WO1997037553A1

WO1997037553A1 - Helmets

Info

Publication number: WO1997037553A1
Application number: PCT/GB1997/000876
Authority: WO
Inventors: James Barron
Original assignee: Rbr Armour Ltd.
Priority date: 1996-04-04
Filing date: 1997-03-27
Publication date: 1997-10-16
Also published as: AU2171197A

Abstract

A ballistic helmet having a ballistic resistant outer shell (10) which is resistant to high and low velocity impacts, a chin strap array (60) for securing the helmet to the head and means for securing the chin strap array to the helmet, in which: the outer shell (10) is a continuous shell free of apertures; an inner liner (30) is provided which conforms closely to the inner surface of the outer shell (10) over at least 70 % of the area thereof, the inner liner (30) carrying the means (50) for securing the chin strap array (60) to the helmet; and the inner liner (30) being secured to the outer shell by a mechanical interlock at the lower edge of the inner liner (30) and the lower edge of the outer shell (10).

Description

HELMETS

The present invention is concerned with helmets . Modern ballistic helmets are now widely used throughout the world and in recent years steel helmets have been replaced by a wide variety of composite helmets. These composite helmets are composed of essentially two parts: a ballistic resistant outer shell eg a fibre reinforced plastic outer shell and an internal harness which is mechanically fastened to the shell by bolts passing through the shell. They are used to protect against blows to the head such as are liable to occur in war, terrorist activities, law enforcement, explosives disposal, climbing and similar situations where life threatening blows or ballistic threats (e.g. from bullets or shrapnel) to the head have to be protected against.

The outer shells with which the present invention is concerned are manufactured from a wide range of fibre reinforced plastic composites. These composites are typically made using high tenacity fibres such as aramid, polyolefin, glass, graphite, or nylon or mixtures thereof. They are also combined with a wide range of plastic matrix materials including thermoset resins, thermoplastic resins and elastomeric materials. Examples of thermoset resins include phenolic/PVB

(polyvinylbutyral) , polyester, vinyl ester, and epoxy, and mixtures thereof. Examples of thermoplastic resins include polyethylene, polypropylene, ethylene vinyl acetate, polyvinyl chloride, and polycarbonate and mixtures thereof. Examples of elastomeric materials include nitrile rubbers, chloroprene rubbers, polyurethane rubbers, and Kraton type rubbers and mixtures thereof. There are also helmets which are made using a dry fibrous matrix encapsulated within a rigid skin structure.

Furthermore, the fibres may be presented in numerous different formats such as woven fabric, unidirectional sheets, felts, knits, and pulps (loose fibres compressed together to form the compound) .

The function of the outer shell is to protect against ballistic type impacts from bullets and fragments as well as protecting the head from low impact blows.

In conventional helmets the outer shell is provided with a number of fittings located within the helmet. These are typically manufactured using a wide variety of webbing, foam, & plastic moulding configurations which have both mechanical fastenings such as plastic or metal buckles, hook and eye fasteners e.g. that sold under the trade mark "Velcro ®", foam inserts and other fasteners for creating adjustment.

The function of these inner fittings which can be called a harness is to sit the helmet comfortably on the head and they also can provide a shock absorbing function for protection against the deformation and transmitted energy from ballistic and low velocity impacts.

The harness is often divided into three structural elements, the chin strap assembly, the head band assembly and the crown pad assembly. The chin strap assembly helps to retain the helmet securely onto the head. The head band assembly reduces lateral movement of the helmet on the head. The crown pad assembly positions the helmet at the correct height relative to the head.

The connection of the harness assembly to the outer shell is conventionally undertaken using a mechanical fixing method such as bolts fixed to nuts or inserts, rivets and other mechanical fastenings which all require holes to be drilled through the outer shell. These holes and fastenings have the following detrimental effects on the helmet .

They cause ballistic flaws and weaknesses in the outer shell. They cause protrusions within the helmet shell which on either high velocity impact or low velocity impact can be driven into the skull. They can cause secondary projectiles inside the helmet under high velocity impact .

They reduce the localised strength of the outer shell and its stiffness and cause greater shell deformation on impact from either low or high velocity impacts.

They can cause the ingress of fluids into the composite structure and within the outer shell.

They can cause electrical conductivity through the outer shell via metallic fasteners.

They can cause thermal conductivity through the outer shell via metallic fasteners.

This present invention is concerned with the provision of a harness system and method of assembly which requires no holes to be drilled in the outer shell whilst retaining the required strength and toughness characteristics for it- to be suitable for use by military or law enforcement personnel, optionally additionally enhancing the ballistic performance of the helmet. Not only does this invention overcome the disadvantages of having mechanical fasteners but it is a better method of manufacture, allowing for higher production rates due to better manufacturing logistics (i.e. the harness assembly does not have to be fitted to the outer shell until the very last stage) and lower assembly times which reduce the cost.

Furthermore, this invention also describes a harness assembly which allows adjustment to all the three basic harness components allowing for variation of fit and for the use of ancillary equipment.

According to the present invention a ballistic helmet is provided having a ballistic resistant outer shell which is resistant to high and low velocity impacts, a chin strap array for securing the helmet to the head and means for securing the chin strap array to the helmet, in which: the outer shell is a continuous shell free of apertures; an inner liner is provided which conforms closely to the inner surface of the outer shell over at least 70% of the area thereof, the inner liner carrying the means for securing the chin strap array to the helmet, and the inner liner being secured to the outer shell by a mechanical interlock at the lower edge of the inner liner and the lower edge of the outer shell. The arrangement is preferably such that the inner liner carries the carrying means in such a way that the combination of the toughness of the inner liner and its configuration are such that when the helmet suffers an impact the securing means for the chin strap array are retained by the inner liner.

In a first preferred embodiment of this invention the securing means for the chin strap array are located between the inner liner and the outer shell; the securing means comprising a plurality of strap means spaced around the inner liner and extending up from the lower edge of the liner to retaining means located on the inner liner or between the inner liner and the outer shell. The securing means for the chin strap array are preferably located between the inner liner and the outer shell so that when the helmet suffers an impact the securing means are retained between the inner liner and the outer shell. In a preferred form of this embodiment the securing means comprises a plurality of strap means {typically two, three or four) spaced around the inner liner and extending up from the lower edge of the liner to retaining means located at the crown of the inner liner. The retaining means in a preferred arrangement, which facilitates assembly, are a pad to which the straps are attached. The attachment very conveniently may be made by hook and eye type fastenings (eg of the type sold under the trade mark "Velcro ^®M) . Conveniently the eyes are on or afforded by the pad and face outwardly and the hooks may be on or afforded by the straps. Alternative less preferred arrangements are described below. The nature of the outer shell has been discussed above. The present invention gives complete freedom to the design of the outer shell and permits use of materials where forming holes is not possible or could severely weaken the material as well as avoiding the need for holes.

Chin strap arrays can be of a variety of forms and three of these are discussed below. The invention provides great flexibility in the choice of chin strap array.

The disadvantages of the conventional means of attaching the chin strap array to the outer shell have been discussed above and the advantages of the present invention are discussed below. The key to the present invention is the inner liner.

The liner desirably is made of a tough material which does not shatter under impact. It need not be rigid but desirably can be flexible to some extent. Clearly it is also desirable that it should be resistant to Nuclear Biological Chemical (NBC) attack as laid down in various country specific standards. It needs to be able to be secured reliably within the outer shell and hold the harness in place in the helmet after a ballistic impact.

