AU723240B2

AU723240B2 - A gas meter with improved resistance to clogging up with dust

Info

Publication number: AU723240B2
Application number: AU49518/97A
Authority: AU
Inventors: Eric Lavrut; John Nicholas Seddon
Original assignee: Itron Soluciones de Medida Espana SA; Schlumberger SA
Current assignee: Itron Soluciones de Medida Espana SA
Priority date: 1996-10-28
Filing date: 1997-10-27
Publication date: 2000-08-24
Anticipated expiration: 2017-10-27
Also published as: HUP9904297A2; KR20000052862A; CN1234864A; AR010046A1; FR2755232B1; CA2268790A1; AU4951897A; PL332943A1; BR9712629A; EP0934508A1; FR2755232A1; WO1998019137A1

Description

-la- A GAS METER WITH IMPROVED RESISTANCE TO CLOGGING UP WITH

DUST

The present invention relates to a gas meter comprising an enclosure fitted with a feed and an exhaust for a flow of gas, and with a measurement block which is disposed inside said enclosure and which is provided with at least one opening enabling the flow of gas to penetrate into said block.

In gas meters of the above-described type, the opening which allows the flow of gas to penetrate into the measurement block is provided in a wall of said block which is situated facing the gas feed. By way of example, such meters are described in the following documents: FR 2 458 798, EP 0 580 099, and WO 94/09342. Such meters are intended for domestic use, and once they are installed on the user's premises, the gas flow feed and exhaust are disposed in a vertical plane with the incoming flow going vertically downwards and with the outgoing flow going vertically upwards. Thus, it is common to find various S 20 particles in such meters that have been entrained by the gas flow into the measurement block, and over time these particles accumulate and end up by partially obstructing the paths taken by the flow, thus leading to *additional headlosses that were not taken into o: 25 consideration in the initial design of the meters.

The present invention attempts to remedy this problem by proposing an alternative gas meter.

According to one aspect, this invention provides a gas meter including an enclosure provided with a feed and an exhaust for a gas flow, and a measurement block disposed inside said enclosure and provided with at least one opening enabling the gas flow to penetrate into said block, and at least one opening enabling the gas to escape from said block via the exhaust, the meter being characterized in that the measurement block has a wall disposed facing H:\Gale\Keep\speci\49518.9 7 .doc 19/06100 2 the gas flow feed and which encounters said flow coming from the feed, said opening being provided solely in the opposite wall of said measurement block.

When the gas meter is installed, the flow coming from the feed does not penetrate directly into the opening (or openings) of the measurement block since the wall of said block situated facing the feed does not include any openings to allow the gas to penetrate into the block.

Consequently, the various particles conveyed by the gas flow can at worst be deposited on said facing wall. To reach the opening(s) provided through the opposite wall of the measurement block, the flow must go round said block which then acts as a screen, and in so doing, the said flow loses most of the particles. Also, when the flow coming from the feed opens out into the enclosure, it first encounters the wall of the block that does not have any i. 2 openings, so when the flow strikes said wall, it also loses a fraction of its particles.

S. The measurement block preferably includes transducers that emit and receive ultrasound waves in the gas flow propagating through said measurement block, it may be advantageous to filter out interfering ultrasound waves that are generated outside the meter at the frequency(ies) used by the transducers and which run the risk of o:o: 25 disturbing measurement. To this end, the meter may include means for attenuating such interfering ultrasound waves, which means are disposed between the gas flow feed and the opening(s).

Preferably, once the meter has been installed on a user's premises, the passage is substantially vertical.

H:\Ga1e\Keep\speci\49518.97.doc 19/06/00 For example, the attenuation means are formed by a plurality of consecutive furrows extending transversely to the main propagation direction of the interfering ultrasound waves in said passage, the furrows being mutually parallel and alternating with ridges so as to set up acoustic impedance discontinuities in the passage.

For example, the ridges and the furrows are formed on the measurement block.

Alternatively, the attenuation means are constituted by a material that attenuates the interfering ultrasound waves and that forms a covering over at least a portion of the surface of the measurement block.

The measurement block may also comprise a fluidic oscillator instead of ultrasound transducers, or indeed a fluidic oscillator combined with such ultrasound transducers, as described in French patent application FR 2 721 360.

