US 11633006

An analysis of U.S. Patent 11,633,006 reveals the following:

Title: Rapid-entry footwear having a stabilizer and an elastic element.

Assignee: FAST IP, LLC

Inventors: Michael Pratt, Craig Cheney.

Filing Date: October 13, 2022.

Issue Date: April 25, 2023.

Abstract: The patent describes a rapid-entry shoe designed with an elastic element to enlarge the foot opening for easy insertion, and a stabilizer to prevent the rear portion of the shoe from collapsing.

Litigation

This patent is the subject of ongoing litigation. In July 2025, HandsFree Labs Licensing, LLC, FAST IP, LLC, and Kizik Design, LLC filed a patent infringement lawsuit against Skechers U.S.A., Inc. in the U.S. District Court for the Eastern District of Texas. The lawsuit alleges that Skechers' "Hands Free Slip-ins" footwear line infringes on U.S. Patent No. 11,633,006 and several other patents.

Skechers has responded by filing a petition for inter partes review (IPR) with the Patent Trial and Appeal Board (PTAB) on April 24, 2026, challenging the validity of the patent. A related patent, U.S. Patent No. 11,871,811, is also being challenged by Skechers in a separate IPR proceeding.

Plain-Language Summary of Independent Claims

U.S. Patent 11,633,006 contains two independent claims:

• Claim 1: This claim describes a "rapid-entry" shoe with an upper, a sole, and a rear portion. The key features are:

  • An elastic element on the side of the shoe that stretches from the sole to the top line (the opening of the shoe).
  • A stabilizer at the rear of the shoe, with a base at least partially inside the sole, to prevent the back of the shoe from collapsing.
  • The base of the stabilizer forms a "closed cup" that extends across the width of the sole.
  • The stabilizer has a specific curved shape that becomes less pronounced as it extends upwards.
  • The top of the stabilizer has a "flare portion" that acts like a shoehorn to guide the foot in.
  • A foam liner, which is concave towards the sole, is also included.

• Claim 4: This claim describes a similar "rapid-entry" shoe but with some key differences in the stabilizer:

  • The elastic element is located on the side of the shoe and extends to the top line but does not extend all the way to the sole.
  • The stabilizer is an arch structure with a "window" or opening in it, positioned above the sole.
  • An "expansion zone," made of an elastic or deformable material, is located exclusively within this window and is connected to the upper part of the stabilizer. This expansion zone helps to enlarge the shoe's opening when a foot is inserted.

As of April 30, 2026, U.S. Patent No. 11,633,006 is involved in the following litigation:

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Case 1:

• Plaintiff(s): Fast IP, LLC, HandsFree Labs Licensing, LLC, and Kizik Design, LLC
• Defendant(s): Skechers U.S.A., Inc.
• Jurisdiction: U.S. District Court for the Eastern District of Texas
• Case Number: 2:25-cv-00744
• Filing Date: July 2025
• Status: The case is currently active. On April 24, 2026, the defendant, Skechers U.S.A., Inc., filed a petition for inter partes review (IPR) with the Patent Trial and Appeal Board (PTAB) challenging the validity of patent 11,633,006. The district court case may be stayed pending the outcome of the IPR proceeding.

Proceedings overview

There is one active inter partes review (IPR) proceeding on file for US Patent 11,633,006, which is currently pending. This means the patent's validity is currently under review by the PTAB, and its claims have not yet been challenged to finality.

IPR2026-00342 — Skechers U.S.A., Inc. v. Fast IP, LLC

• Type: Inter Partes Review
• Filed: 2026-04-24
• Status: Pending. The proceeding is in its early stages, and an institution decision has not yet been issued.
• Judge panel: The judge panel has not yet been made public.
• Petition grounds: The petition was filed by Skechers U.S.A., Inc. against Fast IP, LLC. While specific claims and prior art are not yet publicly detailed in the PTAB Open Data Portal, IPR petitions typically challenge claims on grounds of anticipation under 35 U.S.C. § 102 and/or obviousness under 35 U.S.C. § 103, using patents and printed publications as prior art. This IPR targets U.S. Patent No. 11,633,006, relating to rapid-entry footwear.
• Institution decision: Not yet issued. The PTAB has approximately six months from the filing date to decide whether to institute the IPR.
• Final Written Decision (if issued): Not yet issued.
• Settlement / termination: Not yet settled or terminated.
• Appeal: No appeal has been filed as no Final Written Decision has been issued.
• Defensive value: This proceeding indicates that Skechers is actively challenging the validity of US Patent 11,633,006. As the IPR is still pending institution, the patent's claims remain presumptively valid. A defendant facing assertion of this patent should closely monitor this IPR, as a decision to institute would indicate the PTAB believes there's a reasonable likelihood the challenged claims are unpatentable, providing a potential stay for related district court litigation.

Strategic summary

Currently, all claims of US Patent 11,633,006 remain UNTESTED at the PTAB, as the single IPR (IPR2026-00342) is still in the pre-institution phase. No claims have been canceled or sustained by a Final Written Decision.

