Helmet

A helmet to be worn on a head having an annular headband shaped area. The headband shaped area positioned near an upper junction of the ears and the wearer's head. A top area is centered about a top of the wearer's head. A middle area defined between the headband area and the top area. The helmet includes a shell having an inner surface. A first type of subliner elements extend from the inner surface at a location such that the first type of subliner elements are aligned with the headband area. A second type of subliner elements extend from the inner surface at a location such that the second type of subliner elements are aligned with the middle area. A third type of subliner element extends from the inner surface at a location such that the third type of subliner element is aligned with the top area.

BACKGROUND OF THE DISCLOSURE

The present disclosure generally relates to a helmet whose purpose is to protect a wearer's head during a head impact. Extending radially outward from the wearer's head, the helmet may consist of one or multiple liner portions and one or multiple shell portions. Either way, there is typically a liner portion in contact with the wearer's head initially or during impact, that liner portion being herein defined as the subliner. The subliner may be comprised of individual subliner elements. The subliner is typically attached to an inner shell portion, the term inner having been added to unambiguously differentiate it from an outer shell portion in the case of a helmet with multiple shell portions. In helmets having just a single liner portion and a single shell portion, the liner portion would be the same as the subliner and the shell portion would be the same as the inner shell portion. In some helmets (typically hockey helmets) the inner shell portion may consist of individual shell segments. The subliner and inner shell portion together are herein defined as the helmet subliner system, and the present disclosure comprises an improved helmet subliner system to better protect the wearer from sustaining concussions and other head injuries.

Especially in multiple liner, multiple shell helmets, the subliner, as defined herein has been used primarily for obtaining the best fit and best comfort for the wearer. But as will be shown in this specification, the subliner, and more generally the subliner system may also be used to substantially improve the head protection performance of the helmet. The disclosure recognizes and takes advantage of the fact that all of the forces that are applied to the wearer's head during a head impact are preferably applied through the subliner and its elements.

Recent postmortem brain investigations have found a high instance of chronic traumatic encephalopathy, or CTE, in the donated brains of deceased NFL football players, many of whom had suffered debilitating symptoms during their lifetimes, including unexplained rage, extreme mood swings, and substantial cognitive degeneration, all of which may have begun years after their football playing ended. Current research shows that CTE can almost always be traced back to long term repetitive head impacts which may include both concussive and sub-concussive impacts. It is believed those impacts would have been characterized by a high level of head angular acceleration, sometimes called rotational acceleration. The improved helmet subliner system configuration of the present disclosure, is specifically designed to help reduce the level of head angular acceleration during a head impact.

SUMMARY OF THE INVENTION

Briefly stated, the present disclosure is directed to a helmet to be worn on a head of a wearer. The head has a pair of eyebrows, a pair of ears, and an annular headband shaped area encircling the wearer's head. The headband shaped area being approximately 0.75 to 1.25 inches wide and having a lower edge defining a plane positioned approximately 0.5 to 1.5 inches above the eyebrows and approximately 0.25 to 0.75 inches above an upper junction of the ears and the wearer's head. A top area is centered about a top of the wearer's head and encompasses from 0.44 to 7 square inches. A middle area of the head is defined between the headband area and the top area. The helmet includes a shell comprised of a hard impact resistant material and having inner and outer surfaces. The shell is adapted to surround at least a portion of the cranial part of wearer's head with the inner surface of the shell being spaced from the wearer's head at an initial pre-impact relative position when the helmet is worn. A subliner, at least a part of which is in potential contact with the wearer's head when the helmet is worn prior to an impact and during an impact, includes a plurality of a first type of subliner elements extending from the inner surface of the shell at a location such that the first type of subliner elements are aligned with the headband area when the helmet is worn. The first type of subliner elements are constructed of an energy absorbing viscoelastic foam material capable of exhibiting a compressive stress of at least 50 psi for a dynamic compression of 50%. A plurality of a second type of subliner elements extend from the inner surface of the shell at a location such that the second type of subliner elements are aligned with the middle area when the helmet is worn. The second type of subliner element being constructed of a foam material that can exhibit a compressive stress of less than 10 psi for a static and a dynamic compression of 50%. A third type of subliner element extends from the inner surface of the shell at a location such that the third type of subliner element is aligned with the top area when the helmet is worn. The third type of subliner element is comprised of an energy absorbing viscoelastic foam material capable of exhibiting a compressive stress of at least 50 psi for a dynamic compression of 50%. The third type of subliner element has a substantially flat lower surface which is substantially tangent to the surface of the wearer's head beneath it when the helmet is worn.

