CROSS REFERENCE TO RELATED APPLICATIONS
This application is a United States National Phase application of International Application PCT/EP2008/002809 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2007 025 854.4 filed Jun. 1, 2007, the entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a device for connecting of metal sheets at the edges, particularly body sheet metal in automobiles.
BACKGROUND OF THE INVENTION
A folding method on the one hand and a folding machine on the other hand have become known through U.S. Pat. No. 5,611,133 A as well as U.S. Pat. No. 5,752,304 A. An exterior and an interior preformed metal panel are positioned between lower and upper die halves, wherein the die halves are subsequently jointed and the preformed panels are restrained within the die. A pre-folding of a corner area of the exterior metal panel is performed subsequently. This process is followed by a finish folding process of the pre-folded area. Provided in a non-folded area is at least one welding facility that joins both metal sheets by spot welding.
WO 99/03634 discloses a method and a device for welded joining of metal parts overlapping each other. Proposed therein is a resistance welding process for welding connection of metal sheets, with one end area of a metal sheet being folded around the other metal sheet. Accommodated in the area of the folding machine is at least one welding head comprised of an electrode with welding tip. In the folded area, one of the metal sheets has a kind of a projection. The connection is now achieved in that the welding head exerts a force on the fold so that the fold is fixed between the electrode and a backing plate. Subsequently, a pulsating welding current is generated that joins the two metal sheets with each other.
A method and a device for establishing a projection welding connection between metal sheet parts has become known through EP 1 038 627 BI. A projection having a triangular cross-section is preformed in one of the metal sheets to be welded. The metal sheet plates are laid one above the other so as to overlap each other. A fold is generated in the area of the projection. The metal sheet plates are welded together at the point of the projection by applying an electric current pulse of short duration, with the electric current being supplied from the side of the pressure unit to the metal sheet plate lying on top and being discharged from the metal sheet plate lying at bottom.
DE 199 27 208 B4 discloses a method and a device for connecting metal sheets at the edges, more particularly of car body metal sheets in automobile manufacturing, with the edge of an exterior metal sheet plate being folded beyond the edge of an interior metal sheet plate, and wherein the edges are pressed together and wherein the edge of at least one of the metal sheet plates is provided with embossed projections prior to folding.
While pressing the metal sheet plates together, the projections are connected by projection welding to the relevant other plate, utilizing an electrode arranged at the folding jaw. This actually compact structural form bears a disadvantage in that handling of metal sheet plates within the device is complicated.
SUMMARY OF THE INVENTION
Now, therefore, proceeding from DE 199 27 208 B4, it is the object of the present invention to provide an alternative structural form of a folding and joining machine which allows for a simplified connection of metal sheet plates in the fold area whilst the handling of metal sheet plates within the device is optimal.
This task is solved by a device for connecting metal sheets at the edges, more particularly of car body metal sheets in automobiles, said device being comprised at least of a folding bed to receive at least two metal sheets, and furthermore comprised of folding jaws functionally connected to the pertinent folding jaw supports as well as at least comprising a thermal joining tool and at least a mass electrode, with at least the joining tool being not attached to the folding jaw, and said device comprising a lever oriented away from the folding bed and serving as linear feed device, and wherein said lever has a center of rotation outside the folding bed about which the joining tool can swivel in the manner of a knee lever into an operating and/or non-operating position.
As compared with prior art in technology, it yields the following advantages and benefits:
- metal sheets to be folded can be handled and folded within the device without any problems because there are no interfering joining elements;
- the thermal connection of metal sheets in the area of the fold is performed whilst the tool components are closed, i.e. in a restrained status of metal sheets;
- direct integration of a thermal joining unit in a folding device;
- indirect joining (welding) of a folding flange by way of a unilateral set-up of welding electrodes;
- introducing the welding force by applying a mechanical knee lever principle;
- generating a post-setting movement of the welding electrodes by way of mechanical springs;
- instead of several joining tools configured as welding tools positioned in the area of tool components, it is also feasible to use soldering tools.
The inventive object is illustrated by way of an embodiment shown in the drawing. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a top view onto a partial area of a folding machine;
FIG. 2 is a partial sectional view of the joining tool;
FIG. 3 is a partial sectional view of the joining tool; and
FIG. 4 is a partial sectional view of the joining tool;
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings in particular, FIG. 1 in a top view shows a partial area of a folding device 1. One can see a folding bed 2, folding jaws 3, folding jaw supports 4 as well as joining tool 5 which in this case is configured as a welding tool. The joining tools can equally be configured as a soldering tool, too. A welding electrode 7 is provided at the free end of a lever 6 (welding arm), see FIG. 4. Extending next to lever 6 is a lever element 8 (mass arm), at the free end of which a mass electrode 9, 9′ is arranged. The lever 6 and the lever element 8, 8′ are arranged on a common axis 10.
