DCT

1:26-cv-07374

Zhong v. Ningbo Haoyang Jixie Gongju Youxian Gongsi

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:26-cv-07374, N.D. Ill., 06/24/2026
  • Venue Allegations: Venue is asserted under 28 U.S.C. § 1391(c)(3), which allows a defendant not resident in the United States to be sued in any judicial district, because Defendant is a China-based entity.
  • Core Dispute: Plaintiff alleges that Defendant's weight-adjustable dumbbells, sold in the U.S. via online marketplaces, infringe a patent related to a specific mechanical system for quickly connecting and disconnecting dumbbell weights.
  • Technical Context: The technology concerns modular exercise equipment, specifically the design of locking mechanisms that allow users to rapidly change the weight of a dumbbell without traditional, time-consuming screw-on collars.
  • Key Procedural History: The complaint does not mention any prior litigation, inter partes review proceedings, or licensing history related to the patent-in-suit.

Case Timeline

Date Event
2023-07-08 '453 Patent Priority Date
2026-04-07 U.S. Patent No. 12,594,453 Issued
2026-06-24 Complaint Filed

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

U.S. Patent No. 12,594,453 - "Weight-Adjustable Dumbbell"

  • Patent Identification: U.S. Patent No. 12,594,453 ("the '453 Patent"), "Weight-Adjustable Dumbbell," issued April 7, 2026.

The Invention Explained

  • Problem Addressed: The patent's background describes conventional adjustable dumbbells as requiring the user to fix weight plates with a fixing nut, a method that is "complicated in operation and wastes time and labor" '453 Patent, col. 1:29-33
  • The Patented Solution: The invention proposes a twist-and-lock mechanism to attach and detach auxiliary weight blocks '453 Patent, abstract The system uses a "spinning buckle" on one weight block that has a "stop convex block" '453 Patent, col. 6:9-11 This buckle is inserted into a corresponding "spinning slot" on another block through a "notch" '453 Patent, col. 6:12-13 Once inserted, rotating the buckle moves the convex block out of alignment with the notch, where it is blocked by a "stop edge," thereby locking the two weight blocks together '453 Patent, col. 6:18-25 This allows for the "fast removal of the auxiliary counterweight blocks" '453 Patent, col. 6:1-3
  • Technical Importance: The described solution aims to improve user convenience and efficiency in adjusting dumbbell weights during a workout '453 Patent, col. 3:59-61

Key Claims at a Glance

  • The complaint asserts infringement of at least independent claim 1 Compl. ¶3
  • The essential elements of Claim 1 include:
    • A handle.
    • Counterweight block groups, including main and auxiliary blocks.
    • A detachable connection between the main and auxiliary blocks, comprising a "first connecting part" and a "first connecting fitting part."
    • Each weight block comprising a "counterweight block shell" and a "fixed cover plate" fitted together to form a cavity containing a "counterweight iron plate."
    • The connecting part being a "first spinning buckle" with a "first stop convex block."
    • The fitting part being a "first spinning slot" with a "first stop edge" and a "first notch."
    • A locking mechanism wherein the buckle is inserted through the notch and then rotated so the convex block is "staggered from the first notch," causing the stop edge to block the convex block and secure the assembly.
  • The complaint does not explicitly reserve the right to assert dependent claims.

III. The Accused Instrumentality

Product Identification

The accused products are identified as the "EQUIPRO Adjustable Dumbbell Set, 4 in 1 Free Weights Dumbbells Set for Women, Weights for Women at Home, 2lb 3lb 4lb 5lb with TPU Soft Rubber Handle for Home Gym Exercise Training," sold under the seller name "equipro" on Amazon.com Compl. ¶9 Compl. ¶21

Functionality and Market Context

The complaint alleges the accused products are "weight-adjustable dumbbells" that are offered for sale and sold to consumers in the United States through online marketplace listings Compl. ¶3 Compl. ¶7 The complaint states these products include "a handle, main counterweight blocks, removable auxiliary counterweight blocks, detachable connecting structures...and rotating buckle-and-slot structures" that correspond to the limitations of claim 1 Compl. ¶28 No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint alleges direct infringement of the '453 Patent under 35 U.S.C. § 271(a) Compl. ¶26 It states that infringement is detailed in a claim chart attached as Exhibit C Compl. ¶23 However, Exhibit C was not provided with the complaint document.

