AU725489B2 - Hand operated flame cultivation and flaming torch - Google Patents

Description

F-/UUMui1 2a/5191 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: HAND OPERATED FLAME CULTIVATION AND FLAMING TORCH The following statement Is a full description of this invention, including the best method of performing it known to us 1 1 r i#1 HAND OPERATED FLAME CULTIVATION AND FLAMING TORCH Field of the Invention The present invention is concerned with torches which find application in agricultural and forrestal land management, road surface asphalting and similar tasks which require application of heat or a flame onto objects. In particular, the present invention is concerned with hand-held combustive torches which use liquified petroleum gas (LPG) as a fuel source for the torch burners.

Background of the Invention and Prior Art Hand-operated flaming torches are commonly used to destroy plants (e.g.

bush, forest undergrowth) in land clearing operations. Such torches will generally be constructed to generate high intensity flames capable of penetrating thick foliage and setting aflame dead wood and live plants alike.

Similarly, hand-held, LPG combusting torches have been used in agriculture and horticulture for a number of years as an alternative to 15 environmentally questionable, large scale use of herbicides and pesticides.

Hand-held torches can be used for localised or small scale flame cultivation to control weeds and plant pests, particularly in hard to access locations, such as drainage trenches, irrigation ditches and the like. Such flame cultivation torches are designed such as to direct heat generated by the flame and combustion gases to wilt young weeds, without setting them on fire.

US patents 3,357,474 and 3,486,497 (both granted to Pivonka) describe torches with combined LPG fuel vaporiser and burner arrangements within a burner casing or head that can be integrated in hand-held torches for flame cultivation and igniting vegetation.

Hand held torches for agricultural as well as other purposes, e.g. road works, roof taring and the like, generally share a number of common structural features. They have an elongate handle tube or rod which carries at one of its distal ends the torch head which incorporates one or more burners with fuel discharge jet nozzles arranged within a torch shroud. The specific configuration and constructional elements of the torch head can vary greatly and are influenced by factors such as the type of application the device is mainly intended for, the fuel supply source, the need for fuel supply regulators and 2 control devices, whether continuous or intermittent high intensity heat is to be applied directly or indirectly, the need to maintain a pilot flame, the required heat energy output rate, burner type (ie combustion of priorly vaporised or vaporising liquid fuel) amongst others.

The handle tube or rod, depending on its length, will have either a single handle grip at the terminal end opposite the torch head, and if required, an additional intermediate handle bar or grip to permit balancing by the torch operator.

The fuel supply line to the burners is either provided integrally by or within the tubular handle; some devices use a separate fuel line mounted externally on the handle rod. With simple designs, the fuel supply line is connected directly to a LPG hose without intermediate regulators or valves, the hose itself being secured at the threaded bore of the outlet valve of a LPG storage cylinder. More elaborate torches incorporate a deadman shutter (valve) 15 to turn on or off fuel supply to the burners at the torch itself, instead of relying solely on the LPG cylinder outlet valve which is operated by a turning handle, as well as other regulators and pressure gages in the fuel supply line.

LPG fuel for the torch is provided from an LPG cylinder. The size of the .i cylinder will often be determined by the required heat output capacity of the eeoc torch burners (as represented by fuel consumption) and the manoeuvrability that is required by the torch operator.

oil• For example, small, single hand held torches such as those manufactured by Primus and sold under the label "Gardener" and which are mainly intended for the hobby gardener, can use small capacity, disposable (or refillable) LPG cartridges having a self closing connecting valve. Such cartridges can have a capacity of 1 to 3 litres and are attached directly to the suitably fitted torch handle which is bent.

The main limitation as to possible cylinder sizes, however, will generally be their weight. The cylinder must be refillable and able to be carried by the torch operator. This is usually accomplished either using a customised back pack or a non-motorised cart. Having regard to restrictions imposed by the location where the torch is to be used and the surrounding terrain, the back pack 3 arrangement is often used in flame cultivation and vegetation torching applications where a larger LPG fuel supply is required, e.g. 5 to 15 litres cylinder capacity.

Smaller hand-held flaming torches incorporate a torch burner arrangement that is relatively lightweight, However, heavy duty, high capacity torch burner heads can have a substantial weight, eg 2 to 8 Kg. Whilst this may not seem much, when mounted at the distal end of the tubular torch handle, which can have lengths of greater than 1.5 m, proper balancing of the torch head by an operator is often difficult and tiring.

The present invention sets out to address the above mentioned problems, in particular encountered with flaming torches that have longer torch handles, in a manner which will not or only minimally affect the manoeuvrability of the flaming torch in operation. It would hereby be advantageous for at least a preferred embodiment of the invention to provide a hand-held flaming torch that can be safely carried by an operator together with a fuel supply cylinder or canister.

Summary of the Invention In a broad first aspect of the invention there is provided a hand held flaming torch having an elongate handle, a torch head at one end of the handle and a fuel tank mounting structure at an opposite end of the torch handle wherein the fuel tank mounting structure includes a handle mount fixed at the handle and a tank support structure pivoted at the handle mount, whereby in use of the torch the weight of the torch head is at least partly counterbalanced with the weight of a fuel storage tank secured at the tank support structure and the tank is pivotable with respect to the handle such as to remain in a substantially vertical or upright position during operation of the torch.

The fuel tank mounting structure with its capability of permitting pivotal movement of the fuel tank, eg an LPG cylinder, with respect to the handle allows the LPG cylinder to remain in a substantially vertical or upright position during operation of the torch which involves directional movement and pointing of the torch handle towards a treatment area by an operator. This pivotal mounting of the tank at the handle is desirable from a safety point of view in that the outlet valve of the cylinder, which is located at the top of the cylinder, should remain in fluid communication with the vapour phase of the LPG within the cylinder rather than the liquid, to ensure proper operation of the torch. This is achieved by keeping the LPG cylinder in its upright orientation during operation of the torch.

Also, the pivoting mechanism enables to set down the torch with the cylinder in its upright position on uneven ground.

