GB719191A - - Google Patents

Abstract

719,191. Protractors. GREY, V. H. Jan. 29, 1953, No. 2544/53. Class 97(3) A protractor has a base 1 on which is rotatable a plate 3 which may be clamped in adjusted position by a locking nut 9. A blade 4 is arranged for angular movement with the plate 3 and for movement tangential thereto, this blade having a groove 14 engaged by a projection 13 from a locking member 12 which seats in a recess 11 in an arm 6 attached to the plate 3. The groove 14 and recess 11 allow the locking member a limited radial movement. A screw shank 15 on the locking member passes through a conical bore 16 in the arm 6 and carries a nut 17 having a conical part 18. Thus, by tightening the nut 17, the conical part 18 co-operates with the conical bore 16 to clamp the locking member 12 and thereby the blade 4 to the plate. Nut 17 may be replaced by a screw which threads into the arm 6 and has a conical end co-operating with a conical bore in the locking member 12. In a further form, the arm 6 is omitted and the locking member extends over the plate 3 and is constrained by radial guides, and conically ended screw engages a threaded bore in the locking member with its conical end cooperating with a conical bore in the plate 3. Specification 563,819 is referred to.