JPH05509280A - Detection of filamentous bodies - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Detection of filamentous bodies The present invention detects filamentary bodies, e.g. , textile spinning machines such as cotton frame Continuation of a thread in an espinning machine The present invention relates to a method and apparatus for detecting the presence of

Typically, such a loom (textile machine) Equipped with a draw frame for spinning (drawing) are doing. The attached FIG. 1 shows a schematic perspective view of such a draw frame. Thread material (thread material is entrance roller 200, rubber belt 20 1a and 201b, and of each roller 202 and exit roller 204. go around. Belt 201b is supported by plate 203. each The pair of rollers rotates at different speeds and rotates the raw material 205 (rovingl ] progresses through the machine, progressively faster (encounters rotating rollers) It looks like this. This has the effect of drawing out the fine threads from the rovings 205. The thread is , and finally, successively, respectively known as big-chill and balloon rings. The bobbin 207 passes through two ring-like guides (not shown) and rotates. rolled on top.

Unfortunately, the threads in the loom often break. When this happens, the cut area Subsequently drawn thread is removed through pipe 206 to reject bin 206. or on the exit roller in FIG. 1, as shown at 208. may accumulate on the rollers and form laps. If this is If this process is overlooked, a large amount of valuable raw material will be wasted and the useful material from the machine will be lost. production will decrease. In addition, other problems and Damage may be caused.

Therefore, the thread should be broken as soon as possible so that corrective action can be taken. It is desirable to detect.

Many properties of yarn and looms complicate yarn breakage detection. First, the diameter and density of the thread In terms of texture, color, materials, and other physical properties. different. For example, the yarn material may be cotton, wool, silk or synthetic fibers. sell.

Second, in a loom, where it is most desirable to detect thread breaks, , the space available for the detection device is usually very small. Thirdly , the lateral and angular position of the moving thread is quite variable and therefore detection becomes difficult. Preferably, the driver will take action after such a break occurs. must be accessible in order to repair it.

In addition, to ensure the correct conditions for spinning the yarn, the spinning mill (spinn) It is necessary to control the humidity and temperature of the environment within the environment. This way In such environments, the operating temperature should be 15-35℃ and the humidity should be up to 80% RH (condensation). It is planned that there will be no exposure. In addition, the atmosphere contains fluff on exposed surfaces. Contains small fibers that tend to collect as fl. The detector is preferably , should be able to continue to function reasonably accurately under such conditions.

Several types of thread detectors are already known. For example, U.S. Patent No. 4 ．． Optoelectronic devices such as those described in US Pat. No. 450,677 project an LED light source onto the thread. A photoelectric detector (photodete) monitors the shadow of the thread obtained by I am using ctorl. When the threads involved are very thin, such shadow supervision is When we try to apply the visual method, we run into difficulties. And for larger diameter threads Even so, the operation of such detectors is adversely affected by fuzz build-up.

Additionally, this type of detector has parts located on the other side of the thread, so it is difficult to operate. cause physical obstruction to a person Tend. Additionally, it is sensitive to mechanical vibrations.

Until now, ultrasonic waves have been used to detect thick objects, such as in burglar alarm systems. It has been used to detect However, the method for detecting thin linear bodies Until now, it was not thought that using such ultrasonic detection would be practical. .

For such purposes, it is necessary to use sound waves of very short wavelength and therefore high frequency. However, the reflection coefficient ) (Indicator indicating the ratio of energy reflected back from the object to be detected) ), and ultrasound in a propagating medium. Since both signal attenuation is frequency dependent, When the wavenumber becomes large enough, the detected signal can be expected to become undesirably weak. was thought of.

Surprisingly, however, ultrasound systems have been shown to have the disadvantages mentioned above. Previous systems were designed to eliminate threads in the air in a hassle-free manner. It was discovered that vines can be used to detect linear bodies.

In particular, over a range of frequencies where the wavelength is comparable to the thread diameter, if the wavelength and frequency is chosen correctly, the reduction in reflection caused by the reduction in thread diameter is due to interference effects. The reflection of sound waves by the thread is balanced by the increase in reflection that occurs. It has been found that interference effects can modify L/scattering.

This means that at such wavelengths, the reflection does not increase significantly as the thread dimensions change. It means no change. A thread detector using such waves is therefore , operates to accommodate a wide range of practical thread diameters.

According to a first aspect of the invention, longitudinally extending across a predetermined position. A method for detecting a filament that is supported in an elongated manner is provided, which includes the following: Provided: Ultrasonic waves are applied to the filamentous body toward the predetermined position. The signal is transmitted transversely to the longitudinal axis, and the predetermined position is Such a wave that is diverted back by the filament from the position to monitor.

According to a second aspect of the invention, with respect to the support part of the device, a predetermined means for supporting the filament so as to extend longitudinally across the position; The length of such a body supported in this way is Ultrasound toward the predetermined position above, transverse to the direction axis from that position, with the tendrils actuated to transmit Monitoring comprising an ultrasonic transducer means also operative to detect such waves An apparatus is provided that includes means.

Preferably, the wavelength of the sound wave is equal to the magnitude of the filament diameter. or smaller.

The device of the invention uses an ultrasonic electro-acoustic transducer (the transducer is a a length on which the electrode structure rests (an extended working surface, and a distance from said working surface; an electro-acoustic element having a second surface carrying a second electrode structure; 1 and a second electrode structure, for applying an electrical drive signal between both electrodes. an electric drive circuit for vibrating the element, thereby causing the elongated actuation Propagate ultrasound waves outward from the working surface into the medium driven by the surface There is an electric drive circuit; The electro-acoustic element, the electrode structure, and the drive circuit are configured to control the effect of the electric drive signal. effects are different at different locations along said working surface, otherwise said medium in a predetermined direction parallel to said longitudinal axis and from said actuating surface; Destructive interference effects that occur at points along the target line separated by a distance neutralize (counter act).