Also, the disposition of the opening(s) in the remote wall of the measurement block makes it possible to install, facing said opening, a member which enables the opening to be closed and which is not visible from the gas feed because of the presence of the measurement block.

Such a disposition makes it possible to limit the possibility of fraud that could occur, for example, when a user has not paid a gas bill and consequently the company supplying the gas has caused the opening of the measurement block to be closed, thereby stopping gas delivery.

By way of example, the closure member can be mounted on the measurement block.

Advantageously, the measurement block is made of a plastics material in order to facilitate mounting of the closure member on said block.

Other characteristics and advantages appear from the following description given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic longitudinal section view through a gas meter of the invention; Figure 2 is a section on A-A through the Figure 1 meter; Figure 3 is a section view on B-B through the Figure 1 meter; Figure 4 is a view of the measurement block of the Figure 1 meter, which block includes means for attenuating interfering ultrasound waves generated outside said meter; Figure 5 is a view of a different type of measurement block used in the Figure 1 meter; Figure 6 is a section view on C-C through the measurement block shown in Figure SFigure 7 is a view on a larger scale of the Figure 1 meter and including means for attenuating interfering ultrasound waves generated outside said meter, and constituting a variant of the means shown in Figure 4; Figure 8 is an enlarged cross-section on D-D through the meter shown in Figure 7, with the inside of the measurement block omitted; and Figure 9 is a view of a gas meter analogous to that of Figure 7, but not including means for attenuating interfering ultrasound waves, and in which there can be seen a shutter member for shutting the opening of the measurement block.

As shown in Figures 1 to 3, a gas meter given overall reference 10 comprises an enclosure 12 to which there are connected a gas feed 14 and a gas exhaust 16, and also a measurement block 18 located inside the enclosure 12. The measurement block 18 has a wall 18a situated facing the gas feed 14 and against which the gas flow is split up. Under this dynamic effect, the gas flow loses a fraction of the particles it conveys.

The measurement block 18 is disposed inside the enclosure 12 in such a manner as to leave one or more passages between the block and the enclosure with the fluid flow being shared between the passages (Figures 1 and 3) so as to travel from the feed to an opening formed in the bottom proportion of the measurement block.

A plurality of openings may be formed in the bottom portion of the measurement block instead of only one opening. These vertical passages thus allow the flow to lose most of the particles it is carrying under the effect of gravity, and the particles are then deposited on the bottom of the enclosure where they do not run any risk of subsequently impeding said flow. A dust trap may be provided at the bottom of the enclosure.

The measurement block 18 is held in position inside the enclosure 12 by two projections 22 and 24 which are received in recesses formed in the inside walls of said enclosure 12. As can be seen in Figure 1, the measurement block 18 is substantially in the form of a rectangular parallelepiped and has the opening 20 through which the gas flow penetrates into said block formed in a wall 18b that is remote from its wall 18a, and it also has two ultrasound transducers 26 and 28, each disposed facing one of the opposite ends of a measurement duct of tubular shape which constitutes the ultrasound measurement path. By way of example, the ultrasound transducers operate at a frequency of 40 kHz.

The measurement duct 30 passes through a wall 32 in the form of a solid block between two chambers in which the transducers 26 and 28 are located. The gas penetrates into one of the chambers of the measurement block 18 via the opening 20, as indicated by the arrows in Figures 1 and 3, penetrates into the measurement tube via its end 30a, travels along the inside thereof, leaves the tube via its opposite end 30b, and is subsequently exhausted upwards via the outlet orifice 34 which is connected to the gas exhaust 16 shown in Figure 1.

It is very important for the gas flow to have had the major portion of its dust removed by the time it penetrates into the measurement block since that is where the flow sections are the smallest and thus where any accumulation of dust over time will have the most harmful effects on headloss.

In the above-described ultrasound gas meter, the ultrasound transducers 26 and 28 act in alternation to emit and receive ultrasound waves at a fixed ultrasound frequency, and on the basis of the ultrasound waves received by each of said transducers, the propagation time of said waves is measured, and the fluid flow rate is deduced from the measurements.

Because of the positioning of the opening in accordance with the invention, there is no risk of particles being deposited on the active faces of the transducers, which would modify emission and reception of ultrasound waves, thereby considerably disturbing flow rate measurements.

