US20200163404A1

US20200163404A1 - Strap securing structure of footwear article

Info

Publication number: US20200163404A1
Application number: US16/258,682
Authority: US
Inventors: Cheng-Shu Lien; Chin-Ru Liu
Original assignee: International C & J Ltd
Current assignee: International C & J Ltd
Priority date: 2018-11-22
Filing date: 2019-01-28
Publication date: 2020-05-28
Also published as: TW202019310A

Abstract

An article of sandal includes a sole structure and a strap secured on the sole structure. The sole structure has an upper surface and a lower surface and an aperture penetrating through the sole structure and exposing an engaging surface between the upper surface and the lower surface of the sole structure. The strap is secured on the upper surface of the sole structure by having a joining plug assembled in the aperture. The joining plug has a blocking portion and a pillar portion connected to a top surface of the blocking portion. The top surface of the blocking portion has a plurality of protrusions that are in direct contact with the engaging surface of the sole structure.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally related to a footwear article, and more particularly related to a strap securing structure of a sandal.

2. Description of the Prior Art

A sandal is a type of footwear usually includes a strap secured on a sole structure to provide a room for accommodating the foot and retaining the sandal on the foot of the wearer. The sole structure of the sandal is therefore positioned between the foot and the ground to protect the foot from directly contacting the ground and also attenuate ground reaction force and lessen stresses the foot and leg bearing during walking, running and other ambulatory activities. Due to these advantages such as easy to wear, quick drying, simple structure and easy to clean, sandals have been widely used by people in their daily lives, especially in the occasions need temporary wearing, such as in the hospital, in the hotel or at the beach.
The flip-flop is a kind of sandal including a Y-shaped strap secured to the sole structure. Typically, the Y-shaped strap of a flip-flop usually includes a toe post secured to a fore portion of the sole structure corresponding to the position between the big toe and the next toe of the foot and two sidebands joined at the toe post, extended oppositely and secured to the two side portions of the sole structure respectively corresponding to the inner arch and the outer arch of the foot. One conventional method to secure the Y-shaped strap to the sole structure is by inserting the joining plugs formed at the terminals of the Y-shaped strap through the corresponding apertures in the sole structure and using the apertures to obstructing the joining plugs from being pulled back.
To provide better wearing comfort and reduce manufacturing cost, the strap and the sole structure are usually formed from elastic or flexible plastic materials which are easy to produce in mass production, such as ethylene vinyl acetate (EVA), rubber, polyvinyl chloride (PVC) or thermoplastic polyester elastomer (TPE). However, the elasticity and flexibility of the plastic materials may adversely result in deformation of the joining plugs of the strap and/or the apertures of the sole while being stressed during the activity of the wearer. This may result in unexpected disassembly of the strap and the sole structure and may cause the wearer to fall down during activity. Therefore, there is still a need in the field to provide an improved strap securing structure which may avoid the aforesaid problem.

SUMMARY OF THE INVENTION

In light of the above, the present invention is directed to provide a strap securing structure of a sandal which may avoid the aforesaid problem. The trap securing structure according to the present invention may better secure the strap to the sole structure and be formed integrally with the strap without increasing the manufacturing complicity. The wearing comfort and stability may be simultaneously guaranteed.
According to an embodiment, an article of sandal is disclosed. The article of sandal includes a sole structure having an upper surface and a lower surface and an aperture penetrating through the sole structure and exposing an engaging surface between the upper surface and the lower surface of the sole structure. A strap is secured on the upper surface of the sole structure by a joining plug thereof assembled in the aperture. The joining plug has a widened blocking portion and a pillar portion connected to a top surface of the blocking portion. The top surface of the blocking portion has a plurality of protrusions that are in direct contact with the engaging surface of the sole structure.
It is one feature of the present invention that by forming a plurality of protrusions on the top surface of the blocking portion that are in direct contact with the engaging surface of the sole structure, the friction between the top surface of the blocking portion of the joining plug and the engaging surface of the sole structure may be increased, which may prevent the joining plug from being disassembled from the aperture of the sole structure while being forced to pull away from the upper surface of the sole structure during the activity of the wearer. A better secured assembly of the strap and the sole structure is therefore obtained. Furthermore, the joining plug having protrusions may be integrally formed with other portions of the straps without increasing the cost and complexity of the manufacturing process.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description, embodiments of the present invention will be explained on the basis of the drawings, in which:

