Patent Claim Drafting: Improvements and Jepson Claims

U.S. patent laws specifically allow for the protection of inventions that are improvements upon the work of others. The law says: “Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title.” 35 U.S.C. 101 (emphasis added).  Indeed, virtually all inventions are improvements.  It is quite rare to see a truly pioneering invention, which is one that is the first of its kind.

But how do you go about patenting an improvement?  The first thing you must do is figure out what the advantages are over the prior art. You need to take a critical look at your own invention and identify that which distinguishes it over the prior art.  You should absolutely focus on structure, not on the method of use.  Differences in the method of use will only come into play if you are claiming a new and nonobvious method of using, which is typically not the case.  In the overwhelming majority of cases you want to protect the device or apparatus, which makes use differences irrelevant.To illustrate how you can identify structural differences, take a look at the two inventions below, both directed to a hitch mounted portable toilet seat.



It is probably readily apparent what the improvements are in the ‘860 patent over the ‘480 patent.  In addition to offering a toilet paper holder, there is also a canister under the toilet seat that acts as a collection receptacle, thereby not having to clean up what would otherwise fall on the ground with the invention of the ‘480 patent. For more on this see Improvements: Learning with the Hitch Mounted Toilet Seat.


The focus of this article is not specifically how to identify patentable improvements over the prior art, but rather to discuss one particular patent claiming technique that should, in my opinion, be avoided.

According to 37 C.F.R. 1.75(e), improvement patent claims should follow a specific template.  Rule 75(e) states:

(e) Where the nature of the case admits, as in the case of an improvement, any independent claim should contain in the following order:

(1) A preamble comprising a general description of all the elements or steps of the claimed combination which are conventional or known,

(2) A phrase such as “wherein the improvement comprises,” and

(3) Those elements, steps, and/or relationships which constitute that portion of the claimed combination which the applicant considers as the new or improved portion.

(emphasis added).

No patent attorney in their right mind would follow this suggestion.  There is no absolute mandate that patent claims to an improvement describe what is known or convention in the preamble.  Likewise, there is no absolute mandate that the transition phrase used mentions that the body of the claim relates to an improvement.  Inventors who seek to represent themselves beware!

Claiming done as Rule 75(e) suggests is known as writing a claim in Jepson format, or simply a Jepson claim.  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. Jepson format allows the patentee to use the preamble to recite elements or steps of the claimed invention which are conventional or known.

Those filing patent applications should be given Miranda warnings! Everything you do say can and will be used against you FOREVER!  This relates most directly to what is known as prosecution history estoppel.  When you make an argument to a patent examiner or make certain amendments or responses you are forever prevented from undoing what you did.  For that reason you should not make any admissions unless it is absolutely necessary. A Jepson claim is not something that you must employ and it comes with significant disadvantages with only the most nuanced of advantages the presents in a very rare circumstance.

What difference does it make whether you admit something is in the prior art?  It is all about characterization.  Parents will easily understand this point.  If you arrive home later and tell your 6 year old that there is something you want to talk to them about after dinner they might just yell out: “I didn’t put the cat in the dryer!”  Well now you have two things to talk about after dinner!

If you say the same thing to your teenager the conversation is quite different.  Teenager: “Really? What do you want to talk about.”  The teenager well knows that anything they say without knowing all the facts could only potentially haunt them later.  So while there should be dozens of things they could admit to they won’t.  They will build their story as they see you play your cards.  That is exactly how you must deal with the Patent Office.  If you start characterizing things right at the start and then the Patent Examiner finds some prior art you didn’t know about you are almost certainly going to wish you had made a more nuanced statement or description, or that you hadn’t said anything at all.

When using the format of Rue 75(e) the preamble is considered to positively and clearly include all the elements or steps recited therein as a part of the claimed combination. Therefore, the elements or steps recited in the preamble become a part of the claim and do in fact act as limitations.

