JP2755405B2 - A device that measures the distance to a target using ultrasonic energy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic transducer and method.

EPC Simultaneous Application Serial Number 84,06228.2 dated October 12, 1984
The article describes an ultrasound system and method.
The described ultrasonic transducer is overly complex to us in many applications. Accordingly, there is a need for new and improved ultrasonic transducers.

Briefly, it is an object of the present invention to provide an ultrasonic transducer that efficiently generates ultrasonic energy with a very short rise time.

It is another object of the present invention to provide a transducer of the above character which is extremely durable and can be used in adverse environments.

It is another object of the present invention to provide a transducer of the above character which allows measurements to be made independent of changes in the traveling speed of sound in the air and thus independent of temperature.

It is another object of the present invention to provide an apparatus and method of the above character which can be measured independently of temperature and independently of the precise positioning of the foil from the reference surface.

Additional objects and features of the present invention will become apparent from the detailed description of preferred embodiments thereof, taken in conjunction with the accompanying drawings.

FIG. 1 is a side view of a converter incorporating the present invention, FIG. 2 is an exploded view of the converter shown in FIG. 1, and FIG. 3 is used for the converter shown in FIG. FIG. 4 is a perspective view of another embodiment of a front housing, showing the use of two separate reference surfaces carried by a single reference bar; FIG. 4 is a perspective view of yet another front housing; So,
Figure 5 shows two separate reference bars carrying two separate reference surfaces, Figure 5 is a perspective view of yet another front housing embodiment, wherein two reference bars are positioned at an angle to each other; FIG. 6 is a block diagram illustrating a timing technique for estimating a target distance, and FIG. 7 is a block diagram illustrating a typical echo pulse waveform. FIG. 8 is a block diagram of a circuit for processing an echo pulse, and FIG. 9 is a circuit diagram partially showing a pulse circuit for generating ultrasonic energy in detail. FIG. 10 is a block diagram of a total pulse generation and echo receiving system including a gain compensation circuit, and FIG. 11 is a cross-sectional view of a modified example of the ultrasonic transducer embodying the present invention. Yes, Fig. 12 is a part of Fig. 11 13 is an enlarged view, FIG. 13 is a detailed circuit diagram of a part of FIG. 11, and FIGS. 14A and 14B are side sectional views of a part of FIG. FIG. 14B also shows a block diagram of a modified embodiment of the invention, FIG. 14A is a side view of a modified embodiment of the invention, and FIG. FIG. 16 is a schematic plan view of FIG. 11, which is a schematic plan view of FIG. 11, showing an example of the usage thereof, and FIG. 17 is a schematic plan view of FIG. 6 shows another embodiment of the usage.

The ultrasonic transducer and method of the present invention are used in an apparatus for detecting a distance to an object using ultrasonic energy. Transducers containing foil generate ultrasonic waves. The transducer also includes a reference having a surface that reflects the ultrasonic energy and produces an echo. The reference is positioned between the transducer and the object and is at a known distance from the transducer. The device shall take the ratio of the time required for the ultrasonic energy to travel from the foil to the reference surface and return the echo from the reference surface to the time required for the ultrasonic energy to travel from the foil to the target and return the echo from the target. Therefore, the distance to the target can be determined irrespective of the temperature of the air in which the ultrasonic energy travels. In order to make distance measurements independent of the exact position of the foil in the transducer, a second reference surface arranged between the transducer and the object at a predetermined distance from the first reference surface is provided. Is provided.
The apparatus determines the elapsed time between the echo received from the first reference surface and the echo received from the second reference surface to determine the distance to an object independent of the exact location of the foil in the transducer. Means.

The ultrasonic transducer 11 shown in FIGS. 1 and 2 includes a mounting stud 12 and a front housing 13. Mounting studs
12 is provided with an intermediate cylindrical part 16 and an end cylindrical part 17. The mounting stud 12 can be formed of a suitable material such as aluminum. The mounting stud 12 is provided with a cylindrical hole 18 extending in the longitudinal direction of the stud. The portion within the bore end portion 17 is threaded with standard female threads 19 so that the mounting stud can be threaded onto a piece of conventional 1/2 inch electrical conduit (not shown). The intermediate cylindrical portion 16 is also threaded with a conventional type of external thread to facilitate mounting of the transducer 11 on a device such as a panel (not shown).

