Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR MOMENTARILY HEATING THE SURFACE OF A MOLD AND
SYSTEM THEREOF
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to methods for momentarily heating the
surface of a mold and system thereof, and particularly to a method for
momentarily
heating the surface of a mold and system thereof, which is capable of
momentarily heating
to the surface of the mold prior to injection molding and cooling a molded
product
immediately after the molding, thereby improving the quality of products in
appearance,
preserving the physical and thermal properties of resin in the products, and
increasing the
productivity of a manufacturing process of the products for the reduction of
the
mmufact«ring cost of the products.
Description of the Prior Art
Tn a technical field where resin (such as synthetic resin, plastics or the
like)
products are manufactured, various attempts have been made to momentarily heat
a mold
to the same temperature as that of resin while the cavity of the mold is being
filled with the
2o resin, and to rapidly cool the mold after the cavity of the mold is filled
with the resin. The
object of these attempts is to increase the quality of products in appearance,
to improve the
strength and thermal properties of the products and to increase the
productivity of the
manufacturing process of the products for the reduction of the manufacturing
costs of the
products.
German Pat. Appln. No. 297 08 721.5 and PCT Appln. No. WO 98/51460
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disclose a mold capable of being temporarily heated by the flame of gaseous
fuel and
synthetic resin forming method thereof. According to the above described
patents, a
synthetic resin injecting mold process is automated and the molded products of
synthetic
resin may be manufactured continuously.
However, according to the above-described patents, since a molded product
cannot be cooled immediately a$er the forming of the product, the quality of
the molded
product is reduced in appearance, the strength and thermal properties of the
injection-
molded product are deteriorated and the productivity of the molding process is
reduced.
t o SUMMARY OF TI-~ INVENTION
Accordingly, the present invention has been made leeeping in mind the above
problems occurring in the prior art, and an object of the present invention is
to provide a
method for momentarily heating the surface of a mold, which allows the mold to
be filled
with molten resin for inj ection molding a$er the preheating of the mold to a
predetermined
temperature and allows an injection-molded product to be cooled upon the
completion of
the injection molding, thereby increasing the quality of the injection-molded
product in
appearance and improving the strength and thermal properrries of the injection-
molded
product.
Another object of the present invention is to provide a system for momentarily
heating the surface of a mold, which comprises upper and lower molds for
forming resin
and performing the heating of the upper and lower molds, a supply unit for
supplying air
and gaseous fuel, a safety unit for preventiizg the danger of gas explosion,
and a control
unit for controlling the operation of the above components.
A further object of the present invention is to provide a method for
momentarily
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heating the surface of a mold and system thereof, in which one or more cores
are disposed
between its upper and lower molds, the cores are momentarily heated using
gaseous fuel
or an induction heater, and heating and cooling are performed in the process
of injection
molding, thereby improving the quality of an injection-molded: product.
Heating of the
mold sLU-face~may also be performed by laser, microwave, radiant, resistive,
impingement
(i.e., high velocity gas), piezoelectric or any other suitable heating
technique that can heat
the mold surface quicldy. Another method of heating the mold surface is
alternating or
staged or pulsed between upper and lower molds or external and internal molds.
In order to accomplish the above objective, the present invention provides a
1o method for momentarily heating a surface of a mold, comprising the steps of
opening
upper and lower molds of the mold, and supplying gaseous fuel; injecting and
igniting the
gaseous fuel from the lower mold after allowing the upper and lower molds to
come close
to each other at a predeternlined distance; heating the upper mold for a
predetermined time
period; filling a forming space between the upper and lower molds with molten
material
through the upper mold immediately after stopping heating and closing the,
upper and
lower molds; cooling a molded product in the closed mold, fm-ther cooling a
molded
product by injecting compressed gas to the molded product after allowing the
upper a~zd
lower molds to be opened at a predeternzined distance; and ejecting the molded
product
from the upper and lower molds after allowing the upper and lower molds to be
2o completely opened. In addition to cooling by compressed gas, the molded
product may be
cooled directly or indirectly in the mold by cooling channels in the mold,
condensing of a
vapor, water spr ay, or other suitable means of removing heat quickly.
In addition, the present invention provides a system for momentarily heating
the
surface of a mold, comprising: a casting material feeder for supplying molten
casting
material; upper and lower molds for forming a predetermined shaped cast; an
injection
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molding control for controlling the upper mold and the lower mold; an air and
gaseous
fuel mixture and supply unit for supplying compressed air and gaseous fuel
simultaneously or selectively; a gaseous fuel mixture and supply control for
controlling.the
operation ofthe air and gaseous fuel mixture and supply~unitan ~ntenace for
interfacing:
~ the injection molding control and the gaseol~s fuel: ~mixfizre :and ;supply
control; and: a
control pailel for visually displaying the control, condition and operation of
the
components of the system.
BRIEF DESCRIPTION OF THE DRAWINGS
o
The above and other objectives;, features and other advantages of the present
invention will be more clearly understood from the following detailed
description taken in
conjunction with the accompanying drawings, in which:
Fig. 1 is a schematic diagram showing a system for momentarily heating ti'~e .
surface of a mold using . the flame of gaseous fuel in accordance with the
present
invention;
Fig. 2 is a diagram showing piping for supplying air and gaseous fuel to fne
main
body of the system in detail;
Figs. 3a to 3f are process charts showing the method for temporarily heating
the
z0 surface of a mold using the flame of gaseous fuel in accordance with an
embodiment of
the present illverition;
Figs. 4a to 4d are process charts showing the method for temporarily heating
the
surface of a mold using the flame of gaseous fuel in accordance with another
embodiment
of the present invention;
Figs. 5a to 5d are process charts showing the method for temporarily heating
the
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surface of a mold using the flame of gaseous fuel in accordance with a fiu-
ther
embodiment of the present invention;
Fig. 6 is a block. diagram, illustrating the control panel of the system for
momentarily heating the surface of a rhold; ".
Fig: 7 ~ is a v~sclieniatic wdiagi~am sliowirig a system for'
inomeriCarily'heatirig .'the
surface of a mold using an induction heater in accordance with the present
invention; Fig.
8 is a flowchart showing the operation of the system for momentarily heating
the surface
of a mold using the induction heater;
Fig. 9 is a schematic diagram showing a water-cooled system for momentarily
heating and cooling the surface of a mold in accordance with an embodiment of
the
present invention;
Fig. 10 is a schematic diagram showing a system for momentarily heating and
cooling the surface of a mold in accordance with an embodiment of the present
invention;
Fig. 11 is a schematic diagram showing a system for momentarily heating and
cooling the surface of a mold in accordance vVith an embodiment of the present
invention;
and
Fig.12 is a detailed view of the core shown in Fig. l l .
