ARRANGEMENT FOR CONVERTING ELECTRICAL ENERGY TO HEAT ENERGY

Abstract: An arrangement for converting electrical energy to heat energy, comprising a resistance wire (16), which can be connected to an electrical energy source, and a covering (11, 18) which screens the wire off from the environment. The covering comprises an electrically insulating sleeve (18) surrounding the resistance wire (16), and a plate-shaped support (11) cast from concrete and surrounding the sleeve. A method for producing the arrangement comprises casting a first concrete plate half with a channel (20) designed for drawing through of the resistance wire (16) and its sleeve (18). Thereafter, the resistance wire is placed with its sleeve in the channel (20) and a second concrete plate half is cast on top of the first one.

Description: Arrangement for converting electrical energy to heat energy The present invention relates to an arrangement for converting electrical energy to heat energy, comprising a resistance wire, which can be connected to an electri¬ cal energy source, and a covering which screens the wire off from the environment. The invention also relates to a method for production of the arrangement. Background to the inventiont Known electric radiators with heat-generating resistance wires are usually constructed in a similar manner with a metal tube which is enclosed by plates and accommodates and screens the resistance wire, which wire is held at a distance from the metal tube by means of bodies of an electrically insulating, ceramic material. These known radiators have disadvantages, for example in the form of high temperature of the outer casing and noises upon heating and cooling on account of stresses which can arise from heat expansion. In addition, they cool quickly upon interruption of current. Aim of the invention; The aim of the invention is to provide an arrangement and a method permitting production of electric radiators which do not have the abovementioned disadvantages. Characteristic feature of the invention: To this end, the arrangement according to the invention is characterized in that the covering comprises an electrically insulating sleeve surrounding the resistance wire, and a plate-shaped support of concrete enclosing the sleeve. This arrangement affords a completely silent radiator element, which forms a heat magazine when the current supply is interrupted. According to an advantageous exemplary embodiment of the invention, the concrete is reinforced with fibres of a heat-tolerating material. As a result of this arrange¬ ment, the heat-generating plate can be made thin, with retained strength, for more effective heat emission from the resistance wire. The sleeve advantageously comprises a woven tubing of glass fibres. Such a tubing has very high resistance to wear, which reduces the risk of damage to the electrical insulation during the production procedure. According to a further advantageous exemplary embodiment of the invention, the tubing is impregnated with heat- tolerating silicone rubber. The resistance wire advantageously runs in a zigzag formation across the plane of the plate. In the case of a plate which is designed to be fitted in a standing position, the resistance wire advantageously runs in a zigzag formation in the vertical direction across the plane of the plate, with increasing mutual spacing between parallel wire sections in the upward direction. As a result of this arrangement, the temperature can be distributed more evenly in the plane of the plate, taking into account the fact that the air is heated up as it passes along the outside of the plate. The concrete plate is advantageously fitted inside a container which is provided with vertical air passages and members for temperature regulation of the current to the resistance wire. This affords an electric radiator with an advantageously low outer temperature and a high storage capacity. A method for producing an arrangement for converting electrical energy to heat energy, which arrangement comprises a resistance wire, which can be connected to an electrical energy source, and a covering which screens the wire off from the environment and consists of an electrically insulating sleeve and a plate-shaped con¬ crete support surrounding the sleeve is characterized in that a first concrete plate half is cast with a channel designed for drawing through of the resistance wire and its sleeve, in that the resistance wire with its sleeve is placed in the channel, and in that a second concrete plate half is cast on top of the first one. According to a variant of this method, the first concrete plate half is cast with a number of holes which are directed transverse to the plane of the plate and which diverge in the direction from the second concrete plate half and are intended to be filled with concrete upon casting of the said second half. Brief description of the drawings; The abovementioned characteristics and further charac¬ teristics of the invention will be described in greater detail below with reference to the attached drawings, in which Fig. 1 is a broken perspective view showing an electric radiator with a plate, designed according to the inven¬ tion, for converting electrical energy to heat energy. Fig. 2 is a plan view showing the plate in a section in the plane of the plate, and Fig. 3 shows part of Fig. 2 on a larger scale. Description of embodiments: Fig. 1 shows an electric radiator 10 which has two container halves 10a, 10b made of concrete, which sur¬ round a vertically standing plate 11. The plate 11 is held centred in an inner space between the container halves by means of a number of support shoulders 12, so that air gaps are maintained between the outer sides of the plate and the container halves. The container halves 10a, 10b are provided with a number of vertical air channels 13 which connect the above- mentioned inner space to the atmosphere surrounding the electric radiator. Electric current can be fed to the radiator via a flex 14 and via a thermostat which can be controlled from the operating panel 15. A resistance wire 16 drawn inside the plate 11 is connected to the thermostat and the operating panel. The design of the plate 11 emerges more clearly from Figs. 2 and 3 which show screw connections 17 for con¬ nection lines from the operating panel 15. Like the container halves 10a, 10b, the plate 11 is cast from concrete in such a way that it encloses the resistance wire 16 along the whole of its length, except at the screw connections 17. In order to increase the strength of the concrete and to permit a reduction in the thick¬ ness of the plate, glass fibres have been mixed into the concrete before casting. It can be seen from Fig. 3 that the resistance wire 16, which is wound in a helix and is made for example of nickel kanthal, is surrounded by an electrically insulat¬ ing sleeve, which can consist for example of a woven tubing 18 of glass fibres which has a high heat tolerance and extraordinarily high resistance capacity to mechani¬ cal wear. In order to prevent liquid and concrete from penetrating through the woven tubing during the casting of the plate, the tubing has been impregnated with silicone rubber 19. It can also be seen from Fig. 3 that the helical turning of the resistance wire has been made tighter at the ends in order to form an engagement for the screw connections 17. The plate 11 can be cast in two separate halves, which are provided on the opposite sides with a channel 20 for the resistance wire and its sleeve 18. The resistance wire is laid in place in the channel of one plate half, and the second plate half is stuck or bolted securely on the first one. Thereafter, the plate is fitted between the two container halves 10a, 10b. By virtue of the fact that the resistance wire runs in a zigzag formation in the vertical direction across the plane of the plate with increasing mutual spacing between parallel wire sections 16a, in the upward direction, the temperature is distributed more evenly in the plane of the plate since the air is heated up as it passes along the outside of the plate. Alternatively, the second plate half can be cast on the first one. In order to obtain the best possible fixing between the two plate halves, the first half can be provided with a number of holes 21, which diverge in the direction from the second plate half and are intended to be filled with concrete upon casting of the said second half. The invention is not limited to the exemplary embodiment described above, but instead several variants are con¬ ceivable within the scope of the following claims. For example, the plate 11 can be produced in different sizes and used in contexts other than that shown. Moreover, the radiator shown in Fig. 1 can be produced in different sizes with more than one plate, for example in power sizes of between 500 and 800 W. Conceivable alternative areas of application are hot plates for keeping food hot, and hot-air fans. Teflon tubes can be used as a sub¬ stitute for the glass fibre tubing 18.