Alternatively or additionally, the device of the invention comprises an actuation surface with a first electrode structure; , a piezoelectric ceramic having a second surface remote from the actuation surface and having a second electrode structure; An ultrasonic electro-acoustic transducer may be used, which includes an electrical A drive signal is applied between the first and 21f pole structures to cause the element to vibrate, thus , ultrasonic waves are transmitted from the working surface into a gaseous medium coupled to the working surface. Transmission mode, such as propagating towards a target location at a predetermined distance , and in that mode, an object is located at the target position. Such sound waves scattered back from the body cause the above-mentioned element to vibrate, causing such A short lens that has a receiving mode that produces an electrical signal that indicates the presence of an object. the working surface is connected to the working surface and the gaseous medium; A thin layer of silicone rubber to improve the transmission of acoustic energy between and a region of the other side of the element is covered by a layer, and a region of the other side of the element is between the end of the mode and the start of the receive mode, the energy is dissipated in the element. It is connected in close proximity to a solid damping body of synthetic resin for the purpose of

The waveforms of sound waves are continuous sine waves; other continuous waves; single pulses; train pulses; and sine waves. It can take any shape, including a train of waves.

Both the generation and monitoring of sound waves may be performed in transmitting and receiving modes in some embodiments. It may also be performed by one converting device operating on each. A short acoustic pulse is emitted It takes time for this pulse to travel to the thread and for the reflected echo to return. Karu. The embodiment is such that by the time the echo returns, the transducer is ready to work effectively next time. The transmitting converter has completed its pulse transmission and any post-transmission vibrations have disappeared. seems to be lost (i.e. the converter is settled). There must be.

Transducers come in many different forms, but include electrostatic membrane transducers and especially piezoceramic transducers. is currently preferred.

For a better understanding of the invention and how it can be effectively implemented. In order to illustrate, reference is made in the form of an example to the following attached figures: FIG. 1 (see above) shows a schematic perspective view of a draw frame of a loom.

FIG. 2 shows a loom drawer equipped with a device embodying the aforementioned second aspect of the invention. 1 shows a schematic perspective view of a frame.

FIG. 3 shows a schematic diagram of the parts of the second device.

FIG. 4 shows a block diagram of the electronic circuitry employed in the device of FIG.

FIG. 5 shows a side diagram view of an ultrasonic transducer forming part of the components of FIG. vinegar.

FIG. 6 shows a more detailed longitudinal cross-sectional view of the device of FIG. 5.

FIG. 7 shows a cross section of the device of FIG. 6 taken along the line VII-VII of FIG.

8(A) and 8(B) show the side and rear views of each of the converter sections of FIGS. 6 and 7. Show the face.

Figure 9 shows a schematic diagram of a thread detector arrangement including an elongated ultrasonic transducer different from Figures 6 to 8. It is a schematic perspective view.

Figure 10 shows the results produced by the transducer of Figure 9 as a function of position along the length of the transducer. 2 is a graph illustrating the amplitude of a sound wave generated by

FIG. 11 is a graph illustrating the characteristics of the device of FIGS. 6 and 7, corresponding to FIG. It is.

12 to 15 show views of alternative shapes of the portions of FIGS. 8(A) and 8(B).

FIG. 16 is a polar coordinate plot showing the amplitude variation of the sound waves produced by the apparatus of FIGS. 6 to 8. Lot.

FIG. 17 is a diagram illustrating the outgoing and reflected sound waves to and from the apparatus of FIGS. Diagram diagram is shown.

Figures 18 and 19 show the change effects within the dimensions of the transformer. Each diagram corresponding to FIG. 17 used to illustrate the results is shown. .

The main structure of the draw frame in Figure 2 is similar to that in Figure 1. However, Figure 2 shows the above-mentioned pigtail 5. A and a balloon ring 5b are shown.

The draw frame in Figure 2, however, has a mount that runs along the entire length of the loom. Support members in the form of mounting bars 2 each It is provided between the thread 3 that comes out and the main body of the machine. sensor unit 1 mounted on bar 2, parallel to mounting bar 2, and at the nip point 4 (between rollers 204) and the pig till 5a in a horizontal plane across the thread 3 at a point between , is now able to move. In such a position, the angular and transverse direction of the thread the directional movement is within acceptable limits, and the sensor unit 1 is mounted There's plenty of space for.

The elongated ultrasonic transducer 6 is installed in the sensor unit 1 with the longitudinal axis of the device 6 approximately 4 to the axis of the mounting bar 2, such that the They are mounted at an angle of 5°. Individual sensors throughout the loom It will be understood that the threads are placed apart from each other depending on the spacing of the threads on the machine. cormorant.

In FIG. 3 the sensor unit l is shown in more detail. Unit l is It may be attached to the bar 2 by a plug fastener 8. Preferably, the unit 1 also has an indicator light. 7 (preferably LED).

The position and angle of thread 3 may vary. Therefore, the ultrasonic sound emitted from the converter 6 It is not appropriate to focus the wave beam. yes Then, dead spots are placed within a predetermined area where threads are expected to be found. The conversion device 6 is designed to ensure that there are no dead 5pots. It is measured.

The thread 3 is placed in a horizontal plane at a distance of 27.5 to 42 mm from the sensor unit 1. Adjustments are made so that there is a lateral movement of ±6 mm. Angular change from vertical is ±1 Predicted to be 0°. This movement is based on an imaginary rectangle in which the thread is expected to be found. create a shape (in the horizontal plane), the nearest edge of this rectangle is the longitudinal axis of the transformation device 6 is parallel to This edge is 27.5mmft from the converter 6! 12 It has a length of mm. The length of the rectangle is 14.5+nm. In three dimensions, The volume in which thread 3 is predicted to be found is an imaginary parallelepiped, The dimensions of this parallelepiped are the same as the rectangle above, but the depth is greater) is determined by the depth of field of the conversion device 6.

