| 摘要 |
597,491. Filtering apparatus. PISTA SOC. AXON. Aug. 21, 1945, No. 21387. Convention date, April 26. [Class 46] Filtering apparatus comprises at least one container with a filtering sand layer supported on a pervious fioor, the layer being cleansed by compressed air and filtered liquid flowing back into the container, and the washing liquid being removed by a siphon connected to vacuum, the filtered liquid beneath the pervious floor being always at a pressure greater than that corresponding to the minimum level of liquid allowed above the floor. As shown, containers 100, 101 are each provided with a sand filter 2 on a pervious floor 4 carrying strainer nozzles 103. The filtered liquid flows through a pipe 17 to a basin 104 provided with an overflow. A siphon 29 dips at one end into a trough 107 and at the other end leads to a discharge basin 35. The top of each container is provided with a contactor 33 controlled by a float, so that when, for example, the filter in container 101 is clogged and the liquid rises sufficiently high, the contactor acts to open two electrically controlled valves 110 and 111. The valve 100 opens to connect the siphon 29 to a vacuum pump, and the valve 111 opens to connect a source of compressed air to a pipe 25. The pressure of air in the pipe 25 just balances the pressure due to liquid at a level 22. The water is drawn off by the siphon and eventually below the level 22, whereupon compressed air from the pipe 25 and filtered liquid from the pipe 17 flow through the sand filters and cleanse it. At the same time a float 113 acts to close a valve 112 and stop supply of said water to the containers. The cleansing operation is limited by a timing device, so that after a time the siphon ceases to operate. The liquid in the container 101 again rises to the level 22 whereupon the float 113 opens the valve 112 and admits raw water to the container. Specification 578,811 is referred to. |