In another aspect, the present disclosure is directed to a helmet to be worn on a head of a wearer. The head has a pair of eyebrows, a pair of ears, and an annular headband shaped area encircling the wearer's head. The headband shaped area being approximately 0.75 to 1.25 inches wide and having a lower edge defining a plane positioned approximately 0.5 to 1.5 inches above the eyebrows and approximately 0.25 to 0.75 inches above an upper junction of the ears and the wearer's head. A top area is centered about a top of the wearer's head and encompasses from 0.44 to 7 square inches. A middle area of the head is defined between the headband area and the top area. The helmet includes an inner shell comprised of a hard high strength material and having inner and outer surfaces. The shell is adapted to surround at least a portion of the cranial part of wearer's head with the inner surface of the shell being spaced from the wearer's head at an initial pre-impact relative position when the helmet is worn. A subliner, at least a part of which is in potential contact with the wearer's head when the helmet is worn prior to an impact and during an impact, includes a plurality of a first type of subliner elements extending from the inner surface of the shell at a location such that the first type of subliner elements are aligned with the headband area when the helmet is worn. The first type of subliner elements are constructed of an energy absorbing viscoelastic foam material capable of exhibiting a compressive stress of at least 50 psi for a dynamic compression of 50%. A plurality of a second type of subliner elements extend from the inner surface of the shell at a location such that the second type of subliner elements are aligned with the middle area when the helmet is worn. The second type of subliner element being constructed of a foam material that can exhibit a compressive stress of less than 10 psi for a static and a dynamic compression of 50%. A third type of subliner element extends from the inner surface of the shell at a location such that the third type of subliner element is aligned with the top area when the helmet is worn. The third type of subliner element is comprised of an energy absorbing viscoelastic foam material capable of exhibiting a compressive stress of at least 50 psi for a dynamic compression of 50%. The third type of subliner element has a substantially flat lower surface which is substantially tangent to the surface of the wearer's head beneath it when the helmet is worn. An outer shell comprised of a hard impact resistant material having inner and outer surfaces surrounds at least a portion of the inner shell. The inner surface of the outer shell being spaced from the outer surface of the inner shell at an initial pre-impact relative position. A plurality of outer liner elements is located in the space between the outer surface of the inner shell and the inner surface of the outer shell.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “lower,” “bottom,” “upper” and “top” designate directions in the drawings to which reference is made. The words “inwardly,” “outwardly,” “upwardly” and “downwardly” refer to directions toward and away from, respectively, the geometric center of the helmet, and designated parts thereof, in accordance with the present disclosure. Unless specifically set forth herein, the terms “a,” “an” and “the” are not limited to one element, but instead should be read as meaning “at least one.” The terminology includes the words noted above, derivatives thereof and words of similar import. The terms “angular acceleration” and “rotational acceleration” should be taken as synonymous from a force vector perspective. Similarly, the words “acceleration” and “deceleration” should also be taken as synonymous from a force vector perspective.

Referring now toFIGS. 1, 2 and 4, to best understand the configuration of the helmet subliner system or subliner10, which is the subject of this disclosure, it will be useful to first define certain areas of a potential wearer's head12which could come in contact with various types of subliner elements of the helmet14. In this regard, all the following will be defined: first area A, first plane A1, second plane B1, point b, second area B, and third area C.

FIG. 1is a perspective side view of a wearer's head12having a pair of eyebrows26(only one is shown) and a pair of ears28(only one is shown). The head12includes a first area A, first plane A1, second plane B1, point b, second area B, and third area C. First area A is an annular headband shaped area encircling the wearer's head12. The first or headband shaped area A being approximately 0.75 to 1.25 inches wide, and preferably approximately 1.0 inch wide, and having a lower edge defining a plane positioned approximately 0.5 to 1.5 inches, and preferably approximately 1.0 inch, above the eyebrows26and approximately 0.25 to 0.75 inches, and preferably approximately 0.5 inches, above a location where the ears28join the wearer's head12at the top or, stated differently, an upper junction of the ears28and the wearer's head12. The first plane A1is a hypothetical plane defined by the lower edge of first area A. Picture second plane B1as a lower cover of an imaginary hard cover book being balanced horizontally atop the wearer's head12while the wearer's head12is maintained in an upright position, tilted neither right nor left, nor forward nor backward and where point b is approximately the center of the contact area between the lower cover of the imaginary book and the wearer's head12. Notice that first plane A1is tilted upward in the forward direction (the direction toward the face of the wearer) relative to second plane B. InFIG. 1, the second plane B1is shown as transparent so that the contact area with the wearer's head12, point b, is apparent. The second or top area B is formed by a planar projection of an approximate 2-inch diameter circle (not shown) formed in the second plane B1centered about point b onto the wearer's head. That is, the second area B is generally circular and is centered about a top of the wearer's head12and extends 0.75 to 3 inches, and preferably 2 inches, in diameter in all lateral directions. As will be discussed, the second area B needn't be 2 inches in diameter, nor even circular. That is, the second area B can range from 0.44 to 7 square inches, or preferably 3.14 square inches. The third or middle area C is the area on the wearer's head12between first area A and second area B.