The mounting stud 12 has a radially extending flange
Immediately after 23, an annular recess 22 is also provided. This recess 22 can be omitted if desired, this is simply a mounting stud
It is provided as a relief for the tool when machining 12.
As described later, the outer diameter of the flange 23 is the same as that immediately after the front housing 13. The mounting studs 12
A front cylindrical portion 24 extending forward of the flange 23 is also provided. The front cylindrical portion 24 is provided with an annular recess 26 for receiving an O-ring 27. O-ring 27 forms a water seal between housing 13 and mounting stud 12.

A coaxial cable 31 is connected to the converter 11. The coaxial cable comprises an outer cylindrical ground 32 and a central conductor 33. Outer conductor 32 is connected to stud 37 by suitable means such as brazing by leads 36. The stud 37 is carried by a grounding disc 38 of a suitable material such as brass. The grounding disc 38 is provided with a hole 40 provided in the disc 38.
The cylindrical portion 24 is extended by a pan head screw 39 screwed into a threaded hole 41 provided in the cylindrical portion 24.
It is attached to the front of

The grounding disc 38 is provided with a hole 42 arranged at the center, and through this hole, the center conductor 33 of the coaxial cable 31
Is growing. The center conductor 33 also extends through another hole 43 provided in the piston mounting disk 44. The piston mounting disk 44 supports a disk-shaped piston 46. The piston 46 is provided with a stud 47 which is located at the center, extends rearward, and sits in a hole 43 in a piston mounting disk 44. The center conductor 33 of the coaxial cable 31 is attached to the stud 47 by any suitable means, such as, for example, soldering, using any suitable means, such as an L-shaped lug 48. Lugs 48 are attached to studs 47 by screws threaded into the studs.

The front side of the piston 46 is provided with a flat circular surface 50 which serves as one plate of a capacitor for the converter 11. The piston mounting disk 44 is provided with four grooves 51 on the outer edge thereof, and these grooves accommodate the heads of the pan head screws 39. The piston mounting disk 44 receives four pan head screws 53 used for mounting the front housing 13 to the mounting stud 12.
Two holes 52 are also provided. The support ring 56 sits on the piston mounting disk 44 and has four equally spaced holes 58 adapted to receive screws 53. Support ring 56 can be formed of any suitable material. The support ring 56 need not be conductive, but is made of aluminum to obtain the desired support.

The foil 61 is attached at its outer edge to the support ring 56 by suitable means such as a double-sided adhesive tape (not shown).
The foil 61 is composed of a layer 62 of an insulating material, and the conductive layer 63 formed on the surface of the insulating material faces forward. The layer of insulating material may be, for example, a Kapton film of appropriate thickness (eg, about 0.3
Any suitable type (such as 30 gauge Kapton of mill thickness) can be used. The conductive layer 63 is formed of a suitable material, such as gold, deposited on the front surface of the insulating layer to a suitable thickness, for example, 50 to 500 Angstroms.

The conductive layer 63 formed on the insulating layer 62 of the foil 61
Serves as the second plate of the capacitor for

To assemble the various parts described above, first the piston 46 is attached to the piston mounting plate by suitable means, such as adhesive.
Attach to 44. If desired, an Eastman 910 super glue can be used, for example. Similarly, the piston mounting disc 44 can be attached to the grounding disc 38 by an adhesive. Pass the coaxial cable 31 through the mounting stud 12,
Attach to lug 48 by soldering. Next, the grounding disk
The 38 is secured to the mounting stud 12 using a pan head screw 39 extending through a groove in the piston mounting disk 44.
The foil can then be fixed to the support ring 56 with double-sided adhesive tape, and the support ring 56 can be arranged on the piston 46.

