Patent Application
20190335838
The present disclosure relates to body impact protection equipment such as helmets, and in particular to a helmet having the ability to manage shear and rotational forces when impacted.
The primary purpose of a helmet is to protect the user's head from injury. A helmet typically includes a hard outer shell and an energy absorbing liner. The outer shell is designed to distribute forces in order to engage a greater volume of the energy absorbing liner. The liner usually comprises a compressible material that absorbs impact energy by distorting and absorbing the impact using the resilient and/or compressible properties of the material or by crushing and absorbing energy by material fracture.
Head injuries typically result from linear and/or rotational forces acting on the head. Certain types of head injuries such as skull fractures and intracranial bleeds usually arise from linear accelerations. Injuries such as concussions and subdural hematomas are thought to arise from rotational accelerations. Conventional helmets are primarily designed to manage linear forces and are less effective at managing shear or rotational forces. This has resulted in successful mitigation of injuries associated with linear forces such as skull fractures and intracranial hemorrhaging, but less success in reducing injuries such as concussions that are more closely associated with rotational or shear forces.
Various solutions intended to manage rotational motions have been developed and proposed, such as providing a slippery surface material to cover the helmet thereby decreasing friction between the surface of the helmet and the impacting object. Other solutions include the use of low friction layer between the helmet shell and an inner head-gripping member, or a layer that consists of a gel, liquid or other soft material between the shell and liner, or other layers of materials, to allow the outer shell to rotate and/or slide horizontally independent of the liner or the user's head.
Similar principles apply to body armor used for protecting other areas, but particularly serious injuries are often to the head.
A drawback of at least some conventional solutions that permit independent rotation of the helmet shell is added weight which increases fatigue and can also increase the moment of inertia of the helmet, as well as other drawbacks.
We disclose a body armor system such as a helmet that includes an energy absorbing layer or a shell, and a cushion for installed within the inside (body facing) side thereof. The cushion consists of a bladder comprising a flexible, liquid-filled membrane which houses a compressible and resilient pad.
In one embodiment, the pad has pores or other interstices that are open to the exterior of the pad (such as open cell foam) to permit the liquid to be secreted and absorbed by the pad when the pad is compressed and decompressed. Before an impact occurs, the pad is in an expanded position whereby the liquid is fully or substantially absorbed within the pad and the pad is at least partially saturated. On impact, the pad is compressed. This in turn squeezes the liquid from the pad, which then forms a liquid layer within the bladder around the pad, which in turn increases the ability of the pad to manage shear forces. When the pressure is then released from the cushion, the pad returns to its expanded, saturated status wherein it is more resistant to shear. This combination of properties permits the helmet to remain comfortably seated on the user's head during normal use, without undue rotation, but to have increased rotational freedom when the helmet is impacted.
The presence of free-flowing liquid within the bladder when compressed permits opposing surfaces of the bladder to be displaced in a shearing motion relative to each other, effectively permitting the bladder to “roll”, when the cushion is subjected to a shear force. This allows the cushion to decouple at least a portion of the shear forces that arise between the shell and the user's body when the equipment is subjected to an obliquely-directed impact.
The cushion provides a combination of some or all of the following:
a) The liquid-filled bladder is less compressive than a conventional foam pad and thus provides improved impact protection to attenuate linear (radial) forces.
b) Prior to receiving an impact, the liquid within the cushion is absorbed and/or displaced within the bladder, thereby minimizing rotational movement of the cushion. This improves user comfort and stabilizes the helmet during use.
c) Upon receiving an oblique impact, the liquid within the bladder permits opposing sides of the bladder to slip relative to each other, thereby allowing the shell of the helmet to move laterally relative to the user's head. This permits the helmet to rotate upon impact to attenuate rotational/shear forces imparted to the head. This result occurs because the liquid layer within the cushion creates a slip plane which shifts freely under a shear-type force.
In one aspect, we disclose a cushion for installation between opposing layers, comprising:
According to an aspect, the bladder comprises an elastomeric material such as thermoplastic polyurethane (TPU) or polyvinyl chloride (PVC). The liquid may comprise an oil or a gel. The pad may comprise an open cell foam such as a vinyl nitrile foam or may comprise a closed cell foam.
We further disclose a helmet comprising an outer shell and/or an energy absorbing layer such as rigid foam and an array of cushions as described herein mounted against the user's head.
We further disclose a method of attenuating the impact energy from an incoming force to decrease trauma to a body part, the method comprising using a body protection system such as a helmet that includes and outer shell and/or energy absorbing layer and an array of cushions as described herein mounted against the user. Upon receiving an oblique impact, shear forces are generated between the shell or energy absorbing layer and the user which are managed and attenuated by the cushions.
