DCT

7:26-cv-00246

D&D Designtech Ltd v. Suzhou Tubeplus Stainless Steel Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 7:26-cv-00246, W.D. Tex., 06/29/2026
  • Venue Allegations: Venue is alleged to be proper because the Defendants are not residents of the United States and may therefore be sued in any judicial district. The complaint also notes that the Plaintiff resides in the district and the harm occurred there.
  • Core Dispute: Plaintiff alleges that Defendant's anti-siphon back pressure check valve, used in oilfield chemical injection, infringes a patent related to chemical injection optimization and control valve technology.
  • Technical Context: The technology involves specialized valves used in the oil and gas industry to ensure consistent injection of chemicals into process streams or wells, while preventing siphoning and backflow.
  • Key Procedural History: The complaint alleges that Plaintiff marks its own products with the patent number, providing notice to competitors. It also notes that a related continuation application is currently under examination at the U.S. Patent and Trademark Office.

Case Timeline

Date Event
2023-11-20 '816 Patent Priority Date
2025-08-06 Related Continuation Application Filed
2025-08-26 '816 Patent Issued
2026-06-29 Complaint Filed

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

U.S. Patent No. 12,398,816 - "Chemical Injection Optimization And Control Valve Device For Dispensing And Optimizing Chemical Injection Processes"

  • Patent Identification: U.S. Patent No. 12,398,816, "Chemical Injection Optimization And Control Valve Device For Dispensing And Optimizing Chemical Injection Processes," issued August 26, 2025 Compl. ¶¶12-13

The Invention Explained

  • Problem Addressed: The patent's background section describes how variations in pressure within oil and gas wells can lead to "inconsistent chemical injection rates and undesirable and unintentional siphoning of injection chemicals" '816 Patent, col. 1:31-34 This can result in wasted chemicals and damage to equipment if corrosive fluids flow backward into the chemical pump '816 Patent, col. 1:56-62
  • The Patented Solution: The invention is a compact, multifunctional valve that combines anti-siphon, back-pressure, and check-valve functions into a single device '816 Patent, col. 2:28-31 It uses an adjustable, spring-loaded conical piston that sits against a seating surface to block flow '816 Patent, Fig. 1 When the chemical injection pressure is high enough to overcome the spring force, the piston lifts, allowing the chemical to flow through '816 Patent, abstract This mechanism is designed to maintain consistent pump output and prevent both backflow and siphoning regardless of downstream pressure fluctuations '816 Patent, col. 2:16-24
  • Technical Importance: The invention aims to provide a single, reliable device that solves multiple problems associated with chemical injection, thereby eliminating the need for several separate components on an injection line '816 Patent, col. 2:28-34

Key Claims at a Glance

  • The complaint asserts infringement of at least independent Claim 1 Compl. ¶29
  • The essential elements of independent Claim 1 include:
    • A first tubular housing with a traveling conical piston.
    • A resilient member holding the piston "under tension."
    • A pressure adjustment member at the opposite end of the housing.
    • An external protrusion on the housing for engagement with a fastening tool.
    • A pressure adjustment stop member and a corresponding projection on the adjustment member to limit its travel.
    • A seat body housing with an inlet port, a discharge port, and a seating surface that receives the piston.
    • An inlet port check valve assembly.
    • A series of single, distinct fluid channels (inlet, discharge, vertical) connecting the ports.
    • A final configuration where the piston, in a rest position, contacts the seating surface to prevent fluid communication between the inlet and discharge channels.
  • The complaint's use of "at least claim 1" suggests the possibility that other claims, including dependent claims, may be asserted later in the litigation Compl. ¶29

III. The Accused Instrumentality

Product Identification

  • The "Tubeplus Anti-Siphon/Check Valve" ("Accused Product") Compl. ¶19

Functionality and Market Context

  • The complaint alleges the Accused Product is a "chemical injection and control valve configured to optimize chemical injection processes by retaining desired inlet fluid pressure" Compl. ¶31 It is described as being "virtually identical" in dimension, design, and construction to Plaintiff's own ASV-1100 valve Compl. ¶¶20-21 A side-by-side photograph of the disassembled components of the patented valve and the accused "copy" is provided to illustrate their alleged similarity Compl. p. 6
  • The complaint asserts that the Accused Product is manufactured in China and marketed in the United States, specifically in the Permian Basin, as a "cheaper substitute" for Plaintiff's patented valve Compl. p. 1 Further photographic evidence alleges that the Defendants copied not only the valve's design but also Plaintiff's product labels, including model numbers, performance ratings, and even a U.S.-based address and phone number Compl. p. 7

