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There are thousands of patents for perpetual motion machines. An invention must be novel, useful and non-obvious to be patentable, but it doesn't actually have

• Sharlin 8y ago
  It can’t be very useful if it cannot work even in principle though.
• pjdemers 8y ago
  I thought perpetual motion machines claims were automatically denied. I know they were back in the 1970s when my dad worked at the patent office.
  • andybak 8y ago
    Yes but the interesting aspect of this is that they had to make a specific rule for this case. In the general case of "filing nonsense" the system fails.
  • Alex3917 8y ago
    > I thought perpetual motion machines claims were automatically denied. I think the current policy is they are only patentable if there is a working unit that runs for at least a year when left alone in the patent office.