Apparatus for and method of destroying vegetation

[0001] The invention relates to a device for destroying vegetation.

Background of the Invention [0002] Various methods are known and recognized as effective for controlling the growth of weeds and other undesirable substances. These methods are used in agriculture, as well as by state and governmental bodies such as local pathway councils and other weed-free areas. Many existing methods involve the use of an aqueous solution of chemicals for weeds. Recently, the use of chemical plant destruction agents has become less desirable, both in terms of health and safety in terms of the health of those using chemicals, but also in terms of environmental damage caused by the use of chemicals.

[0003] One known method of destroying weeds that does not use chemicals is to use steam and / or hot water to destroy vegetation. For example, US Patent No. 213255 (Simpson) discloses a device that uses steam and / or hot water to destroy vegetation on railway sleepers.

[0004] Australian Patent Application No. 65573/99, entitled "A method of generating a treatment fluid", discloses a method for combining compressed air with heated water in an applicator nozzle.

[0005] A number of other patents also disclose a device for applying pressurized heated water to vegetation, including AU 668291, which discloses a device for controlling vegetation by applying high pressure water or a spray of liquid, supplying liquid to a spray tip under pressure of 100 psi to about 4000 psi. AU 709493 discloses a method of destroying or controlling weeds in which hot water at a temperature of 75 ° C or higher under pressure is applied to the weeds, supplied at a pump pressure greater than 13.79 bar (200 psi) at a flow rate exceeding 4 liters per minute.

[0006] However, one of the main problems with the existing hot water and steam applicator and generation means is that a considerable amount of energy is required to heat water, due to the high specific heat of the water and the even higher specific heat of the phase change, as the water undergoes from liquid to gas, hence the energy consumption of such devices is a significant disadvantage of controlling weeds with hot water or steam.

[0007] A device that would be able to control or destroy weeds using a smaller volume of water would not only be more efficient in terms of consuming water as a commodity, but also more energy efficient.

[0008] US 5,927,601 discloses a method and apparatus for using pressurized hot water jets to destroy vegetation by directing these hot water jets to foliage of vegetation under pressure from 13.79 to 68.95 bar (200 to 1000 psi), or at least 100 psi. This device includes a spreading bar that defines many holes from which water jets are directed. Such water dissipation under pressure causes a significant drop in temperature, as a result of which the operating temperatures of the streams are around 90 ° C. The device and method consume significant amounts of energy for heating and increasing the pressure of water jets.

[0009] US 6,047,601 is associated with US 5,927,601 and describes a substantially similar device having similar disadvantages.

[0010] Any discussion of documents, statutes, materials, devices, articles and the like which is included in this specification serves solely to provide a context for the invention. This should not be taken as admission that any or all of these matters form part of the background of the prior art or were common general knowledge in the field relating to the invention that existed prior to the priority date of each patent claim of this application.

Summary of the Invention [0011] In a first aspect of the invention there is provided a device for destroying vegetation having an outlet, the device includes means for generating superheated hot water and steam, comprising;

the inlet pipe and the boiler and pumping means for feeding heated water under pressure to the restrictor nozzle, where the restriction nozzle defines an opening that narrows the flow through the inlet pipe; characterized by:

an expansion chamber for expanding the heated water under pressure to the surrounding pressure, which comprises an outlet (17); and in which, when in use, the outlet from the expansion chamber provides superheated hot water and steam to the surrounding atmospheric pressure from the expansion chamber, where in use the superheated hot water and steam are supplied through the outlet for application to the vegetation, where the outlet has a surface that is at least double the surface hole defined by the nozzle.

[0012] The inlet pipe may have a diameter of 8 mm to 25 mm, most preferably 10 to 15 mm.

[0013] The nozzle may define a hole in the pipe having a diameter of 0.5 mm to 3 mm, most preferably about 1 mm.

[0014] The device can be used with an oil-fired boiler and pump to heat and compress water.

[0015] Water may be supplied at a temperature of 90 ° C to 150 ° C, but typically water is supplied to the expansion chamber at a temperature in the range of 100 - 150 ° C and at a pressure of 30 to 100 bar or more, most preferably about 40 to 52 bar .

[0016] Typically, the device uses an oil-fired boiler to heat water, although other heating means such as LPG can be used.

[0017] The device maintains the pressure in the boiler and the flexible supply line so as to keep the water temperature above 100 ° C before releasing the superheated water into the atmosphere, where it transforms into steam. This makes it possible to supply hotter saturated steam than would be possible without compressing the water. Superheated water can be delivered to vegetation at a pressure from 0.069 bar to 6.83 bar (1 to 99 psi) above atmospheric pressure, but most preferably at a pressure from about 0.069 bar to 0.69 bar (1 to 10 psi) above pressure weather. When used, the device typically delivers 2 to 13 liters of water per minute.

