GB2213742A - Heater - Google Patents

Abstract

A cordless plate warmer comprises a housing having upper and lower sections (2, 3) supporting a hot plate surface (1). Located within the housing is a transparent fuel cylinder (5), a catalytic heater and an ignitor (22). The catalytic heater includes a layer of fibre (16) impregnated with a catalyst and through which a mixture of fuel and air are caused to permeate. The mixture burns without a flame when ignited by the ignitor. The lower section (3) of the housing has an array of vents to allow air to pass into the housing for mixture with the fuel and to allow exhaust gases to be discharged from the chamber. The lower section has a slot (41) through which the quantity of fuel remaining in the cylinder (5) can be viewed. The heater is totally portable and is not encumbered by lead wires and the like used in conventional electrical plate warmers. <IMAGE>

Description

HEATERS The present invention relates to heaters and in particular to cordless heaters.

Known hot trays or plates in the form of plate warmers are used to keep food warm on the dining table. Such known plate warmers are generally electrically heated and thus A.C. mains electricity is required either before and/or during use. The electricity is supplied to the plate warmer through a cable coupled to an A.C. electrical supply outlet.

Therefore it, cannot be truly portable.

Electrically heated plate warmers are generally divided into two main groups. The first group is of the type that incorporates an electrically resistive means of heating coupled to an on/off thermostat. This type must, during its entire operation, be connected to A.C. mains. The cable that connects the plate warmer to the A.C. mains may be accidentally tripped over, pulled or yanked, thereby damaging not only the plate warmer but also may cause injuries to persons around the plate warmer by the scattering of hot food from the plate warmer.

The second group is of the type that stores the heat generated by a built-in electrically resistive element. Such plate warmers whilst being partially portable have the disadvantage of having to be "charged with heat" prior to use, for a given time until a working temperature is reached. To use, the cable connecting the plate warmer and A.C. mains is usually removed. Due to heat dissipation, the temperature of the plate warmer will decrease rather rapidly and eventually return to ambient temperature The nature of the material used for heat storage usually tends to be quite dense and therefore the plate warmers tend to be relatively heavy.

It is an object of the invention to provide an improved heater.

According to the present invention there is provided a heater comprising a housing defining a heat transfer surface and enclosing a catalytic heater.

A plate warmer embodying the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is an exploded view of the plate warmer; Figure 2 is a longitudinal section through a valve of the warmer of Figure 1; and Figure 3 is a fragmentary section to an enlarged scale of the plate warmer of Figure 1.

A cordless plate warmer shown in Figure 1 includes a two part housing carrying a heat transfer surface 1 of ceramic material. Instead of ceramic material any other heat conductive material for example, aluminium, steel, glass or plastics may be used. The two part housing includes a top housing 2 of plastics material. The top housing is supported on a bottom housing 3 of similar or dissimilar material. The bottom housing 3 has an array of holes and/or slots arranged in such a way and at different levels in order to allow the free inflow of air into the housing and the unhindered discharge of burned gases. Any turbulence caused by the crossing over or the intermingling of air and the burned gases is kept to minimal level.

The bottom housing 3 includes a dry cell battery compartment 40. A battery cover is provided to retain a battery in the battery compartment by means of a screw 28. The housing defines a compartment which accommodates a fuel container 5 which is preferably of translucent material for example clear plastics but which may also be of metal. The quantity of liquefied pertoleum gas (LPG) in the fuel container 5 is visible via slot 41 in the bottom housing 3. A re-filling valve 6 is coupled to one end of the fuel container 5 to allow the container 5 to be recharged with liquefied petroleum gas in its liquid state. Liquefied petroleum gas is kept in liquid form in this fuel container.

The re-filling valve (being-a one-way valve) is shown in more detail in Figure 3. The valve contains various component parts 140, 141, 142, 143, 144, 145 and 146 and is designed in such a way that it will allow liquefied petroleum gas to pass one way, namely into the cylinder whether in its liquid state or vaporized gas state, irrespective of the vapour pressure inside the fuel container 5.

When the switch 7 of Figure 1 is turned ON liquefied petroleum gas is released through the various components parts 8, 9, 10 and finally 11 of the outlet valve.

The detailed components parts of 11 of Figure 1 is shown in Figure 3 and designated as 89, 90, 91, 92, 93, 94, 95 and 96, have been designed, manufactured and adjusted in such a way that only a certain designated amount of gas is allowed to pass through in a given time. The amount of gas flow can be adjusted.

