U.S. patent application number 10/232654 was filed with the patent office on 2003-01-09 for safety helmets with cellular textile composite structure as energy absorber.
This patent application is currently assigned to Lucky Bell Plastic Factory, Ltd.. Invention is credited to Tao, Xiaoming, Xue, Pu, Yu, Tongxi.
Application Number | 20030005511 10/232654 |
Document ID | / |
Family ID | 24924030 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030005511 |
Kind Code |
A1 |
Tao, Xiaoming ; et
al. |
January 9, 2003 |
Safety helmets with cellular textile composite structure as energy
absorber
Abstract
This invention provides a safety helmet in the form of a cycling
helmet or similar. The helmet has an outer shell and an
energy-absorbing liner within the outer shell. The energy-absorbing
liner is provided by a cellular textile material combined with a
matrix material to form a composite. The composite material retains
some porosity from the original textile material to both improve
breathing of the liner and also its capability for large
deformations to improve energy absorption. The liner may also be
provided with a linkage structure to link adjacent cells to improve
the absorption of impact loads over a number of adjacent cells in
the composite material.
Inventors: |
Tao, Xiaoming; (Shatin,
HK) ; Yu, Tongxi; (Shatin, HK) ; Xue, Pu;
(Clear Water Bay Kowloon, HK) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Assignee: |
Lucky Bell Plastic Factory,
Ltd.
|
Family ID: |
24924030 |
Appl. No.: |
10/232654 |
Filed: |
September 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10232654 |
Sep 3, 2002 |
|
|
|
09727779 |
Dec 4, 2000 |
|
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Current U.S.
Class: |
2/411 ; 2/436;
264/257; 425/436R |
Current CPC
Class: |
A42B 3/122 20130101;
B29L 2031/4821 20130101; B29C 70/22 20130101; B29C 70/086 20130101;
A42C 2/00 20130101 |
Class at
Publication: |
2/411 ; 264/257;
2/436; 425/436.00R |
International
Class: |
A42B 003/00; B27N
003/10; B29C 031/00 |
Claims
1. A safety helmet comprising: an outer shell; an energy-absorbing
liner within said outer shell; and wherein said energy-absorbing
liner includes a cellular textile composite material in which at
least a portion is a porous textile material supported in a matrix
material wherein a plurality of pores are retained in said portion
of the composite.
2. A safety helmet as claimed in claim 1 wherein said cellular
textile composite includes a textile fabric and a matrix material
saturating strands of said textile material and retaining pores
between strands of said textile material.
3. A safety helmet as claimed in claim 2 wherein said textile
fabric includes a fabric manufactured from yarns or fibres of
high-density polymeric materials.
4. A safety helmet as claimed in claim 2 wherein said matrix
material comprises a polymer resin.
5. A safety helmet as claimed in claim 1 wherein said cellular
textile composite provides a plurality of cells in the form of
flat-top conical cell structures.
6. A safety helmet as claimed in claim 1 wherein a linkage
structure is provided to link adjacent cells such that impact
energy may be dissapated by a plurality of adjacent cells.
7. A safety helmet as claimed in claim 6 wherein an interlocking
linkage is provided in the form of a reversibly facing nested
textile composite.
8. A safety helmet as claimed in claim 6 wherein a linkage is
provided in the form of a thin layer of material surrounding and
interconnecting individual cells with adjacent cells.
9. A safety helmet as claimed in claim 6 wherein a linkage is
provided in the form of a foam material surrounding individual
cells and interconnecting adjacent cells.
10. A method of manufacturing a liner for a safety helmet
comprising the steps of: providing a sheet of textile fabric;
forming said textile fabric at controlled temperatures to provide a
plurality of projecting cells; forming said fabric with said cells
into a generally hemispherical shape for use as a helmet liner;
forming linkages of adjacent cells; applying resin as a matrix
material at one or more stages throughout the method to form a
textile fabric composite structure retaining a plurality of pores
of the fabric in at least a portion of the resulting composite; and
curing said composite for use as a helmet liner.
11. A method of manufacturing a helmet liner as claimed in claim 10
wherein a flat textile fabric sheet is formed into a substantially
planar preform with projecting cells prior to formation into a
generally hemispherical three-dimensional shape for use as a
liner.
12. A method of manufacturing a liner as claimed in claim 10
wherein a substantially flat textile fabric is applied directly to
a three-dimensional generally hemispherical mold for simultaneous
formation into the generally hemispherical shape for a liner and
formation of the projecting cells.
