WO2007048187A1

WO2007048187A1 - Methods and apparatus for measuring properties of fibre samples

Info

Publication number: WO2007048187A1
Application number: PCT/AU2006/001587
Authority: WO
Inventors: Russell John Allan
Original assignee: Fourth Wave Pty Ltd
Priority date: 2005-10-25
Filing date: 2006-10-25
Publication date: 2007-05-03

Abstract

An apparatus for measuring at least one property of fibres in a fibre sample includes a transmitter (104) located, in use, on a first side of a fibre sample (102) which is arranged to couple transmitted ultrasonic signals into the fibre sample (102). A receiver (106) is located on a second side of the fibre sample (102) opposed to the first side, which is arranged to detect received ultrasonic signals corresponding with the transmitted ultrasonic signal following transmission through the fibre sample (102). A processing unit (214) processes received ultrasonic signals and determines a measure of at least one property of the fibre sample, such as a mean fibre diameter. A method of operating the apparatus includes coupling transmitted ultrasonic signals into the fibre sample (102), which signals include a plurality of frequencies within a predetermined frequency range. The method further includes measuring a frequency response of transmission of the ultrasonic signals through the fibre sample (102), and analysing the frequency response to determine a measure of at least one property of the fibres in the fibre sample. In one particular embodiment, a peak frequency of the frequency response is determined, from which a mean fibre diameter is calculated.

Description

METHODS AND APPARATUS FOR MEASURING PROPERTIES OF FIBRE

SAMPLES FIELD OF THE INVENTION

The present invention relates generally to the measurement of properties of samples of fibre, for example wool fibres and the like, and is particularly, though not exclusively, directed to the measurement of fibre diameter and related properties. The inventive method and apparatus may enable relevant measurement of fibre properties to be rapidly and conveniently measured in situ, for example at the farm and/or while the fibres are still on the animal. BACKGROUND OF THE INVENTION

Properties of fibres, whether natural or synthetic, used in the manufacture of yarns, textiles and related products, are important in determining the quality and durability of the finished product. The importance of properties such as fibre diameter, fibre strength, fibre diameter variation and so forth, is particularly apparent in the wool industry in which a variety of standard tests of such properties have been developed, in addition to assessments provided by specialist wool classers for gauging the quality and fineness of wool, and thereby assigning a value to it. However, similar considerations apply in the assessment of other natural fibres, such as cotton, angora, llama, alpaca and so forth, and equally, at least in principle, to corresponding properties of synthetic fibres. Within this specification, reference is made primarily to the example of measuring properties of wool, in part because of the maturity of the industry, however it will be appreciated that many similar principles apply to other fibres, and in other industries, and the present invention is therefore not limited to applications within the wool industry.

In the measurement of wool quality there are a number of standard tests that allow the buyer to set prices and gauge the "quality" of the fibre. Two important considerations are the "fineness" of the wool, measured analytically as wool diameter or hauteur, and the variability of diameter down the length of the individual fibres. The variability of diameter down the length of a grown wool fibre reflects the growing conditions at any particular time, as influenced by factors such as changing forage conditions, including water and food availability, seasonal effects and the health of the animal. Such variability affects the breaking strength of the fibre, since portions of the fibre having smaller cross-sections are more likely to fail than thicker portions of the fibre.

The ultimate breaking strength of a wool staple and/or of individual fibres is also an important factor, since it may determine the ease of spinning individual fibres into thread and the extent to which the fibre length is diminished during all stages of wool or fibre processing.

Traditionally, wool classers are trained to gauge the fineness of wool and assign a value to it. In recent times, there has been interest in developing analytic means for determining wool diameter and variation to enable an objective assessment of wool and fibre value. A selection of methods and apparatus that have been developed for assessing and/or measuring key wool fibre properties are summarised in the following paragraphs.

The projection microscope is an instrument for measuring fibre diameter mean and distribution. Magnified images of the profiles of short lengths (snippets) of fibre are projected onto a screen, and their widths measured using a graduated scale.

An airflow method of measuring the mean fibre diameter of a wool sample involves the preparation of a test specimen, which includes a measured mass of scoured, dried and carded wool fibre. The test specimen is exposed to a conditioning atmosphere, compressed to a fixed volume, and a current of air is passed through it. The rate of airflow is adjusted until the pressure drop across the sample equals a predetermined value. The resulting rate of flow is then an indicator of the mean fibre diameter in the wool sample. The instrument used in the airflow measurement technique may be calibrated to international standard wool tops of known fineness.

The LaserScan apparatus is an instrument that detects shadows of fibre snippets in a laser beam as they are carried in solution through the beam. This instrument is used to measure mean fibre diameter and fineness distribution. A corresponding transportable instrument known as FleeceScan includes the LaserScan instrument along with a computer, scales, an automatic fleece corer and a sample washer unit. The FleeceScan instrument can be set up in a shearing shed, moved from one location to another, or may be set up in a centralised classing location, such as a wool store. FleeceScan measures fibre diameter, mean curvature, standard deviation of diameter, coefficient of variation of diameter and fleece weight.

