Legal Definitions - means-plus-function clause

A means-plus-function clause is a specific type of statement used in patent claims, particularly for inventions that describe an apparatus or system. Instead of detailing every physical component or exact structure of a part of an invention, this clause describes that part by stating its function.

For example, an inventor might claim "a means for filtering impurities" rather than specifying "a mesh screen made of stainless steel with 100 micron openings." The purpose is to allow some flexibility in how the function is performed without being overly broad.

The crucial aspect of a means-plus-function clause lies in how it is legally interpreted. While it describes a function, its scope is limited to the specific structure, material, or act that is clearly described in the patent's detailed written specification as performing that function, along with any equivalent structures or acts that existed at the time the patent was filed. It does not cover every conceivable way to perform that function, only those disclosed in the patent or their equivalents.

• Example 1: A System for Secure Data Transmission

  Imagine a patent for a new communication system. One of its claims might include: "a means for encrypting data prior to transmission." In the detailed description of the patent, the inventor specifies that this encryption is performed by a particular cryptographic algorithm, such as AES-256, implemented in a dedicated hardware chip.

  How it illustrates the term: This clause describes a function ("encrypting data") rather than a specific structure. However, the patent's protection for this "means for encrypting data" would be limited to the AES-256 algorithm implemented in a hardware chip, as described in the patent, and any structures considered equivalent to it at the time the patent was filed. It would not automatically cover all possible encryption methods, such as a different algorithm like RSA, unless RSA was considered an equivalent to the described AES-256 hardware implementation.

• Example 2: An Automated Gardening Device

  Consider a patent for an automated plant watering system. A claim could state: "a means for detecting soil moisture levels." The patent's specification describes this function being carried out by a pair of conductive probes inserted into the soil that measure electrical resistance.

  How it illustrates the term: The clause identifies a function ("detecting soil moisture levels"). The legal protection granted by this clause would be tied specifically to the conductive probe method described in the patent and its equivalents. It would not extend to other methods of detecting soil moisture, such as optical sensors or weight-based sensors, unless those were deemed equivalent to the described conductive probes at the time the patent was filed.

• Example 3: A Child Safety Lock Mechanism

  A patent for a new child-resistant container might include the claim: "a means for preventing unauthorized opening." The patent's detailed description explains that this means involves a specific two-step rotational and push-down cap mechanism.

  How it illustrates the term: Here, the clause defines a function ("preventing unauthorized opening"). The patent's coverage for this "means" would be limited to the described two-step rotational and push-down cap mechanism and its structural equivalents. It would not broadly cover every type of child safety lock, such as a button-press mechanism or a key lock, unless those were considered equivalent to the specific rotational and push-down mechanism disclosed in the patent.