FR2799687A1 - Silkscreen cleaning process comprises applying a cleaning composition, removing the inks and masking emulsions and rinsing with water, avoiding phantom images - Google Patents

Abstract

Silkscreen cleaning process comprises applying a cleaning composition, removing the inks and masking emulsions and rinsing with water, avoiding the use of solvents, particularly DMF. Silkscreen cleaning process comprises applying a cleaning composition, removing the inks and masking emulsions and rinsing with water. Independent claims are included for: (1) the cleaning composition used comprising an aqueous solution of 0.05-5 wt.% Na metaperiodate and 0.05-0.75 wt.% H2SO4 and a solution of 0.5-90 wt.% dialkylesters and 0.5-50 wt.% nonionic surfactant; (2) a cleaning device comprising a first section with a first ramp of nozzles for spraying the cleaning composition and a second ramp of nozzles for spraying high pressure water associated with a drain tank for recovering the cleaned product; and (3) a cleaning kit comprising two cavities, each containing one of the two solutions.

Description

The present invention relates to a device for cleaning and de-scouring screens used in screen printing.

Such a screen generally comprises a frame on which is stretched a fabric having very fine holes (of the order of 100 pm). To perform a screen printing, the screen is coated with ink and a masking protection emulsion is also added. When the screen is then used for a different print, it must be cleaned and degraded. This involves removing the ink and the masking protection emulsion from the canvas. This cleaning and this degreasing are performed either manually or in a machine. After removing the ink and emulsion on the screen, there is often still a ghost image on it. To remove this ghost image, a chlorine product is applied in the form of paste or gel on the screen. This product is allowed to work long enough, sometimes for half a day, before cleaning the screen with water under high pressure.

Currently used devices make it possible to clean and unscreen a screen. These devices have four compartments. Each compartment is associated with a container for containing a product. In the first compartment, there is a tank containing a solvent that can dissolve the inks used in screen printing. In this compartment, the screen is sprayed with the product in the tray by nozzles which are mounted on vertical ramp. The vertical ramp moves in a horizontal direction to spray the entire surface of the screen. The sprayed product falls back by gravity, with the ink, into the tank.

The second compartment also has a tank containing solvent. The latter is also sprayed using a vertical ramp moving in a horizontal direction on the screen. This solvent is cleaner than that of the first tank. Solvent recycling devices in the first and second tanks are provided to increase the life of the product contained in these tanks.

Before going from the second to the third compartment, the screen is washed with water under high pressure. In the third compartment, the corresponding tray contains a detergent product for removing the masking protection emulsion. This product is applied on the screen also by means of nozzles arranged on a vertical ramp and moves horizontally.

In the last fourth compartment, the screen is washed with water under high pressure.

The present invention aims to provide a machine for cleaning and degrading a screen and is simpler than the machines of the prior art. Advantageously, this machine will also remove the ghost images. In addition, this machine will preferably provide a better cleaning and disassembly of a screen used in screen printing.

For this purpose, the device it proposes is a device for cleaning and unscreening screens used in screen printing, comprising a first compartment in which there is a first ramp of nozzles intended to spray a cleaning product on the screen and a second boom of nozzles for spraying water under high pressure, and which is associated with a tray for recovering the cleaning product.

According to the invention, this device comprises a reservoir of cleaning product separated from the recovery tank.

In this way, the product that is sprayed on the screen to be cleaned is a clean product, which does not contain diluted ink. As a result, the cleaning is more efficient and there is no need to provide two compartments for cleaning the screen. This structure also makes it possible to use the same bin for the recovery of the product of degreasing. preferably uses a product for performing both cleaning and unscreening of the screen. If, however, two separate products were to be used, a solvent for the ink and a deminer for the emulsion would be possible with a device according to the invention, to provide a reservoir for a product, a reservoir for the other, the first ramp. sputtering then being successively fed by a product and then by the other.

In an advantageous embodiment, first and second ramps are contiguous to one another so as to form only one unit.

Preferably, the ramps are arranged horizontally. In this case, it will preferably be chosen to have mobile ramps and a fixed screen during spraying. The ramps then move advantageously from bottom to top then from top to bottom to obtain a good cleaning.

