Lock for head of draughting machine - has rigidly held locking plate with detent notches spaced radially along circumference

摘要

The drawing head of a draughting machine has a locking plate held rigid against turning on the drawing head, which has a number of locking notches offset against each other at pre-set angular distances along the outer edge of the plate. A spring tensioned locking lever has a swivel linkage, with the scale rulers mounted on a rotatable section and a centring projection in the form of the locking notches. Stops on either side of each locking notch(16) are located radially outside, with hard non-wearing surfaces against which an attachment of the centring projection of the locking lever hits before the centring projection makes soft contact with the fine locking notch.