FIG. 4 shows a block diagram of the electronic circuit (element) related to thread detection by the sensor unit 1. A diagram is shown below.

This circuit (16) is a controller that controls such a sensor unit. between the module board 9 and the sensor board 10 located inside the sensor unit 1. I know.

The operating frequency is: i) the weight of the sound wave when traveling the maximum distance (85 mm) due to air; and ii) the diameter of the thread with a narrow wavelength. (0.1 mm).

In addition, - transducers are used as generators for pulse-echo technology. Since it is used as both a transmitter and a receiver, the transmission vibration between sending and receiving so that the oscillation is attenuated. There should be a sufficient number of cycles. This is based on the operating frequency f, the damping characteristic (da mping characteristics) Q, and the amplitude of the received signal (determined by magnitudfl!l; nearest approach of 27.5 mm In this case, the decay time is 150 μs or less.

Keeping in mind that the received signal changes with thread diameter, the operating wavelength (and therefore frequency) The decrease in reflection with decreasing thread diameter is due to interference effects or reflections caused by balanced by an increase in backscatter, thereby , the total reflection coefficient (overall reflect ion coefficient). . The selected operating frequency is 1.0 MHz. This is a wave of 0.33 fighting in the air It has a length comparable to the diameter of a normal thread. At this frequency, between emission and reflection, 150 cycles and a single transducer in pulse-echo technology sufficient for use. At this frequency, the reflected signal is proportional to the diameter of the thread. and is very independent.

The microprocessor 11 controls the sensor board 10 through the driver 12. Activate, which increases the frequency of transducer 6 (approximately I It has the effect of driving the oscillator 13 which generates a signal tuned to MHz.

This signal is amplified by driver 14 and is applied for 30 half-cycles with an amplitude of +38V. transducer as a burst of half-cycle The signal is applied to the circuit 6.

The transducer thereby emits a burst of sound waves that is reflected by the thread 3. (Fig. 3), the reflected signal is transmitted to the transducer 6. is received by the transducer, which causes the transducer to generate an electrical signal. That will happen. This detected signal is band-pass (band-pass) with Q5. It is amplified by a factor of 3500 by the sl amplifier 15.

This yarn detection system detects the reflection from the yarn - a wave train of 30 pulses at I MHz ( wavetrain) or burst as the power source for the drive motor on the loom. A switched mode power supply allows Designed to distinguish from sharp electrical spikes such as electrical noise It is.

The filtered output of amplifier 15 is sent to detector 1 through line driver 16. Sent to 7. Detector 17 detects whether the signal is detected during a given number of series of 1 μs periods. A predetermined threshold, which is a given number of times, is exceeded. put out

Since the amplifier 15 has a relatively wide pass width, the electrical spikes will have a sharp shape. , and therefore, during that time the reflection of the thread reduces its threshold It crosses that threshold once or twice during a time period that it would cross ten times. Ginai. This ensures that reflected signals are clearly distinguished from such electrical noise. It will be done.

The signal from detector 17 is sent to microprocessor-11 for further analysis. It will be done.

The yarn detection system must sense minute reflection signals from the yarn, but Various other signals from electrical interference may cause such noise to result in false positives. should not be detected in order to minimize the chance of During operation, thread 3 There are both minimum and maximum distances that may be located away from the conversion device 6.

Because the speed of sound is finite, it cannot be reflected effectively outside of that range. This means that there is a range of time after the pulse is sent. if , if the circuit is left insensitive outside of this length of time, noise, false reflections, and other possible It is meaningless and gives incorrect results in that case.

Therefore, only reflections from objects 27.5 to 42.5 mm away are considered. , the reflected signal is time gated by the microprocessor 11. te) to be done.

Microprocessor-11 waits for a delay before the circuit indicates that the thread is not present. This may lead to problems, and a system is activated to take action to repair broken threads. The thread may not be moved by the driver for a short period of time, e.g. to inspect the thread, without I am trying to be able to do this.

In the illustrated example, the detection system searches for thread (3) 125 times per second. If 2 If the thread is not "seen" for a second, it is determined that thread 3 has broken. microprocessor The service 11 is connected to the host system, i.e., by roving the solenoid. ), take corrective action such as applying the brakes or turning on indicator light 7. Messages are sent to further control systems (not shown). Thread 3 is repaired Once repaired, the sensor will run 3 times to determine that the thread is indeed repaired. The system has to “see” it a few (four times) in a second. , sends an appropriate message to the host system and turns off the indicator light 7.

Such a decision system can guarantee low error operation and will not disrupt the repair control system. Allows the yarn to be rethreaded without threading. detection system can sense a 70μV signal. This is due to careful noise reduction and filtering achieved by.

Case of sensor unit 1 and transducer 6 and its transducer The front electrodes of are all connected to a zero potential bin (not shown). This is complete Provides complete earth shielding and is capacitively connected. Isolate the detection system from other noise sources.

The conversion device 50 in FIG. 5 includes a case 51, a backing (backing 1 layer 52, an active piezoelectric element 53 in contact with the packing layer 52 and a piezoceramic element 5 an acoustic matching layer in contact with the working surface of 3; 54 included. Each connecting wire 55 is connected to the actuating surface of the element 53 and the opposite surface thereof. are used to transmit electrical signals to each electrode (not shown) of the.