FIG. 1 is a perspective view of a flip-flop according to an embodiment of the present invention;

FIG. 2 is an exploded perspective view of a flip-flop according to an embodiment of the present invention;

FIG. 3 is an enlarged perspective view of a joining plug of a strap of a flip-flop according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a sole structure of a flip-flop according to an embodiment of the present invention, wherein the upper portion of FIG. 4 is a perspective bottom view of the sole structure, and the lower portion of FIG. 4 is a cross-section view of an aperture of the sole structure along the line A-A′ shown in the upper portion of FIG. 4;

FIG. 5 and FIG. 5A are a schematic cross-section diagrams respectively showing the assembly of a joining plug and an aperture of a sole structure of a flip-flop according to an embodiment of the present invention; and

FIG. 6 shows some modifications of the joining plug of as shown in FIG. 3.

DETAILED DESCRIPTION

To provide a better understanding of the present invention to those of ordinary skill in the art, several exemplary embodiments of the present invention will be detailed as follows, with reference to the accompanying drawings using numbered elements to elaborate the contents and effects to be achieved. The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated in and constitute a part of this specification. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention.
The invention will now be described with reference to the following non-limiting example. In the following description, embodiments of a flip flop type sandal including a Y-shaped strap secured to a sole structure are explanatorily illustrated to show the features of the present invention. It should be understood that the present invention may be applied in other types of footwear, such as one-piece type sandals or other types of sandals. The present application may be also used to secure other footwear components to the sole structures.
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of a flip-flop according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the flip-flop as shown in FIG. 1. As shown in FIG. 1, the sandal 10 is a flip-flop type sandal formed by assembling a sole structure 12 and a Y-shaped strap 20. The sole structure 12 may be a flat sheet piece having a uniform thickness. The sole structure 12 includes an upper surface 14 and a lower surface 16 opposite to the upper surface. The upper surface 14 receives the wearer's foot thereon and the lower surface 16 contacts the ground when the sandal 10 is worn on a foot. Optionally, the upper surface 14 and the lower surface 16 may respectively have designed patterns or textures (not shown in the diagrams) for wearing comfort, providing appearance or functionality. The strap 20 is attached to the sole structure 12 on the upper surface 14 and configured to provide a room for receiving foot and attaching the flip-flop to the foot of the wearer. According to an embodiment, as shown in FIG. 1, the strap 20 includes a toe post 22 and two sidebands 24. The toe post 22 is secured to a fore region 12 a of the sole structure 12 and would be disposed between the big toe and the adjacent toe of the foot. The two sidebands 24 are joined at the toe post 22 and extend oppositely toward the two side portions 12 b of the sole structure 12, respectively correspond to the inner arch and the outer arch of the foot. As shown in FIG. 2, the terminals of the toe post 22 and the two sidebands 24 respectively have a joining plug 26. The strap 20 is secured to the sole structure 16 by inserting the joining plugs 26 of the toe post 22 and the two sidebands 24 through the corresponding apertures 18 from the upper surface 14 of the sole structure and using the apertures 18 to obstructing the joining plugs 26 from being pulled back.
According to one embodiment of the present invention, the strap 20 may be made from plastic materials with elasticity, flexibility and tenacity, such as polyvinyl chloride (PVC) or thermoplastic polyester elastomer (TPE) or the combination therefore, but not limited thereto. The strap 20 in its entirety may be made by injecting molding technology. For example, the strap 20 may be made by injecting a thermal molten plastic material into a lower mold and then laminating an upper mode onto the lower mode. The molten plastic material is cooled in the mold to form the strap 20 with a desired shape.
