CA3234991A1 - A novel protective helmet - Google Patents

Abstract

Provides is a novel protective helmet design that allows helmet designers and manufacturers to create more advanced designs with cavities, converging walls, and movable parts inside a helmet to reduce both linear and rotational forces applied to the head during an impact and as a result, reduce the risk of head injury and concussion. Also provided is a a cost-effective design and manufacturing method that creates helmets that are light-weighted and perform better compared to the conventional helmet designs in terms of reducing linear and rotational forces applied to the head during an impact. The method also allows manufacturing helmets while consuming less raw materials for the shock-absorbing liner which is cost-effective and better for the environment.

Description

A NOVEL PROTECTIVE HELMET
TECHNICAL FIELD
The present invention relates to protective helmets, in particular sports and bicycle helmets and manufacturing thereof.
BACKGROUND
Using a protective helmet is essential for activities such as cycling, hockey, football, rock climbing, skiing, construction, military, or other helmet-required activities.
Helmets are very effective in reducing the risk of head injury and concussion. To reduce the risk of head injury and concussion, a helmet needs to mitigate both linear forces (caused by linear acceleration), and rotational forces (caused by rotational acceleration and rotational velocity) applied to the head during impact. In the past, helmets were mainly designed to reduce the linear forces as standards did not take into account the rotational forces for the purpose of certification.
However, research studies have shown that rotational forces of the head are one of the key factors behind head injury and concussion. Therefore, to enhance the safety of the wearers, when designing a helmet reducing both the linear forces and rotational forces need to be considered. Foams such as expanded polystyrene (EPS) are widely used in protective equipment such as helmets due to their low cost, high shock absorption, good durability, and excellent conformability in moulding. However, manufacturing helmets with rigid foam such as EPS has a number of issues. One issue is related to designing helmets with better shock absorption. In current helmet designs, creating cavities and channels is only possible in the direction of the mould's opening and closing unless the male part of the mould is a multiple-piece male tool. Using multiple-piece mould (e.g. mould with sliders) can be expensive and labour-intensive, has limitations and results in helmets that are heavier and do not necessarily have better overall shock absorption. Another issue is related to having an embedded mechanism for mitigating the rotational forces. Most designs use add-on mechanisms to deal with rotational forces which may not be the best way of addressing the issue as it increases the weight of the helmet. Therefore, any helmet design and manufacturing methodology that could address the aforementioned issues would be desirable to the helmet industry.
In conventional helmets that are made with foams such as Expanded Polystyrene (EPS) and its bio-degradable version Expanded Polylactic Acid (EPA), the helmets are mostly made using a single moulding with a single density for the shock-absorbing liner. In some newer designs, helmets are made with multiple layers of foams with different densities that are laid on top of

2 each other employing multiple moulding processes. In helmets with both single and multiple density shock-absorbing liners, there are restrictions in the direction, shape, and location of the cavities that are introduced in a helmet. At the same time, multi-density shock absorption does not provide an effective mechanism for reducing rotational forces. Designing a helmet with hollow compartments, cavities or channels that are not aligned with the pulling direction of the male and female moulds significantly increases the cost of labour and overhead of manufacturing a helmet. In addition, helmet toolings that are made of multiple parts and consist of sliders for the male mould are less durable and their life cycle is shorter than single-piece male moulds. Using sliders has its own limitations and shock-absorbing liners with closed cavities, and open cavities facing the outer shell are not possible to make or making them is not economically viable. In addition, for every different pulling direction of the cavity, a new slider is needed that usually are manually handled.
SUMMARY
One general aspect provides a protective helmet having an outer shell having an inward surface; a first set of shock-absorbing liners attached to the inward surface of the outer shell; a second set of shock-absorbing liners having multiple parts that can move and deform independently of each other when an impact force is applied to the outer shell of the helmet;
and a fitting liner covering one or more of the parts of the second set of shock-absorbing liners, attachment means connecting an inward surface of the first set of shock-absorbing liners to the second set of shock-absorbing liners; and where a contact area between the first set of shock-absorbing liners and the second set of shock-absorbing liners is smaller than an inner surface area of the first set of shock-absorbing liner.
Implementations may include one or more of the following features. The protective helmet where each of the one or more parts of the second set of shock-absorbing liners are separately attached to the first set of shock-absorbing liners using at least one of the attachment means. The attachment means are made of any mechanical or chemical attachment means such as hook-and-loop fastener, pin, snap pin, snap pin basket, snap fastener, latch-and-hook fastener, clips, hinge, press-fitting, hook plastic insert and loop rubber, rubber holder, mesh holder, silicone rubber holder, tie, connector, spring, buckle, heat-seal, sewing, fusion, elastic, fitting, adhesive, insert, screw, railing, button, buttonhole, rivet, or a combination thereof. The

3 attachment means provide a finite amount of play in the connection between of the second set of shock-absorbing liners relative to the first set of shock-absorbing liners.
The attachment means further attaches to the fitting liner The attachment means is flexible and elongates elastically under the impact force, or plastically when the impact force exceeds a threshold. The attachment means are frangible in order to rupture when the impact force exceeds a second threshold to allow unrestricted movement between the first set and the second set of shock-absorbing liners. The first set of shock-absorbing liners may include a low friction layer. The either of the low friction layers may include a lubricant, plastic, rail, sliding groove, wax, powder, polymer, elastomer, rubber, polycarbonate (pc), acrylonitrile butadiene styrene (abs), carbon fiber, silicone rubber, silicone lubricant, fluid-filled compartment, fabric, fiber, or a combination thereof. The second set of shock-absorbing liners may include a low friction layer. The attachment means elongates, ruptures or dislocates during the impact force to allow the second set of shock-absorbing liners to move relative to the first set in order to reduce rotational and linear forces applied to the head during impact The second set of shock-absorbing liners are made of the same materials with a similar or different density than the first set of shock-absorbing liners. The second set of shock-absorbing liners are made of different materials than the first set of shock-absorbing liners. The two sets of shock-absorbing liners may include micro-porosity, macro-porosity, thin-walled structure, fluid-filled compartment, truss structure, lattice structure, auxetic structure, channeled structure, open cavity, closed cavity, hole, or a combination thereof. The first sets of shock-absorbing liners, or the second set of shock-absorbing liners, or both may include at least some of the attachment means.
One or more shapes and sizes are defined to be used repeatedly for all the parts of the second set of shock-absorbing liners.
One general aspect includes a method of manufacturing a protective helmet. The method includes separately making a) a first set of shock-absorbing liners and b) a second set of shock-absorbing liners, the second set of shock-absorbing liners having multiple parts;
attaching the first set of shock-absorbing liners to each of the multiple parts of the second set of shock-absorbing liners using attachment means, fixing an outer shell at its inward surface to the first set of shock-absorbing liners, and covering a fitting liner around one or more of the multiple parts of the second set of shock-absorbing liners.
DESCRIPTION OF THE DRAWING

