Abstrict The present invention proposes an ultrasonic flow meter, comprising
a conduit for measurement in which a liquid flows therein, and a
pair of measurement sections which are provided in said conduit
for measurement and are spaced apart by a certain interval along
its longitudinal direction, and which obtains the flow velocity
of said flowing liquid from the difference in the propagation time
periods of ultrasonic in the two opposite directions between these
measurement sections, and thereby measures the flow rate thereof;
wherein a pair of fixing portions are provided which respectively
support said conduit for measurement at the exterior side and also
at the interior side in the longitudinal direction of said measurement
sections.
Claims What is claimed is:
1. An ultrasonic flow meter, comprising a conduit for measurement
in which a liquid flows therein, and a pair of measurement sections
which are provided in said conduit for measurement and are spaced
apart by a certain interval along its longitudinal direction, and
which obtains the flow velocity of said flowing liquid from the
difference in the propagation time periods of ultrasonic in the
two opposite directions between these measurement sections, and
thereby measures the flow rate thereof; wherein a pair of fixing
portions are provided which respectively support said conduit for
measurement at the exterior side and also at the interior side in
the longitudinal direction of said measurement sections.
2. An ultrasonic flow meter, comprising a conduit for measurement
in which a liquid flows therein, and a pair of measurement sections
which are provided in said conduit for measurement and are spaced
apart by a certain interval along its longitudinal direction, and
which obtains the flow velocity of said flowing liquid from the
difference in the propagation time periods of ultrasonic in the
two opposite directions between these measurement sections, and
thereby measures the flow rate thereof; wherein said conduit for
measurement is provided with a cutaway portion upon its outer peripheral
surface.
3. An ultrasonic flow meter according to claim 1 wherein said
conduit for measurement is provided with a cutaway portion upon
its outer peripheral surface.
4. An ultrasonic flow meter according to claim 1 wherein each
of said fixing portion has a porous portion which is provided between
the two hole portions which support said conduit for measurement
at the exterior side and also at the interior side in the longitudinal
direction of said measurement sections.
5. An ultrasonic flow meter according to claim 3 wherein each
of said fixing portion has a porous portion which is provided between
the two hole portions which support said conduit for measurement
at the exterior side and also at the interior side in the longitudinal
direction of said measurement sections.
6. An ultrasonic flow meter according to claim 1 wherein each
of said fixing portions has a plurality of engagement grooves having
"V" shaped cross section around the circumferential direction
of said conduit for measurement with a certain gap in the longitudinal
direction of said measurement sections, on a surface which faces
to said conduit for measurement.
7. An ultrasonic flow meter according to claim 3 wherein each
of said fixing portions has a plurality of engagement grooves having
"V" shaped cross section around the circumferential direction
of said conduit for measurement with a certain gap in the longitudinal
direction of said measurement sections, on a surface which faces
to said conduit for measurement.
8. An ultrasonic flow meter according to claim 4 wherein each
of said hole portions has a plurality of engagement grooves having
"V" shaped cross section around the circumferential direction
of said conduit for measurement with a certain gap in the longitudinal
direction of said measurement sections, on a surface which faces
to said conduit for measurement.
9. An ultrasonic flow meter according to claim 5 wherein each
of said hole portions has a plurality of engagement grooves having
"V" shaped cross section around the circumferential direction
of said conduit for measurement with a certain gap in the longitudinal
direction of said measurement sections, on a surface which faces
to said conduit for measurement.
10. An ultrasonic flow meter according to claim 1 wherein the
conduit for measurement is made from a synthetic resin.
11. An ultrasonic flow meter according to claim 2 wherein the
conduit for measurement is made from a synthetic resin.
12. An ultrasonic flow meter according to claim 3 wherein the
conduit for measurement is made from a synthetic resin.
13. An ultrasonic flow meter according to claim 4 wherein the
conduit for measurement is made from a synthetic resin.
14. An ultrasonic flow meter according to claim 5 wherein the
conduit for measurement is made from a synthetic resin.
15. An ultrasonic flow meter according to claim 6 wherein the
conduit for measurement is made from a synthetic resin.
16. An ultrasonic flow meter according to claim 7 wherein the
conduit for measurement is made from a synthetic resin.
17. An ultrasonic flow meter according to claim 8 wherein the
conduit for measurement is made from a synthetic resin.
18. An ultrasonic flow meter according to claim 9 wherein the
conduit for measurement is made from a synthetic resin.
Description BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an ultrasonic flow meter
which measures the flow rate of a liquid which is flowing in a conduit
or the like by using ultrasonic waves.
