Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
Hockey stick blade and a method of making thereof
FIELD OF THE INVENTION
[0001] The present invention relates to hockey sticks. More
specifically, the present invention is concerned with a hockey stick blade and
a
method of making such a blade.
BACKGROUND OF THE INVENTION
[0002] As is now well established in the art, the blade, as the hockey
stick's striking surface, is a part submitted to extreme load conditions
during
shots like a slap shot, for example. The blade may be submitted to impact,
torsion, bending, tension and shearing forces.
[0003] Current methods of making hockey stick blades tend to meet
requirements resulting from such a range of forces to which the blades are
submitted, by resorting to different types of structures, including for
example,
monobloc structures, sandwich structures and reinforced structures. Such
methods yield blades having a weight essentially proportionate to the
respective weight of the materials used, and usually fail to provide an
optimized
combination of minimum weight and maximum stiffness/strength.
[0004] For example, in the case of sandwich-type blades, a main
weakness and a reduced service life are related to a non-satisfactory quality
of
the joining step or of the gluing step between a core and outer walls, thus
resulting in a tendency to delaminate, peel or tear. As soon as peeling
initiates,
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for example, the mechanical properties of the blade as a whole are reduced,
thereby jeopardizing the quality of the hockey stick itself.
(0005] Efforts to optimize a long-term strength of sandwich-type
blades have involved using braids around the core of the sandwich structure,
which results in an effective increase of strength and life limit of so-called
high-
performance blades.
[0006] A method of fabricating such a high performance blade
standardly comprises providing two longitudinal semi-cores made in foam,
pulling on each semi-core a generally tubular jacket made of reinforcing
fibers,
pulling a third generally tubular jacket made of reinforcing fibers on the two
semi-cores individually wrapped and located longitudinally side-by-side, and
impregnating a resulting assembly with resin, thereby yielding a sandwich-type
beam comprising a full core extending from a first edge to a second edge
thereof across the whole width thereof. Then, a molding step yields a blade,
the
performances of which depend on the quality of the assembly between the two
semi-cores and on an adhesion quality between the two semi-core assembly
and outer walls. Such method may be found described in U.S. patent No.
6,918,847 issued July 17, 2005 to Gans.
(0007] The above efforts still fail as far as the weight problem is
concerned. A minimized weight is all the more critical since synthetic fibers
now
allow making increasingly light synthetic fibers shafts for hockey sticks. It
has
been noted that assembling a light shaft and a relatively heavy blade results
in
an unbalanced hockey stick, which is unacceptable in the field of high-
performance hockey.
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(0008] Therefore, there is need in the art for a hockey stick blade
obviating the current drawbacks.
[0009] Conventional molding techniques used to fabricate composite
blade for hockey stick comprising a core made of foam reinforced with layers
of
fibers of carbon, kevlar, polyethylene or glass are in general obtained by a
close-mold process.
[0010] The pre-assembly of "the foam insert - reinforcing fibers"
having the general shape of a straight hockey stick blade is positioned inside
a
two-part mold in which, in a second step, a liquid polymeric resin is injected
under pressure and or vacuum. Under injection pressure and/or vacuum, the
liquid resin will impregnate the entire pre-assembly of foam-carbon fibers and
solidify after under chemical reaction, commonly called polymerization or
cross-
linking. The negative particularity of such molding technology is the fact
that,
when the pre-assembly of the foam insert around which the carbon fiber cloth
or braid is positioned inside the cavity portion of the mold, there is no
specific
fiber strengthening or specific fiber alignment. The dry fiber clothe or braid
is
relatively loose and it is in this state that it will be resin impregnated
after mold
closing and resin injection, thus generating wrinkles, for example, and non
uniform adherence with the foam core. Such situation results in a molded
blade in which the continuous reinforcing fibers are not well aligned and
relatively misoriented inside the solidified resin matrix.
(0011] The same situation exists when molders use "prepreg"
instead of dry reinforcement. Prepreg is a form of material combining, in a
semi-solidified state, fiber reinforcement and resin matrix, ready to mold
only
under pressure and heat in a close-mold process.
