Reflections from the “SK Door” Patent Dispute in Singapore

In December 2025, the Singapore High Court delivered a judgement in the case of Ng Say Keong v Jia Le Aluminium Pte Ltd [2025] SGHC 243 (“Ng Say Keong”), which involved several IP issues including patent validity and infringement. The court proceedings arose from a dispute between a local inventor Mr Ng Say Keong (“Mr Ng”) and his business competitors in the door industry.

The claimant, Mr Ng is the sole proprietor of a local company, S & K Solid Wood Doors in the business of doors and door-related products and is the patent owner of Singapore Patent No. 10201401033R (“SK Patent”) for a slide-and-swing door invention (“SK Door”). The defendants are Jia Le Aluminium Pte Ltd (“Jia Le”) and 9 Power Aluminium & Glass Pte Ltd (“9 Power”), both of which are local companies in the business of aluminium products including doors. 

Mr Ng commenced infringement proceedings against the defendants in the High Court in March 2024, accusing them of infringing the SK Patent with acts of making and importing of their door products (“the SD Door”). Mr Ron Awyong (“Mr Awyong”), a registered Singapore patent attorney, was appointed by the parties as their joint neutral expert witness in this action. 

The issues determined in this case were, among others, whether the SK Patent is valid, and if so, whether the defendants had infringed the SK Patent. 

The SK Patent

The SK Patent was filed on 27 March 2014 and granted on 29 October 2015 by the Intellectual Property Office of Singapore (“IPOS”). Claim 1 of the SK Patent reads: 

A sliding door system, comprising:

a. a door frame having a top inner edge;

b. a first door panel and a second door panel which are slidable with each other, characterized in that both the first door panel and the second door panel are provided with a top horizontal bar and a bottom horizontal bar, wherein the base of the bottom horizontal bar of the two panels is provided with elongated slot and one end of each of the base of the two door panels is extended to form an abutment which is slidable within the slots of each of the bottom bar; and the top horizontal bar has a male abutment and a female recess where the male abutment formed on one of the panel is slidable within the recess of the top horizontal bar of the other door panel, whereby the first door panel and the second door panel are capable of slidably positioned at juxtaposed position;

c. a pair of pivot device to pivotally mounted one panel of the door to the edge of the one of the two door panels, such that the doors at juxtaposed position is capable of swinging open about the pivot point on the door frame, thereby a widest door opening is obtained via sliding of one door panel and the swinging opening of the juxtaposed doors.

Validity Analysis

Infringement proceedings almost invariably attract a challenge to the validity of the patent by way of defence. In the present case, the validity of the SK Patent was attacked under Section 80(1)(a) of the Patents Act 1994 (the “Patents Act”) for being unpatentable Japanese Patent Publication No. JP2005048539.

Although the IPOS Patent Examiner had cited JP2005048539 during examination of the SK Patent and proceeded to allow grant of the SK Patent, the Court must still exercise its original jurisdiction to independently determine the validity of the SK Patent. As emphasised at [52], “The IPOS examiner’s findings cannot be a ground for the court to find the patent valid. If so, that would render the court’s exercise of its original jurisdiction nugatory.” The judge further added that “The court must undertake its own independent assessment of validity based on the evidence before it and in the light of the submissions made by both parties.” Having considered JP2005048539 and the parties’ submissions, the judge concluded that the SK Patent is valid. 

Infringement Analysis

In Singapore, a person infringes on a patent for an invention if the person does any of the prohibited acts under Section 66(1) of the Patents Act in relation to the patented invention without the patentee’s consent. The key issue is whether the allegedly infringing product or process falls within the scope of the patent claims properly construed.

As explained by the Court of Appeal in Lee Tat Cheng v Maka GPS Technologies Pte Ltd [2018] SGCA 18 (“Lee Tat Cheng”) at 41(f): “[i]f an allegedly infringing article falls within the words of one of the claims of a patent properly construed, the patent would have been infringed,” and infringement requires that the article “usurp each and every one of the essential elements of the claim in question.” 

Accordingly, whether the SD door falls within the scope of the SK Patent turns on a question of claim construction, namely whether it includes all the essential elements of the relevant claim.

The dispute centered on whether the underlined feature of claim 1 was present in the SD Door. There was contention over the construction of the terms “elongated slot” and “the slots”, particularly whether they mean the same or different slots, which consequently affected how the term “abutment” was constructed as the abutment is “slidable within the slots”. 

The judge accepted the expert witness’s interpretation as being consistent with the purposive approach to claim construction, finding that the references to the “elongated slot” and “the slots” relate to the same opening, with the earlier singular reference likely being a drafting oversight. The SD Door only has an elongated slot in the bottom horizontal bar of the first door panel, not in both panels as required by the claim, and the abutment of the first door panel starts at the top of the bottom horizontal bar instead of extending from the base (Ng Say Keong at [68]).

