Question & Answer with a patent attorney


Part 2: Patent Claims

We continue our discussion of some common questions encountered in patent law, turning now to the topic of patent claims. You can view Part 1: Prior Art in our series here.

What is a patent claim and why is it important?

Patent claims are one of the most important parts of a patent specification. A claim defines the scope of the monopoly protection conferred by the patent. It is the claim(s) which are examined by a patent office to determine if an invention is patentable (for example, if the invention defined in the claims is novel and inventive, i.e., new and not obvious).

Think of a claim as being like a perimeter fence staked in the ground designating a piece of land for ownership. The broader the fence is staked, the more land there is to own. However, staking the fence too broadly may mean someone else’s piece of land is encroached. If the fence is staked too narrow, valuable land may go unowned. Likewise, a claim that is too broad may be invalidated by prior art, while a claim that is too narrow may render the patent commercially worthless.

Composing a claim of optimum breadth (a so-called ‘goldilocks claim’ – not too broad, nor too narrow, but just right) is the epitome of patent drafting.

How is a patent claim written?

A patent claim is structured to have a beginning, transition and body all compressed into a single sentence with appropriate punctuation.

The beginning or preamble of a claim introduces the invention in general terms by identifying the class or category to which the invention relates. For example, a preamble may simply be “an apparatus” or “a method”. In some instances, the preamble may also recite an intended use – for example, “an apparatus for heating a liquid”. From an Australian law perspective, such an intended use generally places a limitation on what is claimed only to the extent that it must be suitable for the specified purpose – using the example above, the apparatus must be suitable for heating a liquid.

The transition connects or links the preamble with the body of the claim. The transition is commonly an open-ended phrase such as “including” or “comprising”, which has the effect of expanding the scope of the claim by not excluding non-essential elements or features.

The body of a claim recites technical features (otherwise known as elements, integers or limitations) that define the invention. The body should not merely recite a list or catalogue of features but rather should define the relationship and cooperation between each of the features. The body should include one or more features which distinguish the invention from the prior art.

Proper claim drafting is highly nuanced, iterative and complex. We strongly recommend engaging a qualified patent attorney to assist with the drafting process.

How do you read or interpret a patent claim?

It may seem like a patent claim is written in an enigmatic language, making interpretation difficult and subjective. However, there are guiding principles that have been established by common law to assist with an objective interpretation of a claim. These guiding principles may differ between jurisdictions.

Generally speaking, under Australian patent law, claims are given a purposive construction as opposed to a purely literal construction to avoid an overly narrow interpretation of the claims. As a starting point, the terms used in a claim are given plain, ordinary meaning as would be understood by a person having ordinary skill in the art (also known as the skilled addressee). If a term lacks clarity, the term may be interpreted from the description and the drawings of the patent specification. Whilst protection that is fair to the patentee may go beyond the strict textual meaning of the claim, the words that have been chosen to define the invention are the essential starting point of interpretation. The specification and claim(s) are to be read through the eyes of the skilled addressee, being a notional technician familiar with the field of the invention.

Claim construction is a crucial task for courts in infringement proceedings or when determining the validity of a patent. It is common to rely on expert evidence to assist with interpretation of certain claim terms.

Given the intricacies and complexity of claim interpretation, we likewise recommend engaging a patent attorney to assist with claim interpretation.

What is the difference between an independent claim and a dependent claim?

There are usually many claims in a patent specification. The claim of a patent specification that has the broadest protective scope is the independent claim as it is not appended (i.e., linked) to any other claim – it is, by definition, ‘independent’ from all other claims.

An independent claim may be identified by a lack of reference to another claim in its preamble. Usually, the first claim in a numbered set of claims is an independent claim. There may be more than one independent claim in a claim set but all independent claims should relate to the same invention or inventive concept.

The independent claim should capture the inventive concept as broadly as possible by reciting only those features essential to the invention. Using the metaphor mentioned above, the purpose of an independent claim is to stake the fence around a piece of land you wish to own.

On the other hand, a dependent claim refers to one or more other claims in its preamble; for example, the preamble, “The apparatus according to claim 1…” identifies that the claim is a dependent claim that is linked to claim 1. A dependent claim includes each of the features of the claim or claims that it refers to in addition to its own recited feature.

A dependent claim typically narrows the scope of the claim or claims from which it depends. This is usually achieved by identifying features which may be optional or extra to the underlying inventive concept. 

Using the metaphor mentioned above, the purpose of a dependent claim is to provide a retreat or fall-back position if the independent claim is found to ‘stake’ too broadly, i.e., if the independent claim is found to encompass relevant prior art.

How many claims can a patent specification have?

There is generally no limit to the number of claims a patent specification may have.* However, many jurisdictions impose significant excess claim fees for specifications that include claims in excess of a certain number (e.g. 15 in Europe, 20 in Australia and the US). The number of claims is very much influenced by the nature of the invention. Although uncommon, some patent specifications include over 100 claims.

If we can be of assistance or should you have any questions regarding the above, please do not hesitate to contact us.

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