Marmon Foodservice Tech Inc v. Duke Mfg Co

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Marmon Foodservice Technologies, Inc. (Minnesota)
  • Defendant: Duke Manufacturing Co. (Missouri)
  • Plaintiff’s Counsel: Thompson Coburn LLP; Andrus Intellectual Property Law, LLP
• Case Identification: Marmon Foodservice Technologies Inc v. Duke Mfg Co, 4:25-cv-01491, E.D. Mo., 09/18/2026
• Venue Allegations: Venue is based on Defendant being a Missouri corporation that resides in the district, conducts continuous business in the district, has a regular and established place of business in the district, and has allegedly committed acts of infringement within the district.
• Core Dispute: Plaintiff alleges that Defendant’s HS2 and ReadyFlex lines of commercial food holding bins infringe a portfolio of seven utility patents and two design patents related to multi-zone food holding technology.
• Technical Context: The technology relates to heated holding cabinets used in commercial foodservice to keep pre-cooked food items at specific temperatures for extended periods, a key operational component in the quick-service restaurant industry.
• Key Procedural History: The First Amended Complaint follows an original complaint filed on October 3, 2025, and served on October 7, 2025. The complaint alleges that Defendant was put on notice of the asserted patents and infringement allegations as of the service date.

Case Timeline

Date	Event
2014-01-01	Burger King and Tim Hortons merge to form Restaurant Brands International (RBI)
2015-01-01	Plaintiff Marmon introduces its Extended Holding Bin (EHB) product
2016-01-01	Defendant Duke launches its accused HS2 line of holding bins
2016-04-19	Earliest Priority Date for ’322, ’641, and ’981 Patents
2016-04-20	Earliest Priority Date for ’750, ’363, ’002, and ’264 Patents
2017-08-28	Earliest Priority Date for D'455 and D'814 Patents
2018-05-22	U.S. Patent No. 9,976,750 Issues
2018-05-22	U.S. Patent No. 9,980,322 Issues
2019-12-03	U.S. Patent No. 10,492,641 Issues
2019-12-24	U.S. Patent No. 10,512,363 Issues
2020-11-17	U.S. Patent No. 10,841,981 Issues
2020-12-01	U.S. Patent No. 10,852,002 Issues
2023-01-01	Defendant Duke introduces its accused ReadyFlex holding bin
2023-10-03	U.S. Patent No. 11,771,264 Issues
2024-04-02	U.S. Design Patent No. D1,020,455 Issues
2025-03-04	U.S. Design Patent No. D1,064,814 Issues
2025-10-03	Original Complaint Filed
2025-10-07	Defendant served with Original Complaint / Put on notice of patents
2026-09-18	First Amended Complaint Filed

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

U.S. Patent No. 9,976,750 - "Multi-Zone Food Holding Bin," Issued May 22, 2018

The Invention Explained

• Problem Addressed: The patent addresses the challenge in quick-service restaurants of holding various pre-cooked food items for rapid service without sacrificing food quality (US 9976750, col. 1:11-23). Known holding bins have limited hold times, often less than 20 minutes, leading to significant food waste when items are not sold quickly US 9,976,750, col. 1:33-41
• The Patented Solution: The invention is a food holding bin with multiple, distinct temperature zones within a single food holding compartment US 9,976,750, abstract This is achieved through a specific arrangement of heating elements that allows adjacent zones on a continuous surface to be maintained at different, independently controlled temperatures, enabling an operator to hold diverse food products (e.g., eggs and sausage) at their respective ideal temperatures simultaneously US 9,976,750, col. 2:6-29
• Technical Importance: This approach allows foodservice operators to extend the palatable holding time of various foods, thereby reducing waste and improving operational efficiency and product quality Compl. ¶41