One useful measure of the necessary strength is the tear strength of the material of the inner liner. A minimum value of 750 kPa is preferred. Another measure of the necessary strength is the tensile strength which preferably exceeds a minimum value of 690 kPa. There are no upper limits for the tensile and tear strengths. The liner should be a completely separate unit which possesses structural strength and integrity independently of the outer shell. The liner and the harness system exist as a unit separately from the outer shell prior to insertion therein. The outer shell is there to provide ballistic protection. The liner also has an impact absorbing function.

In a finished liner or helmet the tear strength should be measured in a region which is free of any apertures and is preferably flat. Such a region is the crown region.

In a first embodiment the inner liner is not required to be as strong as the outer shell but must be tough enough to withstand the forces which will be exerted on it by the securing means for the chin strap in all the situations in which it is loaded in use. These vary from low loads such as when the helmet is carried by hand by its chin strap and high loads such as when the helmet suffers an impact by a bullet or other ballistic element or a low velocity impact such as a blow from a club.

Materials which can be used for this embodiment of the liner include moulded polypropylene, polystyrene or a closed cell foam cross linked polyethylene e.g. the material manufactured by Zotefoams Ltd. and sold under the trade name Plastazote . These are preferably in foamed form. We have also found that expanded polypropylene materials which might appear likely not to be strong enough are also effective when formed into a close fitting liner of the present invention and supported at the lower edge of the helmet by the preferred mechanical interlock (see Figure 6) .

The means for securing the chin strap array are preferably located between the inner liner and the outer shell . This enables the loads exerted on the chin strap and thus on the securing means to be distributed rather than concentrated at a single location.

As mentioned above in a preferred form of the first aspect of the invention this distribution of the load is achieved by passing strap means from the lower edge of the helmet up over the crown. These strap means may conveniently be secured to each other at the crown or to a pad. This attachment can be by hook and eye type attachment between the straps or the strap and a pad. Such an arrangement facilitates assembly of the harness and liner as described below. Alternatively the straps can be sewn to each other or to the pad.

In another arrangement the securing means do not pass over the crown but are attached to fixture means located around the inner liner intermediate the crown and the lower edge of the liner eg between 1/3 and 2/3 there between. These fixture means may be a strap passing around the inner liner and eg resting in a recess therein. Less preferred arrangements would have slots and loops of fabric therein to which the straps could be secured by hook and eye type attachments or sewing. These arrangements do not distribute the load as well and because they require slots in the liner to some extent will weaken it.

It is much preferred that any slots in the inner liner are in the lower half thereof, removed from the crown, and preferably in the lower quarter proximate to the lower edge of the liner. The inner liner is secured to the outer shell so that it cannot be readily removed therefrom and will not be displaced by impacts on the outer shell .

This attachment is assisted by the close conformity of the inner liner to the outer shell. The securing means can be direct adhesive attachment though there may be problems of finding appropriate adhesives and being certain that the adhesion has occurred. Hook and eye pads or strips could be used but this further complicates the shaping of the inner liner and again there may be uncertainties as to whether the attachment has been satisfactorily made.

The preferred securing means is by a mechanical interlock at or adjacent to the lower edge of the outer shell and the inner liner. Thus the outer shell may have a rubber or plastics locking structure attached to it eg as a clip-on channel or by adhesive or both and the locking structure affords a locking member which engages the inner liner at or adjacent to its lower edge and thereby secures the liner to the outer shell. Again this may be assisted by adhesive.

The locking structure preferably extends around the whole or substantially the whole of the lower edge of the outer shell.

In a second preferred embodiment of this invention the outer shell is ballistic resistant; the inner liner is tough and thin and enhances the ballistic resistance of the outer shell; the tough, thin inner liner contacts at least 95% of the inner surface of the outer shell and the chin strap array is secured to the tough, thin inner liner.

One preferred securing means in this second embodiment comprises adhesive between the inner liner and the outer shell . This helps to provide the enhanced ballistic performance i.e. increased displacement of the inner liner without deformation. More preferable is the combination of adhesive between the inner liner and the outer shell and mechanical securing means located at or adjacent the lower edge.

As stated above, the key to the present invention is the inner liner. In this second embodiment the tough, thin inner liner must be made of material which enhances the ballistic resistance of the helmet. The liner must conform to the inner surface of the outer shell and cover substantially the whole of that inner surface to help enhance ballistic resistance. Preferably the liner is as thin as possible so as not to reduce the internal volume of the helmet. Typical thicknesses for the liner range from 0.5 mm to 3 mm.

As stated above the inner liner must be made of a material which exhibits some ballistic resistance, but it must also be able to allow sewing through it without fracturing or tearing of the liner. Materials which have been found to be suitable include thermoplastic or thermoset plastic materials which have been reinforced with fibre. A rubber reinforced aramid fabric which has been compression moulded has been found particularly suitable .

The liner can be made using a variety of different methods including injection moulding, compression moulding, hand lay up (glass reinforced plastic (GRP) ) , bag moulding, vacuum forming, vacuum bagging, blow moulding, rotation moulding and the like.

For extra protection against impacts it is also possible to bond foam or other impact absorbing structures to the inside of the liner. It is also possible to mould the inner liner to include a lip at the bottom edge of the liner which bends round in a U shape to enclose the outer shell . In a preferred arrangement the securing means for the chin strap array, the head band assembly and the crown pad assembly in this second embodiment consist of stitches to the inner liner. An advantage of this form of attachment is that the liner can be stitched anywhere giving any number of potential configurations of harness.

A further advantage of this method of attachment is that the inner liner contains no apertures which are points of potential weakness and would therefore reduce the ability of the liner to enhance ballistic resistance. The straps all pass down from the inside of the inner liner so that the liner can conform closely to the inner surface of the outer shell .

The inner liner in this second embodiment is secured to the outer shell so that it cannot be readily removed therefrom and will not be displaced by impacts on the outer shell. This attachment is assisted by the close conformity of the inner liner to the outer shell.

The securing means for the second embodiment is by mechanical interlock at or adjacent to the lower edge of the outer shell and the inner liner preferably in combination with adhesive between the inner liner and the outer shell. Thus the outer shell may have a rubber or 12. plastics locking structure attached to it eg as a clip-on channel or by adhesive or both, and the locking structure affords a locking member which engages the inner liner at or adjacent to its lower edge and thereby secures the liner to the outer shell. Again this may be assisted by adhesive in the mechanical interlock.

The locking structure preferably extends around the whole or substantially the whole of the lower edge of the outer shell. An advantage of the mechanical interlock is that it enables the liner to be removed and replaced with the harness as a unit. This replaceability is important for military uses. However, at the same time, it facilitates a stronger ballistic helmet. In both embodiments the preferred securing means comprise mechanical securing means located at or adjacent the lower edge of the.shell. Preferably these securing means are supplied by a separate component located on the outer shell and engaging the inner liner. More preferably the separate component is a resilient channel member clipped over the edge of the outer shell and affording a lip engaging the inner liner to hold it within the outer shell when pushed therein.

The invention also provides an adjustable head band which is secured to the liner at the front thereof but is free and adjustable in diameter in the rear thereof. Preferably there is provided a helmet in which a head band assembly is secured within the inner liner, the front of the head band assembly being secured to the front of the inner liner by securement means so as to be held in fixed relation thereto, the headband assembly being adjustable rearwardly of the front of the inner liner. The head band preferably carries a front pad and the head band or pad or both is secured to the inner liner. This headband assembly securement means may be loops located in slots in the inner liner or loops secured e.g. stitched to the inner liner. ll

This arrangement has considerable advantages which are discussed below. It may be used with any arrangement of inner liner. The head band is desirably provided with a rear pad as well, preferably freely slidable on the head band.

