Kreyenborg launches new backflush screen changer, files suit against PSI

Since only one out of four screens is taken out of the production during backflush or screen change, a new backflush screen changer reportedly maintains higher constant melt pressure during screen change and backflush. The new version of the V-Type backflush screen changer from Kreyenborg GmbH, K-SWE-4K-75-V/RS, was shown to the public for the first time at NPE2012 in Orlando.

Kreyenbourg says the new design results in higher efficiency of backflush, longer screen life and constant process, pressure, and volume flow during backflush. The screen retainers are optimized, resulting in a more efficient backflush due to higher backflush pressure capability. The new V-Type shows low melt volume due to rheologically optimized displacement pistons and flow channels and therefore shorter residence time of the melt. Kreyenborg says the modified design of the displacement pistons makes for an overall smaller footprint.

Prior to backflush, the required backflush melt is stored by a reverse movement of the displacement piston, creating a reservoir. The backflush material is then compressed and discharged for flushing, which cleans the screen. During normal production, this reservoir is always filled by the volume of the displacement piston, therefore eliminating any points of melt stagnation.

During screen change the screen-bearing piston containing the dirty filter elements is driven out of the housing so that the dirty screen pack can be exchanged with new filter elements. At the same time, the second screen in this piston as well as the two screens in the second piston remain in the production position so that the melt flow is not interrupted. In this way, a minimum of 75% of the total filtration area remains in the process melt flow at all times.

One month prior to the show, Kreyenborg filed suit against PSI-Polymer Systems on March 1 in the Georgia Northern District Court claiming patent infringement. That suit cited two Kreyenborg patents:

  • 5,922,194: "Filter changing device for plastics processing plants"
  • 7,419,592: "Device for filtering a fluid especially for plastic-processing installations"

On June 9, 2006, Kreyenborg filed it first amended complaint for an injunction and other relief agasint PSI on the basis of infringement on U.S. patent number 5,922,194. That action was resolved by settlement and dismissed on Sept. 19, 2006.

PSI-Polymer Systems Inc. (Conover, NC) introduced its newest Back Flush Screen Changer design at NPE2012, saying the all-new, patent pending screen changer design included numerous new features that will provide operators with greater safety and higher performance.

PSI-Polymer Systems said one of the most important features of the new screen changer is what it calls its unique back flushing design, where the contaminated screen packs are flushed and discharged through a port underneath the screen changer housing, creating a cleaner, safer environment for operators.