| 摘要 |
PCT No. PCT/GB90/01274 Sec. 371 Date May 21, 1991 Sec. 102(e) Date May 21, 1991 PCT Filed Aug. 14, 1990 PCT Pub. No. WO91/02578 PCT Pub. Date Mar. 7, 1991.A filter element generally indicated at 10 comprising a spring 11 whose coils are so formed that the filter gaps 12 progressively increase in size from one end 13 of the coil to the other end 14. The increase in the size of the gaps is carefully chosen so that the available deflection for any coil section, when the spring is vertically orientated, is sufficient to develop an upward force which can support the coils in the spring 11 which extend above that particular coil section. Similar results can be achieved by varying the resilience or stiffness characteristics through the filter element. |