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference now should be made to the drawings, in which the same reference
numerals are used throughout the different drawings to designate the same or
similar
components.
Fig. 1 is a schematic diagram showing a system for momentarilyheating the
surface of a mold using the flame of gaseous fuel in accordance with the
present invention.
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Fig. 2 is a diagram showing piping for supplying air and gaseous fuel to the
main body of
the system in detail.
Reference numeral 10 designates :a casting material feeder for supplying
molten
casting material: T'he casting material. feeder 10 supplies injectable
nilaterial; .such as
.'°' synthetic resin orwietal;ev
An upper mold 20 is fixed to the lower end of the casting material feeder 10
under
the casting material feeder 10. The upper mold 20 has a casting material
supply hole 22
for supplying casting material from the casting material feeder 10 to the
upper mold 20, a
cavity 24 for forming the casting material into a predetermined-shaped cast.
The upper
mold 20 is provided with a limit switch 83 for sensing the position of the
upper mold 20.
A lower mold 30 is disposed under the upper mold 20. The lower mold 30
comprises a mold portion 32 for insertion into the cavity 24 of the upper mold
20 to form
the casting material into a predetermined-shaped cast, a lower mold supply
conduit 31 ,
formed in the lower mold 30 to supply mixed gaseous fuel and compressed air, a
plurality
~ 5 of discharge holes 34 for heating and cooling the upper mold 20 using the
mixed gaseous
fuel and the compressed air supplied through the lower mold supply conduit 31,
ar~
ignition unit 40 for igniting gaseous fuel injected by an igniter 41 using
high voltage
current generated by a high voltage generator 44 and sensing gaseous fuel
flame by means
of a fla~'ne sensor 42, a limit switch 84 for sensing the position of the
lower mold 30, an air
2o and gaseous fuel mixture and supply unit 90 for supplying air or mixed
gaseous fuel
supplied through an air and mixed gaseous fuel supply conduit 86, and an
elevating
cylinder 80 including an elevating shaft 82 for selectively lifting or
lowering the lower
mold 30 by the control of an injection molding control 50. The discharge holes
34 are
constructed in the foam of slits, respectively having widths of 0.01 to O.I
mm, and are
25 distributed on the surface of the lower mold 30 in accordance with the
shape of the cast.
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Although not depicted in the drawing, conduits for supplying air and gaseous
fuel
acid a coolant supply conduit for supplying coolant are provided in the lower
mold 30.
The upper and lower molds 20 and 30 are separately formed. The upper mold 20
and/or the .lower mold 30 may beprovided v~ith additional parts necessary for
injection
5molding,includingcooling°channels:
The injection molding control 50 controls the upper and lower molds 20 and 30.
In detail, the injection molding control 50 controls the mechanical operation
for an
injection molding process.
The air and gaseous fuel mixture and supply unit 90 serves to supply
compressed
o air and gaseous fuel simultaneously or selectively, and comprises a variety
of pipelines for
supplying air and/or gaseous fuel and a variety of valves and gauges for
controlling the
flow of air and/or gaseous fuel. The air and gaseous fuel. mixture and supply
unit 90 is
divided into an air and gaseous fuel supply line 91 for ignition and an air
and gaseous fuel
supply line 110 for heating. A compressed air supply line 130 for supplying
compressed
15 air and a gaseous fuel supply line 140 for supplying gaseous fuel are
respectively
connected to the air and gaseous fuel mixture and supply unit 90. A compressed
air
supply source 136 for supplying compressed air and a gaseous fuel supply
source 146 for
supplying gaseous fuel are respectively connected to the compressed air supply
line 130
and the gaseous fuel supply line 140.
2o The air and gaseous fuel supply line 91 for ignition includes an air and
gaseoL~s
fuel mixture element 92 for ignition, an air supply line for ignition and a
gaseous fuel
supply line for ignition. The air supply line for ignition includes a first
pneumatic pressure
gauge 93 for measuring the pressure of supplied air, a first needle valve 94
for preventing
compressed air from flowing backward, and a first solenoid valve 95 for
interrupting the
25 supply of compressed air and a first manual valve 96 for regulating the
amount of supplied
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compressed air. The gaseous fuel supply line for ignition includes a first
fluitlic pressure
gauge 101 for measuring the pressure of supplied gaseous fuel, a second needle
valve 102
for preventing gaseous fuel from flowing backward, and a second solenoid valve
103 for
inten-upting the supply of gaseous fuel and..a second manual valve .104 for
regulating the
amount of supplied gaseous fuel. The air and gaseous fuel mixture element 92
for ignition
serves to mix air and gaseous fuel supplied through the air and gaseous fuel
supply lines
for ignition.
The air and gaseous fuel supply line 110 for heating includes an air and
gaseous
fuel mixture element 111 for heating, an air supply line for heating, and a
gaseous fuel
l0 supply line for heating. The air supply line for heating includes a second
pneumatic
pressure gauge 112 for measuring the pressure of supplied air, a third needle
valve 113 for
preventing compressed air from flowing backward, and a third solenoid valve
114 for
interrupting the supply of compressed air and a first pressure switch 115 for
sensing the
pressure of supplied compressed air and interrupting the supply of compressed
air when
the pressure of the supplied compressed air is not equal to a predetermined
value. The
gaseous fuel supply line for heating includes a second fluitlic pressure gauge
120 for
measuring the pressure of supplied gaseous fuel, a fourth needle valve 121 for
preventing
gaseous fuel from flowing backward, and a fourth solenoid valve 122 for
interrupting the
supply of gaseous fuel and a second pressure switch 123 for sensing the
pressure of
2o supplied compressed air and interrupting the supply of gaseous fuel when
the pressure of
the supplied gaseous fuel is not equal to a predetermined value. The air and
gaseous fuel
mixture element 111 for heating serves to mix air and gaseous fuel supplied
through the
air and gaseous fuel supply lines for heating.
The- compressed air supply line 130 is connected to both air supply line for
ignition of the air and gaseous fuel supply line 91 for ignition and the air
supply line for
g
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heating of the air and gaseous fuel supply line 110 for heating, while the
gaseous fuel
supply line 140 is connected to both gaseous fuel supply line for ignition of
the air and
gaseous fuel supply line 91 for ignition and the gaseous fuel supply line for
heating of the
air and gaseous fuel supply line 110 for heating.
The compressed air supply line 130 serves to supply compressed air generated
in
acid supplied from a compressed air supply 136, and the gaseous fuel line 140
serves to
supply gaseous fuel supplied from the gaseous fuel supply source 146.
