System for selecting, on the basis of their size, wood veneers

A system for selecting wood veneers on the basis of their size comprises in combination: a cutter, at least a selector apparatus downstream of the cutter composed of a vacuum conveyor, expellers cooperating with the conveyor to separate the veneer from it, sensors for reading the length of the veneer which are disposed upstream of the cutter and which control the coming into operation of the expellers, and a conveyor for taking the veneers to a stacker downstream of the selector apparatus. The expellers consist of a plurality of compressed air nozzles above the feed path of the veneer which are adapted to direct in a controlled manner jets of air against the veneer so as to detach it abruptly from the vacuum conveyor.

The present invention relates to an improved system for selecting, on the 
basis of their size, wood veneers coming from a cutter. 
As persons with ordinary skill in the art know, in a plant for the 
continuous production of wood veneers the veneer derived from timber is 
fed to a cutter which is required to cut it to measure, with elimination 
of the defects always present on wood. 
However, precisely because of the casual presence of such defects, the 
final result of the cutting of the veneers is pieces of different size 
which need to be selected, plus defective pieces to be discarded. 
The veneer pieces are mostly selected by hand, and thus selection 
efficiency depends on the skill, training and personal judgement of the 
operator; in addition a manual selection conflicts with the aim of greater 
output. 
Automatic apparatus comprising conveyors with aspirator devices have 
hitherto been proposed in an attempt to overcome the problems arising from 
manual selection. 
One apparatus of this type is for example described in the Canadian Pat. 
No. 1018105 and comprises a vacuum selector-conveyor disposed over a free 
interspace between a first belt conveyor which receives the pieces cut by 
the cutter and a second belt conveyor which sends them to a stacker. 
The vacuum selection device is divided into two successive sections 
disposed angularly; the first of these comes into operation selectively 
only, when controlled to do so by sensors provided upstream of the cutter 
which measure the length of the cut piece. The pieces meeting measurement 
requirements are aspirated and sent--through the intermediary of the 
second aspirating section which is constantly in operation--to the second 
conveyor, while the pieces to be discarded are allowed to fall by gravity 
when they reach the end of the first conveyor, as a result of 
non-actuation of the first aspirating section. 
An apparatus of such type featuring two aspirating sections with 
differentiated operation in which the first section for removing the 
pieces from the conveyor downstream of the cutter comes into operation 
only when controlled to do so, while the second section for sending the 
take-off pieces to the second conveyor which forwards them for stacking is 
permanently in operation, also presents problems. 
The chief of these is that the vacuum existing in the second aspirating 
section (permanently in operation) cannot fall below certain values if it 
is to ensure the correct conveyance of the correctly dimensioned pieces, 
the size and weight of which are relatively great. 
But the permanent presence of such a vacuum in the second section makes it 
impossible to discard small-size pieces even if the vacuum in the first 
section is cut-out. 
For, as soon as the small pieces coming at a considerably high speed from 
the cutter arrive with their leading edge beyond the first non-operative 
section, instead of falling by gravity when they reach the end of the 
first conveyor, to be discarded, are taken up by the second aspirating 
section and conveyed to the stacker; this fact causes problems which will 
be self-evident. 
On the other hand, lowering the feed rate of the pieces to allow the 
free-fall of the small pieces to be discarded conflicts with the 
requirements of greater output. 
In addition, the need to have an angular disposition between the first 
alternating vacuum section and the second continuous vacuum section makes 
the structure of the conveyor of the selection device complicated and 
therefore costly. 
The object of the present invention is to obviate the aforementioned 
problems existing in the known art by embodying a system for selecting 
wood veneers on the basis of their size, comprising in combination: a 
cutter, at least a selector device downstream of the cutter consisting of 
a vacuum conveyor, expeller means cooperating with the conveyor to 
separate the veneers from it, sensors for reading the length of the 
veneer, disposed upstream of the cutter and controlling the actuation of 
the expeller means, and a conveyor for conveying the veneers to a stacker 
downstream of the selector device, wherein the expeller means comprise a 
plurality of compressed-air nozzles disposed above the veneer feed path 
and adapted to the controlled direction of air jets against the veneers so 
as to detach them abruptly from the vacuum conveyor. In known U.S. Pat. 
No. 4,397,209 a sensor and electronics apparatus is disclosed for carrying 
out the detection and cutting of veneer imperfections. The sensor checks 
the veneer moving toward the cutter for imperfections and then via the 
electronic apparatus and a cutter cuts the veneer to remove the 
imperfections. 
The structural and functional characteristics of the invention, and its 
advantages over the known art, will become more apparent from an 
examination of the following illustrative description thereof, with 
reference to the appended drawings which show an apparatus realized 
according to an example of practical embodiment of the invention.