Accordingly, the judge found that the differences between the SD Door and the claimed features, placed the SD Door outside the scope of the claims, and that the defendants did not infringe the SK Patent. 

Although the judge did not refer to the description in the specification of the SK Patent, we found that page 6, lines 16–24 of the SK Patent specification state that “[t]he abutment 210 is positioned at the underneath of the bottom bar of the door … and is slidable within the elongated slots 200 provided at the bottom surface of the bottom bar 150 of each of the door panels 120, 130.” This description, when considered together with Figure 4 of the SK Patent specification, supports an understanding of the claims in which the “elongated slots” are intended to be present in both bottom bars, with one slot provided for each door panel.

The specification of the SK Patent thus supports an interpretation of the claimed “elongated slots” consistent with the Court’s interpretation.

The purposive approach to claim construction, as applied by the High Court, has been consistently adopted by the Singapore Courts. The key question under this approach, as articulated in the leading case of Lee Tat Cheng, is what the hypothetical person skilled in the art would have understood the patentee to mean by the language of the claims at the time of the patent application (Lee Tat Cheng at [41(c)]). Accordingly, the starting point of claim construction is the language of the claims themselves and what that language would convey to the skilled addressee.

While the claims are the principal determinant, they should be construed as part of the whole specification. However, where the claims have an ordinary and plain meaning, the Court would not rely on the language used in the body of the specification so as to give the claims a different meaning (see Ng Say Keong at [25] citing First Currency Choice Pte Ltd v Main-Line Corporate Holdings Ltd [2008] at [23]-[24]). This approach is consistent with Section 113(1) of the Patents Act, which provides that the extent of the invention is taken to be that specified in the claims, as interpreted by the description and drawings in the specification. 

In the present case, notwithstanding the ambiguity in the claim language, the Court examined the functional requirements of the door system and considered whether the competing interpretations were supported by the patent specification when read as a whole. The differing interpretations advanced in the case, together with the Court’s analysis, not only illustrate the importance of clear and definitive claim language in delineating the scope of the invention, but also demonstrate that the specification must be drafted in a manner that supports the intended construction of the claims in order to secure the desired scope of patent protection.

Claim Construction Approaches in Different Jurisdictions

It is also worth noting that different approaches to claim construction are adopted across jurisdictions, which may lead to divergent infringement outcomes for the same patent.

The purposive approach to claim construction adopted by the Singapore Courts has its roots in jurisprudence in the United Kingdom, most notably Catnic Components Ltd v Hill & Smith Ltd [1982] RPC 183, Improver Corporation v Remington Consumer Product Limited [1990] FSR 181, and Kirin-Amgen Inc v Hoechst Marion Roussel Ltd [2004] UKHL 46.

Following the UK Supreme Court’s decision in Actavis UK Ltd v Eli Lilly & Co [2017] UKSC 48 (“Actavis”), the UK Supreme Court reformulated the claim construction approach by introducing a distinct doctrine of equivalents alongside purposive claim construction. Under the doctrine of equivalents, a patent may be infringed if the accused product performs substantially the same function in substantially the same way to achieve the same result, notwithstanding differences from the literal language of the claims.

This doctrine of equivalents, and the approach adopted in Actavis, has been expressly rejected by the Singapore Court of Appeal. In Lee Tat Cheng at [51]-[53], the Singapore Court observed that the doctrine of equivalents is inconsistent with Section 113 of the Patents Act, gives rise to undue certainty and that the purposive approach strikes the appropriate balance between affording fair protection to patentees and providing a reasonable degree of legal certainty to third parties.

Conclusion 

The proper construction of patent claims is fundamental in defining the scope of patent protection, and this construction applies equally to both validity and infringement analyses. In the assessment of validity, patent claims are construed and compared against the prior art. In infringement analysis, the construed claims are compared against the alleged infringing acts to determine whether the essential features of the claims are embodied therein.

While some of the prior art documents may be identified at the time of patent drafting and prosecution, patentees inevitably face limited foresight as to the forms that future infringing articles or methods may take. Therefore, claims should be drafted to define a clear and definitive scope of protection capable of withstanding scrutiny in validity challenges, while remaining sufficiently robust to capture foreseeable variations of infringing embodiments. 

Equally important is the role of the description in the patent specification, which must adequately support the claims and provide a clear interpretative framework for the skilled addressee. A well-drafted patent specification ensures that the intended scope of protection is properly disclosed and understood, thereby reinforcing the strength and enforceability of the claims.

For businesses seeking effective protection for their inventions, it is therefore strongly recommended to engage patent professionals to ensure that patent specifications are drafted with precision and clarity.

A well-drafted patent specification ensures that the intended scope of protection is properly disclosed and understood, thereby reinforcing the strength and enforceability of the claims.