Abstrict In an ultrasonic flow meter for measuring the flow rate of a fluid
flowing through a pipe by determining the frequency difference between
ultrasonic waves traveling within the fluid in the direction of
flow of the fluid and in a direction opposite thereto, respectively.
Each of the ultrasonic transmitters and receivers is connected to
the pipe through an individual guide rod having disposed on its
outer surface ridges which are adapted to cause ultrasonic waves
reflected from the ridged surface to conceal one another out, and
a thin gold sheet interposed between the guide rod and the pipe.
Claims What we claim is:
1. An ultrasonic flow meter device comprising a pipe through which
a fluid the velocity of which is to be measured flows, first ultrasonic
transmitter and receiver means disposed on the outer wall surface
of said pipe and including a propagation path for an ultrasonic
wave running within said fluid in the direction of flow thereof
to produce a first sing-around frequency, second ultrasonic transmitter
and receiver means disposed on the outer wall surface of said pipe
and including a propagation path for an ultrasonic wave running
within said fluid in a direction opposite to the direction of flow
of the fluid to produce a second sing-around frequency, detector
means coupled to said first and second transmitter and receiver
means for detecting a difference between said first and second sing-around
frequencies to measure a flow rate of the fluid, each of said first
and second ultrasonic transmitter and receiver means having an ultrasonic
transmitter element and an ultrasonic receiver element, a guide
rod for each of said elements on one end of which the corresponding
element is mounted, each guide rod having on the outer peripheral
surface thereof a plurality of ridges for causing ultrasonic waves
reflected from the ridged surface of said guide rod to cancel one
another out, means securing the other end of each said guide rod
to the outer wall surface of pipe, and a thin sheet of a metallic
material selected from the group consisting of gold, platinum, gold
alloys and platinum alloys between said other end of each guide
rod and the outer wall surface of said pipe.
2. An ultrasonic flow meter device comprising, in combination,
a pipe through which a fluid the velocity of which is to be measured
flows, a first ultrasonic transmitter element for producing a first
ultrasonic wave traveling within said fluid through said pipe and
in the direction of flow of the fluid, a first ultrasonic receiver
element for receiving said first ultrasonic wave from said first
ultrasonic transmitter element through said pipe, a second ultrasonic
transmitter element for producing a second ultrasonic wave traveling
within said fluid through said pipe and in a direction opposite
to the direction of flow of the fluid, a second ultrasonic receiver
element for receiving said second ultrasonic wave from said second
ultrasonic transmitter element through said pipe, one guide rod
connected between each of said elements and the adjacent portion
of the outer wall surface of said pipe, said guide rod having on
the outer peripheral surface a plurality ridges for causing ultrasonic
waves reflected from the ridged surface of said guide rods to cancel
one another out, a thin sheet between each of said guide rods and
the adjacent portion of the outer wall surface of said pipe, said
thin sheet being of a metallic material selected from the group
consisting of gold, platinum, gold alloys and platinum alloys, and
detector means coupled to said elements for detecting a difference
in frequency between said first and second ultrasonic waves received
by said first and second ultrasonic receiver elements respectively
to determine the flow rate of the fluid.
3. An ultrasonic flow meter device as claimed in claim 2 wherein
said guide rods each have a flange member engaging the end thereof
at said pipe, and bolt means extending through said flange member
for fixedly securing the end of said guide rod to said pipe with
said thin sheet held tightly between said guide rod and said pipe.
4. An ultrasonic flow meter device as claimed in claim 2 wherein
said guide rods each have a flange member on one end thereof, and
an annular threaded cap over said flange and an annular threaded
mounting seat on said pipe threadedly engage by said cap for to
fixedly securing said guide rod to said pipe with said thin sheet
held tightly between said flange and said pipe.
Description BACKGROUND OF THE INVENTION
This invention relates to an ultrasonic flow meter device for measuring
the flow rate of a high temperature fluid flowing through a pipe.
