EP1348910A1

EP1348910A1 - Compact stove

Info

Publication number: EP1348910A1
Application number: EP02394036A
Authority: EP
Inventors: Derek. Butler; James. Kearney; Kilian. Seitz.; Gregory. Kelly; Regina. Corcoran; Garry. Tomlins; Maureen. Seitz
Original assignee: BS Manufacturing Ltd
Current assignee: BS Manufacturing Ltd
Priority date: 2002-03-28
Filing date: 2002-03-28
Publication date: 2003-10-01
Also published as: IE20020795A1

Abstract

A stove 1 for maintaining prepared food in a warm state hasa fuel reservoir 2 in the form of a plastics gas tank, a burner unit 4, a flow passage communicating between the fuel reservoir 2 and the burner unit 4; and a control switch for regulating flow of fuel from the fuel reservoir 2 to the burner unit. The burner unit 4 includes at least two catalytic elements. Heat transfer from the region of the burner unit 4 to the interior of the gas tank 2 is effected by way of a metallic member 12. A heat deflector 6 is located between the burner unit 4 and the fuel reservoir 2. The fuel reservoir 2 is a refillable gas tank of less than 250 ml capacity with a diameter substantially equal to the height of the stove 1. The fuel reservoir 2 is a two-part structure having a substantially cup-shaped body portion 2b and a closure portion 2a for co-operative sealing association with the body portion 2b. Interconnection of the closure portion 2b and body portion 2a is effected by screwing together or by a bayonet-type coupling action 36. The flow of gas is regulated by a rotary valve assembly controlled by displacement of the rotary switch 3 between end positions corresponding to full-flow and shut-off conditions.

Description

FIELD OF THE INVENTION

This invention relates to a stove, generally of the catalytic type and often also referred to as a chaffing stove or unit or a bamboree. Of particular interest are portable stoves of the type having a burner to which a compressed gas reservoir is directly attached - the burner being for combustion of the compressed gas. Of special interest is a stove of the type that is easily carried by hand.
Chaffing stoves are primarily used in the cooking areas of restaurants to keep food warm following preparation in the kitchen, before the cooked food is brought to diners. Catalytic stoves of the type to which the present invention is directed are not generally used in the actual dining area. Further uses of the catalytic stove of the invention include use for cooking during outside pursuits, such as hiking, mountaineering, camping, or fishing, as well as therapeutic use and a multiplicity of non-food related functions.

BACKGROUND OF THE INVENTION

The present invention relates to stoves generally and in particular those stoves of the type which burn gas fuel. Such stoves consist of two main parts - a reservoir which holds the gas fuel, and a burner unit which connects to the reservoir and serves for burning fuel from the reservoir. Stoves of this kind may be portable, for example for use as camping stoves or as chaffing stoves of the type for maintaining cooked food at a temperature suitable for serving for eating. Of particular interest are compact stoves of the type that are readily portable. Such stoves often have a burner which is directly attachable to a reservoir of gas. The burner and reservoir together form a self-supporting structure where the burner is arranged above the reservoir in the working orientation of the device. Normally such stoves do not require any additional support or equipment to stand upright and operate. In this respect, the stoves of the invention are distinguished from trolleys or tables and the like which may have one or more burners incorporated into a platform or some such other support for the material (normally food/water) to be heated.
There are many limitations associated with conventional stoves. Some suffer from the problem that the burner may easily be extinguished for example by a gust of wind etc. Other limitations include the fact that the vapour pressure in the gas reservoir can substantially fall off due to cooling when the gas expands from its compressed state. This may result in incomplete emptying of the reservoir or reduced amounts of gas being available for combustion. Also disadvantageous is the fact that the gas reservoir is often a disposable one - not designed for ease of re-filling/re-use. Blocking of the burner nozzle may occur due to deposits from heavier hydrocarbons in the gas fuel, while there may be also an inability to regulate the temperature produced by the burner to a desirable extent - in particular to maintain relatively low temperatures such as about 100°C. Further limitations that can occur include the undesirable transmission of heat to parts of the stove proximate the burner, so that for example materials which have high resistance to heat have to be employed.
US patent no. 4,899,722 (Horewitch) describes a burner assembly for use with a chafing dish of the type supported by legs. The burner is inserted under the chafing dish, which is a large platform supported on legs and covered with a cooking cover or lid. The burner is described as having a unique support structure with a fuel source coupled to the burner head by conduit means of sufficient length to position the fuel source beside the chafing dish.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a stove for maintaining prepared food in a warm state, comprising:
(a) a fuel reservoir,
(b) a burner unit,
(c) flow means communicating between the fuel reservoir and the burner unit; and
(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit

