Die coater

A die coater comprising a die composed of upper and lower mold-pieces which form a manifold and a slit extending from the manifold, a first paint supply pipe communicating with one end portion of the manifold, a second paint supply pipe communicating with another end portion of the manifold and a flow channel closing member disposed in the manifold in a fluid sealing state, the member being movable along the manifold.

BACKGROUND OF THE INVENTION 
The present invention relates to a die coater and, particularly, to an 
improved die coater capable of changing paints from one to another 
efficiently and easily. 
A die coater has a die having upper and lower mold-pieces which form a 
manifold and a slit extending from the manifold. The die coater is used 
for coating the surface of a sheet material under running. For example, 
Japanese Patent Application Laid-Open (KOKAI) Nos. 2-38022(1990) and 
2-214569 (1990) are referred to. 
When color change is conducted by changing paints from one to another in a 
conventional die coater, it is necessary to stop the supply of the paint 
and clean the inside of a manifold, slit or the like by using a solvent, 
but such a cleaning operation usually requires to disassemble the die and, 
thus, it needs much time. 
For solving the foregoing problem, the present inventors have made earnest 
studies and, as a result, have found that by disposing paint supply pipes 
which communicate with both end portions of a manifold and disposing a 
flow channel closing member in the manifold in a fluid sealing state, the 
member being movable along the manifold, paints can be changed from one to 
another efficiently and easily without disassembling the die for the 
cleaning operation when the paint is changed. The present invention has 
been accomplished based on the finding. 
SUMMARY OF THE INVENTION 
In an aspect of the present invention, it is provided a die coater 
comprising a die composed of upper and lower mold-pieces which form a 
manifold and a slit extending from the manifold, a first paint supply pipe 
communicating with one end portion of the manifold, a second paint supply 
pipe communicating with another end portion of the manifold, and a flow 
channel closing member disposed in the manifold in a fluid sealing state, 
the member being movable along the manifold.

