Patent Description:
Style and comfort do not always go hand in hand. This is especially true when it comes to women's footwear. High heels, though a mainstay in most women's closets, fall short of being reasonably designed footwear. The height difference between the front and rear of these shoes causes wobbling and slipping even on unadorned, planar surfaces. Despite this, women continue to wear these fashion statements even though the original purpose of high heels, that of helping a rider secure their stance in the stirrups so they could shoot arrows more effectively from horseback, no longer exists. Through the years, high heels evolved into stilettos and pumps and have succumb to iconic branding such that many see such shoes as status symbols for success and perhaps femininity.

Unfortunately, continued use of elevated footwear leads to a plethora of physical problems manifesting itself in such things as planter fasciitis and neuroma while affecting other areas of the body such as the calves, knees and lower back. The American Podiatric Medical Association reports that women have four times as many foot issues as do men. High heels are dangerous to walk in and are subject to immediate frictional engagement with sidewalk grates and the like. The most common complaint about high heels is that they are slow and uncomfortable to walk in. For this reason, many working women carry a second pair of shoes, ones with a low heel or a shoe of a walking/running variety, to get them to and from the workplace. Since shoes accumulate dirt in use, this strategy not only requires one to carry a second set of shoes, it also requires a bag in which to transport them. For most women who carry a purse, this means both arms are full. The situation is worsened if there is a personal computing device such as a laptop computer or tablet that also must be transported daily to work.

Accordingly, a single pair of shoes that could be converted between a fashionable high and a comfortable low heel would fulfill a long felt need in the footwear industry. This new invention utilizes and combines known and new technologies in a unique and novel configuration to develop a convertible shoe that overcomes the aforementioned problems and provides a solution to a common workplace dilemma.

<CIT> discloses an article of footwear according to the preamble of claim <NUM>.

The invention is defined by an article of footwear as disclosed in claim <NUM>.

The present disclosure provides systems, apparatuses, and methods relating to the construction of footwear, including convertible footwear.

Features, functions, and advantages may be achieved independently in various embodiments of the present disclosure, or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

Various aspects and examples of a shoe that is convertible between high-heel and low-heel modes, as well as related methods, are described below and illustrated in the associated drawings. Unless otherwise specified, a convertible shoe in accordance with the present teachings, and/or its various components may, but are not required to, contain at least one of the structures, components, functionality, and/or variations described, illustrated, and/or incorporated herein. Furthermore, unless specifically excluded, the process steps, structures, components, functionalities, and/or variations described, illustrated, and/or incorporated herein in connection with the present teachings may be included in other similar devices and methods, including being interchangeable between disclosed embodiments. The following description of various examples is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. Additionally, the advantages provided by the examples and embodiments described below are illustrative in nature and not all examples and embodiments provide the same advantages or the same degree of advantages.

This Detailed Description includes the following sections, which follow immediately below: (<NUM>) Definitions; (<NUM>) Overview; (<NUM>) Examples, Components, and Alternatives; (<NUM>) Illustrative Combinations and Additional Examples; (<NUM>) Advantages, Features, and Benefits; and (<NUM>) Conclusion.

The following definitions apply herein, unless otherwise indicated.

"Comprising," "including," and "having" (and conjugations thereof) are used interchangeably to mean including but not necessarily limited to, and are open-ended terms not intended to exclude additional, unrecited elements or method steps.

Terms such as "first", "second", and "third" are used to distinguish or identify various members of a group, or the like, and are not intended to show serial or numerical limitation.

"Resilient" describes a material or structure configured to be deformed elastically under normal operating loads (e.g., when compressed) and to return to an original shape or position when unloaded.

"Rigid" describes a material or structure configured to be stiff, non-deformable, or substantially lacking in flexibility under normal operating conditions.

"AKA" means "also known as," and may be used to indicate an alternative or corresponding term for a given element or elements.

