METHOD AND APPARATUS FOR CLASSIFYING BATCHES OF WOOD CHIPS

Description

[0001] The present invention relates to classification of batches of wood chips or the like, and more particularly to a method and apparatus for classifying batches of wood chips according to light reflection characteristics.

[0002] In the past years, significant efforts have been devoted to develop processes for the production of pulp and paper products aimed at reducing manufacturing costs while improving product quality. Quality control of the raw materials entering in the production of pulp and paper products, particularly regarding wood chips used, has been identified as a key factor in process optimization.

[0003] A known approach to control quality of wood chips consists in treating wood chips at the manufacturing stage. Such an approach is employed in the wood chips manufacturing method disclosed in U.S. Patent 5,577,671 issued on Nov. 26, 1996 to Seppanen et al., which method consists of separating from ground whole-tree chips, bark and cellulose wood chips through a series of separation stages including pneumatic separation, vibration segregation with sieve and color difference sorting. Known method and apparatus for classifying articles according to their color is also disclosed in International PCT Application published under no. WO 94/25838 to Allaire et al. and naming the present Applicant as assignee, which relates more specifically to wood pieces classification. Although not suggested in that prior published application, such method and apparatus could be used as the colour-difference sorting device referred to in U.S. Patent 5,577,671 to Seppanen el al., to detect color of each chip for classification thereof in a specific class according to the color measured, i.e. low bark content, high bark content, in combination with a bark sorter such as the pneumatic separator as taught by Seppanen et al.. The resulting low bark, pale wood chips can be then processed using a minimum quantity of bleaching agent. Although processing cost can be minimized accordingly, added manufacturing cost due to bark separation step may still maintain overall production cost high.

[0004] Another known approach consists of sorting trees according to their types prior to wood chips manufacturing, to produce corresponding batches of wood chips presenting desired characteristics associated with these types. Typically, hardwood trees such as poplar, birch and maple are known to generally produce pale wood chips while conifers such as pine, fir and spruce are known to generally yield darker wood chips. In practice, wood chips batches can either be produced from trees of a same type or from a blend of wood chips made from trees of plural types; preferably of a common category, i.e., hardwood trees or conifers, to seek wood chips uniformity. However, chips characteristics basically depending on initial bark content of wood chips used, knowledge of the types of wood chips for a given batch does not necessarily give a reliable indication of the chips quality.

[0005] It is therefore an object of the present invention to provide a method and apparatus for classifying batches of wood chips or the like according to optical characteristics representative of chips quality or grade.

[0006] According to the above object, from a broad aspect of the present invention, there is provided a method for classifying batches of wood chips or the like according to light reflection characteristics according to claim 1, and a corresponding apparatus according to claim 9.

[0007] The method and apparatus according to the invention allow optimal use of darker wood chips in pulp and paper processes. Although hardwood wood chips generally require more bleaching agent when being processed, their cellulose fibers may exhibit better physical characteristics than fibers found in conifers for the purpose of producing products presenting particular structural characteristics. Therefore, mixing a relatively small batch of such darker wood chips with a large batch of pale wood chips can produce a blend presenting the quality required for optimal processing, provided the characteristics of the darker wood chips batch have been accurately determined, to adjust parameters of the process accordingly.

[0008] A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings in which:

Fig. 1 is a partially cross-sectional end view of a receiving hopper provided with a sampling screw feeding a conveyor transporting wood chips through an inspection station according to the preferred embodiment of the present invention;

Fig. 2 is a partially cross-sectional side view along section line 2-2 of the inspection station shown in Fig. 1 and being connected with a computer unit shown in block diagram and according to the preferred embodiment of the invention;

Fig. 3 is a partial cross-sectional end view along section line 3-3 of Fig. 2, showing the internal components of the inspecting station;

Fig. 4 is a graph showing the inverse relationship between moisture level and luminance level as measured on a sample of wood chips in term of drying time;

Fig. 5 is a graph showing a set of curves representing general relations between measured optical characteristics and dark wood chips contain associated with several samples; and

Fig. 6 is an example of a output data report and image displayed which can be obtained using the method and apparatus according to the present invention.

[0009] Referring now to Fig. 1, an apparatus according to the preferred embodiment of the present invention is generally designated at 10, which includes an inspection station 12 comprising an enclosure 14 through which extends a powered conveyor 15 coupled to a drive motor 18. The conveyor 15 is preferably of a trough type having a belt 13 defining a pair of opposed lateral extensible guards 16, 16'of a known design, for keeping the material to be inspected on the conveyor 15. Adjacent an input end 29 of the conveyor 15 is an hopper 21 for receiving at an upper inlet thereof (not shown) a batch 24 of material to be inspected for classification purposes, which material essentially consists of wood chips 26 in the example shown. However, it is to be understood that batches of other similar wooden materials could be advantageously classified in accordance with the present invention, such as flakes, shavings, slivers, splinters and shredded wood. Typically, the wood chips 26 may be caused to flow under gravity and discharged through a controlled outlet (not shown) provided at the bottom part of the upper 21 for further processing. Radially extending through a pair of opposed openings 22 receiving rotary bearings 17 provided on the peripheral wall 23 of the hopper 21 is a sampling device 19 having an elongated cylindrical sleeve 27 of a circular cross-section adapted to receive for rotation therein a feeding screw 28 of a known construction. The sleeve 27 has a lateral input opening 29 allowing wood chips 26 to cyclically reach an input portion of the screw 28 whenever the sleeve opening 29 passes through an upper position as shown in Fig. 1. The sleeve 27 further has one or more output openings 31 generally disposed over the conveyer input end 29 to allow substantially uniform discharge of the sampled wood chips 26 on the conveyer belt 13. The feeding screw 28 has a base disk 30 being coupled to the driven end of a driving shaft 32 extending from a drive motor 34 mounted on a support frame 36, which motor 34 imparts rotation to the screw 28 at a given RPM. The driving shaft 32 is provided with a small driving gear 38 cooperating with a large gear 40 and a small gear 42 mounted on first idle shaft 44 supported by base 36, to transmit driving couple at a lower RPM to a reversing gear 46 mounted on a second idle shaft 48 rotatably engaging a support member 50 rigidly secured to the outer surface of hopper 21. The sleeve 27 has a driven end 52 provided with an outer annular disk 54 having radially extending gear teeth cooperating with the reversing gear 46 to impart rotation to the sleeve in a direction opposed to clockwise rotation of screw 28 and at a lower RPM, as will be explained later in more detail.

