Obviousness

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.