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JP2009236920

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DESCRIPTION JP2009236920
A waveguide support mechanism and damping mechanism that are easy to manufacture and
assemble. A waveguide suspension (2) and modular structure for an acoustic waveguide (4) for
use with a waveguide (4) generating torsional or longitudinal distortion waves by transmitting
current pulses It has six. The attenuating element 6 is for preventing reflection of the acoustic
strain wave, and includes a sleeve 27 surrounding the waveguide and a mechanism 29 for
applying pressure to the sleeve 27. The sleeve 27 exerts pressure on the waveguide 4 to
gradually attenuate the acoustic strain wave energy along the length of the waveguide 4
surrounded by the sleeve 27 of the attenuating element to reflect the acoustic strain wave To
prevent. Also, the position of the return conductor 1 is determined by the response of the
measurement system so as to minimize ringing of the signal received from the pickup coil 13.
[Selected figure] Figure 1
Acoustic transducer
[0001]
FIELD OF THE INVENTION This invention relates to damping elements for elongated waveguides
in magnetostrictive transducers for displacement or distance measurement, waveguide
suspension devices, and circuits used for such devices. More particularly, the invention relates to
a magnetostrictive transducer of modular construction having a damping element, a waveguide
suspension, and a modular construction provided for displacement or distance measurement and
using a local buffer circuit.
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[0002]
2. Description of the Prior Art A magnetostrictive transducer having an elongated waveguide for
propagating torsional strain waves generated in the waveguide when a current pulse is applied
along the waveguide via a magnetic field is of interest. It is well known in the field. A general
linear distance measuring device is disclosed in U.S. Pat. No. 3,898,555 which uses a moveable
magnet which interacts with the waveguide when a current pulse is applied along the waveguide.
[0003]
Prior art devices of the type as disclosed in U.S. Pat. No. 3,898,555 also have a sensor element
enclosed in a protective housing which also contains at least the electronic circuitry for
generating the pulses, An attachment means is provided which cooperates with the device for the
purchaser.
[0004]
U.S. Pat. No. 5,313,160 teaches a modular design in which the sensor and electronics assembly
can be removed from the application package.
An outer housing is provided in the application package. The outer housing is used by the
purchaser to attach the attachment of the sensor and assembly assembly to the end device whose
position is to be measured. None of the prior art excludes any electronic circuitry except the local
buffer circuitry.
[0005]
Previous sensor designs required careful handling until the entire unit was manufactured,
including the outer housing and electronics. Also, the prior art is difficult to manufacture
waveguides and utilizes expensive methods to support the waveguides and prevent the reflection
of the desired acoustically distorted waves. Conventional high performance waveguide
suspension systems utilize thin elastomeric spacer disks, which are individually located along the
entire length of the waveguide. Installation of the disc is usually time consuming and manual. The
best performing damping devices currently in use are molded rubber elements having a central
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hole. These are difficult to mold and take time to install.
[0006]
Another waveguide damping device is disclosed in U.S. Pat. No. 3,898,555 to prevent reflection
of acoustically distorted waves at both the end of the waveguide and the attachment end of the
waveguide. These devices are generally soft rubber pads that are clamped around the waveguide
to absorb acoustic strain wave energy and minimize reflection of the generated pulse, as well as
reflection and detection. Interference with the acoustic distortion wave signal to be reduced is
reduced. The damping device and the structure for fixing the waveguide at the end are separate
from the acoustic waveguide pick-up element for this type of prior art, as described in U.S. Pat.
No. 3,898,555 It can be quite long at the end. For example, if the fluid level is being detected by
a transducer, make the waveguide as operable and active as close to the bottom of the tank as
possible, and by doing so, the end away from the pickup element It is desirable to minimize the
length of the waveguide support in at, including the length of separate attenuation devices at
such ends and the mounting end of the waveguide to which the pickup element is attached.
[0007]
Furthermore, in the prior art, the mass density of the damping material is of great importance in
order to achieve a mechanical impedance that transmits and dissipates the acoustic strain wave
energy into the damping device. Coupling of the waveguide to the damping device should also be
efficient. It has been considered in the prior art that attenuation is achieved by the dissipation of
acoustically distorted wave energy by the attenuation medium.
[0008]
Rubber-type damping media are also used in the art because of their ability to dampen
vibrations. However, this material cures at temperatures close to the freezing temperature of
water and becomes extremely soft at temperatures below 200 degrees Fahrenheit. The same is
true for epoxy or urethane elastomers. Due to these large changes in properties, the properties of
the "front" end reflection and the "end" end reflection change rapidly with temperature.
[0009]
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Also in the art, silicone rubber dampers with two different hardness and / or different loading
pressures on the waveguide are used. Low pressure, low hardness silicone rubber is used to
minimize front end reflection (input end), and high clamping force and high hardness silicone
rubber are combined to provide damping at the end or end. It's being used. The use of silicone
rubber is considered as a compromise as a damping medium, as it is necessary to make the
damping section longer if it is more resilient and more resilient. Silicone rubber in fact has good
stability over a wide temperature range, which is an important advantage as a damping material.
[0010]
The need for an efficient damping material becomes particularly apparent when the transducer is
using what is known as circulation mode sensing. In the circulating mode, each time the sensor
receives an acoustically distorted wave signal, a new current pulse is sent, which causes the
frequency of the acoustically distorted wave pulse to increase and, as a result of the reflection,
noise is formed. Without effective attenuation, the "noise" formation reduces the usefulness of
the detection technique. This is because, in particular, the acoustic distorted wave signal has a
small amplitude in the prior art. Therefore, in the prior art, it is possible to shorten the damping
material together with the end mounting structure of the waveguide, to improve the coupling
with the waveguide itself and to have the ability to dissipate energy. It is ideal. All these have not
been fully achieved in the prior art. For another approach to increasing signal strength, see US
Pat. No. 4,952,873, which uses phase shifted reflections from the end of the waveguide to
enhance the main signal.