According to one embodiment of the present invention, the sole structure 12 may also be made from plastic materials with elasticity and tenacity, such as ethylene vinyl acetate (EVA), natural rubber, synthetic rubber, polyurethane (PU), polyvinyl chloride (PVC), thermal-plastic polyurethane (TPU), thermal-plastic rubber (TPR) or polyethylene (PE), or the combination thereof, but not limited thereto. Preferably, the sole structure 12 is made of foamed plastic material, such as foamed EVA, foamed TPU or foamed rubber. Soles made from foamed plastic material may have the advantages of light-weight for wearing comfort and environment-friendly for less plastic materials are used. According to an embodiment, the sole structure 12 may be made by the following process. First, plastic raw materials are proportionally fed into an intensive mixer and are blended at a heated temperature thereby forming a molten blend of the plastic raw materials. After that, chemical additives such as foaming agent, cross-linking agent, activate agent, lubricating agent or other types of modifying agents are added into the mixer and blended with the molten plastic raw materials to form a homogenized mixture. The mixture is then transferred to a foam sheet machine and being outputted into a stack of preliminary plastic foam sheet. The preliminary plastic foam sheet is then discharged and cut into a plurality of sole sheets with designed shapes. Each of the sole sheets is then loaded into a mold for vulcanization. Afterward, the vulcanized sole sheet is taken out from the mold and a finished sole structure is thereby obtained. According to an embodiment, the sole structure 12 may include a single layer or multiple laminated layers for providing desired functionality, wearing comfort or wear-resistance.
Please refer to FIG. 3, which is an enlarged perspective view of the joining plug 26 as shown in FIG. 2 according to an embodiment of the present invention. As shown in FIG. 3, the joining plug 26 may include a pillar portion 262 and a blocking portion 264. One end of the pillar portion 262 is connected to the upper surface 266 of the blocking portion 264, while the other end of the pillar portion 262 is connected to the toe post 22 or one of the sidebands 24 of the strap 20. According to one embodiment, the pillar 262 may be cylinder-shaped, and the blocking portion 264 may be circular-plate shaped. The diameter of the pillar portion 262 is smaller than the diameter of the blocking portion 264 to expose a portion of the upper surface 266 of the blocking portion 264. When the pillar 262 is jointed at the center portion of the upper surface 266 of the blocking portion 264, the joining plug 26 may have an upside-down T-shaped cross-sectional profile which corresponds to shape of the aperture 18 (see FIG. 4). In this way, the joining plug 26 may be obstructed or latched in the aperture 18 thereby preventing the disassembling of the sole structure 12 and the strap 20. One feature of the present invention is that, as shown in FIG. 3, the blocking portion 264 of the joining plug 26 has a plurality of protrusions 268 disposed on the region of the upper surface 266 not covered by the pillar portion 262. In some embodiments, the protrusions 268 may be evenly dispersed on the upper surface 266 not covered by the pillar portion 262. In other embodiments, the protrusions 268 may be arranged in a higher density near the pillar portion 262 and in a lower density as being distanced from the pillar portion 262, and vice versa. Optionally, the protrusions 268 may be arranged into a certain pattern, such as a radial pattern centered at the pillar portion 262, a single ring or multiple concentric rings centered at the pillar portion 262. It some embodiment not shown in the diagram, a portion of the protrusions 268 may be joined to form a segment pattern or a contentious ring pattern surrounding the pillar portion 262. Other types of arrangements of the protrusions 268 are also applicable for different design needs.
The entirety of the joining plug 26 (including the pillar portion 262, the blocking portion 264 and the protrusions 268) may be integrally formed with other parts of the strap 20 by, for example, injection molding technology as previously illustrated. That is, no additional manufacturing steps or extra cost are needed for forming the joining plug 26. The protrusions 268 may respectively have a cone shape, a triangle pyramid shape or a square pyramid shape, but not limited thereto. Likewise, in other embodiments, the protrusions 268 may respectively have a cylinder shape or a prism shape. According to an embodiment, the ratio of the diameters of the pillar portion 262 and the blocking portion 264 may range from 1 to 1.5 and 1 to 3. For example, when the diameter of the pillar portion 262 is between 4 to 6 millimeters (mm), the diameter of the blocking portion 264 is preferably between 6 to 18 millimeters. According to an embodiment, the diameter of the pillar portion 262 is 5 mm, the diameter of the blocking portion 264 is 15 mm, and the height of the protrusions 268 protruding from the upper surface 266 of the blocking portion 264 may range from 0.5 mm to 1.5 mm, preferably 1 mm.
