Patents and patent applications have claims that define an invention. Those claims can have various elements or limitations to recite aspects of the invention. But what is a negative limitation? This article explains what they are and some considerations about whether and when they are permitted.
Basic Definition
In the simplest terms, a negative limitation in a patent claim defines an invention in terms of what it is not, rather than what it is. Any limitation in a patent claim that does this can be considered a negative limitation. Although, there are many different ways negative limitations can arise or be worded. There is no standard format for a negative limitation. Indeed, whether or not something constitutes a negative limitation might even be disputed.
When design patent claims include negative limitations is an interesting question that courts have not definitively resolved. The discussion that follows focuses mostly on utility or invention patents.
Example Negative Limitations
The following are some examples of patent claims with negative limitations.
“1. An apparatus comprising: a first panel; and a second panel, wherein the second panel is arranged parallel to and in direct contact with the first panel, wherein the first panel is perforated, and wherein the second panel is a continuous sheet of material without perforations.”
In this example claim 1 above, the limitation that the second sheet is “without perforations” is a negative limitation. It states what is not present (perforations). The negative limitation further defines what the limitation “a continuous sheet of material” means. It also emphasizes a difference from the first panel, which is perforated.
“2. A system comprising a printed circuit board having a first electrical conductor, wherein the first electrical conductor does not have a sinusoidal shape.”
Example claim 2 above includes the negative limitation “wherein the first electrical conductor does not have a sinusoidal shape.” This limitation does not specify the shape of the first electrical conductor. Instead, it specifies the shape that it does not have. That is, this limitation excludes one possible type of shape.
“3. An apparatus comprising: a platform; and one and only one pillar connected to the platform.”
In example claim 3 above, the recitation of “one and only one pillar” includes a negative limitation. It is actually both a positive recitation of a pillar and a negative limitation excluding the presence of more than one pillar. Recitation of a “single” element—as in “a single pillar connected to the platform”—is a similar type of negative limitation.
Different But Related Concepts
There are some other concepts in patent law that have similarities to negative limitations but are distinguishable in some way.
Closed and Partially Closed Transitional Phrases
Transitional phrases in patent claims can be closed or partially closed. The closed transitional phrase “consisting of” excludes the possibility of other elements being present. For instance, in a chemical compound this closed transitional phrase can be used to exclude the presence of additional substances. The partially closed transitional phrase “consisting essentially of” is limited to the explicitly recited elements and those that do not materially affect the basic and novel characteristic(s) of the claimed invention.
Closed and partially closed transitional phrases are not negative limitations in the strict sense. That is because they are transitional phrases and not substantive claim limitations or elements. However, they may have a rather similar effect as exclusionary negative limitations.
Reciting Holes, Voids, Etc.
A limitation directed to “a hole,” “a gap,” etc. is not strictly a negative limitation. But it also can partly resemble one. It is generally preferable to claim surrounding structures that define a hole, aperture, passageway, void, empty space, or the like. This avoids the awkwardness of trying positively claim nothing or the absence of something.
Are Negative Limitations Permitted?
In the U.S., negative claim limitations are not categorically prohibited. But that does not mean they are necessarily proper. Whether they are permitted depends on the context, including the scope of the limitation, support (or lack thereof) in the original disclosure, and the timing of introduction of the negative limitation.
A negative limitation that seeks to exclude the prior art and claim everything else is often problematic. Such claims tend to be based on the desired scope of a patent monopoly rather than pointing out the subject matter regarded as the invention. In other words, this kind of claim tries to carve out and exclude the prior art while preempting everything else. That might mean reciting a given result (perhaps using functional language) while excluding unpatentable prior art solutions. Courts have long disfavored this kind of approach and tend invalidate such claims one way or another. For instance, such a claim may be indefinite. This makes sense because peripheral claiming rather than central claiming is used in the United States.
Attempts to add a negative limitation by way of a later amendment can raise additional issues about support. For instance, if the original disclosure explicitly listed multiple alternatives, that is generally sufficient to later introduce a limitation to exclude one or more of them. However, silence will not generally suffice to support a negative claim limitation. So the ability to later add one by amendment in response to a rejection may depend on the sufficiency of the original disclosure. Claims present at initial filing (including in a preliminary amendment) are considered part of the original disclosure and may support themselves.
Best Practices: Is a Negative Limitation a Good Idea?
Negative claim limitations are generally disfavored. Patent attorneys usually try to avoid using them. As already discussed, they can sometimes raise issues about validity. Negative limitations that make up the entire recitation of the point of novelty, without more, have a greater chance of raising those kinds of problems than ones that merely clarify or elaborate on positively-recited elements. Claims with negative limitations also are sometimes easier to avoid when designing around a patent. This may impact how valuable or desirable it is to have them.
Yet, there are times when negative limitations fairly and helpfully delineate an invention. They are permitted in many instances and may be useful in the right context.
Austen Zuege is an attorney at law and registered U.S. patent attorney in Minneapolis whose practice encompasses patents, trademarks, copyrights, domain name cybersquatting, IP agreements and licensing, freedom-to-operate studies, client counseling, and IP litigation. If you have patent, trademark, or other IP issues, he can help.