[0010] Turning now to Figs. 2 and 3, internal components of the inspection station 12 will be now described. The enclosure 14 is formed of a lower part 56 for containing the conveyor 15 and being rigidly secured to a base 58 with bolt assemblies 57, and an upper part 60 for containing the optical components of the station 12 and being removably disposed on supporting flanges 62 rigidly secured to upper edge of the lower part 56 with bolted profile assemblies 64. At the folded ends of a pair of opposed inwardly extending flanged portions 66 and 66' of the upper part are secured through bolts 68 and 68' side walls 70 and 70' of a shield 72 further having top 74, front wall 76 and rear wall 76' to optically isolate the field of view 80 of a camera 82 for optically covering superficial wood chips 26' included in a representative portion of the inspected wood chips batch and being disposed within an inspection area. The camera 82 is located over the shield 72 and has an objective downwardly extending through an opening 84 provided on the shield top 74, as better shown in Fig. 2. Superficial wood chips 26' are distributed onto the conveyor belt 13 to present light reflection characteristics which are substantially representative of the wood chips 26 of the inspected batch. The camera 82 is used to sense light reflected on superficial wood chips 26' to produce electrical signals representing reflection intensity values for the superficial wood chips 26'. For the example described herein, although any appropriate monochrome camera could be used to provided detection of desired optical characteristics, a color RGB CCD video camera is preferably used to further provide color displaying capability for the operator. Diagonally disposed within shield 72 is a transparent glass sheet acting as a support for a calibrating reference support 88 as better shown in Fig. 3, whose function will be explained later in more detail. A shown in FIG. 2, the camera 82 is secured according to an appropriate vertical alignment on a central transverse member 90 supported at opposed end thereof to a pair of opposed vertical frame members 92 and 92' secured at lower ends thereof on flanged portions 66 and 66' as shown in Fig. 3. Also supported on the vertical frame members 92 and 92' are front and rear transverse members 94 and 94' . Transverse members 90, 94 and 94' are adapted to receive elongate electrical light units 96 which use standard fluorescent tubes 98 in the example shown, to direct light substantially evenly onto the inspected batch portion of superficial wood chips 26'. The camera 82 and light units 96 are powered via a dual output electrical power supply unit 98. Electrical image signal is generated by the camera 82 through output line 100. When used in cold environment, the enclosure 14 is preferably provided with a heating unit (not shown) to maintain the inner temperature at a level ensuring normal operation of the camera 82.

[0011] Referring to Fig. 2, an optional moisture sensing unit 78 is shown which is preferably disposed near the inspection station 12. The sensing unit 78 is used to inspect batches of material exhibiting variations in the moisture content, either between the batches or within any specific batch, which variations may affect reflectance characteristics of the superficial wood chips 26', thereby affecting reflection intensity values as measured by the camera 82. The moisture sensing unit 78 is preferably a non-contact sensing device such as the near-infrared sensor MM55plus supplied by NDC Infrared Engineering, Irwindale CA. The unit 78 generates at an output 79 thereof electrical signals representing average moisture values for the superficial wood chips 26'.

[0012] For example, while batches of wood chips stored in large containers before processing generally exhibit substantially uniform and stable moisture contents, chips batches stored in open sites may present moisture variations which may have a material effect on the reflectance measurements. In processes where high classification accuracy is required, consideration of the effect of moisture variations may be needed. Referring to Fig. 4, the overall inverse relationship between moisture level in percentage and luminance as periodically measured during drying of a sample of wood chips is illustrated, which relation may be roughly expressed by Δl ≈ -kΔm, wherein Δm represents any deviation in moisture value, Δl represents a corresponding variation in luminance value, k being a scale constant having a positive real value. It can be seen that chips showing an initial moisture content of 54 % as shown by curve M intersecting the left vertical axis, are roughly 27% brighter (passing from 54 to 68.5 in luminance as shown by curve L intersecting the right vertical axis) after their moisture was reduced to 26 % after drying. That shift in measured luminance may be compensated by normalizing the reflection intensity values according to corresponding moisture deviations from a predetermined reference moisture value, as will be later explained in more detail.

[0013] Control and processing elements of the apparatus 10 will be now described with reference to Fig. 2. The apparatus 10 further comprises a computer unit 102 having an image acquisition module 104 coupled to line 100 for receiving image electrical signals from the camera 82, which module 104 could be any appropriate RGB image data acquisition electronic card currently available on the marketplace. The computer 102 is provided with an external communication unit 103 being coupled for bi-directional communication through lines 106 and 106' to a conventional programmable logic controller (PLC) 107 for controlling operation of the sample screw drive 28 and conveyor drive 18 through lines 108 and 110 respectively according to a predetermined program. The PLC 107 receives from line 112 batch data entered via an input device 114 by an operator in charge of batch registration and dumping operations, as will be explained later in more detail. The input device 114 is connected through a further line 116 to an image processing and communication software module 118 outputting control data for PLC through line 119 while receiving acquired image data and PLC data through lines 120 and 122, respectively. The image processing and communication module 118 receives input data from a computer data input device 124, such as a computer keyboard, through an operator interface software module 126 and lines 128 and 130, while generating image output data toward a display device 132 through operator interface module 126 and lines 134 and 136. Where a moisture sensing unit 78 is provided, the module 118 also receives the moisture indicating electrical signals through a line 81.