Directional terms, such as "inboard," "outboard," "front," and "rear" (and the like) are intended to be understood in the context of the article of footwear on or in which components described herein may be mounted or otherwise attached. For example, "outboard" may indicate a relative position that is laterally farther from the centerline of a shoe, or a direction that is away from the shoe's longitudinal centerline. Conversely, "inboard" may indicate a direction toward the centerline, or a relative position that is closer to the centerline. Similarly, "forward" or "front" means toward the toe portion of the footwear, and "rear" or "back" means toward the heel portion of the footwear. Similarly, the term "longitudinal" generally refers to the heel-to-toe (length) direction of the footwear, while the term "lateral" generally refers to the side-to-side (width) direction of the footwear. In the absence of a host article of footwear, the same directional terms may be used as if the article were present. For example, even when viewed in isolation, a component may have a "forward" side, based on the fact that the component would be installed with the side in question facing in the direction of the toe portion of a shoe.

"Coupled" means connected, either permanently or releasably, whether directly or indirectly through intervening components.

The following terms relate to portions of a shoe or other article of footwear:.

In general, convertible footwear as disclosed herein may include a heel attachment mechanism that allows heel portions to be easily interchanged by the user, thereby converting the footwear between high-heel and low-heel configurations or modes. Footwear of the present disclosure may include an upper attached to a sole via one or more clamp plates. For example, a toe strap may be attached to the sole via one or more crescent-shaped clamp plates received in recesses on a toe-end of the sole. A heel strap may be attached to the sole via a U-shaped clamp plate received in a recess on a heel-end of the sole. In some examples, the recesses are configured such that, when a clamp plate is received therein, a top surface of the clamp plate is flush with a top surface of the sole.

The following sections describe selected aspects of exemplary convertible shoes, as well as related systems and/or methods. The examples in these sections are intended for illustration and should not be interpreted as limiting the entire scope of the present disclosure. Each section may include one or more distinct embodiments or examples, and/or contextual or related information, function, and/or structure.

As shown in <FIG>, this section describes an illustrative convertible shoe <NUM>. Shoe <NUM> is another example of the convertible shoe described in the Overview above.

<FIG> is a partially exploded isometric view of shoe <NUM>. Shoe <NUM> includes a sole <NUM> and a number of interchangeable heel portions that are releasably securable to the sole. In the present example, shoe <NUM> includes a high heel portion <NUM> and a low heel portion <NUM> (see <FIG>), also referred to as a tall heel portion and a short heel portion, respectively. Shoe <NUM> may also include an upper having suitable portions configured to hold the shoe on a foot of the user. For example, shoe <NUM> may include a toe strap <NUM> and a heel strap <NUM>.

Sole <NUM> includes an insole portion <NUM> generally layered atop an outsole portion <NUM> (see <FIG>). The insole portion and outsole portion may each comprise any suitable materials, such as varieties of thermoplastic polyurethane (TPU). In general, outsole portion <NUM> may include a tougher, less resilient material than insole portion <NUM>, e.g., for wear-resistance. Insole portion <NUM> may include a softer, more resilient material than outsole portion <NUM>, e.g., for comfort. In some examples, outsole portion <NUM> includes a more rigid TPU than insole portion <NUM>, such that chemically speaking the TPU of the outsole has a greater ratio of hard to soft segments than the TPU of the insole. Insole portion <NUM> may be referred to as a soft sole. In some examples, sole <NUM> includes more or fewer layers than the two layers described in this example. Hardness examples of various portions of shoe <NUM> are discussed in more depth below.

Portions of the upper are secured to sole <NUM> by one or more clamp plates. For example, toe strap <NUM>, heel strap <NUM>, and/or other components are secured to sole <NUM> by one or more clamp plates. As shown in <FIG>, clamp plates <NUM>, <NUM> and corresponding recessed clamp plate receivers <NUM>, <NUM> are utilized on a front (i.e., toe) end of the sole. Each clamp plate <NUM>, <NUM> includes a plurality of pins and/or other suitable protrusions configured to pass through corresponding apertures in toe strap <NUM>. In some examples, clamp plates <NUM> and <NUM> are crescent-shaped. The pins are further configured to mate with receiving holes in the corresponding clamp plate receivers <NUM> and <NUM> to secure the toe strap to the shoe.

Similarly, clamp plate <NUM> and corresponding recessed clamp plate receiver <NUM> are utilized on a rear (i.e., heel) end of the sole. Clamp plate <NUM> includes a plurality of pins and/or other suitable protrusions configured to pass through corresponding apertures in heel strap <NUM>. The pins are further configured to mate with receiving holes in clamp plate receiver <NUM>, which is disposed at a heel end of the sole.