4 The foregoing aspects of the present disclosure will become more readily appreciated as the same will become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawing, wherein:
FIGURE 1 is a cross-section of a helmet comprising two sets of shock-absorbing liners in accordance with a number of embodiments.
FIGURE 2A is a side view of a helmet in accordance with a number of embodiments.
FIGURE 2B is a bottom view of a helmet in accordance with a number of embodiments.
FIGURE 20 is a cross-section of a helmet along section A-A from Figure 2B in accordance with a number of embodiments.
FIGURE 3A is a side view of the first set of shock-absorbing liners of a helmet in accordance with a number of embodiments.
FIGURE 3B is a side view of the second set of shock-absorbing liners of a helmet and its fitting liner in accordance with a number of embodiments.
FIGURE 30 is an exploded illustration of connectors for attaching the second set of shock-absorbing liners and the fitting liner to the first set of shock-absorbing liners in a helmet in accordance with a number of embodiments.
FIGURE 4A is a cross-section (Section A-A of FIGURE 3A) of the first set of shock-absorbing liners of a helmet.
FIGURE 4B shows a cross-section (Section B-B of FIGURE 3-B) of the side view the second set of shock-absorbing liners of a helmet.
FIGURE 4-C shows the attachment means associated with the cross-section C-C
(shown in FIGURE 3-C) used for attaching the second set of shock-absorbing liners and the fitting liner to the first set of shock-absorbing liners in a helmet.
DETAILED DESCRIPTION
In the following section, specific details are explained to provide an in-depth understanding of the exemplary embodiments of the present invention. It will be apparent to one familiar with the art that the embodiments shown may be realized without embodying every specific detail. The embodiments of the present invention may also employ any combination of features described below. The following description provides illustrations of a novel helmet design and method of moulding a helmet to include the claimed features.
The following description provides illustrations of a novel helmet design.
The present disclosure describes a novel protective helmet design that allows helmet designers and manufacturers to create more advanced designs with cavities, converging walls, and movable parts inside a helmet to reduce both linear and rotational forces applied to the head during an impact and as a result, reduce the risk of head injury and concussion.
In one embodiment, the design of the shock-absorbing liner of a helmet is divided into two sets (called "the two sets"). The first set of shock-absorbing liners (also called "the first set") is

5 manufactured using a thinner layer of the shock-absorbing liner than a comparable conventional helmet. Then, the second set of shock-absorbing liners (also called "the second set") is separately manufactured. The second set consists of multiple parts that are attached to the designated areas on the surface of the first set that is facing the wearer's head. When the helmet is impacted, the parts of the second set of shock-absorbing liners can move and deform independently of each other.
The attachment means used to attach the first set, the second set, and the fitting liner to one another can be any mechanical or chemical attachment means or fasteners known in the industry.
The present disclosure introduces a cost-effective design and manufacturing method that creates helmets that are light-weighted and perform better compared to the conventional helmet designs in terms of reducing linear and rotational forces applied to the head during an impact.
In an aspect, the present disclosure explains ways for designing and manufacturing a helmet including open cavities, close cavities, converging walls, thin-walled structures, fluid-filled compartments, and deep channels in various directions on the inward surface of the helmet where it is facing the wearer's head without a need to use labour-intensive methods such as using a multiple-piece male mould (i.e. mould with sliders) for manufacturing the helmets.
In an embodiment, the present disclosure describes a novel design and its manufacturing method for helmets to improve them in terms of protection, weight, cost, and ventilation. Such characteristics are desirable in the helmet industry.
The method also allows manufacturing helmets while consuming less raw materials for the shock-absorbing liner which is cost-effective and better for the environment.
In an embodiment, the parts of the second set have different shapes, materials, sizes, or densities which allow customizing the helmet design in terms of improving the head protection, reducing the weight of a helmet, embedding electronics or battery inside a helmet, or other design requirements for a helmet.
Using two sets of shock-absorbing liners gives more freedom to helmet designers and allows them to design helmets optimally. For instance, there are areas in a helmet that due to the geometry and moulding constraints cannot be optimally designed and would usually comprise

6 more shock-absorbing materials than needed. By using two sets of shock-absorbing liners, it is possible to improve the design of these areas.
In addition, by using two sets of shock-absorbing liners, it is possible to easily alter the design when needed. For instance, if preliminary tests show that the helmet performance needs to be improved in certain areas to pass the standard certification, it is possible to only modify the design of one or more parts of the second set by changing their density, material, shape, size or configuration to resolve the issue without getting involved in a lengthy and costly process of updating the entire mould of the shock-absorbing liner of a helmet.
In an embodiment, one or more parts of the second set that are attached to the first set can move and deform independently of the rest of the parts of the second set when the force applied to the helmet exceeds a certain limit. In most impact scenarios, only a limited area of the shock-absorbing liner is mainly engaged and damaged. Allowing only the parts of the second set located on the impacted area to move and deform independently enhances the helmet performance in mitigating the rotational and linear forces applied to the head during an impact.
In one embodiment, the parts of the second set are made of the same type of materials with different density than the first set. This embodiment allows designing helmets by varying the density of the second set to enhance the helmet performance for various impact intensities.
Since the moulding process of the second set is separate from the moulding process of the first set, it is possible to change the density of the second set as needed without applying any changes to the design of the first set. For instance, the first set can be made using higher density EPS than the second set. This allows the helmet to perform better for both high-speed and low-speed impacts.
In one embodiment, the parts of the second set of shock-absorbing liners are made of a different material than the first set of shock-absorbing liners. For instance, the first set of shock-absorbing liners is made of EPS or EPA, and the second set is made of thin-walled plastic structures such as honeycomb or a combination of different materials and structures.
In an embodiment, all the parts of the second set used for a helmet have similar shapes or sizes. The embodiment can reduce the manufacturing cost of the helmet.
In an embodiment, some of the parts of the second set used for a helmet have a similar shape or size.
In an embodiment, the inward surface of the first set that faces the wearer's head is designed to allow using similar shapes and sizes for some or all of the parts of the second set of shock-absorbing liners. The embodiment can reduce the manufacturing cost of producing the helmet.

7 In an embodiment, a helmet comprises an outer shell, the first set, the second set, attachment means for attaching the second set to the first set, a fitting liner, and attachment means for attaching the fitting liner to the helmet.
In an embodiment, the attachment means used for attaching the second set to the first set also attaches the fitting liner to the second set of shock-absorbing liners.
The outer shell is considered to be the outward surface of the first set facing away from the wearer's head.
In one embodiment, the deformation and compression of the second set and the first set result in improving the helmet performance by reducing the linear and rotational forces applied to the head during an impact.
In an embodiment, when the applied force to the helmet exceeds a certain limit the second set can experience a movement relative to the first set The limit depends on various factors such as shape and location of the second set, the type of attachment means used for attaching the second set to the first set, the shape of the first set, the impact force intensity and direction, and where the force was applied to the helmet.
In an embodiment, the movement of the second set relative to the first set is constrained by the type and number of the attachment means used for attaching the second set to the first set.
In one embodiment, the second set is firmly attached to the first set of shock-absorbing liners, but the fitting liner is attached such that the head and the fitting liner can move relative to the rest of the helmet if the applied force to the helmet exceeds a certain limit.
The embodiment can include a low friction layer between the fitting liner and the second set to facilitate the relative movement between the fitting liner and the rest of the helmet. According to this embodiment, the deformation and compression of the first set and the second set, and the movement of the head and fitting liner relative to the rest of the helmet enhance the helmet performance by reducing the linear and rotational forces applied to the head during an impact.
In an embodiment based on the previous embodiment, the attachment means used for attaching the fitting liner to the first set or the second is such that they can dislocate or elongate during impact to allow the fitting liner to move relative to the second set.
For instance, the attachment means can comprise a button, buttonhole in the fitting liner, elastic connector that is attached to the first set, the second set, or both.
In an embodiment, a low friction layer is placed between the first set and the second set to allow a relative motion between the two sets when the applied force to a helmet exceeds a certain limit.