[0014] Turning now to Fig. 5, general relations between measured optical characteristics and dark wood chips contain associated with several samples are illustrated by the curves traced on the graph shown, whose first axis 138 represents dark chips contain by weight percentage characterizing the sample, and whose second axis 140 represents corresponding optical response index measured. In the example shown, four curves 142,144,146, and 148 have been fitted on the basis of average optical response measurements for four (4) groups of wood chips samples prepared to respectively present four (4) distinct dark chips contains by weight percentage, namely 0 % (reference group), 5%, 10% and 20%. Measurements were made using a RGB color camera coupled to an image acquisition module connected with a computer, as described before. To obtain curves 142 and 146, luminance signal values derived from the RGB signals corresponding to all considered pixels were used to derive an optical response index which is indicative of the relative optical reflection characteristic of each sample. As to curve 142, mean optical response index was obtained according to the following ratio:

Wherein I is the optical response index, L_R is a mean luminance value associated with the reference samples and L_S is a mean luminance value based on all considered pixels associated with a given sample. Curve 146 was obtained through computer image processing to attenuate chip border shaded area which may not be representative of actual optical characteristics of the whole chip surface. To obtain curves 144 and 148, reflection intensity of red component of RGB signal was compared to a predetermined threshold to derive the optical response index according the following relation:

Wherein I is the optical response index, P_D is the number of pixels whose associated red component intensity is found to be lower than the predetermined ratio (therefore indicating a dark pixel) and P_T is the total number of pixels considered. As for curve 146, carve 148 was obtained through computer image processing to attenuate chip border shaded areas. It can be seen from all curves 142, 144, 146, and 148 that the optical response index grows as dark chip contains increases. Although curve 148 shows the best linear relationship, experience has shown that all of the above described calculation methods for the optical response index can be applied, provided reference reflection intensity data are properly determined, as will be explained later in more detail.

[0015] Returning now to Figs. 1, 2 and 5, operation of the method and apparatus according to the preferred embodiment of the present invention will be now explained. Referring to Fig. 2, before starting operation, the apparatus 10 must be initialized through the operator interface module 126 by firstly setting system configuration. Camera related parameters can be then set through the image processing and communication module 118, according to the camera specifications. The initialization is completed by camera and image processing calibration through the operator interface module 126.

[0016] System configuration provides initialization of parameters such as data storage allocation, image data rates, communication between computer unit 102 and PLC 107, data file management, wood type identification and corresponding reference threshold levels setting. As to data storage allocation, images and related data can be selectively stored on a local memory support or any shared memory device available on a network to which the computer unit 102 is connected. Directory structure is provided for software modules, system status message file, current accepted batch data, current rejected batch data and recorded rejected batch data. Image rate data configuration allows to select total number of acquired images for each batch, number of images to be stored amongst the acquired images and acquisition rate, i.e. period of time between acquisition of two successive images. Therefore, to limit computer memory requirements, while a high number of images can be acquired for statistical purposes, only a part of these images, particularly regarding rejected batches, need to be stored. The PLC configuration relates to parameters governing communication between computer unit 102 and PLC 107, such as master-slave protocol setting (ex. DDE), memory addresses for a) batch data input synchronization for batch presence checking following dumping information; b) alarm set for indicating a rejected batch; and c) «heart beat» for indication of system interruption, «heart beat» rate and batch presence monitoring rate. Data file management configuration relates to parameters regarding batch input data, statistical data for inspected batches, data keeping period before deletion for acceptable batch and data keeping checking rate. Statistical data file can typically contain information relating to batch number, supplier contract number, wood type, mean intensity values for Red, Green and Blue (RGB) signals, mean luminance, date of acquisition, batch status (acceptable or rejected). Data being systematically updated on a cumulative basis, the statistical data file can be either deleted or recorded as desired by the operator to allow acquisition of new data.

[0017] All desired wood types can be identified as well as associated reference threshold levels used as reference reflectance intensity data. For a given wood type, based on initial visual inspection by the operator of optical characteristics presented by several representative samples for that particular wood type, the operator sets a low threshold value under which an inspected batch shall be rejected as containing an unacceptable amount of dark chips for that type of wood. It is to be understood that batch containing chips blend of known wood types can be characterized in a same way. In addition to visual inspection, process parameters such as required quantity of bleaching agent, processing time or spent energy measured for prior inspected batches can be recorded to find out low threshold value associated with minimum processing yield required to qualify a batch acceptable. Preferably, reference reflection intensity data may include range threshold data delimiting a plurality of wood chips grades. In that case, the operator may also set a maximum threshold value above which an inspected batch could be considered more than acceptable for that particular grade, ex. grade 1, and therefore could be classified in a higher quality grade of wood chips, ex. grade 2. The current levels setting for a current batch can be modified, stored or deleted as desired by the operator. It is to be understood that specific values given to the classification thresholds are also dependent upon calibration performed. Once the camera 82 is being configured as specified, calibration of the camera and the image processing module can be carried out by the operator through the operator interface, to ensure substantially stable light reflection intensities measurements as a function of time even with undesired lightning variation due to temperature variation and/or light source aging, and to account for spatial irregularities inherent to CCD's forming the camera sensors. Calibration procedure first consists of acquiring « dark » image signals while obstructing with a cap the objective of the camera 82 for the purpose of providing offset calibration, and acquiring « lighting » image signals with a gray target presenting uniform reflection characteristics being disposed within the inspecting area on the conveyer belt 13 for the purpose of providing spatial calibration. Calibration procedure then follows by acquiring image signals with an absolute reference color target, such as a color chart supplied by Macbeth Inc., to permanently obtain a same measured intensity for substantially identically colored wood chips, while providing appropriate RGB balance for reliable color reproduction. Initial calibration ends with acquiring image signals with a relative reference color target permanently disposed on the calibrating reference support 88, to provide an initial calibration setting which account for current optical condition under which the camera 82 is required to operate. Such initial calibration setting will be used to perform calibration update during operation, as will be later explained in more detail.

[0018] Where a moisture sensing unit 78 is provided, further calibration steps are carried out, using a chips sample which is subjected to a progressive drying process according to an experimental moisture range that is representative of the actual moisture range, to derive a reference moisture curve through standard measurement in laboratory, such as the curve M shown in Fig. 4. The moisture curve is then compared with a reference moisture curve obtained with the sensing unit 78, allowing an initial calibration thereof. While the chips sample is being dried, luminance values are also measured to derive a luminance curve associated with the obtained moisture curve, such as curve L shown in Fig.4. Then, luminance compensation values to be used for the normalization to the predetermined reference moisture value can be obtained through the relation Δl ≈ -kΔm , with Δm = m_c - m_r, wherein m_c is a current moisture value as measured by the unit 78 and m, is the predetermined reference moisture value.

[0019] Initialization procedure being completed, the apparatus 10 is ready to operate, the computer unit 102 being in permanent communication with the PLC 107 to monitor the operation of the screw drive 28 indicating the presence of a new batch to be inspected. Whenever a new batch is detected, the following sequence of steps are performed: 1) end of PLC monitoring; 2) batch data file reading (type of wood chips, batch identification number); 3) image acquisition and processing for wood chips batch classification according to the set threshold values; and 4) data and image recording after batch inspection.