In this example, clamp plate <NUM> is substantially U-shaped or C-shaped and configured to circumferentially conform to at least a portion of the heel end of the sole. This configuration enables the attachment of a closed-back upper (e.g., heel strap <NUM>).

In addition to the clamp plates and receivers, the attachment of an upper to sole <NUM> may include the use of bonding, adhesive, and/or any other suitable fasteners. For example, one or more of the clamp plates may be attached to the corresponding receiver(s) by adhesive as well as by the pins and receiving holes described above.

In addition to securing the upper to sole <NUM>, clamp plates and receivers increase the stability of the layered sole by preventing lateral movement of the layers relative to each other. In other words, by extending into the holes of the receiver, e.g., in a friction fit, the pins of the clamp plate prevent movement orthogonal to the length of the pins.

In some examples, a single clamp plate and/or a single clamp plate receiver are disposed at a toe portion of the shoe. That is, a single plate may be used instead of the pair of plates <NUM>, <NUM>, and/or a single receiver may be used instead of receivers <NUM>, <NUM>. Additionally, or alternatively, two or more clamp plates and/or two or more receivers may be used at a heel portion of the shoe in place of plate <NUM> and receiver <NUM>.

<FIG> depicts shoe <NUM> having clamp plates <NUM>, <NUM>, and <NUM> in an unattached configuration. Clamp plate receivers <NUM>, <NUM>, and <NUM> are each disposed in a respective recess of sole <NUM>. In this example, clamp plate receivers <NUM> and <NUM> are disposed on an upper surface of outsole <NUM>. Insole <NUM> has corresponding cutouts formed on peripheral edges of the insole to allow clamp plates <NUM> and <NUM> to mate with clamp plate receivers <NUM> and <NUM>, such that top surfaces of the clamp plates lie flush (or substantially flush, or even) with a top surface of the insole (see <FIG>).

Similarly, clamp plate receiver <NUM> is recessed in sole <NUM>. In this example, clamp plate receiver <NUM> is formed as part of a heel attachment mechanism <NUM>, described in more depth below and depicted in <FIG> and <FIG>. Insole <NUM> and outsole <NUM> each have a peripheral cutout (AKA carveout) on the heel side to accommodate clamp plate <NUM>, such that the top surface of clamp plate <NUM> lies flush (or substantially flush, or even) with a top surface of insole <NUM> when the clamp plate is attached to clamp plate receiver <NUM>.

As shown in <FIG>, when clamp plates <NUM>, <NUM>, and <NUM> are attached to their corresponding clamp plate receivers, gaps are formed between the bottom surfaces of the clamp plates and the corresponding top surfaces of the clamp plate receivers to accommodate portions of an upper. The length of the protrusions of the clamp plates may be selected such that the gaps are configured to accommodate an upper of a desired thickness and/or material. For example, the gaps may be configured to accommodate an upper comprising leather, vinyl, fabric, and/or any other suitable material. In some examples, the protrusions are shorter than the depth of the corresponding receiver holes. This may facilitate an increased clamping strength.

In this example, insole portion <NUM> includes an extension or enlargement in the form of a ridged or toothed cushion <NUM> disposed in a region of the insole where a user's metatarsophalangeal (MTP) joints (i.e., the heads of the metatarsal bones) would typically exert pressure. Cushion <NUM> may comprise the relatively soft and/or resilient material of insole portion <NUM>, and may be unitary with the insole portion. As depicted in this example, cushion <NUM> mates with (i.e., is received by) a corresponding cushion receiver <NUM> disposed in outsole portion <NUM>. Cushion receiver <NUM> includes complementary ridges or teeth configured to engage the teeth of cushion <NUM> for security and resilience. Accordingly, a thicker portion of the insole extends into a recess of the outsole in a region of the sole corresponding to metatarsophalangeal joints of a user.

As shown in <FIG>, a heel attachment mechanism <NUM> is included in shoe <NUM>. Heel attachment mechanism <NUM> may include any suitable structure and/or device configured to releasably secure a heel portion to the sole. For example,.

