Face sealing air actuated valve in an intermittent feed device

A feed device for feeding a web material to a work station comprising step-feed means for feeding the web material along a longitudinal direction comprising a stationary gripper and a movable gripper, a pneumatic actuator assembly for operating linear alternative forward and back displacement of the movable gripper relative to the stationary gripper parallel to said longitudinal direction and opening and closing said grippers in synchronism with the alternative displacement of the movable gripper, and an adjustable stop member cooperating with the movable gripper at the end of the forward displacement thereof, wherein said pneumatic actuator assembly comprises a block incorporating a three-way pneumatically piloted control valve for controlling communication between said pneumatic actuator assembly and, respectively, a feedline adapted to be connected to a source of air under pressure and a discharge, said control valve comprising a hollow valve body having an axial inlet passage in communication with said feed line, a radial inlet passage in communication with a pneumatic piloting line, and a first and a second radial outlet passages communicating respectively with the pneumatic actuator assembly and with the discharge, and a spool having at one end thereof a plunger subject to the pressure from the piloting line and at the other end thereof a floating obturator which, in presence of the piloting pressure, face sealingly closes said axial inlet passage and opens the communication between the first and the second radial outlet passages, and in the absence of the piloting pressure closes the second radial outlet passage and opens the communication between the axial inlet passage and the first radial outlet passage, and wherein the valve body and the obturator of the control valve are formed with respective flat face seal surfaces for the closure, in the absence of the piloting pressure, of said second outlet passage, wherein:

• the hollow valve body of the control valve has a first chamber in which said plunger of the spool is sealingly slidable axially, a second chamber in which said floating obturator is axially movable, and an intermediate cavity between said first and second chambers, the first chamber being connected with the radial inlet passage, the second chamber being connected with the axial inlet passage and with the first radial outlet passage, and the intermediate cavity being connected with the second radial outlet passage such that
• a flat annular face seal seat is defined between the second chamber and the intermediate cavity,
• the floating obturator is constituted by a disk element having a first flat face facing towards the axial inlet passage and defining a first flat face seal surface adapted to sealingly engage a flat bottom surface in said second chamber surrounding said axial inlet passage, and a second flat face facing towards the intermediate cavity and defining a second flat face seal surface adapted to cooperate with said flat annular face seal seat in the absence of the piloting pressure.