In use of the device 50, the piezoelectric active element 53 converts electrical vibrations into mechanical vibrations. It plays the role of converting and vice versa. Element 53 typically determines the frequency of the sound wave to be generated. It has dimensions and materials of construction selected to resonate with the

Matching (matchingl rW! In order to make it easier for energy to be transmitted effectively between the wire-like propagation medium It is provided. In practice, the acoustic impedance of practical piezoelectric materials is of interest. Due to their several orders of magnitude larger size of the propagation medium (e.g. air), the elements 5 Energy transfer between 3 and the medium is only possible if a suitable matching layer 54 is present. It turned out to be extremely low. According to traditional acoustic theory, there is a matching layer between the two media. when the thickness of the matching layer is equal to the wavelength of the sound wave in the layer, and Then, at that wavelength, the acoustic impedance of the material of the matching layer is equal to that of each of the two media. The energy transfer between two media is equal to the geometric mean of the acoustic impedance of is maximum.

The backing layer 52 serves to damp vibrations of the active element 53.

The transducer of FIG. 5 may be used in a pulse-echo system, which system In the first (transmission) operation mode, an electric drive signal of a predetermined ultrasonic frequency is transmitted. When a burst of signal is applied to the piezoelectric element 53 through its electrode, the upper surface of the element (the vibrating the moving surface) (in contact with the matching layer 54) at the above ultrasonic frequency; This causes sound waves to propagate from the free surface of layer 54 into the adjacent air. Drive signal The second ( In the receiving) operating mode, the device ff150 is used as a receiver of sound waves and Such waves on the free surface of the laminated layer 54 cause the piezoelectric element 53 to vibrate, causing it to Thus, an electrical signal corresponding to the received sound wave is generated in the connecting wire 55.

By analyzing these electrical signals, an object can be detected at a given distance from the working surface. It is possible to determine whether the target location is present or not.

In some applications, such as sensing the presence of yarn in a loom, spatial constraints can It is necessary to place the sensor device very close to the object to be detected. Essential. In such a case, however, from the end of outgoing mode to the start of receiving mode The above-mentioned predetermined time interval between This means that the sound waves travel from the transducer to the object to be detected and return. This is because it takes less time to complete the process. The transducer device considered earlier is , cannot operate satisfactorily in such a pulse-echo system. , since the vibrations are important for effective detection of the received ultrasound signals to be achieved. This is because it took too long for it to disappear to a sufficient extent.

The apparatus 50 of FIG. 5 is characterized in that its sharpness at resonance is determined by its quality It is considered to be a resonant oscillator described by Q. I wonder The damping characteristics of an oscillator are also characterized by its Q factor, which is The oscillator’s energy lost during each cycle of motion. It is the reciprocal of a fraction.

A high Q is accompanied by sharp resonances and, as a result, a The opposite is accompanied by high operating efficiency. A high Q, however, also removes the electrical drive signal. accompanied by a long decay time of the residual vibrations that follow. The vibration changes in amplitude by a factor of A. The number of periods N required to decay is expressed by the following formula: N=Q1n A The duration T of each cycle at any given frequency is fixed. Therefore, the time required for the vibration to decay in amplitude by a factor A is: Thus, in short range sensing applications, a high Q increases the operating efficiency. Although it is desirable from the perspective of maximizing the ratio, the higher the value of Q, the more However, the minimum separation of the object to be detected from the transducer device must be higher. The difficulty arises of having to do so.

For practical reasons, it is not always possible to simply increase that minimum separation. For example, due to unavailability of space or due to long distance reductions involved. This is because the attenuation is too large for reliable detection of reflected ultrasound waves.

Regarding the individual factors that affect the settling time will be discussed in more detail here.

The transducer 50 of FIG. 5 includes two resonant components, a piezoelectric element 53 and a matching layer 54, and a cage. It consists of two non-resonant components: a base 51 and a backing layer 52.

Case 51 performs no active function as a transmitter and therefore In addition, the device should be installed on the support member (circuit board) on which the device is mounted. (such as a board). Case 51 is also It may function as an extended continuation of packing layer 52.

The remaining components of device 50 can be considered a set of acoustically coupled transmitters, and Each of these oscillators has its own resonant frequency and attenuation characteristics. In the latter perspective , each component can store energy (and dissipate the remaining stored energy). (while spending), sounds even after the electrical drive energy to the device is removed (ring) is possible. Furthermore, since the parts are in contact with each other, their individual According to different properties, vibrational energy is transmitted between different parts.

When the electrical drive signal is removed from such a set of linked transmitters , the remaining energy is due to energy loss within each oscillator and the oscillator with an inherently high Q. energy is transferred from the transmitter to those with lower Q.

Thus, the overall specific Q value of one system of oscillators, i.e. all converters, is: Relies on internal absorption energy of each individual oscillator and energy transfer between them .

In a particular converter 5° operated with air as the propagation medium, the traverse The factor that governs the total decay time of the damper is the decay time of the matching layer 54. was found. This means that layer 54 is preferably made of low density silicone rubber. This is because silicone rubber has a low acoustic impedance. It is ideal as a material for matching layers.

As mentioned above, matching layer 54 conventionally connects element 53 to a propagation medium, in this case air. has an acoustic impedance equal to the geometric mean of each value of acoustic impedance Should. A typical piezoelectric material weighs approximately 3 x 10’ Rayls (kg air has an acoustic impedance of only 400 Ra yls, the impedance of the matching layer 54 is , conventionally, it was around 1, IX 10'Rayls. But like that Continuous homogeneous solids with such low acoustic impedance have not been known.

The solid with the lowest known acoustic impedance is low density silicone rubber.

It has a normally preferred density of around 1,05 x 10"kgm-", It has an impedance of approximately 10' Rayls.

