Device for cutting and stacking strips of wood

A machine for cutting and stacking into layers sheets of a pre-established size from a plurality of strips of wood obtained from a piece of veneer. The pieces of veneer are fed into a cutter by means of a first conveyor belt actuated by a control means which detects flaws in the wood to cut out transverse strips containing the flaws that are then automatically discarded as they come off the cutter. Strips free from defects are then sent on by a second conveyor belt to a deflector which distributes the strips onto two conveyor belts with intermittent movement so as to arrange the strips into compact adjacent groups to form a sheet of desired length. The plurality of adjacent strips forming a sheet are then sent to stackers to form layers of the sheets.

BACKGROUND OF THE INVENTION 
One problem in woodworking is that of cutting veneer into strips, 
eliminating defects such as knots, holes, etc., laying the strips side by 
side and stacking them to form layers of sheets of pre-established width 
and length to be sent on to subsequent manufacturing steps. This invention 
relates to a device for carrying out such an operation completely 
automatically and at high speed. 
SUMMARY OF THE INVENTION 
This is achieved by providing a device for stacking superimposed sheets of 
strips placed side by side to form a sheet of pre-established dimensions, 
the strips being cut from a sheet of veneer, with elimination of its 
defective portions, in which the strips are conveyed from the outlet of 
the cutter by a first conveyor belt towards a second conveyor belt having 
a length not less than the corresponding length of the sheet to be formed, 
means being provided for measuring the width of each strip coming from the 
first conveyor belt to enable the second conveyor belt to advance by a 
step equal to the width of the strip when it receives the strip, and a 
device which adds up the width of the strips accumulated on the second 
conveyor belt and then discharges all the strips accumulated into a 
stacker, when the overall width is substantially equal to a 
pre-established dimension.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the figures, as can be seen in FIG. 1, the machine for 
cutting and stacking strips, generically indicated by reference 10, 
comprises a first conveyor belt 11 (the term "conveyor belt" will be 
hereinafter used to indicate a belt conveying system with belts and 
counterbelts as can be readily appreciated by those skilled in the art) 
along which is disposed a detection means such as an optical scanning 
device 12 of known type, for example with photodiodes, to detect flaws in 
a piece of veneer arriving from a conveyor system 13. 
The conveyor belt 11 leads to a cutter 14 of know type, for example of the 
rotary type, with a cutting direction perpendicular to the direction of 
movement of the belt 11, the outlet of which lies adjacent from above with 
a separating means comprising a vacuum operated deflector 15 and from 
below with a collecting and conveying chute system 16. 
A second conveyor belt system 17 is situated downstream of the cutter 14 
with its counterbelts extending as far as the outlet of the cutter and its 
lower belts extending only as far as the deflector 15, as can be clearly 
seen in FIG. 1. 
Disposed at the other end of the conveyor belt system 17 is a measuring 
means 18 for determining the width of the conveyed strips such as an 
optical sensor with photodiodes and a flap-type deflector 19 of known type 
for distributing the strips conveyed by the belt 17 onto a first lower 
belt with intermittent movement 20 or onto a second upper belt with 
intermittent movement 21. 
Belts 20 and 21 lead to two stacking devices 22 and 23 of know type, 
comprised of movable shelves 24 and 25, which shift vertically from an 
upper position close to the belts to a lower position as shown by the 
broken lines in FIG. 1, and which are movable by means of actuators (for 
example, pneumatic) 26 and 27 respectively. 
All the operations of the machine are monitored by a conventional 
electronic control means 28 (for example, wired logic or, advantageously, 
microprocessor-controlled) of known type and consequently (especially in 
the light of the following operating description) readily apparent to 
those skilled in the art. For this reason, its further description is 
considered unnecessary. 
The above-described machine operates in the following way. The piece of 
veneer, conveyed by means of a belt 13 from previous phases of the 
process, is transferred onto the belt 11 and passes through the scanning 
device 12 which detects the presence of surface defects (knots, holes, 
etc.) and transmits the information to the control means 28 which actuates 
the cutter 14 in order to carry out the cuts extending perpendicular to 
the direction of travel of the piece of veneer in correspondence with the 
defects detected so as to isolate them in thin strips of a size just 
sufficient to contain the defect. This is schematically illustrated in 
FIG. 2, which shows cuts carried out in order to isolate defects 
generically indicated by reference 31. 
