A patent only protects what is set out in its claims. The claims are the numbered statements found at the end of the patent. Each claim sets out a particular aspect of the invention or discovery protected by the patent. The claims of the patent may take many different forms. One form, in which a claim of the patent just says “means for [performing some function]”, can be especially appealing because it avoids having to call out a specific part or component, which could limit the patented invention to the use of that specific part or component. While they may seem appealing, these types of claims can spell disaster for the patent if not done correctly. In fact, entire patents have been declared invalid because they used this type of claim language incorrectly, resulting in significant loss of value to the patent owner.
In many cases, the claims of a patent recite specific elements, such as “connecting rods”, “support columns”, “conveyor belts”, etc., arranged to carry out the invention. However, instead of reciting such specific components, a claim may simply recite the function being performed, e.g., “means for connecting”, “means for supporting”, “means for conveying”, etc. By writing a patent claim in this “means-plus-function” format, the inventor does not mention any particular components or materials. Instead, the inventor simply specifies the function being performed. In return for claiming the invention in this short-hand way, however, the patent must include a description of the structure or material for performing the function.
Advantageously, a claim of a patent written this way will cover the corresponding structure or material disclosed in the patent as well as all equivalents of the disclosed structure or material. 1 That is, products that include either the same structure as described in the patent or something equivalent to that disclosed structure may infringe the patent. Accordingly, a claim element written in means-plus-function form can cover a wide range of infringing products.
Even a computer-based invention can take advantage of this claim writing technique. For example, rather than claiming “a flat screen display, a data store, and a processor coupled to the display that is programmed to mine the data store for census data for presentation on the flat screen display”, the inventor could more simply claim “means for displaying census data.” However, as indicated above, unless it is done properly, using means-plus-function language in a patent claim for a computer-based invention can result in the patent being declared invalid.
In a recent decision, the Federal Circuit Court of Appeals, which hears all appeals of patent cases, reiterated that, for computer-based inventions having claims written in means plus function format, the inventor must do more than simply describe a general purpose computer or microprocessor for performing the function. 2 In this case, the patent owner argued that it was enough to describe a standard microprocessor-based gaming machine with “appropriate programming” to support a claim element calling for means for “pay[ing] a prize when a predetermined combination of symbols is displayed in a predetermined arrangement”. 3 The patent owner also noted that a person of ordinary skill in the art could build the invention based on the patent’s detailed description. 4
The court, however, rejected these arguments and declared the patent invalid as indefinite. 5 The court held that the “corresponding structure” for a computer-implemented means plus function claim is the algorithm which the computer is programmed to carry out. 6 By describing a computer programmed with a specific algorithm, the patent describes a special purpose machine for performing the function, and thus the inventor has met his obligation under the Patent Act. Because the patent in dispute in the case failed to describe any such algorithm, the court declared the patent invalid.
In another recent decision, the Federal Circuit again found a patent to a computer-based invention deficient, and thus invalid. In this case, the patent claimed an information transmission system that included “database editing means … for generating a hierarchically arranged set of indices … and for embedding [the] indices in [an] information database.” 7 The patent itself, however, simply mentioned “software” that generates a hierarchical set of indices and embeds those indices. 8 In other words, the patent did nothing more than simply restate the exact function from the claim in the patent’s detailed description, in no more detail than that contained in the claim itself. The court ruled that “simply reciting ‘software’ without providing some detail about the means to accomplish the function is not enough” to meet the inventor’s obligation when choosing to write a patent claim in means plus function form. 9
The court did describe some of the ways in which a patent might adequately describe an algorithm to support a means plus function claim element. For example, an inventor might set out in the patent a mathematical formula that, when executed by the computer or microprocessor, performs the function. Alternatively, the inventor might include a flow chart showing the various steps of the algorithm. Or, the inventor might provide a written description of the algorithm to be performed by the computer or microprocessor. Any of these more detailed descriptions of an algorithm can be sufficient to support a means plus function claim element. 10
While the court did not mention source code, a computer listing or pseudo code may also satisfy the “corresponding structure” requirement. If the inventor chooses to include source code, however, care must be taken to ensure that the included source code is not missing critical sections. In a case in which the patent included over 600 pages of source code, the judge nonetheless determined that those sections of the source code that performed the recited function of a means plus function claim element were missing. 11 The claim in dispute called for “application task means [for] receiving and processing [] input responses and transferring results into pump directions …” 12 In addition to missing the relevant source code files, the patent did not include any flow charts, mathematical formulas or other detailed written descriptions. 13 As a result, the judge held the patent invalid for failing to disclose adequate corresponding structure.
