AU719752B2 - Improved concentrated heat agricultural flame cultivator apparatus - Google Patents

Description

'CTA 9 7 0 0 2 9 RECEIVED 1 6 JUJN 1998 IMPROVED CONCENTRATED HEAT AGRICULTURAL FLAME CULTIVATOR APPARATUS 1. Background of the Invention This invention relates to combustive plant pest and weed killing apparatus, particularly for thermally killing weeds and plant pests near plants of a valuable crop such as cotton, corn or lucerne. Specifically, the invention relates to an improved gas burner construction, a modified vaporiser arrangement and to an agricultural implement incorporating such vaporisers and burners.

Chemical herbicides and pesticides are commonly used in agriculture, however, there is an ever growing concern about the degradation of the environment and the crops as a result of extensive use of such chemicals. As an alternative hereto, flame treatment or flaming is practiced to control weeds and pests.

Flaming involves the application of a high intensity heat for a short period of time but sufficient to create cell damage in the leaves and stems of the weeds and to kill pests such as bacteria, weevils, insects or fungus spores and the like that are likely to attack the valuable crop plants. Flaming treatment of plant weed does not require actual burning of the plant weed, but merely involves a sudden increase of temperature in the leaf cells of the plant weed to say 50 to 700C.

This leads in time to a withering of the leaves and stems of the plant weed and ultimately results in the death of susceptible weeds.

2 Prior Art to the Invention Agricultural flaming implements (or devices) are known in which a tractor carried (or towed) support frame structure is used to mount a number of burners so as to coincide with the row spacing of crop plants on a field of arable land.

The implement may be moved over the area to be treated at ground speeds of up to 7 km per hour depending upon various environmental factors such as ground and air moisture content, ground temperature and burner flame temperature, as well as the size of the plant weeds.

The use of combustive apparatus in an agricultural implement used to treat large commercial tracts of land requires relatively large volumes of fuel to 41 d AMENDED SHET

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PC/AU9 7 00 4 2 9 RECEIVED 1 6 JUN 1998 2 be supplied to a relatively large number of burners given that the implement is expected to quickly treat such area. With large capacity burners there is inevitably the problem of in maintaining an adequate supply of fuel to the burners at and to achieve optimum combustion efficiency.

As fuel source for the burners it is known to use vaporised liquid petroleum gas (LPG) which is preferably propane or a mixture of propane/butane. Propane has a boiling point of -420C and therefore at ambient temperatures it is stored in fluid form under pressure in tanks, the pressure varying between 40 and 120 psi depending upon ambient and storage temperature. Butane has a higher boiling point temperature and therefore the propane/butane mix will have a higher boiling point temperature than pure propane, and will therefore have lower storage (and fuel supply) pressures.

There have been various apparatus disclosed in the prior art, directed to the provision of vaporisers for agricultural flaming appliances to ensure proper supply of gaseous fuel to the burners, including US Patent No. 3357474 (Pivonka). Pivonka discloses a burner vaporiser construction that is designed to ensure vaporisation of vaporisable liquid fuel, such as butane/propane gas mixtures that are stored in liquid form with the object of burning gaseous fuel at a high rate relative to the size of the burner.

Similarly, US Patent No. 3645664 (Clinton) relates to a vaporiser which is claimed to operate at greater efficiency by supplying vaporised propane fuel to burners in a manner that ensures the fuel is sufficiently burned with little or no smoke being released to the atmosphere.

Current LPG burning apparatus known to the applicant, examples of which are referred to above, exhibit a problem of uneven vaporisation of the liquid fuel at the vaporiser. This problem possibly results from the need to regulate the flow of the pressurised liquid fuel prior to vaporisation and prior to it being fed to the vaporiser. Such regulation inevitably leads to at least partial vaporisation of the liquid down stream of the regulator, with the associated takeup of heat by the vaporising liquid resulting in a severe drop in temperature (and often freezing) of the lines and fittings, as well as the regulator valves.

This means that the vaporiser receives fuel which may be partially NT AMENID SH 'ci 9 7 0 0 4 2 9 3 vaporised, or in some instances fully vaporised, and in other instances still fully liquid depending upon the temperature of the downstream line between the valve and the vaporiser. The temperature of the fuel in the line may vary between the range of ambient temperature, say 250C, and the boiling temperature of the propane fuel which is -420C.

It has been found that the burner temperature in flaming equipment should be kept at a constantly high level, if at all possible, as this is conducive to orderly operating of the flaming equipment over an extended period of time, requiring only minimum adjustment to the burners and to the vaporisers for a given speed of travel over the ground by the flaming implement. The above mentioned wide temperature range of fuel feed to the vaporiser may lead to either inadequate vaporisation of the fuel or in overheating of the fuel to high temperatures. This in turn has an adverse effect on burner efficiency. It has been found that inadequate vaporisation of the fuel fed to the burners will lead to ineffective or inefficient burning of the fuel in most instances, which in turn will cause high fuel consumption and lower than optimum burner temperatures.

It has been also found that existing gas burner designs of flaming apparatus used for agricultural purposes tend to concentrate the heat into rows that are relatively narrow thereby leading to under treatment of portions of the ground or crop. The burners currently being used are large Bunsen type burners in which vaporised gases is mixed with air and burned to form a relatively hot flame of between 9000C to 12000C. It has been established in testing that the temperature of the flame quickly dissipates despite modification of the mouth of the burners to be elongated in a horizontal plane relative to the ground surface to be treated. This necessitates the placement of burners side by side relatively close together in order to avoid strips of ground being untreated through lack of heat.

US Patent No. 3486497 (Pivonka) addresses the problem of achieving a larger coverage area with the flaming technique by discharging a fine stream of liquid fuel at high velocity to an area to create a wide spread of fuel directed at ground level. This device is particularly used for burning-off on roadsides and in irrigation channel clearing and is generally used in hand-held torches.