In a more confined aspect of the invention there is provided a hand held flaming torch including: an elongate, tubular or rod-like torch handle having a longitudinal axis; a first handle grip near a proximal end of the handle; optionally, a second handle grip on the handle located spaced apart from the first handle grip; a torch head supported at or near a distal end of the handle, the torch head having at least one burner arranged for generating a flame; a fuel supply line arranged to deliver fuel to the burner, the fuel supply line being connectable to a fuel storage tank; fuel storage tank mounting structure at the proximal end of the handle, the mounting structure arranged to secure a fuel storage tank in articulated manner at the torch handle such that the torch handle can be swiveled with 20 respect to the fuel storage tank; and preferably, a strap harness removably secured on the handle at a location forward of the first handle such that, in use of the torch, the weight of the fuel storage tank So..

serves to counterbalance the weight of the torch head when an operator shoulders the weight of the torch through the harness.

o* 9 25 Preferably, the fuel storage tank mounting structure includes a shallow bed cradle advantageously having a bed shape conforming with the exterior shape of *i: an LPG cylinder and at least one terminal flange portion for resting the cylinder foot thereon. Straps with quick buckles, which can be secured to the cradle, service to strap down and secure the cylinder on the cradle bed. This enables fast and simple exchange of the cylinder when required.

There are many and different ways in which to provide a mounting structure that permits cardanic (rotational freedom of movement about 3 mutually perpendicular axis), gimbal (rotational freedom of movement about two axis) or simple, uniaxial pivotal movement of the LPG tank in relation to the torch handle. In one preferred form, a simple gimbal mount is provided in that an upper skirt of the cradle is pivotally secured and held between a pair of angled support arms which are welded onto a socket hub in which the proximal terminal end of the torch handle is received fixed against axial movement and, if required, also releasably against rotation.

During the course of operation of the flaming torch, the centre of balance at the handle (the location where the strap harness is preferably secured at the handle) will change as the fuel in the cylinder is consumed. To accommodate this, it is advantageous to provide at the handle a fixing device for the harness arranged for manually compensating this shift by correspondingly shifting the location at which the harness is secured at the handle. In its simplest form, the fixing device can be a bracket having a tubular portion fixed against axial 15 movement on the handle and having a tang with a plurality of eye holes in spaced apart relationship which are disposed to selectively receive a connection shackle of the harness strap. More elaborate arrangements with indexed notches along a horizontal slot (thereby avoiding the need to set down "the torch to make the adjustments) or some other form of variable adjustment 20 mechanism known in the art may equally be employed.

To minimise the amount of effort that is required by the operator to point the torch head in the direction required whilst being shouldered, the second handle grip, which preferably is a loop handle orientated at right angles to the torch handle, is advantageously mounted forward of the harness strap fixing point (that is towards the torch head) but close thereto, and the first handle grip, which is a simple tubular grip member, is located immediately rear of the balance point represented by said fixing point.

To improve the safety of the torch operator, a quick release device can be incorporated either in the shoulder harness strap or the harness fixing bracket at the torch handle thereby allowing the operator to free him or herself from the torch unit in case of an emergency. This improvement addresses concerns that have been expressed in relation to known, back pack shouldered fuel supply 6 tanks.

The present invention is especially suited for hand held torches that incorporate larger torch heads for high energy output Because of their higher weight, the counterbalancing effect of the LPG cylinder will be more appreciated. One such torch head design may incorporate: a primary torch burner having a fuel delivery nozzle or jet arranged within an open combustion chamber defined within a burner skirt such as to direct a stream of fuel towards a flame delivery opening (or mouth) of the skirt, and a vaporiser located in heat exchanging proximity to the primary burner and having a pressurisation chamber with an inlet for liquid LPG fuel and an outlet for gaseous LPG fuel, the inlet being in fluid communication with the LPG cylinder (which provides a source of pressurised LPG) and the outlet being in fluid communication with the nozzle of the primary burner. A metering duct is located in close vicinity or within the vaporiser and arranged to discretely restrict (as compared to restrict in variable or adjustable manner) the amount of liquid fuel entering the vaporisation chamber via its inlet, preferably without a substantial te. 4 pressure drop (as compared to a conventional flow regulator that permits adjustable flow regulation) and the provision of a first pressure reduction duct in the flow path of gaseous fuel between the vaporisation chamber outlet and the nozzle of the primary burner, the first pressure reduction duct arranged to provide a discrete pressure drop between the vaporisation chamber (during normal operation of the torch) and the gaseous fuel delivery nozzle of the first burner (more precisely a drop in pressure of the gaseous fuel passing through the duct), such as to generate a low velocity LPG flame during normal torch operation.

As used herein, a low velocity burner flame is defined as a combustion flame of gaseous LPG delivered through the jet orifice of the burner nozzle at between 20 to max 30 PSI gas pressure, whereas a medium to high velocity combustion flame is generated by gaseous LPG exiting the nozzle orifice at about 35 to 60 PSI gas pressure.

The torch head may further incorporate a booster burner arranged to deliver a medium to high velocity combustion flame through at least one booster nozzle or jet which is in fluid communication with the vaporisation chamber through a second pressure reduction duct arranged to reduce the pressure of the gaseous fuel exiting the vaporisation chamber by an amount required to generate such medium to high velocity flame.

Whilst the nozzles of the primary and booster burners can be arranged within the same burner skirt, it is preferred to arrange the respective nozzles within a respective burner skirt, the burner skirts being arranged such that flames emitting therefrom intersect at a small angle such that the wide spreading, low velocity flame is superimposed with the narrower, high velocity flame.

The torch head is intended to be connected without intermediate flow regulators to the outlet valve of the LPG storage cylinder, the liquid LPG fuel delivery pressure being around 90 to 130 PSI gas pressure, depending on ambient conditions. During steady state operation of the torch head, where the metered liquid LPG entering the vaporiser is fully vaporised in the vaporisation chamber, the pressure within the vaporisation chamber will then be only slightly smaller to the delivery pressure. The pressure drops attributable to the liquid LPG supply conduits and flashing point entry of liquid LPG into the pressurisation chamber will be comparatively small (eg 5 to 10 PSI gas pressure), and it is believed that pressure losses otherwise attributable to the metering duct are offset by the about 280 fold volume increase which the liquid LPG will undergo in attaining its fully vaporised, gaseous state in the confined pressurisation chamber, thereby generating a pressure increase. The only significant pressure reduction the fully vaporised gaseous fuel will undergo is whilst flowing in the pressure reduction ducts (ducts with small bore and substantial extension, see below) towards the jet nozzle(s).

