Importance

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Abstract

An automatic plate-loading cylinder maintains circumferential tension of material wrapped around its exterior surface, the tension being both constant and sufficiently high to keep the material in position against tangential forces (due, for example, to rolling contact with a blanket cylinder). The invention can operate by tying the braking torque exerted on the supply or uptake spool to the radius of that spool, thereby compensating for changes in tension that accompany application of a constant torque. The device can include apparatus for dispensing a consistent amount of material from a supply spool without the need to actually measure the material during a payout cycle. In both aspects, the invention exploits the fact that material is both wound and paid out in an Archimedian spiral. Accordingly, knowledge of an initial radius of one of the spools and the amount of material paid out during each advancement cycle facilitates straightforward computation of the number of necessary rotations of either spool (as well as the resulting new spool radius, which is utilized for the next advancement cycle). The same knowledge additionally allows for straightforward computation of the torque required on the tensioning brake.

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First Claim