The compressed air supply line 130 comprises a first flux regulator 131. for
manually regulating the amount of compressed air, a first filter 132 for
filtering impurities
to included in compressed air, a fifth solenoid valve 133 for interrupting the
supply of
compressed air, a third pneumatic pressure gauge 134 for sensing the pressure
of supplied
compressed air and a fifth manual valve 135 for regulating the amount of
supplied
compressed air. The fuel gas supply line 140 comprises a second flux regulator
141 for
manually regulating the amount of gaseous fuel, a second filter 142 for
filtering impurities
t 5 included in gaseous fuel, a sixth solenoid valve 143 for interrupting the
supply of gaseous
fuel, a fourth pneumatic pressure gauge 144 for sensing the pressure of
supplied gaseous
fuel and a sixth manual valve 145 for regulating the amount of supplied
gaseous fuel.
A gaseous fuel mixture and supply control 70 serves to control the operation
of
the air and gaseous fuel mixture and supply unit 90. The gaseous fuel mixture
and supply
2o control 70 is connected to the injection molding control 50 through m
interface 60, and
receives signals from and transmits signals to the injection molding control
50. The
gaseous fuel mixture and supply control 70 includes a microprocessor.
In addition, there may be included a safety unit that serves to automatically
interrupt the supply of air and gaseous fuel when flames are not sensed by the
flame
25 sensor 42 in a predetermined time period after ignition is performed by the
igniter 41 of
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the ignition unit 40, gas of a predetermined degree of density is detected by
a gas detector
(not shown) disposed near the upper and lower molds 20 and 30, or the
pressures of air
and gaseous fuel inputted from a first pressure switch 115 and a second
pressure switch
123 are higher than a predetermined pressure.
The heating system of the present invention includes a control panel fbi~
controlling the components of the system and inputting the operational
conditions of the
components. The control panel is illustrated as a block diagram in Fig. 6.
The control panel includes a key input unit 151, a sensing unit 152, a Central
Processing Unit (CPU) 153, an alarm 154, a display 155 and an hlsirument panel
156.
1 o The lcey input unit 151 has a plurality of keys, and serves to input
various
operational conditions for injection molding.
The sensing unit 152 serves to sense the various states of the system, convert
a
sensing signal to an electric signal and output the electric signal. The
states include the
elevation of the dies, the pressures and amounts of air and gaseous fuel, the
leakage of gas
I s and the like.
The CPU 153 serves to perform deterniination on the basis on an input signal
and
to output a control signal. The CPU 153 can be included in the injection
molding control
50 and the gaseous fuel mixtl~re and supply control 70.
The alarm 154 serves to wam of system error and danger situations. The alarm
20 154 may be activated when gas leaks or pressure variations outside
predetermined limits
occur.
The display 155 serves to indicate the information of the operation of the
system.
A user can monitor the operation of the system using the display 155.
The instrument panel 156 serves to indicate the operation of various
components
25 of the system. The instrument panel 156 may indicate the pressures of air
and gaseous
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fuel and the state of safety.
Hereinafter, a method for momentarily heating the surface of a mold usilig the
flame of gaseous fuel is described with reference to Figs. 3a to 3f.
In STEP 5100, the upper mold. 20 and the louver mold 30 are opened at a
predetermined distance and the supply of gaseous fuel is prepared.
Iii STEP S 101, the upper mold 20 comes close to the lower mold 30 and gaseous
fuel is injected and ignited. In more detail, compressed air and gaseous fuel
are supplied
from the compressed air supply source 136 and the gaseous fuel supply source
146
through the compressed air supply line 130 and the gaseous fuel supply line
140, enter the
1 o air and gaseous fuel supply line 91 for ignition and are mixed together
while passing
through the air and gaseous fuel mixture element 92, and the mixed air and
gaseous fuel
passes through the supply conduit 31 of the lower mold 30, is injected through
the
discharge holes 34 of the mold portion 32 and is ignited in the igniter 41 of
the ignition
unit 40 using high voltage current generated in the high voltage generator 44.
If flame is
not sensed by the flame sensor 42 after the ignition is performed, the supply
of air and
gaseous fuel is interrupted by the operation of the solenoid valves 95 and
103.
After the air and gaseous fuel supplied through and mixed in the air and
gaseous
fuel supply line 91 for ignition are normally injected, compressed air and
gaseous fuel are
supplied through and mixed in the air and gaseous fuel supply line 110 and are
injected
2o through the lower mold 30. At this time, the supply of the compressed air
and gaseous
fuel being supplied through the air and gaseous fuel supply line 91 for
ignition is
illten~upted and is not supplied to the lower mold 30 anymore.
In STEP S 102, the cavity 24 of the upper mold 20, which comes close to the
lower mold 30 at a predeternzined distance (for example, 1 to 40 cm), is
heated by the
gaseous fuel supplied through the air and gaseous fuel line 110 for heating
and igution,
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for a predetermined time (for example, about 1 to 60 seconds).
In STEP S 103, after the supply of air and gaseous fuel is interrupted and
flame is
extinguished by the interruption of the supply of the air and gaseous fuel,
the elevating
sha$ 82 is elevated by 'the operation of the elevating cylinder 80 and,
accordingly, the
- lower mold 30 is closed by the upper mold 20. As soon as the lower mold 30
is closed by
the upper mold 20, molten casting material is supplied through the casting
material supply
hole 22 of the upper mold 20 from the casting material feeder 10.
After the inj ection of the casting material is completed and the cast part
cools from
5 to 300 seconds, STEP S 104 is performed. In STEP S 104, after the upper and
lower
1o molds 20 and 30 are opened at a predetermined distance (for example, in a
range of 1 to
400 mm), compressed air is injected toward a formed cast (will be described)
through the
air and gaseous fuel supply line 110, the supply conduit 31 and the discharge
holes 34, and
cools the formed cast. At this time, the cooling of the formed cast is
performed for, for
example, 5to 30 seconds.
t 5 Additionally, in STEP S 1 O5, after the upper and lower molds 20 and 3 0
are
completely opened, a formed cast 146 is ejected. With this, the entire
injection molding
process is completed.
A method for momentarily heating the surface of a mold using the flame of
gaseous fuel in accordance with a second embodiment of the present invention
is
2o described with reference to Figs. 4a to 4d. In this case, a core 35 is
disposed between the
upper and lower molds 20 and 30 as an auxiliary mold for the injection molding
of the cast
146.
