| 摘要 |
1,245,097. Mixing liquids in proportionate quantities. C. B. COLEMAN. 27 Aug., 1968 [28 Aug., 1967], No. 40936/68. Heading B1C. Liquids are supplied in proportionate quantities by means of metering pumps 30, 32 to a reservoir 16 to form a mixture having a desired ratio of liquids, the ratio being maintained constant by synchronising the pumps, and the rate of supply of the mixture being, at any time, proportional to the difference between a predetermined pressure and the pressure within the reservoir at that time. The metering pumps are provided with control units 40, 42 comprising pneumatically operated double-acting pistons 44, 70 connected to the pistons 47 (only one shown) of the metering pumps. In use, the pressure of compressed air acting on control pistons 44, 70 is set to a value which balances the back pressure of mixture acting on the metering pump pistons 47 when the reservoir is full. When mixture is withdrawn from the reservoir, there is a resultant drop in back pressure acting on pistons 47, which causes the control pistons to be actuated by the compressed air at higher pressure, and consequently causes the metering pumps to start operating. Pump Synchronisation. The metering pumps 30, 32 are synchronised using a conventional air selector unit 80, in association with appropriate control valves 90, 92, 94, 96, to reverse the direction of travel of both control pistons according to the position of control piston 44, and a restrictor 106, which, by reducing the rate at which air is supplied to control piston 44, causes it to follow control piston 70 and ensures that reversal of direction of travel of piston 70 cannot occur until piston 44 has completed its stroke. Ratio Adjustment. The ratio of liquids supplied to the mixture may be adjusted by adjusting the length of stroke of piston 70 by means of bolt and nut assembly 110, 116. Mixing Apparatus. A rotatable and/or reciprocatable agitator having arms 24 and a hollow stem 22 through which one of the liquids to be mixed is distributed may be mounted in reservoir 16. Regulating Discharge of Mixture. The mixture in reservoir 16 may be discharged to a storage tank via a valve controlled by a float-actuated switch associated with the tank, fall of level in the tank actuating the valve to cause mixture to flow from the reservoir 16 into the tank. Alternatively, the float-actuated switch may be arranged to actuate the metering pumps by causing compressed air to be supplied to the control pistons. In an alternative arrangement, Fig. 26 (not shown), a valve in a pipe leading from reservoir 16 to a point of usage is controlled by a differential pressure switch, which is actuated on detection of a pressure drop across an orifice plate in the pipe indicating consumption of the mixture downstream thereof. Alternatively, the differential pressure switch may be arranged to actuate the metering pumps by causing compressed air to be supplied to the control pistons. |
