Switch assembly for electric hand-tool, e.g. drill - controls speed with reference to direction of rotation using cut-out switch

摘要

The switch assembly is housed in a plastic housing. It has two operator controls: a speed control potentiometer and a rotation direction control. The maximum speed in the reverse direction is limited to a fraction of the maximum speed in the forward direction, by means of a mechanically operated cutout switch. If reverse direction has been selected, the supply to the motor is disconnected automatically if a speed higher than the maximum level is 'dialled' on the rotary speed control. The limiting device can be over-ridden for short periods by pressing a second knob.