Adjustable helmet

Abstract

An adjustable helmet includes a main shell layer having a first side portion and a second side portion. The first side portion and the second side portion are laterally flexible relative to each other. The adjustable helmet includes a secondary shell layer coupled to the primary shell layer at a location between the first side portion and the second side portion. At least a portion of the first side portion and at least a portion of the second side portion each extend over at least a portion of a top surface of the secondary shell layer. The adjustable helmet includes a tensioning device. A first end of the tensioning device is coupled to the first side portion and a second end of the tensioning device is coupled to the second side portion so as to provide tension between the first side portion and the second side portion.

Description

[0001] Related Applications and Priority Claims

[0002] This application is a divisional application of Chinese national phase application 202080070641.8 of PCT international application PCT / US2020 / 051196 with a filing date of September 17, 2020.

[0003] This application claims priority to the following patent applications: (1) U.S. Patent Application No. 16 / 901,363, filed on June 15, 2020, which claims priority to U.S. Provisional Application No. 62 / 911,444, filed on October 7, 2019; and (2) U.S. Provisional Application No. 62 / 911,444, filed on October 7, 2019. The disclosure of each priority patent application is hereby incorporated by reference in its entirety into this document. Background Art

[0004] Protective helmets are used in a variety of applications, particularly in ball and / or contact sports such as, for example, baseball, football, hockey, lacrosse, cricket, and / or similar sports. Generally, these helmets include a single molded plastic shell layer, as well as appropriate levels of padding (e.g., foam padding, gel padding, etc.) depending on the application.

[0005] Generally, the size of the molded plastic shell layer and / or the thickness of the padding define the sizing parameters of the helmet. Thus, users with varying head circumferences and proportions may not be able to utilize the same helmet, and special fittings may be necessary to determine the appropriate helmet size for each user.

[0006] In view of this limitation, adjustable helmets have been developed that allow a user to adjust the size of at least one portion of the helmet to fit the proportions of his or her head. However, such existing adjustable helmets typically rely on complex ratchet systems and / or locking systems to accommodate varying head circumferences. These systems can be difficult to adjust quickly and can also result in varying compression forces on different users' heads.

[0007] Accordingly, this document generally describes various embodiments of an adjustable helmet that allows for simplified user adjustment and substantially equal compression forces regardless of the size of the user's head. Summary of the Invention

[0008] In various embodiments, an adjustable helmet includes a main shell layer having a first side portion and a second side portion. The first side portion and the second side portion are laterally flexible relative to each other. The adjustable helmet includes a secondary shell layer coupled to the main shell layer at a location between the first side portion and the second side portion. At least a portion of the first side portion and at least a portion of the second side portion each extend over at least a portion of a top surface of the secondary shell layer. The adjustable helmet includes a tensioning device. A first end of the tensioning device is coupled to the first side portion and a second end of the tensioning device is coupled to the second side portion to provide tension between the first side portion and the second side portion.

[0009] The first end of the tensioning device may be coupled to the first side portion at a first hardware component, and the second end of the tensioning device may be coupled to the second side portion at a second hardware component. The secondary shell layer may include a first wing portion having a first elongated track formed therethrough and a second wing portion having a second elongated track formed therethrough. The second wing portion may be located on the secondary shell layer laterally opposite the first wing portion. At least a portion of the first hardware component may extend through the first elongated track, and at least a portion of the second hardware component may extend through the second elongated track. The first elongated track may be angled downwardly in a first direction and the second elongated track may be angled downwardly in a second direction such that at least a portion of the secondary shell layer vertically rises when the first side portion and the second side portion of the main shell layer are laterally deflected outwardly relative to each other.

[0010] The adjustable helmet may optionally include an alignment component coupled to the secondary shell layer. A central portion of the tensioning device may be configured to be coupled to the alignment component. The alignment component may be vertically positioned above both the first hardware component and the second hardware component.

[0011] The first side portion of the main shell layer may be configured to be laterally deflected relative to a first curved seam region formed in the main shell layer. The second side portion of the main shell layer may be configured to be laterally deflected relative to a second curved seam region formed in the main shell layer. The secondary shell layer may be coupled to the main shell layer at a tab on the main shell layer formed between the first curved seam region and the second curved seam region. The secondary shell layer may be coupled to the main shell layer by at least one fastener.

