Electronic run=up speed limitation esp. for drill - introducing brief delay with low-speed drive for centring purposes in prepn. for full-speed drilling

摘要

The motor (M) of an electric drill is supplied with current from two speed control circuits (1,2). One circuit (1) is operative immediately to run-up the motor for a drilling speed. of only a few rev/min during a delay (TV) of a few seconds until the other circuit (2) is actiavated. This allows the drill bit to be centred precisely for a preliminary drilling before the main hole is drilled at normal speed. ADVANTAGE - Easily mass-produced device reduces risk of tearing and blockage, and allows accurate centring for all kinds of holes.