Desirably levelling means are also provided to hold the rear part of the head band relative to the liner so as to avoid excessive up or down movement of the rear of the head band and thus of the helmet relative to the users head.

The rear of the headband assembly is preferably stabilised by levelling means which are located at the sides of the inner liner. In use with the first embodiment of the inner liner the levelling means may be secured at one end e.g. their front end to the securing means outside the inner liner, pass through slots in the sides of the inner liner and extend inside the inner liner to provide slots, through which the headband assembly is passed, in the region of the other half e.g. the rear half of the inner liner.

These levelling means are desirably stiff plastic strips on either side of the liner which are fixed at one end against up or down movement relative to the helmet, pass through slots in the sides of the liner and afford slots, in the region of the rear half of the liner, through which the head band is passed.

The headband securement means and preferably also the head band levelling means, when on the outer surface of the inner liner, are located in recesses in the outer surface such that they do not extend out beyond the surrounding outer surface of the inner liner.

In use with the second embodiment of the inner liner the levelling means, e.g. loops, may conveniently be secured to the inner liner, and provide slots or loops, through which the headband assembly is passed, in the region of the half of the inner liner remote from the front of the helmet . The inner liner in both embodiments preferably has a minimum tear strength of at least 750 kPa e.g. at least 1,000 preferably at least 2,000, more preferably at least 3,000 kPa as measured by the procedure of DIN 53571. Preferably the inner liner has a tensile strength of at least 690 kPa e.g. at least 1,000, preferably at least 1,500, more preferably at least 2,000 kPa as measured by the procedure of DIN 53571.

The helmet according to the invention preferably contains a crown strap assembly. In the first embodiment of the inner liner the crown strap assembly preferably comprises crown strap means located outside the inner liner and extending through slots into the interior of the liner, the straps affording loops within the inner liner, draw means being threaded through the said loops.

Preferably when using the first embodiment of the inner liner any securing means in between the inner liner and the outer shell are located in recesses in the outer surface of the inner liner. Most preferably the retaining means and the securing means, when on the outer surface of the inner liner, are located in recesses such that they do not extend out beyond the surrounding outer surface of the inner liner. This ensures the maximum area of close fit between the outer surface of the inner liner and the inner surface of the outer shell.

The recesses are desirably of the minimum thickness necessary to accommodate the securing means.

The inner liner may have localised slots through its thickness for passage of components of the securing means. Such slots are preferably located nearer to the rim of the inner liner than to its crown.

The inner liner preferably extends at least 70% e.g. 80% or 90% and preferably over substantially the whole of the area of the inner surface of the outer shell. The recesses in the inner liner are preferably of a depth which is less than 50% preferably less than 30 or 20% of the thickness of the inner liner. 11

The slots in the inner liner are preferably of a width which is less than 50% preferably less than 30 or

20% of the thickness of the inner liner and of a length not more than 5 times, preferably 4, or 3 or 2 times the thickness of the inner liner.

The slots may be chamfered on one or more edges to facilitate passage of the securing means. When considering the width or length of the slots these chamfers are to be disregarded. A method of assembling a helmet in accordance with the present invention having a chin strap array, a headband assembly, a crown strap assembly and a mechanical interlock at the lower edge of the outer shell, is characterised in that: the chin strap array, the headband assembly and the crown strap assembly are secured to the inner liner; optionally a layer of adhesive is placed between the inner liner and the outer shell; the mechanical interlock at the lower edge of the outer shell is displaced to allow insertion of the inner liner; the complete inner liner is inserted into the outer shell; and the mechanical interlock is established holding the inner liner securely in place.

The invention may be put into practice in various ways and two specific embodiments will be described to illustrate the invention with reference to the accompanying drawings in which;

Figure 1 is a side elevation sectional view of a complete ballistic helmet in accordance with the present invention taken along the fore and aft centre line of the helmet;

Figure IA is a side elevation sectional view of a complete ballistic helmet in accordance with the present invention including a profile of the users head;

Figures 2A and 2B are elevational and sectional views of the helmet from the front seen along the arrow II in Figure 1, the outer shell is shown in section in both Figures; Figures 3A and 3B are views similar to 2A and 2B but from the rear seen along the arrow III in Figure 1;

Figure 4A is a side elevation from the same side as Figure 1 showing the helmet liner and the location of the harness in relation thereto;

Figure 4B is a plan view from below of the head band assembly inside the inner liner and an enlarged view of the joint between the plastic strip of the head band retention means and the loop of the head band assembly; Figure 5 is a plan view of the helmet liner from above along the arrow V in Figure 4 ;

Figure 6 is scrap section view of the edge of the helmet outer shell showing how the liner is attached thereto in a preferred embodiment; this view being on a much enlarged scale;

Figures 7A to 7H illustrate further alternative embodiments of the attachment of the inner liner to the outer shell;

Figure 8 is an elevation view from the front showing the relationship between the point of exit of the straps of the chin harness assembly from between the outer shell and the inner liner and the users head;

Figure 9 is a side elevation sectional view of a complete ballistic helmet in accordance with the second embodiment of the present invention taken along the fore and aft centre line of the helmet;

Figure 10 is a side elevation view of the inner liner and harness attachments in accordance with the second embodiment of the present invention; Figure 11 is a side elevation sectional view of the inner liner and harness assembly in accordance with the second embodiment of the present invention taken along the fore and aft centre line of the inner liner;

Figure 12 is a side elevation sectional view of the second embodiment of the inner liner and harness assembly with the headband removed to reveal the securement means of the harness to the inner liner; Figure 13 is a front elevation view of the inner liner with harness assembly in accordance with the second embodiment of the present invention;

Figure 14 is a cross sectional view of the rear of the second embodiment of the inner liner both with and without the headband to show the securement means of the harness to the inner liner;

Figure 15 is a cross sectional view of the second embodiment of the front of the inner liner both with and without the headband to show the securement means of the harness to the inner liner; and

Figures 16A, 16B and 16C are scrap section views of the edge of the helmet outer shell in the second embodiment showing how the inner liner may be attached thereto in preferred embodiments; these views being on a much enlarged scale.

It will be appreciated that Figures 1 and 4A omit the chin cup from the bottom of the chin strap, the chin cup being shown in Figures IA, 2, 3 and 8. Figures 1 to 8 show a first embodiment of the present invention and figures 9 to 16 show a second embodiment.

Referring now to Figure 1 the helmet has an outer shell 10 and an inner liner 30.

The outer shell 10 has a crown 11, a forehead 12 and a front brim 13 which curves slightly outwardly. The outer shell also has a rear head region 14 and comes down to a plain nape 15 which is slightly below the level of the brim 13. The lower edge 16 of the outer shell curves downwardly from the nape to afford an ear protecting region 17 and then curves up to the brim 13.

The outer shell is made of any suitable ballistic resistant material preferably a fibre resin composite.

This may be of conventional construction appropriate to the severity of the duty for which the helmet is designed.

A key aspect of the present invention is however that the outer shell is free of any holes passing through ii it so that it does not have its strength compromised in any location. The inner surface of the outer shell is a smooth cup shape. The inner liner 30 is moulded so that its outer surface conforms closely to the inner surface of the outer shell over a substantial area of the outer surface of the inner liner.

