Electricity: motor control systems – Open loop speed control system for dc motor with commutator – Analog armature control
Patent
1994-04-25
1996-06-11
Ro, Bentsu
Electricity: motor control systems
Open loop speed control system for dc motor with commutator
Analog armature control
318257, 318268, H02P 729
Patent
active
055264603
ABSTRACT:
An impact wrench having a speed limiting control circuit to allow an operator of the wrench to controllably limit the maximum speed of the wrench to a predetermined value when a trigger thereof is fully engaged. The impact wrench includes a manually adjustable speed limiting control protruding from an outer surface of the impact wrench 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 wrench. The speed limiting potentiometer limits the maximum speed of the motor of the impact wrench (and thus the maximum torque which can be generated by the impact wrench 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.
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Copy of Abstract for JP 4 208 097; published 29 Jul. 1992 (Appln. No. JP 900 339 031, Appln. date 30 Nov. 1990).
DeFrancesco Angelo J.
Elligson Daniel M.
Kunz Michael P.
Black & Decker Inc.
Ro Bentsu
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