[0003] Priority is claimed on Japanese Patent Application No. 2003-176421
filed Jun. 20 2003 the content of which is incorporated herein
by reference.
[0004] 2. Description of the Related Art
[0005] As a flow meter which measures the flow rate of a liquid
which is flowing through a conduit, there is a per se known type
of ultrasonic flow meter which utilizes ultrasonics.
[0006] In this ultrasonic flow meter, there is provided, in a conduit
for measurement of the flow of the flowing liquid, a measurement
section which comprises transducers spaced apart by an interval
in the longitudinal direction. An ultrasonic pulse which is generated
from a first one of these transducers is received by another of
these transducers, and further an ultrasonic pulse which is generated
from that other one of these transducers is received by the first
one thereof, so that the speed of the flow of the liquid within
the conduit for measurement may be obtained from the difference
of the transmission times for these ultrasonic pulses; and the flow
rate is measured from this flow velocity.
[0007] As a conventional ultrasonic flow meter, for example, there
is a per se known prior art (refer to Japanese Patent Application,
First Publication No. Sho 61-132823) in which two ring shaped transducers
are fitted in the flow conduit at a suitable interval so that each
of their central axes matches the central axis of the flow conduit,
with their central open portions being of almost the same size as
the diameter of the flow conduit, and moreover with each of these
ring shaped portions having a width equal to or greater than the
thickness of the flow conduit. In this type of transducer, when
an electrical signal of a predetermined frequency is applied to
one of these ring shaped transducers, the transducer oscilates in
its radial direction, so that, an ultrasonic signal is symmetrically
emitted along the direction of the central axis of this transducer,
which is the direction of the flow conduit. This ultrasonic signal
passes through the central open portion of the other ring shaped
element and oscilates it, and then an electrical signal which corresponds
to the ultrasonic signal is outputted.
[0008] With such a prior art type of ultrasonic flow meter, when
the conduit for measurement in to which both ends of the measurement
section are fixed is oscilated due to reception of some unintentional
external force such as noise or the like, then, when the oscilations
are emitted from the transducer for measuring the flow rate of the
flowing liquid, these oscilations become mixed with the oscilations
of the conduit for measurement which the measurement device has
received from externally, and therefore, the problem arises that
it may become impossible to measure the flow rate of the flowing
liquid accurately with the transducers, due to the ultrasonic signal
which is being inputted from the transducer as a measurement oscilation
becoming superimposed with these oscilations from externally. This
fact becomes a particularly severe problem when the conduit for
measurement is made from a synthetic resin material, since such
a conduit for measurement is not a rigid body.
[0009] The present invention has been conceived in the light of
the above described situation, and its objective is to provide an
ultrasonic flow meter which can measure the flow rate of a flowing
liquid accurately, by suppressing oscilations of the conduit for
measurement which are received from externally.
SUMMARY OF THE INVENTION
[0010] In order to achieve the above described objective, the present
invention proposes an ultrasonic flow meter, comprising a conduit
for measurement in which a liquid flows therein, and a pair of measurement
sections which are provided in said conduit for measurement and
are spaced apart by a certain interval along its longitudinal direction,
and which obtains the flow velocity of said flowing liquid from
the difference in the propagation time periods of ultrasonic in
the two opposite directions between these measurement sections,
and thereby measures the flow rate thereof; wherein a pair of fixing
portions are provided which respectively support said conduit for
measurement at the exterior side and also at the interior side in
the longitudinal direction of said measurement sections.
[0011] According to the present invention as described above, by
providing the pair of fixing portions which respectively support
the conduit for measurement at the outside side and the internal
side of the longitudinal direction of the measurement sections,
it is possible to prevent the mixture of the noise of oscilations
of the conduit for measurement due to the influence of external
forces from externally into the oscilations which are generated
from the measurement sections for measuring the flow rate of the
flowing liquid. As a result, it is possible to prevent these oscilations
from becoming mutually superimposed, and therefore, it becomes possible
to perform measurement of the flow rate of the flowing liquid accurately
and reliably with this ultrasonic flow meter by reducing the noise
of oscilations of the conduit for measurement. In particular, even
if the conduit for measurement is made from a resin material, in
other words even if the conduit for measurement is not extremely
rigid, it is possible to avoid such mutual overlapping of these
oscilations.
[0012] Furthermore, in order to achieve the above described objective,
the present invention also proposes an ultrasonic flow meter, comprising
a conduit for measurement in which a liquid flows therein, and a
pair of measurement sections which are provided in said conduit
for measurement and are spaced apart by a certain interval along
its longitudinal direction, and which obtains the flow velocity
of said flowing liquid from the difference in the propagation time
periods of ultrasonic in the two opposite directions between these
measurement sections, and thereby measures the flow rate thereof,
wherein said conduit for measurement is provided with a cutaway
portion upon its outer peripheral surface.
