Electric heating – Metal heating – By arc
Reexamination Certificate
1999-02-16
2001-03-13
Heinrich, Samuel M. (Department: 1728)
Electric heating
Metal heating
By arc
C219S121740, C219S121760
Reexamination Certificate
active
06201211
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an apparatus for welding together by a laser beam two components that overlap in a subregion of their mutually facing surfaces.
When welding components together, it is known to use not only so-called butt welds but also lap welds. Such lap welds, in which the components to be joined together overlap in a subregion of their mutually facing surfaces, are suitable in particular for the use of laser welding methods, since great welding depths with at the same time low heat input and an associated high welding quality can be achieved with a laser beam with high welding speeds. For production and commercial reasons, in the case of lap welds the components to be joined together are generally joined by a plurality of spaced-apart spot welds.
An apparatus for spot welding with a laser beam is known, for example, from European Patent 0 440 002 B1. In the case of the known apparatus, a laser welding head is disposed at the free end of a multi-jointed robot arm. With such a robot arm, the welding head can be guided freely over the surface of the component to be joined and stopped at the positions predetermined for spot welding. For this purpose, the welding head is positioned with the aid of the robot arm by a fixing element, by which the two components are pressed firmly against each other in an overlapping region. The fixing element includes two clasp-like clamping elements, one of which is provided with a central opening. The laser welding head is positioned and fixed over the central opening. This permits spot welding at a location of the overlapping region at which the components are pressed firmly against each other and as far as possible without any gaps therebetween. With the aid of the robot arm, the laser welding head can be brought successively up to a plurality of spaced-apart clamping elements, in order to ensure the strength of the joint by a multiplicity of such spot welds.
It is known from U.S. Pat. No. 4,654,505 to provide, instead of a single laser welding head which can be guided by a robot arm, a plurality of laser welding heads which are disposed on a clamping apparatus and into which the laser beam produced by a laser and spreading out freely is fed at successive times by adjustable mirrors.
However, the spot weld produced by the laser beam has a relatively small diameter, with the result that the required strength of the joint is ensured only by a correspondingly high number of spot welds. This entails increased expenditure with respect to process engineering, which calls into question the cost-effectiveness of spot-welding methods carried out with a laser beam.
German Patent 43 31 827 C1 discloses an apparatus for securing a screwed joint by a multiplicity of microwelded points produced by a laser beam and provided around the circumference of the screw head or the nut. In the case of this known apparatus, two or more part-beams are formed by a beam splitter disposed in the laser welding head, with the result that a plurality of microwelded points are produced simultaneously. An additional turning of the entire optical configuration within the laser welding head permits multiple setting of the microwelded points around the circumference of the screwed joint, by a single stationary laser welding head.
Japanese Laid-Open Application No. JP 58-68492 discloses an apparatus for spot welding by a laser beam, in which a rotatably mounted deflecting and focussing optical system is disposed in the laser welding head and is turned during the welding operation, with the result that the welded points form a circular line and the strength of the weld is increased.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an apparatus for welding together two components that overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which high cost-effectiveness and speed are accompanied by a welded joint having high strength.
With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for welding together with a laser beam two components which overlap in a subregion of their mutually facing surfaces, including: a laser welding head; a beam-guiding device; an optical beam distributor having an input for receiving a laser beam, a plurality of outputs each coupled optically to the laser welding head via the beam-guiding device, and a distributor for alternately distributing the laser beam between the plurality of outputs; and a focussing and deflecting optical system disposed in the laser welding head receiving, guiding, and focussing the laser beam over a surface of a component facing the laser welding head.
The apparatus for welding together with a laser beam two components which overlap in a subregion of their mutually facing surfaces includes according to the invention an optical beam distributor. The optical beam distributor has an input for receiving the laser beam and a device for alternately distributing the laser beam between a plurality of outputs which are respectively coupled optically to a laser welding head via a beam-guiding device. In addition, there is a focussing and deflecting optical system disposed in the laser welding head for guiding and focussing the laser beam over the surface of the component facing the laser welding head.
By these measures, a linear weld can be produced without moving the laser welding head. That is to say even with the laser welding head disposed stationarily on the apparatus for receiving the parts to be joined, by guiding, i.e. moving, the laser beam over the surface of the component. In other words, instead of a number of spatially separated linear welds corresponding to the number of laser welding heads, the linear form is predetermined by the movement of the focussing and deflecting optical system in the laser welding head. As a result, the strength of the joint between the components is increased, without requiring an increase in the number of welds.
In an advantageous development of the invention, a focussing deflecting mirror is provided in the welding head for focussing the laser beam. As a result, the number of optical elements required in the welding head is reduced.
In particular, the focussing deflecting mirror is mounted in a linearly displaceable manner. As a result, a weld can be produced along a straight line.
In a further advantageous development of the invention, a lens is provided for focussing the laser beam. A plane-parallel plate which can be pivoted about an axis oriented perpendicularly with respect to the center axis of the laser beam is disposed in front of the lens in the direction of propagation of the laser beam. As a result, a weld can likewise be produced along a straight line.
In an advantageous development, a prism mounted rotatably about the center axis of the laser beam is disposed in front of the lens. In this way, a circular weld can be produced. This circular line, the diameter of whose circle can be chosen to be significantly greater than the line width, has the effect of simulating virtually a spot weld of large diameter, and similar strength values are achieved with improved welding quality.
A light-conducting fiber is preferably provided between the beam distributor and the laser welding head as a beam-guiding device. This permits a greater flexibility in the selection of the location of the laser welding heads, since the beam guidance is simplified in comparison with an apparatus in which the laser beam spreads out freely.
In the beam distributor in particular, pivotable or displaceable path-folding mirrors are disposed in the path of rays of the laser beam.
In a particularly preferred development, a path-folding mirror, which is rotatable about the axis of the laser beam falling onto it and to which a plurality of outputs are disposed in a stellar formation about this axis are assigned, is disposed in the path of rays of the laser beam in the beam distributor. As a result, the number of movable path-folding mir
Greenberg Laurence A.
Heinrich Samuel M.
Lerner Herbert L.
Rofin-Sinar Laser GmbH
Stemer Werner H.
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