Functional soles with fusion materials for osteoarthritis

Abstract

There is a need for a sole that provides comfortable wear and reduces medial knee pressure without the need for additional inserts such as wedges. [Solution] A functional sole having a fusion material designed for osteoarthritis is disclosed. The sole according to the present invention comprises heterogeneous materials including a first material portion having a first hardness and a second material portion having a second hardness. The interface between the first material portion and the second material portion has an inclination angle that varies along at least a portion of the longitudinal direction of the sole. This design effectively reduces pain and corrects knee joint misalignment in osteoarthritis.

Description

Technical Field

[0002]

[0001] (Cross - Reference to Related Applications) This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10 - 2024 - 0141821, filed with the Korean Intellectual Property Office on October 17, 2024. The disclosure of the same is incorporated herein by reference in its entirety.

[0002] The present invention relates to a sole containing heterogeneous materials, particularly a functional sole having a fusion material designed for osteoarthritis. More specifically, it relates to a sole composed of two or more materials with different hardnesses, and the interface between these materials is inclined at various angles.

Background Art

[0003] Knee osteoarthritis is suspected when there is knee pain upon standing, tremors in the knee during standing, abnormal sounds when bending or straightening the knee, a knee opening wider than the fist width during standing, severe pain when descending stairs, or long - term pain that persists for several days after walking.

[0004] Also, when the body supports itself on both feet, since the center of gravity passes through the middle between the two feet, a greater load is applied to the medial knee joint than to the lateral knee joint. During single - leg support while walking, the ground reaction force line passes through the center of the foot and the center of the pelvis, and the reaction force moves inward from the center of the knee due to body weight. Therefore, compared to double - leg support, a greater compressive load acts on the medial knee joint. This causes inward rotation of the tibia and femur, repeatedly increasing the load on the medial knee joint during walking, and ultimately gradually leading to the deformation of the legs into an O - shape due to cumulative mechanical stress.

[0005] Conventionally, a wedge has been added to the outer sole of shoes from the outside, and the foot and leg are tilted inward according to the inclination of the insole and the outsole, thereby generating a rotational force that moves the knee joint inward.

[0006] However, this conventional method causes shear forces because the foot slides inward on the inclined sole while walking. To prevent this sliding, excessive force must be applied to the knee and ankle joints, resulting in a heavy load on the inner side of the foot and knee, which exacerbates osteoarthritis of the knee. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Korean Patent Application No. 10-2024-0141821 [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, there is a need for a sole that provides a comfortable fit and reduces medial knee pressure without the need for additional inserts such as wedges.

[0009] The present invention aims to provide a sole that comprises two or more materials having different hardnesses and is designed to have an inclined interface between these materials. [Means for solving the problem]

[0010] To achieve the above objective, one embodiment of the present invention provides a sole comprising a first material portion having a first hardness and a second material portion having a second hardness. The interface between the first material portion and the second material portion has an inclination angle, and the inclination angle varies at least partially along the longitudinal direction of the sole.

[0011] Here, the angle of inclination can vary within the range of 0° to 90° with respect to the horizontal plane.

[0012] In this scenario, the angle of inclination can be maximized in the central region of the sole.

[0013] Furthermore, the first material portion forms the upper layer of the sole, and the second material portion forms the lower layer. In areas where the inclination angle is not 0°, the first material portion of the upper layer is configured not to be exposed on the bottom surface, and the second material portion of the lower layer is configured not to be exposed on the top surface.

[0014] Alternatively, the first material portion may form the upper layer of the sole, and the second material portion may form the lower layer, and in areas where the inclination angle is not 0°, the first material portion of the upper layer may be exposed on the bottom surface, or the second material portion of the lower layer may be exposed on the top surface.

[0015] Here, the first hardness is lower than the second hardness, and due to the inward slope, the first material portion can occupy a larger proportion of the inner region.

[0016] Conversely, the angle of inclination can be minimized in the central region of the sole.

[0017] Furthermore, the interface centerline that intersects all portions of the interface having a varying inclination angle along the longitudinal direction of the sole may coincide with the longitudinal pressure centerline of the sole.

