Apparatus for manufacturing silicone gel sheet

An apparatus for manufacturing a silicone gel material has a pair of tanks for separately storing and kneading first and second liquids gel forming materials, a feeder feeding the liquids while kneading them, a debubbling unit with a debubbling tank for removing air bubbles contained in the materials from the feeder and turning the tank upside down to discharge into a hopper, a nozzle for discharging silicone gel material received from the hopper in a predetermined thickness onto a lower film moving below the nozzle, an upper film supplier placing an upper film onto the film of silicone gel material, upper and lower rollers rolling the upper and lower films and the film of silicone gel material into a laminated strip, a belt conveyor receiving the laminated strip, a heating tunnel for gelling the silicone gel material and a strip take up device at the exit of the heating tunnel.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus to be used to manufacture 
thin sheet material including silicone gel 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 hand held spatula type plate, and heated with a 
flat holding plate made of metal or glass placed on the silicone material 
in the tray type container. 
However, said kneaded silicone gel material has the property that it has a 
viscosity of 1000 to 1200CP when it does not contain other substances and 
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 achieve 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 while 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 the silicone gel material in the form of a 
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 for forming the sheet-formed strip contains 
bubbles, large bubbles will be included in the finished silicone gel sheet 
and the uniform shock absorbing performance of the finished sheet will be 
impaired or the finished 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 remove 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 on both sides and rolling this 
laminated thin sheet-formed strip covered with films on both sides by the 
rollers before heat treatment. Thus, the silicone gel sheet can be formed 
in 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 or use of the 
silicone gel sheet.

PREFERRED EMBODIMENT OF THE INVENTION 
Referring to FIG. 1 which is a partly cutaway 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, including belt conveyor 42, and the heating section 
combined with this transfer unit 40 are shown below said nozzle 30. 
Said hopper 21 can be otherwise constructed so long as 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 
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 has a narrow and long opening 
just above the movable receiving means 41 provided on said transfer unit 
40, which opening extends in the direction of the width of the conveyor 
belt 42, that is, the direction perpendicular to the plane of the drawing. 
The size in the direction of right angles to that width, that is, the 
direction along the conveyor in FIG. 1, can be freely set by, for example, 
replacing the nozzle tip, to change the thickness of the layer of silicone 
gel material 10. 
Silicone gel material 10 discharged from this discharging port 31 is formed 
in a layer on the movable receiving means 41 as a thin sheet-formed strip 
11 which has the thickness determined by the size of the discharging port 
31. 
Said movable receiving means 41 in the embodiment as shown is formed by the 
tray type container which is removably provided on the belt conveyor 42. 
However, depending on the situation, 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 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 the material is extended on the movable 
receiving means 41 which moves at a speed corresponding to 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 a multi-staged 
heating furnace 51 which is constructed so that, for example, a number of 
tray type containers 41 can be stacked therein to separately heat the tray 
contains 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, a 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 the silicone 
gel sheet, liners 44 and 44' with a specified thickness can be provided at 
both sides of the tray type movable receiving means 41 as shown in FIG. 2 
to confine the sheet-formed strip 11 made of silicone gel material between 
these liners 44 and 44' and a smooth flat holding plate 45 can be placed 
on this sheet-formed strip 11 to make the thickness of sheet-formed strip 
11 uniform due just to the weight thereof or by applying a certain 
specified pressure thereto with a separate means. 
It is preferable to apply in advance a parting agent such as, for example, 
a 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 separated 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 rollers. 
In addition, in this embodiment, the sheet-formed strip made of silicone 
gel material is laminated with films on both sides and the lower film is 
placed on 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) hollow particles of silicone material 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, a two-liquid kneaded type silicone material manufactured by Toray 
Silicone Kabushiki Kaisha or KE-1051 (trademark) two-liquid kneaded type 
silicone material manufactured by Shinetsu Kagaku Kogyo Kabushiki Kaisha 
is used as silicone gel material. Such silicone gel is disclosed in the 
U.S. patent application Ser. No. 814,726. 
The apparatus of this embodiment comprises a 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 below the kneading tanks 221 and 221'. 
