NZ534528A - Improved equipment for evaluating properties of trees, logs and lumber - Google Patents

Abstract

Equipment for evaluating the properties of trees, logs and lumber which includes an input probe; two or more matched sensing probes and a recording means associated with each probe; wherein the input probe is isolated from either or any of the sensing probes and from the recording means; and each of the sensing probes is electrically connected to the recording means.

Description

534528 New Zealand Patent App. 534528 Filed: 4 August 2004 Patents Form No. 5 Patents Act 1953 COMPLETE SPECIFICATION IMPROVED EQUIPMENT FOR EVALUATING PROPERTIES OF TREES, LOGS AND LUMBER We, CANTERPRISE LIMITED, a New Zealand company of University of Canterbury, Private Bag 4800, Christchurch, New Zealand., 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: 1 (to be followed by 1a) i i il .. . - ■ - uy • U i t- Title: IMPROVED EQUIPMENT FOR EVALUATING PROPERTIES OF TREES, LOGS AND LUMBER Field of the Invention The present invention relates to improved equipment for, and a method of, evaluating properties of trees, logs and lumber. Although the equipment/method of the present invention may be used for evaluating logs and lumber, they are especially useful for evaluating properties of standing trees, and will be described with particular reference to that application.

Background of the invention There is a substantial commercial advantage in being able to predict properties of standing trees or of logs/lumber before processing. However, to be of value, it must be possible to base the predictions on non-destructive tests which do not significantly diminish the value of the trees, logs or lumber.

It is known that it is possible to predict the properties of trees, logs and lumber by passing an acoustic wave through the test subject and measuring the acoustic velocity. The properties of the timber which can be predicted from acoustic velocity measurements include fibre length and modulus of elasticity (stiffness), among others.

A number of prior patents relate to the measurement of acoustic velocity in finite lengths of timber i.e., sawn logs or lumber:- for example, NZ patents 331527, 377015/337186 and 515734. However, the equipment described in these patents requires both ends of the length of timber being measured to be accessible to the measuring equipment, and obviously this is not possible for a standing tree.

NZ patent 507297 discloses apparatus which can measure acoustic velocities in a standing tree; the apparatus includes an input spike and an output spike, both electrically connected to a recording/processing unit. The input and output spikes are inserted into the tree to be measured, a known distance apart, and acoustic velocity measurements are recorded by generating an acoustic signal through the tree by striking the input spike and recording the time of arrival of the acoustic signal at the output spike. 1a The apparatus of NZ patent 507297 has a number of drawbacks:- firstly, to get a clear, crisp, acoustic signal propagating through the tree, the input spike must be driven well into the tree i.e., through the bark and securely into the outerwood. The input spike needs to be hammered in quite hard to achieve this, and it can be quite difficult to 5 extract. If, as in the apparatus of NZ patent 507297, the input spike incorporates electrical connections, it is easy for these connections to be damaged either when the spike is hammered into position and/or when the spike is pulled to extract it.

Secondly, simple measurements of the elapsed time for an acoustic signal to travel a 10 known distance through the tree do not always give an accurate acoustic velocity measurement, since they do not allow for variations in the shapes of the acoustic wave profiles, or for the speed of acoustic propagation through the probes.

Summary of the Invention It is therefore an object of the present invention to provide equipment which overcomes the above described drawbacks.

The present invention provides equipment for evaluating properties of trees, logs and 20 lumber, said equipment including: an input probe, two or more matched sensing probes, and recording means associated with each probe; wherein the input probe is isolated from either or any of the sensing probes and from the recording means; and each of the sensing probes is electrically connected to the recording means.

As used herein, the term "sensing probe" means a probe designed to detect an acoustic wave and to generate an electrical voltage of an amplitude proportional to the amplitude of the acoustic wave.

Preferably, the input probe is configured as a generally conical/tapered spike with a 30 flat on its wider end and a point at the other end. Towards the tip of the tapered probe at least one flat face is formed on the external surface of the probe.

The present invention further provides a method for using the equipment as claimed in claim 1, said method including the steps of:- a) driving the input probe well into the tree, log or lumber to be measured; b) positioning the sensing probes in the tree, log or lumber to be measured, with a 2 known distance between the sensing probes; c) striking the input probe to generate an acoustic wave through the tree, log or lumber to be measured; d) starting recording with the recording means when any one of the sensing probes registers the arrival of an acoustic wave at a predetermined triggering voltage threshold, and then recording time of arrival of the acoustic wave at the other or each other of the sensing probes; e) analysing the shape of the acoustic wave as received by each of the sensing probes. f) Preferably, steps c/d/e are repeated several times (e.g. 8).

