Note: Descriptions are shown in the official language in which they were submitted.
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DOUBLE PRESSING METHOD AND MACHINE FOR MANUFACTURING A
HOCKEY STICK SHAFT, AND HOCKEY STICK SHAFT MADE
THEREFROM
Field of the Invention
The present invention relates to a method and machine for
manufacturing a composite hockey stick shaft, and to the hockey stick shaft
made therefrom. More particularly, the present invention relates to a double
pressing method and machine for manufacturing a laminated hockey stick shaft
having graphite and fiberglass reinforcement, and to the hockey stick shaft
made therefrom.
Background of the Invention
It is known in the art that hockey sticks have traditionally been
manufactured from wood. The elongated shaft and blade portions of the
hockey stick were both constructed of wood and were joined with one another
through various processes to form a single, integral unit. The traditional
wooden hockey stick has set the standard for weight, feel, and load transfer,
and hockey players have long preferred wooden shafts.
It is also known in the art that during the course of a hockey game, a
hockey stick is subjected to high stresses, which often result in fracture or
breakage of the stick shaft. Additionally, when a wooden hockey stick brakes,
it
tends to splinter which can be hazardous. Consequently, various attempts have
been made throughout the years to improve the durability of hockey sticks
without sacrificing the characteristics of weight, feel, and flexibility that
are
desirable in a hockey stick. As a result, ice hockey sticks have changed from
a
plain wooden stick having a straight blade and shaft to a significantly
improved
stick having a curved blade and shaft reinforced with composite materials.
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It is known in the art that a laminated hockey stick is made of an ordinary
hard wood hockey stick onto which thin layers of reinforcing material are
glued
over each side of the hockey stick shaft and shank portion. Laminated hockey
sticks have been proven to be superior to their solid wood counterparts in
order
to prevent shaft breakage. Known in the art are laminated hockey sticks made
with one reinforcing material such as fiberglass, graphite or the like and an
appropriate resin used to glue the laminate onto the core.
It is also known in the art that the mechanical properties of laminated
hockey sticks will vary depending on the selected reinforcing material and the
type of resin used. Graphite rovings do not absorb polyester resin. A
carbonlpolyester matrix does not benefit fully from the higher modulus of
elasticity of graphite because the filaments remain dry. If one breaks this
type
of laminate, one will see that the rovings remain flexible, proving that they
are
not an integral part of the matrix. This means that they are not contributing
as
much to the rigidity of the finished laminate. In addition, when using
polyester
resin, the bond between the graphite and the wood core is very poor.
It is also known in the art of making laminated hockey shaft sticks that
the traditional polyester process does not control the position of individual
rovings, treating the entire group as a unit. There is an increased risk of
having
nothing but resin in certain portions of the core. Without fibers, the resin
chips
and cracks upon impact. In addition, there is no control over the distribution
of
rovings over the laminate cross section.
It is also known that for a same sample core, the average laminate
thickness is 0.040" (approx. 0.1016 cm) with polyester resin, versus 0.0025"
(approx. 0.00635 cm) with vinyl ester resin. The finished shaft with polyester
is
0.83" (approx. 2.1082 cm) thick versus 0.79" (approx. 2.0066 cm) with vinyl
ester. The industry trend is towards a demand for slimmer shafts. Furthermore,
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for the traditional polyester process, the size of the bath is limited since
the
polyester resin is not refrigerated. On a press with two lengths of sticks,
one
portion of the laminate soaks in resin during the entire pressing cycle or
longer.
The rest simply passes through, for an immersion time of a few seconds. The
weight percent of resin in the soaked section is much higher, and cannot be
removed through wringing, so a portion of the laminate is thicker and heavier
than the rest.
It is also known that the traditional polyester process often requires
viscosity control additives. Fillers such as micro-bubbles are added to
increase
the viscosity of polyester. This is done to reduce leakage of resin from the
molds, which must be scraped off later. This reduces the rate of resin
penetration in the rovings, even for fiberglass.
Finally, it is also known in the art that laminated hockey sticks are made
using a single pressing process wherein the first laminate is glued by
applying
pressure to the unlaminated side of the core. The load is transferred through
the core to the laminate, which is trapped between the core and the mold
surface. This means that one side of the core is pressed by a metal plate
before it is glued to a laminate. The pores of the wood on this side are
smoothed by this, reducing the bond quality when the core is eventually turned
over. The result is that one laminate will have a better bond than the other.
This
can be proven by peeling off cold pressings, and verifying the amount of wood
that comes off in the process. Also, in single pressing, one side can be
allowed
to cool before the other is pressed. The contraction of the laminate will
curve
the shaft to one side.
Therefore, there is a need to provide a method and a machine for
making hockey sticks shafts, which enable to control the position of the
individual rovings. There is also a need to provide a method and a machine for
making hockey sticks shafts, which enable to treat both sides of a stick
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symmetrically, so that the bond quality is equal for the top and bottom
laminates. Furthermore, there is a need for a hockey stick shaft having
improved structural characteristics which lead to improved performance.
Summary of the Invention
The present invention provides a double pressing method and machine
for producing a linear product having a core with two opposite surfaces and
outer laminates, and a linear product made therefrom which satisfy each of the
above mentioned needs.
More particularly, a first object of the invention is to provide a double
pressing method and machine for manufacturing a hockey stick shaft having a
core with two opposite surfaces and outer laminates by simultaneously
pressing a laminate of graphite rovings positioned between fiberglass rovings
onto each opposite surface of the hockey stick core.
