Patent infringement requires the plaintiff to prove unauthorized use of a patented process, while the validity of the patent must meet criteria of novelty, description, and utility.

1. This is a suit for infringement of patent under S.29 of the Indian Patents and Designs Act, 1911 , filed by the plaintiffs who are the legal owners and proprietors of Indian Patent No. 58716 in respect of the manufacture of new sulphonylureas, salts of those compounds and of anti - diabetic preparations containing such compounds. The application for the said patent was made by the plaintiffs on 23rd October 1956 and was accepted on 7th November 1957, but the same took effect from the 8th of May 1956 by reason of the provisions of S.78A of the Patents and Designs Act. One of the chemical compounds comprised in the said patent is Tolbutamide, and since 1957 the plaintiffs have been marketing the same as an anti - diabetic drug in India and all over the world under the trade mark "Rastinon." The suit was originally filed only against the present first defendants who, according to the Plaintiffs, have since May 1961 wrongfully and with full knowledge of the plaintiffs' said patent No. 58716 infringed the said patent by manufacturing, preparing and selling Uni - Tolbid tablets or Tolbutamide manufactured in accordance with and by the use of the invention disclosed in the plaintiffs' said patent "and claimed in Claims 1 and 11" thereof. The first defendants admit having manufactured or sold the said tablets under the name Uni - Tolbid or Tolbutamide but claim that the said tablets had been manufactured by the application of the processes mentioned in another patent, being patent No. 64323 held by the Haffkine Institute of Bombay which is owned by the present second defendant State, under a licence granted to them by the second defendants for the manufacture and sale thereof. The second defendants have, by an order dated 6th February 1967, been made party defendants to this suit on their own application at their own costs throughout, but it may be mentioned that no relief has been claimed against them in the present suit by way of amendment of the plaint after their joinder. It appears that the business of the first defendants has, since the filing of the present suit, been acquired and taken over as a going concern by the third defendants, being a company which was registered under the Companies Act on the 22nd of August 1962, and the third defendants have been manufacturing and selling Uni - Tolbid tablets or Tolbutamide ever since then as successors to the first defendants. The third defendants were, therefore, joined as party defendants to this suit by an order dated the 9th of January 1968, and by the amendments effected pursuant to the said order, the plaintiffs have claimed against the third defendants also the same substantive reliefs which they had claimed against the first defendants in the suit as originally filed. The reliefs claimed by the plaintiffs in the present suit against defendants Nos. 1 and 3 are, an injunction restraining them from infringing the plaintiffs' said patent No. 58716, an order for payment of a sum of Rs. 7,000/- as and by way of damages, or in the alternative, an order for an account of the profits made by defendants Nos. 1 and 3 from the sale of the infringing goods and for payment of the same to the plaintiffs, and for an order to deliver up to the plaintiffs for destruction of all articles i