DCT

4:25-cv-01491

Marmon Foodservice Tech Inc v. Duke Mfg Co

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 4:25-cv-01491, E.D. Mo., 10/03/2025
  • Venue Allegations: Venue is alleged to be proper in the Eastern District of Missouri because Defendant is a Missouri corporation that resides in the district, has committed acts of infringement there, and maintains a regular and established place of business in St. Louis.
  • Core Dispute: Plaintiff alleges that Defendant’s food holding bin products infringe a portfolio of utility and design patents related to multi-zone food warming technology.
  • Technical Context: The technology concerns commercial foodservice equipment used to hold multiple types of pre-cooked food items at different, independently controlled temperatures to maintain quality and extend holding times.
  • Key Procedural History: The complaint alleges a competitive history where Plaintiff's predecessor introduced its Extended Holding Bin (EHB) product in 2015, which gained market share, and Defendant subsequently launched the accused HS2 product line in 2016, which Plaintiff characterizes as a "copy cat."

Case Timeline

Date Event
2015-01-01 Plaintiff's predecessor introduces Extended Holding Bin (EHB) product
2016-01-01 Defendant launches accused HS2 line of holding bins
2016-04-19 Earliest Priority Date for ’322, ’641, ’981 Patents
2016-04-20 Earliest Priority Date for ’750, ’363, ’002, ’264 Patents
2018-05-22 U.S. Patent No. 9,976,750 Issues
2018-05-29 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 introduces 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 Complaint Filing Date

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

U.S. Patent No. 10,492,641 - "Multi-Zone Food Holding Bin," issued Dec. 3, 2019 (’641 Patent)

The Invention Explained

  • Problem Addressed: The patent's background describes the challenge in fast-food restaurants of keeping various pre-cooked food items warm and ready for sale without quality degradation. Known holding bins often have limited holding times (15-20 minutes) before food must be discarded, leading to waste and additional costs (’641 Patent, col. 1:11-40).
  • The Patented Solution: The invention is a food holding cabinet with separate compartments, each containing multiple "food holding zones" on a continuous, planar bottom surface. Each zone can be independently heated to a different temperature, allowing an operator to hold diverse food products with different heating requirements (e.g., french toast and sausage patties) next to each other in the same compartment. The continuous surface is noted as being easy to clean (’641 Patent, col. 2:6-29; col. 3:41-54).
  • Technical Importance: This approach allows for increased energy efficiency, potentially reduced equipment space, and greater flexibility in holding a variety of food items at their ideal temperatures, thereby extending palatable holding times (’641 Patent, col. 2:10-16).

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 (’Compl. ¶¶ 54-55).
  • Essential elements of claim 1 include:
    • A chassis with various panels and a shelf dividing it into at least a first and a second food holding compartment.
    • The shelf defining a first substantially planar surface forming the bottom of the first compartment.
    • A first food holding zone and a second food holding zone formed in the first compartment, each having at least one independently controllable heating element at both a top and a bottom portion.
    • A third and fourth food holding zone formed in the second compartment, each with independently controllable heating elements.
    • A user interface and a controller configured to independently operate each heating element to maintain distinct temperatures in each zone.
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 10,512,363 - "Multi-Zone Food Holding Bin," issued Dec. 24, 2019 (’363 Patent)

The Invention Explained

  • Problem Addressed: Similar to the ’641 Patent, this patent addresses the need to hold various pre-cooked foods at optimal temperatures to maintain quality and reduce waste in a commercial kitchen environment (’363 Patent, col. 1:11-40).
  • The Patented Solution: This invention also describes a multi-zone food holding bin, but its claims are structured around the concept of "food holding bays" within each "food holding zone." Each bay is specifically "configured to receive a food holding tray," providing a more granular organization within the temperature-controlled zones. The solution allows, for example, a first zone to hold sausage in one bay and eggs in another, both at the same temperature, while an adjacent zone holds a different product at a different temperature (’363 Patent, col. 2:1-30).
  • Technical Importance: The system provides a modular structure of "bays" that corresponds to standard food trays, integrating the benefits of multi-zone temperature control with the physical workflow of a commercial kitchen (’363 Patent, col. 2:6-9).

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 (’Compl. ¶¶ 56-57).
  • Essential elements of claim 1 include:
    • A chassis with a shelf dividing it into a first and second food holding compartment.
    • A first food holding zone in the first compartment that includes a first food holding bay and a second food holding bay, where each bay is configured to receive a food holding tray.
    • A second food holding zone in the first compartment that includes a third and fourth food holding bay.
    • A similar structure of third and fourth food holding zones with associated bays in the second compartment.
    • A user interface and a controller to independently operate the heating elements for each zone.
  • The complaint does not explicitly reserve the right to assert dependent claims.

