Abstrict The ultrasonic flow meter of the present invention comprising a
measuring pipe through which liquid flows, and two measuring units
provided at an interval in the lengthwise direction on measuring
pipe. A tightly adhered tube having elasticity is attached to an
attaching indentation formed in the measuring pipe over the peripheral
direction, and its inner peripheral surface is tightly adhered to
the outer peripheral surface of measuring pipe. A transducer is
arranged on the outer peripheral surface of tightly adhered tube
in the state in which it is pressed against the outer peripheral
surface of the tightly adhered tube. In this ultrasonic flow meter,
the transmission of vibrations between the transducer and fluid
inside the measuring pipe can be carried out uniformly.
Claims What is claimed is:
1. An ultrasonic flow meter comprising: a measuring pipe through
which liquid flows; and two measuring units provided on said measuring
pipe at an interval in its lengthwise direction, and which measures
flow volume by measuring the flow rate of said liquid from the difference
in propagation times of ultrasonic waves in both directions between
these measuring units; wherein, said measuring units respectively
have a tubular tightly adhered tube of a prescribed thickness having
an inner diameter which is smaller than an outer diameter of said
measuring pipe; the tubular tightly adhered tube is unitedly made
of material having elasticity attached in the state in which it
is tightly adhered to an outer peripheral surface of said measuring
pipe, and a transducer maintained in the state in which it is pressed
against the outer peripheral surface of said tightly adhered tube.
2. An ultrasonic flow meter according to claim 1 wherein an attachment
indentation is formed in said measuring pipe over the peripheral
direction, and said tightly adhered tube fits into said attachment
indentation.
3. An ultrasonic flow meter according to claim 1 wherein an engaging
indentation is formed in said measuring pipe over the peripheral
direction, and an engaging protrusion is formed on the inner periphery
of said tightly adhered tube over the peripheral direction that
engages with said engaging indentation, said tightly adhered tube
being attached to said measuring pipe by engaging said engaging
indentation and said engaging protrusion.
4. An ultrasonic flow meter according to claim 1 wherein an engaging
protrusion is formed on said measuring pipe over the peripheral
direction, and an engaging indentation is formed in the inner periphery
of said tightly adhered tube over the peripheral direction that
is engaged with said engaging protrusion, said tightly adhered tube
being attached to said measuring pipe by engaging said engaging
protrusion and said engaging indentation.
5. An ultrasonic flow meter according to claim 1 wherein said
transducer is formed in a shape of a circular arc.
6. An ultrasonic flow meter according to claim 1 wherein said
transducer is formed in a shape of a ring.
7. An ultrasonic flow meter according to claim 1 wherein a retaining
tube is covered over the outer periphery of said measuring unit
that tightly adheres said transducer by pressing against said tightly
adhered tube.
8. An ultrasonic flow meter according to claim 1 wherein a stepped
portion for fitting said transducer is formed on said tightly adhered
tube.
9. An ultrasonic flow meter according to claim 1 wherein protruding
walls that surround said transducer and lie between said transducer
and the outside are formed on both sides of said tightly adhered
tube; and said transducer is attached between said protruding walls.
10. An ultrasonic flow meter according to claim 9 wherein a transducer
locking member that presses said transducer against said measuring
pipe is attached to said protruding walls.
11. An ultrasonic flow meter according to claim 10 wherein said
transducer locking member is formed equipped with a contacting portion
that makes point or linear contact with the back surface of said
transducer.
12. An ultrasonic flow meter according to claim 9 wherein a notch
or through hole for suspending a lead wire which is connected to
said transducer is formed in the wall surface of said protruding
walls.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultrasonic flow meter that
measures the flow volume of a liquid flowing through a pipe using
ultrasonic waves.
2. Description of the Related Art
An ultrasonic flow meter is known in the prior art that uses ultrasonic
waves to function as a flow meter that measures the flow volume
of a liquid flowing through a pipe.
This ultrasonic flow meter provides two measuring units having
a transducer and provided at an interval in the lengthwise direction
on a measuring pipe through which liquid flows. Ultrasonic waves
are emitted from one of the transducers which are then received
by the other transducer. Alternatively, ultrasonic waves are emitted
from the other transducer and then received by the first transducer.
