Background of the Invention
(1) Field of the Invention:
[0001] The present invention relates to a method and unit for washing a screen stencil frame
used in a flat screen printing machine. More particularly, the present invention relates
to a method and unit for washing a screen stencil frame used in a flat screen printing
machine, in which the screen stencil frame can be washed without dismounting the frame
from the flat screen printing machine.
(2) Description of the Prior Art:
[0002] Flat screen printing machines have been widely used for printing woven fabrics. In
printing of woven fabrics, one pattern is ordinarily printed with different colors.
Accordingly, every time the printing color is changed, a screen stencil frame is dismounted
from a printing machine and it is secured to the original position after washing.
[0003] Recently, kinds of woven fabrics are increased while manufacturing lots are decreased,
and the number of colors for one pattern is increased. Accordingly, the frequency
of dismounting and attachment of the screen stencil frame is increased and the operation
rate of the printing machine is reduced.
Summary of the Invention
[0004] It is a primary object of the present invention to provide a method for washing a
screen stencil frame in a flat screen printing machine, in which washing of the screen
stencil frame and recovery of a residual color paste can be automatically performed
without dismounting the screen stencil frame from a printing unit at the time of changing
a printing color in one printing pattern or at the time of completion of printing
of all the colors, and a washing unit for use in carrying out this washing method.
[0005] In accordance with one fundamental aspect of the present invention, there is provided
a method for washing a screen stencil frame in a flat screen printing machine, which
comprises arranging a delivery member capable of reciprocatively moving on the screen
stencil frame, arranging a suction nozzle connected to a vacuum device on said delivery
member, reciprocating the delivery member on the screen stencil frame in such a manner
that the suction nozzle confronts a screen stencil of the screen stencil frame, and
washing the screen stencil with water by utilizing a subatmospheric suction pressure
generated by the suction nozzle.
[0006] In accordance with another fundamental aspect of the present invention, there is
provided a unit for washing a screen stencil frame in a flat screen printing machine,
which comprises (A) a delivery mechanism provided with a nozzle, (B) a housing mechanism
for dismountably housing the delivery mechanism therein and (C) a supporting mechanism
for supporting and housing said housing mechanism therein, which is provided with
a vacuum mechanism, wherein said supporting mechanism supports the housing mechanism
so that the housing mechanism can be connected to a printing unit arranged in the
flat screen printing machine, said delivery mechanism comprises a driving member,
said delivery mechanism is released from the housing mechanism and reciprocated on
the printing unit by said driving member when the housing mechanism is connected to
the printing unit, said nozzle is connected to the vacuum mechanism of the supporting
mechanism through a predetermined conduit, and said delivery mechanism is arranged
in such a positional relationship that when the delivery mechanism is reciprocated
on.the printing unit, the delivery mechanism confronts a screen stencil of the screen
stencil frame in the printing unit.
Brief Description of the Drawings
[0007]
Fig. 1 is a side arrangement diagram of a flat screen
Fig. 2 is an enlarged view of a printing unit in the flat screen printing machine
shown in Fig. 1.
Fig. 3 is a diagram showing the using state of a washing unit according to the present
invention.
Fig. 4 is a view showing the section seen in the direction of arrows A-A in Fig. 3.
Fig. 5 is a view showing the section seen in the direction of arrows H-H in Fig. 3.
Fig. 6 is a view showing the section seen in the direction of arrows G-G in Fig. 3.
Fig. 7 is a diagram illustrating the state where a delivery device is housed in a
housing device.
Fig. 8 is a diagram of a delivery device, which shows the section seen in the direction
of arrows F-F in Fig. 3.
Figs. 9 and 10 are diagrams showing preferred examples of a nozzle used in the present
invention.
Detailed Description of the Preferred Embodiments
[0008] The present invention will now be described in detail with reference to embodiments
illustrated in the accompanying drawings.
[0009] Referring to Fig. I which is a side arrangement diagram of a flat screen printing
machine and Fig. 2 which is an enlarged view of a printing unit, a fabric 2 to be
printed, which has been supplied by a fabric supply roller 1, is fixed to the surface
of an endless belt 3 coated with a fixing agent by a fixing agent applying device
(not shown) and is delivered intermittently repeat by repeat integrally with the endless
belt 3 by a driving roller 4.
