HELMET SHELL

Abstract

A helmet includes a helmet shell having an outer surface, an inner surface, and a plurality of slit openings. Each slit opening extends along a portion of the helmet shell. The slit openings include a pair of top slit openings that each extend longitudinally along a top portion of the helmet shell, where each top slit opening has a first length. The pair of top slit opening are spaced apart and define a flexible helmet portion spaced between the pair of top slit openings. The flexible helmet portion extends along the first length from a first end of the flexible helmet portion to a second end of the flexible helmet portion opposite to the first end, and the flexible helmet portion has a stiffness that varies along the first length from the first end to the second end.

Description

TECHNICAL FIELD

This disclosure relates to a helmet shell, for example, for helmets adapted for contact sports.

BACKGROUND

Many modern organized sports employ helmets that are designed to provide the players with significant head protection, with the desire to provide adequate protection from traumatic brain injury (TBI). Since safety is a primary concern, helmets have continually evolved in an attempt to reduce the risk and rate of concussions and/or other repetitive brain injuries, which can potentially end a player's career early and lead to long-term brain damage. This is especially true in American football, where the essential character of the athletic contest involves repeated player contacts, impacts, and tackling.

However, most helmet designs (e.g., for football or other sports or activities) fail to protect or provide inadequate protection against some of the most dangerous impacts within a game.

SUMMARY

This disclosure describes helmets, including helmet shells with slit openings in an outer surface of the helmets.

In some aspects of the disclosure, a helmet includes a helmet shell having an outer surface, an inner surface, and a plurality of slit openings. Each slit opening extends along a portion of the helmet shell, and the slit openings include a pair of top slit openings that each extend longitudinally along a top portion of the helmet shell. Each top slit opening of the pair of top slit openings has a first length. The pair of top slit opening are spaced apart and define a flexible helmet portion spaced between the pair of top slit openings. The flexible helmet portion extends along the first length from a first end of the flexible helmet portion to a second end of the flexible helmet portion opposite to the first end, and the flexible helmet portion has a stiffness that varies along the first length from the first end to the second end.

This, and other aspects, can include one or more of the following features. The stiffness of the flexible helmet portion can include a first stiffness at the first end and at the second end of the flexible helmet portion, a second stiffness at a middle portion of the flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the flexible helmet portion between the first end and the middle portion. The first stiffness can be greater than the second stiffness, and the third stiffness can be greater than the second stiffness and less than the first stiffness. The helmet can include a plurality channels recessed in the outer surface of the helmet shell, the plurality of channels including a pair of top channels along the top portion of the helmet shell, and the pair of top slit openings can reside within the pair of top channels. The pair of top slit openings can be arranged substantially parallel to each other along the top portion of the helmet shell. The pair of top slit openings can be symmetrical with each other across a lateral centerline of the helmet shell. The pair of top slit openings can be linear. Each of the top slit openings can include a laterally outward curve. The top slit opening of each top channel of the pair of top channels can extend along a majority of a length of the pair of top channels. The helmet shell can include a central recession in the outer surface of the helmet shell in a crown region between the pair of top slit openings. The plurality of slit openings can further include a pair of left side slit openings extending along a left side of the helmet shell toward a rear of the helmet shell, and a pair of right side slit openings extending along a right side of the helmet shell toward the rear of the helmet shell. Each left side slit opening of the pair of left side slit openings can have a second length, the pair of left side slit opening can be spaced apart and can define a second flexible helmet portion spaced between the pair of left side slit openings, and the second flexible helmet portion can extend along the second length from a first end of the second flexible helmet portion to a second end of the second flexible helmet portion opposite to the first end, and the second flexible helmet portion can have a stiffness that varies along the second length from the first end to the second end of the second flexible helmet portion. The stiffness of the second flexible helmet portion can include a first stiffness at the first end and at the second end of the second flexible helmet portion, a second stiffness at a middle portion of the second flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the second flexible helmet portion between the first end and the middle portion. The first stiffness can be greater than the second stiffness, and the third stiffness can be greater than the second stiffness and less than the first stiffness. The helmet can include a plurality channels recessed in the outer surface of the helmet shell, the plurality of channels can include a pair of left side channels along the left side of the helmet shell and a pair of right side channels along the right side of the helmet shell, the pair of left side slit openings can reside within the pair of left side channels, and the pair of right side slit openings can reside within the pair of right side channels.

In certain aspects, a helmet shell includes a shell body, an outer surface of the shell body, an inner surface of the shell body, and a plurality of slit openings. Each slit opening extends along a portion of the helmet shell, and the plurality of slit openings include a pair of left side slit openings extending along a left side of the shell body toward a rear of the shell body, where each left side slit opening of the pair of left side slit openings includes a first length, and a pair of right side slit openings extending along a right side of the shell body toward a rear of the shell body, where each right side slit opening of the pair of right side slit openings includes a second length. The pair of left side slit openings are spaced apart and define a left flexible helmet portion between the pair of left side slit openings, the left flexible helmet portion extending along the first length from a first end of the left flexible helmet portion to a second end of the left flexible helmet portion opposite to the first end, and the left flexible helmet portion includes a stiffness that varies along the first length from the first end to the second end. The pair of right side slit openings are spaced apart and define a right flexible helmet portion between the pair of right side slit openings, the right flexible helmet portion extending along the second length from a third end of the right flexible helmet portion to a fourth end of the right flexible helmet portion opposite to the third end, and the right flexible helmet portion includes a stiffness that varies along the second length from the third end to the fourth end.

This, and other aspects, can include one or more of the following features. The stiffness of the left flexible helmet portion includes a first stiffness at the first end and at the second end of the left flexible helmet portion, a second stiffness at a middle portion of the left flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the left flexible helmet portion between the first end and the middle portion. The stiffness of the right flexible helmet portion includes the first stiffness at the third end and at the fourth end of the right flexible helmet portion, the second stiffness at a second middle portion of the right flexible helmet portion between the third end and the fourth end, and the third stiffness at a second intermediate portion of the right flexible helmet portion between the third end and the second middle portion. The first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness. The helmet shell can include a plurality channels recessed in the outer surface of the helmet shell, the plurality of channels can include a pair of left side channels along the left side of the helmet shell and a pair of right side channels along the right side of the helmet shell, the pair of left side slit openings reside within the pair of left side channels, and the pair of right side slit openings reside within the pair of right side channels. The pair of left side slit openings and the pair of right side slit openings can be linear.

