Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 The present invention relates to a plasma
treatment apparatus for activating treatment on the
surfaces of synthetic resin moldings.
BRIEF DESCRIPTION OF T~E DRAWINGS
.
FIG. 1 is a diagram for explaining the
plasma treatment operation carried out through a
first system in an apparatus according to the
present invention.
FIG. 2 is a diagram for explaining the
plasma treatment operation carried out through a
second system in the apparatus according to the
present invention.
FIG. 3 is a diagram for explaining the pre-
operation in the first systemO
~5 FIG. 4 is a diagram for explaining the pre-
operation in the second system.
FIG. 5 is a partially broken side view of a
conventional plasma treatment apparatus.
Conventionally, moldings of nonpolar
polymers such as polyethyLene, polypropylene, or the
like/ adhere poorly to coating materials, and
therefore are surface activated be~ore coating. For
surface activationl various methods of treatment,
for example, ultraviolet ray irradiation, corona
discharge, primer application, and so on have been
used. All these methods, however still have
disadvantages in that adhesion to a coatiny material
is still not sufficient, the cost for treatment is
relatively high, and so on. Because of these
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1 disadvantages, plasma treatment is increasingly
used. Figure 5 shows one con~entional plasma treating
apparatus.
Shower pipes 52 for a plasma generator 51
are provided in a plasma treatment tank 55 which
accommodates resin moldings to be coated. ~ raw
material gas and high frequency waves are fed
respectively from a bomb 53 and a high frequency
generator 54 into plasma generator 51 to produce a
plasma gas. The plasma gas is fed into plasma
treatment tank 55 through shower pipes 52.
In order to evacuate plasma treatment tank
55, the tank 55 is connected to a communicating pipe
56 at its one end. A mechanical booster 58 is
connected with the communicating pipe 56 at its
other end, and a communicating pipe 59 iS attached
at its one end to the booster 58~ A rotary pump 60
is attached to the communicating pipe 59 at its
other end, so that tank 55 ls evacuated when the
mechanical booster 58 and the rotary pump 60 are
operated.
In the thus arranged plasma treatment
apparatus, generally, a number of resin moldings can
be accommodated in the plasma treatment tank 55 so
that it is possible to manufacture a number of
plasma-treated moldings during each treatmentO
Accordingly, the apparatus has high productivity
from the point of throughput.
Recently, however, as demands for such
moldings have become diverse, var;ous kinds of
plasma-treated products must be manufactured in
small quantitles. Because plasma treatment is
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1 performed in a vacuum, moldings to be treated must
be put into and taken out of the space where the
plasma treatment is performed. Thus, every time
moldings are put into and taken out of the tank, the
vacuum is lost and must be recovered.
In manufacturing small quantities of
diverse kinds of products, the number of products
per lot is reduced and the number of the lots is
increased, so that it is necessary to increase the
number of cycles. If the number of the cycles of
plasma treatment is increased, the treatment time
per product is substantially increased. This is
unacceptable in practice and the number of treatment
cycles must be decreased if the conventional plasma
treatment apparatus is to be used as it is. If a
few products are manufactured per cycle of plasma
treatment by using a plasma treatment tank having a
large capacity, there is a further problem that the
manufacturing cost rises.
An object of the present invention is to
provide a plasma treatment apparatu~ which can
effectively and efficiently treat small quantities
of and diverse kinds of resin moldings.
In order to solve the problem~ described
above, according to the present invention, the
plasma treatment apparatus includes a plasma gas
leading-in pipe diverging into a plurality of shower
pipes with a plasma generator connected thereto.
The shower pipes are respectively connected with a
plurality of plasma treatment tanks each having a
vacuum device. Each of the sho~er pipes is provided
with an openable/closable fluid valve.
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- 3a -
1 In one of its aspects the invention resides in a
plasma treatment apparatus comprising a single plasma
generating means; a plurality of plasma treatment tanks
each for receiving workpieces to be treated; first
communicating means for selectively communicating said
plasma treatment tanks to said plasma generating means so
as to introduce plasma to selected tanks; a pluralit~ of
first evacuating means each for evacuating an associated
one of said tanks to produce a vacuum therein; a single
second evacuating means for evacuating said tanks to
produce a vacuum therein; and second communicating means
for selectively communicating said plasma treatment tanks
to their respective associated first evacuating means
directly and via said second evacuating means so as to
produce a Yacuum therein and for selectively communicating
said plasma treatment tanks to said second evacuating
means so as to produce a vacuum therein, said second
communicating means including third communicating means
for selectively connecting said first evacuating means to
said second evacuating means, each of said plasma
treatment tanks further including leak valve means adapted
to return said plasma treatment tanks to atmospheric
pressure.