[0012] At least one of the secondary shell layer or the main shell layer may include at least one ventilation hole formed therethrough.

[0013] The top surface of the secondary shell layer may include at least one protrusion.

[0014] The main shell layer and the secondary shell layer may be formed of an ABS injection molded plastic.

[0015] The adjustable helmet may include at least one padding stack coupled to the main shell layer and at least one padding stack separately coupled to the secondary shell layer. The at least one padding stack coupled to the secondary shell layer may be configured to extend over the tensioning device without contacting the tensioning device.

[0016] In various embodiments, a method of forming an adjustable helmet includes providing a main shell layer. The main shell layer includes a first side portion and a second side portion. The first side portion and the second side portion are laterally flexible relative to each other. The method includes providing a secondary shell layer; coupling the secondary shell layer to the main shell layer at a location between the first side portion and the second side portion such that at least a portion of the first side portion and at least a portion of the second side portion extend over at least a portion of a top surface of the secondary shell layer; coupling a first hardware component to the first side portion of the main shell layer; coupling a second hardware component to the second side portion of the main shell layer; coupling a first end of a tensioning device to the first hardware component; and coupling a second end of the tensioning device to the second hardware component to provide tension between the first side portion and the second side portion.

[0017] The method may include providing a first wing on a first side of the secondary shell layer, providing a second wing on a second side of the secondary shell layer, forming a first elongated track through the first wing, and forming a second elongated track through the second wing.

[0018] The method may include extending a portion of the first hardware component through the first elongated track and extending a portion of the second hardware component through the second elongated track.

[0019] The method may include providing a plurality of padding stacks, coupling at least one of the plurality of padding stacks to the main shell layer, and coupling at least another of the plurality of padding stacks to the secondary shell layer. The at least another of the plurality of padding stacks coupled to the secondary shell layer may extend over the tensioning device without contacting the tensioning device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A front perspective view illustrating an exemplary adjustable helmet.

[0021] Figure 2 A rear perspective view illustrating an exemplary adjustable helmet.

[0022] Figure 3ARear perspective view of an exemplary adjustable helmet in a first configuration.

[0023] Figure 3B Illustrating in a second configuration Figure 1 Rear perspective view of an exemplary adjustable helmet.

[0024] Figure 4 Rear plan view of an adjustable helmet.

[0025] Figure 5 Internal view of an adjustable helmet.

[0026] Figure 6 Rear perspective view of an exemplary main shell of an adjustable helmet.

[0027] Figure 7 Rear perspective view of an exemplary sub - shell of an adjustable helmet.

[0028] Figure 8 Rear perspective view of an exemplary padding arrangement for an adjustable helmet. Detailed Description

[0029] As used in this document, the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the relevant art. When used in this document, the term "comprising" means "including" but not limited to. When used in this document, the term "exemplary" is intended to mean "by way of example" and is not intended to indicate that a particular exemplary item is preferred or necessary.

[0030] In this document, when terms such as "first" and "second" are used to modify a noun, such use is only intended to distinguish one item from another and is not intended to require a sequential order unless specifically stated. The terms "approximate" and "about", when used in conjunction with a numerical value, are intended to include values that are close to but not exactly the number. For example, in some embodiments, the term "approximate" may include values within + / - 10% of the value.

[0031] As used in this document, terms such as "top" and "bottom", "upper" and "lower", "front" and "rear", or "outer" and "inner" are not intended to have an absolute orientation, but rather are intended to describe the relative positions of various components relative to each other. For example, when a device of which a component is a part is oriented in a first direction, a first component may be an "upper" component and a second component may be a "lower" component. If the orientation of the structure containing the components is changed, then the relative orientation of the components may be reversed, or the components may be in the same plane. The claims are intended to cover all orientations of devices containing such components.

