HK1015287B - Device for dispensing a volatile substance - Google Patents

Description

Device for dispensing volatile substances

Technical Field

The present invention relates to devices for dispensing volatile active substances. And more particularly to portable gas-fired devices that use heat to dispense volatile materials into the air.

Background

A variety of portable devices have been made for dispensing volatile materials into the air. Such volatile materials are typically insect repellent active ingredients or air treatment materials (e.g., air fresheners). Many such portable devices employ a battery-powered fan to evaporate the volatile substances without the use of thermal energy.

Devices that utilize thermal energy to evaporate or volatilize an active ingredient or other volatile material are also known in the art. Many of these devices require a power source that is connected to the current in the room or similar to provide power to the heater. They are therefore not portable when located outside the range of power outlets into which their power plugs must be plugged and their power cord lengths.

Flames are another source of heat for dispensing volatile materials in general. For example, scented candles or various wicks that light up in a spice jar are conventional devices for air freshening or adding spices to the air. Citronella candles are one example of the same technology that is applied to repel insects. Similarly, mosquito coils use the heat of combustion to disperse or disperse insect repellent active ingredient into the area surrounding the device. The mosquito coil is made of a velvet structure or other slow burning material, either self-supporting or printed on a substrate. Like an incense burner, the burning of the end of the flock is slow, and like an incense burner, an insect repellent ingredient is emitted by its smoke or by volatilization.

Other devices burn liquid fuels (mostly alcohol) to generate heat to vaporize the insect repellent active ingredient. The device entitled "mosquito killer" (SkeeereEater) manufactured by La Reina Enterprises of Falmouth, Mass is used to vaporize insecticides from an impregnated pad by heating the pad using a hot metal catalyst mesh fueled with alcohol. Similar products are also sold by other companies in europe or japan, sometimes replacing the metal catalyst mesh with only a simple alcohol flame. The insecticide backing plate of the mosquito killer device is a flat rectangle. The device has a flat base which is bridged by a grid. The user slides the insecticidal mat on the base through an opening on one side of the grid and retrieves it from a similar opening on the other side of the base. Liquid fuel devices typically require the user to pour fuel into the device prior to use, which entails the risk of spilling the combustible liquid. Such spillage can cause not only fire but also contamination of the environment, especially when the device is lit with matches or other open-fire equipment.

While such devices and methods are presently known in the art, by way of example only, there is a need in the art for a device that is convenient and safe to use and does not have to be plugged into an electrical outlet, but is instead entirely portable for use at any desired location. There is also a need in the art for a combustion heating device for volatilizing an active ingredient, wherein the device does not require an unprotected or contained fire that could ignite flammable materials in the vicinity, and is also maneuverable, clean, odorless, and reliable in connection with electrical equipment.

Technical scheme of the invention

The apparatus of the present invention for dispensing a volatile substance includes a portable gas-fired heat source having a cylinder union device for hermetically receiving a fuel cylinder; a combustion nozzle; and a metering device for metering the fuel supplied by the fuel cylinder to the flame of the combustion nozzle. The invention also includes a base plate having a heating surface for heating the volatizable material and a heat transfer device for enclosing the combustion nozzle and transferring heat from the flame to the base plate. A heat box substantially surrounding the heat transfer device and the base plate, the heat box being made of a material capable of withstanding the heat radiated from the heat transfer device and the base plate and having a window through which volatile substances released from the base plate can escape the heat box. The apparatus also includes a housing having an inner surface defining an interior chamber, the thermal cartridge being secured within the interior chamber at a distance from the housing, the housing including a housing window adjacent the heating cartridge window. By using this device, a flame is continuously available at the combustion nozzle to heat the soleplate to volatilize volatile substances disposed on the heating surface, and the volatilized substances can then escape into the atmosphere through the heat box window, while the housing is maintained at a lower temperature relative to the temperature of the flame, the heat transfer device and the soleplate.

The method of the present invention for dispensing a volatile material into the atmosphere comprises the steps of: a portable gas-fired heat source for supplying fuel to a combustion nozzle is provided. A soleplate having a heating surface is provided for heating the substance to be volatilized. A heat transfer device is provided for transferring heat from the flame of the combustion nozzle to the base plate. A thermal box is provided that substantially surrounds the heat transfer device and the base plate, the thermal box being formed of a material that is capable of withstanding radiant heat from the heat transfer device and the base plate and having a window through which volatile matter exiting the base plate can escape the thermal box. By the method of the invention a flame is continuously obtained at the combustion nozzle to heat the soleplate to emit volatile substances disposed on the heating surface, and the volatilized substances can then escape into the atmosphere through the heat box window.

