Apparatus for manufacturing silicone gel sheet

An apparatus for manufacturing silicone gel sheet comprising a material supplying means which supplies kneaded silicone gel material to a nozzle, a nozzle which admits to flow silicone gel material supplied from said material supplying means and is provided with a discharging port which is open to be narrow and long, at least one movable receiving means which receives a sheet-formed strip made of silicone gel material discharged from said nozzle and moves in accordance with the discharging speed of the sheet-formed strip, and a heating section for heating and gelling the sheet-formed strip made of silicone gel material on said movable receiving means.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus to be used to manufacture 
gelled thin sheet made of silicone as material. 
Silicone gel is an extremely useful material as a buffer material or a 
shock absorbing material. Silicone gel to be used for such application 
has, in most cases, a penetration value of approximately 50 to 200 
measured according to JIS (Japanese Industrial Standard) K 2530-1976-(50 g 
load) and a small thickness. 
In the conventional method for manufacturing a thin silicone gel sheet 
material as described above, silicone material such as, for example, Toray 
Silicone CY52 (trademark) (manufactured by Toray Silicone Kabushiki 
Kaisha) has been kneaded, transferred into a tray type container, 
uniformly leveled with a spatula type plate used by hand, and heated with 
a flat holding plate made of metal or glass placed on the silicone 
material extended in the tray type container. 
However, said kneaded silicone gel material provides the property that it 
has the viscosity of 1000 to 1200CP when it does not contain other 
substances and that of 5000 to 10,000CP when it is kneaded with fine 
hollow particles and the pot life at a normal temperature is short and 
therefore there has been a problem that the work of filling the tray type 
container with this silicone material and leveling it in the container has 
been extremely troublesome and unsuitable for volume production. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an apparatus capable of 
automatically processing silicone gel material with high viscosity without 
manual operation and thus manufacturing a silicone gel sheet with the 
specified thickness. 
To materialize this object, the apparatus in accordance with the present 
invention is provided with a device having a material supplying means for 
supplying kneaded silicone gel material such as, for example, a storing 
means such as a hopper into which the material is charged and a 
pressurized feeding means for feeding under pressure silicone gel material 
taken out from the hopper, a nozzle for discharging silicone gel material 
supplied from said material supplying means such as, for example, a nozzle 
having a narrow and long discharging port which is connected to said 
pressurized feeding means and horizontally open to discharge silicone gel 
material fed under pressure from said pressurized feeding means in the 
specified thickness and width, at least one movable receiving means which 
receives the sheet-formed strip made of silicone gel material discharged 
from said nozzle and moves keeping pace with the discharging speed of the 
sheet-formed strip such as, for example, a tray type container provided on 
the belt conveyor, and a heating section for heating the sheet-formed 
strip on said movable receiving means and said apparatus is adapted so 
that the sheet-formed strip made of silicone gel material which is 
discharged from said nozzle is extended over the movable receiving means 
along with movement of said movable receiving means and heated by the 
heating section to gel silicone gel material in the form of sheet. 
Another object of the present invention is to provide an apparatus which is 
adapted so that the thin sheet-formed strip supplied to the movable 
receiving means is completely free from bubbles. 
If silicone gel material of the sheet-formed strip contains bubbles, large 
bubbles will be included in the finished silicone gel sheet and its 
uniform shock absorbing performance will be impaired or silicone gel sheet 
will be partly damaged. 
In case of the apparatus in accordance with the present invention, such 
problem is eliminated by sealing the tank which contains silicone gel 
material and reducing the internal pressure of the tank to expel bubbles 
from silicone gel material in the material supplying means, for example, 
immediately before it is fed into the hopper. 
Another further object of the present invention is to provide an apparatus 
for laminating both sides of the sheet-formed strip supplied from the 
nozzle to the movable receiving means, that is, the thin silicone gel 
material with heat-resistant films at its both sides and rolling this 
laminated thin sheet-formed strip covered with films at its both sides by 
the rollers before heat treatment. Thus, the silicone gel sheet can be 
formed to have a uniform thickness. 
These upper and lower films should preferably be easily removable from 
silicone so that they can be replaced with other types of films such as, 
for example, thermoplastic film, depending on the purpose of use of the 
silicone gel sheet.

PREFERRED EMBODIMENT OF THE INVENTION 
Referring to FIG. 1 which is a partly cutaway rough side view illustrating 
the construction of the apparatus in accordance with the present 
invention, there is shown the material supplying means 20 which supplies 
silicone gel material 10. This means 20 is provided with the hopper 21 
which is the storing means and the screw conveyor 22 shown as the 
pressurized feeding means. This screw conveyor 22 is connected to the 
nozzle 30 to which silicone gel material 10 is supplied from the screw 
conveyor 22. The transfer unit 40 and the heating section combined with 
this transfer unit 40 are shown below said nozzle 30. 