Multi-Patent Capsule: U.S. Patent No. 9,976,750 (’750 Patent)

  • Technology Synopsis: This patent, from the same family, describes a multi-zone food holding bin where different zones can be held at different temperatures. It discloses using a combination of conductive heating from below a food tray and radiant heating from above (’750 Patent, Abstract; col. 8:1-13).
  • Asserted Claims: At least independent claim 1 is asserted (Compl. ¶¶ 50-51).
  • Accused Features: The accused products' multi-zone temperature control functionality is alleged to infringe (Compl. ¶¶ 46, 49, 50-51).

Multi-Patent Capsule: U.S. Patent No. 9,980,322 (’322 Patent)

  • Technology Synopsis: This patent claims a multi-zone food holding bin with a shelf that includes both upper and lower heating elements. These elements provide heat to separate, vertically adjacent food holding compartments, enabling independent temperature control for each compartment (’322 Patent, col. 6:36-68).
  • Asserted Claims: At least independent claim 1 is asserted (Compl. ¶¶ 52-53).
  • Accused Features: The accused products' use of independently controllable temperature zones is alleged to infringe (Compl. ¶¶ 46, 49, 52-53).

Multi-Patent Capsule: U.S. Patent No. 10,841,981 (’981 Patent)

  • Technology Synopsis: This patent focuses on a food holding bin with a continuous and planar bottom surface that extends to the front opening. It claims a combination of a first food holding zone and an adjacent second food holding zone, each with top and bottom heating elements, which can be set to different temperatures (’981 Patent, Claim 1).
  • Asserted Claims: At least independent claim 27 is asserted (Compl. ¶¶ 58-59).
  • Accused Features: The accused products' overall structure and multi-zone temperature control capabilities are alleged to infringe (Compl. ¶¶ 46, 49, 58-59).

Multi-Patent Capsule: U.S. Patent No. 10,852,002 (’002 Patent)

  • Technology Synopsis: This patent describes a multi-zone food holding bin where food holding zones are further divided into discrete "food holding bays" configured to receive trays. The claims require a combination of radiant heating from above and conductive heating from below for each zone (’002 Patent, Claim 14).
  • Asserted Claims: At least independent claim 14 is asserted (Compl. ¶¶ 60-61).
  • Accused Features: The accused products' configuration of bays within temperature-controlled zones is alleged to infringe (Compl. ¶¶ 44, 46, 49, 60-61).

Multi-Patent Capsule: U.S. Patent No. 11,771,264 (’264 Patent)

  • Technology Synopsis: This patent claims a method of operating a multi-zone food holding bin. The method involves independently operating heating elements to maintain different temperatures in adjacent food holding zones, which are themselves subdivided into food holding bays (’264 Patent, Claim 1).
  • Asserted Claims: At least independent claim 1 is asserted (Compl. ¶¶ 62-63).
  • Accused Features: The use of the accused products to hold different foods at different temperatures is alleged to infringe (Compl. ¶¶ 46, 49, 62-63).

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities are Defendant’s Duke HS2 line of holding bins (including configurations HS2-23, HS2-24, and HS2-34) and Duke ReadyFlex line of holding bins (including configurations RFHU-23, RFHU-24, and RFHU-34) (Compl. ¶¶ 43, 47, 50-51).

Functionality and Market Context

  • The complaint alleges that both the Duke HS2 and ReadyFlex products feature "independently controllable temperature zones to enhance holding times and product quality" (Compl. ¶¶ 46, 49). A photograph of an exemplary Duke HS2 holding bin shows a two-row configuration with multiple bays for holding food containers (Compl. ¶44). The complaint alleges that Defendant supplies this equipment to Burger King, a customer also supplied by Plaintiff, and introduced the HS2 product line after Plaintiff's EHB product "gained market share" (Compl. ¶¶ 38, 45). The complaint includes a photograph showing the Duke HS2-24 configuration, which represents two rows each having four bays in two zones (Compl. ¶44).

IV. Analysis of Infringement Allegations

The complaint alleges infringement by reference to claim charts attached as exhibits, which were not filed with the complaint itself (Compl. ¶¶ 50-63). The following analysis is constructed based on the narrative allegations and visual evidence within the complaint.

’641 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a chassis having a top panel, a first side panel, a second side panel, a bottom panel... The accused HS2 and ReadyFlex products are food holding bins with a cabinet-like chassis. ¶¶44, 48 col. 2:36-44
a first food holding compartment within the chassis... a second food holding compartment disposed below the first food holding compartment... a shelf... located between the first and second food holding compartments The accused products are shown in multi-row (i.e., multi-compartment) configurations. ¶¶44, 48 col. 2:50-65
a first food holding zone formed in the first food holding compartment... a second food holding zone formed in the first food holding compartment... The accused products are alleged to include "independently controllable temperature zones." ¶¶46, 49 col. 2:6-16
each food holding zone having at least one independently controllable heating element... The accused products' ability to have controllable temperature zones implies the presence of controllable heating elements. ¶¶46, 49 col. 6:36-44
a controller operatively coupled to the user interface and each heating element, the controller configured to independently operate each heating element... The accused products are alleged to feature "independently controllable temperature zones," which requires a controller. ¶¶46, 49 col. 6:16-29

