A patent claim must be limited to one of the various categories laid out in the statute, meaning that so-called “mixed” claims are not allowed. For example, a single claim cannot be both for a “system” and a “method.” This seems like a simple distinction, but of course confusion seems to abound with examiners, and the MPEP is not super helpful.

First to the case law. Mastermine Software is a relatively recent Fed. Cir. case (2017) addressing the issue of determining whether a claim improperly mixes two different subject-matter classes. A previous case (IPXL Holdings, L.L.C. v. Amazon.com, Inc.) is the original case on this point (the “1-click” patent). Both cases made clear that one cannot mix subject-matter classes in a single claim. As explained in Amazon, such a claim is not sufficiently precise to provide competitors with an accurate determination of the metes and bounds and is ambiguous and properly rejected under section 112, paragraph 2. The claim at issue in Amazon was a dependent claim which recited both the system of the independent claim and a method for using that system:

The system of claim 2 [including an input means] wherein the predicted transaction information comprises both a transaction type and transaction parameters associated with that transaction type, and the user uses the input means to either change the predicted transaction information or accept the displayed transaction type and transaction parameters.

So, it is clear that introducing method steps into system claims is a problem (see also In re Katz Interactive Call Processing Patent Litigation and Rembrandt Data Techs., LP v. AOL, LLC). But, this is not to be confused with introducing functional language into a system claim, which is totally fine (HTC Corp. v. IPCom GmbH & Co., KG, MEC, and UltimatePointer). In HTC, the claim seems a lot like a system and method mixed together:

A mobile station for use with a network including a first base station and a second base station that
achieves a handover from the first base station to the second base station by:
storing link data for a link in a first base station,
holding in reserve for the link resources of the first base station, and when the link is to be handed over to the second base station:
initially maintaining a storage of the link data inthe first base station,
initially causing the resources of the first base station to remain held in reserve, and
at a later timepoint determined by a fixed period of time predefined at a beginning of the handover,
deleting the link data from the first base station and freeing up the resources of the first base station,
the mobile station comprising:
an arrangement for reactivating the link with the first base station if the handover is unsuccessful.

But no, according to the Federal Circuit

this claim does not “recite a mobile station and then have the mobile station perform the six enumerated functions,” but rather, this claim “merely establish[es] those functions as the underlying network environment in which the mobile station operates.” Id. at 1277. Accordingly, we held that the “unconventional format” of this claim did not preclude it from being definite because it makes clear “that infringement occurs when one makes, uses, offers to sell, or sells the claimed apparatus: the mobile station—which must be used in a particular network environment.”

In Mastermine, we see the functional language example where a module with software is able to perform certain functions (presenting fields, receiving user selection, etc.).

In all of these cases, the issue is one of whether a system claim is indefinite because it includes things that seem like method steps, but that might be merely acceptable functional limitations.

The MPEP describes what examiners should do in MPEP 2173.05(p)II.

II. PRODUCT AND PROCESS IN THE SAME CLAIM

A single claim which claims both an apparatus and the method steps of using the apparatus is indefinite under 35 U.S.C. 112(b) or pre-AIA 35 U.S.C. 112, second paragraph. See In re Katz Interactive Call Processing Patent Litigation, 639 F.3d 1303, 1318, 97 USPQ2d 1737, 1748-49 (Fed. Cir. 2011). In Katz, a claim directed to “[a] system with an interface means for providing automated voice messages…to certain of said individual callers, wherein said certain of said individual callers digitally enter data” was determined to be indefinite because the italicized claim limitation is not directed to the system, but rather to actions of the individual callers, which creates confusion as to when direct infringement occurs. Katz, 639 F.3d at 1318 (citing IPXL Holdings v. Amazon.com, Inc., 430 F.3d 1377, 1384, 77 USPQ2d 1140, 1145 (Fed. Cir. 2005), in which a system claim that recited “an input means” and required a user to use the input means was found to be indefinite because it was unclear “whether infringement … occurs when one creates a system that allows the user [to use the input means], or whether infringement occurs when the user actually uses the input means.”); Ex parteLyell, 17 USPQ2d 1548 (Bd. Pat. App. & Inter. 1990) (claim directed to an automatic transmission workstand and the method of using it held ambiguous and properly rejected under 35 U.S.C. 112, second paragraph).

Seems OK, I guess. The problem is that examiners get confused when they see a method claim that defines certain actions relative to structure. This of course is a completely different situation than those noted above and should be no problem. In fact you have to actually work pretty hard to draft a method claim that never mentions any system components or structure. Plus even if you can draft such a claim, it is likely to face Section 101 abstract idea issues anyway.

But back to the issue - clearly one would have problems (claiming mixed classes) with a claim such as:

1. A system, comprising

   component A;

   component B coupled to component A; and

   carrying out a method of moving component A coupled with component B.

What should not be a problem (in terms of claiming mixed classes), however, is a claim such as:

1. A method, comprising:

   moving component A coupled to component B.

Yet many examiners are rejecting method claims for allegedly improperly including structure. See our post from a few weeks ago at the very end (here). As the PTAB confirmed in that case, there is no problem with adding structural limitations in a method claim in terms of the actions of the method:

So, if you have a method claim including certain method actions that also define the actions in the context of specific structure, and the examiner is alleging a mixed class claim, the above points may help explain that there is no problem with method claim actions being interacting with specific structure.