Paper winder assembly including pressure modulating valve

Abstract

A paper winder assembly of the type in which a rider roll is positioned to bear against a roll on which the traveling paper web is being wound. The rider roll position is controlled by hydraulically actuated lifting means which vary the pressure at which the rider roll bears against the paper roll. In accordance with the present invention, there is included a pressure modulating valve which converts air pressure signals to hydraulic signals which operate the hydraulically actuated lifting means. The valve includes a pair of flexible diaphragms therein with means to introduce air under pressure on opposite sides of the two diaphragms depending upon whether the rider roll is to be raised or lowered. The valve has a spool actuator therein which is movable in response to the movement of either of the diaphragms. A spring means biases the spool downward and establishes fluid communication between an inlet port and an outlet port for transmitting hydraulic fluid to the hydraulically actuated lifting means. A feedback is provided in the valve body so that fluid pressure acts on the spool in opposition to the spring biasing force and eventually establishes an equilibrium position. When the back pressure of the hydraulic lifting system is sufficiently high, the spool is positioned in valve closing relationship, and excess hydraulic fluid is passed to a drain.