In this example, heel attachment mechanism <NUM> includes a heel receiver <NUM> (AKA a hard sole or hard rear portion). Heel receiver <NUM> is affixed to sole <NUM> using any suitable fastener (e.g., by an adhesive). Here, heel receiver <NUM> is affixed to outsole <NUM> by a plurality of pins or protrusions <NUM> formed in heel receiver <NUM> and configured to mate with receiving holes <NUM> in outsole <NUM>. Additionally, outsole <NUM> has a plurality of pins or protrusions <NUM> configured to mate with receiving holes <NUM> in heel receiver <NUM>. The inclusion of protrusions <NUM> and <NUM> and holes <NUM> and <NUM> on heel receiver <NUM> and outsole <NUM> increases the robustness of heel attachment mechanism <NUM> and enables shoe <NUM> to withstand the forces involved with standing and walking for prolonged times without failure of the heel portions or heel receiver.

Furthermore, in this example, a recess <NUM> is formed in an upper surface of heel receiver <NUM>. A corresponding block <NUM> is formed on or coupled to a bottom surface of outsole <NUM>. Block <NUM> is configured to mate with recess <NUM>, thereby further increasing the security of heel receiver <NUM>.

Alternate embodiments of the outsole and heel receiver, namely heel receiver 546B and outsole 514B, are depicted in <FIG>. Outsole 514B and heel receiver 546B may be substantially similar to outsole <NUM> and heel receiver <NUM>, respectively, except for the differences described below. The features of heel receiver 546B and outsole 514B may be included one or more embodiments of shoe <NUM>.

Outsole 514B includes a slot or space <NUM> configured to accommodate an extension or tongue portion <NUM> of heel receiver 546B. Outsole 514B additionally includes a protective cover <NUM> proximate space <NUM> configured to cover the interface between outsole 514B and heel receiver 546B. This configuration provides increased rigidity in the bottom of shoe <NUM>, e.g., to further withstand the forces involved with prolonged standing and walking. Tongue portion <NUM> includes a curved section configured to follow the curve of shoe <NUM> below the region where the user's MTP joints typically exert pressure. The curved section allows for tongue portion <NUM> to extend further towards the toe-end of shoe <NUM> and accommodate the general curve of sole <NUM>.

When assembled, heel receiver 546B interlocks with outsole 514B such that tongue portion <NUM> is received by (and housed within) space <NUM>.

Returning to <FIG> and <FIG>, heel receiver <NUM> includes a fixed hook portion <NUM> which extends from a base <NUM> of the heel receiver, a movable hook portion <NUM> disposed opposite the fixed hook portion, and an actuator <NUM> configured to move the movable hook portion between a retracted position and an extended position. As shown in the drawings, a wedge <NUM> extends from heel receiver <NUM> between fixed hook portion <NUM> and movable hook portion <NUM>. Wedge <NUM> may have one or more protrusions formed as triangular prisms disposed on outboard sides of the wedge to increase rigidity and decrease lateral motion of the heel portion (e.g., when the wedge is received in a corresponding recess of the heel portion, described below).

Hook portions <NUM> and <NUM> may be oriented in any suitable direction. Here, fixed hook portion <NUM> faces toward the rear of the shoe, and movable hook portion <NUM> faces toward the front of the shoe. Movable hook portion <NUM> is biased toward the extended (e.g., forward) position. Any suitable biasing device may be used (see below).

Actuator <NUM> is operatively connected to movable hook portion <NUM>, such that operation (e.g., manual operation) of actuator <NUM> against the force of the biasing device causes the movable hook to retract. In this embodiment, actuator <NUM> is of a single piece with movable hook portion <NUM>. Specifically, the combined movable hook portion <NUM> and actuator <NUM> includes a generally triangular manual handle <NUM>, textured for enhanced grippability, as well as an elongate body <NUM> on which is formed a hook <NUM> and an integral spring member <NUM>. Manual handle <NUM> is exposed on the underside of the shoe, and accessible by the user.

Body <NUM> has a generally planar top, configured to slide while in contact with an underside of the outsole. A rear portion of body <NUM> is received in a cavity <NUM> formed in heel receiver <NUM>, such that spring member <NUM> is disposed in cavity <NUM>, and is in contact with a wall of the cavity. In this example, spring member <NUM> is substantially as described above with respect to spring member <NUM>. For example, spring member <NUM> includes a plurality of resilient fingers or protrusions extending generally sideways (e.g., laterally) across the rear of body <NUM>, such that distal ends of the resilient fingers are spaced from the rear of the body.

Actuator <NUM> and movable hook <NUM> are guided and retained against outsole portion <NUM> by a pair of side guides <NUM> and a retainer bar <NUM>, although any suitable retainer/guide mechanism may be utilized.