Below is an example of a claim in Jepson format, which is taken from claim 6 of US Patent No. 4,892,244:

In a staple cartridge insertable within a surgical stapler and containing staples and comprising an elongated body including one or more longitudinal slots for slidably receiving one or more longitudinal pusher bars comprising a firing mechanism of said surgical stapler, and a plurality of drivers engageable by said pusher bars for ejecting the staples from the cartridge, said staple cartridge releasably fastened to a said surgical stapler, the improvement comprising a lockout mechanism connected to said longitudinal slots for preventing said pusher bars from passing more than one time through said longitudinal slots.

(emphasis added).

The Jepson preamble in claim 6 of the ‘244 patent (above) is all that comes prior to “the improvement comprising.” That which comes before “the improvement comprising” is describing what is already known in the prior art, a very dangerous thing to do without knowing what prior art the Patent Examiner will use against you. Notwithstanding, here the patentable invention covered by claim 6 of the ‘244 patent takes that which is known in the prior art and adds a lockout mechanism. Notice how easy the Jepson format is to write. The only part of the claim that requires original thought is the description of the improvement.  The ease of writing a Jepson claim is why some inventors write them, but in the patent drafting business if it is easy you are almost certainly doing something wrong!

Here is another example of a Jepson claim, take from claim 9 of US Patent No. 4,007,960:

In a reclining chair having a frame, a back portion, a seat portion, recliner actuator means including means forswinging said back portion between an upright and a reclined position, the improvement comprising elevator means for raising said seat and also tilting said seat forwardly to assist exit from said chair, and power actuated drive means common to both the recliner actuator means and the elevator means for sequentially actuating both the recliner actuator means and the elevator means and being operable sequentially in a first mode of operation to drive the recliner actuator means and operable in a second mode of operation to drive the elevator means, said power-operated drive means comprising an extensible ram which extends in one range during said first mode of operation and in another range in said second mode of operation.

(emphasis added).

Jepson claim meet means plus function claiming!  Yikes!  Means plus function claiming is not evil per se, but is far more nuanced than inventors and newbies are ready to handle, so let’s save that issue for another day.

Claim 9 of the ‘960 patent contains relatively little description of the scope and structure of the prior art. Nevertheless, in the Jepson claim situation, the patentee’s use of the Jepson format is evidence of intent to use the preamble to define the structural elements of the claimed invention. Therefore, when Jepson format is employed, the claim preamble defines the context of the claimed invention, the scope of the claimed invention, and may expand the universe of available prior art for examination purposes.

While it could hardly be argued that it is well known that a reclining chair would at the very least have a frame, back, seat, and means for swinging the back between upright and reclined positions, the patentee must seriously consider the wisdom in making use of such a Jepson claim. The relevant case law on Jepson claims suggests that the preamble elements in a Jepson-type claim are admitted to be prior art. In fact, according to MPEP 2129: “Drafting a claim in Jepson format is taken as an implied admission that the subject matter of the preamble is the prior art work of another.”

There is absolutely no reason why a Jepson claim could not be re-written into traditional format. If you take a look at the toilet hitch patent claims in the patents discussed above it becomes clear that you do not have to use Jepson claim format.  For example, here is claim 1 in the ‘860 patent, which clearly is an improvement on the ‘480 patent, which is even cited as an applicable reference in the ‘860 patent.  Claim 1 says:

1. A portable toilet comprising:

a support stem which may be inserted into a trailer hitch;

a base ring coupled to the support stem;

attachment device coupled to the base ring for removably coupling a waste collection bag to the portable toilet;

a toilet seat assembly coupled to the support stem and resting on the base ring; and
a multi positional toilet paper holder coupled to the support stem, wherein the multi positional toilet paper holder comprises:

a base plate coupled to the support stem;

multi positional latch coupled to the base plate wherein the multi positional latch has an arm member which may be moved and locked in a plurality of positions;

a tissue holder assembly; and

a hinge member coupled to the tissue holder assembly and the multi positional latch for moving the tissue holder assembly in an upward retracted position and a lowered deployed position.