A second object of the present invention is to provide a hockey stick
shaft having a core with two opposite surfaces, each of the surfaces being
provided with a laminate comprising fiberglass rovings along each longitudinal
surface edge and graphite rovings between the fiberglass rovings.
According to the invention, there is provided a double pressing method
for producing a linear product having a core with two opposite surfaces and
outer laminates, said method comprising the steps of:
a) providing a plurality of rovings;
b) guiding said rovings through guide means;
c) soaking said rovings in a liquid bath;
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d) wringing excess liquid from said rovings;
e) positioning an upper set of wetted rovings under an upper mold cavity
and a lower set of wetted rovings over a lower mold cavity;
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f) inserting said core between the upper set and lower set of wetted
rovings;
g) moving the upper mold cavity and the lower mold cavity towards each
other so as to simultaneously press said upper and lower sets of rovings
onto the core; and
h) moving the upper mold cavity and the lower mold cavity away from
each other so as to remove the resulting linear product.
Also according to the invention, there is provided a machine for double
pressing a linear product having a core with two opposite surfaces and outer
laminates, said machine comprising:
feeding means for feeding a plurality of rovings;
guiding means for guiding said rovings ;
soaking means for soaking said rovings;
wringing means for wringing said rovings;
a double pressing mold having an upper mold cavity and a lower mold
cavity;
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separating means for separating said rovings into an upper set of wetted
rovings and a lower set of wetted rovings;
positioning means for positioning the upper set of wetted rovings under
the upper mold cavity and the lower set of wetted rovings over the lower
mold cavity;
insertion means for inserting said core between the upper set and lower
set of wetted rovings;
pressing means for moving the upper mold cavity and the lower mold
cavity towards each other so as to simultaneously press said upper and
lower set of rovings onto the core;
ejection means for moving the upper mold cavity and the lower mold
cavity away from each other so as to remove the resulting linear product.
Also according to the invention, there is provided a hockey stick shaft
comprising an inner core and outer laminates, the inner core comprising a pair
of opposite surfaces, each surface being provided with longitudinal surface
grooves and longitudinal edge grooves; characterized in that each opposite
surface is covered by one of said outer laminates and each outer laminate
comprises graphite rovings positioned between fiberglass rovings.
The invention and its advantages will be better understood upon reading
the following non-restrictive description of a preferred embodiment thereof,
made with reference to the accompanying drawings.
Brief Description of the Drawings
FIG.1 is a partial perspective view of a machine used to carry out the double
pressing method according to a preferred embodiment of the invention, the
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machine being shown with feeding device, guiding device, soaking device and
wringing device.
FIG.2 is a partial perspective view of the machine shown in Fig.1, the machine
being shown with additional mold, separating device, positioning device,
insertion device, pressing device and ejection device.
FIG.3 is a perspective view of the mold, insertion device and pressing device
of
the machine shown in Fig.1.
FIG.4 is a perspective view of the mold, pressing device and ejection device
of
the machine shown in Fig.1.
FIGS is a partial perspective view of the fiberglass spools in a creel used
for
the feeding device shown in Fig.1, the fiberglass spools being shown centered
beneath guides.
FIG.6 is a perspective view of the carbon fiber spools in a creel used for the
feeding device shown in Fig.1, the carbon fiber spools being shown centered
beneath guides.
FIG.7 is a perspective view of a guide plate used for the guiding device shown
in Fig.1, said guide plate being shown initially grouping fiberglass rovings
into
groups 1, 2, 3, 4, 7, 8, 9 and 10.
FIG.8 is a perspective view of the final guide plate used for the guiding
device
shown in Fig.1, the final guide plate being shown grouping graphite rovings
and
fiberglass rovings before their entrance into the resin bath.
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FIG.9 is a perspective view of yet another guide plate used for the guiding
device shown in Fig.1, said guide plate being shown grouping graphite rovings
into groups 5, 6, 11 and 12.
FIG.10 is a perspective view of the rovings as they pass through the final
guide
plate shown in Fig.8 and enter into the soaking device shown in Fig.1, the
soaking device being shown with broken section.
FIG.11 is an exploded perspective view of the soaking device shown in Fig.1.
FIG.12 is a perspective view of the rovings exiting the soaking device,
passing
through the wringing device and into the separating device of the machine
shown in Fig.1.
FIG.13 is a side plan view of the soaking device, wringing device and
separating device shown in Fig.12.
FIG.14 is a schematic cross-sectional view of the separating device oriented
with respect to the mold of the machine shown in Fig.1.
FIG.15 is a schematic cross-sectional view of the separating device and mold
shown in Fig.14, the separating device being shown maintaining the alignment
of the rovings placed in the lower mold cavity.
FIG.16 is a schematic cross-sectional view shown in the mold of Fig.14 closing
onto a core with the rovings correctly aligned.
FIG.17 is a schematic cross-sectional view of the mold shown in Fig.14, the
mold being shown closed onto a core.
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FIG. 18 is an exaggerated top plan view of a crooked wood core in the mold
shown in FIG. 14.
FIG. 19 is a cross-sectional view of the fiberglass and graphite rovings
positioned
with respect to the inner core, said rovings and inner core being shown prior
to
being pressed.