[0010] Printing units 7 are arranged at predetermined intervals above the endless belt 3.
Each printing unit 7 comprises a screen stencil frame 5 and a squeegee 6. While the
endless belt 3 is driven, the printing units 7 are elevated by several centimeters,
and when the endless belt 3 is stopped on completion of feeding of one repeat length,
the printing units 7 are brought down and the squeegees 6 are moved in the widthwise
direction of the endless belt 3 while applying a printing pressure, whereby printing
of the fabric 2 is effected. The printed fabric 2 is introduced into a drying device
8 and is then recovered. The surface of the endless belt 3 is washed with water by
a belt washing device 9.
[0011] Printing of one color in one pattern is completed by the above operation. At this
point, for printing of a next color in the same pattern, the squeegee 6 is dismounted
from the printing unit 7 manually as in the conventional technique.
[0012] Then, the screen stencil frame 5 is washed according to the method of the present
invention.
[0013] According to the present invention, in order to use a washing unit described hereinafter,
as is seen from the right printing unit shown in Fig. 2, an air cylinder 10 which
is supported and fixed on the printing unit is actuated to elevate the screen stencil
frame 5 to a predetermined height together with an adjusting device 11 for supporting
the screen stencil frame 5. In this state, washing is carried out.
[0014] Referring to Figs. 3 and 4 illustrating the state where the washing unit of the present
invention is used for washing the screen stencil frame 5, the washing unit to be used
in the method of the present invention comprises a supporting body 20, a housing device
21 and a delivery device 22.
[0015] The housing device 21 is turnably supported and housed in the supporting body 20.
An air cylinder 25 is arranged above the supporting body 20 and this air cylinder
25 is connected to a chain wheel 29 through a rack 26, a pinion gear 27 and a chain
28. An arm 30 secured to the housing device 21 is connected to the rotation shaft
of the chain wheel 29. It will readily be understood that the housing device 21 is
turned by the operation of the air cylinder 25.
[0016] Referring to Fig. 5 which is a front view of the supporting body 20, a vacuum chamber
31 and a blower 32 are arranged in the supporting body 20, and a subatmospheric pressure
is generated in the vacuum chamber 31 by the operation of the blower 32. The vacuum
chamber 31 is connected to a discharge pump 33 so that a color paste and a washing
waste liquid accumulated in the vacuum chamber 31 can be discharged. This discharge
can automatically be performed by detecting the level of the washing waste liquid
and the like in the vacuum chamber 31.
[0017] The supporting body 20 is placed on a truck 34 and can be moved on rails 35 along
the longitudinal direction of the printing machine.
[0018] When this washing unit is used, the supporting body 20 is moved to a predetermined
position and the air cylinder 25 is actuated to turn the housing device 21 and connect
it to the printing unit 7 for the washing operation.
[0019] In the supporting body 20 shown in Fig. 3, two-dot chain lines indicate the state
where the housing device 21 is housed in the supporting body 20.
[0020] Referring to Fig. 6 which is a sectional front view of the housing device 21 (a view
showing the section seen in the direction of arrows G-G in Fig. 3) as well as Fig.
3, the housing device 21 comprises a frame member 40, and rails 41a and 41b to be
engaged with wheels of the delivery device 22 are arranged on both the sides of the
frame member 40. An air cylinder provided with piston rods 42a and 42b is supported
on the arm 30 secured to the frame member 40 to anchor the delivery device 22. In
short, the delivery device 22 is supported and housed in the housing device 22.
[0021] Referring to Fig. 7 showing this housing state and Fig. 8 which is a front view of
the delivery device (a view showing the section in the direction of arrows F-F in
Fig. 3), the delivery device 22 comprises an upper truck 50a and a lower truck 50b,
and nozzles 5la and 51b are arranged on the trucks 50a and 50b, respectively. Incidentally,
the nozzles 5la and 51b are omitted in Fig. 9 for simplification of the illustration.
[0022] The trucks 50a and 50b are driven by driving motors 52a and 52b, respectively. Wheels
53a and wheels 53b are connected through shafts 54a and 54b. Furthermore, stoppers
55a and 55b are arranged on the upper and lower trucks 50a and 50b, respectively.