To complete the cleaning, the device advantageously comprises motorized rotary brushes, whose axis is substantially perpendicular to the plane of the screen.

In one embodiment, the ramps are movable relative to a screen to be cleaned which remains fixed during the spraying of cleaning product and water, as already mentioned above. However, one could have a mobile screen and fixed ramps. In this, the ramps would preferably be vertical.

To allow better cleaning, the device advantageously comprises a second double ramp arranged so that the screen to be cleaned is between the two double ramps can be sprayed on both sides.

To also allow the elimination of possible ghosting, the device advantageously comprises a second compartment provided with spray means movable relative to the screen. These mobile spraying means comprise for example a double ramp, a ramp being intended for the product spray allowing the elimination of ghosting and the other ramp for spraying under high pressure of water.

In order to allow rapid drying of the product allowing ghosting, the second compartment is advantageously provided with a forced air system for propelling hot air into the second compartment. To further improve drying, it can be provided that the second compartment has a movable ramp relative to the screen for blowing hot air to the screen. Better drying is still achieved when the first compartment has a mobile ramp relative to the screen, this ramp being a suction ramp intended to initiate drying of the screen.

To avoid the appearance of streaks on the screen after passing through the device according to the invention, means are advantageously provided for oscillating the screen. In this way, during operations concerning rinsing and drying of the screen, a better flow distribution is obtained on the screen, which makes it possible to avoid the appearance of streaks corresponding to the spray limits of two adjacent nozzles. In any case, the invention will be better understood from the description which follows, with reference to the appended schematic drawing, showing by way of non-limiting example a preferred embodiment of a device according to the invention.

Figure 1 is a partially exploded perspective view of a device according to the invention, and Figure 2 is a sectional view along the section line II-II of Figure 1.

Figure 1 shows a cleaning device for cleaning, removing and removing ghosting of a screen 2 used in screen printing. It comprises a first compartment 4 and a second compartment 6. Each compartment is in the form of a box. The dimensions of the set are adapted to the size of the screens to be cleaned.

A conveyor is used to introduce a screen 2 in the first compartment and then to pass to the second compartment. This conveyor comprises a motorized endless belt 8 and an upper guide 10. The screen is placed on the endless belt and is held in a vertical position by means of the upper guide 10. An opening 12 made in an outer wall of the first compartment 4 allows introducing the screen 2 on the conveyor.

In the first compartment are associated a reservoir 14 for containing a cleaning solution, a pump 16 for pumping the product in the reservoir 14, a high pressure pump 18 for pumping water, a discharge tank 20, a double ramp of nozzles and a chain system 24 for moving the double ramp 22.

The reservoir 14 is intended to contain a product for both the cleaning and the unscreening of the screen. The product used for this purpose comprises for example 0.5 to 25% by weight of alkyl phenol ethoxide, from 0.05 to 0.75% by weight of sulfuric acid, from 0 to 2% by weight of sodium metaperiodate and from 1 to 22% by weight dialkylesters. This product is an aqueous composition which contains, for example, in one embodiment, 20% by weight of alkyl phenol ethoxide, 0.25% sulfuric acid, 0.25% sodium metaperiodate and 3% by weight. product marketed by Du Pont De Nemours under the brand A perfumed solution can be added to this product.

The pump 16 can pump the product contained in the tank 14 to the double ramp 22. This double ramp 22 is arranged horizontally. It is formed of two parallel, horizontal ramps, contiguous to each other. A first ramp 26 is connected to the pump 16 by a flexible pipe 28. This first ramp 26 is equipped with small nozzles 30 for spraying the product contained in the tank 14. The spray pressure is for example between 2 and 4 bar .

The second ramp 32 of the double ramp 22 is connected to the high pressure pump 18 by a flexible hose 34. This second ramp 32 is provided with larger nozzles 36 for spraying water at a pressure of about 120 bar.