[0018] Furthermore, the interface may have an inclination angle that varies along a transverse direction perpendicular to the longitudinal direction of the sole.

[0019] The sole according to the present invention, comprising two or more fused materials of different hardnesses, forms a continuous hardness distribution through an inclined interface without the irregular sensation associated with a rigid insert by varying the thickness ratio of these materials across the inner and outer regions of the sole. This structure provides a comfortable fit, effectively reduces knee pain, facilitates comfortable walking, and is particularly beneficial for individuals experiencing pain due to osteoarthritis and knee curvature. [Brief explanation of the drawing]

[0020] [Figure 1] This figure shows the coordinate system of the sole as defined by the present invention. [Figure 2]A diagram showing the coordinate system of the sole defined by the present invention. [Figure 3] A diagram showing the sole configurations according to the first and second embodiments of the present invention. [Figure 4] A cross-sectional view showing the sole according to the third, fourth, and fifth embodiments of the present invention. [Figure 5] A cross-sectional view showing the sole according to the sixth embodiment of the present invention. [Figure 6] A cross-sectional view showing the sole according to the seventh embodiment of the present invention. [Figure 7] A cross-sectional view showing the sole according to the eighth embodiment of the present invention. [Figure 8] A diagram showing the sole configurations according to the ninth and tenth embodiments of the present invention. [Figure 9] A diagram showing the effects of the soles according to various embodiments of the present invention.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described in more detail with reference to the drawings. In describing the present invention, detailed descriptions of known functions or configurations that may unnecessarily obscure the gist of the present invention are omitted. The terms used in this specification are defined based on their functionality within the context of the present invention and may vary depending on the intention of the user, the intention of the operator, or the relationship. Therefore, the definitions should be interpreted based on the overall context provided in this specification.

[0022] FIG. 1 and FIG. 2 show the coordinate system defined by the present invention for the sole.

[0023] First, referring to Figure 1, the left sole (100-L) and right sole (100-R) of both feet are shown in plan view. The soles (100-L, 100-R) have a longitudinal direction (30) corresponding to the y-axis direction in the drawing. The soles (100-L, 100-R) have a transverse direction (40) perpendicular to the longitudinal direction and corresponding to the x-axis direction. The soles include an inner side (10) oriented toward the center between the two feet and an outer side (20) oriented toward the outside of the body. As shown in the figure, the left sole (100-L) and the right sole (100-R) are symmetrical. Hereafter, unless otherwise specified, the explanation is based on the left sole (100-L), and it will be clear that the explanation applies equally to the symmetrical right sole.

[0024] Next, referring to Figure 2, the left sole (100-L) is shown oriented so that its side surface faces the y-axis.

[0025] The sole (100-L) includes a bottom surface that contacts the ground, an upper surface that faces the foot or insole, and a side surface that extends as far as the thickness of the sole.

[0026] The sole (100-L) has a thickness direction (50) corresponding to the z-axis direction in the drawing, and the thickness direction can be described as being perpendicular to the ground.

[0027] The sole (100-L) may have various curved surfaces, resulting in a variable thickness along the longitudinal direction (30). Thus, the bottom surface may include concave or protruding regions. Similarly, the top surface may be curved, in particular, having a convex portion supporting the arch or metatarsal region and a concave portion accommodating the heel. Alternatively, the sole (100-L) may have flat top and bottom surfaces, the thickness of which may be uniformly constant along the flat surfaces, or gradually decreasing or increasing. For ease of understanding and explanation, the sole (100-L) will be illustrated and described below as having flat top, bottom, and side surfaces.

[0028] The sole (100-L) can be divided into several regions corresponding to the foot (5). For example, the sole (100) can be divided into a toe region (P1), a forefoot region (P2) extending from the toes to the ball of the foot, a midfoot region (P3) supporting the arch, and a rearfoot region (P4) including the heel.

[0029] Figure 3 shows the configuration of the soles (300, 300') according to the first and second embodiments of the present invention.

[0030] Firstly, the sole according to the present invention comprises dissimilar materials. These dissimilar materials differ in at least hardness. Specifically, the sole comprises a first material portion having a first hardness and a second material portion having a second hardness. Naturally, a third material portion having a third hardness may also be included. Hardness may be substituted for, or considered in conjunction with, other physical properties of the foam, such as elasticity, density, foaming rate, or shrinkage rate.