Referring again toFIGS. 1, 2 and 4and as will be described in detail in subsequent sections of the specification, subliner elements of a first type16are to be located in the first area A; subliner elements of a second type18are to be utilized in third area C, and a subliner element of a third type20is to be used in second area B. Each type of subliner element16,18,20has its own specific physical characteristics in accordance with the purpose of the disclosure which is to be able to reduce the level of head angular acceleration imparted to a wearer's head12during a head impact, regardless of the location or direction of the impact. Each of the subliner elements16,18,20is to be attached to an inner surface22of the inner shell24of the helmet14, preferably utilizing a commonly employed hook and loop type of fastener arrangement which allows for the simple assembly of, and changeout of, individual subliner elements16,18,20during a fitting process, with each subliner element16,18,20being positioned and sized in its thickness direction to best fit the size and shape of a wearer's head12. It will be appreciated by one skilled in the art, that other fastening elements could be used to releasably secure the subliner elements16,18,20to the inner surface22of the inner shell24of the helmet14, such as a releasable adhesive (not shown).

FIG. 2is a perspective upper side view of a wearer's head12showing the first, second and third types of subliner elements16,18,20as they would be located in their respective designated areas shown inFIG. 1, in accordance with the present disclosure. The individual subliner elements16,18,20are not attached to the wearer's head12(as could be falsely assumed fromFIG. 2) but are merely illustrated in the figure where they would be located with respect to the wearer's head12when the helmet14is worn. Typically, they would be attached to the inner surface22of the inner shell24of the helmet14, as shown inFIG. 4, preferably utilizing a commonly employed hook and loop type of fastener arrangement, describe below. The upper side viewpoint enables a fuller view of subliner element of the third type20, which is preferably disc or oval shaped, oriented generally in the second plane B1, and is centered about point b at the top, or crown, of the head12. Subliner element of the third type20has a flat (or nearly flat), horizontal (or nearly horizontal), lower surface20awhich may be either initially in contact with the wearer's head12or slightly spaced therefrom but may come into contact with the wearer's head12during an impact. Subliner element of the third type20is shown here as a circular disc having a two-inch diameter to accommodate any misalignment of the center of the disc with the initial actual point of contact with a wearer's head12and to accommodate lateral displacements between the inner shell24and the wearer's head12during an impact. In general, subliner element of the third type20need not be circular, but it may be of any suitable contiguous shape typically having that approximate area or greater. The important thing is that its lower surface20abe of sufficient area to enable the accommodations described above, and that it be predominately flat and horizontal such that it is substantially tangent to the surface of the wearer's head12beneath it when the helmet14is worn.

To be able to appreciate why the lower surface20aof subliner element of the third type20is preferred to be flat and horizontal, one may perform a simple experiment with one's own hand and one's own head. First, using one's hand, firmly cup the top of one's head. Then while still firmly cupping the head, forcefully move the cupping hand's forearm forward and backward, and side to side, and notice how the head is forced into violent motion likely involving significant head angular accelerations. Next, repeat the experiment while the hand is held flat and horizontal. The result: almost no forced motion of the head, and thus no head angular acceleration.

