Patent GB-758239-A (GB)
Title: Improvements in or relating to measuring wheel meters
IPC: G01F1/08
Filed: 1954-10-21
Abstract: 758,239. Rotary meters. GEHRE, H. Oct. 21, 1954 [Dec. 14, 1953], No. 30375/54. Class 110(2) Relates to rotary fluid meters in which the angle of impact of the fluid on the rotor blades and the size of the inlet to the motor are automatically controlled in dependence on the rate of flow. According to the invention, the meter is provided with a control member subject to the pressure drop at the rotor inlet and independent of the rotor, this member being arranged simultaneously to control the size of the inlet and the variation in the angle of impact. Gas enters the meter casing 1 through -an annular orifice 2 and passes through a cylinder 15 and a variable inlet between the cylinder rim 16 and an annulus 27 to impinge on helically twisted blades 14 of the rotor 6. Thence the gas passes around the housing 13 of the worm drive 7, 8 of counting mechanism (not shown) to an outlet 31. The rotor, which has a shaft 9 operating the drive 7, 8, is supported on a vertical rod 5. At its lower edge, the cylinder 15 is connected by an annular membrane 18 to the casing 1 and also carries supports 19 connected by links 20 to levers 22 pivotally connected to the rod 5 and to rods 25 connected to the annulus 27 which is in turn connected by a membrane 30 to the rod 5. Thus each position of the levers 22 corresponds to a definite position of the cylinder 15 and the annulus 27 the distance between the rim 16 and the annulus, which determines the rotor inlet being dependent upon the distances from the rod 5 at which the links 20 and rods 25 are pivoted. The pressure drop across the rotor inlet acts on both membranes 18, 30 and thus imparts a vertical drive to the system, which is compensated by the weight of the system. For an increase in the rate of flow with consequent increase in pressure drop, the system moves until the rotor inlet is of such a size that the pressure drop is again compensated by the weight of the system. Thus the measuring orifice moves relative to the blades 14, so that, due to the twist in the blades, the angle of impact changes. By so twisting the blades that the change of incidence corresponds to change in the rate of flow, the angular velocity of the rotor for each setting of the measuring orifice is proportional to the rates of flow. To maintain the exit velocity the same for all pressures, the system is given a loading varving directly as the density of the gas. This loading comprises one or more auxiliary membranes 32 exposed to atmospheric pressure on one side and the gas pressure on the other and connected by a rod 33 to a lever 35 connected by a link 36 to the lever 22. For low pressure meters one or more barometric capsules may be used instead of the membranes 32. In the meter of Fig. 3, a closed vessel 37 is suspended from a partition 39 on which the rotor 6 is mounted. The diaphragm 18 joined to a plate 40 forms the top of the vessel 37 through which extends a shaft 41 reciprocable between guides 42, 43. Rods 44 mounted on the plate 40 are connected by cranks 45 to pivoted shutters 46 mounted in outlets 47 communicating with the rotor chamber. The rotor has radial blades 14 extending above the outlet 47 and surrounded by a flow guide 49. Gas entering the casing 1 passes through the outlets 47 guided by the shutters to the rotor blades and thence through the outlet pipe 31 which is in communication with the vessel 37 through a tube 50. Thus variations in the pressure drop actuate the membrane 18 to move the shutters 46 and hence change the angle the flow makes with the rotor. The weight of the system movable with the membrane 18 and the reciprocable drive of the shaft 41 operate in the same sense. The weight is therefore over-compensated by a counterweight on a two-armed lever 54, 55 connected by a rod 52 to the shaft 41. The sector-shaped arm 55 carries pins 57 of stepped lengths which co-operate with loading members 58 independently and pivotally suspended on the pivot 56 of the lever 54, 55 with their free ends resting on a support 59, so that as the sector pivots the member 58 are successively lifted by the pins 57. The counting mechanism (not shown) may be within a housing 61 having a glass window 60. Specification 701,227 is referred to.