| 摘要 |
PCT No. PCT/GB95/00411 Sec. 371 Date Aug. 29, 1995 Sec. 102(e) Date Aug. 29, 1995 PCT Filed Feb. 28, 1995 PCT Pub. No. WO95/23655 PCT Pub. Date Sep. 8, 1995A sifting screen having a rigid frame, a first woven cloth of hard wearing metal wire, stretched thereacross and secured thereto, and a second woven cloth having a coarser mesh than the first cloth and being woven from an elongate material of greater cross-section than the first, also stretched across the frame, and secured thereto, below the first cloth, to support the latter against sagging. In accordance with the invention, at least the wearing surface of the material from which the lower cloth is woven is selected to be significantly less hard wearing than that from which the upper cloth is woven, so that wear due to rubbing and vibration during use, occurs to a greater extent in the lower cloth than in the upper cloth. In one example the upper cloth is woven from stainless steel wire and the lower from phosphor bronze wire. In another example the lower cloth is of wire having a coating of an epoxy based material, or TEFLON TM , or Molybdenum Disulphide. In another example the lower cloth is formed from a plastics material or KEVLAR TM or carbon fiber. The frame may be formed from glass reinforced gas blown polypropylene reinforced by elongate metal reinforcing elements or rods.
|
