Patent Drafting: The Detailed Description Should Include Multiple Embodiments or Examples

By Joseph Root
August 19, 2014

EDITOR’S NOTE: This article is an excerpt from Rules of Patent Drafting: Guidance from Federal Circuit Cases, 2014 Edition, which is now available at This is the second installment of what is scheduled to be a 6 part series. To read other installments please see Joseph Root on Patent Claim Drafting.


Along with their ABC’s and multiplication tables, patent lawyers learn two basic principles. First, claims define the invention. Second, a court should not read limitations from a single embodiment into the claims, absent a demonstrated clear intention by the patentee to do so.

Don’t believe them.

When the Federal Circuit brings up the principle that one should not import the limitations of a single embodiment into a broader claim, expect the opinion to show how, under the particular, specifically limited facts of the present case, the inventor actually intended to limit the claims to the disclosed embodiment. The decision in Abbott Labs. v. Sandoz, Inc. provides an excellent example of the court’s reasoning. There, the specification described only a single embodiment, but the claims extended beyond the embodiment, but no issues of either prior art of enablement were present. The fact that the patent presented only a single example served as a starting point, after which the court was able to find “clear intent” to limit a broad claim term, “crystalline,” to a particular crystal.

The Federal Circuit’s analysis process can be seen clearly in Gen. Am. Trans. Corp. v. Cryo-Trans, Inc., construing a claim limitation of “a plurality of openings . . . adjacent each of said sidewalls and end walls,” in a refrigerator compartment, located above a storage compartment. The openings around the perimeter of the compartment allowed cold air to flow downward and around the walls of the storage compartment located below. The specification and drawings disclosed a single embodiment having separate openings on the end walls and sidewalls. The accused infringing device had openings along two walls, not four. In construing the claim to require the exact structure shown in the embodiment, the court employed language that is practically paradigmatic in single-embodiment cases:

This is not just the preferred embodiment of the invention; it is the only one described. Nothing in the claim language, specification, or drawings suggests that any of the dedicated side or end wall openings may be eliminated, or that an opening may be “adjacent” to more than one wall.

Note clearly the difference between this analysis and the traditional view. In the “claims define the invention” world, the technological territory between the border defined by the disclosure and that defined by the claims constitutes part of the invention. The patentee is allowed to claim beyond the scope of the disclosure, so long as the claim is supported under § 112, ¶ 1 and further, that the claim stops short of the prior art. In Disclosure World, that territory belongs to no one, because the invention is really defined by the specification.

That process is repeated in Netword, LLC v. Central Corp., describing a system for locating and retrieving information on a distributed computer system or network. The claimed system includes a central registry computer; one or more local server computers; and one or more client computers, in which network resources are referred to by aliases; and information about the aliases is maintained in a variety of locations. As described in the specification, local server computers cache frequently accessed data for rapid access. The main claim, however, does not require any caching by the local server computers. Because “the distinct local server functions must be present and be performed as described in the specification,” the Federal Circuit upheld the district court’s claim construction requiring that the local server computer perform caching operations.


Decisions such as Netword may be difficult to understand, but decisions going the other way offer no help in developing any principle underlying these decisions. One of the more notable decisions refusing to import limitations from a single embodiment is Teleflex, Inc. v. Ficosa North America Corp., where the claimed invention was directed to a shift cable that connects a shift knob with an automatic transmission on a vehicle. A claim limitation, reciting a clip for mechanically interlocking several of the components, (Fig. 6) was construed by the district court as requiring a structure identical to that shown in the single disclosed embodiment. The court provided an extended discussion of the law of claim construction and then overturned the district court’s construction, explaining,

The specification describes only one embodiment of the claimed “clip” but in the circumstances of this case the record is devoid of “clear statements of scope” limiting the term appearing in claim 1 to having [the structure disclosed in the embodiment]. Absent such clear statements of scope, we are constrained to follow the language of the claims, rather than that of the written description.

The rationale explaining why Teleflex does not acquire a limitation from the specification, yet Netword acquires exactly such a limitation, does not appear intuitively obvious to the casual observer. Certainly, no express statement appears in the Netword patent that could be construed as a statement of intent to limit claim scope. Similarly, Teleflex contains no statement of contrary intent. Neither decision relied upon any language from the patents, however. Rather, in both instances, the courts looked to the functioning of the inventions and simply made determinations, with no explanation, that the inventor’s clear intent required exclusion of the limitation in Teleflex and inclusion in Netword.

This issue assumes particular importance in determining whether a court will apply the doctrine of equivalents. The court discussed that question in Tanabe Seiyaku Co., Ltd. v. ITC, which discloses and claims a chemical process for preparing diltiazem hydrochloride, a pharmaceutical product used to treat various cardiovascular diseases. Both the claims and the specification set out specific base-solvent combinations rather than categories of bases and solvents. The applicant identified one solvent as a “lower alkyl acetate.” The court noted that the applicant could have described that solvent in broader terms as “acetone,” a description that would have been understandable by those of skill in the art. When the patentee attempted to invoke the doctrine of equivalents to gain coverage for acetone, however, the court refused to expand the claim scope. Use of the narrower term, the court explained, “would suggest to a person skilled in the art that alkyls other than acetone may not be useful for the [claimed] reaction.”

Again, note the search for intent. No question would have been raised had the applicant chosen to describe the solvent as an acetone. Choice of the narrower term, however, was interpreted as choosing in two directions—positively adopting the narrower term, and at the same time deliberately limiting scope by carving acetone out of the application. There, had the applicant added a single sentence, to the effect that choice of the stated solvent did not rule out other suitable choices down to the art, such as acetone, a result most likely would have been opposite.

