Coherent light generators – Particular temperature control
Patent
1990-03-30
1992-01-28
Scott, Jr., Leon
Coherent light generators
Particular temperature control
372 38, 372 33, 372 58, H01S 304
Patent
active
050848852
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Technical Field
The present invention relates to an NC laser device provided with a mechanism for forcibly cooling a laser gas by a blower and a cooling unit, and more particularly, to an NC laser device able to detect abnormalities in a cooling mechanism.
BACKGROUND ART
Gas laser oscillators such as a CO.sub.2 gas laser are highly efficient and have a high-power output and excellent beam characteristics, and accordingly, are widely used in combination with a numerical control device to thereby act as an NC laser device for machining metals, etc. To improve the oscillation efficiency, these types of gas laser oscillators are provided with a cooling mechanism for externally cooling a high-temperature gas heated by laser oscillation, and returning the cooled gas as the laser gas into a discharge tube. The cooling mechanism includes a cooling unit, a blower, and a blower piping connecting these elements to the discharge tube; the blower causing a constant circulation of the laser gas within the discharge tube.
In this cooling mechanism, if the inherent function of the cooling unit is lost, the blower is subjected to a direct flow of the high-temperature gas, and thus the rotors of the blower are overheated to an abnormal level. Even if the cooling unit is operating properly, the rotors can be overheated due to an abnormal increase in the number of rotations of the blower. For example, if a blower originally designed for use at 50 Hz is erroneously used at 60 Hz, the number of rotations thereof is increased, and accordingly, the compression ratio of gas in the vicinity of the rotors is increased and the rotors are overheated.
Namely, various causes of an abnormal heating of the rotors of the blower exist, and if an abnormal heating of the blower rotors eventually occurs due to any one of these causes, the rotors are thermally expanded and come into contact with the casing, whereby the number of rotations thereof is reduced until, finally, a state is reached in which the rotors cannot rotate.
In this case, even if the number of rotations of the blower is monitored, the rotors will come into contact with the casing before a reduction in the number of rotations is observed, resulting in a scattering of the materials forming these elements within the blower system, and an inevitable contamination of the laser oscillator. The gap between the rotor and the casing is 100 to 300 .mu.m in the case of a Roots blower and is as small as 30 to 50 .mu.m in the case of a turbo-blower. The rotors and the casing are made of iron, which has a coefficient of thermal expansion of 10.times.10.sup.-6 /.degree.C., and therefore, if the rotors are heated to a level such that the difference in temperature between the rotors and the casing is several tens of .degree.C., contact between the rotors and the casing is unavoidable.
SUMMARY OF THE INVENTION
The present invention was created in view of the above circumstances, and an object thereof is to provide an NC laser device in which an abnormality in a cooling mechanism is detected at an early stage by monitoring an inlet gas temperature and a casing temperature of a blower, whereby secondary damage to the blower, etc., can be prevented.
To solve the aforementioned problems, the present invention provides an NC laser device which is a combination of a gas laser oscillator provided with a cooling mechanism for forcibly cooling a laser gas by a blower and a cooling unit, a numerical control device (CNC), a gas temperature measuring means for measuring a gas temperature at an inlet of the blower, a casing temperature measuring means for measuring a temperature of a casing of the blower, and an abnormality detecting means for detecting an abnormal state of the cooling mechanism, and stopping an operation of the gas laser oscillator, when the inlet gas temperature becomes higher than a predetermined gas temperature reference value or when the casing temperature becomes higher than a predetermined casing temperature reference value.
The inlet gas tempera
REFERENCES:
patent: 4692924 (1987-09-01), Koizumi et al.
patent: 4697269 (1987-09-01), Ohara
patent: 4935937 (1990-06-01), Yamazaki et al.
Iehisa Nobuaki
Yamazaki Etsuo
Fanuc Ltd.
Jr. Leon Scott
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