GB496573A - Improvements relating to draughting machines - Google Patents

Abstract

496,573. Draughting-machines. NAYLOR, J. W., and HALDEN & CO., Ltd., J. March 4, 1937, No. 6397. [Class 97 (iii)] The initial rotation of a knob 33a de-clutches a rotatable carrier 23 for a straight edge 44 from a non-rotating head 10 which is connected by parallel movement linkage to the edge of the drawing board, and subsequent rotation causes the carrier 23 to move with the knob to the desired new setting. As shown a dial plate 18 carrying a notched ring 21 has a central upstanding cone 17 which is adjustably clamped on the coned base 12 of a boss 11 on the head 10 by the coned lower end of a clamping sleeve 26. Operation of the latter is effected through a bush 27 by a pin 28 in threaded engagement with the boss 11. A sleeve 30 fixed to the knob 33a is mounted by ball bearings 25 on the clamping sleeve 26 and is surrounded by an upstanding sleeve 24 on the carrier 23. Three tongues 34 projecting from the bottom of the sleeve 30 have outer cam faces 36, 37, adapted to co-operate with the cam faces 43 of shoulders 41 on three clutch members 38. The latter are mounted to slide radially in the carrier 23, are urged towards the centre by springs 40, and each carry two teeth 42 to engage the notches in the ring 21. In operation rotation of the knob 33a first causes the cam faces 37 to engage the tapered ends of the shoulders 41 and move the clutch members 38 radially outwards, thus withdrawing the teeth 42 from the notches in the ring 21. Upon further rotation of the knob 33a the cam faces 36 engage the flat central portions 43 of the shoulders 41 and couple the sleeve 30 to the carrier 23. If the movement of the carrier 23 is obstructed the tongues 34 move the clutch members out further causing them to bind against the upstanding flange of the dial plate 18. The straight edges 44 are fixed to a plate 45 which is adjustably anchored to the carrier 23 by a threaded tie bar.