Folding device

Metal deforming – By use of non-deforming work-gripping clamp and relatively... – With interrelated clamp closer and tool mover

Patent

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Details

72451, 2924358, B21D 3902

Patent

active

057351627

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/SE95/00565, filed May 18, 1995.


BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a clinching press, comprising a press tool and a prebending unit for producing a reciprocal movement of a tool holder pivotally joined to a foundation, said tool holder being supported in such a manner that it is displaceable by means of an operating device coupled to a drive means, along a predetermined path of movement between a starting position, a work position and an end position.
2. Description of the Related Art
Bending units of the above mentioned type are well known in a number of different configurations and they are used to prebend a margin of one sheet metal panel around the margin of another sheet metal panel, whereupon the final clinching is carried out separately to provide a seam or welt joining the two panels to each other. Operations of this type are common in the auto industry, for example when manufacturing doors, engine hoods and similar body parts. Conventionally, a bending unit of this type is actuated by an hydraulically operated cam disc engaging a cam roller on a pivotally mounted tool holder, the extension and retraction of the piston rod of the hydraulic cylinder acting on the tool holder via the cam disc arrangement, to impart the desired movement to the tool and produce the required force to enable the tool to carry out the desired bending operation.
By virtue of the cam disc arrangement, extension of the piston rod of the cylinder to its completely extended position and retraction of the same does not automatically return the tool holder. Rather, a spring intended for this purpose returns the tool holder to its starting position spaced from the panels.
One disadvantage of a prebending unit operated in this manner is that the cam disc arrangement generates horizontal forces, which, via the piston rod, are transmitted to the hydraulic cylinder and can disrupt its operation, and therefore special guide means are required to relieve the hydraulic cylinder.
An additional disadvantage of a more serious type is that the return spring of the tool holder can break and the tool will then remain on the workpiece during the subsequent final clinching step, which may result in damage to both the tools and the workpiece bed. Such damage can be costly to repair and disrupts production.


SUMMARY OF THE INVENTION

The purpose of the present invention is therefore to provide a device in a prebending unit of the type described by way of introduction which guarantees the required return of the tool holder and only generates vertical forces on the drive system, as well as being of simple construction and reliable function. This is achieved according to the invention by a device of the type by way of introduction which is characterized in that the operating device has an operating means which is coupled to the movement of the press tool and a knee-joint mechanism, which, in the form of two articulated lengths, is joined, on the one hand, to a pivot point on the tool holder, and, on the other hand, to a stationary pivot point in the foundation, in that the knee-joint mechanism, under the influence of the operating means, can be moved in a continuous movement from a bent-out position when the tool holder is in its starting position, to a completely extended position when the tool holder is in its work position, in that the knee-joint mechanism can be bent-out once again in the opposite direction to assume a bent-out position when the tool holder is in its end position, and in that the knee-joint mechanism is coupled to a return means supported in the foundation, for returning the tool holder to its starting position.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail below with reference to the accompanying schematic drawings, which show one embodiment of the invention and in which
FIG. 1 is an overall sideview of a machine in which two prebending units according to the invention are used, each unit being shown in its sta

REFERENCES:
patent: 468462 (1892-02-01), Kinnear
patent: 2310556 (1943-02-01), Strong
patent: 3058512 (1962-10-01), Chebuhar
patent: 4347754 (1982-09-01), Wehler

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