Brief description of the drawings

FIG. 1 is a right side perspective view of the device for dispensing a volatile material of the present invention as viewed from the rear and above;

FIG. 2 is a right side perspective view of the device of FIG. 1 from the head and above;

FIG. 3 is a cross-sectional view taken along section line 3-3 of FIG. 1;

FIG. 4 is an end elevational view of a heat exchanger in the apparatus of FIG. 1 in combination with a base plate and a combustion chamber.

Detailed description of the preferred embodiments

Turning to the drawings, wherein like parts are designated by like reference numerals, a preferred embodiment of the device for dispensing a volatile material of the present invention is designated by the reference numeral 10 in fig. 1 through 3. The device 10 employs a portable gas-fired heat source. The heat source has a cylinder connector for sealingly receiving a fuel cylinder in a gas tight condition. The heat source also comprises a combustion nozzle, and fuel gas is combusted at the nozzle; and a metering device for metering fuel supplied by the fuel cylinder to the flame of the combustion nozzle. The preferred construction of the portable gas-fired heat source is substantially the same as that of the patent entitled "portable heating device" entitled U.S. patent No.4,669,123 issued 10/13 1987. U.S. Pat. No.4,669,123 is incorporated herein by reference, and U.S. Pat. Nos.4,759,343 and 4,815,441 are also incorporated herein by reference. These patents describe a two combustion chamber system, while the present invention has a single combustion chamber system. All other aspects such as fuel system conditioning, airflow, ignition and operational operation are substantially the same as those of these patents.

The preferred embodiment of the portable heat source shown in fig. 3 employs a fuel cylinder 12 having a fuel cylinder valve 14. The cylinder union device 16 is adapted to mate with corresponding threads on the fuel cylinder 12 to secure the fuel cylinder in place. The use of bayonet, clip and other alternatives to replace the threaded engagement will be apparent to those skilled in the art and are within the scope and spirit of the present invention. When the unit-in-cylinder device 16 is connected to the fuel gas cylinder 12, a valve actuator 18 depresses the fuel gas cylinder valve 14 to release gas from the fuel gas cylinder into the apparatus 10. The pressure regulator 19 controls the flow of gas and can be adjusted by a common method of regulating the flow.

The heat source also includes a combustion nozzle 20. According to the solution disclosed in patent No.4,669,123, a metering device is also provided for metering the fuel supplied by the fuel cylinder 12 to the combustion nozzle 20. The gas exiting the fuel gas cylinder 12 is released through a gas port 24 and directed into a venturi 26 where it is accelerated. As the gas enters the venturi 26, air is mixed with the gas, the air entering through an air inlet 28 and located just upstream of the venturi. The mixture of air and gas is ejected from the combustion nozzle 20 and covered by a nozzle screen 28. A piezoelectric igniter 30 generates a spark to ignite the gas and air mixture that is combusted at the combustion nozzle 20 and whose flame is defined by the nozzle screen 28.

The preferred fuel for the portable heat source is butane, which is convenient and reliable. Additionally, the fuel cylinder 12 and the cylinder union device 16 can be easily removed by unscrewing them to attach a new supply fuel gas cylinder to the apparatus. The invention is not limited to this particular portable gas-fired heat source and it will be apparent to those skilled in the art that other alternative constructions and arrangements may be used. For example, such alternatives include refillable or disposable fuel cylinders, alternative devices for metering fuel, and the like are also within the scope and breadth of the present invention.

The device 10 for dispensing a volatile material of the present invention further includes a soleplate 32 having a heating surface 33 for heating the volatile material. Fig. 3 and 4 show these structures. By adjusting the size of the flame at the combustion nozzle 20, as well as other methods described below, a wide temperature range may be maintained for the base plate 32. Useful temperatures for the sole plate 32 range from a minimum of about 50 deg.C (e.g., useful for certain air treatment materials) to a maximum of about 280 deg.C (e.g., useful for activation of certain melt media of a smoker). A preferred temperature range useful for volatilizing certain insect repellent active ingredients is 125 to 200 deg.C. In fact, this temperature range is practical and effective for a wide variety of insect repellent and air treatment active ingredients available. Higher temperatures become difficult to control. Lower temperatures will not volatilize enough active ingredients for practical use.

