NZ556744A

NZ556744A - Impact method and system for determining the modulus of elasticity in lumber

Info

Publication number: NZ556744A
Application number: NZ55674407A
Authority: NZ
Inventors: Gavin Wallace; Edward Hutchinson
Original assignee: Inst Of Geol & Nuclear Science
Priority date: 2007-07-26
Filing date: 2007-07-26
Publication date: 2009-03-31
Also published as: WO2009014463A1

Abstract

A method for determining a property of a piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it is provided. The method includes the steps of: providing an impact device with an impact member, causing an impact between the piece of lumber and the impact member, where the impact causes a reaction in the impact member and/or in the piece of lumber which is indicative of the mass of the piece of lumber, measuring the reaction of at least one of the impact member and the piece of lumber, and from that measurement determining the mass of the piece of lumber.

Description

*1 00561 45506* No: 556744 Date: 26 July 2007 NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION IMPACT METHOD AND SYSTEM FOR DETERMINING A PROPERTY OF LUMBER We, INSTITUTE OF GEOLOGICAL & NUCLEAR SCIENCES LIMITED, a New Zealand company, 30 Gracefield Road, Lower Hutt, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: INTELLECTUAL PROPERTY OFFICE OF N.Z. 2 8 JUL 201)8 RECEIVED FIELD OF INVENTION This present invention relates to a method and system for determining a property of lumber. More particularly, a preferred form of the present invention relates to a method 5 and system for determining one or more of mass, density, acoustic velocity and modulus of elasticity of lumber.

This present application claims priority from New Zealand patent application 556744, the full disclosure of the specification of which, as originally filed on 26 July 2007, is 10 incorporated herein by reference.

BACKGROUND The strength of a piece of lumber defines the use to which it can be put within the 15 building industry. For example, it is usual to specify that only structural grade lumber is used in building frames and trusses. Structural grade lumber is defined according to various parameters, including its strength.

The strength of lumber can be measured mechanically using machine stress graders 20 after drying. Alternatively, the strength of lumber can be determined using the modulus of elasticity. The modulus of elasticity of a piece of lumber is defined as the product of the density of the lumber and the square of the velocity of an acoustic wave transmitted longitudinally within the lumber. The strength of lumber is proportional to its stiffness, and the stiffness of lumber can be gauged by measuring its modulus of elasticity.

Further, objectives in kiln drying of lumber include drying each piece of lumber as economically as possible, to the same moisture content, and without incurring any degradation in the quality of the wood. With many softwoods, it has been found that lumber can be sorted according to green density and grouped into charges. Different 30 drying regimes can be applied to each charge so that kiln drying can be optimised for efficiency or cost savings, wood quality and wood recovery. Alternatively, it has been found in some woods, such as hard pines, lumber can be sorted into charges according 1569766.1 2 to acoustic velocity or modulus of elasticity, and different drying regimes applied to each charge to optimise kiln drying.

SUMMARY OF INVENTION A preferred embodiment of the present invention seeks to provide an impact method and system for measuring a property of lumber, such as mass, density or modulus of elasticity, or at least seeks to provide the public with a useful choice.

The present invention provides an impact method for determining a property of a piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it, the method comprising: providing an impact device having an impact member; causing an impact between the piece of lumber and the impact member, which impact causes a reaction in the impact member and/or in the piece of lumber indicative of the mass of the piece of lumber; and measuring the reaction of at least one of the impact member and the piece of lumber and from that measurement determining the mass of the piece of lumber.

The term "comprising" as used in this specification and claims means "consisting at least in part of'. That is to say, when interpreting statements in this specification and claims which include ''comprising", the features prefaced by this term in each statement all need to be present but other features can also be present. Related terms such as 25 "comprise" and "comprised" are to be interpreted in a similar manner.

Preferably, the method further comprises categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined mass.

The reaction may include a displacement of the piece of lumber and/or the impact member indicative of the mass of the piece of lumber, and measuring the reaction may 1569766.1 3 include measuring at least one of the displacement of the impact member and the piece of lumber.

The impact device may have one or more springs, the reaction may include a change in 5 length of the spring(s), and measuring the reaction may include measuring the change in length of the spring(s).

The method may further comprise providing a conveyor, or other conveying means, for conveying the piece of lumber. The conveyor may be arranged to cause the impact by 10 driving the piece of lumber with the conveyor into the impact member at a substantially constant velocity. The conveyor may be a belt conveyor or a chain conveyor, for example.

The impact member may be a striker, such as a hammer. The impact may be caused by 15 striking the piece of lumber with the striker.

The impact may displace the piece of lumber, and the displacement of the piece of lumber may be measured using a range finder, for example.

The method may further comprise detecting the presence of the piece of lumber at or near the striker; wherein the striker is arranged to strike the piece of lumber in response to detecting the piece of lumber.

The method may further comprise determining the density of the piece of lumber from 25 the determined mass and the volume of the piece of lumber. The volume of the piece of lumber may be predetermined and known if the piece of lumber is part of a run of standard size lumber, for example. Alternatively, the volume can be determined by measuring length, width and thickness dimensions of the lumber, for example.

The method may further comprise categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined density. 1569766.1 4 The method may further comprise causing vibrations in the piece of lumber; detecting the vibrations in the piece of lumber; and determining the acoustic longitudinal velocity in the piece of lumber from the detected vibrations and the length of the piece of 5 lumber. The detected vibrations may be detected at either end of the piece of lumber. The vibrations may be detected with a microphone, for example.

The length of the lumber may be predetermined and known. Alternatively, the method may include measuring the length of the piece of lumber, such as with a range finder or 10 mechanically, for example.

The method may further comprise categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined acoustic longitudinal velocity. Preferably, the method further 15 comprises digitally recording and Fourier transforming the detected vibrations to determine the resonant frequency of the vibrations in the piece of lumber. Preferably, the digitally recorded vibrations are filtered before Fourier transforming.

The impact may be between one end of the piece of lumber and the impact member, and 20 the impact device may cause the detected vibrations in the lumber.

