Specific Teaching, Not Assumptions: Inventive Step, Overlapping Ranges and Structural Features in Trident Limited v. Controller of Patents

Specific Teaching, Not Assumptions: Inventive Step, Overlapping Ranges and Structural Features in Trident Limited v. Controller of Patents

1. Introduction

The decision of the Delhi High Court in Trident Limited v. Controller of Patents (2025 DHC 10343) is a significant addition to Indian patent jurisprudence on inventive step, particularly in technology areas where:

  • the claimed invention is defined by a structural outcome (here, homogeneous distribution of pores across the yarn cross-section), and
  • that structural outcome is achieved through specific process parameters and composition ranges.

The Court scrutinises the manner in which the Patent Office assessed obviousness in relation to Indian Patent Application No. 1867/DEL/2010, titled “Air Rich Yarn and Fabric and its Method of Manufacturing”. While the Court does not itself grant the patent, it sets aside the refusal order and remands the matter for fresh consideration, laying down important guidance for:

  • how prior art must be analysed and cited in an inventive-step rejection;
  • how overlapping ranges and “routine optimisation” arguments should be handled;
  • how structural product features (like pore distribution) must be treated vis-à-vis process similarity; and
  • the level of reasoning expected from Controllers in refusal orders.

The parties were:

  • Appellant: Trident Limited – a major textile manufacturer (yarn, bath linen, bed linen, paper, etc.).
  • Respondent: Assistant Controller of Patents and Designs, Delhi (Controller).

The central issue was whether the Controller had correctly rejected the application for lack of inventive step under Section 2(1)(ja) of the Patents Act, 1970, in light of four prior art documents (D1–D4) and the common general knowledge of blending fibres in yarn manufacture.

2. Summary of the Judgment

Justice Tejas Karia allowed the appeal in part by:

  • Setting aside the impugned order dated 05.01.2021 passed under Section 15 of the Patents Act refusing the patent application.
  • Remanding the matter to the Patent Office for fresh consideration by a different Controller.
  • Directing the Controller to:
    • grant Trident a fresh hearing,
    • consider the auxiliary set of claims submitted before the High Court (based on claims allowed by the EPO), and
    • decide the matter on merits, uninfluenced by the Court’s observations, within six months.

The Court did not rule that the invention was patentable. Instead, it found the Controller’s reasoning on obviousness to be legally and factually deficient, particularly because:

  • the prior art documents did not expressly disclose the homogeneous distribution of pores across the yarn’s radial cross-section, nor the specific 8–25% weight range of water-soluble fibres; and
  • the Controller failed to engage with the specification and examples that purportedly showed “special measures” and technical effects supporting the claimed invention.

In doing so, the Court re‑affirmed and developed the Indian approach to inventive step, building on earlier authorities such as Enercon (India) Limited v. Aloys Wobben, Pharmacyclics, LLC and Avery Dennison Corporation.

3. Technological and Claim Background

3.1 The Claimed Invention: “Air Rich” Yarn and Fabric

Trident’s invention concerns “air rich” yarns and fabrics, especially terry fabrics (e.g. towels), which are:

  • highly wettable and quick-absorbing,
  • easily dryable and faster drying than normal fabrics (10–30% faster), and
  • thicker and better at retaining body heat.

The core physical idea is to create yarns with “through pores” (continuous channels) that are:

  • formed between base-material fibres (e.g. cotton), and
  • homogeneously distributed across the radial cross-section of the yarn.

To achieve this, the invention uses:

  • a base material fibre (e.g. cotton), and
  • a water-soluble fibre (e.g. PVA – polyvinyl alcohol) that is later dissolved out.

Broadly, the process involves:

  1. Forming blended slivers with:
    • water-soluble fibre slivers at 8–25% by weight of the final yarn, and
    • homogeneous blending of base and water-soluble fibres across the radial direction of the sliver.
  2. Spinning these blended slivers to form yarn.
  3. Weaving/knitting the fabric using that yarn.
  4. Treating the fabric with water to dissolve the water-soluble fibres, thereby creating through pores in the yarn that are homogeneously distributed across the cross-section.

