Snap On Inc v. Milwaukee Electric Tool Corp

1. Case Identification

• Case #: IPR2016-00344
• Patent #: 7,944,173
• Filed: December 16, 2015
• Petitioner(s): Snap-on Incorporated
• Patent Owner(s): Milwaukee Electric Tool Corporation
• Challenged Claims: 1-13

2. Patent Overview

• Title: Rechargeable Battery Pack for Power Tools
• Brief Description: The ’173 patent describes a rechargeable battery pack for use with hand-held power tools. The disclosed technology centers on using lithium-based chemistry cells to power high-current-draw tools, effectively substituting higher-power lithium-ion cells into battery pack structures that were similar to prior art packs using older Nickel-Cadmium (NiCd) or Nickel-Metal Hydride (NiMH) cells.

3. Grounds for Unpatentability

Ground 1: Claims 1-13 are obvious over Takano in view of Yanai.

• Prior Art Relied Upon: Takano (Application # 2003/0096158) and Yanai (Japanese Patent Application No. 2001-118569).
• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that the combination of Takano and Yanai teaches every limitation of the challenged claims. Takano was asserted to disclose a rechargeable battery pack for a cordless power tool, satisfying the claim preamble. Takano further teaches a housing connectable to the tool (limitation 1a), a plurality of battery cells (1b) using lithium-ion chemistry (1d), and terminals for current flow (1e). Petitioner contended that Takano’s disclosure of a removable battery pack inherently teaches a locking assembly (1f) and a movable locking member (claim 13) necessary to secure the pack to the tool.

  • The central limitation of independent claim 1, "the battery cells being capable of producing an average discharge current greater than or equal to approximately 20 amps" (1c), was assertedly met by Yanai. Yanai discloses high-current-discharge, lithium-manganese battery cells and provides sufficient material and performance data for a person of ordinary skill in the art (POSITA) to calculate that standard industry-sized cells (e.g., a single 26650 cell or two 18650 cells in parallel) using Yanai’s materials would generate over 20A of current.

  • Petitioner further mapped the combination to the dependent claims. Yanai was argued to explicitly teach the lithium-manganese chemistry required by claim 2 and the spinel chemistry of claim 3. Combining cells to reach specific counts (claim 4), voltages (claims 5, 7, and 11), and ampere-hour capacities (claim 6) was presented as a matter of routine and predictable design for a POSITA. Takano was argued to teach a removably connectable pack (claim 8), an integrated protection circuit (claim 9), and use with a driver-type tool (claim 10).

  • Motivation to Combine: Petitioner argued a POSITA would be motivated to substitute Yanai’s high-discharge-rate cells into Takano’s battery pack design to satisfy the well-known market demand for more powerful cordless tools. Takano expressly discloses the use of lithium-ion cells, creating a natural fit for an improved lithium-ion cell technology. Furthermore, Yanai specifically touts its high-performance lithium-manganese electrode material as being useful for a wide range of applications, including "electric power tools," providing a direct and explicit reason for the combination.

  • Expectation of Success: A POSITA would have had a reasonable expectation of success because incorporating Yanai's standard-sized cells (e.g., 18650 or 26650) into a battery pack like Takano's would involve predictable design principles. Arranging cells in various series and/or parallel configurations to achieve desired current and voltage profiles was a well-understood and fundamental concept in the art of battery pack design.

4. Key Claim Construction Positions

• "a housing connectable to and supportable by the hand held power tool": Petitioner argued that the terms "connectable to" and "supportable by" are purely functional limitations that recite capability alone, rather than any specific structure. Citing Federal Circuit precedent, Petitioner contended that these terms should be afforded no patentable weight in the obviousness analysis, thereby broadening the scope of applicable prior art to any battery pack housing capable of being attached to a tool.
• "battery cells being capable of producing an average discharge current greater than or equal to approximately 20 amps": Petitioner contended this limitation (the "20 Amp Limitation") is potentially indefinite under 35 U.S.C. §112 because the specification fails to provide any objective standard or method for its measurement, such as the time period of discharge, the load conditions, or the specific application. Under the broadest reasonable interpretation standard used in IPR proceedings, Petitioner proposed the limitation is met by cells that can produce approximately 20 amps when used with a power tool for a duration and application consistent with the tool's intended use, a less stringent standard than a continuous discharge over the battery's entire rated capacity.
• "nominal voltage": Petitioner argued this term, recited in several dependent claims, is also indefinite because it has multiple competing meanings in the art (e.g., the midpoint voltage, the fully charged voltage, or the typical operating voltage). The specification was said to inject further ambiguity by listing multiple different "nominal voltages" (3.6V, 4.0V, 4.2V) without defining the term. Petitioner asserted that under the broadest reasonable interpretation, any of these common meanings would apply, allowing prior art disclosing any such voltage to satisfy the limitation.

5. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1-13 of the ’173 patent as unpatentable under 35 U.S.C. §103.