In reference to the patent: US2949381


The patent must have expired many years ago. Patents can't be "renewed". It is the basic principle with patents that in return for exclusive ownership for a fixed period of time, once expired anyone can use the technology.

Patents filed before June 8th 1995 expire 17 years after the issue date. After that it is 20 years from the filing date. See Wikipedia

  • How long are they for? If they all vary, how do you find out? Thanks. Nov 24 '16 at 18:14
  • It used to be 17 years from the issue date. Now it is 20 years from the application date.
    – Eric S
    Nov 25 '16 at 3:22
  • @Jane Steinhardt: If you find my answer adequate, please accept it.
    – Eric S
    Nov 26 '16 at 17:31
  • @Jane Steinhardt: I appreciate your thanks, but you still would love for you to accept my answer. Look for a check box near the answer.
    – Eric S
    Dec 2 '16 at 22:40

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