Claim 1 is a product claim to a woven/knitted fabric, but defined in part by the process by which the yarn’s porous structure is formed – a typical product-by-process style feature set.

3.2 Key Claimed Feature: Homogeneous Distribution of Pores

A central distinguishing element in Claims 1 and 8 is:

“the pores in the yarn are homogenously distributed across the radial cross-section of the yarn”

and that this pore distribution is achieved by:

  • blending water-soluble and base fibres with a specified weight ratio (8–25% water-soluble), and
  • a specific blending strategy (e.g. 6 cotton slivers surrounding one PVA sliver in the centre, as per Example 2 / Table 6).

The technological problem asserted by Trident is that, in conventional blending of PVA with cotton:

  • finer fibres (PVA) tend to migrate towards the yarn core during spinning,
  • coarser fibres (cotton) accumulate near the periphery,
  • leading to a non-homogeneous radial distribution of fibres and therefore non-homogeneous pore distribution once PVA is dissolved.

Trident claims to have overcome this tendency and obtained genuinely homogeneous pore distribution across the cross-section, with resulting performance benefits.

4. Submissions of the Parties

4.1 Appellant’s (Trident’s) Submissions

Trident advanced several key points:

  1. No prior art discloses homogeneous pore distribution.
    Documents D1 (EP 2172583 B1), D2 (WO 2009/098583), D3 (JPH 05-117966) and D4 (JPS 60-119247) may disclose:
    • blends of water-soluble and base fibres,
    • subsequent dissolution of the soluble component, and
    • certain weight ranges of soluble fibres,
    but none discloses:
    • a yarn whose pores are radially homogeneously distributed, or
    • the particular 8–25% weight range of water-soluble fibres in the blended yarn linked to that structure.
  2. Process similarity does not guarantee identical product structure.
    The Controller’s assumption – that if D1 uses “the same manufacturing steps” it must necessarily produce yarns with the same porous structure – was criticised as a legally unsound shortcut. Trident stressed that:
    • D1’s weight ratios differ from Trident’s claimed 8–25%, and
    • D1 is silent on any homogeneous radial pore distribution.
  3. No obviousness from broad/overlapping ranges.
    Even if D1–D4 disclosed broad ranges that, numerically, “cover” 8–25%, there is:
    • no teaching or pointer in the prior art to select that specific sub-range, and
    • no suggestion that such selection would yield homogeneous pores across the cross-section.
  4. Common general knowledge teaches away from homogeneous distribution.
    Trident relied on a post-priority publication “Technology of Short Staple Spinning: Blow Room to Ring Frame Basics”, whose content is drawn from the earlier Reiter manual (thus treated as indicative of pre‑priority common general knowledge). That literature explains that:
    • blends of different fibres tend to be uneven,
    • fine fibres migrate towards the core and coarse fibres towards the periphery, and
    • unbalanced blends (e.g. 90/10) are particularly streaky and inhomogeneous.
    This supports Trident’s argument that a PSITA would expect non-homogeneity, not homogeneous radial pore distribution.
  5. Evidence of “special measures” in the examples.
    The complete specification, particularly Example 2 (Table 6), describes:
    • a specific sliver layout – “6 cotton: 1 PVA (PVA in centre)” at the finisher/blender stage, and
    • detailed process settings (speeds, drafts, roller gauges, etc.).
    Trident argued these are deliberate, non-routine measures that:
    • address the inherent migration tendency of PVA, and
    • contribute to the homogeneous pore distribution claimed.
    The Controller’s statement that no “special measures” were shown was said to be factually erroneous.
  6. Hindsight bias and improper obviousness analysis.
    Trident invoked:
    • Enercon (India) Ltd. v. Aloys Wobben – emphasising the need for a “coherent thread” from prior art to the invention and the impermissibility of hindsight;
    • Pharmacyclics, Llc v. Controller General Of Patents – on “teaching away”; and
    • Avery Dennison Corporation v. Controller of Patents – reinforcing proper inventive step standards.
    They contended that the Controller’s approach was coloured by knowledge of the invention and its workings, rather than by what a PSITA would have understood at the priority date.
  7. Foreign grants as corroborative (not determinative).
    The invention had been granted in the US and Europe (US 10,196,763 B2; EP 2434035), and Trident offered an auxiliary claim set mirroring the EPO‑allowed claims for consideration. While acknowledging different standards, Trident argued that this at least showed the claimed configuration was not trivially obvious.

