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 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 said
tightly adhered tube is formed so that its inner diameter is smaller
than the outer diameter of said measuring pipe.
3. 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.
4. 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.
5. 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.
6. An ultrasonic flow meter according to claim 1 wherein said
transducer is formed in a shape of a circular arc.
7. An ultrasonic flow meter according to claim 1 wherein said
transducer is formed in a shape of a ring.
8. 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.
9. An ultrasonic flow meter according to claim 1 wherein a stepped
portion for fitting said transducer is formed on said tightly adhered
tube.
10. 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.
11. An ultrasonic flow meter according to claim 10 wherein a transducer
locking member that presses said transducer against said measuring
pipe is attached to said protruding walls.
12. An ultrasonic flow meter according to claim 11 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.
13. An ultrasonic flow meter according to claim 10 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
[0001] 1. Field of the Invention
[0002] The present invention relates to an ultrasonic flow meter
that measures the flow volume of a liquid flowing through a pipe
using ultrasonic waves.
[0003] 2. Description of the Related Art
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] Furthermore, in the ultrasonic flow meter of the present
invention, it is preferable that the transducer is formed in the
shape of a ring.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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
[0041] FIG. 1 is a perspective view explaining the structure of
an ultrasonic flow meter in a first embodiment of the present invention.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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
[0048] The following provides an explanation of the ultrasonic
flow meter of the embodiments of the present invention with reference
to the drawings.
[0049] [First Embodiment]
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] Furthermore, reference symbol 8 in the drawings indicates
lead wires connected to the transducer 5.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] [Second Embodiment]
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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.
[0093] 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.
[0094] 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.
[0095] In addition, since the protruding walls 10a are formed so
as to surround the transducer 5 transducer 5 can be protected from
external interference.
[0096] 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.
[0097] 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.
[0098] 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. |