The subliner element of the third type20is preferably made of relatively stiff, very energy absorbent, viscoelastic foam material, capable of exhibiting a compressive stress of 20 psi for a static compression of 50% and at least 50 psi for a dynamic impact type compression of 50%, for example a vinyl nitrile foam such as IMPAX® VN600, VN740, or VN1000 by Dertex Corporation, or a polyurethane foam such as LAST-A-FOAM® TF 8015 by General Plastics Manufacturing Company. The subliner element of the third type20should be thick enough not to compress all the way to its full densification condition under a peak normal impact force which could easily reach, and possibly even exceed, a thousand pounds. Although the weight of a full helmet would likely be substantially less than that (being typically under five pounds), if all the helmet weight were to be required to be supported by the subliner element of the third type20, with its high dynamic stiffness designed to accommodate a dynamic force of over a thousand pounds, the supporting area around point b for a static force of just five pounds could be so small that the supporting pressure could be uncomfortably high for the wearer were it not for the subliner elements of the second type18, shown in third area C.

Subliner elements of the second type18, located in third area C, would preferably be made of a much more compliant material than that used for the subliner element of the third type20, preferably at least five times more compliant and perhaps more than an order of magnitude more compliant than the stiffer materials recommended for subliner element of the third type20. Such a material could be an extra soft polyurethane foam such as LAST-A-FOAM® EF-4003 by General Plastics Manufacturing Company, or EZ-Dri foam by Crest Foam Industries, both having, a relatively flat static and dynamic compression stress vs. deflection characteristic (the former 2.6 psi at 10%, 2.7 psi at 20%, 2.8 psi at 30%, 3.0 psi at 40%, and 3.4 psi at 50% and the latter 0.3 psi at 10%, 0.35 psi at 20%, 0.4 psi at 30%, 0.45 psi at 40% and 0.55 psi at 50%), so when incorporating the proper total area to accomplish the function of supporting the full weight or nearly the full weight of the helmet with the latter material enabling about five times the support area for extreme comfort, the exact location and thickness of the subliner elements of the second type18would not be that critical for the subliner elements of the second type18to be able to successfully support all, or almost all, of the weight of the helmet, yet contribute very little side force to the wearer's head12during an impact. However, the second type of subliner elements18are preferably positioned generally equidistantly about and between the first and third type of subliner elements16,20in the third area C.

FIG. 1schematically shows the cervical spine13and its seven cervical vertebrae labeled Atlas (C1), Axis (C2), C3, C4, C5, C6 and C7. For both centered (directed toward the center of gravity of a wearer's head) and non-centered impacts having a large horizontal force component, almost all the side forces (and torques) that would be imparted to a wearer's head12during an impact would be imparted through the subliner elements of the first type16, which would be located, or substantially located, in first area A and generally evenly distributed/spaced thereabout. First area A places the point of application of these impact forces as close as possible to the head's two natural pivot points for angular acceleration: a lower pivot point12awhere the C7 cervical vertebrae (which can be located by the prominent bone at the base of the back of the neck) meets the Ti thoracic vertebrae, and an upper pivot point12bwhere the C1 cervical vertebrae (the atlas bone) meets the paired occipital condyle projections of the skull to enable forward and backward rotation (a “yes” motion) of the head and where the atlas bone meets the C2 cervical vertebrae (the axis bone) enabling axial rotation (a “no” motion) and side-to-side rotation of the head, this latter pivot being located approximately just above and slightly in front of the ear lobes. Thus, all the head angular accelerating torques imparted to the user's head during an impact would be kept as small as possible for a given force as a result of this lowest practical positioning of subliner elements of the first type16.

As stated previously, the subliner element of the third type20, due to its flat horizontal lower surface20a, typically does not impart a significant horizontal force to the wearer's head12. Yet, there may be certain impacts during which the lower surface of the subliner element of the third type20would not remain flat but instead would tend to cup around the surface of the wearer's head12. One such type of impact is obvious: a direct downward impact to the crown, or top, of the helmet14, centered toward the center of gravity (e.g.) of the wearer's head12. Although that type of impact would result in cupping the lower surface of subliner element of the third type20around the wearer's head12, little or no horizontal force would be imparted to the wearer's head12.

Another impact case that could cup the lower surface of the subliner element of the third type20might be a downward impact to the top of the helmet at a point located away from the crown and generally directed toward the body of the wearer. Picture a running back diving over the goal line, his helmet getting struck in midair by the shoulder pad of a linebacker diving the other way to stop him. Here, in addition to a significant downward force through the subliner element of the third type20(downward here meaning downward toward the body of the running back), there could be a not-insignificant horizontal force (horizontal here meaning horizontal relative to the body of the running back) imparted to the running back's head through subliner element of the third type20, as well as through the subliner elements of the first type16; for the most part the former would tend to rotate point b on the running back's head about the aforementioned upper pivot point toward the impact location, while the latter would tend to rotate point b about the aforementioned lower pivot point away from the impact location. So even in this case where the subliner element of the third type20cannot avoid imparting a horizontal (sideways) force, the structure of the total subliner system10still tends to cancel the above two rotational head motions and thereby reduce the resultant angular acceleration of the wearer's head12.