AMENED CHEET cr U7 0 0 4 2 9 RECEIVED 16 jU q98 4 Accordingly, in this arrangement, fuel is vaporised in the atmosphere after being released and ignition and burning takes place as the liquid vaporises in a barely controlled manner (aside from regulation of the amount of fuel dispensed). Thus, such device would seem inappropriate for conventional flame cultivation.

Other ways to increase the amount of heat that is directed to an area to be flame treated utilising a tractor carried or drawn flame cultivator with burner batteries is to arrange burners on opposite sides of a cultivation row such that the burner flames converge from opposite sides (compare US Patent 3,16,927 to Holloway) or to arrange the burners in opposite staggered relationship such that the flames pass sequentially over the same area from opposite sides (compare US Patent 3,177,922 to Pardee). Pardee also discloses a combined burner vaporiser device, wherein LPG fuel is supplied in liquid form to each burner for vaporisation within the associated vaporiser prior to being combusted in the burner. The above addressed problem of the burner flames tending to concentrate on a relatively narrow treatment zone are still present in these devices.

Problems are also experienced with flaming treatments caused by overheating in crops, including leaf damage to the crop plants. US Patent No.

5189832 (Hoek et al) discloses one proposal to reduce the heat damage to the plant by creating a horizontal cool air curtain near the base of the plant to restrict rising hot air which can tend to damage the leaves.

Flaming treatment is also utilised to a limited extent in relation to heating of asphalt on asphalt roads, and like surfaces where large quantities of heat are applied to the surface over a relatively large surface area.

Summary of the Invention The present invention has as one objective to provide a vaporiser for LPG fuel such as propane or propane/butane mix in which the above mentioned problems in the prior art are at least partially addressed and which is able to contribute to an improved gas burner efficiency.

It would hereby be desirable if the invention could provide a vaporiser design that permits to reduce the number of vaporisers necessary to vaporise A the amount of LPG required to supply a large number of burners, eg one large ~NT O4 AMENDE1D CXEET IPEAt.as capacity vaporiser capable of vaporising a large volume of fuel.

It would be further advantageous if a LPG fuel vaporiser in accordance with the present invention could be used with high heat output flame cultivators and other implements used in the control of weeds and pests, particularly but not exclusively in agricultural situations, other applications including the control of weeds in public areas, pathways and the like.

In a first aspect, the present invention provides apparatus for vaporising vaporisable hydrocarbon fuels in particular liquified petroleum gas for use in a combustive weed and plant pest control implement, the apparatus comprising a vaporiser for vaporising said fuel and a vaporiser heater for supplying vaporisation heat to the vaporiser for effecting said vaporisation, wherein the vaporiser includes a tubular vaporiser housing defining in its interior a vaporisation chamber, a fuel delivery tube extending into the vaporiser housing and arranged to receive said fuel in-liquid form from a fuel storage vessel and deliver it into the vaporisation chamber, a gas delivery outlet in communication with the vaporisation chamber and arranged to deliver said fuel in gaseous form for subsequent use, and a liquid fuel metering member including an orifice arranged for limiting to a predetermined amount the flow of liquid fuel into the vaporisation chamber via the delivery tube; wherein the

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vaporiser heater includes a bunsen type burner arranged to direct a flame to C.o.

the vaporiser housing so as to heat the vaporisation chamber; and wherein the orifice of the metering member is located at the fuel delivery tube in a zone at the vaporiser housing heated by the vaporiser heater.

S: By locating the metering member orifice, which in effect is flow regulator, in the vaporisation chamber or closely adjacent thereto in a zone that receives heating energy from the vaporiser burner, it will be found that problems associated with icing of the fuel pipeline and fittings, including flow regulators, located upstream of the vaporiser are minimised. This in turn ensures a more steady and constant supply of fuel in a single aggregate state (ie liquid, and not partly vaporised, as is the case in conventional arrangements), to the vaporiser, which in turn enables a better controlled vaporisation to ensure fully vaporised fuel is supplied by the vaporiser.

Consequently, it is possible to use conventional pressure regulation of the 6 gaseous fuel prior to it being fed to the burners of a thermal weed or pest control implement.

Conveniently, the vaporiser may generate the gaseous fuel required for the operation of its associated vaporiser heater.

In a still further aspect of the present invention there is provided a vaporiser apparatus for LPG fuel as described above, wherein the metering member has an orifice of relatively large size, preferably greater than 1 mm. This measure allows to design a single vaporiser unit with large inlet flow capacity, thereby enabling one device to vaporise the entire fuel requirements for a larger number of burners such as used in an agricultural flame cultivator of the type referred to below. The use of a large metering orifice has the added advantage of not being too susceptible to blockages due to dirt particles or impurities in the liquid fuel.

Furthermore, any blockages that may still occur are easier to clear.

Continuity of supply of fully vaporised fuel enables conventional gas pressure and flow regulation techniques to be employed on the outlet side of the vaporiser apparatus, thereby enabling, in turn, operation of the gas burners at their optimum performance level over an indefinite extended period of time with little or no variation in flow patterns in the vaporised fuel.

