Gas laser tube

Abstract: A structure for holding a cathode of a tube type (5) in a gas laser tube of internal mirror type is disclosed. The cathode (5) is provided at one end with a slender projection to be inserted into a hollow portion (2a) attached to one of sealing flush members (2a, 2b) of enclosure members and to be caulked with a groove (13) formed in the hollow member (2a) so as to hold the cathode (5). The cathode (5) is also provided with spring plate members (6) at its other end. A slender discharge tube (7) is provided with an expanded portion (8) serving as a discharge chamber, the expanded portion (8) having a smaller diameter than that of the cathode (5) so as to press the spring plate members (6) thereby supporting the said other end of the cathode.

Description: The invention relates to a gas laser tube, and more particularly to a structure for holding a cathode in a gas laser tube of an internal mirror type in which enclosure members of the gas laser tube at its opposite ends is sealed with sealing flush members provided with hollow members with spot facings and glass face plates are provided at the spot facings of the hollow members. Referring to FIG. 1, in a conventional gas laser tube of an internal mirror type, enclosure members of the gas laser tube comprises a thick glass tube 4, sealing flush members 1a and 1b, hollow members 2a and 2b with spot facings, and mirrors 10. The thick glass tube at its opposite ends is sealed with the sealing flush members 1a and 1b which are respectively provided with the hollow members 2a and 2b with the spot facings. The hollow members 2a and 2b are respectively provided with mirrors 10 at the spot facings. The sealing flush members 1a and 1b are respectively attached with the hollow members 2a and 2b by soldering. A gap between the hollow member and the mirror is sealed with a low melting point glass material 9. The hollow member 2b serves as an anode. A conventional structure for holding the cathode to the enclosure members in the gas laser tube will be described. The cathode of a tube type made of aluminum at its welding region 14 is attached to the sealing flush member 1a by welding. The enclosure members at its anode side is provided therein with a discharge chamber 8 which is provided with an outlet for releasing a gas within the discharge chamber 8. A slender discharge tube 7 at its anode side is attached to a wall of the discharge chamber 8. The thick glass tube 4 and the slender discharge tube are formed in an integral structure through the wall of the discharge chamber 8. The thick glass tube 4, the cathode 5 and the slender discharge tube 7 are arranged in a coaxial position. In such the conventional structure for holding the cathode in the gas laser tube of the internal mirror type as shown in FIG. 1, the cathode 5 is attached to the sealing flush member 1a only by means of a resistance welding. The sealing flush member 1a is made of Kovar (Fernico). In contrast, the cathode 5 is made of aluminium. The sealing flush member has an electrical resistance higher than that of the cathode. Consequently, when the sealing flush member 1a is subjected to the resistance welding, the welding region 14 of the sealing flush member 1a is a tendency of melting or cracking to cause leaks. Assuming that the welding for attaching the cathode 5 to the sealing flush member 1a is carried out with a low welding current, strength of attachment of the cathode 5 to the sealing flush member 1a is weak so as to tend to put out the cathode from the sealing flush member 1a. On the other hand, an alternate conventional structure for holding the cathode to the enclosure members in the gas gas laser tube will be described. Referring to FIG. 2, the cathode 5 at its top portion is provided with a slender projection. The hollow member 2a attached to the sealing flush member 1a is formed at its hollow portion with a ring-shaped groove 13. The slender projection of the cathode is inserted into the hollow member 2a and caulked with the ring-shaped groove 13 formed in the hollow member 2a so as to hold the cathode in the gas laser tube. In such the structure for holding the cathode, the cathode 5 may be held to the enclosure members of the gas laser tube without welding, the gas laser tube therefore has not the set forth problems of melting or cracking of the sealing flush member by welding. The cathode is, however, attached to the sealing flush member only by the caulking of the slender projection of the cathode with the ring-shaped groove in the hollow member. In an operation of the gas laser, the cathode and the hollow member are subjected to a vibration and a thermal expansion. Thus, the caulking of the slender projection of the cathode tends to loose or the cathode tends to put out from the sealing flush member. An object of the present invention is to provide a gas laser tube of an inner mirror type having a novel structure for holding a cathode to enclosure members thereof. A gas laser tube according to the present invention is specified in claim 1, the preamble of which corresponds to EP-A- 0 348 974. According to embodiments of the invention the enclosure members comprise a thick glass tube, sealing flush members provided at opposite ends of the thick glass tube, hollow members with a spot facing attached to each of the sealing flush members, and mirrors attached to each of the hollow members at the spot facing. The cathode at its top portion is provided with a slender projection to be inserted into the hollow member. The slender projection of the cathode is caulked with a groove formed in the hollow member. The expanded portion may serve as a discharge chamber. The above means for making the cathode secure to the inner wall of the enclosure members may comprise at least one spring plate member. In the novel gas laser tube of the inner mirror type according to embodiments of the present invention, the cathode is provided with the means for making the cathode secure to the enclosure members. While the discharge tube is provided with the expanded portion to press the means for making the cathode secure to the enclosure members. Further, the slender projection of the cathode is inserted into the hollow member and caulked with the groove formed in the hollow member. This allows to securely hold the cathode within the gas laser tube of the inner mirror type without the set forth problems associated with the prior arts. Preferred embodiments of the present invention will hereinafter fully be described in detail with reference to the accompanying drawings in which : FIG. 1 is a longitudinal sectional view illustrative of one example