Device for producing square beams from tree trunks

Details Device for producing square beams from tree trunks Device for producing square beams from tree trunks

2000-04-06

2001-12-04

Bray, W. Donald (Department: 3725)

Woodworking

Process

Mechanical cutting or shaping

C083S365000, C083S367000, C083S439000, C083S412000, C083S708000, C083S801000, C144S357000, C144S242100

Reexamination Certificate

active

06325119

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a device for producing square beams from tree trunks with two tools which trim the trunks on two opposite sides, with a holding device in which a tree trunk is grasped on the end face while it is being worked, and the holding device and the tools can be moved relative to one another during working, and with a means for positioning the tree trunk which is opened during working before the trunk is grasped by the holding device.
BACKGROUND OF THE INVENTION
When producing square beams with or without rough edges, it is important for the side surfaces of the square beam to be produced parallel to the lengthwise or middle axis of the tree trunk, since this is important both for the structure and strength of the square beam and also with respect to the cut rough edges when they are processed further for example into small parts (laths). It is therefore important for the tree trunks to be positioned in the same location of the lengthwise axis as much as possible parallel to the direction of motion in which a holding device for the tree trunk and the tools are moved relative to one another in order to minimize the adjustment effort for the holding device and the tools. This however results in the holding device grasping the tree trunks with always the same location of the lengthwise axis.
AT 397 058 B discloses a device of the initially mentioned type which has a means for positioning the tree trunk which is opened during working and the tree trunk is held on the end face during working. If with the known device square beams are to be produced, the tree trunk must be turned 90° after working the two first sides which are opposite one another. Here it is disadvantageous that the tree trunk was originally not grasped in the middle, since based on its conical shape it was positioned with a lengthwise axis which is oblique in the vertical direction. The tree trunk must therefore be positioned again after turning and must be grasped by the holding device so that the other two sides of the tree trunk can also be worked parallel to the lengthwise axis.
EP 222 728 A and EP 217 784 A disclose devices for producing square beams which grasp the tree trunk such that the location of its lengthwise axis viewed in the horizonal direction is always aligned the same. The height of the lengthwise axis of the individual tree trunks or their alignment in the vertical plane however, depending on the diameter of the tree trunk, is not always fixed exactly the same. Furthermore the holding devices described there on the same page are the means for positioning the tree trunks, i.e. there are no additional system parts which position the tree trunk before grasping by the holding device in which it is held during working.
SUMMARY OF THE INVENTION
The object of the invention is to devise a device of the initially mentioned type in which the lengthwise axis of the tree trunks always assumes the same position parallel to the direction of movement in the holding device.
This object is achieved with a device with the features of claim
1
.
With the invention a centering device is proposed which automatically positions the lengthwise axis of the tree trunks in always the same position, i.e. without intervention from the outside via a control means. In this position the tree trunks are grasped by the holding device and the square beam can be easily produced symmetrically to the lengthwise axis of the tree trunk.
Since due to the always same position of the lengthwise axis of the tree trunks they can be grasped exactly centrally by the holders, the tree trunks can be worked without major technical effort first on two opposite sides and then turned by 90°, whereupon they can be worked on the two remaining sides.
In AT 397 224 B a holding device is described which is able to position a tree trunk with a lengthwise axis which is flush to the direction of working, but there it is neither a holding device in which a tree trunk can be swivelled 90°, nor is functional separation of the holding device and centering device shown.
In one preferred embodiment of the device it is characterized in that the centering device has two pairs of legs which have V-shaped recesses which face one another. Here it can either be provided that the legs can be moved translationally towards one another or that the legs can be moved rotationally towards one another.
Here one pair of legs at a time is assigned to one end of the tree trunk, and the tree trunk with its ends which are held in the V-shaped depressions, when the centering device is closed., i.e. when the legs are moved towards one another, is fixed automatically in always the same location of its lengthwise axis.
It goes without saying that by virtue of the circumstance that tree trunks of course are never perfectly round, the location of the lengthwise axis within the framework of these natural fluctuations can deviate from the ideal position which is stipulated purely geometrically by the V-shaped recesses. Other advantageous embodiments of the invention are the subject matter of the other dependent claims.


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