In another aspect of the invention, there is provided an agricultural implement for flame cultivation of arable land, including: eo a support structure arranged to be drawn by or mounted on a tractor; a plurality of burners located on the support structure in spaced apart relationship such as to respectively direct a flame onto a respective zone of flame treatment; a fuel delivery circuit with pipes arranged to deliver fuel from a storage vessel of liquid hydrocarbon fuel, in particular liquified petroleum gas (LPG), to each of the burners; one vaporisation apparatus as herein before described, disposed in the fuel delivery circuit such as to receive liquid fuel from the fuel storage vessel and deliver vaporised fuel to the burners, the vaporised fuel delivery tube heretofore being in fluid communication with a manifold pipe arranged to deliver the vaporised fuel to the burners, the metering member having an -orifice size of at least 1mm; and a gas pressure regulator disposed in the fuel delivery circuit between the vaporiser gas delivery outlet and the burners, fuel supply regulation to the burners being effected such that flow control of fuel in liquid state is substantially only effected by the metering member of the vaporiser and flow control of fuel in vaporised or gaseous state is effected downstream the vaporiser by the gas pressure regulator thereby to enable close regulation of fuel flow to the burners.

In yet another aspect of the invention, there is provided an agricultural implement for flame cultivation of arable land, including: a support structure arranged to be draw by or mounted on a tractor; a plurality of burners arranged in burner banks consisting of a predetermined number of individual burners, the burner banks located on the support structure in spaced apart relationship such as to respectively direct flames into a respective zones of flame treatment; a fuel delivery circuit including pipes arranged to deliver fuel from a storage vessel of liquid hydrocarbon fuel, in particular LPG, to each of the o••o burner banks; S"a number of vaporisation apparatus as hereinbefore described, one vaporisation apparatus being provided for each burner bank, each vaporisation apparatus disposed in the fuel delivery circuit such as to received liquid fuel from the fuel storage vessel and deliver gaseous LPG to the burner banks, the fuel delivery tube of each of the vaporisers heretofore being in fluid 9*o* communication with the fuel storage vessel and the gas delivery outlets of each of the vaporisers being in fluid communication with a manifold pipe arrange to deliver gaseous fuel to an associated one of the burner banks; and a plurality of gas pressure regulators disposed one each in the fuel delivery manifold pipe leading to a respective one of the burner banks such that flow control of fuel in liquid state is substantially only effected by the metering members of the respective vaporisers and flow control of fuel in gaseous state is effected downstream of the respective vaporisers by the respective gas pressure regulators, thereby enabling closer regulation of fuel flow to the burner banks.

SThe implement may take many forms, depending upon the purpose for hich it is used. In conventional row cropping, the implement may be used for 8 weed control, for example cotton or maize corn or similar crops which are heat tolerant, and pre-emergent crops. The implement may contain burner units, such as those described below, which are located such that these travel between the rows of plants, and shielding means associated with the burners, such that heat is directed towards the ground at the weeds and around the base of the plants, whilst the plant leaves are shielded from damage created by heat radiation or hot air draughts.

In specific instances the implement may be a relatively large tractor drawn device suitable for treatment of large areas under cultivation.

Alternatively, the implement may be relatively small having a single or small array of burner units suitable for manual operation.

Advantageously, such agricultural implement, having one or more vaporisation apparatus and a plurality of burners, can incorporate burners of a type which include: :a main burner of bunsen burner type having a burner housing defining a burner chamber with at least one inlet opening for combustion air and an outlet opening arranged to direct a flame and heat into a zone of treatment, at least one fuel delivery jet for delivering gaseous fuel into and being located within the burner chamber, and a gauze or mesh insert member located within the burner chamber at or near the outlet opening and arranged to improve diffusion of combustion gases and enable greater spread of the flame emanating from the outlet opening; and a booster burner of bunsen burner type mounted adjacent to the main burner such that, in operation, a flame emanating from an outlet mouth of the booster burner is directed to impinge on and combine with the flame of the main burner thereby to enhance flame velocity and flame spread of the combined flame into the zone of treatment.

It has been surprisingly found that a wider area of ground surface can be treated for a given size of main burner by inclusion of a gauze or mesh 9 member inserted within the mixing chamber at or near the burner mouth. The gauze or mesh has the effect of improving the diffusion of the air/gas mixture by decreasing the velocity of the mixture within the burner chamber, thereby enabling a greater spread of heat over a wide area near the burner mouth.

Conveniently, the gauze or mesh material is formed to have a concave inward surface completely extending across the burner chamber and the outlet therefrom. Preferably the size of the mesh holes should not exceed 2mm for best results. The mesh insert is preferably of temperature resistant material of the type marketed under the trade mark INCANOL.

The gauze or mesh insert member does compromise the fierceness of the resultant flame at the main burner mouth, both in terms of velocity and impact of the flame at the point of application to the ground surface. Similarly, the heat of combustion emanating from the burner is not always properly focussed at the ground area being treated.

o This is countered by the booster burner in that it directs additional heat o. into the same zone of treatment of the main burner to achieve an improved flame focussing and maintenance of heat at ground level in the zone of treatment. This measure also enhances flame velocity in the vicinity of the insert member. Preferably, the booster bunsen burner providing additional heat is of standard construction and does not include a gauze or mesh insert and may have a burner housing defining a burner chamber in which at least one gaseous fuel delivery jet is located, the burner housing having a flared front section widening towards the burner housing outlet mouth. Thus, apart from the additional heat provided in the zone of treatment, the flame is directed with greater velocity and focus than that provided by a burner with gauze or mesh insert alone. The additional heat will provide greater dwell time for weed and pest control in a wide variety of crop situations.

It has been found that such a burner arrangement, in conjunction with a trailing shroud or skirt drawn behind the agricultural implement such as a tractor, will provide an even spread of high temperature burning gases beneath the shroud and has been found particularly effective in the control of weeds and pests associated with crop cultivation.