The base plate 32 and its heating surface 33 may be of various suitable sizes and shapes, and may include sharply curved shapes, irregular or angled shapes. It is presently preferred that the heating surface 33 and the base plate 32 be substantially planar, and this term should be understood to include gently curved surfaces and structures, as well as surfaces having rims or structures, and the like.

The present invention includes heat transfer means for enclosing the combustion nozzle 20 and transferring heat from the flame burning at the nozzle to the base plate 32, the combination of the heat transfer means and the base plate being referred to herein as the heat exchanger of the apparatus. The heat transfer device is made of a heat conductive material in the preferred embodiment and includes a combustion chamber 34. The combustion chamber 34 substantially encloses the combustion nozzle 20. Although the combustion chamber 34 may have any suitable shape, in the preferred embodiment, the combustion chamber is generally cylindrical with a longitudinal axis extending substantially parallel to the flow of air from the combustion nozzle 20.

The combustion chamber 34 is in heat-conducting connection with the base plate 32. In the preferred embodiment, the combustion chamber has thermally conductive chamber walls 36. At least one pressure relief hole 38 extends through the chamber wall 36 to provide a means for relieving pressure that would otherwise be elevated by the combustion chamber entry of the gas and air mixture exiting the combustion nozzle 20. A flame arrestor prevents flame from escaping the combustion chamber 34. Any conventional flame arresting device may be used. But a preferred form of flame arrester is a screen 40 as shown in figure 3. The screen 40 allows a substantially unobstructed air passage through the pressure relief hole 38. However, if the device 10 is transferred to an explosive environment, the screen 40 serves to confine the combustion within the combustion chamber 34, as does the miner's light, thereby preventing flames from escaping the combustion chamber.

The walls 36 of the combustion chamber 34 may include an outwardly extending heat sink (not shown) or other means of dissipating the excess heat as will be readily apparent to those skilled in the art. Such heat sinks, the size, shape and geometry of the base plate 32, and various other devices for volatilizing, transferring or dissipating excess heat may be used to regulate the temperature of the heated surface 33 of the base plate 32.

In the inventive apparatus 10, a heat box 42 substantially surrounds the heat exchanger. The heat box 42 is made of a material that can withstand the radiant heat of the heat exchanger. Thus, as shown in the preferred embodiment of FIG. 3, the heat box 42 encloses the combustion chamber 34 and the bottom plate 32.

The heat box 42 has an outwardly opening window 44. The heat box window 44 is preferably located above the heating surface 33 of the base 32, although the heat box window could be located on a side wall or other location. Volatile substances heated on the heating surface 33 can escape from the window to the atmosphere.

The device 10 of the present invention further includes a housing 46. Fig. 3 clearly shows that the housing has an inner surface defining an internal combustion chamber 48 within which the heat box 42 is secured. The heat box 42 is fixed within the partial combustion chamber 48 at a distance from the housing 46. As a result, an air gap 50 exists such that the thermal box 42 is substantially spaced from the inner surface of the housing 46. The housing 46 includes a housing window 52 adjacent to the heat box window 44 and preferably openable above the heat box window 44 so that the heat box window is not obstructed by the housing.

Preferably, the thermal box 42 includes at least one thermal box exhaust port 54 that is below the thermal box window 44, and the housing 46 includes a housing exhaust port 56 that is preferably located no higher than the thermal box exhaust port 54. In the preferred embodiment shown in fig. 1-3, the thermal box exhaust port 54 and the housing exhaust port 56 are both located on the underside of the thermal box 42. Through the hot box exhaust port 54 and the housing exhaust port 56, when a flame is ignited at the combustion nozzle 20, a convection current is created which assists in the escape of volatile materials from the hot box window 44. Preferably, the housing exhaust port 56 is intentionally offset from alignment with the thermal box exhaust port 54, thus preventing straight through exhaust ports into the heat exchanger. This arrangement is clearly visible in fig. 3.