In other words, by appropriately sizing the metering duct, the pressure reduction ducts and nozzle gas delivery orifices, it is possible to attain a simple, self-regulating torch construction, where pressure increases within the vaporisation chamber (eg due to full vaporisation of an increased liquid LPG supply via the metering duct against insufficient back pressure) will tend to raise back pressure within the chamber and reduce liquid LPG intake into the 8 vaporisation chamber (assuming constant supply of enough energy to fully vaporise any given LPG quantity within the chamber).

In accordance with a more confined aspect of the present invention, there is provided a hand held torch of the type described above and incorporating a torch head as described above, wherein the torch head incorporates an LPG fuel vaporiser having a) a fuel delivery member having a liquid fuel inlet that is connectable to a pressurised source of liquid LPG fuel, a fuel outlet and a metering duct of predetermined length and cross-sectional area extending between the inlet and the outlet for limiting the volume of liquid fuel flow from said source of LPG fuel past the fuel outlet; b) a vaporiser housing defining a vaporisation chamber, the fuel delivery member outlet arranged to discharge fuel into the vaporising chamber, the metering duct being arranged in heat conducting communication with the vaporising chamber; c) a heater arranged to heat the vaporiser housing to an extent necessary to achieve full vaporisation of liquid LPG fuel entering the vaporising chamber; d) a first pressure reduction duct of predetermined length and crosssectional area having a gaseous fuel inlet in communication with the vaporisation chamber and a gaseous fuel outlet, the pressure reduction duct S".i arranged to cause a drop in pressure of the gaseous fuel entering from the vaporisation chamber, passing there through and exiting via the gaseous fuel outlet; e) at least one primary burner jet nozzle in fluid communication with the gaseous fuel outlet of the first pressure reduction duct and arranged to deliver through at least one orifice a low pressure gaseous fuel stream for the formation, in use of the torch, of a low velocity torch flame; f) a hollow burner skirt that houses the jet nozzle with the orifice arranged to direct the gaseous fuel stream into the interior of the skirt towards an opening mouth at a front end of the skirt; and g) means for ventilating the interior of the burner skirt and supplying 9 combustion air for the burner jet nozzle.

It will be noted that with such a torch head there is no need for any conventional liquid fuel regulators having moving parts to adjust flow of the liquid LPG fuel in the supply line to the vaporiser and conventional gas valves to adjust pressure of gaseous LPG fuel in the flow path between vaporiser outlet and burner nozzles. Instead, fluid flow is "controlled" to one setting (as provided by the metering member), and gas pressure at the burner nozzle(s) is equally set to a non-adjustable level as a function of the pressure and temperature level present in the vaporisation chamber and the dimensions of the pressure reduction duct.

S•The vast majority of flaming torch applications require little or no regulation of the flame velocity once the torch has reached steady state *.operation. Accordingly, manual adjustment of LPG flow into the vaporiser is superfluous (and non-efficient, see above). Hand-held LPG burning torches are generally used with conventional LPG storage cylinders which provide fuel and operating pressure. The outlet or fuel delivery pressure at an LPG cylinder will remain about constant (assuming constant outside temperature and relatively small fuel flow rates compared with cylinder capacity) for as long as there remains fluid LPG in the cylinder; after full vaporisation of liquid LPG in the cylinder, pressure drop will take place over a very short period of time, and torch operation will no longer be possible. Accordingly, it is possible to use a :metering member that does not provide for any manual adjustment, as long as such metering member ensures an appropriate fuel supply to the vaporiser and consequently to the burner to achieve a desired burner operating regime. The additional pressure reduction member, which provides a discrete pressure drop between vaporiser chamber and burner nozzles, is necessary to obtain the required low velocity torch flame.

The metering duct and the pressure reduction duct can be sized such that the volume of liquid LPG entering the vaporiser is restricted to a specified amount that is vaporisable by a given amount of heat transferred thereto by the heater which preferably is the torch burner itself, and obtain a desired burner jet nozzle operating pressure that will generate the low velocity/spreading flame.

Arranging the metering duct in a zone of the vaporiser that is heated during torch operation counters the cooling effect which flow reduction of liquid LPG in the fuel delivery member may cause, thereby ensuring controlled and precise supply of fuel to the vaporiser.

Preferably, the metering duct is comprised of a first duct portion of a predetermined first length and cross-sectional dimension and a second duct portion of a predetermined second length and cross-sectional dimension, the second duct portion being arranged as a separating removable attached part to a main part of the fluid delivery member. This arrangement enables the fuel delivery member to be adapted in discrete steps to different types of LPG fuels for use with the torch, by using exchangeable parts, without the need to exchange the entire fuel delivery member. For example, to achieve the same flow rate for different types of LPG, eg pure propane, pure butane, gas mixtures, the metering duct will have to have different lengths, and/or bore diameters assuming the same fluid delivery pressure at the duct inlet. The length diameter variations may be small, though perceivable as far as torch operating conditions are concerned. Further, the fuel outlet orifice of the fuel delivery member could be incorporated into the exchangeable part, thereby simplifying cleaning operations should the orifice become clogged.

Advantageously, the first pressure reduction duct is provided by a (straight) tube extending into the vaporisation chamber and which is removably fixed at the main fuel delivery member in fluid communication with a gas supply channel leading to the primary burner jet nozzle. The exchangeable nature of the tube enables to incorporate a selected one tube of a plurality such tubes in the torch, each tube having different lengths and bore diameters to cause a numerically different pressure drop between inlet and outlet thereof, and thus provide gaseous fuel to the primary burner jet nozzle(s) at a defined (but selected) pressure.

Whilst it is alternatively also possible to incorporate the first pressure reduction duct in the main body of the fuel delivery member, thereby providing an integral arrangement of metering duct and pressure reduction duct within the same part, the number of possible permutations of liquid fuel flow rate to 11 gaseous fuel pressure reduction to achieve a desired torch operating regime, make this more problematic, mainly ease of manufacturing considerations make a multi-part construction of the fuel delivery member of the torch desirable.

