The present invention relates to an energy absorbing material for use in head protective gear to reduce linear and angular impacts in multiple directions on wearer's head, in particular, a polyurethane-based energy absorbing material configured into a plurality of three-dimensional (3-D) inserts to be disposed on at least an interior surface of the head protective gear adjacent to the wearer's head. The present invention also relates to a method for fabricating the energy absorbing material, the corresponding 3-D inserts, and the head protective gear comprising thereof.
Helmet is a primary head protective gear used in many outdoor activities such as cycling to mitigate head injury. While skull fractures and concussion are the two most common head injuries during cycling, most of the commercially available helmets focus mainly on skull protection and less attentions have been put on concussive injuries. Head injuries resulted from direct impact can be categorized as either linear or angular impact. Head injuries such as skull fracture and intracranial bleeding are caused mainly by linear impact while concussion and diffuse axonal injury (DAI) are mainly associated with angular impact. In real-world accident scenario, most impacts are oblique impacts: the combination of linear and angular impact. Thus, protection against angular injury is as equally important as protection against linear injury.
A cycling helmet comprises an exterior shell and an interior layer (liner or padding). The exterior shell is usually made from a rigid polycarbonate (PC) shell outer part and a flexible expanded polystyrene (EPS) foam inner part. The interior layer displays various designs, and some of which are intended to reduce angular impact.
One conventional design to tackle angular impact was disclosed in U.S. Pat. No. 8,578,520 issued November 2012 by Peter Halldin et al. describing a helmet with an energy absorbing exterior shell and a sliding facilitator located inside the energy absorbing exterior shell. In that patent disclosure, the sliding facilitator is a slip with four fixation members or elastomers. The sliding facilitator is mounted on the helmet device and the slip can move laterally with a certain distance. During impact, the rotational energy can be absorbed by slip-plane sliding motion and fixation members' deformation. However, this invention is designed to reduce rotational impact. The thin slip liner cannot provide sufficient protection against linear impact. In addition, that helmet involves complicated and multiple fabrication processes of the slip liner and fixation members that add fabrication cost.
Another conventional design to tackle angular impact was disclosed in an international patent application publication number WO2017151028 published in September 2017 by Fredrik Hallander et al., which described a pad that is placed around the inside of the helmet. The pad in that patent disclosure is made from a stretchable outer fabric layer, a lubricating silicone gel and a membrane layer in between the gel and the outer layer. The lubricating gel provides shearing motion to reduce oblique impact. The membrane layer has low friction that allows sliding motion with the outer layer during oblique impact. However, it has been reported the helmet with this pad could not provide sufficient angular protection at certain angle, thus prohibiting an all-direction protection.
A further conventional design to tackle angular impact was disclosed in a US patent application publication number US20150047110 published in February 2015 by James A. Chilson et al., which described a honeycomb-shape insert that can be placed around the inside of the helmet. The honeycomb shape of that insert provides high breathability and low density of the helmet. Each honeycomb is hollow that allows collapse and deformation during impact, thereby reducing both linear and angular force. However, no horizontal comparison and solid testing with other rotational prevention technology is provided in the patent disclosure. Thus, the protection performance is still not clear. Also, the honeycomb insert is rigid and may scratch wearer's head, causing discomfort to the wearer. The cellular structure requires high precision molding and thermo-welding technology that add fabrication cost.
A need therefore exists for an improved material and design of the energy absorbing mechanism for use in head protective gear that eliminates or at least diminishes the disadvantages and problems described above.
Accordingly, a first aspect of the present invention provides a head protective gear comprising a plurality of three-dimensional inserts. Exemplarily, the plurality of three-dimensional inserts is made of an energy absorbing material which is a polyurethane-based composite composed of at least two components, a first component of the at least two components comprising one or more isocyanates, one or more chain extenders and optionally plasticizer; a second component of the at least two components comprising at least one hydroxyl-terminated polyol, a catalyst, a blowing agent, a surfactant and a polyolefin. The present head protective gear co-works with the plurality of three-dimensional inserts disposed on at least one surface of the head protective gear to tackle angular impact on the head protective gear, which can reduce the impact of concussion on head section of a wearer.
In certain embodiments, the polyurethane-based composite is formulated to have a density from 0.3 g/cm3 to 0.5 g/cm3.
In certain embodiments, the polyurethane-based composite is formulated to have a transmission force equal to or lower than 30 kN.
In certain embodiments, the at least one surface of the head protective gear includes an interior surface of the head protective gear.
In certain embodiments, the plurality of three-dimensional inserts made of the energy absorbing material is disposed on the interior surface of the head protective gear and is configured into a plurality of hollow members.
In certain embodiments, the plurality of three-dimensional inserts being configured into the plurality of hollow members is by subjecting a homogenous mixture of the first component and the second component to a mold under an elevated temperature, at an elevated pressure and for a duration of time until a “pudding-like” three-dimensional structure is formed.
