Electric heating – Metal heating – By arc
Reexamination Certificate
2000-05-10
2001-08-14
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
By arc
C219S121640, C219S121830, C219S121810, C219S121790
Reexamination Certificate
active
06274843
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an installation for laser welding at least two overlapping metal parts, comprising a laser source, a head for focusing, in the zone of overlap, a laser beam emitted by the source, a mechanism for pressing on a first of the parts and intended to co-operate with means for retaining another part so as to hold the parts that are to be welded pressed together in the region of their zone of overlap, and means for the relative displacement of the head with respect to the zone of overlap of the parts that are to be welded.
The invention applies in particular to the transparency-welding of external body skin panels made of steel sheet for railway vehicles.
Laser transparency-welding allows metal parts to be welded together at their surfaces that face one another in a zone of overlap.
To form a weld between these opposing surfaces in this zone where they are inaccessible, the laser beam impinging on one of the parts passes right through this part and melts the other part. The molten metal solidifies after the laser beam has passed, to form a welded seam.
The use of this transparency-welding technique requires the clearance between the opposing surfaces of the parts that are to be welded to be less than 10% of the total thickness of the zone of overlap.
This constraint on the clearance poses problems in applying this welding technique to railway vehicle exterior body skin panels because of the long lengths over which they need to be welded, it being possible for these lengths typically to be as much as 30 m.
In other fields and for small parts, uniformly spaced rams which clamp the two parts together along the entire length to be welded of the zone of overlap are used in order to comply with this constraint on clearance.
However, this solution would be particularly expensive for welding parts together over relatively long lengths, because of the proliferation in the number of rams.
SUMMARY OF THE INVENTION
The object of the invention is to solve this problem by supplying a low-cost laser-welding installation that makes it possible to transparency-weld overlapping parts over relatively long lengths.
To this end, the subject of the invention is an installation for laser welding at least two overlapping metal parts, comprising a laser source, a head for focusing, in the zone of overlap, a laser beam emitted by the source, a mechanism for pressing on a first of the parts and intended to co-operate with means for retaining another part so as to hold the parts that are to be welded pressed together in the region of their zone of overlap, and means for the relative displacement of the head with respect to the zone of overlap, characterized in that the pressing mechanism is subject to the displacement of the head parallel to the zone of overlap of the parts that are to be welded, so as to keep the parts that are to be welded pressed together locally close to the region of impingement of the laser beam in the zone of overlap.
According to particular embodiments, the installation may have one or more of the following features, taken in isolation or in any technically possible combination:
the pressing mechanism comprises means for pressing on the first part in a region located ahead of the region of impingement of the laser beam, with respect to the sense of displacement of the region of impingement in the zone of overlap of the parts that are to be welded;
the pressing mechanism comprises rolling means intended to roll along the first part;
the installation comprises means for the relative translational displacement of the head and pressing mechanism orthogonally with respect to the zone of overlap of the parts that are to be welded;
the installation comprises a common mobile structure supporting the head and the pressing mechanism, this structure being designed to bring the head into a welding position and, through the pressing mechanism, to exert a pressing force on the parts that are to be welded in their zone of overlap;
the mechanism comprises a tube, one edge face of which is equipped with rolling means intended to roll along the first part;
the installation comprises means for making the tube rotate about its axis so as to orientate the rolling means in a chosen direction of displacement of the head parallel to the zone of overlap;
the tube is free to rotate about its axis, the rolling means automatically orientating themselves in the direction of displacement of the head parallel to the zone of overlap by rotation of the tube about its axis;
the rolling means comprise a ball that is able to move in terms of rotation with respect to the tube about the axis thereof;
the rolling means comprise several balls whose rotation with respect to the tube about the axis thereof is limited.
REFERENCES:
patent: 5389761 (1995-02-01), Kresse, Jr.
patent: 5841098 (1998-11-01), Gedrat et al.
patent: 2 307 096 (1974-08-01), None
patent: 44 15 035 (1995-11-01), None
Patent Abstracts of Japan, vol. 009, No. 256 (M-421), Oct. 15, 1985 & JP 60 106684 A (Kogyo Gijutsuin) Jun. 12, 1985.
Patent Abstracts of Japan, vol. 009 No. 202 (M-405), Aug. 20, 1985 & JP 60 064788 (Nisshin Boseki KK) Apr. 13, 1985.
Patent Abstracts of Japan, vol. 012, No. 292 (M-729), Aug. 10, 1988 & JP 63 068295.
Dabezies Bernard
Delroise Pascal
Alstom Holdings
Elve M. Alexandra
Sughrue Mion Zinn Macpeak & Seas, PLLC
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