Pivoting rotor ratchet mechanism for worm gear potentiometer

In a variable resistor, of the type having a housing, a rotor rotatable in said housing and bearing an electrical contact spring in contact with a resistive element, spur gear means on a peripheral edge of said rotor, and worm gear means in said housing for engagement with said spur gear means to drive said rotor between first and second limits of travel, a ratcheting mechanism comprising:

• first means for (a) limiting the further rotation of said rotor substantially beyond said first limit of travel, and (b) pivotally lifting said rotor against the force of said contact spring, while (c) allowing a momentary disengagement of said spur gear means from said worm gear means;
• second means for substantially stopping said rotor from further rotation beyond said second limit of travel;
• and
• third means, operable with said worm gear means when said rotor reaches said second limit of travel, for (a) pivotally lifting said rotor over said worm gear means against the force of said contact spring, while (b) allowing a momentary disengagement of said spur gear means from said worm gear means;
• whereby said contact spring is compressed by the pivoting of said rotor at said first and second limits of travel, and said spring is released by the disengagement of said spur gear means from said worm gear means, thereby to urge said rotor into a position in which said spur gear means re-engages said worm gear means.

In a variable resistor, of the type having a housing, a rotor rotatable in said housing, an electrical contact spring carried on a first side of said rotor so as to be in contact with a resistive element, spur gear means around less than the entire peripheral edge of said rotor, and worm gear means in said housing for engagement with said spur gear means to drive said rotor between first and second limits of travel, a ratcheting mechanism comprising:

• a first stopping element on a second side of said rotor opposed to said first side and joined therewith by said peripheral edge, said second side of said rotor being adjacent an interior surface of said housing;
• a second stopping element on said interior surface of said housing and having first and second radially-extending surfaces, said first radially-extending surface having an inclined area abuttable by said first stopping means when said rotor reaches said first limit of travel, thereby to pivotally lift said rotor, and said second radially-extending surface being abuttable by said first stopping means when said rotor has reached said second limit of travel, said second radially-extending surface being configured to prevent said rotor from rotation substantially beyond said second limit of travel;
• and
• an axially-shortened spur gear tooth extending only partway across said peripheral edge of said rotor from said first surface thereof, and located on said rotor so as to be engageable with said worm gear means when said rotor has reached said second limit of travel, thereby to pivotally lift said rotor.