Songyang Dafudu E Commerce Co Ltd v. HoMedics USA LLC

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Songyang Dafudu E-Commerce Co., Ltd., Shanxi Tinghao Health & Trade Co., Ltd., and Suzhou ToolWorks Tools Co., Ltd. (China)
  • Defendant: Homedics USA, LLC (Michigan)
  • Plaintiff’s Counsel: Glacier Law LLP
• Case Identification: 2:25-cv-10887, E.D. Mich., 03/31/2025
• Venue Allegations: Venue is based on Defendant's residence in the district, where it is incorporated and headquartered, and where substantial events, including enforcement actions against Plaintiffs' products, occurred.
• Core Dispute: Plaintiffs seek a declaratory judgment that their foot spa products do not infringe Defendant’s patent related to bath apparatuses with removable therapy attachments, and that the patent is invalid.
• Technical Context: The technology concerns therapeutic foot spa baths that employ motorized, interchangeable massage heads to provide targeted treatment to different areas of a user's feet.
• Key Procedural History: The action was precipitated by infringement complaints Defendant submitted to Amazon on March 21, 2025, which resulted in the removal of Plaintiffs' product listings. Plaintiffs allege that during the patent's prosecution, the applicant disclaimed coverage of therapy attachments secured by screws or bolts, which may create a prosecution history estoppel that limits the patent's scope.

Case Timeline

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 8,407,826 - "Bath Apparatus", Issued April 2, 2013

The Invention Explained

• Problem Addressed: The patent's background section notes that while conventional foot baths provide general heat and vibration, a need exists for an apparatus that can "focus therapy at specific locations of the body," such as the ball, heel, or arch of a user's foot, to allow users to "tailor therapy regimens to their individual needs" (Compl. ¶11; ’826 Patent, col. 1:38-48).
• The Patented Solution: The invention is a bath apparatus, such as a foot spa, featuring at least one "therapy center" on its bottom surface. This therapy center is connected to a motor and is designed to receive an interchangeable "therapy attachment" (e.g., a massaging head with nodes or a brush). This design allows a user to swap different attachments to target specific areas of the foot with motorized, rotary motion while the foot remains in the water ('826 Patent, Abstract; col. 2:51-58). Figure 4 provides an exploded view showing how different therapy attachments (34, 36) can be placed onto the gear train assembly (62, 66) within the main housing (20) ('826 Patent, Fig. 4).
• Technical Importance: The invention provides a modular approach to foot therapy, combining the benefits of a heated water bath with customizable, motorized massage functions.

Key Claims at a Glance

• The complaint identifies independent claims 1, 18, and 19 as being at issue (Compl. ¶¶28, 30).
• Independent Claim 1:
  • An apparatus for bathing a body part, comprising:
  • a bath chamber for containing a fluid and receiving the body part;
  • a motor mounted on an underside of the bottom surface; and
  • at least one therapy attachment removably received on the bottom surface and operably connected to the motor for imparting rotary motion to the therapy attachment.
• The complaint notes that dependent claims 2-17 and 20-22 are also implicated (Compl. ¶31).

III. The Accused Instrumentality

• Product Identification: Plaintiffs' "foot spa bath products" sold through the Amazon marketplace, identified in part by ASINs including B0CPLRX3F4 and B09PY33NHB (Compl. ¶¶12-13).
• Functionality and Market Context: The complaint describes the accused products as foot spas that include "therapy attachments." Crucially, it alleges these attachments are "permanently secured by screws" and are "not designed to be removed by ordinary users without professional disassembly" (Compl. ¶15). The products were sold to consumers in the United States via Amazon before being removed following Defendant's infringement assertions (Compl. ¶¶12-13). No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

'826 Patent Infringement Allegations

• Identified Points of Contention:
  • Scope Questions: The central dispute concerns the meaning of "removably received." The case will question whether an attachment secured by screws, which the complaint alleges requires "professional disassembly" to remove, falls within the scope of this term. Plaintiffs argue that it does not, based on alleged disclaimers made during patent prosecution (Compl. ¶¶16-17).
  • Legal Questions: A primary legal question is whether the patentee’s statements during prosecution rise to the level of a "clear and unmistakable disavowal" of subject matter, which would trigger prosecution history estoppel and prevent the patentee from asserting that screw-fastened attachments are equivalent to the claimed "removably received" attachments (Compl. ¶23).

V. Key Claim Terms for Construction

• The Term: "removably received"
• Context and Importance: This term is the lynchpin of the non-infringement argument. The definition will determine whether Plaintiffs' products, which allegedly use screws to fix the attachments, can infringe. Practitioners may focus on this term because the complaint explicitly ties it to a prosecution history disclaimer, suggesting a pre-existing and potentially dispositive legal vulnerability (Compl. ¶23).
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The claims themselves do not specify the mechanism of removal. A party could argue that "removably" simply means "capable of being removed," without limitation as to the ease or method of removal. The specification describes the attachment being "securely received in a recess" on a gear shaft, but does not explicitly forbid the use of tools for removal ('826 Patent, col. 5:52-56).
  • Evidence for a Narrower Interpretation: The complaint alleges that the patentee, during prosecution, distinguished prior art by stating that a component "bolted to the immersing vessel" was a "fixed attachment," in contrast to the claimed "removable" one (Compl. ¶23). This statement, if accurate, provides strong evidence for a narrower construction that excludes attachments fixed by bolts or screws. Furthermore, the specification describes therapy attachments that "can be easily interchanged by a user," which suggests a tool-less or simple removal process not typically associated with screw-based fixtures ('826 Patent, col. 3:32-33).

VI. Other Allegations

• Indirect Infringement: The complaint preemptively argues against infringement under the doctrine of equivalents. It alleges that the patentee is precluded from using this doctrine to capture screw-fixed attachments because it explicitly disclaimed such structures during prosecution to secure the patent (Compl. ¶23).

VII. Analyst’s Conclusion: Key Questions for the Case

The resolution of this declaratory judgment action will likely depend on the court's answers to two central questions:

1. A core issue will be one of claim scope and estoppel: did the statements made during the prosecution of the '826 patent constitute a "clear and unmistakable" disavowal of attachments secured by screws or bolts? If so, the patentee may be estopped from arguing that Plaintiffs' products infringe, either literally or under the doctrine of equivalents.

2. A secondary question will be one of invalidity: do the "Ho" and "Ferber" prior art references, either alone or in combination, disclose all elements of the asserted claims, including a "removable" therapy attachment, such that the '826 patent claims are anticipated or rendered obvious? The strength of the invalidity case will turn on the specific disclosures within those references.