Patent Grant
11678715
It is well documented in various studies (Penn State, BYU, EHP, HC) that artificial synthetic turf is significantly hotter than natural dirt and grass. In a study conducted at BYU in June 2002, results found that synthetic turf was 37° F. hotter than asphalt and 86.5° F. hotter than natural grass under similar environmental conditions. The average air temperature on the day of the study was 81.42° F. and the temperature of the turf reached 157° F. On the same day, the natural grass only reached a maximum temperature of 88.5° F. On a hot summer day during peak hours, the surface temperature of synthetic turf can reach over 200° F., according to the same study. A UNLV study also documents excessive surface temperatures of synthetic turf well into October and November (112.4° F., 32.4° F. higher than the air temperature). The study concluded that surface temperature of turf is affected more by the amount of direct sunlight than air temperature, which explains why even in colder months synthetic turf can be extremely hot.
According to various studies (EHP, HC), any temperature above 122° F. can burn skin in less than 10 minutes. Thus, it is generally accepted that playing on synthetic turf fields is potentially dangerous when the surface temperature exceeds 122° F. With the growing number of synthetic turf fields, the issue of a safe and comfortable playing environment becomes a major issue.
It is well documented in professional sports that athletes have complained of blistering and burned feet from playing on synthetic turf.
In 2007, Sports Illustrated reported six Peruvian soccer players from Sporting Cristal were unable to train because of burns and blisters suffered from hot turf fields. According to a 2010 ESPN article, it was believed that heat from turf caused a teammate's injury.
Solutions have been proposed to counteract the heat of the artificial turf, such as watering the fields and changing the material of the turf itself, but all proposed solutions are either not feasible or have failed. In the BYU study, when the turf field was watered, the temperature immediately dropped from 174° F. to 85° F., but within five minutes it rebounded quickly to 120° F. and within 20 minutes it was back up to 164° F. The method of watering a hot turf field is both expensive and ineffective. Another proposed solution of changing the materials within the turf was tested, but the Penn State study concluded that the drop was at most 10° F. At temperatures still exceeding 150° F., these changes offer virtually no advantage.
The present disclosure describes an insole and/or outsole (a portion of a shoe) as viable solutions to the problem, for example, of athletes playing on hot turf as well as any person whose feet come in contact with other hot surfaces, such as asphalt or cement.
A shoe portion includes a first layer of heat resistant material and a second layer beneath the first layer and made at least in part of a material having a low thermal conductivity and including plural channels on one of a first and second surfaces thereof, the channels separated from one another and creating air space therein.
The channels face downwardly away from the first layer.
The channels have a curvilinear or serpentine configuration.
The heat resistant material first layer is a felt.
The felt includes fibers for limiting heat transfer, and in one embodiment include oxidized polyacrylonitrile fibers.
The channels extend inwardly from the second surface which is a lower surface of the second layer, and the channels extend inwardly from the second surface toward the first surface of the second layer by a dimension of approximately one-half of a total thickness of the second layer.
The first surface of the second layer is an unbroken, continuous surface.
The first and second layers have a same perimeter outline.
The first and second layers form an insole of the shoe, or alternatively the first and second layers form a portion of an outsole of the shoe, or both the insole and the outsole include the first and second layers.
This disclosure minimizes the transfer of heat from hot ground surfaces to the foot. Because heat transfer occurs much more efficiently through two solid objects that touch one another and much less efficiently through two objects that are separated by air, it is advantageous to create as much airspace between the foot and the ground as possible. It is also advantageous to have a heat resistant assembly at the point a foot makes contact with an insole as well as where the shoe comes into contact with the hot ground surface. Thus, an effective insole and outsole that minimize conductive heat transfer would drastically reduce the amount of heat passed to the foot from a hot ground surface.
In a preferred form of the insole, the base material is made of a solid substance that has a particularly low thermal conductivity, such as silicon or cork. A material with a low thermal conductivity is necessary because the lower the thermal conductivity is, the less efficiently that material gets hot. The base material of the insole must also be durable enough to support constant wear from anyone using the insole in a shoe.
This base material of the insole is lined with curved channels or grooves that create air space within the insole. These channels face downwardly so that the design minimizes the surface area of the base material that actually comes in contact with the hot surface below it. Because these downward facing channels create air space within the insole itself, it drastically reduces the conductive heat transfer that has to be counteracted. Therefore, this model changes the mode of heat transfer from conductive to radiant in the spaces within the channels. Conductive heat transfer is by far the most efficient form of heat transfer (i.e. heat passes the easiest between two objects in direct contact), so it is advantageous to create as much airspace as possible between the two objects (in this case, the foot and the hot ground surface), to reduce the amount of heat transferred to the foot.
