The invention relates to a driving device for a bending unit for bending-in a projecting edge flange against a surface of a workpiece, said bending unit comprising a stand, which carries both the driving device and a supporting surface for the workpiece as well as a linkage system, which in turn supports a bending tool in such a manner that the tool is movable relative to the workpiece placed on the supporting surface along a predetermined path of movement .

Bending units of the above mentioned type are well known in a number of different designs, and they are used to bend in, for example, an edge flange on a sheet metal piece around the edge of another sheet metal piece to create a type of folded seam for joining the two metal pieces to each other. Opera- tions of this type are common, for example in the automobile industry to manufacture doors, engine hoods and similar body parts. A common type of driving device for such a bending unit comprises a hydraulic cylinder, which is coupled between the frame and the link system. Extending or retracting the piston rod of the hydraulic cylinder acts on the linkage system to give the tool the desired path of movement and achieve the required force so that the tool will be able to carry out the desired bending operation. In addition to the driving device itself, a hydraulic unit is required to pro- vide the required hydraulic pressure as well as hydraulic lines and control equipment.

The purpose of the invention is to achieve a new type of driving device for a bending unit of the type described by way of introduction, said driving device being of simple construction and having reliable operation as well as re¬ quiring very little space. This is achieved according to the invention by virtue of the fact that a motor is mounted on the stand and is coupled to a crankshaft mounted in the stand, said crankshaft carrying on a crank pin one end of a connecting rod, the other end of which is articulated to a

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The bending device described above and shown schematically in Fig. 1 is of a type which is known per se and is only intend¬ ed to provide an example of a type of bending unit where the driving unit according to the invention can be used. A number 5 of other types of bending devices are known in which the driving device according to the invention can be used, but these are not shown or described in more detail here.

The driving device according to the invention is only shown 10 schematically in Fig. 1, but it is evident therefrom that it comprises an electric motor 14, which is mounted via a trans¬ mission 15 in the stand 1.

It can be seen in Fig. 2 that the transmission 15 is fixed 15 with the aid of a flange 16 to a bearing mounting 17 which is mounted in the frame 1. A bearing 18, which in the embodiment shown is a roller bearing, is mounted in the bearing mounting 17. Spaced from the bearing mounting 17 and coaxial therewith is a second bearing mounting 19, which is also mounted in the 20 frame 1 and carries a bearing 20, which in the embodiment shown is a roller bearing.

The bearings 18 and 20 are arranged coaxial with each other and with an output shaft end 21 from the transmission 15. The 25 shaft end 21 extends into a socket 22 in one end of a crank¬ shaft 23 and is joined to the crankshaft 23 by means of a key 24.

The crankshaft 23 is mounted in the bearings 18 and 20 and is 30 rotatable with the aid of the electric motor 14, the trans¬ mission 15, the shaft end 21 and the key 24.

The crankshaft 23 is made with a crank pin 25, on which a ¹ connecting rod 26 is rotatably mounted at one end. The other 35 end of the connecting rod 26 is connected to the pivot point ' 13 of the link 8 in the linkage system. The pivot point 13 is thus the axis of a pivot pin 27 extending between two paral¬ lel portions of the link 8.

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4 with sufficient force, the geometry of the drive device is such that when the tool 5 reaches its final position, with its edge flange 4 completely bent in, the connecting rod 26 has not yet reached its upper end position. Upon continued turning of the crankshaft 23 past the upper end position of the connecting rod 26, the force-limiting means 28 will therefore be employed. If the predetermined load is exceeded, the gas spring 29 will be pressed together by the rod 34 sliding in the opening 33 and compressing the gas spring 29. This prevents overloading and damage to the component parts of the driving device and the bending unit, at the same time as satisfactory bending-in of the edge flange 4 is assured.

By changing the pressure in the gas spring 29, it is possible to adjust the size of the force which the tool 5 exerts against the edge flange 4. In this manner it is possible to adapt the bending force to current conditions.

As can be seen in Figs. 2 and 3, the crankshaft 23 has at its end remote from the shaft end 21 a shaft end 42. With the aid of this shaft end 42, the crankshaft 23 can be coupled to a corresponding crankshaft in an adjacent drive unit, so that two or possibly more driving units can be driven with the same motor and gearbox. This can be an advantage if a number of bending units are to be arranged adjacent each other in confined spaces.

It should be noted that changes can be made within the scope of the invention. For example, the electric motor 14 can be replaced by any other type of motor. It is also conceivable that the electric motor or any other motor can be coupled directly to the crankshaft 23 without use of any gearbox.