The method may further comprise determining the modulus of elasticity of the piece of lumber from the determined acoustic longitudinal velocity and the determined density.

The method may further comprise categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined modulus of elasticity.

Categorising the piece of lumber by grading it for use may include any one or more of 30 stiffness, strength and stress grading, for example. Categorising the piece of lumber by determining a drying regime for it may include determining a drying regime based on 1569766.1 optimising or at least influencing one or more of drying efficiency and spread of kiln-dried moisture contents of dried charges of lumber, for example.

The present invention further provides an impact system for determining a property of a 5 piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it, the system comprising: an impact device having an impact member, the impact member being arranged to impact with the piece of lumber so as to cause a reaction in the impact member 10 and/or in the piece of lumber, the reaction being indicative of the mass of the piece of lumber; measuring apparatus for measuring the reaction of at least one of the impact member and the piece of lumber; and a computing device configured to determine the mass of the piece of lumber 15 from the measured reaction.

Preferably, the computing device is configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined mass.

The impact member may be arranged to impact with the piece of lumber so as to cause a reaction in the form of a displacement of the impact member and/or the piece of lumber, the displacement being indicative of the mass of the piece of lumber, the measuring apparatus may be arranged to measure the displacement of the piece of lumber and/or 25 the impact member; and the computing device may be configured to determine the mass of the piece of lumber from the measured displacement.

The impact device may have one or more springs, the impact member may be arranged to impact with the piece of lumber so as to cause a reaction in the form of a change in 30 length of the spring(s), the change in length of the spring(s) being indicative of the mass of the piece of lumber, the measuring apparatus may be arranged to measure the change 1569766.1 6 in length of the spring(s), and the computing device may be configured to determine the mass of the piece of lumber from the measured change in length of the spring(s).

The system may further comprise a conveyor, or similar conveying means, for 5 conveying the piece of lumber. The conveyor may be arranged to drive the piece of lumber towards the impact member at a substantially constant velocity to cause an impact between the piece of lumber and the impact member.

The impact member may be a striker, and the striker may be arranged to strike the piece 10 of lumber so as to cause a reaction in the impact member and/or in the piece of lumber, the reaction being indicative of the mass of the piece of lumber.

The striker may be arranged to displace the piece of lumber, and the measuring apparatus may be arranged measure the displacement of the piece of lumber using a 15 range finder, for example.

The system may further comprise a detecting device configured to detect the presence of the piece of lumber at or near the striker, and the striker may be arranged to strike the piece of lumber in response to the device detecting the piece of lumber.

The computing device may be configured to determine the density of the piece of lumber from the determined mass and the volume of the piece of lumber.

The computing device may be configured to categorise the piece of lumber by grading it 25 for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined density.

The system may further comprise a vibration inducer for causing vibrations in the piece of lumber; and a sensor for detecting the vibrations in the piece of lumber; wherein the 30 computing device is configured to determine the acoustic longitudinal velocity of the piece of lumber from the detected vibrations and the determined density. The sensor for detecting the vibrations may be a microphone, for example. 1569766.1 7 The computing device may be configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined acoustic longitudinal velocity.

The impact device may include the vibration inducer, the impact device being arranged to impact with one end of the piece of lumber so as to cause the detected vibrations in the lumber. The impact member may be the vibration inducer. Alternatively, the vibration inducer may be in the form of a second, separate impact device, for example.

The computing device may be configured to determine the modulus of elasticity of the piece of lumber from the determined acoustic longitudinal velocity and the determined density.

The computing device may be configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined modulus of elasticity.

The present invention further provides a method of determining the modulus of 20 elasticity of a piece of lumber comprising the steps of: causing an impact between the piece of lumber and an impact device, determining the mass of the lumber from a reaction of the piece of lumber and/or the impact device caused by the impact, determining the density of the piece of lumber from the mass and volume of the piece of lumber, detecting vibrations in the piece of lumber caused by the impact, determining 25 the acoustic velocity in the piece of lumber from the detected vibrations and the length of the piece of lumber, and determining the modulus of elasticity from the acoustic velocity and density of the piece of lumber.

The reaction to the impact may include a displacement of the piece of lumber and/or the 30 impact device. 1569766.1 8 The impact device may have a spring-loaded plate, the step of causing the impact may include impacting the piece of lumber onto the spring-loaded plate, and the step of determining the mass may include determining the mass of the piece of lumber from a recoil force caused by the piece of lumber impacting with the spring-loaded plate.

The step of causing the impact may include impacting the piece of lumber, and the step of determining the mass may include determining a displacement of the piece of lumber in the direction of the impact.

The present invention still further provides a system for determining the modulus of elasticity of a piece of lumber, the system comprising: an impact device, means for causing an impact between the impact device and the piece of lumber, measurement means to measure a reaction of the piece of lumber and/or the impact device caused by the impact, a microphone arranged to detect vibrations in the piece of lumber caused by 15 the impact, means for measuring the length of the piece of lumber, computation means arranged to determine the acoustic velocity of the piece of lumber from the vibrations detected by the microphone and the means for measuring the length of the piece of lumber, the computation means further arranged to determine the density of tile piece of lumber from the measured reaction of the piece of lumber and/or the impact device, and 20 the computation means further arranged to determine the modulus of elasticity from the acoustic velocity and the density of the piece of lumber.

The reaction may be a displacement and/or change in momentum of the piece of lumber and/or the impact device.

The means for causing an impact may include a striker arranged to provide an impact on one end of the lumber.

The means for causing an impact may be arranged to cause the impact by impacting the 30 piece of lumber onto the impact device, and the measurement means may be arranged to measure a displacement of the impact device as a result of the impact. 1569766.1 9 The impact method and system of the invention can be used on both green and dry lumber. In typical embodiments, the system will be part of a saw mill or other wood processing plant. The system may be arranged so that multiple pieces of lumber are carried on a conveyor or other conveying means and arranged to be processed 5 sequentially. The system determines the modulus of elasticity for each piece of lumber from which the stiffness and/or strength of the piece of lumber can be determined. It is envisaged that the computation means can be arranged to communicate with a marking and/or sorting device so that each piece of lumber can be graded, before or after drying, according to its modulus of elasticity, stiffness, or strength.

