JPS5813354B2 - Ink filter in inkjet printing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention performs desired printing on a recording medium using ink droplets ejected from an inkjet head, and captures and recycles unnecessary ink droplets that are not used for printing with an ink collection gutter. Regarding the improvement of the type of inkjet printing device used, in particular, a preliminary filter is provided in parallel with the main filter provided in the ink supply path between the ink collection gutter and the inkjet head, and the main filter is prevented from clogging. The filter is characterized in that when the filtration function deteriorates, the main filter is automatically switched to the backup filter.

First, an overview of a conventional ink recovery and recirculation type inkjet printing device will be explained with reference to FIG.

In FIG. 1, 1 is the inkjet head body, 2 is an orifice (nozzle), 3 is an electrostrictive vibrator, 4 is a printing signal generator, 5 is a charging electrode, 6a and 5b are deflection electrodes, and 7 is an ink collection gutter. , 8 is a recording medium, 9 is an ink tank,
10 is a pressure pump, 11 is a part of a filter, 12 is a pressure regulating valve, 13 is a charged droplet for printing, and 14 is an unnecessary non-charged ink droplet that is not used for printing. The ink is excited by the electrostrictive vibrator 3 and ejected from the orifice 2, and the ink liquid column ejected from the orifice 2 is separated into ink droplets at the charging electrode 5, and a printing signal generator is applied to the separated ink droplets. 4 applies a charge according to the printing information signal, and the charged ink droplets are deflected by deflection electrodes 6a and 6b according to the amount of charge, thereby reproducing information on the recording medium 8.

Collection of this type of ink. In a recirculation type inkjet printing device, if dust or the like gets mixed into the collected ink through the ink collection gutter 7 and the filter 11 becomes clogged and its filtering function deteriorates, the pressure of the ink supplied to the inkjet head 1 will decrease. This resulted in a situation where the inkjet jetting became unstable.

To deal with this situation, conventional methods have been to generate an alarm by electrically detecting the differential pressure between the ink liquid before and after the filter 11, or to increase the pressure of the ink supplied from the ink pressure pump 10 as needed. The pressure should be higher than that of the ink jetting pressure.
Countermeasures such as adjusting the ink ejection pressure to a desired level using the pressure regulating valve 12 have been taken.

However, even if an alarm is generated, the filter cannot be replaced while printing is in progress, and furthermore, if printing continues for a long time, the printing quality may deteriorate. This could have led to a situation.

Furthermore, in the method of adjusting the injection pressure using a pressure regulating valve, if the filter becomes completely clogged, the filter will be destroyed by the large discharge pressure from the ink pressure pump 10, and the filtration effect will be lost, or a part of the ink supply path will be damaged. There were drawbacks such as ink leakage.

The present invention was made in view of the actual situation as described above.
2 and 3 show details of the filter portion 11 used in the practice of the invention.

2 and 3, 100 is the main filter, 100' is the preliminary filter, 110, 120, 130
, 140 are valves, and during normal printing, these valves are in the position shown in FIG. It is supplied to the pressure regulating valve 12 through a valve 120.

At this time, assuming that the main filter 100 is not clogged, there is almost no pressure difference between points A1 and A2, and therefore the piston 132 of the valve 130 is pushed by the spring 136 to the illustrated position. , the communication hole 137 of the valve 130 is closed.

However, as the main filter 100 becomes clogged, the pressure at point A2 becomes higher than the pressure at point A1.
When the pressure difference between points A1 and A2 reaches a certain amount, for example, the pressure difference cannot be regulated by the pressure regulating valve 12, the piston 132 gradually moves to the left inside the cylinder 131 against the spring 136.

When the piston 132 of the valve 130 moves to the left and the communication hole 137 opens, the ink from the valve 110 flows through the communication hole 13 of the valve 130 as shown by the dashed line B in FIG.
7 and a preliminary filter 100', ink for the inkjet head is also supplied.

That is, ink is supplied to the inkjet head through the preliminary filter 100' before the main filter 100 is completely clogged.

At the same time, the ink flow B that has passed through the communication hole 137 of the valve 130 acts on the piston 142 of the valve 140, and as shown in FIG. Open 147'.