Accordingly, in a further aspect of the present invention there is provided an agricultural implement for flame cultivation of arable land, including: a ground engaging structure to be drawn by or mounted on a tractor; a plurality of main burners as defined above and arranged such as to direct heat beneath a shroud member or skirt of the ground engaging structure, the shroud member being disposed to cover a zone of flame treatment; a plurality of booster burners as defined above, one each associated with a respective one of the main burners, the booster burners being mounted atop the shroud member such that the booster burner outlet mouths are directed through respective apertures in the shroud member and the flames emanating therefrom impinge and combine with the flame of the associated main burner thereby to enhance flame velocity and flame spread of the combined flame into the respective zone of treatment; and one or more vaporisation apparatus as described above for the supply S. of fuel to all the burners.

Embodiments of the present invention will now be described by way of example only, having reference to the accompanying drawings, in which 4. Brief description of the drawings *see Figure 1 shows a tractor drawn flame cultivator implement in accordance with the present invention, fitted with vaporisation apparatus (units) in accordance with the present invention; Figure 2 shows a schematic frontal view of the implement of figure 1 showing the arrangement of flaming burners in module groups or banks; Figure 3 is a schematic diagram illustrative of a first fuel supply circuit for burners arranged in common banks or modules as used with an implement similar to that of fig. 2, utilising a (modified) single vaporiser used to supply gaseous fuel to all burners; Figure 4 is a schematic diagram illustrative of a second fuel supply circuit for burners arranged in common banks or modules as used with an implement similar to that of fig. 2, including a number of vaporiser units for vaporising fuel for the burners and gas regulation control valves in the fuel supply lines; 9b Figure 5 shows in longitudinal schematic section a first embodiment of a vaporisation apparatus (unit) in accordance with the present invention; Figure 6 shows the liquid inlet tube and metering unit of the vaporisation unit of figure Figure 7 shows a schematic longitudinal section of an alternative vaporisation unit embodiment with adjustable metering valve; Figure 8 shows a schematic side view of a vaporiser unit incorporating tie vaporiser of figure 5 and a vaporiser heater arranged in a first configuration; Figure 9 shows a schematic side view of a vaporiser unit incorporating the vaporiser of figure 5 and vaporiser heater arranged in a second configuration within a common burner shield member; Figure 10 shows a schematic, sectional side view of a further flame cultivator implement with a modified burner in accordance with the present invention; Figure 11 shows an end view of the outlet of the modified bumer shown in fig. 11; 9 .9 oei ogoo PcrAt 7 00 4 2 9 RECEIVED 1 6 JUN 1998 Figure 12 shows a schematic, sectional side view of a flame cultivator implement similar to that of fig. 11 but with yet another, modified burner arrangement in accordance with the invention; Figure 13 shows a schematic, sectional side view of a further, modified flame cultivator implement with yet another, modified burner arrangement in accordance with the invention; Figure 14 is a side view of a side plate of the implement of Figure 13; Figure 15 is a plan, schematic view of a Bunsen type burner as used in the flame cultivator implement of figure 1, 12 and 13; Figure 16 is a schematic, side sectional view of the modified burner construction employed in the implement of fig. 14; and Figure 17 is a front elevational view of the burner construction of figure 16 IL Description of modes to carry out the Invention Having reference first to figures 1 and 2, there is shown a tractor-drawn flame cultivation implement 10 incorporating various aspects of the present invention and which can be mounted on the hitch of a tractor (not illustrated) with the assistance of a jockey wheel 12. Implement 10 comprises a number of individual ground engaging units 14 (five shown in fig. 7) supported on a main cross bar 16 which includes lateral end sections 16a and 16b pivoted at 18, thereby enabling the lateral most of the ground engaging units 14 to be pivoted back on itself to reduce the width of the implement during travel on a road, as is schematically illustrated in fig. 2. Individual ground engaging units 14 may be lowered or raised with respect to the ground level about a two bar linkage assembly 20 through link mechanism 22.

The ground engaging units 14 of implement 10 comprise a plurality of burners 24, arranged in blocks or batteries, (four burners per block illustrated in fig. 2) and located around deflector plates 26 such as to direct heat towards the ground and beneath deflector plates 26. Plates 26 ensure that upward flow of heat from the burners 24 is minimised, as is also explained below with reference 0 to the implement embodiments illustrated in figs. 10 and 12. The ground ngaging units 14 can further include ground skids illustrated at 28 in fig. 1. The SAMENDED S1-iT

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9 7 1 0 0 4 RECEIVED 1 6 j i 11 construction of the body of the cultivator may be varied according to whether it will be used for the treatment of row crops, such as cotton or maize, for example, and lucerne or like pasture crops.

The individual burners 24 of implement 10 are large Bunsen type burners in which vaporised fuel is mixed with air and burned to form a relatively hot flame of between 900 0 C to 1200 0 C. The burners 24 utilise LPG in gaseous form.

Heretofore it is necessary to vaporise the fuel which is generally stored in liquid form under pressure in a tank or tanks carried by the tractor, prior to delivery to individual burners 24. This is accomplished using one or more vaporiser units, one of which is schematically illustrated at 30 in fig. 1, which can be arranged in a fuel supply circuit in a manner that will be described in more detail below with reference to figs. 3 and 4.

Turning first to possible vaporiser unit embodiments in accordance with the present invention, figures 5 and 7 illustrate constructional features and the arrangement of two vaporiser embodiments, respectively, whilst figures 8 and 9 illustrate the constructional features and arrangement of two alternative vaporiser units consisting of a vaporiser and its associated heater device used to supply heat to the vaporiser.

Vaporiser 32 illustrated in fig. 5 includesan inlet tube 34 arranged and held within vaporiser housing 36 which provides a vaporisation chamber 38.

Inlet tube 34 is disposed for direct connection with an LPG supply tank (not illustrated) via a hose through fitting 40. A metering orifice member 42 is releasably held on the opposite terminal end of inlet tube 34 by means of fitting 44. Vaporiser housing 36 is provided with a gas fitting 46 through which gaseous fuel generated within vaporisation chamber 38 can be piped away.

