FR2817613A1 - Volumetric flow meter and gas meter with primary pressure relief chamber employing valve connected to pressure operated membrane - Google Patents

Abstract

Between the meter inlet pipe (27) and the intermediate pipe (5) a primary pressure reducer is fitted with a valve (25) connected by an actuating system (22) to a spring loaded membrane. The system consists of a lever arm r linked to the valve and a lever arm R to the membrane and the surface areas of valve seat and membrane are Sc and Sm respectively designed so that the ratio Sc/Smr/R is less than 0.01, preferably less than 0.001.

Description

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The present invention relates to gas flowmeters, as well as to gas meters incorporating flowmeters of this kind and provided with a device for integrating flow rates as a function of time.

It is conventional to manufacture a gas meter using a flow meter and a device for integrating the flow rates of the flow meter as a function of time.

Numerous types of meters are known, such as meters with deformable walls, the ratio of the minimum flow rate to the maximum flow rate also called dynamic measurement is of the order of 140. These meters are very bulky, so that in practice they do not cannot have a maximum flow greater than 1000 m3 per hour. There are also known rotary piston meters with a measurement dynamic which does not exceed 50. Ultrasonic meters are sensitive to dust and require straight lengths, especially upstream of the meter, just like swirl meters and the pressure gauges. There is also known a flow meter implementing a venturi nozzle operating in sonic regime at the neck. This flowmeter is complicated to use and manufacture due to the profile to be machined and gives inaccurate results with dispersion of the results.

The invention relates to a flow meter and thereby even a gas meter of reduced size, even at large flow rates, which can be used in a wide range of fluid pressures at the inlet ranging from 100 mbar to 8 bar, which has a large measurement dynamic greater than 140, which is insensitive to disturbances in the upstream flow profile and which does not

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 therefore requires no long straight lengths, which has good intrinsic precision, while operating in subsonic regime, which is easy to install by a simple connection of two conduits and which is insensitive to dust. The meter even withstands high pressures such as 8 bar and does not create any parasitic pressure drop.

 The flow meter according to the invention comprises a casing subdivided by a flexible membrane into an expansion chamber, where an intermediate duct provided with a shutter valve and an outlet duct opens out and into a chapel in which a means, in particular a spring but this can also be a controlled pressure, applies a force to the membrane. The membrane is integral with the movement of the shutter and there is provided a sensor for the movement of the shutter. According to the invention, means are provided comprising an inlet connection and intended to obtain, for a given flow whatever it is and whatever the pressure prevailing in the inlet fitting for this flow, a difference substantially constant between the pressure prevailing in the intermediate duct and that prevailing in the outlet duct. By substantially constant difference is meant in particular a constant value to within 5% and, preferably to within 1%. The pressure in the inlet pipe can vary from 100 mbar to 8 bar.

 According to one embodiment, the means intended to obtain a substantially constant difference between the pressure prevailing in the intermediate pipe and that prevailing in the outlet pipe consist of a primary gas pressure regulator mounted upstream of the intermediate pipe at a determined distance from the envelope. This primary regulator thus supplies the flow meter with an intermediate pressure which, for any given flow, is substantially constant, it being understood that this pressure can vary from one flow to another.

déplace par rapport à un siège fixe. Le rapport---, Sc étant la surface Sm R du siège du clapet et Sm celle de la membrane est inférieur à 0,01 et, de préférence inférieur à 0,001. Comme le rapport de la variation de la pression intermédiaire à la variation de la pression d'entrée est proportionnelle, d'une The primary regulator may comprise a valve integral with the displacement of a membrane directly by a rod or by means of a mechanism with a multiplication effect of displacement having a lever arm r of the valve shutter and a lever arm R of the membrane. In the present specification, the term “shutter” is understood to mean the movable part of the valve which

moves relative to a fixed seat. The ratio ---, Sc being the surface area Sm R of the valve seat and Sm that of the membrane is less than 0.01 and preferably less than 0.001. As the ratio of the variation of the intermediate pressure to the variation of the inlet pressure is proportional, of a

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 firstly, the ratio of the seat surface to the surface of the diaphragm, and secondly, the ratio of the lever arm of the shutter to the diaphragm lever if there is a mechanism with a multiplier effect , the arrangement mentioned above makes it possible to ensure that there is a substantially constant difference between the pressure prevailing in the intermediate conduit and that prevailing in the outlet conduit. The surface of the membrane is equal to the diameter of the membrane taken on the periphery on which it is fixed.