[0013] According to the present invention as described above, by
providing the cutaway portion upon the outer peripheral surface
of the conduit for measurement, it becomes possible to reduce the
noise of oscilations which are transmitted from externally to the
conduit for measurement. In particular, since it is possible easily
to provide such a cutaway portion upon the exterior peripheral surface
of the conduit for measurement even if the conduit for measurement
is relatively thick. Accordingly, in this case, it becomes easy
to reduce the noise of oscilations which are transmitted to the
conduit for measurement from the outside, and therefore, it becomes
possible to perform measurement of the flow rate of the flowing
liquid accurately and reliably with this ultrasonic flow meter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of a preferred embodiment of
the ultrasonic flow meter of the present invention, for explanation
of the structure thereof.
[0015] FIG. 2 is a sectional view of this preferred embodiment
of the ultrasonic flow meter of the present invention, again for
explanation of the structure thereof.
[0016] FIG. 3 is a sectional view of a fixing portion of this preferred
embodiment of the ultrasonic flow meter of the present invention,
for explanation of the structure thereof.
[0017] FIG. 4 is a plan view of this fixing portion of this preferred
embodiment of the ultrasonic flow meter of the present invention,
again for explanation of the structure thereof.
[0018] FIG. 5 is a partial sectional view of one portion of a fixing
portion of a conduit for measurement in which an ultrasonic flow
meter according to a preferred embodiment of the present invention
is fixed, for explanation of the construction of this fixing portion.
[0019] FIG. 6 is a figure showing the oscilations of a conduit
for measurement of an ultrasonic flow meter of a preferred embodiment
of the present invention in which no cutaway portion is provided
therewith.
[0020] FIG. 7 is a figure showing the oscilations of a conduit
for measurement of an ultrasonic flow meter of a preferred embodiment
of the present invention in which a cutaway portion is provided
therewith.
[0021] FIG. 8 is a magnified cross sectional figure showing one
portion of a fixing portion of a conduit for measurement in which
an ultrasonic flow meter according to a preferred embodiment of
the present invention is fixed, for explanation of the construction
of this fixing portion.
DETAILED DESCRIPTION OF THE INVENTION
[0022] In the following, a preferred embodiment of the ultrasonic
flow meter of the present invention will be explained with reference
to the drawings.
[0023] In FIGS. 1 and 2 the reference symbol 1 denotes an ultrasonic
flow meter as a whole. This ultrasonic flow meter 1 is composed
of a conduit for measurement 2 in which a liquid flows therein and
made from a synthetic resin which has excellent chemical resistance
such as a polyvinyl chloride or fluororesin or the like, and a pair
of measurement sections 3 which are provided in this conduit for
measurement and are spaced apart along a longitudinal direction
of the conduit for measurement by a certain interval, for example.
[0024] Each of the measurement sections 3 is made by closely fitting
a transducer 5 upon the outer circumferential surface of the conduit
for measurement 2. Furthermore, the reference symbols 7 in the figure
denote lead wires for these transducers 5. In addition, cutaway
portions 8 and 9 are provided upon the outer circumferential surface
of the conduit for measurement 2 in positions contacting within
interior hole portions 21 of fixing portions 14 which will be described
hereinafter, and between the measurement sections 3 and these fixing
portions 14 respectively.
[0025] The ultrasonic flow meter 1 made in the above described
manner is housed within a casing 11.
[0026] In this casing 11 there are provided a pair of fixing portions
14 which correspond to the pair of measurements sections 3 and
these fixing portions 14 respectively support the conduit for measurement
2 at the exterior side and also at the interior side in the longitudinal
direction of the measurement sections 3.
[0027] As shown in FIG. 3 each of the fixing portions 14 is made
up from a first fixing member 14a and a second fixing member 14b,
and a hole portion 21 is formed through the middle portion of this
fixing portion 14 so that, the end portion (exterior) in the longitudinal
direction of the measurement section 3 of the conduit for measurement
2 is supported by the fixing portion 14. In addtion, a hole portion
22 is formed in the inner portion (interior) of this fixing portion
14 so that, the inner portion in the longitudinal direction of
the measurement section 3 of the conduit for measurement 2 is supported
by the fixing portion 14.
