DCT
1:03-cv-00990
Mitutoyo Corp v. Central Purchasing LLC
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Mitutoyo Corporation (Japan), Mitutoyo America Corporation (New York), and C.E. Johansson AB (Sweden)
- Defendant: Central Purchasing, Inc. (California)
- Plaintiff’s Counsel: Greer, Burns & Crain, Ltd.
- Case Identification: 1:03-cv-00990, N.D. Ill., 02/10/2003
- Venue Allegations: Venue is alleged based on Defendant having a retail outlet in the district.
- Core Dispute: Plaintiffs allege that Defendant’s "Cen-Tech" line of digital calipers infringes a patent related to capacitive-based electronic measurement devices.
- Technical Context: The lawsuit concerns the technology of electronic digital calipers, which are high-precision hand tools used for length measurement in manufacturing and engineering.
- Key Procedural History: The complaint details extensive prior litigation between the parties over the same patent, initiated in 1995 by Central Purchasing seeking a declaratory judgment of invalidity and unenforceability. That case involved summary judgment motions, court orders dismissing certain invalidity and unenforceability claims with prejudice, and an eventual dismissal of the remaining claims and appeal. Plaintiffs now assert that this history precludes Defendant from re-litigating the patent's validity and enforceability as a matter of law.
Case Timeline
| Date | Event |
|---|---|
| 1977-12-09 | U.S. Patent No. 4,743,902 Priority Date |
| 1988-05-10 | U.S. Patent No. 4,743,902 Issue Date |
| 1994-03-29 | Agreement between parties regarding Defendant's cessation of sales of infringing calipers |
| 1995-03-29 | Defendant files Declaratory Judgment action against Plaintiffs in C.D. Cal. |
| 1995-04-06 | Defendant files First Amended Complaint in Declaratory Judgment action |
| 1997-03-21 | Parties file Stipulated Dismissal of inequitable conduct count in prior litigation |
| 1997-11-25 | Court in prior litigation grants summary judgment that claims 1 and 2 are not invalid under §102 |
| 1998-01-17 | Defendant files Motion to Dismiss remaining claims in prior litigation |
| 1998-06-09 | Court in prior litigation grants motion to dismiss remaining claims with prejudice |
| 1998-10-06 | Defendant appeals the November 25, 1997 Order to the Federal Circuit |
| 1999-06-15 | Federal Circuit dismisses the appeal per parties' stipulation |
| 2003-02-10 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 4,743,902 - "Measuring Device for Capacitive Determination of the Relative Position of the Two with Respect to one Another Movable Parts"
Issued May 10, 1988
The Invention Explained
- Problem Addressed: The patent seeks to create a simple, inexpensive, and low-power electronic measuring device, such as a digital caliper, with high resolution (e.g., 0.01 mm) suitable for a hand tool (’902 Patent, col. 1:16-22). Prior art systems were noted as either requiring complex and costly electronics for linear interpolation or having designs where the scale electrodes were galvanically coupled to each other or the environment, creating maintenance and shielding issues (’902 Patent, col. 1:30-65).
- The Patented Solution: The invention uses a capacitive sensor system to measure the relative position of a movable slide and a fixed scale. The slide contains multiple groups of "supply electrodes" that are fed phased electrical signals (e.g., three-phase rectangular waves) from a generator. The scale features a single pattern of "internally galvanically isolated" electrodes. As the slide moves, a receiving electrode on the slide capacitively picks up a signal from the scale electrodes. The position is determined by a processing unit that analyzes the phase shift of this received signal relative to the original supply signals (’902 Patent, Abstract; col. 2:45-54; col. 4:5-14). The galvanic isolation of the scale electrodes is a key feature, intended to simplify the design and improve robustness by locating all active electronics on the slide (’902 Patent, col. 2:58-65).
- Technical Importance: This design approach aimed to enable more compact, power-efficient, and mass-producible electronic precision measurement tools by simplifying the sensor structure and consolidating the electronics.
Key Claims at a Glance
- The complaint alleges infringement of "one or more claims," and the prior litigation focused on Claims 1 and 2 (Compl. ¶9, ¶24). Independent Claim 1 is the broadest claim.
- Independent Claim 1:
- A measuring device for capacitative determination of the relative position of two relatively movable parts, comprising:
- a slide provided with a number of groups of supply electrodes... n being an integer greater than 2;
- signal generator means... whereby all supply electrodes are supply with voltages according to a cyclic pattern;
- the slide also being provided with at least one receiving electrode;
- a signal processing unit connected to at least one receiving electrode;
- a scale being provided with a single electronic pattern comprising internally galvanically isolated scale electrodes, each scale electrode comprising two mutually galvanically connected parts, one being a detecting part and the other being a transferring part;
- whereby the position of the slide along the scale determines the signal from the at least one receiving electrode, which is derived from at least two adjacent supply electrode signals, and the position... can be determined by the identification in the signal processing unit of the phase position of said signal from the receiving electrode.