A wide variety of converters are available that employ matching layers of silicone rubber such as . However, the same device must be used for both transmitting and receiving ultrasound waves. In some cases, such equipment is not suitable for short range operation. I mean , silicone rubber is inherently (naturally) high Q (low absorption) and its Therefore, the noise from the object to be detected should be reliably determined from the ringing phenomenon. The residual energy stored in the matching layer is fast enough to receive the incoming ultrasound. This is because energy cannot be consumed.

Overall effective qualification of device 50 ityfactor), the dominant oscillator, in this case rubber matching layer 54 It is desirable to vary the efficient property coefficient of . Preferably, each of the component oscillators The efficient property coefficient of also does not unreasonably differ in value from its total efficient property coefficient. .

Energy is dissipated from the matching layer in three ways: dissipation into the air; piezoelectric Transmission into the child; and internal absorption. In practice, the most important dissipative process is This is energy transfer into the lamic element. Consider this process in more detail. Then, the property coefficient Q rubber of the rubber material is expressed as follows.

where R is the reflection constant at the piezoelectric-rubber interface, and 1/α is the coefficient at which the amplitude of a sound wave passing through rubber is attenuated at the distance of the wavelength station. Ru.

From the above expression, we can either increase the internal attenuation to lower α or reduce the reflection coefficient R. It is clear that QruThTh@r can be reduced depending on the

Rubber internal damping can be made of fine glass powder, fly ash, plastic or metal This can be increased by putting a square-shaped material such as powder into a silicone rubber material. can.

The reflection coefficient R is determined by appropriately modifying silicone rubber so that its acoustic impedance becomes piezoelectric. It can be lowered by approaching that of the element. Acoustic properties of materials Impedance is a function of the material density and the propagation velocity of sound waves in the material (at the frequency of interest). given by the product. Therefore, the piezoelectric material is an order of magnitude larger than that of rubber. It has acoustic impedance and reduces the reflection coefficient at the ceramic/rubber interface. One approach to this is to increase the density of the rubber material. rubber density As the temperature increases, the reflection of sound waves at the rubber/ceramic interface decreases, thereby increasing the During the ringing, more energy is transferred from the rubber layer 5 to the backing layer 52. Therefore, it can escape to the piezoelectric element 53 where it is attenuated. Using this method This allows the transducer to be optimized for sensitivity and short working range. It is possible.

As mentioned above, until now materials for matching layers have been used with a density around lXl0"kgm-" It was customary to use silicone rubber (for example, General El (Silicone rubber manufactured by ectric with exclusive code GE RTV615). such a place In this case, the propagation speed of the ultrasonic wave through the rubber material is 100100 O', so the sound of the rubber The acoustic impedance is around 10' Rayls. A device embodying the present invention However, the density of the rubber is between 1.1 and 2. IX increased to 10”kgm-” Therefore, the acoustic impedance is 1.1 to 2.1 It increases proportionally during s. Therefore, the reflection coefficient is reduced and the efficient properties of the rubber are The quality Q rul I, @r has decreased, so the overall properties of the transducer Characteristics are also declining. Such a reduced total Q may occur at a distance of 12 mm or less from the device. The transducer operates reliably to detect objects placed in the It is possible to provide settling time values low enough to allow

By further modifying the properties of rubber matching 1, even It would also be possible to provide transducers that can operate over shorter distances. , it is understood. In such cases, material loading may be necessary to achieve the desired settling time. Combination of loadingl (to increase internal damping) and increased rubber density It may be necessary to adopt a

By careful control of the material properties and the design of the above-mentioned parts of the converter, The applicant seeks to develop a transformer that enables efficient operation with a desirable short settling time. It has been found that it is possible to control the entire Q value of the diffuser. child In this respect, when a device embodying the present invention is employed for short range detection applications, , thanks to its reduced settling time, the minimum distance of the device from the object to be detected. Separation is correspondingly reduced, thereby reducing the Q factor, the loss of operating range. The disadvantages traditionally associated with a decline in

A specific example of an apparatus embodying the invention will be described in further detail with reference to FIGS. 6 and 7. It will be done. In this example, the converter is highly reliable over a minimum range of 27.5 mm. required to operate.

The frequency of actuation is low enough to easily detect threads of diameter down to 0.1 mm. 1 furrow Z is chosen to provide the wavelength of sound waves in the air 0.33+om .

At this minimum range, the time it takes for a sound wave to travel to an object and back is approximately 1 It is 50LLs. This corresponds to 150 cycles of vibration at IMHz. Ru. The amplitude of the transducer vibration is increased by a factor of 5X1 in this number of cycles. Assuming that attenuation is expected to occur at 0' (114 dB), the above equation (1) Therefore, Q must be less than 36.

The device of this example is designed to have a total Q-factor close to 30. like this values yield acceptable efficiency in transmitting and receiving, but silicone small compared to the intrinsic Q value of rubber (of the order of 150 at the frequency of interest). ).

The device 50 comprises a rectangular cross-section plastic plate, generally designated 51, which is open at the rear. Including stick casing. The casing 51 protrudes from its opposite ends. each tab 60.

Each of the protruding tabs 60 supports a support, such as a circuit board, on which the device is supported. It has a locating pin 61 for engaging a corresponding hole in a seat member (not shown). do. Since the bin 61 and tab 6o are relatively small areas, the equipment and support The contact area between the bars is small and provides good acoustic isolation of the device from the support members. Ras. This is desirable to prevent the occurrence of parasitic vibrations.

Each rib 62 extends within the casing 51 with respect to the plane of FIG. vertically).

The casing 51 has an elongated piezoelectric ceramic element 53 on its front surface. A narrow rectangular slot 63 is formed projecting through it. The element 53 is The length 2) is 20.9 mm, the height is 1 mm, and the thickness is 1.5++ m. . The thickness of the element 53 is 1.5 mm (when the height is 1 mm). Since the wavelength of the sound wave at this frequency (I MHz) is approximately 3 times, approximately I Provides a structure with a resonant frequency of MHz. Element length may be varied However, the presence of objects may be delayed depending on the desired extent of the area to be detected. be done.