[0031] Two different materials are combined into a single sole through a manufacturing process. For example, manufacturing may involve placing plastic pellets with different colors, foaming rates, content, or compositions into separate molds, foaming them, and then combining them into a single sole by hot pressing. Thus, the sole comprises a first material portion and a second material portion.

[0032] In another example, the manufacturing method involves processing a sole or sole components from a synthetic resin such as EVA, PU, ​​styrene, or NBR. Sheets or initial products made from these synthetic resins undergo primary processing by cutting, polishing, or similar methods to form multiple intermediate products that are later assembled into a single sole by hot pressing.

[0033] Another manufacturing method involves pouring two different synthetic resin solutions (such as unsaturated resins) into a mold, allowing them to harden to form first and second material components, and then joining or inserting these components to create a single sole.

[0034] The sole includes an interface where a first material portion and a second material portion meet. This interface is a continuous surface adjacent to both material portions and may optionally include an adhesive layer or bonding surface. The interface may extend over the entire area of ​​the sole or over only a portion thereof. For example, the first material portion may extend over both ends, while the second material portion may extend only to the central and rear regions. The interface may be single or multiple and may extend along the entire length of the sole or at least continuously through portions where the angle of inclination changes, as described below.

[0035] Here, the interface has an inclination angle, defined as the angle formed between the interface and the horizontal plane when the sole is laid flat. The inclination angle is defined by the tangent to the interface set in the transverse direction (40) as seen from the cross section of the sole. The inclination angle can vary in the range of 0° to 90° with respect to the horizontal plane.

[0036] Furthermore, the inclination angle changes at least partially along the longitudinal direction of the sole at the interface. In other words, when viewed in cross-section, the thickness ratio of the first material portion to the second material portion changes along the transverse direction due to the inclination angle at a certain point, and these ratios also vary along the longitudinal direction.

[0037] The sole may be used as a midsole made from shock-absorbing foam such as EVA, PU, ​​or rubber, and may be combined in some cases with a harder outsole material such as TPU or rubber on the bottom surface, and a softer insole or sockliner made of PU or EVA on the top surface.

[0038] Referring to Figure 3, the soles (300, 300') according to the first and second embodiments are commonly characterized by interface surfaces (330, 330') whose inclination angle varies along the longitudinal direction. The interface surfaces (330, 330') define the interface centerline, and the soles (300, 300') define the pressure centerline.

[0039] The interface centerline is any line that intersects all portions of the interface (330, 330') where the angle of inclination changes along the longitudinal direction. In the embodiment shown in Figure 3, the interface centerline connects points located at the midpoint of the thickness of the sole (300, 300') on the interface (330, 330'). The interface centerline may be straight or curved. It can also be thought of as the axis of rotation of the inclined boundary line (330, 330') seen in the cross-section along the longitudinal direction. However, the interface centerline may not be the exact midpoint of the sole, but rather connects points located at different thickness ratios within the sole. For example, the interface centerline could connect points located at two-thirds of the height of the sole on the interface.

[0040] The pressure center line, also known as the COP (center of pressure) line, is a line that traces the movement of the center of pressure exerted or applied to the sole during walking. During walking, the left and right feet alternately contact the ground, and the body's center of gravity shifts accordingly. The pressure center line follows a curved path that does not align with the direction of walking, from the initial heel strike to toe-off (stance phase) while the other foot is in the swing phase.

[0041] In the first and second embodiments, the interface centerline connects the points where the thickness ratio of the first material portion (310, 310') and the second material portion (320, 320') is equal (5:5). When the inclination angle is not 0°, the thickness ratio of the first material portion and the second material portion differs on the inside (10) and outside (20) of the sole with respect to the interface centerline. Therefore, by aligning the interface centerline with the pressure centerline, it becomes possible to pre-design the sole hardness based on the ratio of the first and second materials on the inside and outside, centered on the pressure applied by the foot. Specifically, the combined hardness at a point along the pressure centerline where both materials have equal proportions (5:5) can be set as the baseline hardness. Thus, as the proportion of the softer first material increases inward from the pressure centerline, the hardness decreases, while as the proportion of the harder second material increases outward from the centerline, the hardness increases, providing a more rigid external support.