The OFDA-100 (Optical Fibre Diameter Analyser) is an instrument for measuring fibre diameter mean and distribution using automated microscope and image analysis techniques. The portable (suitcase-sized) OFDA-2000 is a fibre measurement instrument, capable of measuring greasy wool staples direct from the sheep's back or from a fleece at shearing time. It requires a mathematical grease-correction factor (GCF) to be applied. The OFDA-2000 is able to measure mean fibre diameter, a diameter distribution histogram, percentage of fibres greater than 30 microns (comfort factor), curvature and standard deviation of curvature, staple length, diameter profile along the staple and the positions of the finest and broadest points along the staple. The OFDA-2000 is perceived to be easier to use than FleeceScan, but is generally considered to be less accurate. As will be appreciated, in most cases the foregoing measurement techniques and apparatus require that samples be specially prepared for assessment. The preparation and/or assessment may be time-consuming and/or inconvenient. Most of the prior art measurement apparatus is not easily transportable or portable, making application in situ, for example at the farm, either difficult or impossible. Of the instruments that are transportable or portable, the smallest is still the size of a suitcase, and is perceived to be less accurate than the more bulky transportable or fixed instruments.

There remains, therefore, an ongoing need for improved methods and apparatus for measuring or estimating key parameters of natural fibres, and particularly wool fibres, including fibre diameter, diameter variation, strength and so forth, which mitigate known limitations of existing methods and instruments.

It is particularly desirable to provide for the measurement of fibre properties in situ, for example measurement of fibre properties of shorn wool or wool that is still growing on the animal. In this regard, it is preferable that the measurement apparatus be portable and convenient to use, and that the measurement method be quick, accurate and reproducible, and that there be no requirement that samples be specially prepared prior to measurement.

The present invention therefore seeks particularly to address these needs. SUMMARY OF THE INVENTION

In one aspect, the present invention provides a method of measuring at least one property of fibres in a fibre sample which includes a plurality of similar fibres, the method including the steps of: coupling transmitted ultrasonic signals into the fibre sample, wherein the signals include a plurality of frequencies within a predetermined frequency range; measuring a frequency response of transmission of said ultrasonic signals through the fibre sample; and analysing the frequency response to determine a measure of at least one property of the fibres in the fibre sample.

The inventive method provides a number of potential advantages over prior art methods. Firstly, the method may be performed in situ, and may require no, or minimal, preparation of the fibre sample prior to measurement. The inventors have observed that attenuation of ultrasonic signals during transmission through a fibre sample is dependent upon properties of the signals, such as frequency content, and also upon the geometry of the medium (Ze the fibres) through which the signals travel. It is presently believed that the method relies upon the effect of fibres included in the sample upon one or more factors determining a frequency dependence of the transmission of ultrasonic signals through the sample, such as reflection, absorption, refraction and/or diffraction of ultrasonic waves having different frequencies. Accordingly, results of the measurement may be substantially unaffected by the presence of common impurities in the sample, such as dirt and/or natural oils. The inventive method may therefore be employed for the measurement of fibre properties at a farm, and even on an animal, without the need for complex and/or time-consuming sample preparation.

Further advantages that may be achieved through the use of embodiments of the inventive method include: rapid measurement (up to 10,000 times faster than current methods); the ability to obtain an average measure of a property of a large number of fibres quickly; the suitability of the method for analysing different types of fibres, including synthetic fibres, cotton and other plant fibres, animal fibres and so forth; the ability of the method to be self-calibrating; potential low cost compared to existing methods; and the potential to implement the method within a small and highly portable device. The fibre sample may include natural fibres, such as animal fibres including wool, plant fibres including cotton, or other natural fibres such as silk. Animal fibres suitable for measurement using the method include the wool of sheep, goats (eg angora), llamas, alpacas, and so forth. The method may also be applied to samples of synthetic fibres.

In preferred embodiments, ultrasonic frequencies in the range of 0.1 MHz to 5 MHz may be used.

In some embodiments of the method, ultrasonic signals may be applied in the form of a swept or stepped frequency within the predetermined ultrasonic frequency range. In alternative embodiments, an ultrasonic signal may be applied which simultaneously includes a plurality of frequencies lying within the predetermined range, such as a white noise type excitation.

However, in a particularly preferred embodiment the transmitted ultrasonic signals include a series of pulses, wherein a pulsewidth of each pulse corresponds with a desired mean ultrasonic frequency according to an inverse relationship well known in the art. For example, a signal having a mean ultrasonic frequency of 1 MHz may be provided by one or more pulses having a pulse width of one microsecond. In a particularly preferred embodiment, the transmitted ultrasonic signals include repetitive pulses, having a repetition frequency that is much lower than the corresponding mean ultrasonic frequency of the pulses. For example, a pulse repetition frequency of 1 kHz may be used. Advantageously, the resulting detected ultrasonic signals may be averaged over a number of pulse periods in order to determine the transmission and/or attenuation of ultrasonic signals passing through the fibre sample at the corresponding mean ultrasonic frequency. The measurement may then be repeated for a series of different pulse widths, corresponding with different mean ultrasonic frequencies.

The measure of said at least one property of the fibre sample is preferably a peak frequency of the frequency response, corresponding with a maximum transmission of ultrasonic signals through the fibre sample within the predetermined frequency range. The property obtained from said measure may be a mean fibre diameter of fibres within the sample. Indeed, trials conducted by the present inventors according to one embodiment of the inventive method have demonstrated a substantially linear relationship between the measured peak frequency, and mean fibre diameter as determined using prior art measurement methods. The method may be repeated at a plurality of selected positions along the fibre sample, in order to measure variations in said at least one property of the fibres along their length. In this form, the method may be particularly useful in the case of natural fibres, such as wool, where properties of fibres may vary as they grow as a result of changing conditions, including water and food availability. In such cases, properties of all fibres in the sample may be similar at each location along the sample, because all were subject to the same conditions at the corresponding time of growth.