In a further aspect the invention resides in a
method of plasma treatment of workpieces in at least two
plasma tanks with plasma generated in a single plasma
generating means, said plasma tanks being selectively
communicated to said plasma generating means by first
openable/closable valve means, said plasma tanks being
selectively communicated by second openable/closable valve
means to associated first evacuating means for producing a
vacuum in said plasma tanks and to a single second
evacuating means for producing a vacuum in said plasma
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1 tanks~ each of said plasma tanks having leak valve means
for introducing air therein, the steps comprising
switching said first openable/closable valve means to
communicate said plasma generating means to selected ones
of said plasma tanks where a vacuum is produced by second
evacuating means, to thereby introduce plasma into said
selected plasma tanks and treat workpiece in said selected
plasma tanks while preparing workpieces for treatment in
the other tanks; closing said leak valve means of the
]o other tanks and switching said second openable/closable
valve means to communicate the other tanks to said first
evacuating means; producing a vacuum in the other tanks by
said first evacuating means; switching said first
openable/closable valve means to separate said selected
plasma tanks from said plasma generating means to stop
treatment of workpieces in said selected plasma tanks,
switching said second openable/closable valve means to
separate said selected plasma tanks from said second
evacuating means; opening said leak valve means of said
selected plasma tanks, switching said second
openable/closable valve means to separate the other plasma
tanks from the associated first evacuating means and
communicate the other plasma tanks to said second
evacuating means; producing a vacuum in the other plasma
tanks by said second evacuating means while replacing
workpieces in said selected plasma tanks; and s~tching
said first openable/closable valve means to communicate
the other plasma tank where a vacuum is produced to said
plasma generating means to introduce plasma into said
other plasma tanks and treat workpieces in the other
plasma tanks.
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1 ~ecause the plasma leading-in pipe is
connected with one plasma generator and diverges
into a plurality of shower pipes, plasma treatment
can be carried out for only the plasma treatment
tank/tanks communicated with the shower pipe/pipes
in which the openable/closable valve/valves are
opened, while the remainder of the plasma treatment
tanks can be prepared for plasma treatment.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to Figs. 1 through 5, an
embodiment of the plasma treatment apparatus
according to the present invention will be described
hereunder. In this embodiment, the plasma treatment
apparatus includes a plurality of plasma treatment
tanks each having a small capacity. Since the
structure per se of each component such as the
plasma treatment tanks, etc., is the same or similar
to that of the above-mentioned conventional
apparatus, the apparatus is srhematically
illustrated in Figs. 1 through 4.
First and a second systems A and B each
include shower pipes 3 diverging from the same
plasma gas leading-in pipe 2. A plasma treatment
tank 5 is connect~d with the shower pipe 3, and a
vacuum device 4 communicates with each treatment
tank 5 through communicating pipes 6, 7 and 8,
etc. Therefore, the apparatus will be described
hereunder with the two systems distinguished from
each other by adding symbols a and b to the
reference numerals of the systems A and B
respectively.
A single plasma generator 1 is fed with a
raw gaseous material such as an oxygen gas from a
bomb 12 through a feedins pipe 14 having an
openable/closable valve 17 disposed midway in the
feeding pipe 14 and supplied with high frequency
energy from a high frequency oscillator 15 through a
waveguide 16.
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1 The plasma generator 1 is preferably
constituted by a plasma generating pipe made o~ a
quartz and a Tesla coil for inducing plasma by
generating a spark in synchronism with the high
frequency oscillator 15 when the high frequency
oscillator is started.
The plasma gas generated in the plasma
generator 1 is led into a single plasma gas leading-
in pipe 2 and then can be fed into plasma treatment
tanks 5a and 5b through two shower pipes 3a and 3b
diverging from plasma gas leading-in pipe 2. An
openable/closable valve 13a for fluid is provided
midway in shower pipe 3a and, similarly, an
openable/closable valve 13b is provided midway in
shower pipe 3b. The openable/closable valves 13a
and 13b are used for feeding the pla~na gas
r gen2rated in the plasma generator 1 into the plasma
trea~ment tanks 5a and 5b respectively.
Accordingly, when plasma gas is being fed
into plasma treatment tank 5a, the openable/closable
valve 13a is in an open state while the openable/
closable valve 13b is in a closed state as shown in
Fig. 1. When the plasma gas is being fed into the
plas~a treatment tank 5b, on the contrary, the
openable/closable valve 13b is in an open state
whil_ the openable/closable valve 13a is in a closed
state as shown in Fig. 2.