A particularly simple torch design is obtainable in that the fuel delivery member is a unitary metallic fitting having an externally threaded front hub portion onto which is sealingly fastened the otherwise closed tubular vaporiser housing. The closed forward end of the vaporiser housing may be T-shaped to reduce overall length of the housing whist providing sufficient volume for the vaporisation chamber formed therein.

Preferably, the fitting incorporates a fluid fuel passage channel which ends at internally threaded connection bores located one in the hub portion and one in a rear mounting portion of the fitting, The fluid fuel passage channel incorporates the metering duct or the first portion thereof, as the case may be; in the latter case, the metering tube which incorporates the second metering duct portion is received and secured in exchangeable manner in the threaded bore located in the hub portion. A fuel supply tube of the torch is secured at the 0. 1threaded bore of the rear fitting portion in sealing manner.

The fitting advantageously further incorporates at least one gas passage channel that terminates in threaded bores which respectively receive and secure the first pressure reduction tube and a rigid gas supply tube or line which supports at its free end the burner jet nozzle, the arrangement being such that the pressure reduction tube extends within the vaporisation chamber in its entirety and the threaded bore supporting the gas supply tube is located outside the vaporisation chamber Accordingly, the burner jet nozzle is also attached to the fitting in most convenient manner, thereby dispensing with the need for a separate support structure.

Advantageously, the fitting comprises a rearward extending cylindrical mounting portion which is externally threaded to receive and secure a hollow rod which provides the support handle of the torch.

Preferably, the primary burner includes a hollow, quadrilateral or cylindrical burner skirt, the primary burner jet nozzle(s) being located within the burner chamber defined within the skirt by means of rigid gas supply tubes 12 which support the nozzle(s) at the fitting. The burner skirt advantageously has an outlet mouth that is covered with a heat and flame resistant gauze that extends into the burner chamber (eg is concave bent into the burner skirt mouth) thereby to enhance formation of a low spreading flame during torch operation.

Preferably, the burner skirt is secured at an appropriately shaped portion of the fuel delivery fitting, for example a radially extending mounting flange portion of the fitting.

The torch head previously described can incorporate additionally h) a second pressure reduction duct of predetermined length and cross-sectional area having a gaseous fuel inlet in communication with the vaporisation chamber and a gaseous fuel outlet, the second pressure reduction duct arranged to cause a drop in pressure of the gaseous fuel entering from the vaporisation chamber, passing there through and exiting via its gaseous fuel outlet which is less than that caused in the first pressure reduction duct; i) at least one booster burner jet nozzle in fluid communication with the gaseous fuel outlet of the second pressure reduction duct and arranged to "::deliver through at least one orifice a medium to high pressure gaseous fuel stream for the formation, in use of the torch, of a medium to high velocity torch flame; and j) a hollow burner skirt that houses the booster burner jet nozzle with its orifice arranged to direct the gaseous fuel stream into the interior of the skirt S.i towards an opening mouth at a front end of the skirt such that the booster burner flame is superimposed to the primary burner flame.

A regulator valve (preferably a shutter valve with on-off regulation only) is disposed between the gaseous fuel outlet of the second pressure reduction duct and the booster burner jet nozzle(s) so that the torch can be operated with only the primary burner, which provides the ground-hogging, wide spreading flame pattern, as well as with the additional booster burner which, with its medium to high velocity, narrower or more confined flame, will provide additional heat energy when required.

Preferably, the booster burner nozzle(s) is arranged in a separate burner skirt to that in which the primary burner nozzle(s) are housed, the arrangement 13 being such that the planes in which the fuel streams are delivered by the respective jet orifices of the nozzles intersect at an oblique or acute angle. Such arrangement will cause the medium to high velocity flame to "impinge" on the low velocity flame and "drag" this flame with it, thereby creating a flame pattern that is wider than a pure high velocity flame and more energetic than the wide spreading flame of the primary burner alone..

The specific ways in which the second pressure reduction duct can be embodied are similar to those of the first pressure reduction duct, the main difference residing in the necessity of incorporating the shutter valve in the fuel flow path to the booster nozzle. Accordingly, in one embodiment of a hand-held torch implementation, a manually operatable shutter valve will be secured on the handle support rod at a location easy to access by the operator, and a gaseous fuel supply line will run from the gas passage channel of the fitting which is in communication with the second pressure reduction tube to an inlet of the shutter valve, and a further gaseous fuel supply line will run from an outlet of the shutter valve to a further gas passage channel in the fitting, which is in communication with the gas supply tube supporting and leading to the booster nozzle (in a manner similar to one of the preferred embodiments described above in relation to the primary burner arrangement).

A preferred embodiment of a hand held flaming torch in accordance with the present invention will now be described by way of an illustrative example •oil only with reference to the accompanying drawings.

Brief Description of the Drawings Figure 1 is a perspective view of a hand-held flaming torch in accordance with the present invention, showing a torch head, torch handle, torch operating elements, torch support harness and fuel tank mounting structure.

Figure 2 is a schematic side view of the hand-held torch with integrated vaporiser of fig. 1 (without the fuel tank mounting structure, second handle and harness); and Figure 3 is an enlarged, longitudinal section of the combined vaporiser/burner arrangement at the lower end of the torch illustrated in figure 1 and 2.

14 Detailed description of embodiment of the Invention Referring to the drawings, first to figure 1, there is illustrated a hand-held, flaming torch 1 which uses LPG as fuel and which can be used in numerous applications, such as for flame cultivation of terrain that is inaccessible to larger, tractor-carried flame cultivator torch batteries, weeding of irrigation channels, burning of tree stumps, softening of bitumen surfaces for road works, spot back burning operations during forest fires and other applications which require localised application of a flame or high heat.

Torch 1 consists of two main structures supported on a common rod, a torch head generally indicated at 2 and a fuel tank mounting structure generally indicated at 3. A straight, aluminium or light weight metal or composite material support tube 12 serves as a handle for the user of the torch and supports at its lower end a primary burner 14, a booster burner 16 and a liquid LPG vaporiser 18, which constitute the torch head 2 and which will be described in more detail below. Handle or support tube 12 can be comprised of a number of individual tube sections for adjusting the length of torch 1 for different applications. Handle 12 incorporates near its proximal end a first grip member 13 for one hand of the torch operator. A second handle grip in form of a loop handle 10 orientated at right angles to the longitudinal axis a of handle 12 is fixed thereon in spaced apart relationship from the first grip member 13.