FIG. 20 is a cross-sectional view of the hockey stick shaft prepared by the
double
pressing method according to a preferred embodiment of the invention.
Detailed Description of a Preferred Embodiment
As shown in the accompanying drawings, the present invention concerns
a method and machine 33 for producing a linear product 35 having a core 37
with two opposite surfaces 39 and outer laminates 41, and the present
invention
also concerns the linear product 35 made therefrom. More particularly, the
present invention discloses a double pressing method and machine 33 for
manufacturing a laminated hockey stick shaft 35 having graphite and fiberglass
reinforcement 43a and 43b, and the present invention also discloses the hockey
stick shaft 35 made therefrom. It should be understood that although the
present
application uses the expression "a plurality of rovings" since such rovings
will
usually be numerous, this expression is meant to include "at least one roving"
if a
single band or strip of reinforcing material is used.
The double pressing method according to the present invention consists
of providing a plurality of rovings 43, guiding them through a series of guide
means, soaking them in resin 51 a, and wringing the excess resin 51 a from the
rovings 43 so that an upper set and a lower set of wetted rovings 59 and 61
can
be pulled through heated mold cavities 55a and 55b. The method further
comprises the steps of inserting a core 37 having opposite surfaces 39
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between the upper set and lower set of wetted rovings 59 and 61 and closing
the mold 55 by means of a press so that upper and lower laminates 41 are
molded simultaneously onto the surfaces 39 of the core 37, using heat and
pressure. The mold 55 is then opened and the resulting hockey stick shaft 35
is
5 removed. Also according to the present invention, there is provided the
machine 33 devised to carry out the double pressing method.
The resulting hockey stick shaft 35 obtained using the double molding
method and machine 33 comprises an inner core 37 and outer laminates 41.
10 More particularly, the outer laminates 41 consist of graphite rovings 43a
positioned between fiberglass rovings 43b. The hockey stick shaft 35 according
to the present invention will be explained in greater detail in the following
text.
The machine 33 according to a preferred embodiment of the invention is
shown in Figs.1 to 4 and is intended for double pressing a linear product 35
having a core 37 with two opposite surfaces 39 and outer laminates 41. More
specifically, the machine 33 shown in the accompanying drawings is a machine
33 for manufacturing a hockey stick shaft 35 having a core 37 with two
opposite surfaces 39 and outer laminates 41 by simultaneously pressing a
laminate 41 of graphite rovings 43a positioned between fiberglass rovings 43b
onto each opposite surface 39 of the hockey stick core 37.
The machine 33 comprises a feeding device 45 for feeding a plurality of
rovings 43, a guiding device 47 for guiding the rovings 43, a soaking device
49
for soaking them in resin 51a and a wringing device 53 for wringing the excess
resin 51a from the rovings 43. The machine 33 also comprises a double
pressing mold 55 having an upper mold cavity 55a and a lower mold cavity
55b. In order to properly feed the rovings 43 to the upper and lower mold
cavities 55a, 55b, a separating device 57 for separating the rovings 43 into
an
upper set of wetted rovings 59 and a lower set of wetted rovings 61, and a
positioning device 63 for positioning the upper set of wetted rovings 59 under
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the upper mold cavity 55a and the lower set of wetted rovings 61 over the
lower
mold cavity 55b are provided. Finally, the machine 33 includes an insertion
device 65 for inserting a core 37 between the upper set and lower set of
wetted
rovings 59 and 61, a pressing device 67 for moving the upper mold cavity 55a
and the lower mold cavity 55b towards each other so as to simultaneously press
the upper and lower sets of rovings 59 and 61 onto the core 37, and an
ejection
device 69 for moving the upper mold cavity 55a and the lower mold cavity 55b
away from each other so as to remove the resulting linear product 35.
The feeding device 45 according to the invention can very well comprise
just one or several creels 71,73, each creel 71,73 having one or several
spools
75,77, the spools 75,77 being of a same type of roving 43 or of different
types.
Consequently, the machine 33 can be used to manufacture laminated hockey
stick shafts 35 made with just one reinforcing material 43 or with several
different
types of reinforcing materials 43. According to a preferred embodiment of the
invention, and as better shown in Fig. 1, the feeding device 45 preferably
consists of a storage rack comprising a creel 71 having a plurality of spools
75 of
graphite rovings 43a and another creel 73 having a plurality of spools 77 of
fiberglass rovings 43b. Preferably, the fiberglass rovings 43b are composed of
continuous glass filaments having no mechanical twist, with a forming agent
designed for vinyl ester or polyester resins. Preferably also, the fiberglass
rovings
43b have fast wet-out, zero catenary, and excellent runnability. The
fiberglass
rovings 43b are placed higher than the top of the resin pot so that gravity
compensates for dynamic friction. Preferably, each fiberglass spool 77 feeds
from the center and each fiberglass spool 77 is centered beneath a first guide
79a as shown in Fig. 5.
The carbon fiber rovings 43a are preferably composed of continuous
filaments, with a surface treatment compatible with vinyl ester resin. Unlike
fiberglass, graphite rovings 43a have medium runnability, which makes them
more susceptible to fraying and fuzz. Preferably, one should ensure that
fraying
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and fuzz particles do not fall into the resin bath 51 because, when in
sufficient
quantities, they cause the viscosity to increase. Preferably also, as shown in
Fig.
6, each carbon fiber spool 75 feeds from the perimeter and a guide 79 is
centered over each spool 75 at a height that ensures no rubbing with the
roving
43 as it unravels.
