In Kamstrup A/S v. Axioma Metering UAB, No. 2021-1923 (Fed. Cir. Aug. 12, 2022) (“Kamstrup”), the Court of Appeals for the Federal Circuit affirmed the holding of the Patent Trial and Appeal Board that the challenged claims of U.S. Patent No. 8,806,957 were unpatentable. See Axioma Metering UAB v. Kamstrup A/S, IPR2019-01640, Paper 32 (P.T.A.B. April 1, 2021). This post focuses on the product-by-process claim element.


Axioma challenged claims 1- 15 of the ’957 patent on anticipation and obviousness grounds. Independent claim 1 recited:

An ultrasonic flow meter housing comprising:

a monolithic polymer structure being cast in one piece, the monolithic structure includes a flow tube and a cavity separated from the flow tube, wherein the flow tube defines a through-going straight flow section arranged for passage of a fluid between an inlet and an outlet, wherein a part of a wall of the flow section is part of an inside surface of the cavity, so that the flow section and the cavity has a shared wall area; and

wherein the cavity is arranged for housing

at least one ultrasonic transducer, at the shared wall area; and

a measurement circuit operationally connected to the at least one ultrasonic transducer so as to allow measurement of a flow rate of the fluid.

Kamstrup at *3 (emphasis in original).

The Board construed the claim phrase “being cast in one piece,” as a product-by-process element. Id. at *4. As such, the phrase was not given patentable weight and, thus, not considered in either the anticipation or the obviousness calculus. Id. Ultimately, the Board found the claims anticipated. Id. at *5.

Federal Circuit

The Federal Circuit agreed with the Board that the phrase “cast in one piece” is a product-by-process claim element because “it describes the structure ‘being’ cast in a particular way.” Id. at *10-11. Kamstrup argued that the “mere mention of a process in a claim limitation does not automatically convert that limitation into a process limitation.” Id. at *11. The Federal Circuit noted, however, that Kamstrup did not explain why the claim should not be considered as a product-by-process claim or show where the specification described structure for the term. Id.

The Federal Circuit also agreed with the Board that the “cast in one piece” limitation did not impart patentable weight. Kamstrup argued that the Board erred in finding that there are no functional or structural differences between polymer structures cast in a single mold versus multiple molds. In response, the Federal Circuit noted that Kamstrup did not identify any functional or structural differences that would distinguish the claimed product from structures made using another method. Id. at *12. The Federal Circuit further noted that Kamstrup’s alleged difference “is detached from the claims” which “state that the structure should be ‘cast in one piece,’ not cast in one mold.” Id. (emphasis in original).

Take Aways

When a novel and patentable product can only be defined by the process that produces it, a claim to such a product defined by its method of preparation is proper. See Manual of Patent Examining Procedure at §2113. Despite the reliance on process limitations, however, a product-by-process claim is not a method claim, but rather a product claim. This type of claim format can provide patent protection to new products that are otherwise incapable of structural characterization. However, several practical disadvantages are associated with the use of product-by-process terminology, since product-by-process claims are construed broadly by ignoring the process limitations for determining patentability, but narrowly by requiring that the accused product was made by the recited method steps for determining infringement. Accordingly, whether use of the product-by-process format is warranted will depend upon the unique circumstances of each case and will require balancing the benefits and the practical disadvantages of the format.

Interestingly, the Federal Circuit (and the Board) did not cite well-established case law about product-by-process claims in this case, such as the en banc holding Abbott v. Sandoz, 566 F.3d 1282 (Fed. Cir. 2009) following Atlantic Thermoplastics Co. v. Faytex Corp., 970 F.2d 834 (Fed. Cir. 1992), which held that process terms are only considered limitations when the issue is infringement, not patentability. Unlike other claim types, product-by-process claims are in fact treated differently for validity and infringement analyses:

In determining validity of a product-by-process claim, the focus is on the product and not on the process of making it. …. That is because of the already described, long-standing rule that an old product is not patentable even if it is made by a new process. As a result, a product-by-process claim can be anticipated by a prior art product that does not adhere to the claim’s process limitation. In determining infringement of a product-by-process claim, however, the focus is on the process of making the product as much as it is on the product itself. … In other words, “process terms in product-by-process claims serve as limitations in determining infringement.” ... As a result, a product-by-process claim is not infringed by a product made by a process other than the one recited in the claim. …

The impact of these different analyses is significant. For product-by-process claims, that which anticipates if earlier does not necessarily infringe if later. That is because a product in the prior art made by a different process can anticipate a product-by-process claim, but an accused product made by a different process cannot infringe a product-by-process claim. Similarly, that which infringes if later does not necessarily anticipate if earlier. That is because an accused product may meet each limitation in a claim, but not possess features imparted by a process limitation that might distinguish the claimed invention from the prior art.

Amgen Inc. v. F. Hoffman-La Roche Ltd., 580 F.3d 1340, 1369–70 (Fed. Cir. 2009) (citations omitted). This principle has been applied in Board proceedings.[1]

For the practitioner attempting to successfully draft (or avoid drafting) a product-by-process claim, first distinguish process limitations from structural limitations. This is not necessarily an easy task because the dividing line between the two categories is not always clear. In a product-by-process claim, the process limitations often comprise verbs in the past tense. Thus, phrases incorporating words such as “obtained by,” “formed by,” “prepared by,” “heated until,” and “vapor-deposited” have all been construed to connote a process. However, process limitations do not exist exclusively in such format. For example, by describing a composition of matter as a “condensation product,” the claim drafter has employed wording that is suggestive of a process—thereby subjecting the language to interpretation as a process limitation. Defining a composition as “fluorinated,” however, may connote structure as well as process. See In re Moore, 439 F.2d 1232 (C.C.P.A. 1971).

If the claim language, as a whole, is found sufficiently structural (in addition to the process connotations), the special rules for prosecuting “product-by-process” claims are not applicable. In Andersen Corp. v. Fiber Composites LLC, 474 F.3d 1361 (Fed. Cir. 2007), the claim term “composite structural members” was construed as limited to composite compositions made with an intermediate step of pelletization or linear extrusion. According to the Federal Circuit, the claimed physical properties of the composite structural members were attributable to the process used to make them. “[P]rocess steps can be treated as part of a product claim if the patentee has made clear that the process steps are an essential part of the claimed invention.” Id. at 1375. This is consistent with the approach taken by the Federal Circuit in Kamstrup.

A prudent practitioner may well observe a self-imposed reluctance to define an article in process terms. Having claims characterized as “product-by-process” claims renders them more vulnerable to patentability/validity attacks. Similarly, the scope of enforceability afforded product-by-process claims may be subject to extremely narrow interpretation, as the alleged infringer may escape if using a different, non-equivalent process. But when used under the right circumstances, product-by-process claims can afford valuable protection to otherwise difficult-to-claim inventions. See, e.g., Application of Pilkington, 411 F.2d 1345 (C.C.P.A. 1969) (finding product-by-process claim covering “float glass” not improper, as the invention could not be adequately claimed by the physical characteristics of applicant’s sheet glass).