PTAB

IPR2018-01415

Berkenhoff Gmbh v. Seong, Ki Chul

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1. Case Identification

2. Patent Overview

  • Title: Electrode Wire for Electro-Discharge Machining and Method for Manufacturing the Same
  • Brief Description: The ’872 patent discloses an electrode wire for electro-discharge machining (EDM) and a method for its manufacture. The wire comprises a core (e.g., copper or brass), a first alloy layer, and a second alloy layer formed via diffusion, with the key feature being cracks on the second alloy layer that form grains on the wire's surface, allegedly created by a "twisting" process using rollers.

3. Grounds for Unpatentability

Ground 1: Claims 1-13 and 15 are obvious over Tomalin in view of Nishioka

  • Prior Art Relied Upon: Tomalin (Patent 5,945,010) and Nishioka (Patent 3,326,025).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Tomalin taught all key elements of the challenged claims except for the specific twisting method. Tomalin disclosed a multi-layer EDM wire with a copper/brass core, a first (gamma-phase brass) and second (epsilon-phase brass) alloy layer formed by heat treatment and diffusion, and cracks in the brittle alloy layers that erupt core material to the surface. Petitioner asserted that Nishioka supplied the missing element: a method of drawing wire using a "zig-zag bending" technique with a plurality of rollers, which corresponds to the "twisting" limitation of the ’872 patent.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine these references as a matter of simple substitution. Tomalin disclosed a wire made by drawing but was silent on the specific drawing technique. Nishioka disclosed a well-known roller-based bending and drawing technique. A POSITA would have been motivated to use the known drawing method of Nishioka to produce the wire of Tomalin. Further motivation stemmed from the known principle, supported by the Kaieda and Oguchi article, that bending brittle zinc-alloy layers (like those in Tomalin) would create the desirable cracks for improved EDM performance.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because applying a conventional wire-bending process (Nishioka) to a wire with known brittle alloy layers (Tomalin) would predictably and successfully induce the claimed cracks.

Ground 2: Claims 1-13 and 15 are obvious over Tomalin in view of Groos and Grandy

  • Prior Art Relied Upon: Tomalin (Patent 5,945,010), Groos (Patent 4,766,280), and Grandy (Patent 3,677,309).

  • Core Argument for this Ground:

    • Prior Art Mapping: This ground was presented as an alternative in case "twisting" is interpreted as rotational or torsional twisting, rather than bending. Tomalin again provided the fundamental multi-layer wire structure with its beneficial coating. Groos taught torsionally twisting an EDM wire to create helical edges, which improves the flushing of eroded material from the cutting gap. While Groos taught the concept, it used clamps for twisting. Grandy was introduced because it disclosed a well-known apparatus for twisting wire continuously using rollers, which is the specific mechanism recited in the claims.
    • Motivation to Combine: The primary motivation was to solve a known problem: improving flushing efficiency in EDM. A POSITA would combine Tomalin's coated wire with Groos's twisting method to achieve enhanced flushing from both the coating and the helical edges. It would then be an obvious substitution to implement this twisting using the well-known and commercially advantageous continuous roller-based method of Grandy instead of the batch clamp-based method of Groos.
    • Expectation of Success: A POSITA would expect success in applying Grandy's established roller-twisting technique to the Tomalin wire to achieve the known flushing benefits disclosed in Groos.

  • Additional Grounds: Petitioner asserted alternative obviousness challenges (Grounds 2 and 4) by adding the ASM Handbook to the combinations above. This was specifically to address the method claim limitation of an "elongation percentage of 5 or more." Petitioner argued that while not explicitly stated in the primary references, the ASM Handbook, a standard industry text, confirmed that a wire with the material properties disclosed in Tomalin would inherently possess an elongation well above 5%, rendering the limitation obvious.

4. Key Claim Construction Positions

  • The petition’s validity arguments hinged on the interpretation of the term "twisting." Petitioner did not propose a single construction but instead presented alternative grounds to cover the two most likely interpretations.
  • Bending vs. Torsion: Ground 1 was based on the premise that "twisting" could be interpreted as the zig-zag bending process disclosed in Nishioka. Ground 3 was based on the alternative premise that "twisting" requires rotational or torsional force, as disclosed by Groos and Grandy. This dual-pronged approach was central to the petition's strategy.

5. Key Technical Contentions (Beyond Claim Construction)

  • A central technical argument, underpinning multiple grounds, was that it was well-known in the art that brittle, high-zinc-content copper-zinc alloys (i.e., gamma-phase brass) would inherently form cracks when subjected to mechanical stress like bending or twisting.
  • Petitioner cited the "Kaieda and Oguchi Article" as evidence that a POSITA would have known that applying a bending or twisting process to the alloy layers disclosed in Tomalin would inevitably create the surface cracks recited in the ’872 patent claims.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review and the cancellation of claims 1-13 and 15 of the ’872 patent as unpatentable.