Device for cutting and stacking strips of wood

Abstract: A device (10) for cutting and stacking into layers of a pre-established size strips of wood obtained from a sheet of veneer, fed into the system by means of a first conveyor belt (11), comprises a cutter (14) actuated by a monitoring device (28) which detects flaws (31) in the wood by means of a scanning device (12) so as to isolate any faulty strips which are automatically discarded as they come off the cutter. The strips free from defects are then sent on by means of a second conveyor belt (17) to a deflector (19) which distributes said strips onto two conveyor belts (20,21) with intermittent movement which arrange the strips into compact adjacent groups which are then sent on to stackers (22,23) to form layers (29,30) of strips of pre-estabished dimensions (l).

Description: One problem in woodworking is that of cutting veneer into strips, eliminating defects such as knots, holes, etc., and stacking said strips so as to form layers of pre-established width and length to be sent on to the subsequent manufacturing stages. US-A-3 560 096 discloses a veneer clipper control system to cut unacceptable portions from a veneer strip. US-A-3 003 541 discloses a device according to the preamble of claim 1. The scope of this invention is to provide a device which cuts, discards defective portions and stacks the strips thus obtained into layers of pre-established dimensions, completely automatically and at high speed. This scope is achieved by providing a device according to the characterizing part of claim 1. The innovatory principles of this invention and its advantages with respect to the known technique will be more clearly evident from the following description of an exemplificative embodiment applying such principles, with reference to the accompanying drawings, in which: figure 1 shows a schematic view of a machine for cutting and stacking strips in pre-established sides obtained according to the innovatory principles claimed herein; figure 2 schematically shows a sheet of veneer with lines of possible sections carried out by the machine of figure 1; figure 3 schematically shows the layout of the useable sections of figure 2. With reference to the figures, as can be seen in figure 1, a 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 easily imagined by the expert in the field) along which is disposed an optical scanning device 12 of known technique, for example with photodiodes, to detect flaws in a sheet of veneer arriving from a conveyor system 13. The conveyor belt 11 leads to a cutter 14 of known technique, for example of the rotary type, with a cutting direction perpendicular to the direction of movement of the belt 11, the outlet of which is provided from above with a vacuum operated deflector 15 and from below with a collecting and conveying system 16. A second conveyor belt system 17 is situated downstream to the cutter with its counterbelts extending as far as the outlet of the latter and its lower belts extending only as far as the aspirator, as can be clearly seen in figure 1. Disposed at the other end of the conveyor belt 17 are a sensor 18 (for example, optical with photodiodes) and a flap-type deflector 19 of known technique for distributing the strips conveyed by the belt 17 onto a first lower belt with intermittent movement 20 and onto a second upper belt with intermittent movement 21. Said belts 20 and 21 lead to two stacking devices 22 and 23 of known technique, composed of movable shelves 24 and 25, which shift vertically from an upper position close to the belt to a lower position shown by the broken line in figure 1, and which are made to move by means of actuators (for example, pneumatic) 26 and 27 respectively. All the operations of the machine are monitored by an electronic device 28 (for example, wired logic or, advantageously, microprocessor-controlled) of known technique and consequently (especially in the light of the following operating description) easily imaginable by the expert technician; for this reason, its detailed description is considered superfluous. The above-described machine operates in the following way. The sheet 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 system 12 which detects the presence of surface defects (knots, holes, etc.) and transmits the information to the monitoring device 28 which actuates the cutter 14 in order to carry out the cuts in correspondence with the defects detected so as to isolate them in thin strips of a size just sufficient to contain the defect, as is schematically ilustrated in figure 2, which shows cuts carried out in order to isolate defects generically indicated by reference 31. At the outlet to the cutter the sections of wood obtained are sorted into strips and rejects or scraps containing the defects, by means of 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 from the cutter is a strip free from defects, so that it adheres to the end of the counterbelts of the conveyor 17 and is then conveyed by the latter towards its other end. Conversely, when the piece discharged from the cutter is a reject the device 28 reverses the operation of the vacuum-operated deflector thereby blowing the scrap into the conveyor belt 16 which conveys it elsewhere, for example towards manufacturing processes which require low-quality material. The strips which reach the conveyor belt 17, in continuous motion, are spaced apart from one another by a variable distance depending upon the width of the reject removed from between them. On arrival of a strip in correspondence with the device 18 the latter detects its leading edge and by means of the monitoring 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 monitoring device 28 to carry out the cuts in order to eliminate the defects and also to carry out cuts in calculated positions so that a sequence of strips placed close together on the intermittently moving belts forms the desired length l of a sheet to be stacked. This is shown schematically in figures 2 and 3; the cut to size 32 shown in figure 2 is carried out in such a position that, by placing together the pieces a, b, c, d obtained by means of the cuts made to eliminate the defects 31, the desired length l is obtained. The monitoring device 28 calculates the position of the cut 32 by adding up the lengths of the strips placed side by side on the intermittently moving belts which are measured by the sensor 18 as the strips pass under 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 under the latter. This continuous length is measured thanks to the fact that the the monitoring device 28 controls the speed of the belt 11 in order to synchronize it with the cutting operations according to the known technique. The figures 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 of the defects in the wood. The monitoring 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 stackable 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 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 strips so as to be ready to receive the subsequent layer. The monitoring 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 greater operating speed from the entire system, as is easily imaginable by the technician. 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 innovatory principles claimed herein can stack strips of wood very rapidly and with a minimum of waste and is also able to easily programme 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 innovatory principles claimed herein and should in no way be intended as a limitation to the sphere of this invention. For example, it is possible to carry out more complex movements by programming the monitoring 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 however deviating from the sphere of the invention claimed herein. The disposition of the various devices making up the machine can differ from 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 pneumatic vacuum-operated, can also be made using different methods, for example with deflector flaps similarly to that used for the deflector 19. Lastly, taping devices of known technique 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 in one piece.