The flow rate of the liquid in the measuring pipe is determined
from the difference in propagation times of these ultrasonic waves,
and flow volume is then measured from this flow rate.
However, although this ultrasonic flow meter has the transducer
formed into the shape of a ring and fixed to the measuring pipe
inserted into the transducer by adhesive, or has the transducer
formed into the shape of a circular arc fixed to the outer periphery
of the measuring pipe by adhesive, in these types of structures,
there is a risk of variation occurring in the thickness of the adhesive
layer in the gap between the transducer and measuring pipe, and
in such case, the characteristics of the measurement data fluctuate
which causes problems in accurate measurement of flow volume.
Moreover, in a case of such a structure in which the transducer
is adhered to the measuring pipe by adhesive, there is the risk
of formation of a void composed of air bubbles and so forth of the
adhesive between the transducer and pipe, thereby preventing adequate
transmission of ultrasonic waves between the transducer and liquid
in the pipe, which again has the risk of causing problems in accurate
measurement of flow volume.
SUMMARY OF THE INVENTION
In consideration of the above circumstances, an object of the present
invention is to provide an ultrasonic flow meter that is capable
of accurately measuring flow volume.
In order to achieve the above object, the present invention provides
an ultrasonic flow meter comprising: a measuring pipe through which
liquid flows and two measuring units provided on the measuring pipe
at an interval in its lengthwise direction, and which measures flow
volume by measuring the flow rate of a liquid from the difference
in propagation times of ultrasonic waves in both directions between
these measuring units; wherein, each measuring unit has a tubular
tightly adhered tube of a prescribed thickness made of material
having elasticity attached in the state in which it is tightly adhered
to the outer peripheral surface of the measuring pipe, and a transducer
maintained in the state in which it is pressed against the outer
peripheral surface of the tightly adhered tube.
In other words, since the transducer is attached to the tubular
tightly adhered tube of a prescribed thickness made of a material
having elasticity, which is attached in a tightly adhered state
to the outer periphery of the measuring pipe, in a state in which
it is pressed against the tightly adhered tube, the transmission
of vibrations between the transducer and fluid inside the measuring
pipe can be carried out uniformly, and as a result, the occurrence
of fluctuations in measurement data, caused by the transducer being
fixed unevenly due to variations in thickness of the adhesive or
by air bubbles remaining in the adhesive as in the case of attaching
the probe to the measuring pipe with adhesive as in the prior art,
can be reliably prevented.
In addition, even in the case of, for example, using adhesive and
so forth for fixing a tightly adhered tube, the transducer can be
fixed to the measuring pipe with a thin layer and small amount of
adhesive. This means that variations in thickness associated with
the use of adhesive as well as fluctuations in measurement data
caused by residual air bubbles and so forth are prevented. In addition,
since ultrasonic waves are transmitted to the transducer or emitted
from the transducer through a tightly adhered tube, the ultrasonic
waves are maintained in a stable state, or in other words, the sensitivity
of the transducer is maintained in a suitable state.
In the ultrasonic flow meter of the present invention, it is preferable
that the tightly adhered tube is formed so that its inner diameter
is smaller than the outer diameter of the measuring pipe.
Namely, since the inner diameter of the tightly adhered tube is
formed to be smaller than the outer diameter of the measuring pipe,
by spreading open the tightly adhered tube and attaching to the
measuring pipe, the inner peripheral surface of the tightly adhered
tube can reliably be suitably tightly adhered to the outer peripheral
surface of the measuring pipe.
In this manner, since the tightly adhered tube is fixed to the
measuring pipe by fastening the tightly adhered tube itself, there
is no need to use an adhesive, and even in the case adhesive is
used, adhesive can be provided between the tightly adhered tube
and measuring pipe in the form of a thin layer of uniform thickness
and without the presence of residual air bubbles.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that an attachment indentation is formed in the
measuring pipe over the peripheral direction, and the tightly adhered
tube fits into the attachment indentation.
In this manner, by fitting the tightly adhered tube into attachment
indentation formed in the measuring pipe, the tightly adhered tube
can be reliably attached to a prescribed position of the measuring
pipe in which the transducer is fixed.