13. A method of manufacturing a liner as claimed in claim 10
wherein said controlled temperatures comprises controlling the
temperature during formation of the cells to a temperature below
the melting point of the fibres in the textile fabric but above the
glass transition temperature.
14. A method of manufacturing a liner as claimed in claim 10
wherein said step of applying resin as a matrix material is
performed at more than one stage throughout the method.
15. An apparatus for the manufacture of a textile composite
structure for use in a liner of a safety helmet comprising: at
least a first temperature controlled mould having co-operating
moulding services to form a plurality of projecting cells into a
substantially planar sheet of textile fabric; a generally
hemispherical head-shaped base shell having a plurality of
projecting mandrels to receive said textile fabric wherein said
mandrels support some or all of said projecting cells; and means to
apply resin at one or more stages throughout the process to form a
textile composite structure.
16. An apparatus for the manufacture of a textile composite
structure as claimed in claim 15 wherein said generally
hemispherical head-shaped base shell is provided as an inflatable
or compressible base shell that may be collapsed after formation of
the textile composite structure for removal.
17. An apparatus for manufacture of a textile composite structure
as claimed in claim 15 wherein said generally hemispherical
head-shaped base shell is provided as a substantially solid
hemispherical base shell carrying a plurality of mandrels, at least
some of said mandrels being removable to assist in release of the
composite structure from said base shell.
18. An apparatus for the manufacture of a textile composite
structure for use as a liner in a safety helmet comprising: at
least one temperature controlled mould having two co-operating
moulding surfaces having a generally hemispherical head-shaped
configuration and carrying a plurality of mandrels to form a
textile fabric into a generally hemispherical head-shaped structure
and simultaneously form a plurality of projecting cells in said
fabric; and means to apply resin before, during or after said
moulding process.
19. An apparatus for the manufacture of a textile composite
structure as claimed in claim 18 wherein one or both of the
co-operating moulds are provided in connectable portions to form
the generally hemispherical head-shaped surface such that, upon
disconnection, said moulding surface can be removed.
20. An apparatus for the manufacture of a textile composite
structure as claimed in claim 18 or 19 wherein at least a portion
of a surface of one of said moulding surfaces is provided with a
biased portion to assist in the release of the composite structure
from said moulding surface.
Description
BACKGROUND TO THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention is concerned with the design, production
technology, tools and machinery for safety helmets by using
three-dimensional cellular textile composite structures. The
invented safety helmets possess a high specific energy absorption
capacity, a long stroke of impact and constant reaction force
during impact as well as good air permeability.
[0003] 2. Description of Prior Art
[0004] Safety helmets for sports like cycling consist of several
main components and each of them has different functions. The hard
outer shell is used to withstand penetration, abrasion and initial
impact. The common materials used for making the outer hard shell
nowadays including polyvinyl chloride (PVC), etc. The most
important component in the helmet is the shock-absorbing liner that
is used for absorbing and distributing the impact energy. Desired
characteristics of suitable shock-absorbing liner include:
[0005] long stroke with a constant reactive force;
[0006] high specific energy absorption capability;
[0007] permanently deformation with irreversible energy absorption
mechanisms, such as plastic deformation involving fibre and matrix
fracture, fibre/matrix debonding and delamination, etc.
[0008] stable mode of deformation under various impact conditions,
e.g., not adversely affected by dirt, corrosion or other
environmental factors; and
[0009] low costs and ease for manufacturing and maintaining.
[0010] Polyurethane and polystyrene foams are widely used as the
shock absorbers in different aspects due to their shock absorption
capacity, strength and their good adhesion to metal, plastic and
wood. Such as the impact cushioning in dashboards and doors, and
even the sports helmets. The foams compress and/or crack during
impact and slow down the transmission of the impact force, and
hence made them suitable material for using as the shock-absorbing
liner in the helmets. However, the safety helmets utilizing such
foams do not have good air ventilation and are relatively
heavy.
[0011] Two kinds of chemical processes have been commonly applied
into PU foam manufacturing.
[0012] The first one is a one-shot process, exothermic process.
Polyisocyanate, polyol, additives and a blowing agent are combined
together at one time during the process. The foam is either poured
in place or rolled out as a continuous slab.
[0013] The second type is a prepolymer process, which is more
expensive as compared with the previous one. Polyisocyanate or
polyol is used in a preliminary chemical reaction to form long
chemical chains. Then the long-chain polymer is mixed with the
desired additives or blowing agents.
