How come sometimes a USPTO application/grant has many numbers form the same patent?

For example:

US6334845 (B1)

is "also published as" US6422996(B2) and as US6413211(B2).

I understand that the same patent has different numbers for different country offices. But how is it that the same patent can have different numbers in the USPTO for different phases (B1 and B2) or even for the same phase (2 names for B2)?

2 Answers 2


When Google patents says "also published as" it is not being precise and that is a primary cause for the confusion. As you are aware, each country has its own system of patent numbering. More fundamentally, the have their own entire patent systems. A Canadian patent number is not just a different name given to a U.S. patent. They may have the same specification and drawings, but different claims. Even if the claim wording is the same, the words are interpreted under each countries laws. The same words can lead to very different scope of claimed material. There are two more dimensions to the multiplicity of numbers. First, these are publication numbers. If the only difference is the number in the suffix, it is a different publication of the same patent. If it is a completely different number but in the same country, the spec. and drawings mat be the same but the claims are to different aspects of the invention.


In ESPACENET search results, under the section Bibliographic data, with "also published as" an "ESPACENET family" is retrieved and all the documents having (exactly) the same priority numbers are listed.

So, according to the fact that three several application have been submitted claiming the (exactly) same set of priority numbers, then the following US pubblications are grouped in the same ESPACENET family:

each line listing different phases of a different application.

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