'This system, which can be applied to this method, further comprises one core
35
disposed between the upper and lower-molds 20 and 30, a upper mold supply
conduit 21
25 for supplying mixed gaseous fuel and compressed air, said upper mold supply
conduit 21
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being formed in the upper mold 20, a plurality of upper mold discharge holes
23 for
heating and cooling the core using the mixed gaseous fuel and the compressed
air supplied
through the upper mold supply conduit 21, a lower mold supply conduit 31 for
supplying
mixed gaseous fuel and compressed air, said lower mold supply conduit 31.
being formed
in the lower mold 30, a plurality of lower mold discharge holes 34 for heating
and cooling ,
the core 35 using the mixed gaseous fuel and the compressed air supplied
through the
lower mold supply conduit 31, and an air and mixed gaseous fuel supply conduit
86 for
connecting the air and gaseous fuel mixture and supply unit 90 respectively to
the upper
mold supply conduit 21 and the lower mold supply conduit 31.
The core 35is formed to come into tight contact with the upper and lower molds
20 and 30 when the upper and lower molds 20 and 30 are closed, so that
injection pressure
is completely transmitted to the upper and lower molds, thus preventing the
core and
upper aild lower molds from being damaged by high injection pressure.
The core 35 has a thickness ranging from 0.1 to 15 mm and is formed to
correspond to the shape of the cast. The discharge holes 23 and 34 are
constructed in the
form of slits, respectively have widths of 0.01 to 5 mm and are distributed on
the surface
of the lower mold 30 to correspond to the shape of the cast.
The method for momentarily heating the surface of a mold in accordance with
the
second embodiment is different from the method for momentarily heating the
surface of a
2o mold in accordance with the first embodiment, in that the core 35 is
disposed between the
upper and lower molds 20 and 30, a supply line is connected to the upper mold
20 to
supply mixed compressed air and gaseous fuel, and an ignition unit (not shown)
identical
to the ignition unit 40 (including the igniter 41, the flame sensor 42 and the
high voltage
generator 44) mounted to the lower mold 30 is preferably mounted to the upper
mold 20.
Additionally, the core 35 is provided with support means for elevating and
supporting the
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core 35.
lii STEP 5200, the upper mold 20, the core 35 and the lower mold 30 are opened
at predetermined distances and the supply of gaseous fuel is prepared.
Thereafter, the
upper mold 20, the core 35 and the lover mold 30 come close to ode another at
s ~ predetermined distances~and gaseous fuel is injected'to the core 35 from
thewpper and/or
lower molds 20 and/or 30 and ignited. In more detail, compressed air and
gaseous fuel are
supplied from the compressed air supply source 136 and the gaseous fuel supply
source
146 through the compressed air supply line 130 and the gaseous fuel supply
line 140,
enters the air and gaseous fuel supply line 91 for ignition and are mixed
together while
to passing through the air and gaseous fuel mixture element 92, and the mixed
air and
gaseous fuel passes through the supply conduits 21 and 31 of the upper and
lower molds
20 and 30, is injected through the discharge holes 23 and 34 and is ignited in
the igniter 41
of the ignition unit 40 using high voltage current generated by the high
voltage generator
44.
I 5 If a flame is not sensed by the flame sensor 42 after the ignition is
performed, the
supply of air and gaseous fuel is interrupted by the operation of the solenoid
valves 95 and
103.
After the air and gaseous fuel supplied through and mixed in the air and
gaseous
fuel supply line 91 for ignition are normally injected, compressed air and
gaseous fuel are
2o supplied through and mixed in the air and gaseous fuel supply line 110 and
are injected
through the upper and lower molds 20 and 30: At this time, the supply of the
compressed
air and gaseous fuel being supplied through the air and gaseous fuel supply
line 91 for
igntion is interrupted and is not supplied to the upper and lower molds 20 and
30
anymore. Accordingly, the cavities 24 and 38 defined by the upper and lower
molds 20
2s and 30 and the core 35, which come close to one another at predetermined
distances (for
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example, the distances between the upper mold 20 and the core 35 and between
the core
35 and the lower mold 30 are in a range of 1 to 40 cm), are heated by the
gaseous fuel
supplied through the air and gaseous fuel line 110 for heating and ignition,
for a
predetemlined time period (for example; about 1 to 60 seconds).
In STEP 5201; after the supply of air and gaseous fuel supplied from the air
and
gaseous fuel supply line 110 is interrupted and the flame is extinguished by
the
intemlption of the supply of the air and gaseous fuel, the elevating shaft 82
is elevated by
the operation of the elevating cylinder 80 and, accordingly, the core 35 and
the lower mold
30 are closed by the upper mold 20. As soon as the core 35 and the louver mold
30 are
to closed by the upper mold 20, molten casting material is supplied through
the casting
material supply hole 22 of the upper mold 20 and the casting material supply
hole 36 of
the core 35 from the casting material feeder 10.
After the injection of the casting material is completed and the formed cast
146 -
has cooled for 5 to 300 seconds, STEP 5202 is performed. In STEP 5202, after
the upper
r 5 and lower molds 20 and 30 are opened away from the core 35 at
predetermined distances
(for example, in a range of 1 to 400 mm), compressed air is injected to the
core 35 and the
formed cast 146 through the air and gaseous fuel supply line I 10, the supply
conduits 2I
and 31 and discharge holes 23 and 34 and cools the core 35 and the formed cast
146. At
this time, the cooling of the formed cast 146 is performed for, for example, 5
to 30
2o seconds.
Additionally, in STEP 5203, after the upper and lower molds 20 and 30 and the
core 35 are completely opened, the formed cast 146 is ejected. With this, the
entire
injection molding process is completed.
A method for momentarily heating the surface of a mold using the flame of
25 gaseous fuel in accordance with a third embodiment of the present invention
is described
IS
CA 02423984 2003-02-24
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with reference to Figs. 5a to 5d. In this case, a plurality of cores are
disposed between the
upper and lower molds 20 and 30 as auxiliary molds for the injection molding
of the cast
146.
The cores consist of a first core 35 in contact with the upper,mold 20 and a
second
core 37 in contact with the lower mold 30,. a casting material supply hole
36.is formed, in
the first core 35 to correspond to the casting material supply hole 22 in the
upper mold 20,
and a forming space 39 is formed between the first and second cores 35 and 37
to form
casting material supplied through the casting material supply hole 36 of the
first core 35.
The method for momentarily heating the surface of a mold in accordance with
the
1o second embodiment is different from the method for momentarily heating the
surface of a
mold in accordance with the first embodiment, in that a plurality of cores,
for example, a
first core 35 and a second core 37, are disposed between the upper and lower
molds 20
and 30, a supply line is connected to the upper mold 20 to supply mixed
compressed air
and gaseous fuel, and an ignition unit (not shown) identical to the ignition
unit 40
(including the igniter 41, the flame sensor 42 and the high voltage generator
44) mounted
to the lower mold 30 is preferably mounted to the upper mold 20. Additionally,
the fast
and second cores 35 and 37 are provided with support means for elevating and
supporting
the cores 35 and 37.