Not only must the “corresponding structure” be adequately disclosed in the patent, e.g., through a flow chart or source code listing, it also must be clearly linked or associated with the claimed function. 14 Without a clear link or association between the described structure in the patent, and the claimed function, a court will not include that structure as part of the “corresponding structure” for the claimed function. 15 One way to clearly link structure described in the patent with the claimed function is to use the same terms when describing what the structure does and when calling out the function that is performed in the claim element. For example, if the claim calls for “means for converting images”, then by explaining that a certain structure, such as a frame grabber, converts images, a court is likely to find that the frame grabber has been clearly linked to the claimed “converting” function.16
Yet another potential trap in the use of means plus function claims concerns an inventor’s reliance on material incorporated by reference into the patent. An inventor may choose to include information in his or her patent by incorporating another document, such as an earlier patent, a patent application or a publication, into his or her patent. Even “essential matter” may be incorporated by reference. An inventor cannot, however, rely on information from a document that was incorporated by reference as disclosing the corresponding structure necessary to support a means plus function claim.17 The corresponding structure must appear in the patent itself.
Courts strictly enforce these rules, and will hold patents invalid for failing to follow them. A federal judge in California, for example, recently decided that a claim for a computer-based invention was invalid, because the inventor failed to adequately describe the “corresponding structure” for means plus function claim element.18 The patent claim at issue called for [means for] automatically updating [a] demographics pattern database by compiling and merging a plurality of end user inquiries and storing said compiled and merged inquiries in said demographics pattern data base.
The inventor noted that the patent described a server running a database program executing typical database functions well known to one skilled in the art. 19 The inventor even provided the judge with a statement from a technical expert who, after reviewing the patent, concluded that the server described in the patent met the corresponding structure requirement. 20 The judge disagreed, holding that the patent failed to show how the updating of the database occurs. 21 Accordingly, the judge ruled that this claim of the patent was invalid. 22
In sum, while the use of means plus function claim language in a computer-based invention can be advantageous, e.g., by providing patent coverage for all equivalents of the disclosed structure, care must be taken to comply with all of the requirements for means plus function claims.
© 2009 Michael Reinemann
1 See Section 112, sixth paragraph of the Patent Act (35 U.S.C. §112, sixth paragraph).
2 Aristocrat Technologies Australia Pty Ltd. v. International Game Technology, 521 F.3d 1328, 1333 (Fed. Cir. 2008).
3 Id. at 1331.
4 Id. at 1336.
5 Id. at 1338.
6 Id. at 1333.
7 Finisar Corp. v. The DirecTV Group, Inc., 523 F.3d 1323, 1340 (Fed. Cir. 2008)
8 Id.
9 Id. at 1340-41.
10 Id.at 1340.
11 Touchcom, Inc. v. Dresser, Inc., 427 F.Supp.2d 730, 735 (E.D. Tex. 2005).
12 Id. at 736-37.
13 Id.
14 Medical Instrumentation and Diagnostics Corp. v. Elekta AB, 344 F. 3d 1205, 1210 (Fed. Cir. 2003) (finding no link between “software” described in the specification and the claimed function of “converting [a] plurality of images into a selected format”).
15 Id. at 1219.
16 Id. at 1210.
17 Amtel Corp. v. Information Storage Devices, Inc., 198 F.3d 1374, 1381 (Fed. Cir. 1999) (while the corresponding structure must appear in the specification, the title of a paper incorporated by reference may provide the requisite structure).
18 Keithley v. The Homestore.com, Inc., slip op. C. A. No. C 03-4447 (N.D. Cal. Nov. 19, 2008).
19 Id.at p. 17.
20 Id. at p. 18.
21 Id.at p. 19.
22 Id.at p. 22.
Cesari & McKenna LLP