The present invention relates to articles of footwear and methods of making the same, in particular protective articles of footwear having improved safety and protection of the toe and forefoot region while simultaneously maintaining a slim and lightweight profile.
Protective footwear including protective devices for shielding the toe and forefoot region of the foot from injury are widely used in various sectors of the footwear industry. These protection devices may be referred to as toe caps, safety toes, safety toe caps, toe protectors, or steel toes and may be employed as independent devices or may be integrated into the shoe or other article of footwear. Common scenarios in which such protective devices may be necessary are in construction applications, in mining, or in other like fields where the foot may be susceptible to injury due to impact with extraneous objects (e.g., falling rocks, lumber, puncture via nails, etc.)
In order for the footwear to be designated as “protective footwear”, certain types of safety footwear must satisfy particular requirements For instance, the American Society for Testing and Materials (ASTM) sets standards for protecting consumer's toes and metatarsal areas in “protective footwear” (e.g., as set forth in ASTM F2413-11). If a safety toe cap is used, it must meet certain impact resistance and compression resistance tests, indicating the toe cap can sufficiently protect a user's foot from injury.
In some cases, while the aforementioned protective devices may provide adequate protection from injury and satisfy ASTM standards, the amount and thickness of material necessary to do so may cause the protective device and footwear to be unduly heavy, bulky, and awkward for a user. A bulky device having a large profile may also be difficult to integrate into an article of footwear without significant alteration to the shape, structure, and aesthetic aspects of the footwear. In addition, a heavy protective device may be expensive to manufacture due to the high amount of metal or other protective material needed to manufacture a thick, heavy device. Other deficiencies not noted here also exist.
A safety toe cap according to the present technology is adapted to provide adequate protection to a user's toe and forefoot region, while maintaining a lightweight, thin, and streamlined profile, so as to be comfortable for a user and easy to incorporate into an article of protective footwear. The safety toe cap of the present technology includes one or more strain hardened regions which provide increased strength with decreased mass, thickness, and material usage.
In particular, in some aspects, the present technology provides a protective toe cap for an article of footwear, comprising a hemi-dome shaped body adapted to cover a user's toes once incorporated into an article a footwear, and having opposing inner and outer surfaces, a forefoot side, a midfoot side, a medial side, and a lateral side, and further including at least one strain hardened portion and at least one non-strain hardened portion.
In an embodiment, in the protective toe cap according to the present technology, the at least one non-strain hardened portion has a yield strength of about 350 MPa to about 880 MPa. Further, the at least one non-strain hardened portion may have a yield strength of about 400 MPa to about 500 MPa. In some embodiments, the at least one strain hardened portion may have a yield strength which is increased by about 1% to about 2% with respect to a yield strength of the at least one non-strain hardened portion. In addition, the at least one strain hardened portion may have a hardness which is increased by about 2% to out 4% with respect to a hardness of the at least one non-strain hardened portion.
In some embodiments, the protective toe cap may have a thickness of no more than about 3.0 mm, while in alternative embodiments, the protective toe cap may have a thickness of no more than about 2.8 mm. Additionally, a thickness of the at least one strain hardened portion may be smaller than a thickness of the non-strain hardened portion by 0.2 mm to 1.0 mm.
In some aspects, the protective toe cap may be formed of a material comprising one or more of aluminum, steel, magnesium, titanium, or an alloy thereof. In one embodiment, the protective toe cap is formed of an aluminum alloy.
In some embodiments, the at least one strain hardened portion may be formed as a continuous channel in at least one of the inner and outer surface of the hemi-dome shaped body running from the medial side to the lateral side.
In some aspect, the at least one strain hardened portion comprises two to four strain hardened portions. In an embodiment, the at least one strain hardened portion is disposed nearer the midfoot side than the forefoot side. Further, the at least one strain hardened portion may be formed as a depression in at least one of the inner surface and the outer surface without a corresponding protrusion present on the opposing surface.
