U.S. patent application number 12/924994 was filed with the patent office on 2011-06-23 for sport racquet.
Invention is credited to Robert Gazzara, Mauro Pezzato, Mauro Pinaffo, Michel Pozzobon.
Application Number | 20110152016 12/924994 |
Document ID | / |
Family ID | 36945709 |
Filed Date | 2011-06-23 |
United States Patent
Application |
20110152016 |
Kind Code |
A1 |
Gazzara; Robert ; et
al. |
June 23, 2011 |
Sport racquet
Abstract
The present invention relates to a method for manufacturing at
least a portion of a sports racquet frame that comprises a step a)
of providing a moldable tube structure containing a first
inflatable bladder and a second inflatable bladder. The first and
second inflatable bladders are positioned on opposite first and
second regions of the moldable tube structure. At an intermediate
region, the tube structure comprises one or more cross channels,
which pass through the moldable tube structure. The method
according to the present invention comprises also a further step b)
of inserting said tube structure inside a mold forming a mold
cavity of a desired shape. Mold members are inserted into the cross
channels of the tube structure, so that the outer surface of the
mold member faces the inner surface of the corresponding cross
channel. The mold members have position and orientation that
correspond to the position and orientation, along the string bed
plane, of the string port holes, which are to be formed on said
frame portion. The method, according to the present invention,
comprises also a step c) of pressurizing the first and second
bladders, so that the tube structure conforms to the shape of the
mold, and heating the mold, so that the tube structure cures. The
method, according to the present invention, comprises a further
step d) of removing the cured tube structure from the mold cavity
and removing the mold members from the cross channels.
Inventors: |
Gazzara; Robert; (Mestre,
IT) ; Pinaffo; Mauro; (Camposampiero, IT) ;
Pozzobon; Michel; (Treviso, IT) ; Pezzato; Mauro;
(Treviso, IT) |
Family ID: |
36945709 |
Appl. No.: |
12/924994 |
Filed: |
October 7, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11707845 |
Feb 15, 2007 |
7811500 |
|
|
12924994 |
|
|
|
|
Current U.S.
Class: |
473/524 ;
264/314 |
Current CPC
Class: |
A63B 49/11 20151001;
B29C 33/505 20130101; B29C 33/0016 20130101; B29C 70/342 20130101;
A63B 2209/023 20130101; B29L 2031/5245 20130101; A63B 51/10
20130101; A63B 49/028 20151001; B29C 70/865 20130101; A63B 49/022
20151001; A63B 2049/103 20130101; A63B 51/00 20130101 |
Class at
Publication: |
473/524 ;
264/314 |
International
Class: |
A63B 49/10 20060101
A63B049/10; B28B 7/32 20060101 B28B007/32 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 11, 2006 |
EP |
06112486.3 |
Claims
1. A sports racquet frame having at least a string port hole formed
therein, said frame having a string bed plane, along which said
string port hole extends, wherein said frame is formed by the
following manufacturing steps: a) providing a moldable tube
structure, which comprises a first tube region containing a first
inflatable bladder, a second tube region containing a second
inflatable bladder and an intermediate tube region that is located
between said first tube region and said second tube region, said
tube structure comprising at least a cross channel, which passes
through said tube structure at said intermediate tube region; b)
placing said tube structure inside a mold which, when closed, forms
a mold cavity of the desired shape of said frame portion, at least
a mold member being inserted into said cross channel, said mold
member having an outer surface, which faces an inner surface of
said cross channel, said mold member having position and
orientation that correspond to the position and orientation of said
string port hole, along said string bed plane; c) pressurizing said
first and second bladders, so that said tube structure conforms to
the shape of the mold and heating said mold, such that said tube
structure cures; and d) removing said cured tube structure from
said mold cavity and removing said mold member from said cross
channel, said cured tube structure thereby forming said frame
portion, said cross channel thereby forming said string port
hole.