Said hopper 21 can be otherwise constructed if it can store silicone gel 
material 10. In the embodiment, the hopper is flared and opened upwardly 
to admit kneaded silicone gel material, which is supplied down to the 
screw conveyor 22 at a lower position by its own weight. 
The screw conveyor 22 supplies under the specified pressure silicone gel 
material 10 supplied from the hopper 21 to the nozzle 30 and silicone gel 
material 10 is extruded from the nozzle 30 by virtue of this pressure. 
The material supplying pressure and speed of the screw conveyor 22 are set 
by the variable speed drive motor 23. 
The discharging port 31 of said nozzle 30 is adapted so that it is open 
narrow and long right above the movable receiving means 41 provided on 
said transfer unit 40 in the direction of width, that is, the direction 
from the surface of the paper with the figure shown to the rear of the 
paper as the horizontal direction and the opening size in the direction of 
thickness at right angles to that of width, that is, the transversal 
direction in FIG. 1, can be freely set by, for example, replacing the 
nozzle tip, and the thickness of silicone gel material 10 is controlled. 
Silicone gel material 10 discharged from this discharging port 31 is formed 
in layers on the movable receiving means 41 as a thin sheet-formed strip 
11 which has the thickness determined by the opening size of the 
discharging port 31. 
Said movable receiving means 41 is formed by the tray type container which 
is remountably provided on the belt conveyor 42. However, depending on the 
case, the upper surface of the belt conveyor 42 can be made of steel to 
directly serve as the movable receiving means. 
Said movable receiving means 41 is arranged so that the direction of its 
width, that is, the direction orthogonally intersecting the forwarding 
direction, matches to the direction of width of the discharging port 31 of 
said nozzle 30 and accordingly the sheet-formed strip 11 made of silicone 
gel material 10 which is discharged from the nozzle 30 is loaded on the 
movable receiving means 41 which moves in the same direction as the 
discharging direction and is extended on the movable receiving means 41 
which moves at the speed kept pace with the discharging speed of silicone 
gel material 10. 
Said movable receiving means 41 is driven by the variable speed drive 43 
which is controlled in relation to the drive motor 23 for said screw 
conveyor 22. 
Said heating section 50 in said embodiment is equipped with the 
multi-staged heating furnace 51 which is constructed so that, for example, 
a number of tray type containers 41 are stacked to separately heat the 
tray container type movable receiving means 41 unloaded from the belt 
conveyor 42. If the upper surface of the belt conveyor 42 is directly used 
as the movable receiving means as described above, the heating section 
through which the belt conveyor 42 passes during running is provided and a 
means for taking up gelled silicone gel sheet after heat treatment is 
provided following said heating section. 
The thickness and the width of said silicone gel sheet can be freely set by 
replacing the discharging tip of said nozzle 30 or forming the nozzle 30 
itself so that the opening width and thickness of the discharging port 31 
can be adjusted. For more strictly setting the thickness of silicone gel 
sheet, liners 44 and 44' with the specified thickness can be provided at 
both sides of the tray type movable receiving means 41 as shown in FIG. 2 
to feed sheet-formed strip 11 made of silicone gel material between these 
liners 44 and 44' and a smoothed flat holding plate 45 can be placed on 
this sheet-formed strip 11 to make the thickness of sheet-formed strip 11 
uniform by its own weight or applying a certain specified pressure with a 
separate means. 
Hereupon, it is preferable to apply in advance a parting agent such as, for 
example, the silicone oil (tradename: SH-3749) which is manufactured by 
Toray Silicone Kabushiki Kaisha, for avoiding adhesion of silicone gel 
material 10 to said movable receiving means 41 and said holding plate 45. 
Thus, the gelled silicone gel sheet can be easily taken off from the 
movable receiving means 41. 
Referring to FIG. 3, there is shown another embodiment of the apparatus in 
accordance with the present invention. 
In this embodiment, bubbles are removed from silicone gel material 100 in 
the material supplying means before it is supplied to the hopper and the 
sheet-formed strip 110 made of silicone gel material is rolled by a pair 
of upper and lower side rollers. 
In addition, in this embodiment, the sheet-formed strip made of silicone 
gel material is laminated with films at its both sides and the lower side 
film is extended over the belt conveyor as the movable receiving means. 
