GB2205940A - Electric space heaters - Google Patents

Abstract

An electric fire has a tray (24) supporting base members (25, 26) in which a single continuous, coiled resistance wire first heating element is mounted. A convection air heating element (37) is located in a convection air passage (33). The two heating elements are connected in series so that the voltage drop across each one is less than mains voltage. The first element may therefore be made of heavier gauge wire with a longer life. Alternatively the first heating element may be in series with a diode. Pieces of imitation solid fuel are disposed above the first heating element to be heated thereby and radiate heat. Spaces between the pieces allow glimpses of the glowing element to be seen, providing a realistic appearance of burning solid fuel. <IMAGE>

Description

1 2205940 ELECTRIC HEATERS.

This invention relates to electric radiart heaters of the kind in which resistance elements are electrically energized te become heated.

Normally the heat is directly radiated into a space be-ing heated from the elements.

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

The invention provides ar electrically-pcwered radiant heater ccmprising one or more coiled resistance electrical heating elements located to heat fuel simulation mc-ans which then radiate heat, and nL- ans for reducing the vcltage across the or each radiant heating element whereby a cciled resistance wire of heavier gauge ard longer life n-Ey be used. Said means for reducing the voltage rrL7-y be a further heating element wInich is net located to heat the fuel simulation means. Said further heating element n.Ey heat air in a convection air path. The heavier gauge wire may be o-\;er 1.00 rmi diameter.

There may also or alternatively be means for reducing the voltage across the or each heating element which corrprises diode mo,-ans.

The electrical heating elements may be designed to glow at their nermal running temperature (preferably 600 0 C or mc.re). The fuel simulation may also glow.

Specific e-mbodiments of the invention are shown in the accompanying drawings, in which:- Figui e 1 Figure 2 Fi gure 3 Figure 4 Figure 5 PB508 is a side section through ar electric fire, is a plan view of a base member of the fire of Figure 1, is a side view of the base member of Figure 2 with a decorative component, is a side view through a second embodiment of ar electric fire, ard is a circuit diagram of the fire of Figure 4.

2 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 groo-,.-es 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, ti ansf erring the heat to the room in which the fire is situated. The 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 Figurel, the base mEmber is tilted forward to present an upwardly sloping array to the,-iewer.

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 mcre 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 and means of varying continuously the intensity of the illumination may be used for greater realism. The lamp or lamps may be of the flickering type or a P3508 1 1 3 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 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 ccntinuous heating element. Switch means (not shown) mounted on housing (11) allows 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. loQs, could be similarly simulated.

The electric fire shown in Figurs 4 and 5 is fitted partially inset into a fireplace (21). The fire has a housing (22) and canopy (23) similar to those showm 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 grocve 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 chrornium, with a small quantity of yttrium. The wire is of relatively heavy gauge, for example 1.2 mm diameter, coiled in a coil of outside diameter 6.4 r=. The coil is of open mesh (i.e. the successive coiled pertions do not touch) with a stretch ratio of 2:1 (i.e. the soace between two successive coiled pcrtions is equal to twice the wire diameter). As described in more detail hereinafter, this heating element has a heat rating of 1750 watts. The base member (26) also provides protrusions (29) in which pieces of coal or coke reprsentations (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 (34) at the bottom of the fire, up at the rear of the fire, and out into the space to PB508 i 4 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 eleirents, 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 tc 1750 watts.

It has been found that if a coiled resistance element of more usual desicm for domestic electric fires is used in the confined space 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 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 rL,--,ping temperature. By using the convection heating element in series with the radiant heating element it has been found De-ssible to select the heavier gauge wire achieving a running temperature of 1200 0 C which is within the normal operating range of the wire. The temperature is a function of the relative resistances of the convection and radiant heating elements, and the gauge and resistivity of the wire. It will be seen that by adjusting these factors the radiant heating element can be desianed 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 eleireents, for example tc 170 volts. Thus the heating effect of both heaters is approximately halved. The wire temperature of the radiant heating element drops to about 800 0 C, at which temperature it is still glowing.

In another arrangement (not shown), a thermostatically-controlled PB508 C p 1 cut-out by-passes the c=ector heater and allows full voltage power to be applied to the radiant heating element while it is below its #?glowing" temperature (about 600 0 c), so as to provide a more rapid warm-up. When the predetermined cut-out temperature is achieved, the full pcwer bypass circuit is cut and the Figure 5 arrangement restored.

In arrangements without a convector heating eleirkent, 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.

PB508 6 CLALMS:

1. An electrically-powered radiant heater comprising one or more coiled resistance electrical heating elements located to heat fuel simulation means which then radiates heat, and means for reducing the voltage across the or each heating element whereby a coiled resistance 5 wire of heavier gauge and longer life may be used. 2. A radiant heater as claimed in claim 1, wherein said means for reducing the voltage comprises a further heating element which is not located to heat the fuel simulation means. 3. A radiant heater as claimed in claim 2, wherein said further heating element is located to heat air in a convection path.

4. A radiant heater as claimed in claim 2 or claim 3, wherein said further heating element is connected in electrical series with the fuel sLm,-,-7ation heating element, the relative resistances of the series of heating elements being selected so that the fuel simulation heating element has an acceptable life expectancy.

5. A radiant heater as claimed in claim 4, wherein said fuel simulation heating element or elements are formed of an alloy of iron, aluminium. and chromium of a diameter of at least 1. 00 mm.

6. A radiant heater as cl-aimed in any of claims 1 to 5, wherein said fuel simulation heating element or elements are designed to operate at 600 0 C minimum temperature, at which the element or elements glow.

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

8. A radiant heater as claimed in any of claims 1 to 7, comprising further selectable means for reducing the voltage across the or each heating element whereby two different heat outputs my be achieved.

9. A radiant heater as claimed in claim 8, wherein said selectable means comprises diode means and a switching circuit whereby the diode means my be switched in or out of circuit. 10. A radiant heater as claimed in any of claims 1 to 9, comprising also thermostatically- controlled by-pass means which operates during a warm-up period to by- pass the voltage reducing means to provide a more rapid warm-up.

PB508 1 k 7 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.

PB508 Ptfelished 1988 a, The Patent Office. State House- 66 -1 High Folborn. London WC1.P. 4TP Further c-pies may, be obtained from The Patent Office, Salles Branch. St Mary Cray. Orpington, Kent BR5 3RD Printed by M1LCItirdex techniques ltd. St Mary Cray, Kent. Con. 1'87.

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