’363 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a chassis having a top panel, a first side panel... a shelf... The accused products are depicted as cabinet-style holding bins with shelves forming multiple rows. ¶¶44, 48 col. 3:1-10
a first food holding zone...including a first food holding bay and a second food holding bay, each of the first and second food holding bays being configured to receive a food holding tray The accused products are depicted with multiple "bays" per row for holding food containers. The HS2-24 has "four bays in two zones" per row. ¶¶44, 48 col. 2:1-9
a second food holding zone...including a third food holding bay and a fourth food holding bay... The accused products are alleged to have multiple "zones" and are depicted with multiple "bays." ¶¶44, 46, 49 col. 2:1-9
a controller operatively coupled to the user interface and each heating element... The accused products are alleged to include "independently controllable temperature zones." ¶¶46, 49 col. 4:50-55
  • Identified Points of Contention:
    • Evidentiary Questions: The complaint alleges the function of "independently controllable temperature zones" but provides no detail on the technical implementation. A central factual dispute may be whether the accused products’ heating systems meet the specific structural requirements of the claims, such as the ’641 Patent's requirement for independently controllable heating elements at both the "top portion" and "bottom portion" of a food holding compartment.
    • Scope Questions: The case may raise questions about the definition of claim terms. For instance, what constitutes a "food holding zone" versus a "food holding bay," and do the sections of the accused products meet the patent's definitions for these structures? Further, does the physical arrangement of heating elements in the accused products satisfy the specific locations recited in the claims?

V. Key Claim Terms for Construction

  • The Term: "food holding zone"

  • Context and Importance: The definition of this term is fundamental to the infringement analysis for all asserted utility patents. The dispute may turn on whether a "zone" is defined functionally (a region capable of being held at a distinct temperature) or requires a specific physical structure and boundary that the accused products may or may not possess.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The specification states that the boundaries of food holding zones "need not have their boundaries identified with any sort of line or other indicia" and that each zone "can be configured to maintain a different food holding temperature" (’641 Patent, col. 2:6-11). This language may support a functional definition based on temperature control capability.
    • Evidence for a Narrower Interpretation: The claims consistently recite zones as being "formed in" a food holding compartment and adjacent to one another "across" a planar surface. Embodiments depict distinct heating elements corresponding to each zone, which a party might argue requires some degree of structural, not just functional, delineation (’641 Patent, Fig. 1; col. 6:36-54).

  • The Term: "independently controllable heating element"

  • Context and Importance: This term is critical for determining whether the control system in the accused products infringes. Practitioners may focus on whether "independently controllable" refers to any system that can create distinct temperature zones or if it requires a specific hardware architecture (e.g., discrete, separately wired heating circuits for each zone).

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The specification describes control being "effectuated in part by using one or more microcontrollers or microprocessors" that can be programmed with software, which could suggest that the "independent control" is achieved through software logic regardless of the underlying hardware arrangement (’641 Patent, col. 6:16-29).
    • Evidence for a Narrower Interpretation: The patent figures and description detail distinct upper and lower heating elements (65, 67) for different zones. A party could argue that "independently controllable" requires physically separate heating elements for each claimed function (e.g., one for the top of zone A, one for the bottom of zone A), as opposed to a single, larger heating element controlled by software to create temperature gradients (’641 Patent, Fig. 4B; col. 7:1-9).

VI. Other Allegations

  • Indirect Infringement: The complaint alleges active inducement of infringement based on Defendant "promoting, advertising, instructing, facilitating, and supporting" the use of the accused products (Compl. ¶75, 86). It also alleges contributory infringement, stating the products are a material part of the invention, are especially adapted for infringing use, and are not staple articles of commerce (Compl. ¶¶ 76-77, 87-88).
  • Willful Infringement: For each asserted patent, the complaint alleges on "information and belief" that Defendant was aware of the patent and aware that its products infringed, and that this infringement was and continues to be "willful, deliberate and intentional" (Compl. ¶¶ 78-82, 89-93). The complaint does not specify whether this alleged knowledge was pre-suit or post-suit.

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

  • A central evidentiary question will be one of technical implementation: Does the specific architecture of the heating elements and control systems within the Duke HS2 and ReadyFlex products meet the structural and functional limitations of the asserted claims, particularly the requirements for heating elements at distinct "top" and "bottom" portions and the configuration of "zones" versus "bays"? The complaint's lack of technical detail on the accused products' internal workings makes this a primary factual hurdle.
  • A key legal question will be one of definitional scope: How will the court construe the term "food holding zone"? The outcome may depend on whether the term is interpreted functionally—as any region that can be held at an independent temperature—or requires a more defined physical structure that the accused products may not possess.
  • For the design patents, a core issue will be the application of the ordinary observer test: As presented through a comparison of patent drawings and product photographs, would an ordinary observer be deceived into purchasing Defendant's product believing it was Plaintiff's? (Compl. ¶¶ 71-72). This analysis will focus on the overall ornamental appearance of the bins, not their functional aspects.