Conventional ultrasonic flow meters have generally included one
connector connecting each of several ultrasonic transmitters and
receivers to the particular pipe through which a fluid to be measured
flows, and oil or grease fills gaps formed on the interfaces between
the connector and the mating transmitter or receiver and between
the connector and the outer wall surface of the pipe. The purpose
of the oil or grease is to increase the transmissibility of the
ultrasonic waves on these interfaces. With the measured fluid maintained
at a temperature as high as about 500.degree. C, such as molten
alkali metals, the oil or grease filling the gaps as above described
can not remain intact. Thus such ultrasonic flow meters have not
been capable to measuring the flow rate of high temperature fluid.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide
a new and improved ultrasonic flow meter device capable of measuring
the flow rate of high temperature fluids.
The present invention accomplishes this object by the provision
of an ultrasonic flow meter device comprising a pipe through which
a fluid to be measured flows, first ultrasonic transmitter and receiver
means disposed on the outer wall surface of the pipe and including
a propagation path for an ultrasonic wave running within the fluid
in the direction of flow thereof to produce a first sing-around
frequency, second ultrasonic transmitter and receiver means disposed
on the outer wall surface of the pipe and including a propagation
path for an ultrasonic wave running within the fluid in a direction
opposite to the direction of flow of the fluid to produce a second
sing-around signal, and detector means for detecting the difference
between the first and second sing-around frequencies to measure
the flow rate of the fluid, wherein each of the first and second
ultrasonic transmitter and receiver means has an ultrasonic transmitter
element and an ultrasonic receiver element each fixedly secured
to the outer wall surface of the pipe through a guide rod having
on the outer peripheral surface thereof a plurality of ridges so
that ultrasonic waves reflected from the ridged surface cancel one
another out.
Preferably the guide rod may have one end surface abutting against
the outer wall surface of the pipe through a thin sheet formed of
a metallic material selected from the group consisting of gold,
platinum, gold alloys and platinum alloys.
Advantageously a flange member may be connected to the guide rod
and fastened to the outer wall surface of the pipe through bolt
means or screw means thereby to fixedly secure the guide rod to
the pipe through the thin metallic sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more readily apparent from the
following detailed description taken in conjunction with the accompanying
drawings in which:
FIG. 1 is a block diagram of a conventional ultrasonic flow meter
useful in explaining the principles thereof with parts illustrated
in perspective;
FIG. 2 is a block diagram of an ultrasonic flow meter embodying
the principles of the present invention with parts illustrated in
perspective;
FIG. 3 is a fragmental perspective view of the ultrasonic guide
rod shown in FIG. 2;
FIG. 4 is a view similar to FIG. 3 but illustrating a modification
of the guide rod shown in FIG. 3;
FIG. 5 is a fragmental plan view of a mounting for an ultrasonic
guide rod constructed in accordance with the principles of the present
invention;
FIG. 6 is a longitudinal sectional view taken along the line VI--VI
of FIG. 5; and
FIGS. 7 and 8 are views similar to FIG. 6 but illustrating different
modifications of the arrangement shown in FIGS. 5 and 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1 of the drawings, there is illustrated an
ultrasonic flow meter constructed in accordance with the principles
of the prior art. The arrangement illustrated comprises a pipe 10
having a fluid to be measured flowing therethrough in the direction
of the arrow F, a first ultrasonic transmitter element 12 and a
first ultrasonic receiver element 14 fixedly secured to the outer
wall surface of the pipe 10 through respective wedge-shaped connectors
16 so as to be opposite to each other and be at a predetermined
angle of .alpha. to a line parallel to the longitudinal axis of
the pipe 10. The arrangement further comprises a second ultrasonic
transmitter element 22 and a second ultrasonic receiver element
24 fixedly secured to the outer wall surface of the pipe 10 through
respective wedge-shaped connectors 16 in the same manner as the
first transmitter and receiver elements 12 and 14 respectively.
