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 according to claim 1 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 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.
4. An ultrasonic flow meter according to claim 2 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 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.
6. An ultrasonic flow meter according to claim 2 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 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.
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 1 wherein the conduit
for measurement is made from a synthetic resin.
10. An ultrasonic flow meter according to claim 2 wherein the
conduit for measurement is made from a synthetic resin.
11. An ultrasonic flow meter according to claim 3 wherein the
conduit for measurement is made from a synthetic resin.
12. An ultrasonic flow meter according to claim 4 wherein the
conduit for measurement is made from a synthetic resin.
13. An ultrasonic flow meter according to claim 5 wherein the
conduit for measurement is made from a synthetic resin.
14. An ultrasonic flow meter according to claim 6 wherein the
conduit for measurement is made from a synthetic resin.
15. An ultrasonic flow meter according to claim 7 wherein the
conduit for measurement is made from a synthetic resin.
16. An ultrasonic flow meter according to claim 8 wherein the
conduit for measurement is made from a synthetic resin.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
Priority is claimed on Japanese Patent Application No. 2003-176421
filed Jun. 20 2003 the content of which is incorporated herein
by reference.
2. Description of the Related Art
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.
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.
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.
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.
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
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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
In the following, a preferred embodiment of the ultrasonic flow
meter of the present invention will be explained with reference
to the drawings.
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.
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.
The ultrasonic flow meter 1 made in the above described manner
is housed within a casing 11.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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. |