Device for producing square beams from tree trunks

Abstract
To produce square beams from tree trunks (13), a device is proposed in which a tree trunk (13) is first positioned by a centering device (4) such that the lengthwise axis (14) of the tree trunk (13) assumes essentially always the same stipulated position. The tree trunk (13) is then grasped by holders (11, 12) of a carriage (8) concentrically to the lengthwise axis (14), whereupon the centering device (4) is opened. Then the tree trunk (13) is guided through a band saw (5) and trimmed on the opposite sides, whereupon it is turned by 90° and the two other sides of the tree trunk (13) are trimmed.
Description




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.











BRIEF DESCRIPTION OF THE DRAWINGS




In the following, embodiments of the invention are described with reference to the drawings.





FIG. 1

shows a first embodiment of the invention in a side view,





FIG. 2

shows a part of the centering device,





FIG. 3

shows a section through the device from

FIG. 1

in the area of the tools,





FIG. 4

shows a detail of a holding device for the tree trunk,





FIG. 5

shows a second embodiment of the device as claimed in the invention in a side view,





FIG. 6

shows a detail of the device from

FIG. 5

in the area of the centering device and





FIG. 7

shows schematically another embodiment of the invention with slanted frame of the device for the holding device and the centering device.











DESCIPTION OF THE PREFERRED EMBODIMENTS





FIGS. 1 and 3

show a first embodiment of the device as claimed in the invention which has a base frame


1


and a guide frame


2


, the guide frame


2


being joined to the base frame


1


via supports


3


. On the base frame


1


the centering device


4


, a saw


5


and a chain conveyor


6


are supported.




The guide frame


2


has two guide rails


7


with a U-shaped cross sectional in which a holding device


8


can be adjusted via three pairs of rollers


9


by a drive (not shown), for example a tackle line. The holding device


8


which is made as a carriage in this embodiment has a frame


10


on which the rollers


9


are supported. From this frame


10


holders


11


and


12


extend downward and grasp a tree trunk


13


on its end faces


15




a


,


15




b


after it has been positioned by the centering device


4


such that its lengthwise axis


14


has essentially assumed a stipulated position.




The centering device


4


consists of two parts


4




a


,


4




b


which are made identical and which grasp the tree trunk


13


in the area of its ends


16


and


17


. The parts


4




a


and


4




b


of the centering device


4


are made as shown in FIG.


2


and have two legs


18


which are arranged in a mirror image and are supported to be able to swivel on the base frame


1


around an axle


19


. The legs


18


on their ends opposite the axle


19


have a fork shape which widens in the manner of a V, the V-shaped recesses


20


facing one another or widening in the direction to one another. The V-shaped recesses


20


are bounded by bottom support surfaces


21


and top support surfaces


22


, the bottom support surfaces


21


being longer than the top support surfaces


22


.




The legs


18


are activated by means of a hydraulic cylinder


23


which on the cylinder side is supported coaxially to the swivel axis


19


of the legs


18


. The piston rod


24


is hinged to the legs


18


via two levers


25


. By extending the piston rod


24


the legs


18


are moved towards one another, and away from one another by retracting the piston rod


24


.




If a tree trunk


13


is supplied using a transverse conveyor means which is not shown, for example a chain conveyor, the legs


18


of the centering device are moved away from one another by retracting the piston rod


24


to such an extent that the tree trunk


13


can drop into the V-shaped recesses


20


in the centering device


4


. This is possible because the top support surfaces


22


are shorter than the bottom support surfaces


21


onto which the tree trunk


13


drops. Then the piston rod


24


on the cylinder


23


is extended, by which the legs


18


are moved towards one another and the tree trunk


13


is fixed in the V-shaped recesses in the manner of tongs. Regardless of the diameter of the tree trunk


13


in the area of the pair of legs


4




a


and


4




b


of the centering device


4


, the lengthwise axis


14


of the tree trunk is essentially always fixed in exactly the same location both in the horizonal and vertical direction. Small deviations from the stipulated position can occur in any case by the deviations of the cross section of the trunk from the ideal round cross section.




So that the location of the lengthwise axis


14


of the tree trunk


13


is also fixed in the horizontal direction, the centering device


4


has means which are not shown in the drawings for holding the device exactly over the swivel axis


19


.




Since the tree trunk


13


has been fixed as centered by the centering device


4


, it is grasped on its end faces


15




a


and


15




b


by the holding devices


11


and


12


. The holding device


12


has a hydraulic cylinder


26


with a piston rod


27


which has centrally on its free end a mandrel


28


and a plate


29


which limits the depth of penetration of the mandrel


28


. The horizontal and vertical location of the mandrel


28


relative to the centering device


4


is aligned such that it penetrates exactly into the end face


15




a


of the tree trunk


13


in the area of the lengthwise axis


14


.




