| 摘要 |
1287076 Screening device COSHAM ENG & DESIGN Ltd 8 April 1971 9115/71 Heading B1D [Also in Divisions B4 and B5] A screening device which is arranged upstream of a plastics extrusion head comprises a body 10 with a through passage 12 intersected by a transverse passage 14, individual screen blocks 18 being slidable through passage 14 to position one block across passage 12, through which the plastics flows, channels 34 and 36 enabling a clean block adjacent passage 12 to be filled with plastics from the upstream end of passage 12 before ram 20 is used to force a third block 18 into passage 14 and thereby push a clogged block out of passage 12 and replace it by said clean block. Passage 14 accommodates three blocks, the centre one across passage 12, and when a fourth block is forced in the lowermost block is forced out. Channel 34 is controlled by a valve 38, 40. In Fig. 2 valve 38 is manually operated and ram 20 actuated by an operator observing an excess upstream pressure registered by means 42, but the valve and ram could be controlled automatically by a pressure switch and timer. Each block 18 comprises an array of through holes 18a and an upstream recess accommodating one or more filter gauzes. Passage 14 is lined by replaceable bearing plates 16, and heater plates 32 engage the outside of the body 10. |
