| 摘要 |
A sifting screen is described comprising a rigid frame, a first woven cloth (10,14) of hard wearing metal wire, stretched thereacross and secured thereto, and a second woven cloth (12,16) having a coarser mesh than the first cloth (10,14) 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 (10,14), to support the latter against sagging. In accordance with the invention, the frame may be formed from heavy guage steel or more preferably glass reinforced gas blown polypropylene reinforced by elongate metal reinforcing elements or rods. |