[0042] While the embodiment aligns the interface centerline perfectly with the pressure centerline, the present invention is not limited thereto. The sole can be designed so that only a portion of the interface centerline, such as the central region (P3), aligns with the pressure centerline.

[0043] In the first embodiment, the first material portion (310) forms the upper layer of the sole (300), and the second material portion (320) forms the lower layer of the sole (300). The interface (330) between the first material portion (310) and the second material portion (320) has different inclinations along the longitudinal direction of the sole (300). Referring to Figure 3, the cross-sectional view shown on the right shows sections AA(a1), BB(b1), CC(c1), DD(d1), EE(e1), FF(f1), and GG(g1). The inclination angle at the interface (330) is approximately 0° at the foremost and rearmost points, gradually increasing toward the central region (d1), reaching a maximum, and then gradually decreasing. Small discontinuities due to manufacturing tolerances that maintain a generally continuous surface are within the scope of the present invention.

[0044] Specifically, in the first embodiment, in the region where the inclination angle at the interface (330) is not 0°, the upper first material portion (310) is not exposed to the bottom surface of the sole (300), and the lower second material portion (320) is not exposed to the top surface. In other words, the change in the inclination angle is limited to the thickness of the sole (300), the first material portion (310) completely covers the top surface, and the second material portion (320) completely covers the bottom surface.

[0045] The second embodiment (300') is similar to the first embodiment (300), except that the interface (330') may have a wider range of inclination angles. Referring to Figure 3, the cross-sectional view on the right shows sections AA(a2), BB(b2), CC(c2), DD(d2), EE(e2), FF(f2), and GG(g2).

[0046] Specifically, in the second embodiment, where the inclination angle at the interface 330' is not 0°, the upper first material portion (310') may be exposed to the bottom surface of the sole (300'), or the lower second material portion (320') may be exposed to the top surface. In the section with the largest inclination angle (d2), the first material portion (310') occupies part of the bottom surface, and the second material portion (320') occupies part of the top surface.

[0047] Furthermore, in one embodiment of the present invention, the first hardness of the first material portion (310) of the sole (300) is lower than the second hardness of the second material portion (320). As shown in Figure 3, the interface (330) is inclined inward toward the inside (10). Therefore, the first material portion (310) occupies a larger proportion in the inner region compared to the second material portion (320), while conversely, the second material portion (320) occupies a larger proportion in the outer region. Since the first material has a lower hardness, the sole (300) can be more easily elastically deformed or compressed on the inside, while remaining relatively rigid on the outside.

[0048] In the first and second embodiments, the inclination angle at the interface (330, 330') varies in one cycle, initially increasing and then decreasing. However, the inclination angle may vary over multiple cycles. Furthermore, the inclination angle may vary along the entire length of the sole or along only a portion thereof. For example, referring to Figure 3, the inclination angle may remain at 0° from cross section AA to BB, vary from BB to FF, and return to 0° from FF to GG. Conversely, the inclination angle may vary from 0° to 15° from AA to CC, remain constant from CC to EE, and then vary again from EE to GG.

[0049] Furthermore, Figure 3 shows a sole (300, 300') having a rectangular cross-section and uniform thickness, but this is not limiting. As shown in Figure 2, the sole (300, 300') may have variable thickness and various side configurations along its length. For example, the sides of the sole may have one or more convex ridges or concave grooves, and one or both sides may be inclined at one or more angles with respect to a vertical line.

[0050] Figure 4 is a cross-sectional view showing the soles according to the third, fourth, and fifth embodiments of the present invention.

[0051] Referring to Figure 4a, the sole (400) according to the third embodiment includes a first material portion (410) forming an upper layer and a second material portion (420) forming a lower layer, characterized by an inclined interface (430) between these portions. Unlike the first and second embodiments (e.g., sections (d1) and (d2) of Figure 3), in the third embodiment (400), the first material portion (410) does not reach the bottom surface, but the upper part (421) of the second material portion (420) is exposed on the top surface of the sole (400). In this third embodiment, the harder second material portion (420) completely covers the bottom surface to protect the softer, more wear-prone first material portion (410), preventing the first material portion (410) from being exposed and worn down by contact with the ground.