[0020] Image acquisition consists in sensing light reflected on the superficial wood chips 26' included in the present batch portion to produce electrical signals representing reflection intensity values for the superficial wood chips 26', forming an image thereof. Although a single batch portion of superficial chips covered by camera field of view 80 may be considered to be representative of optical characteristics of a substantially homogeneous batch, wood chips batches being known to be generally heterogeneous, it is preferable to consider a plurality of batch portions by acquiring a plurality of corresponding image frames of electrical pixel signals. In that case, image acquisition step is repeatedly performed as the superficial wood chips of batch portions are successively transported through the inspection area defined by the camera field of view 80. Where a moisture sensing unit 78 is provided, superficial wood chips 26' are scanned by infrared beam generated by the unit 78 which analyze reflected radiation to generate the moisture indication signals. It is to be understood that while the moisture sensing unit 78 is disposed at the output of the inspection station 12 in the illustrated embodiment, other locations downstream or upstream to the inspection station 12 may be suitable.

[0021] As to image processing, the image processing and communication unit 118 is used to derive from the acquired pixel signals global reflection intensity data for the inspected batch, designated before as optical response index with reference to Fig. 5. Calibration updating of the acquired pixel signals is performed considering pixels signals corresponding to the relative reference target as compared with the initial calibration setting, to account for any change affecting current optical condition. Then, image noise due to chip border shaded areas, snow and/or ice and visible belt areas are preferably filtered out of the image signals using known image processing techniques. Where a moisture sensing unit 78 is provided, the image processing and communication unit 118 applies compensation to the acquired pixel signals using the corresponding moisture indicating electrical signals.

[0022] Global reflection intensity data may then be derived by averaging reflection intensity values represented by either all or representative ones of the acquired pixel signals for the batch portions considered, to obtain mean reflection intensity data. Alternately, the global reflection intensity data may be derived by computing a ratio between the number of pixel signals representing reflection intensity values above a predetermined threshold value and the total number of pixel signals considered. Any other appropriate derivation method known in the art could be used to obtain the global reflection intensity data from the acquired signals. Optionally, the global reflection intensity data may include standard deviation data, obtained through well known statistical methods, variation of which may be monitored to detect any abnormal heterogeneity associated with an inspected batch.

[0023] As to wood chips batch classification, the image processing and communication unit 118 compares the global reflection intensity data to reference reflection intensity data including range thresholds, to provide classification of the inspected wood chips batch into a proper wood chip grade according its light reflection characteristics. As mentioned before, reference reflection intensity data may comprise threshold data respectively corresponding to a plurality of wood chip types. In that case, batch data input device 114 sends to the image processing and communication an electrical signal indicating a specific one of wood types to which the wood chips of the current inspected batch correspond, and classification is performed by comparing the global reflection intensity data to the reference reflection intensity data corresponding to the specific wood chips type accordingly. Alternately, input device 114 can be in the form of an automated reading device capable of detecting machine readable code associated with the inspected batch, the code representing the corresponding one of chips wood type. In a case where the inspected batch is classified as being acceptable for a given grade, the computer unit 102 resumes PLC monitoring for a next batch to be inspected. Otherwise, whenever an unacceptable batch is detected and therefore rejected, the computer unit causes an alarm to be set by the PLC before resuming PLC monitoring. In operation, the computer unit 102 continuously sends a normal status signal in the form of a «heart beat» to the PLC through line 106'. The computer unit 102 also permanently monitors system operation in order to detect any software and/or hardware based error which could arise to command inspection interruption accordingly. Preferably, to save computer memory, the computer unit 102 does not keep all acquired images, so that after a predetermined period of time, images of acceptable inspected batches are deleted while images of rejected batches are recorded for later use. The image processing and communication module 118 performs system status monitoring functions such as automatic interruption conditions, communication with PLC, batch image data file management, dumping monitoring and monitoring status. These functions result in messages generation addressed to the operator through display 132 whenever appropriate action of the operator is required. For automatic interruption conditions, such a message may indicate that video (imaging) memory initialization failed, an illumination problem arose or a problem occurred with the camera 82 or the acquisition card. For PLC communication, the message may indicate a failure to establish communication with PLC 107, a faulty communication interruption, communication of a «heart beat» to the PLC 107, starting or interruption of the «heart beat». As to batch data files management, the message may set forth that acquisition initialization failed, memory storing of image or data failed, a file transfer error occurred, monitoring of recorded is being started or ended. As to chips dumping monitoring, the message may alert the operator that batch data has not been properly read, dumping monitoring being started or ended. Finally, general operation status information is given to the operator through messages indicating that the apparatus is ready to operate, acquisition has started, acquisition is in progress, image acquisition is completed and alarm for rejected batch occurred.

[0024] Referring now to Fig. 6, a typical data output report which can be obtained using the above described method and apparatus is illustrated, which reports presents statistics associated with a selected wood chips image shown, as well as statistics related to the corresponding batch of gray pine wood chips. It can be seen from image statistics shown that although status of the current image indicates that it has been rejected with a mean intensity value of 48 as compared to a low threshold value set to 50, the corresponding cumulative batch data in turn indicate with a mean intensity of 52 that the batch as whole is qualified as acceptable for grade 1, while being not qualified as grade 2 for being lower than the high threshold set to 70.

Claims

1. A method for classifying batches of wood chips according to light reflection characteristics comprising the steps of:

a) directing light onto an area of wood chips (26') included in at least a portion of an inspected one (24) of said wood chips batches, said illuminated wood chips (26') presenting light reflection characteristics being substantially representative of the wood chips of the inspected batch (24);

b) sensing light reflected from the illuminated area of wood chips (26') included in said batch portion to produce electrical signals representing reflection intensity values for the illuminated wood chips (26') included in said batch portion;
   wherein said method is characterized by further comprising the steps of:

c) measuring moisture of said illuminated wood chips (26') to produce second electrical signals representing average moisture values for the illuminated wood chips included in said batch portion;

d) deriving from said first and second electrical signals global reflection intensity data characterizing the inspected batch (24) of wood chips, said global reflection intensity data being normalized according to a predetermined moisture reference value; and

e) comparing the global reflection intensity data with reference reflection intensity data to provide classification of said inspected batch (24) of wood chips according its light reflection characteristics.

