Patent ID: 7431526

Claim:
A barrel for containing a binding slice, comprising: a barrel with a first opening; a singular, unitary reel limited to rotate in the barrel, wherein one end of said reel extends out of the barrel; a volute spring, wherein said volute spring is a volute metallic reed with an inner end fastened on said reel for following the reel to rotate; a binding slice, wherein the inner end of said binding slice is fastened and wound on said volute spring for following the reel to rotate, and the outer surface of said binding slice is pushed by said volute spring to contact the inner surface of said barrel, such that minimal slack of the binding slice is maintained while contacting the inner surface of said barrel, wherein the outer end of said binding slice is reeled in and out by rotating said reel, and wherein the inner surface of said barrel comprises at least one prominent ridge for decreasing the friction between said inner surface of said barrel and said outer surface of said binding slice; and a bottom plate, wherein said bottom plate is connected to form the bottom of said barrel, and said bottom plate has a hole for locating the bottom end of said reel.