GB2604630A - Cradle type safety helmet having a liner to facilitate rotation responsive to oblique impact - Google Patents

Abstract

A safety helmet 1 includes an outer shell 10 suspended by a cradle 20 having a headband 20’, 20’’. A liner 40 is arranged in-between the user’s head and a front portion 20’ of the headband, which is made from a first material and extends around front and side regions of the user’s head. A stiffening strip (50, Fig. 10), made from a second material having a higher stiffness than the first material of the headband, is arranged to extend along the first portion 20’ of the headband and connected to the first portion 20’ of the headband so as to be slidable in rotation together with the first portion 20’ of the headband about the liner 40. The stiffening strip helps to rotationally decouple the shell 10 from the user’s head, particularly for lateral impacts causing rotation in yaw about a vertical axis (Z, Fig. 1). The stiffening strip may be connected to the headband by studs or rivets and may be made from polypropylene. The suspension straps and the first part of the headband may be formed as a unitary plastics body and may be formed of LPDE. The liner may be made of polyketone.

Description

Cradle type safety helmet having a liner to facilitate rotation responsive to oblique impact This invention relates to helmets of the type having a shell and a cradle comprising a headband and a plurality of straps that suspend the shell from the user's head, referred to herein as cradle type safety helmets. Cradle type safety helmets are commonly used in industrial environments, for example on building sites.

Cradle type safety helmets are usually designed so that the straps of the cradle will deform, allowing the shell to move relative to the user's head, when an impact force is applied to the shell. This protects the user's head by absorbing some of the energy of the impact.

The suspension straps and the portion of the headband that extends around the front and sides of the user's head may be formed (e.g. by moulding) as separate parts or as a unitary body, preferably in a relatively pliable plastics material such as LDPE (low density polyethylene). The unitary body may be formed in a flat, rest state, in which all of its parts lie in a common, flat plane, so that it can be stacked with others before assembly. The pliable material allows the straps and headband to bend out of their plane when the cradle is installed in the shell, and allows the straps to stretch to absorb impact energy.

Cradle type safety helmets provide good protection against impact forces that are directed radially inwardly against the shell, particularly vertically downwardly from above, but are relatively less effective in mitigating impacts in an oblique direction, which is to say, in a direction that is not radially inward.

EP2896308A1 to Mips AB discloses a helmet of the type having a rigid outer shell and an energy absorbing layer, such as a foamed polymer layer, moulded inside the shell. An attachment device, similar in form to a cradle, is provided for attaching the helmet to the user's head. A sliding facilitator, e.g. a low friction material, is arranged to facilitate sliding of the energy absorbing layer relative to the attachment device, so as to reduce angular acceleration forces applied to the user's head in the event of an oblique impact against the shell.

"MIPS" (RTM) or "Multi-directional Impact Protection System" helmet liners that work on a similar principle to rotationally decouple the helmet from the head are commercially available from Mips AB of Taby, Sweden (www.mipsprotection.com).

It is a general objective of the present invention to provide a cradle type safety helmet that provides improved protection against oblique impact.

Accordingly the invention provides a helmet as defined in the claims.

The novel helmet includes a cradle, and an outer shell connected to the cradle.

The cradle includes a headband configured to encircle a user's head in a use position of the helmet, and a plurality of suspension straps configured to extend over the user's head to suspend the outer shell in the use position. A first portion of the headband is made from a first material and configured to extend in the use position around front and side regions of the user's head.

The helmet further includes a liner, and a stiffening strip.

The liner is arranged to extend in the use position between the first portion of the headband and the front and side regions of the user's head. The headband is slidable in rotation about the liner to facilitate rotation of the outer shell about the user's head responsive to oblique impact against the outer shell.

The stiffening strip is made from a second material having a higher stiffness than the first material. The stiffening strip is arranged to extend along the first portion of the headband, and is connected to the first portion of the headband so as to be slidable in rotation together with the first portion of the headband about the liner.