2. A method according to claim 1, wherein said reference reflection intensity data include range threshold data delimiting a plurality of wood chips grades to provide said classification accordingly.

3. A method according to claim 1, wherein said reference reflection intensity data correspond to a plurality of wood chip types, said method further comprising between said steps d) and e) a step of: i) providing an electrical signal indicating a specific one of said types to which said wood chips corresponds and wherein said step e) is performed by comparing said global reflection intensity data to said reference reflection intensity data corresponding to said specific one of said wood chips types.

4. A method according to claim 1, wherein said global reflection intensity data include mean reflection intensity data derived by averaging said reflection intensity values, wherein said global reflection intensity data preferably further include standard deviation reflection intensity data derived from said reflection intensity values.

5. A method according to claim 4, wherein said reflection intensities values are being calibrated and filtered prior to be used for deriving said global reflection intensity data.

6. A method according to claim 1, wherein said global reflection intensity data are derived by computing a ratio between a number of said electrical signals representing reflection intensity values above a predetermined threshold value and a total number of said electrical signals.

7. A method according to claim 1, wherein there being a plurality of said representative batch portions including illuminated wood chips (26'), said steps a), b) and c) being repeatedly performed for said batch portions prior to derive said global refection intensity data at said step d), wherein preferably said steps a), b) and c) are repeatedly performed for said batch portions including illuminated wood chips (26') are successively transported through an inspection area.

8. A method according to claim 7, wherein said batch portions including illuminated wood chips (26') are successively sampled from said inspected batch prior to being transported through said inspection area.

9. An apparatus (10) for classifying batches of wood chips according to light reflection characteristics comprising:

illumination means (96) for directing light onto an area of wood chips (26') included in at least a portion of an inspected one (24) of said wood chips batches, said illuminated wood chips (26') presenting light reflection characteristics being substantially representative of the wood chips of the inspected batch (24);

image creating means (82) for sensing light reflected from the illuminated wood chips (26') included in said batch portion to produce first electrical signals representing reflection intensity values for the wood chips included in said batch portion;

   wherein said apparatus is characterized by further comprising:

moisture detector means (78) for producing second electrical signals representing average moisture values for the illuminated wood chips (26') included in said batch portion;

means (118) for deriving from said first and second electrical signals global reflection intensity data for the inspected batch (24), said global reflection intensity data being normalized according to a predetermined moisture reference value; and

means (118) for comparing the global reflection intensity data with reference reflection intensity data to provide classification of said inspected batch (24) of wood chips according its light reflection characteristics.

10. An apparatus according to claim 9, wherein said reference reflection intensity data include range threshold data delimiting a plurality of wood chips grades to provide said classification accordingly.

11. An apparatus according to claim 10, further comprising an operator interfacing unit (126) provided with display means (132) for reproducing created image from said image electrical signals, said unit (126) being provided with data entry means (124) allowing an operator to adjust said range threshold data corresponding to said plurality of wood chips grades for the purpose of said classification.

12. An apparatus according to claim 9, wherein said reference reflection intensity data comprise data respectively corresponding to a plurality of wood chip types, said apparatus further comprising means (114) for generating an electrical signal indicating a specific one of said types to which said wood chips correspond, said data comparing means (118) using said reference reflection intensity data corresponding to said specific one of said wood chips types to provide said classification.

13. An apparatus according to claim 12, wherein said electrical signal generating means (114) include a data input device allowing an operator to select said specific one of said types of wood chips corresponding to said inspected batch (24) and/or include an automated reading device capable of detecting machine readable code associated with said inspected batch, said code representing said specific one of said types of wood chips corresponding to the inspected batch (24).

14. An apparatus according to claim 9, wherein said global reflection intensity data include mean reflection intensity data, said deriving means (118) averaging said reflection intensity values to produce said mean reflection intensity data and preferably further include standard deviation generated by said deriving means (118) from said reflection intensity values.

15. An apparatus according to claim 14, wherein said deriving means (118) calibrate and filter said reflection intensity values to be used for deriving said global reflection intensity data.

16. An apparatus according to claim 9, wherein electrical signals deriving means (118) compute a ratio between a number of said electrical signals representing reflection intensity values above a predetermined threshold value and a total number of said electrical signals to produce said global reflection intensity data.

17. An apparatus according to claim 9, further comprising conveyor means (15) for transporting said batch portion of wood chips through an inspection area associated with said illumination means (96) and said image creating means (82).

18. An apparatus according to claim 17, wherein there being a plurality of said representative batch portions including illuminated wood chips (26'), said illumination means (96) repeatedly directing light onto respective wood chips of said batch portions while said image creating means (82) repeatedly sense light reflected on the illuminated wood chips (26') of said batch portions to produce said image electrical signals representing reflection intensity values for the wood chips of said batch portions.

19. An apparatus according to claim 18, further comprising hopper means (21) for receiving said inspected wood chips batch (24) and means (19) coupled to said hopper means (21) for successively sampling said inspected batch portions prior to being transported through said inspection area.

20. An apparatus according to claim 9, wherein said detector means (78) comprises an infrared detector.

Ansprüche

1. Verfahren zur Klassifizierung von Chargen von Holzschnitzeln gemäß ihrer Lichtreflektionseigenschaften mit den Schritten:

a) Lenken von Licht auf einen Bereich von Holzschnitzeln (26'), die in wenigstens einem Abschnitt einer inspizierten Charge (24) der Holzschnitzelchargen enthalten ist, wobei die beleuchteten Holzschnitzel (26') Lichtreflektionseigenschaften besitzen, die im Wesentlichen repräsentativ für die Holzschnitzel der inspizierten Charge (24) sind;

b) Empfangen des von dem beleuchteten Bereich der Holzschnitzel (26') reflektierten Lichts, welche Holzschnitzel in dem Chargenabschnitt enthalten sind, zur Erzeugung elektrischer Signale, die Reflektionsintensitätswerte für die beleuchteten Holzschnitzel (26') in dem Chargenabschnitt repräsentieren;
wobei das Verfahren gekennzeichnet ist durch die weiteren Schritte:

c) Messen der Feuchtigkeit der beleuchteten Holzschnitzel (26') zur Erzeugung zweiter elektrischer Signale, die einen Durchschnittsfeuchtigkeitswert für die beleuchteten Holzschnitzel in dem Chargenabschnitt repräsentieren;

d) Ableiten von Gesamtreflektionsdaten, die die inspizierte Charge (24) von Holzschnitzeln kennzeichnen, aus den ersten und zweiten elektrischen Signalen, wobei die Gesamtreflektionsintensitätsdaten gemäß eines vorbestimmten Feuchtigkeitsreferenzwerts normiert werden; und

e) Vergleichen der Gesamtreflektionsintensitätsdaten mit Referenzreflektionsintensitätsdaten, um eine Klassifikation der inspizierten Charge (24) an Holzschnitzeln gemäß ihrer Lichtreflektionseigenschaften zu erhalten.