All the elements, 12 14 22 and 24 are disposed in a substantially
common plane passing through the longitudinal axis of the pipe 10
while the first and second transmitter elements 12 and 22 are substantially
aligned with the second and first receiver elements 24 and 14 in
a direction perpendicular to the longitudinal axis of the pipe 10
respectively.
In the arrangement of FIG. 1 an ultrasonic wave delivered from
the first ultrasonic transmitter element 12 passes through the mating
connector 16 and the adjacent portion of the outer wall of the pipe
10 to the stream of fluid F within the pipe 10. Then it traverses
the stream of fluid F at the predetermined angle of .alpha. in the
direction of flow of the fluid until it reaches that portion of
the outer wall of the pipe 10 to which the connector 16 for the
receiver element 14 is connected. Thereafter the ultrasonic wave
is received by the receiver element 14 through the mating connector
16.
An ultrasonic wave from the second ultrasonic transmitter element
22 is similarly received by the second ultrasonic receiver element
24 but it is noted that the second ultrasonic wave traverses the
stream of fluid F at the predetermined angle of .alpha. in a direction
opposite to the direction of flow of the fluid.
As shown in FIG. 1 the first ultrasonic transmetter and receiver
elements 12 and 14 respectively are connected to a first sing-around
device 18 to form a first transmitter and receiver system. Similarly
the second ultrasonic transmitter and receiver elements 22 and 24
respectively are connected to a second sing-around device 28 to
form a second transmitter and receiver system. The sing-around device
18 or 28 is operative to drive the associated transmitter element
12 or 22 to deliver the ultrasonic wave and to convert the ultrasonic
wave received by the associated receiver element to a corresponding
electrical signal in a manner well known in the art.
Both sing-around devices 18 and 28 are connected to a differential
frequency meter 30 for comparing sing-around frequencies from the
devices 18 and 28 to detect a difference therebetween.
The sing-around frequencies from the first and second transmitter
and receiver systems vary in accordance with a speed at which the
fluid F to be measured flows through the pipe 10. The higher the
flow speed of the fluid F the shorter the time interval required
for the ultrasonic wave from the first transmitter element 12 to
be propagated to the first receiver element 14 of the first transmitter
and receiver system and therefore the higher the first sing-around
frequency which is the reciprocal of the required time interval
as above described. On the contrary, if the fluid F has a reduced
flow speed then the sing-around frequency of the second transmitter
and receiver system will become less.
The sing-around frequencies from the first and second transmitter
and receiver systems are applied to the differential frequency meter
30 where a difference between the two frequencies is detected to
provide a measure of the flow speed of the fluid F. Therefore by
maintaining the cross sectional area of the pipe 10 constant, the
flow rate of the fluid F can be measured without any opening or
the like being in the outer wall of the pipe.
In conventional flow meters such as shown in FIG. 1 it has been
essential to fill gaps which may occur at the interfaces between
the first transmitter, second transmitter, the first receiver and
the second receiver and the connectors and between the connectors
and the outer wall surface of the pipe with an oil or a grease in
order to increase the transmissibility of an ultrasonic wave at
those interfaces. However, if the fluid to be measured is for example,
a molten alkali metal at about 500.degree. C, the oil or grease
filling the gaps as above described will not remain intact because
the fluid is at a high temperature. For this reason, the ultrasonic
type of flow meters such as shown in FIG. 1 can not be used for
the measurement of fluids at high temperatures.
The present invention seeks to eliminate the objection to the prior
art device as above described by the provision of an ultrasonic
flow meter capable of measuring the flow rate of fluids at high
temperatures.
Referring now to FIG. 2 wherein like reference numerals designate
the components identical to or corresponding to those shown in FIG.