In this embodiment, a silicone material made up by mixing fine hollow 
particles such as, for example, Fillite (trademark) or Expancel 
(trademark) manufactured by Nippon Fillite Kabushiki Kaisha in a 
two-liquid kneaded type silicone material such as, for example, Toray 
Silicone CF5027 (trademark) or Toray Silicone CY52 manufactured by Toray 
Silicone Kabushiki Kaisha or KE-1051 (trademark) manufactured by Shinetsu 
Kagaku Kogyo Kabushiki Kaisha is used as silicone gel material. Such 
silicone gel is disclosed by the U.S. Patent Application Ser. No. 814726. 
The apparatus of this embodiment comprises the material supplying means 
200, nozzle 300, transfer unit 400 and heating section 500. Said material 
supplying means 200 is provided with the hopper 210, kneading unit 220 for 
kneading and treating silicone gel material 100 and bubble removing unit 
230 following the kneading unit 220. 
Said kneading unit 220 has a pair of kneading tanks 221 and 221' for 
separately storing liquids A and B and the kneading feeder 222 such as the 
kneader pump which is provided at the lower parts of these kneading tanks 
221 and 221'. 
Liquids A and B for silicone gel material 100 are respectively mixed with 
said fine hollow particles in individual tanks 221 and 221'. 
For this purpose, rotary vanes 223 and 223' are respectively provided 
inside the tanks 221 and 221' to individually stir liquid A and liquid B 
to mix it with fine hollow particles. 
Tanks 221 and 221' are respectively provided with valves 224 and 224', 
which will be opened to supply liquids A and B to the feeder 222. In other 
words, the gelling phenomenon during kneading can be prevented by mixing 
fine hollow particles in liquids A and B in different tanks 221 and 221'. 
These tanks 221 and 221' are installed on the upper floor of the plant and 
utilizes the gravity as a supplementary force for pressurized supplying of 
liquids A and B to the feeder 222 located on the lower floor. 
For mixing said fine hollow particles, kneading tanks 221 and 221' are 
provided with the tank 225 for supplying fine hollow particles from which 
a required quantity of fine hollow particles is supplied to a pair of 
kneading tanks 221 and 221' through valves 226 and 226', respectively. 
The feeder 222 kneads liquids A and B which have been mixed with fine 
hollow particles into a gelled solidifiable state of material and feeds it 
to the debubbling unit 230 which removes air bubbles from the material 
100. 
This debubbling unit 230 is constructed with the endless belt 231 which 
circulates in a vertical direction and equipped with a plurality of 
debubbling tanks 232 whereby the debubbling tanks 232 intermittently move 
along with circulatory movement of the endless belt 231 and stop in 
sequence at a position where silicone gel material 100 is supplied from 
the feeder 222, the debubbling position and a position where silicone gel 
material 100 is supplied to the hopper 210. At the debubbling position for 
this tank 232 is provided the cover 233 which lowers from the upper 
position to close the opening of the tank 232 when the tank 232 is 
stopped. The cover 233 is provided with the pressure reducing means such 
as, for example, the vacuum pump 234 etc. to reduce the internal pressure 
of the tank 232 tightly closed by the cover 233. 
Accordingly, air bubbles contained in silicone gel material 100 in the tank 
232 during the kneading process will be removed by reduction of the 
internal pressure of the tank 232. 
The tank 232 turns down to a position above the hopper 210 after air 
bubbles have been removed and stops at this position with its opening 
faced down. 
Accordingly silicone gel material 100 in the tank 232 flows out from the 
tank 232 into the hopper 210. 
At the outlet side of the hopper 210 is provided the pressurized feeding 
means 212 such as, for example, the screw for feeding silicone gel 
material 100 under pressure whereby silicone gel material 100 is pushed 
out by this pressurized feeding means 212 onto the material supplying 
passage. Said passage, for example, a flexible hose 211, preferably a 
transparent hose made of polyvinyl chloride, is connected between the 
output of the hopper 210 and the nozzle 300 and this flexible hose 211 is 
freely reconnectable to the hopper for cleaning after the work has been 
finished. 
The pressurized feeding screw 212 is provided inside the hopper 210 and 
silicone gel material 100 in the hopper 210 is pushed out toward the 
nozzle 300. 
In case that, for example, debubbling is carried out inside the kneading 
tanks 221 and 221', the hopper 210 can be omitted from the material 
supplying means 200 since the kneading feeder 222 can be directly 
connected to the nozzle 300 to supply silicone gel material 100 to the 
nozzle 300. 
The sheet-formed strip 110 discharged from this nozzle 300 is laminated 
with films 410 and 420 at its both sides immediately after it has been 
discharged. 
This nozzle 300 is made so that silicone gel material 100 inside the nozzle 
is discharged out by its own weight and, in this embodiment, accordingly 
the screw conveyor as the pressurized feeding means is not employed. 