When the communication holes 147, 147' of the valve 140 are opened,
Ink from the pressure pump 10 is supplied to the inkjet head 1 through the communication hole 147 of the valve 140 and the preliminary filter 100', as shown by the two-dot chain line C in FIG. The ink acts on the valves 110 and 120 through the communication hole 147', causing the pistons 112 and 122 to move against the spring 116, respectively.
and 126 to the position shown in FIG. 3 to close the communication holes 117 and 127, but the valve 110
and 120 are closed, the ink supply pressure through the preliminary filter 100' is applied to the point A1 through the communication hole 127 of the valve 120, so that the differential pressure between the points A and A2 becomes small and the valves 110 and 120 are closed. Valve 130 closes before or at about the same time.

Therefore, in this state, the passage of the main filter 100 is completely closed, so that the filter paper of the main filter 100 can be replaced.

FIG. 4 shows the valves 110, 1 shown in FIGS. 2 and 3.
FIG. 4 is a side sectional view for explaining the details of the valves 110, 130, and 140. However, for convenience of explanation, only the side sectional view of the valve 140 is shown in FIG.
In FIG. 2 and FIG. 3, the same reference numerals are given to parts having similar functions except for the 10th digit, and detailed explanation thereof will be omitted.

As shown in FIG. 4, the valve 140 is connected to the cylinder 141.
A permanent magnet 143 is provided inside the piston 142, and a permanent magnet 144 having a polarity different from that of the permanent magnet 143 in the piston is provided outside the cylinder 141. 143 and 1
44 ensures that the valve 140 is in the open or closed position, and a spring 146 ensures that the valve 140 is in the open or closed position when the valve is inactive, that is, when no ink pressure is applied to the valve.
The valves 110, 120, and 130 are securely positioned at the positions shown in FIG. 2.

Further, an electromagnet 145 other than the permanent magnet 144 is provided outside the cylinder 141 (not required for the valve 130), and the piston 142 is moved from the position shown in FIG.
When returning to the position shown in the figure, a current is passed through the electromagnet 145 that produces a repulsive magnetic force that has the same polarity as the permanent magnet 143 inside the piston and is stronger than the piston restraining force of the permanent magnet 144 on the outer wall of the cylinder. Turn the valve from the closed state to the open state.

In addition, 147 and 147' are communicating holes explained in connection with FIG. 2 and FIG. 3, and 148a-148e are ring-shaped seal members.

FIG. 5 is a diagram for explaining the relationship between the valve 130 and the alarm switch activated by the valve 130.
FIG. 5A is a plan sectional view of the alarm switch section, and FIG. 5B is a
3 is a side view of the valve 130 and the alarm switch 200. FIG.

As shown in FIG. 5B, the cylinder 13 of the valve 130
An alarm switch 200 is attached to the outer wall of the alarm switch 200, and as shown in FIG. A permanent magnet 204 having a different polarity than the permanent magnet 133 provided in the piston 132 of the spring 20
5 is maintained in the state shown.

However, when the main filter 100 is clogged and the piston 132 inside the valve 130 moves to the left as described above, the permanent magnet 204 follows the movement of the permanent magnet 133 inside the piston 132 and moves onto the guide shaft 206. is moved to the left, and the electrode pair 202a, 20 is moved by the energizing sliding piece 201.
2b is short-circuited, the alarm detection device 300 is activated, and the alarm 400 is activated.

FIG. 6 is an exploded side sectional view for explaining an example of the main filter 100 and the preliminary filter 100'.
01a and 10lb are filter holders, 102 are washers, 103a and 103b are meshes for fixing the filter, 104 is a filter, and 105 is a sealing member such as rubber.As shown in the figure, meshes 103a and 103b are attached on both sides of the filter 104. filter 104 by arranging
It is integrally assembled with a set screw 107 so as not to be deformed or destroyed by the fluid pressure differential.

Note that 1 06a and 1 06b are the input/output ports 108a and 108 of the filter holders 101a and 101b, respectively.
This is a support pipe that is inserted and fixed to b.