The estoppel landscape has not yet been fully formed. If the PTAB institutes the IPR, Skechers (and its privies) would be estopped under 35 U.S.C. § 315(e)(2) from asserting in other proceedings any ground of unpatentability that it raised or reasonably could have raised during the IPR. Given that this is the first IPR against the patent, the full range of prior-art grounds under §§ 102 and 103 are likely still available to Skechers in this proceeding.

There is a clear pattern signal here: Skechers U.S.A., Inc. is the petitioner in IPR2026-00342. This IPR was filed shortly after a patent infringement lawsuit was brought against Skechers by Fast IP, LLC, HandsFree Labs Licensing, LLC, and Kizik Design, LLC in the U.S. District Court for the Eastern District of Texas in July 2025 (Case Number 2:25-cv-00744). Skechers has also filed an IPR against a related patent, U.S. Patent No. 11,871,811 (IPR2026-00343). This suggests a defensive strategy by Skechers to challenge the validity of Fast IP/Kizik's patent portfolio related to hands-free footwear.

Recommended next steps

As IPR2026-00342 is currently pending, a defendant facing assertion of US Patent 11,633,006 should:

• Monitor the institution decision: The PTAB's decision on whether to institute IPR2026-00342 is a critical milestone. This decision is typically due approximately six months from the filing date (April 24, 2026), placing the institution decision deadline around October 24, 2026. If instituted, the District Court litigation may be stayed pending the IPR's outcome. The status can be tracked on the USPTO PTAB Open Data Portal.
• Review the petition: Once publicly available, carefully review Skechers' IPR petition to understand the specific claims challenged and the prior art and arguments presented. This will provide insight into the strongest invalidity arguments against the patent.
• Anticipate the Final Written Decision: If the IPR is instituted, the PTAB has a statutory one-year deadline from institution to issue a Final Written Decision.

Inventors

• Michael Pratt (Fast IP LLC)
• Craig Cheney (Fast IP LLC)

Original assignee

Fast IP LLC. The patent abstract and description indicate that Fast IP LLC is involved in developing rapid-entry footwear, which is consistent with the "Kizik" brand of hands-free shoes mentioned in the prior art analysis. Kizik Design, LLC is listed as a plaintiff in the ongoing litigation, alongside Fast IP, LLC, suggesting a close relationship or a product embodiment by Kizik Design, LLC. Fast IP LLC's primary line of business appears to be intellectual property holding and licensing related to rapid-entry footwear technology. Its current status is operating, as it is actively involved in litigation as a plaintiff.

Assignment timeline

• 2023-01-05 (executed) / recorded 2023-01-05 — Reel 061142/0695
  • Conveyance: Assignment
  • Assignor: Michael Pratt, Craig Cheney
  • Assignee: FAST IP, LLC
  • Correspondent: Jeffrey D. Myers, Kirton McConkie PC, 50 West Broadway, Suite 700, Salt Lake City, Utah, 84101. This correspondent recurs across this patent's chain and other patents tracked on this site.
  • Context: Transfer from inventors to original assignee.
• 2025-06-13 (executed) / recorded 2025-06-13 — Reel 065874/0252
  • Conveyance: Security Interest
  • Assignor: FAST IP, LLC, HANDSFREE LABS LICENSING, LLC, HANDSFREE LABS, INC., KIZIK DESIGN, LLC
  • Assignee: SIENA LENDING GROUP LLC
  • Correspondent: Jeffrey D. Myers, Kirton McConkie PC, 50 West Broadway, Suite 700, Salt Lake City, UT, 84101. This correspondent recurs across this patent's chain and other patents tracked on this site.
  • Context: Securitization of assets.

Timeline diagram

timeline
    title Ownership of US 11633006
    2022 : Filed by Fast IP LLC
    2023 : Assigned to Fast IP LLC
         : Issued
    2025 : Securitized to Siena Lending Group
    2026 : IPR filed by Skechers

NPE / troll-pattern signals

1. Shell-entity transfer — unclear. While Fast IP, LLC is primarily an IP holding and licensing entity, it is directly linked to Kizik Design, LLC, which appears to be an operating company selling products. The transfer from inventors to Fast IP, LLC (Reel 061142/0695) is a common initial step for both operating companies and NPEs. The subsequent securitization to Siena Lending Group LLC (Reel 065874/0252) involves multiple Fast IP-related entities, further complicating a simple "shell-entity" assessment at this stage.

2. Known asserter in the chain — not present. Siena Lending Group LLC is a financial institution and not a known patent asserter. Fast IP, LLC is not on common public NPE lists like Marathon Patent Group or Intellectual Ventures.

3. Repeat correspondent across the chain — present. Jeffrey D. Myers of Kirton McConkie PC is listed as the correspondent for both the initial assignment from inventors to Fast IP, LLC (Reel 061142/0695) and the security interest filing with Siena Lending Group LLC (Reel 065874/0252). The provided context states this correspondent recurs across this patent's chain and other patents tracked on this site, which is a strong signal for a focused IP strategy.

