Electronic clutch for electric tools of selectable speed

Details Electronic clutch for electric tools of selectable speed Electronic clutch for electric tools of selectable speed

1983-10-13

1985-03-05

Weldon, Ulysses

Electricity: motive power systems

Braking

Automatic and/or with time-delay means

318345D, 318345H, G05B 500

Patent

active

045033706

ABSTRACT:
An electronic clutch for a multispeed electric tool includes a voltage sensor having a D.C. voltage output proportional to the current absorbed by the tool's motor and dependent on the motor operating temperature. A comparator compares this D.C. voltage with a suitably generated reference voltage, and if the former exceeds the latter it blocks the oscillation of an oscillator which via a power circuit controls a triac provided in the motor power supply circuit. Blocking the oscillator causes the deactivation of the triac, and thus stops the motor. The proportionality constant of the D.C. voltage, or that of the reference voltage, can be varied as a function of the tool operating speed. For this purpose, the voltage sensor or, respectively, the reference voltage generator includes a voltage divider in which resistors are provided which can be cut in or out by means of electric contacts controlled by the tool's speed change mechanism.

REFERENCES:
patent: 3953776 (1976-04-01), Wolf
patent: 4064443 (1977-12-01), Yamada et al.
patent: 4241299 (1980-12-01), Bertone
patent: 4291259 (1981-09-01), Marumoto et al.
patent: 4322667 (1982-03-01), Ohba
patent: 4384241 (1983-05-01), Stillhard
patent: 4413213 (1983-11-01), Banmagarten

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