In particularly preferred embodiments, the method is used to measure fibre diameter variation at selected positions along a fibre sample. Measurements of fibre diameter variation may be used in the assessment of quality and/or fineness of fibres, or strength of fibres, as well as in the estimation or evaluation of likely properties of fabrics, threads or yams manufactured from the fibres.

In another aspect, the present invention provides an apparatus for measuring at least one property of fibres in a fibre sample which includes a plurality of similar fibres, the apparatus including: a transmitter located on a first side of the fibre sample and arranged to couple transmitted ultrasonic signals into the fibre sample, wherein the signals include a plurality of frequencies within a predetermined frequency range; a receiver located on a second side of the fibre sample opposed to the first side and arranged to detect received ultrasonic signals corresponding with the transmitted ultrasonic signals following transmission through the fibre sample; and a processing unit configured to process the received ultrasonic signals so as to measure a frequency response of transmission of the ultrasonic signals through the fibre sample, and analyse the frequency response to determine a measure of at least one property of the fibre sample. The transmitter preferably includes a transmitting transducer, configured to convert electrical signals into corresponding ultrasonic signals. The receiver preferably includes a receiving transducer, configured to convert received ultrasonic signals into corresponding electrical signals. In preferred embodiments, the transmitting and receiving transducers include piezo-electric elements, such as thin PVDF (polyvinylidene fluoride) layers arranged in contact with one or more suitable ultrasonic coupling media which in turn contact the fibre sample. Suitable coupling media include layers of elastic materials such as elastomers and/or appropriate natural or synthetic rubber materials, such as neoprene. Materials of this type are able to provide good coupling of ultrasonic signals between the piezo-electric elements and the fibre sample held under suitable tension and/or compression between opposed faces of the coupling media of the transmitting transducer and receiving transducer respectively. The receiver may also include associated receiving electronics, such as amplifiers, filters and the like for generating and conditioning electrical signals suitable for further processing.

In preferred embodiments, the apparatus includes a closable structure upon or within which the transducers are disposed, such that when the apparatus is closed over the fibre sample, the sample is held between the transmitting transducer and receiving transducer.

The closable structure may be, for example, a clamp including first and second clamping members, the transmitter being disposed on or in the first clamping member and the receiver disposed in an opposed location on or in the second clamping member. The apparatus may further include clasps for holding the clamp in a closed position with the fibre sample held between the transmitter and receiver when in use.

The first and second clamping members may be joined, with a hinge therebetween, to enable the clamp to be opened and closed. In this form, an apparatus in accordance with the invention may provide a convenient, portable, handheld device for measuring fibre properties.

In preferred embodiments, the apparatus includes a signal generator for generating electrical signals to drive the transmitting transducer. The signal generator may be controlled by the processing unit, to synchronise the generation of transmitted ultrasonic signals with corresponding analysis of received signals.

The processing unit preferably includes a combination of analog and/or digital hardware for processing the received ultrasonic signals to measure the frequency response of transmission and to analyse the frequency response to obtain a measure of the at least one property of the fibres in the fibre sample. The processing unit may include a computer having a central processor, associated memory, and other peripheral hardware arranged to receive an electrical signal corresponding with detected ultrasonic signals, wherein the computer is programmed to process and analyse the received ultrasonic signals.

According to particularly preferred embodiments, the signal generator is controlled, for example by the processor, to generate the ultrasonic signals including a plurality of frequencies within a predetermined ultrasonic frequency range. The ultrasonic signals may include signals having a swept or stepped frequency, or signals which simultaneously include a plurality of frequencies, such as white noise type signals. However, in particularly preferred embodiments the generated signals include sequences of pulses, wherein a pulsewidth of each pulse corresponds with a desired mean ultrasonic frequency. Preferably, the processing unit analyses the received ultrasonic signals including a plurality of frequencies within the predetermined ultrasonic frequency range to determine a peak frequency, corresponding with a maximum transmission of ultrasonic signals through the fibre sample within said frequency range. The processing unit may then further compute a value of the at least one property of the fibre sample, and in particularly preferred embodiments the processing unit computes a mean fibre diameter from the peak frequency value.

In yet another aspect, the present invention provides an apparatus for measuring a variation of at least one property of fibres in a fibre sample which includes a plurality of similar fibres, said variation being measured as a function of position within the sample, the apparatus including: a plurality of transmitters located at selected positions on a first side of the fibre sample and arranged to couple transmitted ultrasonic signals into the fibre sample, wherein the signals include a plurality of frequencies within a predetermined frequency range; at least one receiver located on a second side of the fibre sample opposed to the first side to detect received ultrasonic signals corresponding with the transmitted ultrasonic signals following transmission through the fibre sample; and a processing unit configured to process the received ultrasonic signals so as to measure a frequency response of transmission of the ultrasonic signals through the fibre sample, and to analyse the frequency response to determine measures of at least one property of the fibre sample at positions corresponding with the transmitters, and thereby to measure a variation in said property as a function of position within the sample.

