Zhengzhou Letai v. TowerStar Pets: Pet Feeder Patent Dismissed With Prejudice in 56 Days
Zhengzhou Letai Trading Co. filed suit against TowerStar Pets LLC in Washington’s Western District over US8516975B2, a patent covering pet feeding product designs. The parties reached a stipulated dismissal with prejudice in just 56 days — a resolution pace that typically signals a negotiated settlement or licensing arrangement reached without formal adjudication.
A fast-tracked pet feeder patent dispute ends by mutual agreement
On June 25, 2025, Zhengzhou Letai Trading Co. Ltd., a China-based trading company, filed an infringement action against TowerStar Pets LLC in the U.S. District Court for the Western District of Washington before Judge Kymberly K. Evanson. The complaint centred on US8516975B2, a patent covering pet feeding products, with TowerStar’s product listed under ASIN B0DPFWZ3Z9 identified as the accused product. Plaintiff was represented by Glacier Law LLP and the Law Office of Carl J. Marquardt PLLC.
The case closed on August 20, 2025 — just 56 days after filing — via a stipulated dismissal with prejudice under Federal Rule of Civil Procedure 41(a)(1)(A)(ii). Both parties jointly agreed to terminate all claims, with each side bearing its own attorneys’ fees, costs, and expenses. Dismissal with prejudice is a final disposition: Zhengzhou Letai cannot re-file the same infringement claims against TowerStar based on the same patent and accused product.
The 56-day resolution timeline is notably compressed for patent litigation, which typically spans multiple years. This pace, combined with the mutual fee-bearing arrangement, is consistent with a confidential settlement or licensing agreement reached shortly after filing. The public record does not disclose any financial terms, royalty arrangements, or whether TowerStar obtained a licence to US8516975B2. What drove the rapid resolution — whether a pre-existing commercial relationship, an early licensing offer, or immediate commercial pressure on TowerStar — remains undisclosed.
Filing to Dismissed with Prejudice in 56 days
56 days — well below the median district court patent case duration of 2+ years
Dismissed with prejudice: what the stipulated termination means for both parties
Rule 41(a)(1)(A)(ii): stipulated dismissal with prejudice explained
Under FRCP 41(a)(1)(A)(ii), parties may jointly stipulate to dismiss an action. Adding ‘with prejudice’ makes the dismissal a final judgment on the merits — Zhengzhou Letai is permanently barred from re-asserting the same claims against TowerStar based on US8516975B2 and the same accused product. No judicial ruling on validity or infringement was issued.
Permanent bar on re-filingLetai closes the case permanently — on undisclosed terms
By agreeing to dismissal with prejudice, Zhengzhou Letai surrenders the right to pursue these specific claims against TowerStar again. This is typically accepted only when the plaintiff has obtained satisfactory resolution — such as a licensing fee, product withdrawal, or commercial agreement — making continued litigation unnecessary. The public record does not confirm what, if anything, was received.
Terms undisclosedTowerStar avoids judgment but faces a permanent record
TowerStar Pets LLC avoids any court finding of infringement or validity determination. However, the with-prejudice dismissal does not invalidate US8516975B2 — the patent remains enforceable against other parties. TowerStar may have obtained a licence, modified its product, or reached another commercial arrangement. No defendant agents were listed, suggesting limited formal legal opposition was mounted.
No validity ruling issuedUS8516975B2 remains a live enforcement risk for the pet products sector
The dismissal with prejudice resolves this dispute but leaves the patent fully intact and enforceable. Other sellers of pet feeding products — particularly e-commerce operators listing similar ASINs on Amazon — remain potential targets. The speed of resolution suggests Letai’s enforcement strategy may be focused on rapid, commercially driven settlements rather than protracted litigation seeking invalidation.
Patent still enforceableFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Zhengzhou Letai Trading Co Ltd | Company | China-based trading company — holder of US8516975B2 (pet feeding products)Search in Eureka ↗ |
| Defendant | TowerStar Pets LLC | Company | TowerStar Pets LLC — U.S. pet products seller, operator of ASIN B0DPFWZ3Z9Search in Eureka ↗ |
| Plaintiff counsel | Carl J. Marquardt | Attorney | Counsel for Zhengzhou Letai Trading Co LtdSearch in Eureka ↗ |
| Plaintiff counsel | Jie Li | Attorney | Counsel for Zhengzhou Letai Trading Co LtdSearch in Eureka ↗ |
| Plaintiff counsel | Ruoting Men | Attorney | Counsel for Zhengzhou Letai Trading Co LtdSearch in Eureka ↗ |
| Plaintiff law firm | GLACIER LAW LLP | Law Firm | Representing Zhengzhou Letai Trading Co LtdSearch in Eureka ↗ |
| Plaintiff law firm | GLACIER LAW LLP (CA) | Law Firm | Representing Zhengzhou Letai Trading Co LtdSearch in Eureka ↗ |
| Plaintiff law firm | Law Office Of Carl J. Marquardt PLLC | Law Firm | Representing Zhengzhou Letai Trading Co LtdSearch in Eureka ↗ |
| Presiding judge | Judge Kymberly K. Evanson | Judge | Washington Western District CourtSearch in Eureka ↗ |
Official order — verbatim text
The stipulation invokes FRCP 41(a)(1)(A)(ii), requiring both parties’ signatures and producing a with-prejudice dismissal that functions as a final judgment. Critically, no court found infringement or invalidity — the patent’s legal status is entirely unchanged. The ‘each party bears own costs’ clause is a negotiated term, not a default, and its inclusion suggests both sides were motivated to close cleanly. For practitioners, the absence of any defendant agent on record is notable and may indicate TowerStar had limited formal legal representation throughout the proceeding.
