US Patent 8430180 Control mechanism for a power tool

A speed adjustment mechanism for a power tool is disclosed. The mechanism includes a support, a first toothed gear for rotation by means of an adjustment dial, and a second toothed gear rotatable by means of the first toothed gear and connected to a potentiometer which is connected to a speed control circuit. Limited movement of the first and second toothed gears relative to each other is possible to reduce transmission of impacts from the adjustment dial to the speed control circuit.