Electric radiation and convection heater for domestic use

Abstract

An electric convection and radiation heater for domestic use has a series of heating resistors completely embedded in a solid heat conducting material which adheres to the surface of trapezoidal corrugations of a convection and radiation plate. Each resistor comprises a single length of wire positioned at the summit of a corrugation and coextensive in length therewith. The heat conductive material fills only a minor portion of the depth of each corrugation in covering relation to the resistor therein. The heat conductive material can comprise a hardenable binder such as an epoxy resin containing at least 60 percent by weight of graphite, copper or aluminum powder. The bases of the corrugations are spaced apart a distance greater that the width of the summits.

Description

This invention relates to an electrical appliance for domestic heating by radiation and by convection.

Electric heating units are already known in which the energy is supplied by electric resistors placed within an enclosure which is filled with a liquid such as oil, said enclosure being provided with external fins in order to ensure heat release by radiation and convection. These units are often designed in the form of mobile radiators but require a leak-tight enclosure for the oil and are usually rather bulky.

The aim of the invention is to overcome these disadvantages while ensuring good heat transmission between the electric resistors and the radiant elements and/or convectors which serve to release the heat.

In accordance with the invention, the electric heater for domestic use which comprises a metallic radiation and convection element and a series of electric resistors placed in the vicinity of said element is characterized in that each electric resistor is embedded in solid heat-conducting material which adheres to the surface of the radiation and convection element in the vicinity of said electric resistor.

In a preferred embodiment of the invention, the radiation and convection element comprises a metal plate which is provided with projecting corrugations having a substantially trapezoidal cross-section, the electric resistors being placed in the vicinity of the summits of said corrugations.

Since the transmission of heat between the electric resistors and the radiation and convection element is ensured by means of solid material, there is no need to provide a leak-tight enclosure. The heater can have a very small thickness and its weight is appreciably reduced in comparison with heaters of the prior art.

Further characteristic features of the invention will become apparent from the following description and from a study of the accompanying drawings which are given by way of non-limitative example and illustrate one form of construction of the heater in accordance with the invention, and in which:

FIG. 1 is a front view in elevation showing a heating unit in accordance with the invention;

FIG. 2 is a sectional view taken along line II--II of FIG. 1;

FIG. 3 is a view to a larger scale showing a portion of FIG. 2.

The heater in accordance with the invention and illustrated in FIGS. 1 to 3 essentially comprises a radiation and convection element 7, electric resistors 8 and a system 10 for establishing a thermal bond between said resistors and the element 7.

The radiation and convection element 7 is constituted by a metal plate which is provided with projecting corrugations having a substantially trapezoidal cross-section and formed by two convergent flanks 11 (as shown in FIG. 3) and by a summit portion 9. The portions 13 of the plate 7 which lie between two successive corrugations have a width D which is greater than the width d of the summits 9 of the corrugations.

Insulated electric resistors 8 are placed within the corrugations in the vicinity of their summits 9. It will readily be understood that all the resistors 8 aforesaid are joined to each other at both ends and connected to a current supply point (not shown) through a thermostat 14.

The resistors 8 are embedded in solid heat-conducting material 10 which adheres to the summits 9 and to the flanks 11 of the corrugations of the plate 7 in the vicinity of the resistor 8.

By way of example, the material 10 can be constituted by a heat-conducting powder such as a graphite, copper or aluminum powder and by a hardenable binder such as an epoxy resin, the quantity of heat-conducting powder being such as to represent at least 60 percent of the mixture.

In order to carry out the embedding of the resistors 8, there can be advantageously be employed a multiple injection pump which is first loaded with the desired quantity of material 10 in the state of paste. The initial operation consists in injecting a first quantity of material 10 into the summit portions 9 of the corrugations of the plate 7. The resistors 8 are then placed in position and the remainder of the material 10 contained in the pump is then injected. By means of this technique, the total quantity of material 10 injected can readily be controlled.

Having once hardened, the material 10 maintains the electric resistors 8 in position and ensures excellent transmission of heat between said resistors and the corrugations of the plate 7, with the result that the summit portions 9 and the adjacent portions of the flanks 11 are brought substantially to the same temperature during operation.

The radiation and convection plate 7 is maintained within a frame formed by four U-section casings 1 to 4.

To this end, the plate 7 is folded-back at both ends so as to form two U-section flanges 21, as shown in FIG. 2. The lateral casings 2 and 3 engage over said flanged ends 21 and also engage over the top and bottom casings 1 and 4 as can be seen in FIG. 2, thus ensuring rigidity of the assembly. The casings 1 to 4 as well as the flanged ends 21 of the plate 7 are provided with ribs 22 which ensure snap-on engagement of the casings.

In order to permit heat distribution by convection, the top casing 4 and bottom casing 1 are pierced by a series of apertures 5, as shown in FIG. 2.

The heating unit thus formed is therefore of very simple construction and of very small thickness in comparison with known radiators of the oil-both type. Moreover, there is no problem of leak-tightness and the weight as well as the cost price of the unit are appreciably lower than those of known radiators.

It is readily apparent that the invention is not limited to the embodiment which has just been described and many alternative forms of execution of this latter may accordingly be contemplated without thereby departing from the scope of the invention. In particular, a large number of formulae for hardenable mixtures which are known to those versed in the art are open to selection for the formation of the heat-conducting material 10.

Claims

What I claim is:

1. An electric heater for domestic use comprising a corrugated metallic radiation and convection element, and a series of electric resistors in the corrugations of said element, each resistor being completely embedded in a solid heat-conducting material which adheres to the surface of the corrugations of said element in the immediate vicinity of said resistor, said element comprising a plate having corrugations of substantially trapezoidal cross section each formed by a pair of convergent generally planar flanks joined by a generally planar summit portion, a resistor comprising a single length of wire positioned at the summit of each of said corrugations and coextensive in length with the length of the corrugations, said heat-conductive material filling a minor portion of the depth of each corrugation in covering relation to the resistor therein with the remainder of the corrugation being free of said heat-conducting material so that the surfaces of the flanks are exposed.

2. An electric heater as claimed in claim 1, the portions of said plate between two successive corrugations being wider than said summits.

3. An electric heater as claimed in claim 1, said heat conducting material consisting essentially of at least 60 percent by weight of a heat conducting powder in a hardenable binder.

4. An electric heater as claimed in claim 3, said binder being an epoxy resin.

5. An electric heater as claimed in claim 3, said powder being selected from the group consisting of graphite, copper and aluminum.