Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a method and an apparatus for
producing footwear soles, and in particular to a method and a
machine for molding footwear soles.
The method and machine of the present invention in~
corporate several important innovations, and represent develop-
ments of the apparatus and method disclosed in Canadian Patent
No. 900,116, issued to sata Shoe Company of Canada Limited on
May 16, 1972. When molding soles using the apparatus described
in this patent, a large quantity of sprue is produced. The
sprues must be removed by grippers and recycled or discarded.
Moreover, the use of the apparatus is somewhat labor intensive.
While the soles produced are wiped from the lower molds, they
are not removed from the immediate vicinity of the apparatus,
i.e. the finished soles must be carried away manually from the
apparatus for further processing.
An object of the present invention is to render the
molding of footwear soles more automated. Accordingly, the
present invention relates to a machine for molding footwear soles
comprising:
(a) frame means for carrying a plastic extruder;
(b) bottom mold means mounted on said frame means;
(c) movable top mold means mounted on said frame means
for cooperating with said bottom mold means to define
a mold cavity for receiving plastic from said extruder
for forming a footwear sole;
(d) means for moving said top mold means between a closed
cavity forming position and an open position in which
the molded sole is retained by said top mold means;
(e) gripper means for removing a sole from said top
mold means; and
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(f) transfe~ means carr~ving said gLippe~ means for
moving said sole ~rom the vicinit~ of the top mold for
further processing or packaging.
The invention also relates to a method o producing a
footwear sole comprising the steps of:
(a) forming a mold cavity by mo~ing a top mold assembly
downwardly against a bottom mold assembly;
(b) injecting plastic material into said mold cavity
to form the sole;
(c) opening the mold cavity by moving the top mold
assembly upwardly away from the bottom mold assembly with
the sole attached to said top mold assembly;
(d) gripping said sole and transferring the sole away
from the top mold assembly for further processing or
packaging.
By using a so-called hot runner device in the machine
when molding with a thermoplastic material, the quantity of
plastic used in the molding process is reduced, because the
sprue normally formed is eliminated. A hot runner device is
intended to keep the thermoplastic material in the ~used state
until the material enters the mold. Thus, the sprue normally
associated with the molding of a thermoplastic material is
eliminated. The usual hot runner systems include heating
elements connected to and forming part of the mold. In the
machine of the present invention, the hot runner device is not
a part of the mold which substantially simpli~ies the mold
structure and reduces mold production costs.
The invention will now be described in greater detail
j~ with reference to the accompanying drawings, which illustrate
preferred embodiments of thé invention and wherein:
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Figure 1 is a side elevation view of a moldiny machine
in accordance with the present invention showing a mold in the
open position;
Figure 2 is a plan view of the machine of Fig. l;
Figure 3 is a front elevation view of the machine of
Figs. 1 and 2 with one mold open and one mold closed;
Figure 4 is a longitudinal sectional view of a hot runner
device used in the machine of Figs. 1 to 3;
Figure 5 is-a cross-sectional view of the device oE
Fig. 4;
Figure 6 is a cross-section taken generally along line
VI-VI of Fig. 4;
- Figure 7 is a plan view of a swlvel assembly for the
top mold assembly of the apparatus of Figs. 1 to 3;
Figure 8 is a partly sectioned end view of a post used
in the assembly of Fig. 7;
Figure 9 is a perspective view of a top mold and a
latch therefor;
Figure 10 is a perspective view of the top mold and a
safety lock therefor;
Figure 11 is a longitudinal sectional view of a gripping
device used in the machine of Figs. 1 to 3;
Figure 12 is a partly sectioned side view of the device
of Fig. 11;
Figures 13 to 15 are schematic plan and front elevation
views of the portions of the machine of Figs. 1 to 12 in operation;
Figure 16 is a schematic front view of an alternate
mold structure for use in the machine of Figs. 1 to 3; and
Figures 17 and 18 are schematic elevation views of the
structure of Fig. 16.
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B~SIC M~CHINE
With reference to ~i~s. 1 to 3, the molding machine of
the present invention includes a generally rectangular frame 1
with adjustable feet 2. A carriage 3 carries a pair of extruders
4 at one end of the frame 1. The extruders 4 normally remain
in position for injecting thermoplastic material into a pair of
molds generally indicated at 5, but can be moved away from the
molds for purging or servicing. A thermoplastic material, e.g.
polyvinyl chloride or thermoplastic rubber is fed into the extruders
4 through hoppers 6.