[0032] Reference Figures 1 to 2 , illustrates an adjustable helmet 10 in accordance with one aspect of the present disclosure. In the embodiments shown throughout, the adjustable helmet 10 is configured to be used as a batting helmet for use as part of a sporting activity such as, for example, baseball and / or softball. However, it will be understood that the various systems and configurations described in this document are not limited to use in batting helmets and may be applied to helmets for other sports (e.g., hockey, football, lacrosse, cricket, cycling, auto racing, etc.) and / or helmets for use in other non-sporting applications (e.g., protective helmets for construction, emergency responders, etc.).

[0033] The adjustable helmet 10 includes a main shell 12 and a secondary shell 29. As will be described in further detail below, the secondary shell 29 may be formed separately from the main shell 12 and may be coupled to the main shell so as to allow movement of the shells relative to each other. Both the main shell 12 and the secondary shell 29 may be formed of any suitable material such as, for example, ABS injection molded plastic, polypropylene, etc., and may have any suitable thickness (e.g., 2 mm to 5 mm). However, it will be understood that the main shell 12 and the secondary shell 29 may be formed of different materials and / or have different thicknesses. Additionally, each of the main shell 12 and / or the secondary shell 29 may vary in thickness throughout to account for regions of greater impact strength, greater flexibility, etc.

[0034] The main shell 12 may include a brim portion 14 and a pair of ear flaps 16 having ear holes 18. While a pair of ear flaps 16 is shown, it will be understood that the main shell 12 may be configured to have fewer than two ear flaps 16 (e.g., one ear flap or no ear flaps). Additionally, each ear flap 16 may include a plurality of mounting holes 17 for selective attachment of, for example, cheek guard(s), strap(s), face mask, etc. Further, it should be understood that the main shell 12 may not have a brim or may have an alternative style of brim compared to that Figure 1 illustrated therein.

[0035] Still referring Figures 1 to 2, the main shell 12 may include two corresponding side portions: a first side portion 20A and a second side portion 20B. In the vicinity of the front region of the main shell 12, corresponding seam zone portions 21A, 21B are formed. Each seam zone portion 21A, 21B may be configured as a cut in the main shell 12, which cut allows the corresponding first side portion 20A and second side portion 20B to flex laterally relative to the other parts of the main shell 12 and relative to the sub-shell 29. As will be described in further detail below, such lateral flexibility enables the helmet 10 to be size-adjustable. In various embodiments, one or more of the seam zone portions 21A, 21B may have a curved configuration. In other embodiments, one or more of the seam zone portions 21A, 21B may have different shapes or configurations.

[0036] Since each seam region 21A, 21B can be curved, lateral flexure of the corresponding side portions 20A, 20B to a certain maximum point can be achieved without splitting or otherwise damaging the main shell 12. For example, referring to Figure 3A and Figure 3B , the helmet 10 is shown in its minimum expansion configuration ( Figure 3A ) and its maximum expansion configuration ( Figure 3B ), where the corresponding side portions 20A, 20B flex laterally inwards or outwards depending on the proportions of the user's head. When the user slides the helmet 10 over his or her head, the side portions 20A, 20B flex accordingly, providing the user with an infinitely adjustable fit between the minimum and maximum configurations. In some embodiments, the determination of the minimum expansion configuration and the maximum expansion configuration may be based on the hat sizes commonly utilized. For example, the minimum expansion configuration ( Figure 3A ) may be based on a hat size of 6 3 / 8, while the maximum expansion configuration ( Figure 3B ) may be based on a hat size of 7 5 / 8, where the helmet 10 is infinitely adjustable to any head size within that range. However, it will be understood that the determination of the minimum and maximum configurations is not limited to these stated ranges.

[0037] Referring back to Figures 1 to 2, the sub-shell 29 may include a peak portion 22. The peak portion 22 may rise relative to the remainder of the sub-shell 29 through a pair of side surfaces 28A, 28B such that the peak portion is substantially flush with the outer surfaces of the side portions 20A, 20B of the main shell 12. The main shell 12 itself may rise relative to the sub-shell 29 through the side portions 32A, 32B. The peak portion 22 may include an opening 24 for the insertion of a fastener (not shown) to couple the sub-shell 29 to the main shell 12. Any suitable fastener may be utilized, such as for example screws, rivets, etc. The sub-shell 29 may further include one or more ventilation openings 30 substantially adjacent to the peak portion 22 to allow air to enter the helmet 10 through the sub-shell 29. The sub-shell 29 may extend from the peak portion 22 to a bottom portion 31, and the bottom portion 31 extends as low (or substantially as low) as the side portions 20A, 20B to provide adequate protection to the back of the user's head.