Now, when the main filter 100 is switched to the auxiliary filter 100' as described above, and the filter paper in the main filter 100 is replaced during that time,
First, a current is instantaneously applied to the electromagnets 115 and 125 provided on the outer walls of the cylinders of the valves 110 and 120, causing an instantaneous repulsive force between the electromagnets 115 and 125 and the permanent magnets 113 and 123, and an expansion of the springs 116 and 126. The force pushes pistons 112 and 122 downwardly from the state of FIG. 3, opening valves 110 and 120.

At this time, the ink contained in the cylinders of valves 110 and 120 is pushed back by pistons 112 and 122, respectively, but at this time, since valve 140 is still open, the pushed back ink is pushed back into valve 140.
is supplied to the inkjet head through the communication hole 147' and the preliminary filter 100'.

Next, the electromagnet 145 of the valve 140 is energized to close the valve 140. At that time, the ink contained in the cylinder of the valve 140 is pushed back by the piston 142 and is supplied to the inkjet head through the preliminary filter 100'. be done.

Thus, when valve 140 is closed, the ink flow is completely switched through main filter 100 and returns to the original state shown in FIG.

As is clear from the above description, according to the present invention, even if the filtration function of the main filter decreases, the differential pressure of the ink flow can be used to transfer the flow from the main filter to the auxiliary filter without using electrical detection or driving means. Switching can be performed automatically, and the filtration function can be maintained properly at all times.

In addition, when switching to the spare filter, it automatically warns you if the main filter is clogged, and even when printing is in progress, that is, when ink is being continuously supplied, the main filter can be used without interrupting the ink supply. There are advantages such as being able to replace the filter paper of the filter.

[Brief explanation of drawings]

Figure 1 shows conventional ink collection. FIG. 2 is an overall configuration diagram for explaining an example of a circulating inkjet printing device.
A fluid circuit diagram for explaining the operation of a part of the ink filter according to the present invention during normal use, FIG. 3 is a fluid circuit diagram for explaining the operation when replacing the filter, and FIG. 4 is a fluid circuit diagram for explaining the operation during normal use of the ink filter according to the present invention. FIG. 5 is a plan sectional view for explaining an example of a filter used in the present invention, and FIG. 5 is a diagram for explaining an example of a filter clogging alarm switch used for implementing the present invention. FIG. FIG. 5B is a side view of the whole, and FIG. 6 is an exploded plan sectional view for explaining an example of a filter used in carrying out the present invention. 1... Inkjet head body, 2...
... Nozzle, 3... Electrostrictive vibrator, 4...
・Printing signal generator, 5...Charging electrode, 6a,
6b...Deflection electrode, 7...Ink collection gutter, 8...Recording medium, 9...Ink tank, 10...Pressure Pump, 11...
... Part of the filter, 12 ... Pressure regulating valve, 100.
...Main filter, 100' ...
Preliminary filter, 110, 120, 130, 140...
... Valve, 200 ... Alarm switch, 3
00...Alarm detection device, 400...Alarm device.

Claims (1)

[Claims] 1. Ink recovery and reuse in which desired printing is performed on a recording medium using ink droplets ejected from an inkjet head, and unnecessary ink droplets that are not used for printing are captured in an ink collection gutter and reused. An ink filter for an inkjet printing apparatus of a recirculation type, characterized in that the inkjet printing apparatus is characterized in that a main filter is provided in an ink supply path between the ink recovery gutter and the inkjet head, and a preliminary filter is provided in parallel with the main filter. . 2. The device according to claim 1, wherein switching from the main filter to the auxiliary filter is performed by a fluid pressure-operated valve operated by an ink pressure difference between the input and output sides of the main filter. ink filter. 3. The fluid pressure operated valve is composed of a cylinder and a piston, and a permanent magnet is provided on the outside of the cylinder, and
The ink according to claim 2, wherein the piston has a permanent magnet having a polarity different from that of the permanent magnet, and the piston is positioned by the attraction action of these permanent magnets. filter. 4. An electromagnet is provided outside the cylinder, and the return operation of the piston is performed by passing a current through the electromagnet that causes magnetization of the same polarity as that of a permanent magnet provided inside the piston. The ink filter according to claim 3.