In alternative embodiments, the system may be arranged to determine the mass or density of one or more pieces of lumber. In these embodiments, a microphone may not be present or may not be activated. In some embodiments the mass or density of one or more pieces of lumber could be measured prior to drying and the mass or density used to determine a drying regime for each piece of lumber.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

As used herein the term "and/or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

BRIEF DESCRIPTION OF DRAWINGS 1569766.1 The invention will be further described, by way of example only and without intending to be limiting, with reference to the following drawings, wherein: Figure 1 shows an impact system for determining one or more of the mass, density, acoustic velocity and modulus of elasticity of a piece of limber according to a 5 first embodiment of the present invention; Figure 2 shows a comparison of the mass of a variety of boards of lumber, as determined by the impact system shown in Figure 1, with the actual mass of the boards, as determined by weighing the boards using scales; Figures 3A and 3B are sound recordings of vibrations in two samples of mm 10 lumber; Figures 4A and 4B are frequency spectrums of the sound recordings of Figures 3 A and 3B respectively; Figure 5 shows the distribution of acoustic velocity as measured in a trial of 100 southern yellow pine boards; Figure 6 shows a comparison of the dry modulus of elasticity of mm pinus radiata boards determined after kiln drying, with the green modulus of elasticity of the boards determined before drying; Figure 7 shows the kiln drying results of a southern yellow pine trial; Figure 8 shows an impact device for use in an impact system for determining 20 one or more of mass, density, acoustic velocity and modulus of elasticity according to a second embodiment of the present invention; and Figure 9 is a schematic diagram showing input(s) and output(s) of a computing device for use in embodiments of the present invention.

DETAILED DESCRIPTION Figure 1 shows a system 10 for determining one or more of the properties of mass, density, acoustic longitudinal velocity and modulus of elasticity of pieces of lumber 12 according to a first embodiment of the present invention. One elongated piece of 30 lumber 12 is shown in Figure 1. The elongated pieces of lumber 12 have predetermined width, thickness and length dimensions. The predetermined dimensions of the pieces of lumber 12 may be established by cutting, splitting or sawing logs or larger pieces of 1569766.1 11 lumber into pieces 12, such as boards or planks, having predetermined dimensions, for example. The predetermined dimensions of the sawn, split or cut pieces of lumber 12 may be known or measured before determining the property or properties, or may be subsequently determined within the system 10, where necessary, according to 5 embodiments of the invention.

The modulus of elasticity of a piece of lumber is defined above as the product of the density of the piece of lumber and the square of the velocity of an acoustic wave transmitted longitudinally within the piece of lumber. Therefore, to determine the 10 modulus of elasticity of lumber, both the density of the lumber and the velocity of an acoustic wave transmitted longitudinally within the piece of lumber, referred to herein as "acoustic velocity" or "acoustic longitudinal velocity", need to be determined.

The system 10 includes a chain conveyor 14 for carrying pieces or boards of lumber 12, 15 measuring apparatus 16 and an impact device 18. The pieces of lumber 12 are aligned on the conveyor 14 transverse to the direction of travel 20 of the conveyor 14. The conveyor 14 carries and sequentially moves each piece of lumber 12 past the impact device 18. The impact device 18 includes an impact member in the form of a striker, such as hammer 22, and a vibration sensor in the form of a microphone 24. The system 20 10 also includes computation means in the form of computing device 26 (shown schematically in Figure 9) for calculating one or more of the properties of mass, density, acoustic velocity and modulus of elasticity of the lumber 12, as will be described below.

The hammer 22 is arranged to strike a first end 28 of the lumber 12. The first end 28 of 25 the lumber 12 can be previously aligned to the hammer side of the conveyor 14 by moving the lumber 12 up to a fence (not shown), for example.

The measuring apparatus 16 includes a laser range finder 30 configured to determine the distance the lumber 12 moves (that is, the displacement of the lumber 12) in the 30 transverse direction 34 in response to being struck by the hammer 22. The range finder 30 may be configured to measure a change in the distance 36 from the range finder 30 to a second (or the other) end 38 of the lumber 12, for example. The range finder 30 1569766.1 12 may be positioned to view either the struck end 28 or the other end 38 (as shown in Figure 1) of the lumber 12 to measure the change in distance 36.

Alternatively, instead of a laser range finder, the range finder 30 may be a transducer 5 sonic range finder, for example. Alternatively, the measuring apparatus 16 may include any other suitable means for measuring the displacement of the lumber 12, such as one or more mechanical sensors for example.

In some embodiments, the range finder 30 may also be configured to measure, where 10 necessary, the length of the lumber 12. Alternatively, where necessary, a further range finder, for example, may be used to determine the length of the lumber 12.

The microphone 24 is located to detect vibrations at the first end 28 of the lumber 12. Alternatively, the microphone may be positioned to detect vibrations at the second end 15 38 of the lumber 12.

Thin shaped plates 40 are located along the conveyor 14 adjacent the impact device 18. The plates 40 lift the piece of lumber 12 above the chain links 42. Driving lugs 44 of the conveyor 14 maintain contact with lumber 12 when it is lifted by the plates 40. As 20 the conveyor 14 moves the lumber 12 past the impact device 18, the presence of the lumber 12 within the striking zone of the hammer 22 is detected by a detecting device (not shown). The detecting device may include one or more photocells that detect the lumber 12 when it breaks a light beam striking the photocell(s), for example. When the lumber 12 is detected, the hammer 22 strikes the first end of the lumber 12. The impact 25 between the hammer 22 and the lumber 12 causes a reaction in the lumber 12 in the form of the displacement or movement of the piece of lumber 12 towards the range finder 30 in the direction 34. As discussed above, the range finder 30 is configured to measure the displacement of the lumber 12. The impact also generates an acoustic resonance within the lumber 12 that can be detected by the microphone 24.

