NZ224968A - 'hot coal' electric heater - Google Patents

Description

22 4 9 6 8 'W-% t.

M Priority Date(sfr: .2»rSa-.K7.J Complete Specification Filed:^! !?.'%& Claw: 63/ .C&.-.

Publication Date: 2.7.NQ.V, P.O. Journal, No: . ...63S.-..

Patents Form No, ■i /O NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION ELECTRIC HEATERS N '' ^ j \\ ■9JUN,983^' S£/We, BERRY MAGICOAL LIMITED, a British comply/ &■ J \j X"'^ ' of Spring'Road/ Tyseley, Birmingham Bll 3EG, England/ hereby declare the invention, for which S/we pray that a patent may be granted to-s^/us, and the method by which it is to be performed, to be particularly described in and by the following statement: (followed by page la) ' —..

' -J-Lrtir<f» •'»■•. # la 22 4 9 6 8 ELECTRIC HEATERS. c /""N This invention relates to electric radiant heaters of the kind in which resistance elements are electrically energized to become heated. Normally the heat is directly radiated into a space being heated from the elements.

The invention has for an object the provision of an electric radiant heater which presents more closely the appearance of a fire burning solid fuel.

The invention provides ar electrically-powered radiant heater comprising one or more electrical heating elements located to heat fuel 10 simulation means which then radiate heat.

The fuel simulation means may be such as to glow when heated by the heating elements. The fuel simulation means may comprise heat resistant glass or ceramic simulating individual pieces or heaped arrangements of "coke", and may hide the major part of the heated element or elements. 15 The heating elements may be coiled resistance wire. A heat resistant base member may have the heating elements located thereon and the fuel simulation means located spaced above it.

There may be electrical illumination means for enhancing the effect of burning solid fuel.

According to another aspect, the invention may provide means for reducing the voltage across the or each radiant heating element whereby a coiled resistance wire of higher gauge and longer life may be used.

Said means for reducing the voltage may be a further heating element which is not located to heat the fuel simulation means. Said further 25 heating element may heat air in a convection air path.

There may also or alternatively be means for reducing the voltage across the or each heating element which comprises diode means.

Specific embodiments of the invention are shown in the accompanying drawings, in which 30 Figure 1 is a side section through an electric fire, Figure 2 is a plan view of a base member of the fire of Figure 1, Figure 3 is a side view of the base member of Figure 2 with a decorative component, Figure 4 is a side view through a second embodiment of an electric fire, and (followed by page 2) 2 22 4 9 6 8 Figure 5 is a circuit diagram for the fire of Figure 4.

An electric fire as shown in Figure 1 comprises a housing (11) having an ornamental canopy (12) and a support (13) shaped to hold the operative parts of the fire. A base member (14) of fireclay or other heat resistant material has grooves in its upper surface in which electric elements (15) lie. These elements may be one or more lengths of coiled resistance wire which glow red when electric current is passed through them.

Spaced above the base member is an open mesh screen (16) on which rests a heat conducting and radiating fuel simulation (17).

In use, the elements (15) heat the fuel simulation (17) which radiates, transferring the heat to the room in which the fire is situated. The fuel simulation in one arrangement comprises separate lumps of ceramic simulating coke, which glow when heated and present a very realistic simulation of a burning bed of coke. The glowing elements (15) are either not visible through the simulated coke or sufficiently hidden by the simulated coke to be insignificant in the overall appearance of the fire. There may, however, be irregular gaps between the pieces of "coke" through which glimpses of the glow from the elements can be seen in addition to the glowing "coke" itself.

The base member is of trapezium shape, as shown in Figure 1, and the heater wires follow a serpentine path in the grooves. As seen in Figure 1, the base member is tilted forward to present an upwardly sloping array to the viewer.

In an alternative arrangement, the screen (16) is formed of heat resistant glass. This allows heat to be conducted to the fuel simulation and also allows the red glow from the heater wires to be seen between the "coke" pieces.

To enhance the glowing effect, additional illumination may be provided by an electric lamp or lamps (not shown). These may be mounted in the housing (11) either beneath the fuel simulation or on one or more sides thereof. The support (13) and base member (14) may have holes allowing light to pass through.

Pieces of heat-resisting glass coloured red or orange may be used in place of the "coke". Means of varying continuously the intensity of the illumination may also be used for greater realism. The lamp or lamps 3 22 4968 may be of the flickering type or a spinner may produce a flickering effect. There may be coloured windows at the front of the base member simulating the glow of a fire through the fire bars.

The housing may also have fan means (not shown) driving air over the element or elements and/or the heated fuel simulation to be heated thereby and add to the radiated heat.

The heat output of the fire may be between 2-3 kilowatts. As shown in Figure 2, there is a single continuous heating element. Switch means (not shown) mounted on housing (11) allow the element to be operated, and also allow for manual control of the illumination and fan (if provided).

Although the fuel simulation shown is of separate pieces of "coke", it will be understood that other fuel, e.g. logs, could be similarly simulated.

The electric fire shown in Figures 4 and 5 is fitted partially inset into a fireplace (21). The fire has a housing (22) and canopy (23) similar to those shown in Figure 1. A tray (24) supports fireclay base members (25, 26) of which the upper member has a continuous groove (27) arranged in a serpentine fashion over its surface.