Key Claims at a Glance

• The complaint asserts at least independent Claim 1 Compl. ¶50 Compl. ¶51
• Essential elements of Claim 1 include:
  • A food holding bin with a chassis and a first food holding compartment.
  • A "continuous and planar surface" forming the bottom of the compartment.
  • A first food holding zone with an "independently controllable radiant first heating element" and an "independently controllable conductive second heating element."
  • A second food holding zone, adjacent to the first, with an "independently controllable radiant third heating element" and an "independently controllable conductive fourth heating element."
  • A food holding tray disposed in the compartment.
  • A configuration wherein the first heating element heats the tray "radiantly from above" and the second heating element heats the tray "conductively from below."
• The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 9,980,322 - "Multi-Zone Food Holding Bin," Issued May 22, 2018

The Invention Explained

• Problem Addressed: Like the '750 patent, the '322 patent addresses the problem of limited holding times and subsequent food waste in restaurants that pre-cook food items to ensure fast service (US 9980322, col. 1:11-41).
• The Patented Solution: The patent describes a multi-zone food holding bin where different food items with varying heating requirements can be held in the same compartment at different, independently set temperatures US 9,980,322, col. 2:5-15 The solution centers on a structure with multiple food holding zones over a continuous surface, each with its own set of independently controllable heating elements managed by a controller US 9,980,322, abstract
• Technical Importance: The ability to independently control adjacent temperature zones enhances the flexibility of food holding cabinets, allowing them to accommodate a changing menu mix while improving food quality and reducing waste Compl. ¶41

Key Claims at a Glance

• The complaint asserts at least independent Claim 1 Compl. ¶52 Compl. ¶53
• Essential elements of Claim 1 include:
  • A food holding bin with a chassis and a first food holding compartment.
  • A "continuous and planar surface" forming the bottom of the compartment.
  • A first food holding zone with an independently controllable first heating element and second heating element.
  • A second food holding zone, adjacent to the first, with an independently controllable third heating element and fourth heating element.
  • A "controller" operatively coupled to the heating elements and configured to "independently operate each heating element" to maintain independently controlled temperatures in each zone.
• The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 10,492,641 - "Multi-Zone Food Holding Bin," Issued December 3, 2019

• Technology Synopsis: The patent describes a multi-zone food holding bin with at least two stacked food holding compartments, each of which is subdivided into multiple, independently controllable temperature zones ’641 Patent, abstract ’641 Patent, claim 1 The claims detail a structure with distinct upper and lower compartments, each containing at least two zones with their own heating elements.
• Asserted Claims: At least Claim 1 Compl. ¶54 Compl. ¶55
• Accused Features: The complaint alleges that the Duke HS2 and ReadyFlex products practice the claimed invention Compl. ¶54 Compl. ¶55

U.S. Patent No. 10,512,363 - "Multi-Zone Food Holding Bin," Issued December 24, 2019

• Technology Synopsis: This patent covers a food holding bin with multiple, individually configurable "bays" within larger temperature "zones" ’363 Patent, claim 1 The claims describe a system with multiple stacked compartments, each with at least two zones, and each zone containing at least two bays, allowing for granular control over food holding conditions.
• Asserted Claims: At least Claim 1 Compl. ¶56 Compl. ¶57
• Accused Features: The Duke HS2 and ReadyFlex products are accused of infringing by incorporating the claimed multi-bay, multi-zone structure Compl. ¶56 Compl. ¶57

U.S. Patent No. 10,841,981 - "Multi-Zone Food Holding Bin," Issued November 17, 2020

• Technology Synopsis: The patent claims a multi-zone food holding bin where the bottom surface of a compartment is a continuous planar surface extending to the front opening, with adjacent food holding zones across that surface ’981 Patent, claim 27 The claim details an architecture with heating elements above and below the surface for each zone.
• Asserted Claims: At least Claim 27 Compl. ¶58 Compl. ¶59
• Accused Features: The Duke HS2 and ReadyFlex products are alleged to incorporate the claimed structure of a continuous surface with adjacent, independently heated zones Compl. ¶58 Compl. ¶59

U.S. Patent No. 10,852,002 - "Multi-Zone Food Holding Bin," Issued December 1, 2020

