Patent GB-783174-A (GB)
IPC: G01F5/00
Abstract: 783,174. Flowmeters. NEUHAUS, G. July 9, 1953, No. 19135/53. Class 69 (1). In a flowmeter in which rate of flow in a main conduit is measured by measuring the rate of flow of a gaseous fluid in an auxiliary conduit, which auxiliary flow is proportional to the main rate of flow, two flow controllers are arranged in series in the auxiliary conduit and are controlled by the differential pressures on either side of an orifice plate in the main conduit and an orifice plate in the auxiliary conduit between the two flow controllers. In the form shown in .Fig. 1, the flow in the auxiliary conduit 16, 24, 28 caused by the blower 26 is controlled by valves 20, 21. The valve 20 is attached to a flexible membrane 10, one side 6 of which is connected to the downstream side of an orifice plate 3 in the main conduit 1 and the other side 14 of which is connected to the part 16 of the auxiliary conduit on the upstream side of the auxiliary orifice plate 17, and the valve 21 is attached to a membrane 11, one side 7 of which is connected to the upstream side of the orifice plate 3 and the other side 15 of which is connected to the part 16 on the downstream side of the orifice plate 17. On increase of flow in the main conduit, the pressures on either side of the orifice plates 3, 17 act on the membranes 10, 11 which open the valves 20, 21 and so increase the flow in the auxiliary conduit. The auxiliary flow is measured by a meter 27. Instead of the auxiliary flow following a closed circuit it may exhaust to atmosphere. In another form, Fig. 2 (not shown) the membranes 10, 11 are each replaced by a pair of membranes of unequal size and mechanically connected. The pressures on either side of the orifice plate 3 is applied to the larger membranes and the pressures on either side of the orifice plate 17 are applied to the smaller membranes. In this form, a temperature correction is provided by passing the part 16 of the auxiliary conduit on one side of the orifice plate round or through the main conduit and passing the part 16 on the other side of the orifice plate through a cooling bath. In a modification of this form, the larger of the membranes are replaced by Bourdon tubes each connected by a linkage to the respective smaller membrane. In the form shown in Fig. 4, the pressures on either side of the orifice plate 3 are applied to membranes 102, 103 and the pressures oneither side of the orifice plate 113 in the auxiliary conduit are applied to membranes 110, 111. The membranes are interconnected by a linkage 105, 121, 119. A Bourdon tube 106, to the free end of which is attached the fulcrum of the link 119, provides compensation for the static pressure in the main conduit. Fig. 5 shows a further embodiment in which the flow through the auxiliary conduit is controlled by valves 144, 146. Valve 144 seats on the outlet tube 142 to the auxiliary flowmeter and is mounted on a partition 138 in a cylindrical bellows, the partition also embodying the auxiliary orifice plate. The valve 146 is attached by a rod 145 to the partition and contacts a valve seating on the top 135 of the bellows. The partition 138 is also attached to a pivoted lever 155, the other end of which is connected to a flexible membrane 151. In operation, on increase of flow in the main conduit, the increased differential pressure across the orifice plate 3 moves the membrane 151 and thus opens the valves 144, 146 via the lever 155. The flexible bellows 136 then adjusts itself, and therefore the degree of restriction through the valves, until the flow in the auxiliary conduit is proportional to the flow through the main conduit. A Bourdon tube pressing on a rigid cap on the bellows provides the compensation for the static pressure in the main conduit.