Assembly to coat a moving paper/cardboard web surface, has a jet with pulsation suppression in the feed of the coating medium to the jet to suppress pulsations using a pulsation valve and damper and flexible conduit hose

摘要

The assembly to spray the surface of a moving paper or cardboard web (12) has a jet (14) which sprays an adjustable vol. of the coating medium (16) on to the web surface. A pulsation valve (20) is in the feed of the medium to the jet, where the flow pulsations are damped or weakened. The vol. flow to the jet (14) is set by the pulsation valve (20), which is an armature or plate armature valve. The pulsations in the vol. flow of the coating medium (16) to the jet (14) are suppressed by a pulsation damper (18) in front of the jet (14) and/or by the use of a jet (14) with a larger jet width in the direction (L) of web travel and/or by the use of a flexible feed conduit to the jet (14). The jet width along the direction (L) of web travel can be 30% of the width across the web line and preferably 50% of the lateral width. The jet (14) is preferably an elliptical flat-stream jet, oriented at an angle to the web (12) to spray the surface against the direction (L) of web travel at =80[deg] and preferably =70[deg]. The jet is suitable for webs (12) moving at speeds of =1200 m/min. and preferably =1500 m/min. The jet (14) can also be a solid cone jet. The vol. flow is set by the pulsation valve (20) using pulse width modulation. The pulsation valve is controlled at a constant cycle frequency. An independent claim is included for a web coating assembly (10) with a jet (14) to spray the web (12) surface with a coating medium (16). At least one pulsation valve (20) in the flow feed with units (18,14) to dampen or weaken pulsations in the medium flow.