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[0012] In this particular case, the fiber-braided envelope will be slid
over the foam cores assembly and, after mold closing under pressure, only
heat will be applied to solidify the blade assembly.
[0013] When, in use, the molded blade is put under stress, such as
during a slap shot or equivalent, the not well aligned and/or not-straightened
reinforcing fibers are not reacting instantaneously to generate the optimum or
acceleration or impulse to the puck.
[0014] Under the striking or impact energy generated by the player,
the molded blade will, in that particular situation, deflect more prior to
absorb
energy and finally react with less speed to kick the puck at the speed
anticipated.
[0015] Therefore, molding hockey stick blades according to the
conventional close-mold technology does not generate an optimum stiffness,
which is a main factor required to totally convert the induced energy by the
player into puck speed.
[0016] The extra blade deflection, when subjected to load and due to
carbon fiber molded state (unstraightened and misoriented), is a serious
handicap to optimize puck speed in a slap shot, for example.
SUMMARY OF THE INVENTION
[0017] The present invention concerns an improved hockey stick
blade with added strength and/or stiffness and a method of making thereof.
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[0018] The present invention therefore provides a hockey stick blade
which comprises:
a) a shaft connecting portion;
b) a heel portion;
c) a puck contacting portion consisting of
i) a central core formed of light weight material
defining longitudinal spaced apart sections defining
longitudinal cavities therebetween;
ii) a jacket of fiber braid wrapped around the core;
iii) a polymeric material encapsulating the core and
jacket to form a molded blade part having opposite
sides; and
iv) a cover plate of composite polymeric material
secured to one of the opposite side faces of the
molded blade.
(0019] The present invention is thus concerned in eliminating the
above problems of misaligned and unstraightened continuous reinforcing fibers
inside the molded laminate. This is achieved, instead of using a full size
foam '
core (full height), by using a partly filled foam core defining longitudinal
cavities
inside the blade assembly.
[0020] When combining the partly filled foam core with fiber braids,
the tubular jacket made of continuous fibers completely wraps the blade thus
providing a continuity of fibers on the full perimeter of the blade while
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encapsulating the core parts located at specific localizations. Hence, this
molded blade may be seen as comprising a central beam with localized
longitudinal reinforcing ribs between the foam insert.
[0021] The added strength and/or stiffness to the molded blade is
due to the following. The final braided tubular jacket is positioned over the
foam core prior to be installed in the mold to receive its resin injection.
Mold
closing will generate a tensioning and an alignment of the fibers due to the
presence of the longitudinal cavities inside the foam core. This phenomenon of
tensioning the tubular jacket results from the fact that the molded jacket
perimeter is 10 to 20% (depending on the location on the blade) longer than
the
exterior perimeter of a conventional blade assembly. This extra perimeter is
obtained by an alignment effect because the reinforcing fibers of the laminate
are continuous and cannot elastically stretch or deform axially. Under mold
closing the fiber braids are forced inside the longitudinal cavities resulting
in a
pre-tensioning, straightening and a full contact with the foam core exterior
surface.
[0022] More precisely, such fiber alignment results from a
reorientation of the fiber braids being a particularity of that type of fiber
weaving.
[0023] With the present invention, when the mold is closed over the
foam-core assembly, the outer tubular braid will react by a braid alignment
change to allow its penetration inside the longitudinal cavities requiring a
larger
circumference coverage than the one of a standard blade circumference. This
concept of using the mold closing step to pre-tension and realign the
wraparound continuous fibers results in reducing the area of foam core bonding
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surface and generating locally a direct liaison between the two blade
laminates
(front and rear surfaces) specifically located inside the core cavities.
[0024] It is well known in the composite sandwich structure industry
that the main weakness of this type of construction is the potential debonding
phenomenon between the laminate skins and the foam core. A conventional
hockey blade composed of a full size foam core having, at its surfaces, a
molded laminate will first fail by debonding and this phenomenon is directly
related to the bonded area exposed to impact load and stresses.