4. Cascading transfers — not present. There are only two recorded transactions, occurring more than two years apart, and not involving multiple chained LLCs.

5. Pre-litigation transfer — not present. The most recent assignment (security interest to Siena Lending Group LLC, Reel 065874/0252) was recorded on 2025-06-13. The first infringement suit was filed in July 2025, which is within the 6-month window. However, this was a securitization, not a transfer of ownership for assertion purposes. The initial assignment from inventors to Fast IP, LLC was in 2023, well before litigation.

6. Bankruptcy fire-sale — not present. There is no indication that the patent was acquired through a bankruptcy proceeding.

7. Privateering — unclear. While Fast IP, LLC is asserting the patent, and Kizik Design, LLC appears to be an operating company, the nature of their relationship (whether Kizik is directing the litigation via Fast IP) is not definitively clear from the assignment records alone.

8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at any known defensive aggregator.

Verdict

NPE — moderate confidence. While there isn't a direct transfer to a well-known NPE, the presence of a repeat correspondent (Jeffrey D. Myers, Kirton McConkie PC on Reel 061142/0695 and Reel 065874/0252) across the chain, combined with Fast IP, LLC's role as an IP holding and licensing entity, suggests a focused strategy on patent assertion rather than direct product manufacturing. The securitization also indicates a leveraged IP asset.
For verification, see the USPTO Assignment Center search page: https://assignmentcenter.uspto.gov/.

Prior Art Analysis for U.S. Patent 11,633,006

This analysis examines the prior art cited during the prosecution of U.S. Patent 11,633,006 ("the '006 patent"). Each reference is evaluated for its potential to anticipate the claims of the '006 patent under 35 U.S.C. § 102. The analysis is based on the information available as of today's date, April 30, 2026.

Cited Prior Art References

The following patents and patent applications were cited by the examiner during the prosecution of the '006 patent.

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1. U.S. Patent No. 11,191,320 B2 ("Hedgepeth '320")

• Full Citation: US 11,191,320 B2, "Footwear with vertically extended heel counter," filed by Nike, Inc.
• Filing Date: December 28, 2018
• Publication Date: December 7, 2021
• Brief Description: The Hedgepeth '320 patent describes a shoe with a heel counter that extends upward from the sole. This counter is designed to be semi-rigid and has a curved or "scooped" upper portion that functions as a shoehorn, guiding the user's foot into the shoe. The design is intended to prevent the heel portion of the shoe from collapsing when the user slides their foot in.
• Potential Anticipation of Claims:
  • Claim 1: Hedgepeth '320 discloses a stabilizer (termed a "heel counter") at the rear portion of the shoe that extends from the sole to resist collapse, similar to the stabilizer in claim 1. It also features a flared upper portion that acts like a shoehorn, which corresponds to the "flare portion" in claim 1. However, Hedgepeth '320 does not explicitly teach or suggest an elastic element at the side portion that extends from the topline to the sole portion, nor does it describe the specific "closed cup" structure of the stabilizer base or the progressively lessening curvature as recited in claim 1. Therefore, Hedgepeth '320 likely does not anticipate all elements of claim 1.
  • Claim 4: This claim requires an elastic element on the side portion and a stabilizer with an "arch structure" that defines a "window." Hedgepeth '320 does not appear to disclose this combination of features. Its heel counter is a solid or semi-solid structure without the claimed window or expansion zone.

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2. U.S. Patent No. 10,638,810 B1 ("Pratt '810")

• Full Citation: US 10,638,810 B1, "Rapid-entry footwear having a compressible lattice structure," filed by Fast IP, LLC.
• Filing Date: January 7, 2019
• Publication Date: May 5, 2020
• Brief Description: The Pratt '810 patent, from the same assignee as the '006 patent, discloses a shoe with a heel stabilizer that forms an arch or "window." Within this window is a compressible lattice structure. When a user inserts their foot, the lattice compresses to allow the heel to pass and then recovers, helping to secure the foot. This is a key technology behind the "Kizik" brand of hands-free shoes.
• Potential Anticipation of Claims:
  • Claim 1: This claim requires the stabilizer base to define a "closed cup portion extending completely between lateral and medial sides of the sole portion." The arch structure in Pratt '810, which defines a window, is fundamentally different from this "closed cup" design. Therefore, Pratt '810 does not anticipate claim 1.
  • Claim 4: Pratt '810 is highly relevant to claim 4. It clearly discloses a stabilizer with an arch structure that defines a window, as recited in the claim. The compressible lattice structure within that window serves a similar function to the "expansion zone" of claim 4, as both are designed to deform during foot entry and are located within the stabilizer's window. While the '006 patent's "expansion zone" is described more broadly as an "elastic or resiliently deformable material," the lattice structure of Pratt '810 would likely be considered an embodiment of such a zone. Pratt '810 also describes elastic elements in the shoe's upper. A combination of these teachings could be seen to anticipate or, at a minimum, render obvious the invention described in claim 4.