2. The frame according to claim 1, wherein said step a) of
providing said moldable tube structure comprises the following
manufacturing steps: a.1) providing a chuck member, which comprises
a first chuck element that is inserted into said first inflatable
bladder, a second chuck element that is inserted into said second
inflatable bladder, and an intermediate chuck element between said
first chuck element and said second chuck element; a.2) inserting
said chuck member into a prepreg tube, so as to be completely
surrounded by said prepreg tube; a.3) removing predefined portions
of said prepreg tube, at said first opposite sides of said
intermediate chuck element, so as to form at least a couple of
opposite holes on the opposite surfaces of said prepreg tube, which
cover said first opposite sides of said intermediate chuck element;
a.4) removing said intermediate chuck element from said prepreg
tube; a.5) inserting at least a tube support element through said
couple of opposite holes of said prepreg tube; and a.6) removing
said first and second chuck elements respectively from said first
and second inflatable bladders and from said prepreg tube.
3. The frame according to claim 2, wherein, in said step a.1) of
providing said chuck member, said first chuck element and said
second chuck element are associated to said intermediate element at
second opposite sides of said intermediate element, the coupling of
said first element and said second element to said intermediate
element being performed after having inserted said first element
and said second element respectively into said first inflatable
bladder and said second inflatable bladder,
4. The frame according to claim 3, wherein, in said step a.1) of
providing said chuck member, said intermediate chuck element
comprises at least a couple of chuck cross cavities, which pass at
least partially through said intermediate chuck element at first
opposite sides of said intermediate chuck element.
5. The frame according to claim 4, wherein, in said step a.3) of
removing predefined portions of said prepreg tube, said predefined
portions are the portions of the prepreg tube, which cover said
chuck cross cavities at said first opposite sides of said
intermediate chuck element.
6. The frame according to claim 5, wherein, in said step a.5) of
inserting said tube support element, said support element comprises
one or more layers of moldable material and/or one or more layers
of non-moldable material.
7. The frame according to claim 6, wherein said moldable tube
structure comprises an outer wall, which defines the external
perimeter of said tube structure, and at least an inner wall, which
defines said at least a cross channel passing through said tube
structure.
8. The frame according to claim 7, wherein said cross channel has a
main longitudinal axis, which intercepts the main longitudinal axis
of said tube structure with a predefined angle.
9. The frame according to claim 8, wherein said cross channel has a
main longitudinal axis that is substantially perpendicular with
respect to the main longitudinal axis of said tube structure.
10. The racquet according to claim 9, wherein said inner wall
comprises one or more layers of moldable material and/or one or
more layers of non-moldable material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention is a divisional of U.S. application
Ser. No. 11/707,845, filed on Feb. 15, 2007.
BACKGROUND
[0002] The present invention relates to a method for manufacturing
a sports racquet and a sports racquet obtained by said method,
which may be, for example a tennis, squash, badminton, or
racquetball racquet. More particularly, the present invention
relates to an improved method for manufacturing a sports racquet
comprising a racquet frame formed by a single tube and provided
with enlarged string port holes therein.
[0003] Sports racquets have a head portion containing an interwoven
string bed, a handle, and a shaft portion connecting the head
portion to the handle.
[0004] In conventional racquets, holes for anchoring the ends of
the strings are formed in the frame by drilling small string holes
in the frame after the racquet is molded. Generally, each string
hole accommodates a single string. Plastic grommet pegs, which are
formed on grommet and bumper strips that extend along the outside
surface of the frame, extend through the string holes to protect
the strings from the sharp edges of the drilled holes.
[0005] Co-owned PCT application WO 2004/075996 discloses a sports
racquet, in which some adjacent pairs of small string holes along
the sides, tip, and throat bridge of the racquet are replaced by
enlarged string holes having two inwardly facing string bearing
surfaces, which are spaced apart by a distance corresponding to the
distance between two contiguous main strings or cross strings
(referred to herein as "string ports holes"). Preferably, the frame
is formed of a double tube of carbon fiber-reinforced composite
material (a so-called graphite frame), in which the string port
holes are molded into as the racquet is pressure molded. As a
result of using two tubes, each forming one-half of the enlarged
string hole, the string holes can have rounded edges and do not
require the use of grommet pegs or strips. Also, in the regions
between string holes, the adjoining walls of the two tubes are
fused together to form a stiffening wall inside the frame. The
result is a racquet, which has improved torsional stiffness and
lighter weight. The racquet is made in a mold having a mold cavity
in the desired shape of the frame. The mold has two halves. A
prepreg tube containing an inflatable bladder is placed in each
mold half. A plurality of mold insert members, having an outside
surface in the desired shape of the string port holes, as well as a
plurality of pins to form conventional string holes, are positioned
between the two prepreg tubes and the mold is closed. The bladders
are then inflated while the mold is heated to cure the composite
resin. After removing the racquet frame from the mold, the mold
insert members and pins are removed leaving string port holes and
conventional string holes, respectively.
