Taizhou Suzhong Antenna Group Co., Ltd (“Suzhong”). is a professional antenna manufacturer, who claims itself to be the largest antenna manufacturer in China. Jiang Xiaoping, the legal representative of Suzhong, is the patentee of ZL 200710019425.7 "shark fin antenna" patent (“Plaintiff”). Based on their antenna series patents, Jiang Xiaoping and Suzhong initiated a numbers of lawsuits against domestic and foreign car companies, which were either decided in their favor or settled after the defendants paid royalty fee.

June 2014, Jiang Xiaoping filed a lawsuit at Nanjing Intermediate People's Court against Chongqing Lifan Automobile Sales Co., Ltd. (“Lifan”) and its distributor (jointly the defendants) for patent infringement,pleading the court to order the defendants stop manufacturing and selling "shark fin antenna" products and pay a compensation of 1 million RMB yuan, later increased to 10 million yuan.

During the trial, Lifan filed an invalidation petition against the patent at issue. The Patent Reexamination Board acknowledged existence of different technical features between the claims of the patent at issue and the prior art and accordingly sustained the patent at issue.

However, the differences between the alleged "shark fin antenna" and the patent at issue happen to be the differences claimed by the Plaintiff during the invalidation procedure. In other words, the technical features of the alleged “shark fin antenna”are identical with those of the prior art, but different from the patent at issue. Lifan tried to defend themselves by claiming the doctrine of estoppels but was not supported by the court. The first-instance verdict ordered Lifan and its antenna supplier stop infringement and jointly compensate the plaintiff 2 million RMB yuan.

Dissatisfied with the verdict, Lifan entrusted Unitalen to file an appeal at Jiangsu Higher Court. After holding two hearings and reviewing every focus of the case, the court decided that, because the patentee made restrictive statement to its claims, which was not explicitly denied by the Patent Reexamination Board, Lifan’s defense based on the doctrine of estoppels that the alleged product does not fall within the protection scope of the patent at issue was justified.

Comment

Invalid declaration is the most commonly used defense in a patent infringement ligitation. In addition to invalidating the patent at issue, another important purpose of an invliadation procedure is to force the owner of a patent with low inventiveness to decide between “maintaining patent” and “winning litigation”. Once the patentee’s response in the invalidation proceeding infringer on the independent claims gives room to the principle of estoppel, the alleged infringer will have an assuring win of the litigation case.