As also shown in Fig. 1 and as aforesaid, the machine 23 also comprises
a guiding device 47 for guiding all the rovings 43 individually from the
storage
rack, into the resin bath 51, and finally to the wringing device 53. As better
shown
in Figs. 7 to 10, the guiding device 47 comprises at least one guide plate 81
having at least one hole 83 for guiding at least one roving 43 of the rovings
43 by
passing the at least one roving 43 through the at least one hole 83.
Upon leaving the creel 71,73, the rovings 43 are guided and grouped
together into groups through a series of guide plates 81 in anticipation of
their
positions within the resin bath 51. Preferably, the guide plates 81 are made
of
plastic or ceramic in order to minimize rubbing with the rovings 43. It is
worth
noting that instead, only the holes 83 of the guide plates 81 could be
provided
with plastic or ceramic bushings. Preferably also, the rovings 43 do not cross
paths and each path is as straight as possible.
As also shown in Fig. 1, the storage rack of the feeding device 45
preferably comprises twenty carbon fiber and thirty-two fiberglass spools 75
and
77. The rovings 43 are grouped together through the series of plates 81,
reoriented to enter the resin bath 51, and finally guided to the wringer 53.
For
laminated hockey sticks with graphite reinforcement, there are four to ten
fiberglass rovings 43b and two to twelve carbon fiber rovings 43a per laminate
41. Laminated hockey sticks with only fiberglass reinforcement have ten to
eighteen fiberglass rovings 43b per laminate 41.
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Prior to using the machine 33, each roving 43 is threaded through the
guide plates 81 along its entire trajectory and the groups of rovings 43 are
prevented from crossing each other, making it easy for the operator to
identify
any roving 43 in each group. Preferably also, the rovings 43 are passed
through the group holes 83 which produce the most gradual transition from
their initial trajectory to the resin bath 51.
According to the invention, rovings 43 can be guided and grouped into
any appropriate number of groups, each group comprising an appropriate
number of rovings 43, and this can be done for different types of rovings 43.
As
shown in Fig.7, groups 1,2,3,4,7,8,9,10 preferably have four fiberglass
rovings
43b each. The plastic guide plate 81 shown in Fig.7 prevents them from
crossing or rubbing against each other as the enter the final guide plate 85
before the resin bath 51, as shown in Fig.B. Groups 5,6,11 and 12 shown are
for graphite rovings 43a. Each group preferably contains five individual
rovings
43a. There is also a separate guide plate 81 for the initial grouping of these
rovings 43a, as shown in Fig.9. For simplicity, only roving groups 5 and 11
are
shown.
As shown in Figs.1,10,11, and 12, there are also guide plates inside the
resin bath 51 for each group of fibers 43. These plates will be hereinafter
referred to as "wet fiber guides" 87. These wet fiber guides 87 are used to
maintain the integrity of the roving groups inside the resin bath 51.
Preferably,
there are 4 wet fiber guides 87 and each is fastened to its respective
position in
the bath 51, at roughly 48" (approx. 122 cm) intervals. Each wet fiber guide
87
is bolted to a supporting structure above the resin bath 51. It goes without
saying that prior to using the machine 33, the rovings 43 are passed through
the wet fiber guides 87 before the bath 51 is filled with resin 51 a, as they
are
difficult to manipulate once wetted.
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After passing through the final roving guide plate 85, roving groups 1-12
are passed into the first wet fiber guide 87, as shown in Figs.10 and 11.
Groups
1-4 are indicated in the bottom row of the wet fiber guide 87. The bath 51 is
shown as a broken section, to reveal the wet fiber guide 87. Resin 51 a is
contained by an inner liner 89, with water 91 circulating the length of the
bath
51 between the inner liner 89 and an outer jacket 93. Preferably, all the
roving
groups form straight lines from the creel 71,73 to final alignment guides 95
and
all parts of the guides 81,85, and 87 in contact with the fibers 43 are smooth
and rounded.
As shown in Figs.1,11, and 12, and as aforesaid, the machine 33 also
comprises a soaking device 49 for soaking the rovings 43. As better shown in
Fig.10, the soaking device 49 comprises a refrigerated resin bath 51
comprising an inner liner 89 containing resin 51 a and an outer jacket 93,
wherein water 91 circulates between the inner liner 89 and the outer jacket
93.
As the rovings 43 are pulled through the double pressing mold 55, they
soak in the resin bath 51, then pass through the wringing device 53 to remove
the excess resin 51 a. The resin bath 51 soaks carbon and glass fibers 43a and
43b with a resin mixture 51 a for the duration of the pressing cycle. The
weight
percentage of resin 51 a over the entire length of the laminate 41 is constant
because all the fibers 43 over the length of the laminates 41 have the same
immersion time. The pressing cycle immobilizes the rovings 43 within the resin
pot for its duration. The mechanical resistance of the graphite laminate
increases with the time it spends soaking in resin.
According to a preferred embodiment of the invention, vinyl ester resin is
preferably used and mixed with an appropriate number of catalysts in order to
form the resin mixture 51 a for the resin bath 51. The percentage of each
catalyst is adjusted depending on the desired gel time and preparing this
mixture 51 a is well within the skill of one versed in the art. Gel time is
the time it
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takes for resin to solidify at a given temperature and pressure. There are
several factors influencing the choice of gel time, such as: mold temperature,
pressure time, resin viscosity, and operator dexterity.
