Device for truing planks

An apparatus for truing twisted wooden boards by twisting them in an oppoe direction, comprises an upper set of parallel plates and a lower set of parallel plates. A channel is formed between opposing edges of the upper and lower plates. The upper plates are pivotable about an upper pivot axis, and the lower plates are pivotable about a lower axis. Those axes are oriented transversely relative to a longitudinal axis of the channel and are situated at an inlet end of the channel. A pivoting mechanism causes the plates to be displaced vertically relative to one another to twist the channel about its longitudinal axis.

BACKGROUND OF THE INVENTION 
The invention concerns a process for the rotary truing of boards and 
similar elongated wood products by means of a plurality of adjustably 
supported guide bodies, which together form a flat board guide channel 
extending along the longitudinal axis of the frame and having a twist 
around the longitudinal axis of the frame, said twist being variable by 
the adjustment of the guide bodies. 
Boards and similar plate like elongated wood products may be cut by 
chipless cutting methods from the sides of flattened logs or tree trunks. 
These boards or similar wood products have not only curvatures, but also 
twists, i.e. they are turned or twisted around their longitudinal axis. In 
numerous applications, this deformation prevents any automatic further 
processing of the boards. The intensity of the twist increases with the 
inclination at which the blades cutting the board are set against the 
longitudinal direction of the wood. 
By means of a known apparatus of the aforementioned type (for example, 
Gonner et al U.S. Pat. No. 4,977,940) the boards may be subjected to a 
rotary straightening process, so that they lose their twist due to the 
manufacturing process and become suitable for further processing. 
In the case of this known apparatus in a plurality of successive guide 
stands, rollers are provided as the board guide bodies. The guide stands 
are pivoted around a common axis, for example the longitudinal axis of the 
frame, in a manner such that together they form a board guide channel, the 
twist around the longitudinally axis whereof is chosen so that it 
straightens the existing twist of the boards. 
As the twist of the boards varies depending on the manufacturing 
conditions, the type of wood and its properties, the guide stands of the 
known apparatus are individually equipped with separate pivot drives to 
move them into the pivoting position required. The control of these 
individual pivot drives is relatively expensive. In addition, the 
necessary design effort is relatively high. 
In a known apparatus for example, Hobbs U.S. Pat. No. 2,399,348 for the 
bending of laminated work pieces to be glued together, a plurality of 
parallel bending stops may be moved against the work piece in order to 
press it against a group of stationary stops. However, the work piece is 
not twisted in the process, but bent. Furthermore, the work piece does not 
travel in a guide channel, but is inserted between the two groups of 
bending stops prior to their displacement. 
It is therefore the object of the present invention to develop an apparatus 
of the aforementioned generic type so that it is very sturdy while having 
a simple design configuration; said apparatus making possible the 
adjustment of the board guide channel. 
SUMMARY OF THE INVENTION 
This object is attained according to the invention by that the guide bodies 
are guide plates extending in the longitudinal direction of the frame and 
arranged in two sets of plates, which form with their plate edges facing 
each other the board guide channel, and that the guide plates of each set 
of plates may be pivoted around a common plate pivoting axle extending 
near the inlet of the board guide channel, transversely to the guide 
plates, separately by means of a pivot drive. 
The guide plates of each of the sets of plates may thus be adjusted in a 
fan like manner relative to each other, so that the board guide channel 
formed between the two sets of plates may alter its twist, beginning from 
the inlet which remains unchanged. The twist is altered by rotating the 
boards passing through the board guide channel in its longitudinal 
direction against the twist they had received in the course of their 
production, so that this original twist of the boards is lost and the 
boards are straightened. 
To alter the twist of the board guide channel it is sufficient to change 
the fan like spread of the guide plates of each set of plates by pivoting 
the individual guide plates differently. It is obvious that this pivoting 
adjustment of the individual guide plates is carried out so that the board 
guide channel formed between the set of plates approximately retains its 
width in all of its locations, so that the boards are able to pass through 
the board guide channel, while retaining adequate guidance to carry out 
the rotary straightening process. The design configuration of the 
apparatus is very simple, as only the guide plates are moving parts, aside 
from the pivoting drives. These guide plates may be in the form of highly 
stable parts, which by their flat abutment against each other in the set, 
guide and support each other, so that aside from the pivot bearings of a 
very simple configuration, no other guidance of the guide plates is 
required. This makes a compact layout of the rotary straightening 
apparatus possible, so that it may be located at a short distance after 
the processing station in which the boards are produced by a chipless 
method. 
Preferably, all of the guide plates of each of the set of plates are 
connected with a common pivot drive in a manner such that the individual 
guide plates may be pivoted differently and spread in the shape of a fan. 
This significantly reduces the design effort for the pivot drive. However, 
a separate pivot drive may also be provided for each of the guide plates. 
An especially simple and robust form of embodiment of the pivot drive is 
characterized in that the pivot drive comprises adjusting rods extending 
through bore holes transversely to the guide plates, said rods being 
capable of tilting around axles located parallel to the longitudinal axis 
of the frame. By means of a tilting motion of said adjusting rods all of 
the guide plates of the associated set of plates are pivoted together, but 
at different pivot angles.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
The apparatus shown in the drawing is used in the rotary straightening of 
boards and similar elongated, flat wood products, cut by chipless methods 
from the sides of a flattened log or tree trunk. These wood products, 
designated hereinafter in a simplified manner as "boards 1", enter from 
the inlet side located to the right in FIG. 1 in the direction of the 
arrow 2 and leave the apparatus at the outlet end (left in FIG. 1). 