The stove according to the invention may comprise a multiplicity of catalytic elements arranged one after the other in the direction of gas flow. Suitably, at least one of said catalytic elements has a greater diameter than the diameter of the element immediately preceding it in the direction of gas flow. The burner unit may have a stepped cross-section, each step serving to accommodate a catalytic element and at least step being of greater diameter than the diameter of the step immediately preceding it in the direction of gas flow. In a stove according to the invention, the fuel reservoir is preferably a gas tank, and means are provided for transferring heat from the region of the burner unit to the interior of the gas tank.
In a second aspect, the invention is directed to a stove for maintaining prepared food in a warm state, comprising:
(a) a fuel reservoir,
(b) a burner unit,
(c) flow means communicating between the fuel reservoir and the burner unit; and
(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

At least the burner unit and the flow means are suitably made of metal and a metallic heat transfer element located in the interior of the gas tank is in heat transfer relationship with the flow means. The flow means preferably includes a valve assembly and the heat transfer element may comprise a spring-like member associated with an end region of the valve assembly extending into the interior of the gas tank. Heat deflector means are suitably located between the burner unit and the fuel reservoir.
In a third aspect, a stove for maintaining prepared food in a warm state according to the invention comprises:
(a) a fuel reservoir,
(b) a burner unit,
(c) flow means communicating between the fuel reservoir and the burner unit; and
(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

The heat deflector means may comprise a substantially annular member substantially surrounding the flow means, while the fuel reservoir may be a refillable gas tank of less than 250 ml capacity.
In a fourth aspect of the invention, a stove for maintaining prepared food in a warm state comprises:
(a) a fuel reservoir,
(b) a burner unit,
(c) flow means communicating between the fuel reservoir and the burner unit; and
(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

In a particular embodiment, the fuel reservoir has a capacity of between 100 ml and 250 ml. The diameter of the tank is suitably substantially equal to the height of the stove.
A fifth aspect of the invention provides a stove for maintaining prepared food in a warm state, comprising:
(a) a fuel reservoir,
(b) a burner unit,
(c) flow means communicating between the fuel reservoir and the burner unit; and
(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