[0006] Although such a manufacturing method has shown to be quite
effective in the manufacturing of high quality racquet frames with
string port holes, it has been seen that production costs are
relatively high. This fact necessarily entails higher purchasing
costs for the final consumer and/or lower margins for the
provider.
[0007] It is possible to form a racquet with string port holes
using a single frame tube. For example, the racquet frame can be
molded from a single prepreg tube, with the holes being drilled
after molding. However, drilling holes, particularly drilling large
holes such as the string port holes, is a kind of post-curing
operation on the molded racquet frame, which may weaken the molded
frame, given the fact that the frame fibers are broken.
Alternatively, it is possible to manufacture the frame by molding
two frame halves separately, and then joining the two halves, e.g.,
by gluing, welding, fusing, or electro-fusing. Unfortunately, these
solutions have shown to be quite complicated to be carried out on
industrial large-scale manufacturing processes and to entail
relatively high production costs.
SUMMARY OF THE INVENTION
[0008] The overall object of the present invention is to provide an
improved method of manufacturing a racquet frame, one or more
portions of which comprise port string holes are formed from a
single frame tube.
[0009] Within this overall object, it is a particular object of the
present invention to provide an improved method of manufacturing a
racquet frame, in which port string holes are formed avoiding those
post-curing operations, such as drilling, which may weaken the
racquet frame after the racquet frame is molded.
[0010] A further object of the present invention is to provide an
improved method of manufacturing a racquet frame, which allows
molding together frame regions made of different materials,
particularly in the vicinity of the string port holes.
[0011] It is also an object of the present invention is to provide
an improved method of manufacturing a racquet frame, which is easy
to carry out at relatively low cost.
[0012] Thus, the present invention provides a method for
manufacturing at least a portion of a sports racquet frame that
comprises a step a) of providing a moldable tube structure
containing a first inflatable bladder and a second inflatable
bladder. The first and second inflatable bladders are positioned on
opposite first and second regions of the moldable tube structure.
At an intermediate region, the tube structure comprises one or more
cross channels, which pass through the moldable tube structure.
[0013] The method according to the present invention comprises also
a further step b) of inserting said tube structure inside a mold
forming a mold cavity of a desired shape. Mold members are inserted
into the cross channels of the tube structure, so that the outer
surface of the mold member faces the inner surface of the
corresponding cross channel. The mold members have position and
orientation that correspond to the position and orientation, along
the string bed plane, of the string port holes, which are to be
formed on said frame portion.
[0014] The method, according to the present invention, comprises
also a step c) of pressurizing the first and second bladders, so
that the tube structure conforms to the shape of the mold, and
heating the mold, so that the tube structure cures.
[0015] The method, according to the present invention, comprises a
further step d) of removing the cured tube structure from the mold
cavity and removing the mold members from the cross channels.
[0016] Thus, the cured tube structure forms the portion of a sports
racquet frame to be manufactured and the inner surface of the cross
channel defines the string port hole formed on said frame
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Other features and advantages of the method according to the
present invention, will become apparent from the following
description of preferred embodiments, taken in conjunction with the
drawings, in which:
[0018] FIG. 1 is a perspective view of a sports racquet frame
manufactured by the method, according to the present invention;
[0019] FIG. 2 is a perspective view of a moldable tube structure
relating to a manufacturing step of the method according to the
present invention;
[0020] FIG. 3 schematically shows a manufacturing detail of a
preferred embodiment of said first step of the method according to
the present invention;
[0021] FIG. 4 schematically shows another manufacturing detail of a
preferred embodiment of said first step of the method according to
the present invention;
[0022] FIG. 5 schematically shows another manufacturing detail of a
preferred embodiment of said first step of the method according to
the present invention;
[0023] FIG. 6 schematically shows another manufacturing detail of a
preferred embodiment of said first step of the method according to
the present invention;
[0024] FIG. 7 schematically shows another manufacturing detail of a
preferred embodiment of said first step of the method according to
the present invention;
[0025] FIG. 8 schematically shows another manufacturing detail of a
preferred embodiment of said first step of method according to the
present invention; and
[0026] FIGS. 9a and 9b schematically show two preferred embodiments
of a tube support tube element that is used in the manufacturing
step of FIG. 8; and
[0027] FIG. 10 schematically shows another manufacturing detail of
a preferred embodiment of said first step of method according to
the present invention; and
[0028] FIG. 11 schematically shows another manufacturing step of
method according to the present invention; and
[0029] FIG. 12 schematically shows another manufacturing step of
method according to the present invention; and
[0030] FIG. 13 schematically show a lateral view and two section
views of a portion of the sports racquet frame obtained with the
method, according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Referring to FIG. 1, it is shown a tennis racquet frame 1
manufactured with the method according to the present invention.