[0025] Reducing the importance of the foam surface area and
joining the front and rear laminate skins at specific localizations will
improve
blade performance. Also, the cavity area of the core now includes structural
ribs due to the hardened laminate braid structure therein; hence, there is no
weight penalty or localized weaknesses due to discontinuity of foam core.
[0026] When molded blades resulting from the present concept are
put under impact load or high-speed flexural loading, the added rigidity of
the
blade allows immediate energy loading with minimum deflection to
subsequently return (restitute) the maximum energy to the puck under speed
(minimum loss of energy).
[0027] There is no soft deflection of blade due to misaligned or
misoriented or unstraightened continuous fibers in the molded laminate, which
is situation delaying energy build up prior to energy restitution.
[0028] This concept of using mold closing to force the outer braided
fiber envelope to realign and stretch to its maximum capacity can be utilized
with the following molding technology.
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[0029] A) The pre-assembled envelope and foam cores are
laid down in the mold prior to being impregnated
with liquid resin and solidity.
[0030] B) The fiber envelope is in a prepreg state, which
means that the resin matrix is already incorporated
inside the fiber architecture, resin matrix in a semi-
solid or semi-rigidified prior to be used for molding.
[0031] The present invention therefore concerns a method of making
a hockey stick blade consisting of a shaft connecting portion, a heel portion
and
a puck contacting portion comprising the steps of:
a) sliding a fiber braided jacket over a core formed of light
weight material and including longitudinal spaced apart
sections defining a longitudinal cavities therebetween;
b) positionning the jacket with the foam core in a female part
of a mold having the shape of a blade;
c) closing a male part of the mold whereby the fibers of the
jacket are placed under tension and aligned during mold
closing due to the presence of the longitudinal cavities
inside the core;
d) injecting a polymeric material in the mold to impregnate the
jacket;
e) applying heat and pressure to the mold containing the
impregnated jacket to form, after curing and mold opening,
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a molded blade part having, on one side thereof, aligned
and straightened fibers encapsulated therein; and
f) securing a cover plate over said one side of the molded
blade part.
[0032] Another method of making a blade in accordance with the
present invention includes the following steps:
a) sliding a resin-impregnated fiber braided jacket or prepreg
cloth over a core formed of light weight material and including
longitudinal spaced apart sections defining a longitudinal
cavities therebetween;
b) positionning the jacket or cloth with the core in a female part of
a mold having the shape of a blade;
c) closing a male part of the mold whereby the fibers of the
jacket or the cloth are placed under tension and aligned during
mold closing due to the presence of the longitudinal cavities
inside the core;
d) applying heat and pressure to the mold containing the
impregnated jacket or cloth to form, after curing and mold
opening, a molded blade part having aligned and straightened
fibers encapsulated therein; and
e) securing a cover plate over one side of the molded blade part.
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[0033] Other objects, advantages and features of the present
invention will become more apparent upon reading of the following non-
restrictive description of embodiments thereof, given by way of example only
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] In the appended drawings:
[0035] Figure 1 is a general view of a hockey stick;
j0036] Figure 2 is an exploded close-up view of the blade of the
hockey stick of Figure 1;
[0037] Figure 3 is a cross section of the blade of the hockey stick of
Figure 1;
[0038] Figure 4 is a cross-sectional diagram showing the blade-
making step prior to molding; and
[0039] Figure 5 is a perspective view of a hockey stick blade having
a different cover plate.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0040] This present invention is concerned in providing a hockey
stick blade 10 such as that illustrated in Figures 1 and 2 which is mounted to
a
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hockey stick shaft 11. The blade 10 includes a shaft connecting portion 10a, a
heel portion 10b and a puck contacting portion 1 Oc.
[0041] As illustrated also in Figure 3, the blade portion 10c
comprises a core 12 formed of light weight material, such as low-density foam
or carbon, and a tubular fiber braid jacket 16.