With reference to Figure 7, there is shown a modified vaporiser 32' in which a needle valve assembly 48 replaces the metering orifice member 42 shown in fig. 6, but which is otherwise similar to the previously described vaporiser. Valve assembly 48 is arranged at the incoming end of inlet tube 34 and includes a fitting for connection with the liquid fuel supply line or hose leading to the LPG storage tank. Needle valve assembly 48 includes a needle member 52 movably received within valve socket head 54.

Needle member 52 is threaded and cooperates with lock nut 56 to allow LU AMENDED SH AMENDD SHE= 9 7 0 0 4 2 9 RECEIVED 1 6 JUN 1998 12 movement and locking of needle member 52 in a desired setting of the needle point relative to valve seat 58 and thereby control flow of incoming liquid LPG into vaporiser inlet tube 34. Therefore, valve seat 58 provides a variably adjustable metering orifice. A cap 59 may be provided to cover the rear end of socket head 54. Also illustrated in fig. 7 is a conduit 47 connected to gas fitting 46, which is used to pipe away the gaseous LPG fuel.

Figs. 8 and 9 show two different vaporiser unit embodiments, which in essence consist of a vaporiser such as has been described and a vaporiser burner 60 which is arranged such that flames emanating from its burner jet nozzle 62 impinges on and heats the vaporiser housing 36 to supply the heat necessary for vaporisation of LPG fuel that enters the vaporiser through the metering orifice of member 42 or valve seat 58. In fig. 8 the burner and vaporiser are arranged obliquely to one another, whereas in the embodiment shown in fig.

9 the vaporiser 32 is mounted diametrically opposite the burner jet 62 and within the burner casing or shroud 64, which as illustrated includes breather holes 66 to ensure proper air supply to the Bunsen type burner It has been found that the heating effect in the vaporisation chamber 38 is maximised with the vaporiser unit 30 of fig. 9 where the burner 60 and vaporiser 32 are arranged within the burner casing 64.

In operation of such type of vaporiser units as illustrated, liquid LPG fuel is carried under pressure from the storage tank via hose 50 to the vaporiser 32 where it is supplied in metered manner into the vaporisation chamber 38 via inlet tube 34 through the orifice of metering member 42 (fig. 5) or needle valve 48 (fig. Upon heating of the vaporiser housing 36 and chamber 38 by a flame from burner 60, the released liquid LPG is vaporised in the high temperature environment in chamber 38, from where the gaseous LPG is then piped away through gas fitting 46 and line 47 for further use as will be described below.

In order to achieve full vaporisation of the liquid fuel, which also results in a substantial expansion of the fuel in chamber 38 large amounts of heat have to be delivered to and absorbed by the fuel. Accordingly, heater 60 has to be dimensioned as required. Also, the orifice of metering member 14 is chose to be of predetermined size to supply sufficient fuel in liquid phase to meet the aseous fuel demands or requirements of a bank of burners operating on a Z AMENDED SHEET

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?cTrA9 7 00 4 2 9 RFCrl'fl 1 AMI'WM I998 13 particular fuel circuit of up to say 6 burners supplied by one vaporiser unit, as will be described exemplarily in the following.

Figures 3 and 4 show schematically two different forms of fuel supply circuits for burner bank arrangements as used in flame cultivation implements in accordance with the invention such as the one described with reference to fig. 1 above and other embodiments described below. It will be noted that fig. 3 shows only four banks of burners, identified at 114 (as compared to the five burner banks ground engaging units 14 shown in fig. with four burners (identified at 124) each, and one fuel vaporiser unit 130 that serves to supply all burners 124 with gaseous fuel through a fuel supply circuit.

Fig. 4 shows an arrangement in which six banks 214 are provided in the flame cultivation implement, with three burners 224 each, and five vaporiser units 230, of smaller capacity than the one of fig. 9, switched in a fuel supply circuit to provide gaseous fuel to all burner banks 214. In the arrangement of fig.

4 liquid LPG is supplied via manifold line 250 to the vaporisers 232 of vaporiser units 230 and gaseous fuel exiting vaporisers 232 is then fed into a manifold pipe system 247 for subsequent distribution to the burners 224 of banks 214 through pressure regulator valves 270 or 271. The valves 270 may be low volume flow regulators whilst valves 271 may be of a high volume flow regulator, depending upon the number of burners 224 that are actually operating on the implement. Each burner 224 may include a stop valve for controlling flow of gas to each individual burner, as exemplarily indicated at 272.

Stop valves 273 are also provided to control flow of gas to each bank of burners 214.

Referring again to fig. 3, 16 burners 24 are arranged in four batteries or banks 114 of four and are arranged to be supplied with gaseous LPG fuel from a single vaporiser unit 130 through a common supply circuit. Liquid LPG is stored in storage tank 60 controlled by stop valve 61 and carried under pressure to vaporiser unit 130 through a suitable hose in which a further stop valve 62 is located. Vaporiser unit 130 includes a modified vaporiser 132 in that liquid fuel is released into the vaporiser chamber through metering orifices at each terminal end of an elongate small bore vaporiser inlet tube (not shown). The S volume of fuel to be consumed by the burners 24 of the banks 114 is fully C) AMENDED SHa.T 'P AD 1 AU cTfrAu 7 97/0042 9 rLi i b Ld- i j- 14 vaporised prior to being distributed to the burners. This is not only carried out in order to avoid inefficient use of the fuel, but this also allows: closer (better) regulation of fuel flows in gaseous form to the burners, as compared to liquid fuel flow regulation. One of the burners in one of the banks 114, identified at 160, serves as vaporiser burner to deliver the vaporisation heat required by vaporiser 132.