[0014] After foaming, molding occurs by either a pour-in place or
continuous slab process. For the pour-in place process, the
chemical components are mixed in batches and then the mixture is
poured into an opening where it is going to be used. The mixture
then expands and fills in the area. The mixture can usually expand
to about 30-40 times its original volume. The continuous slab
method usually requires a large working area and is more suitable
for high volume production. During the process, the chemical
components are poured and pumped to a mixer head at a fixed rate.
The mixer head is then moved across a conveyor. Through this kind
of process, the foams can have a more uniform density compared with
the foam made by the pour-in place process.
[0015] Four main US standards have been used by the industry for
such helmets. CPSC Bicycle Helmet Standard (1998), "The Final Rule,
Published in the Federal Resister", which becomes law in US after
March 1998, is comparable to ASTM (American Society for Testing and
Materials) Standard. American Society for Testing and Materials
(ASTM), (1995), "Standard Test Methods for Equipment and Produces
used in Evaluating the Performance" has been widely used since
1995. The B-95 standard is established by the Snell Memorial
Foundation. Most helmets with a Snell sticker meet only the earlier
B-90 standard, which is comparable to ASTM. The old American
National Standards Institute (ANSI), Inc., (1984), "American
National Standard for Protective Headgear for Bicyclists" has
become eliminated some years ago.
[0016] According to the CPSC standard, tests should include
peripheral vision, personal stability, retention system and impact
attenuation. The basic set up that is used to test the energy
absorption capacity of the helmet follows the CPSC standard. There
are several kinds of anvil used for testing, including a flat
anvil, hemisphere anvil and a curbstone. The impact velocity used
for the flat anvil test is about 6.2 m/s and the impact velocity
used for the hemisphere and curbstone is about 4.8 n/s. The peak
acceleration should not be greater than 300 g's. The headform used
in the testing should conform to the A, E, J, M or O geometries
specified in ISO DIS 6220-1983. The helmet is strapped on a
headform and turned up side down. The helmet is then dropped in a
guided free-fall on to the anvil.
[0017] Compared to foams, cellular textile composite energy
absorbers are relatively new. Energy absorbing textile composites
can be designed into different structural forms, such as tubes,
plates, shells, as well as cellular structures. The textile
composites compose of textiles as reinforcing material and a matrix
system. The reinforcing textiles can be in many shapes and forms,
such as continuous filaments, chopped strands, mats, various fabric
structures, which in many cases, are made from glass, carbon,
ceramics, aromatic, ultra high molecular weight polymeric or
metallic fibres. The matrix material is typically a thermosetting
or thermoplastic polymer such as epoxy, polyester, polypropylene,
polyurethane, polyamides, polyvinylester, etc.
[0018] The processing idea of manufacturing a flat panel of
three-dimensional cells by using textile materials is disclosed in
U.S. Pat. No. 5,364,686 by D. Disselbeck. It describes a process
for manufacturing a dimensionally stable, three-dimensionally
shaped, sheet-like textile material using one or more layers of a
deep-drawable textile material, preferably a knitted material. This
textile structure is constructed from reinforcing fibres and a
thermoplastic matrix material in fibre form. Several steps are
taken to produce such a composite material. The material is first
heated to a lower temperature than the melting temperature
reinforcing fibres and formed into the shape desired for the core
material by an area-enlarging shaping process, for example by deep
drawing. The temperature is then reduced to below the melting point
of the thermoplastic matrix material and keeping the shaped
material in the mold until the thermoplastic matrix material has
been sufficiently hardened. Demolding is the last step to give the
resulting shaped textile material.
[0019] Similar patent is also found in U.S. Pat. No. 5,731,062 by
Kim et al. Three-dimensional fibre networks were made in a
semirigid and dimensionally stable form from textile fabrics that
have regular conical projections and optional depressions which are
compressible and return to their original shape after being
compressed. The fibre networks are made by the thermo-mechanical
deformation of textile fabrics that are in turn made from
thermoplastic fibres. The fibre networks have flexibility to be
used as cushioning and impact absorbing materials. In making these
structural fibre network to textle composites, the two-dimensional
textile fabric that is utilized in making the three-dimensional
composite structures is selected from some simple classes of
fabrics, such as knit, woven or non-woven textile fabrics.
[0020] The idea of three-dimensional textile composite structure
was used in producing a cushioning inlay of shoes in U.S. Pat. No.
