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Decreasing Ambiguity in Patent Claims

A well-written claim should not be ambiguous.  At least, that is one goal.  Yet, language is full of imprecision, many words have multiple dictionary definitions, and ofttimes lengthy and complex grammatical constructions in patent claims give rise to multiple possible interpretations.  How can we reduce ambiguity in claims?

Time-honored and valuable techniques are to read, proofread, and reread each claim thoroughly, and have a reviewer do likewise.  A key test is to ask one’s self, is the claim clear?  Could an Examiner, or an opponent in court, misinterpret or twist meaning in some part of this claim?  If so, is there a way of rewriting that part of the claim so as to make it clearer?  Claim drafting is an iterative process, and this test should be applied many times while writing, and again when reviewing each claim.

Here is a misleadingly simple phrase, with multiple interpretations, which could serve as a template for a line or subparagraph in a claim: an X having a plurality of Y with Z.  Does the phrase mean one X that has several instances of Y, and each instance of Y is accompanied by a Z that belongs with the Y?  Or, does it mean one X that has several instances of Y, and the X is also with a Z?  Adding punctuation might not help.  Consider: an X, having a plurality of Y, with Z.  This is no clearer.  How about: an X having a plurality of Y, each Y having a Z.  Or, an X having a plurality of Y, the X with a Z.  These seem clearer.  Breaking up a phrase into sub phrases, and referencing part of one of the sub phrases in another one of the sub phrases can bring clarity. 

A useful exercise, if faced with a challenging, compound phrase, is to take the phrase apart and write a series of separate sentences (e.g., as if drafting an abstract or summary for the patent application).  Make sure each sentence is straightforward and clear.  Then rewrite the original compound phrase in terms of the sentences, re-crafting each sentence as a phrase in the new claim.  Make sure the new phrases connect well, and use proper antecedent establishment and reference.  Then, massage, iterate, smooth and retest the claim.  Does the claim flow?  Is the claim clear?  In time, with practice and experience, this process gets to be part of the toolset.  All part of the art of patenting.

Copyright © 2019 Womble Bond Dickinson (US) LLP All Rights Reserved.


About this Author

Christopher M. Hall, Womble Carlyle Law Firm, patent agent
Patent Agent

Chris Hall counsels clients in preparing and prosecuting patents in the electrical, telecommunications, computer software, and mechanical arts. 

Specifically, Chris has handled patents for:

  • Semiconductor processing, fabrication and integrated circuitry,
  • Optics
  • Optoelectronics
  • Artificial intelligence
  • 3-D imaging and image generation
  • Fault tolerance
  • Robotics

*Chris Hall is a registered patent agent and is not licensed to practice law. His activities are directly supervised by members...