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The Doctrine of Equivalents is an equitable, common law, judge-made principle developed by the Federal Courts over years of litigation. This article explores some of the key cases that have defined and re-defined the Doctrine of Equivalents, including Winans v. Denmead (1853), Graver Tank & Mfg. Co. v. Linde Air Products (1950), and Warner-Jenkinson Co. v. Hilton Davis Chemical Co. (1997).

The Doctrine of Equivalents is an equitable, common law, judge-made principle developed by the Federal Courts over years of litigation. Under the doctrine, an accused product or process must practice each claim limitation or its equivalent. Where direct (or literal) patent infringement does not exist because an accused product or process fails to practice one or more claim limitations, the patent owner may still prove infringement by showing the accused product or process practices the equivalent of the patent absent claim limitations. Furthermore, the patent owner must consider equivalency at the time of infringement, not when the patent is issued.

Always use your trademark as an adjective and never as a noun for the good or service. For example, a brand owner should use the trademark (adjective) followed by the good or service (noun) it modifies (e.g., “APPLE computer”). Using the mark as a noun indicates the mark is a good or service rather than the source of the good or service, which is a hallmark of trademark law.

You can register a trademark with a state government, the federal government, or both. Federally registered trademarks will usually have the ® symbol used next to or in close association with the good. Trademark rights begin with use in commerce.[i],[ii] Generally, "use" means the owner must use the mark in association with particular goods, such as placing the mark on the goods or their packaging, in advertisements for the goods, or at point-of-sale displays, for example.

Trademarks, trade dress, and design patents are each exclusionary intellectual property rights that protect non-functional aspects of an owner’s business operations and product lines by giving the owner legal rights to prevent others from using them. While each of these routes to protect an owner’s intellectual property is somewhat similar and overlapping, differences exist.  Each intellectual property right will be discussed below and then compared and contrasted with the other. This topic will be divided into several blog entries with part I introducing trademarks and providing a little history.

A trademark is a distinguishable word, symbol, slogan, or figure which identifies products or services from a specific source and distinguishes from products or services of other sources. Word marks in particular are evaluated on a sliding scale from most distinctive to least distinctive. More distinctive marks lend themselves to stronger trademarks, and are better candidates for registration on the Principal Register of the USPTO. The most distinctive marks are known as "inherently distinctive," as will be discussed here in greater detail.

Products imported to the United States can infringe on issued U.S. patents. Patent owners have several options for protecting their intellectual property rights, including litigation in either Federal Court or the United States International Trade Commission. We will discuss each type of litigation and its unique advantages in detail below. If a patent owner becomes aware of infringement against their patent, we advise the patent owner to take prompt action to stop the infringement.