5,896,680 by Kim et at. A shoe midsole is made from the formed
fibre network with projections of varying size to contour to the
shape of the bottom of the foot. This fibre network is made from a
textile fabric that has an array of projections made from the same
fabric rising from the plane of the fabric.
[0021] Similar inventions of such structural projections from a
textile material were also found in EP 0559969A1, entitled
"Embossed Fabric, Process for Preparing the Same and Devices
Therefor; EP 0469558A1, entitled "Formable Textile Material and the
Shape of the Mould Obtained"; and EP 0386687B1, entitled "Web-Like
Boundary Layer Connection and Method to Make Same".
[0022] In U.S. Pat. No. 4,890,877 by A. Zarandi et al., a shaped
energy-absorbing panel is used on a vehicle door. It is a
stretchable lightweight resin coated fabric having a plurality of
spaced apart circular conical projections rising from the planar
sheet. The stretching effect is achieved by using weft knit plain
fabric and warp knit fabric. Several molded panels were cut in a
size and shape of the desired energy absorbing panel structure and
assembled with adhesive coated interface panels to give the desired
thickness of the energy absorbing panel structure. The energy
absorbing structure is then mounted on a vehicle door above the arm
rest and below the window opering between the door trim panel and
the door inner panel to absorb energy in the event that the
occupant contacts the door inner panel.
[0023] Another invention U.S. Pat. No. 5,435,619 by Nakae et al.
was also found demonstrating a different design modification to the
energy absorber in an automobile door. The purposes of the
invention was to improve the shock absorbing characteristics and to
reduce the weight of an automobile door. The shock absorber
consists of a plurality of tiered foam main members, and
polypropylene resin foam auxiliary members disposed between and
connecting the main members to form chambers open transverse to the
direction along which the main members are tiered. The connecting
members were modified having semicircular ridges, wave-like form
and sectional squared ridges.
[0024] The previously mentioned cellular composites are flat panels
provided as solid structures. Holes for voids are revoided in such
structures with the matrix material providing a solid panel in
casing and interconnecting all the strands. There is no porosity
retained from the original textile material. Such composites have
disadvantages when considered for use in items such as safety
helmets.
[0025] One disadvantage of such composite materials is that they do
not provide particularly large in-plane plastic deformation. The
reactive pore sets to be higher in order to absorb the required
impact energy.
[0026] A further disadvantage is that the lack of porosity leads to
a compropably heavier composite structure and the structure is
unable to breathe or provide any form of air ventilation.
[0027] A further disadvantage with such solid composite structures
is that, when used to make a three-dimensional shaped item such as
a safety helmet or liner for such a helmet, the energy absorption
behaviour under impact may be relatively poor and even worse than
that of a flat panel made from the same material. With such safety
helmets or liners being generally hemispherical and providing
curved surfaces, relatively a few composite cells are involved in
the dynamic response to any impact.
OBJECT OF THE INVENTION
[0028] It is an object of the present invention to provide a safety
helmet and methods of manufacture thereof that overcome some of the
disadvantages of prior art helmets and manufacturing methods or at
least provide the public with a useful choice.
SUMMARY OF THE INVENTION
[0029] Accordingly, in a first aspect, the invention may broadly be
said to consist in a safety helmet comprising:
[0030] an outer shell;
[0031] an energy-absorbing liner within said outer shell; and
[0032] wherein said energy-absorbing liner includes a cellular
textile composite material in which at least a portion is a porous
textile material supported in a matrix material wherein a plurality
of pores are retained in said portion of the composite.