With reference firstly to FIG. 1 of the drawings, the system according to 
the invention comprises at least a selector device 10 disposed immediately 
downstream of the rotary cutter 11. 
The rotary cutter is not here described in detail, in that it can be of any 
known type, for example that forming subject matter of the co-pending 
patent application No. 23219 B/85, filed on Sept. 25, 1985, in the name of 
the Applicant of the present patent application. 
With reference to FIGS. 2-4 of the drawings, the selector apparatus 10 
consists structurally of a box 12, which extends longitudinally (FIGS. 2 
and 3), at the opposite ends of which there are formed forks 13, 14 which 
respectively support a drive and control means for a continuous vacuum 
conveyor encircling the box 12. 
More specifically, the said continuous conveyor comprises a pair of 
parallel belts 15 which at one end wind onto a freely rotating wheel 16, 
of smaller diameter, supported by the fork 13, and at the opposite end 
onto a pair of driven rollers 17, of greater diameter, supported by the 
fork 14. The rollers 17 are solid with a shaft 18 whose ends protrude from 
the fork 14 and carry solidly a control pulley 19 and a pair of freely 
rotating pulleys 20 for pressure belts 21 the purpose of which will become 
evident hereinafter. Through the intermediary of a belt transmission 22 
the pulley 19 is connected to a power unit (not shown), for example to the 
same power unit that actuates the rotary cutter. 
As FIG. 2 of the drawings clearly shows, the belts 15 of the conveyor 
comprise slack upper deployments or runs 23 and taut lower deployments or 
runs 24, the latter sliding against the back or lower wall 25 of the box 
12. Between the taut deployments or runs 24, the back or lower wall 25 of 
the box 12 comprises an elongated tapered grille 26 (FIG. 4) with fretted 
cross section and featuring a series of aspiration holes 27 which are 
staggered one with respect to the other. The grille 26 closes on its lower 
side an aspiration manifold 28 connected to the aspiration side 29 of an 
overlying fan 30. 
Immediately downstream of the conveyor admission end, the box 12 also 
supports a plurality of compressed-air expeller nozzles 31 which extend 
radially from a manifold 32 of air under pressure. 
In the example shown, the nozzles 31 are three in number, one positioned 
centrally and two laterally. 
With the above described selector apparatus 10 (FIGS. 1 and 5) there also 
cooperate a series of deviation rollers 33 disposed immediately to the 
delivery end of the selector 10, and a conveyor 34 arranged near the exit 
of the same selector 10. 
The manner in which the system according to the invention operates is 
evident from what is specified above with reference to the drawings and is 
briefly as described below. 
The selector 10 being permanently under vacuum, the veneer (not shown) 
coming from the cutter 11 and deviated slightly upwards by the rollers 33 
is aspirated against the taut lower deployments 24 of the belts 15 which 
take it off from the said cutter. The take-off of the veneer by the belts 
15 is facilitated by the higher vacuum existing at the mouth of the 
selector device where the greater cross section of the grille 26, with a 
greater number of aspirating holes, is positioned. 
If the veneer meets dimensional requirements, the dimensions being read by 
a sensor 35 upstream of the cutter 11, the nozzles 31 do not come into 
operation and the belts 14 send the veneer to the conveyor 34, which 
forwards it for example to a stacking station. 
If, however, the sensor 35 reads that the dimensions of the veneer are such 
as to require that it be discarded or not selected, the said sensor 
operates a solenoid valve 36 which admits compressed air into the manifold 
32 with the result that the expeller nozzles 31 comes into operation and, 
by directing powerful jets of compressed air against the veneer, causes it 
to detach positively from the belts 24 and thus to fall by gravity. 
A system according to the invention can also comprise a plurality of 
further selectors 10a, 10b and 10c disposed in cascade arrangement 
downstream of the cutter 11, as shown in FIG. 5, with which respective 
stackers 37a, 37b and 37c cooperate. 
The coming into operation of the expeller nozzles 31 of the selector device 
10a, 10b and 10c is controlled by the sensor 35 upstream of the cutter 11 
so that the veneers can be selected on the basis of their dimensional 
characteristics and quality and sent to the stackers 37a, 37b and 37c 
through the intermediary of conveyors 38a, 38b and 38c. 
During the path travelled by them along the system, the veneers are kept in 
contact with the conveyors 34, 34a, 34b, 34c and 34d by means of the 
lateral belts 21. The conveyor belts 15 of the first selector device 10 
are controlled by the motor of the cutter, while those of the other 
selector devices 10a, 10b and 10c are controlled by an additional power 
unit 39 connected to them by transmission belts. 
With a system comprising a plurality of selector devices the veneers can be 
selected into several groups on the basis of their dimensions and other 
characteristics, a typical selection being one composed of whole formats, 
whole sub-formats, whole-formats with face defects and veneers to be 
discarded.