The largest dimension of the tank is preferably less than 120mm.
In any aspect of the invention, the fuel reservoir preferably comprises a plastics material. Suitably, the fuel reservoir comprises a two-part structure consisting of a substantially cup-shaped body portion and a closure portion for co-operative sealing association with the body portion. Interconnection of the closure portion and body portion of the fuel reservoir may be effected by screwing together, or alternatively by a bayonet-type coupling action. The closure portion may define a base region of the fuel reservoir, or alternatively a top region of the fuel reservoir.
Preferably, at least the flow means incorporates heat exchange features, which may be external cooling fins. Further, the flow means suitably comprises a rotary valve assembly, while the control means may includes a rotary switch for displacement between end positions corresponding to full-flow and shut-off conditions, the control means also optionally enabling adjustment of the rate of release of fuel from the reservoir. Filter means may also be disposed in the flow path for fuel from the reservoir to the burner unit.
There is thus provided by the invention, a catalytic stove which is especially cost-effective, both in respect of manufacture, by virtue of its simple construction and use of low-cost materials, and also in respect of use, because of its employment of a gaseous fuel and the controllability of heat delivery resulting from this. The unit of the invention incorporates a control feature by which the heat generation can be accurately regulated to match the requirements at any particular time.
The stove of the invention overcomes many of the drawbacks of conventional stoves by including one or more of the following features:
a re-usable reservoir for the gas fuel - the reservoir can easily be refilled and reused;
a nozzle arrangement that is less prone to blockage by heavy hydrocarbons;
a heat transmitter for transmitting heat to the gas to compensate for lowering temperature due to expansion of the gas, thus at least partially rectifying any drop in the vapour pressure of the gas that might otherwise occur;
an easily controlled temperature output;
a simply constructed yet versatile stove which may be constructed of
inexpensive yet durable materials.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will now be described having regard to the accompanying drawings in which:
Figure 1 shows a pictorial representation of a stove unit according to a first embodiment of the invention,
Figure 2 is a cross-sectional view of the stove of Figure 1,
Figure 3 is an exploded view of the stove of Figure 1,
Figure 4 shows a pictorial representation of a stove unit according to an alternative embodiment of the invention,
Figure 5 is a cross-sectional view of the stove unit of Figure 4
Figure 6 shows a cross-sectional view of a further embodiment of a stove according to the invention,
Figure 7 shows a perspective view of the stove of Figure 6,
Figure 8 shows a perspective view of a nozzle for use with a stove of the present invention,
Figure 9 shows a cross-sectional view of the nozzle of Figure 8,
Figure 10 shows a perspective view of a nozzle connector for use with a stove of the present invention and in particular the nozzle of Figure 8,
Figure 11 shows a cross-sectional view of the nozzle connector of Figure 10,
Figure 12 shows a perspective view of a fill valve assembly for use with a stove of the present invention,
Figure 13 shows a cross-sectional view of the fill valve assembly of Figure 12,
Figure 14 shows in cross-section a preferred embodiment of stove in accordance with the invention, and
Figure 15 is a perspective view of the stove of Figure 14.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown in the Figures 1 to 5 a stove 1, 101 preferably of the catalytic stove type, according to certain embodiments of the invention, has a catalyst head or burner unit 4, 104 in which heat is developed by combustion of a gaseous fuel, and the burner unit 4, 104 is connected to a fuel storage tank 2, 102 by way of a valve assembly 8, 108 provided with a control feature or switch 3, 103 for turning the stove 1, 101 on and off, and, in certain end-uses of the stove, regulating gas flow during use. The burner unit 4, 104 is mounted directly on the reservoir and in particular is rigidly attached thereto by a rigid assembly 8,108. The mounting of the burner 4,104 directly on the reservoir allows for a very compact arrangement of the stove of the invention. Furthermore the rigid assembly imparts a self-supporting nature to the stove with the base 30,130 of the reservoir acting as a stand for the entire unit.
In the present embodiments, the burner head or unit 4, 104 operates substantially in accordance with catalytic principles, but nonetheless incorporates a number of innovative technical features directed to the specific objective of achieving a relatively low cost of production. The burner 4,104 comprises a venturi nozzle 17,117. The nozzle 17,117 is self-cleaning in a manner which will be described in more detail below. The burner 4,104 operates in catalytic manner by employing catalytic material 16a and 16b, or 116a, 116b and 116c respectively. The catalytic material 16a and 16b, or 116a, 116b and 116c ensures that the flame, once ignited, will not extinguish, even under windy conditions, as the catalytic material will cause the gas to re-ignite immediately the flame is extinguished by a gust of wind or such like.