Preferably, a glow wire 53 is disposed within the combustion chamber 34 at a location such that it can be heated to a glow temperature by the flame emitted from the combustion nozzle 20. The igniter 30 comprises a glow wire and the housing 46 comprises a viewing window 55, and the hot box 42 comprises a viewing aperture 57, the viewing window and aperture being positioned so that a user of the apparatus 10 of the present invention can view the glow condition of the igniter 30 through the viewing aperture. In this way, a user can easily visually observe whether or not a flame is burning at the combustion nozzle 20.

Preferably, the heat box window 44 is closed by an air delivery grille 58 as shown in the preferred embodiment, which can be readily understood from FIGS. 1 and 2. The grid 58 is positioned far enough above the heating surface 33 of the soleplate 32 so that it can withstand the heat from the heating surface. However, if the grid 58 positioned above the heating surface 33 is too far from the heating surface 33, the grid may remain sufficiently cool that volatile materials exiting the heating surface condense on the underside of the grid. The distance between the grid 58 and the heating surface 33 must therefore be carefully adjusted, which has to be determined empirically. Preferably, grid 58 includes at least one fin 59 extending toward heating surface 33 in a selected manner such that the fin acts on a volatile carrier (described below) disposed below the grid and in contact with heating surface 33. The ribs 59 are shown in fig. 3.

In the preferred embodiment, the combustion chamber 34 is a hollow cylinder that is connected to the underside of the sole plate 32 by heat transfer ribs 60 that extend substantially along the length of the combustion chamber, the heat transfer ribs being shown in end view in FIG. 4. Such an arrangement adequately transfers heat within the combustion chamber 34 to the sole plate 32, and also enables the combustion chamber, sole plate and heat transfer ribs 60 to be integrally formed by extrusion from aluminum or other suitable metal or alloy thermally conductive ceramics or the like. When the heat transfer ribs 60 are attached to the centerline of the sole plate 32 as shown in the illustrated embodiment, heat from the combustion chamber 34 is transferred from this location into the sole plate.

With this arrangement, a thermal gradient may be created across the heating surface 33 of the sole plate 32 when the flame is burned at the combustion nozzle 20, with the highest sole plate temperature generally being centrally located on the heating surface. In this case, it is preferable to have the grid 58 near the heat box window 44 curve upward over the heating surface 33 and have the greatest distance from the heating surface at the hottest position in the center of the heating surface. With this arrangement as shown, each portion of the grid 58 above the heating surface 33 is spaced from the heating surface such that they can withstand the heat of the heating surface, regardless of the different temperatures that may be generated, but remain sufficiently heated so that volatile materials leaving the heating surface do not condense on the grid.

In the preferred embodiment, the device of the present invention is prepared for use with a volatile carrier (not shown) carrying the volatile material to be dispensed. The carrier is shaped so that it can be placed in intimate contact with the heated surface 33 of the base plate 32 when placed thereon. The presently preferred shape of the carrier is substantially planar, corresponding to the preferred shape of the heating surface 33. In this context "substantially planar" is to be understood broadly to include rigid or flexible pads, sheets or similar shapes made of suitable materials capable of holding a volatile material and releasing it upon heating. Another alternative example of a carrier may be a gel or the like that has sufficient structural integrity to be supported or held in a cradle. The carrier may be flat, corrugated, pleated, or other suitable form that is rigid or capable of holding a volatile material. Such carriers are to be understood as "substantially planar" so long as they generally exhibit a substantially planar profile when placed on a flat support surface. Desirable materials for making such carriers include cardboard, perforated cellulosic materials, woven cloth and non-woven mats or felts made of any suitable fibrous, colloidal and absorbent solid-cell foam, and plastic or ceramic materials capable of releasing and containing volatile substances.

As shown in fig. 1 and 2, the inventive device 10 includes at least one access opening 62. The access opening 62 is located on the side of the grid 58 that is substantially parallel to the heating surface 33 of the soleplate 32 and at least in the same plane as the heating surface or even higher, preferably extending along the entire length of the heating surface on that side. In any event, the access opening 62 is sized such that volatile material carriers of the type described above can enter or exit the heating surface 33 through the access opening. A particularly convenient arrangement includes an access opening 62 on each of the two opposite edges of the heating surface 33, forming a pair of access openings. With this arrangement, a new volatile carrier can be inserted through one access opening 62 and the spent volatile carrier pushed out of the other access opening. This arrangement of access openings 62 is clearly shown in fig. 1 and 2.

