Court: Court of Appeals for the Federal Circuit; May 29, 2003; Federal Appellate Court
Apex Inc. appeals a final judgment from the United States District Court for the Southern District of New York, which ruled that patents 5,884,096, 5,937,176, and 6,112,264 ("the patents") were not infringed by Raritan Computer, Inc., and dismissed Raritan's counterclaims without prejudice. The Federal Circuit found that the district court misinterpreted key claim limitations of the patents, leading to a vacate and remand for further proceedings.
Apex, the patent owner, sells computer switching systems that connect workstations to remote computers, similar to Raritan's products, specifically the MasterConsole and Paragon lines. The patents in question describe KVM (keyboard, video, mouse) switching systems that allow network administrators to manage multiple servers efficiently without complex wiring. The system includes a signal conditioning pod and a central crosspoint switch that transmits signals between workstations and servers, mimicking direct connections.
A notable feature of the invention is an on-screen programming display that enables users to select specific servers via a visual menu. Apex claims Raritan infringed multiple specific claims from the patents, including independent claims from the '096 and '264 patents and one from the '176 patent. Fourteen disputed claim limitations were identified, indicating significant contention regarding the interpretation of the patents' claims.
The '096 patent includes claims for a programmable switch that routes keyboard and cursor control signals from a workstation to a selected computer and routes video signals from that computer to the workstation's video monitor. It consists of a first interface circuit for receiving control device signals, an on-screen programming circuit for generating video signals, and a second interface circuit that connects the programmable switch to the selected computer to relay control signals. Claim 1 specifies a programmed logic circuit that manages the transmission of control signals and video generation based on user input, while also detecting and responding to additional control signals during video display.
The '176 patent describes multiple first signal conditioning units linked to workstations to create serial data packets from keyboard and mouse signals. A central crosspoint switch routes these packets through various bidirectional inputs and outputs. Additionally, second signal conditioning units connected to remote computer systems receive and supply these packets to the computers' keyboard and mouse inputs, while also transmitting video signals back to the central switch.
The '264 patent outlines a computer-side interface for connecting to dedicated keyboard and video output cables of multiple computers and a user-side interface for connecting to a first keyboard and monitor. It includes an analog video overlay image generating circuit that produces an internal analog overlay video signal and an analog video overlay circuit that combines video signals with overlay signals to output a combined analog signal to the monitor.
After a seven-day bench trial, the district court interpreted all fourteen disputed limitations of the patents.
The district court classified specific limitations such as "first interface circuit" and "programmed logic circuit" as means-plus-function limitations, determining that terms like "circuit," "interface," and "units" did not provide sufficient structural definition to perform the claimed functions, despite Apex's arguments to the contrary. The court interpreted "serial data packet" as one that may include both keyboard and mouse signals, supported by claim language and written descriptions indicating a system for creating such packets. Additionally, the terms "overlay" and "overlaid video signals" were defined to require the capability to superimpose two separate images on the screen simultaneously, based on the prosecution history of the patent. Consequently, the district court concluded that the accused products did not infringe the asserted claims, as they failed to embody every required element of the claims as interpreted. Apex subsequently appealed the decision, with jurisdiction established under 28 U.S.C. 1295(a)(1).
A determination of patent infringement follows a two-step analysis: first, the court assesses the scope and meaning of the asserted patent claims; second, it compares these claims to the allegedly infringing device. Claim construction is a legal question reviewed de novo, while the comparison of claims to the accused device involves factual determinations that require each claim limitation or its equivalent to be present in the accused device. A finding is considered 'clearly erroneous' if the reviewing court is firmly convinced that a mistake has occurred.
For claim construction, the intrinsic evidence—including claims, written descriptions, and prosecution history—is examined first. Courts presume that claim terms carry their ordinary meanings as understood by a person skilled in the art. Dictionary definitions may also be utilized to establish meanings. Extrinsic evidence can aid in understanding the technology but cannot contradict the clear meanings of claim terms.
Means-plus-function limitations under 35 U.S.C. § 112, paragraph 6 allow claim elements to be expressed functionally without detailing the structure or material, thus covering corresponding structures described in the specification and their equivalents.
A claim limitation using the term "means" creates a rebuttable presumption that 35 U.S.C. § 112, paragraph 6 applies, whereas a claim term lacking "means" presumes that this section does not apply. The presence of "means" is crucial in determining the application of the statute. If a party, such as Raritan, aims to rebut this presumption, it must provide evidence showing that the claim term lacks a sufficiently definite structure or describes a function without adequate structural details. This requirement must be met by a preponderance of the evidence, as is typical in civil cases. If Raritan fails to provide enough evidence, the presumption against the application of § 112, paragraph 6 prevails.
Additionally, a claim limitation that does not use "means" can still be considered a means-plus-function limitation if it relies heavily on functional terms rather than structural descriptors. Conversely, when "means" is used, the inquiry centers on whether the claim adequately describes a function or provides enough structural detail for that function. The court assesses whether the term has a recognized meaning within the relevant technical field, noting that a claim term does not need to refer to a singular, well-defined structure to comply with § 112, paragraph 6.
In the case at hand, Raritan's asserted claim limitations do not include the term "means," leading to the presumption that they are not means-plus-function limitations. The district court incorrectly classified most of these limitations as such, relying on isolated words rather than the complete claim limitations. This approach was deemed a legal error, as it disregarded the context of the limitations.