5 The higher the mold temperature, the shorter the gel time. In addition,
the recommended catalysts have a minimum temperature needed to start their
role in the reaction. If this is not achieved, the carbon fiber portion of the
laminate 41 will not be properly cooked. The laminate 41 will have a lower
rupture force.
Pressure time is the phase in which the core 37 is pressurized between
the two laminates 41. A higher percentage of catalyst permits shorter pressure
time.
A higher concentration of the primary catalyst speeds the chemical
reaction, and produces increased viscosity throughout the process. This is
useful to reduce the leakage of resin 51 a from the molds 55 during pressing.
On the other hand, lower viscosity permits more of it to be wrung out of the
laminate 41, resulting in a lighter end-product 35. Preferably, viscosity
range is
between 450-600 for vinyl ester and 1500-2000 for polyester. Higher numbers
make wringing out the excess resin 51a difficult, increases friction, and
cause
resin 51 a to overflow the bath walls during the fiber pull stroke.
Preferably also, shaft cores 37 are placed in the mold 55 by the operator
within a certain appropriate amount of time in order to prevent visible gaps
on
the finished product 35 which result from parts of the laminate 41 hardening
before the shaft core 37 is pressed.
With the fibers 43 in position, the resin mixture 51a is poured into the
bath 51 directly over the wet fiber guides 87. Deviation from this can cause
the
wetted fibers 43 to twist among themselves. Thus, when the rovings 43 are
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pulled, they could become entangled, and would have to be re-threaded
through all the guides 81,85, and 87. The resin level inside the bath 51 is
correct when all rovings are completely covered.
As shown in Fig.10, the soaking device 49 has a cooling system which
must be in operation when using the machine 33 in order to keep the resin 51 a
at an appropriate constant temperature or within a suitable temperature range.
The temperature of the resin 51 a is controlled by circulating water 91
between
the inner liner 89 and the outer jacket 93 in order to obtain an appropriate
heat
transfer. The flowing water 91 acts as a refrigerated jacket, cooling the
liner 89,
and thus the resin 51 a within. The wall temperature of the bath 51 is
preferably
between 5 and 10°C. Reducing the temperature slows down the catalytic
reaction of the resin mixture 51 a and increases the viscosity.
One must verify that no water 91 is leaking into the bath 51, and that
condensation on the walls and floor of the bath 51 a is wiped off. It will not
mix
with the resin 51 a, but its presence on the hot mold surface 55a, 55b will
produce uncooked resin 51 a in that area, due to the energy consumed by
boiling and evaporation. In addition, all debris is preferably removed from
the
bath 51 before filling. The bath 51 is preferably not made of copper, or
aluminum, as these will react with the resin 51 a over time. The resin
container
51 is of sufficient depth to contain the gradient caused by movement of the
rovings 43 during pulling.
As shown in Fig.1 and as better shown in Figs.12 and 13, the wringing
device 53 of the machine 33 comprises at least one tempered blade 97, each
roving 43 passing on said at least one tempered blade 97 so as to remove
excess resin 51 a.
Preferably, there are 11 tempered blades 97 (and more particularly,
preferably tempered black-oxide blades) for each pair of upper and lower
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laminates 41: five touch the wetted rovings 43 from above, six from below, as
shown in Figs.12 and 13. These wring excess resin 51 a from the wetted
rovings 43 as they pass over and under the blades 97.
The machine 33 further comprises separators 99 which maintain the
integrity of the roving groups at the entry and exit of the wringing process.
Roving groups should be confined to these guides 99. If they are not, the
separator's position or orientation is incorrect which adds friction.
One must verify that no fuzz accumulates on the blades 97 and that the
rovings 43 are in position. Fuzz indicates that the contact between blade 97
and roving 43 is harsh. There may be too much friction in the system, the
blades 97 may be scraping too hard, due to their orientation or surface
finish.
This may cause the rovings 43 to break or result in laminates 41 of low
quality.
Resin 51 a from the top laminates 41 should preferably not drip onto their
lower counterparts. If it does, it is worth noting that channels (not shown)
can
be constructed in order to redirect excess resin 51a in to the bath 51, as it
is
extracted from the passing rovings 43.
Prior to use, the wringing device 53 should preferably be soaked in
acetone, and lubricated with wax afterwards. The individual blades 97 are
adjusted for a minimum contact with the fibers 43, as shown in Fig.13.
As shown in Figs.12,13, and 14, and as aforesaid, the machine 33 also
comprises a separating device 57 for separating the rovings 43 into an upper
set of wetted rovings 59 and a lower set of wetted rovings 61. The separating
device 57 preferably consists of a pair of final alignment guides 95 through
which the groups of rovings 43 are passed, as they exit the wringing process.
The upper set of wetted rovings 59 and the lower set of wetted rovings 61,
each consists of graphite rovings 43a positioned between fiberglass rovings
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43b. Fig.14 illustrates the position of the final alignment guides 95 with
respect
of the mold cavities 55a and 55b.
As also shown in Fig.14, the fiberglass rovings 43b of the upper set of
wetted rovings 59 are preferably positioned higher than their graphite
counterparts 43a. Similarly, the fiberglass rovings 43b of the lower set of
wetted rovings 61 are preferably positioned lower than the graphite fibers
43a.
