Method and apparatus for welding
Assigneebielomatik Leuze GmbH & Co.
InventorJoern Korte
Life of this patent
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Abstract
For joining two faces (41, 42) of thermoplastics in a penetration beam welding method the covered face (42) is multiply scanned and thus incremently heated by a laser beam (10) directed through the covering face (41). This preheating is repeated until the melting temperature is attained. In the region of the covered face (42) a melt thus materializes simultaneously over the full seam length which wets the covering face (41) and thus also transfers this face into melt by heat conduction. On completion of material softening the faces (41, 42) are mutually moved until abutting. Thus the two faces (41, 42) weld in principle as if they had been plasticized simultaneously over the full seam length which significantly enhances the seal and strength of the seam, whilst the expenditure the apparatus is low.
Claims20
A method of laser welding a joint, wherein the joint defines a joint field between a first joint face and a second joint face, wherein the first and second joint faces bound first and second cross-sections and have an initial temperature, wherein the first and second cross-sections comprise weldable materials of different physical characteristics such that the material of the first cross-section is substantially transparent to a laser beam, and the material of the second cross-section absorbs the laser beam, wherein the joint field includes field sections, said method comprising:
- directing a laser beam through the first cross-section and the first joint face to the second joint face on which the laser beam impinges, whereby the second joint face is heated within a beam field smaller than the joint field;
- moving the beam field in a sweeping action repeatedly over the joint field, wherein, during each sweeping action, only a portion of the total heating energy needed to attain a welding temperature is transmitted to each field section;
- and
- pressing the first and second joint faces together during at least a portion of the sweeping action;
- whereby the second cross-section and second joint face are incrementally heated and plasticized by the repeated sweeping action of the beam field, and the first cross-section and first joint face are heated indirectly by heat transmitted from the second cross-section to the first cross-section;
- and
- whereby the temperature is raised from the initial temperature to the welding temperature in the first and second cross-sections substantially simultaneously over the whole joint field.
An apparatus for welding a workpiece, wherein the workpiece includes a joint defining a joint field between a first joint face and a second joint face, wherein the first and second joint faces bound first and second cross-sections, wherein the joint field includes field sections, wherein the first and second cross-sections comprise weldable materials of different physical characteristics, wherein the material of the first cross-section is substantially transparent to a laser beam, and the material of the second cross-section is absorbent of the laser beam and is heated thereby, said apparatus comprising:
- means for creating the laser beam;
- means for guiding the laser beam, said guiding means including a beam output directed to pass the laser beam through the first cross-section onto the second joint face, thereby projecting a beam field of the beam onto the second joint face;
- means for advancing the beam field along the second joint face;
- control means for controlling said advancing means, wherein said control means guides the beam field repeatedly and sequentially over each of the field sections while the laser beam penetrates the first cross-section;
- and
- a gripping fixture holding the workpiece and pressing the first and second cross-sections with their joint faces together during heating by the laser beam.
Dependencies are inferred from the claim text.