The plasma treatment tank 5a is constituted
by a pressure-withstanding vessel having a leaking
valve 18a. The shower pipe 3a is connected with
plasma treatment tank 5a to which a communicating
pipe 6a ~s further attached to exhaust gas inside
the tank Sa through a vacuum device which will ~e
described below.
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1 Similarly, plasma treatment tank 5b is a
vessel having a leaking valve 18b and the shower
pipe 3b and a communicating pipe 6b attached to tank
5b.
A stand on which resin moldings arè to be
put or attached is fixedly or movably attached to
the inside of each of the plasma treatment tanks 5a
and 5b. The moldings may be brought into the plasma
treatment tanks 5a and Sb through openable/closable
caps provided on the ront surfaces of the plasma
treatment tanks 5a and 5b, respectively.
Midway in communicating pipe 6a is provided
an openable~closable valve 9a. A mechanical booster
4c is also coupled to pipe 6a. Communicating pipe
6b is also provided with an openable/closable valve
9b and integrated with the communicating pipe 6a so
as to communicate with the same mechanicai booster
4c. The structure of the mechanical booster 4c per
se is conventional and a Roots booster is generally
used. The mechanical booster 4c is connected with a
rotary pump 4a through a communicating pipe 8a ~
provided with an openable/closable valve lla.
Similarly, mechanical booster 4c is connected also
with another rotary pump 4b through a communicating
pipe 8b, partly commonly with the communicating pipe
8a. Midway in communicating pipe 8b is also
- provided an openable/closable valve llb.
As to the four openable/closable valves 9a,
9b, lla, and llb provided in the respective
communicating pipes 6a, 6b, 8ar and 8b, the
openable/closable valves 9b and llb are closed when
the openable/closable valves 9a and lla are being
opened as shown in Fig. 1, while the openable/
closable valves 9b and llb are opened when the
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1 openable/closable valves 9a and lla are being closed
as shown in Fig. 2.
The openable/closable valves 9a and llb,
and the openable/closable valves 9b and lla are
never both opened or closed at the same time,
respectively. If they are operated to open or close
at the same time, such effects as described later
cannot be obtained.
A communicating pipe 7a is also connec~ed
at its opposite ends with the communicating pipes 6a
and 8a. Communicating pipe 7a has an openable/
~losable valve lOa which is opened when openable/
closable valves 9b and llb are opened as shown in
Fig. 2.
Similarly, a communicating pipe 7b is
connected at its opposite ends with the
communicating pipes 6b and 8b, and pipe 7b is
provided midway with openable/closable valve lOb.
As shown in Fig. 1, when the openable/
closable valves ~b and llb are closed and the
openable/closable valves 9a and lla are opened, the
openable/closable valve lOb is opened.
Thus, rotary pumps 4a and 4b are
communicating with plasma treatment tanks 5a and 5b
through parallel paths, one causing the communi-
cating pipes 6a and 6b, the mechanical booster 4c,
and the communicating pipes 8a and 8b to communicate
with each other, and the other rotary pump being
constituted by the other communicating pipes 7a and 7b.
The opening/closing operations of the
openable/closable valves are automatically performed
by conventional control devices (not shown).
The plasma treatment apparatus of the
present embodiment having the above mentioned
structure operates as follows.
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1 After placement of resin moldings in plasma
treatment tank 5a has been finished, the rotary pump
4a is operated with the openable/closable valve lOa
opened while the leaking valve 18a, openable/closable
valves 13a, 9a and lla are closed as shown in
Fig. 3.
Next, after the inside o~ the plasmatreatment tank 5a has reached a predetermined vacuum
state, the mechanical booster 4c and the rotary pump
4a are operated with openable/closable valve lOa
closed and the openable/closable valves 9a and lla
are opened as shown in the first system A of Fig.
1. Thus, the inside of the plasma treatment tank 5a
is in the vacuum state required for plasma
treatment.
~ The openable/closable valve 13a of the
shower pipe 3a is opened, the plasma oscillator 15
is started, and at the same time the Tesla coil is
energized. Then, the openable/closa~le valve 17 of
2Q the bomb 12 is opened so that oxygen gas is fed into
the plasma generator 1 to cause the plasma generator
1 to ~enerate a plasma gas.
When the plasma gas has been generated, the
Tesla coil is deenergized. The plasma gas is led
into the plasma treatment tank 5a and the resin
moldings in the plasma treatment tank 5a are
activated by plasma-treatment with openable/closable
valves 17, 13a, 9a and lla opened as shown in
the first system A of Fig. 1.