In tests, it is found that a helmet including the above mentioned components but without the stiffening strip, referred to herein as the reference helmet, provides improved protection from oblique impacts causing rotation about the liner in Pitch and Roll, when compared with a conventional helmet including the same components but without the stiffening strip and without the liner. Surprisingly however it is found that the reference helmet provides inferior protection, compared with the conventional helmet, against oblique impacts causing rotation in Yaw.

By adding the stiffening strip, improved protection is obtained against oblique impacts causing rotation about all three axes.

Further features and advantages will be evident from the following illustrative embodiment of the invention which will now be described, purely by way of example and without limitation to the scope of the claims, and with reference to the accompanying drawings, in which: Fig. 1 is a side view of a first helmet in accordance with an embodiment of the invention, in a use position on a user's head, and illustrating the rotational displacement referred to herein as Pitch.

Figs. 2 and 3 are respectively, front and top views of the first helmet, illustrating the rotational displacements referred to herein as Roll and Yaw.

Figs. 4 and 5 show the outer shell of the first helmet.

Figs. 6A and 6B show parts of the cradle of the first helmet.

Fig. 6C shows an alternative cradle in a flat, rest state.

Figs. 7 and 8 show the liner of the first helmet.

Fig. 9 shows a cradle type safety helmet, referred to herein as the reference helmet, including the same components as the first helmet with the exception of the stiffening strip.

Fig. 10 and 11 show the stiffening strip of the first helmet, seen respectively from the radially outwardly facing side (Fig. 10) and the radially inwardly facing side (Fig. 11).

Fig. 12 is an inside view of the first helmet.

It should be noted that in the assembled views of Fig. 9 and Fig. 12 the cradle is shown in simplified form for ease of illustration.

Reference numerals and characters appearing in more than one of the figures indicate the same or corresponding features in each of them.

Referring to Figs. 1 -3, the rotational displacements of the first helmet land the reference helmet 1', referred to herein as Pitch, Roll and Yaw, are illustrated by reference to the mutually orthogonal and mutually intersecting X, Y and Z axes about which they occur. The Z axis passes vertically centrally through the helmet in its use position. The X and Y axes pass horizontally centrally through the helmet. The Y axis lies in a vertical plane that bisects the helmet from front to back, while the X axis lies in a vertical plane that bisects the helmet from side to side. The Yaw displacement is defined by rotation about the Z axis, as if the user were looking to the left or right. The Roll displacement is defined by rotation about the Y axis, as if the user were tilting the head towards the left or right shoulder. The Pitch displacement is defined by rotation about the X axis, as if the user were looking up or down.

Referring also to Fig. 9 and Fig. 12, both the first helmet (Fig. 12) and the reference helmet (Fig. 9) include a cradle 20 and an outer shell 10 connected to the cradle 20, these parts being generally conventional.

As shown in Figs. 1 -3, the outer shell 10 has a crown region 14, which lies over the crown of the user's head in the use position as shown, and front, back and side regions. The front region 11 of the shell is located proximate (in front of) a front region of the user's head, while the back region 12 is located proximate (behind) a back region of the user's head. The side regions 13 are located proximate (laterally outwardly of) side regions of the user's head.

Referring to Figs. 4 and 5, the shell 10 may be relatively rigid compared with the cradle, and may include interior connection structures 15 proximate its rim. The shell 10 may be moulded from plastics material which may have relatively higher stiffness than the material forming the first portion 20' of the headband, further discussed below, but may still have limited flexibility to absorb some of the energy of an impact.

Referring again to Figs. 9 and 12, the cradle 20 includes a headband 20', 20" which is configured to encircle the user's head in the use position of the helmet (Fig.1), and a plurality of suspension straps 25 which may be connected to the headband and are configured to extend over the user's head to suspend the outer shell 10 in the use position. A first portion 20' of the headband is made from a first material and is configured to extend in the use position around the front and side regions of the user's head. A second portion 20" of the headband extends behind the user's head, and may include an adjustment means which allows the user to adjust the length of the headband for a snug fit. The second portion of the headband may be made from the same material as the first portion or from a stiffer material.