In preferred embodiments, the at least one receiver includes a plurality of receivers, each of which is located at a position on the second side of the fibre sample substantially opposed to a corresponding one of the transmitters, to detect received ultrasonic signals transmitted through the fibre sample from said corresponding transmitter.

It is especially preferred that the transmitters and receivers be arranged in a linear array, and that fibres in the sample are arranged to extend along the direction of the array, such that the apparatus measures the variation in the property along the length of the fibres. Such an arrangement is particularly advantageous for measuring variations in the properties of natural fibres, for example variations in fibre diameter, where such properties may vary in the course of growth. in a further aspect, the invention provides an apparatus for measuring at least one property of fibres in a fibre sample which includes a plurality of similar fibres, the apparatus including: a transmitting transducer having an electrical input, and which generates a vibrational excitation having a frequency determined by an applied electrical input signal; a receiving transducer having an electrical input, and which generates an electrical output signal corresponding with an applied vibrational excitation; at least one processor; at least one storage medium operatively coupled to the processor; an output peripheral interface between the processor and the electrical input of the transmitting transducer; and an input peripheral interface between the electrical output of the receiving transducer and the processor; wherein, in use, the transmitting transducer and the receiving transducer are arranged such that vibrational excitations generated by the transmitting transducer are coupled into the fibre sample, transmitted therethrough, and detected at the receiving transducer; and wherein the storage medium contains program instructions for execution by the processor, said program instructions causing the processor to execute the steps of: directing the transmitting transducer to generate a vibrational excitation including a plurality of frequencies within a predetermined ultrasonic frequency range; measuring a frequency response of the fibre sample to said excitation, by receiving electrical signals from the receiving transducer corresponding with vibrational excitations transmitted through the fibre sample; and analysing the measured frequency response to determine a measure of at least one property of the fibre sample.

Further preferred features and advantages of the present invention will be apparent to those skilled in the art from the following description of preferred embodiments of the invention, which should not be considered to be limiting of the scope of the invention as defined in any of the preceding statements, or in the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described with reference to the accompanying drawings, wherein like reference numerals refer to like features, and in which: Figure 1 is a schematic diagram showing an arrangement for measuring fibre properties using ultrasonic signals according to a preferred embodiment of the invention;

Figure 2A is a schematic diagram illustrating a measurement apparatus according to an embodiment of the invention; Figure 2B is a block diagram of another measurement apparatus according to an alternative embodiment of the invention;

Figure 3 is a graph illustrating measured ultrasonic transmission as a function of mean frequency of transmitted ultrasonic signals; Figure 4 is a graph illustrating a comparison of measured ultrasonic transmission as a function of mean frequency of transmitted ultrasonic signals for fibre samples having differing mean fibre diameters;

Figure 5 is a graph illustrating a substantially linear relationship between peak frequency of ultrasonic transmission and reported fibre diameter;

Figure 6 is a schematic diagram showing an alternative measurement apparatus in accordance with an embodiment of the invention, for measuring a variation in fibre properties along a length of a fibre sample; and

Figure 7 is a schematic illustration of the operation of the apparatus of Figure 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring firstly to Figure 1 , there is illustrated schematically an arrangement 100 for measuring fibre properties using ultrasonic signals according to a preferred embodiment of the present invention. In the depicted arrangement 100 a fibre sample 102 includes a plurality of similar fibres, which may be natural fibres, such as wool, cotton or the like, or synthetic fibres. For convenience in describing preferred embodiments of the invention, reference will be made to applications involving measurements performed to determine properties of wool fibres, however it will be appreciated that the invention is not limited to measuring the properties of wool, and is more broadly applicable to a variety of natural and/or synthetic fibres.

Within the arrangement 100 the wool sample 102 is held under slight tension between a transmitter 104 and receiver 106. The transmitter 104 is configured to transmit ultrasonic signals, and is located on a first side of the wool sample 102, which is an upper side as shown in the arrangement 100 of Figure 1. A corresponding receiver, configured to receive ultrasonic signals, is located on an opposed second side of the fibre sample, being the lower side in the arrangement 100 depicted in Figure 1.

The transmitter 104 couples transmitted ultrasonic signals 108 into the fibre sample 102. The receiver 106 detects received ultrasonic signals 110 corresponding with the transmitted ultrasonic signals 108 following their transmission through the fibre sample 102. In accordance with the invention, the received ultrasonic signals are analysed to obtain a measure of at least one property of the wool fibres within the wool sample 102.

It is believed that transmission properties of ultrasonic signals 108, 110 through fibre samples, eg wool sample 102, are dependent upon various factors, including the frequency content of the transmitted ultrasonic signals 108, as well as the geometry of the medium through which the signals are transmitted. The received ultrasonic signals 110 generally correspond with the transmitted ultrasonic signals 108, subject to the effects of processes such as reflection, absorption, refraction and/or diffraction of ultrasonic waves within the fibre sample 102. The received signal 110 depends upon the averaged effect of all fibres of the sample 102 through which the signal has passed. Accordingly, if the sample 102 is composed of similar fibres, the results of measurement of the received ultrasonic signals 110 will be generally representative of properties of the individual fibres in the sample 102, as well as the average effect of all fibres in the sample 102.