• Technology Synopsis: This patent describes a multi-zone food holding bin with independently controllable heating elements for each zone, including a specific claim structure requiring both a "radiant heating source" and a "conductive heating element" ’002 Patent, claim 14 The configuration is designed to provide heat from both above and below a food item.
• Asserted Claims: At least Claim 14 Compl. ¶60 Compl. ¶61
• Accused Features: The Duke HS2 and ReadyFlex products are accused of infringing by using the claimed combination of radiant and conductive heating Compl. ¶60 Compl. ¶61

U.S. Patent No. 11,771,264 - "Multi-Zone Food Holding Bin," Issued October 3, 2023

• Technology Synopsis: This patent claims a method of maintaining different temperatures in a multi-zone food holding bin ’264 Patent, claim 9 The method involves independently setting temperatures for adjacent food zones that share an uninterrupted continuous planar bottom surface.
• Asserted Claims: At least Claim 1 Compl. ¶62 Compl. ¶63
• Accused Features: The Duke HS2 and ReadyFlex products are alleged to infringe by performing the claimed method of independent temperature control across adjacent zones Compl. ¶62 Compl. ¶63

U.S. Design Patent No. D1,020,455 - "Food Holding Bin," Issued April 2, 2024

• Technology Synopsis: This patent claims the ornamental design for a food holding bin, as depicted in its figures D'455 Patent, claim
• Asserted Claims: The single claim for the ornamental design Compl. ¶64
• Accused Features: The overall ornamental appearance of the Duke HS2 holding bin is alleged to be substantially the same as the patented design Compl. ¶71

U.S. Design Patent No. D1,064,814 - "Food Holding Bin," Issued March 4, 2025

• Technology Synopsis: This patent claims the ornamental design for a second embodiment of a food holding bin, as depicted in its figures D'814 Patent, claim
• Asserted Claims: The single claim for the ornamental design Compl. ¶68
• Accused Features: The overall ornamental appearance of the Duke HS2 holding bin is alleged to be substantially the same as this second patented design Compl. ¶72

III. The Accused Instrumentality

Product Identification

The accused instrumentalities are the Duke HS2 line of holding bins (including configurations HS2-23, HS2-24, and HS2-34) and the Duke ReadyFlex line of holding bins (including configurations RFHU-23, RFHU-24, and RFHU-34) Compl. ¶50 Compl. ¶51

Functionality and Market Context

The complaint alleges that Defendant Duke, a competitor to Plaintiff Marmon, supplies food holding equipment to the same major customer, Burger King Compl. ¶37 Compl. ¶38 Plaintiff alleges that after it introduced its innovative "Extended Holding Bin" (EHB) product in 2015 and gained market share, Duke launched the accused HS2 line in 2016 as a "copy cat" Compl. ¶¶40-45 The complaint provides a photograph of an exemplary Duke HS2 holding bin, which shows a multi-level cabinet with multiple bays for holding food pans Compl. ¶44 The core accused functionality is the inclusion of "independently controllable temperature zones to enhance holding times and product quality" in both the HS2 and the more recent ReadyFlex products Compl. ¶46 Compl. ¶49 The complaint includes a photograph of the ReadyFlex, showing a similar multi-bay configuration Compl. ¶48

IV. Analysis of Infringement Allegations

The complaint alleges infringement of each asserted patent by referencing claim chart exhibits (Exhibits J-W), which were not provided with the complaint for this analysis Compl. ¶¶50-63 Therefore, the specific mapping of claim elements to accused functionality cannot be presented in a chart format.

The general infringement theory, as inferred from the complaint's allegations, is that the accused Duke HS2 and ReadyFlex products incorporate the core technology of Marmon's patents: a food holding bin with multiple, independently controllable temperature zones within a single compartment or across a continuous surface. The complaint alleges that, like Marmon's products, the Duke HS2 and ReadyFlex products include "independently controllable temperature zones" Compl. ¶46 Compl. ¶49 This feature is central to the independent claims of the asserted utility patents. For the design patents, the complaint alleges that a comparison of the accused Duke HS2 product to the patent figures would lead an ordinary observer to perceive the designs as substantially the same Compl. ¶71 Compl. ¶72 The complaint provides a drawing from Duke's product literature to support this comparison Compl. ¶70

