A Jepson claim is one where the preamble makes some kind of statement that relates to the state of the prior art, and then claims an improvement over the prior art.
Many U.S. patent attorneys consider using Jepson claims "bad practice", because they essentially make a number of admissions regarding components being in the prior art, although there is a general reluctance for a patent attorney to make any admissions of prior art to the USPTO. "Deny everything! Admit nothing!"
However, this style of claim is actually required by many European patent offices. Thus, any advantage you believe you will receive by not making any admissions in a U.S. case will be quickly eliminated once you file for a patent on the same invention in a European country. When that happens, any admissions you make that are present in the claims of the European case will carryover to the U.S. side as well: You are not allowed to admit a component is prior art in a European case, and then simultaneously argue it the same component is novel and non-obvious in the companion U.S. case.
Many U.S. patent attorneys consider using Jepson claims "bad practice", because they essentially make a number of admissions regarding components being in the prior art, although there is a general reluctance for a patent attorney to make any admissions of prior art to the USPTO. "Deny everything! Admit nothing!"
However, this style of claim is actually required by many European patent offices. Thus, any advantage you believe you will receive by not making any admissions in a U.S. case will be quickly eliminated once you file for a patent on the same invention in a European country. When that happens, any admissions you make that are present in the claims of the European case will carryover to the U.S. side as well: You are not allowed to admit a component is prior art in a European case, and then simultaneously argue it the same component is novel and non-obvious in the companion U.S. case.