Patent Application
20070209735
The present invention relates to a method of locating the optimum peeling axis of a peeler log for maximum yield in veneer production by a rotary veneer lathe and also locating the maximum radius point of the log's peripheral surface with respect to the located optimum peeling axis. The invention also relates to an apparatus for performing the method.
A typical apparatus for determining the location of the optimum peeling axis of a log and the maximum radius point thereof is disclosed by the Unexamined Japanese Patent Application Publication (or KOKAI Publication) No. H6-293002. This apparatus has a number of log profile detectors which are disposed very close to each other along the entire length of a log for detecting the cross-sectional profiles of the log at many positions thereof along the log length while the log is rotated for a complete turn about its preliminary axis. The location of the optimum peeling axis of the log is determined on the basis of the information of the detected cross-sectional profiles at at least two positions. The point on the log peripheral surface having the maximum radius with respect to the located optimum peeling axis is determined based on the information of cross-sectional profiles detected at all positions.
For better understanding of the underlying problem in peeling veneer from a log having an irregular peripheral surface by a rotary veneer lathe, the following will explain briefly the reason why the maximum radius point need to be located. In a rotary veneer lathe for peeling a log for production of veneer, the log supported or held at its opposite ends by lathe spindles is rotated about its longitudinal axis. In peeling veneer from the log, a veneer knife mounted in a movable knife carriage is advanced toward the lathe spindles to cut into the log surface for a distance corresponding to the desired thickness of veneer to be peeled from the log for each complete turn of the log. If the knife carriage is located too far from the lathe spindles and hence the cutting edge of the veneer knife is positioned far from the log periphery just before the peeling operation is started, it takes a long time before the cutting edge of the knife reaches the log peripheral surface and actual veneer peeling begins, with the result that non-cutting downtime is increased and, therefore, the productivity in veneer production is affected thereby. For the veneer knife to cut into the log peripheral surface as soon as possible after it is rotated, the location on the log surface which has the maximum radius point should be determined previously and the knife carriage is positioned accordingly so that the veneer knife cuts into the log surface immediately.
According to the above-identified prior apparatus, however, the calculation procedure for determining the location of the maximum radius point with respect to the optimum peeling axis of the log is complicated and hence a time-consuming sequence.
An object of the present invention is to provide a method and an apparatus which can solve the drawbacks of the above-described prior art apparatus.
In order to achieve the object, the present invention provides a method of locating an optimum peeling axis of a peeler log and a maximum radius point on peripheral surface of the log with respect to the located optimum peeling axis and also an apparatus for practicing the method. According to the method of the present invention, the peeler log held at its preliminary axis by spindles is rotated for at least one complete turn and, thereafter, an optimum peeling axis of the log is computed on the basis of radial distances of the log from the preliminary axis to the peripheral surface of the log at a plurality of predetermined locations spaced along the preliminary axis of the log at each of a plurality of predetermined angularly spaced positions of the log.
For determining the location of the maximum radius point on peripheral surface of the log with respect to the computed optimum peeling axis, there is provided a plurality of swingable members which are pivotally mounted on a shaft having a longitudinal axis which extends in parallel to the preliminary axis of the log and have flat contact surfaces each having a width extending along the above longitudinal axis. Each contact surface is swingable with the swingable member relative to, or toward and away from, a reference position which is defined by an imaginary plane extending through the preliminary axis and the longitudinal axis, while in contact with the peripheral surface of the log so that the contact surface follows the peripheral profile of the log being rotated about the preliminary axis.
Angular position of the contact surface of each swingable member with respect to the above-defined reference position at each of the predetermined angularly spaced positions of the log is measured by the swingable member. On the basis of the measured angular positions of the contact surfaces, radial distances of the log from a plurality of predetermined locations on the computed optimum peeling axis to selected contact surfaces is computed. Then, the computed radial distances are compared and the distance having the greatest value is recognized as the maximum radius point of the log.
In computing the above radial distances of the log, they may be the distances as measured along imaginary lines extending perpendicularly to the preliminary axis. In the description of the preferred embodiment, a method of figuring out such distances will be explained in detail. Alternatively, the radial distances may be the distances as measured along imaginary lines extending perpendicularly to the computed optimum peeling axis.