[0038] Reference Figures 1 to 2 and Figure 4 , the main shell 12 may include a pair of embedded portions 26. Each embedded portion 26 may include one or more ventilation openings 27. The inner surface of the embedded portion 26 may be substantially flush with the inner surface of the sub-shell 29, thereby allowing any padding attached within the top inner portion of the helmet 10 to have a consistent thickness and depth for improved fit and user comfort.

[0039] As Figure 2 and Figure 4 shown, a pair of fasteners 33A, 33B may be coupled to (and extend through) the respective side portions 20A, 20B of the main shell 12. More specifically, the fasteners 33A, 33B may extend through respective openings 45A, 45B formed in the main shell 12, as Figure 6 illustrated. The fasteners 33A, 33B may be any suitable fasteners, such as for example screws. As will be further described below, the fasteners 33A, 33B may form part of a tensioning device that enables the side portions 20A, 20B to laterally flex, yet still provide a secure and comfortable fit of the helmet 10 on the user's head. Although a pair of fasteners 33A, 33B is illustrated, it should be understood that an alternative number of fasteners may be used within the scope of the present disclosure.

[0040] Reference Figure 5, showing an internal view of the helmet 10. As described above, the helmet 10 includes a tensioning device 40 that enables the expansion and contraction of the side portions 20A, 20B while providing substantially equal compressive forces regardless of the size of the user's head. In some embodiments, the tensioning device 40 may include an elastic tension cord 36 that extends between corresponding internal components 44A, 44B and is coupled to the corresponding internal components, which are coupled to fasteners 33A, 33B. According to various embodiments, one or more of the internal components 44A, 44B may be nuts. A pair of connectors 39A, 39B (e.g., shoulder screws) may be utilized to hold the looped ends 38A, 38B of the tension cord 36 such that the tension cord 36 moves in unison with any flexing of the side portions 20A, 20B. The tension cord 36 may be of any suitable size and material (e.g., 3 / 32 inch diameter abrasion-resistant elastic cord), and the looped ends 38A, 38B may be formed by any suitable method (e.g., deburred crimp). In some embodiments, the tension cord 36 may have a length, for example, between 3 inches and 4 inches. Additionally, while the tension cord 36 is shown and described, it will be understood that any other suitable tensioning device may be utilized, such as, for example, one or more rubber bands, one or more springs, etc. As another example, the tensioning device may include a molded rubber or thermoplastic polyurethane component.

[0041] The central portion of the tensioning device 40 is configured to contact an alignment member 42 that is attached to the inner surface of the sub-shell 29 at an installation point 43. According to one embodiment, the alignment member 42 may be a nut. For example, the central portion of the tensioning device 40 may be supported over or through the alignment member 42. The alignment member 42 may not physically hold or impede the movement of the tensioning device 40. The fact is that the alignment member 42 may act as a centering point such that the tension imposed on the corresponding side portions 20A, 20B by the tensioning device 40 is substantially equal. Additionally, as Figure 5 shown, the alignment member 42 may be vertically located above the internal components 44A, 44B, which allows for a greater length of the tensioning device 40 than if the tensioning device passed directly between the internal components 44A, 44B. In the case of a longer tensioning device 40, the tensioning device 40 at its maximum point (i.e., Figure 3B the maximum size configuration shown in Figure 3AThe variance of the elastic force between the minimum size configuration (as shown) is minimized. For example, in the minimum size configuration, the tensioning device 40 may have a force preload of, for example, about 1 pound, while in the maximum size configuration, the tensioning device may have a force of 3 pounds or less. Thus, regardless of head size, all users will experience similar compressive forces, and thus similar levels of fit and comfort, because the variance of the compressive forces described above has been found to be hardly perceptible to the user.