The frame 1 includes a head portion 2, which includes a throat
bridge 3 and a tip 12, a pair of converging shafts 4, and a handle
portion 5. The head portion 2 includes a plurality of conventional
string holes 6 and a plurality of consecutive port string holes 7.
A handle (not shown) is mounted on the handle portion 5, and
thereafter the handle may be wrapped with a grip.
[0032] As described in greater detail in WO 2004/075996, which is
incorporated herein by reference, string port holes 7 on opposite
sides of the head 2, as well as opposed port string holes in the
tip 12 and throat bridge 3, are offset relative to one another. In
this manner, e.g., along the sides, a string segment 8, which bears
against the lower bearing surface 9 of one port string hole 7a,
after crossing the string bed, bears against the upper bearing
surface 10 of the string port hole 7b, wraps around the outside
surface of the head 10, and bears against the lower bearing surface
11 of the next adjacent port string hole 7c before again crossing
the string bed. Such stringing is used both for the cross strings 8
and the interwoven main strings (not shown). The interwoven main
and cross strings form a string bed laying substantially on a
string bed plane, along which the port string holes 7 extend.
[0033] In a conventional inflation molding process, a prepreg tube,
formed of sheets of uncured carbon fiber-reinforced epoxy resin,
and containing an inflatable bladder, is placed inside of a mold
which, when closed, has a cavity shaped as a sports racquet frame.
After closing the mold, the bladder is inflated, so that the
prepreg tube assumes the shape of the mold, and the mold is heated
so as to cure the epoxy. The frame is then removed and string holes
are drilled. The present invention relates to a different method to
obtain such a racquet frame.
[0034] The method, according to the present invention, consists
substantially of an inflation molding process, too. But this
process is performed on a moldable tube structure 20 that is quite
more complex with respect to a conventional prepreg tube. As it
will be better seen later, the tube structure 20 can be made of
different moldable and/or non-moldable materials. Further, the tube
structure 20 is structured, so as to basically reproduce, before
its curing, the whole structure of the portion 100 (FIG. 13) of
racquet frame 1 to be formed, including the string port holes 7
formed therein.
[0035] Referring to FIG. 2, the method, according to the present
invention, in fact comprises a manufacturing step a) of providing
the tube structure 20. The tube structure 20 comprises a first tube
region 21 containing a first inflatable bladder 22. The tube
structure 20 comprises also a second tube region 23 in an opposite
position with respect to the first tube region 21. The second tube
region 23 contains a second inflatable bladder 24. The tube
structure 20 comprises also an intermediate tube region 25 that is
positioned between the first tube region 21 and the second tube
region 23. One or more cross channels 26, which pass through the
tube structure at the intermediate tube region 25, are
provided.
[0036] The shape of the tube structure 20 may be any, according to
the needs. In particular, the shape of the cross channels may vary,
in relation to the portion of racquet frame 100 to be formed. The
cross channels 26 have main longitudinal axis 261, which intercepts
the main longitudinal axis 201 of the tube structure 20 with a
predefined angle. Each of the cross channels 26 may have a
different shape and the axis 261 may be differently angled with
respect to the axis 201, according to the needs. This may happen,
for example, when the frame portion 100 to be formed relates to the
throat bridge 3 or the converging shafts 4 of the racquet
frame.