In addition, the present technology provides an article of footwear comprising an upper defining a cavity adapted to receive the foot of a user, wherein the upper is attached to an outsole, and a protective toe cap positioned adjacent a toe region of the footwear, the protective toe cap comprising a hemi-dome shaped body adapted to cover the user's toes, and having opposing inner and outer surfaces, a forefoot side, a midfoot side, a medial side, a lateral side, and a lower lip extending along a perimeter of the body configured to attach the protective toe cap to a sole portion of the article of footwear, the body further including at least one strain-hardened portion and at least one non-strain hardened portion.
The present technology further includes a method of manufacturing a protective toe cap, comprising: (i) providing a sheet of metal; (ii) providing a mold having first and second pressing surfaces, wherein at least one of the first and second pressing surfaces includes a protrusion; (iii) pressing the sheet of metal between the first and second pressing surfaces to produce a hemi-dome shaped body including at least one strain hardened portion formed by the protrusion; (iv) hardening the hemi-dome shaped body by heating to a first temperature within a range of about 500° C. to about 550° C. and maintaining the hemi-dome shaped body at the first temperature for a first period of 60 to 100 minutes to produce a hardened hemi-dome shaped body; and (v) tempering the hardened hemi-dome shaped body by heating to a second temperature within a range of about 150° C. to about 200° C. and maintaining the hardened hemi-dome shaped body at the second temperature for a second period of 10 to 20 hours to produce the protective toe cap.
In some embodiments, the sheet of metal comprises one or more of aluminum, steel, magnesium, or titanium, or an alloy thereof. Further, the pressing may be conducted at a temperature of no more than about room temperature.
In describing aspects of the present technology, specific terminology will be used for the sake of clarity. However, the technology is not intended to be limited to any specific terms used herein, and it is to be understood that each specific term includes all technical equivalents, which operate in a similar manner to accomplish a similar purpose.
As used in the present application, “length” means the longest dimension of any object or shape. As used in the present application, “width” means the shortest dimension of any object or shape existing in the same plane or surface as the length. “Thickness” means the remaining dimension of a three-dimensional object which is not the length or the width.
As used in the present application, “medial” means at, towards, near, or relating to the midline of the human body, i.e. as applied to a shoe as it would be oriented when it is situated on the foot of a wearer. As used in the present application, “lateral” means at, towards, near, or relating to the edge of an object, particularly an edge or end which is away from or opposite the midline (medial region) of the human body. When the terms “medial” and “lateral” are applied to a shoe or other wearable object, they describe portions of the object as they would be oriented when worn by a wearer.
As used in the present application, “strain hardened” means a material or portion of material which has been subjected to a mechanical process in which the material or portion of material has been worked beyond its elastic limit to cause plastic deformation, resulting in increased mechanical strength. Accordingly, the material or portion of material which is “strain hardened” has a higher yield strength and hardness than adjacent areas of the same material which are not “strain hardened”.
The technology disclosed herein includes, in general, protective devices such as safety toe caps, various types of protective footwear including such protective devices, and methods of making the same. The safety toe caps of the present technology include one or more strain hardened portions to increase strength and impact resistance, while simultaneously minimizing weight and material usage. These safety toe caps may be utilized as separate protective devices or may be incorporated into an article of footwear.
For example, as shown in
Safety Toe Cap
As shown in
Safety toe cap 200 is composed of a metal or metal alloy material or any other material of sufficient strength to satisfy safety standards for protective footwear, such as ASTM F2413-11 or ASTM F2413-18. In particular, an appropriate material for safety toe cap 200, may have a yield strength of about 350 MPa to about 880 MPa, preferably about 400 MPa to about 700 MPa, and most preferably about 400 MPa to about 500 MPa, prior to strain hardening. In addition, an appropriate material for safety toe cap 200, may have a hardness of about 60 HRB to about 90 HRB, preferably about 70 HRB to about 90 HRB, and most preferably about 80 HRB to about 90 HRB, prior to strain hardening. Further, the material for safety toe cap 200, may have a density of about 2.5 g/cm3 to about 8.1 g/cm3, more preferably from about 2.5 g/cm3 to about 5 g/cm3, and most preferably from about 2.5 g/cm3 to about 4.5 g/cm3. When the toe cap material has properties within these ranges, it is capable of sufficiently resisting deformation and damage from impact so as to protect a user's toes, as well as having the advantage of providing a lighter weight toe cap which is more comfortable from the perspective of a user.