From the structure described above, it can be seen that approximately 0.100 inches of the outer edge of the foil 61 is secured to the support ring 56. The entire structure described above, which is carried by the front cylindrical portion 24 of the mounting stud 12, is housed in a cylindrical housing 13. The housing 13 is provided with a hole 66 that fits over the front cylindrical portion 24 and forms a water seal with the O-ring 27. The housing also has an annular lip 67 extending inward and located on the outer edge of the foil 61. A recess 68 provided in the lip 67 receives the head of a pan head screw 53 that passes through a hole 69 extending through the recess 68. The screw 53 is also screwed into the hole 41 of the mounting stud 12 through the hole 64 of the foil 61, the hole 58 of the support ring 56, the hole 52 of the piston mounting disk 44, and the hole 40 of the grounding disk 38. This forms a small transducer assembly wherein the outer diameter of the cylindrical housing 13 has the same outer dimensions as the flange 23 of the mounting stud 12.

The housing 13 has two upright posts 71 formed integrally with the housing and extending forward from the housing 13 before. The strut 71 carries a reference bar 72. The reference bar 72 is substantially rectangular in cross section and has a first surface 73 and a second surface 74 that are parallel to each other and substantially parallel to the plane of the foil 61. Reference bar 72 is positioned such that first surface 73 is within 1/2 inch to 1 inch of foil 61. The reference bar is shown as having a rectangular cross section, but need not be. For example, it can be in the form of a small bar or wire if desired. However, the reference bar or member 72
It is desirable that the thickness be relatively small in size so that the reference bar does not unduly interfere with the ultrasonic energy emitted from the transducer. The reference bar should be strong so that it does not bend during normal use of the transducer. However, it must not be so large that it does not unduly interfere with the sound generated by the transducer and reaching the target.

In the embodiment of FIG. 2, the surface 73 is flat and the foil 61
In a plane parallel to the plane. However, the other surface 74 is rounded as it is desirable that the surface receive only the sound reflected from the reference bar 72. In other words, the outer surface or front surface is substantially convex, so that the sound waves transmitted by the transducer wrap around this surface and are not reflected by this surface.

FIG. 3 shows another embodiment of the front housing 76. Also in this embodiment, the front housing 76 has a first surface 79 and a second surface 79.
It has an upright column 77 carrying a reference bar 78 provided with 81, but since both reference surfaces 79 and 81 are plane and parallel to the foil 61, a reference echo is obtained from both surfaces 79 and 81.

FIG. 4 shows yet another embodiment of the front housing 84. In the present embodiment, the upright support 86 has two reference bars 87 and 88.
And these bars are roughly aligned with one another, but one is overlaid on the other and spaced apart from the other. The reference bar 87 is provided with a flat surface 89 parallel to the foil 61 and a curved surface 91 which is curved so as not to cause reflection. Similarly, the reference bar 88 is provided with a flat surface 92 parallel to the foil 61 and also to the surface 89. Also surface 83
Is rounded to avoid echo.

FIG. 5 shows yet another embodiment of the front housing. In this embodiment, the front housing 96 has two pairs of upright posts 97.
And 98 are provided, with the strut 97 carrying one reference bar 99 and the other strut 98 carrying another reference bar 101.
The reference bar 99 is provided with a surface 102 which is a plane parallel to the foil 61. The reference bar 99 also has a surface 103, which is rounded to inhibit echoes therefrom. The bar 101 has a flat surface 104 parallel to the foil 61 and a rounded surface 106 to inhibit echoes. As can be seen from this arrangement, the reference bar can be positioned at any angle with respect to the foil 61 to achieve the desired purpose. Desirably, surfaces 102 and 104 are spaced at different distances from the foil. It should also be understood that if desired, the reference bar can be supported in any suitable manner from the front housing. For example, a single set of struts may be used to support the annulus instead of separate struts, into which the reference bar is inserted as a crossover member.

The outline of the operation and operation of the above-described converter 11 will be described below. Using the transducer 11 in a suitable type of system and device, such as the type described in Serial Number 532,57, filed Oct. 15, 1983, "Ultrasonic Devices, Systems and Methods" And For example, 100 to 500 kHz for the converter 11
Upon providing electrical energy at a suitable frequency in the range of z, preferably 250 kHz, the transducer generates ultrasonic energy at that frequency. As is well known to those skilled in the art, when such energy is applied to the transducer, the foil 61 is caused to move very rapidly, which causes the air to move and propagate acoustic energy.