:.:*.Torch 1 incorporates a trigger guard 20 disposed to cover the first grip :member 13 as well as an actuator lever 22 which operates in known manner on a normally-closed deadman (shutter valve) 24 mounted on handle 12 and which serves to control LPG flow to the torch head 2 as is described below.

Fuel tank mounting structure 3 is supported at the proximal end of handle tube 12, the mounting structure being constructed such as to permit pivotal movement of an LPG storage cylinder 27 received therein about a rotational axis b that is perpendicular to the longitudinal axis a of handle tube 12.

Mounting structure 3 includes a shallow bed cradle 6 made of sheet metal or any other suitable, rigid material. It defines a bed shape which conforms with the exterior shape of LPG cylinder 27 and has bent terminal flange portions 6a for resting the cylinder foot thereon. A number of straps 7, which are secured to the cradle in any appropriate manner, serve to strap down and secure cylinder 27 on the cradle bed. The upper skirt of cradle 6 is provided with suitable fastening points 5 so that it can be pivotally secured and held between a pair of angled support arms 4b which are welded onto the exterior of a socket hub 4a in which the proximal terminal end of tubular handle 12 is received and fixed against axial movement and preferably also against rotation, though the latter is not strictly necessary.

Mounting structure 3 is provided at fastening points 5 with any type of suitable low friction bearing elements that permit weight induced, self-tilting of the LPG tank 27 received in the cradle 6 in relation to the torch handle 12 into its upright or vertical position when the torch head is moved and pointed towards a treatment area.

A main liquid fuel supply line 26 in form of a metal braided, flexible LPG hose is secured in known manner with one of its fitted ends at the outlet valve of the LPG cylinder and is connected with its other end in similar fashion to a fitting at the support bracket of deadman shutter 24. Within handle tube 12 (see figure 2) extends a further fuel supply tube 28 that is suitably connected to the fitting at shutter valve 24. LPG cylinder 27 provides the pressurised liquid fuel supply for torch head 2.

A strap harness 8 is secured' on handle 12 at a location intermediate the first and second handle grips 10 and 13 such that, in use of the torch, the weight *of LPG cylinder 27 serves to counterbalance the weight of torch head 2 when an operator shoulders the harness. A metallic bracket having a tubular portion 9a fixed against axial movement on the handle and having a tang 9b with a plurality of eye holes 9c in spaced apart relationship serves to secure the strap harness on the tubular handle 12. A connection shackle 8a of harness 8 can be selectively inserted and locked in one of eye holes 9c By positioning the shackle in different holes, it is possible to adjust the centre of balance of torch 1, when suspended from harness 8 shouldered by the torch operator. Accordingly, this simple mechanism allows to compensate manually a shift of the centre of balance of the torch which is consequential to fuel consumption by the torch, and thus due to weight reduction of the LPG cylinder during the course of 16 operation of the flaming torch. An alternative arrangement includes a fixing bracket with indexed notches along a horizontal slot instead of discrete eye holes as illustrated.

To minimise the amount of effort that is required by the operator to point the torch head in the direction required whilst being shouldered, second handle grip 10 is mounted forward of harness strap fixing bracket 9 (that is towards torch head 2) but close thereto, and first handle grip 13 is located immediately rear of the balance point represented by the fixing point. To improve the safety of the torch operator, any suitable quick release device can be incorporated either in the shoulder harness strap or the harness fixing bracket at the torch handle thereby allowing the operator to free him or herself from the torch unit in case of an emergency.

Figures 2 and 3 illustrate in greater detail the torch head 2 as well as other components of torch 1. Torch head 2 includes a vaporiser 18 having a metallic main fitting 30 of unitary nature/construction, having a rear cylindrical mounting portion 32, a central, radially enlarged cylindrical mounting flange portion 33 and a forward, externally threaded, cylindrical hub portion 34.

Support tube 12 is mounted and fixed on the rear mounting portion 32 by any appropriate mechanical fastening means, e.g. welding, clamping.

A central channel 35 extends between axially opposite end faces of main fitting 30. As can be seen in figure 2, central channel 35 comprises portions of varying diameter. Bore 35 ends at both sides in internally threaded bores 36, 38, bore 36 disposed to receive in known gas tight manner an appropriately threaded connection bush (not shown) secured at the forward, flared end portion of liquid fuel supply line 28. Bore 38 at the forward hub portion 34 receives a liquid fuel metering tube 39 as described herein below. It will be understood that the thread connections shown in figure 2 are illustrative only of different permanent/non-permanent ways of fastening the respective gas/liquid carrying elements to one another in pressure and leakage proof manner, different connection types being known to those of skill in the art.

Central bore or channel 35 which has an inner diameter of about 6 mm comprises a portion with reduced diameter. This portion serves as a first metering duct 37, the inner diameter being about 1 mm and having a length of about 40 mm in an actually manufactured device. The metering duct 37 is shaped to allow restriction of flow of liquid LPG passing through the central bore without any substantial pressure drop. Metering tube 39 extends forward of main fitting 30 to a length of about 250 mm and is mostly comprised of a tubular section with an inner diameter of about 4 mm, but also incorporates a reduced internal diameter portion (about 1 mm) of about 40mm length at its forward end (indicated at 40) which terminates in a flash outlet orifice 42. Accordingly, the combined length of both flow restricting portions having the reduced diameter (1 mm) totals about 80 mm.

~Vaporiser 18 further includes a tubular vaporiser housing 44 which has e"i an enlarged diameter flared rear portion 48 that is internally threaded for securing the housing in gas tight manner onto the front hub portion 34 of fitting The front portion 46 of housing 34 is shaped as a closed T-tip (not illustrated) in order to reduce the axial extension of housing 44 whilst providing increased volume within housing 44. As will be noted, a mostly annular o vaporising chamber 50 is defined between the coaxially extending housing 44 and metering tube 39, with exception of the housing tip region 46 and the ".Ii radially enlarged coupling zone between housing 44 and main fitting 30. A first o0 ~20 gaseous fuel pressure reduction tube 52 is incorporated into vaporiser 18 by being located within pressurisation chamber 50. Tube 52 is secured in any oo..

suitable manner at hub portion 34 of main fitting 30 by way of a leakageproof threaded connection illustrated at 54) so as to be in communication with a first gas delivery channel 56 formed within the fitting body and extending in the hub and central portions 34 and 33. First pressure reduction tube 52 has a length and inner diameter such that gaseous fuel entering tube 52 from vaporisation chamber 50 at tube inlet 58 will undergo a defined pressure drop before reaching channel 56, as will be explained in more detail below. In an actually manufactured embodiment, tube 52 has a length, of about 150 mm with a bore of 0.8 to 0.9 mm, whilst the diameter of channel 56 is 4 or 6 mm.

