| 摘要 |
1,233,195. Cutting by fusion. LASER TECHNIQUE S.A. 17 Sept., 1968 [25 Sept., 1967; 14 Feb., 1968], No. 44021/68. Heading B3V. [Also in Division H1] A bore is formed in a watch jewel or other workpiece by locating the workpiece at the focus of a laser having an optical focusing system, and subjecting the workpiece to a train of pulses of wavelength exceeding 1 Á, each pulse having an energy content of between 0.1 and 0À8 joule and a duration of 100 Ás or less. The laser may comprise a rod of yttrium-aluminiumgarnet pumped by a flash tube, the output energy being focused by a lens 1, Fig. 1, on to a jewel workpiece 3 held in a chuck 2. Successive laser pulses may be of different energy, the first pulse being relatively weak. Formation of the bore may be assisted by progressively displacing the focus either in the direction of the bore or laterally. Removal of waste products may be effected by passing a gas stream from a nozzle 4 over the workpiece and also through a central duct in the chuck, the gas consisting of air, oxygen, nitrogen or hydrogen. The workpiece may alternatively be bored in a vacuum or in oxygen or an inert gas. A single gas stream applied through an inlet pipe 7 is used in Fig. 2, the gas being directed by a casing 5 through the bore in the jewel as soon as it is formed. A window 6 passes the laser energy. Electrostatic precipitation of particles ejected from the bore is used in Fig. 3 (not shown). In Fig. 4 (not shown) the lens system is protected by a glass screen over which a curtain of flowing liquid is applied, while the gas scavenging medium is applied to the rear of the workpiece. The gas scavenging medium may be applied continuously, pulsed, or alternating in direction and may include a fine abrasive. The workpiece may be preheated. |