When the ultrasonic energy is emitted from the transducer, it strikes the surface 73 of the reference bar 72, which is
A known distance from 61. In this embodiment of the system, two timers are used. One timer measures the reference surface 73 after the acoustic energy has left the transducer.
Used to determine the time to receive an echo from The other timer is used to calculate the time between when the acoustic energy leaves the transducer and when it receives an echo from the target. As mentioned above, the reference bar 72 is sized so as not to block most of the sound energy leaving the transducer, so that the sound energy reaches the target as well as the reference bar. A computer provided in the system uses the two times of the echo energy from the surface 73 and the ultrasound energy from the target to calculate the exact distance to the target. By using a reference and such a calculation, it is possible to eliminate the effect of temperature on the traveling speed of sound in a gas, for example, typically air, where the target is located. Since the reference surface 73 is at a known distance from the foil, the precise distance from the foil to the target can be easily calculated by a computer using the ratio of the two times. In the embodiment of the invention shown in FIG. 2, the surface 74 is rounded and the acoustic energy cannot travel around this surface to produce an echo, so that
74 does not produce significant echo. But the second
It has proven difficult to ascertain the precise or exact position of the foil 61 with respect to the embodiment of the invention shown in the figures. Since the foil is thin and flexible, the foil after excitation does not always return exactly to the same position as before the start of transmission. In other words, the foil was found to be a poor reference point from which to make measurements for calibration purposes to the reference bar. It has been found that this difficulty with foil positioning can be overcome by using two fixed references positioned between the foil and the target. In this case, it is necessary to prepare three timers in order to measure the elapsed time for three possible echoes. Such an arrangement is shown in FIG. In FIG. 3, two reference surfaces are provided, namely surfaces 79 and 81, both plane and parallel to the foil 61, these two reference surfaces 79 and
81 is separated by a known distance. The three timers used in the system start when the acoustic energy leaves the foil, the first timer measures the time until the echo returns from the surface 79, and the second timer measures the time until the sound returns from the foil 61. The third timer measures the time it takes for the echo to return from the second surface 81 as it travels, and the third timer measures the time it takes for the echo to travel from the foil 61 to the target and return from the target. By knowing how far the reference surfaces 79 and 81 are from each other, the precise foil position becomes less important. The computer in the system subtracts the time recorded by the first timer from the time recorded by the second timer.
This difference is then used to calculate the actual distance to the target as was done with the sample reference. However, some scaling value is used to compensate for the difference measurement made for the transit time between the foil and the first and second reference surfaces. It is not necessary to know exactly how far these references are from the foil, as is evident by using two references, and for this reason the measurement should be relatively independent of the foil position And can be done independent of temperature. Another embodiment uses the echo of the inner reference bar to start two timers. One timer is for the target and the other timer is for the second reference echo. This eliminates one set of timers.

The embodiment shown in FIGS. 4 and 5 similarly uses two reference surfaces.

From the foregoing, it should be apparent that there has been provided an ultrasonic transducer and method capable of efficiently propagating ultrasonic energy and providing accurate distance measurements. It also makes it possible to determine the distance between the two objects relatively precisely and substantially independent of the temperature of the air. Furthermore, it is possible to make such measurements accurately without knowing precisely the spacing between the reference and the foil carrying the acoustic energy.

FIG. 6 illustrates the technique for calculating a distance to a target independent of temperature changes, including a target counter 110, a counter 111 responsive to a first reference surface, and a counter 112 responsive to a second reference surface. As is evident from the output of counter 112 as shown by dashed line 113, this counter is optional or can be omitted if only one reference is desired. Further, as described above, the counter start input 114
Is driven by the transmitted converter pulse 116, particularly if the pulse has its first negative falling or dip 117. The stop input 118 is maintained by each counter and is provided to the exact phase point of the received echo as described below with reference to FIGS. Of course,
The associated microprocessor (FIG. 10) determines which is the transmitted pulse, which is the following first reference echo, the second reference echo, and the target echo. used. To calculate the distance to the target, the ratio of the echo to the reference echo is determined at block 119 and multiplied by the known distance to the reference bar as only the first reference counter 111 is used. Since the reference bar must be at a known distance, the preferred technique according to the present invention is to configure a particular device, measure this distance, and assign a particular calibration number to the transducer device. This is represented by the factory transducer calibration input 121. This technique precludes manufacturing with tight tolerances, as it does not require the reference bar to be placed at a precisely known distance.