[0033] Accordingly, in a second aspect, the invention may broadly
be said to consist in a method of manufacturing a liner for a
safety helmet comprising the steps of:
[0034] providing a sheet of textile fabric;
[0035] forming said textile fabric at controlled temperatures to
provide a plurality of projecting cells;
[0036] forming said fabric with said cells into a generally
hemispherical shape for use as a helmet liner;
[0037] forming linkages of adjacent cells;
[0038] applying resin as a matrix material at one or more stages
throughout the method to form a textile fabric composite structure
retaining a plurality of pores of the fabric in at least a portion
of the resulting composite; and
[0039] curing said composite for use as a helmet liner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Preferred embodiments of the invention will now be described
with reference to the following drawings in which:
[0041] FIGS. 1a to 1e are plan views of portions of textile fabrics
that may be used in embodiments of the invention;
[0042] FIG. 2a shows cross-sectional views through various cellular
structures that may be formed as part of the invention;
[0043] FIG. 2b shows a sketch of a rigid-plastic deformation model
of a cell;
[0044] FIG. 2c shows a horizontal circumferential hinge line of the
model of FIG. 2b;
[0045] FIGS. 3a to 3d show cross-sectional views through various
linkages of cellular composites;
[0046] FIGS. 4a to 4c show cross-sectional views through various
liners made by composite structures with a variety of linkages as
shown in FIG. 3;
[0047] FIGS. 5a to 5c show cross-sectional views through helmets
incorporating the composite structures with a variety of linkages
from FIG. 4;
[0048] FIGS. 6a and 6b show the flowcharts of a two-step and a
single step fabrication process respectively;
[0049] FIG. 7a is a schematic view of a process for making liners
using a two step process;
[0050] FIGS. 7b to 7c show cross-sectional views through alternate
flexible and fixed tooling for the head shape formation of a liner
being part of the two-step process of FIG. 7a;
[0051] FIGS. 8a to 8d show views of alternate tooling for a single
step process; and
[0052] FIG. 9 shows a porous textile composite forming part of the
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0053] Referring to the drawings, the invention relates to a safety
helmet 1 that, in the preferred form may comprise a bicycle helmet.
It should be noted that the same technology and invention may be
applied to other safety helmets including motorcycle helmets,
construction work place helmets or any other helmet where impact
absorption is required.
[0054] Bicycle helmets and safety helmets in general comprise a
relatively hard outer shell 2 with an inner liner 3 of energy
absorbing material. The hard outer shell may assist with
penetrative attack and assist to distribute load to the energy
absorption layer underneath in the case of impact resistance.
[0055] This invention provides safety helmets that utilize textile
composite materials in the formation of the energy absorption layer
or liner 3.
[0056] The textile composite materials include a textile 4 and a
matrix system 5. The textile material is coated or bound by the
matrix system to provide the overall composite.
[0057] Referring to FIGS. 1a to 1e, a variety of different textile
materials are shown that can be used in various embodiments of the
invention. The first four of these examples in FIGS. 1a to 1d
comprise knitted or woven structures exhibited as an interlocking
structure in FIG. 1a, a full millano structure in FIG. 1(b), a rib
structure in FIG. 1c and a tricot warp knitted structure in FIG.
1d. By way of contrast, FIG. 1e shows a non-woven structure
comprising a plurality of strands 6 of material.
[0058] Materials for the production of the textiles may vary.
Generally for the manufacture and performance of such textile
composite materials, the individual strands 6 in the woven or
non-woven fabrics are likely to comprise strands of fibre glass,
carbon, ceramics, aromatic fibres, ultra high molecular weight
polymeric fibres or metallic fibres. A variety of yarns can be used
including flat continuous filament yarns, textured filament yarns
and staple yarns. A mixture of these materials may be used in a
single yarn if desired. Preferably, fibres with good mechanical
properties for energy absorption and processing are used such as
high-density polyethylene, polyester, nylon, etc. The yarn can be
straight or textured including crimped or deformed yarns. The
textured yarns may be preferred for the large deformation needed
through formation and for better matrix penetration.
[0059] Where the woven fabrics are likely to use staple or
continuous filaments in the weaving or knitting process, the
non-woven structures may use chopped strands or shorter filaments.
The preferred may be textured stretchable continuous yarns of nylon
or polyester or similar.
[0060] The matrix material to surround and set the composite may be
typically provided by a thermosetting or thermoplastic polymer.
Various resins may be used such as epoxy, polyester, polypropylene,
polyurethane, polyamides, polyvinylester, polycarbonate and other
such polymer resins. In one specific example, polyester resin with
1% methylethyl ketone peroxide (MEKP) as the initiator and 0.5%
cobalt naphthenate as the accelerator was used.
[0061] The textile material and the matrix material may be combined
into a composite into numerous different forms. The formation
method of the composite will be explained later in more detail
although various structures that may result are shown in FIG. 2a as
structures 7, 8, 9, 10, 11 and 12. The textile composites are
formed to retain a plurality of pores, holes or voids by
controlling the resin application process, fabric structure and
fibre surface properties. The voids allow large in-plane
deformation for better energy absorption and air ventilation.
[0062] The structure 7 is a dome-topped wall structure. This
provides a substantially hemispherical or domed configuration on
top of a conical wall section.
