Rotation indicator for screw threaded connectors used to secure railway tracks

摘要

A rotation indicator for screw threaded connectors used to secure railway tracks involves a plastics cap (8) which carries an arrow (9) or other indicator aligned with a datum. The indicator allows the loosening of the screw threaded connector to be detected. Other rotational indicators disclosed include a transmitter attached to the screw threaded connector and mixing two chemicals to emit thermal or visible radiation.