Also incorporated in vaporiser 18 is a second gaseous fuel pressure reduction tube 60 secured in gas-tight manner in a threaded bore 62 in the front 18 end of hub portion 34 of fitting 30 so as to be in fluid communication with a second gas passage duct 64 which ends in a rearward facing surface of central portion 33 of fitting 30 in yet another threaded bore 63. The length between the inlet orifice 66 of second pressure reduction tube 60 and threaded bore 62 in an actually manufactured torch is about 40 mm, whilst the inner diameter is about 1 mm. Accordingly, due to its different dimensions as compared to first pressure reduction tube 52, a different pressure reduction ratio is provided by the second pressure reduction tube 60 for gas entering from pressurisation chamber Turning now to primary burner 14, it will be seen that it comprises a burner skirt or housing 70 of sheet metal which is open at its rear and front end.

The cross-sectional shape can be quadrilateral or cylindrical, and is tapered from the rear to the front. In case of a cylindrical skirt, the front position is ovoid and reduced in diameter. The front end opening 72 is covered by a heat/flame resistant gauze or mesh insert 73 which is bent in concave form into the interior of skirt 70 which defines a burner chamber 71. Heat shield plates 74 can be fastened surrounding the skirt mouth 72, shield 74 serving as a deflector for flames existing the burner mouth 72. In rearward extension of the rear opening 76, which provides an ingress passage for combustion air for the burner, is arranged a tapered-shaped cover 77 which incorporates a rigid gauze or mesh member 79 facing handle or support tube 12 and a sheet-metal shield member 78. Rigid gauze or mesh member 79 prevents ingress of unwanted objects into .toe the burner chamber 71 as the burner is moved close to ground. Cover 77 is fastened at skirt 70 in any appropriate manner, skirt 70 itself being soldered or screwed onto the central flange 33 of main fitting 30, as appropriate.

Primary burner 14 also includes at least one, but preferably three fuel delivery or burner jet nozzles, one of which is shown schematically at 80. Each nozzle has an appropriately dimensioned jet orifice outlet 0.8 or 0.6 mm) disposed to direct a jet stream of gaseous fuel towards the mouth 72 of burner skirt 70. Jet nozzles 80 are held in place within burner chamber 71 near its rearward end by means of a bent gas supply tube 82 which is itself fastened at the flange portion 33 of main fitting 30 (at threaded, sealed connection 84) so as to be in fluid communication with gas passage duct 56 and thereby receive fuel 19 from the vaporisation chamber 50 via pressure reduction tube 52. It should be noted here that the inner diameter of gas delivery channel 56 is chosen such as to avoid a further, notable pressure drop beyond that which is provided for in pressure reduction tube 52. Whilst it would also be possible to entirely omit pressure reduction tube 52 and instead provide gas passage duct 56 to have similar dimensions to those of tube 52 to thereby provide a pressure reduction duct that is integrally formed within main fitting 30, manufacturing considerations make the presently illustrated design preferable. Furthermore, providing the necessary gas pressure reduction conduit/duct in a separate element which is removably fastened to main fitting 30 allows installation and exchanging of pressure reduction tubes that have different dimensions so as to adapt the torch to different fuel types and to achieve different operating gas pressures at the burner nozzles.

Booster burner 16 which is arranged on the opposite side of vaporiser 18 15 has a similar overall layout to that of primary burner 14 and comprises a burner hood or skirt 90 open at its rear end 92 for admitting combustion air (a gauze or cage cover like the one of primary burner 14 being optional) and having a discharge opening/mouth 94 arranged to direct flames emanating therefrom obliquely onto the flames exiting from primary burner 14. It will be noted that only a short portion of vaporiser housing 44, namely the front T-shaped tip 46 extends beyond the plane containing both burner mouths 72 and 94.

Accordingly, only the terminal end of vaporiser housing 44 will be exposed to direct heat in operation of the torch, the burners providing the required vaporising energy (heat) for the liquid LPG fuel supplied to the vaporiser, as was explained above.

It will also be noted that the booster jet nozzle 96 (not necessarily only one provided) is located more in the central zone of burner chamber 91 within burner hood 90, but is similarly supported in place by way of a rigid, bent fuel supply tube 98 whose terminal end 99 is sealingly secured within threaded bore 99 of a gas channel 100 extending in central flange portion 33 of main fitting Channel 100 terminates in a rearward facing side of portion 33 in another internally threaded bore 101. A stainless steel fuel supply tube 102 is appropriately secured at bore 101 and extends towards the middle section of torch rod 12 as can be seen in figure 1, where it is coupled to the outlet of a shutter valve 106 secured on handle rod 12. Shutter valve 106 incorporates in known manner a biased valve body arranged to open and close gas access to fuel supply tube 102 from a valve inlet, the valve body being operated by a cantilever handle 108 in known manner. The gas inlet of shutter valve 106 is in fluid communication via a further copper fuel supply tube 104 with the threaded bore 63 of gas supply channel 64 extending within main fitting 30. Accordingly, fluid communication can be established from vaporising chamber 50 via second gas reduction tube 60, gas passage or channel 64 and supply tube 104 to shutter valve 27, which controls flow of gas, and then via supply tube 102, gas passage 100 and supply tube 98 to the burner nozzles 96 of booster burner 16.

