JP2013238481A - Non-contact flow rate measuring apparatus of fluid in flexible tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for measuring a flow rate of fluid in a flexible tube whose diameter is less than 12 mm in a non-contact state.SOLUTION: A non-contact flow rate measuring apparatus of fluid in a flexible tube is composed of a compact housing 3 having a fixable opening/closing type cover 17 and includes a measurement cell 9 arranged under a housing upper end under the opening/closing cover and a measurement channel 2 into which a flexible tube 18 is to be inserted. The cell is arranged on the center of the measurement channel 2 extending over the whole width of the housing 3 and having a rectangular cross section. The flexible tube to be measured can be introduced into the inside of the measurement channel 2 in a state of being deformed to a fixed shape. The cell includes two pairs of ceramics I to IV (10, 11, 13, 14) attached to the right and left sidewalls 12, 15 of the cell, opposed to each other on diagonal lines and independent from each other in sound waves, and a bottom plate 16 to be a lower part of the cell to close the attachment space side of an evaluating electronic system 7. The bottom plate 16 closes also the lower part of a residual area of the measurement channel 2.

Description

  The present invention relates to a device for non-contact measurement of the flow rate of fluid in a flexible tube having a diameter clearly less than 12 mm.

  Measurement of the flow rate of a sound-transmitting liquid by a non-invasive method in a flexible tube is conventionally known and has been performed up to the above-mentioned diameter range, but the transit time difference method using such a device is also a known method. .

  Conventional techniques include, for example, em-tec GmbH in Finning, 86923, Germany, and Transonic Systems Inc. in New York, 14850, USA. It can be indicated by products such as companies.

  That is, em-tec GmbH is the company's Internet website: http: // www. em-tec. As described in de, a clamp-on transducer (clip-type converter) for measuring flow in an extracorporeal tube system is provided. This uses a clip (click closure) to attach the sensor contained in the housing to the tube for measurement and is therefore non-invasive. And its application is in the medical field, for example, measurements required in cardiopulmonary bypass in intensive care (ICU).

  As a similar transducer (converter), Transonic Systems Inc. Company Internet website: http: // www. transonic. com page: Bypass flowmeters and tube sensors described in “HT100 Bypass Flowmeter & Tubing Sensor” in “Surgery / ICU Products”. This solution also employs a clamp-on-tube sensor that can be sterilized and attached to a flexible tube in the operating room. Here, a part of the flexible tube is arranged in the measurement channel without applying mechanical pressure from the outside, and in this measurement channel, the ultrasonic signal is transmitted in the direction of liquid flow or in the opposite direction. Are coupled.

  These known solutions listed as examples of the prior art employ a lap-on sensor in which the transmitter / receiver transducer and the evaluation electronics are spatially separated, and the connecting line connecting them. Signal interference can occur in Also, measurements with thinner tubes have not been provided so far.

  Therefore, the above-mentioned drawbacks of these devices listed as representative examples of the prior art must be solved.

  Therefore, an object of the present invention is a non-contact flow rate measuring device for in-pipe fluid for non-contact measurement of the flow rate of fluid in a flexible tube (flexible tube) that can be used in medical, industrial and other applications. In order to prevent the signals from multiple ceramics (piezoelectric elements) that generate and receive sound waves from interfering with each other, these ceramics are separated from other parts and attached in a structure that does not come into direct contact. The use of composite ceramics with optimized width / thickness ratios to suppress lateral vibrations and direction selectivity, and relatively simple-ie A / D converters -Based on the concept of an assembly module, i.e. only a few parts are modularly replaced A flexible tube within a defined range of usable diameters is preferably inserted into a rectangular measuring channel so that the coupling area of the sonic signal to the fluid flowing in the flexible tube is as large as possible The measurement space as a measurement channel in the housing of the device is constructed so that it can nevertheless take into account the temperature change and the accompanying viscosity change-the fluid flowing in the flexible tube It is to provide a device characterized in that the evaluation of the received measurement signal has a high significance.

  The problems of the present invention are solved as follows, but please refer to claim 1 for the basic idea of the invention. Further embodiments of the present invention are as shown in claims 2 to 8.

  The device of the present invention is in a so-called clamp-on configuration for measuring the flow rate of a medium having acoustic transmission within a flexible tube having a small diameter, preferably having an outer diameter in the range of 3.5 mm or more. It is designed on the basis of the implemented sensor. The sensor is made of a plastic housing which is compact, particularly preferably made of the same material at the top and has an openable / closable cover which is fixed to the housing with a spring-type fastener in the closed state. . A service interface for connecting a peripheral device for image output and a power source is provided on the outer surface of the housing facing the lock means for the openable cover.