The apparatus comprises a frame 3, in which a lower set of plates 4 and an 
upper set of plates 5 are located above each other. Each of the sets of 
plates 4, 5 consists of flat guide plates 6 standing on edge. 
The guide plates 6 extend in the longitudinal direction of the frame and 
form between opposing edges 7a board guide channel 8, which extends in the 
longitudinal direction of the frame and includes a twist around the 
longitudinal axis of the frame. This twist of the board guide channel 8 
opposes the natural twist of the boards around their longitudinal axis, 
generated in the course of the cutting process. Consequently, the boards 
are subjected during their passage through the board guide channel to a 
rotary truing process, which straightens them. 
The plate edges 7 bordering the board guide channel 8 are--viewed in planes 
normal to the frame axis 9 (see FIG. 2)--rounded, so that no sharp edges 
capable of damaging the boards 1, are projecting into the board guide 
channel 8. As seen particularly in FIGS. 1-3, even in the initial state 
shown, the plate edges 7 are more or less inclined relative to a 
horizontal plane so that the board guide channel 8 even in the initial 
state shown has a predetermined twist. In other words, the guide plates 6 
of each set of plates 4, 5 are spread in the area of their longitudinal 
edges 7 in a fan like fashion, so that the board guide channel 8 is 
thereby given its twist, wherein the term "twist" is intended to signify a 
helical variation of the board guide channel 8 at least approximately 
around the longitudinal axis 9 of the frame. The fan like spreading of the 
guide plates 6 is seen most clearly in FIG. 4. There, the two sets of 
plates 4, 5 are shown drawn apart upward and downward, so that the fan 
like spread becomes apparent. 
The guide plates 6 of each set of plates 4 and 5 may be pivoted separately 
around a common plate pivot axis 10, 11 extending transversely to the 
guide plates 6 near the inlet of the board guide channel 8. This makes it 
possible to vary the twist of the board guide channel 8. The magnitude of 
the twist is always chosen so that the twist present following the 
production of the boards 1 is completely eliminated and straight boards 
are obtained. The twist initially present depends on the manufacturing 
conditions and the properties of the wood, in particular its humidity and 
temperature. 
The guide plates 6 are adjusted by means of a pivot drive, wherein a 
separate pivot drive is provided for each of the two sets of plates, said 
pivot drive being designed so that different pivoting of the individual 
guide plates is possible. 
In the example of embodiment shown this pivot drive comprises for each set 
of plates 4, 5 an adjusting rod 12, 13 extending through bore holes 14 and 
14a transversely to the guide plates 6 of the sets 4, 5. A common variable 
motor 15 (FIG. 3) drives angular gears 16, 16' located on either side of 
the frame 3, with one threaded spindle 17, 17' extending upward from each 
of the angular drives 16, 16'. The two threaded spindles 17, 17' engage by 
means of an articulation 18, 18' the two ends of the of the lower 
adjusting rod 12 projecting laterally from the frame 3. Upon the actuation 
of the variable motor 15 the threaded spindles 17, 17' are driven in 
opposing directions so that one articulation 18' is moved upwards and the 
other articulation 18 downward. In the process the adjusting rod 12 
executes a tilting motion around a tilt axle 19 extending parallel to the 
longitudinal axis 9 of the frame. As seen in FIG. 1, the two adjusting 
rods 12, 13 are located near the outlet end of the board guide channel 8. 
Each of the articulations 18, 18' is connected by means of vertical, 
lateral connecting rods 20, 20' flexibly with an articulation 21, 21' 
located above it, and the two ends of the upper adjusting rod 13. 
Consequently, the upper adjusting rod 13 is also tilted in the 
aforedescribed adjusting motion around a tilt axle 22 extending parallel 
to the longitudinal axis 9 of the frame, while remaining parallel to the 
lower adjusting rod 12. 
This adjusting motion alters--as indicated in FIG. 3--the oblique setting 
of the board guide channel 8 at the outlet end. It is obvious that the 
process described in the example of embodiment using threaded spindles 17 
driven in opposing directions and the tilting drive formed by the 
connecting rods 20, 20', could be carried out in other ways, for example 
with synchronously controlled individual drives engaging the adjusting 
drives 12, 13 or the individual guide plates 6. 
While the lower set of plates 4 is supported directly in the frame 3, the 
upper set 5 is mounted in a support strand 23, that may be raised by means 
of an opening drive, in the example shown by a lifting cylinder 24, in 
order to open the board guide channel 8. This opened state is shown in 
FIG. 5. It is desirable to be able to open the board guide channel 8 for 
the removal of wood rests, which may result from the breakage of boards 1 
in the board guide channel 8. 
To make possible the lifting of the upper set of plates 5, the connecting 
rods 20, 20' are divided so that each has a rod lock 25, 25' that may be 
opened in order to extend the connecting rods 20, 20' in the manner of a 
telescope, if the upper set of plates 5 is raised as described above. 
As indicated in FIG. 1, the outlet end of the frame 3 is followed by a pair 
of rollers 26 with at least one driven roller, to move the boards 1 out of 
the frame 3. The boards 1 may be introduced either by feeder rollers (not 
shown) or by the advance movement during the production of the boards. 
In the example of embodiment shown the board guide channel 8 has a twist 
even in the initial position, i.e. the board guide channel 8, which is 
horizontal at the inlet (FIG. 2), is inclined at the outlet (FIG. 3). It 
is possible, on the other hand, to set the board guide channel 8 in the 
initial position without a twist and then adjust it by varying the guide 
plates 6 to different degrees. 
The adjusting range of the guide plates 6 may be chosen significantly 
larger than indicated in FIG. 3. For particularly large adjusting ranges, 
it is appropriate to provide a separate pivot drive for each guide plate.