The outer shell is typically 5 to 12 mm thick. The inner liner is typically 5 to 20 mm thick. It is tough but bendable in the sense that its lower edge can be flexed inwardly. However it is strong enough to resist crushing pressures applied downwardly to the crown. The lower edge 16 of the inner liner 30 may flex outwardly and the front and rear inwardly when the crown is pressed down but the liner can resist substantial downward pressure on the crown without rupturing. The strength of the liner will be determined in 3 ways: the maximum crown impact, in Joules, without the head exceeding a 3OOG acceleration; the maximum force applied to the chinstrap without breakage; and the roll-off test, the force applied to the edge of the helmet to test positional stability. All of these tests establish the integrity of shell liner bonding. The liner may be made from any material effective to provide such strength in the thickness contemplated. Materials having Tear strengths of at least 750 kPa and Tensile strengths of at least 690 kPa as measured in accordance with DIN 53571 have been found effective. If the tear strength was too low the straps would rip the liner apart and cause it to fail. There is no upper limit to these values but if the material is too brittle it would tend to crack under the loads applied to the straps .

A measure of flexibility is also desirable to facilitate insertion of the inner liner into the outer shell.

Examples of effective mouldable polymers are high and low density polyethylene and ethylene polypropylene beads which are formed to sheet form. Polystyrene may be used but would probably need a tough plastic skin such as ABS (Acrylonitrile Butadiene Styrene) formed around it to give it the required strength. A preferred material is a closed cell foam, cross linked polyethylene sold under the Trade Mark Plastazote, grade HD80 which has a tensile strength of 2300 kPa (DIN 53571) and a tear strength of 3800 N/m (DIN 53571) .

The liner is ideally a tight fit within the outer shell so that the opposed surfaces are a flush contact with each other over about 95% of the area of the outer surface of the liner in the embodiment shown in Figures 1 to 5.

A chin harness securement means 50 is located between the inner surface of the outer shell and the outer surface of the liner in localised spaces formed there between to accommodate the said securement means. Most conveniently these spaces are formed in the inner shell though they could be formed in the outer shell at the cost of increased complexity in production thereof and possibly disadvantageous variations in strength thereof .

As can be seen in Figure IA the users head 40 is spaced from the inner surface of the inner liner. Accordingly the spaces for the securement means can be moulded into the inner liner and result in protrusions on the inner surface thereof without producing disadvantages.

As can be seen from Figure 5 the embodiment illustrated in the drawings shows a three point harness arrangement .

The harness securement means 50 consists of a crown securement pad 51 located in a slightly oversized cooperatively shaped e.g. round recess 31. The recess 31 is of a plan area slightly greater e.g. diameter 10.5 cm than the pad 51 (e.g. diameter 10 cm) and a depth (e.g. 1.5 mm) slightly greater than the thickness (e.g. 1.2 mm) of the pad 51. The pad 51 may be secured in the recess 31 eg with adhesive (not shown) . Three straps 52, 53 and 54 extend down from the crown pad 51. They are located in slightly oversized channels 32, 33 and 34 in the outer surface of the liner. The straps 52, 53, 54 may be about 2 cm wide and 1 mm or less thick and the channels 32, 33, 34 may be 2.5 cm wide and 1.5 mm deep.

The straps pass through slots 35 (see Figure 4A) in the inner liner 30 to the interior thereof. The front straps 52 and 54 are secured e.g. by sewing into a loop to buckles 55 (which may be of the so called Ladderlock type) to which the chin harness assembly can be attached. The rear strap 53 ends in a loop 56 eg formed by sewing or is secured (eg by sewing) to a loop 56 by webbing 57. The rear strap 53 is adjusted using a Triglide type adjuster. Ladderlock and Triglide type adjusters are commercially available plastic components which are used in adjusting and tensioning the harness.

The straps 52, 53 and 54 are preferably secured to the pad 51 by conventional strong hook and eye fabric fastener structures such as are known under the Trade Mark VELCRO.

Versions of greater strength than the original cut loop (hook) and uncut loop (eye) are now available in which a stronger engagement between the hook and eye structures are described as mushroom and eye, the hook in effect having two tongs. This provides a ' stronger connection but the structure is liable to break down if the connection is made and broken repeatedly. The straps 52, 53, 54 may provide a hook type VELCRO structure on one face which conveniently is faced inwardly towards the inner liner 30 and the pad 51 may provide an eye type VELCRO structure facing outwardly.

The straps can thus be press secured to the pad and the close fit between the liner and the outer shell helps li to maintain this strong hold between the straps and the pad. This also provides a very convenient and rapid mode of assembly. The lower ends of the straps can be sewed e.g. at 70 (see Figure 1) to webbing 71 which itself is sewed e.g. at 72 to the buckles 55.

In an alternative less preferred arrangement the straps could be sewed to a pad 51 which would no longer need to be of VELCRO or the pad could be dispensed with and the straps sewn to each other and the lower ends of the straps passed through the slots 35 and provided with a sewn on eye patch so that a loop could be made for securing to the buckle 55 by a hook and eye connection.

Making the straps out of webbing instead of VELCRO fabric might still enable the securement to be achieved but it is thought that it would be more complicated to make and assemble and thus less desirable.

A chin harness assembly 60 is also provided. It consists of chin straps 61 and 62 adjustably secured in the buckles 55 and extending down on each side of the user's face to a pair of strong rings 63, 64, to which the straps are secured e.g. by sewing into a loop through which the ring passes.

A rear strap 65 (see Figure 4A) which is adjustable in length by means of a buckle 66 (not shown) passes through the loop 56 and is secured at each end to the rings 64.

A further strap 67 is secured at one end to one ring e.g. 64 passes through a moulded plastic chin cup 68 and is removably secured e.g. by a conventional looped pressfit stud arrangement to the other ring e.g. 65.

The chin strap has to withstand sufficient load so that the helmet is not easily pulled from the head. The Snell Memorial Foundation test B.95 requires a load of 38 kg dropped from 3 cms without the helmet strap or mounting breaking. Furthermore this invention is IQ. intended to be used in combat helmets which are parachutist certified. As described above this can be achieved by a three point harness having two side straps and one rear strap. The securement means extending fully over the top of the liner ensures that any stresses applied to the chin strap are transmitted right over the crown of the head.

It is important in the design of this embodiment of the invention that the straps are so designed that when they emerge from between the liner and the outer shell they run as close to the users head as possible. If this were not the case they would impose undue stresses on the liner which could cause it to break up and fail. This can be seen in Figure 8 where the dotted lines show a helmet in which the straps extend down from between the outer shell and the inner liner away from the skin and the arrow shows the direction of the stress caused.

There are a number of possible configurations of chin strap, and three can be mentioned. 2 Point restraint which is similar to a standard motorbike helmet. This has two fixing points on the helmet and a single strap that passes under the chin.

3 Point restraint which is preferable for parachutist's helmets. This has two fixing points just in front of the ears and a further point located at the back of the helmet . The chin strap is connected to both the front and rear straps. This is the specific arrangement which as been described with reference to the drawings.

4 Point restraint which has four fixing points equally spaced around the helmet and fixed to the chin strap.

A further important component of the helmet which is also located on the inner liner 30 is a head band assembly 80. The head band assembly 80 is based on a loop 81 of strong webbing which is secured within the inner liner adjacent its lower edge. The loop is provided with a VELCRO hook and eye connection 82 (not shown) so that its length can readily be adjusted. The loop 81 is slotted through a front brow support 83 provided by a tube of padding.

