Electric heating – Metal heating – By arc
Patent
1988-04-26
1989-10-03
Albritton, C. L.
Electric heating
Metal heating
By arc
21912175, 21912178, 21912184, B23K 2616
Patent
active
048718971
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a nozzle for laser processing, such as a cutting, said processing allowing a laser beam to be directed towards an article being processed, and whereby the laser beam is supported by a gas flow directed towards the article through the nozzle.
BACKGROUND ART
It is common knowledge to use a laser for cutting metal, as well as it is common knowledge to use a gas beam including for instance oxygen or a gas mixture together with the laser beam towards the processed area.
DESCRIPTION OF THE INVENTION
Under usual conditions a coaxially positioned laser beam is used, i.e. a laser beam situated in the axis (E) through the centre point (C) of the nozzle. In other words the laser beam is situated on the location having the highest gas pressure/gas flow. Furthermore the symmetrical positioning of the laser beam in the nozzle provides a uniform cutting quality irrespective of the cutting direction. A cut groove is obtained by movement of the laser beam
ozzle relative to the material. The purpose of the supporting cutting gas is substantially to remove melt and vapours from the cut groove. The ability of the process to remove the water material depends on the flow conditions in the nozzle and in the cut groove.
According to the invention, the nozzle is able to maintain a displacement of the focusing point of the laser beam relative to a center of gas pressure for the gas flow through the nozzle, whereby the laser beam is displaced forwards in the processing direction relative to the center of gas pressure. As a result the laser beam meets the article first and melts this portion of the article, said portion subsequently being blown away by the gas flow. In this manner the gas flow is efficiently utilized because it does not meet the article until the material to be removed has melted and is thereby removable by blowing.
The nozzle is preferably circular-cylindrical and able to maintain a predetermined eccentric position of the laser beam in the nozzle. According to an alternative embodiment a circular-cylindrical nozzle is also used, but this nozzle is mounted with the laser beam in the center while an eccentrically located outlet nozzle opening is provided for the gas flow. According to a particular embodiment the nozzle may be radially displaceable relative to the laser beam. Within the scope of the invention the nozzle may, however, be of other shapes than the circular-cylindrical shape.
The laser beam is preferably spaced a distance d from the center of gas pressure, whereby 0.01 D is smaller than the distance d in turn being smaller than D/2, D being the diameter of the nozzle. The distance d corresponds preferably to 0.25 times the diameter of the nozzle.
An external control is preferably provided, said control controlling the nozzle and/or the laser beam in response to the desired direction of processing. Such an external control is advantageously connectable to an existing control of a cutting table and/or the laser head. According to a preferred embodiment, the nozzle maintains a predetermined position of the laser beam in the nozzle relative to the direction of processing in such a manner that the center of gas pressure and the laser beam are substantially always situated on the tangent of the direction of processing.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described below with reference to the accompanying drawings, in which
FIG. 1 is a sectional view through the outer portion of a nozzle according to the invention,
FIG. 2 illustrates the movement of the nozzle of FIG. 1 during the alteration of a cutting direction,
FIG. 3 illustrates a second embodiment of a nozzle according to the invention,
FIG. 4 illustrates a third embodiment of a nozzle according to the invention,
FIG. 5 illustrates a still further embodiment of a nozzle according to the invention, and
FIGS. 6a-6f illustrate further examples of various nozzle openings.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 1 illustrates the principles of the nozzle acc
REFERENCES:
patent: 4461947 (1984-07-01), Ward
Albritton C. L.
Instituttet for Produktudvikling
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