In STEP 5300, the upper mold 20, the first and second cores 35 and 37 and the
lower mold 30 are opened at predetermined distances and the supply of gaseous
fuel is
prepared. Thereafter, the upper mold 20, the first and second cores 35 and 37
and the
lower mold 30 come close to one another at predetermined distances and gaseous
fuel is ,
injected to the first and second cores 35 and 37 from the upper and lower
molds 20 and 30
and is ignited. In more detail, compressed air and gaseous fuel are supplied
from the
compressed air supply source 136 and the gaseous fuel supply source 146
through the
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compressed air supply line 130 and the gaseous fuel supply line 140, enter the
air and
gaseous fuel supply line 91 for ignition and are mixed together while passing
through the
air and gaseous fuel mixture element 92, and the mixed air and gaseous fuel
passes
through the upper and lower molds 20 and 30, is injected through the discharge
holes 23
and 34 and is- ignited in the igniter 41 of the ignition unit 40 using high
voltage. current
generated by the high voltage generator ~44.
If a flame is not sensed by the flame sensor 42 after the ignition is
performed, the
supply of air and gaseous fuel is interrupted by the operation of the solenoid
valves 95 and
103.
~ o After the air and gaseous fuel supplied through and mixed in the air and
gaseous
fuel supply line 91 for ignition are normally injected, compressed air and
gaseous fuel are
supplied through and mixed in the air and gaseous fuel supply line 110 and are
injected
through the supply conduits 21 and 31 of the upper and lower molds 20 and 30.
At this
time, the supply of the compressed air and gaseous fuel being supplied through
the air and
~ 5 gaseous fuel supply line 91 for ignition is interrupted and is not
supplied to the upper and
lower molds 20 and 30 anymore. Accordingly, the cavities 24 and 38 defined by
the
upper and lower molds 20 and 30 and the first and second cores 35 and 37,
which come
close to one another at predetern~ined distances (for example, the distances
between the
upper mold 20 and the first core 35, between the first core 35 and the second
core 37 and
2o between the second core 37 and the lower mold 30 are in a range of 1 to 40
cm), are
heated by the gaseous fuel supplied through and injected from the air and
gaseous fuel line
110 for heating and ignition, for a predeternzined time period (for example,
about 1 to 60
seconds).
In STEP 5301, after the supply of air and gaseous fuel supplied from the air
and
25 gaseous fuel supply line 110 is interrupted and the flame is extinguished
by the
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interruption of the supply of the air and gaseous fuel, the elevating shaft 82
is elevated by
the operation of the elevating cylinder 80 and, accordingly, the first and
second cores 35
and 37 and the lower mold 30 are closed by the upper mold 20. As soon as the
first and
second cores 35 and 37 and the lower:mold 30 are closed by the upper mold 20~
molten
casting material is supplied through the casting material supply hole 22~ of
the upper mold w
20 and the casting material supply hole 36 of the first core 35 from the
casting material
feeder 10.
After the injection of the casting material is completed and the formed cast
cools
for 5 to 300 seconds, STEP 5302 is performed. In STEP 5302, after the upper
and lower
o molds 20 and 30 are opened away from the first and second cores 35 and 37 at
predetermined distances (for example, in a range of 1 to 400 mm), compressed
air is
injected toward the first and second cores 35 and 37 and the formed cast 146
through the
air and gaseous fuel supply line 110, the supply conduits 21 and 31 and the
discharge
holes 23 and 34 and cools the first and second cores 35 and 37 and the formed
cast 146.
At this tune, the cooling of the formed cast 146 is performed for, for
example, 5 to 30
seconds.
Additionally, in STEP 5303, after cooling is performed for a certain time
period,
gaseous fuel is injected from the upper and lower molds 20 and 30, is ignited
and heats the
first and second cores 35 and 37. While the first and second cores 35 and 37
are heated,
2o the first and second cores 35 and 37 are separated and the cast 146 is
ejected. With this, all
the injection mold process is completed.
As described above, in Figs. 3a to 3f, there is depicted the first embodiment
in
which no core exists between the upper and lower molds 20 and 30. In Figs. 4a
to 4d,
there is depicted the second embodiment in which a single core 35 is disposed
between the
upper and lower molds 20 and 30. 1n Figs. 5a to Sd, there is depicted the
third
~s
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embodiment in which a plurality of cores 35 and 37 are disposed between the
upper and
lower mold cores 20 and 30. Of the embodiments, it is preferable that a
plurality of cores
35 and 37 are disposed between the upper and lower mold cores 20 and 30. .
The cores respectively have thiclcnesses of 0.1 to 1 S mm and are formed to'
correspond to the shape of the cast. The discharge holes are constructed in
the form of
slits, respectively have widths of 0.01 to 5 mm and are distributed on the
surface of the
lower mold to correspond to the shape of the cast.
The ignition unit 40 may utilize high voltage current or an electronic spark
for
igniting mixed air and gaseous fuel, and preferably prepares for the failure
of ignition and
1 o an accidental fire after ignition. Such an ignition unit 40 may be
directly mounted on an
injection molding apparatus or separated from the injection molding apparatus.
The
ignition unit 40 is preferably disposed in the mold and attached to the mold.
In the ignition
unit 40, the length of flames may be adjusted to be relatively long or
relatively short using
combustion gas such as gaseous fuel mixed with oxygen or compressed air.
In the air and gaseous fuel mixture and supply unit 90, the gaseous fuel must
be
mixed with the oxygen or compressed air for burning the gaseous fuel prior to
the supply
of the gaseous fuel and the oxygen or compressed air so as to completely burn
the gaseous
fuel in a forming space defined between two molds. Since the danger of
explosion occurs
when the gaseous fuel is kept in a state where the gaseous fuel is mixed with
the oxygen or
2o air, the gaseous fuel is mixed with the oxygen or air in the gaseous fuel
mixture and supply
element 92 for ignition and the gaseous fuel mixture and supply element 111
for heating in
the process of supplying the gaseous fuel and the oxygen or air. The gaseous
fuel and the
oxygen or air are supplied to and mixed in the elements 92 and 11 l, and
immediately the
mixed gaseous fuel and the oxygen or air is supplied to the interior of the
lower mold 30.
