This invention relates to a dry gas meter of the kind in which flexible diaphragms work back-and-forth in chambers to which the gas being metered is alternately admitted and exhausted. It is desired that meters of the kind described should be made adaptable to different mounting configurations, so that they may be used to replace meters in existing installations.

The invention provides a dry gas meter of the kind in which flexible diaphragms work back-and-forth in chambers to which the gas being metered is alternately admitted and exhausted and which has a unitary core providing in one piece the structure for the inner sides of two chambers, characterized by said unitary core also providing internal gasways and by first and second covers secured to the upper and lower sides of the unitary core and providing inlet and outlet connections for connecting the meter into a gas line and by their configuration determining the path taken by gas flowing through the meter.

By selecting appropriate first and second covers the meter may in a first mode be adapted for an in-line gas flow from an inlet boss in the second, lower, cover to an outlet boss in the first, upper, cover. In this adaptation, the outlet boss is connected to an exhaust tube connected to the two chambers and the inlet boss directs gas flow through the said gasways into the said first housing.

In a second mode, the meter connections may be altered to inlet and outlet bosses spaced apart in the first, upper, cover, the second, lower, cover effectively blanking off the said second housing. Thus the gas path does not include said gasways. The said first, upper, cover in this mode is constructed with direct access from the inlet boss to the first housing but with an internal passageway leading fran the outlet boss to the exhaust tube. By the simple provision of appropriate upper and lower covers the meter can be adapted to meet a variety of different connection con¬ figurations, so that it can be used for in-line connections and for replacement of meters having horizontally spaced-apart connections. It should be noted that the majority of the meter is not affected by such adaptation so that virtually the same design of meter can be used

for a number of different applications simply by the use of appropriate covers.

The invention extends to the provision of a meter which can by the selection of simple and appropriate covers be adapted to different connection configurations. It also extends to the provision of a meter having interchangeable covers which affect the direction of gas flow through the meter.

A specific embodiment of the invention is shown in the accompanying drawings, in which:- Figure 1 is an exploded perspective view of the main components of a gas meter, Figure 2 is an exploded perspective view of the upper part of the meter in Figure 1, in one mode, Figure 3 is a vertical section through a central unitary part of the meter of Figure 1,

Figure 4 is an exploded perspective view from the upper end of the gas meter of Figure 1, showing the interior parts, Figure 5 is an exploded perspective view of the upper end of the gas meter of Figure 1 in a second mode, and

Figure 6 is a diagram showing another arrangement and the parts needed for adaptation to the second mode.

The gas meter comprises two chambers (11, 12) each divided vertically by a flexible diaphragm (13) so that gas being measured may be alternately admitted and exhausted from either side of the diaphragm, causing it to oscillate back-and-forth. As is usual, the oscillations of the diaphragm are counted to provide a measure of the volume of gas which has passed through the meter. As seen best in Figure 1, the meter body depends on a unitary core (15) which is an aluminium die casting providing structure for the meter casing, inner gas chamber, valve gear container, index housing and gasways, as described hereinafter in more detail. The core comprises a central vertical partition (16) comprising one side

of each of the chambers (11, 12), and two angled walls (17) either side of the partitions, each forming the dished shape of a chamber. The upper end of the core forms a recess (19) opening to the side which is the index housing, and an irregular housing (23) opening to the top which houses valves, valve drive gear, and index drive means.

The lower end of the core forms a housing (20) across the core connecting at each side with vertically-extending triangular-section gas inlet ways (21, 22) [Figure 3].

The two chambers are completed by cast aluminium outer pans (25,26) [Figure 1], each having a diaphragm (13), both secured to the core (15). Each diaphragm has a central disc (27) secured by a flag arm to a flag (28) [Figure 4] extending into housing (23) to drive the valve drive gear and index drive means.

In a first mode of operation, the lower housing (20) is closed by a cast aluminium lower cover (30) having a central bossed gas inlet (31) which communicates with housing (20) and gasways (21, 22) . The upper housing (23) is closed by a cast aluminium upper cover (33) having a central bossed gas outlet (34\') [Figure 2] which coπmunicates with an exhaust tube (36) [Figure 4] in housing (23). The index housing (19), as best seen in Figure 2, houses an index assembly (34) and a cover (35) having a viewing plate through which the meter reading can be read. A sealed bush bearing (37) in the rear wall of the housing allows a lay shaft (41) [also seen in Figure 4] passage to drive an output gear (38) and through it change gear (39) and index drive gear (40) , which operates the index assembly (34) to count the oscillations of the diaphragms.