Control of fuel flow in the illustrated circuit is essentially in two stages, the first stage involving firing of the pilot (vaporiser) burner 160 to preheat the vaporiser 132 and fuel supplied thereto, and then the second stage which involves ignition of all or a predetermined number of the burners 124 in the other banks 114. Burner 160 is arranged to provide sufficient heat to vaporiser 132 which itself is dimensioned such as to allow ingress of sufficient liquid fuel and conversion thereof into gaseous fuel to meet the fuel requirements of all of the burners 124, regulation of fuel supply to the burner banks 114 being effected in its gaseous form by regulator valve 170. The flow of gas from regulator 170 to the burner banks 114 is controlled by stop valve 172.

The inlet tube of vaporiser 132 is designed to allow relatively large flows of liquid fuel into the vaporisation chamber to meet fuel requirements by all burner banks 114, and the size of the metering orifices (which may be fixed, compare vaporiser embodiment of fig. 5, or adjustable, compare vaporiser embodiment of fig. 7) is therefore relatively large, preferably greater than 1 mm, thereby simultaneously minimising the possibility of blockage occurring in the inlet and metering tube.

Further, vaporiser burner 160 of vaporiser unit 130 which serves as the gaseous fuel supply source for the burner banks 114, is advantageously arranged to be controlled (and therefore control vaporisation of fuel within the vaporiser) in response to the temperature of the gaseous fuel at the outlet of the vaporiser chamber and before entering regulator 170. This not only achieves a self regulating fuel supply system., but also protects the regulators from being subjected to excessively heated gaseous fuel that may cause premature failure of the regulator. Whilst flow of liquid from the fuel tank 100 is controlled by the solenoid valves 102 and 104, liquid fuel flow into the vaporiser is controlled by 3 the (correctly sized) orifice of the vaporiser metering member 42 (fig. 5) or AMENDED SH.

IPEAJi ncTA 7 0 0 4 2 9 RECEIVED 1 63 J; 8 vaporiser needle valve assembly 48 (fig. 7) and is also affected by the line pressure between vaporiser outlet and the regulator 170, this pressure being approximately the difference between the liquid pressure in the tank and the downstream pressure between regulator 170 and burners 124 (neglecting line pressure losses). However, this pressure varies according to the amount of gaseous fuel being consumed by the burners 124. If fuel consumption exceeds the capabilities of the metering orifice to allow enough liquid fuel to pass into the vaporisation chamber and heat is still supplied thereto by vaporiser heater 160 then the temperature of the gaseous fuel will rise. Accordingly, a temperature control switch will then regulate fuel supply to the vaporiser burner 160 allowing relative cooling of the vaporiser 132 and gaseous fuel supplied by it.

The combination of orifice size and pressure and temperature control will so ensure safe and efficient operation of the entire implement equipment.

A further, practical flame cultivator implement with a modified burner in accordance with the present invention will now be described with reference to figures 10 and 11. The flame cultivator implement is similar to the one described with reference to fig. 1, but the arrangement and construction of the burners, generally identified at 70 in fig 10, has been modified in accordance with one aspect of the present invention. The burners 70 are mounted to project a flame approximately horizontally under the implement's deflector skirt (or plate) 26 which is provided with an inclined portion 27 disposed for deflecting the burner flames and heat downwardly towards the ground surface over which the implement is moved, the implement being fitted similarly to the implement embodiment of fig. 1 with ground engaging skids 28 or the like. An aperture or apertures 27a may be located in the deflector 26 to allow partial escape of heat onto an absorber 29 wherever such is fitted. The skids 28 are spaced according to particular crop requirements.

The burner 70 has a burner casing or shroud 72 conveniently formed from thin tubular sheet metal that is heat resistant. Burner casing 72 has one end pressed to form an oblong burner mouth opening 74 in which is mounted a gauze or mesh member 76, also of heat resistant material. A burner nozzle support body 78 carrying one or more gas jet burner nozzles 80 is mounted ihin burner casing 72 which provides at its back an air inlet for combustion air.

AMENDE S., liE:A!Lii 7 10042 9 RECEIVED 1 3 JUI J 16 A mesh material cage 82 covers the open rear of casing 72 so as to prevent draughts and consequent "burning back" of the burner gas flame and ingress of foreign materials into the burner chamber defined by the shroud.

The burner outlet covering gauze member 76 is preferably made from Incanol (Trade Mark) or similar heat resistant material. The surface of the gauze member 76 is depressed inwardly into the burner shroud 72, preferably forming a concave curved surface over the burner mouth 326. It has been found that this measure provides a controlled burner flame in which the area of high temperature surrounding each burner is maximised, thereby enabling a wider area of arable ground surface that can be treated for a given size of burner and minimising the disadvantages of previous burner designs of Bunsen type known to the inventors. The gauze or mesh has the effect of improving the diffusion of the air/gas mix and flame by decreasing the velocity of the mixture within the burner shroud chamber, thereby enabling a greater spread of heat over a wide area near the burner. Preferably the size of the mesh holes should not exceed 2mm for best results.

It is has been also found that a burner design in accordance with fig. when used in conjunction with a trailing shroud or skirt (as provided by the deflector 26 of the implement), will provide an even spread of high temperature burning gases beneath the shroud and has been found particularly effective in the control of weeds and pests associated with lucerne and like crops.

Turning now to figure 12, there is schematically illustrated yet a further, modified flame cultivator implement similar to that of fig. 11 but which is provided with additional burners 124 arranged as illustrated, preferably one each for each main burner 70. Apart from the addition of the burners 124, one which is illustrated schematically in fig. 15, the construction of the cultivator is similar to that shown in Figure 11.