8 In an embodiment, a low friction layer is placed between the second set and the fitting liner to allow a relative motion between the second set and the fitting liner when the applied force to a helmet exceeds a certain limit.
In an embodiment, the low friction layer comprises a lubricant, plastic, polymer, elastomer, polycarbonate (PC), acrylonitrile butadiene styrene (ABS), wax, powder, carbon fiber, rail, sliding groove, rubber, fabric, fiber, silicone rubber, silicone lubricant, or a combination thereof.
In an embodiment, the low friction layer between the two sets is a fluid-filled compartment.
In one embodiment, the second set is attached to the first set of shock-absorbing liners such that if a force applied to the helmet exceeds a certain limit the second set and the fitting liner can move temporarily or permanently relative to the first set. This embodiment improves the ability of the helmet to reduce both linear and rotational forces applied to the head during impact.
In an embodiment, the fitting liner and the head can move in any direction relative to the second set of shock-absorbing liners or the rest of the helmet when the applied force to a helmet exceeds a certain limit.
In an embodiment, the low friction layer is partly or entirely part of the first set.
In an embodiment, the low friction layer is partly or entirely part of the second set.
In an embodiment, the low friction layer is partially part of the first set, and partially part of the second set.
In an embodiment, the low friction layer is an independent layer placed between the first set and the second set.
In an embodiment, the low friction layer is a layer between the second set and the fitting liner.
In an embodiment, the attachment means that attaching the first set to the second set allows a discreet relative movement between the first set and the second set when the applied force to the helmet exceeds a certain limit. There may be a finite amount of play in the attachment between sets of shock-absorbing liners to permit this finite movement. The finite relative movement can enhance the protection of the helmet by reducing the linear and rotational forces apply to the head during most impacts on the helmet.
In an embodiment, the attachment means are frangible and designed to rupture or disconnect when the applied force to the helmet exceeds a certain limit. The rupture or disconnection of the attachment means can further enhance the helmet performance.
In an embodiment, a low friction layer is placed between the two sets. The low friction layer facilitates the relative movement between the two sets when the applied force to the helmet exceeds a certain limit.

9 In an embodiment, the attachment means controls the motion caused by the low friction layer in the presence of an impact force. The embodiment allows the second set and the fitting liner to move finitely relative to the first set to enhance the helmet performance during an impact.
In an embodiment, the attachment means that attach the fitting liner to the first set and the second set elastically or plastically elongates and allows a finite relative movement between the fitting liner and the rest of the helmet when the applied force to the helmet exceeds a certain limit. The finite movement can enhance the protection of the helmet by reducing the linear and rotational forces apply to the head during most impacts on the helmet. A
sufficiently large force can result in one or more of the attachment means being ruptured or disconnected.
In an embodiment, the deformation of the two sets reduces the linear forces and rotational forces applied to the head when the helmet is impacted.
In an embodiment, the deformation and dislocation of the second set further reduce the linear forces and rotational forces applied to the head when the helmet is impacted.
In an embodiment, the deformation and movement of the second set and the fitting liner relative to the first set further reduce the linear forces and rotational forces applied to the head when the helmet is impacted.
In an embodiment, the fitting liner is one piece that covers all the parts of the second set.
In an embodiment, the fitting liner comprises multiple pieces that cover one or more parts of the second set.
In an embodiment, one piece of the fitting liner covers multiple parts of the second set.
In an embodiment, the fitting liner covers some or all of the first set and the second set.
In one embodiment, the first set, the second set, and the fitting liner are attached to one another using any mechanical or chemical attachment means or fasteners such as hook-and-loop fastener, pin, snap pin, snap pin basket, snap fastener, latch-and-hook fastener, clips, hinge, press-fitting, hook plastic insert and loop rubber, rubber holder, silicone rubber holder, tie, connector, mesh holder, spring, buckle, heat-seal, sewing, fusion, elastic, fitting, adhesive, insert, screw, railing, button, buttonhole, rivet, or a combination thereof.
In an embodiment, the attachment means or parts of them are moulded with the first set or the second set or both.
In an embodiment, the attachment means or part of them are included in the fitting liner. For example, the fitting liner can comprise the buttonholes needed for attaching to the buttons as a part of the attachment means.
In an embodiment, the attachment means or parts of them are added to the first set or the second set or both after the moulding process.

In one embodiment, one or more parts of the second set of shock-absorbing liners are detachable from the first set.
In one embodiment, the fitting liner is detachable from the first set or the second set or both.
In an embodiment, the second set of shock-absorbing liners is made in a variety of shapes, 5 materials, and sizes to provide a better fit or better protection for the wearer's head.
In an embodiment, one or more shapes and sizes are defined to be used for all the required parts for the second set. By using only one or more parts repeatedly for all the needed parts of the second set, it is possible to reduce the cost of manufacturing the helmet.
In one embodiment, by changing the size, shape, and configuration of the second set, it is

10 possible to change the size of the helmet and make it suitable for other sizes of the head. For example, the first set and the outer shell of a helmet are designed for the large size head, and by changing the size and shape of the parts of the second set, it is possible to make the helmet suitable for the medium size head. Such an embodiment can reduce the cost of manufacturing.
In an embodiment, one or more parts of the second set of shock-absorbing liners are permanently attached to the first set.
In one embodiment, the surface of the first set of shock-absorbing liners that is facing the second set is covered by a layer of polymer, plastic, elastomer, metal, rubber, silicone rubber, PC, carbon fiber, ABS, lubricant, silicone lubricant, fabric, fiber, or a combination thereof.
In one embodiment, the first set and the second set of shock-absorbing liners comprise EPS, EPA, ABS, PC, Kevlar, titanium, polymer, plastic, polyurethane, foam, textile, elastomer, composite, resin, shock-absorbing foam, rubber, fiber, silicone, non-Newtonian material, organic material, fluid-filled compartment, metal, or a combination thereof.
In one embodiment, the first set, or the second set or both are reinforced during or after manufacturing by means of reinforcing materials such as fabric, fiber, plastic, Kevlar, carbon fiber, PC, ABS, metal, or a combination thereof. For example, the surface area of the second set that faces the first set is moulded with PC sheets.
In an embodiment, the protective helmet is used for any helmet-required activities such as cycling, motorcycling, skiing, rock-climbing, military, football, hockey, all-terrain vehicle (ATV), and construction.
The approach disclosed herein may be used to make various protection equipment where the protected object is any part of the body or any other object that requires protection against impact.
In one embodiment, the first set, the second set, or both or parts of them are made by using additive manufacturing methods.