The double ramp 22 is arranged horizontally. The chain system 24 makes it possible to move this double ramp 22 from bottom to top then from top to bottom in a motorized manner. The double ramp 22 is fixed near each of its ends to a chain itself mounted around two pulleys, one of which is driven by a motor. Such a system is known to those skilled in the art and is not described in detail in the present description. Any other system for moving the double ramp may also be suitable.

On the other side of the screen 2, there is a simple ramp 38 of suction drying. This ramp 38 also extends horizontally and can move up and down from top to bottom using two chain systems 24 as described above.

Under the screen 2 and the endless belt 8, there is the evacuation tank 20. This tank is intended to recover the product and the water falling by gravity after being sprayed by one of the ramps of the double ramp 22. This drain pan is connected to the sewer or a filtration system. If one uses the product indicated above, one can directly connect this tank 20 in the sewer because this product is biodegradable. However, to save water, it is also possible to connect the drain pan to a filtration system to recycle water. Thus, the high pressure pump 18 can be fed directly by a water supply network or it can be supplied with water by recycled water. The filtration system has not been shown in the drawing but it could of course be integrated in this device. The second compartment 6 has a structure very close to that of the first compartment. In this second compartment 6 there is a reservoir 40, a pump 42 associated with this reservoir, a high-pressure pump 44 intended for pumping water, and an evacuation tank, not shown. There is also on one side of the treadmill 8 which also passes through the second compartment, a double ramp mounted on two chain systems such as chain systems 24. On the other side of the treadmill 8 there is also a single ramp mounted on two chain systems. For the sake of clarity, this double ramp and this simple ramp have not been represented in the drawing.

The reservoir 40 contains a product, known to those skilled in the art, for eliminating the ghost images on a screen printing screen. This product is a chlorinated gel. The pump 42 allows, via a hose not shown, to send the product contained in the reservoir 40 to a ramp of the corresponding double ramp. The product for eliminating ghosting is then sprayed by nozzles at a pressure of about 2 bar. The high pressure pump 44 is connected to the other ramp of the double ramp of the second compartment by another flexible hose. This ramp also includes nozzles for spraying water at a pressure of about 120 bar.

The single ramp is, unlike the single ramp of the first compartment 4, provided with nozzles blowing hot air. A fan and a heating resistor, not shown in the drawing, can send air to about 30 to this ramp from which it is blown towards the screen.

The evacuation tank receives the products that gravitatively fall from the screen 2. In addition to the ramp blowing hot air, there is provided at the second compartment a forced air system 46.

The operation of this device is then as follows.

The screen 2 is conveyed automatically by the belt 8 and using the upper guide 10 inside the first compartment 4. The double ramp 22 is then in the low position. Once the screen 2 in place, the first ramp 26 is fed by the pump 16 cleaner / de-cleaner. The double ramp then begins to move upwards. Once at the top of the screen 2, it moves downward while continuing to spray cleaner / de-scrubber. The excess product, mixed with the ink and the masking protection emulsion, then falls into the evacuation tank 20. After allowing the product to act for a few seconds, or a few tens of seconds, on the screen 2 , the second ramp 32 of the double ramp 22 is supplied with water by the high pressure pump 18. The double ramp 22 then moves upward again until it reaches the top of the screen 2 and then moves back to the down to its original position. This rinses the screen perfectly. The rinse water, which is mixed with cleaner / degreaser as well as inks and masking protection emulsion, is then found in the discharge tank 20.

Pre-drying of the screen 2 is achieved by the suction ramp 38. This ramp is also moved from its initial position at the bottom of the screen 2 up to the top of the screen 2 and then to its initial position. This removes from the screen 2 any surplus water. Preferably, the screen 2 oscillates horizontally from left to right to avoid forming vertical streaks. A cam system not shown allows this displacement. The amplitude of the oscillations is for example a few centimeters.