Furthermore, the measuring units provided along the lengthwise
direction of the measuring pipe are required to be arranged at a
prescribed interval in terms of measuring flow volume. Therefore,
the interval of the measuring units can be reliably determined by
specifying the interval of the attachment indentations. In addition,
in the case of producing a plurality of ultrasonic flow meters,
the interval between the measuring units is maintained constant,
thereby resulting in stable product accuracy. In addition, since
the position at which the tightly adhered tube fits is specified,
assembly work is carried out easily.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that an engaging indentation is formed in the measuring
pipe over the peripheral direction, and an engaging protrusion is
formed on the inner periphery of the tightly adhered tube over the
peripheral direction that engages with the engaging indentation,
the tightly adhered tube being attached to the measuring pipe by
engaging the engaging indentation and the engaging protrusion.
In this manner, by fitting an engaging protrusion formed on the
tightly adhered tube into the engaging indentation formed in the
measuring pipe, the tightly adhered tube can be reliably attached
to a prescribed position of the measuring pipe in which the transducer
is fixed.
Here, it is not necessary to fit the entire tightly adhered tube
to the measuring pipe. Furthermore, the shape of the engaging indentation
formed in the measuring pipe can be changed as desired to match
the shape of the engaging protrusion, or the width of the engaging
indentation can be formed to be narrower. Making the width of the
engaging indentation narrower results in a reduction in the number
of positions where the wall thickness of the measuring pipe is decreased,
thereby avoiding a decrease in the strength of the measuring pipe.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that an engaging protrusion is formed on the measuring
pipe over the peripheral direction, and an engaging indentation
is formed in the inner periphery of the tightly adhered tube over
the peripheral direction that is engaged with the engaging protrusion,
the tightly adhered tube being attached to the measuring pipe by
engaging the engaging protrusion and the engaging indentation.
In this manner, by fitting the engaging indentation formed in the
tightly adhered tube into the engaging protrusion formed on the
measuring pipe, the tightly adhered tube can be reliably attached
to a prescribed position of the measuring pipe in which the transducer
is fixed.
In addition, it is not necessary to fit the entire tightly adhered
tube. Furthermore, the shape of the engaging protrusion formed on
the measuring pipe can be changed as desired to match the shape
of the engaging indentation. By providing the engaging protrusion
on the measuring pipe, the wall thickness of the measuring pipe
is maintained, thereby making it possible to maintain the strength
of the measuring pipe.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that the transducer is formed in the shape of a
circular arc.
In this manner, by pressing a transducer in the shape of a circular
arc onto the outer peripheral surface of a measuring pipe over a
tightly adhered tube, the transducer can be evenly attached to the
measuring pipe without difficulty.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that the transducer is formed in the shape of a
ring.
In this manner, by installing the transducer in the shape of a
ring on the outer peripheral surface of a measuring pipe over a
tightly adhered tube, the transducer can be evenly attached to the
measuring pipe without difficulty.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that a retaining tube is covered over the outer
periphery of the measuring unit that tightly adheres the transducer
by pressing against the tightly adhered tube.
In this manner, since the transducer is pressed against the tightly
adhered tube by the retaining tube, the transducer can be evenly
attached to the measuring pipe as a result of being pressed against
the measuring pipe. In addition, this retaining tube protecting
the transducer having precise structures from external shock. As
a result, the durability and reliability of the ultrasonic flow
meter can be improved.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that a stepped portion for fitting the above transducer
is formed on the tightly adhered tube.
In this manner, the transducer is held in a state in which it is
tightly adhered at a prescribed position and without shifting on
the outer peripheral surface of the tightly adhered tube. Therefore,
the shifting of the transducer is eliminated and accurate measurement
of the flow volume can be performed.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that protruding walls that surround the transducer
and lie between the transducer and the outside are formed on both
sides of the tightly adhered tube, and the transducer is attached
between the protruding walls.
In this manner, the transducer is partially separated from the
outside by the protruding walls, and together with the attachment
position of the transducer being clearly indicated, the transducer
is protected from external interference. Therefore, it is possible
to improve the durability and reliability of the ultrasonic flow
meter. Moreover, in the case the interval between these protruding
walls is made to be the width of the transducer, shifting of the
transducer can be reliably eliminated, thereby enabling accurate
measurement of flow volume.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that a transducer locking member that presses the
transducer against the measuring pipe is attached to the protruding
walls.