US8516975B2 — pet feeding product design and structure
US8516975B2 was filed under application number US12/691510 and issued as a granted U.S. patent covering pet feeding product technology. The patent is directed to the structural or functional design of a pet feeder — likely encompassing dispensing mechanisms, container configurations, or related feeding apparatus elements. Letai’s assertion against a specific Amazon ASIN (B0DPFWZ3Z9) indicates the patent covers commercially distributed consumer pet feeding products.
For the pet products sector, US8516975B2 represents an active enforcement asset in the hands of a plaintiff willing to pursue litigation in U.S. federal court. E-commerce sellers, particularly those operating on Amazon’s marketplace with pet feeding SKUs, face meaningful risk if their product design overlaps with the patent’s independent claims. The patent’s continued validity — uncontested in this proceeding — means it can be deployed against additional defendants without the complication of an invalidity defence having been adjudicated.
Should you run an FTO review against US8516975B2?
Any company designing, importing, or listing pet feeding products on U.S. e-commerce platforms should treat US8516975B2 as a relevant prior art and FTO reference. This case confirms the patent holder is actively enforcing the patent through U.S. district court proceedings. Product teams launching pet feeder SKUs — especially those targeting Amazon’s U.S. marketplace — should map their product’s structural and functional features against the patent’s independent claims before listing.
PatSnap Eureka’s FTO Search Agent enables R&D and IP teams to rapidly assess claim-level freedom to operate against US8516975B2. By mapping your product’s design features against the patent’s claim language, Eureka identifies overlap risk and surfaces invalidating prior art that could support a design-around or IPR strategy. For companies scaling e-commerce pet product lines, a targeted FTO review is a proportionate and commercially sensible step given the enforcement activity confirmed by this case.
Run a freedom-to-operate analysis on US8516975B2 to assess your product’s exposure
Run FTO in Eureka →Similar pet product patent enforcement cases in U.S. district courts
Cases involving pet product patent enforcement and e-commerce marketplace infringement actions filed in Washington Western and comparable U.S. district courts.
What this case signals for the pet products IP enforcement landscape
A 56-day dismissal with prejudice in a pet feeder patent case points to a pattern of commercially driven IP enforcement that product sellers should monitor closely.
Rapid dismissals with prejudice often mask undisclosed licence agreements
When a patent plaintiff agrees to dismiss with prejudice in under 60 days, it typically signals that the commercial objective — a licence fee, product withdrawal, or cease of competing activity — has already been achieved. Product sellers operating in the pet feeding category on Amazon should treat this case as a signal of active enforcement around US8516975B2.
No fee award signals a balanced negotiation, not a clear winner
The mutual fee-bearing arrangement indicates neither party sought to characterise the outcome as a clear victory or capitulation. This is consistent with a negotiated resolution where both sides made concessions. Patent attorneys advising e-commerce clients should note that this structure is common in assertion campaigns targeting marketplace sellers with limited litigation appetite.
Zhengzhou v TowerStar — key questions answered
Dismissed with prejudice means the case was terminated permanently. Zhengzhou Letai cannot re-file the same infringement claims against TowerStar Pets based on US8516975B2 and the same accused product. The dismissal was stipulated by both parties under FRCP 41(a)(1)(A)(ii) and does not include any court finding on infringement or patent validity.
Yes. The dismissal with prejudice resolves only the dispute between Zhengzhou Letai and TowerStar Pets. No court ruled on the validity or enforceability of US8516975B2. The patent remains fully enforceable and Letai retains the right to assert it against other parties selling pet feeding products that fall within the patent’s claims.
A 56-day resolution is unusually fast for patent litigation. This pace is consistent with a confidential settlement or licensing agreement being reached shortly after the complaint was filed. The mutual fee-bearing arrangement further suggests a negotiated resolution rather than a capitulation by either party. The specific commercial terms, if any, are not disclosed in the public court record.
The accused product is identified as a pet feeding product listed on Amazon under ASIN B0DPFWZ3Z9, sold by TowerStar Pets LLC. The patent asserted is US8516975B2, which covers pet feeding product technology. No further product-specific technical details are disclosed in the public court record.
Glacier Law LLP, alongside the Law Office of Carl J. Marquardt PLLC, served as counsel of record for plaintiff Zhengzhou Letai Trading Co. Ltd. Attorneys Carl J. Marquardt, Jie Li, and Ruoting Men are listed as plaintiff agents. Glacier Law LLP is known for representing e-commerce and cross-border IP enforcement matters in U.S. federal courts.
PatSnap Eureka searches patents and litigation data to answer instantly.