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TECHNICAL FIELD The present invention relates to a novel and improved acoustic transducer,
and more particularly to a point contact acoustic transducer having sharp or conical elements.
BACKGROUND OF THE INVENTION-In acoustic detectors conventionally used to detect sound
waves and ultrasonic waves emitted from the surface of a given material, in general, attenuating
type to establish an effective frequency range of operation A resonator is used. However, the
level of attenuation obtained with such a detector is, for example, an accurate level of the
broadband response indication which completely covers the predetermined frequency range of
interest of interest, including the frequency range of kilohertz and megahertz, for example. It is
not enough. Furthermore, the conventionally used structures generally rely on receiving an
acoustic signal over a large contact area by a speed sensitive detection element. Such a
configuration greatly deforms the received acoustic information. SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a compact, broadband point contact
acoustic transducer which reduces the contact area and improves the sensitivity in the case of
surface misalignment. One object of the present invention is to provide an acoustic transducer as
described above which does not require a coupling medium to detect the indication of
displacement. Disclosure of the Invention The point contact acoustic transducer of the present
invention is characterized by having a sharp or conical piezoelectric sensing element of an
effective piezoelectric material and having an improved transducer tip. The detection element is
mounted on the conductive damping tie-E and is conical or pointed to eliminate high frequency
ultrasonic waves propagating backward. According to the invention, the tip of the detection
element is convex and, according to one embodiment, provides an electrical ground connection
for the transducer. The electrical connection on the high potential side is provided by a
conductive damping tie. The tip of the detection element extends below the rest of the transducer
so as to be in contact with the acoustically vibrating surface to be measured. According to one
embodiment of the present invention, the flexible sheet of conductive material is transformed to
seal the transducer so that the transducer is protected from harmful ambient and / or electrical
influences. It covers the receiving end of the detector including the tip of the detection element
which projects downward from the sensor. The tip of the sensing element is physically connected
to the sheet of conductive material. The invention will now be described in detail by way of
example with reference to the accompanying drawings. BEST MODE FOR CARRYING OUT THE
INVENTION FIG. 1 shows an acoustic transducer 1o that includes a sharp detection element 11
that receives an acoustic signal from a sound source to be measured for acoustic indication.
The detection element 11 may be in direct contact with the acoustically vibrating surface 10 'or
indirectly with the acoustic i-moving surface via a flexible sheet (17') of conductive material as
shown. The tip of the detection element 11 projects from the transducer 10 towards '10'. The
detection element 11 is preferably shaped in a sharp or conical shape to prevent acoustic
reflections from occurring on the surface 10 'to be measured. The lower end of the detection
element 11, i.e. the receiving end, is directed to the crucible 10 'to be detected. By shaping the
detection element 11 into a sharp shape, the acoustic transducer 10 works effectively even on
relatively rough surfaces and does not have to be precisely aligned with the surface to be
measured. The sensing element 11 is a piezoelectric element, which makes it possible to convert
the energy of 8 into an electrical signal reflecting the frequency of the disturbance applied to the
crucible 10 'to be measured. The preferred piezoelectric material in this case is PZT-4. sound!
Other materials that have relatively large losses and that function the above-described
piezoelectric elements, if not better, include lead zirconate titanate, lead metaniobate, and many
similar optional ceramics. These materials are first machined into the preferred conical shape
and then given electrical polarity in a manner well known in the art. The preferred conical apex
angle of the tip of the sensing element 11 is about 60 ", the diameter of the base is 6.0 OLlll, the
height is 5.0011111, the diameter of the tip is 1 ° 50 ma +, and the wear is The width and
thickness of the shoe are 111 m 10.101111, respectively. The detection element 11 is mounted,
for example, by bonding it on a conductive damping tie 12, preferably with silver epoxy, in which
case the damping tie 12 is cylindrical and preferably made of brass. Due to its conductivity, the
stripe 12 can transmit the electric signal generated in the detection element 11 to the coaxial
cable connector 14 including the inner conductor 141 and the outer conductor 142. The
damping tie 12 is suitably attached by, for example, a method such as interference fitting in the
insulating member 16. Insulating member 16 is preferably cylindrical so that it can effectively
retain cylindrical damping tie 12 without axial slippage. The insulating member 16 has at its
upper edge an inner flange 161 which acts as a stop for holding the damping tie 12 in place. The
insulating member 16 is held in an outer shielding case 17 which is preferably made of steel and
closed by an upper end element 171 made of preferably the same material in order to ensure
shielding from above.