11 In one embodiment, the surface of the second set that faces the wearer's head is considered as the fitting liner.
In one embodiment, the parts of the second set of shock-absorbing liners move in the same or different directions during an impact on the helmet. Since the parts of the second set are attached to the first set separately, depending on the location, direction, and intensity of the impact force the parts can move in directions that are not necessarily the same for all the parts of the second set.
In an embodiment, there are more than two sets of shock-absorbing liners and use the same methods of attachment described herein for attaching the second set to the first set, the third set is attached to the second set, and the fourth set attached to the third set, and so forth.
In one embodiment, the first set and the second set of shock-absorbing liners or part of them are made of structures having geometries, such as trusses, hexagonal, hollow compartments, cylindrical, macro-cavity, micro-cavity, foam, open cavity, closed cavity, channelled structure, fluid-filled compartment, lattice, thin-walled structure, auxetic structure, collapsible geometries or a combination thereof.
The manufacturing process includes designing the two sets of shock-absorbing liners. The shock-absorbing liner of the helmet is divided into two sets with two different thicknesses, called the first set and the second set. The thickness of each set is determined based on the material, density, and structure used for each set of shock-absorbing liners. For bicycle helmets made from EPS, the thickness for the first set and the second set is between 5mm to 35mm. The thickness of each area of the first set and set second varies throughout different areas of the helmet to create the protection needed during impact. It is also possible to use thinner or thicker EPS for certain areas of the first set or the second set by varying the density of the EPS
between 60g/L to 120g/L. Using materials or structures other than EPS will need to be tested to find the proper thickness for a target helmet type Then, the mould of the first set of shock-absorbing liners is designed to have the required thickness and then the first set and outer shell of the helmet are moulded together. In the next step, based on the specifications of the design, the parts of the second set are moulded separately. In the last step, the parts of the second set and the fitting liner are attached to the first set by the attachment means.
Other techniques besides moulding can also be used for manufacturing the two sets such as layering, additive manufacturing, injection moulding or any other method known in the industry for making a helmet.

12 In one method of the manufacturing process, the attachment means or parts of the attachment means are moulded during the moulding process of the first set and the outer shell of the he In one method of the manufacturing process, the attachment means or parts of the attachment means are moulded during the moulding process of the second set.
In one method of the manufacturing process, the attachment means or parts of the attachment means are made separately from moulding the two sets of the shock-absorbing liners.
In one method of the manufacturing process, a low friction layer or parts of it are moulded during the moulding process of the second set.
In one method of the manufacturing process, a reinforcing layer or parts of it are moulded during the moulding process of the second set. For example, a PC sheet can be moulded with the second set where it faces the first set. The moulded PC sheet with the second set can act both as a reinforcing layer for the second set and a low friction layer to reduce friction between the two sets. Another example is using a PC sheet to be moulded with the second set where it faces the fitting liner. The moulded PC sheet with the second set can act both as a reinforcing layer for the second set and a low friction layer to reduce friction between the second set and the fitting liner.
In one method of the manufacturing process, a reinforcing layer or parts of it are moulded during the moulding process of the first set.
In one method of the manufacturing process, a low friction layer or parts of the low friction layer are moulded during the moulding process of the first set and the outer shell of the helmet. For instance, the surface of the first set that faces the second set can be covered by a layer of polycarbonate, lubricant, or both.
In one method of the manufacturing process, a low friction layer or parts of the low friction layer are made independent of the two sets of shock-absorbing liners.
FIGURE 1 discloses multiple embodiments and shows the cross-section of the helmet 101 (side view) worn on the head 100 comprises the outer shell 103, and the first set of shock-absorbing liners (also called the first set") 102 that is attached to the outer shell 103 at one or more locations. The second set of shock-absorbing liners (also called "the second set") 104 comprises multiple parts that one or more of them are separately attached to the first set of shock-absorbing liner 102 by mechanical or chemical attachment means including, but not limited to, hook-and-loop fastener 109, inserts 107, adhesive, snap pin 111 and snap pin basket 110, anchor 108, or any other attachment means or fasteners known in the industry for attaching the second set 104 to the first set 102. The second set 104 can also comprise layer

13 118 as a low friction layer to allow the second set 104 to move relative to the first set 102 when a force applied to the helmet 101 exceeds a certain limit. The layer 118 as a low friction layer can be also attached to the first set 102 (not shown in FIGURE 1) or attached to both the first set 102 and the second set 104 (not shown in FIGURE 1). The layer 118 as a low friction layer can cover one or more surfaces of the first set 102 (not shown in FIGURE 1) or the second set 104.
The second set 104 is covered at one or more locations by a fitting liner 105 where the fitting liner 105 contacts the head 100 at one or more locations. The attachment means used for attaching the fitting liner 105 to the second set 104 or the first set 102 are any mechanical or chemical attachment means such as hook-and-loop 113, adhesive 115, sewing 116, button 112 anchored to the second set 104, button 114, buttonhole (not shown in FIGURE 1) in the fitting liner 105, and connector 121 to attach the fitting liner 105 to the first set 102 by anchor 108 through the opening 126 in the second set 104.
To better show the details, purposely, some of the parts in FIGURE 1 are shown farther than normal from each other. As a result, gaps between different components should not be interpreted as an error or limitation in the presented invention In addition, a helmet normally comprises other parts such as a retention system (chin strap), adjustment mechanism (ratchet), and other accessories that are not shown to keep the description and drawings simple and uncluttered from prior art parts that are not the focus of this invention.
However, such accessories can be considered as part of the helmet.
In an embodiment according to FIGURE 1, the finite relative movement between the second set 104 and the first set 102 during impact to the helmet 101 is facilitated by the layer 118 as a low friction layer and controlled by the anchor 108, the connector 121, the opening 126 in the second set 104, the fitting liner 105, button-hole in the fitting liner (not shown in FIGURE 1), and the button 114. The connector 121 is made of an elastic material such as rubber or spring and it is attached to the fitting liner 105 by an attachment means such as button 114 and a buttonhole (not shown in FIGURE 1) in the fitting liner 105 at one end, and at the other end, the connector 121 is attached to the first set 102 by the anchor 108. The embodiment allows the second set 104 to dislocate and move finitely when the impact force applied to the helmet 101 exceeds a certain limit. The duration of an impact is very short. For instance, for a bicycle helmet made of EPS, the duration is between 0.007 seconds (7ms) to 0.015 seconds (15ms).
Since the duration is very short, the movement of the head is very finite. Normally less than 15mm. However, since the acceleration/deceleration is very high (between 40g to 400g and 1krad/s^2 and 10krad/s^2), the force applied to the head is very injurious and can result in severe head trauma. The