Some aspects of the disclosure encompass a helmet shell including a shell body, an outer surface and an inner surface of the shell body, and a plurality of slit openings extending along a portion of the helmet shell. The plurality of slit openings include a pair of rear slit openings at a rear of the helmet shell, the pair of rear slit openings partially surrounding a rear zone at the rear of the helmet shell and include a first length.

This, and other aspects, can include one or more of the following features. The pair of rear slit openings can be spaced apart and can define a rear flexible helmet portion between the pair of rear slit openings, the rear flexible helmet portion can extend along the first length from a first end of the rear flexible helmet portion to a second end of the rear flexible helmet portion opposite to the first end, and the rear flexible helmet portion can include a stiffness that varies along the first length from the first end to the second end. The stiffness of the rear flexible helmet portion can include a first stiffness at the first end and at the second end of the rear flexible helmet portion, a second stiffness at a middle portion of the rear flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the rear flexible helmet portion between the first end and the middle portion. The first stiffness can be greater than the second stiffness, and the third stiffness can be greater than the second stiffness and less than the first stiffness. The pair of rear slit openings can be straight. The pair of rear slit openings can be symmetrical across a lateral centerline of the helmet shell.

The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are a front perspective view and a rear perspective view, respectively, of an example helmet shell.

FIG. 3 is a rear view of the example helmet shell of FIG. 1.

FIG. 4 is a rear perspective view of the example helmet shell of FIG. 1.

FIG. 5 is a side view of the example helmet shell of FIG. 1.

FIG. 6 is a top view of the example helmet shell of FIG. 1.

FIGS. 7 and 8 are a front view and a front perspective view, respectively, of a second example helmet shell.

FIG. 9 is a rear view of the second example helmet shell of FIG. 7.

FIG. 10 is a rear perspective view of the second example helmet shell of FIG. 7.

FIG. 11 is a side view of the second example helmet shell of FIG. 7.

FIG. 12 is a top view the second example helmet shell of FIG. 7.

Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure describes a helmet shell with one or more slit openings through an outer surface of the helmet shell that provide areas of varying stiffness and flexibility of the helmet shell. The slit openings can provide increased stiffness in certain areas of the helmet and/or can provide flexible zones (e.g., zones between slit openings). The flexible zones are defined by varying stiffness that can transition from high-to-low-to-high stiffness, and are aimed at mitigating or distributing energy and/or force of impacts to the helmet during use. For example, the varying stiffness in the outer surface of the helmet can transition from a zone of high stiffness, low stiffness, and intermediate stiffness between the high stiffness and low stiffness. In some instances, the slit openings reside in recessed channels in the outer surface of the helmet shell, and the channels can define various zones of the helmet. The slit openings, and in some instances, the channels and the slit openings, can provide increased stiffness in areas that are prone to higher volume of impacts, such as sides and rear zones of the helmet relative to a top zone, or crown, of the helmet that generally encounters fewer impacts.

The slit openings can be through-openings that extend from an outer surface to an inner surface of the helmet shell, and the slit openings are continuous openings that span a certain length along the helmet shell. An example slit opening includes a length that is considerably larger than its width, such as a length that is one or more inches long and a width that is less than a half inch. The dimensions of the slit openings can vary, but generally include a longitudinal length that is at least three times its width. The openings can also act to ventilate the outer shell. In some implementations, the slit openings include a pair of parallel slit openings in one or more of areas of the helmet, e.g., a pair of parallel slit openings spanning a portion of the top of the helmet (e.g., openings running from a front of the helmet and along a top of the helmet toward the back of the helmet), one or more pairs of parallel side slit openings spanning a portion of one or both sides of the helmet (e.g., openings running from the front of the helmet along sides of the helmet toward the back of the helmet), and/or one or more parallel rear slit openings spanning a portion of the rear of the helmet (e.g., a openings extending through the rear/back of the helmet, such as from one side of the helmet to the other). The helmet can include different or additional slit openings through helmet shell. Additionally, in some implementations, one or more pairs of slit opening need not be parallel to each other.

FIGS. 1 and 2 are a front view and a front perspective view, respectively, of an example helmet shell 100 with multiple slit openings through the helmet shell 100. The slit openings are disposed along an outer surface 104 of the helmet shell 100. FIGS. 3, 4, 5, and 6 are a rear view, rear perspective view, side view, and top view, respectively, of the example helmet shell 100 with the multiple slit openings. The slit openings are disposed over various zones of the example helmet shell 100, such as on the top, sides, and rear of the helmet shell 100. The slit openings, which are described in greater detail below, create flexible portions of the helmet shell 100 between the slit openings, and these flexible portions of the helmet shell 100 have varying stiffness. For example, the stiffness of the flexible zones can vary at the longitudinal ends of the flexible portions, at a center of the flexible portions, and/or at intermediate areas of the flexible portions between the center and the ends.

In some instances, the flexible portions of the helmet shell 100 have a progressive stiffness, in that the stiffness of the flexible portion progressively decreases from a first longitudinal end to a middle of the flexible portion, then progressively increases from the middle to the second, opposite longitudinal end of the flexible portion. The flexible portions are most flexible at the areas of lowest stiffness, and least flexible at the areas of highest stiffness. Moreover, provision of flexible portions in the helmet via use of the spaced apart slit openings enables achieving varying stiffness at different zones across the helmet and by extension, varying the impact response at these different zones. For example, a conventional spherical helmet generally has the same stiffness throughout the helmet such that an impact to the helmet has the same impact response, regardless of where the impact was made on the spherical helmet. In contrast, a helmet formed with parallel or spaced apart slit openings in some portions of the helmet but not others allows the helmet to have varying impact responses, e.g., certain portions of the helmet can be stiffer (e.g., at a front portion of the helmet where the faceguard is attached to the helmet) and offer a particular impact response compared to the flexible zones (defined by the space between the slit openings) that are relatively more flexible and offer a different impact response. Thus, the use of slit openings and the defined flexible zones therebetween allows customizing and adjusting the impact response for different portions of the helmet. In doing so, the helmet can be further outfitted with impact absorbing pads or other materials that are customized for the certain areas of the helmet corresponding to the flexible zone(s) as well as for other portions of the helmet having different stiffness (e.g., higher stiffness).

