In a patent or patent application, the claims define, in technical terms, the extent, i.e. the scope, of the protection conferred by a patent, or the protection sought in a patent application. In other words, the purpose of the claims is to define which subject-matter is protected by the patent. This is termed as the "notice function" of a patent claim—to warn others of what they must not do if they are to avoid infringement liability. The claims are of the utmost importance both during prosecution and litigation alike. For instance, a claim could read:
"An apparatus for catching mice, said apparatus comprising a base, a spring member coupled to the base, and..."
"A chemical composition for cleaning windows, said composition substantially consisting of 10–15% ammonia,..."
"Method for computing future life expectancies, said method comprising gathering data including X, Y, Z, analyzing the data, comparing the analyzed data results..."
Background
In most jurisdictions, a patent is a right to exclude others from making, using, importing, selling or offering for sale the subject matter defined by the claims when the claim is for a thing. If a claim is for a method, the right to exclude would be to exclude any single party from carrying out all the steps of the claim. In order to exclude someone from using a patented invention, the patent owner, or patentee, needs to demonstrate in a court proceeding that what the other person is using falls within the scope of a claim of the patent; therefore, it is more valuable to obtain claims that include the minimal set of limitations that differentiate an invention over what came before. But the fewer the limitations in a claim, the more likely it is that the claim will cover, or "read on," what came before and be rejected during examination or found to be invalid at a later time for obviousness or lack of novelty.
History
Patents have not always contained claims. In many European countries, patents did not contain claims until the 1970s. Before that time, it was often difficult to decide whether a product infringed a patent, since the sole basis to know the extent of protection was the description, in view of the prior art. Claims have been necessary parts of U.S. patent applications since the enactment of the Patent Act of 1836. However, even among patent legal systems in which the claims are used as the reference to decide the scope of protection conferred by a patent, the way the claims are used may vary substantially. Traditionally, two types of claiming systems exist:
the "central claiming system", according to which the claims identify the "centre" of the patented invention. The exact scope of the protection depends on the actual nature of the inventor’s contribution to the art in the concerned technology.
the "peripheral claiming system", according to which the claims identify the exact periphery, or boundary, of the conferred protection. In this system, the burden of drafting good claims is much higher on the patent applicant. The applicant receives the protection he or she requested and almost nothing more, provided that the invention is new and non-obvious. This theoretically makes it easier for third parties to examine whether infringement may exist or not.
No patent system today is a purely either central or peripheral, but the system used in Germany and most of the other countries of continental Europe is considered more central than the system currently used in the United Kingdom, the United States, and especially Japan, which are more peripheral. In recent years, Japan's system has become more peripheral, while the system used in the United States was becoming more central because of the increasing resort in US patent litigation to the doctrine of equivalents to expand claim scope unpredictably, until the US Supreme Court reversed that trend in the Warner-Jenkinson case in 1997.
Requirements and structure
In most modern patent laws, patent applications must have at least one claim, which are critical defining elements of the patent and the primary subject of examination. In some patent laws however, a date of filing may be obtained for an application which does not contain any claim.
Under the European Patent Convention, a claim must define the matter for which the protection is sought in terms of technical features. These technical features can be either structural or functional. Regarding the structure of a claim, under the EPC, what is called the "preamble" is different from the meaning the "preamble" has under U.S. patent law. In an independent claim in Europe, the preamble is everything which precedes the expression "characterized in that" or "characterized by" in a claim written according to the so-called "two-part form", and therefore everything which is regarded as known in combination within one prior art document, namely the closest prior art document. For this reason, in Europe, the preamble of a claim is sometimes also called "pre-characterizing portion".
United States
A claim may include the following parts:
A preamble that recites the class of the invention, and optionally its primary properties, purpose, or field: "An apparatus..." "A therapeutic method for treating cancer..." "A composition having an affinity for protein X..." This preamble may also reference another claim and refine it, e.g., "The method of claim 1...".
A "transitional" phrase that characterizes the elements that follow. The phrases "comprising", "containing" and "including" are most often used and preferable, as it means "having at least the following elements..." and are therefore open and do not exclude additional limitations. The phrases "consisting of" and "consisting essentially of" are more limiting, as they mean "having all and only" or "virtually only" and are therefore closed. In the US, the phrase "consisting of" excludes additional limitations, while the phrase "consisting essentially of" excludes additional limitations that would "materially affect the basic and novel characteristic of the claimed invention".
A set of "limitations" that together describe the invention: "an X, a Y, and a Z connected to the X and the Y." The elements should be described as though they interact or cooperate to achieve the desired result.
Optionally, a purpose clause that further describes the overall operation of the invention, or the goal that the invention achieves. "Wherein" clauses limit the scope of the claim. Other forms of purpose language are "whereby" and "thereby" clauses, similar to the "wherein" clauses just described, and statements of intended use in a claim preamble.
Interpretation or claim construction
The claims often use precise language. Certain words commonly used in claims have specific legal meanings determined by one or more court decisions. These meanings may be different from common usage. For instance, the word "comprises", when used in the claims of a United States patent, means "consists at least of". By contrast, the word "consists" means "consists only of", which will lead to a very different scope of protection. Furthermore, in U.S. patent practice at least, inventors may "act as their own lexicographer" in a patent application. That means that an inventor may give a common word or phrase a meaning that is very specific and different from the normal definition of said word or phrase. Thus a claim must be interpreted in light of the definitions provided in the specification of a patent. The specification of a patent is a written description of how to make and use the invention. In U.S. law, a claim is given its broadest reasonable interpretation consistent with the specification during prosecution of the application; however, in a suit for patent infringement, a claim is interpreted in a Markman hearing.
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 various embodiments may or may not each be claimed with specificity. They might serve as multiple examples of a more general "genus" that is claimed. In some cases the examiner might declare that what the applicant presented as variations of one invention are actually separate inventions that need to be examined individually. An independent claim does not refer to an earlier claim, whereas a dependent claim does refer to an earlier claim, assumes all of the limitations of that claim and then adds restrictions Each dependent claim is, by law, more narrow than the independent claim upon which it depends. Although this results in coverage more narrow than provided by the independent claim upon which the second claim depends, it is additional coverage, and there are many advantages to the patent applicant in submitting and obtaining a full suite of dependent claims: Under the European Patent Convention, when a claim in one particular category, 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 claims must be referenced in the alternative ; 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 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 an apparatus. The claim is then called respectively "product claim" or "apparatus claim"; or
an activity, i.e. a process or a use. The claim is then called respectively "process claim" or "use claim".
Special types of claims
In addition to the above basic claim types, there are also many special types of claim which are used in different circumstances. Sometimes a particular claim form is required by law if a patent is to be granted for a particular invention, such as for a second medical use of a known substance where the "Swiss-type" claim might be required. Another reason to use a particular claim might be to catch a particular class of infringer.