At the outlet of the cutter, the sections of wood obtained are sorted into 
the strips free from defects and rejects or scraps containing the defects, 
by the vacuum-operated deflector 15. This selection is obtained by a 
control signal from the device 28 which actuates the vacuum of the 
deflector 15 when the piece discharged form the cutter is a strip free 
from defects, so that it adheres to the end of the upper counterbelts of 
the conveyor system 17 and is then conveyed by the system towards its 
other end. Conversely, when the piece discharged from the cutter is a 
strip containing a reject, the device 28 reverses the operation of the 
vacuum-operated deflector and blows the scrap into the chute 16 which 
conveys it elsewhere, for example towards manufacturing processes which 
require lower-quality material. 
The strips which reach the conveyor belt system 17, in continuous motion, 
are spaced apart from one another a variable distance depending upon the 
width of the strip containing the reject removed from between them. On 
arrival of a strip with the sensor 18 the latter detects its leading edge 
and by means of the control device 28 actuates the flap 19 in order to 
send the strip to either of the intermittently moving belts 20, 21, and 
starts up the belt receiving the strip until it detects the trailing edge 
of the latter. In this way, the subsequent strips are transferred onto the 
belts 20 and 21 with their edges placed close together. 
The cutter 14 is controlled by the device 28 to carry out the cuts in order 
to eliminate the defects and also to carry out cuts 32 in calculated 
positions so that a sequence of strips placed close together on the 
intermittently moving belts will form the desired length l of a sheet to 
be stacked. This is shown schematically in FIGS. 2 and 3 where the cut 32 
is carried out in such a position that, by placing that strip d together 
with the strips a, b, c, obtained by the cuts made to eliminate the 
defects 31, the desired length l is obtained. 
The control device 28 calculates the position of the cut 32 by adding up 
the lengths of the strips already placed side by side on the 
intermittently moving belts 20 or 21 which are measured by the sensor 18 
as the strips pass by it, and signals the cutter to make the cut when a 
continuous length of veneer equal to the portion required to make up the 
length l has passed by it. This continuous length is measured due to the 
fact that the device 28 controls the speed of the belt 11 in order to 
synchronize it with the cutting operations according to known techniques. 
The FIGS. 2 and 3 are obviously given purely by way of example, since the 
number and position of the cuts and, consequently, the dimensions of the 
strips, depend upon the position and number of the defects in the piece of 
veneer. 
The device 28 can be programmed so as to offer a certain tolerance in the 
permissible length l, in order to avoid excessively narrow strips, below a 
given value, whenever a defect has been eliminated close to the cutting 
position necessary to obtain a sequence of strips of a precise length l. 
As soon as there is a sufficient number of adjacent strips on the belt 20 
or 21 to form the desired length l (obviously shorter than the length of 
the belt 20 and 21), the belt is made to move continuously until the 
strips have been deposited as a sheet on the corresponding stacker to form 
a layer 29, 30 respectively. After having received the layer, the movable 
shelf descends a distance equal to the thickness of the sheet so as to be 
ready to receive a subsequent layer. 
The device 28 controls the flap 19 in such a way that a consecutive 
sequence of strips to be stacked is formed first on one intermittently 
moving belt and then, while the latter transfers the layer onto the 
stacker, onto the other intermittently moving belt. By alternately serving 
the belts 20 and 21 it is possible to achieve a higher operating speed 
from the entire system. 
The disposition of the belts and counterbelts in the sloping portions of 
the conveyors is advantageously curved (by suitably positioning the 
rollers supporting them) so that in said portions the belts and 
counterbelts are pressed against one another and consequently hold the 
strips tightly between them, thus preventing any relative movement between 
the strips due to possible vibrations in the conveying system or to the 
force of gravity. 
It is clear, from the foregoing description that a machine applying the 
principles of the invention can stack strips of wood very rapidly and with 
a minimum of waste and is also able to easily program both the minimum and 
maximum width of the strips produced as well as the dimensions of the 
layers formed with the latter. 
The above description is obviously understood as being given merely to 
illustrate the principles of the invention and should in no way be 
intended as a limitation of the scope of this invention. For example, it 
is possible to carry out more complex movements by programming the device 
28 so that the distribution of the strips on the belt 20 or the belt 21 is 
carried out in relation to possible optimizations in the cutting to size 
in relation to the positions of the defects and, therefore, of the cuts 
necessary to eliminate the latter. 
Moreover, the expert technician can, in the light of the foregoing 
description, easily imagine possible variations to the embodiment shown 
herein without departing from the scope of the invention. The disposition 
of the various devices making up the machine can differ form those 
described according to the desired overall dimensions. For example, the 
stackers can be placed one on top of the other in order to reduce the 
floor space occupied by the machine. 
The selecting device 15, described above as vacuum-operated, can also be 
made using different methods, for example with deflector flaps similar to 
those used for the deflector 19. 
Lastly, taping devices of know type can be provided to lay adhesive tape 
across the strips once they have been placed side by side on the belts 20, 
21 in order to ensure that they move together as one piece.