It is further believed that the results of the measurement of received ultrasonic signals 110 may be substantially unaffected by the presence of common impurities in the sample, including dirt and/or natural oils. The invention, in various embodiments, may therefore be utilised to measure properties of fibre samples that have not been subjected to special treatment or preparation prior to measurement. In particular, embodiments of the invention may be employed to measure the properties of fibres such as wool in situ, for example, at the farm, in the shearing shed, and even while the wool remains on the animal.

Figure 2 depicts in greater detail a measurement apparatus 200 according to one particular preferred embodiment of the invention. The apparatus 200 includes transmitter 104 and receiver 106 arranged in a convenient, portable and potentially handheld device for use in measuring fibre properties.

The transmitter 104 includes a transmitting transducer which converts electrical input signals into ultrasonic signals. The transmitting transducer includes a piezo-electric element 202, which in preferred embodiments is a relatively thin film of piezo-electric material such as PVDF. The receiver 106 includes corresponding receiving transducer 106a for converting detected ultrasonic signals into corresponding electrical signals. The receiving transducer 106a also includes piezo-electric element 204, which again may be a thin film of piezo-electric material such as PVDF.

The PVDF layers 202, 204 are arranged in mechanical communication with elastic layers, eg 206, 208, 210 which conduct ultrasonic signals to and from a fibre sample 102, and couple the transmitted ultrasonic signals into the fibre 102 from the transmitting piezo-electric layer 202 to the fibre sample 102, and from the fibre sample 102 to the receiving piezo-electric layer 204. In the preferred embodiment 200, the conductive layer 206 is an elastomer bedding, while conducting and coupling layers 208, 210 are fabricated from a suitable elastic material, such as a natural or synthetic rubber material, and may be, for example, made of neoprene.

Further details of the design principles and construction of transducers generally suitable for use in embodiments of the invention may be found in the paper by CC Habeger, WA Wink, and ML Van Zummeren, "Using neoprene-faced PVDF transducers to couple ultrasound into solids", published in the Journal of the Acoustical Society of America Volume 84, No. 4, October 1988, the contents of which are incorporated herein in their entirety by reference.

The measurement apparatus 200 also includes a signal generator 212 for generating electrical signals to drive the transmitting transducer 104. The signal generator 212 may generally be operable to generate a variety of signals useful for measuring properties of the fibre sample 102. For example, useful signals may include sinusoidal signals of varying frequency and amplitude, broadband signals, such as white noise type signals, and/or pulse trains having various pulse shapes, pulse widths and repetition frequencies. As will be appreciated, the aforementioned signals are exemplary only, and not exhaustive of the variety of signals that may be generated by signal generator 212.

The receiver 106 preferably further includes receiving electronics operably connected to the piezo-electric layer 204, including, but not necessarily limited to, an amplification stage 106b, and additional electronics 106c for filtering and/or otherwise conditioning the received signal for further processing and analysis. Such conditioning may include, for example, analog-to-digital conversion of received, amplified, filtered and/or otherwise electronically processed signals for further digital processing, such as by a suitably programmed computer. Accordingly, the apparatus 200 also includes a processing unit 214, which may include analog and/or digital electronics for further processing of received signals, and in particular may include a computer having a central processor, associated memory and other peripheral devices for interfacing with components of the apparatus 200, processing received signals, and/or interfacing with a user of the apparatus for initiating and controlling measurements and presenting measurement results.

In some embodiments of the invention, the signal generator 212 may be interfaced with and/or controlled by the processing unit 214, in order to synchronise the generation of transmitted ultrasonic signals with corresponding analysis of received signals. As will be appreciated, the apparatus 200 may thereby be programmed or otherwise configured to perform a variety of ultrasonic measurements on a fibre sample 102. Alternatively, the signal generator 212 may include a separate controlling processor, with associated memory and peripheral devices.

Figure 2B is a block diagram 250 representing an alternative embodiment of a measurement apparatus in accordance with the present invention. The block diagram 250 illustrates the structure of a self-contained, portable apparatus for measuring fibre properties. The apparatus 250 includes a microprocessor 252 which is operatively coupled to a storage medium 254, which preferably includes a non-volatile memory device permanently containing program instructions for execution by the microprocessor 252. Volatile storage, such as random access memory, for the temporary storage of program variables, data and so forth, may also be provided within the storage medium 254. The apparatus 250 also includes signal generation circuitry 256, and an output interface 258, which together provide a peripheral interface between the microprocessor 252 and an electrical input of the transmitting transducer of the transmitter 104. An input peripheral interface 260 is also provided which receives electrical signals output from the receiving transducer of the receiver 106 for input to the microprocessor 252. As will be appreciated, data is generally output from, and input to, the microprocessor 252 in digital form, and accordingly the signal generation circuitry 256 may include a digital-to-analog converter for converting digital control signals generated by the microprocessor 252 into analog electrical signals suitable for input to the transmitting transducer of the transmitter 104. Likewise, the input peripheral interface circuitry 260 may include an analog-to-digital converter for converting signals received from the receiving transducer of the receiver 106 into a digital format suitable for input to the microprocessor 252.

While the apparatus 250 illustrated in Figure 2B includes a separate microprocessor 252, storage medium 254, signal generation circuitry 256, and output and input peripheral interfaces 258, 260, it will be appreciated that numerous implementations of the functionality of these various components are possible. For example, in alternative embodiments the microprocessor 252 may be a microcontroller device which includes internally all of the required volatile and non-volatile storage, along with various additional peripheral devices for facilitating interfaces with the transmitter 104 and receiver 106, as well as other components that may be included in a portable measurement apparatus. Since the various design and implementation options will be readily apparent to those skilled in the art of electronic circuit design, they are not discussed in detail herein, and for simplicity details of the various storage and peripheral devices are omitted from the drawings.

