DISCHARGE TUBE FOR LASER GENERATOR

Abstract: A discharge tube for a gas laser generator, especially one driven by a high-frequency (including a radio-frequency) AC power supply. At least a pair of electrodes (5a, 5b) are provided on the surface of a dielectric discharge tube (1), and radiating fins (2a, 2b) are mounted each on a part of the electrodes (5a, 5b). A ceramic clamp (3) and a stainless presser bar (4) are provided in the recessed parts of the radiating fins (2a, 2b) to lock the fins (2a, 2b). By dissipating heat through these fins, heat buildup in the electrodes is decreased, thus preventing the peeling or deterioration of the electrodes.

Description: The present invention relates to a discharge tube for use in a gas laser oscillator, and more particularly, to a discharge tube for a laser oscillator adapted to be driven by a high-frequency (including radio frequencies) ac power source. In a gas laser oscillator, a dielectric discharge tube is generally formed of ceramics or quartz, a pair of electrodes are arranged on the outer surface of the discharge tube, and a high-frequency ac power is applied to these electrodes to excite gas in the discharge tube to thereby cause an electric discharge. Reflecting mirrors are provided separately on opposite sides of the discharge tube to thus form a laser oscillator. The electrodes may be formed by a metal deposition process or by bonding a metallic tape to the surface of the discharge tube. When the ac power is applied to the discharge tube to cause an electric discharge, however, the temperature inside the discharge tube rises, and as a result, the discharge tube temperature reaches 300°C or thereabouts. Accordingly, a problem has arisen in that the electrodes are separated due to the difference in coefficient of thermal expansion between a dielectric constituting the discharge tube and a metal constituting the electrodes. Moreover, as the temperature of the electrode rises, the temperature of the ambient air rises, and thus a corona discharge occurs at the end portions of the electrodes, which causes a deterioration of the electrodes. Therefore, to prevent a separation of the electrodes, a cushion is conventionally interposed between the electrodes and the discharge tube, and to prevent the corona discharge, a moulded material, such as silicone, is applied to the end portions of the electrodes. These processes require a reprocessing of the discharge tube, and the manufacture of the discharge tube requires substantial man-hours. To solve the above problem, according to the present invention, a discharge tube assembly for a laser oscillator, the assembly comprising at least one pair of electrodes formed on a surface of a dielectric discharge tube; and radiating fins attached to respective end portions of the electrodes (as disclosed in JP-A-62-88384), is characterised in that each of the radiating fins has a recessed portion in the centre, the recessed portion being fixed to the discharge tube by a clamp and a backup plate. Accordingly, a rise in temperature of the electrodes is prevented by a radiation of heat therein through the radiating fins provided on the electrodes. In the accompanying drawings : Fig. 1(a) is a diagram showing a discharge tube for laser oscillator according to one embodiment of the present invention; and Fig. 1(b) is a side view corresponding to Fig. 1(a). Figure 1(a) is a diagram showing a discharge tube for a laser oscillator according to one embodiment of the present invention, and Fig. 1(b) is a side view corresponding to Fig. 1(a). As shown in the Figures, a ceramic or quartz pipe is used as the discharge tube 1 and a pair of electrodes 5a and 5b are arranged helically on the surface of the discharge tube 1. These electrodes 5a and 5b may formed by a metal deposition process or by bonding a metallic tape thereto. Aluminum radiating fins 2a and 2b are arranged separately on opposite sides of the discharge tube 1, and in close contact with the electrodes 5a and 5b, respectively. This is accomplished by cutting out a quarter circle from an end portion of each of the radiating fins 2a and 2b. Further, the central portion of each radiating fin is recessed to be fixed to the discharge tube 1. A ceramic clamp 3 and a stainless-steel backup plate 4 are engaged with the respective recessed portions of the radiating fins 2a and 2b, to thereby fix the radiating fins 2a and 2b in position. The clamp 3 is formed of ceramic material, and therefore, is coupled to members 6a and 6b by screws 7a and 7b, and the members 6a and 6b are coupled to the backup plate 4 by screws 8a and 8b, respectively. The backup plate 4 is flexible, and thus holds the radiating fans 2a and 2b on the discharge tube 1 by the spring function thereof. The clamp 3 is formed of ceramic material because a ceramic material has a small coefficient of expansion when subjected to a rise in temperature. The backup plate 4 is formed of a stainless steel, because the tenacity of stainless steel is not lowered by a high temperature. Accordingly, even if the temperature of the discharge tube 1 is increased by an electric discharge, the resulting heat is radiated into the air via the radiating fins 2a and 2b, and therefore, a rise in the temperature of the electrodes 5a and 5b, which are heated to a particularly high temperature, is prevented. The use of these radiating fins enables the temperature to be lowered by a margin of about 100 to 150°C, when used in a CO₂ gas laser with an output of 1 kW or thereabout. If the output of the laser is higher, the temperature of the electrodes can be further lowered by air-cooling the radiating fins 2a and 2b by a fan. Therefore, a separation of the electrodes 5a and 5b from the discharge tube 1 can be prevented, and further, a deterioration of the electrodes 5a and 5b due to a corona discharge is also prevented. It is to be understood that this effect can be also produced with the use of electrodes formed by a metal deposition process or by a metallic tape. According to the present invention, as described above, the temperature rise attributable to an electric discharge is reduced by fitting the radiating fins to the end portions of the electrodes, and thus a separation or deterioration of the electrodes can be prevented.

Claims: A discharge tube assembly for a laser oscillator, the assembly comprising at least one pair of electrodes (5a,5b) formed on a surface of a dielectric discharge tube (1); and radiating fins (2a,2b) attached to respective end portions of the electrodes; characterised in that each of the radiating fins (2a,2b) has a recessed portion in the centre, the recessed portion being fixed to the discharge tube (1) by a clamp (3) and a backup plate (4). An assembly according to claim 1, wherein each of the electrodes (5a,5b) is formed by a metal deposition process. An assembly according to claim 1, wherein each of the electrodes (5a, 5b) is formed of a metallic tape. An assembly according to any one of the preceding claims, wherein the radiating fins (2a,2b) are formed of aluminium. An assembly according to any one of the preceding claims, wherein the radiating fins (2a,2b) are air-cooled by a fan.

Inventors: EGAWA AKIRA FANUC MANSION HARI, KOBAYASHI EIJI FANUC MANSION H, EGAWA, AKIRA FANUC MANSION HARIMOMI 3-303, KOBAYASHI, EIJI FANUC MANSION HARIMOMI 4-105
Applicants: FANUC LTD, FANUC LTD.
Application year: 1990
Main classification: H01S3
IPC codes: H01S3