  With the openable cover open, a rectangular measurement channel is visible at the top of the housing that opens to the outside and spans the entire surface. Its dimensions are selected as follows. That is, a flexible tube having a defined diameter can be physically pushed into the measurement channel. When the openable cover is closed, the wall of the flexible tube is pressed against the openable cover. It is selected to fit the wall of the measurement channel and the lower surface of the openable cover that covers the measurement channel in a rectangular shape from above. In the center of the measurement channel, in the upper part of the housing that closes the top of the compact housing, there is a ceramic (piezoelectric element) facing diagonally for each pair fixed to the side, and by the bottom plate in the mounting space of the compact housing A measuring cell is provided which is closed from below. The bottom plate also serves as a bottom plate that closes the entire measurement channel.

  Further, it is a feature of the present invention that the housing of the apparatus has a tube introduction portion and a lead-out portion for attaching a flexible tube, which are at least twice as long as the width of the measurement channel.

  In this way, this defined length of tube inlet and outlet as part of the measurement channel serves as the region of the measurement channel that stabilizes the fluid flowing in the flexible tube, improving measurement stability. Contributing to

  In order for the received signal measurement to always correspond to the actual flow rate of a sound permeable fluid, the change in viscosity with temperature change accelerates or decelerates the flow, so the temperature of the fluid Must also be considered. Therefore, a temperature sensor is provided on one side wall portion of the measurement cell, and the measured value is used as a coefficient when performing calculation for determining the flow rate.

  By exchanging the cross section of the measurement channel in the form of a module, the base plate for closing the measurement channel and the bottom of the measurement cell can be expanded from a square-without changing its width-to a vertically long rectangle, thereby It is also a notable feature of the present invention that measurements can be made on flexible tubes with a small outer diameter, such as a minimum of 3.5 mm or more, within the defined range.

  In so doing, the dimensions of the measuring cell, in particular the spacing of the ceramics attached to the side parts, are maintained within a technically acceptable range. The ceramic is implemented in particular as a composite ceramic and does not compact each casting cell element with a compound. Also, the evaluation electronic system provided in the mounting space for the electronic components under the measurement cell is not solidified with the compound. By avoiding such direct contact of the device and having a structure that can be said to be miniaturized in this dimensional order, it is possible to avoid adverse effects caused by interference between the transmission and reception ceramics of the measurement signal.

  In order to further improve the quality of measurement, it is assumed that the compact housing of the device including the openable cover is made of a material that acts as a shield against surrounding electromagnetic waves. A suitable plastic, preferably polymethyl methacrylate (PMMA), is suitable for this.

A mounting space for electronic components is provided under the measuring cell in the housing of the device.
This includes the following:
a) Multiplexer for transmit signal b) Multiplexer for receive signal c) Adjustable amplifier for receive signal associated with zero-crossing comparator d) Time digital converter (TDC) configurable and controllable by micro-controller (MC) )
e) Transmission means f) Micro controller (MC) as central control unit
g) Output circuit h) Service interface i) Operating voltage supply means

The advantages of the present invention can be summarized as follows:
-The measuring cell components have independent structures;
-The cross section of the measurement channel can be changed for various flexible tubes within the defined range;
-Measurement in a flexible tube with a small outer diameter of 3.5 mm or more is possible;
-The shielded housing can optimally protect the sensor from ambient influences.

FIG. 1 is a perspective view of an apparatus according to an embodiment of the present invention with a cover closed. FIG. 2 is a top view of the apparatus of FIG. 3 is an AA longitudinal sectional view of the apparatus of FIG. FIG. 4 is a top view of the measurement cell. FIG. 5 is a left side view including a partial cross section of the measurement cell. FIG. 6 is a block diagram of the ceramic arrangement and the electronic components of the device.

  Hereinafter, the present invention will be described in detail based on embodiments. Please refer to FIG. 1 to FIG.

  In FIG. 1, the device according to an embodiment of the invention is depicted as a sensor 1 consisting of a compact housing 3 with a closed openable cover 17. In this case, on the upper part of the side wall of the housing 3, a tube introduction part 5 and a lead-out part 6 are provided on the left and right sides of the closed openable cover 17 so as to conduct to the inside of the housing 3 for a defined length. Thus, the measurement channel 2 is formed. In this embodiment, the measurement channel 2 has a square cross section, and the flexible tube 18 is mechanically lightly pressed against the measurement channel 2 with the openable cover 17 closed. As a result, a maximally wide acoustic signal coupling surface for the fluid flowing in the flexible tube 18 is obtained. The deformation of the flexible tube 18 is shown in FIG.

  In FIG. 2, the length of the measurement channel 2 including the tube introduction part 5 and the lead-out part 6 can be seen from above, but the measurement cell 9 is located in the middle of the central part of the measurement channel 2. Each of the measurement cells 9 has a pair of side walls, in other words, ceramics fitted to the left and right side walls 12 and 15 respectively, that is, piezoelectric element ceramics I to IV that act as elements for transmitting and receiving sound wave signals. ; 10, 11, 13, 14; The bottom end of the measurement cell, that is, the bottom end of the measurement channel 2 is a bottom plate 16 whose thickness can be changed. Below the measurement channel 2 or the measurement cell 9, there is a mounting space for the evaluation electronic system 7 connected to the peripheral device, the image output system (not shown), and the operating voltage supply means 25 via the sensor terminal 8. Is provided.

