Plant husbandry – Flame cultivating
Reexamination Certificate
2000-11-01
2003-01-14
Poon, Peter M. (Department: 3643)
Plant husbandry
Flame cultivating
C047S001700
Reexamination Certificate
active
06505437
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to devices which generate a heated flow of fluid that can be used in agriculture and other applications where it is required to raise the temperature of objects or the environment for short periods of time. The invention is also concerned with an improved agricultural implement and method for controlling or eradicating weeds and pests that affect arable land and useful plants, by means of the application of a heated fluid onto areas affected by such unwanted agents.
BACKGROUND OF THE INVENTION
The present invention has been developed in light of perceived shortcomings of known combustive plant pest and weed control apparatus as used in flame cultivation. However, the concept underlying the invention has uses in other fields of application as will be discussed below. Accordingly, whilst the following background description relates to weed control applications in the agricultural field, the invention is not intended to be restricted to such field only.
Within the agricultural industry, various methods are known and recognised for controlling the growth of and eradicating weeds and other undesirable pests that affect useful crops and plants.
Herbicides and pesticides are by far the most commonly used weapons for weed and pest control. However, there is an ever growing concern about degradation of the environment, adverse effects which herbicides have on crops, as well as the creation of herbicide and pesticide resistant strains of noxious weeds and pests. Various alternatives to the (sole) use of chemical agents have thus been proposed in the past.
Flame cultivation and other thermal-energy based weed control methods have been studied over the years as alternatives to or collaterals to herbicide and pesticide use.
Flame cultivation involves the short-time application of high intensity heat that is generated through combusion of liquified petroleum gas (LPG) or other hydrocarbon fuels and carried to the treatment area by the combustion gases. The heat application has to be sufficient to generate a sudden increase of temperature in the leaf cells of the weed to about 50 to 70° C. such as to cause cell damage in the leaves and stems of young, green weeds and to kill pests such as bacteria, weevils, insects or fungus spores and the like that are likely to attack valuable crop plants. This leads in time to withering of the leaves and stems of the weed and ultimately results in the death of susceptible weeds, without destroying the crop plant. U.S. Pat. No. 3,177,922 (Pardee) discloses a flame cultivator with a battery of LPG burners mounted on a tool bar carried by a tractor. The individual burners are adjustably mounted on the traverse support bar in staggered arrangement to coincide with the spacing of crop rows and such as to direct the hot combustion gases to the base of the crop plants. In order to thermally insulate and protect the upper parts of the crop plants it has been proposed to use air curtains to confine the heat of the flames to the base of the plants, see U.S. Pat. No. 3,477,174 (Lalor). Problems are also experienced with flaming treatments caused by overheating of the crop plant such as leaf damage. U.S. Pat. No. 5,189,832 (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 tends to damage the leaves. Other devices such as the one disclosed in U.S. Pat. No. 5,020,510 (Jones) and WO 97/03557 (Waipuna) use tractor-drawn, open-bottomed, rectangular shrouds supported on wheels which are drawn over a weed-infested area, wherein air and some of the combustion gases are recirculated within the shroud plenum chamber using fans and maintained at temperatures of around 300° C. during soil treatment.
U.S. Pat. No. 213,255 (Simpson) and AU-B 50364/93 (P. C. Wagner) disclose a railroad-bound apparatus which uses steam and/or hot water to kill vegetation on railroad beds. The hot water/steam destroys the cells of the plants which eventually wilt. This principle has also found application with devices that can be more readily used in agriculture, compare the hand carried devices of GB-A 2306151 (Arnold) and JP-A 07-274798 (Kubo). Some devices use an electrical heater to generate the steam, as in RU-A 2002410 (Kerimova). Some devices incorporate shrouds or applicator-box constructions to create a more controllable steam application environment, GB-B 2122511 (Makar). Devices have also been proposed which prolong the dwell time which the hot water/steam has to effect thermal damage of the cells of unwanted weeds, including surface contacting structures such as endless belts and aprons. These devices retain and/or “press” the heat into the plants and temporarily maintain the area surrounded by the apron insulated from ambient conditions, compare U.S. Pat. No. 5,430,970 (Thompson) and WO 94/11110 (Aquaheat Technology), the latter document disclosing the use of heated water alone or in mixtures with herbicides/pesticides to effect weed and pest destruction.
In yet another modification of the basic principle of using hot water/steam to kill weeds and crop damaging insects and pests, it is known from WO 94/26102 (Waipuna) to spray the foliage of weeds with pressurised hot water and steam at temperatures ranging from 75° C. to 120° C. The pressurised hot fluid is applied in close vicinity to the ground through jet nozzles at water flow rates of about 4 to 15 liter per minute. The steam generating boiler, the water supply tank and the pressurising pump are carried on a van or tractor, whereas the applicator device, which can be a simple hand-pushed applicator head with fluid delivery jets situated within an open-bottomed box, or a towed boom applicator with multiple jets, is supplied via insulated hoses with the hot treatment fluid. A hand-held device using a single jet of pressurised, electrically heated water steam is known from NZ-A 237524.
In a further modification of the basic principle of using heated fluids to destroy weeds, DE-A 3639705 discloses a mobile weed destroyer that includes a water tank and a steam generator carried on a suitable vehicle. The steam generator, which is a petrol-fired boiler, is arranged to deliver superheated steam at pressures greater than 10 bar and temperatures of more than 180° C. via a suitably insulated, flexible hose to a manually handled spraying head having a jet discharge nozzle disposed within a parabolic-shaped reflector shroud.
Common to all of the above devices and methods is that they use dedicated steam generators or boilers, either electrically heated or fuel-fired, for the generation of the treatment fluid (whether hot water, hot water/steam mixtures, wet steam or super heated steam). The electricity-heated steam generators require a separate power source, like a battery or an electric generator driven by the engine of the vehicle drawing or carrying the steam generator, thus increasing investment costs for such devices. Fuel-fired boilers are energetically inefficient, as they generate a substantial amount of waste heat.
Other devices and methods which rely on thermal shock to control or destroy weeds and vermin simply use a blast of electrically heated air, e.g. GB-A 2278988 (Morgan), or a mixture of pressurised combustion gases and air, e.g. AU-B 10256/83 (Morris). Here, the heated air flow is directed onto a treatment area that is covered by suitably shaped, mobile hood or shroud that is moved over the treatment area and which increases the dwell time the heated gases have to damage the cells of the weeds or plant pests.
One of the main problems which need to be addressed in flame cultivation is the tendency of dry vegetation to ignite even where the burner flames of the flame cultivator are kept well distanced from the treatment zone. Another problem is the tendency of the hot combustion gases to rise away from the treatment zone, i.e. the dwell time is often insufficient to accomplish the required rise in temperature of the weeds. This latter problem has bee
Johnstone Ian
Smith Robert
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Nguyen Son T.
Origin Energy LPG Limited
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