DCT
3:25-cv-01399
Cart Source LLC v. Home Depot Inc
Key Events
Amended Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Cart Source LLC (Florida)
- Defendant: Home Depot U.S.A., Inc. (Delaware)
- Plaintiff’s Counsel: Malloy & Malloy, P.L.
- Case Identification: 3:25-cv-01399, M.D. Fla., 01/16/2026
- Venue Allegations: Plaintiff alleges venue is proper because Defendant "resides" in the district through its regular and established places of business and because a substantial part of the infringing acts occurred there.
- Core Dispute: Plaintiff alleges that Defendant’s use of anti-tilt devices on its shopping carts infringes a patent related to a mechanical device designed to prevent shopping carts from being tilted backwards.
- Technical Context: The technology at issue is a mechanical attachment for shopping cart casters, intended to counteract a common method of defeating wheel-locking anti-theft systems.
- Key Procedural History: Plaintiff alleges it sent a cease and desist letter to Defendant, providing written notice of infringement approximately three months before filing the complaint.
Case Timeline
| Date | Event |
|---|---|
| 2020-08-17 | ’427 Patent Priority Date |
| 2023-06-13 | ’427 Patent Issue Date |
| 2025-10-15 | Plaintiff sent written notice of infringement to Defendant |
| 2026-01-16 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 11,673,427 - *"Caster Anti-Tilt Device"*
- Patent Identification: U.S. Patent No. 11,673,427, "Caster Anti-Tilt Device," issued June 13, 2023 (’427 Patent).
The Invention Explained
- Problem Addressed: Many retail stores use anti-theft systems that lock a shopping cart’s front wheel if it crosses a defined boundary. The patent’s background section notes a "simple work-around" to this system is to tilt the cart rearward, lifting the locked wheel off the ground and allowing the cart to be moved on its rear wheels (’427 Patent, col. 1:22-25). Existing devices to prevent this tilting were sometimes complex to manufacture or could be dislodged (’427 Patent, col. 1:31-37).
- The Patented Solution: The invention is a device, typically formed from a single piece of stamped metal, that attaches to a shopping cart’s rear caster wheel (’427 Patent, col. 4:17-21). It features a bar that extends behind and below the wheel's axle. As described in the detailed description, if someone attempts to tilt the cart backward, this bar makes contact with the ground, preventing the wheel from rolling and effectively stopping the cart’s movement (’427 Patent, col. 3:49-54; FIG. 1A). The device attaches using the same bolt as the caster wheel and includes flanges designed to engage the caster frame to prevent the device itself from rotating around the axle (’427 Patent, col. 4:1-7).
- Technical Importance: The design provides a mechanically simple and robust method to defeat a common circumvention of widely used shopping cart anti-theft systems (’427 Patent, col. 1:36-37).
Key Claims at a Glance
- The complaint asserts independent Claim 1 (Compl. ¶23).
- The essential elements of Claim 1 are:
- An anti-tilt device comprising first and second face plates.
- First and second flanges extending from the edges of each face plate, which wrap beside the face plates for engagement with the caster frame.
- The flanges prevent rotation of the face plates with respect to the caster frame.
- First and second legs extending from the respective face plates.
- A bar extending between the legs across the tread face of the caster wheel.
- The bar is positioned at a defined angle relative to a vertical axis through the wheel’s rotation axis.
- Each leg includes a defined bend to place the bar at that defined angle.
- The complaint does not explicitly reserve the right to assert dependent claims but does seek relief for infringement of "at least one claim" (Compl. ¶42).
III. The Accused Instrumentality
Product Identification
- The accused products are "caster anti-tilt devices installed" on shopping carts used by Defendant at its retail locations, referred to as the "Accused Device" (Compl. ¶15, ¶18).
Functionality and Market Context
- The complaint alleges that Defendant, a national home improvement retailer, uses shopping carts equipped with these anti-tilt devices (Compl. ¶15). The complaint provides photographs of the Accused Device installed on a shopping cart caster, showing a metal bracket attached at the wheel's axle that extends behind the wheel (Compl. ¶32). A photograph in the complaint shows the Accused Device, which appears to be a metal bracket attached to a shopping cart caster wheel (Compl. ¶32). The functionality is not described beyond the allegations that it meets the limitations of the asserted patent claim.
