Patent Application
20120318069
1. Field of the Invention
The present invention relates to a clamp-on type apparatus for measuring a flow rate of a fluid flowing through a conduit by transmitting ultrasonic wave beams to the fluid.
2. Related Art Statements
In the following Japanese Patent Publications, there are disclosed known clamp-on type apparatuses for measuring a flow rate of a fluid flowing through an existing conduit by fitting the apparatus to the conduit from external.
In the known clamp-on type ultrasonic flowmeter apparatuses, a pair of ultrasonic signal transmission and reception elements having a configuration matched with an outer configuration of a conduit must be intimately fixed to the conduit with the aid of a complicated mechanism. Therefore, upon measuring the flow rate, it is rather difficult to fix the ultrasonic flowmeter apparatus to the conduit in an easy manner.
The present invention has for its object to provide ultrasonic flowmeter apparatus which can remove the above mentioned drawback and can be easily fixed to a conduit by means of a simple clamp mechanism.
According to the invention, in order to achieve the above object, an ultrasonic flowmeter apparatus detachably secured to a conduit made of a resilient and soft material for measuring a flow rate of a fluid flowing through said conduit comprises first and second housing halves, said conduit being clamped between said first an second housing halves, a hinge mechanism for supporting one ends of said first and second housing halves in a swingable manner, and a clamp mechanism for closing the other ends of said first and second housing halves to lock in this condition, whereby in each of said first and second housing halves there is formed a groove having at least one flat surface, said grooves of the first and second housing halves forming a clamping space when said first and second housing halves are closed, a pair of ultrasonic wave transmission and reception elements are provided on an inner surface of the flat surfaces of the first housing half forming the grooves, and after clamping said conduit by the clamping space such that the conduit is brought into contact intimately with the flat surfaces forming the groove, an ultrasonic wave beam is projected from one of the ultrasonic wave transmission and reception elements and an ultrasonic wave beam reflected by the flat surface of the second housing half is received by the other ultrasonic wave transmission and reception elements.
In the ultrasonic flowmeter apparatus according to the invention, the apparatus can be easily fitted on a conduit and a flow rate of a fluid flowing through the existing conduit can be measured easily.
Now the present invention will be explained in detail with reference to embodiments shown in the drawings.
The ultrasonic flowmeter apparatus comprises a pair of housing halves 1 and 2 made of a metal block and these housing halves are coupled with each other movably around a shaft 3 by means of a hinge mechanism. In opposite surfaces of the housing halves 1 and 2 are formed V-shaped grooves 1a and 2a, respectively, said grooves being aligned in parallel with the shaft 3 and having a cross section of an isosceles right triangle. Inner surfaces of grooves 1a and 2a are coated with Teflon (registered trade mark) resin such that a conduit can smoothly slide on these surfaces.
As shown in
At an end portion of the housing half 1a remote from the shaft 3 there is formed engaging lug 1c to form an integral body with the housing half 1. In an outer surface of the engaging lug 1c there is formed engaging recess 1b having a semicircular cross sectional configuration opened downward. A part of an end portion of the housing half 2 remote from the shaft 3 is projected outwardly to form and engaging lug 2b, and a lock lever 8 formed by a flat plate is journalled to the engaging lug 2b by means of s shaft 9. A pair of arms 11a and 11b are journalled to the lock lever 8 by means of shafts 10 at positions near the shaft 9. Tip portions of these arms 11a and 11b are coupled with each other by means of a supporting shaft 12, and an engaging tube 13 made of a resilient synthetic resin material is supported by the supporting shaft 12. In this manner, a clamping mechanism for clamping a conduit by engaging the housing halves 1 and 2 together is constructed.
Upon using the ultrasonic flowmeter apparatus according to the present embodiment, at first the housing half 1 is secured to a frame 15 by screwing plural bolts 14 into tapped holes formed in the rear surface of the housing half 1 as illustrated in
After urging the engaging lug 2b of the housing half 2 against the engaging lug 1c and the engaging tube 13 is fit into the engaging recess 1b, the locking lever 8 is turned about the shaft 9 in a direction shown by an arrow in
In this manner, upon clamping the conduit P by the housing halves 1 and 2, the grooves 1a and 2a each having an isosceles right triangle cross sectional configuration form a clamping space having a square cross sectional configuration. Therefore, when the flexible conduit P is pressed by the inner walls of grooves 1a and 2a, the conduit is deformed into a substantially square cross sectional configuration and is substantially intimately contacted with the inner walls of the grooves 1a and 2a.
Since the inner walls of grooves 1a and 2a are coated with the Teflon (registered trade mark) resin, the conduit P can smoothly slide along the inner walls of the grooves 1a and 2a with a reduced friction, and therefore it is possible to bring the conduit P into contact with inner walls of the grooves 1a and 2a within a short time period to attain a stable condition which is suitable for the measurement. It should be noted that the Teflon (registered trade mark) resin may be replaced by other suitable material such as grease. Also in this case, the conduit may slip easily and may be deformed easily.
