Patent GB-698219-A (GB)
Title: Apparatus for measuring the rate of fluid flow in a conduit
IPC: G01F1/37
Filed: 1951-09-05
Abstract: 698,219. Pressure gauges. KONINKLIJKE NEDERLANDSCHE GIST-EN SPIRITUSFABRIEK N.V. Sept. 5, 1951 [Sept. 5, 1950], No. 20927(51. Class 106 (ii). [Also in Group XXIX] A flow measuring apparatus comprises a differential pressure device, in the conduit carrying the flow, which is operatively associated with a first device supplying a force proportional to the pressure difference, a rotating member driven at a speed proportional to the rate of flow and operatively connected with a second device supplying a force proportional to the square of the speed of the rotating member, and a further member, connected to the first and second devices, which upon change of position operates the variable drive of the rotating member so as to restore equilibrium of the two forces. In the form shown, Fig. 1, the differential pressures from the orifice 2 in pipe 1 is applied to a ring balance 5, to which is fixed an arm 9. A synchronous motor 11 drives a friction disc 15 at constant speed via gears 12, 13 and shaft 14. The disc co-operates with a friction roller 16 on a sleeve 17 which is slidable on a splined shaft 18 and rotatable therewith. The lower end of the shaft 18 carries a governor 19, a rod 21 of which bears against a knife edge 10 on the arm 9. One arm 28 of a bell-crank lever bears against an eccentric 29 mounted on the shaft 14 and the other arm 26 carries a frame 25 so that, as the shaft 14 rotates, the frame 25 oscillates in a horizontal direction. The inside of the frame has two ratchet teeth 32, 33 disposed on either side of a ratchet-wheel 34, the distance between the teeth being such that only one can engage the ratchet-wheel at a time. The frame 25 is connected to the arm 9 by a rod 23 and a pinion rotatable with the ratchet-wheel 34 engages a rack 37 on the sleeve 17. In operation, if the rate of flow in the conduit 1 increases, the ring balance will move the arm 9 upwards against the force exerted by the governor 19, and also move the rod 23 upwards, thus causing the lower tooth 33 to engage the ratchet, and by virtue of the oscillation of the frame, rotate it and so move the sleeve 17 downwards via the rack and pinion 36, 37. The friction roller 16 on the sleeve therefore engages at a greater radius on the disc 15 and its speed increases so that the force exerted by the governor increases and returns the arm 9 to the original position. A pointer 38, indicating the rate of flow in the conduit, is attached to the pinion 36 and a counter 44 showing the total amount of flow is driven from the shaft 18. The position of the knife edge 10 is adjustable by the screw 45. In a second embodiment, Fig. 2, the differential pressures from the conduit are led to a casing 50 containing two diaphragms 51, 52 interconnected by a column 53 which engages with a two-armed lever 55 fulcrumed at a knife edge 56. A centrifugal pump 58, driven by an air turbine 65, supplies a fluid pressure which is applied to a diaphragm and, via a rod 63, supplies a force to the lever to balance the differential pressure. The air for the turbine 65 is supplied by a line 66 via a valve 69 coupled to a bellows 70, the bellows being connected to the inlet air line by a line 72 and also vented to atmosphere through an aperture 75 opposite which is disposed a spring 76 mounted on the arm 55. In operation, if the flow rises the right-hand end of the lever 65 is depressed and the spring 76 moved away from the aperture 75 so that the air pressure in the bellows 70 falls and the valve 69 opens. Thus more air is admitted to the turbine and its speed raised so that the output of the pump increases and depresses the diaphragm 62 and the left-hand end of the lever 55 until an equilibrium position is reached. A counter 75a attached to the pump indicates the total flow. The position of the knife edge may be varied.