[0052] Referring to Figure 4b, the sole (400') according to the fourth embodiment includes a first material portion (410') forming an upper layer and a second material portion (420') forming a lower layer, with an inclined interface (430') between them. Unlike the third embodiment, the first material portion (410') in this fourth embodiment has a lower portion (411') exposed to the bottom surface, while the second material portion (420') does not extend to the top surface. In this fourth embodiment, the relatively softer first material portion (410') occupies the entire thickness of the inner (10) along at least a portion of the length of the sole, providing optimal elasticity. Furthermore, since the first material portion (410') completely covers the top surface, it enhances integration with the shoe upper and provides gentle elasticity across the entire foot surface.

[0053] Referring to Figure 4c, the sole (400'') according to the fifth embodiment includes a first material portion (410'') forming an upper layer and a second material portion (420'') forming a lower layer, characterized by an inclined interface (430'') between these portions. In this fifth embodiment, the width (421'') of the second material portion (420'') is greater than the width (411'') of the first material portion (410''). The second material portion (420'') partially encloses the first material portion (410''). The second material portion (420'') forming the lower layer also constitutes the side of the sole. The first material portion (410'') forming the upper layer and having a substantially trapezoidal shape has three faces surrounded by the second material portion (420''). Alternatively, the first material portion (410'') may have a triangular cross-section in which two faces are surrounded by the second material portion (420'').

[0054] The structure of the fifth embodiment allows the harder second material portion (420'') to surround and protect the softer first material portion (410''), thereby providing a stable and robust sole structure.

[0055] Figure 5 is a cross-sectional view showing a sole according to the sixth embodiment of the present invention.

[0056] The sole (500) according to the sixth embodiment includes an interface (530) having a vertical or approximately 90° inclination angle in at least one region, as shown in Figure 5. In this embodiment, at certain points, the first material portion (510) and the second material portion (520) occupy the entire thickness of the sole (500) on the inside (10) and outside (20), respectively, based on the interface centerline or pressure centerline (COP). Thus, the hardness of the sole (500) can be precisely set in these regions.

[0057] Figure 6 is a cross-sectional view showing a sole according to the seventh embodiment of the present invention.

[0058] Referring to Figure 6, the sole (600) has varying thickness along its transverse direction. Specifically, the sole (600) has maximum thickness at the inner and outer edges and minimum thickness in the center, resulting in a concave upper surface that can accommodate the foot.

[0059] In this embodiment, the interface (630) has an inclination angle defined by a tangent that changes across the transverse direction (40). Therefore, the cross-section of the interface (630) may be curved.

[0060] The thickness ratio between the first material portion (610) and the second material portion (620) changes linearly along the thickness direction (50) across the transverse direction (40), but the interface between the first material portion (610) and the second material portion (620) may form a curve in the transverse direction (40).

[0061] Referring particularly to Figure 6, points D1 to D9 on the interface (630) show a linear, gradual change in the thickness ratio between the first material portion (610) and the second material portion (620). For example, between the first material portion (610) and the second material portion (620), D1 corresponds to a thickness ratio of 1:9, D2 to 2:8, D3 to 3:7, D4 to 4:6, D5 to 5:5, D6 to 6:4, D7 to 7:3, D8 to 8:2, and D9 to 9:1. However, since the total thickness of the sole varies along the transverse direction, the displacement in the thickness direction (50) between adjacent points (D1 to D9) is not uniform. Nevertheless, since the ratio of the inner and outer dissimilar materials is symmetrical around point D5, it is possible to effectively design a sole with forces biased inward or outward.

[0062] In the modified embodiment, the seventh embodiment in Figure 6 showed maximum ratios of 1:9 and 9:1. However, if the sole is designed to have an inner portion with a thickness ratio of 0:10 and / or 10:0, the first material portion (610) and / or the second material portion (620) would be exposed on the top and / or bottom surfaces.

