GB2232481A - Flame-effect device - Google Patents

Abstract

A flame-effect device for a room heater comprises a moulding (6) which represents fuel, such as coals or logs, having translucent and opaque regions, and one or more lamps (8) mounted beneath the moulding which transmit light up through the moulding. In place of the usual fan-like rotors which rotate due to hot air convection from the lamps, an array of liquid crystal display segments (13) is interposed between the lamps and the moulding, and the segments are switched in a pseudo-random sequence between transmitting and opaque states, so that a flickering flame effect is produced. <IMAGE>

Description

Heating Appliances This invention relates to heating appliances, and particularly to heating appliances, such as electric fires, in which a flame effect is produced by the variation of light emitted from a region of the fire.

Imitation-fuel flame effect electric fires have been available for a number of years. Such fires include a moulding of fibre glass or other material, shaped and having translucent and opaque areas, such that the moulding represents logs or coals. One or more red or orange electric lamps are positioned beneath the moulding so that light from the lamp or lamps passes up through the translucent areas of the moulding. Some of the light from the lamp or lamps impinges on a generally vertical back panel of the fire.

Above the or each lamp is positioned a light-weight metal fan-like rotor which revolves freely about a substantially vertical axis.

When the lamps are illuminated and warm up, convected air causes each fan to rotate. The rotating fan blades have the effect of chopping the light impinging on the back panel, giving the impression of flickering flames. The rotating blades also cast a moving shadow on the underside of the moulding, and the resulting changing pattern of light passing through the moulding represents light variations such as might be seen from the logs or coals in a real fire. The orange or red light passing through the translucent areas of the moulding gives the impression that the imitation logs or coals are glowing incandescently. The back panel may be shaped with vertical indentations to enhance the appearance of flames.

Such known flame-effect fires suffer from a number of disadvantages. Firstly, when the fire is first switched on, the lamp or lamps will be cold and each fan will be stationary. The 1flames" will therefore be stationary and will therefore not have a realistic appearance. As the lamps warm up, the fan or fans will start to rotate slowly and will gradually accelerate. Secondly, the flickering appearance of the flames will be dictated by the rotor blade configuration and will be cyclic, as distinct from the random flickering of flames from a real fire. Similarly, the variations in the light passing through the moulding will be cyclic and predictable, and therefore unrealistic.

It is an object of the present invention to provide an improved imitation-fuel flickering-flame effect device for a space heater.

According to the invention there is provided an imitation-fuel flame-effect device for a room heater, the device comprising fuel-representing means having opaque regions and translucent regions; light-producing means mounted beneath the fuel-representing means and operative, in use, to transmit light through said translucent regions and to illuminate at least part of a back panel of the heater to produce a representation of flames; a first plurality of liquid crystal display (LCD) segments each operative in response to a control signal applied thereto to switch between a light-transmitting state and a light-impeding state in which, respectively, the segment transmits and impedes said back panel illuminating light; and means to apply a respective control signal to each segment to cause the segment to switch continually back and forth between said states, whereby the representation of flames is caused to flicker.

Preferably the timings of the control signals vary relative to each other in a random or pseudorandom manner.

The device may include a second plurality of LCD segments operable to control the light transmitted through the translucent regions of the fuel-representing means.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a schematic pictorial view showing basic features of a conventional electric room heater; Figure 2 is a cross section taken on a line II-II of Figure 1; Figure 3 is a schematic cross sectional view, similar to Figure 2, but incorporating a flame-effect device in accordance with the invention; Figure 4 is a schematic plan view of part of the heater of Figure 3; Figure 5 is a plan view of one of three liquid crystal displays used in the device of Figures 3 and 4; Figure 6 is a block diagram of a power supply for the device; Figure 7 is a block diagram of a microprocessor for controlling the LCDs of the device; and Figure 8 is a block diagram of one of six buffer amplifiers used for driving the LODs.

Referring to Figures 1 and 2, a conventional flame-effect electric fire comprises a housing 1 which has a rectangular aperture 2 in its front face through which an electric radiant heater 3 protrudes. A vertical back panel 4 is attached to the rear of the housing 1 and extends above the upper face 5 of the housing. A moulding 6, shaped to represent coals, protrudes through an aperture 7 in the upper face 5 of the housing. The moulding 6 may be formed of fibreglass or any other suitable material, and is sprayed or otherwise coloured so that it has dark (e.g. black) opaque regions and light (e.g. grey) translucent regions therebetween.

An orange or red lamp 8 is mounted beneath the moulding 7 and is illuminated when the fire is connected to an electricity supply, irrespective of whether or not the radiant heater 3 is switched on.

A light-weight rotor 9, formed, for example, of thin aluminium sheet is pivotally mounted to a bracket 10 so that the rotor can spin freely about a vertical axis 11. The rotor is formed with fan-like blades, each of which is twisted through a small angle to the horizontal.

The rotor may have equally-spaced blades, or there may be spaces between some of the blades, provided that the rotor remains balanced about its central pivot point.

In operation, the lamp 8 is energised and orange or red light passes through the translucent areas of the moulding, giving the imitation coals a glowing appearance. Light from the lamp also passes through apertures in the back of the moulding and impinges on the back panel, forming flame-like vertical patches of light on the back panel. The back panel may have generally-vertical indentations therein, and may be partially blackened, to enhance the appearance of the flames. It will be apparent that, at this stage, the glowing of the coals is unchanging and the "flames" are stationary, and the appearance is therefore unrealistic.

As the lamp warms up, convected air begins to flow upward through the rotor blades, causing the rotor to start to rotate. As a major part of the useful light from the lamp passes through the rotor, the rotating blades cause chopping of the light, and the "flames" take on a moving flickering appearance. Similarly, the glowing of the coals has a moving and changing appearance. However, the flickering and changing appearance are absolutely cyclic and are therefore not convincing.

Figures 3 and 4 of the drawings, in which components which can be similar to those of the conventional electric fire have the same references as in Figures 1 and 2, illustrate an embodiment of the present invention. The rotor 9 and its mounting bracket 10 are not provided. Instead, three LCDs 12, 13, 14 are mounted horizontally, end-to-end, immediately beneath the moulding 6. Alternatively, a single LCD of three times the length could be used, but the use of three smaller devices makes the LCD manufacturing process considerably easier. Preferably, three lamps 8 are provided, spaced-apart across the width of the moulding.

Referring to Figure 5, each LCD comprises a rear section 15 and a front section 16. The section 15, which lies immediately in front of the back panel 4, comprises twelve side-by-side elongate LCD segments 17, the lengths of which may increase from segment to segment towards the centre of the display, the front edges of the segments being in alignment. The front section comprises two rows, each of four segments 18, the middle two segments of the front row extending slightly further forward than the other two segments in that row.

Each of the twenty segments 17, 18 is connected to a respective contact 19 at the back edge of the display for connection by an edge connector (not shown) to the driver circuitry which will be described later. A transparent metal (e.g. indium tin oxide) layer is provided on the reverse side of the display to act as a common back electrode for all of the segments. The liquid crystal material of the segments is preferably a twisted nematic material.

The positioning of the three LCDs 12, 13,14 is such that light from each lamp passes through the segments 17 before impinging upon the back plate to produce the flame effect, and light passes through the segments 18 before transmission through the translucent regions of the moulding. The segments can all be controlled independently of each other, so that any segment can be switched to transmit the light or to impede the light depending upon a control voltage applied thereto.