The burner unit 4, 104 can only be turned off (the flame may be extinguished), following ignition, by termination of gas flow to catalytic elements 16a and 16b, or 116a, 116b and 116c.
In one embodiment of the invention, the burner 4, 104 has a stepped construction, each step holding an individual catalyst disc 16a, 16b of equal diameter. The burner 4, 104 of the invention preferably has a minimum of two steps in its nozzle 17,117, but as many as five steps may be provided. The provision of multiple steps is to provide for expansion of the gas flow. The increasing step size is in the direction of flow of the gas through the nozzle 17,117. It is a further feature of the invention that the burner 4, 104 can be removed from the valve assembly 8,108 in one piece by virtue of, for example, a screw connection to the valve assembly 8,108.
The temperature of the catalytic elements is controllable within a temperature range of between 100°C and 1300°C. The catalyst may emit primarily infra-red radiation for example in the temperature range of 100°C to 700°C. The stove can thus be used as a source of infra-red radiation, for example for use in therapies such as therapeutic healing.
A cylindrical jet 15,115 is positioned within the burner 4, 104, beneath the catalytic discs 16a, 16b, or 116a, 116b, 116c. The jet or conduit provides a pathway for flow of gas from the tank or reservoir to the burner 4, 104.
In the embodiment of Figures 1-3 , a deflector in the form of a flat annular deflector disc 6 is positioned horizontally externally of head 4 and below the burner 4. The disc acts to deflect heat from the tank or reservoir 2, for example to prevent radiant heat emanating from the burner head 4, or any food-containing vessel supported on the head 4, from heating the top 31 of the tank 2. The top of the tank 2 houses, in the present embodiment, a switch or control feature 3 substantially coextensive in area with the tank top surface 31. The deflector 6 ensures that the top 31 of the tank 2 and the switch arrangement 3 overlying it does not overheat. The efficiency of the catalytic stove 1 is also improved, by re-radiating the radiant heat from a chafing dish or other food vessel back to the dish or vessel. The deflector disc 6 is usually between 60 mm and 100 mm in diameter. A suitable material for the deflector disc 6 is a heat reflecting material, such as (a reflective) metal. Disc 6 thus has dual functionality, acting as a heat shield to protect the gas container, and also as a deflector, for returning radiant heat towards the burner and food container.
In the embodiment of Figures 1 to 3, the burner 4 and deflector 6 arrangement are fixedly attached to each other and are together releasably attached to a substantially standard gas valve 8. In the embodiment of Figures 4-5, no deflector 6 is provided, but otherwise the arrangement is generally similar, having the burner 104 and the valve 108. Within the valve 8,108, a fixed flow nozzle 17,117 is provided, resulting in an economical and cheap construction. The nozzle 17,117 is a venturi type. The nozzle 17,117 also contains a replaceable filter 18,118. The nozzle of venturi construction is designed so as to be self-cleaning. A major problem with many conventional nozzle types is that they have a tendency to block with dust. This may happen due to heavier hydrocarbon impurities in the gas collecting about the orifice of the nozzle due to their generally lower expulsion velocity from the nozzle. These hydrocarbon deposits can attract dust and other particles and may eventually block the nozzle orifice. One particular method of avoiding such blockage is to adopt the nozzle arrangement shown in the present invention where the expanding fuel flow path (stepped in the embodiments shown) allows the heavier hydrocarbons to fall away form the orifice of the nozzle.
The entire nozzle 17,117, valve 8,108 and burner 4,104 assembly can be readily taken apart for servicing and/or replacement of the filter 18,118 and any other component as may be required. The valve 8,108 is provided with lateral heat dissipating fins 19,119 about its upper cylindrical portion 8a, 108a which extends upwardly toward the top of the burner 4,104. A second set of larger more spaced apart fins 20,120 are provided closer to the top end 32,132 of the burner. The heat dissipating fins, in particular the set 20,120 on the burner head, contribute in an innovative manner to the successful performance of the stove of the invention. The lower portion 8b, 108b of the valve assembly 8,108 is mounted in the upper part of the fuel storage tank 2,102 and is hidden from external view, as will be apparent from the Figures, for example Figures 1 and 2.
It will be appreciated that the top end 32,132 of the nozzle of the burner unit acts as a stand, seat or support on which an item to be heated may be placed - for example a kettle or heating dish or tray.
The flow of fuel from the tank 2, 102 to the burner 4, 104, is controlled by relative rotation of the burner 4, 104, and the tank 2, 102. For example, in the embodiment shown in Figures 1 to 5, the entire upper end of the burner structure, namely the upper valve portion 8a and burner head 4, may be rotated through 270°, to switch the flow on and off and to control or regulate the flow rate of the fuel. The switch is thus displaceable between respective end positions. This rotary movement is accomplished by an external switch portion 3, 103 of the tank 2, 102, mounted to surround the valve assembly 8, 108 a short distance below the heat dissipating fins 19, 119.