Once the suction ramp 38 is returned to its initial position, the screen 2 is conveyed to the second compartment 6. The product for eliminating ghosting is then sprayed by the nozzles of a ramp of the double ramp of this compartment. Pump 42 sends the product to this ramp. It moves from bottom to top and then up and down to spray the product on the entire surface of the screen. The forced air system 46 is then turned on. It propels air inside the compartment to try to keep it at a temperature of about 30. A dehumidifier not shown may be associated with the forced air system 46 so that it sends dry air into the second compartment 6. During this time, the single ramp blowing hot air moves from bottom to top then from top to bottom to blow the warm air over the entire screen 2 and to dry the product to eliminate a possible ghost image. Several passages from bottom to top and from top to bottom of the blower ramp can be provided. The product to eliminate ghosting acts when it is dry. Once the product is well dried and it has acted, the double ramp of the second compartment 4 is then supplied with water under pressure by the high pressure pump 44. The ramp then moves from bottom to top then from top to bottom in each time spraying water over the entire surface of the screen 2. The water spray and the product for eliminating ghosting then fall into the drain pan of the second compartment 6.

To avoid making vertical streaks on the screen 2, one can in the second compartment also provide to oscillate the screen in the horizontal direction. Here too, an oscillation of an amplitude of a few centimeters is sufficient.

Once the screen rinsed, it is automatically routed to the outside of the second compartment 6 and the device described above. It can then be received manually or one can also imagine an automatic tray receiving screens at the output of this second compartment 6. Similarly, it is possible to have an automatic screen feeder at the entrance of the first compartment 4.

It goes without saying that the invention is not limited to the preferred embodiment described above by way of non-limiting example; it encompasses all the variants of execution in the following claims framework.

Thus, for example, instead of having a tank with a cleaner / de-stenter at the first compartment, one could have two separate tanks, one of them containing a cleaning product the other a de-stoving product. The same boom could spray these two products successively.

The fact that the ramps move from bottom to top then from top to bottom a preferred embodiment. A vertical ramp moving horizontally may also be considered.

provide for a double ramp (product + water) optional. One could indeed have two distinct ramps.

In some cases, after cleaning and unscreening a screen, no ghosting appears on it. It is then useless to have second compartment.

The suction and blower ramps are optional. As a result, systems for oscillating these ramps are also optional.

Any other conveying system, loading, unloading screens can of course be suitable in the present invention.

Claims (1)

<B> CLAIMS </ B> <B> 1. </ B> Device for cleaning and de-scouring screens (2) used in serigraphy having first compartment (4) in which there is a first ramp (26) of nozzles for spraying a cleaning product on the screen (2) and a second ramp (32) of nozzles for spraying water under high pressure, and which is associated with a tank (20) for recovering the cleaning product , characterized in that it comprises a reservoir (14) of cleaning product separated from the recovery tank (20). <B> 2. </ B> Device according to claim 1, characterized in that the first (26) and second (32) ramps are contiguous to one another so as to form only one unit (22). ). 3. Device according to one of claims 1 or 2, characterized in that the ramps are arranged horizontally. <B> 4. </ B> Device according to one of claims 1 to 3, characterized in that it comprises motorized rotary brushes, axis substantially perpendicular to the plane of the screen. 5. Device according to one of claims 1 to 4, characterized in that the ramps (22) are movable relative to a screen (2) to be cleaned which remains fixed during the spraying of cleaning agent and water. <B> 6. </ B> Device according to one of claims 1 to 5, characterized in that it comprises a second double ramp (22) arranged such that the screen (2) to be cleaned is between the two double ramps and can be sprayed on both sides. 7. Device according to one of claims 1 to 6, characterized in that it comprises a second compartment (6) provided with spray means (22) movable relative to the screen (2). <B> 8. </ B> Device according to claim 7, characterized in that the mobile spraying means comprise a double ramp (22), a ramp (26) being intended for spraying a product allowing the elimination ghosting and the other ramp (32) to spray under high pressure water. 9. Device according to one of claims 7 or 8, characterized in that the second compartment (6) is provided with a forced air system (46) for propelling hot air into the second compartment. 10. Device according to one of claims 7 to 9, characterized in that the second compartment (6) comprises a ramp movable relative to the screen for blowing hot air to the screen. . Device according to one of claims 7 to characterized in that the first compartment (4) comprises a ramp (38) movable relative to the screen (2), this ramp being a suction ramp for initiating a drying of the screen . Device according to one of claims 1 to 1, characterized in that means are provided to oscillate the screen.