Patent Claim Drafting

Jepson Claims

"The improvement comprising" — and why most practitioners now avoid this format.

Quick Answer

A Jepson claim uses the format "In [known combination], the improvement comprising [new elements]." The preamble constitutes an irrevocable admission that those elements are prior art — a dangerous trap that most patent attorneys avoid in favor of conventional claim drafting.

Claim Anatomy

Structure of a Jepson Claim

37 C.F.R. § 1.75(e) authorizes Jepson format for "improvements." The regulation states that where the improvement is claimed in a combination, the preamble may define the context, and the claim body should clearly identify the improvement.

/* Three-part structure */

1. Claim 1. In a widget comprising a housing, a rotor, and a drive mechanism,

the improvement comprising:

a sensor coupled to the drive mechanism configured to measure rotational speed; and
a controller in communication with the sensor configured to adjust drive mechanism output in response to the measured speed.

Preamble (yellow)

States the known combination — housing, rotor, drive mechanism. ADMISSION: all three are treated as prior art for §§ 102/103 analysis. Cannot later argue they are part of the invention.

Transition (green)

"The improvement comprising" is the required language. Alternatives: "wherein the improvement comprises," "characterized in that." The word 'improvement' triggers the APA rule.

Body (white)

The genuinely novel contribution — sensor + controller. Only these elements need to be novel and non-obvious over the prior art combination. These are what the examiner focuses on.

The Risk

Prior Art Admission — Why Jepson Is Avoided

The core danger: once a Jepson preamble is written, the elements stated therein become "Admitted Prior Art" (APA) — and APA can be combined with any other prior art to render the improvement obvious under § 103, even if no single prior art reference contains those preamble elements.

Example: an applicant writes a Jepson claim admitting that "a base station comprising antennas, a transceiver, and a processor" is prior art. During litigation, the defendant can use that APA to satisfy the §103 combination rationale without finding a single reference that shows all three. The combination might not actually have appeared in any prior art reference.

In contrast, a conventional claim ("A base station comprising antennas, a transceiver, a processor, [and the novel elements]") forces any challenger to locate prior art disclosing the entire combination — which may not exist, giving the patentee a stronger validity position.

Practitioner consensus: avoid Jepson format

Nearly all U.S. patent prosecutors today avoid Jepson claims unless the prior art admission is harmless (the combination is unambiguously in the prior art) and the format serves a specific claim clarity purpose. European practitioners who use the "characterized in that" format (European Patent Convention Rule 43(1)(b)) often need to reformat claims for U.S. national phase to avoid unintended APA.

FAQ

What is a Jepson claim format?

A Jepson claim is a patent claim format authorized by 37 C.F.R. § 1.75(e) used to claim improvements to known combinations or apparatus. The format has three parts: (1) a preamble reciting the prior art combination ('In a widget comprising A, B, and C'); (2) a transitional phrase ('the improvement comprising' or 'wherein the improvement comprises'); and (3) the improvement elements ('D and E configured to…'). The format was established in Ex parte Jepson (Ass't Comm'r Pat. 1917).

Why is the Jepson preamble a problem?

The preamble of a Jepson claim constitutes an admission that the elements recited therein are prior art. Under 37 C.F.R. § 1.75(e) and case law (Pentec, Inc. v. Graphic Controls Corp., Fed. Cir. 1984), the preamble elements are treated as admitted prior art (APA) for purposes of § 102 and § 103 analysis — even if those elements were not previously combined or publicly known. This can eliminate novelty arguments and narrow available prior art defenses in invalidity litigation.

When should you use a Jepson claim?

Jepson claims are appropriate when: (1) the combination in the preamble is unambiguously prior art (no need to preserve the possibility of arguing against it); (2) the improvement is truly novel and non-obvious over any prior combination; (3) claim clarity and infringement proof are served by clearly distinguishing the inventive elements from the known combination. In practice, most patent prosecutors avoid Jepson claims because the prior art admission is irrevocable and the same scope can often be achieved with conventional claim drafting.

Can I avoid the prior art admission by using a conventional claim instead?

Yes — the same inventive contribution can often be claimed conventionally: 'An apparatus comprising A, B, C, D, and E, wherein D is configured to…' without any Jepson structure. This conventional approach claims the whole combination without admitting any elements are prior art. The examiner may then need to find prior art to support a § 102/103 rejection rather than relying on a preamble admission. However, the claim may be broader and easier to design around.

Does the examiner require Jepson format for improvement inventions?

No. 37 C.F.R. § 1.75(e) says an applicant 'may' use Jepson format — it is optional, not mandatory. Examiners cannot require Jepson format. If an applicant claims an improvement without Jepson format, the examiner must rely on prior art found in the prior art record, not on admission from a voluntarily-written Jepson preamble.