Variable stiffness rule blade, rule employing same, and method of making same

摘要

A coilable measuring blade for coilable rules has a concavo-convex cross section which has a first portion wherein the length of the arc gradually decreases and the height of the cross section gradually increases to provide greater standout length. The inner or second portion of the blade also has a concavo-convex cross section with a relatively large radius and relatively shallow height. The blade may also have an outer terminal portion of greater height to require its deflection as it enters the rule casing and thereby provide reduction of the speed with which the blade is being retracted into the casing.