!or 0From the previous description it is apparent that torch 1 incorporates only one valve with moveable parts, namely shutter valve 106 in the gaseous fuel Off**: 0 supply path from vaporiser chamber 50 to booster burner 16, the valve 25 to cut/permit liquid fuel flow from the LPG storage cylinder 27 into flexible hose 23 and liquid fuel supply line 26 of the torch being mounted/forming part of the LPG cylinder. However, non of these valves serve as conventional regulators to adjust pressure or flow rate of the fuel, either in liquid or in gaseous form. Of course, shutter valve 106 in the gas supply path of the booster burner could be exchanged for a conventional pressure regulating valve. It is believed, however, that gas pressure regulation of the gaseous fuel delivered to the booster burner 16 during expected operational parameters and application of the hand-held torch will be superfluous. However, such arrangement may be desirable in other torch embodiments, i.e. in burner batteries used in multiburner flame cultivators ad discussed above.

It is expected that hand-held torch embodiments in accordance with the present invention will be operated with gas cylinders with a capacity of between US Gal (5.71) and 5 US Gal (191) under full tank pressures liquid propane) of between about 90 to about 130 PSI gas pressure (6,200 hPa gas pressure to 8,960 hPa gas pressure). In a typical application, a 5 kg gas fuel capacity cylinder full of LPG will have a cylinder outlet pressure of between 21 and 130 PSlg (6,200 hPa to 8,960 hPa gas pressure) depending on the exterior ambient temperature.

This pressure will be substantially maintained in the cylinder for as long as there is liquid LPG in the cylinder and will only drop over a short period of time prior to the tank reaching empty. In the following, an average cylinder tank pressure of 100 PSIg 6900 hPa gas 7900 hPa absolute pressure will be assumed to be present at the storage tank outlet valve. All further pressures mentioned will be absolute pressures expect where stated otherwise. Assuming a pressure drop of 300 hPa in the fuel supply line leading from the tank/cylinder to the vaporiser main fitting 30, liquid LPG will be delivered with 7600 hPa pressure at the entrance of the metering duct 37 of vaporiser 18. A further :.pressure loss of about 200 300 hPa will take place in the metering ducts at 37 and 40 prior to liquid LPG exiting into the vaporisation chamber 50 through flash outlet orifice 42. With the geometrical values given above for pressure reduction tubes 52, 60, nozzles 80, 96 and metering duct portions 37, 40, vaporisation chamber pressure will be in the vicinity of 7400 hPa during normal, steady state burner operation where incoming liquid fuel is fully vaporised into its gaseous state (the fuel experiencing hereby a volume increase of about 280 fold) thereby generating sufficient "back" pressure in chamber 50. The required vaporisation 20 heat is provided by the primary burner to the tip portion 46 of vaporiser housing 44. It has been found during operation of a torch with vaporiser and burners as arranged in figure 2, that vaporise housing 44, will remain relatively cool (due to the uptake of energy of liquid LPG during vaporisation), the temperature of flashing of LPG at the outlet orifice 42 being around 20 30 0 C. Gaseous LPG in other zones of the vaporising chamber 50 will have temperatures ranging between 800C to about 1000C at a pressure of about 7400 hPa. The first pressure reduction tube 52 will reduce the pressure of gaseous LPG delivered to the primary burner nozzles 80 to about 2900 hPa (equivalent to about 25 PSI gas) with burner flame temperature near the transition zone gas to flame of about 6000C. Similarly, the second pressure reduction tube 60 associated with the booster burner 16 will cause a pressure drop of gaseous LPG supplied through the second tube 60 via shutter valve 106 to booster nozzle 90 so that operating pressure at the booster nozzle will be about 4000 hPa (about 40 PSI gas), the gas flame transition temperature being about 670C. Burner gas flow measured showed about 42% delivery rate to the primary burner and 58% to the booster burner whilst the latter was engaged. The above values are approximations only and are valid for torch operation where the booster and primary burners are in use after the vaporiser has reached normal operating temperatures at which the full amount of incoming, liquid LPG is vaporised in the vaporising chamber 50. Different values will apply during torch operations in which the booster burner shutter valve 106 cuts gaseous fuel supply to the S 10 booster burner nozzles 90. However, the operating pressure of the primary burner nozzles will still remain in the vicinity of 2900 hPa such that a low velocity, wide spreading flame is generated in the primary burner 14, widening of the flame being aided by the gauze mesh 73 covering the burner outlet 72.

On the other hand, the comparatively high operating pressure present at 00 15 the booster burner nozzles during booster operation of the torch will provide an S0additional high velocity, and further spreading flame which, due to the oblique arrangement of the flame spreading planes of the primary and booster burners, will enhance flame penetration. The temperature of the actual flame of the primary burner will be about 10800C whereas the high velocity booster burner 20 flame will reach temperatures of around 12000C.

Torch 1 can be ignited by allowing liquid LPG to flow into the vaporiser 18 from where it will exit through the primary burner nozzles 80 where it is subsequently ignited using a conventional separate lighter, or using a piezzo electric lighter unit incorporated into the torch head 2 and which has an operating button near one of the handle grips (not shown). During a short period of time of about 5 to 10 seconds after opening the main valve at the LPG cylinder, liquid LPG entering the vaporiser chamber will vaporise partially (as it can "pick-up" sufficient heat from its surroundings without additional heat transfer into the vaporiser), this partially vaporised fuel mixture being able to be ignited more readily upon exiting the burner nozzles than fully liquid LPG.

Once steady state (normal operation) has been reached, and the vaporiser produces gaseous fuel to supply both burners 14, 16, booster burner Li~' r 23 16 can be fired selectively by means of the handle operated shutter valve 106.

It should be noted that the flow restriction of liquid fuel into the vaporising chamber 50 by way of metering duct 37 and metering tube 39 is such that the fuel amount delivered is about equal to the vaporisation rate achievable during normal torch operating conditions. As alluded to above, because the two pressure reduction tubes 52 and 60 as well as the metering tube 39 (which provides part of the overall length of the metering flow restricting metering duct) are mounted in removable fashion within the vaporisation chamber 50 (the vaporiser housing being readily unscrewed from the main fitting), it is possible to exchange these components to suit the specific type of fuel employed with the otorch in order to obtain a desired burner nozzle operating pressure.

It will be further appreciated that modifications to the presently illustrated embodiment are readily possible without departing from the gist of the present invention. For example, the counterbalancing principle underlying the present 0" 15 invention, which uses the weight of the fuel storage tank of the torch which is *e pivotally supported at or near one end of the elongate torch handle opposite the torch head which includes the torch burners, can equally be applied to flaming 0 torches having a single burner unit or burners that are different to those employed for flame cultivation purposes.