The tube is sewn on either side of the brow to webbing loops 84 provided with cooperating hook and eye VELCRO arrays so that the loops can be passed through slots 36 (see Figure 4A) in the brim region 13 of the inner liner 30. The loops are nested in channels 37 in the outer surface of the inner liner 30 so as to maintain the flush relationship between the outer shell and inner liner. The channels 37 communicate with notches 29 in the lower edge of the inner liner 30. This is to prevent the loops 36 interfering with the edging strip 110 which is described below.

At the rear of the helmet the loop 81 is slotted through a rear nape support 86 (see Figure 1) provided by another padded tube.

Accordingly the head band (and thus the user's head) is held in fixed relationship to the front of the helmet and differences in head size are accommodated at the rear of the helmet. This has the advantage that the users eyes will tend to remain at the same distance from the front of the helmet irrespective of head size.

In order to hold the head band at the same level relative to the crown of the helmet there is provided head band retention means 90. These consist of a pair of thin stiff plastic strips

91 (see Figures 4A and 4B) each provided with loops at

92 e.g. by a piece of webbing sewn to the strips 91 at locations near their front ends. The straps 52 and 54 pass through the loops 92. The strips 91 are nested in channels 38 again to preserve the flush relationship of the contacting surfaces of the inner liner 30 and the outer shell 10. The strips 91 at their rear ends 93 pass through slots 39 in the inner liner and are provided with narrow slots 94. The rear ends 93 are enlarged at 95 (see Figure 1) so that they cannot readily pass back through the slots 39 even though they can be inserted therethrough by flexing them. The loop 81 of the head band assembly is threaded through the slots 94 in the strips 91 and thus the rear part of the head band assembly is held from falling down below the lower rim of the helmet or riding up into its interior while remaining fixed at the front and freely adjustable in circumference to accommodate varying head sizes.

In an alternative arrangement of the head band retention means 90 (not shown) , the thin plastic strips 91 are secured at the rear of the liner. Each strip 91 is provided with a loop e.g. by a piece of webbing sewn to the strips at locations near their rear ends. The strap 53 passes through the loops. The strips are nested in channels to preserve the flush relationship between the contacting surfaces of the inner liner and the outer shell. The strips 91 at their front ends pass through slots 39 in the inner liner and are provided with narrow slots 94 through which the loop 81 of the head band assembly is slotted. These front ends are enlarged so that they cannot readily pass back through the slots 39. As before the rear part of the head band assembly is held from falling down below the lower rim of the helmet or riding up into its interior while remaining fixed at the front and freely adjustable in circumference to accommodate varying head sizes.

The inner liner is also provided with a crown strap assembly 100. This is provided by two lengths of webbing straps 101 and 102 (see Figure 4A) each provided with sewn or VELCRO loops 103 at each end. The rear loop 102 21 passes through two slots 42 and 43 in the liner 30 and nests in a channel 44 in the outer surface of the inner liner with the loops 103 inside the liner.

Similarly the strap 101 also with loops 103 passes through slots 45 and 46 and nests in a channel 47 in the front of the inner liner. A drawstring 105 (see Figure 5) is passed through the four loops 103 and adjusted as desired so as to contact the top of the wearers head and space it from the crown of the inner liner. In an alternative arrangement of the securement means (not shown) the pad 51 is replaced by a loop of VELCRO or webbing which is shaped to rest flat in a channel passing round the inner liner between the crown and the lower edge and the straps are connected by VELCRO loops, sewing or other appropriate means to such a circumferential support loop.

The inner liner 30 is also secured to the outer shell 10. The preferred method is mechanical and is shown in Figure 6. A rigid moulded plastic or rubber edging strip 110 conforming to the profile of the lower edge of the outer shell and affording a channel shape 111 is glued to the lower edge of the outer shell 10. This strip extends around the whole or substantially the whole of the edge of the outer shell, e.g. at least 70%, preferably 80%, more preferably 90 or at least 95% of the length of the said edge. The strip also provides an inwardly and upwardly extending flange 112 adapted to hook substantially over the lower edge of the inner liner 30. The lower edge of the liner 30 is moulded so as to be a close snap or force fit within the channel provided by the flange 112 as shown in Figure 6.

The inner liner can thus be provided with the various assemblies 50, 60, 80, 90 and 100 and then slipped into the outer shell at or near the end of the assembly process. (The chin strap assembly could be connected after this step if desired) .

It will be appreciated that the inner liner could be secured within the outer shell by adhesive or by VELCRO or other fastener means. However the type of mechanical attachment described with regard to Fig. 6 (which may be enhanced by placing adhesive on the flange 112 as well) is simple and is preferred. It also does not interfere with the flush surface contact of the inner liner and outer shell.

The assembly procedure for a conventional helmet involves the attachment, of a fully finished harness assembly to a fully finished helmet using five screws and five inserts. Other components such as anchor brackets and Ladderlock adjusters are also attached to these screws . This assembly procedure takes approximately five minutes. The invention as herein disclosed is assembled by fitting a fully assembled liner into the outer shell. In the process of the present invention the rubber edging can be pulled outwardly and the inner liner pushed into the outer shell . The edging is then allowed to spring back substantially over the edge of the liner holding it in place. This is a much faster process.

As mentioned above the head band is permanently fixed to the front using two mushroom type VELCRO fasteners looping through the helmet liner. The head band is also sewn to the straps 52 and 54 just above the buckles 55 to stabilise both elements at the sides.

Adjustment of the head band (as mentioned above) is generated by increasing or decreasing the head band length whilst keeping the head in the same position at the front. This is highly desirable since it ensures the correct placement of the head of the user relative to the helmet for it to be compatible with modern optical systems. As described above the head band 81 is kept in 23. place at the back of the head by two plastic strips or mouldings 91 which will flex normal to the plane of the head band but not parallel to it (preventing vertical movement of the headband - as can be seen in Figure 4B) ensuring that the helmet does not rock backwards and forwards on the users head. To generate stability to these plastic mouldings they run forward and are secured to the side straps 52 and 54. The head band 81 can be run around the occipital region at the back of the head, as can be seen in Fig. IA. This improves the stability of the helmet on the head since the helmet has severely restricted vertical movement as the head band is run around the region of the head just below the widest section. A crown pad assembly 100 involving the use of webbing has been described. An alternative arrangement

(not shown) is a simple foam pad fastened by a hook and eye attachment eg of VELCRO to the liner crown which is either adjustable by folding in flaps of foam or by the addition of other foam elements.

The fixing of the liner 30 to the outer shell 10 by using a rigid moulded plastic or rubber edging strip 110

(see Fig. 6) which has an internal lip 112 all the way round the inner edge of the helmet and mechanically locks the liner 30 in place has been described.

Alternative ways of fixing the liner 30 to the outer shell 10 are as follows :-

The liner 30 may be bonded in using a suitable adhesive 120 (see Fig. 7F) . The liner 30 may be fixed in using mushroom or unidirectional type VELCRO 120 which is prebonded to the inside of the outer shell 30 and the corresponding VELCRO part either mechanically fixed or bonded to the liner 30.

