IMPACT TOOL HAVING SPEED CONTROL CIRCUIT

摘要

An impact tool having a speed limiting control circuit to allow an operator of the tool to controllably limit the maximum speed of the tool to a predetermined value when a trigger thereof is fully engaged. The impact tool includes a manually adjustable speed limiting control protruding from an outer surface of the impact tool which is conveniently manually adjustable. The speed limiting control is coupled to the wiper arm of a speed limiting potentiometer which is electrically coupled to a speed control circuit within the impact tool. The speed limiting potentiometer limits the maximum speed of the motor of the impact tool (and thus the maximum torque which can be generated by the impact tool 10) to an operator selected percentage of the maximum motor speed which would otherwise be produced when the trigger is fully engaged. In the preferred embodiment the speed limiting potentiometer is electrically coupled in series between a capacitor and speed control potentiometer, which are each coupled to a 555 CMOS timer which controls the duty cycle of an FET used to drive the motor. The speed limiting potentiometer enables the operator to further limit the maximum duty cycle of the output of the timer, which is a pulse-width-modulated like output, to a percentage of that which would otherwise be produced when the trigger is fully engaged.