[0037] In other cases, for example when the frame portion 100
relates to the head 2 of the racquet frame, the cross channels 26
preferably have a cylindrical shape and a main longitudinal axis
261 that is substantially perpendicular with respect to the main
longitudinal axis 201, as shown in the cited figures. Also, the
number of channels 26 of the tube structure 26 may be any,
depending on the number of string port holes 7 that are to be
formed in the frame portion 100 that has to be molded.
[0038] The tube structure 20 can be wholly made of moldable
material, such as, for example, a prepreg material. Alternatively,
the materials forming the outer wall 27 of the tube structure 20
and of the inner walls 28, which define the channels 26, may be
different. For example, the outer wall 27 may comprise a moldable
prepreg material while the inner walls 28 may be made of one or
more layers of moldable material (e.g. prepreg or a plastics
material or the like) and/or one or more layers of non-moldable
material (e.g. aluminum, wood, glass or the like). This solution is
particularly advantageous since, as it will be better shown in the
following, it makes it possible to obtain a racquet frame, which
comprises co-molded regions of different materials, particularly at
the string port holes. Thus, it is possible a higher flexibility in
the design of the sports racquet frame, the mechanical proprieties
of which may be easily changed/improved depending on the chosen
materials.
[0039] Referring now to FIGS. 3-10, a preferred sequence of
manufacturing steps a.1)-a.6) for obtaining the tube structure 20
is described.
[0040] In an initial step a.1), a chuck member 30 is provided. The
chuck member comprises a first chuck element 31 and a second chuck
element 32. The first chuck element 31 is inserted into the first
inflatable bladder 22 and the second chuck element 32 is inserted
into the second inflatable bladder 24. After the insertion into the
respective bladders, the first chuck element 31 and the second
chuck element 32 are associated to an intermediate chuck element
34. The surfaces 311 and 322 of the first and second chuck elements
31 and 32, are associated to the intermediate chuck element 34
respectively at its opposite sides 343 and 342. The coupling
surfaces 311, 322, 343 and 344 may be complementary curved, as
shown in FIG. 3, but they may have also a different shape,
according to the needs. As a result, the chuck member 30 will
substantially consist of the "sandwich" structure that is shown in
FIG. 4. Such a sandwich structure comprises the superimposed first,
intermediate and second chuck elements 31, 32 and 34 and the first
and second inflatable bladders 22 and 24. Said bladders 22 and 24
are positioned respectively between the first chuck element 31 and
the intermediate chuck element 34 and between the second chuck
element 32 and the intermediate chuck element 34. Advantageously,
the intermediate chuck element 34 comprises one or more couples of
chuck cross cavities 35. Each couple of chuck cross cavities
passes, at least partially, through the chuck member 30 at opposite
sides 343 and 342 of the intermediate chuck element 34. Each cross
cavity 35 may have a different shape and a main longitudinal axis
351, which is differently angled with respect to the main
longitudinal axis 301 of the chuck member 30, according to the
needs. Preferably, the chuck cross cavities 35 have a same
longitudinal axis 351 that is substantially perpendicular with
respect to the axis 301. Further, each couple of chuck cross
cavities preferably forms a cross channel 35, which passes through
the entire section of the intermediate element 34. The couples of
chuck cross cavities or the chuck cross channels 35 on the
intermediate chuck element 34 may be in any number, depending on
the number of string port holes 7 that are to be formed on the
frame portion 100.
[0041] A subsequent preferred step a.2) of inserting the chuck
member 30 into a prepreg tube 40 is then performed. As it is shown
in FIG. 5, the chuck member 30 is completely surrounded by the
prepreg tube 40. In this manner, as better shown later, an easy
insertion of the inflatable bladders 22 and 24 into the prepreg
tube 40 is achieved.
[0042] It is then provided a further preferred step a.3) of
removing predefined portions 410 and 420 of the prepreg tube 40.
Particularly, the portions 410 and 420 are the portions of the
prepreg tube 40, which cover the chuck cavities 35 respectively at
the first side 341 and the second side 342 of the intermediate
chuck element 34. The cross cavities 35 are used as guides or
tracks for improving the precision of the removing process of step
a.3), which may be, for example, a punching process or a laser
cutting process.
[0043] In any case, at the end of step a.3), the prepreg tube 40
will be provided with one or more couples of opposite holes 41 and
42, which are positioned on opposite surfaces of the prepreg tube
40 that cover the corresponding opposite sides 341 and 342 of the
intermediate chuck element 34 (FIG. 6). The shape of the opposite
holes 41 and 42 may be any, according to the needs.