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3. U.S. Patent No. 8,516,721 B2 ("Donnadieu '721")

• Full Citation: US 8,516,721 B2, "Articles of footwear," filed by Saucony IP Holdings LLC.
• Filing Date: January 10, 2011
• Publication Date: August 27, 2013
• Brief Description: The Donnadieu '721 patent describes an article of footwear with an upper that includes an elastic gore or panel. This elastic panel is located in the midfoot region and is designed to provide a snug but flexible fit, adapting to the shape of the wearer's foot. The invention is focused on providing a comfortable and secure fit during athletic activities.
• Potential Anticipation of Claims:
  • Claim 1 & 4: Donnadieu '721 discloses an "elastic element" at the side portion of a shoe, which is a key component of both independent claims of the '006 patent. Specifically, Figures 2 and 3 of Donnadieu show an elastic gore (element 22) that extends from near the sole to the topline. However, Donnadieu '721 does not teach or suggest the specific stabilizer structures required by either claim 1 (the closed cup with a flare) or claim 4 (the arch structure with a window and expansion zone). The focus of Donnadieu is on fit and comfort around the midfoot, not on a hands-free entry mechanism supported by a rigid heel structure. Therefore, this patent does not anticipate the claims of the '006 patent.

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4. U.S. Patent Application Publication No. 2017/0303632 A1 ("Pratt '632")

• Full Citation: US 2017/0303632 A1, "Rapid-entry footwear with rebounding fit system," filed by Kizik Design, LLC.
• Filing Date: April 22, 2016
• Publication Date: October 26, 2017
• Brief Description: This application, which is part of the same patent family and from the same inventors as the '006 patent, discloses the foundational technology for a hands-free shoe. It describes an external heel cage or "arch" made of a semi-rigid material that guides the foot into the shoe and prevents the heel from collapsing. It also describes a rebounding mechanism within the arch, such as a spring or elastic band, that deforms upon entry and then returns to its original position to secure the shoe.
• Potential Anticipation of Claims:
  • Claim 1: The '632 application does not describe the "closed cup" stabilizer base as required by claim 1. Instead, it focuses on an external arch or cage structure.
  • Claim 4: The '632 application is highly relevant prior art for claim 4. It describes a stabilizer with an arch structure defining a window. The "rebounding fit system" within this window functions as an "expansion zone" that facilitates entry. This reference discloses the core combination of an arched stabilizer with an internal deformable element to allow for hands-free entry, which is the central novelty of claim 4. An argument for anticipation could be made if the "expansion zone" of claim 4 is interpreted broadly enough to read on the "rebounding fit system" of the '632 application.

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Summary of Potential Challenges:

The prior art cited against US 11,633,006 presents a mixed landscape. While references like Hedgepeth '320 and Donnadieu '721 disclose individual elements of the claims (a rigid heel counter and an elastic side panel, respectively), they fail to teach the specific combination of elements required by the independent claims of the '006 patent.

The most significant prior art appears to be Pratt '810 and the Pratt '632 application, which originate from the same inventors and assignee. These documents disclose the core concept of a rapid-entry shoe featuring a rigid arch-like stabilizer at the heel with a window containing a deformable element. This combination is very close to the invention described in Claim 4. The patentability of Claim 4 will likely depend on whether the "expansion zone" is considered a non-obvious variation of the "compressible lattice structure" (from '810) or the "rebounding fit system" (from '632).

Claim 1 appears more distinct from the cited art due to its specific requirements for a "closed cup" stabilizer base and the particular geometry of its curvature. None of the cited references appear to disclose this specific structure in combination with the claimed elastic element.

Based on the provided prior art, here is an analysis of the obviousness of the claims in U.S. Patent No. 11,633,006 ("the '006 patent") under 35 U.S.C. § 103. This analysis assumes a Person Having Ordinary Skill in the Art (PHOSITA) would be an individual with experience in footwear design and engineering.

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Analysis of Independent Claim 1

Claim 1 is likely obvious over a combination of U.S. Patent No. 11,191,320 B2 ("Hedgepeth '320") and U.S. Patent No. 8,516,721 B2 ("Donnadieu '721").

A PHOSITA would have been motivated to combine these references to create a more effective and comfortable hands-free shoe, with a reasonable expectation of success.

1. Base Invention: Hedgepeth '320

Hedgepeth '320 discloses the foundational elements of the stabilizer described in claim 1. It teaches a shoe with a vertically extended, semi-rigid heel counter that prevents the rear portion from collapsing during foot insertion. This counter also includes a "scooped" or flared upper portion that functions as a built-in shoehorn to guide the foot. This directly addresses the core problem of creating a "rapid-entry" shoe where the heel remains supportive. Hedgepeth '320 thus teaches the "stabilizer disposed at the rear portion," the "flare portion extending rearward," and the configuration "to resist downward collapse."