[0011]
Another method for performing attenuation is described in US Pat. No. 4,958,332. This patent
teaches an improved damping method. The damping device comprises a very viscous flowable
material attached to and coupled to the waveguide. The material has a mass density modifying
additive, such as a metal powder, to vary the mass density along the length. The damping
material is held against the waveguide using a suitable housing. The housing is attached to the
waveguide at a selected pressure. This method is effective but difficult to manufacture.
[0012]
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The prior art also uses two rubber paired members (flat sheets) to surround the waveguide with
metal clamps, hold them around the waveguide and pressure the waveguide on the input side Is
added. But this is quite expensive.
[0013]
Electronic circuitry is included inside the waveguide suspension device, expensive means are
used for the waveguide suspension, the prior art is between the waveguide suspension
mechanism and the damping mechanism The prior art has drawbacks in that it does not mention
relationships. The prior art also does not closely couple the mode converter (any device that
converts mechanical energy to electrical energy or any device that converts electrical energy to
mechanical energy) to the input pulse source. It suffers from the disadvantage of utilizing the
reflected energy from the end of the mode converter's tape component at the input end of the
device.
[0014]
In the prior art, it is also known to use a coil having a large number of windings of, for example,
2400 or more for a mode converter, and a mode converter coil having a small number of
windings as a pickup coil.
[0015]
U.S. Pat. No. 4,952,873 also discloses a waveguide mounting block for supporting a waveguide at
the mounting end, which forms a reflection point for sound waves.
This block is precisely located the distance from the signal sensor. This block is moved by the
sound wave during half of the signal lobe time so that the reflected wave is an additional signal
to the incoming signal wave. Others in the prior art select waveguide lengths without mounting
blocks to achieve the same goal.
[0016]
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For a general background, S. C. Rogers (SCRogers) and G. N. Miller (GNMiller) "Ultrasonic Level
Temperature and Density Sensor" (IEEE) Transactions on Nuclear Science, Vol. NS-29, No. 1,
February 1982). U.S. Pat. No. 3,898,555 U.S. Pat. No. 5,313,160 U.S. Pat. No. 4,952,873 U.S. Pat.
No. 4,958,332 "Ultrasonic Level, Temperature and Density Sensor" by SC Rogers and G.N. Miller,
IEEE Transactions on Nuclear Science, Vol. NS-29, No.1, February 1982
[0017]
An object of the present invention is to provide a waveguide support and damping mechanism
that is easy to manufacture and assemble.
[0018]
Another object of the present invention is to facilitate optional packaging based on removable
and replaceable sensor elements.
[0019]
Another object of the invention is to provide a robust sensor element that is suitable for
purchasers to incorporate into their products.
[0020]
An object of the present invention is to provide a magnetostrictive transducer with a local buffer
circuit which can improve the coupling between the tape and the coil mode converter.
[0021]
Another object of the invention is to provide a local buffer circuit which is compact and provided
inside the sensor shield, while having a signal generator outside the sensor shield.
[0022]
SUMMARY OF THE INVENTION The present invention relates to end structures for elongated
members such as waveguides used in magnetostrictive displacement or distance measuring
transducers.
This end structure suitably prevents reflected waves such as torsional or longitudinal distortion
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waves and does not occupy much length at the end.
Thus, for example, the waveguide can be operated and active close to the end of the elongated
member, while this end structure can reflect the reflection of the acoustic strain wave
propagating along the waveguide. To prevent.
[0023]
The suspension is realized by first limiting the movement of the elongated member and shielding
it from external acoustic energy.
In this way, there is no shock and vibration stimulation that can cause false responses.
This is achieved by enclosing an elongated member, such as a waveguide, with a suspension
element or sleeve.
The dimensions of the sleeve are such that the waveguide makes loose contact with the sleeve,
but does not move too far in the lateral direction. The fibers used to form the sleeve are fine,
hard materials or combinations thereof consisting of ceramic, metal, polymer, glass and the like.
The sleeve may also be a composite tube consisting of layers of different materials. The tube may
be a rubberized composite glass fiber tube structure. An enclosure may be mounted on the
sleeve. Thus, elongated members such as waveguides are cushioned within the enclosure. The
actual damping is performed by the damping element being slipped over the end of the
waveguide. The damping element is similar to the suspension element but is dimensioned to
achieve optimum damping. The end of the transducer facing the head is cut at about 45 ° for
better impedance matching with an elongated member such as a waveguide.
[0024]
The suspension is also realized by terminating the waveguide with a bracket. The bracket is used
to hold the waveguide and the return conductor spaced apart from the pick-up coil and the
magnet and to be attached to the tape inserted into the pick-up coil.
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[0025]
The electronic circuitry for generating the pulse signal for transmission along the waveguide is
not included in the modular electronics of the magnetostrictive transducer. The electronic
circuitry of this device contains the basic signal.
[0026]
The invention also relates to a local buffer circuit used in an end configuration for an elongated
member such as a waveguide, which is used as a magnetostrictive displacement or distance
measuring transducer. The local buffer circuit properly prevents the reflection of torsionally
distorted waves or longitudinally distorted waves at the end, and does not occupy much length at
the end. This local buffer circuit attenuates the influence of the signal at the input. Also, in the
case where the mode converter has a pickup coil having a large number of windings such as 400
to 2500, noise entering the mode converter is suppressed. Thus, for example, the mode converter
is arranged at the input end of the elongate member and is operated and driven close to the end
of the elongate member. On the other hand, the end structure prevents the reflection of
acoustically distorted waves propagating along the waveguide. The local buffer circuit protects
the mode converter from saturation by the received signal by limiting the amount of energy
supplied from the pickup coil and helps the pickup coil recover for the next signal. A diode or set
of transistors in the local buffer circuit is connected in parallel to the pick-up coil to clip the
peaks of the received signal and to limit the energy generated in the pick-up coil as a result of
interrogation pulses Act. Thus, a position magnet (not shown here but described in US Pat. No.
3,898,555) can be brought closer to the head of the transducer.