2. Verfahren nach Anspruch 1, wobei die Referenzreflektionsintensitätsdaten Bereichspeicherdaten umfassen, die eine Mehrzahl von Holzschnitzelgraden abgrenzen, um demgemäß die Klassifikation zu erhalten.

3. Verfahren nach Anspruch 1, wobei die Referenzreflektionsintensitätsdaten mit einer Vielzahl von Holzschnitzelarten korrespondieren, wobei das Verfahren ferner zwischen den Schritten d) und e) einen Schritt aufweist: i) Bereitstellen eines elektrischen Signals, das eine bestimmte dieser Arten anzeigt, der die Holzschnitzel entsprechen, und wobei Schritt e) durch Vergleichen der Gesamtreflektionsintensitätsdaten mit den Referenzreflektionsintensitätsdaten durchgeführt wird, die der bestimmten einen der Holzschnitzelarten entspricht.

4. Verfahren nach Anspruch 1, wobei die Gesamtreflektionsintensitätsdaten durchschnittliche Reflektionsintensitätsdaten umfassen, die durch Mitteln der Reflektionsintensitätswerte gewonnen sind, wobei die Gesamtreflektionsintensitätsdaten vorzugsweise ferner eine Standardabweichung der Reflektionsintensitätsdaten umfassen, die von den Reflektionsintensitätswerten abgeleitet sind.

5. Verfahren nach Anspruch 4, wobei die Reflektionsintensitätswerte kalibriert und gefiltert werden, bevor sie zur Ableitung der gesamten Reflektionsintensitätsdaten verwendet werden.

6. Verfahren nach Anspruch 1, wobei die Gesamtreflektionsintensitätsdaten durch Berechnung eines Verhältnisses zwischen der Anzahl der elektrischen Signale über einem vorbestimmten Speicherwert, welche Signale der Reflektionsintensitätswerte darstellen, und einer Gesamtzahl an elektrischen Signalen abgeleitet werden.

7. Verfahren nach Anspruch 1, wobei es eine Vielzahl der repräsentativen Chargenabschnitte gibt, die beleuchtete Holzschnitzel (26') umfassen, und wobei die Schritte a), b) und c) für die Chargenabschnitte wiederholt durchgeführt werden, bevor die Gesamtreflektionsintensitätsdaten in Schritt d) abgeleitet werden, wobei vorzugsweise die Schritte a), b) und c) wiederholt für die Chargenabschnitte, die die beleuchteten Holzschnitzel (26') umfassen, durchgeführt werden und sukzessive durch einen Inspektionsbereich transportiert werden.

8. Verfahren nach Anspruch 7, wobei für die Chargenabschnitte mit beleuchteten Holzschnitzeln (26') von der inspizierten Charge nacheinander Proben genommen werden, bevor die Charge durch den Inspektionsbereich transportiert wird.

9. Vorrichtung (10) zur Klassifizierung von Chargen an Holzschnitzeln gemäß Lichtreflektionseigenschaften mit:

Beleuchtungsmittel (96) zum Richten von Licht auf einen Bereich von Holzschnitzeln (26'), die in wenigstens einem Abschnitt einer inspizierten Charge (24) von Holzschnitzelchargen umfasst ist, wobei die beleuchteten Holzschnitzel (26') Lichtreflektionseigenschaften präsentieren, die im Wesentlichen repräsentativ für die Holzschnitzel der inspizierten Charge (24) sind;

Bilderzeugungsmittel (82) zum Empfangen von Licht, das von den beleuchteten Holzschnitzeln (26') in dem Chargenabschnitt zur Erzeugung elektrischer Signale reflektiert wird, die Reflektionsintensitätswerte für die Holzschnitzel in dem Chargenabschnitt präsentieren;

wobei die Vorrichtung ferner gekennzeichnet ist durch:

Feuchtigkeitsdetektionsmittel (78) zur Erzeugung zweiter elektrischer Signale, die Durchschnittsfeuchtigkeitswerte für die beleuchteten Holzschnitzel (26') in dem Chargenabschnitt repräsentieren;

Mittel (118) zum Ableiten von Gesamtreflektionsintensitätsdaten für die inspizierte Charge (24) aus den ersten und zweiten elektrischen Signalen, wobei die Gesamtreflektionsintensitätsdaten gemäß einem vorbestimmten Feuchtigkeitsreferenzwert normiert werden; und

Vergleichsmittel (118) zum Vergleichen der Gesamtreflektionsintensitätsdaten mit Referenzreflektionsintensitätsdaten zum Erhalt einer Klassifikation der inspizierten Chargen (24) an Holzschnitzeln nach ihren Lichtreflektionseigenschaften.

10. Vorrichtung nach Anspruch 9, wobei die Referenzreflektionsintensitätsdaten Bereichsspeicherdaten umfassen, die eine Mehrzahl von Holzschnitzelgraden zur Bereitstellung der Klassifikation demgemäß abgrenzen.

11. Vorrichtung nach Anspruch 10, wobei die Vorrichtung ferner eine Bedienerinterfaceeinheit (126) aufweist, die mit Anzeigemitteln (132) zur Wiedergabe eines von den elektrischen Bildsignalen erzeugten Bilds versehen ist, wobei die Bedienerinterfaceeinheit (126) mit Dateneingabemitteln (124) versehen ist, die es einem Bediener ermöglichen, die Bereichsspeicherdaten entsprechend einer Vielzahl von Holzschnitzelgraden für die Zwecke der Klassifikation anzupassen.