In a mechanical context, the same situation can be seen in Sage Prods., Inc. v. Devon Indus., Inc., involving a sharps disposal container. The patent discloses a fairly simple structure with a container having a slot formed in its upper surface and two constrictions in the form of cowls extending over and under the slot to block access to the container’s interior. The claim set out “an elongated slot at the top of the container body . . . [and] a first construction extending over said slot.” The complete description of the slot and its construction follows: “The top 14 includes an elongated access slot, as shown in Fig 3. A first construction is formed over the slot . . ., the first constriction comprising a first cowl extending from and above one longitudinal side of the slot.” The accused device featured a slot located inside container body, with the constriction lying under the slot. The patentee alleged infringement under the doctrine of equivalents.

Here, the Federal Circuit entered into an extended critique of patent drafting, worth considering in full:

The claim at issue defines a relatively simple structural device. A skilled patent drafter would foresee the limiting potential of the “over said slot” limitation. No subtlety of language or complexity of the technology, nor any subsequent change in the state of the art, such as later-developed technology, obfuscated the significance of this limitation at the time of its incorporation into the claim. If Sage desired broad patent protection for any container that performed a function similar to its claimed container, it could have sought claims with fewer structural encumbrances. Had Sage done so, then the Patent and Trademark Office (PTO) could have fulfilled its statutory role in helping to ensure that exclusive rights issue only to those who have, in fact, contributed something new, useful, and unobvious. Instead, Sage left the PTO with manifestly limited claims that it now seeks to expand through the doctrine of equivalents. However, as between the patentee who had a clear opportunity to negotiate broader claims but did not do so, and the public at large, it is the patentee who must bear the cost of its failure to seek protection for this foreseeable alteration of its claimed structure.

In a footnote to the first sentence, the court added, “The public record reflects a manifest intention to claim the structure and no more. Whether actual or constructive, that inattention now binds [the patent owner].”

Whether a narrow claim scope flows from claim construction or the doctrine of equivalents, the results of a narrowly drafted, single embodiment are clearly depicted. Limitations of the single embodiment are likely to be read into the claim, under the rubric of implementing the inventor’s intent, or the application of the doctrine of equivalents will be severely restricted. The primary route circumventing these limitations is clear: always include multiple embodiments. In decision after decision, the Federal Circuit sends one clear thought, one sole idea, written in boldface across opinion after opinion: There is no substitute for embodiments.

The Author

Joseph Root

Joseph Root has served as both IP and General Counsel, in-house and out, for corporations and law firms, in a career spanning three decades. In 2008 he founded QualiPat, a company performing IP services and training. There, he built, trained, and managed an IP team in India that performed patent drafting and analytics, including preparing and filing over 300 US patent applications. He is also the author of Rules of Patent Drafting: Guidelines from Federal Circuit Case Law.

Over the course of his career, Joe has assumed both management and hands-on responsibilities for the identification, protection, and enforcement of both patents and trademarks. His expertise was recently recognized by London-based Intellectual Asset Management magazine, which named him to the “IAM Strategy 250 – The World’s Leading IP Strategists.” Joe received his JD (magna cum laude) at Wake Forest University School of Law, and a BS in engineering from the United States Military Academy at West Point. Prior to law school, he worked as an engineer, production supervisor, and soldier, including a tour commanding an infantry company in Vietnam. He is now a country patent lawyer in the hills of North Carolina, with his wife Natalie and bearded collie Claymore.

Joe can be reached at

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 Read more.

Discuss this

There are currently 7 Comments comments.

  1. John Smith August 20, 2014 10:39 am

    In the Tanabe discussion, it states: “The applicant identified one solvent as a “lower alkyl acetate.” The court noted that the applicant could have described that solvent in broader terms as “acetone,”

    This is nonsensical–acetone is NOT a lower alkyl acetate (an example would be ethyl acetate, an ester); instead, it is a ketone and a specific compound instead of a broader term. It is not a group of compounds such as a “lower alkyl acetate.” Someone has mis-written or misinterpreted the chemistry here!

  2. EG August 20, 2014 11:05 am


    Excellent point about describing multiple embodiments. An obvious principle which should still be stated repeatedly because, as you point out in the reported cases, this principle is REPEATEDLY overlooked or ignored. You can never have “too many” embodiments described in the specification.

  3. Paul Cole August 22, 2014 6:14 am

    At an AIPLA luncheon meeting, Judge Richard Linn pointed out that a single embodiment describes a point. Two embodiments describe a line. Three embodiments can describe an area. Therefore if you wish to claim a field you should endeavour to disclose three or more embodiments.

    Wise and unforgettable advice. And we have it from high authority.

  4. Anon August 22, 2014 11:16 am


    Are you assuming that your invention must fit into a Cartesian working space?

  5. MaxDrei August 22, 2014 11:52 am

    I find it helpful to liken the independent claim to a balloon, protecting that which is inside it. I cannot envisage any space that has more than threee dimensions. I want to claim more than an area. I want a space, but I dispute that I have to disclose a minimum of four Examples.

    The Best Mode is like a nugget (a diamond) within the volume inside the balloon membrane. An enabling disclosure of the Best Mode might then not be enough to support the membrane.

    I liken the supporting disclosure to solid matter within the balloon. It is what stops a pin-prick to the balloon resulting in a collapse down to the diamond. Call this solid matter “embodiments” if you like, but I doubt there is any hard and fast Rule that tells us exactly how many embodiments are enough. It varies, I would suggest, from case to case.

  6. Andrew Schwerin August 25, 2014 3:29 pm

    Gene and Joseph –

    I’m enjoying this little series immensely. These are great little game-ready tidbits to keep my sharp in my practice. Thanks much!


  7. Gene Quinn August 25, 2014 4:38 pm

    Thanks Andrew. We have 4 more parts to come. Part 3 will be published on Tuesday 8/26.