In certain embodiments, the plurality of hollow members is spatially distributed on the interior surface of the head protective gear.
In certain embodiments, each of the hollow members has identical shape and dimension (i.e., length, width, height, top/base surface area, and/or lateral surface area) to the other.
In other embodiments, some of the hollow members may have different shape and/or dimension from the other hollow members.
In certain embodiments, the shape of one or more hollow members is cylindrical, nearly cylindrical, or frustoconical.
In certain embodiments, each of the cylindrical, nearly cylindrical, or frustoconical hollow members has a top or base surface diameter from about 9.33 mm to about 15 mm.
In certain embodiments, the frustoconical hollow members have a base surface larger than a top surface thereof.
In certain embodiments, the frustoconical hollow members have an average base surface diameter from about 10.67 mm to about 15 mm and an average top surface diameter from about 9.33 mm to about 13.5 mm.
In certain embodiments, each of the cylindrical, nearly cylindrical or frustoconical hollow members has the same lateral surface area as that of the other and a lateral height from about 6 mm to about 10 mm.
In certain embodiments, each of the hollow members has at least one open end and a cavity.
In certain embodiments, one or more hollow members have two opposing open ends.
In certain embodiments, the interior surface of the head protective gear has a foam layer as a base layer supporting the base of the hollow members and the plurality of hollow members is disposed on the foam layer.
In certain embodiments, the foam layer on the interior surface of the head protective gear is made of an expanded polystyrene (EPS) foam.
In certain embodiments, the base layer is configured to be in bowl-shaped or hemispherical shape.
In certain embodiments, the base layer is configured into a strip-like structure.
In certain embodiments, the base layer has a thickness from about 2 mm to about 5 mm.
In certain embodiments, the shortest distance between two adjacent hollow members on the base layer is from about 1 mm to about 2 mm.
In certain embodiments, the base surface of the hollow members faces the interior surface of the head protective gear while the top surface of the hollow members faces the wearer's head.
In certain embodiments, the hollow members are deformable (compressible) against and/or reactive to linear or angular velocity or acceleration resulting from one-, two-, or three-axis of motion exerted on the three-dimensional inserts.
The head protective gear according to various embodiments of the present invention includes, but not limited to, safety helmet, bump cap, cycling helmet, motorcycle helmet, horse riding helmet, and climbing helmet.
A second aspect of the present invention provides a method for fabricating the energy absorbing material described in the first aspect and/or certain embodiments described herein, where the method includes:
The polyurethane-based composite as-fabricated according to certain embodiments has a density from 0.3 g/cm3 to 0.5 g/cm3 and/or a transmission force of equal to or lower than 30 kN.
In certain embodiments, the weight ratio between the first component and the second component is not smaller than 1:1. For example, the weight ratio is 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5.
In certain embodiments, the one or more isocyanates of the first component is/are selected from diphenylmethane diisocyanate, phenylene diisocyanate, toluene diisocyanate, naphthalene diisocyanate, or any mixture thereof.
In certain embodiments, the one or more chain extenders of the first component is/are selected from ethylene glycol, 1,3-propylene glycol, dipropylene glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylenetriamine, 1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, or any mixture thereof.
In certain embodiments, the at least one hydroxyl-terminated polyol of the second component comprises one or more hydroxyl-terminated polyether polyols with hydroxyl values ranging from 30 mgKOH/g to 350 mgKOH/g, one or more hydroxyl-terminated polyester polyols with hydroxyl values ranging from 30 mgKOH/g to 350 mgKOH/g, one or more hydroxyl-terminated polyolefin polyols with hydroxyl values ranging from 30 mgKOH/g to 350 mgKOH/g, or any mixture thereof.
In certain embodiments, each of the hydroxyl-terminated polyether polyols, the hydroxyl-terminated polyester polyols, or the hydroxyl-terminated polyolefin polyols has at least two hydroxyl groups.
In certain embodiments, the catalyst of the second component is a compound or a mixture of compounds each containing at least one of the following chemical groups: pyridine, imidazole, piperazine, bis(2-dimethylainoethyl), trimethylamine, triethanolamine, 1,4-diazabicyclo[2.2.2]octane, zinc naphthenate, and dibutyltin dilaurate.
In certain embodiments, the blowing agent of the second component is selected from water.
In certain embodiments, the surfactant of the second component is selected from polysiloxane.
In certain embodiments, the polyolefin is a hydroxyl-terminated polyolefin comprising hydroxyl-terminated polybutadiene (HTPB).
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Other aspects of the present invention are disclosed as illustrated by the embodiments hereinafter.
The appended drawings, where like reference numerals refer to identical or functionally similar elements, contain figures of certain embodiments to further illustrate and clarify the above and other aspects, advantages and features of the present invention. It will be appreciated that these drawings depict embodiments of the invention and are not intended to limit its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale.