[0063] The structures 8, 9 and 10 all show a variety of cell
structures that may be formed providing compression resistance
between the walls of the cells to provide the impact
absorption.
[0064] Structure 11 demonstrates a possible non-woven structure.
Although non-woven structures may be provided in a variety of
forms, simplified structures may be preferred to account for any
irregularities due to the short filaments or strand lengths that
may be incorporated in such a structure.
[0065] The structure 12 shows a truncated conical structure similar
to structure 7 but with a flat top instead of the hemispherical or
domed upper surface to the cell.
[0066] Although any of these structures may be used in the impact
absorption layer, the preferred form utilizes an open cell
structure such as those shown as structures 7, 11 or 12 and, most
preferably, a flat-top conical cell structure 12.
[0067] FIGS. 2b and 2c show sketch of the rigid-plastic deformation
model of a cell and a horizontal circumferential hinge line of the
model respectively. These may be typical models based on a cellular
structure such as the structure 12 in FIG. 2a.
[0068] The cellular textile composite structures formed in this
invention all retain some porosity from the original textile fabric
or provide apertures, holes or pores between strands. The
importance of a substantial number of such pores eyes in the
synergistic affect of providing both air ventilation and ability
for the material to breathe as well as an improved energy
absorption profile from the material. The retention of the porosity
allows for plastic deformation between the strands in the form of a
plastic hinge as opposed to the comprobably little structures
incapable of large in-plane deformation that have been provided as
composite structures in the past. The structure may include a
portion of the porous composite and some solid composites as well
in other embodiments.
[0069] An example of the porous textile composite is illustrated in
the attached diagram. The size and distribution of pores can be
controlled by the combinations of the fibre surface tension, yarn
structure, tension applied during curing process, as well as resin
add-on ratio. In this particular case, a textured continuous nylon
multi-filament yarn was used to knit the interlock fabric. An
unsaturated polyester resin was applied to the tension free fabric
and cured at the room ambient temperature. The resin add-on ratio
was 160%.
[0070] In completing the liner 3, the textile composite material
may be provided with a linkage to assist in the support and
distribution of forces between the cells and to act as a convenient
fixing point for the outer shell and any inner material that may be
used as a final liner inside the helmet.
[0071] A variety of different forms of linkage may be used to
assist in the production of the overall liner. FIG. 3a shows two
layers of textile composite material 14 and 15 that are nested one
within the other. Both layers 14 and 15 may be substantially
similar configurations as shown in FIG. 3a with one layer being
reversed to nest within the other.
[0072] FIG. 3b shows an alternative linkage in which a textile
composite layer 16 is provided with a thin layer 17 placed about
each of the truncated conical cell projections in the layer. In the
preferred form, this layer may be placed at approximately the 2/3
height of the cell.
[0073] A yet further alternative is shown in FIG. 3c where a foam
linkage of greater depth is used to surround each truncated conical
projection. The foam 18 may be placed to progress and rest upon a
base 19 around each of the conical projections.
[0074] A yet further alternative is shown in FIG. 3d in which two
substantially similar textile composite layers 20 and 21 are placed
back to back such that the projections opposed each other.
[0075] The linkages shown in the various versions of FIG. 3 play an
important role in the performance of the helmet liner as a whole.
The linkages provide some interconnection between adjacent cells in
the structure so as to provide a greater dispersion of the impact
energy such that it may be absorbed over a greater number of cells.
The performance of the liner under impact can be greatly enhanced
by such a linkage.
[0076] Such linkages may not be used or necessary with the
substantially on porous solid structures provided as composite
structures in the past. However, with the present invention relied
on greater energy absorption from large scale in-plane deformation,
this deformation can be greatly enhanced by the use of a linkage
that spreads the impact over a number of cells and can do so by
mechanical connection between the cells that due to the relatively
high level of deformation possible from such porous cellular
composite structures.
[0077] Referring to FIG. 4, a liner utilizing the thin layer, foam
and interlocking linkages is demonstrated in FIGS. 4a, b and c
respectively. It is noted that each liner 3 is shown in a
substantially hemispherical configuration for fitment inside a
helmet.
[0078] FIG. 5a demonstrates the construction of a helmet 1
utilizing the interlocking linkage as shown in FIGS. 3a and 4c. The
helmet 1 provides a hard outer shell 2 and the interlocking textile
composite layers, with the projecting cells interlocking in between
each other. The textile composite layers 14 and 15 are shown
individually in an exploded form and in combination within the
completed helmet cross-section.