In the example helmet shell 100 of FIGS. 1-6, multiple pairs of slit openings are shown disposed within multiple channels 102. The multiple channels 102 form an interconnected grid of channels in the outer surface 104 of the helmet shell 100, and all or a portion of the slit openings are disposed within the multiple channels 102. However, the example helmet shell 100 can include the multiple pairs of slit openings without the multiple channels 102 in the helmet shell 100. For example, the multiple slit openings can be formed as cuts in the shell body of the example helmet shell 100 that extend from the outer surface 106 to the inner surface 104 (separate from any channels, if any are present in the helmet shell), or as cuts in the recessed channels 102 of the example helmet shell 100, or a combination of these. While the example helmet shell 100 depicts the slit openings as disposed within the multiple recessed channels 102, the slit openings do not need to reside in the channels 102, and the example helmet shell 100 does not need to include these multiple channels 102 either. For example, the example helmet shell 100 can exclude the channels 102 such that the slit openings are formed in the body of the helmet shell 100.

The slit openings of the example helmet shell 100 includes a pair of top slit openings 120 along a top or crown region of the helmet shell 100, a pair of left side slit openings 134 extending along a left side of the helmet shell 100 toward the rear of the helmet shell 100, a pair of right side slit openings extending along a right side of the helmet shell 100 toward the rear of the helmet shell 100 (e.g., mirroring the left side openings 134 on the opposite side of the helmet shell 100), and a pair of rear slit openings 146 extending along the rear of the helmet in a generally vertical direction and toward a bottom edge of the helmet shell 100 at the rear of the helmet shell 100. Other embodiments of helmet shells may include a different arrangement of slit openings, additional openings, or fewer openings in the outer surface 104 than those slit openings depicted in the example helmet shell 100 of FIGS. 1-6.

In some instances, the multiple slit openings define the various zones of the helmet shell 100, for example, by bordering (partially or completely) these various zones. The slit openings are described in greater detail below. Some of the zones, such as zones on the side and rear of the helmet shell 100, are prone to a higher volume of impact during sporting activity during activities like football gameplay. The slit openings create zones of varying stiffness, such that an impact force against a zone can be dispersed along the flexible portions between the slit openings, and the flexile portions can dent and flex when impacted by an impact force.

The example helmet shell 100 can be used in a helmet, which may also include liners, padding layers, facemasks (e.g., to protect a wearer's face), and/or other features in combination with the example helmet shell 100. The liners and/or padding layers, in combination with the helmet shell 100, can help further absorb, dampen, disperse, and/or deflect forces from impacts against the helmet. The helmet, including the example helmet shell 100, encloses the top, back, and sides of a wearer's head, and a front of the helmet is desirably open to provide an unobstructed line of sight for the wearer of the helmet. While not shown in FIGS. 1-6, the example helmet shell 100 can include perforations, openings, snaps, or other connection points, for example, to connect one or more helmet components to the example helmet shell 100, such as chin straps, facemasks, plate extensions (e.g., jaw plates), a combination of these, or other components. The helmet shell of the present disclosure is described for use in helmets for American football, though the helmet shells can be applicable to other sports, such as baseball, ice hockey, lacrosse, motorsports, cycling, snow sports, or other sports or activities that utilize helmets for head protection and/or impact mitigation.

The helmet shell 100 can be manufactured from a rigid or substantially rigid material, such as polyethylene, nylon, polycarbonate materials, acrylonitrile butadiene styrene (ABS), polyester resin with fiberglass, thermosetting plastics, and/or other rigid thermoplastic materials. Alternatively, the helmet shell 100 can be manufactured from a relatively deformable material, such as polyurethane and/or high-density polyethylene, where such material allows some flexibility and/or local deformation of the helmet shell 100 (and/or an impact mitigation layer attached to an inner surface of the helmet shell 100) upon impact, but provide sufficient rigidity to prevent the breakage or damage to the example helmet shell 100. The helmet shell 100 can be formed of a continuous, single shell, or a multi-piece assembly (e.g., a two-piece shell assembly of a front shell and a back shell) that conforms and surrounds the head of the wearer.

The example helmet shell 100 of FIGS. 1-6 is shown as a single shell structure. However, in some implementations, the example helmet shell 100 can include more than one shell in a stacked configuration, such as an outer shell and an inner shell. For example, the outer shell can generally surround the inner shell, and the inner shell can be a continuous, single shell or a multi-piece shell assembly (e.g., a two-piece shell assembly of a front shell and a back shell) that conforms to and surrounds the head of the wearer. The at least one inner shell can be made of a rigid material, and can have greater rigidity than the rigidity of the outer shell. In some examples, the inner shell is 5 to 100 times stiffer, or more rigid, than the outer shell. The rigid material may include polycarbonate (PC). Alternatively, the inner shell can include a different material, such as a substantially rigid material (e.g., polyethylene, nylon, polycarbonate materials, acrylonitrile butadiene styrene (ABS), polyester resin with fiberglass, thermosetting plastics, and/or other rigid thermoplastic materials; as described above). The substantially rigid material may be stiff or rigid enough to withstand breakage or cracking, but flexible enough to deform slightly and distribute incident forces after an impact. The at least one inner shell may include a thermoplastic material. Thermoplastic materials may comprise polyurethane, polycarbonate, polypropylene, polyether block amide, and/or any combinations thereof. Alternatively, the inner shell may include a deformable material, such as polyurethane and/or high-density polyethylene, where such material allows some flexibility and/or local deformation upon impact, but provide enough rigidity to prevent the breakage or damage to the helmet.

The example helmet shell 100 of FIGS. 1-6 can include additional features not shown. For example, the helmet shell 100 of FIGS. 1-6 includes a shell body that the slit openings are formed through, and that the multiple channels 102 are recessed into. However, the example helmet shell 100 can include additional features or structures coupled to or integrally formed with the shell body. The slit openings and/or channels 102 of the example helmet shell 100 can take different forms based on the zone that the slit openings reside in or are adjacent to. For example, some of the channels 102 may include slit openings, such as through openings extending from the outer surface 104 (e.g., exterior surface) to the inner surface 106 (e.g., interior surface) of the helmet shell 100, and/or other channels 102 may exclude a through opening. The through openings may also be referred to herein as vent openings, holes, or relief vents. In certain instances, the channels 102 include a recession in the outer surface 104 of the helmet shell 100, but the recession does not extend entirely through a thickness of the helmet shell 100 to the inner surface 106 like the through openings do. Instead, the recession may extend to an intermediate dimension between the outer surface 104 and the inner surface 106. In some implementations, the channels 102 are recessed from the outer surface 104 of the helmet shell 100 a depth of up to 3 millimeters. In some examples, some or all of the channels 102 have cross-sectional dimensions of at least 5 millimeters in width and at most 3 millimeters in depth. These dimensions can vary. In alternative embodiments, these widths and depths, and whether one or more channels should have openings, can be varied by a helmet designer.

