专利名称：Screw
发明人：BRADSHAW GRANVILLE 申请号：US24383438
申请日：19381203
公开号：US2244046A
公开日：
19410603
专利内容由知识产权出版社提供
摘要：511,033. Screwdrivers; screws. BRADSHAW, G. Dec. 7, 1937, No. 33785. [Class
truncated form
61(iii)] [Also in Groups XXII and XXV] A screw 1 which can be inserted or removed only by a suitably formed tool has an axial recess comprising a plain cylindrical or slightly tapered bore 3 extending into the shank and outwardly into a flared conical portion 2 of a diameter at its open end at least equal to that of the screw shank at its junction with the head 4, the driving tool 6 having a nose or shank 7 formed with a continuous or interrupted hardened screw cutting thread 9 to engage the bore 3 in the screw and with a flange 8 having a toothed &c. clutch surface 10 of truncated conical form to engage the flared portion 2 of the screw. In the modification shown in Fig. 2 the centre bore and flared recess of the screw 13 are merged into one curved recess 15, the tool 16, Fig. 5, for use with this screw having a screw cutting thread 19 extending continuously from the nose 17 to the base part 18. The recesses in the screw heads may be closed by plugs as described in Specification 501,548.
申请人：THE BRADSHAW PATENT SCREW COMPANY (FOREIGN) LIMITED
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