4.2 Respondent’s (Controller’s) Submissions

The Controller, defending the refusal, argued:

  1. Different standard of inventive step in India vs US/EU.
    Relying on F. Hoffmann-La Roche Ltd. v. Cipla Ltd., the Controller emphasised that:
    • the Indian “person skilled in the art” (PSITA) concept,
    • and the criteria for inventive step under Section 2(1)(ja),
    differ from the US “PHOSITA” and the US TSM (teaching-suggestion-motivation) framework criticised in KSR v. Teleflex. Thus, foreign prosecution outcomes and US-style TSM arguments were not controlling.
  2. Process and product essentially known from prior art.
    The impugned order, and the defence, characterised D1–D4 as disclosing:
    • blending water-soluble and insoluble fibres on draw frames,
    • spinning, weaving and then dissolving the water-soluble component to obtain porous or “air-rich” yarns/fabrics,
    • with weight percentages of soluble fibres from 2% to as high as 80%.
    The Controller argued that this was substantially similar to Trident’s process, so that a PSITA applying routine optimisation would arrive at the claimed structure.
  3. “Homogeneous distribution” allegedly unsubstantiated.
    The Controller argued Trident had no quantitative data or measurement to prove pore homogeneity. Without experimental validation, the assertion of homogeneous distribution was said to be a mere “qualitative hypothesis” contrary to natural expectations.
  4. Prior art and common practice targeting uniform blending.
    D1 and D2 in particular referred to uniform blending of fibres for quality yarn. The Controller reasoned that:
    • the goal of any spinner is a homogeneous blend,
    • draw-frame blending is a routine operation to achieve that,
    • so a similar process, with similar materials, would naturally lead to “homogeneous” distribution of fibres (and hence pores).
  5. Specification allegedly does not support pore homogeneity claim.
    It was contended that the specification:
    • speaks of blend homogeneity of fibres,
    • not expressly of pore homogeneity across the radial cross-section,
    • and thus does not adequately describe or support the claimed structural feature.
    Further, the claimed homogeneity was said to be “theoretical” and “practically impossible” per state-of-the-art literature.
  6. No hindsight, but legitimate reliance on prior art.
    The Controller denied any hindsight, asserting that:
    • prior art in the same field already aimed at even distribution of fibres for porous yarns,
    • D1–D4 provided sufficient motivation to blend soluble PVA with carrier fibres and wash out PVA,
    • and hence a PSITA would be led to similar “air-rich” structures without any inventive effort.
  7. Auxiliary claims not part of prosecution.
    The Controller also noted that the auxiliary claim set (mirroring EPO claims) had not been proposed during prosecution and therefore had not been examined.

5. The Court’s Legal Analysis and Reasoning

5.1 Framework for Inventive Step under Indian Law

While the judgment does not restate Section 2(1)(ja) in full, it clearly applies the Indian definition of inventive step:

a feature of an invention that involves technical advance as compared to existing knowledge or having economic significance or both, and that makes the invention not obvious to a person skilled in the art (PSITA) having regard to the prior art.

In line with F. Hoffmann-La Roche v. Cipla, the Court:

  • acknowledges that India’s PSITA standard and inventive-step analysis are not dictated by US or EPO law, but
  • nonetheless draws on Indian case law which has evolved robust tests against hindsight and for coherent reasoning, including:
    • Enercon (India) Ltd. v. Aloys Wobben,
    • Pharmacyclics, LLC, and
    • Avery Dennison Corporation.

Two key principles stand out from the Court’s approach:

  1. Mere presence of elements in prior art is insufficient.
    Citing Enercon, the Court emphasises:
    “The mere existence in the prior arts, of each of the elements in the invention, will not ipso facto mean obviousness… There must be a coherent thread leading from the prior arts to the invention… If it is hindsight deduction it is not acceptable.”
  2. Where common knowledge “teaches away”, obviousness must be clearly and carefully established.
    Referring to Pharmacyclics, the Court reiterates that if combining prior art documents fails to yield the claimed solution or contradicts common technical expectations, the art may be said to teach away from the invention rather than render it obvious.