In the example helmet shell 100 of FIGS. 1-6, the multiple channels 102 include two top channels 110 along a top or crown region of the helmet shell 100, a pair of left side channels 112 extending from a front left edge of the helmet shell 100 toward the rear of the helmet shell 100 along the left side of the helmet shell 100, a pair of right side channels 114 extending from a front right edge of the helmet shell 100 toward the rear of the helmet shell 100 along the right side of the helmet shell 100, a continuous rear channel 116 on the rear of the helmet shell 100, and a pair of rear bottom channels 118 extending from the continuous rear channel 116 toward a bottom edge of the helmet shell 100 at the rear of the helmet shell 100. Other embodiments of helmet shells may include a different arrangement of channels 102, additional channels 102, or fewer channels 102 in the outer surface than those channels 102 depicted in the example helmet shell 100 of FIGS. 1-6. Also, in the example helmet shell 100 of FIGS. 1-6, the pair of top slit openings 120 reside in the pair of top channels 110, the pair of left side slit openings 134 reside in the pair of left side channels 112, the pair of right side slit openings reside in the pair of right side channels 114, and the pair of rear slit openings 146 reside in the pair of rear bottom channels 118. The pairs of slit openings are depicted as disposed within respective channels, however, the slit openings may be disposed on shell body of the example helmet shell 100 without some or all of the channels.

In the example helmet shell 100 of FIGS. 1-6, the pair of top slit openings 120 (and the two top channels 110) extend along the top of the helmet shell 100, and are spaced apart from each other. The pair of top slit openings 120 and the two top channels 110 extend longitudinally along the top of the helmet shell 100, for example, from the front to the back of the helmet shell 100. The top slit openings 120 and the two top channels 110 are symmetrical with each other across a lateral centerline of the helmet shell 100. The lateral centerline can include a plane that splits the left side of the helmet shell 100 from the right side of the helmet shell 100. Some or all of the slit openings, channels 102, or both, can be symmetrical across the lateral centerline of the helmet shell 100. In some implementations, the entirety of the helmet shell 100 including the multiple channels 102 and slit openings is symmetrical across the lateral centerline of the helmet shell 100.

The pair of top slit openings 120 and the two top channels 110 are arranged to be substantially parallel to each other along the top of the helmet shell 100, though the top channels 110 and/or top slit openings 120 may not be exactly parallel to each other (at some or all points along the length of the two channels or openings). For example, the pair of top slit openings 120 and the two top channels 110 of the example helmet shell 100 of FIGS. 1-6 run generally parallel to a longitudinal line from a front of the shell 100 to a back of the shell 100, but the channels 110 and openings 120 can have a bow, or curve, along its respective longitudinal length, thereby creating a channel, opening, or both, that is substantially, but not exactly, linear in the longitudinal direction. For example, the top view of FIG. 6 shows the two top channels 110 and the pair of top slit openings 120 of the example helmet shell 100 as having a laterally outward curve, or bow, along their respective lengths between the front and the back of the example helmet shell 100.

In some instances, such as depicted in the top view of FIG. 6, each of the top channels 110 include the top slit opening 120, or vent, that runs along a length of the top channels 110. In the example helmet shell 100 of FIG. 6, the slit opening 120 spans a majority of the length of the top channels 110, though the length of the top slit opening 120 can vary. The slit opening 120 can be a continuous opening along the length of the top channels 110, or a segmented opening with multiple uniform or non-uniform openings within the top channels 110. Uniform openings can share the same longitudinal length, the same lateral width, the same shape, a combination of these, and/or other similarities.

The stiffness of the helmet shell 100 varies along the top channels 110 and between the top channels 110 due, at least in part, to the top slit openings 120. For example, the portion of the top channels 110 that do not include the slit openings 120 form areas of high stiffness 122, the portion of the top channels 110 that include the slit openings 120 form areas of low stiffness 124 (i.e., lower than the high stiffness), and the portion of the helmet shell 100 between the top slit openings 120 form a flex zone 126 configured to be more flexible than adjacent portions of the example helmet shell 100. The construction of the top channels 110 and the slit openings 120 creates areas on the helmet shell 100 that transition from high-to-low-to-high stiffness. In some instances, the top slit openings 120 along the top channels 110 also provide ventilation between an exterior and an interior of the helmet shell 100. The varying stiffness and flexibility of the helmet shell 100 in the high stiffness areas 122, low stiffness areas 124, and flex zones 126 create local flexibility (i.e., localized to the area represented by the flex zone 126) that can be advantageous for absorbing, mitigating, and/or deflecting impact forces against the helmet shell 100.

In some implementations, each top slit opening of the pair of top slit openings 120 has a first length, and the flex zone 126 defines a flexible helmet portion of the example helmet shell 100. The flexible helmet portion extends along the first length and between the pair of top slit openings 120, and a stiffness of the flexible helmet portion varies along the first length from a first longitudinal end of the flexible helmet portion (e.g., a front end) to a second longitudinal end of the flexible helmet portion (e.g., a rear end). For example, the stiffness of the flexible helmet portion includes a first stiffness at the first end and at the second end of the flexible helmet portion, a second stiffness at a middle portion of the flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the flexible helmet portion between the first end and the middle portion, and between the second end and the middle portion. The first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness. In other words, the stiffness of the flexible helmet portion varies from the first (highest) stiffness at the first end, to the third (intermediate) stiffness adjacent to the first end, to the second (lowest) stiffness at the middle of the flexible helmet portion, back to the third stiffness between the middle and the second end, and further back to the first stiffness at the second end. The size, location, and shape of the top slit openings 120 can affect the first, second, and/or third stiffness at the flexible helmet portion. For example, a width and/or length of the slit opening may impact the flexibility and stiffness of the flexible helmet portion.

The pairs of slit openings, such as the pair of top slit openings 120, create flexible helmet portions at the portions of the shell body between the pairs of slit openings. The flexibility and relative stiffnesses of these flexible portions can vary based on the length, size, and/or shape of the slit openings. In the present disclosure, slit openings are identified in pairs to define a flexible helmet portion between the pairs of openings. However, flexible helmet portions can exist between slit openings on the example helmet shell 100 that are not identified as pairs. For example, a flexible helmet portion may exist between one of the top slit openings 120 and one of the left side slit openings 134.