Claims (14)

1. A hand held flaming torch having a rod-like handle, a torch head at one end of the handle and a fuel tank mounting structure at an opposite end of the handle, wherein the fuel tank mounting structure includes a handle mount fixed at the handle and a tank support structure pivoted at the handle mount, whereby in use of the torch the weight of the torch head is at least partly counterbalanced with the weight of a fuel storage tank secured at the tank support structure and the tank is pivotable with respect to the handle such as to remain in a substantially upright position during operation of the torch.

2. A hand held flaming torch including: an elongate, tubular or rod-like torch handle having a longitudinal axis; a first handle grip at or near a proximal end of the handle; an optional second handle grip on the handle and spaced apart from the first handle grip; •o a torch head supported at or near a distal end of the handle, the torch head having at least one burner arranged for generating a flame; a fuel supply line arranged to deliver fuel to the burner, the fuel supply line being connectable to a fuel storage tank; and a fuel storage tank mounting structure at the proximal end of the handle, the too. mounting structure arranged such as to enable pivotal movement of the storage S tank, when received therein, about a pivot axis that is perpendicular to the longitudinal axis of the handle, wherein, in use of the torch, the weight of the fuel storage tank serves to counterbalance the weight of the torch head when an operator holds the torch at the handle grip(s).

3. Hand held flaming torch according to claim 2, further including: a strap harness removably secured on the handle at a location forward of the first handle and intermediate the first handle grip and the second handle grip, where such second handle grip is provided, the strap being arranged to allow an operator of the torch to shoulder the weight of the torch and the weight of the fuel storage tank serves to counterbalance the weight of the torch head.

4. Hand held flaming torch according to claim 1, 2 or 3 wherein the mounting structure includes a shallow bed cradle having a bed shape conforming with the exterior shape of a LPG cylinder and at least one terminal flange portion for resting the cylinder foot thereon. Hand held flaming torch according to claim 4, wherein straps, which are secured to the cradle, serve to strap down and secure the cylinder on the cradle bed.

6. Hand held flaming torch according to claim 4 or 5, wherein the mounting structure includes a simple gimbal mount in which an upper skirt of the cradle is pivotally secured and held between a pair of angled support arms which are secured on a socket hub in which the proximal terminal end of the torch handle is received and fixed against axial movement and optionally also against rotation.

7. Hand held flaming torch according to any one of claims 3 to 6, wherein a S. fixing device for the harness is mounted at the handle, the fixing device being arranged to allow shifting the location at which the harness is secured at the handle to compensate for a shift of centre of balance of the torch as a result of fuel consumption during operation of the torch.

8. Hand held flaming torch according to claim 7, wherein the fixing device is a bracket having tubular portion fixed against axial movement on the handle and having a tang with a plurality of eye holes in spaced apart relationship which are disposed to selectively receive a connection shackle of the harness strap.

9. Hand held flaming torch according to claim 7, wherein the fixing device is a bracket having a tubular portion fixed against axial movement on the handle and having a tang with indexed notches along a horizontal slot, the notches being disposed to selectively receive a connection shackle of the harness strap. Hand held flaming torch according to claim 3 to 8, wherein the second handle grip is mounted forward of the harness strap fixing point but close thereto and includes a loop handle portion orientated at right angles to the torch handle, and wherein the first handle grip includes a tubular grip member that is located immediately rear of the balance point represented by said fixing point.

11. Hand held flaming torch according to any one of claims 3 to 10, wherein a quick release device is incorporated either in the shoulder harness strap or the harness fixing device at the torch handle thereby to allow an operator to free him or herself from the torch unit in case of an emergency.

12. Hand held flaming torch according to any one of the preceding claims, wherein the torch head includes: a primary burner having at least one fuel delivery jet nozzle arranged in an open combustion chamber defined within a burner skirt such as to direct a stream of fuel towards a flame delivery opening of the skirt; and a vaporiser located in heat exchanging proximity to the primary burner and having a pressurisation chamber with an inlet for liquid fuel and an outlet for vaporised, gaseous fuel, the inlet being arranged to receive fuel in liquid state from a source of pressurised liquid fuel and the outlet being in fluid communication with the nozzle of the primary burner, characterised in that a metering duct is located in close vicinity or within the vaporiser and •arranged is to discretely limit the amount of liquid fuel entering the vaporisation chamber via its inlet, and in that a first pressure reduction duct is provided in the flow path of gaseous fuel between the vaporisation chamber outlet and the nozzle of the primary burner, the first pressure reduction duct arranged to impart a discrete pressure drop to gaseous fuel flowing there through from the vaporisation chamber to the nozzle of the primary burner, the discrete pressure drop being such as to generate a low velocity combustion flame in the primary burner during normal torch operation.

13. Hand held flaming torch according to claim 12, further including a booster burner having at least one booster jet nozzle which is in fluid communication with the vaporisation chamber through a second pressure reduction duct which is arranged to reduce the pressure of gaseous fuel exiting the vaporisation chamber by a predetermined amount required to generate a medium to high velocity combustion flame in the booster burner during normal torch operation.

14. Hand held flaming torch according to claim 13, wherein the at least one nozzle of the booster burner is disposed in an additional burner skirt defining a booster combustion chamber, the primary and booster burner skirts being arranged such that flames emitting through the flame delivery openings intersect at a small angel such that the wide spreading, low velocity combustion flame of the primary burner is superimposed with the narrower, high velocity combustion flame of the booster burner. Hand held flaming torch according to claim 14, wherein a manually operable shutter valve is provided at the second handle grip to selectively permit and cut-off gaseous fuel flow to the booster burner.

16. Hand held flaming torch substantially as illustrated in and hereinbefore described with reference to the accompanying figures. DATED this 4 th day of August, 2000 ORIGIN ENERGY LPG LIMITED WATERMARK PATENT TRADE MARK ATTORNEYS UNIT 1, THE VILLAGE RIVERSIDE CORPORATE PARK

39-117 DELHI ROAD NORTH RYDE NSW 2113 P2659AU00 CJS:MM 9 *oo ooo