2. Modification with Donnadieu '721

While Hedgepeth '320 provides a rigid entry path at the heel, a PHOSITA would recognize that the instep and side portions of the shoe must also expand to accommodate the foot. The primary motivation would be to further improve the ease of entry. Donnadieu '721 provides a known solution by disclosing an elastic gore on the side of the shoe upper to provide a flexible and adaptable fit.

A PHOSITA would be motivated to incorporate the elastic side panel from Donnadieu '721 into the shoe design of Hedgepeth '320. This combination would allow the forward portion of the upper to flex and pivot away from the foot during entry, creating a wider opening and complementing the function of Hedgepeth's rigid heel counter. This directly teaches the claimed "elastic element disposed at the side portion" that "enlarges the foot opening" and enables the "forward portion... to flex and/or pivot forward."

3. Addressing the Remaining Limitations of Claim 1

The other limitations of claim 1 would have been obvious to a PHOSITA when implementing the combined teachings of Hedgepeth and Donnadieu:

• Stabilizer Base as a "Closed Cup Portion": Standard heel counters in footwear are almost universally designed as cup-shaped structures to cradle the calcaneus (heel bone) for stability and fit. A PHOSITA implementing the extended counter of Hedgepeth '320 would naturally form its base into a "closed cup" that extends between the medial and lateral sides as a matter of standard and sound footwear design.
• Progressively Lessening Curvature: This describes a shape that is wide at the bottom to cup the heel and narrows toward the top as it approaches the Achilles tendon. This is a basic principle of anatomical design in footwear to ensure a proper fit without causing irritation. A PHOSITA would shape the stabilizer in this manner to conform to the natural shape of the human foot.
• Foam Liner: Adding a foam liner to the interior of a heel counter is a common and obvious step to enhance comfort, particularly when the counter is made of a rigid material as in Hedgepeth '320.

Therefore, the combination of a rigid, shoehorn-like heel counter (Hedgepeth '320) with a side elastic gore (Donnadieu '721) would render the invention of claim 1 obvious to a person of ordinary skill in the art of shoe design.

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Analysis of Independent Claim 4

Claim 4 is likely obvious over U.S. Patent No. 10,638,810 B1 ("Pratt '810") either alone or in view of Donnadieu '721.

The core technology of claim 4 is substantially disclosed in prior art from the same inventors and assignee, making it highly susceptible to an obviousness challenge.

1. Base Invention: Pratt '810

Pratt '810, which shares inventors with the '006 patent, discloses the central concept of claim 4. It teaches a rapid-entry shoe with a stabilizer that forms an "arch structure" defining a "window" at the rear of the shoe. Within this window, Pratt '810 places a "compressible lattice structure" designed to deform upon foot entry and then recover.

This "compressible lattice structure" in Pratt '810 performs the identical function as the "expansion zone" recited in claim 4. A PHOSITA would understand that the term "expansion zone" is a broader, functional description for the specific lattice structure disclosed in Pratt '810. It would be obvious to a PHOSITA that other resiliently deformable materials or structures (e.g., a simple elastomeric panel, a foam block, a different geometric lattice) could be used in place of the specific lattice shown in Pratt '810 to achieve the same result. Substituting one known deformable material for another to serve the same purpose within the same overall structure would be considered an obvious design choice.

2. Combination with Donnadieu '721

Even if the "expansion zone" were considered a non-obvious element over Pratt '810 alone, claim 4 would be obvious over the combination of Pratt '810 and Donnadieu '721.

• Motivation to Combine: A PHOSITA starting with the Pratt '810 design would have a shoe with a sophisticated hands-free heel mechanism. To further enhance the shoe's fit and ease of entry, they would be motivated to improve the flexibility of the upper, particularly around the instep. Donnadieu '721 teaches using an elastic side element for precisely this purpose. Combining Donnadieu's side elastic with Pratt '810's heel system is a logical step to create a superior rapid-entry shoe.
• Result of the Combination: This combination directly results in a shoe that has:
  • A stabilizer with an arch structure and a window (from Pratt '810).
  • A deformable element within that window (the "compressible lattice structure" from Pratt '810, which reads on the "expansion zone" of claim 4).
  • An elastic element at the side portion (from Donnadieu '721).
• Limitation: "not extending to the sole portion": The specific configuration of the elastic element in claim 4 (extending to the topline but not to the sole) is a matter of routine design choice. A footwear designer would vary the length and placement of an elastic gore to control the amount and location of stretch, and limiting its extension to avoid interference with the sole structure is a common practice.

In summary, the core inventive concept of claim 4—an arched heel stabilizer with a window containing a deformable element—is already present in the inventors' own prior art (Pratt '810). The remaining elements are either obvious equivalents or well-known features in the art that a PHOSITA would be motivated to combine to improve the shoe's overall function.