Claims: Device (10) for cutting, assembling and stacking superimposed sheets of strips of wood 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 a cutter (14) by a first conveyor belt (17) towards at least a second conveyor belt (20 or 21) having a length not less than the corresponding width of the sheet to be formed, the second conveyor supplying the sheet to a stacker (22 or 23) characterized by means being provided for measuring the width of each strip coming from the first conveyor belt (17), to enable the second conveyor belt (20 or 21) to advance by a step equal to the width of the strip when it receives the strip, and a device (28) which adds up the width of the strips accumulated on the second conveyor belt (20 or 21) piloting the discharge of all the strips accumulated into the stacker (22 or 23), when the overall width is substantially equal to a pre-established quantity. Device as claimed in Claim 1, characterized by the fact that the first conveyor (17) is provided with a deflector (19) which alternately transfers the incoming strips onto either of two second conveyor belts (20, 21) each of which discharges them onto a stacker (22, 23). Device as claimed in Claim 1, characterized by the fact that the adding device (28) signals the cutter (14) to cut when a sensor (28) detects that a continuous length of veneer equal to the difference between the overall length of the strips accumulated on the second conveyor belt and the pre-established overall width has passed beneath it. Device as claimed in Claim 2, characterized by the fact that said deflector consists of a movable flap (19). Device as claimed in Claim 1, characterized by the fact that a vacuum-operated deflector (15) is disposed at the outlet of the cutter (14) to support the strips by suction as they are conveyed towards the first conveyor (17) and blow the defective portions into an outlet (16) towards the outside of the device. Device as claimed in Claim 1, characterized by the fact that an optical scanning device (12) is disposed at the inlet of the cutter (14) to identify the defective portions of the veneer. Device as claimed in Claim 1, characterized by the fact that the cutter (14), the conveyors (17, 20, 21), the strip length measuring means (18), and the stackers (22, 23) are operatively connected to an electronic monitoring device (28). Device as claimed in Claim 1, characterized by the fact that the conveyors (17, 20, 21) are of the belt and counterbelt type. Device as claimed in Claim 8, characterized by the fact that in the sloping portions of the conveyors the belts and counterbelts are curved in the direction of movement so as to compress the strips conveyed between them and prevent their relative movement.

Inventors: CREMONA LORENZO, CREMONA, LORENZO
Applicants: CREMONA ANGELO & FIGLIO, ANGELO CREMONA & FIGLIO S.P.A.
Application year: 1990
Main classification: B27G1
IPC codes: B27D5, B27D1, B27G1