In one embodiment, we disclose a body armor system comprising an outer impact-receiving layer and an at least one cushion interior to said layer for managing shear forces impacting the outer impact-receiving layer, said cushion comprising a sealed flexible bladder filled with a liquid and containing a compressible and resilient solid element therein, wherein the solid element is configured to permit the liquid to flow at least partially around the element.
In one embodiment, we disclose a cushion for managing shear forces in a body armor, the cushion comprising a sealed flexible bladder filled with a liquid and containing a compressible and resilient solid element therein, wherein the solid element is detached from at least an upper or lower surface of the bladder to permit the liquid to flow at least partially around the element.
Unless otherwise specified, directional references herein refer to the helmet and head in an upright position. Furthermore, the detailed description herein is only intended to provide examples and representative embodiments of the invention and is not intended to limit the scope of the invention. The full scope of the invention is presented in the specification as a whole.
Shown in
Helmet 100 includes an outer shell 102 which is normally (but not necessarily) relatively rigid and may comprise polycarbonate, polyethylene or other suitable material. The shell material and its thickness and other parameters will depend on the functional requirements of the intended use. For example, the shell of a snow sports or downhill cycling helmet may comprise a relatively thick and rigid fiberglass or carbon fiber layer, while a road cycling helmet shell may comprise a thin, somewhat flexible material. Outer shell 102 may be intended for disposal after a single hard impact or for withstanding repeated impacts.
Shell 102 has an inner layer or liner 104 for absorbing energy. Liner 104 may comprise a compressible material such as vinyl nitrile, polystyrene (EPS) or polypropylene (EPP) foam. Liner 104 may substantially line the entire interior surface of shell 102 or alternatively may have windows or other gaps in the structure.
An array of cushions 200 is installed inside shell 102. Cushions 102 may be attached directly to shell 102 whereby they are located between shell 102 and liner 104 or alternatively, cushions 200 may be attached to the inside surface of liner 104 to more directly contact the user's head 10. A further innermost liner such as a thin fabric or mesh material may be provided for user comfort.
As shown in
Liquid 204 can be oil, a gel or an aqueous liquid that remains in the liquid phase over a wide range of ambient temperature conditions. Suitable examples include oils, preferably a low viscosity oil such as vegetable or mineral oil. A suitable mineral oil is crystal plus oil, which is an odorless, tasteless, crystal clear, food-grade white mineral oil.
Referring to
According to one example, pad 206 is fabricated from a resilient, compressible material, such as open cell foam which may have a shore 00 hardness of about 20. The open structure of pad 206 is provided by pores 212 or other interstices for absorbing liquid 204, which and allow pad 206 to sequentially absorb and squeeze out liquid 204 when expanded and compressed, respectively. Pad 206 is highly compressible whereby it can be easily compressed to a small percentage of its original thickness. Suitable open cell foam materials have relatively low density, firm support, good durability, good shock absorption and vibration dampening, and resistance against degradation by exposure to the selected liquid 204. Examples include open cell vinyl nitrile or polyurethane foam. Other suitable foams include K329 or similar low density foams.
In another example, pad 206 comprises a compressible lattice structure, for example a structure formed from beads or other units fused together, in which the beads can individually compress or distort. This structure has interstices between the beads that alternately retain and expel liquid as the structure is decompressed and compressed. For example, as shown in
In an alternative example, pad 206 may comprise a closed cell foam such as ethylene-vinyl acetate (EVA) foam, or a composite of open and closed cell components.
As shown in
Pad 206 is normally uncompressed or only lightly compressed when helmet 100 is worn during normal use, prior to any impact thereon. The term “uncompressed” as used herein includes, unless otherwise stated, a small amount of compression that might occur during such normal wearing of the helmet. In this state, at least a portion and preferably most of liquid is absorbed within pad 206. Pad 206 may be substantially saturated with liquid 204 whereby an impact on helmet 100 quickly releases a substantial portion of liquid 204 from pad 206, whereby liquid 204 is then free-flowing within bladder 202.
As used herein, the terms “absorption” and similar terms refer to the property of pad 206 to draw in and retain liquid 204 within pores 212 in a reversible fashion in a physical process.