DETAILED DESCRIPTION OF THE INVENTION 
A die used in the die coater according to the present invention is 
basically similar to a known die and the die is constituted by upper and 
lower mold-pieces (3, 4) which form a manifold (5) and a slit (6) 
extending from the manifold. The mold-pieces are usually disposed between 
right and left side plates (1, 2). Both end portions of the manifold (5) 
are usually formed by the side plates (1, 2) which are properly shaped, 
respectively. 
Paint supply pipes (7a, 7b) communicate with both end portions of the 
manifold (5) and are usually disposed to the side plates (1, 2), 
respectively. Paint supply pumps (8a, 8b) are connected to the paint 
supply pipes (7a, 7b), respectively. Preferably, joints (9a, 9b) are 
respectively disposed to the midway of the paint supply pipes (7a, 7b) so 
that the paint supply pumps (8a, 8b) are detachable from the die. 
Paints in paint reservoirs (10a, 10b) are respectively sucked by way of 
paint sucking pipes (21a, 21b) by the paint supply pumps (8a, 8b) and 
supplied through the paint supply pipes (7a, 7b) into the manifold (5). 
Then, one of the paints is distributed in the manifold (5) and extruded as 
a thin film from the slit (6). 
Preferably, the side plates (1, 2) have recycling pipes (11a, 11b) each 
communicating with the manifold (5), and branched pipes (12a, 12b) leading 
to liquid waste reservoirs (13a, 13b) are disposed to the recycling pipes 
(11a, 11b), respectively. Valves (14a, 14b and 15a, 15b) are disposed to 
the recycling pipes (11a, 11b) and the branched pipes (12a, 12b), 
respectively. In addition, valves (22a, 22b) are disposed also to the 
returning side of the recycling pipes (11a, 11b), respectively. 
A circulation line is constituted by the paint reservoir (10a) , the paint 
sucking pipe (21a) , the paint supply pump (8a), the paint supply pipe 
(7a) and the recycling pipe (11a), while the other circulation line is 
constituted by the paint reservoir (10b), the paint sucking pipe (21b), 
the paint supply pump (8b) , the paint supply pipe (7b) and the recycling 
pipe (11b). Preferably, air vent pipes (16a, 16b) which communicate with 
the manifold (5) are disposed to upper parts of the side plates (1, 2), 
and valves (17a, 17b) are disposed to the air vent pipes (16a, 16b), 
respectively. 
A flow channel closing member (18) is disposed in the manifold (5) in a 
fluid sealing state as it is movable along the manifold (5), i.e., movable 
leftward and rightward. The flow channel closing member (18) shown in the 
drawings as an example is an ellipsoidal member having such a size as 
capable of fitting to the inside of the manifold (5) in a fluid sealing 
state and being contained in the side plates (1, 2). Then, as an example 
of a means for moving the flow channel closing member (18), drawing 
strings (19a, 19b) are respectively connected to right end and left end of 
the flow channel closing member (18). Each of the drawing strings (19a, 
19b) is taken out through each of side walls of the side plates (1, 2) to 
the outside and a take-out port for each of the drawing strings (19a, 19b) 
is sealed with each of packings (20a, 20b). 
There is no particular restriction on the material of the flow channel 
closing member (18) so long as the material has a corrosion resistance 
against paint cleaning solvent, but it is preferably made of TEFLON. 
Further, a nylon thread is preferred for the drawing strings (19a, 19b). 
The flow channel closing member (18) may have a cylindrical shape. 
The die coater of the present invention is used, for example, as described 
below. 
1. Supply of Paint A (FIG. 4) 
Paint A is supplied from the paint supply pipe (7a) in a state where the 
flow channel closing member (18) is shifted to the rightmost end by an 
operation of the drawing string (19b). 
The paint A is supplied by operating the paint supply pump (8a), with the 
valves (14a, 14b and 17a, 17b) being kept closed. 
2. Preparation for the Supply of Paint B (FIG. 5) 
The paint supply pipe (7b) and the paint supply pump (8b) are connected by 
the joint (9b), the valve (14b) is opened and circulation of the paint B 
is started by operating the paint supply pump (8b). The paint B is 
circulated through the recycling pipe (11b) to the paint reservoir (10b) . 
3. Changing Operation to Paint B (FIG. 6) 
The valve (14a) is opened and the valve (14b) is gradually closed and the 
drawing string (19a) is gradually drawn to shift the flow channel closing 
member (18) leftward. Further, the valves (17a, 17b) are gradually opened 
and then returned to the closed state. 
By the operations as described above, the circulation amount of the paint B 
is decreased and the amount supplied to the manifold (5) is increased. 
Further, air vent is conducted in the paint B supplied in the manifold 
(5). 
In the paint changing operation described above, as the flow channel 
closing member (18) is shifted gradually, pressure of the inside of the 
manifold is prevented from reducing to a negative pressure and, as a 
result, the paint A staying in the slit (6) can be substantially prevented 
from being sucked and mixed into the paint B. 
Further, the paint A having stayed in the manifold (5) can be recovered 
easily through the recycling pipe (11a) to the paint reservoir (10a). In a 
case where the recycling pipe (11a) is not disposed, the paint is returned 
by way of the paint supply pipe (7a) and pump (8a) into the paint 
reservoir (10a). 
The paint A having stayed in the slit (6) is extruded by the paint B now 
changed. Then, the extruded paint B can be recovered, for example, by a 
tray (not shown in the drawing) disposed ahead of the slit (6). 
4. Cleaning Operation After Completion of Color Change to Paint B (FIG. 2) 
Cleaning is conducted by opening the valve (15a) while closing the valve 
(22a) and by switching from the paint reservoir (10a) to a solvent 
reservoir (not shown in the drawing). Cleaning liquid wastes are recovered 
through the branched pipe (12a) into the liquid waste reservoir (13a). 
According to the present invention described above, it can been provided an 
improved die coater capable of changing paints from one to another 
efficiently and easily without disassembling the die. 
Therefore, the present invention is of a significant industrial value.