[0027]
In general, the mode converter has a pickup coil mounted coaxially around the tape. The local
buffer circuit is incorporated directly behind the pickup coil. The local buffer circuit has an
emitter amplifier provided in parallel with the pickup coil so that the impedance of the pickup
coil can be lowered by several orders of magnitude. When the mode converter is shielded by a
housing or the like, the buffer is located inside the shield or housing and the signal generator or
drive circuit for the magnetostrictive device is located outside the shield. The use of local buffer
circuits can reduce the sensitivity to electrical noise, maintain signal quality, and transmit signals
over long distances.
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[0028]
The electronics for generating and transmitting the pulse signal along the waveguide are not
included in the electronics of the magnetostrictive transducer. The electronics of this device
include the basic signal and the local buffer circuit.
[0029]
For a further understanding of the features and objects of the present invention, reference should
be made to the following drawings. Similar parts in the drawings are denoted by like reference
numerals.
[0030]
Detailed Description of the Preferred and Alternative Embodiments Conventional as described in
US Pat. No. 3,898,555, or currently commercially available transducers, or others that may be
introduced in the future for the purpose of attenuating elements A transducer or sensing element
assembly, including any transducer of the following, is shown in FIG. Although the transducer 25
is used to measure displacement and / or distance or for other measurements, the attenuation
device of the present invention is applicable to any of them. The type of transducer used in the
present invention should not be considered as limited to the disclosure herein regarding the
damping element used in conjunction with the transducer. Also, with the exception of mechanical
structures showing a preferred mechanical attachment of the waveguide, the general type of
transducer should not be considered as being limited to the description herein for the waveguide
suspension. Also, except for the local buffer circuit, it should not be considered as limiting the
mode converter used just like a waveguide. The transducer should not be considered limited to
the particular type of electronic circuit used like a waveguide, except for the local buffer circuit.
In addition, the general types and features of the transducer in electrically generating the return
pulse and in interfacing with any electronics of the purchaser or user of the device via the return
pulse are shown as examples It should not be considered as limited to the description herein,
except for printed circuit boards which include mechanical structures and local buffer circuits.
[0031]
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Transducer 25 comprises an elongated waveguide assembly housed within enclosure tube 3. The
enclosure tube 3 and the waveguide assembly are mechanically supported by the housing 17 via
an end flange 19 at one end. The waveguide assembly has an enclosure tube 3 on the outside,
which encloses the coaxial elongated inner waveguide 4 (see FIG. 2). In this specification, the
reference to "Fig. 2" always implies all the embodiments of Figs. 2a to 2d. The current flows
through the waveguide 4 and returns via the return conductor 1 electrically connected to the
waveguide 4. In general, a magnet (not shown) coaxially mounted on the enclosure tube 3 is
mounted on top of the waveguide assembly and enclosure tube 3. The magnet interacts with the
current pulse as described in more detail in US Pat. No. 3,898,555. After passing through the
waveguide 4 and the return conductor 1 any type of suitable mode converter (partially shown)
will be or will be known in the art when the strain wave pulse returns to the housing 17 ),
Electrical signals are provided through connector 21 to any electronic circuitry, such as
electronic circuitry 26 connected thereto. The installation of the waveguide 4 and the return
conductor 1 will be described in more detail below.
[0032]
The structure of the circuit 26 depends on the use of the transducer 25 and operates in
cooperation with the waveguide suspension sleeve 2 and the modular structure element of the
invention despite the difference in structure. The structure of circuit 26 should not be considered
as limiting the invention. Thus, for the sake of generality, with the exception of the local buffer
circuit 95 shown in FIG. 14 or FIG. 15, the particular mechanism for the circuit 26 is not shown,
and any of the signals to the circuit 26 are not shown. Conditions can be used. Furthermore, the
mechanism of the waveguide suspension sleeve 2 of the present invention is applied to any
transducer 25, applied to the waveguide 4 for measuring displacement and / or distance, and /
or magnetostriction or other principle (piezoelectricity It should be noted that it is possible to
apply to the waveguide 4 for measurement with or as described in U.S. Pat. No. 3,898,555.
However, for modular assemblies, it depends to some extent on the mechanical arrangement of
the elements within the housing 17. Thus, for example, the particular mechanical arrangement of
elements within the housing 17 is shown as being preferred for mounting, but is not limiting on
generality. Mechanisms other than attachment may be arbitrary, including those shown in US
Pat. No. 3,898,555, and others known in the art may be considered in the art And may be under
design in the art. For the same reason, the type of magnet used and the application used are not
described, and the application may be arbitrary. Finally, there is a need to show some interaction
between the damping element 6 (see FIG. 2) and the waveguide suspension sleeve 2 and the
other parts of the transducer 25 at the end of the waveguide assembly. An example of an
enclosure tube 3 (see FIG. 2) described below is shown together with a waveguide suspension
04-05-2019
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sleeve 2 and a damping element 6. This is not a limitation of the invention, but merely for the
purpose of explanation. The waveguide suspension sleeve 2 can be used with any type of
waveguide assembly described above.
[0033]
A cross-sectional view of the end of the enclosure tube 3 remote from the housing 17 is shown in
FIG. 2 and provided with an end plug 20 at the end. An inert gas is introduced into the enclosure
tube 3 to enhance insulation and sealing. The end plug 20 prevents fluid or other material from
flowing into the enclosure tube 3. The end of the waveguide assembly with the end plug 20 is
usually the end located at the bottom of the tank when the transducer 25 is used to determine
the level of liquid in the tank, and the transducer 25 is the distance When used to measure the
position of the displacement. As mentioned in the background, the dead zone adjacent to the end
plug 20, i.e. the area which does not generate the signal, is as short as possible, and the purpose
of attenuating the acoustically distorted wave signal is that the reflected distorted wave is As
described in U.S. Pat. No. 3,898,555, it is desirable not to interfere with the desired distorted
wave return signal representing distance or level.