In order to regulate the amount of the gaseous fuel and the amount of the
oxygen or air,
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the manual valves 96, 104, 135 and 14S and the flux regulators 131 and 141 are
employed. One selects between the oxygen and the air, depending upon the
material of
the molded products. That is, the oxygen is employed for manufacturing
relatively precise
-, . injection molding products of.synthetic resin, while the corripressed
air:is employed for
manufacturing, relatively rough injection molding products. While the 'oxygen
or
compressed air is supplied, impurities, such as humidity and dust, must be
filtered off
through the first filter 132. In the case of the gaseous fuel, various
impurities must be
filtered off through the second filter 142 and thereafter be supplied to the
lower mold 30.
In the safety unit of the present invention, when it is sensed that the
pressure of the
1 o gaseous fuel or the oxygen or air supplied through the pneumatic pressure
gauge 93 or
112, the fluidic pressure gauge 101 or 120 or the pressure switch 134 or 144
is greater or
less tlian a predetermined pressure, the related supply line 91, 110, 130 or
140 is stopped
up by the solenoid valve 95, 103, 114, 122, 133 or 143, thereby preventing
danger due to
abnormal pressure. If the gas detector is mounted to the lower portion of the
system of the
~ 5 present invention or on the ceiling of a room where the system of the
present invention is
installed, the supply of the gaseous fuel and oxygen or compressed air is
interrupted when
the leakage of gas is detected. Additionally, when the flame sensor 42 of the
ignition unit
40 senses the failure of ignition and an accidental fire, the supply of the
gaseous fuel and
oxygen or compressed air is interrupted.
?o The safety unit and the gaseous fuel mixture and supply control 70.for
controlling
the air and gaseous fuel mixture and s~.ipply unit 90 allows their operating
time period,
position and numerical value to be set and controlled by means of the control
panel 150.
All thermoplastic polymers can be injection molded according to the present
invention. Suitable polymers for use in the present invention include -those
from group
25 consisting of a.lkylene aromatic polymers such as polystyrene; ntbber-
modified alkylene
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aromatic polymers or copolymers, more commonly known as high impact
polystyrene
(HIPS) or ABS, alkylene aromatic copolymers such as styrene/acrylonitrile or
styrene/butadiene; hydrogenated alkylene aromatic polymers and copolymers such
as
hydrogenated polystyrene 'and hydrogenated styrene/butadiene copolyrriers;
alpha-olefin
homopolymers such as low density polyethylene, ' high density polyethylene and
polypropylene; linear low density polyethylene (an ethylene%ctene-1 copolymer)
and
other copolymers of ethylene with a copolymerizable, mono-ethylenically
unsaturated
monomer such as an alpha-olefin having from 3 to 20 carbon atoms; copolymers
of
propylene with a copolymerizable, mono-ethylenically unsaturated monomer such
as an
o alpha-olefin having from ~4 to 20 carbon atoms, copolymers of ethylene with
a vinyl
aromatic monomer, such as ethylene/styrene interpolymers; ethylene/propylene
copolymers; copolymers of ethylene with an alkane such as an ethylene/hexane.
copolymer; thermoplastic polyurethanes (TPU's); and blends or mixtures
thereof,
especially blends of polystyrene and an ethylene/styrene interpolymer
Other suitable polymers include polyvinyl chloride, polycarbonates,
polyamides,
polyimides, polyesters such as polyethylene terephthalate, polyester
copolymers such as
polyethylene terephthalate-glycol (PETG), phenol-formaldehyde resins,
thermoplastic
polyurethanes (TPUs), biodegradable polysaccharides such as starch, and
polylactic acid
polymers and copolymers.
2o Certain blends and alloys of these polymers can also be injection molded in
accordailce with the teachings of the present invention.
The polymers listed above, together with alloys and blends made therefrom, can
optionally contain mold release agents, fillers (such as glass fibers,
stainless steel fibers,
nickel-coated graphite fibers,carbon fibers, nanocomposite clay particles,
metallic
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particles, talc, and the Iike), pigments, colorants, flame retardants,
antioxidants and other
additives.
The present invention can also be employed effectively with generally well
known fabrication techniques, which can be used alone.or in combination; such
as foam
molding, blow molding, thermoforming, extrusion, SCORIM; gas-assisted
injection
molditlg, co-injection, in-mold lamination, and like.
In connection with foam molding and related processes involving expanded
thermoplastic or thermoset polymers disclosed herein, certain chemical blowing
agents
(such azodicarbonamide, sodium bicarbonate, and the like) and/or physical
blowing
a 0 agents ( such as COa,N2, steam, and like.) can also be used.
In addition to thermoplastics, this process is considered suitable for
thermosetting
resin materials formed by molding techniques generally referred to as reaction
injection
molding (Rllvl) or resin transfer molding (RT1V1]. Examples of thermosetting
resin
materials include epoxies, urethanes, acrylates, and vinyl esters.
~5 Rapid heating of the mold is desirable for rapid polymerization of
thermosets.
The large heat of polymerization encountered with materials such as epoxies
can be
effectively managed by rapidly heating the mold selectively, thereby allowing
for a large
thermal mass to absorb the heat of polymerization.
The teachings of the present invention can also be used with a group of high
density
20 foams having microcelhilar closed cell structures disclosed in LT.S. Patent
4,473, 66~,
5,674,916 and 5,8b9,544 teachings of which are incorporated herein by
reference.
The operable mold surface temperature ranges from the applicable melting point
(m.p.) or glass transition temperature (Tg), as the case may be, depending, on
the polymeric
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material being processed, to 300 ° C above the relevant m.p. or Tg,
preferably 200 °C, more
preferably 150 °C, most preferably 100 °C.
EXAMPLE
Whee1 caps.for automobiles were injection-molded ofpolycarbonate/ABS alloy
resin. The method for momentarily heating the surface of a mold using the
flame of
gaseous fuel and system thereof in accordance with the present invention was
applied to
the manufacture of the wheel caps. The molding pressure of the system was 405
tons. No
resin weld line and no flow mark appeared on the exterior of the molded
products.
Additionally, pinholes that inevitably appear on the general products of
1 o polycwbonate/ABS alloy resin did not appear on the products of this
example.
FLU~thennore, the brilliance, impact strength and thermal deformation
temperature of the
products manufactured by the method and system were improved as described in
table 1
in comparison with the products made by the conventional method and system.
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TABLE 1
Product made by the Product made by the method
conventional method and and system of the present
~,~em invention
B~liance (the angle of
reflection: 60°) 75 100
Impact strength ( 1 /8",
notched ASTM D-256)
52 62
(Kg~cm/cm)
Thermal deformation
temperature (1/8", 123 141
1.80N/mm2 ASTM D-648)
(°
As can be seen from the above example, since products of polycarbonate/ABS
alloy resin having no defect in appearance can be manufactured in accordance
with the
present invention, wheel caps of superior quality can be manufactured without
coating,
thereby reducing its manufacturing cost and improving its quality.