Brief Description of the Drawings By way of example only, a preferred embodiment of the present invention is described in detail with reference to the accompanying drawings in which:-Fig. 1 shows a diagrammatic longitudinal section through part of a tree with the equipment of the present invention in position; and Fig. 2 shows a longitudinal section through an input probe in accordance with the present invention, and a section on line A-A.

Detailed Description of the Preferred Embodiment Referring to the drawings, the equipment 2 of the present invention consists of an input probe 3, sensing probes 4,5 and a recording device 6. Each of the sensing probes 4,5 is shown as electrically wired to the recording device 6, but a wireless connection may be substituted if required. Although only two matched sensing probes 4,5 are shown, it is emphasised that more than two sensing probes may be used, each being wired to, or in wireless communication with, the recording device 6. Alternatively the sensing and recording electronics may be incorporated within the probe.

Each of the sensing probes 4,5 is an acoustic probe of known general type e.g., probes sold under the trade marks Fakopp, IML Hammer, Metriguard and Sylvatest. The sensing probe is designed to detect an acoustic wave and to generate an electrical voltage of an amplitude proportional to the amplitude of the acoustic wave; the electrical voltage generated by the probe is transmitted to the recording device 6 and processed as described hereinafter. 3 The sensing probes 4,5 are inserted into the tree 7 so that the tips 4a,5a, penetrate the bark layer 8 of the tree 7, but it is not necessary to drive the sensing probes deeply into the tree; thus they can be removed with little physical effort. The sensing probes 4,5 should be well spaced apart, either by a predetermined distance or by any measured distance. It is not necessary to locate sensing probes in any precise configuration with reference to the input probe or with reference to each other, so it is easy to locate the sensing probes at a convenient height for the user and to avoid any obvious discontinuities in the tree e.g., knots or side branches. Generally, the three probes should be in a straight line aligned along the axis of the tree or along the inclination of its grain.

The recording device 6 is arranged to receive and record the electrical voltages from sensing probes and, includes matched or compensated receivers/recorders for each probe. The device 6 may further process this data as discussed below.

The input probe 3 is shown in greater detail in Fig. 2 and consists of a tapered conical spike made of tough, impact resistant material. The wider end 9 of the spike is used as a striking surface, and the narrower end is formed to a pointed tip 10. A hole is formed through the probe adjacent to the end 9 to receive a handle 9a. A pair of opposed flats 11 is formed down each side of the probe a short distance back from the tip 10. Typically, the input probe 3 is 10-15 centimetres long and roughly half of this length penetrates into the tree.

As shown in Fig. 1, in use the input probe 3 is hammered into the tree sufficiently to penetrate well through the bark layer 8 and securely into the outerwood. It is important that the input probe 3 penetrates securely into the outerwood to give a good sharp acoustic signal through the tree when the wider end 9 is struck. Since the input probe 3 does not carry any instrumentation or electrical cables or any other delicate devices, it can be driven in deeply and then struck hard without any risk of damage. The provision of the flats 11 makes the probe 3 comparatively easy to withdraw from the tree:- the probe can be manually rotated about its longitudinal axis using the handle 9a and the presence of the flats allows the capillary tension between the probe surface and the tree to be broken easily, so that the probe can be extracted by hand.

The above described equipment is used as follows:- the input probe 3 is hammered into the tree as described above. Each of the sensing probes 4,5 is inserted into the 4 tree, with the probes well spaced apart (e.g., 1-1.5 metres apart). The sensing probes need only be lightly tapped into the tree:-just enough to penetrate the bark and enter the outer sap wood. Each of the sensing probes 4,5 is electrically connected to the recording device 6.

The probes 3,4,5 usually are aligned in a straight line up one side of the tree.

Good results have been obtained by inserting the input probe lower down the tree than the sensing probes, with the pointed end of the input probe angled upwards at no 10 more than 45° to launch the acoustic stress wave of the hammer tap up the tree towards the sensing probes. The sensing probes preferably are inclined downwards at no more than 45°.

The input probe 3 is then struck sharply (e.g., with a hammer) to generate a stress 15 (acoustic) wave that spreads throughout the wood and is reflected at the boundaries of the outerwood and the bark. If the equipment of the present invention is used on a debarked log or on sawn timber, the stress wave is reflected at the edges of the log or timber.

The recording device 6 is pre-armed and is triggered when the first of any of the sensing probes registers the arrival of the acoustic wave. The acoustic wave can be approximated by a Gaussian weighted sine wave form and arrival times are recorded when the arriving wave reaches two or more predetermined voltage settings for the probe. These times together with the voltage settings may be used to determine the 25 compensated time equivalent to the first arrival of the acoustic wave at a probe, i.e., the zero voltage threshold:- the acoustic wave generates in the probe a voltage proportional to the amplitude of the wave, and the recorded arrival times for the voltage values are compared and processed to give a compensated time equivalent to a zero voltage value.