[0044] At a subsequent preferred step a.4), the intermediate chuck
element 34 is removed from the prepreg tube 40 (FIG. 7).
[0045] Forming the holes 41 and 42 on the prepreg tube 40 may
entail a weakening of the structure of the prepreg tube 40. Thus,
on a following preferred step a.5) one or more tube support
elements 50 are adopted to sustain the prepreg tube 40. Each
support element 50 is inserted through a couple of opposite holes
41 and 42 of the prepreg tube 40 (FIG. 8).
[0046] The shape of the support elements 50 may vary and they
preferably have main longitudinal axis 501, which intercepts the
main longitudinal axis 401 of the prepreg tube 40 with a predefined
angle. Each of the support elements 50 may have a different shape
and axis 501 differently angled with respect to the axis 401,
according to the needs. Preferably, as shown in the cited figures,
the support elements 50 are cylindrically shaped and have a
longitudinal axis 501 that is substantially perpendicular with
respect to the main longitudinal axis 401 of the prepreg tube 40.
In FIG. 9a, it is shown a support element 50 comprising a single
layer 502 while in FIG. 9b, it is shown a support element 50
comprising a two layers 503 and 504. Of course, a support element
50 may comprise also a different number of layers. In addition, the
layers 502-504 may be made of a moldable or a non-moldable
material.
[0047] Advantageously, each of the opposite ends 51 and 52 of the
support element 50 may comprise an edge 53, which externally
protrudes from the outer surface of the support element 50. The
edge 53 can be obtained by folding the opposite ends 51 and 52
after having inserted the support element 50 into the holes 41 and
42. In alternative, the edge 53 may be pre-formed. The use of the
edge 53 is particularly advantageous since it allows improving the
joint between the support element 50 and the prepreg tube 40,
thereby preventing from the arising of possible defects of the
frame 100 in the vicinity of the string port hole 7, during the
molding process.
[0048] Further, the edge 53 may protrude from the ends 51 and 52
with a sharp angle (not shown) or, preferably, with a certain
radius of curvature (as shown in FIG. 9a). This last feature allows
obtaining entrances to the string port holes 7, which are rounded
and thus do not require the use of bumper or grommet strips or the
need of abrasion operations on the molded frame.
[0049] Finally, it is performed the preferred step a.6) of removing
the first and second chuck elements 31 and 32 respectively from the
first and second inflatable bladders 22 and 24 and from the prepreg
tube 40. The inflatable bladders 22 and 24 are thereby confined in
two regions 45 and 46 of the prepreg tube 40, separated by an
intermediate region 47 of the prepreg tube 40, at which the support
elements 50 are inserted.
[0050] As a result of the preferred processing steps a.1)-a.6), the
moldable tube structure 20 is thus obtained. The outer wall 27 of
the tube structure 20 is formed by the prepreg tube 40. The inner
walls 28, which define the channels 26 of the tube structure 20,
are formed by the support elements 50. The regions 45, 46 and 47
correspond respectively to the mentioned regions 21, 23 and 25 of
the tube structure 20.
[0051] After the tube structure 20 is provided, the method
according to the present invention, comprise a sequence of
manufacturing steps b)-d), which basically performs an inflatable
molding process on the tube structure 20.
[0052] At a step b), the tube structure 20 is placed inside a mold
60, a portion of which is shown in FIGS. 11-12. Preferably, the
mold 60 comprises two halves 61 and 62, which form a mold cavity 63
of the desired shape of the frame portion 100, when they are joined
together. The mold cavity may not be perfectly oval as shown in
FIGS. 11-12. For example, one wall of the mold cavity may be
inwardly curved to form a string groove. One or more mold members
64 are inserted into the cross channels 26 of the tube structure
20. Each mold member 64 has an outer surface 641, which faces an
inner surface 261 of the corresponding cross channel 26 (FIG. 12).
Thus, the shape and orientation of the mold members 64 may be any,
depending on the shape and orientation of the cross channels
26.
[0053] The use of the mold members 64 is particularly advantageous,
since it allows forming the string port holes 7 during the molding
of the frame portion 100. Thus, the mold members 64 will have
position and orientation corresponding to the position and
orientation of the string port holes 7, which are to be formed on
the frame portion 100.