(!) Calculating mass m 1569766.1 13 The mass of the piece of lumber 12 can be determined by the computing device 26 from the displacement of the lumber 12 in the transverse direction 34 as a result of the lumber 12 being struck by the hammer 22. The transverse motion of the struck lumber 12 has two stages. In the first stage, the piece of lumber 12 is accelerated by the difference 5 between the force F supplied by the striking hammer 22 and the frictional force due to the weight of the piece of lumber 12 on the plates 40. The piece of lumber 12 will reach a maximum transverse velocity vt in a time t. In the second stage, only the frictional force is present, and the piece of lumber 12 decelerates over a distance s until the transverse velocity vt is reduced to zero. The mass m of the piece of lumber 12 can 10 therefore be calculated as: The displacement of the struck lumber 12, which corresponds to the change in the distance 36, can be measured by the range finder every millisecond, for example. From these displacement against time measurements, the maximum transverse velocity vt and 15 the time t at which the maximum transverse velocity vt occurs can be calculated. The maximum velocity vt will generally occur shortly after the lumber 12 stops being pushed by the striking hammer 22. The impact force F can be assessed by calibration, and the coefficient of friction between the plates 40 and the lumber 12 does not need to be assumed as it is determined for each piece of lumber 12 from the displacement 20 against time measurements.

Figure 2 shows the correlation between the mass in kilograms of a variety of different sized boards of lumber as determined by the impact system 10 (labelled the "impact mass" on the y-axis), and the actual (or weighed) mass in kilograms of the same boards 25 as determined using scales (labelled the "weighed mass" on the x-axis). The impact masses were determined with the boards being conveyed at a rate of 30 boards per minute, and the weighed masses were measured using scales following their recovery. As can be seen in Figure 2, the impact mass provides a good estimate of the actual mass of each board. The impact mass m and the weighed mass have a linear relationship (y = 1569766.1 14 0.996x, R = 0.9652). This relationship can be used to further calibrate the impact system 10 for use to determine the mass of lumber. (2) Calculating density p The density of the piece of lumber 12 is the mass divided by its volume. The computing device 26 is able to determine the density p of the piece of lumber 12 from the mass and dimensions of the lumber. The dimensions of the lumber 12, which may be predetermined by sawing etc, may be measured by any suitable measuring means. The dimensions may be measured nominally using mechanical sensors, for example, or 10 more precisely, such as with laser or transducer sonic range finders, for example. The dimensions of the lumber 12 may be determined before (upstream), substantially at the same location as, or after (downstream) the hammer 22 and microphone 24.

Alternatively, the lumber may be sawn to predetermined and known thickness, width 15 and length dimensions before being moved to the impact device 18, with the known dimensions provided to or stored by the computing device 26. Alternatively, initially only transverse cross-section dimensions of the piece of lumber 12 may be known, such that only the length of the lumber 12 needs to be measured to calculate the volume. For example, if a standard run of lumber 12 is being carried by the conveyor 14, a known 20 width and thickness for each piece of lumber can be stored in the computing device 26, and the length of each piece of lumber 12 can be measured, such as with the range finder 30. (3) Calculating acoustic longitudinal velocity va The acoustic waves detected by the fixed microphone 24 are converted to digital signals in an A/D converter. The conversion into digital signals may take place at either the microphone 24 or the computing device 26. The signals can then be filtered to remove unwanted noise. Following digitisation and filtering, the computing device 26 is able to transform the signals from time based signals to frequency based signals using a Fourier 30 transform. 1569766J Figures 3A and 3B show examples of wavelengths in two pieces of green 100 x 50 x 6000 mm lumber recorded with a microphone 24 after the pieces of lumber have been struck by a hammer. The left hand sides of Figures 3A and 3B show the background noise before the acoustic wave impacted on the microphone 12. The acoustic wave then 5 echoed through the lumber and produced the decaying images of Figures 3 A and 3B.

The Fourier transformed images of Figures 3A and 3B (following digitisation and filtering) are shown in Figures 4A and 4B respectively. Both of Figures 4A and 4B clearly show a resonant peak and harmonics of the acoustic velocity wave in the lumber.

The wavelength of the resonance modes of a piece of lumber of length L are /i = 1,2,3,... (2) where both ends of the lumber are free. The corresponding resonant frequencies are f =i- (3) Jn X„ where is the acoustic longitudinal velocity. Because of secondary effects, the base frequency fj can be perturbed and it is preferable to use an average of the harmonics of 15 the base frequency to calculate the base frequency//. As can be seen in Figures 4A and 4B, the harmonics above the fundamental frequency are clearly distinguishable and easy to measure.

The computing device 26 is able to determine the acoustic longitudinal velocity from 20 the length of the lumber, the wavelengths of at least one resonant mode and at least one resonant frequency, as shown in equations (2) and (3). The length of the piece of lumber is measured or known from when determining the density. The two pieces of lumber subject to measurement in Figures 3A, 3B, 4A, and 4B were 6 metres long. These two pieces of lumber had acoustic longitudinal velocities of 3488 and 3056 m/s. 25 The typical distribution of acoustic longitudinal velocities of 100 pieces of green southern yellow pine (SYP) 94 x 42 * 4900 mm lumber is shown in Figure 5. (4) Calculating modulus of elasticity MOE The computing device 26 is able to determine the modulus of elasticity MOE from the 30 density p and the acoustic longitudinal velocity v„. The modulus of elasticity is 1569766.1 16 MOE = /?va2 (4) The computing device 26 is configured to communicate with a sorting and/or marking system 46 (shown schematically in Figure 9) to sort or mark each piece of lumber 12 based on the determined mass, density, acoustic velocity or modulus of elasticity. The 5 sorting and/or marking system enables embodiments of the present invention to categorise the lumber 12 for use, such as by stiffness, strength, and/or stress grading of lumber 12 based on the calculated modulus of elasticity. It will be understood that the grading of the lumber 12 may occur before or after drying. An embodiment of the present invention can therefore be used to determine and mark which pieces of lumber 10 12 are structural grade lumber etc, before drying.