A layer of heat resistant felt is placed above the channeled layer of base material in the insole. This felt, preferably made of oxidized PAN (polyacrylonitrile) fibers, must be particularly effective at preventing the transfer of heat. PAN is a synthetic, semi-crystalline organic polymer resin. When oxidized, PAN is thermally stable and will not melt, burn, soften or drip. Oxidized PAN fibers are used by an array of companies and manufacturers who specialize in heat and flame resistant products. The nature of oxidized PAN fibers makes them a preferred material to be layered above the channeled solid layer as the oxidized PAN fibers aid in the prevention of heat transfer to the foot from a hot ground surface.
A similar channeled solid layer and heat resistant felt assembly is used in the outsole of an athletic shoe or cleat. By creating a heat resistant assembly within the outsole, the problem of heat transfer to the foot is combated at its source (contact with the ground). The outsole has a thin base layer of durable, solid plastic that extends the length of the shoe, of which the studs for the cleat are molded. The top of the plastic mold has walls that extend up to the base of the upper of the shoe, which separates the plastic from the upper, and a layer of plastic above this that extends the length of the outsole. This top layer of plastic acts as support for the upper of the shoe and prevents pressure from being put on the heat resistant assembly itself. This creates a hollow space within the plastic mold, for example about ¼″ in height, that runs along the length of the shoe. Inside this space is the assembly of a downward facing channeled solid layer, preferably silicon, beneath a layer of heat resistant felt, preferably oxidized PAN fibers. Because this assembly is encased in a shell of thin plastic, it reduces virtually all pressure that would be put on it by the foot and allows for more efficient insulation.
An insole or insole assembly 100 is shown in
As evident in
The insole 100 also preferably includes a second layer 120 that is provided above first layer 110. Preferably the second layer 120 extends over an entirety of the first layer 110 and has the same perimeter or outline as the first layer. The second layer 120 is preferably a heat resistant felt made of oxidized PAN (polyacrylonitrile) fibers with a thickness ranging between ⅛″ and ⅓″ and more preferably on the order ¼″.
An outsole or outsole assembly 200 shown in
An assembly 220 (virtually identical to the insole 100 described in connection with
Ideally, tread, studs, spikes 230 for the athletic shoe are provided in the second layer 214 and would preferably be molded from the same plastic mold as the assembly of outsole 200 and would extend downward toward the ground surface from the underside of layer 214.
Below is a table of various materials and substances with their respective thermal conductivity where thermal conductivity, k−W/(m·K), is conductive heat transfer vs. radiant heat transfer.
A preferred substance for this insole would have a low thermal conductivity with a particular durability to withstand normal use within a shoe. Thus, from this list, steel, iron, Mylar and silver materials have a substantially high thermal conductivity in comparison to the other listed materials which are more preferred. Rather, these materials are listed to give a range and understanding of thermal conductivity.
Testing Results
Testing for an embodiment was conducted using an electric hotplate in a controlled environment. The stovetop maintained a consistent temperature range of 175-185 F. Preliminary testing for this insole used a variety of heat resistant fabrics and materials, such as high and low density cork, firm and medium cellular silicon, high temperature fiber-glass substrates (commercially available under the tradenames Design Engineering Inc. or DEI Under Carpet Lite), high temperature fiberglass material with reflective aluminized Mylar (commercially available under the tradename DEI aluminized heat barrier), oxidized polyacrylonitrile (PAN) fibers (commercially available under the tradenames CarbonX, Koolmat felt, DJ-1, DJ-77), textured aluminum face with glass-fiber composite cores (commercially available under the tradename DEI Floor and Tunnel Shield), Mylar composites with a high temperature silica felt center (commercially available under the tradename Koolmat Shiny), heavy acrylic coated fiberglass (commercially available under the tradename Steiner BlackFlex), and woven silicon fiberglass composites (commercially available under the tradenames Koolmat or Koolmat Lite) to determine which would be the most effective at preventing heat transfer. Stock insoles for various soccer cleats were also tested for comparison.
Below is a table listing the thermal conductivity of the samples and materials used in the testing.