To be able to match the device as claimed in the invention to different tree trunk lengths (generally 4, 5, or 6 m), both the holder


12


and also the part


4




a


of the centering device


4


can be adjusted incrementally or continuously in the length-wise direction. For this reason the stroke of the hydraulic cylinder


26


need also be only relatively small, for example


15


cm, in order to press the tree trunk


13


securely against the other holding device


11


.




The second holding device


11


has a pivotally mounted disk


30


which has several mandrels


31


distributed over the periphery and which are pressed into the end face


15




b


of the tree trunk


13


. The piston rod


32


of a hydraulic cylinder


33


engages the disk


30


eccentrically and is supported on the cylinder side on the holding device


11


. The axis of rotation of the disk


30


is flush with the lengthwise axis


14


of the tree trunk


13


. By actuating the hydraulic cylinder


33


the disk


30


can be turned with the tree trunk


13


by 90°.




After the tree trunk


13


has been inserted into the centering device


4


, the latter is preferably closed automatically by a sensor being activated which activates the hydraulic circuit of the closing cylinder


23


. The sensor can be a mechanical lever which is moved by the tree trunk


13


and thus opens a valve in the hydraulic circuit or, for example a photoelectric barrier which actuates a solenoid valve in the hydraulic circuit.




By clamping the tree trunk


13


the pressure in the hydraulic circuit of the centering device


4


rises and this pressure rise can be used to activate the hydraulic circuit of the hydraulic cylinder


26


of the holder


12


by means of a pressure-dependent valve in order to clamp the tree trunk


13


between the mandrel


28


and the disk


30


in the axial direction. The associated pressure rise in the hydraulic circuit of the hydraulic cylinder


26


can in turn be used to open the hydraulic circuit of the hydraulic cylinder


23


of the centering device


4


. For example, a three-way valve is activated which bypasses the reversal in the supply of the hydraulic cylinder


23


with a feed line to the hydraulic circuit of the cylinder


26


. Movement of the carriage


8


with the holders


11


,


12


is not hindered by the opened pair of legs


4




a


and


4




b


. With the same means and at the same time the advance of the carriage


8


is turned on and the carriage is driven for example by a tackle line or a rack gear drive. The tree trunk


13


then passes through two band saws


34


of the saw


5


, which are shown schematically in FIG.


3


. The band saws


34


can be moved synchronously towards or away from one another on a guide


35


, among others to be able to match the cut width to the diameter of the tree trunk


13


.




During passage of the tree trunk


13


through the band saws


34


the tree trunk


13


is trimmed on two opposite sides. On the end of the conveyor path of the tree trunk


13


, i.e. in

FIG. 1

fully to the right, there is a starting switch which is not shown and which causes return of the carriage


8


. During return, the band saws


34


are moved apart in order to prevent damage to them. Then the tree trunk


13


is turned by 90° by activating the hydraulic cylinder


33


and the tree trunk


13


is trimmed in the second passage through the hand saws


34


on the third and fourth side.




After the second passage, when therefore all fours sides are worked, this is recognized by a photoelectric barrier and it switches the hydraulic circuit of the cylinder


26


via a relay and a solenoid valve to “open”, by which the piston rod


27


of the holder


12


is retracted and the beam falls onto the underlying chain block


6


and is discharged laterally.




Alternatively, when the band saws


34


are provided with two-sided teeth, the tree trunk


13


can be turned directly after the first pass through the band saws


34


by 90° and upon return are worked by the band saws


34


on the third and fourth side. It goes without saying that the chain block


6


is eliminated in this case and instead a removal device must be provided for the square beam in the area of the centering device


4


.




The band saws


34


are adjusted as already mentioned by means of motor actuators which are not shown and which are controlled by a computer. For example, on the pair of legs


4




b


of the centering device


4


, i.e. the pair which is adjacent to the saw


5


, there is a rotary pulse generator which acquires the swivel angle of a leg


18


which corresponds to the diameter of the clamped tree trunk


13


and routes the adjustment values for the saws to a computer which is provided with an optimization program with consideration of the choice between a pure square beam or square beams with rough edges. The individual sequences in the course of centering and working a tree trunk


13


can also be controlled in any other way, for example with photoelectric barriers, feelers, or the like.