III. The Accused Instrumentality
Product Identification
The complaint identifies the accused products as the "Cen-Tech 4", 6", 8" and 12" digital calipers," providing specific item numbers for each (Compl. ¶9).
Functionality and Market Context
The complaint describes the accused products simply as "length measurement devices" and "electronic digital calipers" (Compl. ¶9, ¶31). It does not provide any specific technical details regarding their method of operation, such as their sensor type, electrode configuration, or signal processing method.
IV. Analysis of Infringement Allegations
The complaint does not contain a claim chart or detailed infringement theory. It asserts infringement in a conclusory manner. The following chart is constructed based on the elements of the primary independent claim and the general allegations.
No probative visual evidence provided in complaint.
’902 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a slide provided with a number of groups of supply electrodes distributed along the direction of relative movement, each of the groups having n number of supply electrodes, n being an integer greater than 2; | The complaint alleges the accused Cen-Tech digital calipers contain infringing functionality but does not specify the electrode structure. | ¶9 | col. 11:5-9 |
| a scale being provided with a single electronic pattern comprising internally galvanically isolated scale electrodes, each scale electrode comprising two mutually galvanically connected parts... | The complaint alleges the accused Cen-Tech digital calipers contain infringing functionality but does not specify the scale structure. | ¶9 | col. 11:18-24 |
| the position of the slide with respect to the scale can be determined by the identification in the signal processing unit of the phase position of said signal from the receiving electrode. | The complaint alleges the accused Cen-Tech digital calipers contain infringing functionality but does not specify the processing method. | ¶9 | col. 12:1-8 |
Identified Points of Contention
- Evidentiary Question: What evidence will Plaintiffs produce to show that the accused Cen-Tech calipers, which began selling years after the prior litigation, practice each element of the asserted claims? The complaint itself offers no technical specifics.
- Technical Question: Do the accused calipers' sensors actually use "internally galvanically isolated scale electrodes" as required by Claim 1, or do they employ a different capacitive sensing architecture (e.g., one with grounded or interconnected scale elements) that falls outside the claim scope?
- Functional Question: Do the accused calipers determine position by identifying the "phase position" of a received signal derived from multiple supply signals, as claimed, or do they use another measurement technique, such as amplitude or frequency analysis?
V. Key Claim Terms for Construction
- The Term: "internally galvanically isolated scale electrodes"
- Context and Importance: This term appears to be a primary point of novelty, distinguishing the invention from prior art with wired or grounded scale components. The infringement analysis will likely depend on whether the physical and electrical structure of the accused calipers' scale meets this limitation. Practitioners may focus on this term because its definition is central to the patent's described operational principle of having all active electronics on the slide.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: A party might argue that "internally galvanically isolated" simply means the electrodes are not connected to an external power source or ground, consistent with the patent's goal of placing all electronics on the slide (col. 2:58-65).
- Evidence for a Narrower Interpretation: A party could point to the detailed description, which states, "the electrodes of the scale are galvanically coupled nor to each other neither to the environment" (col. 2:58-61) and consists of distinct "detecting" and "transferring" parts (col. 11:20-24). This suggests a more stringent requirement of complete electrical isolation from each other and any common reference, not just from an external circuit.
VI. Other Allegations
- Willful Infringement: The complaint alleges that Defendant’s infringement was "willful and deliberate" and occurred with "full knowledge" of the ’902 Patent (Compl. ¶10). This allegation is based on the extensive prior litigation between the parties from 1995-1999 concerning the same patent, which Plaintiffs allege provided Defendant with actual notice and knowledge (Compl. ¶8, ¶12-28).
VII. Analyst’s Conclusion: Key Questions for the Case
- A central issue will be one of claim preclusion: To what extent, if any, does the prior declaratory judgment action—which resulted in court orders dismissing with prejudice counts of unenforceability and invalidity under 35 U.S.C. §102—bar the Defendant from challenging the validity and enforceability of the ’902 Patent in this new action?
- A key evidentiary question will be one of technical proof: Given that the current complaint provides no technical details, what evidence can Plaintiffs marshal to demonstrate that the accused Cen-Tech calipers, sold years after the prior dispute, actually implement the specific technological features of Claim 1, particularly the "internally galvanically isolated scale electrodes" and the phase-detection measurement method?