Patents by Inventor Todor Kostadinov Trifonov

Todor Kostadinov Trifonov has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Method of producing molded parts with a smooth noncellular skin and a cellular core from foamable thermoplastic material
    Patent number: 4092385
    Abstract: A method of injection molding foamed articles wherein, after the mold is closed and while the mold is held closed, a gas counterpressure is generated within the mold cavity against which a portion of the foamable resin is injected under a pressure which prevents foaming. Thereafter, a shape-forming element adapted to be retracted to be flush with a wall of the mold cavity in the final phase thereof, is advanced to force the nonfoamed material, still against the gas counterpressure, into the remainder of the cavity. After a skin has formed, on the mass within the mold cavity the latter element is retracted to permit foaming, preferably after foaming has been initiated by allowing a portion of the foamable mass to recede into the injection cylinder during the inception of the foaming process.
    Type: Grant
    Filed: November 24, 1975
    Date of Patent: May 30, 1978
    Assignee: Institute Po Metaloznanie I Technologia Na Metalite
    Inventors: Angel Tonchev Balevski, Ivan Dimov Nikolov, Evgeni Hristov Mateev, Todor Kostadinov Trifonov, Vassil Vladimirov Kojuharov