Spring coilable top reading rule with improved guide structure for coilable blade

摘要

A top reading power return rule has a shock-absorbing rib adjacent the spool, to prevent kinking upon retraction of the blade. The rib is positioned so as to be normally out of contact with the blade, but to intercept the blade when engagement of the hook member upon the casing causes it to abruptly stop and snap inwardly. The rib functions by decreasing the deflection of the taut blade about the small roller closest to the spool; excessive deflection is also avoided by providing a contact surface portion on the rib that is of relatively large area.