Process and apparatus for veneer cutting

[57] ABSTRACT

A method and apparatus for scanning veneer logs or blocks to obtain the maximum amount of veneer from each block. The method includes the positioning of a veneer block along a predetermined reference axis, electronically scanning the block along one side to determine its profile dimensions with respect to a first plane intersecting the ends of the block, computing the true center line of the block in the first plane, and repositioning the block along that true center line. The block is then rotated by a predetermined angle, such as 90°, and rescanned along a second side to determine its profile dimensions with respect to a second plane intersecting the ends of the block. The true center line of the block in the second plane is then computed and the block is repositioned along the true center line in that plane prior to processing by a rotary veneer lathe. A particular scanning and processing apparatus is disclosed for practicing the steps of the method in processing veneer blocks of different diameters into veneer.

Claims, 4 Drawing Figures

Primary Examiner— Eugene G. Botz Attorney—Kolisch, Hartwell & Dickenson

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Patented July 17, 1973

3,746,065

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ATTY.

Patented July 17, 1973 3,746,065

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3,746,065 ing through the ends of the block, and apparatus for repositioning the block with respect to a veneer peeling knife along an optimum center line computed from such measured dimensions.

⁵ BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying draw10 ings, wherein:

FIG. 1 is a schematic diagram of a veneer processing apparatus adapted to process veneer blocks in accordance with the invention;

FIG. 2 is a diagrammatic side elevation view of a 15 scanner and block charger for positioning blocks, of the type used in the apparatus illustrated in FIG. 1;

FIG. 3 is a partial top elevation view of the scanner and block charger illustrated in FIG. 2, showing the outline of a veneer block as initially positioned in the 20 charger and the outline of another block positioned in the carriage arms; and

FIG. 4 is a diagrammatic view of a scan grid illustrating the axial alignment of a block along a reference axis before scanning and the alignment of the same block in the charger of FIG. 2 after repositioning along the true center line.

DETAILED DESCRIPTION OF THE INVENTION

According to the invention, softened veneer blocks or logs of different diameter are automatically processed to obtain an optimum amount of veneer of a predetermined quality from each block. A given block is moved to a block-positioning device where it is aligned along a reference axis. The block is then ³⁵ clamped in a block charger and moved through a scanning device, such as a photoelectric scanner, where the profile dimensions of the log are measured in a first plane extending through the ends of the block and supplied to a data processing unit. This permits the plotting ⁴θ of a two-dimensional representation or planer profile of the dimensions of the log. The term plotting is used to mean either the physical plotting of dimensions on paper under the control of data processing apparatus or the orientation of appropriate data representations within the processing equipment itself. The measured dimensions of the log are used to compute the true center line of the largest rectangular section that can be superimposed within the log profile. Subsequently, the block is repositioned in the block scanner along the true center line computed for the first plane of the block.

The block is then rotated in the block charger by a predetermined angle, which conveniently can be 90°, and the block is moved through the scanner again to measure the profile dimensions of the block in a second plane extending through the ends of the block. These profile dimensions, as measured by the scanning device, are again supplied to the data processing unit wherein the true center line of the largest rectangular section that can be superimposed within the profile of the second plane is determined. The veneer block is then repositioned along the true center line of the block computed for the second plane.

Since the first and second scans are taken in planes that are non-parallel, the second repositioning orients the veneer block in the block charger along an optimum axis which is the center axis of the largest cylinder

PROCESS AND APPARATUS FOR VENEER CUTTING

BACKGROUND OF THE INVENTION

In the usual rotary veneer peeling system heated and softened blocks, such as 8-foot blocks of diameters ranging from 18-48 inches are clamped in a rotatable spindle and presented to an elongate veneer peeling knife extending along the entire 8-foot length of the block. The spindle is rotated and the knife is moved with respect to the spindle to progressively peel a continuous layer of veneer from the outside of the block, continuing along an inwardly progressing spiral path toward the center of the block until only a nonprocessable central core of wood is left. With such operations the accurate and consistent centering of the veneer blocks along an optimum center line with respect to the knife is essential to provide maximum veneer recovery from a given block.

Heretofore in the prior art, the centering of veneer blocks has been carried out by various means which did not result in the recovery of the maximum amount of veneer. For example, blocks have been centered by placing them in a pair of opposed V’s prior to clamping the blocks in a charger for transfer to the veneer lathe spindle. The use of such equipment, and other operator-controlled mechanisms which might rely upon the visual impression of the operator to control the centering of a given block, do not result in the evaluation of many factors that should enter into a determination of the alignment of a given veneer block.

