GB535698A - Mechanism or apparatus for producing a step-by-step motion - Google Patents

Abstract

535,698. Drawing-apparatus; step-by-step mechanism. EVANS, W. J. Oct. 13, 1939, No. 27809. [Class 97 (iii)] [Also in Group XXIV] A mechanism for producing a step-by-step motion (for example for traversing a straightedge over a drawing board) comprises a screw 10 driven intermittently under the operator's control by a motor 11 so as to advance a half-nut 12 thereon, a spring 15 for returning the nut after each advance, a clutch 22 for connecting the half-nut to an axially-movable rod 14 (which moves the straight-edge) and control means whereby, after a pre-determined traverse of the axiallymovable rod, the nut and rod are liberated in order to allow the nut to be returned by its spring in readiness for a further step-like advance. In use, the operator closes a starting switch, thereby causing a solenoid 30 (operating through connections 41, 42, 20) to raise a shaft 18 and cause the clutch 22 to grip the axially-movable rod 14, at the same time placing the half-nut 12 in engagement with the screw 10 and starting-up or coupling-up the motor 11. The half-nut is thus advanced along the screw carrying with it the rod 14. At the end of the traverse a limit contact 33<SP>11</SP> on the half-nut engages a limit contact stop 33 and re-arranges the circuit causing disconnection of the half-nut 12 and the clutch 22 to permit the half-nut to be returned by its spring 15, the parts then being in position for a further step when the operator again closes the starting switch. The stop 33 is adjustable by a micrometer mechanism 34 to vary the extent of the traverse. The return movement of the half-nut is arrested by contact with one of three stops 32a, 32b, 32c any one of which may be brought into operative position by rotation of a knob 37. The stops are of different lengths to provide for different extents of traverse of the nut. Specification 485,146 is referred to.