In this manner, the transducer is pressed towards the measuring
pipe side from the back surface by the transducer locking member
attached to the tightly adhered tube. Therefore, the transducer
can be reliably tightly adhered to a tightly adhered tube, thereby
enabling accurate measurement of flow volume. In addition, the transducer
can be attached without applying a substance such as an adhesive
to the contact surface with the tightly adhered tube.
It is further preferable that the transducer locking member is
formed equipped with a contacting portion that makes point or linear
contact with the back surface of the transducer.
In this manner, differing from that in which the entire back surface
is pressed, the transducer is pressed at a partial contacting portion
that makes point or linear contact. As a result of the partial position
of the back surface of the transducer is pressed, a pressing force
is transmitted throughout the entire transducer and deflection of
the transducer is obtained thereby resulting in it being reliably
tightly adhered to the tightly adhered tube. Therefore, inclination
of the transducer and uneven pressing force are eliminated, thereby
making it possible to improve the sensitivity of the transducer
and accurately measure flow volume. In addition, even in the case
of, for example, applying a substance such as an adhesive between
the tightly adhered tube and the transducer, the adhesive film can
be obtained having a uniform thickness, thereby enabling accurate
measurement of flow volume.
Moreover, since the partial position of the transducer at which
pressing force is not applied becomes a free end and is not restrained,
vibrations of the transducer are reliably obtained resulting in
enhanced sensitivity.
Furthermore, in the ultrasonic flow meter of the present invention,
it is preferable that a notch or through hole for suspending a lead
wire connected to the above transducer is formed in the wall surface
of the protruding walls.
In this manner, as a result of the lead wire connected to the transducer
is suspended the notch or through hole provided in the wall surface
of a protruding wall, excess space required for wiring the lead
wire is eliminated, thereby making it possible to realize conservation
of space in the vicinity of the measuring unit. In addition, the
lead wires can be protected from external interference. Moreover,
as a result of suspending the lead wire in the notch or through
hole, the transducer is temporarily restrained and the fixed position
of the transducer can be determined, thereby making it possible
to perform the assembly work of the ultrasonic flow meter easily.
In other words, this functions as an auxiliary means of fixing the
transducer.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1 is a perspective view explaining the structure of an ultrasonic
flow meter in a first embodiment of the present invention.
FIG. 2 is a perspective view of a measuring unit that explains
the structure of an ultrasonic flow meter in a first embodiment
of the present invention.
FIG. 3 is a cross-sectional view of a measuring unit that explains
the structure of an ultrasonic flow meter in a first embodiment
of the present invention.
FIG. 4 is a partial perspective view of a measuring pipe that explains
the shape of the measuring pipe of an ultrasonic flow meter in a
first embodiment of the present invention.
FIG. 5 is a cross-sectional view of a measuring unit that explains
a variation of the ultrasonic flow meter in a first embodiment of
the present invention.
FIG. 6A is a cross-sectional view as viewed from the cross-section
along the axial direction of the measuring pipe for explaining the
structure of an ultrasonic flow meter in a second embodiment of
the present invention.
FIG. 6B is a partial cross-sectional view as viewed from the cross-section
perpendicular to the axis of the measuring pipe as viewed from arrows
A in FIG. 6A for explaining the structure of an ultrasonic flow
meter in a second embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following provides an explanation of the ultrasonic flow meter
of the embodiments of the present invention with reference to the
drawings.
[First Embodiment]
FIGS. 1 through 4 are drawings that explain an ultrasonic flow
meter of a first embodiment. In these drawings, reference symbol
1 indicates an ultrasonic flow meter. This ultrasonic flow meter
1 is formed from a synthetic resin having superior chemical resistance
such as vinyl chloride or Teflon, and has a measuring pipe 2 through
which liquid flows, and two measuring units 3 provided on this measuring
pipe 2 at an interval in its lengthwise direction.
As shown in FIGS. 2 and 3 each measuring unit 3 is provided on
the outer periphery of measuring pipe 2 and is composed of a material
having satisfactory elasticity such as silicon rubber. The measuring
unit 3 has a tightly adhered tube 4 formed into the shape of a pipe
of a prescribed thickness, and a transducer 5 attached in a state
in which it is tightly adhered to the surface of the tightly adhered
tube 4 and its outer periphery is covered by a retaining tube 6.