For example, all blocks are tapered from one end to the other to a certain extent. Consequently, some wastage will always occur in producing veneer of a predetermined width and regular thickness from such blocks. In addition, veneer blocks are commonly of irregular or elliptical diameter. Also they can include crooks even though they are of relatively short length, and can have depressions or extensions in their outer surfaces. For obvious reasons, each of these factors has a significant effect upon the way the veneer block should be centered with respect to the knife to achieve optimum veneer recovery. Accordingly, it would be desirable to eliminate operator judgment from the determination of how to center each block in favor of a system which ⁴⁵would precisely and' automatically evaluate all the above factors in arriving at an optimum block alignment.

SUMMARY OF THE INVENTION 50

Accordingly, it is an object of the invention to provide a method and apparatus for processing veneer blocks that overcomes the disadvantages of conventional practice.

It is another object of the invention to provide a method for processing veneer blocks to obtain the maximum amount of veneer of a predetermined quality from a given block.

It is a further object of the invention to provide a method for processing veneer blocks wherein the dimensions of each block are accurately measured and the true center line of the largest cylinder of usable wood that can be superimposed within the measured dimensions is determined.

It is yet a further object of the invention to provide scanning apparatus for measuring the dimensions of a veneer block along at least two different planes extend3,746,065 of usable wood that can be superimposed within the dimensions of the veneer block as determined from the measurements taken along two sides of the block. The veneer block is then moved by the block charger to a veneer carriage where the block is clamped along the optimum axis and moved into operating relationship with a knife of a conventional rotary veneer lathe. The veneer lathe is utilized to reduce progressively and veneer block to veneer of a predetermined thickness.

If a more complete profile of the dimensions of a given block is desired, it is possible to scan the block along more than two sides or planes, for example by rotating the block by less than 90° and performing three or more scanning operations. This has not been found to be desirable in the processing of the relatively short veneer blocks, however.

Also, if desired, it is possible to simultaneously scan the block along two intersecting planes by utilizing two separate scanning devices. However, this scanning mode is not preferred since it requires the use of an additional scanner and is advantageous only in that it reduces the scanning time. In the usual veneer processing system, ample time exists for the successive scanning of a veneer block with a single scanning device.

Referring now to the drawings, one preferred apparatus for practicing the method of the invention is illustrated in the form of a veneer processing system. Referring to the left side of FIG. 1, a block steaming compartment 10 is diagrammatically indicated. Each veneer block is supplied to the compartment, by means not shown, wherein it is subjected to a treatment of steam and hot water for a predetermined time to heat and soften the block to reduce splitting and tearing of the block upon processing by the veneer lathe.

A block infeed conveyor 12 is arranged at an outlet of compartment 10 to receive heated blocks for transfer of such blocks to the rest of the processing system. Conveyor 12 is a conventional chain conveyor adapted to be driven in the direction indicated by the arrow by a suitable motor, not illustrated. The conveyor motor can be suitably controlled, such as by means of a limit switch relay type circuit, to maintain one block at a ready position against a fence 13 on the outlet end of the conveyor at all times.

A block indexing unit 14 is provided at the outlet side of infeed conveyor 12 for receiving blocks, individually, from conveyor 12 and delivering such blocks to the next section of the veneer system comprising a block measurement apparatus generally indicated at 16. As illustrated, the block indexing unit includes a first chain conveyor 18 and a second chain conveyor 20, both of conventional design, adapted to be moved in a direction indicated by the arrows. Conveyors 18, 20 are arranged in line, with conveyor 18 being positioned in a relatively horizontal attitude and conveyor 20 being upwardly inclined with respect to conveyor 18. Suitable operator controlled means are provided for selectively placing a given block on conveyor 18 with the length of the block extending across with width of the conveyor. The block is then delivered by conveyors 18, 20 to the block measurement apparatus.

Referring now to FIGS. 1-4, the block measuring apparatus is particularly illustrated, comprising a block alignment yoke 30 comprised of two sets of generally opposed V’s or V-members 32, 34. Each set of V’s includes a lower V 41 and an upper V 42 adapted for powered movement between a closed or clamped posi tion shown in solid outline in the drawings and an open or retracted position shown in dotted outline in the drawings.