There is a lot here, but notice how everything is positively introduced and the claim contains no admissions of any kind relative to prior art.  Every piece is introduced separately with proper antecedent basis (i.e., “a” or “an” the first time introduced and “the” or “said” when subsequently discussed).  You don’t need Jepson format.  For more on basic claiming with use of antecedent basis see Drafting Patent Applications: Writing Patent Claims and Drafting Patent Applications: Writing Method Claims.

Overcoming the admission implicitly created by a Jepson claim is not an easy task and, therefore, Jepson claims should be avoided in all but rare circumstances. Truthfully, I think Jepson claims should never be in a patent application but prefer not to say that the must be avoided in all circumstances.  It is certainly fair to say that inventors should always avoid Jepson claims.  The language will not be interpreted as you likely expect, so leave Jepson claiming to the trained professionals.  Consider it like a stunt, if you will.  Please do not attempt this at home!

As with all general rules, there are exceptions and circumstances where Jepson format may be useful. One such situation is where it may be appropriate to use a Jepson claim is when the patentee is attempting to overcome, or prevent, a double patenting rejection. Recall that certain art may be prior art to one inventive entity and not to another inventive entity. For example, a patentee’s own foundational work is not necessarily treated as prior art unless there is a statutory bar.  Therefore, when the patentee employs the Jepson format to avoid a double patenting rejection over the patentee’s own work, the use of the Jepson format causes no deleterious effects. In fact, in some circumstances the examiner may even suggest the use of a Jepson claim to clearly delineate the fact that the patent will only be covering the improvement and not the underlying work of the patentee.

For those who didn’t understand the previous paragraph, the rule for you is simple: DO NOT USE JEPSON CLAIMS!

For more information on patent application drafting please see:



Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of

Join the Discussion

4 comments so far.

  • [Avatar for GJ]
    November 10, 2012 08:15 pm


    A helpful article. I am sure you are aware that a similar two-part format is also preferred for EP applications. As in the US, there are ways around this however as it is not a statutory requirement and, although there is no estoppel with an EP, your advice not to admit anything initially is good advice for an EP too – let the Examiner determine the closest prior art and go from there.

    Btw, just a minor point, but in the example given above (referring to claim 9 of US 4,007,960), I think the second “means for” that you have underlined is not intended to be conjoined, i.e. I think the emphasis should be as follows: “power actuated drive MEANS common to both the recliner actuator means and the elevator means FOR sequentially actuating both the recliner actuator means and the elevator means…”.

    Keep up the good work!


  • [Avatar for CK]
    April 10, 2012 12:41 pm


    I disagree with some of this article. You say ” The language will not be interpreted as you likely expect, so leave Jepson claiming to the trained professionals.”. However, this is true for any claim whatsoever. The examiner is likely to interpret the claim in ways you never expected whether it is a Jepson claim or not.

    You also say that the Jepson claim protects the inventor from double patenting, which is telling only a part of the story. While it will protect from statutory double patenting, Jepson format does nothing to protect from non-statutory double patenting. If you have trouble with statutory double patenting, you are probably incompetent at claim drafting, so it’s moot.

    Certainly it is not a good idea in most cases to use Jepson format, and depending on the art, it may not ever be a good idea. What the Jepson claim does for the client is simplify prosecution. That’s it. That’s the only reason to use it.

  • [Avatar for Oleg]
    April 2, 2012 10:51 am

    In former USSR countries (I believe that in China too) there is a statutory requirement that independent claim must have structure which is akin to Jepson claim. Every claim must have limitation part which contains all mutual features of prior art and invention and distinctive part which contains features that distinguish invention from prior art. There are few exemptions related to methods, compositions and pioneer inventions. What’s interesting is that Russian or Ukrainian examiner will demand to rewrite a claim in accordance with aforementioned rules if an application was filed by national procedure, but if it was a PCT application not every examiner demands compliance of said rules.

  • [Avatar for anon]
    April 2, 2012 05:26 am

    I know a few Examiners who construe every Applicant response to read “It wasn’t me who put the cat in the dryer”!