IV. Analysis of Infringement Allegations
’427 Patent Infringement Allegations
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| first and second face plates | The Accused Device is alleged to comprise first and second face plates that mount to the caster. | ¶33 | col. 2:65-66 |
| first and second flanges extending from opposing edges of said first [and second] face plate...wrapping beside the...face plate for engagement with the frame | The Accused Device allegedly includes flanges that extend from the face plates and engage with the caster frame. | ¶34, ¶35, ¶36 | col. 3:1-17 |
| wherein the first and second flanges...prevent rotation of the first and second face plates with respect to the caster frame | The complaint alleges that the flanges on the Accused Device prevent its rotation relative to the caster frame. A photograph is provided to support this allegation. | ¶37 | col. 4:1-7 |
| first and second legs extending from the first and second face plates, respectively | The Accused Device is alleged to have two legs extending from the face plates. A photograph depicts these legs. | ¶38 | col. 3:20-24 |
| a bar, extending between the first and second legs across a tread face of said caster wheel | The Accused Device allegedly includes a bar that connects the two legs and spans the width of the wheel tread. | ¶39 | col. 3:27-33 |
| at a defined angle of the tread face, as measured from a vertical axis...when said caster is level | The complaint alleges the bar is mounted at a defined angle and provides a photograph of the Accused Device alongside the patent’s FIG. 1A to illustrate this geometric relationship. | ¶40 | col. 3:34-49 |
| wherein each of said first and second legs includes a defined bend to place said bar at said defined angle | The Accused Device allegedly contains a bend in each leg to achieve the claimed angle for the bar. | ¶41 | col. 4:9-14 |
Identified Points of Contention
- Scope Questions: The claim requires flanges that "prevent rotation" of the device relative to the caster frame. A potential point of dispute may be whether the flanges on the Accused Device actually perform this function, or if rotation is prevented primarily or exclusively by the clamping force of the axle bolt and nut. The complaint's allegation will likely be tested by evidence regarding the precise fit and interaction between the flanges and the caster frame (Compl. ¶37).
- Technical Questions: Claim 1 recites that each leg "includes a defined bend to place said bar at said defined angle." The interpretation of "defined bend" may become a central issue. The question is whether the Accused Device's structure, as shown in the complaint's photograph (Compl. ¶41), constitutes a "bend" as contemplated by the patent, or if it is more accurately described as a continuous curve, potentially distinguishing it from the claim language.
V. Key Claim Terms for Construction
The Term: "prevent rotation"
- Context and Importance: This term is critical because it defines the function of the claimed flanges. The infringement analysis will depend on whether the Accused Device's flanges perform this specific function. Practitioners may focus on this term because if the axle bolt alone prevents rotation, this limitation may not be met.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification states that "flanges 32 prevent the rotation of anti-tilt device 20" without requiring that they be the sole means of doing so (’427 Patent, col. 4:1-3). This could support an interpretation where the flanges need only contribute to preventing rotation.
- Evidence for a Narrower Interpretation: The specification describes the flanges creating "pockets" that "receive a side wall 28 of caster 22" (’427 Patent, col. 3:9-12). This language, combined with descriptions of the flanges causing the device to "tightly engage the edges of walls 28a and 28b" (’427 Patent, col. 4:3-5), could support a narrower construction requiring a specific, tight-fitting mechanical interlock, not just incidental contact.
The Term: "a defined bend"
- Context and Importance: This term describes the structure of the legs connecting the face plates to the anti-tilt bar. Whether the Accused Device possesses this feature is a direct question of infringement. The dispute may center on whether a gradual curve constitutes a "bend."
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification notes that in an alternative embodiment, the "leg 34 could be curved to place bar at the desired offset," suggesting the patentee may have considered "bend" and "curve" to be functionally similar for achieving the desired geometry (’427 Patent, col. 4:15-16).
- Evidence for a Narrower Interpretation: The patent also describes forming the device from a flat metal strip "at bend lines 116a and 116b," which may imply a more discrete, angular change rather than a continuous curve (’427 Patent, col. 4:42-43). The figures depicting the flat pattern (FIG. 6) and the final product could be used to argue that a "bend" is structurally distinct from a "curve."
VI. Other Allegations
Willful Infringement
- The complaint alleges willful infringement based on Defendant's alleged pre-suit knowledge of the ’427 Patent (Compl. ¶45). The basis for this knowledge is a cease and desist letter Plaintiff sent to Defendant on October 15, 2025, which allegedly provided notice of the patent and the infringing activity (Compl. ¶18, ¶43). The complaint alleges that Defendant continued its infringing conduct despite this notice (Compl. ¶26, ¶44).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of definitional scope: can the structural term "a defined bend," which is described in the patent specification with reference to specific "bend lines," be construed to read on the geometry of the Accused Device, which may be characterized as a continuous curve?
- A key evidentiary question will be one of functional performance: does the evidence show that the flanges on the Accused Device actually "prevent rotation" of the device on the caster's axle, or is that function performed entirely by the axle bolt, rendering the claim limitation unmet?
- The case may also turn on the question of willfulness: given the explicit pre-suit notice alleged in the complaint, Defendant’s conduct after receiving the cease and desist letter will be a central focus in determining whether any potential infringement was willful.