[0034]
As shown in FIG. 2, the waveguide 4 is surrounded by an enclosure mechanism consisting of
concentric layers including the suspension sleeve 2 and the enclosure tube 3. The suspension
sleeve 2 consists of a tubular mating sleeve, an elastomeric sleeve or a composite sleeve. The
suspension sleeve limits the lateral movement of the waveguide 4 despite not being in contact
with the waveguide 4 to attenuating the acoustically distorted wave signal generated by the
interaction of the current with the external magnet , And has a geometry that isolates the
waveguide 4 from vibration and external sound noise. The suspension sleeve 2 is coaxial with the
waveguide 4 and surrounds or at least a major part of the waveguide 4 substantially over its
entire length. The suspension sleeve 2 is mounted coaxially with the inside of the outer enclosure
tube 3 over substantially the entire length of the waveguide 4 or at least a majority thereof.
[0035]
The inner diameter of the suspension sleeve 2 must be small enough to limit the movement of
the waveguide 4 but sufficiently not to hold, grip, clamp or compress the waveguide 4 It must be
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big. When the suspension sleeve 2 compresses, holds, grips or clamps the waveguide 4, the
acoustic strain wave signal along the waveguide 4 is attenuated. The Wiedemann effect does not
enhance the large acoustically distorted wave signal in the prior art, making it difficult to
distinguish it from noise generated by other mechanisms. Therefore, it is known that signal
attenuation is a phenomenon that must be avoided in the prior art.
[0036]
The outer diameter of the suspension sleeve 2 must be large enough to limit the lateral
movement of the suspension sleeve 2 within the enclosure tube 3 but, as will be explained below,
be it the return conductor 1 In addition, it must be small enough to be easily mounted inside the
inner diameter of the enclosure tube 3. It is also possible to provide the suspension sleeve 2
without having to limit the enclosure tube 3 and the use of the enclosure tube 3 should not be
considered as limiting the invention or limiting the waveguide suspension. Overall, the waveguide
4 must be supported so as to be cushioned against shock and vibration stimuli and to eliminate
the associated false response.
[0037]
The suspension sleeve 2 has an inner layer 27 and an outer layer 29. The fibers forming the
inner layer 27 of the suspension sleeve 2 are non-conductive and may be a thin, hard material
such as ceramic, glass, metal, polymer or a combination thereof. The number of strands of such
fibers and the weave structure are generally 8 to 16 strands of diamond, regular, hercules or
other weave patterns. With such a strand number and weave structure, the suspension sleeve 2
can act as a cushion between the waveguide 4 and the enclosure tube 3. A gap 28 is provided
inside the inner layer 27 and outside the waveguide 4 so that the inner layer 27 loosely engages
around the waveguide 4. The outer layer 29 of the suspension sleeve 2 helps to keep the shape
of the inner layer 27 and insulates the inner layer from the enclosure tube 3. Outer layer 29 is
generally a soft material such as silicone rubber and is a second layer of inner layer 27.
[0038]
The suspension sleeve 2 terminates in a distal end 31 facing the end plug 20. Attenuation
elements 6 are juxtaposed at the end 31 of the suspension sleeve 2. The damping element 6 is
slipped over the end of the waveguide 4 and is coaxial with the waveguide 4 and has a generally
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cylindrical shape as the suspension sleeve. However, the damping element 6 is not loosely
engaged above the waveguide 4 but is clamped above the waveguide 4 to provide damping. Thus,
as shown in FIGS. 2a and 2b, the outer layer 29 of the damping element 6 is closely fitted around
the waveguide 4. Also, although the outer layer 29 of the damping element 6 is usually formed of
a soft material such as silicone rubber, it is not normally in contact with the enclosure tube 3 like
the outer layer 29 of the suspension sleeve 2. However, instead pressure is applied to the inner
layer 27 and is sized to control the amount of this pressure. As a result, pressure is applied to the
waveguide 4. Thus, a gap is formed between the outer layer 29 of the damping element 6 and the
inner surface of the enclosure tube 3.
[0039]
In addition, a tuning wire 5 (see FIG. 2b) having a diameter in the range of 0.127 mm to 0.406
mm (0.005 to 0.016 inches) is used as a wedge and the pressure of the inner layer 27 against the
waveguide 4 Is controlled. The tuning wire 5 is adjacent to the waveguide 4 and extends
substantially along the inner layer 27 of the damping element 6 and is surrounded by the inner
layer 27. This is used to change the acoustic impedance of the attenuating element 6, but by
doing so gradually the acoustic strain wave signal is gradually attenuated along the waveguide 4
surrounded by the attenuating element 6 It is supposed to be. Thus, the impedance does not
suddenly change to cause reflection, but instead the attenuation of the amplitude of the
acoustically distorted wave along the attenuation element 6 is performed. The tuning wire 5
shown only in FIG. 2b can be used equally with any of the structures of FIGS. 2a-2d, and with any
other damping element for the purpose described above It should be noted that
[0040]
Also, since the attenuating element 6 is used to achieve optimal attenuation of the acoustic strain
wave pulse propagating in the waveguide 4, the appropriate acoustic matching between the
waveguide 4 and the attenuating element 6 is Other mechanisms besides the tuning wire 5 can
also be used, as it depends on the pressure applied to the waveguide 4 by the inner layer 27. As
shown in FIGS. 2c and 2d, the damping element 6 which can be used over a wide temperature
range consists of a short wound sleeve 8 of the same type as the inner layer 27, but this wound
sleeve 8 are coaxially inserted into the larger diameter metal sleeve 9. The assembly of the
sleeves 8, 9 is slid into the end of the waveguide 4. The metal sleeve 9 is crimped so that the
mating sleeve 8 contacts the waveguide 4 with sufficient pressure to achieve the necessary
damping action.
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[0041]
Thus, as can be seen from FIGS. 2a-2d, through the pressure of the outer layer 29, through the
tuning wire 5 trapped in the inner layer 27, through crimping of the metal sleeve 9, or by
experimentation. Attenuation is performed by any other mechanism that applies an appropriate
pressure to control the impedance match along the predetermined length of the attenuation
element 6 that is being used.
