Delhi High Court Upholds Rejection Of Swiss Company's Patent For Plastic Static Mixer

The Delhi High Court on Wednesday upheld the rejection of Swiss company Sulzer Mixpac AG's patent application for a plastic static mixer used to mix molten polymers.

It held that the claimed invention did not involve an inventive step over the company's own earlier patents and amounted to "a mere modification" based on prior art.

A division bench of Justice C. Hari Shankar and Justice Om Prakash Shukla upheld the earlier decision rejecting the application filed by the Swiss company. It found no error in the Single Judge's judgment or the order of the Assistant Controller of Patents and Designs (ACPD).

The bench held, "Clearly, therefore, all that the appellant undertook, while proceeding from its own prior documents D1 to D4, to the subject invention, of which the appellant sought to patent, was a mere modification, using the disclosures and teachings available in prior art documents, of which the main prior art D1 was of the appellant itself."

Sulzer Mixpac had applied for a patent in 2012 for a plastic static mixer used to mix molten polymers. The invention comprised multiple installation bodies connected through a common bar element.

The company claimed the inventive feature lay in connecting more than five installation bodies through a single common bar element. According to it, the design improved the homogeneity of mixing and reduced internal pressure. It also produced a stiffer mixer that was less prone to breakage.

The ACPD rejected the patent application in March 2021 after concluding that the claimed invention lacked novelty and inventive step. A Single Judge later affirmed that decision. The Single Judge held that the prior art already disclosed multiple installation bodies connected through mechanical equivalents of the claimed common bar element, including reinforced walls.

Examining the prior art, the division bench found that D1, the closest prior art and one of Sulzer Mixpac's own earlier patents, disclosed connection elements that were mechanical equivalents of the claimed common bar element. It also taught arrangements comprising up to 12 installation bodies connected through a common connection element.

The court further observed that D3 and D2 disclosed multiple installation bodies connected through reinforced strips. It held that replacing those strips with a bar element would have been obvious to a person skilled in the art. The court also noted that the inventor of the earlier patent and the claimed invention was the same.

The bench observed, "We have to bear in mind the fact that the aspect of inventiveness has to be seen from the point of view of a person skilled in the art and, especially in a case where the inventor is the same, the leap from prior art to the subject invention is much more easily scaled."

Sulzer also attempted to distinguish its invention on the basis that each installation body divided the fluid into three streams. The court declined to consider the contention because it had not been raised before the Controller.

It further observed that the feature was not described in the patent specifications as one of the invention's principal features.

Finding no infirmity in the earlier rulings, the division bench dismissed the appeal. It upheld the rejection of Sulzer Mixpac's patent application.