Possible to patent an old patent?

[Mec4040]

What is the name of your state?NY

Hello,

I know it sounds confusing but will explain. I ask this question when I first noticed they are selling a new post hole digger.

I noticed in Home Depot they have this new post hole digger, which is way different then the old style. It made sense to use, I often asked myself when using an old hole digger, why they were made that poorly and here someone put together a very useful one, solving a few issues with the old one.

** My question, I know patents expire after I think 30 years...so lets say the old digger was patent 30 years ago. Here comes this guy with an idea to make the one we have now, the better one. Can he improve on the old patent and get his own?

If you cannot patent the old one, then how did this person make the new post hole digger? If the answer is he did it without a patent, then I ask doesn't that open your product (new hole digger) to being copied and sold?

Hope I didn't confuse anyone, and looking forward to hearing the answers


Me

 

[divgradcurl]

I know patents expire after I think 30 years

Actually, patents expire 20 years from the "earliest effective filing date" of the underlying application. There are a bunch of exceptions to this, but this is the rule the vast majority of the time.

Here comes this guy with an idea to make the one we have now, the better one. Can he improve on the old patent and get his own?

You can't "repatent" a patent -- once a patent is expired, its expired. However, you can obtain a patent on an invention that is based upon a previously patented invention, whether or not the earlier invention's patent is expired or not.

However, the new patent is limited. In you example, the underlying post hole digger no longer has a patent, but the new one does. For the new one, only those improvements that are really new are covered by the new patent -- any "old" stuff is not covered under the new patent. That makes sense if you think about it -- if you could just add something new and get a new patent that covered the old + the new, then patents would effectively never expire.

So, yes, it is perfectly acceptable to have a new type of post hole digger that is patented -- but anyone can manufacture the "old" type of post hole digger, because that part is NOT patented.

If the answer is he did it without a patent, then I ask doesn't that open your product (new hole digger) to being copied and sold?

Yes. Without a patent, anyone could copy it and there is nothing he could do about it.