The released petroleum gas usually in its gaseous state is allowed to be mixed with air by "venturi tube principle" in the ratio of about 8 parts of air to 1 part of gas fuel, into a conduit tube 12 of Figure 1 made of steel or the like.

The conduit tube 12 feeds the air and fuel mixure to a burner assembly. The burner assembly comprises a base cover 13, ceiling cover 14, a central support ring 15, a layer of fibrous material 16 impregnated with a catalyst or a mixture of catalysts, a hold-down outer ring 17, and a set of hold-down screws 18. The covers 13 and 14 and the support and outer rings 15 and 17 may be of mica, plastics or of metal. The tube 12 is held in postion by a clamp 19 and a screw 20.

The ceiling cover 4 contains holes, which are so designed (by size and disposition) to ensure an even flow of gas from the chamber formed by base cover 13 and ceiling cover 14 through the fibrous material 16.

A heat insulation shield 21 is located spaced below the base cover 13 leaving an air gap of about 5 mm there between. A similar air gap is provided between base cover 13 and bottom housing 3, in order to protect against possible overheating of the bottom housing 3 by the burner assembly.

Fixed onto the hold down outer ring 17 of the burner is an electrical ignition device 22 for example of tungsten, connected to the battery box via cables 23 a switch P.C.3. board 24, a contact 25, a contact screw 26 and a pair of battery terminals 27.

The switch assembly includes an unlocking button 29 connected via a pin 30 with a return spring 31 attached. The pin 30 passes through the switch 7 and the switch control plate 32 and is held in position by a holding ring 33 and and a fixed ring 34.

The switch control plate 32 is secured to the bottom housing 3 by screw 35, the switch 7 with its associated unlocking button 29 slides on its surface, and is pulled constantly by a spring 36 secured at one end by a screw 37.

Contact 25 is fastened to the switch 7 by screw 26.

The switch P.C.B. board 24 is secured to the switch control plate 32.

In operation when the switch 7 is turned ON it pushes the metal lever 39 and thus opens the outlet valve 11 allowing liquefied pertoleum gas to flow out of the fuel tank 5 at a predetermined rate.

At the same time the contact 25 slides over the switch P.C.B. board 24, and via the various circuits on the switch P.C.B. board 24 connects the battery electrical source to the circuit. This action momentarily turns the electrical ignition device 22 ON and at the same time turns the L.E.D.

indicator ON. The ignition device triggers combustion of the fuel as it passes through the layer of catalyst impregnated fibrous material. The combustion of the fuel occurs without producing a flame i.e. it works on the "flameless cataylst heating principle". When the switch 7 is turned OFF the valve is closed and the heating ceases. Plates placed on the heating transfer surface 1 are in this way kept warm.

It will be appreciated that the plate warmer described is truly cordless, totally portable, can be used indoors or outdoors and A.C. mains electricity is not required before, during or after use. The plate warmer employs the "catalytic heating principle" that converts energy directly into heat without passing through the flame stage. A self contained fuel container is incorporated into the plate warmer and ignition is by a battery operated device embedded in the catalytic material.

Claims (12)

1. A heater comprising a housing defining a heat transfer surface and enclosing a catalytic heater.

2. A heater according to Claim 1 including a fuel container incorporated in said housing.

3. A heater according to Claim 2 including mixing means for mixing any fuel released from the fuel container with air, a distribution chamber for receiving the mixture of fuel and air and a fibre mesh carrying a catalyst supported by the distribution chamber so that the fuel and air mixture from the distribution chamber can permeate therethrough.

4. A heater according to Claim 1 or to Claim 2 including electrically operable ignition means for igniting the fuel and air mixture as it passes through the fibre mesh.

5. A heater according to any preceding claim wherein said heat transfer surface comprises a ceramic material.

6. A heater according to any preceding claim wherein the housing is defined by upper and lower sections and wherein the lower section is provided with an array of openings to provide for the inflow of air to feed the catalytic heater and to provide for the dischagre of exhaust gases from said catalytic heater.

7. A heater according to Claim 6 as dependent upon Claim 2 wherein the fuel container is transparent or translucent and wherein the lower section of the housing includes a slot through which the quantity of fuel remaining in the container can be viewed.

8. A heater according to any preceding claim including an indicator for indicating when the heater is being supplied with fuel.

9. A heater according to Claim 8 wherein said indicator comprises a light emitting diode.

10. A heater according to any preceding claim wherein said catalytic heater produces flameless combustion.

11. A heater substantially as hereinbefore described with reference to the accompanying drawings.

12. A plate warmer including a heater according to any preceding claim.