[0054] The method, according to the present invention provides a
step c) of pressurizing the first and second bladders 22 and 24
(FIG. 12). In this manner, the tube structure 20 expands within the
mold cavity 63 and it conforms to the shape of the mold 60. If a
moldable material is used for the walls 28 of the channels 26, the
inflation of the bladders 22 and 24 causes also the inner surface
261 of the channels 26 to conform to the shape of the outer surface
641 of the mold members 64. Additionally, thanks to the inflation
of the bladders 22 and 24, the portions 271 of the outer wall 27 of
the tube structure 20, in the vicinity of the ends of the channels
26, will stick to the end portions 281 of the inner walls 28 of the
tube structure 20 and/or to the edges 53 provided in the support
elements 50. This feature further reduces the arising of defects on
the molded frame structure.
[0055] After the pressurization of the bladders 22 and 24, the mold
60 is then heated at a suitable temperature, such that the tube
structure 20 cures.
[0056] At the following step d), the cured tube structure 20 is
removed from the mold cavity 63 and the mold members are removed
from the cross channels 26.
[0057] The cured tube structure 20 form the portion 100 of a sports
racquet frame 1 and the inner surface 261 of the cross channels 26
define the inner surface of the string port holes 7, in particular
the bearing surfaces 10 and 11.
[0058] The frame portion 100, resulting from the method according
the present invention, is better shown in FIG. 13. At a cross
section 102 along a section plane AA' that passes through a string
port hole 7, the frame portion 100 comprises two separated cavities
102a and 102b, which are divided by the string port hole 7. The
string port hole 7 is defined by the bearing surfaces 10 and 11. At
a cross section 103 along a section plane BB' that does not pass
through a string port hole 7, the frame portion 100 comprises a
single cavity 101.
[0059] The foregoing represents preferred embodiments of the
invention. Variations and modifications will be apparent to persons
skilled in the art, without departing from the inventive concepts
disclosed herein. For example, the port string holes 7 may have a
round, oval, or otherwise curved cross sectional shape or other
shapes such as rectangular shape. The port string holes 7 may have
a main longitudinal axis along the string bed plane, which may be
differently angled with respect to the main longitudinal axis of
the frame portion 100, according to the needs. Thus, as already
stated above, also the shape and orientation of the channels 26, of
the chuck cross cavities 35, of the support elements 50 and of the
mold members 64 may be any, according to the needs. The method,
according to the present invention may therefore be adopted for
manufacturing any portion 100 of the sports racquet frame 1. Thus,
it may be used to manufacture portions of the head 10, of the
throat bridge 12, of the shafts 14 and of the handle 16 of the
sports racquet frame 1. The method according to the present
invention may be used to obtain also string holes having the same
cross section of conventional string holes 18. To this aim, it is
sufficient to reduce the section of the corresponding channels 26
of the tube structure 20.
[0060] Grommet members may be selected to change the weight,
balance, and moments of inertia (mass and polar) of the racquet.
Conventional grommet or bumper strips are preferably used with the
conventional string holes, since these may still have sharp edges,
which could otherwise damage the strings, given the fact that they
have a very small diameter.
[0061] The method according to the present invention allows
achieving the intended aim and objects. Enlarged string holes on
the racquet frame are easily obtainable with the method according
to the present invention. This allows the overall weight of the
racquet to be reduced and makes stringing easier. Enlarged string
holes also improve the performance of the racquet, reduce
production costs, vibration, and shock, and improve comfort. The
enlarged holes are obtained with a single molding operation without
the need of removing portions of the racquet frame after the
molding process is completed. It therefore possible to avoid those
post-curing operations, such as drilling, which may weaken or
damage the molded racquet frame.
[0062] This feature allows maintaining unchanged the structural
integrity of the racquet frame, thereby improving its mechanical
properties. Furthermore, it is possible to provide a racquet frame
with regions of different materials, particularly at the string
port holes. Thus, with an appropriate choice of materials, it is
possible to further improve the mechanical properties of the
racquet frame. From the above description, it is evident that the
method according to the present invention can be carried out in a
simple manner, which is particularly suitable for industrial
implementation and processing. This feature allows reducing the
production costs of the racquet frame.
* * * * *