Each of the molds 5 (Fig. 3) include a movable top mold
assembly 7 and a fixed bottom mold assembly 8. The bottom mold
assembly 8 is mounted on a -table or platen 9. The top mold
assembly 7 is moved vertically between a closed position ~right
mold - Fig. 3) and an open position (left mold - Fig. 3) by a
large cylinder 10, the piston rod 11 of which is connected to the
top mold assembly 7. The top mold assembly 7 is guided by a rod
12 extending upwardly through a fixed top platen 13, which is
supported by posts 14. Soles 16 molded in the molds 5 are
removed from the molds by automatic transfer devices generally
indicated at 17 which include gripping devices 18, and swing
arm assemblies 19 for transferring the soles 16 to conveyors 20.
The soles 16 can also be transferred directly t~ containers
(not shown) for packaging. The conveyors 20 are mounted on
stands 21 parallel to the longitudinal axis of the frame 1 for
conveying the soles 16 away from the machine for further process-
ing or packaging. The operating of the machine, including the
extruders 4 is controlled simply using a console 22 mounted
on the outer end of a boom 23 at the mold end of the machine.
The boom 23 is rotatably mounted on the frame 1 by means of a
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post 24 in a bracket 25. Panels 26 and doors 27 (Figs. 1 and 2)
are provided on the mold end of the machine for protecting the
operator of the machine. Of course, the doors 27 permit access
to the molds for servicin~, etc.
HOT RUNNER S~STEM
Referring now to Figs. 4, 5 and 6, as mentioned hereinbefore,
each bottom mold assembly 8 is fixedly mounted on the machine
platen 9. Such bottom mold assembly 8 includes a bottom mold
30, which defines a mold cavity 31 with a top mold 32 for receiv-
ing a thermoplastic sole-forming material from a nozzle 33 of
the extruder 4. The bottom mold 30 is mounted on a cooling plate
35 provided with a passage 36 for circulating coolant which
ensures that the sole 16 hardens quickly for removal from the
mold.
The bottom mold assembly 8 is mounted on a hot runner
system generally indicated at 37, which keeps the plastic liquid
until it enters the mold cavity 31. The hot runner system in-
cludes a casing defined by a top wall 38, an end wall 39, side
walls 40 (Fig. 6), and partitions 42. The casing must be suffi-
ciently strong to support the mold 5 under high molding pressures,and sufficiently open to prevent heat transfer. A cover plate
43 (Fig. 4) at one end of the casing permits access to the
remainder of the hot runner system.
Plastic from the extruder 4 is fed into the mold cavity
31 through a heated manifold defined by a block 44 and tubular
nozzle assemblies 45. The block 44 is generally V-shaped (Fig.
6) with U-shaped channels in the top and bottom surfaces thereof
for receiving tubular heating elements 46~ Ends 47 of each
heating element 46 are threaded for connecting the elements to
electrical leads (not shown)-. Thermocouples 48 are mounted in
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the top o~ the block 44 fox controlling the temperature. The
thermocouples 4~ are mounted at the ends and vertex o~ a V-shaped
channel ~9 in the block 44. Heating coils 51 are provided
around the nozzle assemblies 45 for ensuring that thermoplastic
material therein remains liquid until entering the mold cavity 31.
It is important to keep the nozzle assemblies 45 aligned
with the injection ports 52 in the bottom mold 30. Accordingly,
longitudinal and transverse stops 53 and 54, respectively (Fig. 6)
are provided for retaining the block 44 and consequently the nozzle
assemblies 45 in proper alignment. The longitudinal or front
stop 53 is merely a post for engaging front end 55 of the block
44. The transverse stops 54 include hooks 56 for engaging
vertical projections 57 on the front end 55 of the block 44 to
prevent transverse spreading of the arms of the block. The stops
53 and 54 are on the longitudinal and transverse centre lines of
the nozzle assemblies 45, preventing any movement due to heat
expansion of the block 44. Contact between the stops 53 and 54,
and the block 44 is kept to a minimum to keep heat transfer from
the block 44 to the hot runner casing to a minimum.
The rear end of the block 44 is retained between top and
bottom plates 60 and 61, respectively. The bottom plate 61-is
supported on the casing bottom wall by a post 62. Sleeves 63
support the front end of the block 44. The sleeves 63 have
bevelled bottom ends for further reducing contact with the casing,
and consequently heat transfer. The hot runner structure described
to this point ensures minimum heat transfer, so that heat is applied
only to those elements requiring such heat, and heat transfer to
the remainder of the machine is kept to a minimum.