For example, Figure 6 shows the correlation between the modulus of elasticity (in GPa) of 100 x 50 x 6000 mm pinus radiata boards after drying (labelled "dry MOE" on the y-axis) with the modulus of elasticity of the same boards before kiln drying (labelled 15 "green MOE" on the x-axis). A regression analysis was performed on (see the line labelled "linear (kiln MC<20%)") for the boards having a kiln dried moisture content below 20%. The boards having a kiln dried moisture content (MC) above 20% were ignored so as not to distort the relationship between the green modulus of elasticity and the dry modulus of elasticity. Boards having a dried moisture content above 20% are 20 typically considered under dried, and generally unsuitable for structural use without further drying. It can be seen from Figure 2 that a good correlation (y = 1.0245x + 0.8143, R2 = 0.9692) exists between the dry MOE and the green MOE, which allows the accurate prediction of the dry MOE from the determined green MOE, if the boards are dried to about the same moisture content. The predicted dry modulus of elasticity for 25 each board (from the determined green modulus of elasticity) can then be used for structural grading of the board, such as structural grading based on one or more of elasticity, stiffness, strength and stress grading, for example, before drying.

Alternatively or additionally, embodiments of the present invention can used for 30 categorising the lumber 12 by determining drying regimes for green lumber from the mass or density of the lumber. The computing device 26 may be configured to 1569766.1 17 communicate with the sorting and/or marking system 46 to sort or mark each piece of lumber 12 according to the determined drying regime. Many softwoods can be sorted according to green density into drying charges to optimise drying conditions. Alternatively or additionally, green lumber may be sorted into groups for drying based 5 on mass, and drying regimes determined for the sorted groups when the lumber has previously been cut to a standard or known length, width and thickness, for example.

Alternatively or additionally, embodiments of the present invention can used for determining drying regimes for green lumber from the acoustic velocity and/or the 10 modulus of elasticity of the lumber. Hard pines, such as the softwood class collectively known as southern yellow pine, have a very narrow distribution in green density, and kiln drying optimisation based on a green density sort is not viable. Such hard pines may be sorted according to acoustic longitudinal velocity or modulus of elasticity into drying charges to optimise drying conditions. For example, the southern yellow pine 15 pieces depicted in Figure 5 were kiln dried under the same conditions, and their subsequent moisture contents measured. The mean kiln-dried moisture content (MC) was found to be 8.6% (standard deviation 1.42%), and the moisture was spread over a range of 5.5% to 13.9%. When the pieces or boards of lumber 12 were sorted into two groups using a threshold green acoustic velocity of 2700 m/s, the mean moisture 20 content for the low velocity group was 9.2% (standard deviation 1.31%), and 7.9% (1.12%) for the high velocity group. This separation is shown in Figure 7. Clearly, the high velocity group required less drying time, and a reduction in spread of the kiln-dried moisture contents could be achieved by sorting the two groups before drying and applying drying conditions customised to each group.

The sorting and/or marking system 46 may be any suitable system. Suitable systems include, but are not limited to, marking systems that use paint to mark grades or other indications on each piece of lumber, and sorting systems that direct each piece of lumber to a selected destination depending on the assessed drying regime, strength, 30 stiffness etc. 1569766.1 Jg The skilled addressee will appreciate that there are many alternative impact devices and methods that fall within the scope of the present invention. Figure 8 is a perspective view of one alternative impact device 48 for use to determine one or more of the mass, density, acoustic longitudinal velocity and modulus of elasticity of lumber 12 according 5 to a second embodiment of the present invention. The impact device 48 includes a vibration inducer in the form of an inertial hammer 50, an impact member in the form of an impact plate 52, compression springs 54, spring retaining plate 56, shock damping buffers 58, wire coil formers 60, microphone 62 and associated microphone damper 64, and mounting plate 66.

Each piece of lumber 12 may be arranged to move longitudinally (indicated schematically by the arrow 68) relative to the impact plate 52 at an assumed constant speed so as to cause an end 70 of the lumber 12 to impact with the impact plate 52. The impact device 48 may be mounted so that the impact plate 52 is substantially stationary 15 prior to impact. The impact causes a reaction in the impact plate 52 that can be used to determine one or more properties of the lumber 12. The pieces of lumber 12 can be impacted against the impact plate 52 using a conveyor (indicated schematically by the reference number 72), such as a belt conveyor or a chain conveyor similar to the conveyor 14 in Figure 1, for example. Alternatively, any other suitable apparatus can 20 be used to sequentially move the ends 70 of pieces of lumber 12 into the impact plate 52.

Before impacting on the impact plate 52, the end 70 of the piece of lumber 12 will strike the hammer 50, setting up an acoustic resonance within the piece of lumber 12. In 25 alternative embodiments, any suitable device may be used to establish an acoustic resonance within the piece of lumber 12. In this embodiment, the hammer 50 is in the form of a piston that projects beyond the plate 52, the piston supported in a weak compression cylinder (not shown). The momentum of the piece of lumber 12 drives the hammer 50 flush with the surface of the impact plate 52, When the end 70 of the piece of lumber 12 impacts on the plate 52, the momentum of the lumber 12 drives the impact plate 52 and the hammer 50 towards the mounting plate 1569766.1 19 66. In doing so, the impact plate 52 compresses the springs 54 that absorb and store the kinetic energy of the piece of lumber 12, stopping the motion of the piece of lumber 12 before recoiling. The end of the lumber 12 remains in contact with the spring-loaded plate 52 and the hammer 50 until the springs 54 recoil.

The mass of the impacting piece of lumber 54 can be determined by measuring the relative displacement of the impact plate 52. If the lumber piece 12 impacts with a velocity vi, and results in a compression of the spring sc, then the mass is given by m \ (5) m = (2ls-sc) — v, where k is the spring constant and ls is its length. The compression of the spring can be made small so that the measured mass is substantially directly proportional to the spring compression. Further, belt-driven pieces of lumber can be made to impact with constant velocity.