In the above method, the predetermined locations on the computed optimum peeling axis correspond to the points of intersection between the optimum peeling axis and respective imaginary planes extending across the log at a side of the width of the contact surfaces in perpendicular relation to the preliminary axis of the log. In this case, angles of any two adjacent contact surfaces with respect to the reference position are compared on the basis of the angular positions of such two adjacent contact surfaces measured at each of the predetermined angularly spaced positions of the log and the above selected contact surfaces include one of the two adjacent contact surfaces whose angle with respect to the reference position is larger than that of the other of the two adjacent contact surfaces.
Alternatively, the above predetermined locations on the computed optimum peeling axis may be the points of intersection between the optimum peeling axis and respective imaginary planes extending across the log at a substantial center of the width of the contact surfaces in perpendicular relation to said preliminary axis of the log.
An apparatus of the present invention for performing the above method includes a pair of spindles for holding therebetween the log at the preliminary axis thereof and a drive such as electrical motor for driving at least one of the paired spindles thereby to rotate the log about the preliminary axis for at least one complete turn. A first sensor is provided for detecting a plurality of angularly spaced positions of at least one of said spindles and hence of the log.
The apparatus further includes a plurality of substantially the same swingable members as those described with reference to the method, a plurality of second sensors arranged at a spaced interval along the preliminary axis of the log for measuring distances from the respective second sensors to the peripheral surface of the log at each of the angularly spaced positions of the log, and a plurality of third sensors operable in conjunction with the above swingable members to measure angular positions of the contact surfaces with respect to the reference position at each of the angularly spaced positions of the log.
There is provided control means in the apparatus which is operable to compute the optimum peeling axis of the log on the basis of the distances measured by the second sensors. The control means is further operable to compute also the above-described radial distances of the log from the predetermined locations on the computed optimum peeling axis to the selected contact surfaces along imaginary lines extending perpendicularly either to said preliminary axis of the log or to the computed optimum peeling axis on the basis of the measured angular positions of the contact surfaces. The computed radial distances are compared and the distance having the greatest value is recognized as the maximum radius point of the log by the control means.
The control means is also operable to compare angles of any two adjacent contact surfaces with respect to the reference position on the basis of the angular positions of such two adjacent contact surfaces measured at each of the predetermined angularly spaced positions of the log so that the radial distance of the log from the predetermined location on the optimum peeling axis to the selected contact surface whose angle with respect to said reference position is larger than that of the other of said two adjacent contact surfaces.
It is to be noted that the method of locating the optimum peeling axis of a peeler log prior to locating the maximum radius point on peripheral surface of the log has been already known in the art and, therefore, it does not form a part of the present invention. However, since the method of locating the maximum radius point can be performed only after the location of the optimum peeling axis has been determined, the following description of a preferred embodiment of the invention will cover the method of locating the optimum peeling axis of a log.
Features and advantages of the present invention will become more apparent to those skilled in the art from the following description of preferred embodiment of the invention, which description is made with reference to the accompanying drawings, wherein:
The following will describe a preferred embodiment of a method of locating the optimum peeling axis of a peeler log having irregularities on the peripheral surface thereof and locating the maximum radius point on the log peripheral surface with respect to the located optimum peeling axis according to the present invention by way of describing an apparatus for performing the method while having reference to the accompanying drawings.
Referring to
The apparatus further has three laser-operated devices 9a, 9b, 9c which are provided at locations spaced along the longitudinal axial line 3b as shown in
These distance measuring laser devices 9a, 9b, 9c are connected to the control unit 20 and provide information of the measured distances L2 to the control unit 20 which is operable to compute or figure out radial distances of the log W between the longitudinal axial line 3b and the peripheral points of the log surface by subtracting the measured distances L2 from the predetermined distance L1. Repeating such calculation on the basis of distance measurements at a number of angularly spaced positions of the log W, the control unit 20 computes to determine the peripheral profiles of the log W, as will be described in later part hereof.
The apparatus further has a number of swing arms. For the sake of simplified illustration and description of the embodiment, five swing arms 10a, 10b, 10c, 10d, 10e are shown, e.g. in
As shown in
It is noted that the above standby position X-X of the swing arm 10a, 10b, 10c, 10d, 10e is merely an arbitrary position which is angularly spaced from an imaginary plane extending through the preliminary axis 3b and the longitudinal axis O at an angular distance that is large enough for the contact plate to be clear of a log W held between the spindles 3 and that the imaginary plane passing through the preliminary axis 3b and the longitudinal axis O is a reference position of the apparatus.