1 there is illustrated an ultrasonic flow meter constructed in
accordance with the principles of the present invention. The arrangement
illustrated is different from that shown in FIG. 1 principally in
the construction of the connector for connecting each of the ultrasonic
transmitter and receiver elements to the outer wall surface of the
pipe. Each of the connectors 16 serving to propagate an ultrasonic
wave therealong is in the form of a guide rod and includes one end
surface formed into an abutting surface 16a causing the guide rod
to be fixedly secured to a predetermined portion of the outer wall
surface of the pipe 10 so as to form a predetermined angle .alpha.
between the longitudinal axes of the rod and pipe. Each connector
or guide rod 16 has the other end surface formed into a mounting
surface 16b for one of the ultrasonic transmitter and receiver elements
12 14 22 or 24 respectively. However, means for fixedly securing
the guide rod 16 to the pipe 10 as above described and means for
mounting the transmitter and receiver elements to the guide rod
are not illustrated in FIG. 2 for purposes of keeping the figure
simple.
According to the principles of the present invention, the guide
rod 16 is provided on outer peripheral surface thereof with a plurality
of ridges in a predetermined regular pattern so that during the
propagation of an ultrasonic wave along the guide rod from one to
the other end, those portions of the ultrasonic wave reflected from
the ridged surface thereof are damped and disappear. For example,
FIG. 3 shows a guide rod 16 provided on the outer peripheral surface
thereof with spiral ridges or threads 16a having a predetermined
pitch while FIG. 4 shows a guide rod 16 having a plurality of longitudinal
ridges 16c disposed at predetermined equal angular intervals on
the entire outer peripheral surface thereof. If desired, the ridges
on the guide rod 16 may any desired configuration other than those
shown in FIGS. 3 and 4.
Assuming that a fluid F flowing through the pipe 10 is even on
the order of 500.degree. C, the first and second ultrasonic transmitters
12 and 22 as well as the first and second ultrasonic receiver elements
14 and 24 as shown in FIG. 2 can be mounted on respective mounting
surfaces 16b maintained at low temperatures because all the elements
are connected to the pipe 10 through the individual guide rods 16.
As a result, conventional mounting means can be used to mount the
transmitter and receiver elements on the mounting surfaces 16b of
the mating guide rods 16.
On the other hand, each of the guide rods 16 has the abutting surface
16a maintained at a high temperature. This leads to the necessity
of using connection means capable of withstanding such a high temperature
and having excellent transmissibility of ultrasonic waves. Further,
in the measuring device embodying the principles of the present
invention it is essential to increase the accuracy of the distance
between each of the first and second ultrasonic transmitter elements
12 or 22 and the associated ultrasonic receiver elements 14 or 24.
In addition, measuring devices with which the present invention
is concerned are, in may cases, assembled in the field. Thus it
is necessary to provide mounting means for easily assembling the
devices in the field with a predetermined accuracy and without the
necessity of performing special operations.
FIG. 5 shows a plan view of mounting means for the guide rod constructed
in accordance with the principles of the present invention to meet
the requirements as above described and FIG. 6 shows a longitudinal
sectional view of the mounting means shown in FIG. 5 with the section
being taken along the line VI--VI of FIG. 5. As best shown in FIG.
6 the guide rod 16 includes the abutting surface 16a formed to
abut against the outer wall surface of the pipe 10 at the predetermined
angle of .alpha. thereto and a disc-shaped flange 30 fixed thereto
as by welding so as to be substantially parallel to the abutting
surface 16a of the guide rod 16. Then a disc-shaped mounting seat
32 substantially equal in outside diameter to the flange 30 is fixedly
secured to the outer wall surface of the pipe 10 at such a predetermined
position that an elongated opening disposed along the diameter of
the seat permits the abutting surface 16a of the guide rod 16 to
abut against a predetermined portion of the outer wall pipe surface
through a filler 34 in the form of a thin sheet interposed therebetween
and within the opening. A plurality, in this case four, of bolts
36 on the mounting seat 32 extend through the flange 30 and have
nuts theaded thereon to press and fix the abutting 16a of the guide
rod 16 against and to the predetermined portion of the outer wall
surface of the pipe 10 by the engagement of flange 30 with guide
rod 16.