14 allowed finite movement between the first set 102, the second set 104, and the fitting liner 105 and compression of the first set 102 and the second set 104 during impact can significantly reduce the force applied to the head 100. As a result of the finite movement of the second set 104 relative to the first set 102, the rotational and linear forces applied to the head 100 during an impact on the helmet 101 will be mitigated.
In an embodiment according to FIGURE 1, the connector 121 circles around the second set 104 (not shown in FIGURE 1), instead of going through them similar to opening 126.
In an embodiment according to FIGURE 1, the layer 118 is a low friction layer made of materials such as a lubricant, polymer, elastomer, plastic, rail, sliding groove, wax, powder, PC, ABS, Teflon, carbon fiber, rubber, silicone rubber, silicone lubricant, fluid-filled compartment, fabric, fiber, foam, or a combination thereof. In an embodiment according to FIGURE 1, one or more surfaces of the second set 104 are covered by a reinforcing layer such as the layer 117 or the layer 118 as a reinforcing layer to reinforce the structure of the second set 104. The layer 117 or the layer 118 as a reinforcing layer can be made of materials such as polymer, plastic, thermoplastic, organic materials, metal, fiber, fabric, PC, carbon fiber, resin, ABS, Kevlar, titanium, or other common materials used for a helmet The layer 117 or the layer 118 as a reinforcing layer can also be in form of a reinforcing means which is partly or entirely embedded inside the second set 104 similar to the concept of reinforcing bar in concrete or plastic keel in the EPS helmets. The layer 117 or the layer 118 as a reinforcing layer can cover a portion or all surfaces of the second set 104.
In an embodiment according to FIGURE 1, the layer 117 and the layer 118 as a reinforcing layer can comprise openings to allow the connector 121 to pass through the opening 126 in the second set 104.
In an embodiment according to FIGURE 1, the layer 117 is both a low friction layer and a reinforcing layer for the parts of the second set 104. For example, the layer 117 can be made of a polycarbonate sheet with or without a layer of lubricant to enforce the second set 104 and also facilitate the movement of the second set 104 relative to the fitting liner 105.
In an embodiment according to FIGURE 1, the layer 118 is both a low friction layer and a reinforcing layer for the parts of the second set 104. For example, the layer 118 can be made of a polycarbonate sheet with or without a layer of lubricant to enforce the second set 104 and also facilitate the movement of the second set 104 relative to the first set 102.
In an embodiment according to FIGURE 1, the layer 117 reduces the friction between the fitting liner 105 and the second set 104 and it allows the fitting liner 105 and the head 100 to have a relative movement with respect to the rest of the helmet 101 when an impact force applies to the helmet 101. This relative movement can enhance the performance of the helmet 101 by reducing the linear and rotational forces apply to the head 100 during an impact.
In an embodiment according to FIGURE 1, the layer 117 is a lubricant, polymer, elastomer, fabric, plastic, wax, powder, PC, ABS, carbon fiber, Teflon, or a combination thereof, or any 5 other low friction layers.
In an embodiment according to FIGURE 1, the second set 104 comprises multiple parts that can move and/or deform independently of each other when the force applied to the helmet exceeds a certain limit. The limit normally is around 10g and 0.5krad/sA2, depending on the density and structure of the material used for the second set 104.
10 In an embodiment according to FIGURE 1, the attachment means such as the attachment means 106 to 111 allow the second set 104 and the fitting liner 105 to have finite movements relative to the first set 102 when the applied force to the helmet exceeds a certain limit. That is, the second set 104 is free to move a small distance before it is bounded by the attachment means 106 to 111.

15 In an embodiment according to FIGURE 1, the finite movements of the parts of the second set 104 relative to the first set 102 during an impact enhance the helmet 101 performance by reducing linear and rotational forces applied to the head 100.
In an embodiment according to FIGURE 1, the finite movements of the second set 104 relative to the first set 102 during an impact can be translational, rotational or both.
In an embodiment according to FIGURE 1, the anchor 108, insert 107, snap pin 111, snap pin basket 110, button 112, button 114, and the connector 121 are partly or entirely made of rigid or flexible materials such as plastic, polymer, fiber, fabric, rubber, elastic, silicone rubber, metal, or a combination thereof.
In an embodiment according to FIGURE 1, the anchor 108 can be any other attachment means described herein.
In an embodiment according to FIGURE 1, the presence of the hollow compartment 119, the open cavity 120, indentation 125, opening 126, recess 127, and recess 128 results in a better shock-absorption of the first set 102, and the second set 104 during an impact.
In an embodiment according to FIGURE 1, the hollow compartment 119, and the open cavity 120 comprise or are filled with another type of shock-absorbing materials to create multi-stage shock-absorption for the second set 104.
In an embodiment according to FIGURE 1, the hollow compartment 119, the open cavity 120, indentation 125, opening 126, recess 127, and recess 128 can have any shape, size, direction, or form based on the design requirements.

16 In an embodiment according to FIGURE 1, the second set 104 includes open cavity 120, hollow compartment 119, or any other macro-cavities, closed cavities, fluid-filled compartments, thin-walled structure or a combination thereof to improve the energy absorption of the second set 104 during an impact to the helmet 101.
In an embodiment according to FIGURE 1, the first set 102 and the second set 104 comprise EPS, EPA, plastic, polymers, rubber, silicone rubber, elastomer, resin, metal, fiber, fabric, PC, carbon fiber, ABS, foam, Kevlar, or a combination thereof, or any other materials known in the industry for making a helmet.
In an embodiment according to FIGURE 1, the first set 102 and second set 104 comprise structures such as a thin-walled structure, honeycomb structure, auxetic structure, fluid-filled compartment, collapsible structure, macro-cavity structure, micro-cavity structure, closed-cavity structure, open-cavity structure, or a combination thereof. Since the two sets are made in separate processes, different densities, structures, or materials can be used for the first set 102, and the second set 104.
In an embodiment according to FIGURE 1, the first set 102. or the second set 104, or both are made by additive manufacturing In FIGURE 1 a limited number of configurations and attachment means for attaching, the first set 102, the second set 104, and the fitting liner 105 are shown. However, other configurations and attachment means can be used in the design as well without departing from the spirit and scope of the invention. All the shown configurations and attachment means in FIGURE 1 are not necessarily needed to be in one design. A design can use one type or more of the configurations, features, or attachment means shown in FIGURE 1.
In an embodiment according to FIGURE 1, the deformation of the first set 102 and the second set 104 and the relative movement of the fitting liner 105 and the second set 104 with respect to the first set 102 enhance the helmet 101 performance and reduce the linear and rotational forces applied to the head 100 during an impact.
In an embodiment according to FIGURE 1, the fitting liner 105 covers multiple parts of the second set 104.
In an embodiment according to FIGURE 1, the anchor 108 attaches the first set 102 to the second set 104, and the fitting liner 105 by means of the connector 121 and the button 114 through the opening 126 in the second set 104 and a buttonhole in the fitting liner 105 (not shown in FIGURE 1). The connector 121 can be elastic to elongate when the applied force exceeds a certain limit or it can be rigid and have minimal elongation under the force. The