The top slit openings 120 have a rectangular shape along the top channels 110. However, the shape of the slit openings 120 can vary. For example, the slit openings 120 can take on a non-uniform shape or another appropriate shape, such as a shape that substantially or exactly mirrors the channel in which the opening is formed. The top slit openings 120 can have a consistent/uniform width along its longitudinal length, and/or one or more of its longitudinal ends can have a taper, rounded end, angled end, or other shape. Alternatively, in some implementations, the slit openings (including the top slit opening 120) can have widths that vary at different points along the longitudinal length of the opening. For example, the top slit openings 120 (and/or other slit openings of the present disclosure) can include tapered ends, such that the top slit openings 120 are widest at a middle of the slit opening 120, and gradually taper to a smaller width at ends of the slit openings 120. Varying a width of the top slit openings 120 provides a varying flexibility (i.e., varying stiffness) in the adjacent flexible portions of the example helmet shell 100.

The slit openings, such as the top slit openings 120 of the example helmet shell 100, can vary in size, shape, and location to provide a desired flexibility and stiffness to the adjacent flexible portions of the helmet shell 100. For example, the slit openings can be straight, can include one or more angles along its length, can include a curve (e.g., single curve, sinusoidal shape, or other curved shape), and/or a combination of these.

The flexible portions of the helmet shell 100 that reside between pairs of the slit openings provide flexibility that stems from the fact that two sides of the flexible portion are not directly connected to a side of the helmet shell 100. Instead, the flexible portions are directly connected at two opposing sides and disconnected at the other two opposing sides adjacent to the slit openings. This disconnect provides the flexible portion of the helmet shell 100 a localized flexibility and a localized impact response. The slit openings are disposed along the example helmet shell 100 to provide stiffer zones for certain types of impact (e.g., stiffer areas near the faceguard), and less stiff zones for other types of impact (e.g., on the sides for side helmet impact).

In some implementations, the flexible portions of the example helmet shell 100 (e.g., flex zone 126 and other flexible portions described below) allows a designer to apply impact mitigating pads or other structures to the interior of the example helmet shell 100 that are designed for particular types of impact, thereby achieving a custom impact response throughout the helmet. In some instances, a larger distance between pairs of slit openings provide for greater flex in the flexible portion between the pair of slit openings as compared to the pair of slit openings with a shorter distance between the slit openings. In certain instances, shorter pairs of slit openings create less flexible and smaller flex portions of the helmet shell 100 compared to longer pairs of slit openings, which would create more flexible and larger flex portions of the helmet shell 100.

In some implementations, the portion of the example helmet shell 100 that resides between the two top channels 110 includes a central recession 128 in the outer surface 104 of the helmet shell 100. The central recession 128 resides between the two top channels 110, and extends along the lateral centerline of the helmet shell 100 between the two top channels 110. The central recession 128 includes a shallow divot, concave recession, or other shaped recession in the outer surface 104 of the helmet shell 100, where the central recession 128 is recessed into the outer surface 104 of the helmet shell 100 such that it is more recessed than adjacent portions of the outer surface 104 that reside between the central recession 128 and the two top channels 110.

The example helmet shell 100 includes a front center plate 130 at a front center of the helmet shell 100. The front center plate 130 is integrally formed with the helmet shell 100, and can be used as an attachment point for a face guard, face shield, face mask, or other face protection that covers at least part of the face opening of the example helmet shell 100. In the example helmet shell 100 of FIGS. 1-6, the front center plate 130 includes a trapezoidal shape, where an upper width of a top of the front center plate 130 is greater than a lower width of a bottom of the front center plate 130. However, the shape of the front center plate 130 can vary. In some implementations, such as in the example helmet shell 100 of FIGS. 1-6, the multiple channels 102 includes a continuous front channel 132 that partially surrounds the front center plate 130. The continuous front channel 132 borders the top and sides of the front center plate 130, and can extends from a front edge of the example helmet shell 100, around the front center plate 130, and back to the front edge. In some examples, the continuous front channel 132 excludes any through openings, for example, to provide sufficient stiffness to the front center plate 130 in the event of impact forces against a face mask attached to the front center plate 130. In the example helmet shell 100 of FIGS. 1-6, the two top channels 110 extend rearwardly from the continuous front channel 132, and in some examples, can share the same dimensions as the continuous front channel 132.

In certain implementations, the multiple channels 102 do not include the continuous front channel 132, in that the example helmet shell 100 does not include a channel surrounding the front center plate 130.

The pair of left side channels 112 extend from a front left edge of the helmet shell 100 toward the rear of the helmet shell along a left side of the helmet shell 100, and the pair of right side channels 114 extend from a front right edge of the helmet shell 100 toward a rear of the helmet shell 100 along a right side of the helmet shell 100. The pair of left side channels 112 is symmetrical with the pair of right side channels 114 across the lateral centerline. The pair of left side channels 112 and right side channels 114 have portions that extend substantially linearly rearward from the respective front edges of the example helmet shell 100, then turn at an angle (e.g., at transition section 113) toward a rear top of the example helmet shell 100, and further extend along a generally linear path. The shape of the pair of left side channels 112 and pair of right side channels 114 can vary from the angled shape of the example helmet shell 100 of FIGS. 1-6.

The pair of left side channels 112 are depicted in the side view of the example helmet shell 100 of FIG. 5. In some instances, each of the left side channels 112 include the side slit opening 134, or vent, that runs along some or all of the lengths of the left side channels 112. In the example helmet shell 100 of FIG. 5, the left side slit openings 134 span a majority of the length of the left side channels 112, though the length of the side slit openings 134 can vary. The left side slit opening 134 can be a continuous opening along the length of the left side channels 112, or a segmented opening with several uniform or non-uniform openings within the left side channels 112. The pair of left side slit openings 134 extend along the left side of the example helmet shell 100 toward the rear of the helmet shell 100, for example, along the pair of left side channels 112. However, the pair of left side slit openings 134 may reside on the helmet shell 100 without the pair of left side channels 112. The right side slit openings can be the same or similar to the left side slit openings 134 except mirrored on the right side of the example helmet shell 100. The left side slit openings 134 include portions that extend substantially linearly rearward from a respective front end of the slit opening, proximate to a front edge of the example helmet shell 100, then turn at an angle (e.g., at the transition section 113) toward the rear top of the example helmet shell 100, and further extend along a generally linear path. The shape of the pair of left slit openings 134 (and the mirrored pair of right slit openings) can vary from the angled shape of the example helmet shell 100 of FIGS. 1-6.

