Linear induction control system

Claim 1

For a transportation system of the type having movable structures adapted to follow a guideway, a plurality of linear induction primary elements fixedly mounted in the guideway, mutually spaced along the guideway, and having respective first and second end portions directioned in first and second directions, respectively, along the guideway, and elongated, linear induction secondary structures connected, respectively, to each of the movable structures, a control system comprising: a plurality of sensing means, each corresponding to a respective primary element and each comprising means operable for detecting the proximity of one of the secondary structures to the respective primary element; and control means, operatively associated with the proximity sensing means, for conducting multi-phase electrical power to any of the primary elements when any portion of one of the secondary structures lies within a region approximately bounded by first and second, parallel planes perpendicular to the guideway and extending through the first and second end portions, respectively, of a respective primary element, for urging the respective secondary structure in the first direction, the control means further including time responsive Switching means, operable in response to detection by any respective one of the sensing means of the proximity of one of the secondary structures, for preventing operation of at least one primary element spaced a predetermined distance in the second direction along the guideway from the respective sensing means during a preselected time period following detection by the respective sensing means of the proximity of a respective secondary structure.