The outer shell 10 could be moulded in a manner to allow push fit connection of the harness/liner to the shell (see Fig. 7C) . This could be mouldings on the inside of the shell. However, these would be detrimental if they protruded badly into the liner area. Alternatively they could be mouldings on the exterior of the shell around the rim of the helmet, but these considerably complicate production of the outer shell. In this case a liner which also incorporated an edge trim could be attached as a push fit (see Fig.7A) .

The liner 30 may be held by a combination of a moulding of the outer shell 10 and a rubber edge trim 110 (see Fig. 7D) .

Alternative arrangements of the rubber edge trim 110 may be used (see Figs. 7B and 7E) .

The liner 30 may be held by an extra layer made up of a plastic shell such as ABS 130. This extra shell 130 may be attached to the outer shell 10 using an adhesive or velcro 120 (Fig. 7G) or by a mechanical fit (Fig.7H) .

However the arrangements in which the lower edge of the outer shell is plain and a mechanical interlock is used (Figures 7B and 7E) are much preferred.

A second embodiment of the present invention is shown in figures 9 to 16. Referring now to Figure 9 the helmet has an outer shell 210 and a thin inner liner 230.

The outer shell 210 has a crown 211, a forehead 212 and a front brim 213 which curves slightly outwardly. The outer shell also has a rear head region 214 and comes down to a plain nape 215 which is slightly below the level of the brim 213. The lower edge 216 of the outer shell curves downwardly from the nape to afford an ear protecting region 217 and then curves up to the brim 213.

The outer shell 210 is made of a ballistic resistant material, which for the purposes of the present case is defined as a material having the following properties: a

V₅₀ greater than 300 m/s when tested with a 1.016 gram (17 grain) fragment in accordance with STANAG 2920. V₅₀ is the theoretical failure value of the armour at which velocity 50% of the fragments pass through the sample and 50% are stopped by the sample. Thus the test V₅₀ (velocity 50%) is the average of the velocities recorded for six fair impacts consisting of the three lowest velocities for complete penetration and the three highest velocities for partial penetration, i.e. at which the fragment is stopped, provided the spread is not greater than 40 metres/second. The test is effected using a cylindrical steel fragment. Typically the 17 grain fragment is used as the simulator. The fragment is loaded into a plastic sabot and fired using compressed air or explosive powder loads.

Typically a fibre reinforced composite is suitable. A specific composite which is effective has the following composition and structure: 16 layers of 410 gms/sqm Aramid fabric laminated with 12% phenolic/PVB resin.

A key aspect of the present invention is that the outer shell 210 is free of any holes passing through it so that it does not have its strength compromised in any location. The inner surface of the outer shell 210 is a smooth cup shape. The thin inner liner 230 is moulded so that its outer surface conforms closely to and contacts the inner surface of the outer shell 210. The outer shell 210 is typically 5 to 12 mm thick.

The thin inner liner 230 is preferably 0.5 to 3 mm thick. The thin liner 230 is of substantially uniform thickness over its whole area, any differences in thickness being less than 10%. The ratio of the thickness of the inner liner to the outer shell is preferably 1:10 to 1:4. The inner liner is desirably such as to contribute to the ballistic resistance of the helmet as a whole by at least 10% and desirably 10 to 20% of the total ballistic strength. By ballistic strength we mean: as measured using the V₅₀ test in accordance with STANAG 2920. 23.

The liner is tough enough to enhance the ballistic resistance of the helmet but bendable in the sense that its lower edge can be flexed inwardly. The lower edge of the inner liner 230 may flex outwardly and the front and rear inwardly when the crown is pressed down but the liner can resist substantial downward pressure on the crown without rupturing. It is also important that the liner 230 is able to be sewn through without fracturing or tearing. The strength of the liner 230 will be determined in

3 ways: the maximum crown impact, in Joules, without the head exceeding a 300G acceleration; the maximum force applied to the chinstrap without breakage; and the roll- off test, the force applied to the edge of the helmet to test positional stability. All of these tests establish the integrity of shell liner bonding. The liner 230 may be made from any material effective to provide such strength in the thickness contemplated.

Materials having Tear strengths of at least 750 kPa and Tensile strengths of at least 690 kPa as measured in accordance with DIN 53571 have been found effective. If the tear strength was too low the stitching of the straps to the liner would rip the liner apart and cause it to fail. There is no upper limit to these values but if the material is too brittle it would tend to crack under the loads applied to the straps.

A measure of flexibility is also desirable to facilitate insertion of the inner liner 230 into the outer shell 210. A preferred material for the construction of the inner liner 230 is a rubber reinforced aramid fabric which has been compression moulded. Typically the fabric is a woven fabric having 4 to 10 picks/cm and 4 to 10 ends/cm. An alternative material is a felt or a unidirectional fabric. A preferred range for the ratio of 23. the polymer to the fabric is 10 to 30%.

Other suitable materials are thermoplastic or thermoset plastic materials which are fibre reinforced.

The liner 230 is ideally a tight fit within the outer shell 210 so that the opposed surfaces are a flush contact with each other over substantially the whole e.g. at least 95% or 99% of the area of the outer surface of the liner 230 in the embodiment shown in Figures 9 to 15.

A chin harness securement means 260 is provided. It consists of chin straps 261 and 262 adjustably secured in the buckles 267 and 268 and extending down on each side of the user's face to a pair of strong rings 264 and 265, to which the straps 261 and 262 are secured e.g. by sewing into a loop through which the ring passes . The chin straps 261 and 262 are attached to the inner liner 230 by some webbing 270 and 271 which is stitched to the inner liner 230 at the temple points 231 and 232 (see Figures 10 and 12) . This webbing 270 and 271 passes down through the buckles 267 and 268 to the chin straps 261 and 262.

The stitching used has to be of sufficient strength and quality to ensure that the chin strap cannot be ripped out of the helmet under the dynamic chin strap test and the roll off test. A typical tensile strength of 850 Newtons in accordance with DIN EN ISO 13935 Pt 1 has been found to be suitable.

Suitable types of stitching are plain type 301 or zig zag or bar tack type in accordance with BS 3870. It is also not desirable to use tight stitching otherwise this will cause the liner to be cut through with excessive perforations. For this stitching, Ticket No. 36 sewing thread to BS 6157 and plain stitched at 3 to 4 stitches per cm using two lines of back stitched stitching 20 mm long gives a breaking strength of 850 Newtons in accordance with DIN EN ISO 13935 Pt 1.

A rear strap 263 which is adjustable in length by means of a buckle 274 (see Figure 13) passes through loop 20

269 and is secured at each end to the rings 264 and 265. The loop 269 is stitched to the inner liner 230 at the rear of the liner (see position 235 on Figure 10) .

A further strap 272 is secured at one end to one ring 265 (see Figure 13) , passes through a moulded plastic chin cup 266 and is removably secured e.g. by a conventional looped pressfit stud arrangement 273 to the other ring 264.

The chin strap has to withstand sufficient load so that the helmet is not easily pulled from the head. The Snell Memorial Foundation test B.95 requires a load of 38 kg dropped from 3 cm without the helmet strap or mounting breaking. Furthermore this invention is intended to be used in combat helmets which are parachutist certified. This can be achieved by a three point harness having two side straps and one rear strap.

The three configurations of chin strap mentioned above can be used.