17 anchor 108 can be in form of a snap pin and snap pin basket, and the connector 121 can include a hole to attach to the first set 102 by means of the snap pin and snap pin basket.
According to the previous embodiment of FIGURE 1, during an impact, parts of the second set 104 can each move separately relative to the first set 102 based on the location, direction, and intensity of the impact. The movement of the parts of the second set 104 relative to the first set 102 improves the helmet performance in reducing both linear and rotational forces.
In an embodiment according to FIGURE 1, the button 114 is a continuation of the connector 121.
In an embodiment according to FIGURE 1, using the second set 104 in conjunction with the first set 102 allows for designing helmets with reduced overall raw material used for the shock-absorbing liner of the helmet 101 and reduces the weight of the helmet 101.
In an embodiment according to FIGURE 1, each part of the second set 104 consists of subparts that are attached to each other by a rigid or flexible attachment means.
Using the second set 104 reduces some of the limitations in designing such as convergence. In moulding, to be able to release a rigid moulded object there should be a draft angle meaning the facing walls should diverge in the direction that a mould opens Otherwise, if the facing walls converge the mould cannot release the moulded object (e.g. helmet). In an embodiment according to FIGURE 1, it is possible to allow wall 122 and wall 123 to converge, as the parts of the second set 104 are made separately and then assembled. Having no convergence limitation opens up many different possibilities for designing high-performing shock-absorbing liners for helmets.
In an embodiment according to FIGURE 1, certain shapes are defined for the second set 104 to match the curvature of the inward surface of the first set 102 that is facing the wearer's head 100.
In an embodiment according to FIGURE 1, the surface of the first set 102 that faces the second set 104 is designed to facilitate the movement of the parts of the second set 104 relative to the first set 102.
In an embodiment according to FIGURE 1, the surface of the second set 104 that faces the first set 102 is designed to facilitate the movement of the parts of the second set 104 relative to the first set 102.
In an embodiment, one or more shapes and sizes are used repeatedly for all the required parts for the second set 104 of the helmet 101. By using one or more similar parts for all the required parts for the second set 104, it is possible to reduce the cost of manufacturing.

18 In an embodiment according to FIGURE 1, universal shapes are designed for all the parts of the second set 104. The universal shapes can be used for some or all the required parts of the second set 104 of an array of different helmets. For helmets with various shapes and curvatures, the design of the inward surface of the first set 102 that faces the wearer's head 100 can be modified accordingly to allow one or more universal shapes to be used for the parts of the second set 104 and the corresponding fitting liner 105 of different helmet models. This is a cost-effective method for adopting this invention for various existing or new helmet models and types. By changing the moulding tool of the helmet and creating the needed surface for the inward surface of the first set 102 of the helmet 101, it is possible to use the universal shapes for some or all the parts of the second set 104. The embodiment can be arranged to be used for different helmets of the same or different sizes. For instance, if the universal shapes for the parts of the second set 104 are defined for the size medium bicycle helmet.
Then, by modifying the inward surface of the first set 102 of other helmet designs, it is possible to use the same universal shapes for the parts of the second set 104 for different bicycle helmet designs that have a size medium.
In an embodiment according to FIGURE 1, the first set 102 includes the protrusion 124 and the second set 104 includes the indentation 125 (open-cavity) that is used for fitting or press-fitting the second set 104 with or without the attachment means to the first set 102.
The fitting can also be done by an indentation in the first set 102 instead of protrusion 124 and protrusion in the second set 104 (not shown in FIGURE 1).
In an embodiment according to FIGURE 1, the outward surface of the first set 102 that is facing away from the wearer's head 100 is considered as the outer shell 103.
In an embodiment according to FIGURE 1, the second set 104 can include sensors, electronics, batteries, communication devices, and wiring. For example, an impact-sensing device can be included in the second set 104 to detect, record, or send a signal about a crash incident.
In an embodiment according to FIGURE 1, the second set 104 is detachable and can be replaced when needed and allowed by the standard body.
In one embodiment according to FIGURE 1, the connector 121 is elastic and elongates and results in temporary or permanent dislocation of the second set 104 when the applied force to it exceeds a certain limit. For instance, silicone rubber can be used for the connector 121.
In one embodiment according to FIGURE 1, the surface of the second set 104 that faces the first set 102 has the recess 127 to not obstruct the finite movement of the second set 104 relative to the first set 102 when the connector 121 is present. The recess 127 can be in any size, shape, or direction. For example, the open cavity 120 can be where the opening 126 of the

19 connector 121 faces the first set 102 to facilitate the movement and dislocation of the second set 104 when the applied force to the helmet exceeds a certain limit.
In one embodiment, the opening 126 is an all-the-way-through hole or groove in the second set 104 that allows the first set 102, the second set 104, and the fitting liner 105 to attach to each other by means of anchor 108, the connector 121, buttonhole in the fitting liner 105 (not shown in FIGURE 1), and the button 114.
In one embodiment, the opening 126 is an all-the-way-through hole or groove in the layer 118, the second set 104, and the layer 117 to allow the first set 102, the second set 104, and the fitting liner 105 to attach to each other by means of anchor 108, the connector 121, buttonhole in the fitting liner 105 (not shown in FIGURE 1), and the button 114.
In one embodiment according to FIGURE 1, the surface of the second set 104 where it faces away from the wearer's head 100 comprises the recess 127 where it faces the anchor 108. The recess 127 does not allow the attachment means such as anchor 108 or the connector 121 to obstruct the finite movement of the second set 104 relative to the first set 102 when the applied force to the helmet 101 exceeds a certain limit.
In one embodiment according to FIGURE 1, the surface area of the second set 104 facing away from the wearer's head 100 is smaller than the surface area of the first set 102 that is facing the wearer's head. This is a geometric constraint to ensure that the second set 104 does not cover the entire surface of the first set 102 that is facing the wearer's head 100.In one embodiment according to FIGURE 1, the surface of the first set 102 where the anchor 108 is placed and where it faces the connector 121 comprises the recess 128. Having the recess 128 reduces the chance of the attachment means such as anchor 108 or the connector 121 to obstruct the finite movement of the second set 104 relative to the first set 102 when the applied force to the helmet 101 exceeds a certain limit.
In one embodiment according to FIGURE 1, the recess 127 and the recess 128 are facing each other. Such an embodiment further helps the finite movement of the second set 104 relative to the first set 102 in the presence of the connector 121.
In an embodiment according to FIGURE 1, the number and type of the attachment means 106-111 define whether or not the second set 104 can move relative to the first set 102 during an impact.
In an embodiment according to FIGURE 1, the number and type of the attachment means 106-111 define the type of movement (translational, rotational, or both) of the second set 104 relative to the first set 102 during an impact.

