A solid understanding of how dependent claims can limit structure in relation to method claims is something all patent professions should understand, even quality assurance specialists at the USPTO. Unfortunately, a recent appeal case illustrates that some still struggle with this concept. This misconception leads to unnecessary rejections, so perhaps it is worth addressing in detail.

Under 35 U.S.C. § 112(d), a dependent claim must refer back to a previously set forth independent claim and further limit the subject matter claimed. This means that dependent claims are designed to add specific limitations or details to the independent claim—for example by further limiting an element of the independent claim, or adding additional elements to the claim.

Confusion can arise with method claims, where examiners incorrectly assume that structural elements cannot be introduced in dependent claims. While it's true that a method claim cannot directly add structural elements as elements of the claim (whether independent or dependent) because this would mix method and structural elements, there is no prohibition on specifying further details of structure that is involved in the actions of the method.

To understand why dependent claims can add structural limitations when depending from method claims, it is important to recognize the nature of method claims. Method claims define a series of steps or actions, but these actions often involve specific structural components to carry out the method. For example, a method for operating a conveyor system could involve actions such as moving items, aligning them with a V-belt, or cushioning them as they fall onto a conveyor. These actions may depend on particular structural components—such as the V-belt itself, a cantilevered bed portion, or other mechanical features.

The point is that dependent claims can further specify the structure of these components and how they are used to perform the actions defined in the independent method claim. These structural limitations are tied directly to the actions described in the method and are entirely permissible under patent law.

Which brings up a recent PTAB decision. Appeal 2023-003935, Application 16/211,490. The case involves a method of delivering packages to a customer for pick-up. The independent claim is set forth below:

A method of delivering packages to a customer for pick-up comprising:
[a)] receiving an order from a customer,
[b)] preparing a package containing the order, the package having package specific identifying information;
[c)] delivering the package into a facility unit body, the facility unit body providing a secure internal storage for an automatic package receiver and distributor service module, the service module comprising:
[d)] at least one package receiving port for receiving a plurality of individual packages into the facility unit body, the package receiving port accessible from an exterior of the facility unit,
[e)] a package storage area for securely storing the packages in the facility unit body,
[f)] a package discharge access point accessible from the exterior of the facility unit body, and
[g)] a package delivery mechanism in the facility unit body for moving packages between the at least one package receiving port, the package storage area and the package discharge access
point,
[h)] the package delivery mechanism including a conveyor belt apparatus, the conveyor belt apparatus configured to transport selected individual packages between the package storage area and the package access discharge port, the conveyor belt apparatus comprising a
[h1)] a dual cantilevered conveyor belt bed configured to create a V-track space between opposing cantilevered bed portions, and
[h2)] a belt component having a V-belt member on a lower side thereof, wherein the V-belt member is configured to run in the V-track space between the opposing cantilevered bed portions;
[i)] the service module in two-way communication with higher level components, the higher level components including a cloud server and an external database,
[j)] transmitting the package specific identifying information to the external database via the cloud server for storage of the package specific identifying information in the external database,
[k)] receiving an input for delivery of the package from the facility unit body,
[l)] retrieving package specific identifying information for the package from the external database via the cloud server,
[m)] using the retrieved package specific identifying information for the selected individual package to retrieve the selected individual package from the package storage area, and
[n)] releasing the selected individual package to the package discharge access point for pick-up by or delivery to a customer

The examiner rejected several dependent claims that added structural limitations (where these rejections were after two appeal briefs), arguing that these features were improperly included in a method claim.

32. The method of claim 31, wherein the V-belt member and corresponding V-track space maintain the belt member in alignment in the conveyor belt apparatus.
33. The method of claim 31, wherein the cantilevered bed portions have a spring-like resilience for cushioning products dropped onto the belt component.
34. The method of claim 31, wherein the V-belt member is comprised of a single tooth having a wide end positioned at the lower belt member surface and a narrow end positioned to enter the V-track space.
35. The method of claim 31, wherein the V-belt member is configured to be engaged by a motor for operating the belt member in either direction.

The dependent claims referred to specific mechanical features, such as a V-belt and cantilevered bed portions, which were part of the method for delivering a package. The examiner’s reasoning was that these structural features did not limit the method, but the PTAB disagreed. The PTAB explained that the dependent claims properly specified structural limitations related to how the machine was used to execute the method steps. Specifically, these limitations were not intended use or functional limitations, but rather specific structures that further defined how the method was performed.

The PTAB noted as follows:

The Examiner cites no authority supporting the logic that particular mechanical features, when recited as limitations on a method claim using the machine, fail to limit the method claim. The Manual of Patent Examining Procedure (9th Ed., Rev. 01.2024 (Nov. 2024)) (“MPEP”) states, for example, that: ‘The fact that the independent and dependent claims are in different statutory classes does not, in itself, render the latter improper. Thus, if claim 1 recites a specific product, a claim for the method of making the product of claim 1 in a particular manner would be a proper dependent claim since it further specifies limitations relating to the method of making the product of claim 1.’ MPEP § 608.01(n)(III). The facts here are directly analogous, as claim 31 is a method of using a particular machine and the machine elements in claims 32‒35 relate to specific limitations that define how the machine is used to deliver the package to the customer.

The examiner’s Answer was signed by not only a supervisory patent examiner (SPE), but also a quality assurance specialist (RQAS).

So, when dealing with an examiner (or their supervisor or a quality specialist) that argues a structural limitation does not further limit the action of an independent method claim, consider the following response strategies:

1. Explain the Relationship Between the Structure and the Method: Explain that the independent claim describes a method that involves the use of a particular mechanism or structure (e.g., a conveyor system), and there is not issue in further limiting such mechanisms or structure via a dependent claim.

2. Emphasize the Role of the Structural Elements: Highlight that the dependent claim’s structure is not simply a generic "functional" element but a specific feature that further defines how the method operates.

3. Cite Supporting Authority: Refer to the Manual of Patent Examining Procedure (MPEP) for guidance. Specifically, cite MPEP § 608.01(n)(III).