In the impact device 48, there are rods 74 located within the springs 54 that are attached to the impact plate 52. Rod magnets (not shown) are mounted on the free ends of the rods 74 within the coil formers 60. The momentum of the impacting piece of lumber 12 drives the magnets through the coil formers 60, and the associated magnetic fields induce electrical currents in the coil windings. When the coils are connected to low 20 resistances, voltage pulses corresponding with the acceleration of rod magnets can be measured, and the size of these voltage pulses can be calibrated to measure the spring compression s.

The density may be determined using the mass determined from equation (5), and the 25 volume of the piece of lumber 12. As discussed with reference to the impact device 18 shown in Figure 1, the volume of the lumber 12 may be known or assumed if the lumber is first cut to a known size, or may be measured with any suitable measuring means, including either before, generally at the same time as, or after determining the mass. 1569766.1 The acoustic velocity in the lumber 12 may be determined using equations (2) and (3). The microphone 62 can detect the acoustic wave established by the hammer 50, and the length of the lumber 12 may be known if the lumber is first cut to a known size, or again may be measured in any suitable way, as described above with reference to the impact 5 device 18 shown in Figure 1.

The modulus of elasticity (equation (4)) of the piece of lumber 12 can be similarly determined, as described with reference to the impact device 18 shown in Figure 1.

Both the impact device 18 (Figure 1) and the impact device 48 (Figure 8) enable the mass of a piece of lumber 12 to be determined from an impact between the lumber 12 and an impact member (hammer 22 or plate 52). The impact causes a reaction in the impact device and/or the piece of lumber in response to the impact force that is applied to either to the piece of lumber or to the impact device. The reaction is indicative of the mass of the lumber 12. The reaction includes a displacement or movement of at least one of the piece of lumber 12 and the impact member of the impact device 18 (or 48). The mass of the piece of lumber 12 can be determined from the displacement or movement, based on kinematics, for example.

In embodiments where the impact member is arranged to move to cause an impact by impacting against an end of the piece of lumber, the force of the impact may be controlled in any suitable manner. For example, the force of the impact between the impact member and the lumber may be regulated based on a pressure change. An impact device may a have chamber and an impact member in communication with the chamber. The chamber may be a bore and the impact member may be an associated piston, for example. The pressure of a gas, or other fluid, in the bore can be controlled to regulate the force with which the piston moves out of the bore and impacts with and pushes the piece of lumber.

In still further alternative embodiments, for example, separate impact devices can be provided for use in determining the mass and, where necessary, acoustic velocity of the pieces of lumber. The piece of lumber may be travelling either longitudinally or 1569766.1 21 transversely when impacted with either of the separate impact devices. Further, when two separate impact devices are used, the order in which acoustic velocity and mass are assessed is not important. For example, an end of a longitudinally or transversely travelling piece of lumber on a conveyor may be arranged to impact with a first impact 5 device for determining mass of the piece of lumber, and at a later stage that end (or the other end) of the lumber may be impacted with a second impact device for creating an acoustic resonance within the lumber so that the acoustic velocity in the lumber can be assessed. Again, the piece of lumber may be travelling either longitudinally or transversely when the second impact occurs.

Figure 9 is a block diagram showing inputs and outputs of the computing device 26 according to one embodiment. Inputs to the computing device 26 include one or more of input 76 representative of lumber dimensions, and input 78 representative of reactions to impacts that are indicative of mass of pieces of lumber.

As described above, the lumber dimensions of each piece of lumber may be predetermined and known for a run of standard size pieces of lumber, or can be determined in many ways as described above. For determining the density of the piece of lumber, the volume of the piece of lumber must be known or measured. The length, 20 width and thickness dimensions may be determined and provided to the computing device separately using different devices, for example. Further, length, width and thickness measurements may take place at one or several different points along a conveying or processing line for the pieces of lumber. For determining the acoustic velocity of the piece of lumber, the length of the piece of lumber must also be known or 25 measured.

Measurements representative of the reaction caused by the impact may be measurements of one or more of displacement, momentum and pressure, for example, that are indicative of the mass of the piece of lumber 12. Reaction measurements may 30 be obtained by using any suitable impact device, such as the impact device 14, to impact with the lumber 12, and measuring the reaction caused by the impact, such as by measuring the displacement of the lumber 12 using the range finder 30, for example. 1569766.1 22 Examples of how the mass of a piece of lumber 12 can be determined from the displacement and/or momentum of either the piece of lumber or of an impact device impacted by the piece of lumber and also the displacement/momentum data required to calculate the mass are discussed above. Many alternatives that fall within the scope of 5 the present invention, as will be understood to those skilled in the art, could also be used.

In embodiments where the acoustic velocity or the modulus of elasticity of lumber is determined, inputs of the computing device 26 also include input 80 from a vibration 10 sensor, such as a microphone. The input 80 may be an analog waveform, a digital waveform or any other suitable input from the microphone.

The computing device 26 is able to assess the mass of the piece of lumber from the reaction measurement input 78 and the density of the lumber from the mass and lumber 15 dimension input 76. The acoustic velocity may be determined (if required) additionally from the microphone input 80. Example equations that can be used for assessing each of the mass, density and acoustic velocity have been previously provided. The modulus of elasticity of the pieces of lumber can be determined from the density and acoustic velocity.

Stiffness, strength, and/or stress grading of the pieces of lumber can be determined from the modulus of elasticity. Alternatively, the computing device 26 can assess a drying regime for green lumber from the mass, density, acoustic velocity and/or the modulus of elasticity of the pieces of lumber. In preferred embodiments, the computing device 26 25 communicates (as indicated by output 82) with the sorting and/or marking system 46 configured to sort or mark each piece of lumber according the assessed grade or drying regime.

Preferred embodiments of the invention have been described by way of example only 30 and modifications may be made thereto without departing from the scope of the invention. For example, the skilled addressee will appreciate that there are many 1569766.1 23 alternative methods and devices suitable for causing the impact and measuring a reaction caused by the impact to determine mass. Any suitable device may be used.

