Patent GB-1215713-A (GB)
Title: Improvements relating to thermal cutting apparatus
Inventor: SULLIVAN ARTHUR BASIL JOSEPH
IPC: B23K26/14
Filed: 1967-03-16
Abstract: 1,215,713. Working stove. NATIONAL RESEARCH DEVELOPMENT CORP. 11 March, 1968 [16 March, 1967; 31 July, 1967 (2); 1 Aug., 1967; 23 Nov., 1967; 5 Dec., 1967], No. 12447/67. Heading B5E. [Also in Divisions B3, C1 and H1] In the cutting or gauging of a workpiece 42 by means of a laser beam 26, a stream of gas is directed on to the cutting zone to provoke an exothermic reaction and sweep away the products of combustion. The laser 10 is of the carbon - dioxide - nitrogen - helium type having electrodes 12 supplied from A.C. or D.C. power sources 14, gas inlet and outlet ports 22, 24, a gold-surfaced stainless steel mirror 18 and a semi-reflecting germanium disc 20. The laser beam 26 is deflected by a mirror 28 through safety shutter 30 and focusing lens 32 into a chamber 36 where oxygen is admitted through port 38 and is discharged with the beam through nozzle 40. The focusing lens 32 may be omitted if a parabolic mirror 28 is used. The oxygen chamber 36 may also be omitted and the oxygen supplied by a separate oblique nozzle (50), Fig. 2c (not shown). Nozzle 40 may also be arranged obliquely to the workpiece 42, Figs. 2a, 2b (not shown). Relative movement 44 is provided between the workpiece 42 and the nozzle. To increase the width of cut when cutting thick workpieces, the beam may be slightly defocused or it may be given an orbital motion, Fig. 3 (not shown), by revolving mirrors (58), (62) or a prism driven through gearing (60), (64) or by an induction motor. The orbiting beam may be parallel or oblique or an elliptical beam movement may be produced. In another embodiment, Fig. 4, the laser beam 26 is deflected by prisms 92, 94 into a cutting head 74 which has two directional movement produced by lead screws 78, 86 driven by motors 84, 88. A rack and pinion (70), (72), Fig. 3 (not shown), provide adjustment of the cutting head towards and from the workpiece. Oxygen is supplied by pipe 78a. In another embodiment, Figs. 5, 6 (not shown), the laser beam is directed through guide tubes (98-104) having rotatable adjustable joints (108, 110). This arrangement may be used in a lathe for machining a tubular workpiece (124). Oxygen is supplied through pipe (126). In a further embodiment, Fig. 7, the laser beam is guided through telescopic tubes 130, 132 fitted with reflectors 138, 140. The tubes are adjustable by rack and pinion mechanism 134, 136, 142. The windows and lenses used for the laser beam may be of germanium or potassium bromide; in the latter case warm nitrogen is circulated through the guide tubes to prevent deterioration of the potassium bromide surfaces. The invention may be used for cutting aluminium, stainless steel or other refractory metals, ceramic material, brick, tile, concrete, stone, rock and glass. When cutting non-metals or aluminium a fluxing agent such as a volatile or vaporized halide or iron powder, wire or strip is introduced into the oxygen jet. For gauging, two laser beams each surrounded by a gas jet converge on the workpiece. Reference is made to Specification 1,215,714 which is divided from the present Specification.