 Another way of obtaining a constant difference between the pressure prevailing in the intermediate duct and that prevailing in the outlet duct consists in providing an articulated parallelogram of which one of the vertices is fixed, the opposite vertex of which is integral with the membrane of the mechanism with a multiplier effect and between the two other vertices of which extends a spring mounted so as to take over from a main spring of the primary regulator as it relaxes. When the membrane of the primary regulator is lowered, the main spring of this primary regulator, which applies an antagonistic force to the intermediate pressure while relaxing, applies a force whose intensity is less and less. By providing the spring-loaded articulated parallelogram acting in traction, which can be accommodated either in the chamber containing the main spring, or in the chamber of the primary regulator in which there prevails the intermediate pressure and which is on the other side of the membrane as the main spring, we make sure that the intermediate pressure remains as constant as possible even if the inlet pressure varies for the same flow. An articulated parallelogram can be used alone or in combination with the arrangement implementing the ratio of the surfaces of the seat and the membrane.

 It is also possible to use means designed to ensure that the pressure prevailing in the inlet fitting applies to an area on one side of the valve plug smaller than an area on the opposite side of the shutter where the intermediate pressure is applied. This also allows the same intermediate pressure to keep the intermediate pressure constant, even if the inlet pressure varies. As a means of ensuring that the pressure prevailing in the inlet connection does not apply on a surface on one side of the valve plug equal to a surface on the opposite side where the intermediate pressure applies, we can provide a cylinder

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 fixed to the shutter on the side opposite to the seat and an orifice made in the shutter and going from one side to the other thereof. The intermediate pressure thus prevails on the side opposite the seat as well as on the other side throughout the part of the shutter located opposite the seat. This embodiment is preferably combined with that with a parallelogram.

 Another preferred means, so that the difference between the pressure prevailing in the intermediate duct and that prevailing in the outlet duct is substantially constant, consists in that the primary regulator comprises a body subdivided by a membrane into a expansion and in a reference chamber and means are provided for causing a reference pressure to prevail in the reference chamber. The means intended to set the reference pressure may include a reference pressure reducer, the outlet duct of which opens into the reference chamber. However, the inlet conduit of the reference regulator or of the primary regulator can communicate with the expansion chamber. We thus obtain a control of the intermediate pressure.

This embodiment can be combined with the preceding modes and in particular with that comprising means intended to ensure that the inlet pressure does not apply to a surface on one side of the valve shutter.

 According to the most preferred embodiment, the reference regulator and the primary regulator have the same body. This gives a very compact arrangement in one piece.

 The reference pressure prevailing in the reference chamber can be equal to the outlet pressure by means of a conduit connecting the reference chamber and the expansion chamber. The difference between the intermediate pressure and the outlet pressure is thus made more constant with less possibility of dispersion.

 The displacement sensor can be of the conventional type. It can in particular consist of a gear between the valve stem and the axis of a potentiometer. It can also be a linear displacement sensor preferably arranged in alignment with the valve stem. It can also be a differential transformer system, an optical sensor or a capacitive sensor or the like.

 According to a preferred embodiment, a means is provided for reducing the value of the displacement of the shutter, for example

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en prévoyant une crémaillère sur la tige du clapet qui engrène dans un train d'engrenage dont la roue de sortie peut comporter, répartis sur la circonférence, des aimants aptes à agir sur des interrupteurs à lame souple (Reed). On déduit le débit de la durée de maintien sur les diverses positions.

by providing a rack on the valve stem which meshes in a gear train, the output wheel of which may comprise, distributed around the circumference, magnets capable of acting on flexible reed switches (Reed). The flow is deducted from the holding time at the various positions.

According to another embodiment, the means intended to obtain a substantially constant difference between the pressure prevailing in the intermediate conduit and that prevailing in the outlet conduit comprise a conduit for communicating the intermediate conduit and the chapel. In this case, whatever the pressure prevailing in the intermediate duct and therefore in the chapel, the pressure difference between this last pressure and the pressure prevailing in the intermediate duct is constant for a given flow whatever this flow, it being understood that this pressure difference can vary depending on the flow.