[0063] Another modified embodiment may vary the spacing between points D1 to D9 across the transverse direction (40). For example, by decreasing the spacing between points D1 to D8 and increasing the spacing between points D8 and D9, the volume ratio of the first material portion (610) toward the inside of the sole can be further increased.

[0064] Figure 7 is a cross-sectional view showing a sole according to the eighth embodiment of the present invention.

[0065] Referring to Figure 7, the sole (700) comprises a first material portion (710) and a second material portion (720), and the interface (730) between these two portions has an inclination angle that varies over a transverse direction (40) perpendicular to the longitudinal direction (30). The cross section of the interface (730) shown in Figure 7 includes a first inclined portion (731), a second inclined portion (732), and a third inclined portion (733). In this embodiment, the inclination angle (741) of the first inclined portion (731) is smaller than the inclination angle (743) of the third inclined portion (733). Alternatively, the inclination angle (741) of the first inclined portion (731) may be larger than the inclination angle (743) of the third inclined portion (733). The inclination angle of the second inclined portion (732) is approximately 0°. Alternatively, the inclination angle of the second inclined portion (732) may be greater than 0°, but smaller than the inclination angles of the first inclined portion (731) and the third inclined portion (733).

[0066] Figure 8 shows the sole structure according to the 9th and 10th embodiments of the present invention.

[0067] The soles (800, 800') according to the ninth and tenth embodiments include a first material portion (810, 810') and a second material portion (820, 820'). The interface between these portions (830, 830') has an inclination angle that varies along at least a portion of the longitudinal direction (30) of the sole (800, 800').

[0068] Unlike the first and second embodiments (300, 300') in Figure 3, in the ninth and tenth embodiments (800, 800'), the boundary center line intersecting the inclination angle, which varies along the boundary surface (830, 830'), coincides with the geometric center (M) of the sole cross section. Here, the geometric center (M) represents the dimensional center including the horizontal width, vertical height, and cross-sectional area. Thus, the center (M) can be the centroid of the cross section. In these embodiments, the boundary surface (830, 830') intersects with the center of the thickness and / or width of the sole (800, 800').

[0069] Referring to the first column of the right-hand section of Figure 8 for the ninth embodiment (800), sections (h1) to (l1) represent the HH, II, JJ, KK, and LL sections, respectively. In the ninth embodiment (800), the inclination angle of the interface (830) is smallest in the central region (P3) of the sole (800). In this embodiment, the inclination angle of the interface (830) is largest (90° or nearly 90°) in the section (h1) of the foremost toe region (P1) and the section (l1) of the rearmost hindfoot region (P4), while it is smallest (0° or nearly 0°) in the central region (P3). In this ninth embodiment (800), the inclination angle of the interface (830) is also inclined inward (10).

[0070] Referring to the second column of the right-hand section in Figure 8 for the tenth embodiment (800'), sections (h2) to (l2) represent sections HH, II, JJ, KK, and LL, respectively. The tenth embodiment (800') is very similar to the second embodiment (300'), except that the interface centerline coincides with the geometric center of the sole. The inclination angle of the interface (830') starts at 0° or nearly 0° in the front region, reaches a maximum (90° or nearly 90°) in the middle region, and returns to 0° or nearly 0° in the rear region.

[0071] In the ninth and tenth embodiments (800, 800'), the interface centerlines are aligned with the midpoints dividing the sole width, but the present invention is not limited thereto. The interface centerlines may simply pass straight along the longitudinal direction (30), or they may be inclined obliquely with respect to the longitudinal direction. Furthermore, in modified examples, the interface centerlines may move along the transverse direction (40), the thickness direction (50), or a combination of both directions obliquely across the cross section.

[0072] Figure 9 shows the effects of the sole according to various embodiments of the present invention.

[0073] Referring to Figure 9, a cross-section of a left foot sole (900) is shown, comprising a first material portion (910) and a second material portion (920), each having an inwardly inclined interface (930). The first hardness of the first material portion (910) is lower than the second hardness of the second material portion (920). Due to the inward inclination, the first material portion (910) occupies a larger proportion on the medial side (10) compared to the second material portion (920). As a result, when weight is applied, the medial side of the sole (900) is compressed more than the lateral side, allowing the foot and knee to move inward and reducing pressure on the medial knee joint, which is generally associated with O-shaped legs. Furthermore, during movement such as walking, the corrective effect resulting from the inward movement of the knee distributes impact over a wider range of the knee, reducing pain.