Referring to Figure 6, a power unit for the device comprises a transformer/rectifer unit 20 which provides a 12 volt d.c. supply on lines 21, 22. This supply is fed to a voltage regulator 23 and associated smoothing capacitors 24, 25 and resistor 26, which circuit provides a stabilised 5 volt output between lines 27 and 22. The 12 volt supply is also fed to a voltage regulator circuit 28, the output of which can be preset over a range of 2-12 volts d.c. by adjustment of a variable resistor 29. This output is provided between lines 30 and 22. The 5 volt output is used as a power supply for the electronic circuitry to be described below, and the 2-12 volt supply acts as the switching supply for the LCD segments.

The LCD segments are controlled by a microprocessor chip 31 (Figure 7) which produces output signals on twenty-four lines, eight at each of three ports A, B and C. The microprocessor includes an EPROM which is programmed to provide pseudo-randomly varying strings of output pulses which vary in a different manner on each of the twenty-four output lines. A clock signal is produced in the microprocessor 31 by dividing down the output of an oscillator controlled by a 4MHz crystal 32.

Two types of pulse strings are produced by the microprocessor. One type comprises a string of pulses of fixed mark/space ratio. Each string of those pulses is followed by a gap, such that the molecules of the liquid crystal material are caused to align during the first few pulses and then to remain aligned during the remainder of the pulse string. The molecules then relax during the first part of the gap. The switching sequence of alignment and relaxation of the molecules is repeated at a repetition rate of around 8Hz, which is varied pseudo-randomly by the microprocessor over a range of, say, + 3Hz. This type of pulse string is used for switching the small flame-effect segments 17.

The other type of pulse string, which is used for switching the large segments 18, comprises a string of pulses having a variable mark/space ratio such that the ratio increases gradually at the beginning of the string and decreases gradually towards the end of the string, so that the segment aligns gradually and relaxes gradually, giving a gradual brightening and dimming of the light. These pulse strings, and the gaps therebetween, are arranged to give a segment switching repetition rate of around 2Hz which is varied over a range of, say, iO.5Hz.

Polarity reversal is used with both types of pulse string to ensure that each LCD element experiences no average DC component.

The eight outputs from each port A,B and C are divided into two sets of four outputs, and each set is fed to a respective buffer amplifier, one of which is illustrated in Figure 8. The respective four microprocessor output signals are fed to the amplifier 33 over lines 34-37, and corresponding output signals of amplitude determined by the selected level of the 2 to 12 volt supply are fed out to the corresponding four segments over lines 38-41. The level of the 2-12 volt supply is set at that required to ensure proper operation of the LCD segments; too high a level will result in a permanently aligned state of the segments, while too low a level will result in inability of the segments to align. Once it is set during manufacture of the fire, no further adjustment of the voltage should be necessary.

The six buffer amplifiers provide a total of twenty-four signal lines. Eight of the lines are used for driving the large segments 18. As there are three sets of eight large segments, each large segment of each LCD has to be connected to a large segment of each of the other two LCDs. The segments to be interconnected are chosen at random, so that segments having corresponding positions in the three LCDs are not interconnected. This gives a more random appearance to the changes in light emitted from the translucent regions of the moulding.

Twelve of the lines are used for driving the small segments 17. Again, each segment 17 of each LCD is connected to a segment 17 of each of the other LCDs, and again they are interconnected in random manner, so that corresponding segments in the three LCDs do not operate simultaneously.

By use of the LCD segments which are switched on and off in a pseudo-random manner across the width of the fire (apart from the interconnection of the segments in groups of three mentioned above), a far more realistic flickering flame effect is achieved than that obtained by use of cyclic chopping of the light using a rotating fan.

Similarly, the relatively slow pseudo-random switching on and off of the large segments 18 provides a far more realistic appearance of the glowing coals than that achieved by the rotating fan.

An even more random effect could be achieved by driving every segment from an entirely separate microprocessor output, but this would greatly increase the complexity and cost of the electronics.

It would be possible to reduce the size of the segments and to provide more of them, again at increased cost. Alternatively, it would be possible to use LCD segments to provide only the improved flickering flame effect, while still using one or more rotors to provide the changing appearance of the coals. Two LCDs might be used, with a conventional rotor in the central region between them.