453 is preferably hard (cl, ass 4) or soft (class 5) Quiz commercially available lead zirconate titanate co+iat, ptj, tanate) made from ceramic elements. blood An example suitable for ceramic materials is company code PZ. T5 In the name of H Morgan k4atroc's Vernit, ron Manufactured by Division. This material is sensitive to relatively high ultrasonic frequencies. and has high operating efficiency. The piezoceramic element 53 has a characteristic coefficient of approximately 60. (naturaJ, quality factor) QIIIIIILOs and has an acoustic impedance of 3 x 10' Rayls.

Respective front and rear electrodes 70 and 71 are connected to the front (actuation surface) and It is formed on the rear surface. A front electrode 7o extending over the entire length of the front surface is located at the rear of the element. An end 72 that wraps around one end of the element 53 to provide a connection point on the surface. have.

The rear electrode 71 does not extend the entire length of the rear surface of the element, but rather The ribs 62 extend approximately 14 mm in length. Each connection wire 55 is Connected to their inner ends of electrodes 70 and 71.

Inside the rear surface of the casing 51 is a backing layer 5 of synthetic resin such as epoxy resin. It is filled by 2. Polyurethane and other resins may be used alternatively.

Suitable epoxy resins have the company-owned name “Devcon five-minute” known as. The resin 52 surrounds the rear part of the piezoelectric ceramic element 53. There is. The resin 52 has a relatively low Q value and does not cause "ringing" within the piezoelectric element 53. ” in close contact with the surface area of the element 53 so that the energy caused by the It is connected to the.

A rubber matching layer 54 extends over the front electrode 70. The thickness of layer 54 is %6 of the wavelength of the ultrasonic wave, etc.11. It has been chosen. Thus, I MHz Sound wave at the frequency of: simply the wavelength of the wave passing through the silicone rubber polishing 54 Li: Since j is approximately 6, the thickness of Y is preferably about 0.25 mm.

Suitable materials for forming matching N54 can be manufactured by down-toning. This is a low-density silicone rubber manufactured under the code 170. This example The density of the rubber in is 1.38×L O”kgm−11.

In using the apparatus of FIGS. 6 and 7, the apparatus is connected to the threads whose presence is to be monitored. located on the support material at a distance between 7.5 and 42.5 mm . During the transmit mode of the device, at a frequency of I MHz and an amplitude of 38 V, A burst of zero half-cycle pulses causes the ceramic piezoelectric element 53 to connect to the front and rear electrodes 70. 71. The vibration of element 53 then disappears before the receive mode. During the subsequent receive mode, the ultrasound waves scattered from the thread and returned to the transducer are The piezoelectric element 53 vibrates depending on the received waves. and provides an output signal between the connecting wires 55 in accordance with such received waves. Ru.

70 at MHz for ultrasound when connected to a suitable signal processing circuit A sensitivity of μ■ is achieved.

Figures 8(A) and 8(B) further illustrate the transducer element 53 and electrodes 70 and 71 of Figure 6.7. Show in detail.

The front electrode 70 extends over the entire length of the active surface of the element 53 and covers one side of the element 53. The end 72 of the electrode 70 is attached to the rear surface of the element 53. So, it seems to be extended by one angle.

The rear electrode 71 does not extend over the entire length of the element 53, but is located on the rear surface of the element 53. Portions 73 and 74, each 3 mm long, are not covered by electrode 71.

The reason for using such an electrode structure will be explained with reference to FIGS. 9 to 11.

FIG. 9 shows front and rear electrodes 82 extending over the entire front and rear surfaces of the element 81. and 83 (a typical example employing a transducer 80 having an extended piezoelectric element 81) 1 shows a simplified diagram of a typical detection device; FIG. Electric drive and reception circuit 84 connects electrode 82 and 83.

The thread 85 to be monitored is placed under tension at a short distance d from the converter 8o. the device is maintained in such a way that its longitudinal axis extends perpendicular to the axis of the thread 85. It is located. The distance d from the conversion device 80 to the thread 85 is such that the thread is in the near field of the device ( The interval is such that it occupies the target position within the The near field extends a distance 22/4λ from the device, where 2 is the length of the element and This is the wavelength of the emitted sound wave in the air.

In using the transducer 80, the piezoelectric element 81 serves as an ultrasonic signal emitter and Acts both as a receiver (so that in the first mode of operation, the piezoelectric element 8 An electrical drive signal at a frequency essentially equal to the resonant frequency of A signal is applied to electrodes 82 and 83 by a signal circuit 84 . Such a pulse signal The element 81 is expanded and contracted in the rear direction, and the element 81 with the electrode 82 is placed in front of the element 81 (operation). A surface is displaced in response to an electrical pulse signal. Therefore, if the sound waves are in front of the device It is radiated in the direction of the filament 85.

Subsequently, in the second operating mode, the electric drive and reception circuit 84 is operated by the thread 85. The collision (im the electrical signal generated by the piezoelectric element 81 in response to the Becomes active to receive. Circuit 84 analyzes the received signal and determine whether they match the presence of threads in the target area.

As mentioned above, in a practical thread detection device, it is necessary to ensure that the thread position does not change. It is usually not possible to prove it. Thus, the position of thread 85 in FIG. In the front-back direction and in the direction parallel to the longitudinal axis of the device 80 (taper indicated by xx in FIG. 9) along the target line).