The stiffness of the helmet shell 100 varies along the left side channels 112 and between the left side channels 112 due, at least in part, to the side slit openings 134. For example, first portions 136 of the pair of left side channels 112 adjacent to longitudinal ends of the side slit openings 134 include a first, higher stiffness, second portions 138 of the pair of left side channels 112 at the side slit openings 134 include a second, lower stiffness (e.g., lower stiffness than the first, high stiffness), and an intermediate portion 140 of the helmet shell 100 between the side slit openings 134 of the left side channels 112 form a flex zone configured to flex more than adjacent portions of the example helmet shell 100. The construction of the side channels 112 and the side slit openings 134 create areas on the side of the helmet shell 100 that transition from high-to-low-to-high stiffness. In some instances, the side slit openings 134 along the left side channels 112 also provide ventilation between an exterior and an interior of the helmet shell 100. The varying stiffness and flexibility of the helmet shell 100 in the high stiffness areas 136, low stiffness areas 138, and flex zones 140 create local flexibility (represented by the flex zone 140) that can be advantageous for absorbing, mitigating, and/or deflecting impact forces against the helmet shell 100.

In some implementations, each side slit opening of the pair of side slit openings 134 has a second length, and the flex zone 140 defines another flexible helmet portion of the example helmet shell 100. The flexible helmet portion extends along the second length and between the pair of side slit openings 134, and a stiffness of the flexible helmet portion varies along the second length from a first longitudinal end of the flexible helmet portion (e.g., a front end) to a second longitudinal end of the flexible helmet portion (e.g., a rear end). For example, the stiffness of the flexible helmet portion includes a first stiffness at the first end and at the second end of the flexible helmet portion, a second stiffness at a middle portion of the flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the flexible helmet portion between the first end and the middle portion, and between the second end and the middle portion. The first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness. In other words, the stiffness of the flexible helmet portion varies from the first (highest) stiffness at the first end, to the third (intermediate) stiffness adjacent to the first end, to the second (lowest) stiffness at the middle of the flexible helmet portion, back to the third stiffness between the middle and the second end, and further back to the first stiffness at the second end. The size, location, and shape of the side slit openings 134 can affect the first, second, and/or third stiffness at the flexible helmet portion. For example, a width and/or length of the slit opening may impact the flexibility and stiffness of the flexible helmet portion.

The side slit openings 134 of the example helmet shell 100 have a rectangular shape along the left side channels 112 that taper in width at a back end of the left side channels 112. However, the shape of the side slit openings 134 can vary. For example, the side slit openings 134 can take on a non-uniform shape or another appropriate shape, such as a shape that substantially or exactly mirrors the channel that the opening is formed in. The side slit openings 134 can have a consistent width along its longitudinal length, and/or one or more of its longitudinal ends can have a taper, rounded end, angled end, or other shape. For example, the left side slit openings 134 (and/or right side slit openings) can include tapered ends, such that the left side slit openings 134 are widest at a middle of the slit opening 134, and gradually taper to a smaller width at a rear end of the slit openings 134. Varying a width of the side slit openings 134 provides a varying flexibility (i.e., varying stiffness) in the adjacent flexible portions of the example helmet shell 100.

The slit openings, such as the side slit openings 134 of the example helmet shell 100, can vary in size, shape, and location to provide a desired flexibility and stiffness to the adjacent flexible portions of the helmet shell 100. For example, the slit openings can be straight, can include one or more angles along its length, can include a curve (e.g., single curve, sinusoidal shape, or other curved shape), and/or a combination of these.

The right side channels 114 can include the same features as the left side channels mirrored on the right side of the example helmet shell 100. For example, the right side channels 114 can include right side openings to create areas of high stiffness, areas of low stiffness, and a flex zone on the right side of the helmet shell 100.

The continuous rear channel 116 at least partially surrounds a rear center zone 142 on the rear of the helmet shell 100. In the example helmet shell 100 of FIGS. 1-6, the continuous rear channel 116 completely surrounds the rear center zone 142. In other instances, the continuous rear channel 116 can partially surround the rear center zone 142, such as only on the sides and/or top of the rear center zone 142. The pair of rear bottom channels 118 extend from the continuous rear channel 116 toward a bottom edge of the helmet shell 100 at the rear of the helmet shell 100. The pair of rear bottom channels 118 can extend laterally outward as the rear bottom channels 118 extend from the continuous rear channel 116 to the bottom edge of the helmet shell 100 at the rear of the helmet shell 100. For example, the rear bottom channels 118 border the sides of a rear zone 144 of the helmet shell 100, where the rear zone 144 has an up tack shape.

In some implementations, the rear center zone 142 includes a trapezoid shape, and the continuous rear channel 116 surrounds the trapezoid shape of the rear center zone 142.

The rear center zone 142, rear zone 144, continuous rear channel 116, and rear bottom channels 118 are depicted in the rear view of FIG. 3. In the example helmet shell 100, the continuous rear channel 116 excludes through openings between the inner surface 106 and the outer surface 104 of the helmet shell. However, the continuous rear channel 116 may include slit openings, or vents. In some implementations, the rear bottom channels 118 each include a rear slit opening 146, or vent, that runs along a portion of the length of the rear bottom channels 118. In the example helmet shell 100 of FIG. 3, the rear slit openings 146 span a portion of the length of the rear bottom channels 118, though the length of the rear slit openings 146 can vary. The rear slit openings 146 can be continuous openings along the portion of the length of the rear bottom channels 118, or a segmented opening with multiple uniform or non-uniform openings within the rear bottom channels 118. Uniform openings can share the same longitudinal length, the same lateral width, the same shape, a combination of these, and/or other similarities.

The stiffness of the helmet shell 100 varies along the rear bottom channels 118 and within the rear zone 144 due, at least in part, to the rear slit openings 146 within the rear bottom channels 118. For example, first portions 148 of the rear bottom channels 118 adjacent to longitudinal ends of the rear slit openings 146 include a first, higher stiffness, second portions 150 of the pair of rear bottom channels 118 at the rear slit openings 146 include a second, lower stiffness (e.g., lower stiffness than the first, high stiffness), and an intermediate portion 152 of the rear zone 144 of the helmet shell 100 between the rear slit openings 146 of the rear bottom channels 118 form a flex zone configured to flex more than adjacent portions of the example helmet shell 100. The construction of the rear bottom channels 118 and the rear slit openings 146 create areas on the rear of the helmet shell 100 that transition from high-to-low-to-high stiffness. In some instances, the rear slit openings 146 along the rear bottom channels 118 also provide ventilation between an exterior and an interior of the helmet shell 100. The varying stiffness and flexibility of the helmet shell 100 in the high stiffness areas 148, low stiffness areas 150, and flex zones 152 create local flexibility (represented by the flex zone 152) that can be advantageous for absorbing, mitigating, and/or deflecting impact forces against the helmet shell 100.