The first portion of the headband and the suspension straps may be formed as an integral body, or may be connected together as an assembly, either by fasteners that connect them together directly, or indirectly by other parts.

Figs. 6A and 6B show a more detailed view of parts of the cradle 20 as also illustrated in Figs. 9 and 12. A cradle of this type as illustrated and made from LDPE (low density polyethylene) was used in each of the Conventional Helmet, the Reference Helmet, and the First Helmet during the tests referred to below.

Fig. 6C shows by way of example an alternative cradle 20 as disclosed in W02018/215083A1 (W0'083) to the present applicant. This and other known cradles (for example, the alternative types also disclosed in WO'083) could be used in place of the cradle of Figs. 6A and 6B.

Referring first to Figs. 6A and 6B, in the cradle 20 of the first helmet 1 as shown in these figures and used in the tests referred to below, the first portion 20' of the headband is made as one unitary plastics piece (e.g. a moulding), shown in Fig. 6A, and the suspension straps 25 as another unitary plastics piece (e.g. another moulding) shown in Fig. 6B. The two pieces are connected together directly by connecting each fastener 34 on the strap part to its corresponding fastener 34' on the headband part, and each fastener 35 on the strap part to its corresponding fastener 35' on the headband part.

Each suspension strap 25 may be provided with a connector 29 which is connected with a corresponding one of the connection structures 15 in the outer shell 10, as shown in Figs. 9 and 12, to suspend the shell 10 from the cradle 20, with the headband 20', 20" serving to retain the assembly on the user's head.

Small holes 38 may be formed in the first portion 20' of the headband to accommodate studs or rivets 52 of the stiffening strip, further discussed below.

The second portion 20" of the headband (not shown in Figs. 6A and 6B but visible in Figs. 9 and 12) is formed as a separate part and connected to the first portion 20', e.g. via fasteners 36 of the second portion 20" which engage in apertures 36' of the first portion 20'. A length adjustment means, represented in simplified form by a knob 37, may be provided to adjust the circumferential length of the headband 20. For this purpose the knob 37 may cooperate with other parts (not shown) or may join together two parts of the rear portion 20", which for ease of illustration is shown as a single part in Figs. 9 and 12.

Referring now to the alternative cradle of Fig. 6C, in alternative arrangements as shown, the first portion 20' of the headband may include a front part 21 and side parts 22, which may be connected together by fasteners or, as illustrated, may be connected integrally together and to the suspension straps 25, e.g. via integral connecting parts 30, 31 as shown.

The second portion 20" may include two rear parts 23 and 24 which when coupled together form an adjustment means for adjusting the circumferential length of the headband 20', 20".

In yet further alternative arrangements, the second (rear) portion of the headband could be formed integrally with the first portion.

As shown in the example of Fig.6C, the suspension straps 25 and the first portion 20' (front part 21 and side parts 22) of the headband may be formed (e.g. by moulding) as a unitary plastics body, preferably from a pliable material, for example LDPE, which allows the straps 25 to stretch so as to absorb some of the energy of an impact against the shell 10.

The unitary plastics body 25, 21, 22 may be formed in a flat, rest state as shown in Fig. 6C, in which the suspension straps 25 and the first portion 20' (21, 22) of the headband lie in a common, flat plane (the plane of the drawing) when the cradle 20 is disconnected from the shell 10, so that it can be conveniently stacked. The unitary plastics body is sufficiently pliable to be deformable from this flat rest state to the use state, as shown in Figs. 9 and 12, in which the suspension straps 25 and the first portion 20' (21, 22) of the headband extend out of the flat plane, when the cradle 20 is connected to the shell 10 during assembly. This is achieved by connecting together each pair of adjacent male and female male connectors 26, 26' and 27, 27', and connecting the second portion 20" to the first portion 20' by connecting together the pairs of connectors 28, 28' which as shown may also provide further length adjustment.

