Electric heating – Metal heating – By arc
Reexamination Certificate
1999-10-21
2002-03-12
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06355905
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser processing apparatus using a light source as laser excitation means.
2. Description of the Related Arts
A laser oscillation unit of the laser processing apparatus using solid-state laser comprises a solid-state laser medium, e.g., a YAG rod; a light source for excitation, e.g., an excitation lamp; and a pair of optical resonator mirrors disposed on the optic axis of the solid-state laser medium.
When the excitation lamp is lit as a result of reception of electric power from the laser power supply unit, its optical energy excites the YAG rod, allowing beams of light emerging from both end surfaces of the YAG rod onto its optic axis to be repeatedly reflected for amplification between the pair of the optical resonator mirrors, after which the beams of light exit the output mirror in the form of laser beams. After having left the output mirror, the laser beams are transmitted via a predetermined transmission optical system to an output unit at the site to be processed and are then projected from the output unit onto the workpiece.
In such a laser oscillation unit, in accordance with the number of times that the laser oscillation increases, the laser oscillation efficiency may lower due to the degradation of the excitation lamp or to the dirt or the like on the YAG rod or the optical resonator mirrors.
In order to keep the laser output at its set value in the face of degradation over time in the laser oscillation unit, the laser power supply unit is typically provided with a laser output feedback function. Such a feedback function provides a control of the electric powers, currents or voltages fed to the excitation lamp by use of optical sensors or the like for measuring the laser output (optical intensity) of the laser beams, to thereby allow the laser output measured value to coincide with the laser output set value.
The above laser output feedback function ensures compensation for deterioration over time in the laser oscillation unit, thereby retaining the laser output of the laser beam at its set value.
Nevertheless, with deterioration increasing with time, a difference (error) will become greater between the laser output of the laser beams oscillatorily emitted from the laser oscillation unit and the electric power input (fed) from the laser power supply unit to the excitation lamp. This means that a greater electric power is required for compensation of deterioration over time in the laser oscillation unit.
While the lamp input power becomes greater as deterioration increases with time in the laser oscillation unit, the excitation lamp itself has a limit value for the input power. If this limit value is exceeded, the excitation lamp will break (usually, the lamp glass tube will break), thereby stopping laser oscillation.
At that time, in most cases, the excitation lamp is replaced with a new one. Upon the lamp replacement, scattered fragments of the broken glass tube of the existing excitation lamp must be cleaned up, which was very cumbersome. In addition, an unexpected, abrupt interruption of the laser processing caused by breakage of the excitation lamp often reduces productivity.
SUMMARY OF THE INVENTION
The present invention was conceived in view of the above problems involved in the prior art. It is therefore the object of the present invention to provide a laser processing apparatus having a function which ensures a precise prediction or notice of the time to replace the light source for excitation, achieving improved maintenancability and productivity.
In order to attain the above object, according to an aspect of the present invention there is provided a laser processing apparatus comprising a laser oscillation unit having a light source for excitation which issues optical energies to excite a solid-state laser medium, to thereby allow an oscillatory emission of laser beams therefrom; a laser power supply unit for supplying electric powers to the light source for excitation; input power measurement means for measuring electric powers fed to the light source for excitation; input power limit value setting means for setting limit values of input powers to the light source for excitation; power input ratio computing means which accept input power measured values from the input power measurement means to figure out a ratio of the input power measured value to the input power limit value; and power input ratio display means for providing a display output of the ratio figured out by the power input ratio computing means.
Preferably the laser processing apparatus of the present invention further comprises power input ratio upper limit setting means for setting a desired upper limit of the ratio, and alarm signal output means for issuing a predetermined alarm signal when the ratio figured out by the power input ratio computing means reaches or exceeds the upper limit value.
The laser processing apparatus of the present invention may further comprise alarm display means for providing a display output of predetermined alarm information in response to the alarm signal.
The laser processing apparatus of the present invention may further comprise laser oscillation stop means for ceasing laser oscillation in response to the alarm signal.
In such a case, the laser processing apparatus of the present invention preferably further comprises laser output setting means for setting a desired laser output of the laser beam; laser output measurement means for measuring laser output of the laser beam; laser output comparison means for comparing laser output measured values acquired by the laser output measurement means with laser output set values from the laser output setting means, to find a comparison error; and laser output control means for providing a control of electric powers, currents or voltages fed to the light source for excitation in response to the comparison error so as to ensure that the laser output measured value coincides with the laser output set value.
According to the laser processing apparatuses of the present invention as described hereinabove, the ratio (power input ratio) of the input power measured value to the input power limit value is figured out for the excitation light source within the laser oscillation unit and the thus obtained ratio is output for display, whereby it is possible to provide a precise prediction or notice of the time to replace the excitation light source, remarkably improving the maintenance of excitation light source and the productivity of the laser processing.
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Kawamura Kouji
Sasaki Haruki
Heinrich Samuel M.
Miyachi Technos Corporation
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