EP0152156A2

EP0152156A2 - Method and unit for washing a screen stencil frame used in a flat screen printing machine

Info

Publication number: EP0152156A2
Application number: EP85200188A
Authority: EP
Inventors: Shiro Ichinose; Kunio Katsuuma
Original assignee: Toshin Kogyo Co Ltd
Current assignee: Toshin Kogyo Co Ltd
Priority date: 1984-02-13
Filing date: 1985-02-12
Publication date: 1985-08-21
Also published as: KR850005971A; JPS60184850A; EP0152156A3

Abstract

Disclosed is 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.

Description

Background of the Invention

(1) Field of the Invention:

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:

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.
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

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.
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.
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

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

The present invention will now be described in detail with reference to embodiments illustrated in the accompanying drawings.
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.
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.
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.
Then, the screen stencil frame 5 is washed according to the method of the present invention.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
Incidentally, the portion X in Fig. 4 shows the section seen in the direction of arrows B-B in Fig. 3.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The printing unit 7 is brought down, and printing of a next color is performed.
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.
The effects attained by the present invention will now be described.

(a) A labor-saving effect is attained.

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.
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.

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.
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.

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.
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.
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.

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.
In contrast, the majority of the residual color paste can be recovered and utilized again.

Claims

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.