Each suspension strap 25 may be provided with a connector 29 which is connected with a corresponding one of the connection structures 15 in the outer shell 10 as described above with reference to the cradle of Figs. 6A and 6B.

A chinstrap, ear defenders or other accessories (not shown) may be coupled to other ones of the connection structures 15 or to the cradle. The suspension straps 25 may include additional features, as illustrated in the example of Fig. 6C, such as apertures 33 facilitating local deformation and comfort pads 32 which may be co-moulded from an elastomer as discussed in WO'083.

Both the first helmet land the Reference Helmet 1' differ from a conventional cradle type safety helmet in that a liner 40, which may be a known type of low friction liner such as a "MIPS" (RTM) liner, is installed inside the shell 10. The liner 40 is arranged to extend in the use position between the first portion 20' of the headband and the front and side regions of the user's head. The headband 20', 20" is slidable in rotation about the liner 40 to facilitate rotation of the outer shell 10 about the user's head responsive to oblique impact against the outer shell 10.

The liner 40 used in the first helmet 1 and the reference helmet 1' is shown in Figs. 9 and 12 and best seen in Figs. 7 and 8. As shown, the liner 40 may be formed with a central portion 41 that covers the crown of the user's head, a front portion 42 that extends from the central portion 41 to cover the front (forehead) region of the user's head, and two elongate lateral portions 43 extending from the front portion 42 around the sides of the user's head. Optionally, the lateral portions may be divided from the central portion 41 as shown, providing more flexibility to adapt to different head or helmet shapes and sizes.

The liner 40 may be made, e.g. moulded, from plastics material, which may be selected to have a relatively low coefficient of friction, and may be formed as a relatively thin sheet or layer, e.g. having a radial thickness of about 1.2mm, that wraps around the user's head as shown. The plastics material may be, for example, nylon or polypropylene. The plastics material may include polyketone. The plastics material may include a major proportion (i.e. more than SO wt.%) of polyketone.

The liner 40 may be arranged to extend in the use position between the suspension straps 25 and the user's head; in such arrangements, small regions of the straps 25 may extend between the liner and the user's head to retain the liner 40 in position.

The liner 40 may be attached to the cradle 20, for example by forming apertures 44 in the liner and passing selected ones of the suspension straps 25 (e.g. a pair of suspension straps 25 at the rear of the helmet 1) through the apertures, as shown, or alternatively for example by means of elastic connectors (not shown) that connect the liner 40 to the suspension straps 25. The apertures 44 may be enlarged, e.g. elongated, or the connectors may be sufficiently elastic, to accommodate movement between the cradle 20 and the liner 40.

Each aperture 44 may be elongated in a transverse (width) direction of the strap 25 that passes through it, allowing the straps 25 to move within the apertures 44 relative to the liner 40 responsive to rotation of the helmet 1 about all three axes X, Y, Z. Thus, the suspension straps 25 at the rear of the helmet 1 may slide along their length direction through the apertures 44 when the helmet moves in pitch, and move laterally to their length direction along the apertures 44 when the helmet moves in yaw, and move in both of these vectors when the helmet moves in roll.

For ventilation and comfort, the liner 40 may be perforated as shown, and/or soft pads (not shown), e.g. foam pads, may be arranged inside the liner 40 to separate the liner from the user's head.

The helmet may include various other conventional features, e.g. a soft pad at the rear of the helmet (not shown), and/or a soft (e.g. textile) forehead pad (not shown) that extends in the use position between the liner 40 and the front and side regions of the user's head.

The liner 40 may include connection features (each of which may be for example a tab 45, extending in the local plane of the liner, that can be used as a hook) to which the forehead pad (not shown) can be attached along its upper edge, e.g. with a cord, e.g. an elastic cord, that passes over the hook. The lower edge of the forehead pad may be attached to hooks or other connection features formed on the radially outwardly facing surface of the first portion 20' of the headband or the radially outwardly facing surface of the stiffening strip SO, further discussed below (so facing the inside of the shell 10), e.g. by a cord, e.g. an elastic cord. In this way, the forehead pad may secure and retain the front and lateral portions 42,43 of the liner 40 in their use position inside the headband 20', 20" and stiffening strip 50. The elastic cord or other connection features accommodate rotational movement of the headband 20', 20" and stiffening strip 50 relative to the forehead pad and the liner 40, e.g. by sliding and/or stretching elastically in the event of an impact against the shell 10.