As explained above, the conduit P is deformed into a rectangular shape, and thus parts of the conduit can be intimately brought into contact with the ultrasonic signal transmission and reception elements 4a and 4b and at the same time, diametrically opposite portions of the conduit at which the ultrasonic wave beams are reflected can be closely contacted with the inner walls of the grooves 1a and 2a. If the grooves 1a and 2a are shaped to form a clamping space having a circular cross sectional configuration, the grooves 1a and 2a should be precisely formed such that the circular cross sectional configuration is matched with an outer configuration of the conduit P. If there is a small error in size, there might be introduced a space or gap between the inner walls of the grooves 1a and 2a and the conduit P, and this gap might interfere the good propagation of the ultrasonic wave.
According to the invention, an inner circumference of the clamping space is slightly longer than an outer circumference of the conduit P, and therefore the conduit is deformed into an arcuate shape at corners of the rectangular clamping space. If an inner circumference of the clamping space is not large than an outer circumference of the conduit P, undesired corrugations might be formed in the conduit and undesired gap might be formed between the inner walls of the grooves and the outer surface of the conduit upon clamping the conduit. However, if an inner circumference of the clamping space is too longer than an outer circumference of the conduit p, it would be difficult to bring the conduit into intimate contact with the inner walls of the grooves.
Upon measurement, a fluid F whose flow rate is to be measured is flown through the conduit P, one of the ultrasonic wave transmission and reception elements 4a and 4b projects an ultrasonic wave beam B into the fluid F via the ultrasonic wave propagating members 6 and 7. The ultrasonic wave beam B is reflected by the conduit P toward the other of the ultrasonic wave transmission and reception elements 4a and 4b and is received thereby.
The emitted ultrasonic wave beam B is reflected by the inner surface of the conduit P to produce an inner surface reflection beam Ba, and is also reflected by a boundary surface between the outer surface of the conduit and the inner wall of the groove 2a to produce an outer surface reflection beam Bb owing to a reason that a specific impedance of the conduit P differs greatly from that of the groove 2a. It should be noted that a level of the outer surface reflection beam Bb is larger than that of the inner surface reflection beam as depicted in
The ultrasonic wave transmission and reception elements 4a and 4b repeat alternately the emission and reception of the ultrasonic beams several times. According to the invention, the reflection beams of the ultrasonic beam B can be obtained by the flat surface of the conduit P, and thus it is possible to obtain the reflection beams having a higher reflection efficiency than circular conduit used in the known flowmeters.
In this manner, forward propagation times of the ultrasonic beams propagating in an forward direction of the fluid F and backward propagation times of the ultrasonic beams propagating in a direction opposite to the forward direction of the fluid F are measured, and then an average value of differences between the forward and backward propagation times is calculated by the calculation and control unit 21. The calculation and control unit 21 calculates a flow speed of the fluid F from the thus calculated time difference in accordance with the well known method.
In the calculation and control unit 21, a flow rate of the fluid P is obtained by multiplying the flow speed by an inner cross sectional area of the conduit P. According to the invention, sometimes an inner cross sectional area of the conduit P could not be known, because the conduit is deformed by the housing halves 1 and 2. Therefore, it is preferable to perform a calibration by streaming a fluid through the deformed conduit P at known flow rates. A finally calculated flow rate is displayed on the display unit 22.
In an actual measurement, when the fluid F flows through the conduit P, the conduit P is further deformed by a pressure of the fluid F and the cross sectional area of the conduit is liable to increase. Therefore, an accurate value of the flow rate can be obtained after elapsing a certain time period.
After the measurement, the conduit P may be removed from the ultrasonic flowmeter apparatus in the following manner. At first, the lock lever 8 is pulled up from the position shown in
In the first embodiment 1, the clamping space formed by the housing halves 1 and 2 has a square cross sectional configuration, but according to the invention the clamping space may be formed to have any other cross sectional configuration. For instance, in a second embodiment 2 shown in
It should be noted that in the second embodiment as well as in a third embodiment to be explained later, the hinge mechanism and clamping mechanism are not shown in the drawings of
In a third embodiment, the clamping space has a hexagonal cross sectional configuration. In this case, one of the ultrasonic wave transmission and reception elements 4a and 4b may be arranged in any one of inner surfaces of the groove 1a and the other of the ultrasonic wave transmission and reception elements 4a and 4b may be provided in a diametrically opposed inner surface of the groove 2a. The hexagonal cross sectional configuration of the clamping space is much more similar to the circular cross sectional configuration of the conduit P in a free condition, and therefore deformation of the conduit can be performed much more easily.
It should be noted that in the above explained first to third embodiments, the clamping space is formed solely by the flat surfaces, but according to the invention it is sufficient to form parts of the clamping space by flat surfaces at least at portions at which the ultrasonic transmission and reception elements 4a and 4b are arranged and at portions at which the ultrasonic beam is reflected, and the remaining portions of the clamping space may be formed by curved surfaces.
In the above embodiments, the housing halves 1 and are formed by metal blocks, but according to the invention major portions of the housing halves may be formed by a metal and the remaining portions may be formed by a synthetic resin.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-016639 | Jan 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/064038 | 6/20/2011 | WO | 00 | 4/3/2012 |