[0042] In the present embodiments, the core 12 is formed of three
longitudinal spaced-apart sections 12a, 12b, 12c, onto which the fiber braid
jacket 16 has been pulled or slid. Core section 12a is located at about the
middle of the blade while core sections 12b and 12 are respectively located at
the bottom and at the top of the blade. Each section may have a selected
width. A combined height of these three sections may represent about half the
height of the blade 10 as a whole. However, the number of core sections 12
may be varied and additional oblique core sections may be provided to connect
the three longitudinal sections.
(0043] In the present embodiment, the tubular jacket 16 consists of a
number of sleeves 16a, 16b, 16c of braided fibers having a predetermined bi-or
tri- directional orientation. Such a jacket is known to protect the blade 10
against delaminating and/or peeling under multiple impacts during use, and to
contribute to an increased strength thereof. Moreover, it provides an outer
skin
on one side of the blade 10 once molded.
[0044] The assembly of sleeves and core is encapsulated in a
thermoset resin coating of polyester, vinyl ester, epoxy or urethane for
example, thereby encapsulating the spaced-apart core sections to form a
molded blade part having one side 19a representing one side face of the blade
and one opposite side 19b having a discontinuous surface reinforced by
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longitudinal ribs in those area having a core section, but also inside the
cavities
where the thermoset sleeves are considered also as reinforcing ribs. The
resulting blade part is characterized by a continuous distribution of the
reinforcing fibers along a transverse section thereof.
[0045] A cover 20 is provided over the surface 19b of the blade. The
cover 20, made in a thermoplastic or a thermoset fiber reinforced material,
such
as polycarbonate (PC) or polyvinyl chloride (PVC) or polypropylene (PP) for
example, may be secured by gluing. Interestingly, it may have a texturized
outer surface, with such a texture as of a diamond point-type or a sanded
paper-type for example, thereby allowing an adjustment of the friction
coefficient.
[0046] The cover may be tailored so as to slightly overlap a bottom
edge 22 (see reference 24 in Figure 5) of the blade, as an edge liner, thereby
providing a protection against wear.
[0047] Preferably, a roving 24 is inserted between layers 16a and
16b to provide wear resistance along the edge 24.
[0048] One method of making the above-described blade in
accordance with the present invention consists in providing a core of low-
density foam, the core having a series of longitudinal sections defining
longidutinal cavities therebetween; pulling a braid fiber jacket onto the
core;
compressing and impregnating the overall jacket containing the wrapped core
with a thermoset resin, such as polyester, vinyl ester, urethane or epoxy for
example, as known in the art; and finally securing over the thus molded blade
a
cover plate of wear resistant material. Securing may be done by gluing or
otherwise.
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[0049] The method may also comprise incorporating a member in a
desired material, such as foam, or providing a foam core having oblique
sections interconnecting the longitudinal core sections in the longitudinal
cavities between the core sections to add rigidity if required.
[0050] The method of the present invention yields a blade having a
foam core and a laminated wall, whereby an adhesion surface between the
laminated wall and the foam core is reduced due to the discontinuity of the
core
along the height of the blade. Moreover, the laminated wall has an increased
thickness between each core member, the core sections acting as longitudinal
reinforcing ribs. The present method allows encapsulating each core section on
four sides thereof, which results in an improved adhesion, further
contributing
to increasing resistance of the blade, in particular in the central region
thereof.
[0051] The outer tubular jacket, made of a weaving of continuous or
braid fibers, completely wraps the blade, providing a continuity of fiber on a
perimeter of the blade, while encapsulating the core sections located at
target
locations. This blade may be seen as a central beam with localized
longitudinal
reinforcing ribs.
[0052] The resulting blade proves to be more resistant to repeated
impacts, more resistant to combined torsion and impact as well as to
delaminating, peeling and tearing, while lighter in weight than current
blades.
[0053] Although the present invention has been described
hereinabove by way of embodiments thereof, it may be modified, without
departing from the nature and teachings of the subject invention as defined in
the appended claims. For example, the cavities could receive an additional
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element of material, liquid or granular, to generate an anti-vibration effect
or a
center-of-gravity displacement effect.