It should be observed that the space available in the bottom of the enclosure is generally occupied by appropriate electronics together with an energy source (not shown) required for determining the gas flow rate.

Sometimes, a pressure regulator (not shown in the figures) is located upstream from the gas meter and generates interfering ultrasound waves in the pipework and in the meter, e.g. at a frequency equal to 40 kHz, thereby disturbing the measurement of gas flow rate.

Given that the measurement block acts as a screen between the feed and the opening into said block, and therefore acts somewhat like a soundproofing wall, the interfering waves which reach the enclosure together with the gas flow are naturally attenuated by the multiple reflections generated by coming into contact with the wall 18a and the inside walls of said enclosure.

It should be observed that when the opening into the measurement block is provided in the wall 18a facing the gas feed (prior art), the noise propagating in the flow penetrates more easily into the measurement block than it does with the novel disposition where the opening faces the bottom of the enclosure. Nevertheless, as shown in Figure 4 (where elements that are unchanged from Figures 1 to 3 retain the same references), it can be advantageous to line the measurement block 36 with a layer of material that is suitable for further attenuating the interfering waves, e.g. so as to prevent the structure of the measurement block (which is often made of metal) from itself facilitating the propagation of such waves.

Figures 5 and 6 show a measurement block 40 of a gas meter analogous to that of Figures 1 to 3, and in which elements that are unchanged relative to Figures 1 to 3 retain the same references. This measurement block is constituted by a fluidic oscillator into which the gas flow penetrates via the opening 20 and enters a channel 42 which terminates via a slot 44 of elongate shape looking into a chamber 46. An obstacle 48 is located in the middle of the chamber facing the slot 44. The slot transforms the flow into a fluid jet that oscillates naturally in the chamber 46, thereby sweeping the front face 48a of the obstacle 48 at an oscillation frequency that is representative of the flow rate that has passed through the fluidic oscillator. As the jet oscillates it gives rise to flows that pass alternately via lateral channels 50 and 52 on either side of the obstacle 48, which flows are reunited downstream from said obstacle and take the vertical channel 54 that is connected to the outlet orifice 34.

Figures 7 and 8 show a gas meter 56 analogous to that of Figures 1 to 3, but which also includes means for attenuating interfering ultrasound waves generated outside said meter. These means are different from those shown in Figure 4. Elements which are unchanged relative to Figures 1 to 3 retain the same references. To clarify the description below, the measurement block 58 is omitted from Figure 8.

Given that the opening 20 is on the side of the measurement block 58 that is remote from the gas feed 14, and that the passages 60, 62, 64, and 66 are formed between the enclosure 12 and said measurement block, it is possible to put attenuation means in said passages, and thus to propose a solution for attenuating noise that is effective and inapplicable to prior art meters. In these figures, each of the above-mentioned passages 62, 64, and 66 is defined by two facing surfaces respectively 68 70, 72 74, 76 78, and 80 82, and one of each of them the surfaces 70, 74, 78, and 82 of the measurement block 58) is covered in a plurality of consecutive ridges 84, e.g. obtained by overmolding, and alternating with furrows 86.

By dimensioning these passages so that their transverse dimension (Figure 8) perpendicular to their longitudinal dimension b is much shorter than the wavelength of the interfering ultrasound waves in the gas under consideration, it is possible to ensure that only the plane mode of the ultrasound wave propagates therein, so that that is the mode which needs to be attenuated.

These means form a plurality of reductions in section over the ridges 84, thereby constituting an impedance discontinuity in the propagation medium, and thus reflecting a portion of the energy contained in the plane mode of the incident interfering wave.

Figure 9 shows another advantageous characteristic associated with the disposition of the invention for the opening of the measurement block. Elements that are unchanged relative to Figures 1 to 3 retain the same references in this figure.

The gas meter 88 shown comprises a measurement block whose opening 92 is, for example, offset towards the central portion of the meter in order to ensure that it is not vertically below the gas feed, thereby further reducing any risk of fraud.

A cutoff member 94 is mounted beneath the measurement block, in register with the opening 92 in order to close it, should that be necessary. This may be appropriate, e.g. in the event of a fire being detected downstream from the meter, for the purpose of avoiding an explosion. It may also be desirable to cut off the supply of gas when the user on whose premises the meter is installed has not paid a gas bill.