Smaller LCDs might be used, positioned closer to the lamps, provided that the LCDs do not thereby become overheated. It will be appreciated that the use of the above-described large LCDs allows modulation of all of the useful light from the lamps even though the LCDS are well spaced from the hot lamps.

It will be apparent that the imitation "coal" moulding could be replaced by a moulding representing logs. Alternatively, separate lumps of material representing coals might be used. Although the flickering flame effect device has been described in relation to an electric fire, clearly it could alternatively be used on any other suitable type of room heater, such as a gas fire or an oil heater, provided that a suitable electric power supply is available.

It has been found that a number of other improvements can be effected in both conventional imitation-fuel flickering flame effect heaters and those using the LCD device of the present invention.

Firstly, the use of orange or red lamps gives a warm glow, but other colours present in a real fire are missing from the imitation fuel and flames. An improvement can be effected by using lamps in which the usual orange or red varnish coating is interspersed with patches of,for example, blue and/or yellow colouring.

Coloured patches could alternatively be formed on the underside of the moulding. Alternatively, where LCDs are being used in accordance with the present invention, clear lamps could be used, with red or orange filter plates, together with yellow and/or blue filter plates, all positioned above the lamps. The colours might alternatively be provided by use of coloured films on the LCDs or by the use of coloured polarisers or by the use of variable birefringence effects in which the LCD and its polarisers are arranged in a configuration such that the LCD is optically equivalent in function to a birefringent plate, the birefringence of which is controlled by the applied voltage.In each case, it is preferable to position the blue patches or filters such that blue light is not transmitted through the translucent areas of the imitation fuel to an appreciable extent, because this gives an unrealistic appearance.

Another possible improvement might be effected by painting regions of the device, such as the moulding, with thermochromic liquid crystal materials or mixtures of such materials. Such materials have the property of selectively scattering light of a particular wavelength at a particular temperature. Hence, as the temperature of the material changes, for example during the warming up of the lamps on first switching the heater on, changing colours will be produced.

It has also been found that the appearance of the imitation fuel may be improved by providing some transparent refractive areas in the moulding filled, for example, with a wrinkled layer of epoxy resin. This creates brighter areas in the glowing "fuel". Such bright areas might additionally or alternatively be provided by incorporating light-guiding structures in the device.

Claims (28)

1. An imitation-fuel flame-effect device for a room heater, the device comprising fuel-representing means having opaque regions and translucent regions; light-producing means mounted beneath the fuel-representing means and operative, in use, to transmit light through said translucent regions and to illuminate at least part of a back panel of the heater to produce a representation of flames; a plurality of liquid crystal display (LCD) segments each operative in response to a control signal applied thereto to switch between a light-transmitting state and a light-impeding state in which, respectively, the segment transmits and impedes said back panel illuminating light; and means to apply a respective control signal to each segment to cause the segment to switch continually back and forth between said states, whereby the representation of flames is caused to flicker.

2. A device as claimed in Claim 1, including a second plurality of LCD segments operative in dependence upon control signals applied thereto to transmit or impede said light through the translucent regions of the fuel-representing means.

3. A device as claimed in Claim 2, wherein segments of said first plurality and segments of said second plurality are provided in a common LCD unit.

4. A device as claimed in Claim 3, including a number of said units together providing said first plurality of segments and said second plurality of segments.

5. A device as claimed in Claim 4, wherein segments of each unit are individually connected to like segments of each other unit, whereby the interconnected segments switch simultaneously.

6. A device as claimed in Claim 5, wherein the relative positions of interconnected segments in the units are selected substantially randomly.

7. A device as claimed in any one of Claims 2-6, wherein the control signals for said second plurality of LCD segments are operative to switch the segments relatively slowly between their impeding and transmitting states during each switching operation.

