Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
  • B23D59/00—Accessories specially designed for sawing machines or sawing devices
  • B23D59/008—Accessories specially designed for sawing machines or sawing devices comprising computers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27B—SAWS FOR WOOD OR SIMILAR MATERIAL; COMPONENTS OR ACCESSORIES THEREFOR
  • B27B31/00—Arrangements for conveying, loading, turning, adjusting, or discharging the log or timber, specially designed for saw mills or sawing machines
  • B27B31/06—Adjusting equipment, e.g. using optical projection

Definitions

• the present invention relates to a method for machine- working elongate pieces of timber, by which method blocks are produced which have a cross-section comprising two arcuate green surfaces facing in opposite directions and two worked planar sides which are substantially parallel and form, with said green surfaces, intersections ex ⁇ tending irregularly along the block.
• the blocks are moved longitudinally one by one along a reference plane extending through the block and being substantially parallel to the planar sides, the block passing through a measuring zone which extends transversely of said reference plane and in which cross-sectional dimensions of the block can be repeatedly measured, as the block is moving through said measuring zone, by means of a photoelectrically operating measuring system scanning said measuring zone.
• the invention also relates to a plant making use of the above-mentioned method and comprising means for longitudinally moving the blocks one by one along a reference plane which extends through the block and is substantially parallel to said planar sides, a measuring zone extending transversely of said re ⁇ ference plane, such that the moving block passes there- through, said plant comprising a photoelectrically operating measuring system adapted to scan said measur ⁇ ing zone and to repeatedly measure cross-sectional dimensions of the block, while this is being moved through said measuring zone.
• two side boards are usually sawn off, one on either side of the log, such that the piece of timber which is discharged from the edger and which is now termed block, is defined by two parallel planar sides which form intersections with the remaining arcuate green surfaces and from which one proceeds for further working of the block.
• the manner in which the timber is handled by the edger, and in which positions the planar sides are cut, there ⁇ fore is of the utmost importance to the timber yield.
• a rule of thumb for log infeed is to seek an orientation which results in a symmetrical position of the planar sides relative to the log centre plane, in which case - if the log has an ideal cylindrical shape - the planar sides will be congruent.
• Laying the cuts for the planar sides symmetrically along the log also usually means that the volume of the material which is separated in the form of the two side boards and which largely goes to waste, will then be minimal.
• Another fault encountered in edging work may be due to the fact that the block height, i.e. the distance between the planar sides, deviates from the dimension that must be maintained for cutting up the log in a correct manner.
• the present invention which is based upon the insight that one should be able to discover and cor ⁇ rect as soon as possible a fault which occurs in a plant for edging timber to blocks, aims at providing a method and a device for determining the geometry of pieces of timber which, in a sawmill machine ? are formed into blocks, and to use the geometrical block data thus obtained for supervising that the feeding of the pieces of timber into the machine and the sub ⁇ sequent machining will be effected in a correct manner.
• a special object of the invention is to check, on the basis of the measuring data of a block which is being discharged, or has been discharged, from an edger, if the two planar sides of the block de ⁇ viate in nonpermissible manner from predetermined positions and, if this is the case, to provide an indication to the sawmill workers that the edging operation in progress should be interrupted.
• Another aspect of the invention issues from the fact that, in order to optimise the cutting-up of pieces of timber, it is essential to know the configu ⁇ ration of the two planar sides of timber blocks.
• Fig. 1 is a diagram showing the underlying principle of a plant according to the invention
• Figs. 2-3 are respec ⁇ tively a side view and an end view of parts of the plant and a block conveyed edgewise therethrough
• Figs. 4-5 illustrate, in analogous manner, the corresponding parts of an embodiment in which the block is conveyed lying on its flat side.
• the plant illustrated in Fig. 1 is assumed to be a station in a sawmill in which timber is sawn into boards and other wood products.
• a primary operation in this machine work is the feeding of the timber into an edger in which the logs are conducted one by one past two parallel saw blades or cutting disks removing the outer log parts.
• the pieces of timber obtain the form of blocks which, depending upon the starting material, may have highly varying thickness but are essentially uniform in cross-section.
• B denotes a block cut from a thick log, while b may be assumed to represent the smallest block cross- section occurring in the plant. Regardless of the thick ⁇ ness, the cross-section of the blocks has two arcuate green surfaces 1 and 2 which face in opposite directions and are rough and irregular, especially if the saw timber is delivered unbarked.
• planar sides 3 and 4 represent the cuts which are obtained upon edging and which are called the planar sides in the following. If edging is carried out correctly, the planar sides are mutually parallel and approximately equally wide.
