1. Introduction
A product invention is usually defined by structural or parameter features, while a process invention is usually defined by process steps. If those forms cannot accurately define a technical feature or adequately protect the invention, a claim may use a feature defined by function. In essence, a functional feature is defined by the function or effect it is intended to achieve.
What requirements apply to functional features in Chinese patent examination? What objections may arise, and what should applicants consider when drafting? These questions are discussed below.
2. Relevant provisions and analysis
Part II, Chapter 2, Section 3.2.1 of the Guidelines for Patent Examination sets out the following principal requirements.
Product claims should generally avoid defining an invention by function or effect. Such language is permitted only where a technical feature cannot be defined structurally, or a functional or effect-based definition is more appropriate, and the stated function or effect can be directly and positively verified through experiments or operations described in the specification, or through customary means in the art.
A claim feature defined by function is construed as covering all means capable of performing that function.
If the description merely states vaguely that alternatives may be used, without enabling the skilled person to understand what they are or how to use them, the functional definition is not permitted.
A purely functional claim lacks support in the description and is therefore not permitted.
The following points follow from these provisions.
1. The context matters. Process claims are not subject to the particular conditions imposed on product claims. In a product claim, a functional or effect-based feature is permitted only where structural definition is unavailable or less appropriate and the function or effect can be directly and positively verified.
2. Once a feature is defined by function, it covers every means capable of performing that function. The description must provide sufficient support for that scope.
3. In addition to the implementation described in detail, alternative implementations must be clearly explained in the description.
4. Functional features cannot stand alone: they must be combined with structural features or process steps.
3. Common examination objections
Objections concerning functional features generally fall into two categories.
First, the examiner assesses whether the skilled person knows an existing way of performing the function and whether other means covered by the functional language, beyond the implementation expressly described, can perform the same function and achieve the same technical effect. If not, the claim may be held to lack support in the description.
Second, the examiner assesses whether the claim merely states an objective or desired effect through functional language without specifying actual technical means of achieving it. Such a claim may also be held to lack support.
4. Drafting considerations
To avoid those objections, applicants should consider two points when drafting.
First, describe as many specific implementations of a functional feature as possible, explaining the principles and procedures by which each performs the function. Where several embodiments are equivalent, one or two representative embodiments may be described in detail. The others may refer to them, with their distinctive aspects explained separately.
Second, consider drafting at least one dependent claim for each specific implementation. If the functional feature is challenged during substantive examination or invalidation proceedings, an appropriate dependent claim may provide a basis for amendment. In infringement litigation, the patentee can also compare a dependent claim specifying an implementation directly with a component of the allegedly infringing product, helping the court determine whether that product falls within the patent's scope.