Heel portions <NUM> and <NUM> include respective upper mounting surfaces <NUM>, <NUM> for attaching the respective heel portion to heel receiver <NUM>. Upper mounting surface <NUM> includes a first recess <NUM> configured to engage fixed hook portion <NUM>, and a second recess <NUM>, configured to engage movable hook portion <NUM>. Similarly, upper mounting surface <NUM> includes a first recess <NUM> configured to engage fixed hook portion <NUM>, and a second recess <NUM> configured to engage movable hook portion <NUM>. Accordingly, heel portion <NUM> or <NUM> is secured to the heel receiver when the movable hook portion is in the extended position. The heel portion is releasable from the heel receiver when the movable hook portion is in the retracted position.

Each of upper mounting surfaces <NUM> and <NUM> further includes a respective wedge receiver <NUM>, <NUM>. Each of these wedge receivers is configured to snugly mate with wedge <NUM> of the heel receiver. Specifically, installing heel portion <NUM> or <NUM> onto the heel receiver causes wedge <NUM> to mate with receiver <NUM> or <NUM>, adding further security and stability to the heel-shoe connection.

In operation, shoe <NUM> may be converted between two or more interchangeable heels (e.g., heel portions <NUM>, <NUM>).

Turning now to <FIG>, an example of shoe <NUM> is configured to be transitionable between first (heel raised) and second (heel lowered) states A and B. In first state A, shoe <NUM> has a first shape or configuration, and in second state B, shoe <NUM> has a second shape or configuration. The first shape is generally more curved or bent than the second shape. As shown in <FIG>, shoe <NUM> in the first shape (state A) curves and/or bends at a bending region disposed at a generally midfoot portion of the sole (e.g., near adjacent a user's MTP joints, and/or at any other suitable part of the shoe). In the first shape the sole is bent at an obtuse angle such that the sole is divided into a generally planar toe portion and a generally planar heel portion. In the second shape (state B), shoe <NUM> has a less curved and/or a substantially flat shape, as shown in dashed lines in <FIG>.

Sole <NUM> is formed in particular to bias shoe <NUM> toward state A, such that sole <NUM> has a shape memory of state A. In other words, state A is a default state or shape of the sole, and sole <NUM> comprises suitable resilient material(s) in suitable configuration(s) for urging the shoe into or toward state A if displaced. For example, the layers of sole <NUM> may be formed (e.g., 3D printed, extruded, etc.) in the bent configuration of state A, with materials of differing hardness (and therefore differing resilience). In some examples, the following materials (or the like) may be used: heel receiver <NUM> may be formed with TPU having a hardness (i.e., Shore durometer) of 90D, outsole portion <NUM> may be formed with TPU having a hardness of 80A, and insole portion may be formed with TPU having a hardness of 35A. This layering of softer materials onto harder materials imparts an overall resilience to sole <NUM>, biasing the sole toward state A.

If a downward force flattens sole <NUM> with respect to state A, the configuration of the resilient layers urges the sole back to state A. Additionally, the plurality of pins or protrusions securing the layers of sole <NUM> to each other restricts the layers from sliding or shifting with respect to each other, thereby increasing tension (e.g., in the form of elastic and/or shear strain) in the plurality of pins or protrusions when the sole is deformed from state A. The tension built in the plurality of pins or protrusions complements the resilience of the material, further biasing shoe <NUM> back toward state A.

The natural resting state (state A) of sole <NUM> corresponds to the high-heeled configuration of shoe <NUM> described above, even when the shoe is in a low-heeled configuration. In other words, the bend/curve of the sole at the generally midfoot portion corresponds to the natural shape of the sole in the high-heeled configuration. Any downward force on the sole while in the high-heeled configuration is countered by an upward force from high heel portion <NUM>, thereby maintaining shoe <NUM> in state A. When shoe <NUM> is transitioned to the low-heeled configuration (i.e., when low heel portion <NUM> is attached), sole <NUM> remains biased to maintain state A.