In the groove is arranged a radiant heating element comprising a single continuous coiled resistance wire (28). This is formed of a heat resistant alloy of iron, aluminium and chromium, with a small quantity of yttrium. The wire is of relatively heavy gauge Over 1.00 mm diameter, for example 1.2 mm or 1.3 mm diameter, coiled in a coil of outside diameter 6.4 nrti. The coil is of open mesh (i.e. the successive coiled portions do not touch) with a stretch ratio of 2:1 (i.e. the space between two successive cciled portions is equal to twice the wire diameter). As described in more detail hereinafter, this heating element has a heat rating of 1750 watts when operating on a mains voltage of 240 volts. The base member (26) also provides protrusions (29) on which pieces of coal or coke representations (not shown) are laid. Spaces between the representations allow glimpses of the red glowing wire and base member to be seen.

In space (30) below the heating element are lamps (shown at (38) in Figure 5) which shine through a red glass window (31) to add to the realistic impression of a burning fire. The front of the fire is protected by a guard (32).

A convection air passage (33) is directed from an inlet at the 22 4 9 6 8 4 bottom of the fire, up at the rear of the fire, and out into the space to be heated under the canopy. In the passage (33) is a fireclay mounting (36) In which is located a convection air resistance heating element (37). Air is heated by convection heating element (37) and rises through the passage (33).

As seen in Figure 5, the two heating elements (37) and (28) are arranged in electrical series. This has the effect of reducing the voltage drop across each of the heating elements, thus reducing their individual heat outputs. The resistances of the two heating elements are selected taking into account the reduced voltages so that the convector heater (37) has a heat output equivalent to 500 watts, while the radiant heater (28) has a heat output equivalent to 1750 watts.

It has been found that if a coiled resistance element of mere usual design for domestic electric fires is used in the confined spice beneath the fuel simulation with the full available voltage drop across it, it has a reduced life, burning out sooner than is desired, although it still provides a good radiant heating and a realistic effect. In order to increase the life, heavier gauge wire is needed, but this has the effect of increasing the running temperature. By using the convection heating element in series with the radiant heating element it has been found possible to select the heavier gauge wire achieving a running temperature of 1200°C which is within the normal operating range of the wire, giving an acceptable life of the order of 5000 hours. The temperature is a function of the relative resistance of the convection and radiant heating elements, and the gauge and resistivity of the wire. It will be seen that bv adjusting these factors the radiant heating element can be designed as required.

Since it is important to maintain the whole glowing effect of the bed, it is preferred not to provide for the usual switching in or out of sections of the heating element to give different heat outputs.

Between the two heating elements a switching circuit (40) provides a diode (41) in parallel with a manual switch (42). When switch (42) is open, the diode operates to cut down the overall voltage applied to the heating elements, for example to 170 volts. Thus the heating effect of both heaters is approximately halved. The wire temperature 22 4 9 6 8 of the radiant heating element drops to about 800°C, at which temperature it is still glowing.

In another arrangement (not shown), a thermostatically-controlled cut-out by-passes the convector heater and allows full voltage power to be applied to the radiant heating element while it is below its "glowing" temperature (about 600°C), so as to provide a more rapid warm-up. When the predetermined cut-out temperature is achieved, the full power bypass circuit is cut and the Figure 5 arrangement restored.

In arrangements without a convector heating element, the voltage applied to the radiant heating element may be reduced by using a diode in series with it, thus increasing the life of the heating element.

Although the exarrpie discussed above refers to mains voltage of 240 volts, it will be appreciated that similar effects are obtained using other mains supplies. 2 2 4 9 G 8 6

Claims (11)

WHAT WE CLAIM IS:

1. An electrically-powered radiant heater comprising one or more electrical resistance heating elements located to heat fuel simulation means adapted to radiate heat and having means for reducing the voltage across the or each radiant heating element whereby to extend the life of reducing the voltage comprises a further heating element which is not located to heat the fuel simulation means.

2. A radiant heater as claimed in claim i, wherein said further heating element is located to heat air in a convection path.

3 . A radiant heater as claimed in claim l or claim 2, wherein said further heating element is connected in electrical series with the or each fuel simulation heating element, the relative resistances of the series of elements being selected so that the fuel simulation heating element cr elements may have an acceptable life expectancy.

4. A radiant heater as claimed in any one of claims 1 to 3, wherein the or each said fuel simulation heating element is a coiled resistance wire.

5. A radiant heater as claimed in claim 4, wherein the or each said fuel simulation heating element is formed of an alloy of iron, aluminium and chromium, of diameter at least 1.00 mm.

6. A radiant heater as claimed in any one of claims 1 to 5, wherein the or each fuel simulation heating element is designed to operate at 600°C minimum temperature, at which temperature it glows.

7. A radiant heater as claimed in claim 1, wherein said means for reducing the voltage across the or each heating element comprises diode means.

8 A radiant heater as claimed in any one of claims 1 to 7» wherp^-^y^ the fuel simulation means comprises heat resistant glass or ceranyfo^ '/a/ oi| 1 5MAY!990'r/ .9249 0 7 arranged to hide the major part of the or each heating element from view.

9 . A radiant heater as claijned in any one of clains 1 to 8 , wherein there is a heat resistant base on which the or each fuel simulation 5 heating element is mounted, the base being arranged at an angle to the horizontal and the fuel simulation means being located spaced above the or each element.

10. A radiant heater as claimed in any one of claims 1 to 9 , having electrical illumination means for enhancing the glowing appearance of the 10 heater.

11. A radiant heater substantially as described hereinbefore with reference to Figures 1 to 3 or to Figures 4 and 5 of the accompanying drawings. BERRY MAGICOAL LIMITED by their attorneys / Baldwin Sdji & Carey