2/8" at the raised portions and 1/8" between same. The heating element 2 may be 250W 240V a.c. rating.

The device may be used for any suitable domestic, commercial or industrial purpose. For example, it may be used for drying, curing or heating purposes. It is hard wearing and has a long life. In particular, it can withstand splashes of cold water when at operating temperature, and stains on the front surface thereof are easily burnt off in use.

The distribution of the heating element 2 over the front surface ensures that an even heating effect over the surface can be achieved The ceramic body 1 is thin walled and ofconstant thickness (except for the variation between the raised portions 4 and the recessed portions 5) apart from the central region which has the projection 9 thereat. To compensate for the projection 9 and to prevent the formation of a cold spot there is the short linking reach 8 of the heating element 2 centrally of the front surface.

The heating device of Fig. 4 is similar to that of Fig. 1 except that the thin-walled body la is curved in part-cylindrical form.

This acts to focus the heat and a higher temperature can thereby be achieved. This embodiment may also incorporate a thermocouple or other temperature sensor.

The device of Fig. 5 has the heating element 19 incorporated in a circular ceramic disc 20 which extends across the larger end of an integrally formed frusto-conical body 21.

The shorter end has a screw threaded neck 22 thereat and a screw-type electrical connector 23 is applied thereto. The heating element 19 has two free end portions 24, 25 which are connected to the side and centre terminals of the connector 23. The element 19 is arranged spirally in the disc 20.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiments which are described by way of example only, and thus for example, a heating device according to the invention may be formed in any suitable size, and shape and may be used for any suitable purpose. In one alternative embodiment, a heating device of, say, square or rectangular form and which may be constructed similarly to the device of Fig.

1, may be arranged for use in a domestic environment as a grill or hot plate. For use as a grill, the device may be provided with legs at each corner by means of which the device can stand on an appropriate surface with the heating surface facing downwardly.

Attention is drawn to our co-pending Patent Applications Nos. 27508/79 (Serial No 1581128) and 27509/79 (Serial No 1581129) both divided from this Application and directed to a method of forming the heating device herein proposed and to the provision of an expanded heating element in register with a projection to the body part to avoid the formation of a cold spot in register with such projection, respectively.

WHAT WE CLAIM IS: 1. An infra-red heating device comprising a solid body part of refractory ceramic material and a heating element wholly embedded in such body part with all surfaces thereof in intimate contact with such material, the body part having a corrugated or quasi-corrugated surface thereto defining alternate side-by-side peaks and troughs, and the heating element having successive reaches thereof in register with respective such peaks and so located in relation thereto as at least to extend to that side of a notional plane extending between the bottoms of the troughs immediately adjacent the said respective peaks remote from such peaks.

2. A device according to claim 1, wherein the heating element is an elongated resistive metal heating element.

3. A device according to claim 2 wherein the metal heating element is a coiled wire.

4. A device according to claim 2 or 3, having a single element with electrical connections only at the two ends thereof.

5. A device according to any one of claims 2 to 4 wherein the element is arranged in a plurality of reaches.

6. A device according to claim 5 wherein at least some of said reaches are parallel to each other.

7. A device according to any one of claims 1 to 6 wherein the body part is of a common thickness in positions in register with the peaks and troughs respectively.

8. A device according to any one of claims 1 to 7, wherein the said body part is of plate-like form.

9. A device according to claim 8, wherein the said body part comprises a flat plate.

10. A device according to claim 8, wherein the said body part comprises a curved plate.

11. A device according to claim 8, wherein the said body part comprises circular disc forming the larger diameter end of a hollow frusto-conical structure.

12. A device according to any one of claims 8 to 10 wherein an integral mounting projection is provided at that face of the body part remote from the corrugations therein.

13. A device according to claim 12, wherein the heating element has connecting wires which have free ends supported by the projection.

14. A device as claimed in any one of the preceding claims, having a temperature sensor arranged on or outwardly of the corrugated surface of the body part.

15. A device according to claim 14, wherein the sensor has connecting leads which extend through bores in the body part.

16. A device according to claim 15, when dependent on claim 12, wherein the leads are supported by said projection.

17. A heating device as claimed in claim 1 substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3, Fig. 4 or Fig. 5 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. short linking reach 8 of the heating element 2 centrally of the front surface. The heating device of Fig. 4 is similar to that of Fig. 1 except that the thin-walled body la is curved in part-cylindrical form. This acts to focus the heat and a higher temperature can thereby be achieved. This embodiment may also incorporate a thermocouple or other temperature sensor. The device of Fig. 5 has the heating element 19 incorporated in a circular ceramic disc 20 which extends across the larger end of an integrally formed frusto-conical body 21. The shorter end has a screw threaded neck 22 thereat and a screw-type electrical connector 23 is applied thereto. The heating element 19 has two free end portions 24, 25 which are connected to the side and centre terminals of the connector 23. The element 19 is arranged spirally in the disc 20. It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiments which are described by way of example only, and thus for example, a heating device according to the invention may be formed in any suitable size, and shape and may be used for any suitable purpose. In one alternative embodiment, a heating device of, say, square or rectangular form and which may be constructed similarly to the device of Fig. 1, may be arranged for use in a domestic environment as a grill or hot plate. For use as a grill, the device may be provided with legs at each corner by means of which the device can stand on an appropriate surface with the heating surface facing downwardly. Attention is drawn to our co-pending Patent Applications Nos. 27508/79 (Serial No 1581128) and 27509/79 (Serial No 1581129) both divided from this Application and directed to a method of forming the heating device herein proposed and to the provision of an expanded heating element in register with a projection to the body part to avoid the formation of a cold spot in register with such projection, respectively. WHAT WE CLAIM IS:

1. An infra-red heating device comprising a solid body part of refractory ceramic material and a heating element wholly embedded in such body part with all surfaces thereof in intimate contact with such material, the body part having a corrugated or quasi-corrugated surface thereto defining alternate side-by-side peaks and troughs, and the heating element having successive reaches thereof in register with respective such peaks and so located in relation thereto as at least to extend to that side of a notional plane extending between the bottoms of the troughs immediately adjacent the said respective peaks remote from such peaks.