Jack mechanism having safety protection for workers

摘要

A high/low screw jack stand mechanism is presented having inner and outer telescoping tubes for coarse elevational adjustment and having an adjustment screw and nut assembly for fine elevational adjustment. For coarse adjustment a thrust washer, surrounding the inner work elevation tube, permits free upward movement of the elevating tube relative to the outer support tube and is automatically positioned in angular binding relation with the elevating tube by a thrust washer positioner which has supporting engagement with one side of the thrust washer to restrain downward movement of the elevating tube. A thrust washer restraint member extends upwardly from and in spaced relation with the thrust washer positioner to restrain the thrust washer from moving upwardly along with the elevation tube. To ensure against possible injury to workers when the thrust washer is manually moved to its release position, an inner stop is provided within the support tube to limit downward movement of the elevating tube to a position at which the adjustment nut and elevation tube support flange is sufficiently spaced from the thrust washer and its restraint that injury cannot occur.