Variable resistance switch

Details Variable resistance switch Variable resistance switch

1987-08-06

1988-09-13

Goldberg, E. A.

Electrical resistors

Mechanically variable

Movable contact electrically adjustable over length of...

338306, 338314, H01C 1038

Patent

active

047712635

ABSTRACT:
The variable resistance speed control switch for a power tool has a wiper which slides over a resistor which has a non-linear resistance curve matched to the motor. The resistor is made by thick film technology and has a ceramic substrate covered by 950.degree. C. glass and fired to give the substate a glass smooth surface. Then a 100K ohm ink is applied in a pattern designed to give a non-linear resistance curve tailored to the performance of the motor. A resistive termination is provided to diffuse the power concentation under the stationary contact. A 1 meg ohm ink covers the 100K layer and part of the terminaton. The 1 meg ink contains a lot a glass which fuses and flows out when fired. The 1 meg ink will flow out to the same glass smooth condition as the glass bottom layer. The wipers are not subject to much abrasion or wear.

REFERENCES:
patent: 4495524 (1985-01-01), Kakuhashi et al.
patent: 4680570 (1987-07-01), Hehl

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