Previously, various systems have been used for driving the sheet advancing chains in machinery of this character and, for example, various systems are disclosed in U.S. Pat. Nos. 2,451,467; 2,708,575; 2,862,233; 2,991,826; 3,217,852; 3,748,078; 3,776,804; and 3,884,129.
In one such prior art patent, a rack gear is used to power the drive transmission shaft, in contradistinction to the present invention, wherein a rack functions as a stroke measuring element and accomplishes a different purpose. In other systems, special and expensive (to purchase and service) hydraulic motors are required.