machinery feature | Screenchangers & melt fi ltration products’ effi ciency and quality.”
The seal has a provisional patent, awaiting pending status.
Dispute settled
On the subject of patents, PSI and Nordson have reached an out-of-court
settlement regarding a patent dispute over a screen changer design.
Maag’s CSC 116-RS arched screenchanger allows the screen surface area to be enlarged up to four times, compared with conventional designs
low viscosity polymers and fl uids. With bolt-type screen changers and divert valves,
there is a correlation between the viscosity of the polymer and the ability of the screenchanger to maintain a reliable, leak-free seal. This is because the precisely machined clearance between the housing and bolts relies on the viscosity of the polymer to create a balance between providing minimal lubrication between the housing and bolts while also inhibiting fl ow across the bolt L/D to the atmosphere. Until now, low and very low-viscosity melts have been problematic for bolt-type screen changers because of the limitations on the clearances that must be maintained. Common with hot melt adhesives and low viscosity
polymers, these leaks are a serious problem, as they not only create a mess and require shutting down the machine for repair and cleaning, but they also can become a serious fi re and safety hazard. Now, PSI has invented a seal technology that will
PSI-Polymer Systems has developed a
seal for its bolt type screen- changers, to prevent
leakage of very low viscosity
polymers and fl uids
18
work effectively for polymers with very low viscosities. So far, the new seal has been successfully tested on viscosities as low as 1 cP (toluene, etc) to 300,000 cP and has proven capable of sealing nitrogen at over 2,000 psi. The design is equally effective at higher viscosities that can be handled by existing seal types. It can be used in any PSI piston type screen changer unit or divert valve, and is ideal for processing high melt materials, adhesives, solvents, etc. “This seal is a perfect solution for the leaks that many customers experience when using low viscosity polymers,” said Glenn Woodcock, president of PSI-Polymer Systems. “We know that our customers’ success is tied to our own success, and this new seal will help all of our customers improve their
PIPE & PROFILE EXTRUSION | January/February 2015
In 2012 – previous to its takeover by Nordson – Krey- enborg GmbH of Germany fi led the suit against PSI, alleging that PSI’s CSC-BF Continuous Backfl ush Screen Changers infringed Kreyenborg’s patents. A Joint Motion to Dismiss with Prejudice, fi led in the US District Court, Western District of North Carolina in September last year said that both parties had resolved and settled their disputes.
“We feel vindicated with this settlement, as we
always felt the lawsuit was baseless,” said Glenn Woodcock, president of PSI. The terms of the agreement remain confi dential, but PSI says it is free to market, sell and support its current CSC-BF design globally, free from any claim by Nordson or Kreyenborg. “We always believed strongly that our CSC-BF design did not infringe on Kreyenborg’s patent,” said Don Macnamara, general manager of PSI. “We felt we had to fi ght – it was a matter of integrity for us.” PSI’s CSC-BF screen changer design is patent pending, and has “several features” that make it unique, said Macnamara. The company plans to market the product to the recycling industry, which is its biggest user. “Demand for continuous backfl ush screen changers
has grown signifi cantly over the past few years, largely due to the growth of recycling,” he said. “PSI has led, not followed, the growth of this market.” The screen changers were
originally used only on reclaim pelletising lines, but are now more of a main- stream product, used on
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