As shown in FIG. 4 an attachment indentation 7 is formed along
the peripheral direction on the outer peripheral surface of the
measuring pipe 2 in which each measuring unit 3 is fixed, and the
tightly adhered tube 4 is fitted into this attachment indentation
7.
Here, the inner diameter of the tightly adhered tube 4 prior to
attachment is smaller than the outer diameter of measuring pipe
2 at the attachment indication 7. Thus, by fitting this tightly
adhered tube 4 into the attachment indentation 7 of the measuring
pipe 2 by spreading open its inner diameter, the inner peripheral
surface of tightly adhered tube 4 is reliably tightly adhered in
the attachment indentation 7 of the measuring pipe 2 without any
gaps in its outer peripheral surface.
The transducer 5 which is in the shape of a circular arc and provided
on the outer peripheral surface of the tightly adhered tube 4 tightly
adhered to the outer peripheral surface of the measuring pipe 2
is also maintained in a state of being tightly adhered to the outer
peripheral surface of the tightly adhered tube 4 by being pressed
against the outer peripheral surface of tightly adhered tube 4 by
retaining tube 6.
Here, the retaining tube 6 which holds the transducer 5 in a state
in which it is pressed against the tightly adhered tube 4 is formed
from a synthetic resin having thermal contractility, and is attached
in a state in which the transducer 5 is arranged on the outer peripheral
surface of the tightly adhered tube 4 so as to cover the attached
position of the transducer 5. By then applying heat in the state
in which the retaining tube 6 is covered, thermal contraction takes
place and the transducer 5 is pressed against the tightly adhered
tube 4 and held in a tightly adhered state by the thermally contracted
retaining tube 6.
Furthermore, reference symbol 8 in the drawings indicates lead
wires connected to the transducer 5.
In this manner, according to the ultrasonic flow meter 1 having
the above structure, since the transducer 5 is attached in a state
in which it is pressed against the tightly adhered tube 4 made of
an elastic material and attached in a tightly adhered state to the
outer peripheral surface of the measuring pipe 2 the transmission
of vibrations between the transducer 5 and the liquid inside measuring
pipe 2 can be carried out uniformly. Therefore, measurement of flow
volume can be carried out accurately by being able to reliably prevent
the occurrence of fluctuations in measurement data caused by the
transducer being fixed unevenly due to variations in the thickness
of adhesive or by residual air bubbles being present in the adhesive
as in the case of directly attaching the transducer by adhesive
as in the prior art.
Moreover, by fitting the tightly adhered tube 4 into the attachment
indentation 7 formed in the measuring pipe 2 the tightly adhered
tube 4 can be reliably attached at a prescribed position of the
measuring pipe 2.
Moreover, since the inner diameter of the tightly adhered tube
4 is formed to be smaller than the outer diameter of the attachment
indentation 7 of the measuring pipe 2 by attaching the tightly
adhered tube 4 to measuring pipe 2 by spreading it open, the inner
peripheral surface of tightly adhered tube 4 can be reliably and
satisfactorily tightly adhered to the outer peripheral surface of
the measuring pipe 2.
In addition, the position of the measuring unit 3 can be determined
by the attachment indentation 7 thereby making it possible to simplify
assembly work and provide the arrangement of measuring units at
prescribed positions without error. As a result, even in the case
of mass production of the ultrasonic flow meter, a plurality of
ultrasonic flow meters can be provided that are capable of performing
accurate and stable measurement of flow volume.
Furthermore, although an explanation was provided of the ultrasonic
flow meter 1 that uses transducers in the shape of a circular arc
in the above example, as shown in FIG. 5 a ring-shaped transducer
5 may also be engaged with the outer periphery of the tightly adhered
tube 4 by tightly adhering its inner peripheral surface to the tightly
adhered tube 4.
In addition, although an explanation has been provided in which
the shape of the outer peripheral surface of the tightly adhered
tube 4 is smooth, a protrusion(s) or indentation(s) that matches
the shape of the transducer 5 may be formed in this outer peripheral
surface, and the transducer 5 may be tightly adhered and fixed by
fitting into said stepped portion. According to this, shifts in
the peripheral direction of the transducer 5 as well as shifts in
the axial direction can be suppressed without covering with the
retaining tube 6.