Upon completion of plasma treatment in the
plasma treatment tank 5a oxygen gas flow from bomb
12 is stopped, and plasma generator 1, booster pump
4c, the rotary pump 4a, etc., are tem?orarily
stopped to switch the operation to the second system
B. Then, openable/closable valve 13a, 3a, and lla
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1 are closed and leaking valve 18a is opened to return
the inside of the plasma treatment tank 5a to an
atmospheric state. Finally, the plasma-treated
resin moldings are taken out of the tank, and the
cycle of plasma treatment in the first system A is
terminated.
After the placement of ~he resin moldings in
the plasma treatment tank Sa in the irst system A
has been completed, placement of workpieces in
plasma treatment tank 5b of second system B is
carried out.
A~ter this is done, as shown in Fig. 4, the
openable/closable valve 10b is opened with leaking
valve 18b closed, and rotary pump 4b is operatedO
Because the above-mentioned operations are
carried out in para].lel with plasma treatm2nt in the
plasma treatment tan~ 5a in the first system A,
openable/closable valves 13b, 9b, and llb have been
already closed.
The schedule is preferably arranged such
that when the preparation for the plasma treatment has
proceeded to this point, the inside of plas~a treatment
tank 5b is in a predetermined vacuum state and the plasma
tre~tment in the first system A is terminated. Now,
opelable/closable valve 10b is closed and openable/
closable valves 9b and llb are opened successively
in second system B shown in Fig. 2. The mechanical
booster 4c and the rotary pump 4b are also operated
together~ Thus, the inside of plasma treatment tank
5b s evacuated as required for plasma treatment.
Openable/closable valve 13b o shower pipe
3b is opened. The plasma oscillator lS is started
and at the same time the Tesla coil is energized.
Then, the openable/closable valve 17 of the bomb 12
is opened so that an oxygen gas is ed into the
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1 plasma generator 1 to cause the plasma generator 1
to generate a plasma gas. Then, the plasma gas is
led into plasma treatment tank Sb and the resin
moldings in the plasma treatment tank 5b are
activated.
Upon completion of the plasma txeatment in
the plasma treatment tank 5b, the oxygen gas flow is
stopped and plasma generator 1, booster pump 4c,
rotary pump 4b, etc., are temporarily stopped to
switch operation back in the first system A. Then,
openable/closable valves 13b, 9b, and llb are closed
and leaking valve 18b is opened to return the inside
of plasma treatment tank 5b into an atmospheric
state. Finally, the plasma-treated resin moldings
are taken out of the tank, and the cycle of plasma
treatment in the second system B is terminated.
As described above, a plurality of plasma
treatment tanks are used in the plasma treatment
apparatus of the present embodiment, so that the
~0 apparatus is applicable to a so-called "Toyota
manufacturing system" in which a small quantity of
various kinds of resin moldings are plasma-treated.
Further, not only can the operations of the
first system A and the second system B be
efficiently performed, but the first system A can be
prepared during the operation of the second system B
and the second system B can be prepared during the
operation of the first system Af so that each plasma
treatment cycle can be shortened to remarkably
improve productivity.
Conventionally, a plasma treatment tank
having large capacity has been required to be
operated even when a small quantity of resin
moldings are treated. According to the present
invention, on the contrary, if a plurality of plasma
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1 treatment tanks of various capacities are arranged
in the plasma treatment apparatus, a proper
combination of plasma treatment tanks can be matched
to the quantity of resin moldings to be treated, and
hence operation cost can be reduced.
Further, the plasma oscillator can be used
without reducing the output thereof and almost
without stopping the operation of the same.
The present invention is not limited to the
arrangement as described above but can be carried
out, for example, in the modified mode as follows.
The vacuum device 4 may have any suitable structure
and the plasma treatment tank 5 can be evacuated by
using only either the mechanical booster or the
rotary pump. Further, a vacuum device 4 may be
provided for each plasma treatment tank S.
According to the present invention,
remarkable effects can be obtained. Preparation for
plasma treatment in one plasma treatment tank can be
carried out during plasma treatment in other plasma
treatment tank/tanks, so that the plasma treatment
cycle can be made fast without reducing the rate of
operation of the plasma generator.
Further, because a plurality of plasma
treatment tanks are provided, any one or ones of the
plas~a treatment tanks can be selectively used in
accordance with the number of moldings to be
trea ed, plasma treatment can be carried out with a
reduced output of the plasma generator, and the
plas~a oscillator can be used without reducing the
output thereof and almost without stopping the
operation of the same, so that the manufacturing
cost can be reduced.