In an embodiment. the first set 102, the second set 104, and the fitting liner 105 are attached by the connector 121 and the button 114. The connector 121 can elastically or plastically elongate when the applied force to the helmet exceeds a certain limit. The elongation of the connector 121 allows the second set 104 to move relative to the first set 102. The movement of the second 5 set 104 relative to the first set 102 and compression of the first set 102 and the second set 104 reduce the rotational and linear forces applied to the head 100 during impact.
In an embodiment, the fitting liner 105 movement relative to the second set 104 reduces the rotational forces applied to the head 100 during impact.
FIGURES 2-A, 2-B, and 2-C disclose multiple embodiments of the invention and show a helmet 10 in various views. FIGURE 2-A shows the side view of the helmet 201 comprising the vent 206, outer shell 210, and the chin strap hole 209.
FIGURE 2-B shows the bottom view of the helmet shown in FIGURE 2-A. According to FIGURE
2-B, the helmet 201 comprises the outer shell 210, the first set 202, the second set 203, the fitting liner 204, and the attachment means 205. In an embodiment, the second set 203 can 15 have an extension 208. The second set extension 208 can further enhance the protection of the helmet by protecting the wearer's head from impacting certain surfaces such as sharp and wedge-shaped surfaces.
In an embodiment according to FIGURES 2-A to 2-C, the second set extension 208 surfaces facing the wearer's head can be lower than the rest of the second set 203 and have no contact

20 with the fitting liner 204 or wearer's head during normal use and the absence of an impact. The attachment means 205 passes through an opening in the fitting liner 205 and an opening in the second set 203 and attaches to the first set 202.
In an embodiment according to FIGURES 2-A to 2-C, the attachment means 205 eliminates the need of using other types of fasteners such as the hook-and-loop fastener to attach the fitting liner to the second set 203.
In an embodiment according to FIGURES 2-A to 2-C, one end of the attachment means 205 is like a button, and there is a buttonhole in the fitting liner 204 to hold the fitting liner 204 in place.
The other end of the attachment means 205 comprises multiple holes and by using a snap-pin and an embedded snap-pin basket in the first set 202, the attachment means 205 attaches the fitting liner 204 and the second set 203 to the first set 202. The thickness of the second set 203 may vary in various locations, therefore, the multiple holes in the other end of the attachment means 205 allows the attachment means 205 to use the suitable hole for the snap-pin and the snap-pin basket to provide the required tightness for the attachment means 205 during assembling the helmet 201.

21 In an embodiment according to FIGURES 2-A to 2-C, the attachment means 205 is made of rubber, metal spring, plastic spring, fabric, elastics, silicone rubber, or a combination thereof or any other materials that stretch under the force and return to their original length after being stretched.
FIGURE 2-C shows the cross-section of the helmet shown in FIGURE 2-A, and 2-B.
According to FIGURE 2-C, the helmet 201 comprises the first set 202, the second set 203, the fitting liner 204, the attachment means 205, and the outer shell 206. In an embodiment according to FIGURE 2-C, the portion 207 of the attachment means 205 is embedded in the first set 202. An example of the portion 207 can be found in a design that includes a snap pin and an embedded snap pin basket as the portion 207 in the first set 202 to attach the fitting liner 204, and the second set 203 to the first set 202.
In one embodiment according to FIGURES 2-A to 2-C, the attachment means 205 is made of an elastic such as silicone rubber and is slightly stretched (preloaded) during assembling the helmet parts which allows the fitting liner 204 and the second set 203 to attach to the first set 202. When the helmet is impacted the attachment means 205 elongates further to allow the second set 203 and the fitting liner 204 to move relative to the first set 202 The movement of the second set 203 and the fitting liner 204 reduces the rotational and linear forces applied to the head during impact.
In an embodiment according to FIGURES 2-A to 2-C, the first set 202, the second set 203, and the fitting liner 204 are attached by the attachment means 205 that can elastically or plastically elongate when the applied force to the helmet exceeds a certain limit. The elongation of the attachment means 205 allows the second set 203 to move relative to the first set 202. The movement of the second set 203 relative to the first set 202 and compression of the first set 202 and the second set 203 reduce the rotational and linear forces applied to the head during impact. In an embodiment, the fitting liner 204 movement relative to the second set 203 reduces the rotational forces applied to the head during impact as well.
In an embodiment according to FIGURES 2-A to 2-C, the surface area of the second set 203 facing away from the wearer's head is smaller than the surface area of the first set 202 that is facing the wearer's head. This is a geometric constraint to ensure that the second set 203 does not cover the entire surface of the first set 202 that is facing the wearer's head.
FIGURES 3A to 3C show an exploded view of a helmet according to a number of embodiments comprising the outer shell 301, the first set 302, the second set 303, the fitting liner 304, and attachment means 305. FIGURE 3-A shows the first set 302 and in an embodiment, it comprises the outer shell 301 and air vents 306. FIGURE 3-B shows the second set 303 and

22 the fitting liner 304. In an embodiment according to FIGURE 3-B, the second set 303 comprises open cavities 308, the open cavities 308 can enhance shock absorption of the helmet and also reduce the weight of the second set 303. The open cavity 308 can be in any shape, size, and form. In an embodiment according to FIGURE 3-B, the second set 303 has the extension 3011 to better protect the head for areas between two or more second sets 303. The extension 311 can have a lower thickness than the adjacent parts of the second set 303. The extension can be covered or not covered by the fitting liner 304.
In an embodiment according to FIGURES 3-A and 3-B, the second set 303 is covered by the layer 309 where it comes into contact with the first set 302. The layer 309 can reinforce and strengthen the structure of the second set 303 and also control and reduce the friction between the second set 303 and the first set 302. For example for helmets made of EPS, the layer 309 can be made of a thin layer of polycarbonate.
In an embodiment according to FIGURE 3-B, the layer 309 covers the surface area of the second set 303 where it comes into contact with the fitting liner 304.
In an embodiment according to FIGURE 3-B, the existence of the layer 309 further enhances the helmet performance in terms of reducing linear and rotational forces In one embodiment according to FIGURES 3-A to 3-C, there is a through-hole 310 which allows the attachment means 305 to pass through the second set 303 and attach the fitting liner 304 and the second set 303 to the first set 302. In one embodiment according to FIGURE 3-B, there is a recess 307 adjacent to the hole 310. The recess 307 reduces the chance of the attachment means 305 to be snagged by the second set 303 during its movement due to impact and hence it facilitates the movement of the second set 303 and the fitting liner relative to the first set 302.
In an embodiment according to FIGURE 3-A to 3-C, sensors, electronics, batteries, impact alert system, and positioning system can be placed in the open cavities 308.
In an embodiment according to FIGURE 3-C, the attachment means 305 are used to attach the fitting liner 304 and the second set 303 to the first set 302. In an embodiment according to FIGURE 3-C, the attachment means 305 at one end has a button-shaped, and at the other end has multiple holes which makes it adjustable, and therefore, suitable for various thicknesses of the second set 303.
In an embodiment according to FIGURE 3-C, one end of the attachment means 305 is button-shaped and by having a button-hole on the fitting liner 304, the attachment means 305 attaches the fitting liner 304 and the second set 303 to the first set 302.