For ease of illustration, the liner 40 is shown in Figs. 9 and 12 without the forehead pad, and so the lateral portions 43 of the liner are shown in their unrestrained position; it will be understood however than in practice, these portions 43 will be retained in their use position between the user's head and the first portion 20' of the headband and stiffening strip 50 by suitable retaining means, preferably a forehead pad as just described.

Table 1 shows the results of tests carried out on the reference helmet 1' generally as shown in Fig. 9, including the shell 10 and cradle 20 and the liner 40 which was retained at the front and sides by a forehead pad (not shown) as described above, and having a soft comfort pad (not shown) at the rear. The first material forming the first portion 20' of the headband and the suspension straps 25 was LDPE (low density polyethylene), and the liner 40 was made from a plastics material including polyketone.

For comparison, the same tests were carried out on a conventional helmet which was closely similar to the reference helmet 1' as just described, including the same shell 10 and cradle 20 and rear comfort pad and a generally similar forehead pad, except that the liner 40 was absent, the forehead pad being attached only to the headband.

Both helmets were the same, medium size.

The tests were carried out according to industry standard procedures by mounting each helmet on an instrumented headform representing the user's head, and dropping the helmet containing the headform onto an anvil surface arranged at an angle of 45° to vertical. The orientation of the helmet when dropped determined the direction of impact with respect to the pitch, roll and yaw axes X, Y, Z. The resultant translational acceleration, rotational acceleration, and rotational velocity, and the first principal strain were determined based on the output from the headform sensors as known in the art. The first principal strain represents the proportion of the applied force of the impact that is transferred to the headform.

Table 2 presents the relative difference between the values presented in Table 1 for the conventional and reference helmets.

In the table, "Pitch" indicates an oblique impact downwardly (relative to the normal use position) against the front end 11 of the helmet causing the helmet to rotate in pitch.

"Roll" indicates an oblique impact downwardly (relative to the normal use position) against one side 13 of the helmet equidistant between its front and rear ends 11, 12, causing it to rotate in roll.

"Yaw" indicates an oblique impact laterally (from one side 13) of the helmet against its front end 11 (across the forehead portion), causing it to rotate in yaw.

Table 1

Helmet Impact Resultant translational acceleration (g) Resultant rotational acceleration (krad/s2) Resultant rotational velocity (rad/s) 1st principal strain (1) Reference Pitch 104.1 3.1 12.0 0.14 Conventional Pitch 105.2 3.3 14.8 0.16 Reference Roll 81.1 2.2 13.1 0.11 Conventional Roll 81.8 3.2 16.2 0.13 Reference Yaw 127.5 5.7 24.5 0.29 Conventional Yaw 146.7 6.1 23.8 0.27

Table 2

Impact RELATIVE DIFFERENCE: Resultant translational acceleration RELATIVE DIFFERENCE: Resultant rotational acceleration RELATIVE DIFFERENCE: Resultant rotational velocity RELATIVE DIFFERENCE: ft principal strain Pitch 1.0% 7.5% 19.4% 13.0% Roll 0.8% 32.6% 19.4% 11.6% Yaw 13.1% 7.6% -2.9% -7.2% Compared with the conventional helmet, the presence of the liner 40 in the reference helment 1' was found to reduce the rotational forces transferred to the instrumented headform when the impact was directed to cause rotation of the helmet in pitch or roll.

Surprisingly however, it was found that presence of the liner increased the transferred force when the impact was directed to cause rotation of the helmet in yaw, causing the headband to break during the test.