Each swing arm 10a, 10b, 10c, 10d, 10e is operatively connected to a rotary encoder 19a, 19b, 19c, 19d, 19e, as shown in
The angular position of each contact surface which follows an irregular peripheral profile of the log W in contact therewith is varied as the log W is rotated about its preliminary axis 3b and the contact surface is swung reciprocally up and down according to the irregularities of the log peripheral surface. Based on information provided by the respective rotary encoders 19a, 19b, 19c, 19d, 19e about the angular positions of the contact surface 11a′, 11b′, 11c′, 11d′, 11e′, the control unit 20 is operable to compute to figure out angles O (shown
Receiving information from the distance measuring devices 9a, 9b, 9c and the rotary encoders 7, 19a, 19b, 19c, 19d, 19e, the control unit 20 is also operable to generate various control or command signals for controlling the operation of the servo motor 5 and cylinders 17 and also to compute the optimum peeling axis of the peeler log W and the maximum radius point of the log's peripheral surface with respect to the computed optimum peeling axis, as will be described in detail below.
The following will explain the operation of the above-described apparatus for determining the location of an optimum peeling axis and determining the location of a maximum radius point on peripheral surface of a log with respect to the located optimum peeling axis.
In the initial state of the apparatus, the piston rods 17a are fully retracted in the cylinders 17, so that the swing arms 10a, 10b, 10c, 10d, 10e are positioned with the contact surfaces 11a′, 11b′, 11c′, 11d′, 11e′ of their contact plates 11a, 11b, 11c, 11d, 11e placed in the horizontal plane X-X, as shown in
After an elapse of time that is long enough for the log W to be held securely by the spindles 3, the cylinders 17 are activated by application of air pressure thereby to extend their piston rods 17a. Accordingly, the arms 10a, 10b, 10c, 10d, 10e are swung downward about the support shaft 13 until the contact surfaces 11a′, 11b′, 11c′, 11d′, 11e′ are brought into contact with the outer peripheral surface of the log W, as shown in
After the log W has been held securely by the spindles 3, on the other hand, the distance measuring laser devices 9a, 9b, 9c make the first measurements of the distances L2 and transmit information of the measurements to the control unit 20. As mentioned earlier, the control unit 20 figures out the difference between the distances L1 and L2 thereby to determine the peripheral point on the log surface that is spaced radially from the preliminary axis 3b of the log W.
Subsequently, the servo motor 5 is started to rotate the spindles 3 and hence the log W in arrow direction (
After the log W has been rotated for a complete turn, the cylinders 17 are operated so as to retract their piston rods 17a thereby to restore the swing arms 10a, 10b, 10c, 10d, 10e to their original standby positions, as shown in
During the above rotation of the log W, the contact surfaces 11a′, 11b′, 11c′, 11d′, 11e′ follow the peripheral profile of the log W and the swing arms 10a, 10b, 10c, 10d, 10e make an up-and-down swinging motion, as mentioned earlier. It is assumed that the log W is divided into a plurality of log sections corresponding to the width of the respective contact surfaces 11a, 11b, 11c, 11d, 11e, as shown in
For each of the cross-sectional planes A2, A3, A4, A5 which is shared by any two adjacent contact surfaces, the control unit 20 compares the swung angles θ of such two adjacent contact surfaces and selects the angle of a smaller value for storage in memory of the control unit 20. The reason for selecting the smaller value will be described in later part hereof. Accordingly, for the first sectional plane A1, the swung angle of the first contact surface 11a′ is selected for storage in memory. For the second sectional plane A2, the swung angles of the first and second contact surfaces 11a′ and 11b′ are compared and a value determined to be smaller by comparison is selected and stored in memory. Similarly, for the third, fourth and fifth sectional planes A3, A4 and A5, the swung angles of the two adjacent contact surfaces are compared and a value determined as smaller by comparison is selected for storage in memory. For the last sixth plane A6, the swung angle of the fifth contact surface 11e′ is stored in memory of the control unit 20.
