Variable stiffness rule blade, rule employing same, and method of making same
AssigneeThe Stanley Works
InventorsEdward C. Rutty, Carl C. Stoutenberg
Life of this patent
Estimating the term…
Abstract
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.
Claims20
A coilable rule blade having greater standout length comprising an elongated strip of resiliently deflectable metal having a substantially unform width in its coiled flattened state and, in its uncoiled state, a concavo-convex cross section along substantially its entire length, said cross section having a central segment of arcuate configuration defined by a radius R and having a depth H, said blade having a first portion in which the radius R of the central segment of the cross section gradually decreases and the depth H of the cross section gradually increases from values R.sub.1 and H.sub.1 respectively adjacent one end to values of R.sub.2 and H.sub.2 respectively at a point beyond the normal breakpoint of a blade of that width and having a cross section approximating that of the value of 1/2(R.sub.1 +R.sub.2) and 1/2(H.sub.1 +H.sub.2) respectively, said radius thereafter increasing and said depth of cross section decreasing towards the other end of the blade to values of R.sub.3 and H.sub.3 respectively;
- and a second portion in which the radius R.sub.3 and depth of cross section H.sub.3 are substantially uniform over the length thereof and which extends to adjacent said other end of said blade.
A coilable rule comprising
- A. a casing having end walls and a peripheral sidewall defining a chamber therebetween, said sidewall having an exit aperture therethrough;
- and
- B. a coiled rule blade in said chamber having one end extending outwardly of said casing aperture, said blade comprising an elongated strip of resiliently deflectable metal having a substantially uniform width in its coiled flattened state and, in its uncoiled state, a concavo-convex cross section along substantially its entire length, said cross section having a central segment of arcuate configuration defined by a radius R and having a depth H, said blade having a first portion in which the radius R of the central segment of the cross section gradually decreases and the depth H of the cross section gradually increases from values R1 and H.sub.1 respectively adjacent one end to values of R.sub.1 and H.sub.2 respectively at a point beyond the normal breakpoint of a blade of that width and having a cross section approximating that of the values of 1/2(R.sub.1 +R.sub.2) and 1/2(H.sub.1 +H.sub.2) respectively, said radius thereafter increasing and said depth of cross section decreasing towards the other end of said blade to values of R.sub.3 and H.sub.3 respectively;
- and a second portion in which the radius R.sub.3 l and depth of cross section H.sub.3 are substantially uniform over the length thereof and which extends to adjacent said other end of said blade.
In a method for making a coilable rule blade, the steps comprising
- A. providing a length of resiliently deflectable metal strip having a width W;
- B. forming a first portion of said length into a concavo-convex cross section having a central segment of arcuate configuration defined by a radius r and having an overall depth H and in which the radius R of the central segment of the cross section gradually decreases and the depth H of the cross section gradually increases from values R.sub.1 and H.sub.1 respectively adjacent one end to values of R.sub.2 and H.sub.2 respectively at a point beyond the normal breakpoint of a blade of that width and having a cross section approximating that of the values of 1/2(R.sub.1 +R.sub.2) and 1/2(H.sub.1 +H.sub.2) respectively, said radius thereafter increasing and said depth of cross section decreasing towards the other end of said blade to values of R.sub.3 and H.sub.3 respectively;
- and a second portion of concavo-convex cross section in which the radius R.sub.3 and depth of cross section H.sub.3 are substantially uniform over the length thereof and which extends to adjacent said other end of said blade.
Dependencies are inferred from the claim text.