[0042]
Preferably, the end 32 of the damping element 6 facing the end 31 of the suspension sleeve 2 is
cut between 40 ° and 50 ° so that its impedance is properly matched to the impedance of the
waveguide 4, The angle is preferably about 45 °.
[0043]
Another way to minimize end reflections from the damping element 6 is to place another
damping element 33 with a different material, size and pressure on the front of the damping
element 6 (with the suspension sleeve 2 facing) It is.
The attenuation element 33 should be designed to have an acoustic impedance that is more
matched to the waveguide 4.
That is, it must have a smaller pressure, or smaller outer diameter, or smaller mass density than
the attenuating element 6, or if it is an elastomer, it has less hardness and minimal reflection at
the front end. Need to be limited. The damping element 33 has a surface 34 facing the end face
32 of the damping element 6. The face 34 usually has a face substantially perpendicular to the
longitudinal axis of the waveguide 4. The damping sleeve 33 can be used as any of the damping
elements of FIGS. 2a, 2b, 2c, 2d, and the description shown only in FIG. 2a is its generality There
is no limit. Also, even if damping sleeves 33 are used, as in the damping sleeves 6 of FIGS. 2b, 2c,
2d, each having a beveled surface 32, the orientation of the faces 34 does not change. Again, the
surface 34 has a plane substantially perpendicular to the longitudinal axis of the waveguide 4. In
general, the damping sleeve 33 does not effectively damp like the damping element 6 but
reduces the total acoustic energy from the damping system by damping the reflection from the
damping element 6. The damping element 6 acts as the main attenuator and the damping sleeve
33 acts as a secondary attenuator.
04-05-2019
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[0044]
Yet another way to minimize front end reflections from the damping element 6 is to increase the
inner diameter of the damping element 6 at the front end. This end faces the suspension sleeve 2.
This may be achieved by inserting a flaring tool into the front end of the damping element 6 just
prior to placing the damping element 6 on the waveguide 4.
[0045]
Yet another way to minimize front end reflection from the attenuating element 6 is to remove
material from the outer diameter of the front end of the attenuating element 6. The removed
portion should be 0.125 inches to 0.5 inches, measured from the front end of the damping
element 6. This can be accomplished, for example, by using a set of wire strippers to remove a
portion of the elastomer covering the weld.
[0046]
The return conductor 1 has to pass over the damping element 6 as shown in FIGS. 2a, 2b, 2d or
through the damping element 6 as in FIG. 2c. In FIG. 2c, the return conductor 1 is insulated (as
would be the case in all other cases) and can operate in the same way as the tuning wire 5 of FIG.
2b. In any case, the return conductor 1 must be attached to the end of the waveguide 4 using
solder or crimp ring 7 and be electrically connected to form the rest of the circuit transmitting
the current pulses. The current pulses originate from the housing 17, pass through the
waveguide 4 and return via the return conductor 1. The return conductor may be arranged as
described in US Pat. No. 3,898,555 or in any manner or as will become known in the art.
[0047]
The pressure exerted by the inner layer 27 is substantially uniform, but by preventing the
reflection by making the pressure smaller on the side facing the housing 17 and larger on the
side facing the end plug 20, It is also possible to shorten the length of the damping element 6
which performs a given damping effect.
[0048]
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Further, the return conductor 1 may be wound together to form the suspension sleeve 2, the
enclosure tube 3 may be made conductive, or the return conductor 1 may be electrically
connected to the enclosure tube 3.
Otherwise, the return conductor 1 and the suspension sleeve 2 are inserted into the enclosure
tube 3 during assembly. The waveguide 4 is then pulled into the suspension sleeve 2. This is
because the dimensions of the suspension sleeve 2 are such that the waveguide 4 is in loose
contact with it, but can not move in an excessive lateral direction. Furthermore, the damping
element 6 is slid onto the waveguide 4.
[0049]
Instead of a single continuous suspension sleeve 2, a series of short suspension sleeves 2 may be
arranged along the length of the waveguide 4 as shown in FIG. 16. This is another example and is
considered more difficult to manufacture. In the case of such a series of sleeves, attention must
be paid to the space in order to block or suppress the coupling of external or internal mechanical
noise.
[0050]
The return conductor 1, the suspension sleeve 2, the enclosure tube 3 and the waveguide 4 are
supported in the housing 17 by means of a bracket 10 (see FIG. 4) which is preferably made of
plastic. The details of the bracket 10 are shown in FIGS. The bracket 10 has a base 60. The outer
diameter of the base 60 is approximately equal to the inner diameter of the main enclosure 62 of
the housing 17. The base 60 has two flanges 64, 66 disposed on either side of the recess 68 of
the base 60. According to this arrangement, a groove 70 (see FIG. 4) can be provided between
the two flanges 64, 66. A seal ring 16 is installed inside the groove 70. As shown in FIG. 4, the
seal ring 16 is engaged sealingly against the side walls 72, 74 of the flanges 64, 66 and the
outwardly facing wall 76 of the recess 68. As used before, the term "diameter" does not imply a
circular shape. As best seen in FIG. 4 and the shape of the flanges 64 and 66, the interior 62 of
the housing 17 is more square in shape and has two opposite curved sides. Thus, due to the
shape and size of the flanges 64, 66, the seal ring 16 is also in contact with the inner sidewall
surface 78 of the main enclosure 62 of the housing 17. Thus, the seal ring 16 functions to seal
the wiring and connector inside the housing 17 against the surface 80 of the flange 66 (see FIGS.
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4 and 9).
[0051]
The end of the housing 17 is closed by a flange 19. An opening 82 is formed in the flange 19.
The opening 82 is dimensioned to allow the enclosure tube 3 to be tightly engaged in the
opening 82 and extends into the opening 84 formed in the flanges 64, 66 and the recess 68 of
the base 60 ing. Opening 84 is coaxial with opening 82 and has the same dimensions as opening
82. The base 60 also has a second opening 86 formed adjacent to the flange 66. The opening 86
is coaxial with the opening 84 but has a smaller diameter than the opening 84 and forms a
shoulder 88 between the openings 84, 86. The shoulder 88 bears against the end 90 of the
combination of the suspension sleeve 2 and the enclosure tube 3.