Finally, according to an alternative embodiment using a second reference counter 112, the counter is subtracted from the first reference counter, as indicated at 122, and a scaled value is added to determine the same ratio.

FIG. 7 shows the waveform of a typical echo signal received from a reference or target. In order to obtain repeatable and accurate information, it is necessary to supply a stop pulse at the exact same phase position of the echo pulse or echo signal. In the technique used in the present invention, the echo signal must exceed a certain threshold positively, and the stop signal occurs at the next O-crossing.
This threshold is shown at 123 at about 400 mV. 12 stops
Occurs at O-crossing in 4 and is so indicated.
Note that in the description with respect to FIG. 6, the start signal occurs on the first dip and is so indicated.
Since the time span from start to stop is 4 microseconds,
The timing in this case is extremely precise. Of course, the second
Other variations may be used, such as using an O-cross.

In any case, in order to realize the stop method shown in FIG. 7, a comparator having a large hysteresis is used as shown in FIG. 400m comparator threshold
Indicated by V (this is an arbitrary value). With large hysteresis, the first O after reaching the threshold
A stop signal is generated at the intersection. As described above, this is the target counter 110, the reference counter 111,
Generate stop signals for both 112.

To obtain a received signal that can be predicted in the form shown in FIG. 7, the transmitted pulse envelope must have a very fast rise time. This is not the same as the transducer surface making the short wave having sudden ultrasonic motion.
To achieve a fast rise time, a pulse generation circuit that avoids inductive components (ie, inductorless) is used, as shown in FIG. This is in opposition to conventionally used pulse transformers. In the present invention, for example, a fixed high-voltage power supply 126 having a DC voltage of 300 V is connected to the converter 31 only through the resistor 127. As mentioned above, the converter is effectively a capacitor. Thus, during operation, the capacitor is charged through resistor 127. The field effect transistor switch 128 is triggered by a control pulse from the transmit / receive switch 33 to generate a pulse that is then transmitted to the target and reference bars. All stored energy contained in the capacitor of the converter 31 is rapidly converted to ultrasonic energy. Thus, the echo signal has a precise waveform suitable for accurate analysis of the type shown in FIG.

However, the transducer must recharge in order to receive the echo signal (and the received signal is sent to the transmit / receive switch 33 via line 129), and this charge is based on the echo pulse received from the reference bar. Must be done very quickly (preferably less than 100 nanoseconds) so that it is not masked. The use of a resistor 127 acting as an inductorless circuit and a damping resistor performs the operations described above. In practice, ring down time is minimized.

The specific receiving circuit on the line 129 includes a DC blocking capacitor 131, a current limiting resistor 132, and a pair of blocking diodes 133. As described above, in short, the resistance 127
Acts as a charge resistor and as a damper to mitigate ring-down oscillations after a sudden discharge.

For example, the sensitivity of the converter 31 may change with time due to aging, so it is necessary to provide the gain compensation circuit shown in FIG. In summary, FIG. 10 is a comprehensive circuit diagram of the electrical components required to process and generate pulses and to process echo signals. The converter 31 is connected to a receiving circuit including a voltage controlled amplifier 134, the output of which is applied to a voltage to digital word converter 136, whose information is processed by a microprocessor 137. Microprocessor 137 is responsible for other phases of the process (eg, selection of reference echo)
In addition to the above control, the digital word / voltage converter 138 is driven to change the gain of the amplifier 134. Finally, of course, the microprocessor 137 controls the transmission circuit 139, for example, as shown in FIG. This will be part of the transmit / receive switch 33.