As previously mentioned, the storage medium 254 includes a body of program instructions for execution by the microprocessor 252, which implement the various functions of the measurement apparatus 250. The body of program instructions includes instructions for controlling the signal generation circuitry 256, and for receiving and processing the electrical input received from the receiver 106 via interface 260 in accordance with a method embodying the present invention, such as will be described in greater detail below. However, before describing a preferred measurement method the discussion now turns back to Figure 2A, and a preferred mechanical arrangement of the transmitter 104 and receiver 106.

In particularly preferred embodiments, the measurement apparatus 200, 250 is arranged in a closable structure, with the transducers 104, 106a being disposed therein, such that the apparatus may be closed on the fibre sample 102 whereby the sample 102 is held securely between the transmitter 104 and receiver 106. Such an arrangement may conveniently provide suitable coupling pressure between the facings 208, 210 and the opposed sides of the fibre sample 102, and may also be arranged to provide an appropriate light tension upon the fibre sample. In this respect, the provision of fibre guides, eg 216, assists in confining the fibre sample 102 within the measurement apparatus 200.

The apparatus 200, 250 may function as a clamp wherein the transmitter 104 is disposed within a first clamping member, and the receiver 106 is disposed within a second clamping member, whereby the fibre sample 102 may be clamped and held between said clamping members. Clasps may be provided, either integrated with the guides 216, or located elsewhere on the apparatus 200, 250, to hold the clamp arrangement shut during measurement. A convenient, portable, handheld device may potentially be provided in which the clamping members are joined, with a hinge therebetween, to provide a single clamp unit that is easy to handle and to close upon a fibre sample 102, even when the sample is, for example, still located on the animal.

As will be appreciated, the apparatus 200 and/or 250 may be utilised to transmit and receive a wide variety of ultrasonic test signals, which may potentially be used to measure various different properties of fibre samples, eg wool sample 102, under test. In general, embodiments of the invention utilise ultrasonic signals which include a plurality of frequencies within a predetermined frequency range, to determine a frequency response of ultrasonic transmission through a fibre sample which amy be analysed to determine a measure of at least one property of the sample. However, without limitation to the generality of the invention in this respect, one particularly preferred method of operation of the apparatus 200 will be described which is useful for measuring the diameter of the fibres within the fibre sample 102. As will be appreciated, the method may be adapted for use with alternative embodiments, such as with apparatus 250 illustrated in Figure 2B.

According to the exemplary method for measuring fibre diameter, signal generator 212 is operated to generate signals including a plurality of frequencies within a predetermined ultrasonic frequency range. While suitable signals may include swept or stepped sinusoidal signals, or broadband signals such as white noise type signals, according to a particularly preferred method the signals generated by signal generator 212 include periodically repeating pulses, each pulse having a pulsewidth selected to correspond with a desired mean transmitted ultrasonic frequency. For example, a signal having a mean ultrasonic frequency of 1 MHz may be conveniently generated in the form of one or more repeated pulses having a corresponding pulse width of 1 microsecond. By using a plurality of periodically repeating pulses of the same pulse width, a received ultrasonic signal may be averaged over a number of pulses in order to obtain a desired accuracy and/or precision of measurement of the transmitted ultrasonic energy. Furthermore, according to the preferred method of operation, such a measurement is repeated for pulses having a variety of different pulse widths, in order to measure the ultrasonic signal transmission as a function of mean pulse frequency.

Figure 3 shows a graph 300 illustrating a measured ultrasonic transmission as a function of mean frequency of transmitted ultrasonic pulses ⁽Je an ultrasonic frequency response of transmission through a fibre sample). The x-axis of the graph 300 represents pulse frequency in megahertz, while the y-axis represents the average magnitude of received pulses. The resulting frequency response curve 302 exhibits a clear maximum value 304 occurring at a corresponding peak frequency 306. Figure 4 illustrates a further graph 400 illustrating a comparison of measured frequency response curves for three different fibre samples having differing mean fibre diameters. Frequency response curve 402 corresponds with a fibre sample having a mean fibre diameter of 15.8 microns, frequency response curve 404 corresponds with a fibre sample having a mean fibre diameter of 21.5 microns, and frequency response curve 406 corresponds with a fibre sample having a mean fibre diameter of 30.5 microns. The three frequency response curves 402, 404, 406 have corresponding peak values 408, 412, 416 occurring at peak frequencies 410, 414, 418.

Figure 5 is a graph 500 illustrating a relationship between the peak frequency measured in accordance with the aforementioned method embodying the present invention, and the reported wool fibre diameter measured using the more involved, expensive and time-consuming methods and apparatus of the prior art. The graph 500 includes a number of points, eg 502, each of which represents a correspondence between a peak frequency measurement and the reported wool fibre diameter in accordance with the prior art. The graph 500 demonstrates a substantially linear relationship 504 between a measurement embodying the present invention, and the prior art diameter measurement. Accordingly, it is apparent that embodiments of the present invention may be used to determine fibre diameter, by converting peak frequency measurements to corresponding fibre diameter values in accordance with a substantially linear relationship.

