Reflecting mirror for a laser beam and laser beam welding apparatus, including the same laser beam reflecting mirror

A laser beam welding apparatus comprising:

• a flexible tube having an optical fiber extended therethrough for transmitting a welding laser beam, said flexible tube being insertable into a work tube;
• a position detector for detecting a relative position of said flexible tube with respect to said work tube;
• fixing means for fixing said flexible tube within said work tube, said fixing means comprising an expansible member provided at the front end portion of said flexible tube;
• a rotary cylinder rotatably supported from said flexible tube;
• guide support means rotatably mounted to said rotary cylinder such that said guide support means can be held in contact with the inner wall surface of said work tube for holding said rotary cylinder concentrically with said work tube;
• rotary drive means having its output shaft disposed coaxially with said rotary cylinder for rotatably driving said rotary cylinder;
• an optical condensing system disposed within said rotary cylinder for leading said welding laser beam emanating from the front end of said optical fiber to the inner wall surface of said work tube in a condensed state;
• gas scavenging means for discharging metal vapor produced during welding of said work tube;
• gas cooling means for cooling said optical condensing system;
• and wherein said optical condensing system includes a reflecting mirror comprising a mirror base member, a high-reflectivity metal coating layer formed on the mirror base member for reflecting a laser beam, and at least one dielectric coating layer provided on the surface of said high-reflectivity metal coating layer.

A laser beam welding apparatus comprising:

• a flexible tube having an optical fiber extended therethrough for transmitting a welding a laser beam, said flexible tube being insertable into a work tube;
• a position detector for detecting a relative position of said flexible tube with respect to said work tube;
• fixing means for fixing said flexible tube within said work tube, said fixing means comprising an expansible member provided at the front end portion of said flexible tube;
• a rotary cylinder rotatably supported from said flexible tube;
• guide support means rotatably mounted to said rotary cylinder such that said guide support means can be held in contact with the inner wall surface of said work tube for holding said rotary cylinder concentrically with said work tube;
• rotary drive means having its output shaft disposed coaxially with said rotary cylinder for rotatably driving said rotary cylinder;
• an optical condensing system disposed within said rotary cylinder for leading said welding laser beam emanating from the front end of said optical fiber to the inner wall surface of said work tube in a condensed state;
• gas scavenging means for discharging metal vapor produced during welding of said work tube;
• gas cooling means for cooling said optical condensing system;
• and wherein said optical condensing system includes a reflecting mirror comprising a mirror base member, a high-reflectivity metal coating layer formed on the mirror base member for reflecting a laser beam, a coating layer having a small diffusion coefficient provided on the back surface of said high-reflectivity metal coating layer, and at least one dielectric coating layer provided on the surface of said high-reflectivity metal coating layer.

A reflecting mirror for a welding laser beam, comprising:

• a base member formed of a metal of high thermal conductivity;
• a diffusion barrier layer, formed of a metal of high melting point, mounted on a surface of said base member;
• and
• a high-reflectivity metal layer, mounted on a surface of said diffusion barrier layer opposite said base member, for reflecting the welding laser beam.