Preferably, the access opening 62 is sufficiently narrow and deep, and the bottom panel 32 prevents direct contact with the bottom panel by a user's hand, depending on the positioning of the access opening.

In use, the device 10 of the present invention further includes a volatile material disposed on the heated surface 33 of the soleplate 32. Preferably, the volatile material is supported on a carrier that is replaceably supported on the heating surface 33, so that the volatile material of the device 10 can be renewed by replacing the carrier. It is the carrier of the type described above that employs the device having the access opening 62 described above that is illustrated in the preferred embodiment of the present invention.

A preferred volatile material is an insect repellent active ingredient. "insect repellent active ingredient" is understood to include a substance which is capable of repelling, killing or otherwise affecting the activity of insects. Examples include pyrethroids (pyrethides) such as the insecticides (pyramin-forte) sold by Sumitomo corporation, pyrethroids.

Volatile materials for use as air treatment materials (e.g., air fresheners, etc.) include a variety of fragrances.

Preferably, the housing 46 encloses not only the thermal box 42 but also the fuel cylinder 12, the cylinder union device 16 and the remainder of the aforementioned operating members. Fig. 1 to 3 show such an arrangement. This preferred form of the housing 46 provides a suitable structure for securing the control buttons, first and second control buttons being indicated at 64 and 66, respectively. Actuation of the first control button in the preferred embodiment shown causes gas to flow from the fuel gas bottle through the pressure regulator 19 at a predetermined fixed rate. The pressure regulator may employ a variety of connections to control the air flow, and thus the pressure regulating air flow within the button control regulator 19 provides a controlled motion that allows both the size and heat of the resultant flame at the combustion nozzle 20 to be controlled by the control button 64. The second control button 66 of the preferred embodiment activates the piezoelectric igniter 30. These specific control arrangements are only possible examples and of course should not be construed as limiting the invention in any way. Particularly in the preferred form of the housing 46, the housing includes at least one air inlet duct 67 as a source of fresh air for supplying fresh air to the flame of the combustion nozzle 20 and for ventilating the housing. The air introduction tube 67 is better shown in fig. 1 and 3. An access cover 68 is provided to enable a user to utilize and replace the fuel cylinder 14. The access cover 68 is adapted to be replaceably removed from the housing 46 by finger actuation of a conventional latch, shown at 70 in FIG. 3.

Feet 72 are provided below the housing 46 for raising the housing above any surface on which it may be placed. This elevation ensures that air can flow freely through the housing exhaust 56 and air intake 67 if they are located on the underside of the housing 46 as shown in the preferred embodiment. In addition, foot 72 provides the advantage of reducing temperature increases above device 10.

The method of the present invention for dispensing volatile substances into air includes the step of providing a portable gas-fired heat source that provides fuel to the flame of a combustion nozzle. The method further comprises the step of providing a substrate having a heating surface for heating the material to be volatized. Preferably, the heated surface may be maintained at a temperature in the range of 50 to 280℃, or more preferably in the range of 125 to 200℃. The method of the present invention further comprises providing a heat transfer device for transferring heat from the flame of the combustion nozzle to the base plate. Further included is providing a heat box substantially surrounding the heat transfer device and the base plate, the heat box being made of a material capable of withstanding radiant heat from the base plate and the heat transfer device and having a window through which volatile substances can escape from the heat box. Through these steps, a flame may be maintained at the combustion nozzle to heat the soleplate and volatile substances placed on the heating surface of the soleplate. The volatile material can then be dispensed to the atmosphere by escaping through the window of the thermal cartridge.

Preferably, the method of the present invention further comprises providing a housing having an interior surface defining an interior chamber, and securing the thermal cartridge within the interior chamber so that it is spaced from the housing, the housing including a housing window adjacent to and preferably open above the thermal cartridge window. By this step, the enclosure can be kept at a low temperature relative to the flame, heat transfer equipment and base plate temperatures.

Another preferred step of the present invention is to apply a volatile material to the heated surface of the soleplate, wherein the volatile material is selected from the group consisting of insect repellent active ingredients, air treatment materials, and mixtures thereof. The volatile material is preferably an insect repellent active ingredient.