8. A device as claimed In any one of Claims 2-7, wherein the LCD segments of said second plurality are switched at a lower repetition rate than the LCD segments of said first plurality.

9. A device as claimed in Claim 1, wherein the segments of said first plurality are continually switched between their impeding and transmitting states independently of each other and with pseudo-random timing relative to each other.

10. A device as claimed in any one of Claims 2-9, wherein the segments of said second plurality are continually switched between their impeding and transmitting states independently of each other and with pseudo-random timing relative to each other.

11. A device as claimed in Claim 9 or Claim 10, wherein the switching of the segments is controlled by a microprocessor.

12. A device as claimed in any preceding claim, wherein said light-producing means comprises at least one lamp which produces red or orange light.

13. A device as claimed in any one of Claims 1-11, wherein said light-producing means comprises at least one lamp coloured to produce patches of red or orange light and patches of yellow and/or blue light.

14. A device as claimed in any one of Claims 1-11, wherein said light-producing means comprises at least one lamp and colour filter means.

15. A device as claimed in Claim 14, wherein the colour filter means produces red or orange light and yellow and/or blue light.

16. A device as claimed in any preceding claim, wherein portions of the fuel-representing means are coloured red and/or orange and/or yellow.

17. A device as claimed in ay preceding claim, wherein at least one portion of the device is coated with thermochromic liquid crystal material, whereby a colour change is produced in dependence upon the operating temperature of the coated portion.

18. A device as claimed in any one of Claims 1-11, wherein polarisers are provided in conjunction with the LCD segments, whereby light of a plurality of colours is provided for said transmission and illumination.

19. A device as claimed in any one of Claims 1-11 or Claim 18, wherein light of a plurality of colours is provided for said transmission and illumination by a variable birefringence effect.

20. A device as claimed in any preceding claim, wherein the fuel-representing means comprises a moulding representing coals or at least one log.

21. A device as claimed in Claim 20, wherein the moulding includes at least one transparent refractive region.

22. An imitation-fuel flame-effect device for a room heater, comprising fuel-representing means having opaque regions and translucent regions; at least one lamp mounted beneath the fuel-representing means; and at least one rotor rotatable by air convected from the or each lamp to impede and pass light alternately; wherein the or each lamp is coloured to produce patches of red or orange light and patches of yellow and/or blue light.

23. An imitation-fuel flame-effect device for a room heater, comprising fuel-representing means having opaque regions and translucent regions; at least one lamp mounted beneath the fuel-representing means; and at least one rotor rotatable by air convected from the or each lamp to impede and pass light alternately; wherein the or each lamp is colourless and filter means is provided to produce patches of red or orange light and patches of yellow and/or blue light.

24. An imitation-fuel flame-effect device for a room heater, comprising fuel-representing means having opaque regions and translucent regions; at least one lamp mounted beneath the fuel-representing means; and at least one rotor rotatable by air convected from the or each lamp to impede and pass light alternately; wherein the fuel-representing means comprises a moulding representing coals or at least one log; and wherein the moulding includes at least one transparent refractive region.

25. An imitation-fuel flame-effect device for a room heater, comprising fuel-representing means having opaque regions and translucent regions; at least one lamp mounted beneath the fuel-representing means; and at least one rotor rotatable by air convected from the or each lamp to impede and pass light alternately; wherein the fuel-representing means comprises a moulding representing coals or at least one log; and wherein regions of the moulding are coloured.

26. An imitation-fuel flame-effect device for a room heater, comprising fuel-representing means having opaque regions and translucent regions; at least one lamp mounted beneath the fuel-representing means; and at least one rotor rotatable by air convected from the or each lamp to impede and pass light alternately; wherein at least one region of the device is coated with a thermochromic liquid crystal material.

27. An imitation-fuel flame-effect device for a room heater, substantially as hereinbefore described with reference to Figures 3-8 of the accompanying drawings.

28. A room heater including a device as claimed in any preceding claim.