[0079] In addition to the placement of the liner within the outer
shell 2, an additional inner liner, material or, in this preferred
embodiment, plurality of pads 22 may be provided for greater
comfort against the head of a user.
[0080] A yet further helmet construction is shown in FIG. 5b, in
this case utilizing a foam linkage 18 in conjunction with the
textile composite, the outer shell 2 and the pads 22 in which the
same manner as the construction in FIG. 5a.
[0081] It should be noted that additional buttons or fixings 23 may
be provided. These buttons or fixings 23 may be placed
intermittently over projections from the textile composite to
provide a greater surface area for attachment of the outer shell to
the composite liner. This may be required in this instance as the
foam linkage 18 is not provided to the full depth of the conical
projection.
[0082] FIG. 5c shows a yet further alternative utilizing the thin
layer linkage together with the textile composite layer in
formation of the liner. As with the previous embodiment, buttons 23
may be used for further attachment of the outer hard shell 2.
[0083] As shown, the thin layer linkage 17 may be placed about the
projections from the textile composite layer with the buttons 23
placed between the thin layer linkage and the outer shell at
particular intervals.
[0084] FIG. 6a shows the flowchart of a two-step fabrication
process. In this process, the flat panel with protruding cells may
burst and then followed by a second step of shaping it into a
generally hemispherical head shape. Resin can be added at various
points throughout the process and the linkages can be applied at or
after the curing stage of the process.
[0085] FIG. 6b illustrates a single-step processing route where the
hemispherical head shape composite structure with protruding cells
is formed in a single step from a flat sheet of textile material.
The resin can be applied before, during or after the forming
process. If applied after the formation of the cells, alternative
methods like resin transfer or low pressure assisted resin transfer
moulding can be used.
[0086] Although the single step processing route may buy some speed
advantages, the tooling is generally more complex.
[0087] It should be noted that the introduction of resin before or
at multiple stages during the manufacturing process can provide
some advantages in reducing the curing time. This may prove
particularly important on processors in which the old or a base
shell is required to be retained with the composite during curing.
Actually, a reduced curing time reduces the number of such moulds
or base shells necessary to be in use to maintain a particular
target production rate.
[0088] The curing times can vary according to the methods by which
the resin is introduced and can vary from twelve minutes to one and
a half hours on different production routes buy thus far. Further
reduction of the curing time may be possible.
[0089] Referring to the FIGS. 6a and 6b, it should be noted that
the addition of resin is generally expressed in the alternative at
points 1, 2 and 3 in FIG. 6a and points 1 and 2 in FIG. 6b. In many
cases, it may be desirable to progressively add resin at more than
one point throughout the process rather than purely at alternative
points.
[0090] FIG. 7a provides a schematic view of the apparatus and
process used in the two-step manufacture of a composite textile for
use as a liner.
[0091] Referring to FIG. 7b, a suitable textile fabric 30 may be
introduced to the process and passed through an initial heater 31
to heat the fabric for easier formation. The preheating 31 assists
in formation although may be used in conjunction with a heater 32
in a suitable mold press 33 to raise the fabric to its ideal
formation temperature. Preferably, this temperature would be below
the melting point of the fibre but above the glass transition
temperature.
[0092] The mold press 33 provides an upper and lower mold 34 and 35
respectively that may be brought together by means of a suitable
mechanism such as a hydraulic press 36 to form the fabric into flat
fabric panels (preforms) with the cells protruding from one side of
the panel.
[0093] As this may be done to a large two-dimensional sheet, the
sheet may then be cut and trimmed into the desired shape for a
single liner by a suitable cutting or trimming apparatus 37.
[0094] The formed two-dimensional fabric may then be placed onto a
three-dimensional mold 38 so that it may be formed into the
suitably generally hemispherical shape required for fitment inside
the helmet. The mandrels may support the formed cells and resin may
be provided by, for example, a resin sprayer 40.
[0095] The sprayed composite fabric, still on the mold 38 may then
be suitably cured, and to the extent that a specific curing
temperature or atmospheric condition is desired, a specific curing
box or room 41 may be provided.
[0096] Referring again to the two-dimensional preformation of the
sample as shown in FIG. 7a, a preform 90 may be introduced to
suitable tooling as shown in FIG. 7b.