[0042] Still referring to Figure 5 , closer to the bottom portion 31, the sub-shell 29 may include a pair of opposing wings 34A, 34B. Each wing 34A, 34B may have a respective elongated track 35A, 35B formed therethrough. A portion of the respective track hardware components 52A, 52B (the respective track hardware components consisting of fasteners 33A, 33B, internal components 44A, 44B, and connectors 39A, 39B) extends through the respective tracks 35A, 35B. In this way, the tracks 35A, 35B can define the minimum and maximum adjustment limits for the helmet 10. In some embodiments, at least a portion of each track hardware component 52A, 52B may be configured to be cylindrical (or substantially cylindrical), which can enable that portion of the track hardware component to freely and smoothly traverse the tracks 35A, 35B during a user's fitting of the helmet 10.

[0043] In some embodiments, one or more of the tracks 35A, 35B may be angled in a downward direction from the proximal end of the wings 34A, 34B (i.e., the end closest to the center of the sub-shell 29) to the distal end of the wings 34A, 34B (i.e., the end farthest from the center of the sub-shell 29). When the respective side portions 20A, 20B flex to accommodate the user's head, this angling of the tracks 35A, 35B can serve to lift the bottom portion 31 of the sub-shell 29 in an upward direction. In this way, any vertical gap formed between the outer surface of the sub-shell 29 and the inner surface of the main shell 12 due to the flexure / separation of the side portions 20A, 20B can be accounted for (and closed) by the corresponding upward movement of the sub-shell 29 in contact with the track hardware and the angled tracks 35A, 35B. Since the sub-shell 29 may be attached to the main shell 12 at only one point, such movement can be made possible. For example, as Figure 6 shown, the main shell 12 may include a tab 48 having an opening 49. The peak portion 22 may be coupled to the tab 48 by a fastener extending through, for example, the opening 24 ( Figure 1 shown) and the opening 49. Alternatively, the sub-shell 29 may be coupled to the main shell 12 by non-fastening means (e.g., an adhesive), or the sub-shell may be integrally formed (or molded together) with the main shell at or near the location of the tab 48.

[0044] When a user initially places the helmet 10 on his or her head, the side portions 20A, 20B can flex laterally, causing the fasteners 33A, 33B (and the coupled internal components 44A, 44B) to move correspondingly relative to the tracks 35A, 35B. Such movement of the components 44A, 44B can cause the coupled tensioning device 40 to extend, thereby slightly increasing the tension on the tensioning device. Once the user has finished placing the helmet 10 on his or her head, the tension from the tensioning device 40 can act on the internal components 44A, 44B (and the coupled fasteners 33A, 33B) to pull the side portions 20A, 20B inwardly, creating a secure and comfortable fit on the user's head without the need for a ratchet mechanism, locking mechanism, etc.

[0045] Although the use of only one tensioning device is shown and described in the present disclosure, it will be understood that, in accordance with one or more other embodiments of the present disclosure, more than one tensioning device (and thus, additional track hardware components, additional wings, additional elongated tracks, and / or other components) may be utilized.

[0046] Reference Figure 7 , a detailed view of the outer surface of an exemplary sub-shell 29 is shown. As described above, the sub-shell 29 can be embedded relative to the main shell 12, and the side portions 20A, 20B of the main shell 12 can flex laterally relative to the sub-shell 29. Specifically, the side portions 20A, 20B can move laterally relative to the respective top surfaces 50A, 50B of the sub-shell 29. To minimize the frictional force between the side portions 20A, 20B of the main shell 12 and the top surfaces 50A, 50B of the sub-shell 29, the sub-shell 29 can include one or more protrusions 46A, 46B. The purpose of the protrusions 46A, 46B will be to provide a purposeful friction surface between the main shell 12 and the sub-shell 29. This friction surface can limit the friction area between the two shells and can allow for smoother movement of the side portions 20A, 20B on the top surfaces 50A, 50B of the sub-shell 29. Although two protrusions 46A, 46B are shown, it will be understood that additional or fewer protrusions 46A, 46B may be utilized.

