Electric heating – Metal heating – By arc
Reexamination Certificate
1999-10-29
2001-09-25
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121740, C219S121770, C219S121840
Reexamination Certificate
active
06294754
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser beam machining head. More specifically, the invention relates to a laser beam machining head for feeding a filler wire, or having an electrode for various types of arc welding, such as inert gas shielded tungsten (TIG) arc welding, metal active gas (MAG) arc welding, and plasma arc welding, the head being useful as a tip machining optical system for laser beam machining.
The present invention is also useful when applied to a laser beam machining head of a laser beam machine for cutting or piercing a workpiece of a metal or the like.
2. Description of the Related Art
FIG. 21
is an explanation drawing conceptually showing a composite welding head according to an earlier technology. As shown in the drawing, a composite welding head
223
performs laser welding and TIG welding, and has two welding heads, i.e., a laser welding head
224
and a TIG welding head
225
. With such a composite welding head
223
, the same site of welding is machined with laser light and a TIG arc, so that it is impossible to set both welding heads
224
and
225
vertically relative to a base material
216
. Thus, either the welding head
224
or the welding head
225
is inclined forward or rearward, namely, is given an angle of advance or an angle of backing to carry out welding. In
FIG. 21
, a tungsten electrode
210
at the tip of the TIG welding head
225
is inclined forward so that an arc
213
will reach a condensing site
206
a
for a laser beam
206
.
FIG. 22
is an explanation drawing conceptually showing a filler wire-coaxial laser welding head
226
according to an earlier technology. As shown in the drawing, the filler wire-coaxial laser welding head
226
has a structure in which a filler wire
207
is passed through holes perforated at the center of a total reflection mirror
214
and an imaging lens system
204
. The filler wire
207
and an optical axis of a laser beam are rendered coaxial, and the filler wire-coaxial laser welding head
226
is designed to perform welding while feeding the filler wire
207
via a filler wire feed pipe
208
. With the filler wire-coaxial laser welding head
226
, a laser beam
206
launched from an optical fiber
201
is reflected by the total reflection mirror
214
, and condensed by the imaging lens system
204
for use in fusing a base material
216
and the filler wire
207
. The filler wire
207
is fed by a filler wire feeder
209
.
FIG. 23
is an explanation drawing conceptually showing a TIG arc-coaxial laser welding head
227
according to an earlier technology. As shown in the drawing, this TIG arc-coaxial laser welding head
227
arranges an electrode
210
for TIG welding and a laser beam optical axis coaxially, thereby performing TIG welding and laser welding simultaneously. Its constitution is basically the same as the constitution of the filler wire-coaxial laser welding head
226
shown in
FIG. 22
, the difference existing only in the electrode
210
, an electrode holding pipe
211
for holding the electrode
210
, and a welding power source
212
.
FIG. 24
is a vertical sectional view showing the constitution of a tip portion of a conventional, typical laser beam machining head. A laser beam machining head
301
shown in the drawing is provided in a laser beam machine (its machine body is not shown) which cuts an object
302
to be cut, such as carbon steel.
As shown in
FIG. 24
, a lens-barrel
305
houses a condensing optical system (an imaging lens system)
304
composed of a plurality of lenses
310
, and a protective glass
307
for protecting the condensing optical system
304
. The condensing optical system
304
condenses laser light
303
, and projects it onto a cutting site
302
a
of the object
302
to be cut. On this occasion, a focal position, f, of the laser light
303
condensed by the condensing optical system
304
is usually adjusted to lie within the object
302
to be cut, as illustrated in the drawing. The laser light
303
is generated by a laser oscillator such as a YAG laser oscillator (not shown), and then transmitted to the condensing optical system
304
by an optical transmission means such as an optical fiber or mirrors (not shown).
On a laser light ejection side of the condensing optical system
304
(i.e., a lower end portion of the lens-barrel
305
), an assist gas nozzle
306
is attached in such a manner as to surround the laser light
303
that has been ejected from the condensing optical system
304
. The assist gas nozzle
306
is shaped like a truncated cone with a tip side (lower end side) becoming thin, and has an opening
306
a
at the tip side. To a side surface of the assist gas nozzle
306
, an assist gas supply pipe
308
is connected. The assist gas supply pipe
308
is tied to an assist gas supply device (not shown). That is, an assist gas Q
T
transported from the assist gas supply device is introduced into the assist gas nozzle
306
via the assist gas supply pipe
308
, and is jetted through the tip opening
306
a
of the assist gas nozzle
306
toward the cutting site
302
a
of the object
302
to be cut.
A cutting operation for the object
302
to be cut, by means of the laser beam machine equipped with the laser beam machining head
301
of the above-described constitution, is performed in the following manner: First, the laser beam machining head
301
is brought close to the object
302
to be cut, by the use of a laser beam machining head moving device (not shown). Also, the distance between the tip of the assist gas nozzle
306
and the surface of the object
302
to be cut (i.e., work distance), h, is kept so that there will be no contact between the assist gas nozzle
306
and the object
302
to be cut. In this condition, either the laser beam machining head
301
is moved by the laser beam machining head moving device in a direction perpendicular to the sheet face of
FIG. 24
, or the object
302
to be cut is moved by a work moving device (not shown) in a direction opposite to the moving direction of the laser beam machining head.
In accordance with this movement, the laser beam machining head
301
condenses the laser light
303
by the condensing optical system
304
, and projects it onto the cutting site
302
a
of the object
302
to be cut, thereby fusing the cutting site
302
a
. Simultaneously, an assist gas is jetted toward the cutting site
302
a
from the tip opening
306
a
of the assist gas nozzle
306
, and introduced into the cutting site
302
a
, to blow away and remove fused metal within the cutting site
302
a
. Thus, the object
302
to be cut is laser cut.
SUMMARY OF THE INVENTION
Of the earlier technologies described above, the composite welding head
223
shown in
FIG. 21
has two welding heads, i.e., the laser welding head
224
and the TIG welding head
225
. This composite welding head
223
is large in size, and its direction of welding cannot be selected freely, because the two constituent welding heads are at fixed positions, i.e., front and rear positions. Thus, this type of welding head is not suitable for welding an object of a three dimensional shape. With the filler wire-coaxial laser welding head
226
shown in
FIG. 22
, the center of the laser beam
206
launched from the optical fiber
201
is the site of the strongest intensity distribution of light. This site is the very place where the filler wire feed pipe
208
is situated. The laser beam
206
projected onto the filler wire feed pipe
208
is irregularly reflected, causing a beam transmission loss. Such a laser beam may not be used effectively depending on a purpose to be attained. The TIG arc-coaxial laser welding head
227
shown in
FIG. 23
, like the filler wire-coaxial laser welding head
226
shown in
FIG. 22
, poses the problem that the laser beam
206
is irregularly reflected by the electrode holding pipe
211
, causing a beam output loss.
The present invention has been accomplished in view of the above-described problems with the earlier technologies. It is an object of th
Akaba Takashi
Hashimoto Yoshio
Ishide Takashi
Michishita Yukio
Nagashima Tadashi
Evans Geoffrey S.
Mitsubishi Heavy Industries Ltd.
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