[0018] In a related aspect, there is provided a method of destroying vegetation using a device according to the invention;

wherein the method comprises the steps of supplying hot water under pressure to the inlet pipe at a temperature in the range of 100 ° C to 150 ° C and a pressure of 40 to 52 bar; passing water through the nozzle to the expansion chamber; and supplying hot water and saturated steam to ambient atmospheric pressure to the outlet of the expansion chamber.

Brief Description of the Drawings [0019] Specific embodiments of the invention will now be described, by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a section through the first steam / water inflow head / nozzle; and

Figure 2 is a schematic drawing illustrating the steam and water applicator head in use.

Detailed description of preferred embodiments [0020] Referring to the drawings, Figure 1 shows an applicator head 10 for a drip steam / water generator for use in destroying or controlling vegetation. The setting head includes an inlet pipe 12 along which superheated water under pressure is pumped from the boiler. Typically, the input supply pipe 12 is a cylindrical pipe having an annular cross-section and an inner diameter of 12 mm and is made of stainless steel, capable of operating at operating water pressures exceeding 150 bar.

[0021] Inside the pipe 12, near one of the ends 12a, there is an expansion / containment nozzle 14 that narrows the flow of water through the pipe 12 and helps maintain pressure between the pipe and the boiler. The inner diameter of the nozzle can be varied depending on the desired water flow rate and the required pressure. In a particular embodiment, the opening 15 has a diameter of 1.0 mm, but can vary in the range from 0.5 mm to 3.0 mm [0022] Near the expansion nozzle 14 there is the expansion chamber 16 in the form of a rectangular box, as a chamber having an enlarged diameter relative to the diameter of the inlet pipe 12. The volume of this chamber is not critical as long as it is a larger volume than the volume of water that the restrictor nozzle can release. The chamber can be made of any material that is able to maintain water pressures exceeding 52 bar and temperatures up to 150 ° C, where stainless steel is one of the suitable materials.

[0023] The outlet 17 having a size from 2 mm to 10 mm and being larger than the opening defined by the nozzle 14, preferably at least twice the diameter, from the expansion chamber 16 is connected fluidly to the distribution strip or pipe 18. The distribution pipe 18 defines a series of ports or holes 20, having a diameter of 6 mm, which, however, can be changed to fit the desired volume of water flow and can typically be in the range of 3 mm to 15 mm in diameter. The distribution pipe comprises a hollow cylindrical pipe made of ductile, non-corrosive material. The number and size of the pressure bores 20 are adjusted to suit the water flow, guaranteeing no back pressure. The distribution pipe 18 can be made in any desired shape suited to various applications.

[0024] The operation of the system will now be described with reference to Figure 2. The oil-fired boiler 30 and pump 22 are used to produce pressurized water at a temperature in the range 90 ° to 115 ° C and a pressure of 40 to 52 bar . At atmospheric pressure, water at this temperature would transform into steam, however, due to the fact that the water remains under pressure, it remains liquid. Water flows into the inlet feed pipe 12 until it reaches nozzle 14. Water flows through the nozzle 14 and then flows into the expansion chamber 16, where the pressure is approximately the value of the surrounding atmospheric pressure. As described above, the expansion nozzle 14 helps to maintain water pressure in the inlet pipe at 40 to 52 bar. However, as the water passes through the nozzle 14, it flows into the expansion chamber 16, where the pressure decreases approximately to the surrounding atmospheric pressure. This reduction of water pressure to ambient atmospheric pressure lowers the boiling point of water, creating water in an overheated state. When superheated water leaves ports 20 in the distribution pipe, it contacts the normal ambient temperature and is transformed into a combination of water vapor and water droplets, inflicted on weeds 36, which are to be destroyed. The distribution pipe is preferably partially shielded by an insulating cap 22 to preserve heat and maintain the overheating environment.

[0025] The applicator head can operate efficiently by delivering water at any rate ranging from 2 liters per minute to about 13 liters per minute, and typically works at an output of about 5.5 liters of water per minute. Larger machines are provided that produce an output stream giving more liters per minute, for use in vineyards or multi-hectare agriculture. Providing the expansion nozzle 14 and the expansion chamber enables the supply of hotter saturated steam than would be possible if the water were not under pressure. However, by expanding the water before applying superheated steam to the weeds, it improves machine efficiency and reduces the amount of water required.

[0026] The application can be used to control weeds in both urban and rural / agricultural environments. It is also envisaged that the device would be applicable in the field of cleaning or other fields where efficient delivery of steam and water droplets is desired.

Dorota Rzążewska Patent attorney