I 1569766.1 24

Claims

WHAT WE CLAIM IS:

1. An impact method for determining a property of a piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it, the method comprising: providing an impact device having an impact member; causing an impact between the piece of lumber and the impact member, which impact causes a reaction in the impact member and/or in the piece of lumber indicative of the mass of the piece of lumber; and measuring the reaction of at least one of the impact member and the piece of lumber and from that measurement determining the mass of the piece of lumber.

2. An impact method for determining a property of a piece of lumber as claimed in 15 claim 1, comprising categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined mass.

3. An impact method for determining a property of a piece of lumber as claimed in claim 1 or claim 2, wherein the reaction includes a displacement of the piece of lumber and/or the impact member indicative of the mass of the piece of lumber, and measuring the reaction includes measuring at least one of the displacement of the impact member and the piece of lumber.

4. An impact method for determining a property of a piece of lumber as claimed in any one of claims 1 to 3, wherein the impact device has one or more springs, 30 the reaction includes a change in length of the spring(s), and measuring the reaction includes measuring the change in length of the spring(s). 5 10 20 25 1569766-2 25 INTELLECTUAL PROPERTY OFFICE OF N.Z. 21 DEC 2008 RECEIVED

5. An impact method for determining a property of a piece of lumber as claimed in any one of claims 1 to 4, comprising: providing a conveyor for conveying the piece of lumber; and causing the impact by driving the piece of lumber with the conveyor into the 5 impact member at a substantially constant velocity.

6. An impact method for determining a property of a piece of lumber as claimed in any one of claims 1 to 3, wherein the impact member is a striker, and 10 the impact is caused by striking the piece of lumber with the striker.

7. An impact method for determining a property of a piece of lumber as claimed in claim 6, wherein: the impact displaces the piece of lumber, and 15 the displacement of the piece of lumber is measured using a range finder.

8. An impact method for determining a property of a piece of lumber as claimed in claim 6 or claim 7, comprising: detecting the presence of the piece of lumber at or near the striker; 20 wherein the striker is arranged to strike the piece of lumber in response to detecting the piece of lumber.

9. An impact method for determining a property of a piece of lumber as claimed in any one of claims 1 to 8, comprising: 25 determining the density of the piece of lumber from the determined mass and the volume of the piece of lumber.

10. An impact method for determining a property of a piece of lumber as claimed in claim 9, comprising 30 categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined density. 1569766-2 26 INTELLECTUAL PROPERTY OFFICE OF N.Z. 2* DEC 2008;

11. An impact method for determining a property of a piece of lumber as claimed in any one of claims 1 to 10, comprising:;causing vibrations in the piece of lumber;;5 detecting the vibrations in the piece of lumber; and determining the acoustic longitudinal velocity in the piece of lumber from the detected vibrations and the length of the piece of lumber.;

12. An impact method for determining a property of a piece of lumber as claimed in 10 claim 11, comprising categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined acoustic longitudinal velocity.;15

13. An impact method for determining a property of a piece of lumber as claimed in claim 11 or claim 12, wherein the impact is between one end of the piece of lumber and the impact member,;and the impact device causes the detected vibrations in the lumber.;20;25;

14. An impact method for determining a property of a piece of lumber as claimed in any one of claims 11 to 13 when dependent on claim 9, comprising:;determining the modulus of elasticity of the piece of lumber from the determined acoustic longitudinal velocity and the determined density.;

15. An impact method for determining a property of a piece of lumber as claimed in claim 14, comprising categorising the piece of lumber by grading it for use or categorising the piece of lumber by determining a drying regime for it, based at least in part on the determined 30 modulus of elasticity.;1569766-2;27;INTELLECTUAL PROPERTY OFFICE OF N.Z. .•;2 4 DEC 2008;RECEIVED;

16. An impact system for determining a property of a piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it, the system comprising:;an impact device having an impact member, the impact member being arranged to impact with the piece of lumber so as to cause a reaction in the impact member and/or in the piece of lumber, the reaction being indicative of the mass of the piece of lumber;;measuring apparatus for measuring the reaction of at least one of the impact member and the piece of lumber; and a computing device configured to determine the mass of the piece of lumber from the measured reaction.;

17. An impact system for determining a property of a piece of lumber as claimed in claim 16, wherein the computing device is configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined mass.;

18. An impact system for determining a property of a piece of lumber as claimed in claim 16 or claim 17, wherein the impact member is arranged to impact with the piece of lumber so as to cause a reaction in the form of a displacement of the impact member and/or the piece of lumber, the displacement being indicative of the mass of the piece of lumber,;the measuring apparatus is arranged to measure the displacement of the piece of lumber and/or the impact member; and the computing device is configured to determine the mass of the piece of lumber from the measured displacement.;

19. An impact system for determining a property of a piece of lumber as claimed in any one of claims 16 to 18, wherein the impact device has one or more springs,;1569766-2 2 8;INTELLECTUAL .PROPERTY OFFICE OF N.Z.;2 4 DEC 2008;RECEIVED;the impact member is arranged to impact with the piece of lumber so as to cause a reaction in the form of a change in length of the spring(s), the change in length of the spring(s) being indicative of the mass of the piece of lumber,;the measuring apparatus is arranged to measure the change in length of the 5 spring(s), and the computing device is configured to determine the mass of the piece of lumber from the measured change in length of the spring(s).;

20. An impact system for determining a property of a piece of lumber as claimed in 10 any one of claims 16 to 19, comprising:;a conveyor for conveying the piece of lumber, the conveyor being arranged to drive the piece of lumber towards the impact member at a substantially constant velocity to cause an impact between the piece of lumber and the impact member.;15

21. An impact system for determining a property of a piece of lumber as claimed in any one of claims 16 to 18, wherein the impact member is a striker, and the striker is arranged to strike the piece of lumber so as to cause a reaction in the impact member and/or in the piece of lumber, the reaction being indicative of the 20 mass of the piece of lumber.;

22. An impact system for determining a property of a piece of lumber as claimed in claim 21, wherein the striker is arranged to displace the piece of lumber, and 25 the measuring apparatus is arranged measure the displacement of the piece of lumber using a range finder.;

