This invention relates to a dry gas meter of the kind in which flexible diaphragms work back-and-fort-h in chambers to which the gas being metered is alternately admitted and exhausted. Such meters will be termed hereinafter "meters of the kind described". It is desired that meters of the kind described be made smaller, neater and of simpler construction without loss of strength or durability.

The invention provides a meter of the kind in which flexible diaphragms work back-and-forth in two chambers to which the gas being metered is alternately admitted and exhausted by valve means, the oscillations of the diaphragms being translated through an index drive means for counting to give an indication of the volume of gas which has passed through the meter, the meter being formed by a unitary core providing in one piece the structure for the inner halves of the two chambers and two separate pan covers attached to the core to coπplete the chambers, characterized by said unitary core also providing a first housing for the valve means and the index drive means and first gasways connecting the two chambers to the said first housing, and second gas¬ ways connecting a gas inlet to the said first housing; and by there being upper and lower covers for said unitary core providing gas inlet and outlet means, the unitary core, pan covers and upper and lower covers being of sufficiently strong construction for no outer cover to be needed for normal use.

The invention also provides for the quick and easy assembly of the meter, wherein the operation of attaching the pan covers completes the gasway connections to the pans which are otherwise integral in the core. Since no outer casing is needed, the time and difficulty of the assembly is very much reduced.

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 of Figure 1,

Figure 3 is a vertical section through a central unitary part of the meter of Figure 1, Figure 4 is a horizontal section on the line V - V of

Figure 3, Figure 5 is a vertical section on the line Y - Y of

Figure 3, and Figure 6 is an exploded perspective view from the upper end of the gas meter of Figure 1.

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 a complex aluminium die casting providing structure functioning as 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 partition each forming one 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), [Figures 3 and 5] 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 gasways (21, 22) , seen best in Figures 3 and 4. These gasways lie in between the angled walls (17) using space which would otherwise be wasted. The two chambers are completed by cast aluminium outer pans (25, 26) [Figure 1], each having a flexible diaphragm (13), and both secured to the core (15). Each diaphragm has a central disc (27) secured by a flag arm to a flag (28) [Figure 6] extending into housing (23) to drive the valve drive gear and index drive means. The lower housing (20) is closed by a cast aluminium lower cover (30) [Figure 1] havirig a central bossed gas inlet (31) which coπtπunicates 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' ) which coirmunicates with an exhaust tube (36) [Figure 6] in housing (23). The index housing (19), as best seen in Figure 2, houses an index assembly (34) and has 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) [seen also in Figure 6] passage to drive anoutput 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) [Figure 1], which mates with a similarly angled face (45, 46) on the corresponding outer pan. Gasways (47, 48) in the core connect with ports (50) in the faces (45, 46) 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 upper housing (23) ending in the same plane as seen best in Figure 3. Exhaust tube (36) [Figure 6] 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) [Figure 6] 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 diaphragms back-and-forth and oscillate flags (28) . Flags (28) drive top arms (64) which are connected to cranks (65) to rotate a gear box (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.

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. Moreover, the spaces between the outer edges of the chambers, which are usually wasted, have been used here to provide inlet gasways (20, 21, 22) which thus do not add to the overall size of the meter. This is most conveniently effected by the core being a die casting allowing all the passageways to be preformed without extra paths or assembly work.

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 separately put together and then secured to the core. The lower cover is secured in position, thus completing all the gasway connections. 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.