Further reductions of imparted torque levels can be achieved by lowering the impact force levels, which can be accomplished by a proper choice of material for the subliner elements of the first type16, and by including specific structural features in the subliner elements of the first type16. Especially during an impact involving mostly a horizontal force component, only about one third of the subliner elements of the first type16(those located in the wide general region beneath the impact point) would be imparting most of the side normal force and side tangential force to the wearer's head12since the remaining subliner elements of the first type16would have tended to move away from the wearer's head12during the impact as the force-imparting subliner elements of the first type16compress and/or flex as a result of the high impact forces. The force levels could be of the same order of magnitude as those potentially experienced by the subliner element of the third type20(up to, and perhaps even more than a thousand pounds), and so the same energy absorbing viscoelastic foam materials cited for subliner element of the third type20would be in order for subliner elements of the first type16, where their high energy absorption capability will help reduce the level of the high impact forces. The radial (thickness) dimension of the subliner elements of the first type16should be of sufficient length and have sufficient area to be able to avoid full densification at the maximum expected peak dynamic impact force, which could still be in the thousand-pound range for the total aggregate number of forces imparted on the subliner elements of the first type16. On average the radial thickness of the subliner elements of the first type16would be approximately 0.25 to 1.25 inches, and preferably 0.75 inches.

In a preferred embodiment, to help further reduce the imparted tangential side forces, the subliner elements of the first type16may be partitioned into multiple segments which emanate in a substantially perpendicular direction from the inner surface22of the inner shell24. The partitioning may be in the form of like-shaped segments having a particular cross-sectional shape, or it could be in the form of different shaped segments, as for instance an outer square cross-sectional shaped segment36having a centered circular cutout38, along with a circular cross-sectional segment40to fill the circular cutout space, seeFIG. 3. In order to best achieve the goal of reduced imparted side forces, the side surfaces of the partitioned side-by-side segments should be at least partially free to slide relative to each other in the segments' general radial direction. Each segment's generally parallel partitioned surfaces cannot be exactly radial from the standpoint of the wearer's head12due to the width of the partitioned element, but they are substantially radial. The partitioning or segmenting might be implemented using a simple “cookie cutter” approach. Other examples of partitioning subliner elements that could be used for the first type of subliner element16are described below inFIGS. 7a-7bthrough 15a-15b.

FIG. 3is an exploded perspective view of a partitioned subliner element of the first type16and its attachment to a portion of the inner surface22of the inner shell24, showing the portion of the inner shell24, the hook part30and the loop part32of a hook and loop fastener mechanism of a type in common usage today for such applications, along with an optional covering34over the subliner element of the first type16. Any of the subliner elements, of any of the three subliner element types16,18,20may include a full covering34formed from a fabric or a film34to improve the comfort of the wearer, to improve the durability of the subliner element types16,18,20, or to improve the functioning of the subliner element types16,18,20, the latter possibly including, but not being limited to, its ability hold partitioned columns of a subliner element type16,18,20in place, its ability to protect against moisture and contaminants, its ability to improve air flow, and its ability to improve moisture dissipation. The optional covering34need not be full as shown but may be partial if the circumstances warrant. The fabric of choice may be any of a wide range of suitable fabrics, while the film of choice could be any suitable polymer or elastomer film having a suitable thickness for the application.

FIG. 4is a cross-sectional side view located at the midsagittal plane of the wearer's head12showing the three types of subliner elements16,18,20as located inFIG. 2and the inner shell24to which they are attached. The inner shell24may be part of a single liner, single shell helmet14as illustrated in the figure, or it may be part of a multiple liner, multiple shell helmet, as discussed in more detail below. The relative size of the inner shell24shown inFIG. 4at the lower end of the indicated radial thickness range would be consistent with the former case if the helmet were for example an equestrian helmet or a ski helmet, and the relative size of the inner shell shown inFIG. 4would also be consistent with the latter case if the helmet were for example a football helmet or a motorcycle helmet. A football helmet or a motorcycle helmet of the single liner, single shell type would typically have a larger subliner system10at the higher end of the indicated radial thickness range, which in that case would also be the outer shell. Thus, in a football helmet or motorcycle helmet of the single liner, single shell type embodiment, the radial spacing of the inner shell24from the head12would typically be greater than that shown inFIG. 4and the subliner elements of the first, second and third types16,18,20would accordingly have a greater radial dimension.