Preferably, the heat transfer device is made of a heat conductive material and comprises a combustion chamber substantially enclosing the combustion nozzle and any flame burning at the combustion nozzle, the combustion chamber being connected to the base plate in a heat conductive manner. Preferably the combustion chamber has a thermally conductive chamber wall through which at least one pressure relief aperture passes, and a flame arrester for preventing flame from escaping the combustion chamber whilst substantially unblocking the passage of air through the pressure relief aperture.

Preferably, the heat box window is closed by a grille of delivered air that is spaced far enough from the heating surface of the base plate that it can withstand the heat from the heating surface, but spaced close enough so that volatile materials leaving the heating surface do not condense on the grille.

Preferably, the method of the present invention further comprises carrying the volatile material to be dispensed by a substantially planar carrier adapted to be mounted on and heated by the heated surface of the sole plate. Preferably, at least one access opening is also provided on one side of the grid, substantially parallel to and at least as tall as the heating surface of the base, the access opening being sized so that the volatile material carriers can enter or exit the heating surface through the access opening.

The non-metallic parts of the device 10 of the present invention may be conveniently formed of a suitable plastic or ceramic by conventional molding techniques. The metal part may be made by conventional methods including extrusion. The volatile material carrier may be formed by impregnating the carrier by various impregnation techniques known to those skilled in the art, and may include, for example, simply soaking the carrier with a solution of the volatile material to be dispensed and drying the solution, although this is not a limitation.

Industrial applications

The efficient distribution of volatile materials into the air has industrial applications for insect control, as well as air treatment for fragrance and other purposes. The portable nature of the device 10 of the present invention makes it useful in any situation, but is particularly valuable outdoors and in other locations where electrical power is not readily available.

While the preferred embodiment of the invention has been illustrated by the accompanying drawings and described above, it will be apparent to those skilled in the art that various modifications can be made therein without departing from the scope of the invention. The invention should therefore not be limited to the particular preferred embodiments described, but should be understood in light of the following claims.

Claims (24)

1. An apparatus for dispensing a volatile material includes

a. A portable gas-fired heat source having a cylinder connector for hermetically receiving a fuel cylinder; a combustion nozzle; and a metering device for metering fuel supplied by the fuel cylinder to the flame of the combustion nozzle;

b. a base plate having a heating surface for heating the volatizable material;

c. heat transfer means for enclosing the combustion nozzle and transferring heat from the flame to the base plate;

d. a heat box substantially surrounding the heat transfer device and the base plate, the heat box being made of a material capable of withstanding radiant heat from the heat transfer device and the base plate and having a window through which volatile substances released from the base plate can escape the heat box; and

e. a housing having an interior surface defining an interior chamber, the thermal cartridge secured within the interior chamber at a distance from the housing, the housing including a housing window adjacent the thermal cartridge window;

a flame is therefore continuously available at the combustion nozzle to heat the sole plate to volatilize volatile substances disposed on the heated surface, and the volatilized substances can then escape into the atmosphere through the heat box window, while the housing is maintained at a lower temperature relative to the flame, the heat transfer device and the sole plate temperature.

2. An apparatus according to claim 1, wherein the fuel cylinder is replaceable so that it can be refilled by removing a spent fuel cylinder and replacing it with a full one.

3. The device of claim 1 wherein the volatile material is selected from the group consisting of insect repellent active ingredients, air treatment materials and mixtures thereof.

4. The apparatus of claim 1, wherein the thermal cartridge includes at least one thermal cartridge vent located below the thermal cartridge window, the housing including a housing vent opening no higher than the thermal cartridge vent opening, the housing vent opening being offset from the thermal cartridge vent opening such that straight entry into the heat transfer device through the vent opening is prevented, such that when a flame at the combustion nozzle is ignited, convection currents are created which assist in the escape of volatilized material from the thermal cartridge window.

5. An apparatus as claimed in claim 1, characterized in that the heat-transfer means are made of a heat-conducting material and comprise a combustion chamber which substantially encloses the combustion nozzle and the flame burning at the combustion nozzle, the combustion chamber being connected in a heat-conducting manner to the base plate, and a heat-transfer element which is arranged between the combustion nozzle and the base plate and has a heat-transfer opening

a. A thermally conductive combustion chamber wall;

b. at least one pressure relief hole through the combustion chamber wall;

c. a flame arrester which prevents flame from escaping from the combustion chamber but which permits substantially unobstructed air flow through the pressure relief opening.

