JPS647587B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for discharging anti-clogging liquid in an ink droplet ejecting device that controls the main part of an in-jet printer.

It is widely known that the biggest drawback in ink droplet ejecting devices is clogging of the orifice through which the ink droplets are ejected. In particular, in the case of on-demand type ink droplet ejecting devices that eject ink droplets by applying minute pressure changes to the ink near the orifice, the above-mentioned clogging occurs because the ink droplets are ejected using a minute pressure force. Once this occurs, the clogging cannot be easily recovered by itself, and therefore it is necessary to prevent the clogging in advance during non-printing operations.

FIG. 1 shows a cross-sectional view of an on-demand type ink droplet ejecting device during printing operation. In the figure, 1 is an on-demand type ink droplet ejecting device, and the ejecting device 1 responds to an image signal. A piezoelectric diaphragm 2 that vibrates in a curved manner, a horn-shaped pressure chamber 3 with the piezoelectric diaphragm 2 disposed at the opening on the long diameter side, and a thin plate-like A vibrator 4, an ink chamber 5 holding ink on the front side of the vibrator 4, a front plate 6 facing the vibrator 4 with the ink chamber 5 in between, and a vibrator 4 on the front plate 6. A first orifice 7 with a minute diameter is bored at a location opposite to the center of vibration.
and an air layer 8 provided in front of the first orifice 7, through which ink droplets 9 ejected from the first orifice 7 pass through. A second orifice 10 having an opening diameter twice or more larger than that of the first orifice 7.
It is equipped with. Reference numeral 11 denotes an ink tank for supplying ink to the ink chamber 5 of the ink droplet ejecting device 1, and several hundred c.c. of ink is stored in a bag made of polymer film or the like with low air permeability. 12 is an ink supply pipe that connects the ink tank 11 and the ink chamber 5; 13 is an ink coupler inserted in the middle of the ink supply pipe 12; The supply pipe 12 is freely attachable, and ink can be replenished by replacing each ink tank 11. 14 is a chamber 8 and an ink tank 1 in front of the ink droplet ejecting device 1;
1 is an air pump that appropriately adds an air flow 16 as shown by the arrow through an air supply pipe 15; 17 is an air supply pipe 1 between the air pump 14 and the air layer 8;
A valve device provided at 5 is, for example, a three-way solenoid valve, and communicates with the air pump 14 and the air layer 8 during printing operation. Reference numeral 18 denotes a recording medium placed in front of the second orifice 10 of the ink droplet ejecting device 1 at a short distance from the rotating drum 1.
9 and is main scanned in the rotational direction.

When an image signal is applied to the piezoelectric diaphragm 2 of the ink droplet ejecting device 1, the piezoelectric diaphragm 2 suddenly bends and vibrates in its thickness direction to pressurize the pressure chamber 3. This pressurization is amplified together with the horn shape of the pressure chamber 3 and is propagated to the vibrator 4, causing the vibrator 4 to bend significantly. That is, the piezoelectric diaphragm 2, the pressure chamber 3, and the vibrator 4 act as a pressure changing means that rapidly changes the pressure on the ink in the ink chamber 5. Therefore, the ink in the ink chamber 5 that has undergone a sudden pressure change from the vibrator 4 is transferred to the first orifice 7.
The ink droplet 9 is pushed out from the coaxial second orifice 1 while being surrounded by the air stream 16.
Discharged from 0. The ejection of the ink droplets 9 by the air flow 16 is described in more detail in Japanese Patent Laid-Open No. 51-37541, so a detailed explanation thereof will be omitted here. These ink droplets 9 ultimately adhere to a recording medium 18 that is being rotated and scanned by a drum 19 to print images such as characters and figures.

In this way, the ink droplet ejecting device 1 in which the first orifice 7 for ejecting the ink droplets 9 is not exposed to the outside in a straight line is designed to prevent clogging of the first orifice 7 during non-printing operation. As a result, clogging could not be prevented.