IV. Analysis of Infringement Allegations

'816 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
a first tubular housing in which a conical piston travels... The Accused Product features a tubular housing containing a conical piston. ¶32; ¶37 col. 3:22-24
a resilient member holding said piston under tension... The Accused Product features a resilient member. ¶32 col. 3:26-28
a pressure adjustment member disposed at the opposite end of said tubular housing from said piston... The Accused Product includes a pressure adjustment member intended to be received at the opposite end of the tubular housing. ¶35; ¶36 col. 3:28-31
a seat body housing, comprising a seating surface... wherein said seating surface receives said piston... further comprising an inlet port and a discharge port... The Accused Product comprises a seat body housing with a seating surface configured to receive a conical piston, and it includes an inlet port and a discharge port. ¶33; ¶34 col. 3:52-62
an inlet port check valve assembly comprising an inlet fitting, a check ball, and a resilient member... The Accused Product features an inlet port check valve assembly comprising an inlet fitting. ¶32 col. 4:14-19
wherein when the tubular housing... is fastened to the seat body housing, the piston sits immediately above and in physical contact with the conical seating surface... The complaint alleges the Accused Product is a "virtual copy" of the patented design, which operates in this manner. ¶21 col. 4:8-13

Identified Points of Contention

  • Scope Questions: A potential dispute may arise over the claim term "under tension." The claim requires a "resilient member holding said piston under tension" '816 Patent, cl. 1 However, the patent's figures appear to show a Belleville spring, which typically operates under compression (a pushing force), not tension (a pulling force). This raises the question of whether the claim language accurately describes the embodiment shown in the patent and, by extension, the accused device which appears to operate similarly.
  • Technical Questions: The complaint's infringement theory rests heavily on the allegation that the Accused Product is a "knock-off" and "virtually identical" copy Compl. p. 1 Compl. ¶20 The central technical question will be whether discovery reveals any material differences in the components, their assembly, or their method of operation that could support a non-infringement argument, despite the external similarities. For example, a defendant might argue that its internal fluid channels are not "single" channels as required by the claim.

V. Key Claim Terms for Construction

The Term

  • "resilient member holding said piston under tension"

Context and Importance

  • The construction of this term may be critical. If "under tension" is given its strict technical meaning of a pulling force, it could create a significant non-infringement defense, as the springs in both the patented embodiment and likely the accused device appear to function via compression. Practitioners may focus on this term because of the apparent inconsistency between the claim language and the patent's own drawings.

Intrinsic Evidence for Interpretation

  • Evidence for a Broader Interpretation: A party could argue that, within the context of the specification, "under tension" is used more broadly to mean "under a pre-loaded force." The patent repeatedly uses the phrase to describe the function of the spring without further definition, suggesting it was intended to describe the illustrated embodiment '816 Patent, col. 3:26-28
  • Evidence for a Narrower Interpretation: A party could argue for the plain and ordinary meaning of "tension" as a pulling force, distinct from compression. They may assert that the claim language is precise and that the depicted embodiment, if it operates via compression, does not fall within the literal scope of the claim as written.

VI. Other Allegations

Indirect Infringement

  • The complaint alleges induced infringement, stating that Defendants "have induced their customers to use the subject matter of at least claim 1" by "directing, encouraging, and inducing third parties to use the Accused Product" in the U.S. Compl. ¶44

Willful Infringement

  • Willfulness is alleged based on Defendants having "actual knowledge" of their infringement Compl. ¶41 The complaint supports this by claiming that Plaintiff's products are marked with the '816 patent number and that Defendants are "copying a patented article" Compl. ¶¶39-40 The allegation is further strengthened by evidence that Defendants allegedly copied product labels, including serial numbers and Plaintiff's business information, suggesting deliberate and egregious copying Compl. ¶¶23-25 Compl. p. 7

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

  • A core issue will be one of direct copying versus patent validity: The complaint presents compelling visual evidence that the accused product is a "virtual copy" of the patented device Compl. ¶21 This may shift the primary focus of the case from technical non-infringement arguments to the ultimate validity of the '816 patent's claims in view of the prior art.
  • A dispositive question may be one of claim construction: The case could turn on the interpretation of the phrase "under tension" in Claim 1. The court's decision on whether this term can encompass a compressive spring force, as depicted in the patent's own figures, or is strictly limited to a pulling force, may resolve the question of literal infringement.
  • A key evidentiary question will concern the extent of willfulness: The complaint's allegations go beyond simple product copying to include the reproduction of product labels, serial numbers, and business addresses Compl. ¶¶23-25 A central factual dispute will be whether Plaintiff can prove these acts occurred and, if so, whether they constitute the type of egregious conduct that would justify a finding of willful infringement and enhanced damages.
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