| 摘要 |
767,931. Extruding; making screw conveyers. BITUMEX, Ltd. April 24, 1952 [April 27, 1951], No. 9920/51. Classes 83 (2) and 83 (4). [Also in Groups V and XXX] An extruding-screw has a thread or threads A of constant pitch, the depth D of each thread groove diminishing progressively along its length and the width W of its crest surfaces progressively increasing as the depth decreases. The crest surfaces lie on an imaginary cylindrical surface. Such a screw may be made by taking a conical screw blank, Fig. 2 (B indicating the cone angle), cutting on it a thread of constant pitch and constant depth, and machining it to cylindrical form. Specification 685,043, [Group V], is referred to.
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