23. An impact system for determining a property of a piece of lumber as claimed in claim 21 or claim 22, comprising:;30 a detecting device configured to detect the presence of the piece of lumber at or near the striker, and;INTELLECTUAL PROPERTY OFFICE OF N.Z.;1569766-2 2 9;21 DEC 2008;RECEIVED;the striker is arranged to strike the piece of lumber in response to the detecting device detecting the piece of lumber.;

24. An impact system for determining a property of a piece of lumber as claimed in 5 any one of claims 16 to 23, wherein the computing device is configured to determine the density of the piece of lumber from the determined mass and the volume of the piece of lumber.;

25. An impact system for determining a property of a piece of lumber as claimed in 10 claim 24, wherein the computing device is configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined density.;26 An impact system for determining a property of a piece of lumber as claimed in claim 24 or claim 25, comprising:;a vibration inducer for causing vibrations in the piece of lumber; and a sensor for detecting the vibrations in the piece of lumber;;wherein the computing device is configured to determine the acoustic longitudinal velocity of the piece of lumber from the detected vibrations and the determined density.;27. An impact system for determining a property of a piece of lumber as claimed in claim 26, wherein the computing device is configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined acoustic longitudinal velocity.;28. An impact system for determining a property of a piece of lumber as claimed in 30 claim 26 or claim 27, wherein;15;20;25;1569766-2 3 0;INTELLECTUAL PROPERTY OFFICE OF N.Z.;2 4 DEC 2008 RECEIVED;the impact device includes the vibration inducer, the impact device being arranged to impact with one end of the piece of lumber so as to cause the detected vibrations in the lumber.;5 29. An impact system for determining a property of a piece of lumber as claimed in claim 28, wherein the impact member is the vibration inducer.;30. An impact system for determining a property of a piece of lumber as claimed in;10 any one of claims 26 to 29 when dependent on claim 24, wherein the computing device is configured to determine the modulus of elasticity of the piece of lumber from the determined acoustic longitudinal velocity and the determined density.;15 31. An impact system for determining a property of a piece of lumber as claimed in claim 30, wherein the computing device is configured to categorise the piece of lumber by grading it for use or to categorise the piece of lumber by determining a drying regime for it, based at least in part on the determined modulus of elasticity.;20;32. A method of determining the modulus of elasticity of a piece of lumber comprising the steps of: causing an impact between the piece of lumber and an impact device, determining the mass of the lumber from a reaction of the piece of lumber and/or the impact device caused by the impact, determining the density of the piece of;25 lumber from the mass and volume of the piece of lumber, detecting vibrations in the piece of lumber caused by the impact, determining the acoustic velocity in the piece of lumber from the detected vibrations and the length of the piece of lumber, and determining the modulus of elasticity from the acoustic velocity and density of the piece of lumber.;30;1569766-2;31;2 4 DEC;R E C EIV E D;33. The method of determining the modulus of elasticity of a piece of lumber of claim 32, wherein the reaction to the impact includes a displacement of the piece of lumber and/or the impact device.;5 34. A method of determining the modulus of elasticity of a piece of lumber as claimed in claim 33, wherein the impact device has a spring-loaded plate, the step of causing the impact includes impacting the piece of lumber onto the spring-loaded plate, and the step of determining the mass includes determining the mass of the piece of lumber from a recoil force caused by the piece of lumber impacting with the spring-;10 loaded plate.;35. A method of determining the modulus of elasticity of a piece of lumber as claimed in claim 33, wherein the step of causing the impact includes impacting the piece of lumber, and the step of determining the mass includes determining a;15 displacement of the piece of lumber in the direction of the impact.;36. A system for determining the modulus of elasticity of a piece of lumber, the system comprising: an impact device, means for causing an impact between the impact device and the piece of lumber, measurement means to measure a reaction of the piece;20 of lumber and/or the impact device caused by the impact, a microphone arranged to detect vibrations in the piece of lumber caused by the impact, means for measuring the length of the piece of lumber, computation means arranged to determine the acoustic velocity of the piece of lumber from the vibrations detected by the microphone and the means for measuring the length of the piece of lumber, the computation means farther;25 arranged to determine the density of the piece of lumber from the measured reaction of the piece of lumber and/or the impact device, and the computation means further arranged to determine the modulus of elasticity from the acoustic velocity and the density of the piece of lumber.;30 37. A system for determining the modulus of elasticity of a piece of lumber as claimed in claim 36, wherein the reaction is a displacement and/or change in momentum of the piece of lumber and/or the impact device.;1569766-2 32;INTELLECTUAL PROPERTY OFFICE OF N.Z.;21 DEC 2008;RECEIVED;5;10;15;20;25;38. A system for determining the modulus of elasticity of a piece of lumber as claimed in claim 36 or claim 37, wherein the means for causing an impact includes a striker arranged to provide an impact on one end of the lumber.;39. A system for determining the modulus of elasticity of a piece of lumber as claimed in claim 36 or claim 37, wherein the means for causing an impact is arranged to cause the impact by impacting the piece of lumber onto the impact device, and the measurement means is arranged to measure a displacement of the impact device as a result of the impact.;40. An impact method for determining a property of a piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it, the method being substantially as hereinbefore described with reference to the accompanying drawings.;41. An impact system for determining a property of a piece of lumber, the determined property for categorising the piece of lumber by grading it for use or for categorising the piece of lumber by determining a drying regime for it, the system being substantially as hereinbefore described with reference to the accompanying drawings.;42. A method of determining the modulus of elasticity of a piece of lumber, the method being substantially as hereinbefore described with reference to the accompanying drawings.;43. A system for determining the modulus of elasticity of a piece of lumber, the system being substantially as hereinbefore described with reference to the accompanying drawings.;INSTITUTE OF GEOLOGICAL & NUCL1 ENCES LIMITED;By the d agents;A J PA Per:;1569766-2;33;2 4 DEC 2008 •;* RECEIVED