Radiant energy – Irradiation of objects or material
Patent
1996-12-05
1999-07-27
Nguyen, Kiet T.
Radiant energy
Irradiation of objects or material
25045511, G05D 2502
Patent
active
059294558
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling vegetation, where vegetation is undesirable. Furthermore, the invention relates to an apparatus for performing said method.
By control of vegetation is in this context to be understood a limitation of vegetation which may both comprise weed control, stopping growth of plants and growth-retardation of plant. Such a control has hitherto to a great extent been performed by chemical sprays, where there has been no possibility of or resources for a mechanical removal or control of plant growth. Another used method for weed control or for limiting the growth thereof has been to subject it to heat from a gas burner frying the leafage of the plants.
Control of undesirable vegetation by chemical sprays is effective and cheap, but occasions severe worry on account of the risk of percolation through the ground and contamination of the subsoil water. The percolation is in particular considerable on railway track beds, where crushed rocks and lack of vegetation constitute a kind of cesspool. As during the last 100 years comprehensive railway systems with an underlayer of crushed rocks have been built, the load carrying ability of which requires a complete removal of vegetation, the risk of chemical sprays has had to be accepted. The railway authorities have, however, in an attempt to avoid chemical sprays looked for alternative methods, including irradiation with electromagnetic waves in the lower end of the electromagnetic spectrum through tests with radio waves, micro waves and rays of heat. The plant parts are, however, so small and thin that none of these wave lengths has especially good possibilities of discharging sufficient energy to influence the plants. On the contrary, the major part of the energy passes through the plants and down into the crushed rocks and soil, where the energy is transformed into heat. Moreover, these electromagnetic waves spread along tracks and wires at the track bed and electronic installations, which are damaged, as energy dosages have to be used which correspond to those emitted by the biggest known radio transmitters. The burning of electronics and cables is expected to happen with such a force that there is a risk of fire around the electric installations.
Other alternative methods may be spraying with steam or boiling water, which requires very huge amounts of energy, as well as frying with gas burners, which will likewise require huge amounts of energy and constitute a great danger of leaf fire and thermal damages to cables. None of these methods are therefore widely used in general, and not for vegetation control along railway lines either.
The object of the invention is on this background for use in vegetation control to provide a method which does not entail the risk of percolation of chemical compounds and which can be performed with a moderate consumption of energy.
DESCRIPTION OF THE INVENTION
The invention is based on the observation that the energy of ultra-violet light contrary to more long-waved light is absorbed in a thin surface layer of biological materials which are irradiated. Measurements of grass and green leaves show that very little ultra-violet light is reflected and transmitted, so that nearly the whole energy (approx. 90%) is transformed into heat in the outermost 0.1 mm. These conditions apply to both UVA-, UVB-, and UVC-light. The effective energy consumption means that it is possible with a comparatively short, intense irradiation to transfer so much energy to the leaves of the plant that the green plant parts are destroyed. In this connection, it is a question of a irradiation dosage which exceeds a minimum dosage which the plant can survive without substantial damage.
According to the invention this minimum dosage is experimentally determined, as it has turned out that this dosage may be composed of several shorter or less intense irradiation periods or may consist of one single, more strong or longerlasting dosage. For a given light source, several sets coherent v
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patent: 5395591 (1995-03-01), Zimlich, Jr. et al.
patent: 5744094 (1998-04-01), Castberg et al.
D. Hansson, et al., "Keeping weeds down without herbicides", Real Business Report, 1995, pp. 36-37.
Nguyen Kiet T.
Niels Lang Mathiesen and Knud Andreasen
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