• the sawmill station which the plant according to the invention is intended to constitute may be located between the edger and a resaw (none of which is shown in the drawings), and in such cases the blocks B, b are longitudinally fed by a conveyor which, in Figs. 1-3, is generally designated 9 and on which the blocks arrive one by one.
• the station may be located within the working range of the edger, in which case the pieces of timber are supplied by the drive means of the sawing machine itself. In those instances where side boards are separated from the piece of timber, it is possible in this alternative, that such boards still adhere to the piece of timber on either side of the block when this is passing through the station, but this does not obstruct the operation in the station.
• a reference plane 10 is parallel to the planar sides 3, 4 of the blocks as these are being longitudinally fed on the conveyor 9. The direc ⁇ tion of this reference plane coincides with the con ⁇ veyor.
• a measuring zone 11 is provided which generally is a narrow area located at an angle to the conveying direction and the reference plane 10. The blocks are conducted through this area which contains two measuring planes 12, 13 directed such that their intersections with the reference plane 10 and thus with the sides 3, 4 will be perpendicular to the conveying direction. In Fig. 1, both measuring planes coincide with the plane of the drawing.
• the plant For measuring each block advanced through the measuring zone, the plant is equipped with a photo- electric measuring system comprising two cameras 14 and 15, each of which operates in one of the measuring planes 12, 13 and is directed toward the respective planar side of the block.
• the cameras which may be of the well-known type having an array of photodiodes and whose construction and mode of operation therefore need not be described in detail, each provide, in a rapid and repeated measuring sequence, an electro- nically readable linear image of the object which the camera at the moment is "seeing" within the area it is scanning (16 in Fig. 2).
• the measuring system images, at mutually close intervals, transversely locat- ed segments of the block as this is being advanced through said measuring zone.
• the measuring signals from the cameras are fed to an electronic unit 17 comprising a microcomputer and processing the measuring data repre ⁇ senting the said segments.
• an electronic unit 17 comprising a microcomputer and processing the measuring data repre ⁇ senting the said segments.
• Cooperating with the measuring system is a system of radiation sources adapted to irradiate, in a manner advantageous to the measuring, that part of the block which is in the measuring zone 11.
• the plant comprises two oppositely directed radiation sources 18 and 19 disposed on opposite sides of the conveyor 9 and so arranged that their radiation beams 20 and 21 fall along the reference plane 10, i.e. substantially parallel to the planar sides 3, 4 of the block. In this manner, the two green surfaces
• 1, 2 of the block in the measuring zone will be intense ⁇ ly irradiated and reflect light which is received by the cameras 14 and 15.
• the two planar sides will not be irradiated or but slightly irradiated by the radiation sources, for which reason the planar sides will reflect substantially only the weak light from the surroundings.
• the result is that the two green surfaces will appear in each camera in contrast to the planar side which is facing the camera, and this in turn will result in two positions within the scanned area 16 where the received radiation shows an intense decrease or increase, respectively, which is readily indicated by the electronic unit.
• Correspond ⁇ ing points naturally occur in the scanned area of the other camera, although in positions which here may be different, depending upon the irregular form of the edged log and any faults that may occur during the edging operation.
• the said four positions represent points on the intersecting lines 5-8 of green surfaces and planar sides.
• the plant also comprises means for indicating the positions of the two planar sides 3, 4 relative to the cameras 14, 15.
• these means are laser transmitters 22, 23, one for each camera and mounted such that their lobe directions fall from outside obliquely into the measuring zone and along the measuring planes 12, 13 of the respective camera.
• the beam lobes 24 from the laser transmitters are of narrow cross-section, for which reason each lobe projects a small light spot 25 when, as is best seen in Fig. 1, the radiation impinges upon a block that has entered the measuring zone.
• the light spots will impinge upon the essentially nonirradiated planar sides 3, 4 and therefore are easily detected by the cameras and electronics of the measuring system.
• the positions thus are an exact measure of the distance between the planar side in question and the focal plane F of the camera (see Figs. 3 and 5) where the photodiode array is located.
• the measuring system will thus have access to a combination of six positions in the camera arrays, a combination unique to the block segment which is being scanned, i.e. the four above-mentioned positions corresponding to the detected points on the intersections 5-8 and the two positions corresponding to the detected laser light spots 25.
• the electronic unit also is supplied with data indicating the position of the block in the measuring zone 11 the moment a measuring sequence is carried out. These data can be obtained on the basis of a pulse signal from a pulse transducer 26 coupled with the conveyor 9, and a photo cell signal generated when the leading end of the block intersects the mea- suring planes 12, 13.
