By Jigyasa Pareek

In Sulzer Mixpac AG vs Assistant Controller of Patents and Designs [LPA 545/2024, decided on July 1, 2026], the Division Bench of the Delhi High Court dismissed the Letters Patent Appeal challenging the Single Judge’s decision to uphold the rejection of patent application number 1329/DEL/2012, entitled “Static Mixer”, holding that the claimed invention lacked an inventive step in view of the cited prior art documents.

While affirming the Controller’s findings on obviousness, the Division Bench also addressed three important questions:

• Whether a Letters Patent Appeal is maintainable against a Single Judge’s decision rendered under Section 117A(2) of the Patents Act, 1970, notwithstanding the bar under Section 100A of the Code of Civil Procedure, 1908;
• Whether the five-step test for assessing inventive step, laid down in F. Hoffmann-La Roche Ltd. vs Cipla Ltd. [2015 SCC OnLine Del 13619], is a mandatory checklist for Courts, and
• Whether incremental improvement over a patentee’s own prior art can qualify as an invention.

The invention

The subject patent application (No. 1329/DEL/2012) claimed a plastic static mixer for injection moulding where the inventive feature was the connection of more than five installation bodies through a common bar element.  The application was rejected by the Controller on the ground of lack of inventive step in view of prior art document D1-D4.

As regards D1(Sulzer’s own earlier European patent), the Controller found that it disclosed experimentally manufactured mixers containing twelve installation bodies; and that the connection elements in D1 constituted a mechanical equivalent of the common bar element claimed in the subject application. D3 disclosed a reinforced strip element equivalent to the common bar, with more than five installation bodies visible in its drawings. D2 disclosed more than five installation bodies. D4 disclosed a common connecting element mechanically equivalent to the common bar claimed.

The Division Bench endorsed the Controller’s findings and added a pointed observation: where the cited prior art is an invention of the same inventor, “the leap from prior art to the subject invention is much more easily scaled”.

The Bench also declined to permit Sulzer to introduce, at the appellate stage, a new ground based on the number of fluid streams into which each installation body divides the flow, noting that it had neither been raised in the reply to the First Examination Report nor in the written submissions as a ground of inventiveness. The Bench noted further that this feature was not one of the prime features of the invention even as per the complete specification.

On comparative data, the Bench reaffirmed that technical advantages must be demonstrated against the specific prior art cited by the Controller. Sulzer’s comparative data, measured only against EP 1426099B1, which was not among the Controller’s cited prior art documents D1-D4, was found to be inadequate for the purpose of assessing inventive step.

The Roche Test

Sulzer’s counsel argued that the Single Judge had failed to follow the five-step test for assessing inventive step laid down in Roche, and that this failure alone vitiated the judgment. The Division Bench rejected this argument in terms that deserve close reading:

“The five steps enumerated in para 120 of Roche merely provide guidance as to how, in a particular case, the court has to proceed while examining the aspect of inventiveness or obviousness of an invention… They cannot be regarded as commandments cast in stone, implicit compliance with which is essential in every case. Where the case is capable of being decided without strictly following the rigour of the said five steps, it cannot be said that the decision is vitiated solely on that ground.”.

Two points of precision are critical here. First, the Bench’s relaxation is addressed to Courts, not to the Controller. The passage says nothing about how the Controller’s examination should be structured. This distinction matters: the latitude belongs to Courts sitting in appellate review; administrative adjudicators remain bound by the duty to reason.

Second, the formulation “where the case is capable of being decided without strictly following the rigour of the said five steps” raises an unresolved question: which cases qualify? The present case was arguably so clear-cut (D1 disclosed twelve installation bodies connected by equivalent elements) that the Bench found the answer obvious without formal step-sequencing. But the anti-hindsight function of Step 5 of Roche exists precisely for cases that are not obvious at first blush, and the Bench’s broad formulation could be misread as licensing Courts to skip Step 5 in less clear-cut cases. That risk deserves warrants judicial attention going forward.

LPA Maintainability

The preliminary objection to the LPA’s maintainability was raised by the Controller relying on Section 100A of the CPC, which operates as an absolute, non-obstante bar on any further appeal from the judgment and decree of a Single Judge of a High Court when that Single Judge has heard and decided an appeal from an original or appellate decree or order. It overrides, expressly and completely, any right of appeal that may otherwise arise from the Letters Patent. The Division Bench rejected this argument by applying the ratio of Promoshirt SM SA vs Armasuisse [2023 SCC OnLine Del 5531]. The Promoshirt line of reasoning holds that Section 100A is triggered only where the authority below is a “Civil Court” within the meaning of the CPC. Since the Controller of Patents is not a Civil Court within the meaning of Section 2(14) of the CPC, and since Section 117A of the Patents Act does not incorporate the CPC’s appellate framework so as to attract Section 100A, the LPA was held maintainable. 

This holding, however, sits in direct contradiction with the Madras High Court’s Division Bench decision in Italfarmaco SPA vs Controller of Patents & Designs [2025 SCC OnLine Mad 13148]. In this case, the Registry had raised a maintainability objection when Italfarmaco sought to file an intra-court appeal before the Commercial Appellate Division after its appeal under Section 117A was dismissed by the Single Judge. The Division Bench affirmed the Registry’s objection.

The Madras Court reasoned that issues relating to patents squarely fall within the definition of “commercial dispute” under Section 2(1)(c)(xvii) of the Commercial Courts Act, 2015. It examined whether an appeal from the Single Judge’s judgment could be maintainable before the Commercial Appellate Division under Section 13 of the Commercial Courts Act.

Section 13(1A), which enumerates the only permissible further appeals, limits them to orders falling under Order XLIII of the CPC (such as orders granting or refusing injunctions, appointment and discharge of receivers, or rejecting applications under specific procedural provisions) and orders under Section 37 of the Arbitration and Conciliation Act, 1996. Section 13(2) is a non‑obstante clause which expressly overrides the Letters Patent and forecloses resort to Clause 15 as an independent appellate route.

The Court held that an order passed by a Single Judge in a statutory patent appeal under Section 117A does not fall within any of the categories enumerated under Order XLIII. Put differently, the combined effect of Section 13(1A) (which does not positively authorise an appeal from such an order) and Section 13(2) (which bars any appeal outside the Act’s framework) is that no intra‑court appeal lies from a Single Judge’s decision in a Section 117A patent appeal.

The two High Courts have thus approached the question through fundamentally different statutory frameworks. While the Delhi High Court examined the applicability of Section 100A of the Code of Civil Procedure and held that the Controller is not a “Civil Court”, the Madras High Court located the answer within the appellate scheme of the Commercial Courts Act, holding that Section 13 exhaustively governs further appeals from commercial disputes. The consequence is that the maintainability of a Letters Patent Appeal against a Single Judge’s decision under Section 117A presently depends upon the jurisdiction of the High Court concerned, leaving an important procedural question awaiting authoritative resolution.