FIGS. 5 and 6

show a second embodiment of the invention in which a holding device or a carriage


36


is guided for the tree trunk


13


underneath the latter in the guide rails


37


which are permanently connected to the base frame


1


. Aside from this, the embodiment of the holders


11


,


12


corresponds to that of the holders


11


,


12


as were described in conjunction with the embodiment of

FIGS. 1

to


4


.




Furthermore, the embodiment of

FIGS. 5

to


7


differs from the embodiment of

FIGS. 1

to


4


by the legs


41


of the centering device


4


being opened and closed not by swivelling, therefore rotationally, but by linear movements, therefore translationally.




To do this the legs


41


are supported to be able to move on the guide rails


38


and are driven in opposite directions by the threaded spindles


39


by means of motor actuators


40


. Aside from this, the legs


41


however correspond to the legs


18


from

FIG. 2

, i.e. that they have V-shaped recesses


20


with bottom support surfaces


21


which are longer than the top support surfaces


22


.




Also in the embodiment which is shown in

FIGS. 5 and 6

the tree trunk


13


can be worked by passing twice through the saw


5


in the same direction or by the fact that two sides of the tree trunk


13


are worked upon passage in one direction and the two other sides are worked when conveyed back.




As can be seen in

FIGS. 5 and 6

, on the carriage


36


between the holders


11


and


12


there is a slide sheet


42


via which the separated sections and the finished square beam slide onto an outgoing chain conveyor.




In order to facilitate the removal of the cut parts and the square beam, the base frame


1


as is shown in

FIG. 7

can be tilted at an angle between 30 and 45° to the horizontal, so that a removal means


43


can be guided more easily to under the tree trunk


13


.




In summary, one preferred embodiment of the device as claimed in the invention can be described as follows.




To produce square beams from tree trunks


13


, a device is proposed in which a tree trunk


13


is first positioned by means of a centering device


4


such that the length-wise axis


14


of the tree trunk


13


assumes essentially always the same stipulated position. The tree trunk


13


is then grasped by holders


11


,


12


of a carriage


8


concentrically to the lengthwise axis


14


, whereupon the centering device


4


is opened. Then the tree trunk


13


is guided through a band saw


5


and trimmed on the opposite sides, whereupon it is turned by 90° and the two other sides of the tree trunk


13


are trimmed.



Claims
  • 1. Device for producing square beams from tree trunks, which comprises:two tools which trim the trunks on two opposite sides; a holding device structured and arranged to grasp a tree trunk having a lengthwise axis on an end face while said trunk is being worked; said holding device and said tools being movable relative to one another during working; means for positioning the tree trunk; said means being opened during working before the trunk is grasped by the holding device; and said means for positioning comprising a centering device which positions the tree trunk automatically in essentially always the same stipulated position of the lengthwise axis of the tree trunk parallel to the direction of movement.
  • 2. The device according to claim 1, wherein the centering device has two pairs of legs which have V-shaped recesses which face one another.
  • 3. The device according to claim 2, wherein the legs have a fork shape which widens in a V-shape.
  • 4. The device according to claim 2, wherein the legs laterally engage the tree trunk, and wherein bottom support surfaces of the V-shaped recesses are longer than top support surfaces.
  • 5. The device according to claim 2, wherein the legs are adapted to move translationally towards one another.
  • 6. The device according to claim 5, wherein the legs are supported for movement on guide rails and are driven in opposite directions by a threaded spindle by motor actuators.
  • 7. The device according to claim 1, wherein the legs are adapted to move rotationally towards on another.
  • 8. The device according to claim 7, wherein the legs are adapted to swivel around a same axle.
  • 9. The device according to claim 7, further comprising a hydraulic cylinder assigned to each pair of legs for driving the legs, said hydraulic cylinder being hinged to a leg via one lever at a time.
  • 10. The device according to claim 1, wherein the holding device runs on guide rails located under the tree trunk and provided on a frame, and said centering device being tilted at an angle relative to the horizontal.
  • 11. The device according to claim 10, wherein the angle is between 30 and 45°.
  • 12. The device according to claim 3, wherein the legs laterally engage the tree trunk, and wherein bottom support surfaces of the V-shaped recesses are longer than top support surfaces.
Priority Claims (1)
Number Date Country Kind
612/99 Apr 1999 AT
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Number Name Date Kind
4294149 Olsson Oct 1981
4697487 Cameron Oct 1987
4846237 Wolf Jul 1989
5035166 Carlson et al. Jul 1991
5109899 Hendrickson May 1992
5135037 Wijesinghe Aug 1992
5228490 Wolf Jul 1993
5253685 Wolf Oct 1993
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