There are several reasons why this is important. Firstly, each set of wetted
rovings 59, 61 must be narrower than the mold cavity 55a, 55b in order to fit
inside. Furthermore, in order to properly bond the laminate 41 to the core
material, fiberglass and graphite rovings 43b and 43a must be separated,
because there is no cross-linking between the two materials. Preferably also,
graphite 43a must be in direct contact with the core 37 during pressing,
without
the interference of fiberglass 43b. The final alignment guides 95 maintain
this
control, as shown in Figs.15 and 16. As also shown, the glass and carbon
fibers 43b and 43a are compressed separately between the wood core 37 and
mold surfaces 55a, 55b, without any crossover. In addition, the carbon group
is
the first to encounter the core 37 as the pressing begins.
As shown in Figs.14,15, and 16, and as aforesaid, the machine 33 also
comprises a double pressing mold 55 having an upper mold cavity 55a and a
lower mold cavity 55b. As better shown in Fig.17, the profile of the mold
cavity
55a, 55b is preferably composed of an entry radius 101 followed by a reversed
radius 103 which horizontally compresses the shaft core 37, sealing in the
excess resin 51 a. Preferably also, the lateral sides of the profile are
tapered for
further compression as the core 37 enters into the mold cavity 55a, 55b and
the
bottom of the profile is transversely flat. The width of the entrance is equal
to
the largest shaft width. Preferably also, 47 to 50% of the core depth is
covered
by each mold cavity 55a, 55b. It is worth noting that the mold 55 can have
various other types of transverse cross-sectional shapes in order to be able
to
manufacture laminated hockey stick shafts 35 with different cross-sectional
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final shapes. The mold 55 further comprises a heating device for heating the
upper mold cavity 55a and the lower mold cavity 55b.
Referring now back to Fig. 2 and as aforesaid, the machine 33 also
comprises a positioning device 63 for positioning the upper set of wetted
rovings
59 under the upper mold cavity 55a and the lower set of wetted rovings 61 over
the lower mold cavity 55b. The positioning device 63 comprises a holding
station
105, a pulley 107, an intermediate support and clamps 111. The holding station
105 holds the rovings 43 in position for the pulley 107 and the pulley has
jaws
107a for gripping the rovings 43 and pulling them through the mold cavities
55a
and 55b. The clamps 111 insert the lower set of wetted rovings 61 into the
lower
mold cavity 55b, and the upper set of wetted rovings 59 is held in position by
the
pulley 107, the intermediate support, and the wringing device 53.
More specifically, after the rovings 43 are threaded through the final
alignment guides 95, they are passed through the holding station 105, into the
pulley 107, as shown in Fig. 2. The holding station 105 serves to hold the
rovings
43 in position for the pulley 107 to grab them at the beginning of each cycle.
It
must maintain the integrity of the alignment in the guides 95. The pulley 107
has
jaws 107a which hold the rovings 43, preferably without slipping, as it tows
them
longitudinally through the mold cavities 55a and 55b to extend the full length
thereof. Preferably, fibers 43 are pulled through the pot at variable speed:
acceleration from rest to 75 ft/min (approx. 22.875 m/min) through the first
few
inches traveled, high speed is maintained for the length of the molds 55, then
deceleration to rest in the final inches. With graphite rovings 43a, the
velocity
should not exceed 80 ftJmin (approx. 24.4 m/min), because they are more
fragile.
The jaws 107a of the pulley 107 have rack-type serrations clamping onto the
wetted rovings 43, closed with 400 Ibs per laminate 41.
After the pull stroke is complete, the lower set of wetted rovings 61 are
CA 02310802 2006-02-21
clamped into the bottom mold cavity 55b by the clamps 111, while the upper set
of wetted rovings 59 are supported between the mold cavities 55a and 55bby the
puller 107, the intermediate support, and the final alignment guides 95.
Otherwise, there would be over 120" (approx. 305 cm) of unstable rovings 43
(two lengths of 62" (approx. 157.5 cm) senior shafts) spanning the press 55.
Unless they are sustained, the wetted rovings 43 will oscillate when the
puller
107 stops, which could result in the rovings 43 losing their alignment with
respect
to the mold cavities 55a and 55b.
As aforesaid, the lower set of wetted rovings 61 is inserted into the bottom
mold cavity 55b by the clamps 111 and tension is maintained for the first
minute
of pressing. When under tension, the final alignment guides 95 at the exit of
the
wringing device 53 maintain the carbon 43a in the center of each mold cavity
55a, 55b, with fiberglass 43b on in each comer. Tension is introduced to the
upper set of wetted rovings 59 by the closure of the press 55. The top mold
cavity 55a is lowered towards the top laminate 41, held in position by the
puller
jaws 107a, an intermediate support, and friction in the wringing device 53.
As better shown in Figs. 3 and 4, and as aforesaid, the machine 33 also
comprises an insertion device 65 for inserting the core 37 between the upper
set
and lower set of wetted rovings 59 and 61. The insertion device 65 comprises
insertion shaft cylinders 113 which are sequentially lowered for installing
the core
37 in the lower mold cavity 55b.