The "circuit" limitations in the asserted claims of the '096 and '264 patents do not include the term "means," which leads to a presumption that 35 U.S.C. § 112, paragraph 6 does not apply. Raritan failed to provide sufficient evidence to demonstrate that the term "circuit" does not convey adequate structure to someone skilled in the art. The district court prematurely concluded that "circuit" lacks sufficient structure by itself, but the term, especially when combined with identifiers like "interface," "programming," and "logic," does convey structural meaning. The definition of "circuit" as a combination of electrical devices fulfilling a function supports this structural connotation. Raritan's evidence, including prior district court rulings and specification descriptions, did not challenge the presumption effectively. Claims must be interpreted with the specification and common understanding in mind, and Raritan's expert testimony only indicated that "circuit" is a broad term without disproving its structural adequacy. Each claim uses "circuit" with additional qualifiers that enhance its definition, indicating that the district court incorrectly treated all limitations as means-plus-function limitations without considering the claims holistically.
Claim construction is recognized as a legal question, but not all claim limitations will be construed due to an insufficiently developed record. To determine if claim limitations qualify as means-plus-function, understanding the perspective of a person of ordinary skill in the art is essential, necessitating the use of extrinsic evidence like dictionaries and expert testimony. The ordinary meaning of the terms "first interface circuit" and "second interface circuit" is established, with "interface" defined as the signal connection and associated control circuits connecting devices. The definitions from relevant dictionaries indicate that these terms convey specific structures to one skilled in the art, and there is no evidence the inventors intended a different meaning. Raritan's argument to limit the term "interface circuit" to a preferred embodiment is rejected. As Raritan did not successfully challenge the presumption against means-plus-function application, the terms are deemed to not fall under this category, with "interface circuit" defined broadly as any circuit linking different logic systems.
The district court is instructed to apply a similar analysis to other limitations related to "circuit," "interface," and "unit," determining their ordinary meanings and whether they provide definite structures. Raritan carries the burden of proof to show that the limitations lack sufficient structural connotation. The court refrains from performing this analysis due to the existing underdeveloped record, which could unfairly affect the parties involved.
Regarding the term "serial data packet," the district court interpreted it as a packet that may include both keyboard and mouse signals. The specification and the Examiner's Reasons for Allowance indicated that this capability was required, emphasizing that the prior art did not suggest a system integrating circuitry for creating such packets from keyboard and mouse signals, along with a crosspoint switch for multiple workstations connecting to several remote computer systems.
The standard reason for the allowance of the patent merely indicates that prior art does not teach or suggest the claimed system arrangement without specifically stating that patentability hinges on the inclusion of keyboard and mouse signals in a serial data packet. Claim 1 defines a serial data packet as containing "electronic signals" from the keyboard and mouse, and it is clarified that a data packet does not necessarily need to include both types of signals, contrary to the district court's interpretation. The court acknowledged that a data packet could consist of either keyboard or mouse signals individually. The term "serial data packet" should be understood in its ordinary sense, meaning it can include either type of signal or both, leading to the reversal of the district court's claim construction.
Regarding the terms "overlay" and "overlaid video signals," the district court interpreted them to require simultaneous display of two separate images. This interpretation relied on the prosecution history of the related patent, suggesting that "overlay" implies placing one signal over another. However, the claim language does not mandate simultaneous display but rather requires circuitry for producing "overlay" signals. The ordinary understanding of "overlay" in computer graphics involves superimposing one image over another, which does not necessitate simultaneous visibility of both images.
The definition of "overlay" and "overlaid" does not necessitate the simultaneous display of two video images, contrary to the district court's interpretation. The written description of the patent provides various methods for displaying overlaid images, supporting the ordinary meaning of these terms. The prosecution history fails to limit the terms as the district court concluded; instead, it reinforces their ordinary meanings, defined as superimposing one graphic image over another without requiring both images to be displayed simultaneously. Consequently, the court reverses the district court's claim construction regarding these terms.
Regarding the term "switch," the district court's narrow interpretation, suggesting it only refers to a device that opens or closes a circuit, is rejected. The ordinary meaning in networking is a device that forwards packets to specific network addresses. The patent's written description details a "crosspoint switch" that processes data packets, which does not conform to the district court's limited definition. The court reverses the claim construction of "switch" to reflect its broader meaning as a programmable device capable of forwarding packets between systems.
Raritan's assertion that the claim limitations are confined to a single disclosed embodiment is also rejected. The record does not support Raritan’s claim that Apex admitted its preferred embodiment encompasses the entire invention. Testimony from one of the inventors indicates that the overall concept of using an on-screen display with KVM switches was considered novel, without suggesting that the described embodiment represents the entirety of the invention.
Raritan argues that the claims of the Apex patents should be limited to a single preferred embodiment due to a lack of alternatives in the patents. However, this assertion is incorrect under patent law. Courts may only limit claim terms if a clear definition has been provided by the patentee in the written description, which is not applicable in this case. Claim terms generally maintain their ordinary meanings unless a patentee has explicitly redefined them or limited their scope through clear disavowal in the intrinsic evidence.
The second step of the infringement analysis involves comparing the correctly interpreted claims with the allegedly infringing devices, a factual determination reviewed for clear error. The district court concluded that there was no infringement, stating that the accused products must embody every element of the claims as interpreted. However, due to errors in claim interpretation and a need for further evidence regarding the ordinary meanings of disputed terms, the appellate court vacated the district court's non-infringement ruling.
The case is remanded for a proper infringement analysis, including both literal infringement and the doctrine of equivalents, as these require distinct evaluations. The appellate court also notes that the evidence related to the doctrine of equivalents must not be included merely under the literal infringement analysis. The summary judgment of non-infringement is vacated, and costs are awarded to the appellant.