In some implementations, each rear slit opening of the pair of rear slit openings 146 has a third length, and the flex zone 152 defines a flexible helmet portion of the example helmet shell 100. The flexible helmet portion extends along the third length and between the pair of rear slit openings 146, and a stiffness of the flexible helmet portion varies along the third length from a first longitudinal end of the flexible helmet portion (e.g., a top end) to a second longitudinal end of the flexible helmet portion (e.g., a bottom end). For example, the stiffness of the flexible helmet portion includes a first stiffness at the first end and at the second end of the flexible helmet portion, a second stiffness at a middle portion of the flexible helmet portion between the first end and the second end, and a third stiffness at an intermediate portion of the flexible helmet portion between the first end and the middle portion, and between the second end and the middle portion. The first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness. In other words, the stiffness of the flexible helmet portion varies from the first (highest) stiffness at the first end, to the third (intermediate) stiffness adjacent to the first end, to the second (lowest) stiffness at the middle of the flexible helmet portion, back to the third stiffness between the middle and the second end, and further back to the first stiffness at the second end. The size, location, and shape of the top slit openings 120 can affect the first, second, and/or third stiffness at the flexible helmet portion. For example, a width and/or length of the slit opening may impact the flexibility and stiffness of the flexible helmet portion.

The rear slit openings 146 of the example helmet shell 100 have an irregular shape along an angled portion of the rear bottom channels 118. However, the shape of the rear slit openings 146 can vary. For example, the rear slit openings 146 can take on a uniform shape, non-uniform shape, or another appropriate shape, such as a shape that substantially or exactly mirrors the channel that the opening is formed in. The rear slit openings 146 can have a consistent width along its longitudinal length, and/or one or more of its longitudinal ends can have a taper, rounded end, angled end, or other shape.

Forming the slit openings in the example helmet shell 100 can provide multiple advantages, including providing areas of increased stiffness, such as in areas that are prone to higher volume of impacts (e.g., at the side and rear zones of the example helmet shell 100). The slit openings, and in some examples the slit openings and the channels, formed in the rear of the example helmet shell 100 can define higher stiffness zones, which is beneficial to mitigate the forces and energy of impacts to the rear of the example helmet shell 100.

The multiple channels 102 in the example helmet shell 100 form an interconnected grid of channels in the outer surface 104 of the helmet shell 100. For example, the two top channels 110 extend into, or intersect, the continuous rear channel 116, and the pair of left side channels 112 and right side channels 114 intersect with the top channels 110 at a rear top of the helmet shell 100. This interconnected grid construction allows the impact forces against the helmet shell 100 to be dispersed or dampened along the multiple channels 102. The multiple channels 102 may include additional channels within the interconnected grid of channels. For example, an intermediate channel 154 extends between the two top channels 110 and between the longitudinal end of the topmost channel of the left side channels 112 and the longitudinal end of the topmost channel of the right side channel 114. The intermediate channel 154 can be an extension of the left side channel and/or right side channel that intersects one or both of the top channels 110 along a top rear of the example helmet shell 100. The intermediate channel 154 is shown as aligned with the topmost channels of the left side channels 112 and right side channels 114, though this can be misaligned in other embodiments, such as further forward or further back from the position shown in the example helmet shell 100 of FIGS. 1-6. In certain instances, a top portion of the continuous rear channel 116 extends between the longitudinal end of the bottommost channel of the left side channels 112 and the longitudinal end of the bottommost channel of the right side channel 114. The intermediate channel 154 and the top portion of the continuous rear channel 116 can connect the pair of left side channels 112 with the pair of right side channels 114 to form a continuous pair of channels that extend entirely around the example helmet shell 100.

In some instances, two adjacent slit openings (e.g., a top slit opening 120 and an adjacent left side slit opening 134 or right side slit opening) can form another flex zone and additional areas of higher and/or lower stiffness of the example helmet shell 100. For example, the construction of the top slit opening 120 of the leftmost top channel 110 and the side slit opening 134 of the topmost left side channel 112 create areas on the side of the helmet shell 100 between the top channel 110 and the left side channel 112 that transition from high-to-low-to-high stiffness, and a flex zone between these respective openings. The mirrored construction on the right side of the example helmet shell 100 can form a mirrored version of the same high-to-low-to-high stiffness and flex zone.

FIGS. 7 and 8 are a front view and a front perspective view, respectively, of a second example helmet shell 200 with slit openings and multiple channels 202 disposed along the outer surface 104 of the helmet shell 200. FIGS. 9, 10, 11, and 12 are a rear view, rear perspective view, side view, and top view, respectively, of the second example helmet shell 200 with the multiple slit openings. The second example helmet shell 200 is similar to the example helmet shell 100 of FIGS. 1-6, except that the second example helmet shell 200 does not include a continuous front channel 132, does not include the central recession 128, the left side channels 112′ and right side channels 114′ are shaped to have a smaller angle (e.g., at transition section 213) along its length than the left side channels 112 and right side channels 114 of the example helmet shell 100 of FIGS. 1-6, and a rear of the second example helmet shell 200 includes a rear center zone 142′ and a rear zone 144′ that is not separated by the continuous rear channel 116′.

The outer surface of the helmet shell 100 along the rear center zone 142′ and the rear zone 144′ are flush, in that the outer surface at the rear center zone 142′ and the outer surface at the rear zone 144′ are flush with each other. The flex zone 152 of the second example helmet shell 200 may be the same size or a different size as the flex zone 152 of the example helmet shell 100 of FIGS. 1-6, for example, based on the size and/or shape of the rear slit openings 146 along the pair of rear bottom channels 118.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any features or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

Claims

1. A helmet, comprising: a helmet shell comprising an outer surface, an inner surface, and a plurality of slit openings, wherein each slit opening extends along a portion of the helmet shell;the plurality of slit openings comprising a pair of top slit openings that each extend longitudinally along a top portion of the helmet shell, each top slit opening of the pair of top slit openings has a first length;the pair of top slit opening being spaced apart and defining a flexible helmet portion spaced between the pair of top slit openings; andwherein the flexible helmet portion extends along the first length from a first end of the flexible helmet portion to a second end of the flexible helmet portion opposite to the first end, and the flexible helmet portion has a stiffness that varies along the first length from the first end to the second end.