Thanks to this substantially constant difference between the pressure prevailing in the intermediate duct and that prevailing in the outlet duct, the movement of the valve shutter accurately represents the flow rate. By simply calibrating the device, in which the flow rates are carried as a function of the movement of the shutter, it is thus possible to immediately obtain the flow rates by simply recording the movement of the shutter.

It is also possible to provide a pressure sensor prevailing in the intermediate pipe and calculation means which calculate the gas flow rate from the pressure signal supplied by the sensor and the pressure prevailing in the outlet pipe. It is also possible to provide a sensor of the pressure prevailing in the outlet conduit, and that the calculation means calculate the gas flow rate from the pressure signal supplied by the sensor of the pressure prevailing in the intermediate conduit and the signal supplied by the pressure sensor prevailing in the outlet duct.

According to an improvement, there is provided a temperature sensor prevailing in the inlet duct, this temperature sensor providing a signal to the calculation means so that they correct the gas flow as a function of the temperature.

The calculation means can be used as a device for integrating the flow rates as a function of time to produce a counter.

The shutter preferably comprises, in addition to an elastic part ensuring sealing, a rigid part making it possible to determine exactly

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 relative displacement.

 In the accompanying drawing, given solely by way of example: FIGS. 1 to 4 are sectional views of four embodiments of the invention, and FIG. 5 is a sectional view of the mechanism for reducing the displacement of the shutter.

 The flowmeter represented in FIG. 1 comprises an envelope 1 subdivided by a flexible membrane 2 into an expansion chamber 3 and into a chapel 4. The envelope 1 comprises an intermediate conduit 5 and an outlet conduit 6 both opening into the chamber 3 relaxation. The intermediate conduit 5 is provided with a valve comprising a seat 7 and a shutter 8. The shutter comprises a resilient part 9 ensuring sealing and a rigid part 10 which comes first into contact with the seat 7 when the valve is closed. Thanks to this contact between the rigid seat 7 and the rigid part 10, the position of the shutter 8 is determined exactly, even when the flow is almost zero. The shutter 8 is carried by a rod 11 mounted on bearings formed in the casing 1, so as to be able to move in translation. The rod 11 is articulated by an arm 12 to a journal 13 of the membrane which is integral with the membrane 2. Next to the rod 11, a position sensor 14 is provided, which makes it possible to determine the displacement of the rod 11 and therefore shutter 8.

 In the chapel 4, a spring 15 is mounted in the conventional manner for a gas pressure regulator, one of the ends of which rests on the membrane 2, while the other rests on the upper face of the casing 1.

 The intermediate conduit 5 opens upstream in a chamber 16 for expansion of a primary gas regulator comprising a body 17 subdivided by a membrane 18 into a first compartment 19 in which is housed a main spring 20, one of the ends of which applies to the membrane 18 and the other end of which applies to the upper face of the body 17 and in the chamber 16. A journal 21 of membrane integral with this is articulated to a lever 22 acting on a rod 23 of a valve shutter 25 which, depending on its position, may or may not be applied to a seat 26. An inlet connector 27 opens into the chamber 16.

 When gas passes through the flow meter, the shutter 8 deviates more or less from the seat 7 depending on the flow rate. This gap is detected by

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 the sensor 14 which displays the instantaneous flow. If we want to transform this flow meter into a meter, it suffices to add a device for integrating the flow rates as a function of time.

 There is provided in chamber 16, a pressure sensor 29 connected by a line 30 to a computing device 31, as well as a temperature sensor 32 connected by a line 33 to the computing device. There is also a pressure sensor 34 in the chamber 3. This sensor 34 is connected by a line 35 to the computing device 31 and the sensor 14 is also connected to the computing device 31 by a line 36. In the device 31 , the pressure difference is calculated from the signals supplied by the sensors 29 and 34 and from this pressure difference signal and the signal supplied by the position sensor 14, the instantaneous flow rate can be determined, the device 31 calculation integrating these flows immediately as a function of time to provide an indication of the cumulative flows corresponding to what a meter must provide. The calculation preferably incorporates a temperature correction based on the signal emitted by the sensor 32.

 In FIG. 2, the flow meter is similar to that of FIG. 1, except that there is provided a conduit 28 for communication between the chamber 16 and the chamber 4 and that the spring 15 is not plus a compression spring but a spring acting in traction. The membrane 2 is thus subjected to this tensile force and a force resulting from the difference between the large pressure prevailing in the chapel 4, and the smaller pressure prevailing in the expansion chamber 3.

