TPTA «RYTM» Inc., a Client of «A.Zalesov & Partners» Patent & Law Firm, a local manufacturer of breaks systems for trains from the City of Tver, was faced a patent infringement lawsuit filed by the major Russian railroad machinery manufacturer «Transmash», who claimed permanent injunction and seizure and destroying of the devices in dispute, because of the alleged infringement of an invention patent RU 2578400. Due to the plaintiff, all the row of defendant's break pressure distributors was under the scope of the patent claims, therefore the selling of the client's products should be stopped. Both parties agreed that there is no literal infringement, therefore the main dispute was regarding the possibility of applying the doctrine of equivalents to the case. The patent claim under dispute had a very long list of features, some of them very specific. Some of these features were further developed by the defendant, and such development was considered novel and inventive by Rospatent since respective invention patents protecting these amended features were granted. It should be also noted, that previously and apart from this court case, the defendant tried to invalidate the patent basing on the lack of inventive level, and the Rospatent found, that these very features of the patent in question were not known from the prior art, and therefore ensured inventive level of the invention. So, the question was, whether a doctrine of equivalents should be applied to the situation, when a feature A, distinguishing the invention from the prior art, was substituted by the defendant by another feature B, which in its turn was considered by Rospatent a substantial achievement, novel and inventive. The experts nominated by court agreed with the defendant's position, that in this case such a substitution cannot be considered an equivalent, but should be treated as further innovation, and therefore cannot be within the scope of the patent claims. The Arbitration Court of the Tver Region took the decision on March 25, 2019, by which agreed with the experts and refused in claims in full. The plaintiff appealed the decision, meanwhile, the appeal instance agreed with the defendant's position and confirmed the decision by its Ruling as of June 06, 2019. The court case number is А66-28/2018, full file of the court case can be seen here. The case was very important both for our client, who was facing the threat of full stop of operation and for the court practice since the decision shed some further light to principles of application of the doctrine of equivalents in Russia. The defendant was represented in both instated by the «A.Zalesov & Partners» Patent & Law Firm: by Aleksey Zalesov, Managing Partner, Irina Ozolina, Senior Partner and Vladislav Ryabov, Senior Associate.