With continued reference toFIG. 4, the inner surface22of the inner shell24above subliner element of the third type20is shown to have a flat horizontal surface42rather than a concave surface. The inner shell24may be molded that way to achieve the flat horizontal surface42. The flat horizontal surface42is not absolutely necessary but it is preferred to enable subliner element of the third type20to be flat on its upper surface as well as its lower surface20a, which helps to assure a horizontal lower surface20a, and makes it simpler and more controllable to determine, select, and properly align and apply a proper thickness subliner element of the third type20so that it's lower surface20aremains horizontal and preferably barely touches the wearer's head12. As shown inFIG. 4, the two cross-sectioned subliner elements of the second type18are shown in the third area C, properly radially compressed, as would be all of the other subliner elements of the second type18not shown in the cross-section, when all are supporting the full weight of the helmet, even though the full helmet with all its potential parts, including a potential face guard and a potential chin strap or jaw strap system, is not shown inFIG. 4. Finally, the subliner elements of the first type16in the first area A each have a thickness to yield a snug but not uncomfortable fit with the wearer's head12.

FIG. 5is a left side elevational view of the wearer's head12showing the inner shell24ofFIG. 4located over the wearer's head12with all the subliner elements of the first, second and third type16,18,20positioned as shown in phantom and as inFIG. 2; all of the sub liner elements of the first, second and third type16,18,20being attached to the inner surface22of the inner shell24, typically by the easy-on, easy-off, hook and loop fastener mechanism30,32shown inFIG. 3. The easy-on, easy-off capability helps in being able to customize the helmet for an individual wearer. The potential materials to be used for the inner shell24would depend upon which embodiment it is being used in. In the single liner, single shell helmet embodiment the inner shell24(which is now also the outer shell) must be able to handle a direct impact, so an impact resistant material such as polycarbonate or high impact ABS would be appropriate. In the multiple liner, multiple shell helmet embodiment described in more detail below, the inner shell24need not handle a direct impact, but it still would need to be able to handle high forces so a high strength polymer composite containing either glass fibers, carbon fibers, or KEVLAR® fibers (commonly understood as heat-resistant and strong synthetic fibers) or a composite utilizing a combination of different fibers could be appropriate. Also, for this embodiment, the inner shell24could be constructed of a thin metal, such as stainless steel or an aluminum alloy (either perforated, or not perforated), and in large quantities could be fabricated by pressing it to shape in a die with a large machine press. Such a thin metal shell, perhaps a thirty-second of an inch or less in thickness, could weigh even less than a comparable polymer composite shell.

FIG. 6is a cross-sectional side view located at the midsagittal plane of a wearer's head12, showing a two liner, two shell, helmet14embodiment of the present disclosure.FIG. 6shows the subliner system10ofFIG. 4, plus a second or outer liner44and a second or outer shell46which together form an outer shell system48. Five outer liner elements50are shown in the second liner44because they cross the midsagittal plane. Typically, there may be ten to fifteen additional liner elements50in the second liner44which are not shown inFIG. 6because they do not cross the midsagittal plane. That would add up to a likely total of fifteen to twenty total liner elements50in the second liner44, spread out more or less equidistantly throughout the available space between the inner shell24and the second or outer shell46.

All the liner elements50of the second liner44are firmly attached to both the outer surface of the inner shell24and the inner surface of the outer shell46. By contrast, subliner elements of the first, second and third types,16,18,20in the subliner system10can only be attached to the inner shell24(they cannot be attached to a wearer's head). The firm attachment of the liner elements50of the second liner44to both the inner and outer shells24,46enables liner elements50to experience not just high compression forces, but high shear forces and high tensile forces as well. As a result, the attachment requirement here is beyond the capability of a standard hook and loop fastener and is more in the realm of a high strength, wide temperature range, flexible adhesive, such as LOCTITE® 4902™, or LOCTITE® Plastic Bonder, both by Henkel Corporation. The former is a one-part adhesive, the latter a two-part adhesive, and both are quick curing.