In particular, the switch portion 3, 103 engages around the external periphery of the valve assembly 8, 108, such as by way of splines, so that rotation of the switch effects corresponding rotation of the valve. Rotation of the valve controls the flow rate of gas through the valve and thus from the tank 2, 102 to the burner. Suitably, the switch 3 is disc shaped with a downwardly extending peripheral skirt 22, the disc portion of the switch having a diameter approximately equal to that of the tank 2. The downwardly extending peripheral skirt 22 is substantially coaxial with a cylindrical outer wall 33 of the gas tank 2. The switch portion 3 overlies the upper surface 34 of the fuel tank 2, which is not normally visible to the user. The peripheral skirt region 22 is provided with raised radially projecting vertical grips or ribs 23 for ease of gripping for manual turning. End stops 24 to limit the rotational displacement of the control disc 3 are provided on the underside of the switch portion 3 for co-operation with upstanding projections or lugs 25 extending from the upper portion or top surface 34 of the tank 2. These technical features of the switch 3 are hidden from external view in the assembled structure as seen in Figure 1. A retaining nut 5 is provided to secure the switch portion 3 on the valve 8.
The switch arrangement 3 described enables close and accurate regulation of the supply of fuel from the tank 2 of the unit to the burner head 4 and thereby facilitates adjustment of the heat release from the stove 1 to the items to be heated. In this way, not only is economy in usage of fuel achieved, but in chaffing use, the degree of heating applied to the food to be kept warm can be matched exactly to requirements, so that the correct temperature is maintained, but there is minimal continuing cooking of the prepared dishes. Thus excellent chaffing performance is provided by the unit 1 of the invention.
The entire valve 8, 108 and burner 4, 104 assembly structure is screw threadingly connected to a mounting arrangement in an upper portion of a fuel storage portion of the apparatus, i.e. the tank 2, 102. This detachable feature of the assembly allows for compact storage of the stove 1, 101, in particular during hiking, camping etc. The tank 2, 102 contains a gas supply for providing the requisite heat output by combustion of the gas in the vicinity of the catalyst discs 16a and 16b, or 116a, b and c. The gas is held in liquid form in the tank 2, 102.
The main body of the tank 2 according to the embodiment of the invention shown in Figures 1-3 is of a two part construction 2a, 2b. A plastic cup-shaped portion 2a with a concave base forms the base and sides of the tank, closed off at its upper end by an upper closure portion 2b which is screwed into the main body or cup-shaped lower portion 2a of the tank 2. Top portion 2b is defined by a dished or concave generally disc-shaped part with an integral downwardly-depending skirt, which extends into the cup-shaped base 2a in the assembled condition of the gas tank. The screwing-in takes place by way of a deep cut thread 26 provided on the downward peripheral skirt of closure portion 2b, which thread is resistant to any pressure exerted by the liquid gas within the tank 2. Sealing between the two portions is completed by a sealing ring 11 held in a recess on the periphery of the downwardly-directed skirt of the upper closure portion 2b near its lower edge. The top surface of the upper closure portion 2b is, as already noted, concave. The centre of the concavity is provided with an aperture to furnish the mounting arrangement into which the valve assembly 8 fits and in which it is secured by a nut 9. The nut 9 further comprises an annular receiving portion or lip at its base, onto which a heat transmitter such as a spring may be attached, as will be described below.
The lower portion 8b of the valve assembly 8 extends through the mounting arrangement into the interior of the tank 2. A hole is provided horizontally through the lower end of the valve, through which a cylindrical wick 13 is fed. Inside the tank 2, this lower portion 8b of the valve is surrounded by a bell-shaped heat spring 12, the top of which is associated with the body of the tank and the valve assembly 8 by means of the receiving portion of the nut 9. The heat spring 12 defines a conductive feedback system which returns heat from the burner and valve assembly back into the heat tank 2. As the gas boils off, it cools. The conductive feedback system keeps the gas reservoir at temperatures around 20°C, thus helping the gas to maintain its vapour pressure.
The design of the individual parts of the stove according to this first embodiment of the invention allows for ease of assembly as described below.
The pre-assembled gas valve 8 is lowered into the central aperture of the upper closure portion of the tank and is secured at its base by the nut 9. The heat spring may then be attached to the nut/valve assembly. The wick 13 is fed through its corresponding hole at the base of the valve 8, and the assembled upper closure portion 2b of the tank is subsequently screwed into the lower cup-shaped portion 2a of the tank. The switch portion 3, followed by the valve nut, is lowered over the upper part of the valve which is now extending from the top of the tank 2. The switch comes to rest on the top surface of the tank. Tightening of the nut secures the switch to the valve. Finally, the burner and deflector arrangement is attached to the top of the valve. The assembled stove is now ready for filling before operating.