6. A device according to claim 1, wherein the heat box window is closed by an air delivery grid located above the heating surface of the base plate, the grid being located sufficiently far from the heating surface to withstand the heat therefrom, but close enough to be heated sufficiently so that material to be volatilised leaving the heating surface does not condense on the grid.

7. A device according to claim 6, for use with a planar volatile substance carrier for carrying volatile substances to be dispensed, the device comprising at least one access opening on one side of the grid, substantially parallel to and at least at the same height as the heating surface of the soleplate, the access opening being dimensioned so that the volatile substance carrier can enter or exit the heating surface through it.

8. The apparatus of claim 7, wherein the access opening is sufficiently narrow and of sufficient depth that positioning of the panel relative to the access opening limits direct access to the panel by a user's hand.

9. A device according to claim 5, characterised in that

a. Heat is transferred from the combustion chamber of the heat transfer device to the base plate near the central location of the base plate, and when a flame is burned at the combustion nozzle, a heat gradient may be created across the heating surface of the base plate, with the highest temperature of the heating surface being generally at the central location; and

b. the heat box is closed by an air delivery grid which is positioned above the heating surface and bent upwardly, the hottest position on the heating surface being at a maximum distance from the grid to the heating surface, each portion of the grid being positioned above the heating surface at a distance sufficiently far enough to withstand heat therefrom, while being close enough to heat sufficiently so that volatile substances leaving the heating surface do not condense on the grid.

10. A device according to claim 9, for use with a planar volatile substance carrier carrying volatile substances to be dispensed, the device comprising at least one access opening on one side of the grid, substantially parallel to and at least at the same height as the heating surface of the soleplate, the access opening being dimensioned so that the volatile substance carrier can enter or exit the heating surface through it.

11. The apparatus of claim 10, wherein the access opening is sufficiently narrow and of sufficient depth that positioning of the panel relative to the access opening limits direct access to the panel by a user's hand.

12. The apparatus of claim 1, further comprising a volatile material disposed on the heated surface of the soleplate.

13. A device as claimed in claim 12, wherein the volatile substance is carried by a carrier which is replaceably located on the heating surface, whereby the volatile substance of the device can be renewed by replacement of the carrier.

14. A device according to claim 13, wherein the carrier is made of cardboard, perforated cellulose material, woven cloth, non-woven pad, or felt made of any suitable fiber, gel and absorbent solid-pore foam, and plastic or ceramic material capable of releasing and containing volatile substances.

15. A device according to claim 12, wherein the volatile material is an insect repellent active ingredient.

16. The apparatus of claim 1, wherein the temperature of the sole plate is maintained in the range of 125 to 200 ℃.

17. An apparatus for dispensing a volatile material, the apparatus comprising:

a housing;

a portable heating appliance mounted within said housing, said portable heating appliance including a source of butane gas, and heating appliance having a temperature related to the amount of said butane gas flowing into said heating appliance, said butane gas flowing continuously;

a heat exchanger surrounding said heating device;

a heat box surrounding said heat exchanger;

a pad of material containing said volatile substance, said pad being mounted in a compartment adjacent said heat exchanger,

said heat exchanger comprises a metal plate radially surrounding said heating means to be heated and causing said material mat to be heated;

said heating means and said metal plate causing an air flow caused by the continuous flow of said butane gas around said mat of material, on which volatile substances are heated and dispersed;

the housing is kept at a low temperature with respect to the temperature of the heating device and the heat exchanger.

18. The apparatus for dispensing a volatile material according to claim 17, wherein said heating device includes an igniter and a burner tube, said butane gas flowing into said burner tube to form a flame for said heating device.

19. The apparatus for dispensing a volatile material according to claim 17, wherein said heating device includes a regulator to control the flow of butane gas.

20. The apparatus for dispensing a volatile material according to claim 19, wherein said actuator is adjustable by a user to adjust the heat of said heating device.

21. The apparatus for dispensing a volatile material according to claim 18, wherein said heating device includes a regulator for controlling the flow of butane gas.

22. The apparatus for dispensing a volatile material according to claim 21, wherein said actuator is adjustable by a user to adjust the heat of said heating device.

23. The device for dispensing a volatile material of claim 17, further comprising a viewing window through which the flame is viewable.

24. The device for dispensing a volatile material of claim 21, wherein the device for dispensing a volatile material is an outdoor insect repellant device.