[0028] Here, the hole portions 21 which are formed in the fixing
portions 14 are made so that their internal diameter is set to
be a little bit smaller than the external diameter of the conduit
for measurement 2. Furthermore, as shown in FIGS. 4 and 5 in each
of the hole portions 21 of the fixing portions 14 there are formed
a plurality of engagement grooves 31a having "V" shaped
cross section around the circumferential direction of the hole portion
21 with a certain gap in the axial direction of the hole portions
21.
[0029] Furthermore, as shown in FIG. 3 a plurality of engagement
grooves 31b having "V" shaped cross section are formed
in each of the hole portions 22 of the fixing portions 14 around
their circumferential direction of the hole portion 22. In this
case as well, the internal diameter of these engagement grooves
31b is also set to be a little bit smaller than the external diameter
of the conduit for measurement 2.
[0030] In addition, a threaded hole 23 is formed in each of the
fixing portions 14 and the first fixing member 14a and the second
fixing member 14b are fixed together by inserting a screw 24 into
this threaded hole 23 thus constituting the fixing portions 14.
[0031] Yet further, in each of the fixing portions 14 a porous
portion 25 is provided between the hole portion 21 which supports
the conduit for measurement 2 at the end portion in the longitudinal
direction of the measurement section 3 and the hole portion 22
which supports the conduit for measurement 2 at the inner portion
in the longitudinal direction of the measurement section 3.
[0032] When measuring the flow rate of a liquid which is flowing
in the conduit for measurement 2 by using this ultrasonic flow meter
1 an ultrasonic pulse is emitted from one of the transducers 3
and is received by the other transducer 5 and also an ultrasonic
pulse is emitted from said other of the transducers 3 and is received
by said one transducer 5 and the flow velocity of the flowing liquid
within the conduit for measurement 2 is obtained from the difference
of propagation times of these ultrasonic pulses, so that thereby
the flow rate may be measured from this flow velocity.
[0033] In this case, the fixing portions 14 which are provided
in each of the pair of measurement sections 3 support the conduit
for measurement 2 at the end portions in the longitudinal direction
of the measurement sections 3 by the hole portions 21 which are
provided at the central portions of each of these fixing portions
14 and also they support the conduit for measurement 2 at the inner
portions in the longitudinal direction of the measurement sections
3 by the hole portions 22 which are provided at the end portions
of each of these fixing portions 14. Therefore, since both ends
of the measurement sections 3 are strongly fixed, it is possible
reliably to reduce the noise of oscilations which are caused by
exterior forces, such as for example the flow of the flowing liquid
or the like. In particular, when the conduit for measurement 2 is
made from a synthetic resin, the strength of this conduit for measurement
2 itself is low, and, although thereby it becomes easy for the influence
of oscilations due to an external force to be experienced, it is
possible easily to reduce the noise due to these oscilations by
utilizing this type of fixing portion 14 as described above.
[0034] Accordingly, since both ends of the measurement sections
3 are strongly fixed by the conduit for measurement 2 being supported
by the hole portions 21 and 22 thereby, when oscilations are generated
from the transducer 5 of one of the measurement sections 3 which
is provided in the hole portions 21 22 of the conduit for measurement
2 thereby the conduit for measurement 2 comes to oscilate only
due to the oscilations which are generated from this transducer
5.
[0035] As a result, it is possible to avoid the oscilations which
are generated from the measurement sections 3 for measuring the
flow rate of the flowing liquid, and noise of oscilations of the
conduit for measurement 2 which is experienced due to external forces,
becoming mixed and these oscilations becoming superimposed over
one another. As a result, it becomes possible to perform measurement
of the flow rate of the flowing liquid accurately with this ultrasonic
flow rate measuring device 1 according to the present invention.
[0036] Yet further, by these fixing portions 14 being made integrally
and incorporating the hole portions 21 and the hole portions 22
thereby both ends of the measurement section 3 are strongly fixed,
and, since it becomes easy to hold the conduit for measurement 2
stably and reliably in place against oscilations, thereby it becomes
possible for the oscilations which are generated by the transducers
5 themselves to be properly transmitted.
[0037] Furthermore, the noise of oscilations which are transmitted
to the conduit for measurement 2 from the outside comes to be reduced,
due to the conduit for measurement 2 being provided with the cutaway
portions 8 and 9 around its outer peripheral surface. In particular,
it becomes easy to reduce the noise of oscilations which are transmitted
from the outside to the conduit for measurement 2 when the conduit
for measurement 2 is thick, since then it is possible easily to
provide the cutaway portions 8 and 9 upon its outer peripheral surface.