Figures 4 and 5 show a second embodiment 101 of the stove according to the invention. In this second embodiment, as shown in Figure 5 in particular, the stepped construction of the burner head 104 again narrows or tapers in a downward direction (in the opposing direction to the direction of flow of the gas), with each step holding an individual catalyst disc 116a, 116b, 116c. As shown in Figure 5, the burner head 104 has three steps and is provided with three catalytic discs 116a, 116b, 116c, each of increasingly greater diameter in the upward or ascending direction. The burner unit 104 of the invention preferably has a minimum of two steps, but as many as five steps may be provided. The provision of multiple steps with a widening or tapering outflow region in the upward direction is to provide for expansion of the gas flow. (Expansion occurs in the direction of flow). It is a further feature of the invention that this catalytic head 104 can be removed from the valve 108 in one piece by virtue of, for example, a screw connection to the valve 108.
Moving downward from the burner head 104, the feed tube or valve 108 is provided with lateral heat dissipating fins 119, as also is the lower region of the burner head 104 itself. The burner head fins are designated by reference 120. The use of the heat dissipating fins 119, 120 in both sections contributes in an innovative manner to the successful performance of the unit 101 according to the invention.
Within the valve 108, a fixed flow nozzle 117 is provided, resulting in an economical and cheap construction. The valve region of the unit also contains a replaceable filter 118. The entire nozzle 117, valve 108 and catalyst head 104 assembly can be readily taken apart for servicing and/or replacement of the filter 118 and any other component as may be required. In particular, the lower end 108b of the valve is screw threadingly connected to a mounting arrangement fitted into the top of the tank 102 and adapted to secure and accommodate the nozzle portion 117 and the filter 118.
In order to control the flow of fuel from the tank 102 to the burner 104, the entire upper end of the burner structure, namely the valve 108 and burner head 104, may be rotated through 180° between end positions, to switch the flow on and off. This rotary movement is accomplished by an external adjustment knob 103 mounted to surround the lower end 108b of the valve 108 and engaging on the external periphery of the valve by way of splines or longitudinal protrusions 121. Referring again to Figure 4, a radially extending lug or tab 128 provides for displacement of the knob between the open and closed positions by manual engagement. End stops (not shown) to limit the rotational displacement are provided within the adjustment knob structure 103 for co-operation with at least one upstanding projection or lug 125 between the switch 103 and body of the tank 102. Suitably the switch 103 is of disc shape with a downwardly extending peripheral skirt 122, within which the other technical features of the knob arrangement are hidden from external view in the assembled structure as seen in Figure 4. The diameter of the switch 103 is approximately half that of the fuel tank 102.
This alternative embodiment does not feature the heat shield or deflector of the construction first described. The control switch arrangement is of lesser diameter than that of the gas tank and requires therefore a lesser degree of shielding than does the larger switch of the first embodiment.
The main body of the tank 102 consists of an inverted cup-shaped portion 102a, closed off at its lower end by a closure portion 102b which is screwed into the main body or inverted cup part 102a of the tank. The screwing in takes place by way of a deep cut thread 126, which is resistant to any pressure exerted by the liquid gas within the tank 102. Sealing is further guaranteed by an O-ring or similar seal accommodated in a peripheral groove provided in the threaded annular skirt portion of closure 102b, which skirt portion carries the screw thread 126. At ambient pressure, the contents of the tank 102 in liquid form in fact exert a pressure of no greater then 4-6 bar, but because of the relatively large quantity of fuel held within the tank 102, the consequences of any inadvertent leakage or fracture of the tank 102 are nonetheless potentially hazardous, possibly explosive. Hence the necessity for the tank 102 to possess appropriate strength and to be substantially leak-proof.
The particular shapes of the tank 2, 102 represented in Figures 1 to 5 is not definitive. In alternative embodiments, a dome shaped upper surface may be provided.
In any embodiment of the invention, in order to provide an economical and visually attractive construction, the tank for the liquid gas is made from a plastics material. The capacity of the unit as represented in the drawings is substantially 160 ml. A preferred diameter for the tank is 95 mm and the overall height of the entire unit, from the base of the tank to the top of the burner, is also suitably 95 mm.
A particular novel feature of the container or tank of the unit of the invention is that it is refillable through a fill valve 7, 107 at the base of the tank 2,102 which is believed not to have been hitherto provided in a container of the relatively large dimensions or proportions applied in the present instance. This refillable capability can be effected using standard butane or propane containers, each such standard container of capacity 300 ml providing approximately two refills for the tank of the unit of the invention.
