Claim (patent) - Basic Types and Categories

Basic Types and Categories

There are two basic types of claims:

• the independent claims, which stand on their own, and
• the dependent claims, which depend on a single claim or on several claims and generally express particular embodiments as fall-back positions.

The expressions "in one embodiment", "in a preferred embodiment", "in a particular embodiment", "in an advantageous embodiment" or the like often appear in the description of patent applications and are used to introduce a particular implementation or method of carrying out the invention. These embodiments usually correspond to a dependent claim or could form the basis of a dependent claim. Each dependent claim is, by law, more narrow than the independent claim upon which it depends. Accordingly, it might appear that there would be little purpose to the dependent claim. In reality, however, there are at least three advantages to the patent applicant in submitting and obtaining a full string of dependent claims:

• Clarification of the independent claim language: Independent claims are typically written with very broad terms, to avoid permitting competitors to circumvent the claim by altering some aspect of the basic design. But when a broad term is used, it may raise a question as to the scope of the term itself. For example, does a "base" include a "set of legs"? A dependent claim, including the phrase, "wherein said base comprises a set of legs," if allowed by the patent examiner, clarifies that it does. In practice, dependent claims are often used to home in on the inventor's preferred embodiment of the invention (e.g., the actual product design that the inventor intends to use.) The independent claim broadly describes the invention; dependent claim #1 describes the invention in a narrower aspect that more specifically describes the preferred embodiment; dependent claim #2 is narrower still; etc.

• Possible invalidity of base claim: It is impossible to know, when beginning the application process and even at the time of patent issuance, if a patent claim is valid. This is because any publication dated before the application's priority date and published anywhere in any language can invalidate the claim (excluding publications by the inventor published during the grace period in certain countries such as U.S., Canada and Japan). Furthermore, even applications that were not yet published at the time of filling, but have a priority date prior to the priority date of the application, can also invalidate the claim. As it is impossible to gain an absolute and complete knowledge of every publication on earth, not to mention unpublished patent applications, there is always some degree of uncertainty. If the independent claim is determined to be invalid, however, a dependent claim may nevertheless survive, and may still be broad enough to bar competitors from valuable commercial territory.

• Claim differentiation: In United States patent law, under the doctrine of claim differentiation, each claim is presumed to cover a different aspect of the invention than in each other claim. This doctrine may be relied upon to help maintain broad claim scope in the case where a claim standing alone might be construed as having either a broad or a narrow interpretation. If a dependent claim is added that depends from this "parent" claim but is specifically drawn to the narrower interpretation, then the parent claim must necessarily be different - i.e., it must be the broader interpretation. As construed in the courts, the doctrine of claim differentiation dictates that it "is improper for courts to read into an independent claim a limitation explicitly set forth in another claim."Environmental Designs Ltd. v. Union Oil Co. of California, 713 F.2d 693, 699 (Fed. Cir. 1984). This means that if an independent claim recites a chair with a plurality of legs, and a dependent claim depending from the independent recites a chair with 4 legs, the independent claim is not limited to what is recited in the dependent claim. The dependent claim protects chairs with 4 legs, and the independent claim protects chairs with 4 legs as well as chairs having 2, 3, 5 or more legs.

Under the European Patent Convention, when a claim in one particular category (see below), e.g. a process claim, depends on a claim from a different category, e.g. a product claim, it is not considered to be a dependent claim but an independent claim. Under U.S. law, this is still counted as a dependent claim, regardless of the class change.

The rules of claim drafting also permit "multiple dependent claims" that reference more than one other claim, e.g.: "3. Method of claim 1 or 2, further comprising..." The rules for this are quite specific: specific claims must be referenced ("the method of any of these other claims" is incorrect); the claims must be referenced in the alternative ("the method of claims 1 and 2" is incorrect); etc. While still acceptable, this claim style is seldom used in the U.S. because it is counted for filing fee purposes according to the number of claims that it references. Thus, if the claim depends from three former claims, it is counted for fee purposes as three dependent claims. In light of the "excess claim" fees currently imposed by the USPTO, this tactic can quickly become expensive. Multiple dependent claims are, however, very commonly used in other jurisdictions, including Canada and Europe.

Claims can also be classified in categories, i.e. in terms of what they claim. A claim can refer to

• a physical entity, i.e. a product (or material) or an apparatus (or device, system, article, ...). The claim is then called respectively "product claim" or "apparatus claim"; or
• an activity, i.e. a process (or method) or a use. The claim is then called respectively "process claim" (or method claim) or "use claim".