While the foregoing discussion relates to the measurement of fibre properties at a single location in a fibre sample, corresponding with the location of a single transmitter 104 and receiver 106, the present invention also encompasses methods and apparatus for measuring the variation in fibre properties at different locations within a single fibre sample. Figure 6 illustrates schematically one arrangement 600 envisaged to measure a variation of at least one property of fibres within a fibre sample.

The apparatus 600 includes a plurality of transmitters 604 located at selected positions on a first side of a fibre sample 602. According to the depicted embodiment 600, the transmitters are arranged in a linear array, which is particularly useful for measuring the variation of fibre properties along the length of a particular fibre sample 602. However, it will be appreciated that alternative geometric arrangements of transmitters 604 may be envisaged which would also fall within the scope of the present invention.

At least one receiver is located on a second side of the fibre sample 602, opposed to the first side, for detecting ultrasonic transmissions generated by the transmitters 605. According to the preferred arrangement 600, however, a corresponding array of receivers 606 is provided, each receiver in the array 606 being arranged in a position substantially opposed to a corresponding one of the transmitters 604. Each transmitter/receiver pair, eg 608, 610, 612, may be operated in sequence in accordance with a method embodying the present invention, in order to measure fibre properties at corresponding locations in the fibre sample 602.

Figure 7 is a schematic illustration 700 of the operation of the apparatus 600 when used to measure the variation in fibre diameter along the length of a wool fibre sample 602. The array of transmitters 604 and receivers 606 is operated sequentially, for example commencing with transmitter/receiver pair 704, at a start location in the fibre sample 602, and ending with transmitter/receiver pair 706 at an end location of the fibre sample 602. The graph 702 represents the sequence of measurements of the fibre diameter along the fibre length. In the case of a natural wool fibre, it is expected that fibre properties, such as fibre diameter, will vary along the length of the sample as a result of changing growing conditions, affected by factors such as water and food availability, seasonal effects and the health of the animal. As shown in the exemplary illustration 700, a minimum fibre diameter occurs corresponding with transmitter/receiver pair 708, and a maximum fibre diameter occurs corresponding with the location of transmitter/receiver pair 710. The overall fibre diameter variation 712 is the difference between the maximum and minimum fibre diameters along the sample 602. Measurement of the variation of fibre properties, such as fibre diameter, within a sample may be of great practical importance, since such variation may have significant effects upon the overall fineness, quality, strength and so forth of the fibres. For example, as will be readily apparent, the overall breaking strength of a fibre is likely to depend substantially upon the weakest portion of the fibre, which in turn may be that part of the fibre having the smallest diameter. The coarseness of the fibre, on the other hand, may be strongly influenced by the maximum diameter occurring within the fibre sample.

As will be appreciated from the foregoing discussion, the present invention encompasses a variety of methods and apparatus for performing ultrasonic measurements to determine properties of fibre samples. Embodiments of the invention are applicable to a wide range of natural and synthetic fibres, and encompass methods and apparatus which may provide a convenient, portable, and potentially handheld solution for the measurement of fibre properties in a variety of situations, including at-farm and on-animal measurements. While particular examples relating to the wool industry, and involving the measurement of fibre diameter, have been presented, it will be understood that the invention is not limited to the particular embodiments described herein, but rather the scope of the invention is defined by the claims appended hereto.

Claims

CLAIMS:

1. A method of measuring at least one property of fibres in a fibre sample which includes a plurality of similar fibres, the method including the steps of: coupling transmitted ultrasonic signals into the fibre sample, wherein the signals include a plurality of frequencies within a predetermined frequency range; measuring a frequency response of transmission of said ultrasonic signals through the fibre sample; and analysing the frequency response to determine a measure of at least one property of the fibres in the fibre sample.

2. The method of claim 1 wherein the transmitted ultrasonic signals include a series of pulses, wherein a pulsewidth of each pulse corresponds with a desired mean ultrasonic frequency within the predetermined frequency range.

3. The method of claim 2 wherein the series of pulses includes periodic repetitive pulses, having a repetition rate that is much lower than the corresponding mean ultrasonic frequency of the pulses.

4. The method of claim 3 wherein the step of measuring the frequency response includes averaging the response to said repetitive pulses over a number of pulse periods in order to determine a transmission and/or attenuation of ultrasonic signals passing through the fibre sample at the corresponding mean ultrasonic frequency.

5. The method of any one of the preceding claims wherein the step of analysing the frequency response includes identifying a peak frequency of the frequency response, corresponding with a maximum transmission of ultrasonic signals through the fibre sample within the predetermined frequency range.

6. The method of claim 5 wherein the peak frequency provides a measure of a mean fibre diameter of fibres within the fibre sample.

7. The method of claim 6 wherein the mean fibre diameter of fibres within the fibre sample is determined in accordance with a substantially linear relationship between the peak frequency and a corresponding mean fibre diameter.

8. The method of any one of the preceding claims wherein the steps of coupling transmitted ultrasonic signals into the fibre sample, measuring a frequency response of transmission, and analysing the frequency response are repeated at a plurality of selected positions along the fibre sample, so as to measure variations in said at least one property of the fibres along a corresponding length thereof.

9. The method of claim 1 wherein the step of coupling transmitted ultrasonic signals into the fibre sample includes applying signals having a swept or stepped frequency within the predetermined ultrasonic frequency range.

