Valtrus Innovations Ltd v. Stack Infrastructure Inc

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Valtrus Innovations, Ltd. and Key Patent Innovations, Ltd. (Ireland)
  • Defendant: STACK Infrastructure, Inc. (Delaware)
  • Plaintiff's Counsel: Reichman Jorgensen Lehman & Feldberg LLP
• Case Identification: 2:26-cv-00287, E.D. Tex., 06/18/2026
• Venue Allegations: Venue is alleged to be proper in the Eastern District of Texas because Defendant STACK Infrastructure operates three data centers at its DFW01 campus in Plano, Texas, which constitutes a regular and established place of business where the alleged acts of infringement occurred.
• Core Dispute: Plaintiff alleges that Defendant's methods of cooling its data centers infringe two expired patents related to efficient and responsive cooling systems for electronic equipment.
• Technical Context: The technology concerns advanced cooling and energy management systems for data centers, a critical infrastructure component where thermal management is a significant operational cost and crucial for equipment reliability.
• Key Procedural History: The asserted patents were originally developed by inventors at Hewlett Packard Enterprise (HPE). Plaintiff Valtrus alleges it sent a letter to STACK on January 13, 2025, notifying it of the patent portfolio, offering a license, and providing exemplary claim charts, but the parties were unable to reach a resolution. The asserted patents have expired, limiting remedies to past damages.

Case Timeline

Date	Event
2001-10-05	Earliest Priority Date for '287 and '682 Patents
2005-02-15	'287 Patent Issued
2005-03-22	'682 Patent Issued
2025-01-13	Plaintiff sent pre-suit notification letter to Defendant
2026-06-18	Complaint Filing Date

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

U.S. Patent No. 6,854,287 - "Cooling System"

• Patent Identification: U.S. Patent No. 6,854,287, "Cooling System," issued February 15, 2005.

The Invention Explained

• Problem Addressed: The patent describes conventional data center air conditioning as inefficient because it typically operates at or near maximum capacity based on a "worst-case scenario," regardless of the actual, distributed heat load from computer racks, resulting in excessive energy consumption and operating costs ʼ287 Patent, col. 2:10-29
• The Patented Solution: The invention proposes a more granular cooling system using multiple heat exchanger units (HEUs) placed near the computer racks ʼ287 Patent, Fig. 1 The system senses temperatures at various locations in the room and, in response, controls the temperature of a cooling fluid and/or the rate of cooled air delivery to specific areas ʼ287 Patent, abstract A key aspect is the ability to "individually manipulat[e]" the mass flow rate of cooling fluid to each HEU, allowing for targeted cooling where it is most needed ʼ287 Patent, col. 14:34-41
• Technical Importance: This approach represented a shift from brute-force, room-level cooling to a more intelligent, zonal methodology, offering the potential for significant energy savings in large-scale data center operations.

Key Claims at a Glance

• The complaint asserts independent claim 1 Compl. ¶25
• The essential elements of independent claim 1, a method claim, include:
  • Providing a plurality of heat exchanger units.
  • Supplying the units with cooling fluid from an air conditioning unit.
  • Cooling air via heat exchange in the units.
  • Sensing temperatures at one or more locations in the room.
  • Controlling the cooling fluid temperature and/or air delivery in response to the sensed temperatures.
  • Wherein controlling air delivery comprises "individually manipulating a mass flow rate of the cooling fluid supplied to each of the plurality of heat exchanger units."
• The complaint refers to exhibits containing exemplary claim charts, but reserves the right to assert other claims Compl. ¶25

U.S. Patent No. 6,868,682 - "Agent Based Control Method and System for Energy Management"

• Patent Identification: U.S. Patent No. 6,868,682, "Agent Based Control Method and System for Energy Management," issued March 22, 2005.