A head band assembly 280 is also provided. It is based on a loop of strong webbing 285 which passes around the inside of the inner liner 230 and is secured to it adjacent its lower edge. The loop 285 is attached to the inside surface of the inner liner 230 at the front by means of a hook and eye fabric fastener e.g. that sold under the Trade Mark "Velcro ^®" at point 286 and is stitched to the inner liner 230 at the temple points 231 and 232 (see Figure 15) . This stitching may or may not be at the identical position to that which secures the chin straps . Accordingly the head band (and thus the user's head) is held in fixed relationship to the front of the helmet and differences in head size are accommodated at the rear of the helmet. This has the advantage that the users eyes will tend to remain at the same distance from the front of the helmet irrespective of head size.

At the front of the helmet the loop 285 has an additional leather covered foam pad 281 to help the 11 helmet rest more comfortably on the head.

The loop 285 passes through a series of plastic loops 283 and 284 (see Figures 11 and 12) which are attached to the inner liner 230 by stitching at a point backward of the user's ear (see positions 233 and 234 on Figures 12 and 10 respectively) . A typical distance for this stitching 233 and 234 may be 25 mm behind the ear. The plastic loops 283 and 284 are constructed so that they allow the head band 280 to expand or contract but do not allow it to move significantly up or down the head.

At the rear of the helmet the loop 285 is slotted through a rear nape support 282 (see Figure 14) provided by another padded tube.

The head band is adjusted on one side by means of an eye and loop fastener e.g. such as that sold under the

Trade Mark "Velcro ^®" or a flat three bar buckle. This adjustment mechanism is not shown in the accompanying figures .

Adjustment of the head band (as mentioned above) is generated by increasing or decreasing the length of loop 285 whilst keeping the head in the same position at the front. This is highly desirable since it ensures the correct placement of the head of the user relative to the helmet for it to be compatible with modern optical systems.

As can be seen from Figure 11 the embodiment illustrated in the drawings shows a crown assembly consisting of a textile mesh 241.

This textile mesh 241 is particularly suitable as it allows for good distribution of load and minimal thermal build up on the head. The mesh 241 typically consists of a knitted nylon or polyester material arranged in a honeycomb-like structure.

The textile mesh 241 is sewn along its bottom edge at the front to the foam pad 281 of the headband assembly

280. This stitching is shown at position 236 in Figures

11 and 15 and will be of similar form to that attaching 2 the chin straps to the inner liner.

The textile mesh 241 then extends back over the head to three attachment points. These attachments points consist of plastic loops 242, 243 and 244 which are sewn to the inside of the inner liner 230. Loops 242 and 244 may be stitched to the liner 230 at the same positions as the plastic loops 283 and 284 from the headband assembly 280. This is typically 25 mm behind the ear on each side. The loop 243 at the rear may be stitched to the liner 230 at the same position as the loop 269 which is passed through by the rear chin strap 263.

The height of the textile mesh 241 is adjusted by the use of hook and loop fasteners 245, 246 and 247 such as those sold under the Trade Mark "Velcro ^®" which are fed through each plastic loop 242, 243 and 244. The crown assembly 240 is therefore completely adjustable.

Use of the correct textile mesh 241 and a mushroom type fastener to adjust the height of the crown assembly will ensure that this configuration will meet the crown impact test in EN397.

Alternative forms of crown assembly are possible including, for example, webbing straps passing over the top of the head which may be stitched at the front end to the headband assembly and pass through loops at the rear. Adjustment would be in a similar fashion to that described for the textile mesh.

Another alternative would be webbing straps 'attached to the headband assembly at both the front and the rear of the helmet and then passing the straps through a loop at the top of the helmet. Adjustment would be made by varying the length of the loop.

A further alternative would be to bond a soft pad to the inside of the liner in the crown region. Adjustment could be made by increasing the amount of padding included.

The inner liner 230 is also secured to the outer shell 210. The preferred method is by a mechanical II interlock at the lower edge of the helmet. A modification of this is shown in Figure 16A in which adhesive (e.g. as a continuous layer) is located between the inner liner 230 and the outer shell 210 as is shown in Figure 16A.

The inner surface of the outer shell 210 is coated with an adhesive 250 such as two part polyurethane rubber adhesive and the liner 230 is then inserted into the outer shell 210. This adhesive is highly elastic and tacky. Figure 16A shows the layer 250 on an exaggerated scale; typically it will only be 0.05 to 1.0 mm thick. The use of a suitable adhesive increases the ballistic performance of the helmet. The aim is to increase displacement without deformation so that on impact greater protection is provided from more powerful impacts.

Once inside the outer shell 210 the inner liner 230 is further held in position by use of a rubber edge trim 251. This encloses both the inner liner 230 and the outer shell 210 and will be secured to both the outer surface of the outer shell 210 and the inner surface of the inner liner 230 by being a force fit or by adhesive or both.

An alternative arrangement (Figure 16B) shows a rigid moulded plastic or rubber edging strip 251 conforming to the profile of the lower edge of the outer shell 210 and affording a channel shape 252. This is glued to the lower edge 216 of the outer shell 210. This strip 251 extends around the whole or substantially the whole of the edge 216 of the outer shell 210, e.g. at least 70%, preferably 80%, more preferably 90 or at least 95% of the length of the said edge 216. The strip 251 also provides an inwardly and upwardly extending flange 253 adapted to hook substantially over the lower edge of the inner liner 230. The lower edge of the liner 230 is moulded so as to be a close snap or force fit within the channel provided by the flange 253 as shown in Figure 16B. i

The inner liner 230 can thus be provided with the various assemblies 240, 260 and 280 and then slipped into the outer shell 210 at or near the end of the assembly process. It will be appreciated that the inner liner 230 could be secured within the outer shell 210 using a suitable adhesive alone.

A further alternative attachment means could be provided by a lip from the inner liner 230 extending out over the lower lip 216 of the outer shell 210 (see Figure 16C) .

However the type of mechanical attachment described with regard to Fig. 16A is simple and is preferred. It helps provide the enhanced ballistic performance required and is strong and secure under impact .

The assembly procedure for a conventional helmet involves the attachment of a fully finished harness assembly to a fully finished helmet using five screws and five inserts. Other components such as anchor brackets and Ladderlock adjusters are also attached to these screws. Ladderlock type adjusters are commercially available plastic components which are used in adjusting and tensioning the harness. This assembly procedure takes approximately five minutes. The invention as herein disclosed is assembled by fitting a fully assembled liner 230 into the outer shell 210. In the process of the present invention the inner lip 254 of the rubber edging 251 can be pulled outwardly and the inner liner 230 pushed into the outer shell 210. The lip 254 of the edging 251 is then allowed to spring back substantially over the edge of the liner 230 holding it in place. The adhesive 250 is applied to the inside of the outer shell 210 prior to the insertion of the liner 230. This is a much faster process. The head band assembly 280 can be run around the occipital region at the back of the head. This improves the stability of the helmet on the head since the helmet 5 has severely restricted vertical movement as the head band is run around the region of the head just below the widest section.

Ballistic helmets in accordance with the present invention possess a number of advantages as discussed below.

The ballistic performance remains unchanged overall but the ballistic flaw at the bolts is removed.

The comfort remains unchanged overall; however, as the system uses no metallic fasteners or bulky hard plastic fasteners or other metallic components actually inside the helmet there are no parts that could create uncomfortable rubs or pressure points .

Compatibility with accessories remains unchanged and largely depends upon the other equipment in service.

As already mentioned a great advantage is that the liner need only be fitted at the last stage and therefore it can be produced independently of the outer shell of the helmet. Furthermore, with good investment in tooling the manufacturing time of this harness system could be dramatically reduced over a conventional harness assembly.