5.2 Treatment of Prior Art D1–D4: No Disclosure of the Critical Structural Feature

The Court conducts a focused comparison between:

  • the essential claim features (homogeneous radial pore distribution; 8–25% water-soluble fibre), and
  • the content of D1–D4.

Its key findings are:

  1. D1 (EP 2172583 B1)
    D1 discloses:
    • blend spinning of ramie fibres with a water-soluble carrier fibre,
    • subsequent weaving into fabric, and
    • washing to remove the soluble fibre and obtain a de-weighted, porous fabric.
    It also provides composition ranges for ramie vs water-soluble fibres, but:
    • it does not teach that the resulting pores are homogeneously distributed across the radial cross-section of the yarn;
    • its weight ratios and process priorities differ from the claimed 8–25% range and objectives in Trident’s patent.
  2. D2 (WO 2009/098583)
    D2 discloses:
    • mixtures of first (insoluble) and second (soluble) fibres,
    • humidifying, mixing, recombing slivers, spinning and weaving,
    • dissolving the soluble fibres to obtain a fabric of only first fibres.
    It emphasises recombing “to mix the first and second fibres in a closer and more even manner”, and suggests soluble fibre content below 80%, preferably 30–60%. However:
    • D2 does not disclose pores that are radially homogeneous in the yarn,
    • nor does it teach or motivate selection of the specific 8–25% range.
  3. D3 (JPH 05‑117966)
    D3 gives examples with:
    • pineapple fibres and water-soluble vinylon fibres at 70/30% by weight,
    • other ratios up to 60% water-soluble fibres and an example with 5% water-soluble fibre.
    Yet, the Court notes:
    • D3 does not describe the method steps that would lead to Trident’s specific pore distribution, and
    • like D1 and D2, it is silent on homogeneous radial pore distribution.
  4. D4 (JPS 60‑119247)
    D4 discloses yarns with PVA at 2–80% by weight along with water-insoluble fibres. But again:
    • there is no teaching or suggestion that the pores (after dissolution) are homogeneously distributed across the cross-section,
    • nor any articulated linkage between a narrower sub-range (like 8–25%) and such a structural outcome.

The Court therefore rejects the Controller’s sweeping conclusion that these documents disclose “overlapping ranges” sufficient to render Trident’s specific 8–25% range obvious. It stresses that:

  • the ranges are wide and varied, and
  • there is no explicit or implicit pointer in D1–D4 that would guide a PSITA to select 8–25% to obtain a yarn with homogeneous pores across the cross-section.

5.3 Overlapping Ranges and Selection Inventions

Although the Court does not explicitly use the term “selection invention”, its reasoning aligns closely with that doctrine:

  • The prior art documents disclose broad ranges of water-soluble fibre content.
  • Trident claims a narrower sub-range (8–25%) associated with a specific technical effect – homogeneous pore distribution and improved absorbency/drying.

The Court implicitly applies a test akin to that used for selection inventions:

  1. Is the selected sub-range narrow compared to the prior art’s broad range? – Yes, 8–25% is a more confined slice of 2–80% (D4) and 30–60% (D2).
  2. Is the sub-range purposively selected, not arbitrary? – Yes, it is linked to the desired homogeneous pore structure and performance.
  3. Is there a new technical effect associated with that sub-range, not clearly taught or foreshadowed by the prior art? – That is Trident’s contention, and the prior art does not contradict it on the face of the record.

Accordingly, the Court concludes that:

  • the mere numerical “overlap” with broad ranges in D1–D4 does not support a finding of obviousness;
  • in the absence of a teaching that 8–25% would achieve the claimed homogeneous pore structure, the Controller’s “overlapping range” argument is insufficient.

5.4 Structural Features vs Process Similarity: Rejecting the “Same Process, Same Product” Shortcut

A central error the Court identifies is the Controller’s assumption that:

if the process of manufacture in D1 is similar to Trident’s process, the resulting product must be structurally identical (i.e. have homogeneous radial pore distribution).