of the conventional structure for holding a cathode to enclosure members in the gas laser tube of the inner mirror type ; FIG. 2 is a longitudinal sectional view illustrative of an alternate example of the conventional structure for holding a cathode to enclosure members in the gas laser tube of the inner mirror type ; FIG. 3 is a longitudinal sectional view illustrative of one embodiment of a novel structure for holding a cathode to enclosure members in a gas laser tube of an inner mirror type according to a first embodiment of the present invention; and FIG. 4 is a longitudinal sectional view illustrative of an alternate embodiment of a novel structure for holding a cathode to enclosure members in a gas laser tube of an inner mirror type according to a second embodiment of the present invention. A first embodiment of a novel structure for holding a cathode to enclosure members in a gas laser tube of an inner mirror type according to the present invention will be described. Referring now to FIG. 3, the enclosure members comprise a thick glass tube 4, sealing flush members 1a and 1b, hollow members 2a and 2b with a spot facing, and mirrors 10. The thick glass tube 4 is made of a sodium borosilicate glass which is sealed at its opposite ends with the sealing flush members 1a and 1b made of Kovar (Fernico). The sealing flush members 1a and 1b are respectively provided with the hollow members 2a and 2b with the spot facing which are made of 426-alloy. The hollow members 2a and 2b are respectively provided with mirrors 10 at the spot facing. The flush members 1a and 1b are respectively attached with the hollow members 2a and 2b by a soldering material 3. A gap between the hollow member and the mirror is sealed with a low melting glass material 9. The hollow member 2b serves as an anode. A novel structure for holding the cathode to the enclosure members in the gas laser tube according to the invention will be described. A cathode 5 of a tube type made of aluminum is provided with a slender projection to be inserted into the hollow member 2a. The slender projection of the cathode is caulked with a ring-shaped groove formed in the hollow member 2a to hold the cathode. A slender discharge tube 7 is provided with an expanded portion serving as a discharge chamber 8 which has a smaller diameter than that of the cathode 5. The slender discharge tube 7 and the discharge chamber 8 are made of a sodium borosilicate glass. The slender discharge tube 7 and the discharge chamber 8 are also formed in an integral structure by flare processing. The slender discharge tube 7 at its anode side is attached through the discharge chamber 8 to the enclosure members of the gas laser tube. The thick glass 4, the cathode 5, the slender discharge tube and the chamber 8 are arranged at a coaxial position. The sealing flush member 1b is provided with an outlet 12 for releasing a gas within the discharge chamber 8. A plurality of V-shaped spring plate members 6 made of stainless are attached to an inner wall of the cathode at its anode side by welding so as to be pressed with the discharge chamber 8. The spring plate members 6 allow to operate to make the cathode 5 secure to an inner wall of the sealing flush member 1a. Further, the slender projection of the cathode is inserted into the hollow member 2a and caulked with the ring-shaped groove formed in the hollow member 2a. Whereby the cathode may securely be held within the enclosure members of the gas laser tube. A second embodiment of a novel structure for holding a cathode to enclosure members in a gas laser tube of an inner mirror type according to the present invention will be described. Referring to FIG. 4, with regard to means for making the cathode secure to the enclosure members, a plurality of arched spring plate members 11 made of SUS304 are attached to the cathode at its anode side by welding so as to be pressed with the discharge chamber 8. The spring plate members 6 allow to operate to make the cathode 5 secure to the sealing flush member 1a of the enclosure members. Whereby the cathode may securely be held within the enclosure members of the gas laser tube. In the gas laser tube according to the present invention, the means for making the cathode secure to the enclosure members may comprise a member with elasticity, for example, a spring plate member. The spring plate member for making the cathode secure to the enclosure members may be modified to various shapes. The means for making the cathode secure to the enclosure members may comprise one or more members having a elasticity. The location of the spring plate member may be selected associated with various structures in gas laser tubes. Such the novel structure for holding the cathode in the gas laser tube according to the invention allows to hold the cathode to the enclosure members without the resistance welding, the novel gas laser tube has no problem of melting or cracking in the sealing flush member to cause leaks or of putting out the cathode from the sealing flush member. Further, since the spring plate member allows to make the cathode secure to the sealing flush member of the enclosure members, the cathode 5 is securely held without looseness of caulking of the slender projection of the cathode or putting out from the sealing flush member of the enclosure members.

Claims: A gas laser tube comprising a plurality of enclosure members, a cathode (5) of a tube type, a discharge tube (7) provided at its one end with an expanded portion (8) having a smaller diameter than that of said cathode (7), said discharge tube (7) being attached to said enclosure members at their one end through said expanded portion (8), characterised by means (6) for making said cathode (5) secure to an inner wall of said enclosure members at their opposite end, said means (6) being attached to said cathode (5) so as to be pressed against said expanded portion (8). A gas laser tube as claimed in claim 1, wherein said expanded portion comprises a discharge chamber. A gas laser tube as claimed in claim 1, wherein said means for making said cathode secure to said inner wall of said enclosure members comprises at least one member having elasticity. A gas laser tube as claimed in claim 3, wherein said member having elasticity comprises a spring plate member. A gas laser tube as claimed in claim 4, wherein said spring member comprises a V-shaped winding plate. A gas laser tube as claimed in claim 4, wherein said spring member comprises an arched plate.

Inventors: HAYASHI KOJI C O NEC CORPORATI, HAYASHI, KOJI, C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1992
Main classification: H01S3
IPC codes: H01S3