I have two interrelated apparatus like a socket and a plug. I'd like to draft one independent claim for each one. Is it possible to draft 3rd independent claims included both apparatus? And if it is possible, after three independent claim, am i allowed to draft 4th independent claim for a system also comprises 3rd independent claim?

Note: Both of apparatus can be sold seperatly so I'd like to protect both. I believe, both of them novel but the second one may be not inventetive. So i don't want a second application for 2nd apparatus. Besides that their best use is provided together, because of that may be a good idea 3rd claim (if possible) to cover both if a problematic document appears. For same reason, if possible i'd like to draft 4th indepent claim for a system which 1st and second 2nd is actually is used in it.

Another note: It's EPO application and I know interrelated apparatus can be claimed in one application in a different independent claims. Please interpret my question taking this into consideration.

  • You edited the question to the point that the answers may not make sense.
    – George White
    Dec 26, 2020 at 20:07
  • 1
    I don't have time for a full answer, but the EPO guidelines say that independent claims may be used for socket/plug combinations and for system claims which are basically dependent claims anyways, citing all features of the other devices - so yes, you can do this
    – user18033
    Dec 26, 2020 at 20:18

1 Answer 1


You an do this, in fact it doesn't even need the third claim to be independent. I do not know EPO law very well but there are innumerable U.S. patents with a claim 1 to a transmitter that sends a particular signal to a receiver, a claim 2 to receiver that receives that same particular signal from a transmitter; and a system including both a transmitter and a receiver. The claim for the complete system can be a dependent claim to either 1 or 2. It could also be an independent claim.

EPO law allows only one independent claim for each aspect - apparatus, method, system, etc. Socket and plug might be two different things each due one independant claim.

Other examples are clients/servers and plugs sockets. If there is something that makes the interaction of plug and socket novel and inventive the same principle may be at ply in both the plug and the socket. IF you are not sure abut the inventiveness of either the plug or the socket it is good to claim each and claim the combination of the two.

U.S. examples (found using a search at the USPTO in the form ACLM/"a plug" AND ACLM/"a socket")

  • 9,583,897 Electrical connection system with annular contact
  • 9,306,325 Plug, socket and their combined structure of electrical connector
  • 10,791,311 Transmitting apparatus, transmitting method, receiving apparatus, and receiving method also pending as EP3591977A1 with claims to both transmitter and receiver.
  • +1 for citing examples.
    – Eric S
    Dec 26, 2020 at 19:49

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