The Court rejects this, noting that:

  • the prior art does not describe homogeneous pore distribution as a structural feature;
  • variations in:
    • weight percentages,
    • fibre properties (denier, length), and
    • process conditions and layout (e.g. 6 cotton: 1 PVA at centre),
    can materially affect the microstructure of the yarn even if broad process stages (blend, spin, weave, wash) look similar; and
  • without experimental evidence or at least a technical explanation, one cannot simply infer that a known process will inevitably produce the same structural micro-outcome.

This is important for all product-by-process or “structural outcome” claims: Indian patent examiners cannot:

  • rely solely on the similarity of high-level process steps, and
  • must instead ask whether the prior art explicitly or inherently teaches the specific structural feature claimed.

5.5 Homogeneous Fibre Distribution vs Homogeneous Pore Distribution

The Court is particularly critical of Paragraph 20 of the impugned order, where the Controller stated:

“a homogeneous distribution of fibres along the radial cross section of the yarn is the ultimate goal for any blending of fibres”.

The Court highlights that this mischaracterises the invention:

  • Claim 1 is directed to homogeneous distribution of pores across the radial cross-section,
  • not merely homogeneous distribution of fibres themselves.

This distinction is not semantic. The structural novelty lies in:

  • the arrangement and distribution of voids (pores) created after removing PVA,
  • which depends not only on initial fibre blending but also on:
    • the relative location of PVA vs base fibres in the radial direction,
    • migration behaviour under spinning conditions, and
    • the exact weight percentage of PVA.

By conflating fibre homogeneity (a general quality goal) with pore homogeneity (a specific structural claim feature), the Controller:

  • ignored the true technical contribution alleged by Trident, and
  • failed to appreciate how the prior art might actually teach away from such pore homogeneity.

5.6 Common General Knowledge and “Teaching Away”

The Court attaches significant weight to the spinning literature placed on record by Trident (derived from the Reiter manual), which underscores that:

  • blended yarns tend to be non-uniform,
  • fibres of different fineness migrate differently under drafting forces, causing de-blending and clustering, and
  • even if distribution is uniform at blending, it is hard to maintain through subsequent drafting and spinning.

This literature shows that:

  • a PSITA would not naturally expect homogeneous radial distribution of fibres,
  • still less would they expect homogeneous radial distribution of pores after dissolution of one fibre type.

Accordingly, the Court states that:

  • in such a scenario, it is “crucial to establish obviousness clearly”, because common knowledge actually teaches away from the claimed outcome;
  • the Controller’s cursory reliance on generic goals of uniformity does not discharge this burden.

5.7 Hindsight Bias and the “Coherent Thread” Requirement

Building on Enercon and Pharmacyclics, the Court reinforces that:

  • it is not enough that, after learning of Trident’s homogeneous pore structure, one can retrospectively locate individual elements (PVA, cotton, blending, washing) in disparate prior art documents;
  • there must be a coherent, forward-looking thread that would have guided a PSITA at the priority date to:
    • select the 8–25% PVA range,
    • configure the blending process (e.g. 6:1 sliver arrangement), and
    • seek and expect homogeneous radial pore distribution.

Because:

  • D1–D4 do not provide such guidance, and
  • common general knowledge in fact suggests difficulties and non-homogeneity,

the Court concludes that the impugned order’s obviousness analysis reflects an unacceptable hindsight reconstruction.

5.8 Adequacy of Reasoning and Engagement with the Specification

The Court is also critical of the quality of reasoning in the Controller’s order:

  • The order did not:
    • cite specific passages from D1–D4 that allegedly disclose or suggest homogeneous radial pores or the 8–25% range;
    • meaningfully engage with Trident’s examples (Tables 6–11), which specify process settings and fibre arrangements;
    • address how, despite the literature showing blending difficulties, a PSITA would have found the claimed outcome obvious to attempt.
  • The conclusion in Paragraph 24 that “no special measures” were shown is inconsistent with:
    • Paragraph 19 of the impugned order (which accepts homogeneous distribution of PVA fibres within base fibres as the cause of homogeneous pores), and
    • the detailed process parameters and sliver configurations set out in the specification (e.g. “6 cotton : 1 PVA (PVA in centre)” in Example 2).