These flexible, high strength attachments make it possible for all the liner elements50of the second liner44to participate in mitigating any impact to the wearer's head12, regardless of the impact's location or direction. That mitigation is accomplished through the widespread positioning of the liner elements50and their ability to efficiently absorb energy in three different modes: compression, shear, and tension. For example, for any centered impact the liner elements50of the second liner44generally located in the region beneath the impact will experience compression, those located to the side of the impact will experience shear, and those located opposite the impact will experience tension, while those located in between will experience some combination of compression, shear, and tension. For any non-centered impact most of the liner elements50of the second liner44will experience a higher degree of shear. Because every impact is different in its location and direction, each liner element50in the second liner44must be able to absorb energy at all the expected possible levels of compression, shear, and tension, and combinations thereof.

Furthermore, in order to even be in a position of optimally absorbing energy, each liner element50of the second liner44must become deformed during an impact to its full extent by the outer shell46, not just those liner elements50beneath the impact, but those to the side of the impact, and those opposite the impact as well, and the outer shell46must remain rigid enough during the impact to be able to accomplish that. Because the outer shell46is relatively thin and typically made of a polycarbonate or high impact ABS, this requires that the outer shell46be rigidized, especially near its opening to accommodate a wearer's head12, which is the place where it is the weakest. Notice in the figure, that there are two molded-in internal rings52near the opening to accomplish the rigidizing, but other rigidizing approaches such as severe contouring or metal banding (not shown) would also be acceptable.

Achieving the optimum energy absorption by all the liner elements50of the second liner44also requires they be fabricated of a material having an inherent high energy absorbing capability, and that the material also have a proper level of dynamic stiffness for the total second liner element50footprint area. To meet these criteria, the liner elements50of the second liner44may be fabricated from the same list of materials recommended for subliner elements of the first and third types16,20, the list including: a vinyl nitrile foam such as IMPAX® VN600, VN740, or VN1000 by Dertex Corporation, or a polyurethane foam such as LAST-A-FOAM® TF 8015 by General Plastics Manufacturing Company. However, in block form, each material likely presents too much dynamic stiffness in shear as compared to its dynamic stiffness in compression and tension. So to reduce a second liner element's dynamic stiffness in shear, without at the same time reducing its dynamic stiffness in compression or tension, partitioning of each liner element50into discrete adjacent segments is preferred, somewhat similar to what has been previously discussed for subliner elements of the first type16, but even more so for the second liner elements50because the potential shear levels experienced by the second liner elements50are greater.

The cross-sectioning of the second liner elements50inFIG. 6reveals each element to be partitioned into five equal segments50a,50b,50c,50d,50e. However, one skilled in the art will understand that there are several partitioning possibilities, all of which could be acceptable options if they can achieve the proper level of reduction in the total shear force as compared to the total compression and tensile forces.

FIGS. 7athrough 15ashow nine such partitioning possibilities, illustrated in plan view (from the viewpoint of the outer shell46) to be able to see what they actually could represent. Cross-sectional views inFIGS. 7bthrough 15bshow the same sectional view as what is shown inFIG. 6. However, even these nine are still an extremely reduced sample of what may be possibly used as partitioning arrangements for the second liner elements50.FIGS. 7aand 7bshow twenty-five equal square shaped segments or foam columns54arranged in a 5×5 square array. That is, the foam columns54form a plurality of generally radially oriented side-by-side flexible individual and independent foam columns54. The columns54are preferably formed entirely of foam and having a top surface54a, a bottom surface54b, and foam side surfaces54cwhere the top surface54ais directly attached to the inner surface of the outer shell48and the bottom surface is directly attached to the outer surface of the inner shell24and the foam side surfaces54cof adjacent columns54are unattached and are situated side-by-side in slidable direct contacting frictional engagement.FIGS. 8aand 8bshow a liner element50having an outer circumferential square wall56and an inner square cutout58, filled with nine equal square shaped segments arranged in a 3×3 square array.FIGS. 9aand 9bshow a liner element50having an outer annular wall60, an inner annular wall62complementarily positioned in the outer annular wall60and an innermost cylinder64complementarily positioned within the inner annular wall62.FIGS. 10aand 10bshow a liner element50having a square outer annular wall66, a square inner annular wall68complementarily positioned in the square outer annular wall66and an innermost generally square in cross section cylinder70complementarily positioned within the square inner annular wall68.FIGS. 11aand 11bshow a liner element50having octagonal outer annular wall72, an octagonal inner annular wall74complementarily positioned in the octagonal outer annular wall72and an innermost generally octagonal in cross section cylinder76complementarily positioned within the octagonal inner annular wall74.FIGS. 12aand 12bshow a liner element50having a hexagonal outer annular wall78, a hexagonal inner annular wall80complementarily positioned in the hexagonal outer annular wall78and an innermost generally hexagonal in cross section cylinder82complementarily positioned within the hexagonal inner annular wall80.FIGS. 13aand 13bshow a liner element50having square outer annular wall84, a square inner annular wall86complementarily positioned in the square outer annular wall84and an innermost generally circular in cross section cylinder88complementarily positioned within the square inner annular wall86.FIGS. 14aand 14bshow a liner element50having octagonal outer annular wall90, an octagonal inner annular wall92complementarily positioned in the octagonal outer annular wall90and an innermost generally circular in cross section cylinder94complementarily positioned within the octagonal inner annular wall92.FIGS. 15aand 15bshow a liner element50having a hexagonal outer annular wall96, a hexagonal inner annular wall98complementarily positioned in the hexagonal outer annular wall96and an innermost generally circular in cross section cylinder100complementarily positioned within the hexagonal inner annular wall98.