Then, the control unit 20 computes to figure out a radial distance of the log W from a predetermined location on the computed optimum peeling axis HS to each of those contact surfaces whose swung angles were selected and stored in memory of the control unit 20 for being determined through comparison to be smaller than the angle of the adjacent contact surface. The above predetermined location on the computed optimum peeling axis HS is a point of intersection between the optimum peeling axis HS and each of the respective imaginary cross-sectional planes A1, A2, A3, A4, A5, A6 of the log. As shown in
In this case, two different distances are conceivable as the radial distance from a predetermined location on the optimum peeling axis to a selected contact surface. Referring to
The following will describe a procedure of calculating the radial distances L001, L002, L003, L004, L005, L006. The following description will be made for the radial distance L001 at the first cross-sectional plane A1 while having reference to
Since the optimum peeling axis HS has been already computed in terms of three-dimensional coordinates, the coordinates of the point G1 with reference to a given point on the axis O is computable. In
Referring again to the schematic diagram of
The control unit 20 performs similar computations for the other radial distances L002, L003, L004, L005 and L006 according to the same procedure of calculation as described above. As mentioned earlier, the control unit 20 compares swung angles of any two adjacent contact surfaces and selects the angle of smaller value for storage in memory. Accordingly, the control unit 20 computes to determine the radial distance L002 from the point G2 to the contact surface 11a′ whose swung angle is smaller than that of its adjacent contact surface 11b′ at the cross-sectional plane A2. Similarly, the radial distances L003 from the point G3 to the contact surface 11b′ whose swung angle is smaller than that of the contact surface 11c′ at the plane A3 is computed for storage; the radial distances L004 from the point G4 to the contact surface 11d′ whose swung angle is smaller than that of the contact surface 11c′ at the plane A4 is computed for storage; and the radial distances L005 from the point G5 to the contact surface 11d′ whose swung angle is smaller than that of the contact surface 11e′ at the plane A5 is computed and stored, respectively. At the sixth cross-sectional plane A6, the radial distance L006 from the point G6 to the contact surface 11e′ is computed.
It is noted that description of a radial distance to a specific contact surface refers not only to a distance directly to the contact surface, but also to a distance to an imaginary extension surface of that contact surface.
Referring to
The radial distance L011 from the point H1 to the contact surface 11a′ at the plane A1 is computed and stored in memory. The radial distance L012 from the point H2 to the contact surface 11b′ whose swung angle is smaller than that of the contact surface 11a′ at the plane A2 is computed and stored; the radial distances L013 from the point H3 to the contact surface 11b′ whose swung angle is smaller than that of the contact surface 11c′ at the plane A3 is computed; the radial distances L014 from the point H4 to the contact surface 11d′ whose swung angle is smaller than that of the contact surface 11c′ at the plane A4 is computed; and the radial distances L015 from the point H5 to the contact surface 11e′ whose swung angle is smaller than that of the contact surface 11d′ at the sectional plane A5 is computed and stored in memory of the control unit 20, respectively. For the sixth sectional plane A6, the radial distance L016 from the point H6 to the contact surface 11e′ is computed for storage in memory. Such radial distances are computed by the control unit 20 for the other angular positions of the log W.
For determining the location of the maximum radius point of the log W with respect to the optimum peeling axis HS, the control unit 20 then compares the values in the memory thereof and determines the greatest value as representing the maximum radius point on the log's peripheral surface as measured from the optimum peeling axis HS.
It is to be noted that, while the radial distances L001 through L006 have been computed for locating the maximum radius point, distances from the points G1, G2, G3, G4, G5, G6 to the contact surfaces along lines passing through such points and extending perpendicularly to the optimum peeling axis HS, as referred to in
After the locations of the optimum peeling axis HS and the maximum radius point of the log W have been thus determined, the knife carriage (not shown) of a rotary veneer lathe (not shown either) is moved relative to lathe spindles (not shown either) and set in the veneer lathe at such a position that the cutting edge of a veneer peeling knife (not shown either) mounted on the knife carriage is spaced from the longitudinal axial line of the lathe spindles at a distance that corresponds to the value of the distance for the maximum radius point of the log W. In view of possible mechanical errors of the veneer lathe, the above spaced distance may be slightly greater than the valve for the maximum radius point.
Then the log W is released from the spindles 3 and transferred to and set in the veneer lathe between the lathe spindles in such a position that the calculated optimum peeling axis HS of the log W coincides with the aligned axes of the lathe spindles. By so doing, when the log W clamped by the lathe spindles is driven to rotate, veneer peeling is initiated after an elapse of a very short time and, therefore, the downtime during which no peeling is performed is minimized and the productivity of the veneer lathe is improved.