[Second Embodiment]
Next, an explanation is provided of an ultrasonic flow meter in
a second embodiment using FIGS. 6A and 6B. FIG. 6A shows a cross-sectional
view in the axial direction of the measuring unit 3 while FIG.
6B shows a partial cross-sectional view taken along arrows A of
FIG. 6A.
In the drawings, reference symbol 10 in FIG. 6A indicates a tightly
adhered tube, which together with being equipped with protruding
walls 10a on both the left and right sides, tightly adheres and
holds the transducer 5 in the shape of a circular arc by fitting
it between the protruding walls 10a on both sides, and has the same
function as the tightly adhered tube 4 shown in the first embodiment.
In addition, reference symbol 13 indicates a transducer locking
member that presses against the transducer 5 tightly adhered to
the tightly adhered tube 10 from the outside.
The tightly adhered tube 10 is made from a material having satisfactory
elasticity such as silicon rubber in the same manner as the first
embodiment, and together with being formed into the shape of a cylinder
of a prescribed thickness, and protruding walls 10a, which protrude
towards the outside, are respectively formed on the ends located
in the lengthwise direction of the measuring pipe 2 on both sides.
Moreover, stepped portion 10c for the fitting transducer 5 is formed
in an indentation B formed around the protruding walls 10a on both
sides, and the width of the stepped portion 10c is formed to match
the width of the transducer 5.
In addition, these protruding walls 10a have an egg shape formed
by having a partially higher height relative to the axial direction
of the measuring pipe 2 so that the opposing faces overlap, and
holes 10d are respectively formed in the protruding walls 10a having
this higher height to be mutually coaxial and in parallel with the
axial direction of the measuring pipe 2.
Moreover, as shown in FIG. 6B, a lead wire guide hole (notch) 11
in which the lead wires 8 (see FIGS. 1 through 3) are provided therein
is formed in the side of the protruding walls 10a, and fulfills
the role for leading an intermediate portion of the lead wires 8
until it is connected to the outside.
The lead wire guide hole 11 leads lead wires 8 that are connected
to the transducer 5 as mentioned above, and fulfills the role of
restraining the lead wires 8 in a simplified manner. As a result
of restraining the lead wires 8 the position of the transducer
5 is maintained at the attachment position of the tightly adhered
tube 10 in that state, and for example, in the case of fixing the
transducer 5 with adhesive, the lead wire guide hole 11 fulfills
the role for supporting the transducer 5 at the prescribed position
until the adhesive hardens.
An engaging protrusion 10b that engages with an after-mentioned
engaging indentation 7a formed at the attachment position of the
measuring unit 3 of the measuring pipe 2 is formed on the inner
peripheral surface of the tightly adhered tube 10. In other words,
the inner peripheral surface of the tightly adhered tube 10 is partially
in the shape of a protrusion, and employs a different shape than
the case of the tightly adhered tube 4 being entirely fit into the
measuring pipe 2 as indicated in the first embodiment.
The transducer locking member 13 has the shape of a column, and
locking protrusions 13a and 13b formed on both of its ends are respectively
fixed on holes 10d of both protruding walls 10a of the tightly adhered
tube 10 described above.
A gap for providing the transducer 5 is formed between the transducer
locking member 13 and tightly adhered tube 10 and the transducer
locking member 13 presses against the transducer 5 from the back
side when the transducer 5 is arranged in this gap. Thus, the outer
diameter of the transducer locking member 13 is formed in consideration
of the dimension of thickness of the transducer 5.
Since the back surface of the transducer 5 and the outer peripheral
surface of the transducer locking member 13 are mutually contacted
by two curved surfaces thereof, a linear contact portion in parallel
with the axial direction of the measuring pipe 2 is formed between
the back surface of the transducer 5 and the outer peripheral surface
of the transducer locking member 13.
As a result, the central portion in the peripheral direction of
the transducer 5 is pressed on by the tightly adhered tube 10 and
this pressing force is transmitted over the peripheral direction
of the transducer 5. This transmitted force then acts to deflect
the transducer 5 and tightly adheres it to the tightly adhered tube
10 over the transducer 5 entirely.
