Title: Screen changer with pre-fill screen blocks

Abstract: A screen changer mounted between a flowable plastic extruder and a die has a clamp frame movable rectilinearly across the extrusion passage by fluid piston and cylinder means to successively position one of four screen blocks across the passage. A used block is removable from the frame at one end, whereupon latch mechanism retains three blocks while the frame retracts to receive a fresh block. Each block contains a filter recess, a purge recess and a pre-fill groove in the upstream face, so that the incoming block is pre-filled with plastic and purged while moving into position across the passage.

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Inventors: Mladota, John (Lausanne, CH)

Application Number: 619795
Filing Date: 1975-10-06
Publication_date: 1977-05-24
Assignee: Bolton-Emerson, Inc. (Lawrence, MA)
Primary Class(es): 210/236 210/447, 210/455, 425/197
Other Classes:
US Patent Ref:

2786504	Mar, 1957	Samler	210/236.
3455357	Jul, 1969	Zink	425/153.
3653419	Apr, 1972	Schutter	425/183.
3804758	Apr, 1974	Cooper et al.	210/65.
3856680	Dec, 1974	Elmore	210/236.
3900399	Aug, 1975	Kreyenborg et al.	210/236.

Other Refs:
Primary Examiner: Hart, Charles N.
Assistant Examiner: Burks, Richard W.
Attorney: Pearson & Pearson