Each of the lower V’s 41 is supported above a base or platform 45 by an elevator unit 46 of conventional design, such as a hydraulic or electric elevator, that serves to move the V-member between its clamped and retracted positions, selectively. Each of the upper V’s is connected to the lower end of an elevator unit 48. Each unit 48 is suspended by its upper end from an elongate overhead arm 49 shown best in FIG. 3, that projects inwardly from an upright 50 attached to the platform. Uprights 50 are positioned outwardly from the ends of the block to provide clearance for movement of the block charger arms therebetween as will become apparent hereinafter.

The lower and upper V’s of each set are laterally offset with respect to each other, again as shown in FIG. 3, to enable the V’s to close or clamp tightly upon blocks of small, as well as large diameter. Both sets of V’s are positioned at the same horizontal level along a line transverse to the direction of movement of blocks along the block indexing conveyors, and are positioned beneath the upper or outlet end of conveyor 20 to receive and support a block in the open V’s as it drops off the end of conveyor 20. The elevator units are adapted to be operated in unison so that the lower V’s Of each set are raised at the same time, and the upper and lower V’s of a given set are also closed in unison.

When the V’s are retracted they occupy a noninterfering position that permits a block to drop off the end of conveyor 20, and to be cradled or substantially centered in the lower V’s. Thereafter, the upper and lower V’s are moved towards each other so that the block is gripped and firmly clamped at each end by the corresponding sets of V’s. The block is thereby positively centered in the V’s and retained in a fixed position along a lengthwise axis that is arbitrarily used as a reference axis during the first scanning operation described hereinafter.

It should be apparent that, due to log taper as well as crooks and deformations in the surface of the log, the reference axis is not coincident with the center axis of the log either in a horizontal sense or in a vertical sense. However, the reference axis always intersects the ends of the block.

A data processing unit 60 is provided that is electrically connected by suitable means to the elevator units. Accordingly, the positioning of each block on the V’s is automatically controlled by the processing unit. If desired, a manually controlled override switch and block rotating mechanism can be provided by which the V’s can be opened and the block rotated for realignment. This enables each block to be clamped with its best side up as determined by an operator. It further enables blocks which are not suitable for processing into veneer to be rejected onto a reject chain, such as chain 62.

The block measuring apparatus also includes a block charger 70 having arms 72, 74 positioned outwardly on either side of the V’s to selectively engage the ends of a block clamped in the V’s. To facilitate the gripping of a block, each charger arm is provided with spikes 75 secured to the outer end 76 thereof. Each charger arm otherwise includes a multiposition stacked hydraulic cylinder set works 80 adapted for extending the length of the arm, independently, in increments such as onetenth inch increments.

3,746,065

The upper end of each charger arm is secured to a power assembly 82 automatically controlled by processing unit 60. The power assembly includes an overhead shaft 85 to which the upper ends of the arms are fixedly secured. The ends of shaft 85 of the power assembly can be selectively extended for moving the arms selectively into and out of contact with the ends of a block positioned in the V’s. In addition, shaft 85 can be rotated to pivot the charger arms and block upwardly, to the position shown in dotted outline in the drawings, wherein the block is generally positioned along a scanning path indicated at 88.

The power assembly is further adapted for power movement along supporting rails 86 whereby the charger arms and block are moved as a unit so that the block traverses the scanning path through a block scanner 105 and ultimately is stopped in a region adjacent a clamping carriage 96.

The block scanner 105 is positioned proximate the scanning line, and includes an upper hood 107 and a lower hood 109 spaced on opposite sides of the scanning line. The upper hood is positioned above the scan line and serves as a housing and reflector for a line source of light 110, such as a neon tube, supported in the upper hood extending parallel to the length of a block oriented in the charger arms. Source 110 produces light of an appropriate intensity and direction to illuminate the upper half of each block as it traverses the scanner. Lower housing 109 supports a plurality of light-responsive elements 112, such as photocells, and ³θ the electrical circuitry associated therewith. The photocells are arranged in a line directly beneath light source 110 for exposure by the light therefrom. The photocells are interspersed at predetermined intervals along the length of the lower hood. The photocells are adapted to produce an electrical output in the presence of light, and to produce no output in the absence of light. Accordingly, the presence of any portion of a block between the light source and each individual photocell can be detected upon passage of the block.

