Patent ID: 7013833
Filing Date: 2006-03-21
Classification: B60C

Abstract:
1. A tire valve stem cap incorporating a visible air pressure indicator, said cap comprising: a hollow outer tube having a closed hemispherical transparent upper end and open lower end; a stem connector for attachment at one end to an existing tire valve stem, said stem connector being sized for a close fit in the open outer end of said outer tube; an indicator comprised of a hemispherical head conforming to the closed transparent upper end of said outer tube and visible there through, and a body protruding therefrom, said hemispherical head being defined by a lateral annular groove and a first O-ring seated in said groove to create a seal against said hollow outer tube said indicator further having a central air passage through the head and body, said indicator being slidable within said outer tube from an up to a down position; a compression spring having a calibrated bias encircling said indicator and biased against the hemispherical head for biasing said indicator toward said up position; whereby when said tire valve stem cap is engaged on an existing tire valve stem, pressurized air from said tire passes from said tire stem valve through said indicator central air passage to maintain said indicator in equilibrium in said down position against the bias of said spring, but if, but if air pressure in the tire drops below a calibrated level the excess spring bias of said spring will cause said indicator to pop up and become visible inside said transparent end of said outer tube.