Additionally, in accordance with the present invention, the strength and
thermal
properties of the products can be improved, and the resin of high strength can
be freely
formed regardless of its fluidity.
Meanwhile, in accordance with a feature of the present invention, the upper
and
lower molds 20 and 30 may be heated by an induction heater that generates high
temperature heat using electricity instead of gaseousfuel. When the molds 20
and 30 are
heated using gaseous fuel, heat is directly applied to the molds 20 and 30;
whereas when
the molds 20 and 30 are heated using an induction heater, electricity flows
into the molds
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20 and 30 by the action of induction and heat is generated in the molds 20 and
30 by the
resistance of the molds 20 and 30. When the induction heater is employed to
heat the
molds 20 and 30, the constructions concerning the supply of gaseous fuel are
not
necessary. However,. the constructions concerning the supply of compressed air
for
cooling the molds 20 and 30 are preferably provided. . . .
That is, in the method and system of the present invention, the upper and
lower
molds 20 and 30 can be momentarily heated by heating means such as the
induction
heater.
Fig. 7 is a schematic diagram showing a system for momentarily heating the
to surface of a mold that employs an induction heater and two cores. This
system for
momentarily heating the surface of a mold comprises a casting material feeder
10 for
supplying molten casting material, upper and lower molds 20 and 30 for forming
a
predetermined shaped cast, an injection molding control 50 for controlling the
upper and
lower molds 20 and 30, a compressed air supply line 130 for supplying
compressed air,
one or more cores 35 and 37 disposed between the upper and lower molds 20 and
30, a
voltage generator 73 for generating voltage of a predetermined level,
induction heaters 74
and 75 for heating the cores 35 and 37 using current applied from the voltage
generator
73, the induction heaters 74 and 75 being mounted on the inner porrtion of the
upper mold
and the upper portion of the lower mold 30, a controller 72 for controlling
the
20 compressed air supply line 130 and the voltage generator 73, an interface
60 for
interfacing the injection molding control 50 and the controller 72, and a
control panel 150
for visually displaying the control, condition and operation of the components
of the
system.
The system further comprises a plurality of supply conduits 21 and 31 and a
plurality of discharge holes 23 and 34 in the upper and lower molds 20 and 30.
The
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supply conduits 21 and 31 are respectively connected to a compressed air
supply conduit
87 for supplying compressed air provided by the compressed air supply line
130. The
cores 35 and 37 respectively have thiclcnesses of 0.1 to 15 mm and are formed
to
con despond to the shape of the cast. The discharge holes 23 and 34 are
constructed in the
. form of slits, respectively have widths of 0.01 to 5 mm'and are distributed
on thc'surfaces
of the molds 20 and 30 to correspond to the shape of the cast.
When the induction heaters 74 and 75 are employed as heating means, the lower
and upper molds 20 and 30 are momentarily heated using current generated by
the voltage
generator 73 and are cooled by the molds 20 and 30 andlor by means of
compressed air of
1 o high pressure after injection molding, thereby producing injection- molded
products.
Fig. 8 is a flowchart showing the operation of the system for momentarily
heating
the siu-face of a mold that employs the induction heaters 74 and 75 and the
two cores 35
and 37. First of all, in STEP 5400, the upper and lower molds 20 and 30 are
momentarily
heated by the induction heaters 74 and 75 using current generated by the
voltage generator
73 after the upper and lower molds 20 and 30 are caused to come close to each
other at a
predetermined distance. In STEP 5401, molten casting material is injected from
the
casting material feeder 10 and is molded after the heated lower mold 30 is
raised to and
engaged with the upper mold 20 and the formed cast cools for 5 to 300 seconds.
In STEP
5402, compressed air is supplied from a compressed air supply line 130 to the
cores 35
2o and 37 through a compressed air supply line 87, the supply conduits 21 and
31 and the
discharge holes 23 and 24, and cools the molded product. 1n STEP 5403, the
molded
product is ej ected after the molded product is cooled sufficiently. . .
A user can select one of the two heating fashions, that is, one heating
fashion
using gaseous fuel and the other heating fashion using an induction heater,
depending
upon the type or features ofthe products to be injection-molded.
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Iii the meantime, when the induction heaters 74 and 75 are employed, the
injection molding control 50 and interface 60 for controlling the components
of the system
and a controller 72 for transmitting and receiving control signals are
included in the
. . system. The controller 72 includes a control program:
Fig. 9' is. a schematic diagram showing a water-cooled system for momentarily
heating and cooling the heated surface of a mold.
That is, although in the previous embodiments a mold is heated by the air and
gaseous fuel mixture and supply unit 90 using an air and gaseous fuel mixture
and cooled
using compressed air, there is shown the water-cooled system that cools a
heated mold by
injecting cooling water to the heated mold.
To this end, cooling water passages 204 and 206 are arranged through upper and
lower molds 20 and 30, a cooling water supply conduit 203 is connected to the
cooling
water passages 204 and 206, an electronic valve 200 is positioned on the
cooling water
supply conduit 203 to selectively open or close the cooling water supply
conduit 203, and
a motor pump 202 is positioned on the cooling water supply conduit 203 to
supply cooling
water through the cooling water supply conduit 203.
In such a system, although the surface of the mold is heated in the same
manner as
that shown in Fig. 5, the heated surface of the mold is cooled using cooling
water instead
of compressed air. Molds and cores are heated using air and gaseous fuel
mixture
2o supplied by the air and gaseous fuel mixture and supply unit 90. After the
molds and the
cores have been heated, the upper and lower molds 20 and 30 and the first and
second
cores 35 and 37 are closed and molten material is injected into the mold.
Thereafter, the
upper and lower molds 20 and 30 are allowed to be opened away from the first
and
second cores 35 and 37 at predetermined distances (for example, 1 to 400mm).
When the
upper and lower molds 20 and 30 have been opened, the electronic valve 200 is
opened
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WO 02/16110 PCT/KRO1/01160
and the motor 202 is operated by the control of the controller 72.
Consequently, cooling
water is supplied to the upper and lower molds 20 and 30 through the cooling
water
supply conduit 203, so the cooling water is injected to the first and second
cores 35 and 37
through the supply holes 205 and 207 of the cooling water passages 204 and 206
and
cools the first and second' cores 35 and~37: In this case, a time period for
cooling a molded
product 146 is, for example, in the range of 5 to 300 seconds. The system of
this
embodiment may be applied to a case where cooling faster than cooling using
compressed
air is required.
Fig. 10 shows a system for momentary heating the surface of a mold, in which
the
o surface of the mold is cooled using cooling water in the same manner as that
of the
embodiment shown in Fig. 9, while the surface of the mold is heated by a
variable electric
resistance heater.
A variable electric resistance heater 210 is positioned between the upper mold
20
and the first core 35, and generates heat by its own electric resistance using
a voltage
~ 5 supplied from a voltage generator 73.
I11 the system shown in Fig. 10, an upper mold 20 and a first core 35 are
heated by
the electric resistance heater 210 for a predetermined time period, for
example, about 1 to
300 seconds.
After the upper mold 20 and the first core 35 are heated, the upper and lower
2o molds 20 and 30 and the first and second cores 35 and 37 are closed and
molten material
is injected into the mold. Thereafter, the upper and lower molds 20 and 30 are
allowed to
be opened away from the first and second cores 35 and 37,at predetermined
distances (for
example, 1 to 400mm). Additionally, it is desirable to keep a predetermined
distance
between the upper mold 20 and the electric resistance heater 210; for example,
in the rmge
25 Of 0.1 t0 30mm.
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WO 02/16110 PCT/KRO1/01160
At this time, when the upper and lower molds 20 and 30 have been opened, the
electronic valve 200 is opened and the motor 202 is operated by the control of
the
controller 72. Consequently, cooling water is supplied to the upper and lower
molds 20
and 30 through the cooling water supply conduit 203, so the cooling water is
sprayed oii
the first and second cores 35 and 37~ through he supply holes 205 and 207 "of
cooling
water passages 204 and 206 and cools the first and second cores 35 and 37. In
this case, a
time period for cooling a molded product 146 is, for example, in the range of
5 to 300
seconds.
In the system for momentarily heating the surface of a mold shown in Fig. 10,
the
l0 molds and the cores are heated by the variable electric resistance heater
210 instead of air
and fuel gaseous mixture and the surface of the molds and the cores are cooled
by cooling
water. The system of this embodiment may be applied to a case where cooling
faster than
cooling using compressed air is required. While cooling water is sprayed, a
voltage is not
supplied to the electric resistance heater 210.
The variable electric resistance heater 210 can be inserted not only between
the
upper mold 20 and the first core 35 but also between the lower mold 30 and the
second
core 37. Additionally, the variable electric resistance heater 210 can be
inserted between
the upper mold 20 and the first core 35 and/or between the second mold 30 and
the second
core 37. The variable electric resistance heater 210 is preferably made of
silicon line
2o material having superior resistance.
In an embodiment shown in Fig. 1 l, the molds and the cores are cooled in the
same water-cooled manner as that for the embodiments shown in Figs. 9 and 10,
while the
molds and the cores are heated by a coating type electric resistance heater.
The system for momentarily heating the surface of a mold is similar in
construction to the system shown in Fig. 10, but the surface is coated with a
coating type
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WO 02/16110 PCT/KRO1/01160
electric resistance heater 220 is formed on the upper stu~ace of the first
core 35. The
coating type electric resistance heater 220 generates heat by its own electric
resistance
using a certain voltage supplied from a voltage generator 73.
As shown in Fig. 12, the coat of the electric resistance heater 220 is formed
by
coating the upper surface of the core 35 primarily with a fast insulating
layer 221, coating
the fast ixrsrrlatixrg layer 221 with an electric resistance layer 222 and
coating the electric
resistance layer 222 secondarily with a second insulating layer 223. The first
insulating
layer 221. is to insulate the electric resistance layer. 222. from the core.
35, and the second
insulating layer 222 is to insulate the electric resistance layer 222 from the
upper mold 20.
~o The electric resistance layer 222 and a plurality of insulating layers 221
and 223 are
stacked together with one on top of another, so the amount ofheat applied to
the layers can
be controlled.
The insulating layers 221 and 223 and the electric resistance layer 222 each
have a
tluclazess ranging fiom 0.01 to lOmrn. The insulating layers 221 and 223 are
preferably
~ 5 formed of Mg0 + Teflon having insulation and heat-resistance
characteristics, while the
electric resistant layer 222 is preferably formed of conductive metal or
thermopolymer line
material having superior electric resistance.
In the system shown in Fig. 1 l, the first core 35 is heated by the electric
resistance
heater 220 for a predetermined tune period (for example, about 1 to 300
seconds).
3o At tlus time, when the upper and lower molds 20 and 30 have been opened, an
electronic valve 200 is opened and a motor 202 is operated by tlxe control of
a controller
72. Consequently, cooling water is supplied to the upper and lower molds 20
and 30
through a cooling water supply conduit 203, so the cooling water is sprayed on
the first
arid second cores 35 and 37 through the supply holes 205 and 207 of cooling
water
?5 passages 204 and 206 and cools the first and second cores 35 and 37. In
this case, a tune
CA 02423984 2003-02-24
WO 02/16110 PCT/KRO1/01160
period for cooling a molded product 146 is, for example, in the range of 5 to
300 seconds.
In the system for momentary heating the surface of a mold shown in Fig. 11,
the
molds and the cores are heated by the coating type electric resistance heater
210 instead of
an air and fuel gaseous mixture, and are cooled using cooling water. The
system of this
embodiment may be applied to a case where cooling faster than cooling using
compressed
,.
air is required. While cooling water is sprayed, a voltage is not supplied
from a voltage
generator 73 to the coatung type electric resistance heater 220.
The coating type.. electric resistance heater 220 may be formed on~ the -upper
siuface of the first core 35 or the lower surface of the second core 37. In
accordance with
~ o products, tlne coating type electric resistance heater 220 may be foamed
on the upper
surface of tine first core 35 and/or the lower surface of the second core 37,
and may heat
the cores.
TZne method and system of the present invention is not limited to the
injection
molding of synthetic resin products, but the method and system can be applied
to reactive
~ 5 injection molding, metallic cast fomning and ceramic fornning and the
like.
As described above, tine present invention provides a method for momentaaily
heating the sLUface of a mold and system thereof which is capable of improving
the
quality of products in appearance, preserving the physical and thernnal
propeues of resin
in the products, increasing the productivity of the manufacturing process of
the products
2o and reducing the manufacturing cost of the products.
Although the preferred embodiments of the present invention have been
disclosed
for illustrative purposes, those skilled in the art will appreciate that
various modifications;
additions and substitutions are possible, without departing from the scope and
spirit of the
iunvention as disclosed in the accompainying claims.
31