Thus for each probe the recording device records and displays in real time the time delay between the acoustic wave reaching the predetermined voltages. Also the recording device records and displays the time differences between the first sensing probe to receive the acoustic wave and the other sensing probes, i.e. for each probe 35 the zero voltage arrival times are being compared.

These triggering voltages can be changed in the software to take account, for example, of acoustic propagation characteristics when a different tree species is being studied. It is possible to set up the sensing probes and the recording device so that more than two voltage readings are taken from each probe, if required.

In the matter of one or two seconds, it is possible to record a number of taps (typically eight) without having to re-set the system. For each tap, time the recording device records and displays:- (1) the time-delays (also called variously the transit time or time of flight) between probes by comparing at the zero voltage values; and (2) the time delay (voltage rise time) between the triggering voltage thresholds for each probe.

These values can be viewed in real time and immediately accepted or rejected. For example, where the hammer tap has generated a poor quality acoustic wave, the voltage rise times for all probes will be longer than anticipated and that particular data set can be deleted. Where the voltage rise time for a single probe is longer than expected the probability is that that particular probe is making poor contact with the wood beneath the bark; the data set can be deleted and that particular probe tapped a bit further into the tree to ensure better contact before further measurements. With other tools, which do not record and display the voltage rise time, it is not clear whether a reading is a genuine reading or not and to partially compensate it is necessary to hammer the stop probes deep into the wood (which slows the gathering of data as the probes are harder to remove).

For an experienced operator, the visual display of both transit times between probes and the rise times at each probe indicate whether one has gathered genuine, reproducible data or whether there is a problem in gathering the data.

At the simplest level, the recording device 6 records at least two magnitude/time readings for each probe. Once these have been accepted and retained then further processing is carried out after the data from the recording device 6 have been uploaded to a computer. Alternatively, the recording device may be programmed to carry out the further processing as well.

The provision of taking more than one reading from each probe and then determining the compensated time equivalent to the first arrival of the acoustic wave greatly 6 enhances the accuracy of the reading. This avoids the sort of anomalies that can occur when using recording probes which only trigger once, when the detected acoustic wave reaches a single predetermined value. This type of setup can cause problems if the amplitude of the wave is below the predetermined value or if the wave 5 form is a comparatively "gentle" one which peaks over a long period. Thus, the setup of the present invention also helps to make the measurement relatively independent of the type of initial impact given to the input probe.

In a normal measuring process, eight sets of readings are taken for each tree, with the 10 same positions of input and sensing probes. The recording device 6 preferably allows any obviously invalid data to be deleted on the spot. The recording device 6 also records the tree identity number for each set of data.

With large diameter trees, say greater than 300 mm in diameter, generally 15 measurements are repeated on the opposite side of the tree, as wood properties can vary around the circumference of the tree. Measurements on two or more sides gives a much more accurate average for the tree, When the sets of readings have been completed, the readings plus the corresponding 20 tree identity numbers are uploaded to a computer for further processing.

The said invention measures acoustic velocity on the outside of a standing tree. It is necessary to relate such a measurement to the value of the wood that eventually will be cut or taken from that tree. The value of a mature tree or the potential value of a 25 young tree is better understood if the standing tree velocity can be expressed in terms of the acoustic properties of the whole stem section and not just to the outer part assessed this said invention.

Two equations have been developed which relate the standing tree acoustic velocity to 30 the equivalent value of the whole log were the tree to be felled. In the first instance, to do this the measured acoustic velocity (Vm) along any given tree is adjusted to take account of the length/diameter aspect of the stem, where the term "length" (L) relates to the length of the anticipated sawlog (were the log to be felled), and the "diameter" (D) is the average diameter of the stem over the distance that the acoustic velocity 35 was measured [both L and D expressed in the same units]. 7 The equation: \ 0.076 modified velocity = 0.7245 * Vm * — has been found to give a satisfactory results, \DJ that correspond to acoustic properties of the entire cross-section A slightly better equation (which requires more information about the trees being measured) is Modified velocity = 0.9049 * Vm * ((S/DBH)/GR)°052 where S is the span length, Vm is the measured acoustic velocity, DBH is the diameter at breast height and GR is DBH/age.

Span length is the distance between the sensing probes [both span length and DBH expressed in millimetres]. The relationship is an empirical one, however, the same coefficient values are found applicable to a range of data sets.