The liquefied gas used is preferably butane or a propane/butane mix ratio of 30:70 to 1:100. A particular statutory requirement for the pressure resistance of propane/butane containers is 20 bar. The designs of tank provided in conjunction with the present invention are expected to be pressure resistant up to 50 to 60 bar.
In order to achieve this strength, the material of the tank is suitably a particularly tough plastics material, for example a glass-filled nylon. Alternatively, nylon may be used on its own, with no glass-filling. Typical wall thickness is 4 mm to 5 mm, and the range of wall thickness is normally at least 3 mm to 6 mm. In general, it is anticipated that the minimum wall thickness will not be less than 3 mm, while the maximum wall thickness is unlikely to require to be greater than 6 mm. Above 6 mm, the balance between economy and strength becomes less favourable.
The structure of the tank as described herein is resistant to any pressure exerted by the liquid gas within the tank. At ambient pressure, the contents of the tank in liquid form in fact exert a pressure of no greater then 4-6 bar, but because of the relatively large quantity of fuel held within the tank, the consequences of any inadvertent leakage or fracture of the tank are nonetheless potentially hazardous, possibly explosive. Hence the necessity for the tank to possess appropriate strength and to be substantially leak-proof. The tank may be finished in a choice of colours, or alternatively, the finished unit may be coated in a shiny metallic material or otherwise metallised.
Figures 6 and 7 show a third embodiment of the invention, this being of generally similar construction to that of Figures 1 to 3. The same reference numerals are applied in the drawings as for Figures 1-3.
A nozzle assembly for use with the present invention is shown in Figures 8 and 9. The nozzle assembly is generally designated 40 and is shown in perspective view in Figure 8. A cross-sectional view is shown in Figure 9. The nozzle assembly is shown without the catalytic head. The main parts of the assembly are a body portion 41, having a cavity 42 defined therein. In the cavity 42 is housed a holder 43. The holder 43 has two main functions, namely first of all to hold a sintered filter 44 which filters the gas coming through the nozzle assembly, and secondly to hold a domed piece 45. Dome 45 in turn has defined therein an orifice through which the gas passes. This orifice acts as the jet through which the gas is burned. An 0-ring 46 is provided so that the nozzle is sealing engageable in the structure of the burner. The dome shape provides for clean burning of the gas fuel as deposits are less likely to collect about the orifice. The remainder of the assembly includes fins 47 on the body and a head 48 for accommodation of the catalytic element(s).
Figures 10 and 11 show a connector piece 60 for connecting the nozzle assembly of Figures 8 and 9 to the tank 2. When in place, the connector piece 60 is seated between the upper portion 2b, 102b of the tank 2, 102 and the switch portion 3, 103. The connector piece 60 has two main body parts - a first upper part 61 for engagement with the switch portion 3, 103 and a second lower part 62 which engages with the upper part 2b, 102b of the tank 2, 102. The arrangement of the connector piece 60 within the burner structure is best seen for example from Figure 2. The parts 61 and 62 are rotatable relative to each other to open and close gas flow. There is sealing between parts 61 and 62 by an O-ring 64 disposed between internal surfaces 65 of the connector. Internal 0- rings 65, 67 are provided in grooves along the periphery of the part 61 to provide sealing between the outer surface of part 61 and the internal surface of part 62.
The connector piece 60 includes an external O-ring seal 63 for sealing placement of the connector within the overall assembly. The serrated or keyed rim engages within the top part 2a, 102a of the tank. An adjuster 68 is also provided in the gas flow path.
Figures 12 and 13 show a fill valve assembly 70 in more detail. The fill valve is generally indicated by the reference numeral 7,107 in earlier figures and is depicted in most detail in Figure 6. The valve comprises a housing 71 and valve spool 73 displaceable against a compression spring 76. An internal O-ring 75 provides internal sealing and external O-rings 74 provide sealing between the fill valve assembly and valve-receiving portion of the tank 2, 102. An external serrated portion 71 enables retention of the valve portion within the tank base.
Referring now to the embodiment of Figures 13 and 15, this is generally similar to that of Figures 6 and 7 in having a substantially pot-shaped lower tank body portion 2b closed at its upper periphery by a tank lid or cover portion 2a. Those features of these drawings which are the same as those of earlier figures are indicated by the same reference numerals. The principal differences reside in the tank top 2a being connected to the tank body 2b by a bayonet fitting 36 rather than the screw thread 26 previously described, and the provision of an overall top cover 37, to enclose the burner region during transport or storage. The top cover 37 is arranged to snap down onto the tank portion perimeter over the control switch 3. The bayonet assembly 36 is most suitably one-way, i.e. once the tank top 2a and body or base 2b have been assembled by a relative twisting movement, they cannot readily be separated again. Reverse movement of the bayonet arrangement is inhibited to preclude reopening the tank in this manner.