Although not fully understood, it is believed that motion of the reference helmet 1' in yaw may cause the relatively pliable first portion 20' of the headband to ruck or gather about the liner 40, binding against the liner and transferring more of the applied force to the headform.

Referring now to Figs. 10, 11 and 12, the first helmet 1 as tested is identical to the reference helmet 1' except that it includes a stiffening strip 50 which is made from a second material having a higher stiffness than the first material of the first portion 20' of the headband.

The stiffening strip 50 is arranged to extend along the first portion 20' of the headband, so that it extends together with the first portion 20' of the headband around the front and side regions of the user's head, and is connected to the first portion 20' of the headband so as to be slidable in rotation together with the first portion 20' of the headband about the liner 40.

As shown in Fig. 12, the stiffening strip SO may be arranged to extend along the first portion 20' of the headband in-between the first portion 20' of the headband and the liner 40. In this configuration, a radially inwardly facing surface 51 of the stiffening strip 50 confronts the radially outwardly facing surface of the liner 40. In this arrangement the materials of the stiffening strip 50 and the liner 40 may be selected to minimise friction between them.

The stiffening strip 50 may be formed (e.g. moulded) from plastics material, for example, PP (polypropylene), ABS (acrylonitrile butadiene styrene), or HDPE (high density polyethylene).

The stiffness of the first and second materials may be taken as the shear modulus or modulus of rigidity -which is to say, the elastic shear stiffness of the material, defined as (shear stress)/ (shear strain). The higher the modulus, the stiffer the material.

The stiffening strip SO may be connected to the first portion 20' of the headband at multiple points along the circumferential length of the first portion 20' of the headband, for example, by means of studs or rivets 52 which may be moulded integrally with the stiffening strip 50. In the tests carried out on the first helmet land referred to below, the stiffening strip SO was formed as illustrated and the studs or rivets 52 were inserted through the small holes 38 in the first portion 20' of the headband to project radially outwardly through the first portion 20' of the headband as can just be seen in Fig. 12.

The multiple connection points help to maintain the front portion 20' of the headband in an extended configuration, so that the stiffness of the stiffening strip SO prevents the headband from rucking or gathering responsive to rotation of the helmet in yaw.

Additionally or alternatively, by arranging the stiffening strip in-between the front portion 20' of the headband and the front and lateral portions 42, 43 of the liner 40, the stiffening strip 50 helps to maintain a sliding interface between the assembly and the liner. In each case, the force transferred to the user's head when the helmet 1 moves in yaw is reduced by the presence of the stiffening strip which helps to rotationally decouple the shell 10 from the user's head for rotations about the Z axis.

Advantageously, since the cradle 20 may be of generally conventional design, it can be used for manufacturing other helmets that do not include the liner 40.

As shown in Figs. 10 and 11, the stiffening strip 50 may include hooks 53 on its radially outwardly facing surface for attaching the forehead pad as previously described.

Table 3 presents the relative difference between the values presented in Table 1 for the conventional helmet, and the values obtained in the same tests carried out on the first helmet 1 in three variants. In each variant, the shell 10, cradle 20, liner 40, soft rear comfort pad (not shown) and forehead pad (not shown) were the same as those of the reference helmet 1', the liner 40 being made from a plastics material including polyketone and the first portion 20' of the headband and suspension arms 25 from LDPE. The stiffening strip 50 was arranged and connected to the first portion 20' of the headband as described above to extend along the first portion 20' of the headband in-between the first portion 20' of the headband and the liner 40.

The variants differed only in the material of the stiffening strip 50, which was made respectively from ABS, HDPE, and PP.