[0023] More specifically, the upper and lower trucks 50a and 50b are housed in the housing
device 21 along the rails 41a and 41b of the housing device 21. In this case, the
rods 42a and 42b are projected upward and downward from the air cylinder 43 to impinge
against the stoppers 55a and 55b, whereby the trucks 50a and 50b are secured in the
housing device 21 (see Fig. 7).
[0024] The upper nozzle 51a is pivoted and supported on the upper truck 50a through an air
cylinder 60 so that the angle of an open surface of the upper nozzle 51a can be appropriately
changed by the operation of the air cylinder 60.
[0025] The lower nozzle 51b is arranged on the lower truck 50b so that the lower nozzle
5lb is always opened upward and the open surface is always horizontal. The nozzles
51a and 51b are connected to the vacuum chamber 31 of the supporting body 20 through
conduits 6la and 6lb such as rubber hoses. More specifically, a subatmospheric pressure
is produced by the operation of the blower 32 of the supporting body 20, and a sucking
effect is generated on the nozzles 51a and 51b to effect washing.
[0026] The washing method using the nozzles 5la and 51b mounted on the moving trucks 50a
and 50b will now be described with reference to Figs. 3 and 4.
[0027] Horizontal rails 70a and 70b are arranged in the printing unit 7 and extended in
the widthwise direction of the machine, and the upper and lower moving trucks 50a
and 50b are reciprocated along these rails 70a and 70b in the widthwise direction
of the machine.
[0028] Incidentally, the portion X in Fig. 4 shows the section seen in the direction of
arrows B-B in Fig. 3.
[0029] The housing device 21 is turned and secured so that the raisl 41a and 41b are connected
to the rails 70a and 70b arranged in the printing unit 7, and in this state, the rods
42a and 42b are sunk inwardly by the operation of the air cylinder 43 arranged in
the housing device 21 to release anchoring of the upper and lower moving trucks 50a
and 50b.
[0030] The driving motors 52a and 52b of the trucks 50a and 50b are turned in the normal
rotation direction and the upper and lower moving trucks 50a and 50b are moved to
the position of the end of the screen stencil frame 5 (the position Yl in the drawings).
At this position, the air cylinder 60 of the truck 50a is actuated to bring the upper
nozzle 5la close to a screen stencil 5a. Namely, the screen stencil 5a to be washed
is gripped between the upper and lower nozzles 5la and 51b. Furthermore, the blower
32 of the supporting body 20 is actuated to produce a subatmospheric pressure and
generate sucking forces in the nozzles 5la and 51b. In this state, the moving trucks
50a and 50b are moved to effect washing of the screen stencil 5a. When the trucks
50a and 50b arrive at the position Y2 in the drawings, the motors 52a and 52b are
driven in the reverse rotation direction and the trucks 50a and 50b are moved to the
opposite side.
[0031] In the above-mentioned embodiment, the motors 52a and 52b are synchronously driven
to synchronously move the upper and lower moving trucks 50a and 50b, and washing is
always effected in the state where the upper nozzle 51a confronts the lower nozzle
51a. However, since the upper and lower moving trucks 50a and 50b can independently
be driven, there may be adopted a modification in which suction washing by the upper
nozzle 51a and suction washing 51b are separately performed.
[0032] Referring to Fig. 9 (showing the section seen in the direction of arrows E-E in Fig.
3), in order to perform washing effectively, cleaning members 72a and 72b such as
sponges or brushes are arranged in the nozzles 5la and 5lb through sucking spaces
7la and 71b, and it is preferred that water supply pipes 73a and 73b be laid out in
these cleaning members 72a and 72b to supply washing water. In this case, the cleaning
members 72a and 72b are brought into close contact with the screen stencil 5a, and
the trucks 50a and 50b are moved to effect sucking and washing while supplying washing
water through the water supply pipes 73a and 73b, whereby washing can be carried out
very effectively. Since the washing waste liquid is recovered into the vacuum chamber
31 of the supporting body 20, the washing method of the present invention is advantageous
in that the region other than the washing zone is not unnecessarily wetted.