[0052]
The bracket 10 has an extension 91 which extends beyond the base 60 towards the end face 92
of the enclosure or housing 17. The extension 91 has an intermediate opening 94 spaced
between the opening 86 and the end face 96 of the bracket 10 and the end 98 of the bracket 10.
Opening 94 is coaxial with openings 84 and 86. The opening 94 is also partially formed by the
bracket cover 14 (FIG. 8). When this opening 94 is formed, the side opening 100 is formed by
the gap between the bracket 10 and the notch 61 of the cover 14. The opening 100 connects the
inside between the opening 94 and the opening 86 with a channel 30 formed in the bracket
cover 14.
[0053]
When the combination of the suspension sleeve 2 and the enclosure tube 3 abuts or terminates
on the shoulder 88, both the return conductor 1 and the waveguide 4 extend from the end 90
into the interior of the housing 17. The return conductor 1 extends through the opening 100 into
the channel 30 with special alignment as described below. The waveguide 4 is coaxial with the
opening 94 and is fixed by means of a waveguide fixing 11 which is preferably made of brass.
The waveguide fixing member 11 has a cylindrical lower end 101 having a diameter sufficient to
engage into the opening 94. A larger, generally square cap 103 forms the top of the waveguide
fixing member 11. In the meantime, a shoulder 105 is formed. The shoulder 105 rests on the
surfaces 102, 104 forming the upper or inward facing surface of the opening 94. Another
04-05-2019
17
opening 55 is provided in the extension 91. The axis of the opening 55 is perpendicular to the
axis of the openings 84, 86, 94 (FIG. 10). The same opening 55 is formed on the other side of the
extension 91 as shown in FIG. The waveguide securing member 11 is sized such that the
securing member 11 does not extend over the opening 55 in its seated condition where the
shoulder 105 contacts the surfaces 102, 104. The waveguide fixing member 11 further has a
central opening 106 coaxial with the suspension sleeve 2 and the waveguide 4. The opening 106
is dimensioned to allow the waveguide 4 to be inserted therein.
[0054]
Cylindrical shaped members 108, 110 extend from end 98 and face end 92 of housing 17. The
upper surface 114 of the cylindrical member 110 is substantially coplanar with the end face 96
and acts as a support for the printed circuit board 12 mounted near the end 92. A cylindrically
shaped member 108 extends from the end face 96 and engages the circuit board 12 in a
mutually disposed manner (not shown) to position and align the circuit board 12. The printed
circuit board 12 is provided with a series of openings 116, 118 (two not shown), the return
conductor 1 passes through the opening 116 and the waveguide 4 is in the opening 118.
Through, another two leads from the pick-up coil 13 which have not yet been mentioned pass
through the local buffer circuit which has not yet been mentioned. The printed circuit board 12
also has an opening 120. Openings 120 allow leads 50 to pass from connector 21 into printed
circuit board 12. Thus, the return conductor 1, the waveguide 4, the dummy leads 50 and the
leads 35 of the pickup coil 13 (which will now be described) through the local buffer circuit
which will now be described all pass through the printed circuit board 12 and the five leads. 50
are electrically connected to the electrical connector 21 by the printed circuit board 12 (FIG. 3).
The connector 21 is mounted on the printed circuit board 12 and extends therefrom through an
opening 122 formed in the end 92 of the housing 17 and the connector 21 is shown in FIG. It is
made available. The housing 17 is closed by a flange 19. The flange 19 has an extension 124
which is provided with an opening 126 therethrough to allow the housing 17 to be attached to
the purchaser or user's device.
[0055]
As shown in FIG. 7, two further openings 128, 130 are provided in the extension 91 of the
bracket 10. The axis of each opening 128, 130 is perpendicular to the axis of the other openings
described above. The opening 128 is larger than the opening 130 and can accommodate the
pickup coil 13 (FIG. 4). The pick-up coil 13 may be any type of coil, and instead of the small
number of turns as in the prior art, it has a large number of turns (preferably 1800 turns) such
04-05-2019
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as 400 to 2500 turns as shown. Is preferred. However, without limiting the generality of the
invention, any design can be made. Pickup coil 13 has copper winding 40 wound on bobbin 45
in FIG. Two leads 35 extend from the pickup coil 13 into the printed circuit board 12. A local
buffer circuit is disposed on the printed circuit board 12 where the leads 35 are electrically
connected as described above. The pick-up coil 13 is coaxially mounted around the tape 15
which is reciprocally mounted in the opening 132 of the pick-up coil 13. The tape 15 passes
from the end of the bobbin 45 facing out towards the housing 17 through the pick up coil 13 to
the waveguide 4 where it is welded or otherwise mechanically connected to the waveguide 4
Connected by the way. The tape 15 extends over the length 15 'beyond the end of the bobbin 45.
This length 15 'structurally interferes with the signal. The signal is formed as a voltage across the
coil 13. This structural interference is that the signal wave continues past the coil 13 and reflects
off the end of the tape 15 including all of the length 15 'and returns an additional effect on the
coil 13 with a delay time Generated by This results in structural interference to the circuits
associated with any type of tape 15 or coil 13. Fixing members or brackets to the end of the tape
15 can also be used to set the length 15 '. The tape 15 is generally formed of a ferromagnetic or
magnetostrictive material and may be the same material as the waveguide 4 but may be
subjected to different metallurgical processes. Thus, the opening 128 can be placed close to the
channel 30 to place the pickup coil 13 close to the return conductor 1 so that the energy of the
input pulse to the waveguide 4 can be reduced.
[0056]
As shown in FIG. 14, the local buffer circuit or amplifier has a buffer amplifier 24, and diodes 22
and 23 which are clipper diodes are connected to the pickup coil 13. The purpose of the buffer
amplifier 24 is to provide a low output impedance drive for isolating the pickup coil 13 from
electrical external interference and connecting it to the remotely located electronic circuit 26.