It will be apparent to those skilled in the art that modifications, including additions and/or substitutions, may be made without departing from the scope and spirit of the invention. Specific details may be omitted so as not to obscure the invention; however, the disclosure is written to enable one skilled in the art to practice the teachings herein without undue experimentation.
As used herein, the term “isocyanate index” refers to a ratio of the equivalent amount of isocyanate used relative to the theoretical equivalent amount times 100. A theoretical equivalent amount is equal to one equivalent isocyanate per equivalent OH group. For example, when an isocyanate is reacted with one or more polyols, one NCO group reacts with one OH group. In that example, the number of NCO groups is equal to the number of OH groups, and the result is a stoichiometric NCO:OH ratio of 1.0.
The following examples are intended to assist the understanding of the present invention, but should not be considered limiting the scope of the invention. The scope of the present invention should be defined by the appended claims.
In this example, a first formulation of the energy absorbing material comprising a polyurethane-based composite made of two components is provided. A first component of the polyurethane-based composite comprises aromatic diisocyanate and chain extender. In particular, diphenylmethane diisocyanate (MDI) is mixed with dipropylene glycol in a weight ratio of 90:10 to form a first mixture. The first mixture is stirred at room temperature for 4 hours before use.
A second component of the polyurethane composite comprises 4 different polyols, namely polyols A, B, C, and D, where polyol A is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 100 to 120 mgKOH/g; polyol B is a polyether polyol having 3 hydroxyl groups and a hydroxyl value from 30 to 35 mgKOH/g; polyol C is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 300 to 350 mgKOH/g; and polyol D is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 270 to 290 mgKOH/g. Polyol A, B, C and D are first mixed in a weight ratio of 58:30:4:8 to form a polyol mixture before mixing with bis(2-dimethylaminoethyl), trimethylamine, dibutyltin dilaurate, water, silicone oil, and hydroxyl-terminated polybutadiene (HTPB) in a weight ratio of 1:10:25:1:5:40 until a second mixture is obtained, where the weight ratio between the polyol mixture and the rest of the compounds/chemicals is 10:1. The second mixture is further stirred before use.
The first and second components are mixed in a weight ratio of 1:1.3 to form a homogeneous mixture. The homogeneous mixture is then poured into a mold for forming the hollow members with a desired three-dimensional geometry, followed by molding at a pressure of 600 psi under a temperature of 50° C. for 15 minutes in a heated oven. The as-prepared energy absorbing material is configured to have a density of 0.5 g/cm3 and a transmission force of equal to or lower than 15 kN.
In this example, a second formulation of the energy absorbing material comprising a polyurethane-based composite made of two components is provided. The first component of the polyurethane-based composite comprises aromatic diisocyanate, chain extender, and plasticizer. In particular, diphenylmethane diisocyanate (MDI) is mixed with ethylene glycol, and bis(2-ethylhexyl) phthalate in a weight ratio of 87:7:5 to form a first mixture. The first mixture is stirred at room temperature for 4 hours before use.
The second component of the polyurethane-based composite comprises 2 polyols, namely polyol A and polyol B, where polyol A is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 270 to 290 mgKOH/g; polyol B is a polyether polyol having 3 hydroxyl groups and a hydroxyl value from 50 to 60 mgKOH/g. Polyol A and polyol B are mixed in a weight ratio of 1:1 before mixing with delayed action catalyst A400, dibutyltin dilaurate, water, surfactant silicone oil and hydroxyl-terminated polybutadiene (HTPB) in a weight ratio of 5:3:1:3:40 until a second mixture is obtained, where the weight ratio between the polyol mixture and the rest of the compounds/chemicals is 15:1. The second mixture is further stirred before use.
The first and second components are mixed in a weight ratio of 1:1.3 to form a homogeneous mixture. The homogeneous mixture is then poured into a mold for forming the hollow members with a desired three-dimensional geometry, followed by molding at a pressure of 600 psi under a temperature of 50° C. for 15 minutes in a heated oven. The as-prepared energy absorbing material is configured to have a density of 0.35 g/cm3 and a transmission force of equal to or lower than 30 kN.
It should be understood that the formulation of the energy absorbing material is not limited to the examples described herein, but can vary according to the needs or requirements for meeting certain standard of personal protective equipment such as the rotational impact testing of helmets by RI.SE (Research Institutes Of Sweden).
In this example, a third formulation of the energy absorbing material comprising a polyurethane-based composite made of two components is provided. A first component of the polyurethane-based composite comprises aromatic diisocyanate and chain extender. In particular, diphenylmethane diisocyanate (MDI) is mixed with dipropylene glycol in a weight ratio of 90:10 to form a first mixture, which is stirred at room temperature for 4 hours before use.