In the preferred embodiment, fifty-five photocells are utilized, spaced at 2-inch intervals over a 110-inch span along the length of the scanner. The output of each photocell is connected to a conventional amplifier unit for amplifying the output of the photocell and supplying the output to processing unit 60.

The photocell array is adapted for actuation upon the approach of the charger arms and 550 readings are obtained from each photocell during the traverse of a block, with each reading being taken at a one-tenthinch interval of horizontal travel of the block through the scanner. The data provided from each scanning sequence is utilized in the calculation and plotting of the block dimensions by the processing unit. From such data the processing unit calculates the true center line of the largest rectangle that can be superimposed within the measured two dimensional profile of the block. The processing unit then controls the operation of the hydraulic set works of each charger arm independently to realign the block with the true center line parallel to an index line. The block is then engaged at its ends by clamping carriage 96 which serves to retain the block along the new center line.

The clamping carriage includes spaced-apart carriage arms 122, 124 adapted to engage the ends of the block. The arms are formed with knife edges 126 at their ends, designed to slice into the ends of the block for firm engagement. The knife edges are adapted to engage the block away from the center thereof so that the arms of the charger arm can reclamp the ends of the block without contacting the carriage arms, after rotation of the block. A power unit 125 is provided for moving the carriage arms selectively into engagement with a block and for releasing the arms when desired. The power unit is also utilized for rotating the carriage arms with the block gripped therein. In the preferred embodiment the block is rotated by 90° after the first scanning operation. However, the block could be rotated through some other angle without departing from the invention. The block is then reclamped in the charger arms.

After rotation of the block and its reclamping in the charger arms, the charger is withdrawn to its original position and then advanced through the scanner a second time. The profile measurements of the block along the second plane are detected by the scanner, with the second scan being taken along a plane rotated 90° with respect to the plane of the first scan. Upon completion of the second scan, a second profile is calculated by the processing unit and the true axis of the largest rectangle that can be superimposed within the measured dimensions of the block is again calculated. The processing unit then controls the movement of the charger arms set works to reorient the block along the second true axis. At that time, the clamping carriage again engages the ends of the block and the block charger arms are released and returned to their original position for handling the next block. The clamping carriage is at that time referenced to an index line so that the relative alignment of the block with respect to the index line is maintained. It should be noted that the second movement of the hydraulic set works does not disturb the relative positioning of the block along the first true centerline, since the first scanning plane is at right angles to the second scanning plane. Accordingly, the block is now positioned along an “optimum” center line for veneer processing.

The clamping carriage is adapted for movement, by suitable means to transfer the block from the index line to a veneer lathe of conventional rotary design, such as lathe 130. The block is then clamped in the veneer ⁴⁵ lathe along the optimum center line so that the block can be reduced to veneer with the alignment of the block permitting recovery of the maximum amount of veneer from the given block.

₅θ A tipple tray system 135 is provided at the outlet of ^υ the veneer lathe adapted to receive veneer sheets on a tray storage system. This enables the lathe to operate on an intermittent basis at relatively high rates of speed against one or more clippers, such as clippers 137. Each of the clippers is of conventional design and provides veneer cut into predetermined sheet widths to a veneer sorter, such as sorters 140, 141 via conveyors 143,144 respectively. The veneer is graded by the sorters and provided to an outlet platform for subsequent handling.

Referring now to FIG. 4, the profile of a typical block is shown in solid outline sumperimposed upon a grid that schematically represents the block scan grid. The widest rectangle that can be superimposed within the ₆₅ block profile is represented by a rectangle A and the center axis of rectangle A is represented by a line R. Line T1 represents the position of the reference axis of the block during scanning, and line T2 represents the

3,746,065 position of the reference axis after the block is repositioned in the clamping carriage arms. It should be apparent that the block is repositioned after scanning so that the true axis of the rectangle is parallel to the base of the scan grid, which is in turn parallel to the index line and occupies a known location relative to the veneer lathe. As illustrated, the repositioning results in movement of both ends of the block, and this causes both angular and lateral adjustment of the reference center line.

The repositioning of the block in the second instance is identical to that previously described. Thus, each block is aligned, prior to delivery into the carriage arms, along an axis which closely corresponds to the true geometric axis of the largest cylinder of usable wood that exists within the block. As a result, the subsequent processing of the block in the veneer lathe results in recovery of the maximum amount of wood that is usable for veneer. This results in significantly improved production rates and the elimination of any human judgment factor from the processing system.