With reference to
An oblique (i.e. “angled”) or rotational force acting on shell 102 generates shear forces on cushion 200. Depending on the direction of the impact, the resulting rotational acceleration imparted to the user's head 10 in a conventional helmet can increase the risk of subdural haematomas or concussions. In the case of helmet 100, cushion 200 attenuates these rotational forces by uncoupling the movement of shell 102 from head 10, which in turn permits shell 102 to rotate relative to the user's head 10. A rotational force on shell 102 generates shearing force acting on cushion 200. Liquid layer 216 generated within cushion 200 following an impact acts as a slip plane which allows opposing upper and lower portions of bladder 202 to be freely displaced relative to each other, effectively allowing cushion 200 to “roll”, thereby allowing a degree of rotational freedom of shell 102 relative to the user's head. It will be seen that the degree of “roll” is based in part on the thickness of cushion 200.
Cushion 200 also serves to attenuate linear forces directed radially inwardly towards the center of the user's head 10 by compression of pad 206 and flexibility and distortion of bladder 202 when compressed.
After the initial force of the impact is removed, the resilience of pad 206 causes it to expand back to its pre-impact thickness, which in turn re-absorbs liquid 204 into pad 206, as shown in
Cushion 200 and pad 206 may comprise a range of configurations, as required for different applications. By way of example, as shown in
As shown in
Suitable dimensions include, for cushion 200 is round may be provided having a diameter of about 65 mm and a height of about 4 mm, a bladder thickness of about 0.5 mm, a flange length of about 3 mm, a foam diameter of about 59 mm and foam thickness of about 4 mm, and a gap distance of about 3 mm. In this example, bladder 202 is filled with about 3.0 ml of vegetable oil. In other examples, cushions 200 is round with a diameter of about 35 mm, a height of about 5 mm, a bladder thickness of about 0.5 mm, a flange length of about 3 mm, a foam diameter of about 29 mm, a foam thickness of about 4 mm, a gap 214 of about 3 mm, and about 1.2 ml of fluid 204.
Dimensions of cushion 200 should be suitable to permit sufficient lateral movement between upper and lower surfaces of bladder 202 to attenuate shear forces to a degree that is effective for the body armour. It will be seen that different uses and applications will require different configurations and dimensions, especially when taking into account additional requirements such as weight limitations and the overall thickness of the helmet or other armour. The configuration of cushion may thus be optimized for any given application.
An advantage of cushion 200 is reduced weight as compared to a similarly dimensioned bladder filled with liquid alone. The present example is estimated to be about half the weight of a bladder having similar dimensions that houses only liquid.
Cushion 200 may be covered with material 300 to enhance user comfort, protect bladder 202, improve attachment to other helmet components, etc. As shown in
Cushions 200 can be configured for use in a variety of body armor devices, including helmets for many activities. The numbers, placement and configurations of cushions 200 will reflect the desired properties of the body armor device. For example,
As shown in
Table 1 shows the measurements of linear and rotational acceleration at four locations (front, side, rear, and crown) around a conventional helmet and a helmet according to the present invention including four cushions 200 installed on a skull grip 108 with a 6 mm cushion at crown and 4 mm cushions at each side and the front (all with vinyl nitrile foam). In table 1, a helmet according to the present invention provides an average decrease in linear acceleration of about 13.9% and an average decrease of rotational acceleration of about 14.7%, as compared to the conventional helmet.
Table 2 shows the measurements of linear and rotational acceleration at four locations (front, side, rear, and crown) around a conventional helmet and a helmet according to the present invention including two cushions 200 installed on a skull grip with a 6 mm cushion at the crown and a 4 mm cushion at the front (all with vinyl nitrile foam). In table 2, a helmet according to the present invention provides an average decrease in linear acceleration of about 12.3% and an average decrease of rotational acceleration of about 9.4%, as compared to the conventional helmet.
The experimental results of tables 1 and 2 were obtained under testing conditions performed in accordance with CE-1077/1078.
In other embodiments, helmet 100 may also include other components for decreasing and/or redirecting rotational or shear forces such as force redirection cushions 400 of the type disclosed in applicant's PCT application no. PCT/CA2017/050109, which is incorporated by reference in its entirety.
The embodiments described herein are intended merely to provide examples of the invention. Various alterations, modifications and variations to these embodiments may be made without departing from the intended scope of the invention. Features from one or more of the above-described embodiments may be selected to create alternate embodiments comprised of a sub combination of features which may not be explicitly described above. The subject matter described herein intends to cover and embrace all suitable changes in technology.
This application claims priority to U.S. provisional application No. 62/433,551 filed Dec. 13, 2016, which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2017/051507 | 12/12/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62433551 | Dec 2016 | US |