Moreover, since both sides excluding the central portion of the
transducer 5 in the peripheral direction are free ends, vibrations
produced by ultrasonic waves can be reliably received together with
the tightly adhered tube 10 with which it makes contact. In other
words, sensitivity is increased by partially holding down the transducer
5.
As described above, at the attachment position of the measuring
unit 3 of the measuring pipe 2 the engaging indentation 7a is formed
over the peripheral direction, and the engaging protrusion 10b of
the tightly adhered tube 4 is fitted into this engaging indentation
7a. In other words, in comparison with the attaching indentation
7 shown in the first embodiment previously described, the engaging
indentation 7a is formed to a size that matches the engaging protrusion
10a formed on the inner periphery, and does not have a size that
engages with the entire width of the tightly adhered tube 10.
In addition, the inner diameter of the tightly adhered tube 10
at the inner periphery of the portion of the engaging protrusion
10b, which is its smallest inner diameter, is formed to be smaller
than the outer diameter of the measuring pipe 2.
Thus, in the case of this tightly adhered tube 10 by spreading
open the inner diameter of the engaging protrusion 10b and fitting
into the engaging indentation 7a of the measuring pipe 2 the engaging
protrusion 10b formed on the inner peripheral surface of the tightly
adhered tube 10 is reliably tightly adhered to the engaging indentation
7a of the measuring pipe 2 without forming a gap in the outer peripheral
surface.
Similar to the attaching indentation 7 shown in the first embodiment,
the distance between each measuring unit 3 is reliably determined
by the engaging indentations 7a formed in the measuring pipe 2.
As a result, accurate flow volume can be measured.
In the case of mass producing the highly accurate ultrasonic flow
meter 1 it is necessary to make the interval between the measuring
units 3 fixed without variation, and this is realized by the engaging
indentations 7a defining that interval. In addition, during assembly,
the engaging protrusion 10b is simply required to be attached in
the engaging indentation 7a, thereby enabling assembly work to be
carried out easily.
Furthermore, in order to reliably transmit ultrasonic waves between
the transducer 5 and the measuring pipe 2 it is preferable to interpose
a gel-like substance between the tightly adhered tube 10 and the
measuring pipe 2. Therefore, in the present embodiment, the above
gel-like substance is employed, and in order to promote even greater
sealing to the tightly adhered tube 10 an adhesive in gel form
is used.
The adhesive is applied between the engaging protrusion 10b and
the engaging indentation 7a, and fixed by allowing to dry in a vacuum
chamber under a vacuum. As a result, the air bubbles entrapped in
the adhesive are drawn out to the vacuum and removed from the adhesive
resulting in drying in a gel-like state. Thus, a film consisting
of the gel-like adhesive, which is free of residual air bubbles
and uniformly interposed in the form of a thin layer, is formed
between the tightly adhered tube and the measuring pipe 2.
Furthermore, the process for drying the adhesive in a vacuum chamber
is carried out after the assembly of the measuring unit 3 in which
the transducer 5 is attached to the outer periphery of the tightly
adhered tube 10 is finished. Consequently, air bubbles formed in
the case of interposing and fixing a gel-like adhesive between the
transducer 5 to be described later and the tightly adhered tube
10 as well as air bubbles that have become entrapped between the
adhesive and the tightly adhered tube 10 as well as between the
adhesive and measuring pipe 2 etc., being completely removed. Thus,
since air bubbles are eliminated between the transducer 5 and the
liquid in the measuring pipe, the emitted state of the ultrasonic
waves as well as the reception sensitivity are enhanced.
Furthermore, in this embodiment, a reduced outer diameter portion
2a, in which the outer diameter becomes smaller in the vicinity
of the engaging indentations 7a, is formed in the measuring pipe
2. This reduced outer diameter portion 2a is formed in the outer
peripheral portion of the measuring pipe 2 at the suitable position
between the end of the measuring pipe 2 where the tightly adhered
tube 10 is inserted and the position where the measuring unit 3
is fixed, and in FIG. 6A, is located to the left of the engaging
indentations 7a.