The additional burners 124 are preferably supported atop the shield or skirt 26 of the cultivator implement such that the mouth of burner 124 is passed through an appropriately located aperture in the skirt 26 and combustion flames emanating therefrom are directed to impinge with an incidental angle onto the burner flames of burner 70 into the flaming zone that is treated by the latter urner 70 (which is provided with the gauze diffuser insert 76) mounted beneath cTAU 97 0 0 4 9 RECEIVED 1 6 JUN 1998 17 the skirt. As can be seen from fig. 15, burner 124, which is a Bunsen type burner of similar construction to the burners 24 employed in the flame cultivator of fig. 1, has a box-like burner shroud or housing 126 defining the burner chamber in which is supported in known manner one or more burner jet nozzles 128 so as to direct a burner flame towards the flared (diverging) front housing portion to exit the burner mouth 129. The flared outlet enables directing the flame to cover a relatively wide area at a relatively high velocity.

It will be appreciated that the number of active burners 124 can be varied according to the requirements of a particular flaming situation, may be controlled by the temperature of the combustion gases concentrated beneath the shroud member 26, and may take into consideration factors such as the nature of the application, including the crop to be treated, the amount of moisture, weeds surrounding the crop material and the like.

Burners 124 (as do burners 24) are arranged to produce a flame which has a higher temperature and higher velocity than those achievable by the burners 70 provided with the gauze insert 76 alone, and thus act as "boosters" when combined with the gauze burners, to thereby produce a hotter flame with wider reach and spread as compared to single burner operation and consequentially cover a relatively wide area in the zone of treatment beneath the shroud member.

It will be appreciated that the shroud member (or deflector plate assembly) of the flaming implements shown in figs. 11 and 13 is an optional feature in as much as it will assist in the focussing of the heat generated by the burners 70, 124 down to ground level and maintaining the heat in the area where it is most useful in flame treatment of crops, eg lucerne/pasture cropping.

It will also appreciated that the layout of burner 124 may be varied according to the needs, however, it has been found that the burner casing 126 should be of open construction without a gauze or mesh insert as provided for with the burner Figure 13 illustrates yet a further modified flaming implement similar to those previously described but for the features referred to in the following. As can be seen also in figs. 16 and 17, the main burners 70 are of the type cluding a gauze member 76 over the burner mouth or outlet 74 as previously E~D St Ci- AMENDED S-IJ.Y IPEAIA3 CrAU 97/00 42 9 RECEIVED 1 6 JUN 1998 18 described, the burner casing 72, however, comprising a rear portion 72a, with burner mesh cage 82 covering the rear open end, and a relatively hereto angled forward portion 72b flaring towards the burner mouth insert gauze 76. As can be seen in fig. 13, the main burners 70 are disposed on an implement frame 26a such that flames emanating therefrom are directed with a slight angle off the horizontal towards the ground, and booster burners 124 (of similar type to those previously described) are arranged adjacent thereto to cooperate in focusing the flames towards the ground. Implement frame 26a supports a number of air deflector foils 26b as shown to maintain the hot air draught created by the burners 70, 124 underneath the implement shroud directed downwardly toward the ground surface. Figure 14 shows a side plate 26d supported by implement frame 26a and which carries a side wind break member 26c.

AMENDED x'"r

IPEA/AS

Claims (18)

1. An apparatus for the vaporisation of vaporisable hydrocarbon fuels, in particular liquified petroleum gas (LPG) for use in a combustive weed and plant pest control implement, the apparatus comprising a vaporiser for vaporising said fuel and a vaporiser heater for supplying vaporisation heat to the vaporiser for effecting said vaporisation, wherein the vaporiser includes: a tubular vaporiser housing defining in its interior a vaporisation chamber; a fuel delivery tube extending into the vaporiser housing and arranged to receive said fuel in liquid form from a fuel storage vessel and deliver it into the vaporisation chamber; a gas delivery outlet in communication with the vaporisation chamber and arranged to deliver said fuel in gaseous form for subsequent use; and a liquid fuel metering member including an orifice arranged for limiting to a 15 predetermined amount the flow of liquid fuel into the vaporisation chamber via the delivery tube; wherein the vaporiser heater includes a bunsen type burner arranged to direct a flame to the vaporiser housing so as to heat the vaporisation chamber; and wherein the orifice of the metering member is located at the fuel delivery tube in a zone at the vaporiser housing heated by the vaporiser heater.

2. Vaporisation apparatus according to claim 1, wherein the metering member includes a fixed orifice member attached at a terminal end of the fuel delivery tube within the vaporisation chamber.

3. Vaporisation apparatus according to claim 1, wherein the metering member includes a needle valve providing an adjustable size orifice located at an inlet side of the fuel delivery tube to enable adjustment of liquid fuel flow into the vaporisation chamber.

4. Vaporisation apparatus according to claim 1, 2 or 3, wherein the orifice has a diameter of at least 1 mm.

5. Vaporisation apparatus according to any one of claims 1 to 4, wherein the vaporiser housing and the bunsen burner type vaporiser heater are arranged in an axially facing relationship, and wherein the vaporiser heater includes a shroud member that is disposed to surround at least a terminal front end of the vaporiser housing.