The embodiment shown in Figure 3 is identical to that shown in Figure 1 but with the following differences:
There is now provided a conduit 37 for communication between the expansion chamber 3 and the compartment 19. It is preferable indeed for the precision that prevails in the compartment 19 the pressure of the chamber 3, for example 20 mbar , instead of atmospheric pressure.

In addition, the embodiment of FIG. 3 includes the following two improvements:
On the lower face (in the figure) of the shutter 25, that is to say on the face which is distant from the seat 26, is fixed a cylinder 38 which slides with sealing in a sleeve 39 coming from the body 17. In the the shutter 25 is pierced with an orifice 40 which connects the space included in the cylinder 38 and the chamber 16. The inlet pressure therefore does not apply to

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 the shutter 25 in the part thereof facing the cylinder 38, so that, even if this pressure varies, it has little influence on the intermediate pressure.

 An articulated parallelogram 41 is provided, one of the vertices 42 of which is articulated on the lever 22, while the opposite vertex 43 is articulated to the body 17. Between the two other vertices 44, 45 is mounted a spring 46. Thanks to this articulated spring parallelogram, when the main spring 20 of the primary regulator relaxes and thus exerts an increasingly small force on the membrane 18, a compensating force is exerted in the same direction on the membrane 18 by the parallelogram device. This helps to maintain the intermediate pressure at a substantially constant value.

 The embodiment shown in Figure 4 repeats that shown in Figure 1 with the following difference.

 The body 17 is subdivided from top to bottom in the figure by successively an upper membrane 50, an upper partition 51, a lower partition 52 and a lower membrane 53 into an upper chamber 54, an upper intermediate chamber 55, a lower intermediate chamber 56 and a lower room. The lower intermediate chamber 56 communicates via a conduit 58 with the inlet connector 27. The upper chamber 54 communicates via a conduit 59 with the relaxation chamber 3. The upper intermediate chamber 55 communicates via a conduit 60 with the expansion chamber 16 of the primary regulator. The conduit 60 is calibrated. The upper intermediate chamber 55 communicates with the lower chamber 57 via a calibrated conduit 61. The lower chamber 57 communicates with the expansion chamber 16 of the primary regulator through a calibrated orifice 62.

The orifice 62 has a smaller diameter than the diameters of the conduits 60 and 61.

 In the upper chamber 54 is mounted a reference spring 63, one of the ends of which applies to the body 17 and the other end of which applies to the upper face of the membrane 50. To the opposite face of the membrane 50 is fixed a reference shutter 64 which is arranged in the lower intermediate chamber 56 and whose rod passes through the partition 51 so as to be secured to the underside of the membrane 50. The shutter 64 can be applied to a seat 65 formed on the underside of the partition 51. The rod 21 is fixed to the underside of the membrane 53. The body 17 contains all of the parts which come

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 to be described.

 The flow meter operates as follows. The inlet pressure prevails through the conduit 58 in the lower intermediate chamber 56. Depending on the pressure prevailing in the expansion chamber 16 of the primary regulator and which applies in the upper intermediate chamber 55, there passes a very low flow rate between the valve 64 and the seat 65 thus maintaining the reference pressure in the lower chamber 57 via the conduit 61 at a given value which corresponds to the load of the spring 63. The gas can escape from the lower chamber 57 through the orifice 62. The pressure prevailing in the chamber 16 is thus substantially constant for a given flow rate and for a wide range of inlet pressure.

 In Figure 5, there is mounted on the rod 11 a rack 66 which meshes with a pinion 67 integral in rotation with a toothed wheel 68. The wheel 68 meshes with a pinion 69 integral with another toothed wheel 70 realizing the multiplier effect. The wheel 70 meshes with an output wheel 71 carrying at its periphery eight magnets 72 which pass successively as the wheel 71 turns in front of a switch 73 with a flexible blade.

The switch 73 is connected to the computer 31.