Claims: Patent claims 1. Arrangement for converting electrical energy to heat energy, comprising a resistance wire (16), which can be connected to an electrical energy source, and a covering (11, 18) which screens the wire off from the environment, characterized in that the covering comprises an elec¬ trically insulating sleeve (18) surrounding the resis¬ tance wire (16), and a plate-shaped support (11) cast from concrete and surrounding the sleeve. 2. Arrangement according to Claim 1, characterized in that the concrete is reinforced with fibres of a heat- tolerating material. 3. Arrangement according to Claim 1 or 2, characterized in that the sleeve comprises a woven tubing (18) of glass fibres. 4. Arrangement according to Claim 3, characterized in that the tubing (18) is impregnated with heat-tolerating silicone rubber (19). 5. Arrangement according to any one of Claims 1-4, characterized in that the resistance wire (16) runs in a zigzag formation across the plane of the plate. 6. Arrangement according to Claim 5, which arrangement is designed to be fitted in a standing position, charac¬ terized in that the resistance wire (16) runs in a zigzag formation in the vertical direction across the plane of the plate with increasing mutual spacing between parallel wire sections (16a) in the upward direction. 7. Arrangement according to any one of the preceding claims, characterized in that the concrete plate (11) is fitted inside a container (10a, 10b), which is provided with vertical air passages (13) and members (15) for temperature regulation of the current to the resistance wire ( 16 ) . 8. Method for producing an arrangement for converting electrical energy to heat energy, which arrangement comprises a resistance wire (16), which can be connected to an electrical energy source, and a covering (11, 18) which screens the wire off from the environment and consists of an electrically insulating sleeve (18) and a plate-shaped support (11) cast from concrete and sur¬ rounding the sleeve, characterized in that a first concrete plate half is cast with a channel (20) designed for drawing through of the resistance wire (16) and its sleeve ( 8), in that the resistance wire is placed with its sleeve in the channel (20), and in that a second concrete plate half is cast on top of the first one. 9. Method according to Claim 8, characterized in that the first concrete plate half is cast with a number of holes (21) which are directed transverse to the plane of the plate and which diverge in the direction from the second concrete plate half and are intended to be filled with concrete upon casting of the said second half.

Inventors: GERMUNDSSON LARS, GERMUNDSSON, LARS
Applicants: LG INNOVATIONS AB
Application year: 1989
Main classification: H05B3
IPC codes: F24C7, F24H3, H05B3