Adjustment is an important design feature that has been incorporated into our invention as not only does adjustment allow for correct fit it also allows other equipment to be used such as winter caps and respirators . A helmet without adjustment would not be suitable for use as a combat helmet . In the second embodiment the thin nature of the inner liner allows space around the head for extra equipment to be accommodated without discomfort .

The correct choice of materials and manufacturing method will ensure that there is no change in the durability of the helmet. The development of clip on head bands which need no bolting or riveting to the helmet has meant there are many different units such as visors and special optical i equipment that can be quickly and simply attached to the helmet without losing its ballistic integrity.

The centre of gravity remains unchanged.

The full size spectrum from a small female head (51 cm) to a large male head (64 cm) can still be achieved with a maximum of four sizes.

Bulk is not affected.

Systems can be employed in the present design that will allow those parts that are in contact with the head to be removed and replaced.

The basic shape of the helmet will remain and this invention is applicable to all existing shapes of ballistic helmets.

This invention dramatically improves the shock absorption. Firstly, the whole area of the head has a shock attenuating liner which is unlike a lot of other current helmets which only offer protection to the crown e.g. US army PASGT helmet. Secondly, there are no protrusions within the helmet that could cause injury. Thirdly, the avoidance of hard materials within the helmet shell means that the potential dangers of metal fasteners being driven into the skull are eliminated. This is unlike a lot of other current helmets e.g. US army PASGT helmet. Fourthly, the absence of holes means that there are no structural weakness in the shell and therefore the deflection of the shell on impact is improved in these regions. Fifthly there is optionally a layer of high elongation adhesive which helps to provide enhanced ballistic resistance. Lastly, there is no threat of transmitted shock through a metallic fastener.

In its broader aspects the first embodiment extends to four separate aspects which may be used in any compatible combination e.g. first with second or third or fourth; or second with third or fourth; or third with fourth; or first with second and third, or second and fourth or second with third and fourth or preferably all four in combination. According to the first aspect a helmet has an outer shell which is resistant to high and low velocity impacts, a chin strap array for securing the helmet to the head and means for securing the chin strap array to the helmet characterised in that the outer shell is a continuous shell free of apertures, and in that an inner liner is provided which conforms closely to the outer shell, and in that the securing means for the chin strap array are located between the inner liner and the outer shell, and in that the securing means comprise a plurality of strap means spaced around the inner liner and extending up from the lower edge of the liner to retaining means located on the inner liner or between the inner liner and the outer shell, and in that the inner liner is secured to the outer shell by mechanical securing means located at or adjacent the lower edge of the outer shell, the inner liner being of a toughness such that when the helmet suffers an impact the securing means for the chin strap array are retained by the inner liner.

According to the second aspect a helmet has an outer shell which is resistant to high and low velocity impacts, a chin strap array for securing the helmet to the head and means for securing the chin strap array to the helmet characterised in that the outer shell is a continuous shell free of apertures, and in that an inner liner is provided which conforms closely to the outer shell, and in that a head band assembly is secured within the inner liner and in that the front of the headband assembly is secured to the front of the inner liner by headband securement means so as to be held in fixed relationship thereto, the headband assembly being adjustable rearwardly of the front of the inner liner.

According to the third aspect a helmet has an outer shell which is resistant to high and low velocity impacts, a chin strap array for securing the helmet to the head and means for securing the chin strap array to 18 the helmet characterised in that the outer shell is a continuous shell free of apertures, and in that an inner liner is provided which conforms closely to the outer shell, and in that a crown strap assembly is secured within the inner liner.

According to the fourth aspect a helmet has an outer shell which is resistant to high and low velocity impacts, a chin strap array for securing the helmet to the head and means for securing the chin strap array to the helmet characterised in that the outer shell is a continuous shell free of apertures, and in that an inner liner is provided which conforms closely to the outer shell, and in that the inner liner is secured to the outer shell by a mechanical interlock at the lower edge of the inner liner and the lower edge of the outer shell.

Claims

ϋ CLAIMS

1. A ballistic helmet having a ballistic resistant outer shell which is resistant to high and low velocity impacts, a chin strap array for securing the helmet to the head and means for securing the chin strap array to the helmet, in which: the outer shell is a continuous shell free of apertures; an inner liner is provided which conforms closely to the inner surface of the outer shell over at least 70% of the area thereof, the inner liner carrying the means for securing the chin strap array to the helmet; and the inner liner being secured to the outer shell by a mechanical interlock at the lower edge of the inner liner and the lower edge of the outer shell.

2. A helmet as claimed in claim 1 in which: the inner liner is tough and thin and enhances the ballistic resistance of the outer shell; the tough, thin inner liner contacts at least 95% of the inner surface of the outer shell; and the chin strap array is secured to the tough, thin inner liner.

. A helmet as claimed in claim 2 in which adhesive is located between the inner liner and the outer shell .

4. A helmet as claimed in claim 2 or claim 3 in which the chin strap array is secured to the tough, thin inner liner by stitching.

5. A helmet as claimed in one of claims 2 to 4 in which a head band assembly and the crown strap assembly are secured to the tough inner liner by stitching.

6. A helmet as claimed in any one of claims 2 to 5 in which the tough, thin inner liner is constructed from a thermoplastic or thermoset plastic material reinforced with fibres.

7. A helmet as claimed in claim 6 m which the tough, thin inner liner is constructed from a rubber reinforced aramid fabric which has been compression moulded.

8. A helmet as claimed in any one of claims 2 to 7 in which the tough, thin inner liner has a thickness between 0.5 and 3 mm.

9. A helmet as claimed in any one of claims 2 to 8 in which the ratio of the thickness of the inner liner to the outer shell is in the range 1:10 to 1:4.

10. A helmet as claimed in claim 1, in which the securing means for the chin strap array are located between the inner liner and the outer shell; the securing means comprising a plurality of strap means spaced around the inner liner and extending up from the lower edge of the liner to retaining means located on the inner liner or between the inner liner and the outer shell.

11. A helmet as claimed in any one of claims 1 to 10 in which the mechanical interlock is provided by a separate component located on the outer shell and engaging the inner liner.

12. A helmet as claimed in claim 11 in which the separate component is a resilient channel member clipped over the edge of the outer shell and affording a lip engaging the inner liner to hold it within the outer shell when pushed therein.

13. A helmet as claimed in any preceding claim in which the helmet contains a head band assembly secured within the inner liner, the front of the headband assembly being secured to the front of the inner liner by headband securement means so as to be held in fixed relation thereto, the headband assembly being adjustable rearwardly of the front of the inner liner.

1 . A helmet as claimed in claim 13 in which the rear of the headband assembly is stabilised by headband levelling means located at the side of the inner liner.

15. A helmet as claimed in any preceding claim in which the inner liner has a tear strength of at least 750 kPa.

16. A helmet as claimed in any one of the preceding claims in which the inner liner has a tensile strength of at least 690 kPa.

17. A method of assembling a helmet as claimed in any of the preceding claims having a chin strap array, a head band assembly, a crown strap assembly and a mechanical interlock at the lower edge of the outer shell, in which: the chin strap array, the head band assembly and the crown strap assembly are secured to the inner liner; optionally a layer of adhesive is placed between the inner liner and the outer shell; the mechanical interlock at the lower edge of the outer shell is displaced to allow insertion of the inner liner; the complete inner liner is inserted into the outer shell; and the mechanical interlock is established holding the inner liner securely in place.