For the latter change (along X The resulting amplitude of the ultrasound waves reaching the position is not uniform and is shown schematically in Figure 1o. It shows a changeable nature. The maximum amplitude of the ultrasonic wave is in the longitudinal direction of the device 8o. It occurs at a position directly opposite the central point. However, as shown in Figure 10 In other words, the resultant amplitude is the amplitude from the center point. The dead spots (d At the position of ead 5potl, the combined amplitude of the ultrasonic wave from the device 8o is at the point The amplitude is much smaller than that at A. The distance from point A further increases. The amplitude then drops to a further minimum at positions called D and E, respectively. rises again.

When the thread 85 is located at the center position A, the emitted ultrasonic waves reaching the thread 85 are The composite amplitude is at its highest. Therefore, a relatively strong reflected signal is generated and the reflected The signal is now meaningful (si Generates a gnificantl electrical signal. However, as is clear from Figure 10, The composite amplitude of the emitted ultrasonic signal increases rapidly as the thread moves away from the central position A. As the detected electrical signal decreases, the detected electrical signal also decreases considerably. In the end, it is close to B and C. At low locations, the detected signal will be indistinguishable from the background noise.

Thus, the position along line XX at which the thread can be reliably detected using the apparatus of FIG. The useful range of is relatively small, perhaps only <10% of the transducer length β. Dew. The amplitude is sufficient between B and 0 and 1 and between C and E positions to detect the thread. The fact that If not, it has little practical value.

The amplitude change shown in Figure 1o is caused by diffraction and interference of the sound waves emitted from the transducer. due to In the converter of FIG. 9, each point on the front surface of the device 80 corresponds to a wavelet (wav Acts as a point source of eletl (paint 5 sources), each such The wave front from a point source is spherical. radiated from a point source In principle, the wavelets have the same frequency and amplitude of vibration, and their vibrations are , are always in phase with each other. These sources are Well, it's a coherent source. Their combined effect at a given point is , obtained by algebraically summing the displacements due to the individual sources at the point of interest. This is known as the principle of superposition.

At very long distances from the individual sources, each individual source on the front of the transducer the distance from the point of interest to the transducer itself is essentially the same (very long compared to the dimensions of the The phases of the waves are also substantially the same. In such a far place 1, therefore , the transducer may be considered as a point source.

However, at locations close to the transducer, small waves reaching the location of interest from individual sources The phases of each differ considerably from each other depending on their distance from their location to the source. Ru. Therefore, in some positions (positions A, D and E) the waves are constructive to each other. structurally interfere with other points (for example, B and B in FIG. 9). and C) are destructive and interfere with the destructive behavior shown in Figure 10. Gives the amplitude profile.

In the device of FIG. 9, the thread 85 is must be located relatively close to the transducer due to the relatively high attenuation of the ultrasound at the No. Therefore, it is sufficient to ensure that the transducer acts as a point source of ultrasound waves. The transducer cannot be separated from the string by a distance of

To alleviate this problem, as seen in Figures 8(A) and 8(B), the The rear electrode 71 of the device does not extend over portions 73 and 74, so that element 5 The amplitude of the vibration caused by the edge of 3 is the same as that of the remaining (center) SiJ of the element. ! smaller than that occurring within the area. Thus, the amplitude profile of the devices of Figures 6 and 7 9 is fundamentally different from that of apparatus 80 of FIG. In particular, as shown in FIG. As shown, the change in amplitude has been significantly reduced, so that the lowest point is no longer clear. , thus the lowest point of the first pair on either side of central position A' (position B' and C') at the corresponding positions, the profiles in Fig. 10. is significantly larger than the amplitudes at locations B and C. Therefore, positions B′ and and C', the amplitudes at these locations are reliable It is large enough for detection so no dead spots occur.

(Thus, due to the special electrode structure shown in FIGS. 8(A) and 8(B), the applied The effect of the electrical drive signal is that at different locations along the front (actuation) surface of the device 50. Therefore, if not, I would like to follow the target line XX (at a certain point) counteract the destructive interference effects that may occur in This allows the translation device to be positioned within which the thread can be reliably detected. It provides a useful range extending over approximately 70% of the length of the station.

12 to 15 illustrate alternative preferred embodiments for use in apparatus embodying the invention. FIG. 3 is an inverted view of each of the elements and their associated electrodes;

In FIG. 12, piezoelectric element 90 has a single continuous electrode 91 on one side thereof. The electrode structure 92 on the opposite side of the element 90 is separated into five parts. It is constituted by portions 92a to 92e spaced apart from each other. 92a to 9 Each part of 2e, however, receives the same electrical signal. Figures 8(A) and 8(B) ) Compared to the device shown in Figure 12, the device in Figure 12 is more complex; It is clear that it provides finer control of the width profile.

The piezoelectric element 100 of FIG. 13(A) also has a continuous electrode 10 along one surface thereof. 1, but on the opposite side there are a plurality of individually driven, separated voltages. It has pole portions 102a to 102k. Each of sections 102a to 102 The driving voltages are different from each other, as shown in FIG. 13CB). Individual Each electrode portion 102a or 102 has a single continuous electrode on the face of the associated element. After deposition, the continuous electrode is shaped by scribing it into a line. may be made. Electrode 101 may also be provided as a plurality of individual electrode sections. good.

In FIG. 14, the piezoelectric element 110 again extends along the entire length of one surface. It has a single continuous electrode 111 but has a dielectric material on the opposite side. tric) layer 112 is sandwiched between the second electrode 113 and the element 10. . The thickness of the layer 112 increases as the distance from the longitudinal center point of the element 110 increases in both elongated directions. It is gradually increasing.