~, Plastic enters the rear end of the block 44 via an inlet
opening 64, and passes through horizontal passages 65 to vertical
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passages 66 in th,e block 44 to the nozzle assemblies 45. Each
nozzle assembly 45 contains a valve including an elongated rod
or valve stem 68 slidably mounted in a bushing 69 in the block
4~. The top end o~ the valve stem 68 is tapered for mating with
a correspondingly tapered injection orifice 70. Annular sealing
grooves 71 are provide~ in the bottom end of the valve stem 68.
The grooves are filled with plasti.c during injection to seal the
'stem 68 in the bushing which prevents leakage of molten plastic
between the bushing and the valve stem. The valve stem is reci-
procated in the passage 66 by tubular rod 72 connected to thebottom end of the valve stem 68 and extending downwardly through
holes 73 in the platen 8 to a lever mechanism generally indicated
at 75.
The lever mechanism 75 includes a pair of levers 76
connected to the rods 72 by pins 77 extending through the bifur--
cated upper end 78 of the levers 76 and through the bottom ends
of the rods 72. The levers 76 are pivotally mounted for rotation
around a horizontal axis on the front end 79 of a bracket 80. A
pivot pin 82 extends between downwardly extending sides 83 of
the bracket 80 for rotatably supporting the levers 76. A pair of
cylinders 84 are also mounted on the bracket 80. A clevis 85
on the rear end of each cylinder 84 pivotally connects the cylinder
to an arm 86 extending downwardly from the rear end of the bracket
80. A piston rod 87 extends outwardly from the front end of each
cylinder 84, and the front end of the rod is pivotally connected
to one of the levers 76 by a clevis 88. Thus, extension or
retraction of the rod 87 causes closing or opening, respectively
of the injection orifice 70. Upward or closing movement of the
valve stems 68 is limited by stop bolts 89 extending through
the bottom end of each lever 76. The bolts 89 engage the ends of
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a horizontal arm 90 o~ an inverted T-shaped support 91, which
extends downwardl~ from the bracket 80. By adjusting the bolts 89,
the degree of opening of the valve stems 68 can be altered to
change the mold filling characteristics.
TOP MOLD ASSEMBLY
Referring now to Figs. 7 to 10, each top mold assembly
7 includes the top mold 32, which is connected to a cooling
plate 95. The top mold 32 and the cooling plate 95 are pivotally
mounted on a vertically movable platen 96, which is connected
to the bottom end of the piston rod 11 of the cylinder 10. A pivot
plate 97 is connected to each side of the front end 98 of the
cooling plate 95. A pin 99 extends through the top end of each
plate 97 into a block 100 on each side of the top of the platen
96 for pivotally supporting the top mold 32 and the cooling plate
95 for rotation around a horizontal axis defined by the pins 99.
Thus, the top mold 32 can be rotated from a horizontal position
; to a substantially vertical position (approximately 15 from the
vertical), as described hereinafter in greater detail.
As shown in Fig. 8, the bloc~ 100 is connected to the
platen 96 by a pair of bolts 101 and disc springs 102 sandwiched
between the head of each bolt 101 and a countersunk recess 103
in the block 100. Thus, there is a .030" gap between the block
100 and the platen 96 when the top mold 32 is in the closed
position against the bottom mold. When the pressure on the top
mold 32 is released, i.e. when the top mold 32 is moved away
from the bottom mold 30, the springs 102-press the block 100
down, so that the gap is between the platen 96 and the cooling
plate 95, (Fig. 10) which facilitates rotation of the top mold
32 and cooling plate 95.
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` 30 Rotation of the top mold 32 is effected by a swing out
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cylinder 108 (Fi~s. 7, 9 and 10)~ the xear end o~ which is
pivotally connected to ~ post 109 on the rear end of the platen
96 A piston rod 110 extends forwardly from the cyllnder 108
and is pivotally connected to an arm 112 extending inwardly
from one of plates 97 by a clevis 113. Retraction and e~tension
of the piston rod 110 causes opening and closing, respectively
o~ the top mold 32, i.e. swinging movement of the top mold
from the horizontal to the vertical position and vise versa.
The cooling plate 95 is guided into position against the platen
96 by guidé lugs 114 extending downwardly from the platen.