Please refer to FIG. 4. The upper portion of FIG. 4 is a perspective bottom view of the sole structure 12, and the lower portion of FIG. 4 is a cross-section view of the aperture 18 in the sole structure 12 along the line A-A′ shown in the upper portion of FIG. 4. As shown in FIG. 4, the aperture 18 comprises an passage hole 182 adjacent to the upper surface 14 of the sole structure 12 and a receiving hole 184 connected to the passage hole 182 and adjacent to the lower surface 16 of the sole structure 12. The passage hole 182 and the receiving hole 164 have shapes respectively corresponding to the pillar portion 262 and the blocking portion 264 of the joining plug 26. For example, the passage hole 182 may be a cylinder hole, and the receiving hole may be a circular-plate hole. It is important that the diameter of the passage hole 182 is smaller than the diameter of the receiving hole 184 so as to form an engaging surface 186 near the terminal of the receiving hole 184 connecting the passage hole 182. According to an embodiment, as shown in FIG. 4, the passage hole 182 is aligned to the center of the receiving hole 184. The aperture 18 has an upside-down T shaped cross-sectional profile corresponding to the shape of the joining plug 26 as shown in FIG. 3.
Please refer to FIG. 5 and FIG. 5A, which are cross-sectional diagrams showing the assembly of a joining plug 16 and an aperture 18 of the sole structure 12. According to an embodiment, the assembly may be formed by pressing the joining plug 16 from the upper surface 14 of the sole structure 12 into the aperture 18 by the pliability of the joining plug 16 and the sole structure 12. The upper surface 266 of the blocking portion 264 of the joining plug 26 would be stopped against the engaging surface 186, thereby preventing the joining plug 26 from being pulled back through the aperture 18. Please refer to FIG. 5A, according to an embodiment when a force 270 pulling away from the upper surface 14 of the sole structure 12 is applied to the strap 20, for example, during the activity of the wearer, the joining plug 26 is pulled up, and the protrusions 268 on the upper surface 266 would be at least partially pressed into the sole structure 18 by the pliability of the sole structure 12. The contacting area of the upper surface 266 of the blocking portion 264 and the engaging surface 186 is therefore increased, and the friction between the upper surface 266 and the engaging surface 186 is further increased. Consequently, the possibility of the disassembling between the joining plug 26 and the aperture 18 is further reduced and a more secured engagement between the strap 20 and the sole structure 12 is achieved.
Please refer to Table 1 as shown below. Table 1 shows the experimental data of a pulling stress test of the assembly of the strap and the sole structure according to one embodiment of the present invention. The experiment is performed by the following steps. First, an assembly of a strap and a sole structure is provided. The sole structure is then held on a base of a pulling testing machine and the end of the strap opposite to the sole structure is clamped and pulled by a force vertical to the upper surface of the sole structure and away from the sole structure. The magnitude of the force is gradually increased and the reaction force detected by the clamped is also increased until a sudden drop of the reaction force is detected. The magnitude of the force is referred as the maximum pulling stress. In Table 1, two sole structures, first sole structure (S1) and second sole structure (S2) are provided for the testing. The first sole structure and the second sole structure may comprise different materials and may comprise different elasticity or flexibility. Test 1, Test 2 and Test 3 are three different regions of the first sole structure the strap to be attached to. For example, Test 1, Test 2 and Test 3 respectively correspond to the fore region 12 a and the two side regions 12 b of the sole structure 12 as shown in FIG. 1. Similarly, Test 4, Test 5 and Test 6 respectively correspond to the fore region 12 a and the two side regions 12 b of the second sole structure for the strap to be attached to. In Table 1, column A shows test results of joining plugs without protrusions, and column B is average of column A. Column C shows test results of joining plug including protrusions, and column D is average of column C. Column E shows the difference between column D and column B. Column F shows the percentage of the increment of the tensile stress. It is shown in Table 1 that, assembly of the strap and the sole structure having the joining plug with protrusions may increase the maximum tensile stress by about 3 kilograms. This amount of increment is about 20% to 30% of the assembly of the strap and the sole structure without protrusions. According to the experimental result, it is known that the joining plug with protrusions is beneficial for assuring the assembly of the sole structure and the strap of a flip flop.