Therefore, the applicant of the present application has developed the first and second orifices 7, 10 coaxially arranged with the air layer 8 in between.
A method for preventing clogging in an ink droplet ejecting device 1 equipped with the same has been filed as Japanese Patent Application No. 112727/1983. FIG. 2 shows the state during the printing operation disclosed in the above-mentioned Japanese Patent Application No. 56-112727. It's covered. During this non-printing operation, the first orifice 7 is covered with ink supplied to the air layer 8.
That is, the first orifice 7 is filled with ink as the anti-clogging liquid in the air layer 8.
Clogging caused primarily by dryness and dust adhesion in the process is prevented.

To explain for a moment about the filling of ink as the anti-clogging liquid, after the printing operation is completed, the ink droplet ejecting device 1 passes from the print position PP to the standby position SP and returns to the home position as shown in Fig. 3. Return to HP. 2nd time after return
The orifice 10 is covered with a lid 20, and the air layer 8 is cut off from the outside. Next, in order to supply ink to the air layer 8 through the ink system from the ink tank 11 to the first orifice 7, the valve device 17 is switched to communicate the air layer 8 with the outside air.
This switching of the valve device 17 brings the air layer 8 and the air pump 14 into a closed state. In this state, air pump 1
4, the air flow 16 flows into the ink tank 11.
The ink in the ink tank 11 is pressurized. This increase in the pressure of the ink in the ink tank 11 propagates through the ink supply pipe 12, the ink coupler 13, and further the ink supply pipe 12, and pressurizes the ink in the ink chamber 5. Therefore, the pressure of the ink in the ink chamber 5 near the first orifice 7 gradually increases compared to the pressure in the air layer 8. When this pressure difference reaches a threshold value that overcomes the equilibrium state of the ink in the first orifice 7, the ink flows out from the first orifice 7 into the air layer 8. When an electric signal is applied to the piezoelectric diaphragm 2 to make the vibrator 4 continuously vibrate in a curved manner to assist the ink to flow out, the balance of the ink immediately collapses and the ink flows from the first orifice 7 into the air layer 8. Start. Once the ink starts to flow, even if the application of the electric signal to the piezoelectric diaphragm 2 is stopped, the pressure in the air layer 8 (air pressure) is lower than the ink pressure in the ink chamber 5, so the ink supply continues. . In this way, the first orifice 7
is covered with ink supplied into the air layer 8. The supply of ink is controlled by the detection output of a suitable detection means 21 provided in the air layer 8 or the air supply pipe 15 in the vicinity of the air layer 8.

When the detection means 21 detects that the front chamber 8 has been filled with ink, the air pump 14 stops operating and the pressure in the ink tank 11 gradually decreases. On the other hand, the air tank 8 is in communication with the outside air via the air supply pipe 15, and when the pressure of the ink tank 11 decreases as described above in this state, the ink supplied and filled into the air tank 8 is transferred to the ink tank 11. The valve device 17 is closed in order to allow the flow to flow backwards. Therefore, the system of the air layer 8 and the air supply pipe 15 is closed, and the backflow of ink is prevented by the so-called Torricelli principle.

In this way, the ink droplet ejecting device 1, which has been supplied with ink into the air layer 8 at the home position HP to prevent clogging of the first orifice 7, needs to discharge the ink before the printing operation. be. Therefore, conventionally, the ink droplet ejecting device 1 is moved to the standby position SP, and the gutter 2 is moved to the standby position SP.
The valve device 17 was operated while facing the air pump 2, and the air pump 14 was brought into communication with the air layer 8, and at the same time, the air pump 14 was operated. Then, the ink filled in the air layer 8 is pressurized from the outer circumferential direction by the air flow 16, and is discharged from the second orifice 10 that is opened at the center, and is discharged into the gutter 22 arranged oppositely. be captured.