The High Court holds that, in these circumstances:

  • the Controller’s assertion that no “special measures” were adopted is unsustainable unless:
    • the specific examples and parameters are carefully examined and
    • either discounted for valid technical reasons or shown to be routine from the prior art.
  • The failure to engage with these aspects renders the refusal order legally infirm.

5.9 Support in the Specification for the Claimed Structural Feature

The Controller had also contended that the complete specification did not mention homogeneous pore distribution across the radial cross-section. The Court rejects this:

  • The “Process of Manufacturing the Fabric” section explicitly states that:
    giving one or more draw-frame passages to achieve blending homogeneity in the radial direction is the ideal method for achieving “through pores on the surface of the final yarn and making the porous yarn structure in final fabric”.
  • The summary of the invention depicts the objective as obtaining pores “throughout the surface of the final yarn” and a porous yarn structure in the fabric stage.

Taken together, the Court finds that:

  • the specification does aim at and describe homogeneous porous structure across the yarn,
  • and the Controller ought to have addressed this instead of asserting that the feature was unsupported.

Even if the Controller disagreed with Trident’s interpretation of these passages, the Court notes that:

  • it was incumbent on the Controller to reasonably discuss the issue in the order,
  • rather than dismissing the claimed feature as unbacked by the description.

5.10 Role of Foreign Grants and Auxiliary Claim Sets

The Court is careful to:

  • accept the Respondent’s submission that Indian inventive-step standards are not bound by US or EPO practice; and
  • refrain from treating foreign grants as conclusive on patentability in India.

However, it also:

  • recognises that Trident had filed an auxiliary set of claims identical to those allowed by the EPO, and
  • directs the new Controller to consider those auxiliary claims while re‑examining the application.

The practical effect is to affirm that:

  • applicants can legitimately propose narrower claim sets at the appellate stage; and
  • the Patent Office is expected to examine such auxiliary sets on merits, even if they were not part of the original prosecution history.

6. Complex Concepts Simplified

6.1 Person Skilled in the Art (PSITA)

A PSITA is a hypothetical person who:

  • has ordinary technical skills and knowledge in the relevant field (here, textile spinning and yarn manufacture),
  • is aware of common general knowledge and relevant prior art, but
  • is not inventive; they do not exercise creativity beyond routine development.

Inventive step is assessed from the perspective of this PSITA, not with hindsight knowledge of the invention.

6.2 Inventive Step vs. Obviousness

An invention has an inventive step if:

  • it represents a technical advance or economic significance over prior art, and
  • would not have been obvious to a PSITA at the relevant date.

An invention is obvious (and thus unpatentable) if a PSITA, using their ordinary skills and routine experimentation, would have been led to the invention without needing inventive ingenuity.

6.3 Hindsight Bias

Hindsight bias in patent law occurs when:

  • the decision-maker evaluates prior art with the knowledge of the invention already in hand, and
  • concludes that the invention was obvious simply because, retrospectively, the pieces can be assembled.

The law requires that obviousness be assessed as of the priority date, asking: would a PSITA, without knowledge of the inventive concept, have been led to the solution?

6.4 Teaching Away

Prior art or common knowledge teaches away from an invention when:

  • it advises against the claimed solution, or
  • suggests that trying such a configuration would be unworkable, inferior or impractical.

When art teaches away, it becomes harder to argue that the invention was obvious; a PSITA is less likely to attempt something technical literature warns against.

6.5 Overlapping Ranges

In many technologies, prior art discloses a broad range (e.g. 2–80% of a particular component). If a new patent claims a narrower sub-range (e.g. 8–25%), the question is:

  • Is the selection of that sub-range arbitrary, or
  • Is it purposive, yielding a new or improved technical effect not taught by the prior art?

If the sub-range is purposive and associated with a technical effect (like homogeneous pore distribution), and the prior art does not suggest selecting that sub-range, the invention may still involve an inventive step despite numerical overlap.

6.6 Product-by-Process Claims

A product-by-process claim defines a product in terms of the process by which it is made (e.g. “a fabric obtained by blending X and Y and then dissolving Y”). In law:

  • the protection is still for the product, but
  • patentability often hinges on whether the product has a novel and non-obvious structure or property, not merely that a process step is different.