[0038] Here, an experiment was performed in order to compare the
oscilations of a conduit for measurement 2 in which such cutaway
portions were provided, and the oscilations of a conduit for measurement
2 which was not provided with any such cutaway portions. FIG. 6
is a figure showing the oscilations of a conduit for measurement
2 in which no such cutaway portions were provided. Furthermore,
FIG. 7 is a figure showing the oscilations of a conduit for measurement
2 in which such cutaway portions were provided.
[0039] Referring to FIG. 6 when the conduit for measurement 2
has no cutaway portions, the result is obtained that, due to noise
of oscilations of the conduit for measurement 2 being transmitted
from the outside, the conduit for measurement 2 oscilates at a relatively
great amplitude. On the other hand, referring to FIG. 7 when the
conduit for measurement 2 does indeed have cutaway portions, the
result is obtained that, due to noise of oscilations transmitted
from the outside to the conduit for measurement 2 being reduced
by the cutaway portions, the conduit for measurement 2 oscilates
at a relatively small amplitude.
[0040] According to the above described structure, by the fixing
portions 14 which are provided as a pair, respectively supporting
the conduit for measurement 2 at the exterior and at the interior
of the longitudinal direction of the measurement sections 3 mixing
together of the oscilations which are generated from the measurement
sections 3 for measuring the flow rate of the liquid which is flowing,
and noise of oscilations of the conduit for measurement 2 due to
external forces being experienced from the outside, and superimposition
of their oscilations, are reliably prevented, and accordingly, since
it becomes possible to perform measurement of the flow rate of the
flowing liquid accurately by this ultrasonic flow meter according
to the present invention, it is possible to measure the flow rate
of the flowing liquid accurately and reliably while minimizing noise
of oscilation of the conduit for measurement 2 which is experienced
due to external forces.
[0041] Furthermore, by providing the conduit for measurement 2
with the cutaway portions 8 and 9 upon its outer circumferential
surface, the noise of oscilations which is transmitted to the conduit
for measurement 2 from externally is reduced, and, in particular,
when the conduit for measurement 2 is thick, since it is easy to
reduce the noise of oscilation which is transmitted to the conduit
for measurement 2 from externally by the provision of these cutaway
portions 8 and 9 upon its external circumferential surface which
is easy, therefore it is possible to measure the flow rate of the
flowing liquid accurately while reducing the noise of the oscilations
of the conduit for measurement 2 which is transmitted from the outside.
[0042] Furthermore, when the conduit for measurement 2 of this
ultrasonic flow meter is fixed by the above described fixing portions
14 as shown in FIG. 8 the conduit for measurement 2 is securely
held due to the outer peripheral portion of the conduit for measurement
21 being gripped in the engagement grooves 31a of the hole portions
21 of the fixing portions 14 and displacement in the axial direction
of the conduit for measurement, and in the left and right and upwards
and downwards directions as well, is reliably prevented. Due to
this, it becomes easy to reduce the noise of oscilations from the
outside which is transmitted to the conduit for measurement 2. Thus
it becomes possible to measure the flow rate of the liquid which
is flowing reliably and accurately while reducing the noise of the
oscilation which is received by the conduit for measurement 2 from
externally.
[0043] Furthermore, by providing the porous portions 25 in the
fixing portions 14 between the hole portions 21 and the hole portions
22 it becomes possible to reduce the weight of the fixing portions
14 so that further it becomes possible to reduce the weight of
the ultrasonic flow meter 1. Moreover since, by providing the porous
portions 25 the surface of the conduit for measurement 2 contacts
the external atmosphere, and thereby the temperature of the conduit
for measurement 2 is brought to be close to the ambient temperature,
thereby, along with the temperature of the liquid which is flowing
in the conduit for measurement 2 being brought close to the ambient
temperature, also it becomes possible to bring the temperature of
the transducers 5 which are provided upon the exterior surface of
the conduit for measurement 2 and which are now in contact with
the external atmosphere, close to the ambient temperature. Therefore
it becomes possible to suppress measurement errors due to differences
of temperature to the minimum limit. Yet further, since the heat
capacity of the fixing portions 14 is reduced by the provision of
these porous portions 25 thereby the rise of temperature due to
heat which is transmitted from the fixing portions 14 to the conduit
for measurement 2 or to the transducers 5 is small.
[0044] It should be understood that the cutaway portions 8 and
9 which are provided upon the outer peripheral surface of the conduit
for measurement 2 are not limited to being in the shown positions
in which they contact between the measurement sections 3 and the
fixing portions 14 and within the hole portions 21 of the fixing
portions 14; they could be positioned in any of various other positional
arrangements, provided that they were in positions which provided
the beneficial effect of enabling reduction of the noise of external
oscilations.
|