A second component of the polyurethane composite comprises 4 different polyols, namely polyols A, B, C, and D, where polyol A is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 100 to 120 mgKOH/g; polyol B is a polyether polyol having 3 hydroxyl groups and a hydroxyl value from 30 to 35 mgKOH/g; polyol C is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 300 to 350 mgKOH/g; and polyol D is a polyether polyol having 2 hydroxyl groups and a hydroxyl value from 270 to 290 mgKOH/g. Polyol A, B, C and D are first mixed in a weight ratio of 58:30:4:8 to form a polyol mixture before mixing with bis(2-dimethylaminoethyl), trimethylamine, dibutyltin dilaurate, water and silicone oil in a weight ratio of 1:10:25:1:5 until a second mixture is obtained, where the weight ratio between the polyol mixture and the rest of the compounds/chemicals is 10:1. The second mixture is further stirred before use.
The first and second components are mixed in a weight ratio of 1:1.3 to form a homogeneous mixture. The homogeneous mixture is then poured into a mold for forming the hollow members with a desired three-dimensional geometry, followed by molding at a pressure of 600 psi under a temperature of 50° C. for 15 minutes in a heated oven. The as-prepared energy absorbing material is configured to have a density of 0.5 g/cm3 and a transmission force of equal to 40 kN.
Table 1 below compares transmission force of the energy absorbing material prepared according to the formulations of Example 1 and Example 3, where the difference between two formulations is one with a polyolefin (e.g., HTPB in Example 1) whereas the other without the polyolefin (Example 3) in the second component of the polyurethane-based composite.
From the above comparison, it is suggested that polyolefin in the second component plays an important role in enhancing the energy absorbing performance (by significantly lowering the transmission force).
Turning to
Turning to
Apart from bowl-shaped or hemispherical shape, the base layer supporting the base of the hollow members according to certain embodiments can be made into a strip-like structure. Two embodiments of said strip-like structure are schematically depicted in
In
In
The following examples will provide results of an oblique impact test on different configurations of the three-dimensional inserts of the energy absorbing material according to different embodiments of the present invention in terms of their performance in absorbing and/or reducing translational acceleration (
Turning to
In
Turning to
In
Turning to
Turning to
In
In
In
From the results in
In
In
Table 2 summarizes the measurements of angular (rotational) velocities and accelerations exerted on the simulated head section by different prototypes depicted in
Overall, prototypes 6a-6c can reduce certain angular impact exerted on the simulated head section, compared with the control helmet, but seem not to be as effective as prototypes. 5a-5c.
In addition, it is suggested that the formulation of energy absorbing material in the present invention with a lower first component to second component weight ratio is generally softer than that with a higher first component to second component weight ratio. In other words, the hardness of the energy absorbing material of the present invention is attributed more to the first component, whereas the softness thereof is attributed more to the second component.
To further compare the protective ability of the energy absorbing material and the EPS foams, and to demonstrate the possibility of replacing certain amount of EPS foams by the energy absorbing material in fabrication process without compromising the protection ability of the head protective gear, the polyurethane-based composite prepared according to one of the embodiments of the present invention with a density of 0.35 g/cm3 is subjected to an impact test and compared with two EPS foams having a density of 0.09 g/cm3 and 0.10 g/cm3, respectively, by measuring the transmission force from the corresponding material. In
Besides the density of the energy absorbing material itself, the present invention also proposes a hollow configuration of 3-D inserts in a shape of nearly cylindrical or frustoconical formed by the energy absorbing material and a spatial distribution of the inserts on at least the interior surface of the head protective gear to form an energy absorbing layer or pad in order to maximize the energy absorbing potential of the head protective gear. In particular, the impact is usually non-linear on the head section of the wearer when head injury happens in road incidence, sports event, and other occasions such as performing certain statutory duties with potential risks of head injury. Since the surface of the object to be protected, i.e., head, is not a planar surface, and the impact on which usually includes rotations around x-, y-, and z-axes of the head, the proposed hollow 3-D inserts spatially distributed on the interior surface of the head protective gear according to certain embodiments does not only provide a crushing mechanism to counter-act the linear impact, but also other mechanisms such as rotation and shearing to effectively counter-act the angular impact on the head of the wearer, thereby mitigating any potential damages to the wearer's brain and other structures of his/her head.
Although the invention has been described in terms of certain embodiments, other embodiments apparent to those of ordinary skill in the art are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by the claims which follow.
The present head protective gear comprising the plurality of three dimensional inserts configured into hollow members made of energy absorbing material is not just applicable to bicycle helmet head protective gear, but also to other protective gears for different helmets which function as or require a means to absorb and/or reduce linear and non-linear impacts.
This application claims priority from the U.S. provisional patent application Ser. No. 63/379,013 filed Oct. 11, 2022, the disclosure of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
63379013 | Oct 2022 | US |