10. The method of claim 1 wherein the step of coupling transmitted ultrasonic signals into the fibre sample includes applying an ultrasonic signal which simultaneously includes a plurality of frequencies lying within the predetermined frequency range.

11. The method of any one of the preceding claims wherein said predetermined frequency range includes the range of 0.1 MHz to 5 MHz.

12. An apparatus for measuring at least one property of fibres in a fibre sample which includes a plurality of similar fibres, the apparatus including: a transmitter located on a first side of the fibre sample and arranged to couple transmitted ultrasonic signals into the fibre sample, wherein the signals include a plurality of frequencies within a predetermined frequency range; a receiver located on a second side of the fibre sample opposed to the first side and arranged to detect received ultrasonic signals corresponding with the transmitted ultrasonic signals following transmission through the fibre sample; and a processing unit configured to process the received ultrasonic signals so as to measure a frequency response of transmission of the ultrasonic signals through the fibre samples, and to analyse the frequency response to determine a measure of at least one property of the fibre sample.

13. The apparatus of claim 12 wherein the transmitter includes a transmitting transducer configured to convert electrical signals into corresponding ultrasonic signals, and the receiver includes a receiving transducer configured to convert received ultrasonic signals into corresponding electrical signals.

14. The apparatus of claim 13 which includes a closable structure upon or within which the transmitting and receiving transducers are disposed, such that when the apparatus is closed over the fibre sample, the sample is held between the transmitting transducer and the receiving transducer.

15. The apparatus of claim 14 wherein the closable structure is in the form of a clamp including first and second clamping members, the transmitter being disposed on or in the first clamping member and the receiver being disposed in an opposed location on or in the second clamping member.

16. The apparatus of any one of claims 13 to 15 further including a signal generator for generating electrical signals to drive the transmitting transducer so as to generate ultrasonic signals for transmission into the fibre sample.

17. The apparatus of claim 16 wherein the signal generator is configured to generate signals including sequences of pulses, wherein a pulsewidth of each pulse corresponds with a desired mean ultrasonic frequency.

18. The apparatus of any one of claims 12 to 17 wherein the processing unit is configured to analyse the received ultrasonic signals including a plurality of frequencies within the predetermined ultrasonic frequency range to determine a peak frequency, corresponding with a maximum transmission of ultrasonic signals through the fibre sample within said frequency range.

19. The apparatus of claim 18 wherein the processing unit is further configured to compute a value of said at least one property of the fibre sample, which is a mean fibre diameter corresponding with the peak frequency.

20. An apparatus for measuring a variation of at least one property of fibres in a fibre sample which includes a plurality of similar fibres, said variation being measured as a function of position within the sample, the apparatus including: a plurality of transmitters located at selected positions on a first side of the fibre sample and arranged to couple transmitted ultrasonic signals into the fibre sample, wherein the signals include a plurality of frequencies within a predetermined frequency range; at least one receiver located on a second side of the fibre sample opposed to the first side and arranged to detect received ultrasonic signals corresponding with the transmitted ultrasonic signals following transmission through the fibre sample; and a processing unit configured to process the received ultrasonic signals so as to measure a frequency response of transmission of the ultrasonic signals through the fibre sample, and to analyse the frequency response to determine measures of at least one property of the fibre sample at positions corresponding with the transmitters, and thereby to measure a variation in said property as a function of position within the sample.

21. The apparatus of claim 20 wherein the at least one receiver includes a plurality of receivers, each of which is located at a position on the second side of the fibre sample substantially opposed to a corresponding one of the transmitters, to detect received ultrasonic signals transmitted through the fibre sample from said corresponding transmitter.

22. The apparatus of claim 21 wherein the transmitters and receivers are arranged in a linear array, and wherein fibres in the sample are arranged to extend along the array, such that the apparatus measures the variation in the property along the length of the fibres.

23. An apparatus for measuring at least one property of fibres in a fibre sample which includes a plurality of similar fibres, the apparatus including: a transmitting transducer having an electrical input, and which generates a vibrational excitation having a frequency determined by an applied electrical input signal; a receiving transducer having an electrical input, and which generates an electrical output signal corresponding with an applied vibrational excitation; at least one processor; at least one storage medium operatively coupled to the processor; an output peripheral interface between the processor and the electrical input of the transmitting transducer; and an input peripheral interface between the electrical output of the receiving transducer and the processor; and wherein, in use, the transmitting transducer and the receiving transducer are arranged such that vibrational excitations generated by the transmitting transducer are coupled into the fibre sample, transmitted therethrough, and detected at the receiving transducer; wherein the storage medium contains program instructions for execution by the processor, said program instructions causing the processor to execute the steps of: directing the transmitting transducer to generate a vibrational excitation including a plurality of frequencies within a predetermined ultrasonic frequency range; measuring a frequency response of the fibre sample to said excitation, by receiving electrical signals from the receiving transducer corresponding with vibrational excitations transmitted through the fibre sample; and analysing the measured frequency response to determine a measure of at least one property of the fibre sample.

24. The apparatus of claim 23 wherein the program instructions cause the processor to execute the step of determining a peak frequency of the measured frequency response corresponding with a maximum transmission of ultrasonic signals through the fibre sample within the predetermined ultrasonic frequency range.

25. The apparatus of claim 24 wherein the storage medium contains program instructions causing the processor to execute the step of computing a mean fibre diameter of the fibre sample based upon the determined peak frequency.