The first series of tests involved placing a sample on the hotplate for two minutes, measuring the temperature of the top (where the foot would be) every 30 seconds. Each sample was approximately 6.25 square inches. Below is the table listing the results of the first tests.
CarbonX B03RC
66
102
107.4
110.6
116.6
Koolmat felt
¼
″
67.4
99.7
103
105
108
Koolmat
66
87
98.3
103.5
115.8
Koolmat Shiny
66
100.1
114.3
117.9
119.3
DEI Under Carpet
65.2
71.6
75.9
83.9
85.9
Lite
DEI Floor & Tunnel
64.9
81.5
93.5
102.2
107.1
Shield
3/16
″ corkboard
68
83.3
105.5
109.6
113.2
¼
″ low dens. Cork
68.7
80.5
96.9
108.8
110.2
¼
″ high dens.
69
75.8
91.7
96.1
102.1
Cork
½
″ charcoal cork
65.3
69.2
75.1
83.4
88.6
¼
″ firm silicon
66.6
72.4
87.1
102.4
110.7
¼
″ med. Silicon
66.9
70.1
83.2
92.9
98.4
From this set of data, the samples that performed the best (highlighted in bold) were measured again with constant pressure for an additional two minutes and readings taken at 30 second intervals. Pressure was applied to the samples to simulate the environment within an insole, which would certainly endure constant pressure from a foot. To simulate the surface that would be applying pressure to the insole (foot), a hand pressed down on the samples with an average force of 2.5 pounds per square inch, or approximately 16 pounds for the entire sample. This number was found by taking the average weight of a person, 180 lbs, dividing it by two (for each foot), and again dividing it by 35 square inches (average surface of the bottom of a foot). This number, 2.57, is the amount of pounds per square inch of force that is exerted on the ground, or insole, by one foot, assuming equal distribution of weight throughout a foot. To find out how much force should be applied to a 6.25 square inch sample, 2.57 was multiplied by 6.25 (size of sample). A scale was used to insure consistency of weight applied by the hand. Below is a table listing the results of the pressure tests.
The results appear surprising at first; i.e., it appears the samples perform better with pressure, which seems to defy logic. Upon further investigation, it was concluded that the hand that applied pressure absorbed some of the heat from the sample being tested, which led to slightly cooler results. However, the trends of what samples worked the best certainly remained true. Also, some of the samples, including Koolmat and the three athletic shoes #1, #2, and #3 insoles performed significantly worse.
The stock athletic shoes #1 and #2 insoles both exceeded 122° F. in just two minutes. Per findings of various studies (HC, EHP), contact with a surface of a temperature over 122° F. can burn skin in less than 10 minutes. Because the insoles of the athletic shoes exceed 122° F. in an environment that simulates a hot day on turf, athletes using such insoles expose themselves to potential blistering and burning during practice and games.
The materials that performed the best were firm and medium cellular silicon and medium and low density cork. While the temperatures of these samples were significantly lower than the stock insoles, further tests were done using a combination of materials and samples to see if lower temperatures could be achieved. Tests were again done using a combination of heat resistant felt (made of oxidized PAN fibers) and the four samples that performed the best in the pressure test. Channels were also carved into additional samples of the high and medium density cork and silicon of the same size (6.25 square inches), which were to be tested independently as well as in combination with the felt.
Identical two minute tests were done, one without pressure and one with pressure, measuring the top temperature every 30 seconds. The following were tested in this series of tests: ¼″ firm and medium cellular channeled silicon with downward*facing channels, ¼″ firm and medium cellular non-channeled silicon with felt on the top/bottom, ¼″ firm and medium cellular channeled silicon with upward facing channels and heat resistant felt on top, and ¼″ firm and medium cellular channeled silicon with downward facing channels and heat resistant felt on the top/bottom. Cork was not tested because it was evident that silicon performed better and was a more viable material to be used because of its durability. However, any material similar to silicon or cork (i.e. similar thermal properties, elasticity, density, etc.) should be expected to perform similarly. The oxidized PAN fiber felt that was used was the Koolmat felt because it performed the best of all the similar felts. Below is a table listing the results of the tests.
Silicon with upward facing channels was not documented by itself because the temperature was drastically higher within the channels than it was on the ridges of the channels as the space within the channels was much closer to the hotplate.