As of May 1, 2026, the following details pertain to U.S. Patent No. 11,633,006 ("the '006 patent"):

Patent Term and Expiration

• Patent Term Adjustment (PTA): There has been no Patent Term Adjustment granted for this patent. The term has not been extended due to delays by the USPTO during prosecution.
• Patent Term Extension (PTE): There is no indication of any Patent Term Extension under 35 U.S.C. § 156. Such extensions are typically granted for products that undergo a pre-market regulatory review (e.g., pharmaceuticals or medical devices) and would not apply to this technology.
• Projected Expiration Date: The patent's term is calculated from the filing date of the earliest non-provisional application in its family, which is U.S. Application No. 16/942,335, filed on July 29, 2020. Therefore, the standard 20-year term expires on July 29, 2040.

Continuity and Family Data

The '006 patent is part of a larger family of patents and applications that claim priority back to U.S. Provisional Application No. 62/879,883, filed on July 29, 2019.

• Parent Application: The '006 patent issued from U.S. Application No. 17/965,501, which is a continuation of U.S. Application No. 16/942,335 (now issued as U.S. Patent No. 11,633,005). Both patents share the same title and specification.

• Related U.S. Family Members: This patent is part of a significant portfolio of related patents and applications assigned to Fast IP, LLC, all stemming from the same original priority document. Other members of this patent family include, but are not limited to:

  • U.S. Patent No. 11,633,005: The direct parent of the '006 patent.
  • U.S. Patent No. 11,871,811: A related patent, also subject to an inter partes review (IPR) petition by Skechers.
  • U.S. Patent No. 12,121,096
  • U.S. Patent No. 12,274,325
  • U.S. Patent No. 12,471,660

• International Counterparts: The patent family also includes international applications, indicating an effort to secure patent rights in multiple jurisdictions. These include:

  • PCT Application: WO2021021917A1
  • European Application: EP4640101A3
  • Chinese Application: CN114206153A
  • Australian Patent: AU2020322008B2
  • Canadian Application: CA3148597A1

Defensive Disclosure and Inventive Concepts

This document details novel and non-obvious variations, extensions, and applications of the core technologies described in U.S. Patent No. 11,633,006. The purpose of this disclosure is to place these concepts into the public domain, thereby establishing them as prior art for patent examination purposes. The following disclosures are intended to be enabling for a Person Having Ordinary Skill in the Art (PHOSITA).

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Derivatives of Independent Claim 1

Claim 1 describes a rapid-entry shoe featuring an elastic element extending from the sole to the topline and a rigid, "closed cup" stabilizer with a flared top.

1. Material & Component Substitution

Derivative 1.1: Magnetorheological (MR) Custom-Fit Stabilizer

• Enabling Description: The stabilizer's rigid structure is replaced by a semi-flexible, hollow shell constructed from a non-magnetic polymer like PEEK (Polyether ether ketone). This shell is filled with a magnetorheological (MR) fluid. The foam liner is integrated with a network of fine-gauge copper coils connected to a piezoelectric generator embedded in the shoe's outsole. During foot entry, the MR fluid is in a liquid state, allowing the stabilizer shell to flex. Once the foot is in place, the kinetic energy from the user's first few steps generates a current via the piezoelectric element, which energizes the coils. The resulting magnetic field instantly increases the viscosity of the MR fluid, causing the stabilizer to become rigid and conform precisely to the user's heel. This creates an active, adaptive fit that is firm during wear but flexible for entry/exit.
• Mermaid Diagram:

  graph TD
      A[Piezo Generator in Outsole] --Kinetic Energy--> B(Power Management IC)
      B --Regulated Current--> C{Coil Network in Liner}
      C --Magnetic Field--> D[MR Fluid in Stabilizer Shell]
      D --Viscosity Increase--> E(Rigid, Conforming Heel)
      D --No Field--> F(Flexible Heel for Entry)
  

Derivative 1.2: Pneumatically-Actuated Elastic Element

• Enabling Description: The passive elastic element is replaced with a series of interconnected, low-profile pneumatic bladders made of durable Thermoplastic Polyurethane (TPU), integrated into the shoe's side portion. These bladders are connected via micro-tubing to a miniature, low-power diaphragm pump and release valve located within the sole. A pressure sensor in the heel detects the initial insertion of the foot, triggering the valve to release air, which allows the bladders to collapse and the foot opening to enlarge. Upon full insertion of the foot, the sensor signals the pump to inflate the bladders to a pre-set pressure (e.g., 2-5 psi), securing the foot. This allows for a wider opening than passive elastic and an adjustable level of midfoot support.
• Mermaid Diagram:

  sequenceDiagram
      participant User
      participant HeelSensor
      participant Microcontroller
      participant Valve
      participant Pump
      participant AirBladders
  
      User->>HeelSensor: Inserts Foot
      HeelSensor->>Microcontroller: Pressure Detected
      Microcontroller->>Valve: Open Valve
      Valve-->>AirBladders: Deflate
      User->>HeelSensor: Foot Fully Seated
      HeelSensor->>Microcontroller: Full Pressure Signal
      Microcontroller->>Pump: Activate Pump
      Pump->>AirBladders: Inflate to Set Pressure
  