[0047] Now refer to Figure 8, showing an exemplary padding arrangement 60 according to one aspect of the present disclosure. One or more pads in the padding arrangement 60 may be formed of any suitable material such as, for example, ethylene-vinyl acetate (EVA) foam, polyurethane (PU) die-cut comfort foam, and / or combinations thereof. Additionally, the pads in the padding arrangement may have the same or different thicknesses. The padding arrangement 60 may include a front padding stack 62, a top padding stack 64, and / or one or more ear pads 65. In use with the helmet 10 described above, the front padding stack 62 and / or the ear pad(s) 65 may be configured to adhere to at least a portion of the main shell layer 12. Such adhesion may be by any suitable method such as, for example, gluing, strapping, etc. Thus, the front padding stack 62 and / or the ear pad(s) 65 may be able to move in concert with the movement of the side portions 20A, 20B of the main shell layer 12, thereby ensuring safety and proper fit for the user. The top padding stack 64 may be configured to adhere to at least a portion of the main shell layer 12, at least a portion of the secondary shell layer 29, and / or at least a portion of both the main shell layer and the secondary shell layer.

[0048] Additionally, the padding configuration 60 may include a rear padding stack 66. The rear padding stack 66 may be configured to adhere to the secondary shell layer 29. Thus, the rear padding stack 66 may be able to move in concert with the secondary shell layer 29. The geometry of the secondary shell layer 29 may allow the rear padding stack 66 to be positioned within the main shell layer 12.

[0049] As Figure 8 further shown, the rear padding stack 66 may be configured to cover at least a portion of the tensioning device 40 described above without interfering with the operation of the tensioning device. The rear padding stack 66 may include a lower adhesive surface 68 which may be configured to adhere to, for example, the lower portion 31 of the secondary shell layer 29, and an upper adhesive surface 67 may be provided for the rear padding stack 66 to adhere to the secondary shell layer 29 at a position above the tensioning device 40. In this way, the tensioning device 40 may be able to operate without interference, and the user may not feel or otherwise be aware of the presence of the various components of the tensioning device 40 due to the stacked padding. The rear padding stack 66 may generally cover the entire rear of the helmet 10, the main shell layer 12, and the secondary shell layer 29 in all adjustment configurations.

[0050] In various embodiments, the adhesion points of the rear padding stack 66 may be positioned such that when the helmet 10 is adjusted, the wings 34A, 34B of the secondary shell layer 29 may flex and not collide with the track hardware components 52A, 52B.

[0051] Although the rear padding stack 66 is illustrated as a single padding stack having two adhesive surfaces, it will be understood that the rear padding stack 66 can be formed as two (or more) separate padding stacks. It should also be understood that, in various embodiments, alternative padding arrangements and / or configurations can be used with the adjustable helmet 10 described in the present disclosure.

[0052] As described above, the adjustable helmet 10 described in this document is configured to be a playing helmet for use in, for example, baseball and / or softball. However, it will be understood that the various systems and configurations (including the tensioning device 40) described in this document are not limited to use in playing helmets and can be applied to helmets for other sports (e.g., hockey, football, lacrosse, cricket, cycling, racing, etc.) and / or helmets for use in other non-sporting applications (e.g., protective helmets for construction, emergency responders, etc.).

[0053] The features and functions described above, as well as alternatives, can be combined into many other different systems or applications. Various alternatives, modifications, variations, or improvements can be made by those skilled in the art, each of which is also intended to be covered by the disclosed embodiments.

Claims

1. An adjustable helmet, comprising: A first shell layer, comprising: A first side portion; and A second side portion; A second shell layer positioned between the first side portion and the second side portion, wherein the first side portion and the second side portion of the first shell layer (a) at least partially overlap the second shell layer and (b) are laterally flexible relative to each other to facilitate adjustment of the size of the first shell layer between a minimum size and a maximum size; and A size adjustment mechanism comprising a tension member extending between the first side portion and the second side portion, wherein the size adjustment mechanism facilitates ratchet - free and infinite adjustment of the size of the first shell layer between the minimum size and the maximum size without the user operating the size adjustment mechanism.

2. The adjustable helmet according to claim 1, wherein the tension member comprises an elastic cord, a first end of the elastic cord being coupled to a first interface of the first side portion, and an opposite second end of the elastic cord being coupled to a second interface of the second side portion.

3. The adjustable helmet according to claim 2, wherein the second shell layer defines a third interface, wherein the elastic cord extends from the first interface of the first side portion to the third interface of the second shell layer and from the third interface of the second shell layer to the second interface of the second side portion.