¼
″ med silicon,
67.6
80.2
81.1
84
86
channels down, felt
on top
¼
″ med silicon,
68.6
76.3
78.4
84
86.3
channels down, felt
on bottom
¼
″ firm silicon,
68
79.8
81
84.4
86.4
channels down, felt
on top
¼
″ firm silicon,
68
76.5
79.3
84.1
86.6
channels down, felt
on bottom
As evident, a combination of the ¼″ silicon with downward facing channels and heat resistant felt performed the best, significantly better than non-channeled silicon with the same felt.
The downward facing channeled silicon (firm and medium) by itself performed poorly, but when used in conjunction with the heat resistant felt above it, became the best combination (bold). This is attributed to the airspace created within the assembly by the channels in the silicon. Because there is about half as much surface area that comes into physical contact with the hotplate because of the channels, the amount of conductive heat transfer is reduced by half. It is therefore advantageous to have a channeled assembly of solid material, such as silicon, used in conjunction with heat resistant felt, preferably made of oxidized PAN fibers to reduce the amount of heat transferred to the foot from a hot ground surface.
An additional set of testing was done with the samples on the hotplate for a longer duration of time: six minutes. These tests involved placing the combination of materials and samples on the hotplate for six straight minutes, once with constant pressure and another with no pressure, to conclude what the maximum temperature would be in such an environment similar to a hot day on turf. The following samples were tested: ¼″ firm and medium cellular non-channeled silicon with felt on the top/bottom, ¼″ firm and medium cellular channeled silicon with downward facing channels and felt on the top/bottom, and ¼″ firm and medium cellular channeled silicon with upward facing channels and felt on top. Also, athletic shoes #1, #2, and, #4 insoles were tested for comparison. Below is a table listing the results of these tests.
Athletic shoe #1 insole
144.6
Athletic shoe #2 insole
142.8
Athletic shoe #4 insole
134.2
¼
″ med silicon, channels down, felt on top
94.3
¼
″ med silicon, channels down, felt on
93.2
bottom
As evident, the ¼″ medium cellular silicon with the downward facing channels performed the best in the six minutes. Because the athletic shoes #1, #2, and #4 insoles would always endure pressure when used in an athletic cleat, there was no need to test them without pressure. It is already evident that they exceed the threshold temperature of 122° F., above which skin burns in less than 10 firm and medium cellular channeled silicon with downward facing channels and felt on the top/bottom. Below is a table listing the results of these tests.
¼
″ med silicon, channels down, felt on top
97.2
¼
″ med silicon, channels down, felt on
98.9
bottom
99.2
Again, the hand that applied the pressure absorbed some of the heat, but the trend is still the same. The reason that the IA″ medium cellular channeled silicon with downward facing channels and felt on the bottom performed better than the firm cellular channeled silicon with downward facing channels and felt on top is because the medium cellular silicon has a lower thermal conductivity than the firm cellular silicon, as evident by their independent tests. The medium cellular channeled silicon with downward facing channels and heat resistant felt above it performs the best. This combination reaches a maximum top surface temperature of 97.2° F., 37 degrees cooler than the athletic shoe #4 insole, 45.6 degrees cooler than the athletic shoe #2 insole, and 47.4 degrees cooler than the athletic shoe #1 insole. 97.2° F. is 24.8 degrees cooler than the 122° F. threshold at which skin burns within 10 minutes. With this combination of silicon and heat resistant felt, athletes greatly reduce the risks of incurring burns and blisters while playing on hot turf.
In another embodiment (
It will be appreciated that the teachings of the present disclosure need not be necessarily limited to the preferred use as an athletic use, but may also find application in other shoes such as construction boots and the like where extreme heat may be encountered.
This written description uses examples to describe the disclosure, including the best mode, and also to enable any person skilled in the art to make and use the disclosure. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. Moreover, this disclosure is intended to seek protection for a combination of components and/or steps and a combination of claims as originally presented for examination, as well as seek potential protection for other combinations of components and/or steps and combinations of claims during prosecution.
This application is a continuation and claims the priority benefit of pending U.S. application Ser. No. 14/777,366, filed Sep. 15, 2015, which is the national entry filing of PCT/US14/30807, filed Mar. 17, 2014, which claims the priority benefit of U.S. provisional application Ser. No. 61/800,055, filed Mar. 15, 2013.
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| Entry |
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| Number | Date | Country | |
|---|---|---|---|
| 20210307451 A1 | Oct 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61800055 | Mar 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14777366 | US | |
| Child | 17234900 | US |