Identified Points of Contention

• Scope Questions: A primary issue will be whether the specific architecture of the accused products' heating and control systems falls within the scope of the patent claims. For example, for the ’750 Patent, a question is whether the accused products utilize both "radiant" and "conductive" heating elements as required by Claim 1.
• Technical Questions: A key evidentiary question for the court will be how the accused products technically achieve multi-zone temperature control. The analysis will likely focus on whether the heating elements and controllers in the Duke products operate in a manner that is functionally and structurally equivalent to the specific configurations defined in the asserted claims. The complaint’s allegation that Duke's product is a "copy cat" suggests Plaintiff will argue for a high degree of similarity in technical operation Compl. ¶45

V. Key Claim Terms for Construction

The Term: "independently controllable"

Context and Importance

This term is the technological linchpin of the dispute, appearing in the asserted claims of multiple patents (e.g., ’750 Patent, cl. 1; ’322 Patent, cl. 1). The definition of the degree of electrical and thermal independence required to meet this limitation will be critical to determining infringement. Practitioners may focus on this term because it defines the core novelty alleged by the plaintiff.

Intrinsic Evidence for Interpretation

• Evidence for a Broader Interpretation: The specification suggests the purpose is to allow an operator to hold different foods at different temperatures, which could support an interpretation covering any system with separate temperature setpoints for different zones ’641 Patent, col. 2:9-16
• Evidence for a Narrower Interpretation: The specification also describes specific embodiments with distinct heating elements for each zone, coupled to a microprocessor, which could support a narrower construction requiring a particular hardware architecture for achieving independent control ’641 Patent, col. 6:1-15

The Term: "continuous and planar surface"

Context and Importance

This term appears in claims of several asserted patents (e.g., ’750 Patent, cl. 1; ’322 Patent, cl. 1). It is described as facilitating easier cleaning by being "substantially free of any dividing walls or other structure" ’641 Patent, col. 3:22-25 The dispute may focus on whether any seams, dividers, or support structures in the accused products' holding compartments prevent the surface from being "continuous" as claimed.

Intrinsic Evidence for Interpretation

• Evidence for a Broader Interpretation: The term "substantially" suggests that minor interruptions might not defeat the claim, as long as the overall planarity and continuity for cleaning are maintained.
• Evidence for a Narrower Interpretation: The explicit functional purpose of easy cleaning could be used to argue that any feature impeding a simple wipe-down, such as a raised seam or significant gap between zones, would mean the surface is not "continuous" in the patented sense ’641 Patent, col. 3:24-25

VI. Other Allegations

Indirect Infringement

Plaintiff alleges both induced and contributory infringement for each of the asserted utility patents. The inducement allegations are based on Defendant's alleged "promoting, advertising, instructing, facilitating, and supporting others" through materials such as the "Duke Dual Heatsink Holding Units Operator's Manual" Compl. ¶77 The contributory infringement allegations assert that the accused products are a material part of the infringement and are not staple articles of commerce suitable for substantial noninfringing use Compl. ¶79

Willful Infringement

Plaintiff alleges that Defendant had knowledge of the asserted patents and the alleged infringement "at least from October 7, 2025, the date of service of the original Complaint" Compl. ¶80 The complaint further alleges that Defendant specifically intended to induce infringement and knew its acts constituted infringement from at least that date, forming a basis for post-suit willful infringement Compl. ¶82

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

• A central issue will be one of technical specificity: does the accused products' method of heating—particularly in relation to the '750 and '002 patents—employ the specific combination of "radiant" and "conductive" heating elements as recited in the claims, or is there a fundamental mismatch in the type and arrangement of the heating technology?
• The case will also turn on a question of definitional scope: how will the court construe the term "independently controllable"? The outcome will depend on whether the term requires a specific hardware and software architecture for achieving thermal separation, or if it can be read more broadly to cover any system that allows an operator to set different temperatures for adjacent zones.
• For the design patents, a key question for the fact-finder will be one of visual perception: would an ordinary observer in the commercial foodservice equipment market be deceived into purchasing a Duke HS2 product, believing it to be the Marmon product depicted in the D'455 and D'814 patents, based on the overall ornamental appearance?