Shoe <NUM> can be forced from state A to state B by a suitable force or pressure. For example, if a toe portion of shoe <NUM> is held in a fixed position (e.g., between a wearer's foot and the ground), a sufficient downward force applied to sole <NUM> to the rear of the bending region (e.g., by the wearer's heel) causes the shoe to assume state B. In the absence of such a downward force (e.g., if the wearer's heel is lifted), the resiliency (e.g., bias) of sole <NUM> urges shoe <NUM> from state B to state A. In the context of a walking gait, first state A corresponds to a state of shoe <NUM> after a user has released the downward force of their foot, such as during a swing phase of the gait (e.g., when the shoe is spaced from the ground). Second state B corresponds to a state of shoe <NUM> while a user presses down on a rear or midfoot portion of the shoe (i.e., applying a downward force with at least their heel), such as during a stance phase of the gait. As the user walks, each foot typically alternates between the swing phase and the stance phase, thereby causing shoe <NUM> to alternate between state A and state B.

In a typical walking gait, an initial contact phase (i.e., heel strike) of the gait occurs when the heel strikes the ground and begins a rotational transition to a mid-stance of the stance phase. In mid-stance, a bottom surface of the heel of shoe <NUM> and the ground-contacting, toe-end bottom surface of outsole <NUM> are substantially coplanar with the ground. During the transition from initial contact to mid-stance, sole <NUM> of shoe <NUM> transitions (e.g., at least partially flattens) from state A to state B. During this transition, the bottom surface of the user's foot remains in contact with the top surface of insole <NUM> (e.g., as the foot pushes the sole toward the ground).

As the user continues through the walking gait (i.e., during the swing phase and heel strike of the contralateral leg), a corresponding transition from mid-stance to a terminal stance occurs. The transition from mid-stance to terminal stance corresponds to the user shifting their center of mass forward and lifting their heel from the ground. During this transition, shoe <NUM> transitions from state B to state A as the heel of the shoe lifts from the ground, due to the resilience of sole <NUM>. The toe-end of outsole <NUM> remains planted on the ground. The spring-bias of sole <NUM> allows the bottom surface of the user's foot to remain in contact with the top surface of insole <NUM>. Said another way, the spring-bias of sole <NUM> automatically causes the top surface of insole <NUM> to remain substantially in contact with the user's foot, as opposed to simply flapping up and down in a hinging action.

Shoe <NUM> remains in state A during the entirety of the swing phase of the gait (i.e., while the user's foot is lifted off the ground), before the heel strikes the ground again (i.e., during the next stride's initial contact). This transition between state A and state B while walking advantageously provides continuous contact between the bottom of the user's foot and shoe <NUM>. Due to the resilience of sole <NUM>, this continuous contact occurs even in the absence of a heel-end upper, for example heel strap <NUM>. Common examples of a shoe having only a toe-end upper are sandals, flip flops, etc. In known examples of footwear having no heel-end upper, as a user walks, the heel end of the shoe separates from the user's foot as they step forward, and subsequently flaps against the bottom of the foot. In contrast, the bias of shoe <NUM> toward state A enables the bottom of the user's foot to remain in continuous contact with the shoe during walking, even in the absence of a heel-end upper.

The different embodiments and examples of the convertible footwear described herein provide several advantages over known solutions. For example, illustrative embodiments and examples described herein allow simple and secure interchange of different-height heels.

Additionally, and among other benefits, illustrative embodiments and examples described herein improve the user experience by maintaining contact with the bottom of the user's foot while walking, even in the absence of a heel-end securing mechanism.

Additionally, and among other benefits, illustrative embodiments and examples described herein provide a simple yet secure connection between the sole and the upper, and a method for providing that secure connection during shoe construction.

No known system or device can perform these functions. However, not all embodiments and examples described herein provide the same advantages or the same degree of advantage.

Claim 1:
An article of footwear (<NUM>), comprising:
a sole (<NUM>) having an insole (<NUM>) and an outsole (<NUM>), and an outer layer on a rear portion of the outsole, wherein the outer layer is not present on a toe portion of the outsole, and wherein the outer layer is more rigid than the outsole; and
an upper, characterized in that the upper is clamped to the sole by one or more clamp plates (<NUM>, <NUM>, <NUM>)
wherein each of the one or more clamp plates includes first mating features configured to mate with corresponding second mating features in the sole via corresponding apertures in the upper;
wherein the one or more clamp plates include a U-shaped heel clamp plate configured to fit into a corresponding U-shaped recess in a heel end of the sole, such that a top surface of the heel clamp plate is flush with a top surface of the sole.