Electric heating – Metal heating – By arc
Patent
1996-01-23
1998-06-09
Walberg, Teresa J.
Electric heating
Metal heating
By arc
2191216, B23K 2614
Patent
active
057638551
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to a method and apparatus for supplying nitrogen gas to an optical path system of a laser beam machine, and to a laser head provided for the same. Nitrogen gas is supplied to an optical path system to protect bend mirrors arranged in the optical path system, and further to a laser beam head as an assist gas.
2. Description of Background Information
As is well known, a laser beam machine is provided with a laser beam oscillator and a laser beam head. Further, a plurality of bend mirrors are arranged between the laser beam oscillator and the laser beam head, to guide the laser beam generated by the laser beam oscillator to the laser beam head.
The laser beam path from the laser beam oscillator to the laser beam head is referred to as an optical path system, and is usually partitioned from outside air by a pipe member, for safety purposes and for protection of the optical path system from dust.
Further, in known laser beam machines having a movable laser beam head, since the optical path length from the laser beam oscillator to the laser beam head changes, both are connected by use of a bellows or a telescopic tube, etc.
In order to prevent outside air from entering the optical path system in this type of system, dry air cleaned by an air drying unit is usually supplied into the optical path system to protect various optical elements such as bend mirrors, lenses, etc.
Since the dry and clean air is supplied into the optical path system for prevention of outside air from entering the optical path system, dust levels are kept extremely low, compared with the outside air. However, there exists a problem in that the optical elements deteriorate more rapidly due to exposure to and/or very small amounts of moisture contained in the dry and clean air, when the laser beam machine has been used for many hours.
In addition, an assist gas such as air, oxygen, nitrogen, argon, etc. is usually used in the laser beam machines. The appropriate assist gas is selected according to the sort of plate materials, laser beam machining conditions, etc.
However, air, oxygen and nitrogen are generally chosen as the assist gases, because argon is costly (except the case where the material to be processed is titanium).
In the case where air is used as the assist gas, a compressed air can be obtained easily by use of a compressor. In the case of oxygen or nitrogen, however, an oxygen bomb or a nitrogen bomb must be prepared, so that the assist gas is not economical.
To overcome these problems, Japanese Published Unexamined (Kokai) Patent No. 5-84590 (referred to as a prior art, hereinafter) discloses such a construction that oxygen and nitrogen in air are separated from each other by an air separator so that the separated oxygen and nitrogen can be used as the assist gas. In this method, since oxygen and nitrogen in air can be used after separation without using any gas bombs, the assist gas can be obtained at a relatively low cost.
In the above-mentioned method, however, since the pressure of the assist gas supplied to the laser beam head must be adjusted according to the laser beam machining conditions, there exists another problem in that the purity of oxygen or nitrogen separated by the air separator varies whenever the assist gas pressure is adjusted. This results in the potential that a harmful influence will be produced upon the laser beam processing, if the purity of the assist gas varies out of a normally acceptable range.
SUMMARY OF THE INVENTION
With these problems in mind, therefore, it is an object of the present invention to provide a method and apparatus for protecting the optical path system more reliably from deterioration (due to oxidation, moisture, etc.).
Another object of the present invention is to effectively use separated nitrogen as an assist gas and an optical path system protective gas simultaneously.
A further object of the present invention is to supply separated nitrogen gas as an assist gas within a constant purity r
REFERENCES:
patent: 4945207 (1990-07-01), Arai
patent: 4977566 (1990-12-01), Herbst et al.
patent: 5334816 (1994-08-01), Sugiyama
patent: 5374803 (1994-12-01), Yamada
patent: 5539180 (1996-07-01), Mori et al.
patent: 5559584 (1996-09-01), Miyaji et al.
Patent Abstracts of Japan, vol. 17, No. 410 (M-1455), and JP-A-05 084590.
Amada Company Limited
Mills Gregory L.
Walberg Teresa J.
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