TABLE 1

	A		C
	without	B	with	D	E	F
	protrusions	average	protrusions	average	D-B	E/B(%)

S1	Test 1	11.83	10.50	14.79	13.71	3.21	30.57
	Test 2	9.49		12.40
	Test 3	10.18		13.95
S2	Test 4	17.32	15.01	19.18	18.09	3.08	20.52
	Test 5	14.23		16.16
	Test 6	13.49		18.94

Unit: kilogram (Kg)

According to another embodiment of the present invention, a constant stress magnitude, for example, 11.3 Kg may be applied to the assembly of the sole structure and the strap to examine the yield of the assembly. If no released reaction force is detected, the assembly is considered to pass the test. Otherwise, if a released reaction force is detected, the assembly is considered to fail. Please refer to Table 1 again, the testing result in column C (joining plug with protrusions) are all larger than 11.3 Kg. That is, the assemblies would all pass the pulling stress test. However, test 2 and test 3 in column A (joining plug without protrusions) are smaller than 11.3 Kg and are considered fail. According to the above, it is obvious that the joining plug having protrusions are beneficial for securing the strap to the sole structure. The flip flop assembly including the joining plug having protrusions may have better yield.
Please refer to FIG. 6, which shows some modifications of the joining plug according to some embodiments of the present invention. The blocking portion 264 of the joining plug 26 may have various shapes, such as a square-plate shape as shown in the left portion of FIG. 6, oval-shape as shown in the middle portion of FIG. 6, or polygon-plate shape as shown in the right portion of FIG. 6, but not limited thereto. Similarly, although not shown in the diagram, it should be understood that the pillar portion 262 of the joining plug 26 may have various shapes, such as square, oval or polygon, but not limited thereto. Furthermore, the shape of the aperture 18 may be adjusted according to the shape of the blocking portion 264 and/or the pillar portion 262. For example, the receiving hole 184 may be a square opening corresponding to a square blocking portion 264.
Overall, the present invention provides a novel strap securing structure of a sandal which is able to prevent the disassembling of strap and sole structure occurring in conventional sandals and thereby providing better wearing comfort and stability to the wearer. Furthermore, as the environmental awareness has already drawn a lot of attention in the industry of footwear manufacturing, eco-friendly materials such as bio-degradable EVA or bio-degradable PVC have gradually taken the place of conventional plastic materials for forming the sole structure. As known in the art, bio-degradable plastic materials are usually more flexible than conventional plastic materials and therefore the disassembling problem of a sandal made from bio-degradable plastic materials would be worse than made from conventional plastic materials. Advantageously, by using the trap securing component having a joining plug with protrusions provided by the present invention, the disassembling problem confronted when using bio-degradable plastic materials may be effectively eliminated.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims

What is claimed is:

1. An article of sandal, comprising:

a sole structure having an upper surface and a lower surface;

an aperture penetrating through the sole structure and exposing an engaging surface between the upper surface and the lower surface; and

a strap secured on the upper surface of the sole structure, wherein the strap includes a joining plug having a blocking portion and a pillar portion connected to a top surface of the blocking portion, wherein the top surface of the blocking portion has a plurality of protrusions that are in direct contact with the engaging surface of the sole structure.

2. The article of sandal according to claim 1, wherein the aperture comprises an passage hole close to the upper surface and a receiving hole connected to the passage hole and close to the lower surface of the sole structure, wherein the engaging surface is between the passage hole and the receiving-hole portion of the aperture.

3. The article of sandal according to claim 1, wherein the pillar portion is connected to a center portion of the top surface of the blocking portion, wherein the joining plug has an upside-down T shaped cross-sectional profile.

4. The article of sandal according to claim 1, wherein the aperture has an upside-down T shaped cross-sectional profile.

5. The article of sandal according to claim 1, wherein the blocking portion of the joining plug is circular-plate shaped.

6. The article of sandal according to claim 1, wherein the strap and the joining plug are formed in one integral structure.

7. The article of sandal according to claim 1, wherein the strap is a Y-shaped strap comprising a toe post secured to a fore region of the sole structure and two sidebands are joined at the toe post and respectively secured to two side regions of the sole structure.

8. The article of sandal according to claim 1, wherein the protrusions are evenly distributed on the upper surface of the blocking portion exposed from the pillar portion.

9. The article of sandal according to claim 1, wherein the sole comprises foamed ethylene vinyl acetate (EVA) or foamed rubber.

10. The article of sandal according to claim 1, wherein the strap comprises polyvinyl chloride (PVC).