GB2242273A - Dry gas meter - Google Patents

Abstract

In a dry gas meter of the type having one or more pans (11, 12) across which flexible diaphragms work, flag rods (14, 15) translate oscillations of the diaphragms through a lever system (17, 18, 20, 21, 23, 24, 26, 27, 28, 29) to drive levers (30, 31) having extension tags (33, 34). A valve plate (40) carries pivoted valve covers (45, 46) and the tags (33, 34) extend through valve openings in plate (40) to engage and drive the valve covers to open and close gratings (42, 43) in the plate (40). An electrical reed switch (56) senses the movements of a magnet (54) so as to produce a series of electrical pulses representing the metered quantity. The pulses are fed to electronic circuitry on a board (59) to compute the gas volume used, a temperature compensation signal being provided by a gas temperature sensor. The output volume signal is fed to an l.c.d. display and to a socket for external transmission. The lever system is compactly housed beneath the valve plate (40), and the mechanical power used by the meter is reduced since no drive shafts pass through the plate, the reed switch and electronic system also being beneath the plate. <IMAGE>

Description

DRY GAS METER.

This invention relates to a dry gas meter of the kind having a mechanical metering mechanism comprising one or more flexible diaphragms which are moved back-and-forth in pans by the gas, valve means opening and closing to admit and exhaust gas from each side of the pan in timed relationship to the diaphragm mcveeent, which movement-provides a measure of the gasvolumepassing through. Such meters are referred to hereinafter as "meters of the kind set forth".

Meters of the kind set forth have been used for many years ar.d provide a reliable gas measuring means, but it is now desired to reduce the size of the meters. Efforts to reduce the size heve involved an increase in the speed of the movements so that the gas is mcved more rapidly through the stroller volume available.

The invention provides a meter of the kind set forth having a casing divided into a gas inlet compartment and a gas outlet compart rnE.nt by a sealed valve plate having one or more openings over which one or ore valve covers work to admit gas from the inlet compartment through the mechanical metering mechanism to the outlet ccapartzent, the mechanical metering mechanism being wholly contained within one of sai, compartments together with mechanical lever means for drixtins the valve cover or covers and means for producing an electrical OL'IDlt fro:: the mechanical metering movements.

It will be appreciated that a meter of the kind set forth is dri--en by the gas pressure and an energy loss is therefore inevitable.

Witr increased velocity the energy loss tends to increase. Previous meters have used mechanically driven counters to determine the gas vcl ne passing, and these contributed to the energy loss, and also reuired relatively bulky gearing and drive arrangements. According to this invention such counters are nct used, but are replaced by electrical sensors taking very little er.ergy to drive them. Mcreover, because the gearing and drive arrangements are smaller, it has been found possible to fit the whole of the necessary lever means beneath the valve plate.No driving shafts are required to pass through the valve plate needing sealed bearings which set up resistance to rotation and therefore contribute to the energy loss. Thus the overall energy loss through the meter is much reduced.

The mechanical lever means for driving the valve cover er covers may comprise an oscillating lever having a tag which protruces through said opening in the valve plate to engage the valve cover without extending into the other compartment. The means for producing an electrical output may comprise a reed switch operated by sensed movement of a part of the mechanical lever means. Said one compartment may also contain electronic computing means for receiving said electrical output and computing therefrom a calibrated gas volume. The computing means may include temperature correction means. In one arrangement the electronic computing means is located in the gas stream near the outlet and has a temperature sensor.

An electronic display may be controlled by the computing means so as to show a visual display of the computed gas volume, and there may be means for transferring the value cf computed gas vol -,R to a rert:ote location. A replaceable lithium battery may be provided to cower the electrical items.

A specific embodiment of the invention is shown in the accompanying dr wings, in which: Figure 1 is an exploded view of the construction of a gas meter with the outer casing members omitted, Figure 2 is a side view of the assembled meter of Figure 1 with the outer casing members missing, Figure 3 is a perspective view, partly exploded, of rrt of the gas meter of Figure 1, without the valve plate or valves, and Figure 4 is a side external view of the gas meter of Figure 1 in its casing, indicating the internal electrical connections in the meter.