The coaxial cable connector 14 extends through the steel case 17 in a screwed state. The coaxial
cable connector 14 further includes an insulating material 140 effective to electrically isolate the
inner conductor 141 and the outer conductor 142. As shown in FIG. 2, a conductive overlay 33 is
suitably provided on the lower end, that is, the tip of the detection element 11. The overlay 33 is,
for example, a metallic layer sprayed on the tip of the detection element 11. This overlay 33 is
preferably formed J: including an upwardly extending tab 34 away from the crucible 10 'to be
measured. The size of the tab 34 is approximately Q, 5ssxQ, 5mn + so that its area is relatively
small compared to the total area of the tip 35. Further, the overlay 33 is provided with a wear tip
35 which will be described in detail later. As shown, the wear tip 35 is convex so that it can
function effectively on rough surfaces without accurate alignment. 1, · In Fig. 1, the insulation
member 16 is such that the suitably electrically insulated conductor wire 67 extends through the
insulation member 16 to electrically connect the overlay 33 to the coaxial cable connector 14 A
duct 66 is provided which enables it. In particular, according to one preferred embodiment of the
present invention, the leads 67 connect the tabs 34 of the overlay 33 to the conductors 141 or
142. FIG. 1 shows one embodiment of such an arrangement, wherein the tab 34 is connected to
the outer conductor 142 of the coaxial couple connector 14. The inner conductor 141 of the
coaxial cable connector 14 is connected to the damping weight 12 by a conducting wire 121.
The coaxial cable connector 14 is configured to be capable of processing radio frequency signals
in view of the shielding effect of the outer conductor 142. This ensures that the broadband signal
frequency provided by the converter 10 is secured. The wear tip 35 is a convex disk of a given
hardened silver-copper alloy brazed G in place on the overlay 33. The wear tip 35 provides a
convex, smooth abutment surface which is brazed in place for effective point contact with the
surface to be measured. The outer shielding case 17 has a hole at its lower side so that the
detection element 11 can extend towards the acoustic imaging surface 10 'to be measured.
Furthermore, the outer shielding case 17 includes, for example, the upper member 1111 to
ensure the operation completely shielded from above.
The measurement is started when the detection element 11 directly or indirectly contacts the
acoustic imaging surface. A lubricant, solvent, gel or other material need not be applied to the
surface to be measured in order to perform the operation. The reason that a lubricating medium
does not have to be applied is that the tip 35 of the transducer 10 extends beyond the body of
the transducer so that it can be in contact with the acoustically vibrating surface 10 'measured.
The tip 35 causes the flexible sheet 17 'to curve uniformly, thereby causing the surface 10' to
bulge downward. This allows the measurement to be carried out even on surfaces with a rougher
'10' to be measured. For the purpose of electrically shielding, it is preferable that the partial
shielding member 88 be mounted on the lower surface of the outer shielding case 17 in contact
therewith. In this case, the 711M member 88 has a central hole 188 which allows the detection
element 11 to extend beyond the plane of the lower end of the outer shielding case 17 so as to
be in contact with the surface 10 '. A lock ring 99 is used to secure the shield 88 to the case 17.
One real 1il of the present invention! According to iV / 4, the S-conductive flexible sheet 17
'extends to cover the open end of the outer shielding case 17 and acts as a complete electrical
shielding means. In order to seal the vessel 10 in a sealed manner, it is intended to protect the
converter under changing environmental conditions and under N11 atmospheric effects. The
sheet 17 '' is preferably made of metal. The preferred metal is aluminum. One way to form the
sheet 17 'is to heat treat it and then form it into a tightly stretched form on the erosion detection
element 11. Transducer 10 is used in the state arrange | positioned on the selected arbitrary
acoustic vibration surface. In order to ensure that the transducer 10 abuts the selected surface, it
is often sufficient to tap the transducer 10 into position on the surface to be measured. In such
operation, the coaxial cable connector 14 is connected to the display or processing unit 113 as
shown in FIG. Such an apparatus is effective to properly analyze and provide a broadband signal
generated by setting the transducer 10 on the acoustically vibrating surface 10 'to be measured.
According to such a configuration, the converter frequency path st! Of a very wide band covering
at least 50 kHz to about 1 and 51 t-1 z. The range can be secured. Although the invention has
been described in detail with reference to specific embodiments, the invention is not limited to
such embodiments, and various other embodiments are possible within the scope of the
invention. It will be apparent to those skilled in the art.
Brief description of the drawings
FIG. 1 is a schematic cross-sectional view of the transducer of the present invention showing the
conductive damping member and the tip of a sharp transducer projecting from the member and
extending towards the acoustically vibrating surface to be measured.
FIG. 2 is a schematic enlarged partial perspective view of the tip of the transducer as viewed
obliquely from below. FIG. 3 is a block diagram of an arrangement including a signal processing
and display device that may be employed in combination with the converter of the present
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