Within the experimental ranges studied, the equations given above are the optimised equations. However, in principle, the numeric constants in the equations may need to be modified for other species.

The said invention measures outerwood properties at breast-height, but these need to be related to whole-log properties, i.e. comparing standing tree values to log values. The modified velocity is within 1 % of the stand-average velocity that can be obtained subsequently by other tools which assess the whole-log after felling; further the modified individual butt log velocity is within 5% of the value obtained by those other tools.

Having described the preferred embodiments of the invention it will be apparent to those skilled in the art that various changes and alterations can be made to the specific embodiments and methods and yet still come within the general concept of the invention. All such changes and alterations are intended to be included in the scope of this specification. 8

Claims (18)

1. Equipment for evaluating the properties of trees, logs and lumber, said equipment including: an input probe, two or more matched sensing probes, and recording means associated with each probe; wherein the input probe is isolated from either or any of the sensing probes and from the recording means; and each of the sensing probes is electrically connected to the recording means.
2. Equipment as claimed in claim 1, wherein the input probe comprises a tapered spike with a flat on its wider end and a point at the other end.
3. Equipment as claimed in claim 2 wherein at least one flat face is formed on the external surface of the probe adjacent the point.
4. Equipment as claimed in any one of the preceding claims wherein each of the sensing probes is connectable to the recording means by wires.
5. Equipment as claimed in any one of claims 1-3 wherein each of the sensing probes is connectable to the recording means by a wireless connection.
6. Equipment as claimed in any one of claims 1-3 wherein each probe incorporates recording means.
7. A method for using the equipment as claimed in claim 1, said method including the steps of: a) driving the input probe well into the tree, log or lumber to be measured; b) positioning the sensing probes in the tree, log or lumber to be measured, with a known distance between the sensing probes; c) striking the input probe to generate an acoustic wave through the tree, log or lumber to be measured; d) starting recording with the recording means when any one of the sensing probes registers the arrival of an acoustic wave at a predetermined triggering voltage threshold, and then recording time of arrival of the acoustic wave at the other or each other of the sensing probes; 9 e) analysing the shape of the acoustic wave as received by each of the sensing probes.
8. 8. The method as claimed in claim 7 wherein in step (d), multiple measurements 5 are taken at each sensing probe.
9. 9. The method as claimed in claim 7 or claim 8 wherein steps (c), (d) and (e) are repeated several times.
10. 10 10. The method as claimed in any one of claims 7-9 wherein each of the sensing probes is only lightly tapped into the tree, log or lumber to be measured.
11. 11. The method as claimed in any one of claims 7-10 wherein the input probe and the sensing probes are aligned in a straight line along one side of the tree, log 15 or lumber to be measured.
12. 12. The method as claimed in any one of claims 7-11 wherein the input probe is inserted into the tree, log or lumber below the sensing probes, with the point of the input probe angled towards the sensing probes at an angle not greater than 20 45°, and the sensing probes angled towards the input probe at an angle not greater than 45°.
13. 13. The method as claimed in any one of claims 7-12 wherein in step (e), after the arrival times have been recorded for specific voltage values, a compensated 25 time equivalent to a zero voltage value is calculated.
14. 14. The method as claimed in claim 13 wherein the recording means is adapted to record and display the time delay between probes by comparing the zero voltage values and the time delay between triggering voltage thresholds for 30 each probe.
15. 15. The method as claimed in claim 14 wherein the method is used in relation to a standing tree, further including the step of relating the measured acoustic velocity to the equivalent acoustic velocity value of the whole log obtainable 35 from that tree using the equation 10 modified (whole log) velocity = 0.7245 * , y.o* j)s where Vm is the measured acoustic velocity along the tree, L is the length of the anticipated sawlog, 5 D is the average diameter of the stem over the distance that the acoustic velocity was measured.
16. 16. The method as claimed in claim 14 wherein the method is used in relation to a standing tree, further including the step of relating the measured acoustic 10 velocity of the equivalent value of the whole log of obtainable from that tree using the equation Modified (whole log) velocity = 0.9049 * Vm * ((S/DBH)/GR)°052 where Vm is the measured acoustic velocity along the tree 15 S is the span length DBH is the diameter at breast height GR is DBH divided by the age of the tree.
17. 17. Equipment for evaluating the properties of trees, logs and lumber, substantially 20 as hereinbefore described with reference to and as shown in the accompanying drawings.
18. 18. The method for using the equipment as claimed in claim 1, substantially as hereinbefore described with reference to and as shown in the accompanying 25 drawings. iistiwu" «" '..i t.y Oil,;.-: Oi !!"' 2^5 RFH * V F- n 1 I y W L-.uo. La-l/