4. The adjustable helmet according to claim 3, wherein the third interface is vertically offset from the first interface and the second interface.

5. The adjustable helmet according to claim 4, wherein the elastic cord passes over the third interface and is supported by the third interface.

6. The adjustable helmet according to claim 2, wherein the first interface is a first opening defined by the first side portion, and the second interface is a second opening defined by the second side portion, the adjustable helmet further comprising: A first fastener extending through the first opening and engaging the first end of the elastic cord; And A second fastener extending through the second opening and engaging the opposite second end of the elastic cord.

7. The adjustable helmet according to claim 6, wherein the second shell layer comprises: A first wing portion extending laterally from a first edge of the second shell layer, the first wing portion defining a first slot that aligns with the first opening of the first side portion and receives the first fastener; And A second wing portion extending laterally from an opposite second edge of the second shell layer, the second wing portion defining a second slot that aligns with the second opening of the second side portion and receives the second fastener.

8. The adjustable helmet according to claim 1, wherein the first shell layer defines a cutout separating the first side portion from the second side portion, and wherein the second shell layer is positioned along the cutout.

9. The adjustable helmet according to claim 8, wherein the second shell layer defines a plurality of ventilation openings, and wherein the plurality of ventilation openings are exposed via the cutout.

10. The adjustable helmet according to claim 8, wherein the first shell layer has a tab extending into the notch, wherein the second shell layer defines an interface that engages with the tab, and wherein the interface and the tab define corresponding openings that receive fasteners to couple the interface to the tab.

11. The adjustable helmet according to claim 1, wherein the second shell layer includes a plurality of protrusions extending from the surface of the second shell layer, and wherein the plurality of protrusions are positioned to engage corresponding surfaces of the first side portion and the second side portion to limit contact and thus friction between the surface of the second shell layer and the corresponding surfaces of the first side portion and the second side portion.

12. An adjustable helmet comprising: A first shell layer including: A first side portion defining a first opening; and A second side portion defining a second opening; A second shell layer positioned between the first side portion and the second side portion, the second shell layer including: A first wing portion extending laterally from a first edge of the second shell layer, the first wing portion defining a first slot aligned with the first opening of the first side portion; and A second wing portion extending laterally from a second, opposite edge of the second shell layer, the second wing portion defining a second slot aligned with the second opening of the second side portion. A first fastener extending through the first opening of the first side portion of the first shell layer and the first slot of the first wing portion of the second shell layer; A second fastener extending through the second opening of the second side portion of the first shell layer and the second slot of the second wing portion of the second shell layer; and An elastic tension member extending between the first fastener and the second fastener.

13. The adjustable helmet according to claim 12, wherein the second shell layer defines an interface that is vertically offset from the first slot and the second slot, and wherein the elastic tension member extends from the first fastener around the interface to the second fastener.

14. The adjustable helmet according to claim 12, wherein the arrangement of the first shell layer, the second shell layer, and the elastic tension member facilitates adjustment of the size of the first shell layer between a minimum size and a maximum size.

15. The adjustable helmet according to claim 14, wherein the adjustable helmet does not include a ratchet mechanism or a locking mechanism to maintain the size of the first shell layer at one or more discrete sizes between the minimum size and the maximum size.

16. The adjustable helmet according to claim 14, wherein the size of the first shell layer is infinitely adjustable between the minimum size and the maximum size.

17. The adjustable helmet according to claim 14, wherein the size of the first shell layer adjusts to fit the wearer's head in response to the wearer's head being inserted therein, without the wearer operating a size adjustment mechanism.

18. An adjustable helmet comprising: A multi-piece shell layer having an infinitely adjustable size between a minimum size and a maximum size.

19. The adjustable helmet according to claim 18, wherein the infinitely adjustable size of the multi-piece shell is adjusted to fit the head of the wearer in response to the head of the wearer extending therein, without the wearer operating a size adjustment mechanism.

20. The adjustable helmet according to claim 18, wherein the multi-adjustable helmet does not include a ratchet mechanism or a locking mechanism to hold the multi-piece shell at a discrete size.

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