FIGS. 2 to 4 show various partial views and/or sections of the joining tools. One can see the following components: folding bed 2, folding jaw 3, folding jaw support 4, lever 6, lever element 8, welding electrode 7, mass electrode 9 as well as the common axis 10. Lever 6 and lever element 8 can tilt in the manner of a knee lever about the swiveling axis 10′ of axis 10.
FIG. 2 shows the non-operating position of joining tool 5. In this example, a forward stroke cylinder 11 functionally connected to a bottom wedge 13 having an inclined plane 12 is utilized for simultaneous swiveling of lever 6 and lever element 8 about swiveling axis 10′. A vertically arranged guide bolt 14 with an upper cap 15 co-acts with a top wedge 17 comprised of a second inclined plane 16. Helical springs 18 (merely shown indicatively) are provided in the area of guide bolt 14. Furthermore, a backward stroke cylinder 19, the piston rod 20 of which carries a cover 21 at its free end, is positioned above lever 6.
FIG. 3 shows the set-up of welding electrode 7 onto fold 22. One can also see the mass electrode 9 which rests on an interior metal sheet 23. Lever 6 including lever element 8 has now been swiveled about swiveling axis 10′ into its operating position, with the greatest force being applied here onto fold 22.
FIG. 4 shows the process of welding in which welding electrode 7 presses fold 22 together and in which this area is thermally joined. In this state, lever 6 has reached its maximum swiveling angle. Two metal sheets 23, 23′ which are connected to each other in the area of fold 22 rest on the folding bed 2 within the device 1. Lever 6 is guided in the area of a recess 23 provided in the folding jaw 3 in the direction of the fold 22. Beneath lever 6, respectively beneath lever element 8, there is a hinged lever 25 provided with axis 10.
By integrating several welding units 5 into the folding device 1, the process sequence is as follows:
Setting out from a pre-folded component flange at the exterior metal sheet 23′, it is finish folded at the folding jaw 3 by an upward movement of folding bed 2. Fold 22 is laid at the interior metal sheet 23, except for the welding spot 24 recessed in the folding jaw 3, with it being possible for the welding electrode 7 to immerse contact-free into the folding jaw 3.
Subsequently, the welding electrodes 7 are now set onto fold 22. This is accomplished by activating the two cylinders 11, 19 of the joining tool 5. While the backward stroke cylinder 19 moves upwardly and releases the movement of the welding arms 6, the piston rod of the forward stroke cylinder 11 takes a move to the left. By this movement, the bottom edge 13 is pressed against the top wedge 17. The force diverted via the wedge translation presses the guide bolt 14 and the cap 15 against the arms 6,8, 8′ carrying electric current. Fixed and arranged in a pivoting support in the hinged lever 25, the welding electrodes 7 are set via these arms onto the fold 22 of the exterior metal sheet 23′. By the existing force of forward stroke cylinder 11, a pre-tensioning force is built-up in each helical spring (18). This force is necessary to press the fold 22 at the exterior metal sheet onto an embossed projection in the interior metal sheet 23 and to establish an electrical contact between both metal sheets 23, 23′ which is required for welding. By applying an electric current pulse at all arms 6, 8, 8′ carrying electric current, both parts are welded with each other by means of ohmic transition resistance between fold 22 of exterior metal sheet 23′ and embossed projection in the interior metal sheet 23. The process force required for resistance welding is assured by a post-setting of all welding unit components carrying electric current, i.e. welding electrodes 7, 9, 9′ and welding arms 6, 8, 8′. All components carrying electric current are electrically isolated versus the bearing rack. Upon collapsing of the embossed projection, fold 22 of exterior metal sheet 23′ rests on interior metal sheet 23, the supply of electric current is interrupted and welding has been completed. Subsequently, by way of moving forward stroke cylinder 11 backwards, the entire movement chain up to the welding electrodes 7, 9 is made powerless and the bottom wedge 13 is released. Next the backward stroke cylinder 19 moves downwards, thus lifting the welding electrodes 7, 9 via welding arms 6,8 and hinged lever 25 from metal sheets 23, 23′ and arresting them. Subsequently, the folding bed 2 again moves downwards and the folding process is completed.
While a specific embodiments of the invention has been described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.