The invention is directed to a hold-down device for plate shears which can be pressed on a plate to be cut by a mechanically controlled, invariable displacement in accordance with the preamble of patent claim 1 and the preamble of patent claim 2.
The object of the hold-down device is to press on the lower shear table while the plate is being cut. It must be free of the plate while the plate is being transported. In particular, the following cycles are run through: forward transport, safety angle, cut, safety angle, forward transport.
In practice, the hold-down device must usually cover the entire range of thickness of the plate from about 5 mm to about 50 mm. This requires a large displacement of the hold-down device. The design of the hold-down device is oriented to the thinnest plate in order to achieve the necessary contact pressing force. Its constant displacement is compensated for in spring sets. Consequently, the contact pressing force increases as the thickness of the plate increases. But thicker plates require less contact pressing force or none at all because of their greater inherent weight. The running of the hold-down device is continuous owing to its mechanical coupling and its displacement cannot be varied.
DE 35 46 859 C2 discloses a hold-down device for plate shears which is movable with a constant displacement by means of articulated levers.
It is the object of the invention to provide a hold-down device whose contact pressing force is variable and which therefore enables a longer edge life, shorter displacements and, in turn, shorter switching times.
This object is met according to the invention by a hold-down device according to the preamble of patent claim 1 in that the initial position of the hold-down device before the start of the displacement is adjustable.
Further, the above-stated object is met by a hold-down device according to the preamble of patent claim 2, wherein a threaded rod with right-handed and left-handed thread is provided between the roller lever and the actuating levers so that the distance between the roller lever and the actuating levers can be varied by means of rotation.
The adjustable hold-down device according to the invention is positioned at a constant distance above the upper edge of the plate and therefore has the same spring path, i.e., the same contact pressing force, for every plate thickness. The displacement can accordingly be reduced and the switching time can therefore be shortened. The hold-down device can be set down on the plate sooner and can exert its force for a longer time. The hold-down device is on the plate at the start of the cut and is only displaced at the end of the cut. By further displacement over the end positions of the hold-down device, this hold-down device can also be switched off, for which purpose the roller lever can be raised from the cam disk.
According to an embodiment, the threaded rod can be rotated by means of a drive unit.
According to another embodiment, springs can be provided between the parts of the threaded rod to hold the thread without play in order to prevent damage to the thread and in particular to prevent movements due to play during a change in force.
The invention will be described in the following with reference to an embodiment example which is shown schematically in the drawings.
An embodiment example of a hold-down device is shown in vertical section in
Number | Date | Country | Kind |
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10 2006 047 078.8 | Sep 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DE2007/001472 | 8/16/2007 | WO | 00 | 3/27/2009 |