Liquids A and B for combining into 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 are 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 
utilize 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 the 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 and feeds it to the 
bubble removing unit 230 which removes air bubbles from the material 100. 
This debubbling unit 230 has an endless belt 231 which circulates in a 
vertical direction and is equipped with a plurality of bubble removing 
tanks 232 which intermittently move along with the endless belt 231 and 
stop in sequence at a position where silicone gel material 100 is supplied 
from the feeder 222, a bubble removing position and a position where 
silicone gel material 100 is supplied to the hopper 210. At the bubble 
position for this tank 232 is provided a cover 233 which lowers from an 
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, a vacuum pump 234 etc. to reduce the internal pressure in 
the tank 232 tightly closed by the cover 233. 
Accordingly, air bubbles entrained in the silicone gel material 100 in the 
tank 232 during the kneading process are removed by reduction of the 
internal pressure in 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, a screw for feeding silicone gel material 
100 under pressure whereby silicone gel material 100 is pushed out by this 
pressurized feeding means 212 into 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 nd 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. 
If, for example, bubble removal 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 
between films 410 and 420 on both sides immediately after it has been 
discharged. 
This nozzle 300 is made so that silicone gel material 100 inside the nozzle 
is discharged by its own weight and, in this embodiment, accordingly a 
screw conveyor as a 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 have wound 
thereon the upper film 420 and the lower film 410 serving as the movable 
receiving means. The lower film 410 moves horizontally below the 
discharging port 310 so that the lower film 410 receives the sheet-formed 
strip 110 and the upper film 420 is supplied from a position above the 
discharging port 310 so that the upper 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 on 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 to the specified thickness by a pair 
of upper and lower rollers 450 and 450' before it reaches the heating 
section 500 during transportation. Though the rollers 450 and 450' also 
serve as the feeding rollers in this embodiment, the embodiment is not 
restricted to this construction. 
Said films 410 and 420 are preferably such that they can be removed when 
the sheet-formed strip 110 is taken out as the finished silicone gel 
sheet. Thus, films 410 and 420 can be removed from the finished silicone 
gel sheet and covering films suitable for 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 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 401 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, a 
parting agent is applied to films 410 and 420 by an applying means such 
as, for example, felt brushes 460 and 460' before the films are laminated 
onto the sheet-formed strip 110 and the parting agent is 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 a heating means 
such as, for example, a 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 this 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 on wheels 434 and 434'. 
Said framework 432 is urged by the spring mechanism 435 away from said 
heating tunnel 510 as the fulcrum and the belt conveyor 440 is thus 
tensioned by the repulsive force of this spring. 
The silicone gel sheet 100' whose gelling has been completed is taken up at 
the taking-up section 530 located at the end of the heating tunnel 510. 
However, the silicone gel sheet cannot be actually used in the form in 
which it is taken up and generally it is sealed into a covering member 
such as a covering film, and it is used as a so-called "gel-filled pad". 
If said upper and lower films 410 and 420 are suitable as the covering 
material for an application environment where a 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, film 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 is suitable for the application 
environment should replace films 410 and 420 for use on the finished 
silicone gel sheet 100'. 
For example, an extremely thin polyester film is suitable for films 410 and 
420 when manufacturing the silicone gel sheet, and polyvinyl chloride 
film, polyurethane film or a copolymerized film of polyurethane and 
polyvinyl chloride is favorable as a covering material for the finished 
product gel-filled pad. 
For replacing the films, a continuous silicone gel sheet 100' with films 
410 and 420 thereon can be cut in appropriate sizes, the films applied to 
the upper and lower sides of the cut silicone gel sheets removed and films 
suitable for the application environment adhered to the upper and lower 
surfaces of the silicone gel sheet as the covering material. 
If the films are replaced on the continuous silicone gel sheet, the films 
410 and 420 can be wound up by the wind-up reels 410 and 402 to remove 
them from the silicone gel sheet 100' and as shown in FIG. 4, 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 above-described embodiment and 
is available in various variations within the range of the claims and 
spirit of the present invention.