[0074] Furthermore, the inclination angle of the interface (930), which continuously varies along the longitudinal direction (30), gradually changes the ratio of the first material portion (910) and the second material portion (920) along the inner and outer sides of the sole (900), minimizing the feeling of foreign body or discomfort under the foot. Thus, the sole (900) can provide uniform support in the flat areas corresponding to the forefoot region (P2) and hindfoot region (P4), as well as asymmetrical support in the thicker area corresponding to the midfoot region (P3), which can be adjusted to suit individuals with osteoarthritis of the knee.

[0075] Conversely, unlike embodiments designed for O-shaped legs with concentrated pressure on the medial knee joint, if the first hardness of the first material portion is higher than the second hardness, or if the interface is inclined outward (20), the sole can reduce pressure on the lateral knee joint associated with X-shaped legs by spreading the foot and knee outward.

[0076] A method for manufacturing a sole containing different materials according to other embodiments of the present invention is also disclosed. Such a sole can correspond to any of the first to ninth embodiments described above.

[0077] The first manufacturing method involves placing plastic pellets into two different molds (e.g., injection molds), foaming them, and combining the foamed intermediates into a single sole by hot pressing. The plastic pellets may be of different materials or have different foaming rates depending on the shape of the mold to achieve varying hardness for the first and second material parts.

[0078] The second manufacturing method includes injecting different synthetic resin solutions into two separate molds, curing them to form first and second material components, removing these cured components from the molds, optionally trimming their initial forms, and then joining or inserting these components to form a sole.

[0079] A third manufacturing method includes providing foamed sheets of a first material and a second material having different hardnesses. These materials may be EVA foams having different foaming rates or porosity.

[0080] Next, this method involves cutting each foam sheet to a size larger than the final sole. The cutting can be done using a cookie cutter-like shaping tool, followed by trimming with a grinder.

[0081] This method then involves placing the cut intermediate components of the first and second materials into a sole mold and forming a single sole via hot pressing.

[0082] The joining of the first and second materials by hot pressing described above can be combined with or replaced by other bonding methods, such as fusion welding or cement bonding using neoprene adhesive.

[0083] While preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to these specific embodiments. Various modifications and alternative embodiments within the scope of the claims are possible, and such modifications should not be construed as separate from the technical spirit or scope of the present invention.

Claims

1. A sole comprising a plurality of different materials, wherein the sole includes a first material portion having a first hardness and a second material portion having a second hardness, and the interface between the first material portion and the second material portion has an inclination angle, and the inclination angle varies along at least a portion of the interface in the longitudinal direction of the sole.

2. The sole according to claim 1, wherein the angle of inclination varies between 0° and 90° with respect to the horizontal plane.

3. The sole according to claim 2, wherein the first hardness is lower than the second hardness, and due to an inward inclination angle, the first material portion occupies a larger proportion than the second material portion in the inner region.

4. The sole according to claim 3, wherein the angle of inclination is maximum in the central region of the sole.

5. The first material portion forms the upper layer of the sole, The second material portion forms the lower layer of the sole, The sole according to claim 4, wherein in the region where the inclination angle is not zero, the upper first material portion is not exposed to the bottom surface of the sole, and the lower second material portion is not exposed to the top surface of the sole.

6. The first material portion forms the upper layer of the sole, The second material portion forms the lower layer of the sole, The sole according to claim 4, wherein in the region where the inclination angle is not zero, the upper first material portion is exposed on the bottom surface of the sole, or the lower second material portion is exposed on the top surface of the sole.

7. The sole according to claim 2, wherein the angle of inclination is minimized in the central region of the sole.

8. The sole according to claim 1, wherein the interface surface whose inclination angle varies along the longitudinal direction of the sole, and the interface surface center line intersecting it, coincide with the pressure center line in the longitudinal direction of the sole.

9. The sole according to claim 1, wherein the interface has an inclination angle that varies along a transverse direction perpendicular to the longitudinal direction of the sole.

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