Soft start AC tool handle trigger switch circuit

Details Soft start AC tool handle trigger switch circuit Soft start AC tool handle trigger switch circuit

1992-06-29

1994-03-15

Pellinen, A. D.

Electrical transmission or interconnection systems

Switching systems

Condition responsive

307125, 323324, 363 49, H01H 4722

Patent

active

052948390

ABSTRACT:
A soft start tool handle trigger switch circuit (10) applies voltage from an AC source (12) to a portable tool electric motor (10). A current limiter (30) is connected in series between the AC source (12) and motor (14). A first sub-circuit (32) is connected in parallel with the motor (14) and includes actuator circuitry (34) tripping an actuator solenoid (36). A second sub-circuit (40) is connected in parallel with the current limiter (30) and has a pair of contacts (44, 46) actuated from an open condition to a closed condition upon movement of an actuator plunger (38). An NTC thermistor (48) is connected in series with the actuator circuitry and is physically proximate and heated by heat from the current limiter (30) to reduce the resistance of the NTC thermistor (48) and supply increased current to the actuator circuit (34) for earlier closing of the bypass sub-circuit (40), to stop the current-induced heating of the current limiter (30). Positive kick-off opening of the bypass contacts (44, 46) is provided upon release of the user finger engaged trigger (28) as the latter moves from its depressed to its extended position. Voltage sensitive (34) and time sensitive (70) circuitry is provided.

REFERENCES:
patent: 4008416 (1977-02-01), Nakasone
patent: 4271460 (1981-06-01), Baker
patent: 4405975 (1983-09-01), Overstreet et al.
patent: 4555741 (1985-11-01), Masaki
patent: 4668908 (1987-05-01), Aoki et al.
patent: 4686616 (1987-08-01), Williamson
patent: 4716511 (1987-11-01), Masaki
patent: 4719553 (1988-01-01), Hinckley
patent: 4855649 (1989-08-01), Masaki
patent: 4928218 (1990-05-01), Kluttz
patent: 4992718 (1991-02-01), Kumaki

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