[0097] In this process, the mandrels 92 may be carried on a
flexible mold 93. Compressed air may be introduced through an inlet
94 to expand the flexible mold 93 into the desired generally
hemispherical shape, the preform 90 may be put onto the mold and
resin added. Once cured, the compressed air may be released and the
resultant product 96 easily removed.
[0098] A valve 95 may be provided so that, once the compressed air
is added, the inlet 94 may be closed and there is no need to
maintain air at the inlet 94 during the curing process.
[0099] In FIG. 7c, the preformed sample 100 is shown having been
cut into a suitable shape to complete a generally hemispherical
liner. The portions making the preform 100 may include connection
points 101 as shown. The preform 100 may then be fitted onto a
suitable mold 102 and held by fixing pegs 103 while the resin is
supplied by a resin sprayer 104.
[0100] An alternative method of formation is to form the fabric
from a flat sheet without cells directly into the
three-dimensionally generally hemispherical shape necessary for
production of the liner. This alternative three-dimensional forming
system may follow some of the same general steps as the
two-dimensional forming system described previously. Again the
fabric may be preheated together with heating of the molds to
generate sufficient temperature for easy forming of the fabric. The
fabric may be precut into the necessary area for fitment to a
three-dimensional mold suitable for production of a single cellular
composite for a helmet liner.
[0101] FIGS. 8a to 8d provide examples of tools for the single-step
process.
[0102] Referring to FIG. 8a, tooling for the formation of the
three-dimensional composite structure is shown in both completed
form as mold 50 and in an exploded form. The mold may provide a
base shell 51 onto which the bottom mold 52 is fitted. The bottom
mold 52 may be formed in sections for fitment around the base shell
51 and include a releasing shell 53 that may be provided with
biasing means 54 in the form of a spring or similar to assist in
the release of the formed composite from the mold.
[0103] Like the lower mold, the upper mold 55 may also be formed in
segments and carry mandrels 56 to make the three-dimensional cell
structures from the flat fabric provided. Suitable connections 57
may be provided between the components of the upper mold to keep
the mold in place and in connection with the base shell or lower
mold. This may then be placed into an autoclave machine for setting
the fabric and resin may be added.
[0104] A yet further mold configuration is shown in FIG. 8b. In
this configuration, the mold comprises an inner shell 60 and an
outer shell 61. At least the inner shell 60 may be formed in a
number of segments.
[0105] The mandrels 62 can be added through a shell 63 containing
air nozzles. The air may then be vacummized and the air nozzles
shut. The entire set up can then be placed into an oven for heating
in order to form the fabric into a suitable structure.
[0106] A yet further configuration is shown in FIG. 8c. In this
configuration, a top mold 70 is again provided in a plurality of
segments that may include suitable connection means 71. The lower
mold 72 is provided with a releasing shell 73 suitably biased by
biasing means 74. The bottom mold may be placed around a rubber bag
or similar expandable diaphragm 75 and compressed air introduced
through inlet 76 on a base support 77 so as to inflate the
diaphragm 75 within the bottom mold 72. This will push the bottom
mold 72 towards the top mold to form the product.
[0107] A yet further mold design is shown in FIG. 8d. In this case,
a base support 80 supports a bottom shell 81. Within the shell 81,
the bottom mold 82 carrying mandrels 83 may be placed and it will
be again noted that this bottom mold 82 is provided in a plurality
of segments.
[0108] A segmented top mold 84 can be positioned to co-operate with
the bottom mold in the formation of the product and a top shell 85
used to support the top mold 84. A hinged joint 86 can be used to
bring the top shell 85 and bottom shell 81 together and compress
the top and bottom molds therebetween.
[0109] Following completion of the formation of a suitable liner
sample in accordance with the various alternative processes, the
linkage structure may be applied and the pads and/or buttons as
required and the completed liner may then be fixed into the outer
shell to complete the helmet.
[0110] Thus it can be seen that this invention describes a safety
helmet that includes a textile composite liner. The provision of
linkage components with the liner assist in distributing loads over
the various cells and the cellular textile liner as a whole may
provide an improved energy-absorption capability as well as better
ventilation and the advantages over prior safety helmet liners.
[0111] The preferred embodiments of this invention have been
described with reference to specific integers and it will be
appreciated by those skilled in the art that many variations could
apply. The reference to specific integers is deemed to incorporate
known equivalents where appropriate. The description of the
preferred embodiments is not to be considered limiting to the
generality of the invention as defined in the appended claims.
* * * * *