Chervon North America, Inc. v. Milwaukee Electric Tool Corporation

1. Case Identification

• Patent #: 7,944,173
• Filed: January 21, 2015
• Petitioner(s): Chervon North America, Inc.; Hilti, Inc.; Positec Tool Corporation; Positec USA, Inc.; and Tooltechnic Systems LLC
• Patent Owner(s): Milwaukee Electric Tool Corporation
• Challenged Claims: 1-13

2. Patent Overview

• Title: Lithium-Based Battery Pack for a High Current Draw, Hand-Held Power Tool
• Brief Description: The ’173 patent describes a rechargeable battery pack for high-current-draw, hand-held power tools. The invention uses a plurality of lithium-based battery cells within a housing that connects to the power tool, purportedly capable of producing a high average discharge current.

3. Grounds for Unpatentability

Ground 1: Claims 1-13 are obvious over Kasahara in combination with Linden and further in view of Anthony.

• Prior Art Relied Upon: Kasahara (WO 02/03484), Linden (The Handbook of Batteries, 3rd Ed., 2001), and Anthony (Patent 5,213,913).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Kasahara taught the core elements of a rechargeable battery pack for hand-held power tools, including the use of lithium-based chemistry, a housing, and terminals. However, to meet the limitation of producing approximately 20 amps, Petitioner turned to Linden, which disclosed commercially available lithium-cobalt oxide cells capable of producing 10 amps each; Petitioner asserted that placing two such cells in parallel was a simple and obvious configuration to achieve the claimed 20 amps. To meet the "locking assembly" limitation of claim 1, Petitioner asserted that Anthony taught an improved, resiliently biased latching mechanism for removably connecting a battery pack to a power tool.
  • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine Kasahara and Linden because Kasahara expressly taught using lithium batteries, and Linden provided a well-known, commercially available lithium cell type suitable for the application. A POSITA would incorporate Anthony's latching mechanism because Kasahara's pack required attachment to a tool, and Anthony provided a known, predictable solution to the common design need for a removable, cordless connection, enhancing convenience and portability.
  • Expectation of Success: A POSITA would have had a high expectation of success as the combination involved arranging old, well-understood elements (a power tool battery pack, standard lithium cells, a common latch) to perform their known functions, yielding predictable results.

Ground 2: Claims 1-8 and 10-13 are obvious over Yamaki in combination with Anthony.

• Prior Art Relied Upon: Yamaki (Application # 2002/0168568) and Anthony (Patent 5,213,913).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that Yamaki taught a lithium-ion battery pack for "portable electromotive tools" (power tools) and disclosed the fundamental design considerations, including cell chemistry, geometry, and pack management. Yamaki also taught cells that, when combined in a common parallel configuration, could achieve the claimed discharge current of approximately 20 amps. As Yamaki did not explicitly detail a locking assembly, Petitioner again relied on Anthony to teach its well-known latching mechanism for removably securing the battery pack to the power tool, satisfying limitations of claims 1 and 8.
  • Motivation to Combine: A POSITA would combine the references because Yamaki and Anthony were complementary; Yamaki taught the battery pack technology for a power tool, and Anthony taught a known locking assembly for such a tool. Given the trend toward cordless tools, a POSITA would have naturally sought a known method like Anthony's to make Yamaki's battery pack removably attachable to a power tool.
  • Expectation of Success: Success was expected because it involved applying a standard mechanical latching solution (Anthony) to a battery pack (Yamaki) to achieve the known benefit of a secure, removable connection.

Ground 3: Claim 9 is obvious over Yamaki in combination with Anthony and further in view of Staarman.

• Prior Art Relied Upon: Yamaki (Application # 2002/0168568), Anthony (Patent 5,213,913), and Staarman (Patent 5,179,337).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground specifically targeted claim 9, which added a "protection circuit" to the combination of claim 1. Petitioner argued that the base combination of Yamaki and Anthony taught the elements of claim 1. While Yamaki mentioned using "protection circuit units," it did not disclose their inner workings. Staarman was introduced to remedy this, as it explicitly taught a protection circuit using a field-effect transistor to protect rechargeable batteries from over-discharge by monitoring voltage, a function analogous to that required for the battery pack in Yamaki.
  • Motivation to Combine: A POSITA, seeking to implement the protection circuit units called for in Yamaki, would have been motivated to consult a reference like Staarman, which taught a known, effective, and predictable circuit design for that exact purpose. Staarman itself suggested its circuit was useful for lithium batteries in portable electric tools, providing an express reason to combine its teachings with Yamaki.
  • Expectation of Success: A POSITA would have expected success in integrating Staarman's standard protection circuit into Yamaki's battery pack, as it was a straightforward implementation of a known solution to a known problem.

4. Key Claim Construction Positions

• Petitioner argued that several key claim terms should be construed based on their ordinary meaning, prosecution history, and constructions from related litigation, but also contended that some terms were indefinite.
• "battery cells being capable of producing an average battery pack discharge current greater than or equal to approximately 20 amps": Petitioner argued this term was indefinite under 35 U.S.C. §112 because the patent failed to specify the conditions for measuring this "average" current, such as the time period, the specific tool used, or the load applied. However, for the purposes of the IPR, Petitioner proceeded under the broadest reasonable interpretation that the limitation is met by cells capable of producing ~20 amps for any application consistent with the tool's intended use.
• "nominal voltage": Petitioner also argued this term, recited in claims 5, 7, and 11, was indefinite because the art supported multiple competing definitions (e.g., midpoint voltage, fully-charged voltage, or typical operating voltage), and the patent specification used the term inconsistently without providing a clear definition. Petitioner proceeded by showing the prior art met the claim limitations under any of these potential interpretations.

5. Relief Requested

• Petitioner requested that the Board institute an inter partes review (IPR) of claims 1-13 of the ’173 patent and find those claims unpatentable and cancelled.