The transfer unit 400 is provided with the film supplying unit 430 and a 
pair of reels 431 and 431' of this film supplying unit 430 are wound with 
the upper side film 420 and the lower side film 410 serving as the movable 
receiving means. The lower side film 410 is extended horizontally below 
the discharging port 310 so that the lower side film 410 comes in contact 
with the sheet-formed strip 110 and the upper side film 420 is supplied 
from a position above the discharging port 310 so that the upper side film 
420 is laminated onto the upper surface of the sheet-formed strip 110. 
The sheet-formed strip 110 thus covered with films 410 and 420 at its both 
sides is horizontally transferred by the carrying means such as, for 
example, the belt conveyor 440 etc. and guided to the heating section 500. 
The sheet-formed strip 110 is rolled in the specified thickness by a pair 
of upper and lower side rollers 450 and 450' before it reaches the heating 
section 500 during transportation. Though the rollers 450 and 450' also 
serve the feeding-out rollers in the embodiment, the embodiment is not 
restricted to this construction. 
Said films 410 and 420 are preferably set so that they can be removed when 
the sheet-formed strip 110 is taken out as the silicone gel sheet. Thus, 
films 410 and 420 can be removed from the product silicone gel sheet and 
the covering films conforming to the use of the silicone gel sheet can be 
instead laminated onto the silicone gel sheet. 
In the embodiment, a pair of recovery wind-up reels 401 and 402 which are 
driven by the means (not shown) are provided at the end part of the 
heating section 500 to remove and take up films 410 and 420 from the 
sheet-formed strip 110, and these reels 432 and 402 may be used as the 
supplying side reels 431 and 431'. 
To ensure easy removal of films 410 and 420 from the silicone gel sheet, 
the parting agent is applied to films 410 and 420 by an applying means 
such as, for example, the felt brushes 460 and 460' before they are 
laminated onto the sheet-formed strip 110 and dried by the fans 470 and 
470' after it has been applied. 
The sheet-formed strip 110 rolled by the rollers 450 and 450' is guided 
into the heating tunnel 510 of the heating section 500 by the belt 
conveyor 440. Inside this heating tunnel 510 is provided the heating means 
such as, for example, the far infrared heater 520 and the gelling of the 
sheet-formed strip 110 is completed while it passes through this heating 
tunnel 510. 
Said belt conveyor 440 is provided at the heating section side of the 
rollers 450 and 450' in the embodiment. 
The roll 441 at the starting end of this belt conveyor 440 is supported by 
the framework 432 of said film supplying unit 430 and the framework 432 is 
loaded on the rail 433 with wheels 434 and 434'. 
Said framework 432 is tensioned by the spring mechanism 435 with said 
heating tunnel 510 as the fulcrum and the belt conveyor 440 is also 
tensioned by the repulsive force of this spring. 
The silicone gel sheet 110' whose gelling has been completed is taken up at 
the taking-up section 530 located beside the heating tunnel 510. However, 
the silicone gel sheet cannot be actually used as having been taken up and 
generally it is sealed into a covering member such as a covering film, and 
it is used as the so-called "gel-filled pad". 
If said upper and lower films 410 and 420 are suitable as the covering 
material to an application environment where the gel-filled pad is to be 
used, the films 410 and 420 can be adhered to make the gel-filled pad. 
However, since the application environment where the gel-filled pad is 
used varies differently, films 410 and 420 which are inexpensive, 
non-massive and heat resistant should be used when manufacturing the 
silicone gel sheet and another type of covering material which meets the 
application environment should be replaced with films 410 and 420 for use 
on the product silicone gel sheet 100'. 
For example, an extremely thin polyester film is suitable as films 410 and 
420 to be used only when manufacturing the silicone gel sheet, and 
polyvinyl chloride film, polyurethane film or a copolymerized film of 
polyurethane and polyvinyl chloride is favorable as the covering material 
for the product gel-filled pad. 
For replacing the films, a continuous silicone gel sheet 100' is cut in 
appropriate sizes, the films applied to upper and lower sides of the cut 
silicone gel sheets are removed and the films suitable to the application 
environment are adhered again to the upper and lower surfaces of the 
silicone gel sheet as the covering material instead of the previously used 
films. 
If the films are replaced on the continuous silicone gel sheet, the film 
420 (410) can be wound up by the wind-up reel 401 (402) to remove it from 
the silicone gel sheet 100' and new covering films 420' (one of which is 
not shown) unwound from the film supplying reel 436 can be immediately 
adhered onto the upper and lower surface of the silicone gel sheet 100'. 
The present invention is not limited to the abovementioned embodiment and 
is available in various variations within the range of the claims and 
spirit of the present invention.