2. The helmet of claim 1, wherein the stiffness of the flexible helmet portion comprises: a first stiffness at the first end and at the second end of the flexible helmet portion,a second stiffness at a middle portion of the flexible helmet portion between the first end and the second end, anda third stiffness at an intermediate portion of the flexible helmet portion between the first end and the middle portion.

3. The helmet of claim 2, wherein the first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness.

4. The helmet of claim 1, wherein the helmet comprises a plurality channels recessed in the outer surface of the helmet shell, the plurality of channels comprising a pair of top channels along the top portion of the helmet shell, and the pair of top slit openings reside within the pair of top channels.

5. The helmet of claim 1, wherein the pair of top slit openings are arranged substantially parallel to each other along the top portion of the helmet shell.

6. The helmet of claim 1, wherein the pair of top slit openings are symmetrical with each other across a lateral centerline of the helmet shell.

7. The helmet of claim 1, wherein the pair of top slit openings are linear.

8. The helmet of claim 1, wherein each of the top slit openings comprise a laterally outward curve.

9. The helmet of claim 4, wherein the top slit opening of each top channel of the pair of top channels extends along a majority of a length of the pair of top channels.

10. The helmet of claim 1, wherein the helmet shell comprises a central recession in the outer surface of the helmet shell in a crown region between the pair of top slit openings.

11. The helmet of claim 1, wherein the plurality of slit openings further comprises: a pair of left side slit openings extending along a left side of the helmet shell toward a rear of the helmet shell, anda pair of right side slit openings extending along a right side of the helmet shell toward the rear of the helmet shell.

12. The helmet of claim 11, wherein: each left side slit opening of the pair of left side slit openings has a second length;the pair of left side slit opening are spaced apart and define a second flexible helmet portion spaced between the pair of left side slit openings; andthe second flexible helmet portion extends along the second length from a first end of the second flexible helmet portion to a second end of the second flexible helmet portion opposite to the first end, and the second flexible helmet portion has a stiffness that varies along the second length from the first end to the second end of the second flexible helmet portion.

13. The helmet of claim 12, wherein the stiffness of the second flexible helmet portion comprises: a first stiffness at the first end and at the second end of the second flexible helmet portion,a second stiffness at a middle portion of the second flexible helmet portion between the first end and the second end, anda third stiffness at an intermediate portion of the second flexible helmet portion between the first end and the middle portion.

14. The helmet of claim 13, wherein the first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness.

15. The helmet of claim 11, wherein: the helmet comprises a plurality channels recessed in the outer surface of the helmet shell,the plurality of channels comprising a pair of left side channels along the left side of the helmet shell and a pair of right side channels along the right side of the helmet shell,the pair of left side slit openings reside within the pair of left side channels, andthe pair of right side slit openings reside within the pair of right side channels.

16. A helmet shell, comprising: a shell body;an outer surface of the shell body, an inner surface of the shell body, and a plurality of slit openings, wherein each slit opening extends along a portion of the helmet shell; andthe plurality of slit openings comprising: a pair of left side slit openings extending along a left side of the shell body toward a rear of the shell body, each left side slit opening of the pair of left side slit openings comprising a first length, anda pair of right side slit openings extending along a right side of the shell body toward a rear of the shell body, each right side slit opening of the pair of right side slit openings comprising a second length;wherein the pair of left side slit openings being spaced apart and defining a left flexible helmet portion between the pair of left side slit openings, the left flexible helmet portion extending along the first length from a first end of the left flexible helmet portion to a second end of the left flexible helmet portion opposite to the first end, and the left flexible helmet portion comprising a stiffness that varies along the first length from the first end to the second end; andwherein the pair of right side slit openings being spaced apart and defining a right flexible helmet portion between the pair of right side slit openings, the right flexible helmet portion extending along the second length from a third end of the right flexible helmet portion to a fourth end of the right flexible helmet portion opposite to the third end, and the right flexible helmet portion comprising a stiffness that varies along the second length from the third end to the fourth end.

17. The helmet shell of claim 16, wherein the stiffness of the left flexible helmet portion comprises: a first stiffness at the first end and at the second end of the left flexible helmet portion,a second stiffness at a middle portion of the left flexible helmet portion between the first end and the second end, anda third stiffness at an intermediate portion of the left flexible helmet portion between the first end and the middle portion.

18. The helmet shell of claim 17, wherein the stiffness of the right flexible helmet portion comprises: the first stiffness at the third end and at the fourth end of the right flexible helmet portion,the second stiffness at a second middle portion of the right flexible helmet portion between the third end and the fourth end, andthe third stiffness at a second intermediate portion of the right flexible helmet portion between the third end and the second middle portion.

19. The helmet shell of claim 17, wherein the first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness.

20. The helmet shell of claim 16, wherein: the helmet shell comprises a plurality channels recessed in the outer surface of the helmet shell,the plurality of channels comprising a pair of left side channels along the left side of the helmet shell and a pair of right side channels along the right side of the helmet shell,the pair of left side slit openings reside within the pair of left side channels, andthe pair of right side slit openings reside within the pair of right side channels.

21. The helmet shell of claim 16, wherein the pair of left side slit openings and the pair of right side slit openings are linear.

22. A helmet shell, comprising: a shell body;an outer surface and an inner surface of the shell body, and a plurality of slit openings extending along a portion of the helmet shell; andthe plurality of slit openings comprising a pair of rear slit openings at a rear of the helmet shell, the pair of rear slit openings partially surrounding a rear zone at the rear of the helmet shell and comprising a first length.

23. The helmet shell of claim 22, wherein: the pair of rear slit openings are spaced apart and define a rear flexible helmet portion between the pair of rear slit openings,the rear flexible helmet portion extending along the first length from a first end of the rear flexible helmet portion to a second end of the rear flexible helmet portion opposite to the first end,the rear flexible helmet portion comprising a stiffness that varies along the first length from the first end to the second end.

24. The helmet shell of claim 23, wherein the stiffness of the rear flexible helmet portion comprises: a first stiffness at the first end and at the second end of the rear flexible helmet portion,a second stiffness at a middle portion of the rear flexible helmet portion between the first end and the second end, anda third stiffness at an intermediate portion of the rear flexible helmet portion between the first end and the middle portion.

25. The helmet shell of claim 24, wherein the first stiffness is greater than the second stiffness, and the third stiffness is greater than the second stiffness and less than the first stiffness.

26. The helmet shell of claim 22, wherein the pair of rear slit openings are straight.

27. The helmet shell of claim 22, wherein the pair of rear slit openings are symmetrical across a lateral centerline of the helmet shell.