During molding, the top mold 32 is locked in the closed
(horizontal position) against the platen 96 by a latch generally
indicated at 115 (Fig. 9) on the rear end of the platen 96.
The latch 115 includes a lug 116 extending outwardly from the
rear end of the cooling plate 95. The lug 116 is engaged by
a hook 117, which is mounted on a shaft 118 extending between a
pair of blocks 119 on the rear end of the platen 96. The shaft
118 and the hook 117 are rotated from the latched position to
the release position by a cylinder 120 when air is supplied to
the cylinder. A spring (not shown) in the cylinder 120 returns the
hook 117 to the latch position. The rear end of the cylinder 120
is pivotally mounted on a post 121 on the platen 96. A piston
rod 122 extending outwardly from the other end of the cylinder
120 is pivotally connected to the top end of a lever 123 by a
clevis 124. The lever 124 is fixedly connected to the shaft 118,
so that retraction of the piston rod 122 causes the hook 117 to
release the lug 116 and consequently the cooling plate 95 and
the top mold 32.
,; A safety lock generally indicated at 125 (Fig. 11) for
the top mold ~ssemblv prevents closing of the top mold _f the
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doors 27 are open. The lock 125 is mounted on the front end of
the platen 96 and ~ncludes a block 126 in which a pin 127 is
slidably mounted. The pin 127 normally abuts one of the plates
97. When the top mold 32 and cooling plate 95 swing out the
pin 127 remains retracted in the block 126 The pin 127 is
connected to the piston rod 128 of an air cylinder 129 mounted
on the block 126 by a plate 130. If one of the doors 27 (Fig. 2)
is opened, a spring (not shown) in the cylinder 129 pushes the
pin 127 behind the plate 97 to hold the top mold 32 and the cooling
plate 95 in the swung out position. As soon as the door 27 is
closed, air is supplied to the cylinder 129 to retract the pin
127, allowing the top mold 32 to swing in to the closed position.
Thus, the possibility of injury to the operator is reduced.
GRIPPING DEVICE
After the top mold 32 has been swung out, (Fig. 1) each
sole 16 is gripped by a gripping device generally indicated at
18 (Figs. 1, 11 and 12). A pair of gripping devices is mounted
in the rectangular bracket 135 on one end of the arm 19. Each
gripping device 18 includes a pair of jaws 136 with opposed
serrated inner edges 137. The inner ends 138 of the jaws 136
are pivotally mounted on pins 139 in a generally cylindrical
casing 140. The outer, gripping ends of the jaws 136 are biased
apart by a helical spring 141 extending between opposed recesses
142 in the jaws. The jaws 136 are closed by a frusto-conical
plunger 143 on the outer end of a piston rod 144. The plunger
143 slides between and presses against rollers 146 mounted in the
inner opposed ends of the jaws 136. The inner end of the piston
rod 144 is connected to a piston 147, which is slidably mounted
in a chamber 148. The inner end of the chamber 148 is closed
by a cover 150, which is attached to one end of another piston rod
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~ l~7~D~l~i. The piston rod 151 an~ consequently -the entire casing
140 are slidable in a chamber 152 in one end of a larger casing
153. A vent 154 is provided in the chamber 152. The rear end
of the piston rod 151 is connected to a double actin~ piston
155 slidably mounted in a chamber 156 in the casing 153. The
casing 140 is provided with an air inlet 157 (Fig. 12). The
air inlet 156 is also used for venting the chamber 148 to atmos-
phere. Air inlets 158 and 159 are provided for introducing air
- into and venting the chamber 155 for extending or retracting the
piston rod 151.
When air is introduced into the chamber 148 via inlet 157,
the plunger 143 moves outwardly to close the jaws 136. When air
is vented from the chamber 148 through the inlet 157, the spring
141 forces the jaws 136 open and returns the plunger to the
retracted position.
When air is introduced into the chamber 156 via inlet 158,
the piston 155 and consequently the casing 140 move outwardly to
extend the jaws 136 for gripping a sole 16. When air is introduced
into the inlet 159 and vented through inlet 158, the jaws 136
are retracted with the casing 140, piston rod 151 and piston 155.
OPERATION
Referring now to Figs. 13 to 15, the operation of the
machine will be described. It will be appreciated that the
operation of one half only of the machin~ is described, the oper-
ation of the other half being the same.
With the extruder 4 in position and the mold 5 closed,
thermoplastic material is injected through the hot runner system
37 into the mold 5 to form a sole 16. Each mold 5 contains a
pair of mold cavities 31, so that two soles 16 are molded simult-
aneously in each mold 5. Of course, during molding, the top mold
32 and cooling plate 95 are ~ocked in position against the platen 96
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and the entire top mold assembly 7 is clam~ed against the bottom
mold assembly 8 by the clamping cylinder 10.
During the molding step, the gripping devices 18 are swung into
position in front of the mold 5 (Fig. 13). For such purpose, the
automatic transfer device 17 of the machine includes the swing arm
assemblies 19, which are rotatably mounted on rotary actuators 160
for rotation around a vertical axis. Each actuator 160 is mounted on
a bracket 161 (Fig.l) for vertical sliding movement on th~ machine
frame 1. Vertical adjustment is required for different molds, i.e.
depending on the mold size, the location of the portion of the sole
to be gripped may vary. Arm 162 of the swing arm assembly, carrying
the bracket 135, is rotatably mounted in a sleeve 163 for rotation
around a hori~ontal axis. Such rotation is effected using a rotary
actuator 164. Upon completion of molding step, the clamping cylinder
10 and the piston rod 11 raise the top mold assembly 7 (Fig. 14). The
cooling plate 96 and the top mold 32 are swung forwardly (Figs. 1
and 14). The casing 140 of each of the gripping devices 18 is al-
ready extended and the jaws 136 are closed to grip the soles 16. The
soles 16 include a hollow heel with cruciform partitlons, which are
gripped by the jaws 36. At the same time as gripping, the soles 16
are ejected in the conventional manner using air and ejector pins
(not shown). The jaws 136 with the soles 16 are retracted by
supplying air to the chamber 156 through inlet 159. The swing
arm assembly 19 is swung through approximately 90 to position
the soles 16 over the conveyor 20. The arm assembly 19 is
rotated 90 so that the grippers 18 point downwardly. The jaws
136 are opened and the soles 16 are dropped onto the conveyor 20.
As mentioned previously, the soles 16 can also be dropped into
cartons (not shown) or other containers for shipping, The
jaws 136 and the casing 140 are then returned to the extended
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position, the swing ar~ assembly 19 is rotated to place the gripping
devices 18 in the horizontal position, and the swing arm assembly
19 is returned to the sole gripping position (Fig. 13). This
cycle is repeated indefinitely.
TURRET ASSEMBLY
An alternative to the top mold assembly 7 is shown in
Figs. 16 to 18 of the drawings where, whenever possible the
reference nurnerals of Figs. 1 to 15 are used to identify the same
or similar elernents.
The turret assembly of Figs. 16 to 18 includes a yoke
165 carrying a square top mold assembly de~ined by a square
turret 166. The yoke 165 is slidably mounted on the piston rod 11.
The turret 166 is mounted on a shaft 167 in the yoke 165 for
rotation around a horizontal axis. The turret 166 includes a top
mold 168 on each surface thereof. Cooling plates (not shown) and
air ejectors are built into the turret 166 for ejecting soles
from each surface of the turret. Following each 90 rotation of
the turret 166, the turret is locked in position by a piston rod
169, which extends outwardly from a cylinder 170 on the yoke 165
into an aperture in an arm 171 on the turret 166. In this embodi-
ment of the invention, the gripping device jaws are replaced by
suction heads 172, because this embodiment of the invention is
intended for the production of thin soles without hollow heels.
In operation, the turret 166 is moved against the bottom
mold assembly 8 to form mold cavities ~not shown), soles are molded
(Fig. 17), and the piston rod 11 and movable top platen 96 are
raised. As the top platen 96 rises, it engages the yoke 165,
carrying the ~oke 165 and the turret 166 upwardly to create a
gap between the turret 166 and the bottom mold assembly 8. Near
3G the top of the stroke of the piston rod 11, the yoke engages the
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bottom surface o~ the top fixed pl~ten 13, The movable platen 96
continues to rise while the turret 166 remains in one position.
Thus, a gap is created between the top of the turret 166 and the
platen 96. With this arrangement, the turret 166 can be rotated
in the yoke 165 to present a second top mold 16~ to the bottom
mold assembly 8. The platen 96, yoke 165 and turret 166 are
lowered and a second molding operation is carried out. The cycle
is repeated until the fourth molding operation at which time the
first soles oppose the suction heads 172. While the fourth molding
operation is being effected, the first pair of soles is removed
from the turret 166. Thereafter, the molding and sole removal
operations are continuous.
3~
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