Referring first to Figures 1, 2 and 3, two flexible diaphragm work back-and-forth in two pans (11, 12) arranged side by side, so that the gas being measured is alternately admitted and exhausted from either side of each diaphragm, through valves described here below. Flag rods (14, 15) (Figure 3) extend from the chambers and at one end are pivotally connected to the diaphragms so that they are oscillated as the diaphragms move. Top arms (17, 18) are secured to the other, upper, ends of the flag rods so that they oscillate with the flag rods.

Forearms (20,21) are pivotally mounted respectively on the top arms (lot, 18) and are eccentrically secured to drive a pair of rotating tangent discs (23, 24). As seen in Figure 1, the tangent discs (23, 24) are mounted coaxially to rotate with gears (26, 27) which mesh so that they are constrained to rotate together. Gear plate (55) provides a stationary mounting for the gears. Pivotally mounted eccentrically on the gears (26, 27) are crank arms (28, 29) which are at their outer ends pivoted to drive valve drive levers (30, 31).

Extension tags (33, 34) from these levers (30, 31) extend upwardly to drive the valves.

The pan assembly is formed integrally with upward hollow pillars which form enclosed gas ways (35, 36, 37, 38) from the pans. On these pillars is mounted a valve plate (40) having valve gratings (42, 43) which communicate through openings (41) in the valve plate with the gas ways (35, 36, 37, 38)in the pillars. Valve covers (15, 46) are pivoted at (47, 48) to oscillate across the gratings to open and close the gas ways. Extension tags (33, 34) from levers (30, 31) extend through the valve plate and gratings to engage in slots on the underside o ne valve covers wherebv to drive the valve covers back and forth.

The timing of the valve cover movement is related to the movement of the diaphragms in the pans through the relative locations of the drive connections of the crank arms (28, 29) and the forearms (20, 21), so that the valves open and close in a preselected phase relationship to the diaphragm movement.

Gas way (35) communicates with the interior of pan (11) on one side of the diaphragm while gas way (36) communicates with the interior of pan (11) on the other side of the diaphragm. Gas way (38) communicates with the interior of pan (12) on one side of the diaphragm while gas way (37) communicates with the interior of pan (12) on the other side of the diaphragm. Spaces (51, 52) between gas ways (35) and (36) and between gas ways (37) and (38) form gas passages within the outer casing (49) (Figure 4). As seen in Figure 1, the gratings (42, 43) are each divided into three sections. The underside of the valve covers (not seen) are shaped to provide two flats divided by a radial central depression. As each valve cover oscillates over the respective grating each gas way is in turn open to the space above the valve plate, closed, open to the gas passageway (51) or (52), and closed.

As shown in Figure 4, the casing (49) comprises a deep lower casing and a shallow top cover. A gas inlet(67) is formed in the top cover and a gas outlet (66) in the bottom surface of the lower casing.

The edges of the valve plate (40) are sealed between the two casing parts so that the casing is divided into two with gas communication between the two parts being only via the valves. As set out above, the timed relationship of the valve and diaphragm movements is such that as each gas way is open to the space above the valve plate incoming gas is supplied to one side of the diaphragm which IS thereby moved across the pan. I5hen the same gas way is open to gas passage- way (51) or (52) gas is delivered from the passageway down hrough the casinos surrounding the pans and out of the gas outlet (66).

As can be seen best in Figure 2, the spaces between the pillars forcing gas ways (35, 36, 37, 38) are big enough so that all cf the valve drive members (17, 20, 23, 26, 28, 30) are contained i-. the sealed area beneath the valve plate (40). Even the valve operating tags (33, 34) extend up through the centre opening of the respective gratings (42, 43) to engage the valve cover and never enter the area above the val plate. Thus the need for sealed openings through the valve plate allowing drive members to pass through is avoided.

The gas meter output is electronically gathered and prczessed.

A permanent magnet (54) is mounted on the gear plate (55). .- reed switch (56) is mounted on a retainer (57) on the stationary structure of the pans adjacent the magnet. A metal interference strip (58) is secured to the top arm (17) so that it moves back-and-forth between the magnet and the reed switch causing magnetic field changes which make the reed switch open and close at the same rate as the top arm.