Also, although this is not preferred, it may be used to amplify the signal. The local buffer circuit
is mounted close to the pickup coil 13 to reduce the capacitance. The local buffer circuit
incorporates certain signal limiting devices such as diodes 22, 23 or transistor 36, and in
combination with the amplifier 24 of FIG. Limit the signal at the rated level.
[0057]
The local buffer circuit or amplifier of FIG. 14 or 15 is incorporated immediately after the pickup
coil 13 and is housed in a housing or shield 17. The circuit driving the waveguide 4 is disposed
outside the housing or shield 17. In FIG. 14, the two diodes 22 and 23 are connected in parallel
in the opposite direction to the pickup coil 13. One side of the pickup coil 13 and one side of
04-05-2019
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each diode are connected to the base of the buffer amplifier 24. The collector of the buffer
amplifier 24 is connected to the pickup coil 13 and the other end of the diodes 22 and 23. A
signal from pickup coil 13 is supplied into buffer amplifier 24. As a result, the magnitude of the
electrical impedance of the pickup coil 13 is reduced by several orders of magnitude. The emitter
of buffer amplifier 24 is the output in both embodiments. In use, the receiver circuitry on
substrate 157 (FIG. 13) uses pull-up resistors (not shown), as described in more detail below. The
local buffer circuit is used because the number of windings of the pickup coil 13 is large. In the
prior art, only a few turns were provided to avoid noise, thus producing only a few millivolts of
output signal. As mentioned above, a large number of turns (preferably 800 turns) such as 400
to 2500 turns for the pickup coil 13 will result in signals in the range of several hundred
millivolts. However, the pickup coil 13 having a large number of windings has a large impedance
and causes potential noise between the pickup coil 13 and the electronic circuit 26 to which the
output signal is led. As described in more detail below, the electronic circuitry 26 is typically
provided on a separate substrate 157 (FIG. 13). The electronic circuit 26 is disposed at a distance
of 5.08 cm (two inches) or more from the position of the pickup coil 13. The local buffer circuit
lowers the high impedance and thus the pickup coil 13 and the electrical circuit on the substrate
157 (FIG. 13) that processes the signal supplied from the lead 35 via the lead 156 as described
in more detail below Reduce the noise picked up by the leads 35, 156 between them. Also, the
metal housing 17 has disposed therein both the pickup coil 13 and the local buffer circuit, which
enhances the utilization of the new high impedance by blocking external noise, thus utilizing the
low impedance outside of the transducer. Generate high signal levels.
[0058]
The diodes 22, 23 clip or limit the peaks of the signal generated in the pickup coil 13 and thus
the peaks of energy by the signal received via the magnetostrictive device. This helps restore the
pickup coil 13 to the next input by limiting the amount of energy supplied by the pickup coil 13.
Thus, the position magnet is brought closer to the head of the transducer 25.
[0059]
The local buffer circuit of FIG. 15 is another embodiment using two PNP transistors. One of the
transistors is an emitter follower buffer amplifier 24 and the other is a reverse clipper diode 36.
Therefore, instead of the diodes 22 and 23, the collector of the transistor 36 is connected to the
base of the buffer amplifier 24 and the base of the transistor 36 is connected to the collector of
the buffer amplifier 24 in order to perform peak clipping of the signal. . The emitter of transistor
36 is not connected anywhere. The base to collector of transistor 36 is used as a diode, which is
04-05-2019
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aligned with the base to collector junction of emitter amplifier 24, which acts as a reverse diode.
[0060]
Single-transistor circuits with limiting diodes or transistors are the preferred method to achieve
minimal cost and size. Other embodiments are possible, and multiple transistor circuits may be
used to perform amplification, impedance matching, amplitude control or voltage stabilization.
Such circuits may have op amps or other integrated circuits to improve performance, but at a
cost.
[0061]
The use of a local buffer circuit with a housing or shield 17 can reduce the sensitivity to electrical
noise, maintain the quality of the signal, and transmit the signal over long distances. The reduced
saturation due to the diodes 22, 23 or the transistors 24, 36 brings the return signal closer to the
mode converter and the response time after interrogation is very short.
[0062]
The opening 130 is sized to receive the bias magnet 18 or non-magnetized magnet material
positioned to be subsequently magnetized during the assembly process.
[0063]
To assemble the waveguide assembly into the housing 17, the waveguide 4 is inserted after the
suspension sleeve 2, the waveguide 4 and the enclosure tube 3 have been inserted into the
flanges 19 and the openings 82, 84 of the bracket 10. It is installed in the waveguide fixing
member 11.
After the waveguide 4 is inserted into the fixing member 11, it is connected to the printed circuit
board 12. The suspension sleeve 2 and the enclosure tube 3 are held in the bracket 10 by means
of glued or suitable holding members not shown.
04-05-2019
21
[0064]
After the waveguide 4 is placed in the brass waveguide fixing member 11 and connected to the
printed circuit board 12, the pickup coil 13 is attached. The return conductor 1 is held in place,
the bracket cover 14 is installed, and then the tape 15 is mechanically connected to the
waveguide 4 through the opening 55 by welding or otherwise. The tapes do not need to be
attached in the order described above. This order should not be considered as a constraint on all
the inventions described herein. The bias magnet 18 is then installed, or the unmagnetized
magnet material is pre-installed and then magnetized as described above. Finally, the seal ring 16
is placed in the groove 70 of the bracket 10. Thereafter, the bracket 10, the waveguide 4 and the
flange 19 (if the flange 19 is used) are inserted into the housing 17 as an assembly. The housing
17 is crimped and / or welded in place. Finally, the air inside the device is replaced by a dry, inert
gas and the end plug 20 is held in place by an appropriate means such as an adhesive.
[0065]
The distance and position of the return conductor 1 with respect to the waveguide 4 can be
adjusted in a suitable manner so that the magnetic fields generated in these two wires cancel
each other. In addition, by optimizing the path of the return conductor 1 in the region
immediately adjacent to the pickup coil 13, the ringing of the interrogation pulse can be
significantly reduced by 50 percent or more. The dimensions and magnetic properties also affect
ringing, such as using copper as described above for tuning wire 5.
