Electric heating – Metal heating – By arc
Patent
1996-07-23
1998-07-28
Evans, Geoffrey S.
Electric heating
Metal heating
By arc
21912167, B23K 2614
Patent
active
057865612
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national stage of PCT/DE95/100050 filed 18 Jan. 1995 and based upon German national application P44 02 000.7 of 25 Jan. 1994 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a nozzle assembly for laser beam cutting, which has a frustoconical nozzle body surrounding the focussed laser beam, having a nozzle sleeve concentrically surrounding the nozzle body and forming an annular gap therewith, the sleeve having an outlet opening coaxial with a passage bore for a stream of cutting gas flowing from the annular gap connected to a gas source, whereby the outlet opening is located on the side of the workpiece in front of the passage bore and has a diameter which exceeds the diameter of the passage bore.
BACKGROUND OF THE INVENTION
A nozzle assembly is known from JP-84589 A in: "Patent Abstracts of Japan" 1993, Vol. 17/No. 410, Sec. M-1455. The wall of the nozzle sleeve forming the annular gap projects by more than 0.5 to 5 mm beyond the end of the nozzle body, in order to achieve a perfect shield against the environmental air.
U.S. Pat. No. 4,121,085 describes a nozzle assembly for laser beam cutting, which has a nozzle body in the shape of a truncated cone fitting the focussed laser beam and surrounding it, with a passage bore for the laser beam, with a nozzle sleeve concentrically surrounding the nozzle body at a distance. The sleeve, coaxially with the passage bore has an outlet opening for the cutting gas beam on the workpiece side in front of the passage bore of the nozzle body. The delivery cross section of the outlet opening is smaller than the cross section of the inlet into the space between the nozzle body and the nozzle sleeve. In this way a reverse gas flow is supposed to be generated, with the purpose of cutting the air flow to the workpiece.
DE 36 37 568 A1 describes a nozzle assembly for laser beam cutting, which has nozzle body shaped like a truncated cone, fitted to and surrounding the focussed laser beam, with a passage bore for the laser beam, with a nozzle sleeve concentrically surrounding the nozzle body forming an annular gap therewith, the sleeve having an outlet opening, which is coaxial with the passage, for a cutting gas supplied by a gas source. In this known nozzle arrangement the nozzle sleeve is screwed onto the nozzle body and is provided on the inside surface of the sleeve with individual longitudinal grooves, separated from each other. When the sleeve is slightly unscrewed, a conical annular gap is created between the sleeve and the nozzle body. The annular gap surrounds the passage of the nozzle body at a distance which is determined by the wall thickness of the nozzle body in the area of the passage bore. The exiting cutting gas beam is like a hollow cylinder. This known nozzle arrangement can also be used for cutting, but is not specialized for this operation and creates a relatively large cutting kerf due to the hollow cylindrical shape of the burning gas beam.
DE 38 24 047 A1 describes a nozzle assembly with a nozzle sleeve, which concentrically surrounds a nozzle body shaped like a truncated cone and has a bore arranged on the workpiece side in front of the passage bore. By means of this bore of the known nozzle assembly a negative pressure is generated on the workpiece surface, in that the annular gap between the nozzle sleeve and the nozzle body is subjected to suction. A considerable beam disturbance takes place in the area of the outlet bore, so that this particular nozzle arrangement is not suited for laser beam cutting, especially in the case of high cutting efficiency and/or high cutting gas pressures, for instance with laser power exceeding 3 kW and gas pressure of more than 10 bar.
In order to be able to cut workpieces at high cutting speeds it is known to use cutting gas supplied at high velocities for blowing away the material from the cutting clearance. The velocity of the cutting gas lies within the ultrasonic range. From DE 36 30 127 A1 such a nozzle assembly
REFERENCES:
patent: 4121085 (1978-10-01), Diemer et al.
patent: 5418350 (1995-05-01), Freneaux et al.
Petring Dirk
Zefferer Hartmut
Dubno Herbert
Evans Geoffrey S.
Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung
Kateshon Yori
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