  FIG. 6 schematically shows how the measurement cell 9 is connected to the evaluation electronic system 7 and what components the evaluation electronic system 7 is composed of. In this embodiment, in particular, multiplexer transmit signal 20, multiplexer receive signal 21, amplifier receive signal 22, TDC 23, microcontroller 24, operating voltage supply means 25, service interface 26, output circuit 27 and ultrasound (US) ) A signal transmission means 28 is provided.

  The structure of the measuring cell 9 and the components of the evaluation electronic system 7 are independent, ie not all components are compacted. As a result, as described above, transmission / reception signal interference can be avoided and the quality of measurement can be improved.

DESCRIPTION OF SYMBOLS 1 ... Sensor 2 ... Measurement channel 3 ... Housing 4 ... Catch hook 5 ... Tube introduction part 6 ... Tube lead-out part 7 ... Electronic system for evaluation 8 ... Sensor Terminal 9 ... Measurement cell 10 ... Ceramic I
11 ... Ceramic II
12 ... Side wall, left 13 ... Ceramic III
14 ... Ceramic IV
15 ... side wall, right,
16 ... bottom plate 17 ... openable cover 18 ... flexible tube 19 ... temperature measuring means (temperature sensor)
20 ... Transmission signal multiplexer 21 ... Reception signal multiplexer 22 ... Reception signal amplifier 23 ... Time digital converter (TDC)
24 ... Micro controller (MC)
25 ... Operating voltage supply means 26 ... Service interface 27 ... Output circuit 28 ... Transmission means for ultrasonic (US) signal

Claims (8)

A compact housing (3) having an openable / closable cover (17) that can be fixed is provided with a measuring cell (9) at the lower part of the upper end of the housing under the openable / closable cover (17). A device for measuring the fluid in the flexible tube (18) in a non-contact manner, in which a measuring channel (2) is inserted,
The measurement cell (9) is in a measurement channel (2) having a rectangular cross section, the measurement channel (2) extending over the entire width of the housing (3), into which the measurement object is flexible. The tube (18) can be introduced in a deformed state, the measurement cell (9) is arranged in the center of the measurement channel (2), and the measurement cell (9) Two sets of ceramics I, II, III, IV (10, 11, 13, 14) which are attached to the left and right side walls (12, 15), face diagonally and are acoustically independent, and The measurement cell (9) includes a bottom plate (16) that closes the mounting space side of the evaluation electronic system (7), which is the lower part of the measurement cell (9), and the bottom plate (16) Also closes the bottom Non-contact flow measuring device of the flexible tube fluid characterized and. The housing (3) of the device comprises a tube introduction part (5) and a tube lead-out part (6) for attaching a flexible tube (18) having a length at least twice based on the width of the measurement channel (2). The non-contact flow rate measuring device for fluid in the flexible tube according to claim 1, wherein: The fluid in a flexible tube according to claim 1 or 2, wherein a temperature measuring means (19) is arranged next to the measurement cell (9) on one side wall of the measurement channel (2). Non-contact flow measuring device. The bottom plate (16) is modularly formed to be exchangeable so that the cross-sectional shape of the measurement channel (2) can be either a square or a vertically long rectangle. Item 4. The non-contact flow measuring device for fluid in a flexible tube according to any one of Items 1 to 3. The said housing (3) of the said apparatus containing the said openable cover (17) consists of a material which acts as a shielding body with respect to a surrounding electromagnetic wave. The possible as described in any one of Claims 1-4 characterized by the above-mentioned. Non-contact flow measuring device for fluid in flexible tube. The non-contact flow rate measuring device for fluid in a flexible tube according to claim 5, wherein polymethyl methacrylate (PMMA) is used as a material of the housing (3) and the openable cover (17). The outer diameter of the flexible tube (18) through which the fluid flows is at least 3.5 mm, and does not change the width of the measurement channel (2) and is larger than that defined by making the cross section rectangular. A non-contact flow rate measuring device for fluid in a flexible tube according to claim 1 or 4, characterized in that a flexible tube (18) having an outer diameter of can be inserted. The evaluation electronic system in the mounting space includes the following electronic components:
a) Multiplexer for transmission signal (20),
b) Multiplexer (21) for received signals,
c) Adjustable amplifier for the received signal associated with the zero-crossing comparator d) Time digital converter (TDC) (23), configurable and controllable by the micro-controller (MC)
e) Transmission means (28),
f) Micro controller (MC) (24) as central control unit,
g) Output circuit (27),
h) service interface (26), and i) operating voltage supply means (25)
The non-contact flow rate measuring device for fluid in the flexible tube according to any one of claims 1 to 7, wherein

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