[0066]
The transducer 25 is manufactured in 2.54 cm (1 inch) length increments or other length
increments on the order of 1.27 cm to 10.2 cm (1/2 inch to 4 inch). This is done by reducing the
total number of unique lengths when cutting the waveguide 4, the suspension sleeve 2, the
return conductor 1 and the enclosure tube 3. This reduces the cost and complexity of
manufacturing the transducer 25 and results in a more cost effective product. A complete sensor
assembly utilizing transducer 25 can be manufactured at any desired length or any length
increment. This provides a means of mounting the transducer 25 within the finished sensor
assembly which allows the transducer 25 to be positioned anywhere within ± 1.27 cm (1/2
inch) of the axial center position within the finished sensor assembly. It is realized by doing.
Thus, by placing the transducer 25 within 1/2 inch of the desired length for the finished sensor
assembly within the finished sensor assembly, the desired sensing length is precisely determined.
04-05-2019
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realizable.
[0067]
FIG. 13 is a 2.54 cm (1 inch) length increment (or other length increments on the order of 1.27
cm to 10.2 cm (1/2 inch to 4 inches)) using the tonation reducer 25. An example of the
attachment means for producing a sensor assembly 158 of any length is shown. Sensor assembly
158 includes an application housing 150 having an end cap 155. Transducer 25 is secured to
application housing 150 with threaded fasteners 152 or other suitable attachment means
threaded through openings 126 in extension 124 of mounting housing 17. A spacer block 151 is
placed between the transducer 25 and the application housing 150 when proper engagement is
required. Spacer block 151 is utilized in various thicknesses and is not used at all depending on
the required sensing length of sensor assembly 158 and the standard length of enclosure tube 3
including waveguide 4 supplied as part of transducer 25. Fasteners 152 are also used in various
lengths depending on the thickness of spacer block 151. In FIG. 13 the transducer 25 is depicted
in the center of the movable position within the end cap 155. The wire harness or lead 156
transmits signals and supply voltages between the transducer 25 and the electronic circuit board
157 supplied by the buyer or seller. The lead 156 is of sufficient length and flexibility so that the
transducer 25 can be secured anywhere within the permitted position range after connection to
the electrical connector 21. Electronic circuit board 157 provides the necessary interrogation
and signal conditioning circuitry (well known in the art) to communicate with the end user's
system and provide the desired position feedback signal. The wire harness 153 is connected to
the electronic circuit board 157 and transmits signals and supplies voltage between the electric
circuit board 157 and the external connector 154 attached to the end cap 155. External
connector 154 provides a means of connection to an end user system (not shown).
[0068]
Also, the transducer described in this patent application is completely shielded from all devices
by the housing 17 or shielded with an electric shield or the like. In this case, the transducer is
further attached by using an insulating material 200 between the tube 3 and the external
extension tube 202 by using a mounting or spacer block 151 and a screw fastener 152 formed
of a non-conductive material . In an effort to emphasize the generality of the specification, not all
features of a particular embodiment of a waveguide assembly are set forth in the above
description.
04-05-2019
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[0069]
Because many different embodiments are possible within the scope of the invention as taught
herein, including many variations in the embodiments detailed herein according to the
expression requirements by law, the details herein will be described Not for limiting the
invention.
[0070]
FIG. 1 is a side view of a complete sensing element assembly.
FIG. 2a is a sectional view of the sensing element assembly of the preferred embodiment of the
present invention of FIG. 1, taken along line 2-2 of FIG. 1, showing a waveguide and a part of a
sleeve surrounding it; Fig. 6 shows a damping element provided at the end of the tube. FIG. 2b is
the same cross-sectional view as FIG. 2a, but in a first variant using a tuning wire between the
damping element and the waveguide. FIG. 2c is the same cross-sectional view as FIG. 2a, but
showing a second variant of the outer tube crimped onto the damping element. FIG. 2d is the
same cross-sectional view as FIG. 2a, but showing a third variant of the return conductor
provided in another position, the outer tube being crimped onto the damping element. FIG. 3 is
an end view of the housing showing the connector. 4 is a cross-sectional view taken along line 44 of FIG. 1 of the sensing element assembly of the preferred embodiment of the present
invention of FIG. 1, and shows a cross section of the housing, a waveguide and a part of a sleeve
surrounding it. Although shown, the damping mechanism is not shown. FIG. 5 is a plan view of
the bracket of the preferred embodiment of the present invention. FIG. 6 is a plan view of a
bracket cover of a preferred embodiment of the present invention. FIG. 7 is a perspective view of
the bracket of the preferred embodiment of the present invention. FIG. 8 is a first perspective
view of a bracket cover according to a preferred embodiment of the present invention. FIG. 9 is a
second perspective view of the bracket of the preferred embodiment of the present invention,
showing the bracket in juxtaposition with the bracket cover of the preferred embodiment of the
present invention. FIG. 10 is a third perspective view of the bracket of the preferred embodiment
of the present invention, showing the juxtaposed bracket covers. FIG. 11 is a perspective view
from the end opposite to the end of the bracket of the preferred embodiment of the present
invention shown in FIGS. 9 and 10, showing the bracket cover juxtaposed to the bracket. FIG. 12
is another side view of the bracket of the preferred embodiment of the present invention. FIG. 13
is a cross-sectional view of a sensor assembly using the transducer of the preferred embodiment
of the present invention. FIG. 14 is a preferred embodiment of the local buffer circuit of the
present invention. FIG. 15 shows a preferred embodiment of the local buffer circuit of the
present invention. 16 is a cross-sectional view of the sensing element assembly of another
embodiment of the present invention of FIG. 1 taken along line 2-2 of FIG. 1, showing the
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waveguide and a portion of the sleeve surrounding it; Fig. 6 shows a damping element provided
at the end of the wave tube.
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