I am the inventor of patent 4131769. When I lost my home in 1990,my patent certificate was left behind. I didn't know my patent number until 2007, when I found my patent the Internet. I've been trying to find out what happened to my patent of a phone lock.

After describing my phone lock to a few people, I was told that their parent had a lock on their phone like the lock I described to them, thus I'd like to know who sold and who purchased patent #4131769.

  • To be clear, are the modern phone locks you're talking about locks on smartphones? If so, I have to imagine that a 1977 patent on the historical telephone devices would be substantially different? The pocket computers we call "phones" today are not really the same devices as the early those primitive proto-"phones" that would've existed in the 70's...
    – Hack-R
    Jul 12, 2016 at 2:42

2 Answers 2


Since you are the assignee, you would be the only one allowed to sell the patent. Although a patent provides you with a limited term of exclusivity, it is up to the patent owner to enforce the patent. At this point so long after the expiration of the patent, there would likely be no way to obtain royalties even if you could prove someone made your device during the patent's term.

I did a Google image search of telephone locks and didn't see anything that looks the same as what is described in the patent so it may be that your friends recollection is faulty.


It shows as original assignee Sylvia Davis on the patent site and no other assignees:


It's long expired as you know. Hope this helps.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .