Note: Descriptions are shown in the official language in which they were submitted.
CA 02377082 2002-03-15
1
METHOD FOR MAKING A FOOTWEAR HAVING A MIDSOLE
SURROUNDED BY A COVER SHEET
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings which illustrate an embodiment
of the invention,
Fig. 1 is a cross-sectional side view to
illustrate a conventional method for making a shoe;
Fig. 2 is a cross-sectional side view to
illustrate another conventional method for making a
shoe ;
Fig. 3 is a block diagram to show consecutive
steps of a method embodying this invention for making
a footwear;
Figs. 4 and 5 illustrate how a midsole of the
footwear is formed in a mold according to the method
of this invention;
Fig. 6 is a fragmentary cross-sectional side
view to illustrate cushioning pads which can be
optionally embedded in the midsole of Fig . 5 according
to the method of this invention;
Fig. 7 is a fragmentary cross-sectional side
view to illustrate the cushioning pads of Fig. 6 in
the form of air bag units that can be exposed from
the footwear;
Figs. 8 to IO illustrate how a sandal is made
according to the method of this inverition.
CA 02377082 2002-03-15
2
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a method for making
a footwear, more particularly to a method for making
a footwear having an outsole, an upper, and a midsole
that is surrounded by a cover sheet:
2. Description of the related art
Fig. 1 illustrates a conventional method for
making a shoe including an upper 4 , an outsola 3 , and
a midsole 5 interconnecting the upper 4 and the
outsole 3. The midsole 5 has a base portion 51 in
contact with and bonded to the outsole 3, and an upper
flange portion 52 extending upwardly from the base
portion 51 and banded to a bottom portion 41 of the
upper 4. The method employs a mold 10 including an
upper mold part with a last 12, a bottom mold part
11, and side mold parts, which define a mold cavity
13. The midsole 5 is formed by filling a foamable
material into an inner cavity 130 that is confined
by the outsole 3, the upper 4, and inner walls of the
side mold parts.
The midsole 5 normally includes filler (not
shown) in the form of pellets which are disposed on
the outsole 3 in the mold. cavity 13 :before the closing
of the mold parts and which are enclosed by the midsole
5 during the formation of the same.
The aforesaid method for making the shoe is
CA 02377082 2002-03-15
3
disadvantageous in that the pellets of the filler tend
to move in the inner cavity 13 during filling of the
foamable material. As a consequence, some of the
pellets may protrude outwardly from an outer surface
of the upper flange portion 52 of the midsole 5,
thereby adversely affecting the appearance of the
shoe. Moreover, since the upper flange portion 52 of
the midsole 5 is exposed, it tends to deteriorate and
discolor.
Fig. 2 illustrates a shoe prepared by a method
that is disclosed in European Patent No. 0830935. The
method uses an outsole 6 that has a flange portion
601 extending to and cooperating with a peripheral
side wall 701 of an upper 7 to confine an inner cavity
60 therebetween. The upper 7 and the outsole 6 are
placed in a mold 10. A midsole is formed in the inner
cavity 60 by filling a foamable material into the
inner cavity 60. A sealing member 8 is employed to
press a tip portion 602 of the flange portion 601
against the peripheral side wall '701 of the upper 7
so as to prevent formation of flash on an exterior
of the inner cavity 60. The conventional method is
disadvantageous in that a precise match between an
inner wall of the mold 10 and an outer surface of the
flange portion 601 is needed prior to the formation
of the midsole in order to permit t:he flange portion
601 of the outsole 6 to have a shape conforming to
CA 02377082 2002-03-15
4
the inner wall of the mold 10. Moreover, it is
relatively difficult to form a precise pattern on the
outer surface of the flange portion 601 of the outsole
6 according to the conventional method.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention
is to provide a method for making a footwear that is
capable of overcoming the aforementioned drawbacks.
According to the present invention, a method for
making a footwear. comprises the steps of : preparing
an out sole having a peripheral side wall; preparing
an upper that is vertically aligned with and that is
spaced apart from the outsole and that has a
peripheral side wall; preparing a flexible elongated
cover sheet that is disposed between and that
interconnects the peripheral sides walls of the
out sole and the upper so as to confine an inner cavity
among the outsole, the upper, and. the cover sheet,
the cover sheet being expandable outwardly of the
inner cavity when an inner pressure in the inner
cavity is increased; preparing a mold that has an
inner wall defining a mold cavity, an upper mold part
with a last, a bottom mold part opposite to the upper
mold part, and at least two opposite side mold parts;
placing an assembly of the outsole, the upper, and
the cover sheet in the mold cavity such that the
out sole is mounted on the bottom mold part, that the
CA 02377082 2002-03-15
S
upper is fittingly sleeved on the last, and that the
cover sheet confronts the side mold parts; and filling
a foamable material into the inner cavity and
permitting curing and expansion of the foamable
material to take place and to form a midsole bonded
to the upper, the outsole, and the cover sheet, which,
in turn, increases the inner pre~;sure in the inner
cavity to result in expansion of the cover sheet, and
which permits the cover sheet to press against the
inner wall of the mold and to form into a shape that
conforms to the inner wall of the mold.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 3 shows consecutive steps of a method
embodying this invention for making a shoe . Figs . 4
to 6 illustrate how a midsole 40 of the shoe is formed
according to the method of this invention. The method
includes the steps of : preparing an outsole 20 having
a peripheral side wall 202 ; preparing an upper 3 0 that
is vertically aligned with and that is spaced apart
from the outsole 20 and that has a peripheral side
wall 301; preparing a flexible elongated cover sheet
21 that is disposed between and that interconnects
the peripheral side walls 202, 301 of the outsole 20
and the upper 30 so as to confine .an inner cavity 90
among the outsole 2 0 , the upper 3 0 , and the cover sheet
21, the cover sheet 21 being expandable outwardly of
the inner cavity 90 when an inner pressure in the inner
CA 02377082 2002-03-15
d
cavity 90 is increased; preparing a mold 100 that has
an inner wall 101 defining a mold cavity 102 , an upper
mold part 111 with a last 110, a bottom mold part 112
opposite to the upper mold part lll, and at least two
opposite side mold parts 113; placing an assembly of
the outsole 2 0 , the upper 3 0 , and the cover sheet 21
in the mold cavity 102 such that the outsole 20 is
mounted on the bottom mold part 112, that the upper
30 is fittingly sleeved on the last 110, and that the
cover sheet 21 confronts the side mold parts 213 ; and
filling a foamable material into the inner cavity 90
by injecting the foamable material from a feeding
device 200 through a feeding channel 130 and
permitting curing and expansion of the foamable
material to take place and to form the midsole 40
bonded to the upper 30, the outsole 20, and the cover
sheet 21, which, in turn, increases the inner pressure
in the inner cavity 90 to result in expansion of the
cover sheet 21, and which permits the cover sheet 21
to press against the inner wall 101 of the mold 100
and to form into a shape that conforms to the inner
wall 101 of the -mold 100. It is noted that the air
in the inner cavity 90 is simultaneously evacuated
through vent-holes (not shown ) and is discharged to
an exterior of the mold 100 in such. a manner that the
inner pressure in the inner cavity 90 is sufficient
to press the cover sheet 21 against the inner wall
CA 02377082 2002-03-15
7
101 of the mold 100 during the expansion of the
foamable material.
Preferably, the peripheral side walls 202 , 301
of the outsole 20 and the upper 30 are adhesively
bonded to the cover sheet 21 so as to be interconnected
by the same before placing the same in the mold cavity
102. More preferably, the peripheral side wall 202
of the outsole 20 is adhesively bonded to the cover
sheet 21, and the peripheral side wall 301 of the upper
30 is stitched to the cover sheet 21 . A pair of sealing
strips 140, 150 are used to surround the tip portion
of the cover strip 21 so as to seal a seam between
the tip portion of the cover sheet 21 and the upper 30.
The cover sheet 21 can be made from ethylene
vinylacetate copolymer, polyurethane, rubber,
resilient cloth, leather, and the like. Preferably,
the cover sheet 21 is made from ethylene vinyl acetate
copolymer, and has a thickness in a range of from 0 . 5mm
to 8.Omm, and more preferably in a range from l.Omm
to S.Omm. The foamable material preferably is a
mixture of polyo:ls and isocyanate so as to form the
midsole 40 of polyurethane.
The mold 100 is preferably operated at a molding
temperature in a range of from 40 to 120°C for forming
the midsole 40 of polyurethane with the cover sheet
21 made from ethylene vinylacetate copolymer. The
inner wall 101 of the mold 100 can be patterned so
CA 02377082 2002-03-15
8
that when the cover sheet 21 is p~:essed against and
is heated by the mold 100 upon foaming of the foamable
material in the mold 100, the cover sheet 21 can be
patterned as well. Since the cover ;sheet 21 is pressed
S against the inner wall 101 of the mold 100, the pattern
formed on the cover sheet 21 can precisely conform
to that of the inner wall 101 of the mold 100.
Preferably, an inert gas is filled into the inner
cavity 90 prior to the injection of the foamable
material into the inner cavity 90 so as to enhance
the pressing of the cover sheet 21 against the inner
wall 101 of the mold 100 during the forming of the
midsole 40 in the inner cavity 90.
The method of this invention can further include
a step of loading a filler 45 (see Fig. 6) in the inner
cavity 90 before placing the assembly of the outsole
2 0 , the upper 3 0 , and the cover sheet 21 in the mold
cavity 102 so that the filler 45 will be embedded in
the midsole 40 after formation of t:he midsole 40. The
filler 45 can be in the form of pellets; and can be
made of a plastic material selected from a group
consisting of ethylene vinylacetate copolymer,
rubber, and polyurethane.
Referring now to Fig . 7 , in combination with Fig .
6, the method of this invention can further include
a step of disposing a plurality of cushioning pads
50, such as air bag units, in the inner cavity 90 before
CA 02377082 2002-03-15
9
placing the assembly of the outsole 2 0 , the upper 3 0 ,
and the cover sheet 21 in the mold cavity 102 so that
the cushioning pads 50 can be embedded in the midsole
40 after formation of the midsole 40. Each cushioning
pad 50 can have extensions 51 extending through the
cover sheet 21 so as to be exposed from the cover sheet
21. As such, the inner wall 101 of the mold 100 is
provided with positioning holes 10:3 for receiving the
extensions 51 during the formation of the midsole 40.
Preferably, the extensions 51 a re provided with
sleeves 62 which are received in the positioning holes
103 during the formation of the midsole 40.
Thefollowing Examples illustrate the advantage
of using the cover sheet 21 according to the method
of this invention.
Example 1
Material of the cover sheet: ethylene vinylacetate copolymer.
Thiclmess of the cover sheet: 2.0 mm.
Shape of the inner wall of the nbld: concave with shallow pattern.
Foamable material: polyols and isocyanate
Arr~unt of the foarnable material: 133 grams.
Molding temperature: 50~C.
Molding time: '7 minutes.
Result: Density of the midsole is 0.:34 g/cm3, profile of the
cover sheet is consistent with that of the inner wall of the mold,
clear pattern is formed on the cover sheet, and no flash is formed
on the seam between the cover sheet and the upper.
CA 02377082 2002-03-15
1
Example 2
Material of the cover sheet: ethylenevinylacetate copolymer.
Thicl~ess of the cover sheet: 5.0 mm.
Shape of the inner wall of the mold: concave with shallow pattern.
Foamable material: polyols and isocyanate
Amount of the foamable material: 133 grams.
Molding temperature: 70°C.
Molding time: '7 minutes.
Result: Density of the midsole is 0.:34 g/cm3, profile of the
cover sheet is consistent with that of the inner wall of the mold,
clear pattern is formed on the cover sheet, and no flash is formed
on the seam between the cover sheet and the upper.
Example 3
Material of the cover sheet : ethylene vinylacetate copolymer.
Thicl~.ess of the cover sheet: 8.0 mm.
