This case originates from a civil dispute heard by Guangzhou Intellectual Property Court, involving utility model patent infringement for household folding hardware products. All enterprise names are anonymized to meet requirements. The plaintiff, Alpha Hardware Co., Ltd., obtained an authorized utility model patent for a foldable furniture connection structure, which is widely applied in folding tables and storage cabinets. The defendant, Beta Manufacturing Co., Ltd., engages in hardware production and distributes similar products via cross-border e-commerce platforms. This case focuses on the identification of equivalent technical features and the application of the doctrine of prosecution history estoppel, two core disputed issues in Chinese patent litigation.
Alpha Hardware submitted the patent application to the China National Intellectual Property Administration (CNIPA) in late 2021, and the patent was officially granted in April 2023. The independent claim defines a connecting assembly including a rotary base, locking spring and limit baffle. During the substantive examination phase, the applicant made restrictive statements to overcome rejection opinions, clarifying that the locking structure relies on a cylindrical compression spring to achieve automatic positioning. This written record in the patent file would become critical evidence in subsequent infringement proceedings. After authorization, Alpha discovered that Beta Manufacturing produced and sold folding hardware adopting a similar connecting structure, and initiated notarized purchase and evidence preservation.
In litigation, Alpha claimed that Beta’s products fell within the patent protection scope under the doctrine of equivalents. The plaintiff argued that although Beta replaced the cylindrical compression spring with a torsion spring, the two components adopted substantially identical means, achieved identical locking and positioning functions, and generated equivalent technical effects. According to the equivalent feature rule under China’s patent judicial interpretation, such simple component substitution should be recognized as equivalent infringement. Alpha requested the court to order Beta to cease manufacturing and sales, destroy dedicated production molds, and compensate economic losses plus reasonable litigation expenses totaling 380,000 RMB.
Beta Manufacturing raised two major defenses. Firstly, the torsion spring structure adopted by the accused product differed obviously from the cylindrical compression spring recorded in the patent claim. The technical means were not identical, so equivalent infringement should not be established. Secondly, the doctrine of prosecution history estoppel shall apply. When obtaining patent authorization, Alpha deliberately narrowed the protection scope by emphasizing the indispensable role of the cylindrical compression spring. The patentee cannot expand the protection scope again through the equivalent principle in infringement lawsuits for structures excluded during examination.
The court organized technical comparison and invited a technical investigator to participate in the trial. The judgment clarified important judicial standards. First, the equivalent judgment requires comprehensive review of all technical features of the claims, instead of separate comparison of individual components. Second, prosecution history estoppel restricts the patentee from claiming equivalent protection for technical solutions abandoned during authorization procedures. Since Alpha explicitly relied on the cylindrical compression spring to distinguish prior art and obtain authorization, it cannot claim that torsion spring alternatives constitute equivalent features.
The court held that the accused product’s locking assembly adopted torsion spring force transmission, which differed from the compression spring solution described in the patent. Combined with the applicant’s restrictive opinions during examination, the torsion spring structure was excluded from the patent protection scope. Therefore, Beta’s products did not fall into the protection scope of the involved utility model patent. The court ruled to reject all litigation claims proposed by Alpha Hardware.
This case delivers profound guidance for domestic and foreign enterprises implementing patent layout in China. Many applicants tend to make limiting statements to acquire patents, yet ignore the subsequent binding effect of prosecution history estoppel. Enterprises must fully predict potential impact on patent enforcement when responding to CNIPA office actions. Blindly narrowing technical definitions to secure authorization may greatly weaken the stability of rights protection in future infringement lawsuits.
For manufacturing enterprises engaged in hardware, consumer goods and cross-border supply chains, this case provides clear compliance reminders. Enterprises should conduct comprehensive patent retrieval before launching new products. When designing alternative structures, R&D teams need to form written records of technical differences to prepare effective defense materials once sued. Meanwhile, patentees shall balance the authorization prospects and enforcement capability of patents, and avoid excessive concessions during the patent examination stage.
In recent years, Chinese intellectual property courts have strictly standardized the application of the equivalent principle to balance the interests of patentees and the public. Courts prevent patentees from flexibly expanding patent boundaries through equivalent theories after limiting claims to obtain authorization. This judgment restrains improper expansion of patent protection scope, maintains public confidence in the stability of patent right scope, and promotes orderly technological competition in the manufacturing industry.