Adjacent each outer pan (25, 26), the core (15) has an angled face (43, 44) which mates with a similarly angled face (45, 46) on the corresponding outer pan. Gasways (47, 48) connect through openings (50) into the interior of the pans on the outer side of diaphragms (13).

On the inner side of the diaphragms (13) the core provides gasways (51), also connected to the interior of the chambers (11, 12).

Gasways (51, 48, 47) all extend up through the core and through a lower wall of the upper housing (23) ending in the same plane as seen best in Figure 3. Exhaust tube (36) [Figure 4] is forked to provide a pair of entrances (61) and the tube is mounted so that these lie in the same plane as the entries to gasways (51, 48, 47). A valve grating

(60) for each chamber (11, 12) covers the two gasways to either side of the diaphragm and one of the exhaust tube entrances (61) . Inlet gasways (21) and (22) open into the upper housing (23) so that it is at all times filled with the gas being metered. An oscillating valve cover (62) for each valve grating alternately admits gas from housing (23) to either side of the diaphragm and exhausts it from the chambers into exhaust tube (36) and out of outlet (34\'). Thus the flowing gas is forced to move the diaphragm back-and-forth and oscillate flags (28) . Flags (28) drive top arms (64) which are connected to cranks (65) to rotate a gearbox (66) . Gear (67) driven by the gearbox connects with output gear (68) which rotates layshaft (41) which, as discussed above, drives the index.

Cover drive arms (69) are driven from gears (70) of the gearbox and connected to the valve covers (62) to oscillate them as described above.

In this first mode of operation as described above, the gas enters at the bottom of the meter and exits at the top so that the meter can readily be mounted in-line. However, it is frequently desired to replace existing meters which have traditionally been connected to two spaced apart connections on the top surface of the meter.

It has been found that the meter may be adapted into a second mode of operation in which it may be used as a replacement meter by only changing two components, the lower cover (30) and the upper cover (33) . In both Figure 5 and Figure 6, the two replacement components comprise a new lower cover (30\' ) and a new upper cover (33\' ). The lower cover (30\' ) simply blanks off the bottom of the meter so that gas¬ ways (21, 22) are closed at the bottom. Upper cover (33\') is a complex aluminium casting providing an outlet boss (71) and an inlet boss (72), the distance between these bosses being equal to the traditional connection arrangement so that the meter can be attached to existing connections. Boss (71) leads into a chamber (73) having an opening (74)located to engage and seal onto the exhaust tube (36) [Figure 4]. Boss (72) leads directly into the housing (23) from which gas enters the chambers (11, 12). In the arrangement of Figure 6, the distance between the bosses (71, 72) is so great that the upper cover (33\') has to have a greater width than the width of the meter itself, because the meter is smaller than previous designs.

It will be appreciated that the major working part of the meter is standard and unchanged, so that a single design can be used for a number of different connection requirements, with only minimum and simple refitting. It will be noted that the meter design is distinguished by a particularly efficient use of space so that the overall size is kept to a minimum. The two pan covers (25) and (26) fit neatly against the core, their outer surfaces being flush with the outer surfaces of the upper part of the core. Since the pan covers, the top cover and the lower cover are all rigid aluminium castings, the core and its covers are all of strong and durable enough construction to need no outer casing for protection, this also contributing in major part to the reduced size of the meter. The assembly of the meter is also very much simplified by the use of the unitary core. In assembly, the pan covers and diaphragm and flag structures are sep>arately put together and then secured to the core. The lower cover is secured in position, thus determining the gas flow direction. The valves and drive gear are assembled in housing (23) and the upper cover secured over the top. The index is then assembled and attached into the index housing. No casing operations as such are required, the unitary core, pan covers and upper and lower covers together forming the outer surfaces of the meter. The selection of the upper and lower covers determines the connection configuration of the meter, without any other alteration to the meter.