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2. Operational Parameter Expansion

Derivative 2.1: High-G Flight Boot Application

• Enabling Description: An adaptation for aviators in high-performance aircraft. The stabilizer is constructed from a carbon fiber/Aramid (e.g., Kevlar®) composite to withstand extreme forces. The elastic element is a high-tension, fire-retardant elastomer. Integrated within the sole and stabilizer are liquid-filled capillaries connected to the aircraft's G-suit pressure system. As G-forces increase, the system automatically pressurizes the capillaries, causing the entire shoe structure—including the stabilizer and areas around the elastic element—to become progressively more rigid. This provides enhanced ankle support to prevent G-induced pooling of blood in the lower extremities and ensures the boot does not deform or loosen during high-G maneuvers, while still allowing for rapid, hands-free donning and doffing on the ground.
• Mermaid Diagram:

  stateDiagram-v2
      state "Ground (1G)" as S1
      state "High-G (5-9G)" as S2
  
      [*] --> S1: Pre-flight
      S1 --> S2: Onset of High-G / Pressure from G-suit
      S2 --> S1: Return to 1G / Pressure Release
  
      S1: Stabilizer: Nominally Rigid<br>Capillaries: Unpressurized<br>Fit: Snug
      S2: Stabilizer: Hyper-Rigid<br>Capillaries: Pressurized<br>Fit: Compression
  

---

3. Cross-Domain Application

Derivative 3.1: Medical - Articulated Ankle-Foot Orthosis (AFO)

• Enabling Description: The invention is applied to an AFO for patients with drop foot or ankle instability. The "sole portion" is a custom-molded orthotic footplate. The "stabilizer" is a rigid polypropylene upright that cups the heel and extends vertically along the calf. The "elastic element" is a hinged, elasticated strap system on the lateral side, allowing the AFO to be opened widely. The "flare portion" at the top of the stabilizer acts as a guide for the user's leg. This design allows a patient with limited hand strength or mobility to don and doff their own brace without assistance, a significant improvement over complex Velcro strap systems.
• Mermaid Diagram:

  graph LR
      subgraph AFO [Ankle-Foot Orthosis]
          A(Polypropylene Stabilizer) --extends up calf--> B(Flare Guide)
          A --forms--> C(Heel Cup)
          C --connects to--> D(Orthotic Footplate)
          A --connected by--> E(Elasticated Hinge)
          E --allows opening--> F(Side Portion)
      end
      G[User's Leg] -->|Slides Down| B
      F -->|Expands| G
  

Derivative 3.2: Industrial Safety - Self-Securing Equipment Holster

• Enabling Description: A tool holster for a duty belt. The "stabilizer" is a Kydex or molded carbon fiber shell shaped to the tool (e.g., a power drill, scanner). The "elastic element" is a high-retention elastic band or a spring-loaded gate on the side. The "flare portion" is a flared opening at the top of the holster. The user can insert the tool with one hand; the flared opening guides it into place, and the elastic gate expands and then snaps shut, securing the tool. This provides Level II retention without requiring the user to manually operate a thumb break or strap.
• Mermaid Diagram:

  graph TD
      subgraph Holster
          A[Flared Opening] --> B{Holster Body};
          B --contains--> C(Tool);
          D[Spring-Loaded Gate] --secures--> C;
          B --attached to--> E[Belt Mount];
      end
  
      Tool_In --Pushes against--> D;
      D --Opens--> Allows_Entry;
      Tool_In --> B;
      D --Spring Action--> Closes;
  

Derivative 3.3: Sporting Goods - Quick-Release Bicycle Cleat Cover

• Enabling Description: A walkable cover for recessed SPD-style bicycle cleats. The "stabilizer" is a rigid polymer frame that surrounds the cleat area on the sole of the cycling shoe. The "elastic element" is a stretchable rubber membrane that forms the body of the cover. To install, the user simply steps down onto the cover. The flared edges of the stabilizer guide the shoe, and the elastic membrane stretches over the sole, snapping securely into the recess around the cleat. Removal is hands-free by hooking a tab on the cover with the opposite shoe and pulling away. This allows cyclists to quickly transition from cycling to walking without fumbling with covers.
• Mermaid Diagram:

  flowchart LR
      subgraph Shoe
          A(Cycling Shoe Sole) --> B(Recessed Cleat);
      end
      subgraph Cleat Cover
          C(Rigid Frame) --surrounds--> D(Elastic Membrane);
      end
      A --Applies Force--> C;
      D --Stretches over A--> E{Cover Secured};
      E --Release Tab Pulled--> D;
      D --Contracts--> F{Cover Removed};
  

---

Derivatives of Independent Claim 4

Claim 4 describes a rapid-entry shoe with a stabilizer forming an "arch structure" with a "window" containing an "expansion zone."