As seen in Figure 4, the reed switch (56) is connected in a circuit to printed circuit board (59) which has circuits for counting electrical pulses received as the reed switch is opened and. closed.

The total counted is representative of the volume of gas which has passed through the meter. The circuit board also has a permanent memory containing calibration factors for the meter so that the pulse count is translated into a calibrated volume reading. A temperature sensor mounted on the printed circuit board provides a temperature correction factor to correct the calibrated volume reading for the effect of gas temperatures other than the calibration temperature.

It will be noted that the printed circuit board is in the oas stream so that the temperature sensor is exposed to the gas as it leaves the meter, giving an accurate measurement of gas temperature. Other anti-fraud devices such as a tilt switch may be incorporated.

A display panel (60) mounted on the outside of the meter contains a liquid crystal (61) on which the corrected volume reading is displayed.

Connections from the printed circuit board (59) maintain this reading, while a socket (62) allows for the reading to be relayed to a remote reading station or to be read by a plug-in reading unit. A housing (63) for a replaceable lithium battery is also provided in the display panel, this powering the electrical components.

Provision is also made for a fixed pressure correction factor to be fec into the meter. It has been found that by far the largest pressure variation in the gas is due to the height of the installation above sea level. Other pressure variations are small by comparison. Pressure correction is therefore limited to a fixed altitude-related factor which is supplied to the meter at installation or when the area of installation is known. The factor is preferably supplied to the memory on the printed circuit board through an optical system having an optical sensor (65) in the display panel (60). This sensor is able to read an optically-carried data input, and to translate it to an electrical signal carrying the data to the printed circuit board for storage and use.

Other data transfer and interface functions may also use the optical sensor rather than the electrical socket input.

In another arrangement the printed circuit board (59)is replaced by a connection block on which the temperature sensor is mounted. The computing circuits are then mounted in a computing block in the casing of the display (60) on the outside of the meter.

Claims (11)

CLAIMS:

1. A meter of the kind set forth having a casing divided into a gas inlet compartment and a gas outlet compartment by a sealed valve plate having one or more openings over which one or more valve covers works to admit gas from the inlet compartment, through the mechanical metering mechanism to the outlet compartment, the mechanical metering mechanism being wholly contained within one of said compartments together with mechanical lever mear.s for driving the valve cover or covers and there being electrical means for producing an electrical signal from the mechanical metering movement representing a metered quantity.

2. A meter as claimed in claim 1, wherein said gas inlet compartment has a gas inlet connection, and said gas outlet compartment has internal gas ways leading to an outlet connection at the opposite end of the meter from the gas inlet connection.

3. A meter as claimed in claim 1 or claim 2, wherein said mechanical metering mechanism and said electrical means are housed in the said outlet compartment.

4. A meter as claimed in claim 3, wherein said valve cover or covers operate so as to allow gas to flow from the inlet compartment to the metering mechanism and from the metering mechanism to the outlet compartment, in a timed relationship.

5. A meter as claimed in claim 4, wherein said metering mechanism includes one or more flag rods which are arranged to be oscillated by the back-and-forth movements of the diaphragm or diaphragms, a lever system for translating the oscillations into rotations of one or more tangent discs which in turn drive crank arms having tags which extend through said valve openings to engage and drive said valve covers.

6. A meter as claimed in claim 5, wherein said electrical means comprises a reed switch which co-operates with a permanent magnet, mounted so that movements of the lever system produce relative movement between the switch and the magnet and a consequent electrical pulse.

7. A meter as claimed in claim 6, having also electrical computing means connected to receive and count the electrical pulses, which computing means is located in said outlet compartment.

8. A gas meter as claimed in claim 7, wherein said computing means has a temperature sensor and a circuit for correcting the count of pulses for temperature variations.

9. A meter as claimed in claim 7 or claim 8, wherein said computing means has a circuit for applying a fixed altitude-related factor to the count of pulses to correct it for altitude variations.

10. A meter as claimed in any 'of claims 1 to 9, having a display panel on the outside on which the metered quantity is displayed.

11. A meter of the kind set forth substantially as described hereinbefore with reference to the accompanying drawings.