In place of a claim chart, the complaint's narrative theory alleges that the accused EQUIPRO dumbbells embody the elements of claim 1 Compl. ¶28 Specifically, the complaint asserts that the products possess a "handle," "main counterweight blocks," "removable auxiliary counterweight blocks," and "detachable connecting structures" Compl. ¶28 Crucially, it alleges the presence of "rotating buckle-and-slot structures" that correspond to the patented locking mechanism Compl. ¶28 The infringement claim rests on the allegation that the mechanical assembly and operation of these accused features map onto the specific structures recited in claim 1 of the '453 Patent.

  • Identified Points of Contention:
    • Scope Questions: A central issue may be the interpretation of the term "spinning buckle." The dispute could turn on whether the accused product's locking component has the specific "stop convex block" structure recited in the claim and depicted in the patent's figures '453 Patent, col. 6:9-11, or if it uses a functionally similar but structurally different locking feature.
    • Technical Questions: A key factual question will be whether the accused product's mechanism for adding and removing weights operates by rotating a component into and out of alignment with a "notch" to achieve a locked state, as required by claim 1 '453 Patent, col. 6:18-25 Evidence will be needed to show that the accused device's functionality is achieved through the specific sequence of insertion and rotation described in the claim.

V. Key Claim Terms for Construction

  • The Term: "first spinning buckle"

    • Context and Importance: This term defines the core moving part of the patented locking mechanism. Its construction will be critical to determining whether the accused product's connection system falls within the claim's scope.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The patent also refers to this element more generally as a "first buckle part" '453 Patent, col. 6:6-7, which a plaintiff might argue suggests the term should encompass a category of rotating fasteners, not just the exact embodiment shown.
      • Evidence for a Narrower Interpretation: The claim itself, along with the specification, defines this buckle by its specific features, including a "first stop convex block" '453 Patent, claim 1 The detailed description and figures further illustrate this as a particular geometric shape (e.g., element 121 in FIG. 7) that interacts with a corresponding "notch" and "stop edge," potentially limiting the term to structures that possess these exact features.

  • The Term: "counterweight block shell"

    • Context and Importance: Claim 1 requires each weight block to be constructed from a "shell" and a "fixed cover plate" that form a "cavity" for an iron plate '453 Patent, claim 1 The construction of the accused dumbbell's housing will be compared against this element.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: A party could argue this term simply requires a two-part housing for the weight, without limitation as to how the two parts connect.
      • Evidence for a Narrower Interpretation: The specification describes and illustrates a specific method of joining the shell and cover plate, using a "fixed clamping block" and a "fixed clamping slot" '453 Patent, col. 9:1-4 '453 Patent, FIG. 5 A defendant may argue that this disclosed method of fitting the shell and plate together informs the meaning of the claim terms, limiting them to such a specific assembly.

VI. Other Allegations

  • Indirect Infringement: The complaint does not plead any counts for indirect infringement (inducement or contributory infringement).
  • Willful Infringement: The complaint includes a conclusory allegation of willful infringement "on information and belief" Compl. ¶32 It does not allege any specific facts to support pre-suit knowledge of the '453 Patent, such as a cease-and-desist letter or prior dealings.

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

The resolution of this dispute will likely depend on the court's findings regarding two primary issues:

  • A core issue will be one of claim construction: how narrowly will the court define the specific mechanical components of the locking system, such as "spinning buckle" and "stop convex block"? The case's outcome may depend on whether these terms are construed to cover only the precise geometric structures shown in the patent or a broader category of rotating locking mechanisms.
  • A key evidentiary question will be one of structural correspondence: does the accused dumbbell's mechanism for attaching weights utilize a component that is inserted through a "notch" and then rotated to a "staggered" position where it is blocked by a "stop edge," as claimed? The infringement analysis will require a direct, feature-by-feature comparison of the accused product's physical structure and operation against the limitations recited in claim 1.