Competition in the technological marketplace is fierce, with companies constantly attempting to gain competitive advantages. Companies are often left with the options of buying or licensing patent rights or run the risk of becoming obsolete. However, buying and licensing patents also has risks and can end up costing large sums of money for relatively little return. Therefore, it is important that decision-makers have a general understanding of interpreting patents to better assess their relative strength.

Even though the cover sheet provides a lot of important information, the heart of a patent is its claims, the numbered sentences in the back of all issued patents. Claims outline the limits of patent protection and are interpreted in light of the specification that comes before it, along with the arguments that were made at the U.S. Patent and Trademark Office (USPTO) in getting the patent allowed. And that’s only part of the analysis. Under the new changes to the patent law under the America Invents Act, a patent is also limited in that it does not cover what was known by those having ordinary skill in the art of the invention prior to the filing of the patent application. (For patent applications filed before March 16, patents don’t cover what was known more than a year prior to when the invention was made. However, this is further limited by public uses or sales in the United States and publications or patents issued anywhere more than one year before the filing date.) A patent is further limited by the patent law and the opinions of the courts.

Nevertheless, simply looking at the patent document will give you some idea of what to expect. The thinner the patent application, the smaller the likely scope of patent protection. One reason is that while claims are often interpreted to cover the components or steps of a claimed invention, as well as its reasonable equivalents, those equivalents are more likely to be protected if they were described or suggested in the patent. A patent document with fewer pages implies a specification with fewer details of the invention and little discussion of alternatives. On the other hand, a thicker patent document implies a specification with more detail, more discussion of variations and, simply, a stronger patent.

The claims determine the "metes and bounds" of the claimed invention. The numbered claims that don’t refer to any other claim are "independent claims" and each wholly identifies the patented invention. Claims that refer to earlier numbered claims are "dependent claims" and are interpreted to include all limits of the earlier numbered claims. A single patent may include several independent claims, each describing a single invention in slightly different ways. For example, one independent claim may describe a device, another may claim a system incorporating that device and a third may claim a method of using that device. The dependent claims modify the independent claims to add limitations, other features or further steps in the claimed invention.

To infringe a patent, all of the features or steps listed in a claim must be present in the accused device, system or method. Leaving out just one feature is often enough to avoid patent infringement. Therefore, independent claims that are long, claiming a multitude of features that are not important to the novelty of the invention, tend to be weaker than those that are more focused on the patentable elements of the invention. It tends to be easier to avoid infringement of longer claims by doing without an unnecessary claimed element or step or finding a non-equivalent alternative.

Do the claims appear to cover what you want, by identifying the product or service you intend to use? Reconsider the patent if the claims have additional elements that don’t make sense or elements that you would never implement. Also, consider how your competitors could be affected by these claims. Even if you would never exploit the claimed technology, it may create a barrier against unwanted competition.

Pay close attention to the language of the claims and whether you can find that language in the specification. Claims are interpreted in light of the specification that precedes them, so any term or feature that is unclear should be defined or described in the specification. In stronger patents, claim terms tend to be repeated throughout the specification, leaving little doubt as to the scope of the claimed invention. In weaker patents, the meaning of claim terms has to be interpreted or extrapolated, leaving room for doubt in the claim scope. Note any inconsistencies in the claims and between the claims and the specification. Word choice can broaden or narrow the scope of the claimed invention. Scope broadening amendments cannot be made to the patent except through a reissue proceeding filed within two years after it has been issued. Some courts have held that even when the language has clearly been drafted in error, whatever is stated within an issued patent is what the owner will be stuck with.

Look for language that describes equivalent and interchangeable features to claimed elements. Identified equivalents broaden the scope of the claims, allowing the inventor to claim that the equivalents were considered to be within the claim scope. Disclosed equivalents also make it harder to make insubstantial changes to design around the broadest claim. For example, the specification could identify various construction materials, assembly methods, alternative steps or other modifying features of the basic invention. Often, these variations are covered by dependent claims, but if the elements of the independent claims have equivalent components or steps, those should also be identified in the specification.

Equivalents could also be identified in the specification through different embodiments of the invention. A stronger patent discloses many embodiments, not just the preferred or most efficient embodiment. The more embodiments disclosed, the harder it will be for competitors to design around the claims, even when certain embodiments are not efficient or economical. Each embodiment left unsaid leaves room for a competitor to avoid infringing the claimed invention. The more embodiments discussed, the greater the value of the patent.

Another consideration is that in exchange for the rights granted by the issuance of a patent, the inventor must provide sufficient detail to enable one to practice the claimed invention without undue experimentation. If your technical staff can’t read the specification and figure out how to implement the claims, then you should reconsider the worth of the patent.

The patent document itself is not the only place to look to interpret the scope of the claims. Courts have held that anything that has been presented to the USPTO as argument in support of obtaining the patent can be used for claim interpretation. Communications between the USPTO and the patent attorney who worked on getting the patent issued (the patent prosecution history) are available on the USPTO website. Any interpretation of claim elements, affidavits explaining terms or procedures, clarifications of prior art documents and amendments to claims made in the normal course of patent prosecution can be used to narrow the scope of the issued claims. A prosecution history with a lot of action between the USPTO and the patent attorney has more places to attack the patent.

Many times during patent prosecution, applicants must amend claims to comply with patentability requirements. To do this, applicants submit claim amendments showing exactly what changes are made, making it easy to track how the claims came to be issued. However, amendments made to narrow claim scope could be subject to interpretation under the doctrine of prosecution history estoppel. According to this doctrine, any narrowing amendment made to a claim to circumvent a prior art disclosure will limit the scope of the claim to the amended elements and possibly no equivalents. Therefore, the patent prosecution history must be examined to determine why amendments were made during prosecution and their effects on claim scope.

Any review of a patent is incomplete without understanding the prior art to the patent. It is important to look for patents and other public documents that pre-date the filing date of the patent you are reviewing. This can be done by searching libraries or Internet databases or ordering a prior art search through a patent-search company. Finding a prior disclosure or a combination of prior disclosures that show each and every element of the claims could make that patent unenforceable and severely reduce its value.

While this article is in no way exhaustive, the discussion here should help to give a general understanding of some basic issues to be aware of when reviewing a patent. The review of every patent should at least consider the items discussed herein. While it is recommended that such reviews be conducted by a trained patent attorney, decision-makers should have some idea of what such a review entails to have greater confidence in their final decision.  •

David S. Willoughby is a patent attorney at MacDonald, Illig, Jones & Britton. He can be contacted at or 814-870-7662.

Jonathan D’Silva, chairman of the firm’s intellectual property group, is a patent attorney who practices various aspects of intellectual property law from prosecuting patent, trademark and copyright applications, to drafting agreements for the sale or licensing of intellectual property, to the enforcement of intellectual property rights.