[0033] In order to enhance the sucking effect, it is preferred that the top peripheral edges
75a and 75b of the nozzles 51a and 51b are slightly separate from the screen stencil
5a. Namely, air around the nozzles is promptly sucked in the nozzles.
[0034] Since the moving direction of the nozzles 5la and 51b is defined by the rails 70a
and 70b laid out in the printing unit 7, it is indispensable that the nozzles 51a'and
51b should have such a width as completely covering the width of the screen stencil
5a and especially, the upper nozzle 51a should have a width adapted to the inner width
of the screen stencil frame 5.
[0035] In order to recover the residual color paste, it is preferred that as shown in Fig.
10, the top end portion of the upper nozzle 51a be tapered and if the nozzle 51a is
vertically positioned, the top end 75a of the nozzle 51a be slightly lifted from the
screen stencil 5a. If this arrangement is adopted, even the residual color paste left
in the corner portions of the screen stencil frame 5 can be removed effectively. Incidentally,
in this embodiment, cleaning members need not particularly be arranged in the nozzles.
[0036] As is apparent from the foregoing description, according to the present invention,
the screen stencil frame 5, that is, the screen stencil 5a, is washed by the nozzles
with the reciprocative movement of the trucks 50a and 50b.
[0037] After completion of washing, the operation of the blower 32 is stopped, the trucks
50a and 50b are housed in the housing device 21 again, the air cylinder 43 is turned
off, the rods 42a and 42b are projected, and the trucks 50a and 50b housed in the
housing device 21 are supported and secured. In this state, the housing device 21
is turned downward and connection to the printing unit 7 is released, and the housing
device 21 is supported and housed at the predetermined position in the supporting
body 20 again.
[0038] The printing unit 7 is brought down, and printing of a next color is performed.
[0039] Incidentally, driving and stopping of the above-mentioned air cylinder and driving
motors can be performed wholly automatically by generating predetermined electric
signals by a sequential starting-stopping circuit.
[0040] The effects attained by the present invention will now be described.
(a) A labor-saving effect is attained.
[0041] In a flat screen printing machine, one worker is sufficient for the ordinary printing
operation. However, at the color-changing step, two or three workers are necessary
for dismounting, washing and attachment of the screen stencil frame. Namely, at least
one additional worker should be stationed.
[0042] Recently, the printing repeat length is increased and the fabric width is broadened.
Accordingly, the weight of the screen stencil frame is increased, and it is very difficult
for one worker to effect dismounting and attachment of the printing stencil frame
and this operation requires a great labor and a high skill. According to the present
invention, the operation of dismounting and attaching the screen stencil frame need
not be performed at the color-changing step, and hence, no additional worker is necessary.
(b) Since the time of stoppage of the printing machine at the color-changing step
can be shortened, the manufacturing efficiency can be increased.
[0043] In flat screen printing machines now used in the art, at the color-changing step,
the screen stencil frame is once dismounted from the printing machine and the screen
stencil frame is washed by a screen stencil frame washing machine. However, the number
of screen stencil frames that can be washed at one time by an ordinary screen stencil
washing machine is 3 to 4 at most, and if the amount of the residual color paste is
large, a long time is required for completion of the washing operation.
[0044] According to the present invention, if washing units are arranged in a number corresponding
to the number of colors to be printed, all the screen stencil frames can be simultaneously
washed in the state where they are attached to the printing machine. Therefore, the
time required for washing the screen stencil frames can be shortened to 5 minutes
or less.
(c) The rejection rate of the printed fabric is reduced and a guide cloth is saved
at the color-changing step.
[0045] In the case where the screen stencil frame is once dismounted from the printing unit
for washing and the same screen stencil frame is attached to the printing unit for
performing the printing operation, improper registration is readily caused by a slight
error when the screen stencil frame is attached to the printing unit again, and the
registering operation should often be conducted again.
[0046] According to the present invention, since the screen stencil frame need not be dismounted
from the printing unit at the cclor-changing step, no improper registration is caused
after washing of the screen stencil frame.