Shape of the inner wall of the mold: concave with shallow pattern.
Foamable material: polyols and isocyanate
Amount of the foamable material: 133 grams.
Molding temperature: 120°C.
Molding time: S minutes.
Result: Density of the rnidsole is 0.34 g/cm3, profile of the
cover sheet is consistent with that of the inner wall of the mold,
clear pattern is formed on the cover sheet, and no flash is formed
on the seam between the cover sheet and the upper.
Example 4
Material of the cover sheet: ethylene vinylacetate copolymer.
Thicl~.ess of the cover sheet: 5.0 mm.
CA 02377082 2002-03-15
11
Shape of the inner wall of the mold: concave with shallow pattern.
Foamable material: polyols and isocyanate
Amount of the foamable material: 133 grams.
Molding temperature : 12 0 °C .
Molding time: 5 minutes.
Result: Density of the midsole is 0.34 g/cm3, profile of the
cover sheet is consistent with that of the inner wall of the mold,
clear pattern is formed on the cover sheet, and no flash is formed
on the seam between the cover sheet and the upper.
The inventor of this application found that when
the thickness of the cover sheet of ethylene
vinylacetate copolymer is less than 0.5 mm and the
molding temperature is above room temperature, the
cover sheet tends to break, which leads to the
formation of flash on the seam between the cover sheet
and the upper, and that when the thickness of the cover
sheet of ethylene vinylacetate copolymer is greater
than 9 . Omm; the cover sheet is dif f icult to be shaped
during the molding process even at a molding
temperature of about 120°C. Moreover, when molding
proceeds at room temperature, poor~profile of and
obscure pattern on the cover sheet of ethylene
vinylacetate copolymer result dueto poorflexibility
of the ethylene vinylacetate copolymer under room
temperature. The drawback can be overcome by using
polyurethane film as the cover sheet, which is
relatively soft and flexible under room temperature.
CA 02377082 2002-03-15
12
Figs. 8 to 10 illustrate how a sandal is made
according to the method of this invention. The sandal
includes an outsole 20' , an upper 30' with an upper
flange 21' disposed over and connected to the out sole
20' , a midsole 40' formed according to the method of
this invention and enclosed by th.e outsole 20' and
the upper 30' , and a strap unit 31' having four end
portions 32'. The function of the upper flange 21'
is similar to that of the cover sheet 21 shown in Fig. 4.
The outsole 20' is provided with a pair of
linking straps 24' having end portions which are
stitched onto the end portions 32' of the strap unit
31' . The upper 30' is formed with four slits 411' for
passage of the end portions of the linking straps 24' .
Before the formation of the midsole 40', the upper
30' and the outsole 20' are respectively mounted on
the upper mold part 111' and the bottom mold part 112' ,
and four positioning sleeves 26' and four support
sleeves 25' are provided and are disposed in a manner
that the four positioning sleeves 26' extend through
the upper mold part 111' and respectively into the
slits 411', that the four support sleeves 25' are
disposed between the outsole 20' and the upper 30'
at the slits 411' and respectively receive the end
portions of the linking straps 24' , and that the end
portions of the linking straps 24' extend outwardly
of the upper mold part 111' through the positioning
CA 02377082 2002-03-15
13
sleeves 26' . After the formation of the midsole 40' ,
the positioning sleeves 26' can be removed from the
upper mold part 111', and the end portions of the
linking straps 24' can be stitched onto the end
portions 32' of the strap unit 31' after removal of
the upper and bottom mold parts 111' , 112' . It is noted
that the end portions 32' of the strap unit 31' can
be stitched onto the end portions of the linking
straps 24' and the thus formed assembly is then
disposed in the mold cavity 90' for subsequent
processing steps for the formation of the midsole 40' .
By using the cover sheet 21 according to the
method of this invention, the aforesaid drawbacks as
encountered in the prior art can be eliminated.
With the invention thus explained, it is apparent
that various modifications and variations can be made
without departing from the spirit of the present
invention. It is therefore intended that the invention
be limited only as recited in the appended claims.