12. Vorrichtung nach Anspruch 9, wobei die Referenzreflektionsintensitätsdaten Daten umfassen, die jeweils einer Mehrzahl von Holzschnitzelarten entsprechen, wobei die Vorrichtung ferner Mittel (114) zur Erzeugung eines elektrischen Signals umfasst, das eine bestimmte Art der Arten anzeigt, die den Holzschnitzeln entsprechen, wobei die Datenvergleichsmittel (118) die Referenzreflektionsintensitätsdaten, die einer bestimmten Art der Holzschnitzelarten entsprechen, zur Bereitstellung der Klassifikation verwenden.

13. Vorrichtung nach Anspruch 12, wobei die Mittel (114) zur Erzeugung elektrischer Signale eine Dateneingabeeinrichtung umfassen, die es einem Bediener ermöglicht, die bestimmte Art der Arten an Holzschnitzeln auszuwählen, die der inspizierten Charge (24) entspricht und/oder eine selbsttätige Lesevorrichtung umfassen, die in der Lage ist, einen maschinenlesbaren Code zu detektieren, der der inspizierten Charge zugeordnet ist, wobei der Code die spezifische Art der Arten an Holzschnitzeln entsprechend der inspizierten Charge (24) repräsentiert.

14. Vorrichtung nach Anspruch 9, wobei die Gesamtreflektionsintensitätsdaten durchschnittliche Reflektionsintensitätsdaten umfassen, wobei Ableitemittel (118) zur Mittlung der Reflektionsintensitätswerte zur Erzeugung der mittleren Reflektionsintensitätsdaten vorgesehen sind, und vorzugsweise ferner Standardabweichungen umfassen, die von den Ableitemitteln (118) aus den Reflektionsintensitätswerten erzeugt sind.

15. Vorrichtung nach Anspruch 14, wobei die Ableitemittel (118) die für die Ableitung der Gesamtreflektionsintensitätsdaten zu verwendenden Reflektionsintensitätswerte kalibrieren und filtern.

16. Vorrichtung nach Anspruch 9, wobei Ableitemittel (118) zur Ableitung elektrischer Signale ein Verhältnis zwischen einer Anzahl von elektrischen Signalen über einem vorbestimmten Speicherwert, welche Signale Reflektionsintensitätswerte repräsentieren, und einer Gesamtzahl an elektrischen Signalen zur Erzeugung der Gesamtreflektionsintensitätsdaten berechnen.

17. Vorrichtung nach Anspruch 9, wobei die Vorrichtung ferner Fördermittel (15) zum Transport der Chargenabschnitte an Holzschnitzeln durch einen Inspektionsbereich aufweisen, der den Beleuchtungsmitteln (96) und den Bilderzeugungsmitteln (82) zugeordnet ist.

18. Vorrichtung nach Anspruch 17, wobei bei einer Vielzahl von repräsentativen Chargenabschnitten mit beleuchteten Holzschnitzeln (26') die Beleuchtungsmittel (96) wiederholt Licht auf die jeweiligen Holzschnitzel der Chargenabschnitte richten, während die Bilderzeugungsmittel wiederholt Licht empfangen, das an den beleuchteten Holzschnitzeln (26') der Chargenabschnitte reflektiert wird, um die elektrischen Bildsignale zu erzeugen, die die Reflektionsintensitätswerte für die Holzschnitzel der Chargenabschnitte repäsentieren.

19. Vorrichtung nach Anspruch 18, wobei die Vorrichtung ferner Trichtermittel (21) zur Aufnahme der inspizierten Holzschnitzelcharge (24) und Mittel (19) aufweist, die an die Trichtermittel (21) zur sukzessiven Entnahme von Proben der inspizierten Chargenabschnitte gekuppelt sind, bevor die Abschnitte durch den Inspektionsbereich transportiert werden.

20. Vorrichtung nach Anspruch 9, wobei die Detektionsmittel (78) einen Infrarotdetektor umfassen.

Revendications

1. Méthode pour classifier des lots de copeaux de bois selon les caractéristiques de réflexion de lumière comprenant les étapes consistant à :

a) diriger la lumière sur une zone des copeaux de bois (26') se trouvant dans au moins une partie d'une zone inspectée (24) des lots de copeaux de bois, ces copeaux de bois illuminés (26') présentant des caractéristiques de réflexion de la lumière étant sensiblement représentatives des copeaux de bois du lot inspecté (24) ;

b) capter la lumière réfléchie depuis la zone illuminée des copeaux de bois (26') compris dans la portion de copeaux pour produire des signaux électriques représentant les valeurs d'intensité réfléchies des copeaux de bois illuminés (26') comprises dans cette partie du lot ;
cette méthode étant caractérisée en outre en ce qu'elle comprend les étapes consistant à :

c) mesurer l'humidité des copeaux de bois illuminés (26') pour produire des deuxièmes signaux électriques représentant des valeurs d'humidité moyenne des copeaux de bois illuminés compris dans la partie du lot ;

d) dériver depuis les premiers et deuxièmes signaux électriques des données d'intensité de réflexion globale caractérisant le lot inspecté (24) de copeaux de bois, ces données d'intensité de réflexion globale étant normalisées en fonction des valeurs de référence d'humidité prédéterminées ;

e) comparer les données d'intensité de réflexion globale avec les données d'intensité de réflexion de référence pour obtenir la classification du lot inspecté (24) de copeaux de bois selon ses caractéristiques de réflexion de la lumière.

2. Méthode selon la revendication 1, dans laquelle les données d'intensité de réflexion de référence comprennent des données à gamme de seuil délimitant une pluralité de qualité de copeaux de bois pour obtenir la classification en conséquence.

3. Méthode selon la revendication 1, dans laquelle les données d'intensité de réflexion de référence correspondent à une pluralité de types de copeaux de bois, cette méthode comprenant en outre entre les étapes d) et e) une étape consistant à : i) fournir un signal électrique spécifique de l'un de ces types auxquels les copeaux de bois correspondent et dans lequel l'étape e) est réalisée en comparant les données d'intensité de réflexion globale aux données d'intensité de réflexion de référence correspondant au type spécifique des types de copeaux de bois.

4. Méthode selon la revendication 1, dans laquelle les données d'intensité de réflexion globale comprennent des données d'intensité de réflexion moyenne dérivées en faisant la moyenne des valeurs d'intensité de réflexion, dans laquelle les données d'intensité de réflexion globale comprennent de préférence et en plus des données d'intensité de réflexion de déviation standard dérivées des valeurs d'intensité de réflexion.