However, according to such an ink discharge method, communication switching between the air pump 14 of the valve device 17 and the air layer 8 is performed at the same time as the operation of the air pump 14, so that the ink in the air layer 8 is drained at the initial stage of operation. The pressure of the pressurizing air stream is at a low level and the second
From the orifice 10, there is a gutter 2 placed oppositely.
As shown in FIG. 4, the ink could not be ejected and discharged toward the second orifice 10 and dripped down the wall surface of the second orifice 10. As a result, the dripped ink not only contaminates the vicinity of the ink droplet ejecting device 1, but also contaminates the ink droplet ejecting device 1 and the recording medium 18.
Since the facing distance between the recording medium 18 and the recording medium 18 is small, such as a few mm, the recording medium 18 may come into contact with the recording medium 18, thereby staining the printing surface.

The present invention has been made in view of this point, and provides a method for reliably discharging the anti-clogging liquid from the ink droplet ejecting device 1.

FIG. 5 is a curve diagram showing the pressure of the air flow 16 applied to the air layer 8 of the ink droplet ejecting device 1 over time. In this way, the pressure of the air flow 16 reaches the predetermined level Po after a certain period of time and reaches an equilibrium state.
That is, immediately after operating the air pump 14, the valve device 1 is
7 until the pressure of the air flow 16 reaches the predetermined level Po.
If the air pump 14 and the air layer 8 are made to communicate with each other when the air rises above this level, the ink acting as the anti-clogging liquid in the air layer 8 will be vigorously discharged from the second orifice 10 and captured by the gutter 22 disposed opposite to the air layer 8. be done. FIG. 6 shows the above-mentioned ink discharge operation, in which the air flow 16 whose pressure has increased above the predetermined level Po as described above pressurizes the ink from the outer periphery of the air layer 8 and
The ink is vigorously discharged from the orifice 10 toward the gutter 22, and after discharge, the ink enters a standby state as shown in FIG.

As is clear from the above description, in the present invention, in order to prevent clogging of the first orifice for ejecting ink droplets, the anti-clogging liquid that is filled into the air layer during non-printing operations is used to prevent clogging during printing operations. Since the air layer is pressurized by applying an air flow whose pressure has increased to a predetermined level or higher from the outer periphery of the air layer in advance, the air layer is pressurized vigorously and reliably from the second orifice opened approximately at the center of the air layer. The liquid is discharged and is therefore prevented from flowing out as droplets on the wall surface of the second orifice, thereby avoiding contamination of the vicinity of the apparatus and the printing surface of the recording medium. Furthermore, the anti-clogging liquid that is vigorously discharged from the second orifice can also eliminate the coagulated substances that tend to adhere to the second orifice itself.

[Brief explanation of drawings]

1 to 3 are cross-sectional views and schematic diagrams for explaining a conventional method for preventing clogging in an ink droplet ejecting device, FIG. 4 is a cross-sectional view for explaining a conventional method, and FIG. 5 to FIG. 7 shows a curve diagram and a cross-sectional diagram for explaining the method of the present invention. DESCRIPTION OF SYMBOLS 1... Ink droplet ejecting device, 7... First orifice, 8... Air layer, 10... Second orifice, 14... Air pump, 16... Air flow, 17
...Valve device, 22...Gutter.

Claims (1)

[Claims] 1. A first and a second orifice arranged coaxially with an air layer in between, and ink droplets ejected from the first orifice during printing operation are passed through the second orifice. In the ink droplet ejecting device, prior to the printing operation, the ink droplets are deposited on the recording medium, and during non-printing operations, the air layer is filled with an anti-clogging liquid to prevent clogging of the first orifice. By pressurizing the air supplied into the air layer to a predetermined level or higher and applying the pressurized air as an air flow from the outer periphery of the air layer, the anti-clogging liquid filled in the air layer can be removed. A method for discharging anti-clogging liquid in an ink droplet ejecting device, characterized in that the anti-clogging liquid is discharged from a second orifice into a gutter disposed opposite to the second orifice. 2. A method for discharging anti-clogging liquid in an ink droplet ejecting device according to claim 1, wherein the anti-clogging liquid is ink.