DRY GAS METER AND METHOD OF ASSEMBLING A FLAG ROD

Abstract: A flag rod assembly for transmitting the reciprocating movement of a diaphragm (13) out of a gas chamber comprises a straight flag rod (24) secured to flag (22) which in turn is pivoted to the diaphragm. An end stop (30), bearing (31) and shoulder (32) hold the flag rod and flag in position in their normal arc of movement. For assembly and disassembly the flag (22) may be rotated out of said normal arc whereby it is moved out of alignment with shoulder (32), allowing endwise movement of the flag rod.

Description: Dry Gas Meters. This invention relates to gas meters of the kind in which a gas chamber is divided by a flexible diaphragm and gas is admitted alternately to either side of the diaphragm whereby the diaphragm reciprocates back and forth. The reciprocating movements are used to measure the volume of gas flowing and are transmitted from the gas chamber via a flag rod assembly. Flag rod assemblies, for instance as shown in U.K. patent No. 1,058,751, have usually comprised a cranked rod one end of which is attached to the diaphragm and the other extends out of the gas chamber. Such cranked rods are difficult to manufacture accurately and also to assemble. This invention provides a gas meter of the kind in which a gas chamber is divided by a flexible diaphragm and gas is admitted alternately to either side of the diaphragm whereby the diaphragm is moved back and forth, which movements are transmitted through a flag rod assembly to measure the volume of gas flowing, said flag rod assembly including a flag secured at one end to the diaphragm with freedom to pivot with respect thereto about a first axis, characterized by said flag having its other end fixed to a straight flag rod which is mounted at one end in the gas chamber with freedom to oscillate about its own axis which is parallel to but spaced from said first axis, the other end of the flag rod extending out of the gas chamber, whereby the back and forth movements of the diaphragm are translated into oscillations of the flag and flag rod through an arc about the flag rod axis. The mounting for the flag rod in the gas chamber may comprise an end stop for said one end limiting endwise movement of the flag rod in one direction, a bearing opening through which the flag rod passes and a shoulder which in use is contacted by the flag to limit endwise movement of the flag rod in the opposite direction. Said shoulder may be located to be contacted by the flag only in that arc of pivotal positions of the flag which is encountered in use, so that the flag rod assembly may be assembled with the flag rotated out of said arc and thereby free of the constraint of said shoulder. A specific embodiment of the invention is shown in the accompanying drawings, in which: Figure 1 is an exploded view of part of a gas meter showing a diaphragm and one of its flag rod assemblies with an inset of part thereof enlarged, and Figure 2 is a detail view of another flag rod assembly for the gas meter of Figure 1. The gas meter includes a pair of dished pans (11, 12) clamped together to form a gas chamber with a diaphragm (13) of a flexible fabric held therebetween. Valves (not shown) admit gas alternately to either side of the diaphragm and then exhaust it so that the diaphragm is moved back and forth in the chamber, the number of such movements being a measure of gas flowing through the chamber. Referring first to Figure 1, centrally of the diaphragm are a pair of flat metal plates (14, 15) one on either side of the diaphragm. The plates are secured to the diaphragm by a bracket member (17) of acetal plastics material which has a pair of pins which pass through aligned openings (18) in the plates and can be ultrasonically welded thereto, or conventionally screwed or rivetted. Bracket me-mber (17) provides a pair of vertically spaced pins (20) which engage in openings (21) in one end of a flag (22) to allow the flag to rotate about a vertical axis relative to the diaphragm as the diaphragm reciprocates. The other end of flag (22) terminates in a sheath (23) in which a straight metal flag rod (24) is tightly fitted. The flag rod extends through a vertical opening (2k') in the pan (11) and has a flag arm (25) secured thereto. The flag arm drives a valve opening mechanism (not shown) and an index (not shown). The gas meter also includes another gas chamber of opposite hand to that shown in Figure 1 but otherwise identical. The flag rod assembly shown in Figure 2 is that of this second gas chamber and so shows the flag rod assembly from an opposed angle. It has the same reference numerals as that of Figure 1. The pans (11) for both chambers are formed with mountings allowing the flag rod freedom to oscillate about a vertical axis and also to be quickly assembled into the pans. The mountings comprise an end stop (30), a bearing (31) and a shoulder (32) which lies adjacent the sheath (23). To assemble it, the flag rod is secured to the flag (22), and its upper end fed up into the opening (24') until the lower end can be dropped into the bearing (31). It will be found that this assembling action can only performed with the flag (22) rotated out of the pan in the direction of arrow A, since the flag has ridges (seen best in Figure 1) which contact the shoulder (32) and prevent the flag rod (24) being aligned with bearing (31). The flag rod is dropped into contact with end stop (30), which action drops the ridges out of alignment with the shoulder (32). The flag (22) can then be rotated in the opposite direction to arrow A into the position shown in Figure 2, where shoulder (32) abuts the top edge of the flag and locks the flag so preventing the flag rod being lifted out of its bearing (31). The normal reciprocation of diaphragm (13) moves the flag (22) through a restricted arc of movement in which it is never rotated sufficiently in the direction of arrow A to allow the flag to move out of contact with shoulder (32). The flag rod and flag are therefore locked between the lower end stop (30) and the upper shoulder (32). In assembly and disassembly when the dished pans (11, 12) are not joined together the diaphragms can be moved further than their normal reciprocating motion so allowing the additional movement of the flag necessary to clear the shoulder (32). When the pans art secured together, however, the diaphragm movement is restricted and the flag cannot clear the shoulder. It will be noted that this form of assembly depends on the flag rod being a simple straight rod which can be threaded through the various openings. The rod may be formed of a metal while the other parts are mouldings of a plastics material, 0.6. acetal. Where the passa (11, 12) are formed of moulded acetal material, the end stop ()ops shoulder (32) and bearing (31) are moulded intewalljr therewith Alternatively they may be secured thereto with adhesive.