[0047] In the conventional method, in order to prevent falling of water drops from the screen
stencil frame after washing, both the front and back sides of the screen stencil frame
are carefully drained. In some plants, in order to save this labor, primary printing
is carried out by using a guide cloth having a good water-absorbing property to drain
the screen stencil frame. In contrast, according to the present invention, water on
the screen surface is sucked by the air- sucking action, and an especially draining
operation need not be carried out and a draining guide cloth need not be used.
(d) The residual color paste can be used again.
[0048] In the conventional method, after completion of printing of every color, the color
paste left in the screen stencil frame is manually recovered by a worker. However,
since this operation is complicated and work clothing or the like is readily contaminated,
the residual color paste is not substantially recovered.
[0049] In contrast, the majority of the residual color paste can be recovered and utilized
again.
1. A method for washing a screen stencil frame in a flat screen printing machine,
which comprises arranging a delivery member capable of reciprocatively moving on the
screen stencil frame, arranging a suction nozzle connected to a vacuum device on said
delivery member, reciprocating the delivery member on the screen stencil frame in
such a manner that the suction nozzle confronts a screen stencil of the screen stencil
frame, and washing the screen stencil with water by utilizing a subatmospheric suction
pressure generated by the suction nozzle.
2. A washing inethod'according to claim 1, wherein the delivery member is a moving
truck capable of reciprocatively moving along horizontal rails arranged in the printing
unit.
3. A washing method according to claim 1, wherein the delivery member comprises an
upper delivery member moving above the screen stencil frame reciprocatively and a
lower delivery member moving below the screen stencil frame reciprocatively, a suction
nozzle confronting the top face of the screen stencil is arranged on the upper delivery
member, a suction nozzle confronting the lower face of the screen stencil is arranged
on the lower delivery member, and suction washing is effected from both the faces
of the screen stencil.
4. A unit for washing a screen stencil frame in a flat screen printing machine, which
comprises (A) a delivery mechanism provided with a nozzle, (B) a housing mechanism
for dismountably housing the delivery mechanism therein and (C) a supporting mechanism
for supporting and housing said housing mechanism therein, which is provided with
a vacuum mechanism, wherein said supporting mechanism supports the housing mechanism
so that the housing mechanism can be connected to a printing unit arranged in the
flat screen printing machine, said delivery mechanism comprises a driving member,
said delivery mechanism is released from the housing mechanism and reciprocated on
the printing unit by said driving member when the housing mechanism is connected to
the printing unit, said nozzle is connected to the vacuum mechanism of the supporting
mechanism through a predetermined conduit, and said delivery mechanism is arranged
in such a positional relationship that when the delivery mechanism is reciprocated
on the printing unit, the delivery mechanism confronts a screen stencil of the screen
stencil frame in the printing unit.
5. A washing unit as set forth in claim 4, wherein the vacuum mechanism comprises
a blower and a vacuum chamber connected to the blower.
6. A washing unit as set forth in claim 4, wherein the housing mechanism is pivoted
and supported on the supporting mechanism and the housing mechanism is connected to
the printing unit by turning the housing mechanism by the supporting mechanism.
7. A washing unit as set forth in claim 6, wherein in the supporting mechanism, an
air cylinder, a rack, a pinion gear, a chain and a chain wheel are arranged in this
order, and an arm mounted in the housing mechanism is connected to the rotation shaft
of the chain wheel so that the housing mechanism is turned by the operation of the
air cylinder.
8. A washing unit as set forth in claim 4, wherein the delivery mechanism is a truck.
9. A washing unit as set forth in claim 8, wherein the delivery mechanism comprises
an upper truck moving above the screen stencil frame reciprocatively, a lower truck
moving below the screen stencil frame reciprocatively, and a suction nozzle is arranged
on each truck.
10. A washing unit as set forth in claim 9, wherein the sucking direction of the suction
nozzle arranged on the upper truck is freely adjustable.
11. A washing unit as set forth in claim 9 or 10, wherein driving motors are arranged
on the upper and lower trucks, respectively, and the driving motors are independently
driven.
12. A washing unit as set forth in claim 4, wherein a cleaning member is extended
into the interior of said nozzle so that a suction space is left, and a washing water
supply pipe is laid out within the cleaning member.
13. A washing unit as set forth in claim 9 or 10, wherein the top end portion of the
suction nozzle of the upper truck is tapered.