6. Agricultural implement for flame cultivation of arable land, the implement S comprising: a support structure arranged to be drawn by or mounted on a tractor; a plurality of burners located on the support structure in spaced apart gi00 15 relationship such as to respectively direct flames into a respective zone of flame treatment; a fuel delivery circuit with pipes arranged to deliver fuel from a storage .vessel of liquid hydrocarbon fuel, in particular liquified petroleum gas (LPG), to *000 each of the burners; one vaporisation apparatus according to any one of claims 1 to disposed in the fuel delivery circuit such as to receive liquid fuel from the fuel storage vessel and deliver vaporised fuel to the burners, the vaporiser fuel delivery tube heretofore being in fluid communication with the fuel storage vessel and the vaporiser gas delivery outlet being in fluid communication with a manifold pipe arranged to deliver the vaporised fuel to the burners, the metering member having an orifice size of at least 1 mm; and a gas pressure regulator disposed in the fuel delivery circuit between the vaporiser gas delivery outlet and the burners, fuel supply regulation to the burners being effected such that flow control of fuel in liquid state is substantially only effected by the metering member of the vaporiser and flow control of fuel in vaporised or gaseous state is effected downstream the vaporiser by the gas pressure regulator to enable closer regulation of fuel flow to the burners.

7. Agricultural implement for flame cultivation of arable land, the implement comprising: a support structure arranged to be draw by or mounted on a tractor; a plurality of burners arranged in burner banks consisting of a predetermined number of individual burners, the burner banks located on the support structure in spaced apart relationship such as to respectively direct flames into a respective zones of flame treatment; a fuel delivery circuit including pipes arranged to deliver fuel from a storage vessel of liquid hydrocarbon fuel, in particular liquified petroleum gas (LPG), to each of the burner banks; a plurality of vaporisation apparatus according to any one of claims 1 to 15 one such vaporisation apparatus being provided for each burner bank, the °i plurality of vaporisation apparatus disposed in the fuel delivery circuit such as to receive liquid fuel from the fuel storage vessel and deliver vaporised fuel to the burner banks, the fuel delivery tube of each of the vaporiser apparatus heretofore being in fluid communication with the fuel storage vessel and the gas delivery i: 20 outlets of each of the vaporiser apparatus being in fluid communication with a manifold pipe arranged to deliver the vaporised fuel to an associated one of the burner banks; and a plurality of gas pressure regulators disposed one each in the fuel delivery manifold pipe leading to a respective one of the burner banks such that flow control of fuel in liquid state is substantially only effected by the metering members of the respective vaporiser apparatus and flow control of fuel in vaporised or gaseous state is effected downstream of the respective vaporisation apparatus by the respective gas pressure regulators, thereby enabling closer regulation of fuel flows to the burner banks.

8. Agricultural implement for flame cultivation in accordance with claim 6 or 7, further comprising a plurality of stop valves for controlling flow of gaseous fuel to each individual burner and optionally to each bank of burners.

9. Agricultural implement for flame cultivation according to claim 6, 7 or 8, further comprising a controller arranged to regulate the flow of fuel to the vaporiser heater burner in response to the temperature of the vaporised fuel delivered through the vaporiser gas delivery outlet to the gas pressure regulator.

10. Agricultural implement for flame cultivation in accordance with claim 9, wherein the controller includes a temperature control switch for cutting off fuel supply to the vaporiser heater burner.

11. Agricultural implement for flame cultivation according to any one of claims 15 6 to 10, wherein each or selected ones of the burners are comprised of gas burner arrangements that include: a main burner of bunsen burner type having; a burner housing defining a burner chamber with at least one inlet :oe, opening for combustion air and an outlet opening arranged to direct a flame and S. 20 heat into a zone of treatment; lest one fuel delivery jet for delivery of gaseous fuel into and being located within the burner chamber; and a gauze or mesh insert member located within the burner chamber at or near the outlet opening, the insert member arranged to improve diffusion of combustion gases and enable greater spread of a flame emanating from the outlet opening; and a booster burner of bunsen burner type mounted adjacent to the main burner such that, in operation, a flame emanating from an outlet mouth of the booster burner is directed to impinge on and combine with the flame of the main burner thereby to enhance flame velocity and flame spread of the combined flame into the zone of treatment.

12. Agricultural implement for flame cultivation according to claim 11, wherein the gauze or mesh insert member of the main burner is mounted adjacent to and covering the flame outlet opening, the insert member being configured to have a concave surface bent towards the burner chamber.

13. Agricultural implement for flame cultivation according to claim 12, wherein the gauze or mesh insert member has mesh holes not exceeding 2mm in size.

14. Agricultural implement for flame cultivation according to any one of claims 11 to 13, wherein the booster burner has a burner housing defining a burner chamber in which at least one gaseous fuel delivery jet is located, the burner housing having a flared front section widening towards the burner housing outlet mouth. 0. g Agricultural implement for flame cultivation according to any one of claims 11 to 14, wherein the burner housing of the main burner comprises a thin, sheet metal, tubular shroud having one end pressed to form an oblong shape that *554 provides the outlet opening.

16. Agricultural implement for flame cultivation according to any one of claims 11 to 15, wherein the support structure for the burners is a ground engaging structure arranged to be drawn by or mounted on a tractor; wherein the plurality of main burners are arranged such as to direct heat beneath a shroud member supported at the ground engaging structure, the shroud member being disposed to cover a zone of flame treatment; and wherein the plurality of booster burners, one each associated with a respective one of the main burners, are mounted atop the shroud member such that the outlet mouth of each booster burner is directed through an aperture in the shroud member and the flames emanating therefrom impinge and combine with the flame of the associated main burner.

17. Agricultural implement according to claim 16, wherein the ground engaging structure includes a number of deflection foils or vanes arranged to direct air heated by the burners down to ground level.

18. A liquified petroleum gas (LPG) vaporisation apparatus for use with an agricultural implement for flame cultivation as hereinbefore described with reference to the accompanying drawings. DATED this 28 th day of February 2000 0* Boral Gas (NSW) Pty Ltd 15 WATERMARK PATENT TRADEMARK ATTORNEYS UNIT 1 THE VILLAGE S* RIVERSIDE CORPORATE PARK

39-117 DELHI ROAD NORTH RYDE NSW 2113 AUSTRALIA CJSMM CJS:MM