In Trident, the key structural property is the homogeneous radial distribution of pores, even though that property is achieved through a particular blending and dissolution process.

7. Impact and Implications

7.1 For the Patent Office (Controllers and Examiners)

The decision sends clear signals on how inventive-step assessments must be conducted:

  • Specific citation and analysis. Controllers must:
    • identify which claim features are anticipated or rendered obvious by which prior art passages,
    • avoid general statements like “similar processes” or “overlapping ranges” without showing how they lead to the specific claimed structure.
  • Engagement with the complete specification.
    • Detailed examples, process parameters, and configurations (like the 6:1 cotton:PVA arrangement) must be examined,
    • and cannot be ignored when claiming that “no special measures” exist.
  • Avoiding mischaracterisation of the invention.
    • Controllers must frame the inventive concept correctly (pores vs fibres, structural outcome vs generic process aim),
    • and ensure their analysis reflects that understanding.
  • Recognising teaching away.
    • Where literature or common practice indicates that a certain configuration is difficult or counter-intuitive,
    • the burden of explaining obviousness becomes higher and must be discharged with rigorous reasoning.
  • Reasoned orders as a legal requirement.
    • Refusal orders must be speaking orders, demonstrating application of mind and adherence to statutory standards.

7.2 For Patent Applicants and Practitioners

For applicants, especially in textiles and material sciences, the judgment highlights the value of:

  • Emphasising structural properties.
    • Clearly articulate how process choices (composition ranges, blending sequences) produce distinct structural outcomes (e.g. pore distribution) and technical advantages.
  • Providing detailed working examples.
    • Include tables of process parameters, layouts, machine settings and their link to the claimed effects.
    • These can later help rebut assertions that “no special measures” were used.
  • Using common general knowledge strategically.
    • Citing standard textbooks or manuals to show that the art teaches away from the invention can strengthen non-obviousness arguments.
  • Deploying auxiliary claim sets.
    • Proposing narrower, fall-back claim sets (even at the appellate stage) is legitimate and may be specifically directed for reconsideration, as in this case.

7.3 For Future Litigation on Inventive Step

The case will likely be cited for several propositions:

  • Inventive step cannot be found lacking merely because:
    • each element is somewhere in the prior art, or
    • a broad prior-art range numerically covers the claimed range.
  • Where the critical advance lies in a microstructural configuration (homogeneous pores, crystal form, morphology, etc.), courts will require:
    • evidence or at least analytic reasoning that the prior art inherently or obviously yields that structure.
  • Patent Office decisions on inventive step are subject to substantive judicial review, not mere formality review. Courts will:
    • scrutinise whether Controllers have adhered to anti-hindsight principles and engaged properly with technical evidence.

8. Conclusion

Trident Limited v. Controller of Patents is not a case that decides the ultimate patentability of “air rich” yarns and fabrics. Rather, its importance lies in the discipline it imposes on how inventive step is to be analysed, especially when:

  • the claimed invention hinges on a specific structural outcome (homogeneous pore distribution) achieved via tailored process and composition choices; and
  • prior art discloses only broad, generic solutions without that structural detail.

The judgment clarifies that:

  • Controllers may not assume that “similar processes” or “overlapping ranges” necessarily make a claim obvious, particularly when common knowledge indicates that the claimed outcome is counter-intuitive;
  • they must provide a coherent, non-hindsight explanation of how a PSITA would arrive at the claimed invention, citing specific prior art passages;
  • they must grapple with the applicant’s specification, examples and claimed structural features, rather than recasting the invention in more generic terms.

By setting aside the refusal and remanding the matter to a different Controller with directions to consider both main and auxiliary claims, the Court reinforces an important constitutional value in patent administration: reasoned, transparent decision-making that respects both the technical complexity of inventions and the statutory criteria of the Patents Act.

In sum, this decision solidifies an Indian doctrine that can be succinctly stated as follows:

In assessing inventive step, specific teaching – not assumption or hindsight – must link the prior art to the claimed structural features and selected composition ranges. Where such a link is absent, and common knowledge even teaches away from the claimed outcome, a bare assertion of obviousness will not withstand judicial scrutiny.

Case Details

Year: 2025
Court: Delhi High Court

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