• the measuring system has obtained all information required for making, in a triaxial coordi ⁇ nate system, a complete and accurate determination of the geometry of the two planar sides 3, 4 of the piece of timber.
• the neutral position of the planar sides has been determined, i.e. the measure of the block height can be readily established at different points along the block, and such measurements can be displayed block by block on a display unit 27 connected to the microcomputer or recorded centrally in a main computer 28.
• the geometrical determina ⁇ tion of the planar sides may be used as a basis for a check-up calculation showing the position in which the planar sides have been cut, and whether or not this is acceptable.
• the check-up calculation can be carried out in many different ways and preferably follows an algorithm which also may be implemented in the electronic unit.
• the values of the average width of the planar sides are used as a basis for determining the skewness that may have occurred during the edging operation, i.e. the possible lack of symmetry that can be established between the planar sides of a block and the original geometrical centre plane of the log, it being preferred first to compile values of the average width, calculated on different predetermined sections along the block length, whereupon the existing asymmetry is calculated section by section by means of experience values of the curvature of the log cross- sections and the compiled width values.
• the skewness values obtained are then related to the requirements valid which may be expressed in the form of limit values.
• the quotient between the average widths of the two planar sides is calculated, whereupon this quotient which may be regarded as a measure of the skewness, is compared block by block with a limit value.
• the said limit values therefore are selected such that they distinguish those deviations in the block form which affect the yield during the subsequent cutting-up.
• statistic analysis of the skewness values may show whether the equipment suffers from systematic faults, and whether its quality and status are changed.
• the coordinates obtained during measuring of the blocks may also be utilised for checking the block height, i.e. the distance between the planar sides, a . dimension which is of fundamental importance to the cutting-up of the block.
• the electronic unit in synchronism with the block transport through the measuring zone, calculates data showing how the requirements of accuracy that apply to the edging operation, are satisfied. These data can be indicated to an operator on the display unit 27.
• the electronic unit 17, can be made to give a warning signal when a predetermined tolerance value is exceeded.
• the warning signal is transmitted via a line 30 to a mains-supplied unit 31 which controls the current supply to the radiation sources and laser transmitters of the plant and which also releases an optical or acoustic alarm device 32 in response to the warning signal.
• the alarm function should not be released until the electronic system 12 indicates that the nonpermissible deviation was not accidental but occurs similarly for a succession of blocks, since it will be appreciated that the occur ⁇ rence of an occasional defect block may not be due 5 to malfunction of the equipment or skewing but, for example, to an abnormal geometrical log form.
• the conveyor 9 may comprise a driving chain 33 which is located in the reference plane 10 and is narrow in relation to the minimum block cross-section b in order not to prevent irra ⁇ diation of the outer parts of the lower green surface
• the conveyor also has a number of pressure rollers 34 which are held in engagement with the upper green surface 1 of the blocks and has a concave profile, as shown in Fig. 3, whereby said pressure rollers
• a sloping planar side causes the coordinate determination of its inter ⁇ sections 5, 7 or 6, 8 to be erroneous, and that these
• the radiation sources 18, 19 may consist of lamps arranged in pairs and provided each with one reflector to provide for adequate parallelism.
• the blocks are conveyed by means of belts or similar broad driv ⁇ ing means on which the blocks are advanced lying on one of their flat sides 3 so that the reference plane 10 will be horizontal.
• the conveyor is constructed in two units 37 and 38 mu ⁇ tually spaced apart in the conveying direction, such that the camera 39 and the laser transmitter 41 acting in the measuring plane 40 of the said camera may be ar- ranged underneath the conveyor, while the corresponding components 42, 43 for measuring the blocks from above may be arranged in a vertical measuring plane 44 which should intersect the reference plane 10 at the point where this is intersected by the lower measuring plane 40.
• a screen 45 should be provided to protect the two components 39 and 41 which are both sloping upwardly, against dust and similar soiling.
• a protective screen 46 should be provided in the embodiment according to
• the coordinate determina ⁇ tion of the blocks according to the present invention may also contribute to higher timber yields.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 1984
  • 1984-08-27 SE SE8404253A patent/SE447303B/sv not_active IP Right Cessation
• 1985
  • 1985-08-22 WO PCT/SE1985/000314 patent/WO1986001590A1/en not_active Application Discontinuation
  • 1985-08-22 EP EP19850904301 patent/EP0221903A1/de not_active Withdrawn
• 1986
  • 1986-09-24 FI FI863847A patent/FI863847A0/fi not_active Application Discontinuation

Non-Patent Citations (1)

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