For example, safety toe cap 200 may be preferably formed of a material comprising one or more of aluminum, steel, magnesium, or titanium, or an alloy thereof. The material of safety toe cap 200 may further comprise additional alloying elements, such as carbon, zinc, magnesium, copper, silicon, iron, manganese, chromium, or any combination therein. In a preferred embodiment, safety toe cap 200 is formed of 7075 aluminum alloy (AA7075).
The safety toe cap 200 may have a thickness 302 (
As shown in
According to an aspect of the disclosure,
In particular, as depicted in
In some embodiments, as represented in
Hardening and tempering according to these process relieves stresses created in the material of safety toe cap 200 during pressing. In particular, since the material of safety toe cap 200 is shaped from a flat sheet into a hemi-dome shape, the required bending creates a high amount of latent stress in the material. If hardening and tempering are not performed according to the presently disclosed processes in order to relieve this stress, the toe cap 200 will lack the strength and material properties needed to satisfy safety standards.
Strain hardened portions 300 of the present technology may have a thickness 306 which is smaller than the thickness 302 of adjacent areas 304 which are not strain hardened. For example, a strain hardened portion 300 may have a thickness 306 which is smaller than the thickness 302 of the rest of toe cap 200 by 0.2 mm to 1.0 mm, or preferably 0.2 mm to 0.5 mm. The strain hardened portion 300 of the present technology may form a depression in one of either the inner 204 or outer 208 surfaces of safety toe cap 200, as shown in
The strain hardened portions 300 may also have increased hardness in relation to adjacent portions 304 of safety toe cap 200. For example, the hardness of the strain hardened portion 300 may be greater than that of adjacent portions 304 of the safety toe cap 200 by about 2% to about 4% and more preferably about 3% to about 4%. In addition, the strain hardened portions 300 may also have increased yield strength in relation to adjacent portions 304 of safety toe cap 200. For example, the yield strength of the strain hardened portion 300 may be greater than that of adjacent portions 304 of the safety toe cap 200 by about 0% to about 3%, or more preferably about 1% to about 2%.
In some aspects, the strain hardened portions 300 may be formed as continuous lines or channels in a surface of safety toe cap 200. Such channels may be substantially linear, or may form various different patterns or shapes, such as curved lines, sinusoidal or wavy lines, or zig-zag lines. In some embodiments, the strain hardened portions 300 may be provided in a configuration capable of strengthening a portion of the toe cap 200 which is structurally weaker than adjacent portions. Additionally or alternatively, the strain hardened portions 300 may be provided in a location which tends to be subjected to greater stresses during use or during impact from above. Accordingly, the strain hardened portions 300 may be provided in a configuration which reinforces these locations and dissipates stress to underutilized and understressed areas of the structure of the toe cap 200.
As shown in
In some embodiments, as shown in
Further, in some embodiments, as shown in
In addition, the one or more strain hardened portions 300 may be formed in various alternative configurations designed to reinforce safety toe cap 200 against impact. For example, as shown in
A safety toe cap 200 according to the present technology may be provided as a separate protective device or may be incorporated into an article of footwear 100, as depicted in
Toe cap 200 can be incorporated into a variety of different types of footwear, to allow for safety and protection of the toes of a user from impacts and falling objects while also providing lightweight footwear with a slim, streamlined profile.
Referring back to
Footwear 100 according to the present technology also includes a toe cap 200 embedded within its forefoot region 106. Toe cap 200 may be incorporated into the toe region of footwear 100 and may be arranged with its lip 220 adjacent outsole 104, so that its outer surface 208 sits flush against upper 102. Inner surface 204 of toe cap 200 may be covered by a lining, mesh, or other fabric or padding disposed within upper 102. Toe cap 200 may therefore provide protection for a user's toes against, for example, a falling object.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.