FIGS. 7aand 7bshow a specific case of the general class of a radially partitioned second liner element50into side-by-side segments.FIGS. 8aand 8bthroughFIGS. 15aand 15bshow specific cases of the general class of radially partitioned second liner elements50into nesting and nested segments. Note that some segments can be both nesting and nested. Also noteFIG. 3shows an example of a nesting and nested segmented element, although not a second liner element50but a subliner element of the first type16.

In general, the segment boundaries of the liner elements50(all formable by a “cookie cutter type slicer”) would be oriented in a substantially radial direction (from the standpoint of the wearer's head12, or the outer shell46, etc.) but most can never be oriented exactly in the radial direction, in part due to the extended width dimensions of a liner elements50. Nevertheless, for simplification purposes, this specification will still be referred to them as “radial.” During an impact that results in a shearing motion of the liner elements50, at least some of the adjacent segment surfaces may move relative to each other along their boundaries in the radial direction to form S curves (not shown), and through dynamic friction to thereby provide some additional energy absorption. The concept of absorbing energy through adjacent surfaces moving relative to each other to form S curves is fully described in U.S. Pat. No. 9,032,558, which is hereby incorporated by reference in its entirety. It is possible that too much static friction when all the motion has stopped would be problematic if the liner elements50do not fully return to their initial position following an impact. In practice, though, the static friction is not likely to be large enough to cause this problem. But whether it would become a problem or not, an inventive “solution” to the problem will be herein described which could add an additional, adjustable, energy absorption mechanism if it were needed.

The indicated solution is to thinly coat adjacent segment boundaries with a viscous material (not shown), especially near the center of the span between the inner and outer shells24,46where the relative motion is the greatest. This not only would eliminate any residual static friction, it would, at the same time, provide additional dynamic friction, the degree of which could be controlled by altering the viscosity of the coating material used. High viscosity silicone fluids having various viscosities from under 100,000 cSt to over 1,000,000 cSt are available from Clearco Products. Furthermore, to assure that the coating material stays in place long term under the action of gravity and short term during impacts it is advisable to thoroughly mix in fumed silica to the silicone fluid, typically more than 5% by weight. Cab-O-Sil TS-720 by Cabot Corporation would be suitable for this purpose. Note thatFIGS. 6 and 7athrough15bwould look the same regardless of whether or not the segment boundaries in the second liner elements50would be coated or not coated.

FIG. 16illustrates a left side elevational view showing the outer shell46ofFIG. 6positioned on a wearer's head12. The size and shape of the outer shell46might be typical of a football helmet.

FIG. 17is a left side elevational view of a wearer's head12showing a face guard102attached to the outer shell46ofFIG. 8, and a chin strap104positioned on the wearer's chin and attached to the inner shell24ofFIG. 5, both typical of a football helmet application.

Finally, although only a first preferred embodiment having a subliner system10, and a second preferred embodiment having a subliner system10and an outer shell system48have been described in significant detail, the addition of a third liner and a third shell (not shown) would still be within the scope of the present disclosure. It will also be appreciated by those skilled in the art that changes or modifications could be made to the above described embodiments without departing from the broad inventive concepts of the disclosure. Therefore, it should be appreciated that the present disclosure is not limited to the particular use or particular embodiments disclosed but is intended to cover all uses and all embodiments within the scope or spirit of the described disclosure.