Method of accurately joining together two sheet sections

Metal fusion bonding – Process – With supplementary mechanical joining

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228171, 228102, B23K 1500, B23K 2600

Patent

active

055053653

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a method of accurately joining together two sheet sections along edges of said sheets having complementary shapes, and wherein the edge of at least one sheet section is formed by means of a numerically controlled machine with the sheet section fixed in a fixture by moving a cutting member relative to the sheet section according to a predetermined path, whereafter complementary edges of said two sheet sections are made to abut each other and the two sheet sections are welded together in a numerically controlled machine, said one sheet section being fixedly retained in said fixture and the knowlegde of the path used during cutting is used to determine the path of the welding means at the welding of the sheet sections.


BACKGROUND ART

In the fabrication of motor vehicles a method of the above type is known, whereby a trimming of the edge of a first sheet section is carried out in a numerically controlled laser cutting/welding machine, said first sheet section being fixedly retained in a fixture, whereafter a second sheet section, which is also fixed in the said fixture, is cut along an edge and the two edges are brought into abutment for a subsequent welding together of the sheet sections. The fixture used at said method is very strong and comparatively complicated construction.
German patent No. 1.119.057 discloses joining of two metal strips by forming a dovetailed protrusion in the first strip and forming a complementary tab in the second strip, which are subsequently brought into engagement with each other. The two sections are then connected by means of welding, for instance by resistance spot welding. The object is to hold the ends of the two strips together to form a coherent strip at a subsequent processing thereof.
Finally, from U.S. Pat. No. 3,091,844 it is known to provide the ends of strips of metal with complementary dovetailed protrusions and tabs for keeping the strips together during a subsequent compression of the joint and in a subsequent processing in a roller. Thus, no accurate joining of sheet parts is disclosed.


DISCLOSURE OF INVENTION

The object of the invention is to provide a method of the type stated in the introduction enabling an accurate weld joint of sheet sections by means of more simple fixtures than hitherto.
The method according to the invention is characterised in that the complementary edges are arranged in at least one projecting area on one sheet section and in a complementary area on the other sheet section, and the two complementary areas have interlocking shapes for preventing mutual displacement of the sheet sections at least in directions parallel to the surfaces thereof in the joint area. Due to the accurate geometrical interlocking, the stress produced by the heat during welding are absorbed by the inter-gripping areas of the sheet sections. As the sheet sections thus merely are to be controlled transversely to their surface, much simpler and thinner fixtures may be used than hitherto. At the same time, the accurate geometrical interlocking ensures that a minimal and accurate joint gap is maintained between the sections. As a result, very smooth welds are obtained without the use of filler materials. Consequently, most advantageously only minimal or no further machining of weld seam is necessary. In order to obtain a weld seam requiring very little or no further machining, the sheet sections have to be cut out with such an accuracy that the width of the gap between the complementary edges does not exceed 0.2 mm and preferably are less than 0.1 mm. To obtain such tolerances it is advantageous to carry out machining in a combined laser cutting and welding machine. It is, however, evident that also other cutting and welding methods having the required accuracy may be used, such as plasma cutting and water jet cutting. Beside laser welding other welding methods may be used, such as electron beam welding and plasma welding.
According to the invention the edge faces or cut faces of the edges may be arranged on mutually compl

REFERENCES:
patent: 1773068 (1930-08-01), Vienneau
patent: 1863873 (1932-06-01), Quarnstrom
patent: 4215299 (1980-07-01), Edwin et al.
patent: 4741471 (1988-05-01), Sullivan
patent: 5190204 (1993-03-01), Jack et al.

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