Electricity: motive power systems – Braking – Automatic and/or with time-delay means
Patent
1981-10-23
1985-03-12
Weldon, Ulysses
Electricity: motive power systems
Braking
Automatic and/or with time-delay means
310 95, 318325, 318326, 361 51, H02P 512
Patent
active
045047693
ABSTRACT:
In an electrically-powered tool, the driving motor of the tool and a switching element for a phase control circuit for controlling the number of revolutions of the motor are connected in series. The switching element is fixed to a field core of the motor. In the phase control circuit for the switching element, a bias resistance between the base and the emitter of a pulse phase controlling transistor for changing the amplification degree by the output from a pulse generating circuit for generating pulses having frequencies corresponding to the numbers of revolutions of said motor is connected in parallel with a capacitor for effectively slowly starting said motor, a first amplifier for changing the output in response to the number of revolutions of said motor and for stabilizing the rotation of said motor, and a second amplifier for producing output upon falling of the number of revolutions of said motor below the preset number of revolution and for limiting overload current. A governor like brake shoe is fixed to an armature shaft of the driving motor in the electrically-powered tool. A ring is mounted to the fixed portion of the motor, being contacted with the brake shoe deformed in the direction of centrifugal force caused by the high-speed rotation of the armature shaft under no load condition of the motor, and adapted to apply a brake force to the armature shaft.
REFERENCES:
patent: 1900589 (1933-03-01), Seeley
patent: 2416122 (1947-02-01), Shaffer
patent: 2794163 (1957-05-01), Hall et al.
patent: 3250929 (1966-05-01), Maier
patent: 3523234 (1970-08-01), Turtle
patent: 3538412 (1970-11-01), Graf et al.
patent: 3564372 (1971-02-01), Vogelsberg et al.
patent: 3584248 (1971-06-01), Higashino et al.
patent: 3950626 (1976-04-01), Greenhut
patent: 4317176 (1982-02-01), Saar et al.
Fushiya Fusao
Iwatuki Takao
Makita Electric Works Ltd.
Weldon Ulysses
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