Eaton Corporation

Milwaukee Electric Tool Corporation

Michael E Bauer

Earl T Piber

James E Hansen

Peter K Moldovan

William J Janutka

Dale Louis Gass

Glenn H Simonsen

Michael A Urbassik

Kurt D Matschull

Brad L Myers

Stephen R Fiacchino

A control circuit drives the coil of a contactor in response to a control voltage being applied. The control circuit includes a power supply that produces a regulated output voltage from the control voltage. The onset of the regulated output voltage starts a timer which controls the width of pulses produced by a PWM controller. The pulses control a transistor that applies the control voltage to the coil. Initially the pulses cause a high current to flow through the coil to close the contactor and after an interval of time the timer signals the PWM controller to shorten the pulses which applies lesser current to the coil to keep the contacts closed. A flyback circuit provides a relatively low reverse voltage drop path in parallel with the coil to maintain the electromagnetic field during the periods between the pulses. When the control voltage is removed to open the contactor, the flyback circuit provides a high reverse voltage drop path to promptly dampen the coil current.

Circuit for controlling application of electricity to a coil of and

A control circuit for an overhead crane motor includes a low supply voltage monitor to disconnect the motor from the control circuit and ensure brakes engage in the event of interruption of power supplied to the crane. A sensor circuit detects whether voltage supplied to the control circuit drops below a predefined threshold level which is greater than a voltage magnitude produced by the motorN operating in a regenerative mode during a power interruption. A switching circuit responds to sensing supply voltage below the threshold level by disconnecting electrical current to a relay coil which causes contacts to open which result in the motor being electrically disconnected from the control circuit. As a result of that disconnection, voltage produced by the motor operating in a regenerative mode does not inhibit electrically controlled mechanical brakes from engaging.

Motor control circuit with a low voltage monitor

A sealed contactor for switching electric current has a switching assembly that includes a movable contact which selectively bridges a pair of stationary contacts to provide an electrical path therebetween. The moveable and stationary contacts are mounted to a body of electrically insulating material to form a unitized structure. A separate actuator assembly has an enclosure which contains an electrically operated driver with a linkage that extends into the switching assembly to alternately operate the moveable contact into engagement with and disengagement from the stationary contacts. The switching assembly is sealingly attached to the actuator assembly in an interlocking manner that prevents arcs produced between the contacts from escaping outside the electric current switching apparatus. Nevertheless, the switching assembly is capable of being easily removed and replaced as a single unit from the actuator assembly when repairing the contactor.

Electric current switching apparatus with unitized removable contacts

An electric tool including a variable speed switch assembly including a potentiometer having a central rotatable member defining a bore with a noncircular cross section and a molded plastic speed control wheel housing the potentiometer. The speed control wheel includes a central post with a cross section corresponding to the cross section of the central potentiometer bore such that the central post can be housed in the central bore in only one relative position with respect to the central rotatable member. The variable speed switch assembly also includes a switch cover having projections which snap into designated holes provided in a circuit board such that the switch cover and the circuit cannot be incorrectly assembled. The switch cover includes a stop member that extends into a semi-circular recess in the speed control wheel to provide mechanical stops so that rotational movement of the speed control wheel corresponds with the range of the potentiometer. The variable speed switch assembly also incorporates a detent arrangement integrated into the switch cover and the speed control wheel and including a resilient finger, the end of which is received in a series of detent grooves in the speed control wheel to maintain the speed control wheel in a desired angular position corresponding to a desired speed setting.

Dial speed control for hand-held power tool

Growing community of inventors

Hartland, WI, United States of America

Michael E Bauer