Production of wood sheets by transverse cutting performed by special automatic cutters from a continuous sheet of veneer is known. The cutter is usually commanded to cut sheets in preset dimensions or transverse strips to be eliminated because they contain defects of the wood, e.g. holes.
For example, CH-354 890 discloses a transverse cutting apparatus wherein cutting means comprises two side-by-side transverse blades. If the sheet is wide, the two blades are operated simultaneously, whereas if the sheet is narrower than one blade, only one blade is operated.
With this procedure it is obvious that the waste of material is quite high since it is necessary to cut a strip of material as long as the longitudinal dimension of the defect and as wide as the entire veneer strip even if the transverse width of the defect is very limited. In addition, because of the repeated defects the possibility of obtaining long sheets is compromised.
Subject matter of the co-pending application EP-A-O 500 161 is a machine for carrying out transverse cuts selectively on the entire width or on a portion of the veneer width in connection with longitudinal cuts, so as to enable the scrap of defective parts with minimal wood waste.
The general purpose of the present invention is to provide a cutting device for carrying out accurate transverse cuts.
In view of said purpose it has been sought to provide in accordance with the present invention a device as defined in claim 1.
To further clarify the explanation of the innovative principles of the present invention and its advantages as compared with the known art there is described below with the aid of the annexed drawings a possible embodiment as a nonlimiting example applying said principles. In the drawings:
With reference to the figures, FIG. 1 shows a cutting device 15 comprising a rotating blade consisting of two blade sections 21 and 22 arranged side by side to rotate coaxially between bucking rollers 23 and 24 by motors 25 and 26 respectively having position sensors.
While the blade 21 is supported at the motor end to rotate without axial sliding, the blade 22 is supported at the end near its own motor by an axially sliding support 27.
Axial sliding is controlled by a double action piston 28 driven hydraulically through the ducts 40, 54 by a hydraulic control unit 29 connected to electronic processing and control means 19.
Between the two blades 21 and 22 is placed an axially sliding clutch 30 having a spring 31, e.g. the Melville type, which usually holds it in engagement of the two blades (blades brought near). Another spring 32, weaker than the spring 31, placed in the piston 28, maintains axial tension of the blades.
FIG. 2 shows schematically an example of an embodiment of the axial clutch 30. As may be seen in the figure, integral with the blade 21 is a supporting and containing structure 46 in which a shaft 47 integral with the blade 22 is inserted in a sliding manner. Reciprocal rotation between the structure 46 and the shaft 47 is permitted by bearings 48 and 49.
The spring 31 pushes between an element 50 integral with the shaft 47 and an element 51 rotating with the shaft 47, sliding coaxially thereto and butted axially on the structure 46 with an interposed bearing 52.
The bearing 48 is of known type permitting mutual axial translation of the parts between which it is placed.
In this manner is assured firm coaxial alignment of the rotation axes of the blades 21 and 22, allowing simultaneously their reciprocal axial sliding away against the action of the spring 31.
Between the structure 46 and the element 50 are arranged facing rings with frontal teeth 53, 55 for engagement between the parts brought together by the thrust of the spring 31.
Thus the axial traction of one of the blades (in this specific case the blade 22 by means of the piston 28) to permit disengagement and independent rotation.
The various parts of the station are controlled and commanded to operate by electronic processing and control means 19, e.g. provided by programmed logics such as a microprocessor of the known art programmed in accordance with the description given below and optionally interconnected to a personal computer or the like.
Such a device, especially in the light of the following operation description, can readily be imagined by those skilled in the art and therefore is not further described here.
The control device 19 synchronises the movements of the blades 21, 22 and commands coupling or not of the two blades of the transverse cutter depending on requirements.
In particular, if independent operation is necessary, the device 19 commands the control unit 29 to supply fluid to the piston through the duct 54. In this manner the piston moves the blade 22 axially away from the blade 21, thus disengaging the clutch 30 and permitting the two motors 25 and 26 to rotate the respective blade independently with independent speeds.
To engage again the blades so that they behave substantially as a single blade the control device 19 first resynchronizes them electronically, putting the motors in step (by means of the signals emitted by their position sensors), so that the blades are rearranged as much as possible with parallel faces, and then commands the control unit 29 to supply the piston 28 with a fluid counterpressure through the duct 40, thus reconnecting the mechanical clutch 30 between the blades.
It is therefore apparent how the proposed purposes are achieved, providing a device performing an accurate and quick transverse cut on the entire width of a veneer or only on a half.
In use the device is usually utilized in a station for combined transverse and longitudinal cuts, as disclosed, for example, in the above mentioned application EP-A-500 161, so as to receive between blades and bucking roller an unbroken strip of wood veneer separated or not longitudinally by a known longitudinal cutting blade.
In this way, the device is controlled for cutting transversely a half-strip or the entire strip (depending on what is the case) in connection with longitudinal cuts, so as to form wood sheets having a size suitable for minimizing wood scrap.
Figure 3 shows schematically a different embodiment 15' of the cutting device according to the present invention.
As may be seen in said figure, the cutter 15' comprises a shaft 56 on which are supported independently in a rotating manner two blade holder units (57, 58) or sections, each having a plurality 59, 60 of equally spaced radial blades (as may be seen well in FIG. 4).
Parallel to the shaft 56 is a bucking roller 61 on which slides the veneer 12.
Each blade holder 57 and 58 is rotated by a motor 62 or 63 through a kinematic transmission, e.g. with a chain, 64 and 65. The motors are mechanically engaged together through an electromechanical joint of the known art, e.g the electromagnetic type controlled by the device 19.
In use the cutting station operates as described above. When cuts are to be made on half strips the joint 66 is disengaged and the motors drive the blade holders independently. When a full transverse cut is required, the device 19 first synchronizes the blades by controlling the motors 62, 63 through position sensors, similarly to the motors of the cutter 15, and then operates the clutch 66 so that the blades of the two blade holders rotate integrally and with mated cutting edges.
Obviously, the above description of an embodiment applying the innovative principles of the present invention is given merely by way of example and therefore is not to be taken as a limitation of the patent right claimed here.
For example, although FIG. 4 shows three blades for each blade unit, as a compromise between cutting speed and manufacturing cost it is also possible to use cutters with a different number of blades.
In addition the connection means between the blades of the cutters 15 or 15' can be provided differently than described schematically or could even be replaced by only electronic synchronization of the rotation of the respective motors.