The present invention relates to a discharge lamp apparatus having no electrode, that is, a non-electrode discharge lamp apparatus, and a liquid treatment apparatus for treating liquid such as water with ultraviolet rays emitted from such a lamp apparatus.
More particularly, in the non-electrode discharge lamp apparatus dipped in liquid, the present invention relates to a lamp apparatus having an improved support structure of a discharge tube and an improved feeding structure and to a liquid treatment apparatus using such a lamp apparatus.
As a conventional non-electrode discharge lamp apparatus, there is an apparatus disclosed in Japanese Patent Application KOKOKU Publication No. 62-163927. This apparatus has the structure as shown in FIG. 1. More specifically, the lamp apparatus comprises a cylindrical discharge tube 1, and the interior of the discharge tube 1 is filled with mercury and rare gas. Then, a plurality of exciting coils 2a, 2b, and 2c are wound around an outer periphery of the discharge tube 1. These exciting coils 2a, 2b, and 2c are connected to each other in parallel, and a high frequency current is supplied thereto from a high frequency generator 3. Reference numeral 4 is a commercial power supply source.
In such a lamp apparatus, when the high frequency current is supplied to the exciting coils 2a, 2b, and 2c, a light emitting region is formed in the discharge tube 1. Then, ultraviolet rays are emitted to the outside through a tube wall of the discharge tube 1. In this kind of the lamp apparatus, the exciting coil is divided into three, that is, exciting coils 2a, 2b, 2c, and these coils are connected to each other in parallel. As a result, inductance of the assembly of these exciting coils is reduced, the necessary amount of apply voltages may be small, and this brings about an advantage in the circuit design of the high frequency generator 3.
This kind of non-electrode discharge lamp is used in various kinds of liquid treatment apparatus in which ultraviolet rays are emitted to e.g., sewage to be sterilized. In the general structure, the non-electrode discharge lamp apparatus is dipped in liquid such as sewage, and ultraviolet rays are efficiently emitted to sewage.
However, this kind of non-electrode discharge lamp has the following disadvantages:
First of all, if the discharge tube 1 is dipped in sewage directly contacts the tube wall of the discharge tube 1, the tube wall is excessively cooled. In this type of the discharge lamp apparatus, radiation efficiency of the ultraviolet rays becomes the highest when the temperature of the coolest portion of the tube wall of the tube 1 is around 40.degree. C. However, since the tube wall is excessively cooled, the temperature of sewage is also reduced. As a result, the radiation efficiency of the ultraviolet rays is largely reduced.
Moreover, if sewage contacts the exciting coils 2a, 2b, and 2c, inductance of these coils changes by the dielectric constant of sewage. Then, the dielectric constant of sewage is not fixed. As a result, the efficiency of these exciting coils varies, and the generation efficiency of the ultraviolet rays is reduced.
Furthermore, if sewage directly contacts the exciting coils, their feeders, terminal, etc., a water-proof treatment and an insulating treatment must be completely prepared. As a result, the structure becomes complicated, and reliability is reduced.