Table 3

Impact Stiffening strip RELATIVE DIFFERENCE: Resultant translational acceleration RELATIVE DIFFERENCE: Resultant rotational acceleration RELATIVE DIFFERENCE: Resultant rotational velocity RELATIVE DIFFERENCE: ft principal strain material Pitch ABS 10.0% 20.9% 0.3% 5.1% HDPE 15.8% 33.7% 14.0% 12.2% PP 16.6% 40.5% 6.7% 21.6% Roll ABS -7.3% 41.3% 28.9% 19.9% HDPE -2.9% 43.9% 32.1% 25.8% PP -2.6% 27.4% 19.3% 21.2% Yaw ABS 16.0% -5.0% 52.2% 37.6% HDPE 12.1% -19.3% 36.7% 27.2% PP 11.6% 3.7% 57.3% 51.7% When compared with the conventional helmet, the presence of the liner 40 in combination with the novel stiffening strip 50 in all the tested materials provided a reduction, represented by the relative difference in the first principal strain, in the force transferred by oblique impact about all three axes.

In particular, it was found that when used in combination with the polyketone based liner 40, the PP stiffening strip 50 substantially outperformed the other stiffening strip materials in decoupling impacts in the pitch and yaw directions, and was nearly as effective as HDPE in the roll direction.

Thus, it may be preferred to make the stiffening strip 50 from PP, particularly when the liner 40 is made from a plastics material including polyketone, and most particularly when the stiffening strip 50 is arranged as shown to extend along the first portion 20' of the headband in-between the first portion 20' of the headband and the liner 40.

In summary, embodiments provide a safety helmet 1 including an outer shell 10 suspended by a cradle 20 having a headband 20', 20". A liner 40 is arranged in-between the user's head and a front portion 20' of the headband, which is made from a first material and extends around front and side regions of the user's head. A stiffening strip 50, made from a second material having a higher stiffness than the first material of the headband, is arranged to extend along the first portion 20' of the headband and connected to the first portion 20' of the headband so as to be slidable in rotation together with the first portion 20' of the headband about the liner 40. The stiffening strip helps to rotationally decouple the shell 10 from the user's head, particularly for lateral impacts causing rotation in yaw about a vertical axis Z. Many further adaptations are possible within the scope of the claims.

In the claims, reference numerals and characters may be provided in parentheses, purely for ease of reference, and should not be construed as limiting features.

Claims (10)

17 CLAIMS 1. A helmet including: a cradle, and an outer shell connected to the cradle; the cradle including: a headband configured to encircle a user's head in a use position of the helmet, and a plurality of suspension straps configured to extend over the user's head to suspend the outer shell in the use position; a first portion of the headband being made from a first material and configured to extend in the use position around front and side regions of the user's head; the helmet further including: a liner, and a stiffening strip; the liner being arranged to extend in the use position between the first portion of the headband and the front and side regions of the user's head; the headband being slidable in rotation about the liner to facilitate rotation of the outer shell about the user's head responsive to oblique impact against the outer shell; the stiffening strip being made from a second material having a higher stiffness than the first material; the stiffening strip being arranged to extend along the first portion of the headband; the stiffening strip being connected to the first portion of the headband so as to be slidable in rotation together with the first portion of the headband about the liner.

2. A helmet according to claim 1, wherein the stiffening strip is arranged to extend along the first portion of the headband between the first portion of the headband and the liner.

3. A helmet according to claim 1 or claim 2, wherein the stiffening strip is connected to the first portion of the headband at multiple points along the first portion of the headband.

4. A helmet according to claim 3, wherein the stiffening strip is connected to the first portion of the headband by studs or rivets.

5. A helmet according to any preceding claim, wherein the suspension straps and the first portion of the headband are formed as a unitary plastics body.

6. A helmet according to claim 5, wherein the unitary plastics body is formed of LDPE.

7. A helmet according to claim 5 or claim 6, wherein the unitary plastics body is deformable from a flat, rest state, in which the cradle is disconnected from the shell and the suspension straps and the first portion of the headband lie in a common, flat plane, to a use state in which the suspension straps and the first portion of the headband extend out of said flat plane when the cradle is connected to the shell.

8. A helmet according to any preceding claim, wherein the stiffening strip is made from polypropylene.

9. A helmet according to claim 8, wherein the liner is made from a plastics material including polyketone.

10. A helmet according to any preceding claim, wherein the liner is arranged to extend in the use position between the suspension straps and the user's head.