The operation will be described. First, the converter 31 is insulated by the transmission circuit 139 and generates an ultrasonic pulse. Microprocessor 137 then causes the receiving circuit to listen for echo signals from one or both reference and targets. Initial, peak voltage detector
135 is inserted into the circuit by the microprocessor 137 and the peak voltage of the reference echo is converted by the converter 136 into a digital number. If this is less than the preset value, it indicates that the signal is too weak, so the gain of the receiver / amplifier 134 is increased by the microprocessor 137. That is, the feedback process is effectively realized. Next, normal processing as schematically illustrated in FIG. 6 is performed by the microprocessor 137, the ratio is obtained, and the distance to the reference is multiplied. As described above, an improved device for detecting a distance to an object has been provided. Although a single transducer has been shown to function as a transceiver (ie, both transmitting and receiving ultrasound information), it should be emphasized that the present invention also includes the use of separate units.

In the embodiment shown in FIG. 11, the ultrasonic transducer is a coaxial cable 31 '.
1 and 2 in that it includes a cylindrical mounting stud 12 'having a front end and a front cylindrical housing 13' carrying a suitable reference bar.

For example, anodized aluminum housing 13 'is fixed to mounting stud 12' and piston 14
Housing the transducer assembly including the zero and the associated foil 141. An aluminum piston 140 includes a stud portion 142 and is generally held by a plastic disk 143 having a recess 144 on the upper surface. This is shown in detail in FIG.

Please refer to FIG. 14A and FIG. 14B. The surface 143a of the mounting disk and the surface 140a of the piston 140 are flush with each other. This is done by first retracting the piston 140 as shown in FIG. 14A.
Glue into 144. Next, this combination is plane-cut as shown by the broken line 146 to obtain the same views 140a and 143a shown in FIG. 14B. This provides a good surface for the foil 141. Foil 141
Is fixed to the surface 143a later and freely vibrates with respect to the surface 140a. With particular reference to FIG. The foil consists of a Mylar or Kapton insulating layer 147, with a very thin layer of gold 148 deposited. In the center of the gold foil 148, a non-conductive protective layer 149, such as a silicon-based plastic, is typically present by evaporation. A suitable material is parylene. When using the ultrasonic transducer in harsh ambient conditions,
This layer 149 protects the very thin gold layer from chemicals and abrasives. This is necessary, for example, because gold is only 300 mm thick. The parylene layer may be about 2 μm thick. The parylene's thinness does not affect the generation of a beam of ultrasonic energy transmitted from the surface of the foil.

Finally, an annular ring 151 of, for example, silver paint is coated on the gold surface 148 to provide more effective conductive contact with the housing 13 'as shown in FIG. To elaborate,
This contact is an effective grounding of the foil and is achieved by the presence of retaining screws 152 that hold the housing 13 'to the mounting studs 12'. Contact also occurs at interface 153 between the housing and the mounting stud. As described above, the mounting stud is essentially a ground connection and is connected to the ground of the coaxial cable 31 'as shown by terminal 154.

Refer to FIG. 13 for a while. Inner cable 15 of coaxial cable 31 'with the outer cable grounded as shown at 154.
6 supplies an appropriate alternating voltage to generate an ultrasonic beam. In other words, an appropriate voltage is applied to the effective capacitor line 156 formed by the aluminum piston 140 and the grounded foil 141. To prevent accumulation of static voltage on the piston 140, a bypass leakage resistance 157 having a relatively high resistance, for example, 10 MΩ, is provided between the line 156 and the ground. This resistor is housed in a cover 157 as shown in FIG. The center cable 156 is connected to the stud 142 of the piston 140.

In operation, of course, the foil 141 is
Because it is fixed only to the piston 140, it can freely vibrate, that is, freely move with respect to the piston 140. According to patent application Ser. No. 532,576 “Ultrasonic system and method” filed Oct. 15, 1983, the surface 140 of a piston 140 interacting with a foil
a has been processed to enhance the generation of ultrasonic energy. Of course, a substantial part of the foil 141 is the housing 13 '
Is exposed because of its cylindrical shape, and the almost vertical axis 161
An ultrasonic beam can be generated along.

