Electric power machine with protection against overspeed

Details Electric power machine with protection against overspeed Electric power machine with protection against overspeed

1984-05-14

1985-05-07

Budd, Mark O.

Electrical generator or motor structure

Dynamoelectric

Rotary

200 80R, H02K 1100

Patent

active

045160457

ABSTRACT:
An electric power machine, particularly an angle grinding tool is provided with a centrifugal overspeed protecting device including a fly weight in the form of a severing blade which interrupts a power supply conduit when the rotary speed of the machine is excessive. The protective device includes a cylindrical housing attached face to face to the shaft of the electric motor. The severing blade is in the form of a quadrangular frame defining a center opening. The cylindrical housing is provided with a diametric through bore of a rectangular cross-section matching the frame-like severing blade. A blind bore of a circular cross-section is coaxially superposed on the rectangular through bore and its upper part is formed with inner thread for receiving a setting screw. A helical tensioning spring is inserted in the center opening of the frame-like severing blade and rests on the bottom of the blind bore to urge the centrifugal severing blade against the setting screw. When the rotary speed of the shaft and thus of the housing exceeds a predetermined value the severing blade is displaced by centrifugal force out of the rectangular through bore and severs a conduit in the power supply circuit for the motor whereby the compressed biasing spring acts as a buffer. The setting screw adjusts the distance on the center of gravity of the severing blade from the axis of rotation of the motor shaft and thus determines the value of the limit rotary speed.

REFERENCES:
patent: 1075987 (1913-10-01), McMahon
patent: 3790730 (1974-02-01), Wyland
patent: 4205245 (1980-05-01), Hildebrandt et al.
patent: 4423346 (1983-12-01), Nakazawa

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