As mentioned earlier in the description with reference to
In
As seen in
That is, the distance from the optimum peeling axis HS to the contact surfaces 11c′, or the distance between the points G3 and P3 at the plane A3 as calculated according to the procedure described with reference to
If the distance between the points G3 and P3 is regarded as the point for the maximum radius of the log W and the knife carriage is set with the cutting edge of the veneer peeling knife spaced from the axial line of the lathe spindles based on such information, the projection Wa will collide against the knife on the knife carriage when the log W is rotated, thereby inviting a breakage not only to the knife but also to any other part of the veneer lathe. As would be now apparent, when the space between the computed optimum peeling axis HS and any contact surface (e.g. the contact surface 11c′) is widened away from the location (or the plane A3 in the case of the contact surface 11c′) which was selected as the location for calculation of the distance based on the swung angle of the contact surface as in the case shown in
If the computed optimum peeling axis HS extends declining leftward as viewed in 12 and the swung angle of the swing arm is taken at a position corresponding to the right side of each contact surface, on the other hand, the same problem as described above will take place.
To forestall such selection of a wrong distance for the maximum radius point on the log W, the control unit 20 is operable to compare angles swung by any two adjacent contact surfaces and selects the angle of a smaller value for calculation of a distance between the computed optimum peeling axis and the contact surface. In the case of
In the above-described embodiment, the control unit 20 has operated to figure out the angle θ swung by the contact surface, i.e. the angle θ then made between the horizontal plane X-X and the plane of the contact surfaces, on the basis of information of the angular position provided by the rotary encoders. For understanding the present invention, however, it is important to note that what determines the dimension of a radial distance, e.g. L001, is not the angle of a contact surface relative to the arbitrary standby position X-X, but the angle of that contact surface relative to the reference position that is defined by an imaginary plane passing through the fixed axes 3b and O. Therefore, the control unit 20 may be operable to figure out an angle made between the contact surface and the reference position on the basis of information of angular position of the contact surface and also to compare such angles of any two adjacent contact surfaces. The angle between the contact surface and the reference position can be found easily merely by subtracting the angle θ from the known angle made between the reference position and the horizontal plane X-X. In computing to figure out a radial distance, e.g. L001, therefore, 0001 may be substituted by the difference between angle made between the reference position and the horizontal plane X-X and the angle θ in equation (11), i.e. L001=(T2−T1×tan θ001)×cos θ001.
Although the foregoing has described the present invention by way of a specific embodiment, it is to be understood that the present invention is not limited to the illustrated embodiment, but it can be practiced in other various changes and modifications, as exemplified below.
Imaginary cross-sectional planes of a log W, such as A1, A2 and so forth in
If a peeler log has a peripheral profile which is approximate to a circular cylinder, the calculation procedure may be simplified as follows. At each of the equiangularly spaced positions of the log W, angles swung by the respective contact surfaces 10a, 10b, 10c, 10d, 10e are compared and the smallest angle is selected. Then, on the basis of such selected angles, distances from the optimum peeling axis HS to the respective contact surfaces along a line extending perpendicularly to the contact surface are computed. Of all such computed distances, the largest distance is taken as the distance for the maximum radius of the log. This simplified calculation helps to shorten the time for the calculation.
Though all contact surfaces 11a′, 11b′, 11c′, 11d′, 11e′ in the preferred embodiment have substantially the same width extending along the axis O of the support shaft 13 as shown, e.g. in
In the preferred embodiment, the contact surfaces 11a′, 11b′, 11c′, 11d′, 11e′ are swung into contact with the peripheral surface of the log W after it has been held by the spindles 3. According to the present invention, however, the contact surfaces may be moved into contact with the log periphery before it is held by the spindles or substantially simultaneously with the holding by the spindles.
Though, according to the preferred embodiment, the laser devices 9a, 9b, 9c and the rotary encoders 19a, 19b, 19c, 19d, 19e are operable to make measurements simultaneously for the distances and the angles, respectively, at each of the equiangularly spaced positions of the spindle 3 or the log W, the laser devices and the rotary encoders may be operated independently at different angularly spaced positions of the log W.