The filler 34 is preferably a thin gold sheet and subject to a
plastic deformation, by means of the action of the force exerted
by the nuts on the bolts 36 acting on flange 30 to fill any gap
between the abutting surface 16a of the guide rod 16 and the adjacent
portion of the outer wall surface of the pipe 10. This results in
an increase in transmissibility of the ultrasonic waves at the interface
therebetween.
In the mounting means as shown in FIGS. 5 and 6 the filler 34
is required to have suitable plasticity and heat resistance at the
operating temperature involved. In other words, the filler 34 is
required to have a high melting point, oxidation resistance etc.
Suitable examples of the material of the filler 34 are, in addition
to gold, platinum, gold alloys, platinum alloys etc. In this connection,
it has been found that copper, aluminum etc. have inferior oxidation
resistance as compared to the material of the filler 34 as above
specified and decrease the transmissibility of the ultrasonic waves.
It has been found also that the guide rod 16 should preferably
formed of Hastelloy (trade mark), SUS27(JIS) which corresponds to
SISI364(ASTM) or the like from the standpoint of the transmissibility
of ultrasonic waves, the workability etc.
In FIG. 7 wherein like reference numerals designate components
identical or similar to those shown in FIGS. 5 and 6 there is illustrated
a modification of the arrangement as shown in FIGS. 5 and 6. In
FIG. 7 the mounting seat 32 as shown in FIG. 6 is omitted and the
bolts 36 are directly provided in the outer wall of the pipe 10.
In other respects the arrangement is substantially identical to
that shown in FIGS. 5 and 6.
Another modification of the arrangement as shown in FIGS. 5 and
6 is illustrated in FIGS. 8 wherein like reference numerals designate
the components identical or similar to those illustrated in FIGS.
5 and 6. As shown in FIG. 8 the guide rod 16 has fixedly secured
to one end thereof a disc-shaped flange 30 including the abutting
surface 16a as above described. The flange 30 is positioned within
a circular opening on the mounting seat 32 fixed to the predetermined
portion of the outer wall of the pipe 10. Then an apertured cap
38 through which the guide rod 16 is loosely extended engages threads
disposed on the outer peripheral wall surface of the mounting seat
32 whereby the flange 30 is pressed and fixed against and to the
outer wall surface of the pipe 10.
In summary, the present invention provides an ultrasonic flow meter
device comprising a first ultrasonic transmitter and a receiver
disposed on an outer wall surface of a pipe having flowing therethrough
a fluid the velocity of which is to be measured and including a
propagation path for an ultrasonic wave running within the fluid
in the direction of flow thereof to produce a first sing-around
frequency, a second ultrasonic transmitter and a receiver disposed
on the outer wall surface of the pipe and including a propagation
path for an ultrasonic wave running within the fluid in a direction
opposite to the direction of flow of the fluid to produce a second
sing-around frequency, and detector means for detecting the difference
between the first and second sing-around frequencies to provide
a measure of the flow rate of the fluid. Each of the transmitters
and receivers is fixedly secured to a predetermined portion of the
outer wall surface of the pipe through a guide rod having on the
outer peripheral surface a plurality of ridges in a predetermined
pattern so that ultrasonic waves reflected from the ridged surface
of the guide rod cancel one another out. This ensures that the transmitters
and receivers are maintained at permissible temperatures even when
the fluid has high temperature.
In addition, each of the guide rods is fixed to the predetermined
portion of the outer wall surface of the pipe through a thin sheet
of gold or platinum or an alloy thereof. Therefore the present device
can be operated with a fluid having a high temperature without the
deterioration of the transmissibility of the ultrasonic waves at
the interface between the guide rod and the pipe. This produces
the result that the flow rate of a fluid at a high temperature can
be measured without contacting the fluid.
While the present invention has been illustrated and described
in conjunction with a few preferred embodiments thereof it is to
be understood that numerous changes and modifications may be resorted
to without departing from the spirit and scope of the present invention.
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