Preferably, non-laminated hockey shaft cores 37 are placed manually by
the butt ends into an ejector 115, which also serves as a locating tool. The
butt
ends are oriented towards each other longitudinally and each core surface 39
is
substantially parallel to the bottom of its corresponding mold cavity 55a,
55b. The
ejector profile is larger than the shaft core width, so as to act as a
locating
CA 02310802 2000-06-07
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tool, ensuring that the portion of core 37 inserted here is true to the mold
cavities 55a and 55b. The tapered profile of the mold 55 holds the shaft core
37
in position. Vertical downward forces are applied and maintained in sequence
every 10 to 33 cm of shaft length by the shaft insertion cylinders 113,
depending upon the crookedness of the shaft core 37. Fig.4 shows the
sequential nature of the shaft insertion device 65. The cylinder 113 closest
over
the ejector 115 descends first, ensuring that this section of the core 37 is
true
with respect to the mold cavities 55a and 55b. Wood cores 37 are naturally
crooked. Figure 18 shows an exaggeration of a crooked core 37 in a mold
cavity 55a, 55b. The distance between the insertion cylinders 113 determines
how crooked the core 37 can be. For example, a given core 37 will have much
less deviation over a length of 15.24 cm than 60.96 cm.
As better shown in Figs.2, 3 and 4, and as aforesaid, the machine 33
also comprises a pressing device 67 for moving the upper mold cavity 55a and
the lower mold cavity 55b towards each other so as to simultaneously press the
upper and lower set of rovings 59 and 61 onto the core 37. The pressing device
67 preferably comprises a hydraulic system 117 for moving the upper mold
cavity 55a and the lower mold cavity 55b towards each other so as to
simultaneously press the upper and lower set of wetted rovings 59 and 61 onto
the core 37 but could be realized in any other way.
Prior to pressing, the shaft insertion cylinders 113 sequentially install the
cores 37 in the bottom mold cavities 55b. The mechanism retracts out of the
way, and the hydraulic system 117 closes the top mold cavity 55a on the
bottom one 55b, pressing the upper set of wetted rovings 59 onto the core 37,
which in tum is pressed onto the lower set of wetted rovings 61. This causes
the transversal flattening of the rovings 43 onto the core surfaces 39 and
their
complete filling of the mold cavities 55a, 55b resulting in laminates 41, as
shown in Fig.20, which adhere to the corresponding surface 39 of the shaft
core 37. The press 55 remains closed until the resin 51 a is fully
crystallized.
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22
The time required to cure the sets of wetted rovings 59 and 61 onto the core
37
depends on the recipe used for the resin mixture 51 a.
As better shown in Figs.3 and 4, and as aforesaid, the machine 33
comprises an ejection device 69 for moving the upper mold cavity 55a and the
lower mold cavity 55b away from each other so as to permit removal of the
resulting linear product 35. The ejecting device 69 comprises the above-
mentioned hydraulic system 117 for moving the upper mold cavity 55a and the
lower mold cavity 55b away from each other and further comprises top and
bottom ejectors 115 pushing onto the linear product 35 so as to separate the
same from the mold cavities 55a, 55b.
The force fit of the core 37 and mold 55 means that the core 37 will
remain in the upper or lower mold cavity 55a, 55b when they separate.
Therefore, upon completion of the pressing cycle, hydraulics 117 lift the top
molds into their start positions, and the top and bottom ejectors 115 extend.
Preferably, an appropriate mold release agent is also used. Figure 18 shows
the end of this process, with the pressed shaft 35 ready for removal.
The double pressing method according to the preferred embodiment of
the invention as can be inferred from the description of the above-mentioned
machine 33 and from the accompanying drawings, is intended for producing a
linear product 35 having a core 37 with two opposite surfaces 39 and outer
laminates 41. More specifically, the double pressing method is a method for
manufacturing a hockey stick shaft 35 having a core 37 with two opposite
surfaces 39 and outer laminates 41 by simultaneously pressing a laminate 41
of graphite rovings 43a positioned between fiberglass rovings 43b onto each
opposite surface 39 of the hockey stick core 37.
The double pressing method according to a preferred embodiment of the
invention comprises the steps of a) providing a plurality of rovings 43; b)
CA 02310802 2006-02-21
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guiding the rovings 43 through the guides 81, 85, and 87; c) soaking the
rovings
43 in the resin bath 51; d) wringing excess resin 51 a from the rovings 43; e)
positioning an upper set of wetted rovings 59 under the upper mold cavity 55a
and a lower set of wetted rovings 61 over the lower mold cavity 55b; f)
inserting a
core 37 between the upper set and lower set of wetted rovings 59 and 61; g)
moving the upper mold cavity 55a and the lower mold cavity 55b towards each
other so as to simultaneously press the upper and lower sets of wetted rovings
59 and 61 onto the core 37; and h) moving the upper mold cavity 55a and the
lower mold cavity 55b away from each other so as to remove the resulting
linear
product 35.
Preferably, step a) of the process comprises the steps of providing a
plurality of roving sources from the storage rack of the feeding device 45
comprising a plurality of spools, and the rovings 43 provided are preferably
fiberglass and graphite rovings 43b and 43a, as shown in Figs. 1,5, and 6.
Step
b) of the process preferably comprises the sub-steps of controlling the
position of
the individual rovings 43 and controlling the direction of the same by means
of
the guides 81, 85, and 87, as shown in Figs. 1,7,8,9,and 10. All the rovings
43
are preferably individually guided from the storage rack, into the resin bath
51,
through the wringer 53, and finally to the final alignment guides 95.