4. Integration with Emerging Tech

Derivative 4.1: AI-Modulated Variable Stiffness Arch

• Enabling Description: The "expansion zone" within the stabilizer's window is an Electroactive Polymer (EAP) actuator. An integrated System-on-Chip (SoC) runs a lightweight neural network. Multiple pressure sensors in the insole provide real-time data on foot position, weight distribution, and activity type (e.g., walking, running, standing still). The AI model processes this data and dynamically adjusts the voltage applied to the EAP. This allows the expansion zone to change its stiffness: it becomes very soft for easy foot entry, provides firm, responsive support during athletic movements, and can offer gentle, compliant support when the user is stationary. The user's gait data and the AI's adjustments are logged to a private blockchain, creating an immutable record for performance analysis or medical history.
• Mermaid Diagram:

  graph TD
      subgraph ShoeSystem
          A[Insole Pressure Sensors] --> B(Microcontroller with AI);
          B --> C[EAP Driver Circuit];
          C --> D(EAP Expansion Zone);
          B --> E(Bluetooth LE);
      end
      subgraph External
          F(User's Foot) --interacts with--> A;
          E --> G(Smartphone App);
          B --> H(Private Blockchain);
      end
      A --Gait Data--> B;
      B --Control Signal--> C;
      C --Voltage--> D;
      B --Log Data--> H;
  

---
#### **5. The "Inverse" or Failure Mode**

**Derivative 5.1: Fail-Safe Mechanical Latch Expansion Zone**

*   **Enabling Description:** The "expansion zone" is not elastic but is a hinged, rigid gate connected to a bi-stable latching mechanism. As the foot enters, it pushes the gate rearward, which travels past a mechanical detent and clicks into an "open" position, creating maximum space. Once the foot is in and the heel settles, a small, user-actuated lever (or a secondary pressure plate in the heel) releases the latch, causing a pre-loaded torsion spring to snap the gate forward into a "closed" position, locking the heel. This system is designed for a "fail-safe" state; if the spring or latch mechanism fails, the gate remains in the open position, and the shoe can still be worn loosely or secured by a backup lace threaded through the window. This prioritizes guaranteed operation over a soft, elastic feel.
*   **Mermaid Diagram:**
    ```mermaid
    stateDiagram-v2
        [*] --> Unlatched
        Unlatched: Gate is closed.
        Latched_Open: Gate is open for foot entry.

        Unlatched --> Latched_Open: Heel pressure overcomes latch detent.
        Latched_Open --> Unlatched: User actuates release lever.
        Latched_Open --> Failsafe_Mode: Mechanical failure of spring/latch.
        Unlatched --> Failsafe_Mode: Mechanical failure of spring/latch.

        state Failsafe_Mode {
            direction LR
            [*] --> Open_State
            Open_State: Gate remains open. User can add manual lace.
        }
    ```

---
### **Combination Prior Art with Open-Source Standards**

**1. Combination with WebXR for Custom Orthotics:**
*   **Enabling Description:** A web-based application utilizing the open WebXR standard allows a user to perform a 3D scan of their foot using a standard smartphone. This application uses an open-source point-cloud processing library (e.g., PCL.js) to generate a high-fidelity 3D model. The application then algorithmically generates a customized CAD model for the stabilizer arch and window structure of Claim 4, conforming it to the user's specific heel and ankle geometry. The output is a standard STL file, ready for 3D printing on any consumer-grade printer using open-source slicer software like Ultimaker Cura. This makes the concept of a parametrically-designed, user-printable, custom-fit version of the patented invention obvious.

**2. Combination with an Open-Source RTOS for Haptic Feedback:**
*   **Enabling Description:** The stabilizer arch of Claim 4 is built to house a small microcontroller running an open-source Real-Time Operating System (RTOS) such as Zephyr or FreeRTOS. The "expansion zone" is fitted with a piezoelectric film sensor and a small linear resonant actuator (LRA). When the user's foot is properly seated, the piezoelectric sensor registers a specific pressure signature. The RTOS, executing a simple open-source algorithm, triggers the LRA to produce a short haptic buzz, confirming to the user that the shoe is securely on without them needing to look or feel manually. The code for this haptic feedback loop, along with hardware schematics for integrating common LRA modules, is published on a public code repository, making the addition of this sensory feedback feature obvious.

**3. Combination with Open-Source BLE Protocols for 'Find My Shoe' Functionality:**
*   **Enabling Description:** A low-power System on a Chip (SoC) like the nRF52 series, which supports open Bluetooth Low Energy (BLE) protocols, is integrated directly into the rigid material of the stabilizer during the molding process. The device is programmed with open-source firmware to continuously broadcast a BLE advertising packet, similar to beacon standards like iBeacon or Eddystone. A user can use any generic open-source BLE scanner app on their smartphone to detect the shoe's signal strength, allowing them to locate a misplaced shoe within a room. This combines the shoe's structure with universally accessible, open wireless standards, rendering the addition of a simple location-finding feature obvious.