Claims

A stove for maintaining prepared food in a warm state, comprising:

(a) a fuel reservoir,

(b) a burner unit,

(c) flow means communicating between the fuel reservoir and the burner unit; and

(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit

wherein
the burner unit includes at least two catalytic elements.
A stove for maintaining prepared food in a warm state, comprising:

(a) a fuel reservoir,

(b) a burner unit,

(c) flow means communicating between the fuel reservoir and the burner unit; and

(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

wherein
the fuel reservoir is a gas tank, and
means are provided for transferring heat from the region of the burner unit to the interior of the gas tank.
A stove for maintaining prepared food in a warm state, comprising:

(a) a fuel reservoir,

(b) a burner unit,

(c) flow means communicating between the fuel reservoir and the burner unit; and

(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

wherein
heat deflector means are located between the burner unit and the fuel reservoir.
A stove for maintaining prepared food in a warm state, comprising:

(a) a fuel reservoir,

(b) a burner unit,

(c) flow means communicating between the fuel reservoir and the burner unit; and

(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

wherein
the fuel reservoir is a refillable gas tank of less than 250 ml capacity.
A stove for maintaining prepared food in a warm state, comprising:

(a) a fuel reservoir,

(b) a burner unit,

(c) flow means communicating between the fuel reservoir and the burner unit; and

(d) control means for regulating flow of fuel from the fuel reservoir to the burner unit,

wherein
the diameter of the tank is substantially equal to the height of the stove.
A stove according to any preceding claim, wherein the fuel reservoir comprises a plastics material.
A stove according to Claim 6, wherein the fuel reservoir comprises a two-part structure consisting of a substantially cup-shaped body portion and a closure portion for co-operative sealing association with the body portion.
A stove according to Claim 7, wherein interconnection of the closure portion and body portion of the fuel reservoir is effected by screwing together or by a bayonet-type coupling action.
A stove according to any preceding claim, wherein at least the flow means incorporates heat exchange features.
A stove according to any preceding claim, wherein the flow means comprises a rotary valve assembly and the control means includes a rotary switch for displacement between end positions corresponding to full-flow and shut-off conditions.