Claims: Claims: 1. A gas meter of the kind in which a gas chamber (71, 12) is divided by a flexible diaphragm (13) and gas is admitted alternately to either side of the diaphragm whereby the diaphragm is moved back and forth, which movements are transmitted through a flag rod assembly (22, 24, 25) to measure the volume of gas flowing, said flag rod assembly including a flag (22) secured at one end to the diaphragm with freedom to pivot with respect thereto about a first axis, characterized by said flag (22) having its other end fixed to a straight flag rod (24) which is mounted at one end in the gas chamber with freedom to oscillate about its own axis which is parallel to but spaced from said first axis, the other end of the flag rod extending out of the gas chamber, whereby the back and forth movements of the diaphragm are translated into oscillations of the flag and flag rod through an arc about the flag rod axis. 2. A gas meter as claimed in claim 1, further characterized by the mounting for the end of the flag rod in the gas chamber comprising an end stop (30) limiting endwise movement of the flag rod in one direction, a bearing (23) through which the flag rod passes and a shoulder (32), which shoulder is located so that it acts as a stop preventing movement of said flag and flag rod in a direction opposite to said one direction only in said arc of movement of the flag and flag rod, whereby for assembly and disassembly purposes the flag may be rotated out of said arc of movement to clear said shoulder and leave the flag rod free to be moved in said opposite direction. 3. A gas meter as claimed in claim 2, further characterized by said flag (22) being formed with a ridge located to contact said shoulder in said arc of movement. 4. A gas meter as claimed in claim 2 or claim 3, further characterized by said end stop (30) said bearing (23) and said shoulder (32) being integral with or secured to the interior surface of said gas chamber. 5. A gas meter as claimed in any of claims 2 to 4, further characterized by said arc of movement being limited by the end surfaces of the gas chamber (11, 12) whereby said flag (22) cannot be rotated out of said arc of movement when the chamber is assembled. 6. A method of assembling a gas meter flag rod assembly of the kind claimed in any of claims 2 to 5, characterized by the steps of securing one end of the flag (22) to the flag rod (24) pivoting the other end of the flag (22) to the diaphragm (13), moving the diaphragm out of its normal arc of movement, passing one end of the flag rod up through an opening in the gas chamber, dropping the flag rod down through bearing (31) to contact the end stop (30) and rotating the flag and diaphragm back into the normal arc of movement thereby engaging the flag under the shoulder (32).

Inventors: PYE, ALFRED EDWARD
Applicants: UNITED GAS INDUSTRIES LIMITED
Application year: 1980
Main classification: G01F3
IPC codes: G01F3