Claims (18)

CLAIMS 1. Gas flow meter, comprising a casing (1) subdivided by a flexible membrane (2) into an expansion chamber (3), where an intermediate conduit (5) provided with a shutter valve (8) and a outlet duct (6), and in a chapel (4) in which a means (15) applies a force to the membrane (2), which is integral in movement with the shutter (8) and a sensor (14) of the movement of the shutter (8), characterized by means comprising an inlet connector (27) and intended to obtain, for a given flow rate whatever it is in the inlet fitting (27) and whatever this flow the pressure prevailing in the inlet fitting (27), a substantially constant difference between the pressure prevailing in the intermediate pipe (5) and that prevailing in the outlet pipe (6). 2. Flow meter according to claim 1, characterized in that said means consist of a primary regulator (16 to 27) of gas mounted upstream of the intermediate conduit (5) at a determined distance from the envelope, which gives into the conduit (5) intermediate a substantially constant pressure, for a given flow whatever it is. 3. Flow meter according to claim 2, characterized in that the primary regulator comprises a shutter (25) integral in displacement of a membrane (18) directly by a rod (21) or by means of a mechanism (22) displacement multiplier having a lever arm r of the shutter (25) of the valve and a lever arm R of the membrane (18), the ratio ---, where Sc is the surface of the seat of the valve and Sm that of the Sm R membrane (18), being less than 0.01 and preferably less than 0.001. 4. Flow meter according to claim 2 or 3, characterized by a <Desc / Clms Page number 11>  articulated parallelogram (41) of which one of the vertices (43) is fixed, of which the opposite vertex (42) is integral with the membrane (18) or of the mechanism with a multiplier effect and between the two other vertices (44,45) of which extends a spring mounted so as to take over from a main spring (20) of the primary regulator as it expands.  5. Flow meter according to one of claims 2 to 4, characterized by means intended to ensure that the inlet pressure is applied to a surface on one side of the shutter (25) of the valve smaller than '' a surface on the opposite side of the shutter where the intermediate pressure is applied.  6. Flow meter according to claim 5, characterized by a cylinder (38) fixed to the shutter (25) on the side opposite the seat (26) and by an orifice (40) formed in the shutter (25) and going from side to side of it.  7. Flow meter according to one of claims 2 to 6, characterized in that the primary pressure regulator comprises a body (17) subdivided by a membrane into a chamber (16) of expansion and into a chamber (19) of reference and means (20) intended to maintain a reference pressure in the reference chamber.  8. Flow meter according to claim 7, characterized in that the means intended to make the reference pressure prevail comprise a reference regulator, the outlet conduit (61) of which opens into the reference chamber (57).  9. Flow meter according to claim 8, characterized in that the inlet conduit of the reference regulator communicates with the expansion chamber (16).  10. Flow meter according to one of claims 7 to 9, characterized in that the reference regulator and the primary regulator have the same body.  11. Flow meter according to one of the preceding claims, characterized in that the means intended to obtain a substantially constant difference between the pressure prevailing in the intermediate conduit and that prevailing in the outlet conduit comprise a conduit (28) for communication of the intermediate duct (5) and of the chapel (4).  12. Flow meter according to one of the preceding claims, <Desc / Clms Page number 12>  characterized by a sensor (29) of the pressure prevailing in the intermediate conduit (5) and by calculation means (31) which calculate the gas flow from the pressure signal supplied by the sensor (29) and the pressure prevailing in the outlet conduit (6).  13. Flow meter according to one of the preceding claims, characterized by a sensor (34) of the pressure prevailing in the outlet pipe (6) and by calculation means (31) which calculate the gas flow from the signal of pressure supplied by the sensor (29) of the pressure prevailing in the outlet duct (6) and of the pressure signal supplied by the sensor (34) of the pressure prevailing in the outlet duct (6).  14. Flow meter according to one of the preceding claims, characterized by a temperature sensor (32) in the intermediate conduit (5).  15. Flow meter according to one of the preceding claims, characterized in that the shutter (8) comprises, in addition to an elastic part (9) ensuring sealing, a rigid part (10) making it possible to determine its relative displacement exactly.  16. Flow meter according to one of the preceding claims, characterized by a means for reducing the displacement value of the shutter (8).  17. Meter, characterized in that it comprises a flow meter according to one of the preceding claims and a device for integrating the flows as a function of time.  18. Flow meter according to one of claims 2 to 10, characterized in that the compartment (19) or the chamber (54) communicates by a conduit (37,59) with the expansion chamber (3).