In FIG. 15(A), the bare piezoelectric element 120 has its opposing sides facing each other. and second poling electrodes 121 and 122 and a temporary (temp) electrode. prepared by contacting with orarilyl. 1st polling The electrode 121 extends along the entire length of the element 120, and the second poling electrode 1 22 only extends over its central longitudinal area. Poling electrode 1 21 and 122 may be conductive rubber pads, for example. Example λ2000- A high DC voltage of 3000V is applied between electrodes 121 and 122 for a short period of time, for example, several minutes. is applied, and the temperature of element 7o rises to perhaps 90° C. during this time. after that, The poling electrodes 121 and 122 are removed and then the electrodes shown in FIG. 15(B) are removed. All continuous electrodes 123 and 124 are mounted on opposing surfaces of element 120 so that be given When using the element 120 of FIG. 15(B), at the end of the element 120, Poor polling is the preferred amplitude profile. wake up

The electrode structures shown in Figures 8(A) and 8(B) and in Figures 12 to 15 are , other forms such as electrostatic elements It can also be effectively applied to other piezoelectric elements, and the amplitude profile of those other elements can be It will be understood that similar modifications may be made.

For reasons explained below with reference to Figures 16 to 19, this is an elongated piezoelectric element. The narrower dimensions of the working surface of the child, 1. The transducer has a preferred height of otnm Ru.

It should be noted that the thread is located in the far field region of the vertical field of view of the transducer. . This area is defined by D”/(4) from the transducer, where D is the height of the transducer. Start from the distance you can reach.

For example, for a transducer with a height D that generates sound at a wavelength ahead, the generated sound wave has a height D This would correspond to the diffraction pattern generated by a plane wave hitting the slit. So This is thus, Sinθ=λ/D Equation A The main lobe (pri Mary 1 obe) and many secondary lobes seen in FIG.

The sound wave travels to the thread 3, which is placed at an angle α to the vertical, and enters the transducer. reflected towards. As can be seen from Fig. 16, the amplitude of the main lobe is the same as that of the secondary lobe. Much bigger than that.

Thus, if some recognized signal is to be received, Sound from the main lobe must be reflected back onto the transducer. From Figure 17 As can be seen, with the wave-front at an angle θ with respect to the zone normal, The upper section of the beam, which advances to , hits the thread 3 at an angle α to the vertical is reflected so that it travels at an angle of (2α−〇) with respect to the vertical. Bee in this part The beam reaches the transducer at a height of 2d(α-0) below the transducer. The beam In order to hit the transducer, this distance must be less than half the height of the transducer. stomach. That is, 2d(α−θ)<D/2 As mentioned, d can be up to 42.5 mm and α can be up to 10''. and 7, the operating frequency of the device, i.e. I MHz, then using equation A, θ If we replace , this means: D<2.0011! l or D>28mn+ When D is larger than 2.0 mm, for example 5 mm, as shown in FIG. , a narrow cone of sound is generated from the transducer and reflected by the thread 3 placed at an angle of 10°. Later, I lost track of the converter.

A further restriction is that in order to avoid destructive interference, The phase of the signal in return is significantly smaller than one cycle across the surface of the transducer. only has to change. That's Dα-kun Or by substituting α and λ, D<1.9mm Thus, by choosing D to be less than 1.9 mm, the thread can be adjusted to its maximum angle of 10'. At some point, the reflected beam hits the transducer and picks up a component across the surface. nt) will not interfere destructively, but will reduce the received signal amplitude, so , it is important that the beam is not too divergent (as shown in Figure 19).

As can be understood, the wide cone created by the transducer (of 0,5 mm height) is , allows the detection of threads placed at an angle from the vertical, but the reflection A branch tip that falls into a transducer, only a small portion of which is received by the transducer. If the beam has a half angle θ than the part of 41θ 41mm Since the amplitude is also proportional to D, the dimension of the aperture, the pressure amplitude (pr Essure amplitude) is: F/G, 6° abstract Colorless body Omega Sumire 1 1. A thread supported so as to extend in the longitudinal direction across a predetermined position. The existence of a body is: Direct the ultrasound toward the predetermined location along the longitudinal axis of the filament. The thread is sent across from the above predetermined position. By the method consisting of monitoring such waves that are inverted by the body, Detected.

Submission of translation of written amendment (Patent Law Article 184-8'!###) January 25, 1993

Claims (10)

[Claims] 1. a thread supported so that it extends longitudinally across a predetermined position A method for detecting a shaped object, the method comprising: directing ultrasonic waves to the predetermined position. , the signal is transmitted transversely to the longitudinal axis of the filament, and the above-mentioned Divert back from a predetermined position by the filament. A method for detecting filaments that monitors such waves. 2. longitudinally across a predetermined position with respect to the support of the device. a means for supporting the filamentous body so as to extend therein; and a means mounted on the support portion; and transverse to the longitudinal axis of such a body so supported the ultrasonic wave to the predetermined location. as well as detecting such waves inverted by such a body from that position Apparatus comprising monitoring means comprising ultrasonic transducer means also operable to 3. The wavelength of the sound wave is on the order of the magnitude of the diameter of the filament, or smaller. 4. The ultrasonic converting means alternately transmits ultrasonic waves and has a single ultrasonic transducer operable to detect such waves received from 4. The apparatus according to claim 2 or 3. 5. Claims 2, 3 or 3, wherein the ultrasonic transducing means includes a piezoelectric ceramic element. 4. The device according to 4. 6. Said monitoring means further comprises: a signal generated by said ultrasonic transducing means; An electronic signal processing circuit for distinguishing whether a wave is caused by an inverted wave such as 6. A device according to any one of claims 2 to 5, comprising: 7. Claims wherein the frequency of the ultrasonic waves is within the range of 0.8 to 1.2 MHz. 7. The device according to any one of 2 to 6. 8. 8. The apparatus of claim 7, wherein said frequency is substantially 1.0 MHz. 9. A claim in which the thread-like body is a thread supported by a draw frame of a loom. The device according to any one of ranges 2 to 8. 10. Claim 1 employing the device according to any one of Claims 2 to 9 the method of.