23 In one embodiment according to FIGURE 3-A to 3-C, the attachment means also includes snap-pins and snap-pin baskets to attach the other end of the attachment means 305 to the first set 302. The snap-pin basket can be embedded in the first set 302 during its moulding.
FIGURES 4-A to 4-C show the cross-section view of FIGURES 3-A to 3-C, respectively.
FIGURE 4-A shows the cross-section of the first set 402. In an embodiment according to FIGURE 4-A, the first set 402 comprises the outer shell 401 and air vents 406.
In one embodiment, parts 412 or 413 of the attachment means 405 are embedded in the first set 402.
The depth that parts 412 and 413 can vary depending on the thickness of the first set 402 where the parts 412 and 413 are embedded in the first set 402 and the thickness of the second set 403 where the hole 411 (hole 411 also represents the buttonhole in the fitting liner) is facing the parts 412 and 413. For example, the parts 412 and 413 can be snap-pin and snap-pin baskets to attach one end of the attachment means 405 to the first set 402. FIGURE 4-B
shows the cross-section of the second set 403. In an embodiment according to Figure 4-B, the second set 403 comprises the layer 408, the recess 407, and extension 411.
In an embodiment according to Figure 4-B, the fitting liner 404 comprises a recess 414 and also the buttonhole 411 The button-hole 411 is used for attaching the fitting liner 404, and the second set 403 to the first set 402 by the attachment means 405 to the parts 412 and 413 of the first set 402.
FIGURE 4-C shows the cross-section of FIGURE 3-C. The attachment means 405 and parts 412 and 413 are used to attach the fitting liner 404 and second set 403 to the first set 402.
In an embodiment, the surface area of the second set 403 facing away from the wearer's head is smaller than the surface area of the first set 402 that is facing the wearer's head. This is a geometric constraint to ensure that the second set 403 does not cover the entire surface of the first set 402.
FIGURES 2-A to 2-C, FIGURES 3-A to 3-C and FIGURES 4-A to 40 show only examples of using features, aspects and embodiments explained in the rest of this invention. All the embodiments, features, and aspects explained for FIGURE 1 regarding the first set, the second set, the fitting liner, and the attachment means, where applicable, can be considered for the examples provided in FIGURES 2-A to 2-C, FIGURES 3-A to 3-C and FIGURES 4-A to 40.
While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made. The detailed description set out above in connection with the included sketches, where like numerals reference like elements, is intended as a description of various embodiments of the claimed subject matter and is not intended to represent the only embodiments. Any reference to a direction is specific only to the diagram, to further clarify the

24 explanation, not to limit the actual use of the invention in that direction.
The intention for the illustrated examples is not to be exhaustive or to limit the invention to the precise forms shown.

Claims (17)

PCT/1B2022/059258

1. A protective helmet comprising:
an outer shell having an inward surface;
a first set of shock-absorbing liners attached to the inward surface of the outer shell;
a second set of shock-absorbing liners having multiple parts that can move and deform independently of each other when an impact force is applied to the outer shell of the protective helmet; and a fitting liner covering one or more of the parts of the second set of shock-absorbing liners, attachrnent means connecting an inward surface of the first set of shock-absorbing liners to the second set of shock-absorbing liners; and wherein a contact area between the first set of shock-absorbing liners and the second set of shock-absorbing liners is smaller than an inner surface area of the first set of shock-absorbing liner.

2. The protective helmet of Claim 1, wherein each of the one or more parts of the second set of shock-absorbing liners are separately attached to the first set of shock-absorbing liners using at least one of the attachment means.

3. The protective helmet of Claim 1, wherein the attachment means provide a finite amount of play in the connection between of the second set of shock-absorbing liners relative to the first set of shock-absorbing liners.

4. The protective helmet of Claim 1, wherein the attachment means further attaches to the fitting liner.

5. The protective helmet of Claim 1, wherein the attachment means is flexible and elongates elastically under the impact force, or plastically when the impact force exceeds a threshold.

6. The protective helmet of anyone of Claims 1-5, wherein the attachment means are made of any mechanical or chemical attachment means selected from the list comprising:
hook-and-loop fastener, pin, snap pin, snap pin basket, snap fastener, latch-and-hook fastener, clips, hinge, press-fitting, hook plastic insert and loop rubber, rubber holder, mesh holder, silicone rubber holder, tie, connector, spring, buckle, heat-seal, sewing, fusion, elastic, fitting, adhesive, insert, screw, railing, button, buttonhole, rivet, or a cornbination thereof.

7_ The protective helmet of Claim 1, wherein the attachment rneans are frangible in order to rupture when the impact force exceeds a second threshold to allow unrestricted movement between the first set and the second set of shock-absorbing liners.

8. The protective helmet of Claim 1, wherein the first set of shock-absorbing liners cornprises a low friction layer.

9. The protective helmet of Claim 1, wherein the second set of shock-absorbing liners cornprises a low friction layer.

10. The protective helmet of Claims 8 or 9, wherein either of the low friction layers cornprises a lubricant, plastic, rail, sliding groove, wax, powder, polymer, elastomer, rubber, polycarbonate (PC), acrylonitrile butadiene styrene (ABS), carbon fiber, silicone rubber, silicone lubricant, fluid-filled compartment, fabric, fiber, or a combination thereof.

11. The protective helmet of Claim 1, wherein the attachment means elongates, ruptures or dislocates during the impact force to allow the second set of shock-absorbing liners to move relative to the first set.

12. The protective helmet of Claim 1, wherein the second set of shock-absorbing liners are cornprised of rnaterials with a similar or different density than the first set of shock-absorbing liners.

13. The protective helmet of Claim 1, wherein the second set of shock-absorbing liners are made of different materials than the first set of shock-absorbing liners.

14. The protective helmet of Claim 1, wherein the two sets of shock-absorbing liners cornprise micro-porosity, macro-porosity, thin-walled structure, fluid-filled compartment, truss structure, lattice structure, auxetic structure, channeled structure, open cavity, closed cavity, hole, or a combination thereof.

15. The protective helmet of Claim 1, wherein the first sets of shock-absorbing liners, or the second set of shock-absorbing liners, or both comprise at least some of the attachment means.

16. The protective helmet of Claim 1, wherein one or more shapes and sizes are defined to be used repeatedly for all of the multiple parts of the second set of shock-absorbing liners.

17. A method of manufacturing a protective helmet, the rnethod comprising:
separately making a) a first set of shock-absorbing liners and b) a second set of shock-absorbing liners, the second set of shock-absorbing liners having multiple parts;
attaching the first set of shock-absorbing liners to each of the multiple parts of the second set of shock-absorbing liners using attachment means;
fixing an outer shell at its inward surface to the first set of shock-absorbing liners;
and covering a fitting liner around one or more of the multiple parts of the second set of shock-absorbing liners.