Furthermore,
step c) of the process preferably comprises the sub-steps of controlling the
temperature of the resin bath 51, and controlling the immersion time of the
rovings 43 in the resin bath 51. This is done with the refrigerated resin bath
51
shown in Fig. 11. Preferably also, step d) of the process comprises the sub-
steps
of guiding the rovings 43, passing them through the wringing device 53, and
removing excess resin 51 a from the rovings 43, as shown in Figs. 12 and 13.
Preferably, step e) of the process further includes the steps of positioning
the graphite rovings 43a between the fiberglass rovings 43b for each set of
wetted rovings 59, 61 and positioning the graphite rovings 43a closer to the
core
37 than the fiberglass rovings 43b and separately from these so as to be in
direct
contact with the core 37 during pressing, keeping the fiberglass rovings 43b
from
CA 02310802 2006-02-21
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interfering with the graphite rovings 43a. This is done with the final
alignment
guides 95 as shown in Figs. 12,14, and 15.
Preferably also, step e) further comprises the sub-steps of i) heating the
upper and lower mold cavities 55a and 55b; ii) positioning the upper and lower
sets of wetted rovings 59 and 61; iii) holding the upper and lower sets of
wetted
rovings 59 and 61; iv) pulling the upper and lower sets of wetted rovings 59
and
61 across the mold cavities 55a and 55b; v) clamping the lower set of wetted
rovings 61 onto the lower mold cavity 55b; and vi) supporting the upper set of
wetted rovings 59 between the mold cavities 55a and 55b. This is done with the
final alignment guides 95, holding station 105, puller 107, clamps 111, and
supports shown in Figs. 2, 3, and 4.
After a core 37 has been inserted in the lower mold cavity 55b, step g) of
the double pressing process preferably comprises the sub-steps of i) closing
the
upper mold cavity 55a onto the lower mold cavity 55b; ii) pressing the upper
and
lower set of wetted rovings 59 and 61 against the core 37 so as to mold them
on
the same; and iii) using heat and pressure provided by mold cavities 55a and
55b to cure sets of wetted rovings 59 and 61 onto the core 37. This is done
using
the hydraulic system 117 and mold cavities 55a and 55b shown in Figs. 2, 3,
and
4. Preferably also, step g) of the process further includes the step of
pressing the
graphite rovings 43a longitudinally onto the center of each opposite surface
39 of
the core 37 and pressing the fiberglass rovings 43b onto the edges of the
surfaces 39, as shown in Fig. 16, in order to obtain the hockey stick shaft 35
shown in Fig. 20. Finally, step h) of the process further comprises the sub-
steps
of i) allowing the linear product 35 to cool off; and ii) ejecting the linear
product
35.
The double pressed hockey stick shaft 35 according to the preferred
embodiment of the invention as shown in Fig. 20 has an inner core 37 and outer
laminates 41, the inner core 37 comprising a pair of opposite surfaces 39 and
CA 02310802 2000-06-07
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each surface 39 being provided with longitudinal surface grooves 119 and
longitudinal edge grooves 121. The doubled pressed hockey stick shaft 35 is
characterized in that each opposite surface 39 is covered by one of the outer
laminates 41 and each outer laminate 41 comprises graphite rovings 43a
5 positioned between fiberglass rovings 43b, as shown in Fig.19. The graphite
rovings 43a are placed along the center of each surface 39 so as to cover
some of the surface grooves 119 and the fiberglass rovings 43b are placed
along the edges of each surface 39 so as to cover the remaining surfaces
grooves 119 and fill the edge grooves 121, as shown in Fig.20.
As is better shown in Fig.19, there are preferably eight 0.11" (approx.
0.2794 cm) x 0.370" (approx. 0.9398 cm) surface grooves 119 on the top and
bottom surfaces 39, which improve the bond between the outer laminates 41
and the core 37. The edge grooves 121 at each corner are preferably 0.115"
(approx. 0.2921 cm) x 0.15" (approx. 0.381 cm) and are filled with the
resin/fiberglass matrix, providing slash resistance and increasing the
stiffness
in the x-axis.
Preferably also, core materials are chosen so that they are able to
withstand 190 psi with less than 2.5% plastic deformation at 145°C.
Four
quarter aspen wood is a typical example. In this case, humidity is preferably
less than 6%, otherwise the core 37 will shrink as the water evaporates during
the press cycle.
Finally, it is worth noting that the invention presents several advantages
over the prior art. The invention uses a refrigerated resin bath 51, which
allows
for a resin bath 51 as long as the total laminate length to be pressed.
Therefore, all rovings 43 in the laminate 41 receive a uniform wet-out time,
promoting an even thickness and weight percent of resin 51 a. Furthermore, the
invention uses no fillers for the resin 51 a, so that wetting is improved, and
more
excess resin 51 a is removed during wringing. This reduces the laminate
CA 02310802 2000-06-07
26
weight. Also worth of noting is that the double pressing process treats both
sides symmetrically, so that bond quality is equal for the top and bottom
laminates 41. Double pressing guarantees that both sides cool simultaneously
so that any stresses induced by the cooling laminates 41 are evenly
distributed
on both sides. Moreover, the double pressing system produces twice as many
shafts 35 per unit time as the single pressing technology.
Of course, numerous modifications could be made to the above-
described embodiments without departing the scope of the invention as defined
in the appended claims. For example, the rovings could be any other type of
fiber that is impact resistant, such as the fibers sold under the trade-marks
KEVLAR and VEXTRAN.