5. Méthode selon la revendication 4, dans laquelle les valeurs d'intensités de réflexion ont été calibrées et filtrées avant d'être utilisées pour en dériver les données d'intensité de réflexion globale.

6. Méthode selon la revendication 1, dans laquelle les données d'intensité de réflexion globale sont dérivées en calculant un rapport entre un nombre des signaux électriques représentant les valeurs d'intensité de réflexion au-dessus d'une valeur de seuil pré-déterminée et un nombre total des signaux électriques.

7. Méthode selon la revendication 1, dans laquelle il y a une pluralité de portions de lot représentatives comprenant les copeaux de bois illuminés (26'), les étapes a), b), et c) étant répétées pour les portions de lot avant d'en dériver les données d'intensité de réflexion globale à l'étape d), dans laquelle de préférence les étapes a), b) et c) sont répétées pour les portions du lot comprenant les copeaux illuminés (26') successivement transportées à travers une zone d'inspection.

8. Méthode selon la revendication 7, dans laquelle les parties de lot comprenant les copeaux de bois illuminés (26') sont successivement échantillonnées à partir du lot inspecté avant d'être transportées à travers la zone d'inspection.

9. Appareil (10) pour classifier des lots de copeaux de bois selon des caractéristiques de réflexion de la lumière comprenant :

des moyens d'illumination (96) pour diriger la lumière sur une zone des copeaux de bois (26') compris dans au moins une portion d'un lot inspecté (24) des lots de copeaux de bois, les copeaux de bois illuminés (26') présentant des caractéristiques de réflexion de la lumière étant sensiblement représentatives des copeaux de bois du lot inspecté (24) ;

des moyens de création d'image (82) pour capter la lumière réfléchie depuis les copeaux de bois illuminés (26') compris dans la partie de lot pour produire des premiers signaux électriques représentant des valeurs d'intensité de réflexion pour des copeaux de bois compris dans la partie du lot ;

cet appareil est caractérisé en ce qu'il comprend en outre :

des moyens de détection de l'humidité (78) pour produire des deuxièmes signaux électriques représentant des valeurs moyennes d'humidité des copeaux de bois illuminés (26') compris dans cette partie du lot ;

des moyens (118) pour dériver depuis les premiers et deuxièmes signaux électriques des données d'intensité de réflexion globale pour le lot inspecté (24), les données d'intensité de réflexion globale étant normalisées selon une valeur de référence d'humidité pré-déterminée ; et

des moyens (118) pour comparer les données d'intensité de réflexion globale avec les données d'intensité de réflexion de référence pour fournir la classification du lot inspecté (24) des copeaux de bois selon ses caractéristiques de réflexion de la lumière.

10. Appareil selon la revendication 9, dans lequel les données d'intensité de réflexion de référence comprennent des données à gamme de seuil délimitant une pluralité de qualités de copeaux de bois pour fournir la classification en conséquence.

11. Appareil selon la revendication 10, en ce qu'il comprend une unité interphasage opérateur (126) comprenant des moyens d'affichage (132) pour reproduire les images créées à partir des signaux électriques d'image, cette unité (126) comprenant des moyens d'entrée de données (124) permettant à l'opérateur d'ajuster des données à gamme de seuil correspondant à la pluralité de qualités des copeaux de bois dans le but de leur classification.

12. Appareil selon la revendication 9, dans lequel les données d'intensité de réflexion de référence comprennent des données respectives correspondant à une pluralité de types de copeaux de bois, cet appareil comprenant en plus des moyens (114) pour générer un signal électrique indiquant un des types spécifiques auxquels correspondent les copeaux de bois, des moyens de comparaison de données (118) utilisant les données d'intensité de réflexion de référence correspondant aux types spécifiques des types de copeaux de bois pour fournir la classification.

13. Appareil selon la revendication 12, dans lequel les moyens (114) générant un signal électrique comprennent un dispositif d'entrée de données permettant à l'opérateur de choisir un type spécifique des types de copeaux de bois correspondant au lot inspecté (24) et/ou comprennent un dispositif de lecture automatique capable de détecter un code de machine lisible associé avec le lot inspecté, ce code représentant le type spécifique des types de copeaux de bois correspondant au lot inspecté (24).

14. Appareil selon la revendication 9, dans lequel les données d'intensité de réflexion globale comprennent des données d'intensité de réflexion moyenne, les moyens de dérivation (118) faisant la moyenne des valeurs d'intensité de réflexion pour produire des données d'intensité de réflexion moyenne et comprennent de plus la déviation standard générée par les moyens de dérivation (118) à partir des valeurs d'intensité de réflexion.

15. Appareil selon la revendication 14, dans lequel les moyens de dérivation (118) calibrent et filtrent les valeurs d'intensité de réflexion qui sont utilisées pour en dériver les données d'intensité de réflexion globale.

16. Appareil selon la revendication 9, dans lequel les moyens de dérivation (118) des signaux électriques calculent un rapport entre un nombre de signaux électriques représentant les valeurs d'intensité de réflexion au-dessus d'une valeur de seuil pré-déterminée et un nombre total de signaux électriques pour produire les données d'intensité de réflexion globale.

17. Appareil selon la revendication 9, comprenant en outre des moyens de transport (15) pour transporter une partie de lot de copeaux de bois à travers une zone inspection associée avec des moyens d'illumination (96) et les moyens de création d'images (82).

18. Appareil selon la revendication 17, dans lequel il y a une pluralité de parties de lots représentatives comprenant les copeaux de bois illuminés (26'), les moyens d'illumination (96) dirigeant de façon répétitive la lumière sur les copeaux de bois respectifs des parties de lot tandis que les moyens de création d'images (82) captent de façon répétitive la lumière réfléchie sur les copeaux de bois illuminés (26') des parties du lot pour produire des signaux électriques d'images représentant des valeurs d'intensité réfléchie pour les copeaux de bois des portions du lot.

19. Appareil selon la revendication 18, comprenant un hopper (21) pour recevoir les lots de copeaux de bois inspectés et des moyens (19) couplés au hopper (21) pour échantillonner successivement les parties du lot inspecté avant d'être transportées à travers la zone d'inspection.

20. Appareil selon la revendication 9, dans lequel les moyens de détection (78) comprennent un détecteur infra-rouge.

Drawing