Patent GB-672893-A (GB)
Title: Improvements in or relating to apparatus for measuring or controlling the rate of flow of a fluid
IPC: G05D7/06
Filed: 1949-01-24
Abstract: 672,893. Electric indicating systems. LINDARS, H. Jan. 24, 1950. [Jan. 24, 1949] No. 1938/49. Class 40 (i). [Also in Group XXXV] The rate of flow of a fluid is determined by measuring the volumetric flow for repeated short equal time intervals. A volumetric meter drives a member intermittently for a predetermined time from a zero position, the member at the end of each time interval causing a controlled device to 'move to a corresponding position indicative of the fluid flow after which the member is zeroized ready for the next cycle. The fluid flow may also be maintained automatically at a preset value. As shown, Fig. 1, the volumetric meter 1 drives through a shaft 3 the sun wheel 8 of a differential gear 7. The second sun wheel 9 is carried by a shaft 10 normally held in a zero position by a biassing spring 21 which holds a radial. arm 11 on the shaft 10 against a fixed stop 22, so that normally the planet carrier 15 idles. A timer 6 comprises a synchronous motor 35 .driving a cam 36 which at the beginning of each predetermined interval closes contacts 38 to energize a relay A which locks at contacts A1 and at A2 de-energizes the normally energized brake magnet 18 to lock the planet carrier 15 whereupon the meter 1 advances the sun wheel 9 from its zero position against the tension of the spring 21. At the end of the interval cam operated contacts 37, in the timer are closed to energize a relay B which trips A. Relay B trips the normally energized brake magnet 40 to lock the sun wheel 9 and at the same time closes a circuit over the radial arm 11 and one or other of the segments of a follow-up switch mounted on a disc 4, to energize a relay C or D. The operative relay C, D stops the timer motor at C2 or D2 and energizes the corresponding vibratory type step-by-step motor 27 or 28 which through a differential gear 25 and gearing 26 drives the follow-up disc 4 into correspondence with the position of the radial arm 11, when the operative relay C, D is de-energized, the timer motor restarts, relay B falls off and the brake magnet 40 then energizes to release the sun wheel 9 which is zeroized by the spring 21 ready for the next cycle.of operations, which starts with the closure of contacts 38 as indicated above. A potentiometer 31 operating a voltmeter 5 is driven from the shaft 24 of the follow-up disc 4, and, provided the operational cycle is sufficiently short, the voltmeter will indicate the fluid flow. In a modification, Fig. 2, the shaft 10 and radial arm 111 are also movable axially under the control of the normally de-energized magnets 118, 140. Relay A is energized as before at the beginning of each timing period but in this case energizes the clutch magnet 118 which through the pivoted lever 48 moves the shaft 10 downwardly whereupon the friction disc 45 at the bottom of a pillar 46 carried by the radial arm 111 is engaged by the driving disc 44 of the meter 1 to drive the arm 3. Relay B operates as before at the end of the timing period, and energizes the clutch magnet 140 as 118 de-energizes, whereupon the shaft 10 moves axially upwards and is locked by a fixed friction disc 54 in the position to which it has been driven. The follow-up disc switch 112 is now driven by a reversible motor 42 under the control of the relays C, D, and actuates the fluid flow indicator 5 as before, the shaft 10 being zeroized at the end of each timing period by the biasing spring 21. In another modification, Fig. 3 (not shown), the shaft carrying the radial arm 11 is movable axially under the control of the magnets 118, 140 in a manner analogous to that of Fig. 2, but is zeroized by a magnet acting on the shaft through a rack and pinion arrangement. In a further modification, Fig. 4 (not shown), the two magnets for clutching the shaft 10 respectively to the meter 1 and to the fixed clutch plate are pivotally mounted on a sleeve rigid with the shaft 10, the pivotal movement of the second magnet to lock the shaft 10 also rocking the radial arm 11 axially to engage the follow up switch elements on the disc 4. In another embodiment, Fig. 7, for remote control of the fluid flow through the volumetric meter 1 a potentiometer 92 is set in accordance w)th the desired rate of now. The potentiometer forms with resistors 94, 96 and the potentiometer 131 an automatically balanced bridge. As before, the rate of fluid flow is measured by the volumetric meter 1 and associated apparatus which sets the potentiometer 131 in accordance with the rate of flow under the control of the reversible motor 42. Should this rate disagree with the setting of the control potentiometer 92, owing, e.g., to a fresh setting thereof, the bridge unbalance current operates a polarised relay 95 in the appropriate sense so that during each cycle of the timer 6 when contacts 91 are closed bv the cam 89 a reversible, motor 88 is energized in the appropriate sense to adjust the valve 87 controlling the fluid flow, the adjustment being effected by a series of inching movements during successive cycles of the timer 6. Duplicate follow up switches may be provided so that one may be effecting a control or indicating operation whilst the other is being moved during the measuring operation. The frictional brake elements described may be replaced by electromagnetically operated clutches.