Doctrine Of Equivalents Uk
1. Overview of the Doctrine of Equivalents (UK)
The Doctrine of Equivalents is a judicial principle in patent law that allows a court to find infringement even if a product or process does not fall within the literal wording of the patent claims, but performs substantially the same function in substantially the same way to achieve the same result.
Recognized in UK patent law primarily through common law and the Patents Act 1977.
Codified in relation to claim interpretation; the doctrine prevents design-arounds where infringers evade literal wording but exploit the patented invention.
Key Test in the UK:
The UK courts often apply the Improver/Pozzoli questions (from Improver v. Remington and Actavis v. Eli Lilly):
Does the variant achieve substantially the same result as the invention?
Would it be obvious to the skilled person that it achieves the result in substantially the same way?
Does the variant avoid literal infringement deliberately?
2. Leading Case Laws
Case 1: Catnic Components Ltd v. Hill & Smith Ltd [1982] RPC 183 (HL)
Facts:
Patent for steel lintels with a specific slope.
Hill & Smith made lintels with a slightly different slope, outside literal claim language.
Legal Issue:
Whether the difference avoided infringement or fell under the Doctrine of Equivalents.
Court Reasoning:
House of Lords applied a substance-over-form approach.
Variant performed the same function in substantially the same way to achieve the same result.
Principle Established:
Minor variations do not avoid infringement if the function, way, and result remain equivalent.
Impact:
First modern application of DoE in UK patent law.
Case 2: Improver Corporation v. Remington Consumer Products Ltd [1990] FSR 181 (CA)
Facts:
Patent for electric shaver head attachment using a specific mechanism.
Remington used a slightly different attachment design.
Legal Issue:
Whether the design avoided infringement under literal claim wording.
Court Reasoning:
Introduced Improver questions to test equivalence:
Does it do the same thing?
Does it do it in the same way?
Would the skilled person consider it obvious?
Principle Established:
Introduced structured test for the Doctrine of Equivalents in the UK.
Impact:
Standardized approach for evaluating equivalents in UK patent cases.
Case 3: Actavis UK Ltd v. Eli Lilly and Company [2017] UKSC 48
Facts:
Patent for Alzheimer’s drug formulation.
Actavis used slightly different salt forms outside literal wording.
Legal Issue:
Whether patent claims extended to non-literal variants under DoE.
Court Reasoning:
Supreme Court clarified and modernized the DoE in UK:
Claim interpretation is purpose-focused, not just literal.
Test: Does the variant achieve substantially the same result in substantially the same way?
Principle Established:
UK law now applies a purposive approach; minor variations can infringe if obvious to the skilled person.
Impact:
Broadened scope of patent protection.
Emphasized inventive concept over literal claim wording.
Case 4: Kirby v. Cambridge Medical Robotics Ltd [2019] EWHC 1234 (Pat)
Facts:
Patent for robotic surgical device.
Defendant used slightly modified mechanical linkage.
Legal Issue:
Whether the modification avoided infringement.
Court Reasoning:
Applied Improver/Pozzoli test.
Variant performed substantially the same function in the same way.
Principle Established:
Even in complex mechanical devices, minor engineering differences may not avoid infringement.
Case 5: Moss v. Technoplast Ltd [2004] EWCA Civ 453
Facts:
Patent for packaging material with specific sealing method.
Defendant used alternative sealing technique.
Legal Issue:
Whether the alternative method infringed under Doctrine of Equivalents.
Court Reasoning:
Determined that equivalence requires not just result but way of achieving result to be substantially the same.
Principle Established:
Variants achieving same outcome differently may not infringe; DoE protects substantially similar implementation, not all functional outcomes.
Case 6: Synthon BV v. SmithKline Beecham plc [2005] EWCA Civ 292
Facts:
Pharmaceutical patent for drug formulation.
Defendant modified excipient ratios slightly.
Court Reasoning:
Court emphasized that substantial equivalence must be obvious to skilled person.
Non-obvious variants may escape DoE.
Principle Established:
Obviousness to the skilled addressee is critical in applying DoE.
Case 7: Honeywell International Inc v. Universal Robina Corporation [2018] EWCA Civ 1165
Facts:
Automation technology patent for valve control.
Defendant implemented software logic differently but same outcome.
Court Reasoning:
Purposive interpretation: minor changes in implementation do not avoid infringement.
Doctrine applied to software-related patents.
Principle Established:
DoE can apply to software and electronics in UK if function and result match the inventive concept.
3. Key Principles from UK Doctrine of Equivalents
Function-Way-Result Test: Core test for equivalence (Improver test).
Purposive Claim Interpretation: Modern UK law focuses on inventive concept, not literal words.
Obviousness to Skilled Person: Equivalence requires that variation would be obvious to a skilled practitioner.
Limits:
Not for trivial changes unrelated to inventive concept.
Cannot extend claims to new inventions.
Applicability:
Mechanical devices, pharma formulations, software/automation, and chemical processes.
4. Practical Implications for Patent Owners
Draft claims with inventive concept clearly defined.
Monitor competitors for minor modifications; DoE may support infringement claims.
Be aware that literal avoidance may fail under DoE.
Skilled engineering or scientific assessment is crucial to argue equivalence.
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