The Invention Explained

• Problem Addressed: The patent addresses the same general problem as the '287 Patent: conventional data center cooling is inefficient because it is not responsive to distributed, location-specific needs and relies on centralized control that measures temperature at the main cooling unit, not where the heat is actually being produced ʼ682 Patent, col. 2:10-29
• The Patented Solution: The invention discloses a control system using a "hierarchy of agents"-distributed software entities that manage cooling at different levels ʼ682 Patent, abstract A "first agent" (e.g., a "rack agent") monitors a local area and attempts to resolve thermal issues autonomously. If it cannot, it "request[s]" assistance from a "second agent" (e.g., a "row agent") higher in the hierarchy, which can coordinate resources over a wider area ʼ682 Patent, abstract '682 Patent, Fig. 4 A third, higher-level agent (e.g., a "CRAC agent") can adjust the overall cooling output for the entire facility.
• Technical Importance: This agent-based architecture provides a scalable and intelligent framework for managing complex, dynamic thermal environments, enabling more precise energy use than centralized control systems.

Key Claims at a Glance

• The complaint asserts independent claim 1 Compl. ¶28
• The essential elements of independent claim 1, a method claim, include:
  • Receiving sensory data (temperature) from a subsystem.
  • Processing the data with a "first agent in a hierarchy of agents" to determine if the temperature is within a predetermined range.
  • Adjusting a cooling fluid delivery rate using the first agent to maintain the temperature.
  • "Requesting a second agent from the hierarchy of agents to process the sensory data when the first agent cannot keep the temperature range within the predetermined temperature range" unless the second agent redistributes the cooling fluid.
• The complaint refers to exhibits containing exemplary claim charts, but reserves the right to assert other claims Compl. ¶28

III. The Accused Instrumentality

Product Identification

• The accused instrumentalities are the methods of cooling performed in Defendant STACK's data centers, which utilize cooling equipment from various suppliers Compl. ¶15

Functionality and Market Context

• The complaint alleges that STACK operates numerous data centers across the United States and uses cooling equipment from suppliers including Stulz and Trane to perform the infringing methods Compl. ¶¶15-17 The complaint provides visual evidence to support these allegations. One image, taken from an online virtual tour, depicts a Stulz-branded cooling unit inside a STACK data center Compl. p. 4 Another visual is a table, reportedly from a STACK government submission, that details specifications for 78 Trane chiller units using R-134a refrigerant, including charge amounts and leak rates Compl. p. 5 The complaint suggests that the operation and control of these and other cooling systems constitute the infringing activity Compl. ¶25 Compl. ¶28 STACK is positioned as a significant market participant, advertising 23 data center campuses in the Americas Compl. ¶15

IV. Analysis of Infringement Allegations

The complaint alleges infringement of at least claim 1 of the '287 and '682 patents and references non-provided exhibits (Exhibits 3-10) that purportedly contain detailed infringement claim charts Compl. ¶25 Compl. ¶28 As these exhibits were not included with the complaint, a detailed element-by-element analysis is not possible. The narrative infringement theories are summarized below.

• '287 Patent Infringement Allegations: The complaint alleges that STACK directly infringes the '287 Patent by "performing methods of cooling its data centers" Compl. ¶25 The theory of infringement is that STACK's use of cooling equipment from suppliers like Stulz and Trane constitutes performance of the claimed method Compl. ¶25 The complaint points to specific equipment allegedly used by STACK as the means by which the infringing method is carried out, suggesting their operation involves sensing local temperatures and responsively controlling cooling fluid delivery to targeted areas Compl. ¶¶16-17 Compl. ¶24

• '682 Patent Infringement Allegations: The complaint alleges that STACK infringes the '682 Patent by "performing methods of cooling its data centers" that use a system for controlling temperature based on sensory data Compl. ¶27 Compl. ¶28 The infringement theory posits that the software and control systems used to manage STACK's cooling equipment from Stulz, Trane, and others implement the patented "agent based control method" Compl. ¶28 This suggests that STACK's control architecture functions as a "hierarchy of agents" that make distributed decisions to manage thermal loads, mirroring the structure claimed in the patent Compl. ¶27 The complaint notes that its pre-suit notice letter included claim charts demonstrating this infringement Compl. ¶20

• Identified Points of Contention:

  • Evidentiary Questions: A primary point of contention will be evidentiary. For both patents, the plaintiff must prove that the accused cooling methods, as actually performed by STACK, meet every limitation of the asserted claims. This will require discovery into the precise operational logic and functionality of STACK's control software and hardware.
  • Technical Questions ('287 Patent): A key technical question will be whether STACK's systems "individually manipulat[e] a mass flow rate of the cooling fluid supplied to each... heat exchanger unit" in response to localized sensor data. The case may turn on the granularity of STACK's control-whether it is truly individual to each unit as the claim requires, or if it operates on a larger, more aggregated zone.
  • Scope and Definitional Questions ('682 Patent): The infringement analysis for the '682 Patent raises a significant definitional question: does STACK's control system, regardless of its function, possess the specific structure of a "hierarchy of agents" where a "first agent" makes a "request" to a "second agent"? The dispute will likely involve claim construction of these terms and a technical comparison to determine if STACK's software architecture maps onto the claimed hierarchical structure.

V. Key Claim Terms for Construction

• The Term: "individually manipulating a mass flow rate" (from claim 1 of the '287 Patent)
• Context and Importance: This term is central to the claimed invention's granularity and efficiency. The infringement analysis will depend on whether STACK's system is capable of controlling the flow of cooling fluid to each heat exchanger unit independently, as opposed to controlling groups of units or the entire system globally. Practitioners may focus on this term because it defines the required level of discrete control.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The specification discusses controlling cooling based on the needs of racks, which could suggest that "individually" might apply to a rack-level unit, not necessarily every single component within a larger system ʼ287 Patent, col. 4:39-46
  • Evidence for a Narrower Interpretation: The claim language "to each of the plurality of heat exchanger units" suggests a one-to-one control relationship. Embodiments show configurations with distinct valves and pumps for different HEUs or HEU banks, supporting a narrow interpretation of discrete, independent control ʼ287 Patent, col. 5:16-24 ʼ287 Patent, Fig. 3
• The Term: "first agent in a hierarchy of agents" (from claim 1 of the '682 Patent)
• Context and Importance: This term, along with the related "requesting a second agent," defines the specific, distributed software architecture of the invention. The case will likely turn on whether STACK's control system can be characterized as having this structure. This is a critical structural limitation, and its construction will likely determine infringement.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The specification describes agents in somewhat abstract terms as software entities that can "summon assistance from other peer components or higher order components," which could be argued to encompass a variety of modular software interactions ʼ682 Patent, col. 4:18-21
  • Evidence for a Narrower Interpretation: The patent explicitly illustrates a three-tiered structure of "Rack Agents," "Row Agents," and "CRAC Agents" (ʼ682 Patent, Fig. 4). The detailed description explains how control and information flow up and down this specific hierarchy, which may support an argument that the term requires such a multi-level, structured organization ʼ682 Patent, col. 13:17-48

VI. Other Allegations

• Willful Infringement: The complaint does not contain an explicit count for willful infringement. However, it lays the factual groundwork for such a claim by alleging pre-suit knowledge. The complaint states that Valtrus sent a letter to STACK's Chief Legal Officer on January 13, 2025, identifying the patent portfolio, offering a license, and providing claim charts demonstrating infringement of patents including the '682 Patent Compl. ¶20 This alleged notification could be used to argue that any infringement after this date was willful.

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

This dispute appears to center on highly technical questions of how Defendant's data center cooling systems operate and how that operation maps to the language of two expired patents. The key questions for the court will likely be:

• A core issue will be one of definitional scope: For the '682 patent, can the terms "hierarchy of agents" and "requesting a second agent," which describe a specific software architecture, be construed to read on the control systems used by STACK? The case may turn on whether there is a fundamental structural match or a legally significant mismatch between the patent's claims and the accused system's design.

• A second issue will be one of functional proof: For the '287 patent, does the evidence show that STACK's systems perform the specific function required by the claims-namely, "individually manipulating" the cooling fluid flow to each cooling unit in direct response to localized temperature sensing? This presents a significant evidentiary hurdle for the plaintiff.

• Finally, as the patents have expired and only past damages are at stake, a central focus will be on quantifying infringement. Assuming infringement and validity are found, the litigation will concentrate on establishing the historical scope of use of the accused methods and calculating a reasonable royalty for that past use.