Such a member 94 comprises a flap 96 that comes into contact with a seat for the flap that coincides with the opening in Figure 9, a rack mechanism 98, shown in part only, and a driving motor 100 thus serving to move said flap in rotation about an axis 102. By placing the cutoff member beneath the measurement block, risk associated with fraud is reduced compared with prior art meters in which such a member is necessarily placed close to the gas feed. Nevertheless, the opening 92 could be placed at some other location providing the shutter member remains masked from the feed 14 by the measurement block Also, since the particles conveyed by the flow are dumped on the bottom of the enclosure 12, they do not deposit themselves on the flap, as they do in the prior art, and thereby they do not prevent the cutoff member from sealing properly, nor do they subject it to wear.

There is more room in the bottom portion of the meter for receiving the motor 100 of the cutoff member than there is in the top portion thereof where the feed 14, the orifice 34, and the exhaust 16 occupy sites that might otherwise be available.

Advantageously, by making the measurement block out of a plastics material, it is easy to overmold parts on the outside wall of said block, which parts enable the cutoff member 92 to be secured reliably to said block bearings in which a shaft on the axis 102 pivots).

In prior art gas meters, the cutoff member is fixed inside the meter on the gas feed 14 or in the vicinity thereof. Since the enclosure 12 of the meter is made of metal in order to provide it with the ability to withstand high temperatures, it is difficult to fix the cutoff member in a manner that is simple and reliable.

Also, it should be mentioned that by placing the shutter member 94 on the measurement block, any increase in the pressure of the gas flow coming from the feed 14 tends to urge the flap 96 towards its seat, and thus to close the opening 92, and this is advantageous. In contrast, if the shutter member is installed in register with the feed 14, any increase in the pressure of the flow upstream from the meter will tend to force the flap open, thus making it more difficult to close said flap.

It should also be observed that by placing the opening of the measurement block in accordance with the teaching of the invention, it is possible to avoid receiving directly in said opening any disturbances propagated in the gas flow and due, for example, to a bend located upstream from the meter.

Claims

2. A gas meter according to claim 1, in which the closure and the measurement block leave between them at least one passage enabling the gas flow from the feed to reach the opening.
3. A gas meter according to claim 2, in which the passage is substantially vertical.
4. A gas meter according to any one of claims 1 to 3, in which the measurement block includes transducers emitting and receiving ultrasound waves in the gas flow which propagates through said measurement block. A gas meter according to claim 4, including attenuation means for attenuating interfering ultrasound 25 waves generated outside the meter, which means are disposed between the gas flow feed and the opening.
6. A gas meter according to claims 2 and 5, in which the means for attenuating interfering ultrasound waves are disposed in the passage.
7. A gas meter according to claim 6, in which the attenuation means are formed by a plurality of consecutive furrows extending transversely to the main propagation direction of the interfering ultrasound waves in said passage, the furrows being mutually parallel and alternating with ridges so as to set up acoustic impedance discontinuities in the passage.
8. A gas meter according to claim 7, in which the H;\Ga1e\Keep\speci\49518. 9 7 .doc 19/06/00 C- 12 ridges and the furrows are formed on the measurement block.
9. A gas meter according to claim 5, in which the attenuation means are constituted by a material that attenuates the interfering ultrasound waves and that forms a covering over at least a portion of the surface of the measurement block. A gas meter according to any one of claims 1 to 3, in which the measurement block includes a fluidic oscillator.
11. A gas meter according to any one of claims 1 to including a shutter member for shutting the opening of the measurement block.
12. A gas meter according to claim 11, in which the shutter member is disposed facing the opening.
13. A gas meter according to claim 11 or 12, in which the shutter member is masked from the feed by the :i measurement block.
14. A gas meter according to any one of claims 1 to 13, in which the measurement block is substantially in the form of a rectangular parallelepiped. A gas meter according to any one of claims 11 to 14, in which the shutter member is mounted on the measurement block.
16. A gas meter according to any one of claims 1 to 19, in which the measurement block is made of a plastics material.
17. A gas meter, substantially as herein described *:'with reference to the accompanying drawings. Dated this 19th day of June 2000 SCHLUMBERGER INDUSTRIES S.A By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H:\Ga1e\Keep\speci\49519.97.doc 19/06/00