When attaching the tightly adhered tube 10 to the position where
the measuring unit 3 is fixed, the tightly adhered tube 10 is moved
from the end of the measuring pipe 2 and passes the reduced outer
diameter portion 2a. When the tightly adhered tube 10 reaches the
reduced outer diameter portion 2a, since the inner diameter of the
tightly adhered tube 10 is larger than the outer diameter of the
reduced outer diameter portion 2a, a gap is formed between the tightly
adhered tube 10 and the reduced outer diameter portion 2a. And then,
by pouring an adhesive into this gap, adhesive is coated onto the
inner peripheral surface of the tightly adhered tube 10 and the
tightly adhered tube 10 coated with this adhesive is moves to the
engaging indentations 7a side.
As a result, since the tightly adhered tube 10 is away from the
reduced outer diameter portion 2a, the gap in which adhesive is
coated gradually becomes narrower due to the outer diameter of the
measuring pipe 2. As a result, adhesive is gradually spread out
in the form of a thin film.
Consequently, the gel-like adhesive formed in the form of the thin
film can be interposed between the tightly adhered tube 10 and the
measuring pipe 2 without containing air bubbles.
Furthermore, in this embodiment, in order to reliably fix the transducer
locking member 13 to the transducer 5 the gel-like adhesive is
further coated onto the back surface of the transducer 5. This is
carried out for the purpose of ensuring the durability and reliability
of the ultrasonic flow meter 1 by preventing the removal of the
transducer locking member 13 from the tightly adhered tube 10 when
the distance between the protruding walls 10a is spread due to the
flexibility of the tightly adhered tube 10.
Moreover, as described above, the gel-like adhesive may be coated
between the transducer 5 and the tightly adhered tube 10. In this
case, the fixation of the transducer 5 is carried out by the adhesive
being spread to the thin film of uniform thickness due to the pressing
force resulting from attaching the transducer locking member 13.
As a result, accurate measurement data can be obtained even in the
case of fixing the transducer 5 using the adhesive.
However, the composition in which the gel-like adhesive explained
above is used for indicating one example of the present embodiment,
and the application of the adhesive is not necessarily required.
According to the ultrasonic flow meter 1 of the above structure,
since the transducer 5 which is attached in a state in which it
is pressed on by the transducer locking member 13 is attached to
the tubular tightly adhered tube 10 of the prescribed thickness
made of an elastic material that is attached in a state in which
it is tightly adhered to the outer peripheral surface of the measuring
pipe 2 the transmission of vibrations between the transducer 5
and liquid inside the measuring pipe 2 can be carried out uniformly.
Therefore, the occurrence of fluctuations in the measurement data
can be reliably prevented, and the measurement of flow volume can
be carried out accurately. In addition, even in the case of using
the adhesive as in the prior art, the occurrence of fluctuations
in measurement data can also be reliably prevented since there is
no variation in the thickness of the adhesive.
Moreover, by fitting the engaging protrusion 10a of the tightly
adhered tube 10 into the engaging indentation 7a formed in measuring
pipe 2 the tightly adhered tube 10 can be reliably attached to
the prescribed position of the measuring pipe 2 and the measurement
interval can be reliably determined, thereby resulting in improved
measurement accuracy. Furthermore, the ultrasonic flow meter 1 can
be assembled with simple processes.
In addition, since the protruding walls 10a are formed so as to
surround the transducer 5 transducer 5 can be protected from external
interference.
Moreover, in the process of fixing the transducer 5 the transducer
5 can be temporarily attached by restraining the lead wires 8 thereby
facilitating positioning and fixing of the transducer 5.
Furthermore, although the composition was shown in the above-mentioned
example in which the engaging indentation 7a is formed in the measuring
pipe 2 and the engaging protrusion 10b is formed on the tightly
adhered tube 10 the engaging protrusion may be formed in the fixed
portion of the measuring unit 3 of the measuring pipe 2 and the
engaging protrusion may be formed in the tightly adhered tube 10.
In addition, although the lead guide hole 11 was shown in the form
of being cut out from the outside, a through hole that is bored
in the protruding walls 10a may also be formed as the lead guide
hole. In this case, the lead wires 8 are inserted into the lead
guide hole in the form of the through hole from the end on the opposite
side of the position where they are connected with the transducer
5 so as to be suspend by the lead guide hole, thereby enhancing
the restraint of the lead wires 8.
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