Usually the holder of a patent does not have to inform others of the existence of it and can start a lawsuit for infringement without notifying anybody. This happens because patents are public documents that, in theory, everyone can see; therefore whoever copies a patented item commits an illegal action, whether he was aware or not, of the existence of the patent relative to the object. In this case, however, first you received the summons and then also the text of the patent. This particular course of action would have an explanation if the patent were not still “accessible to the public”, which normally happens after 18 months. In the secrecy period, in fact, anyone can legitimately produce the inventive object, unless he receives an official notification of the text of the patent marking the time from which any production is considered illegal. If this was the real situation, first the text of the patent should have been notified, and then the summons, as, if the two actions have been inverted, the first act received could be faulty and therefore the civil procedure could be unacceptable. However this is a complicated situation to be resolved only by a competent lawyer who, after having checked the documentation, could advise you.