The inside of the transducer, i.e. the interface between the foil 141 and the piston 140, must be sealed to avoid environmental pollution, which can be static at relatively hot ambient temperatures or when atmospheric pressure is reduced. May result in pressure build-up. Hole 163 cut through the centerline of the piston to release air
As a result, the air flow path 162
Is provided. Next, a screw 164 is arranged in the hole 163, and the flow path 162 is provided again by cutting the center.

As shown in FIG. 11, in one embodiment, an elastic bag or balloon 166 is attached to the air flow path. The balloon is housed in a plastic tube 167. Tube 167 is a fitting
Retained at 168, the fitting 168 is secured to a small diameter rubber tube 169 mounted at the end of a screw 164. In this way, a complete confinement of the atmosphere is obtained.

As a variant, a coaxial cable 171 having an air passage 172 therein can be used, as shown in FIG. 14B.
According to this, air can freely pass between the converter and the electronic processing unit 173 that is remote from the surrounding state of the converter. In the processing unit the air can be vented to the surrounding air, or alternatively a resilient bag can be used in the unit. This special coaxial cable 171 which, of course, also contains the appropriate electrical connections for driving the transducer, is available under the trade name "HELI-AX"
May be the type commercially available as This is a spirally wound coaxial cable.

As shown in FIG.15A, a coating material in the form of a cone 173 is placed on the housing 13 'and reference bar legs 71' to protect the transducer from industrial contamination such as oil, water, sawdust, etc. I have. This material is typically made of polyester cloth, the weave of which is sufficiently packed to eliminate dust, but allows for efficient transmission without unduly attenuating the ultrasonic energy.

FIG. 15C shows the fabric when first cut, folded at line 174 and placed on housing 13 'to bake or fuse the edges of the fabric together at 176 and 177 as shown in FIG. 15B. And a leak-free fit.

As shown in Figure 16, if the test object at 178 is about 1/4 inch in diameter, or very close to other non-interesting structures, an effectively smaller beam should be used. Is useful. Thus, a plate 179 is placed at a predetermined distance from the transducer foil, and an aperture 181 centered on the nominal beam axis 161 is provided. This results in a smaller sensing beam 182, which can be reflected back to the transducer. At the same time, if the plate 179 is angled at an acute angle to the axis 161, the beam is deflected to 183 and unnecessary reflection is prevented.

As a variant, if the plate 179 is perpendicular to the axis 161, this unwanted deflection beam can be reflected back to the transducer and removed by using a distance measuring technique. In other words, the plate 179 is closer than the object 178. Finally, the extremely small object 184 as shown in FIG.
This can be accomplished if relatively sensitive testing is required by focusing the focal point 187 using a parabolic reflector 186 mounted at a predetermined distance from the housing 13 'and on the beam axis 161. can do. This is a whole 18
This is an extremely small area for the beam indicated by 8. Reflector 186 may be a linear or circular paraboloid. As described above, an improved ultrasonic transducer is provided.

Continuing on the front page (72) Inventor Hossack James M. USA 98052 Washington State Redmond Northeast AT / Force Street 17117 (72) Inventor Lecoq Walter United States of America 98224 Burling Piobox 74 (56) References JP Sho 62 -282284 (JP, A) JP-A-61-130885 (JP, A) JP-A-56-147020 (JP, A) JP-A-52-13183 (JP, Y2)

Claims (1)

(57) [Claims] 1. A converter comprising a foil for generating ultrasonic energy and having a transducer mounted on the housing, and having a surface for reflecting the ultrasonic energy to generate an echo, mounted in the housing and including the converter. A first reference surface at a known distance from the transducer means between the instrument means and the object; and a second reference surface mounted to the housing and spaced a predetermined distance from the first reference surface. And means located between said converter means and said object; and said acting as effective capacitance to create an inductance-free pulse generating means for operating said converter means. An electrical device connected to the transducer means within the housing to utilize the foil of E .; echoes received from the first and second reference surfaces and echoes received from the object Means for measuring the time elapsed between and the distance to the object irrespective of the exact position and temperature of the foil of the transducer means. A device that measures the distance to the target.