JPS6058705B2 - Multi-head of inkjet printing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved multi-head inkjet printing device.

Conventionally, a charge deflection type inkjet printing apparatus is constructed as shown in FIG.

In FIG. 1, 1 is an ink tank, 2 is a pump, 3 is an accumulator, 4 is a three-way solenoid valve, 5 is an inkjet head, 6 is a charging electrode, 7 is a detection electrode, 8 is a deflection electrode,
9 is a drum, 10 is a recording paper attached to drum 9, 11
is a gutter. A plurality of inkjet heads 5 are arranged in a horizontal row, and a charging electrode 6, a detection electrode 7, a deflection electrode 8, and a gutter 11 are respectively provided corresponding to each inkjet head 5, thereby forming a multi-head. In the conventional example configured in this way, the ink pressurized by the pump 2 is smoothed by the accumulator 3, and when the three-way solenoid valve 4 opens, the ink is guided to each inkjet head 5, and the ink is provided at the tip of the inkjet head 5. The ink is ejected from the nozzle 5a and becomes minute ink droplets.

The ink droplets are selectively charged by the charging electrode 6, the charged ink droplets are detected by the detection electrode 7 as having passed through a predetermined trajectory, and deflected by the deflection electrode 8 onto the recording paper 10, while Uncharged ink droplets go straight to the gutter 11
and collected in the ink tank 1. However, when the Ξ-side solenoid valve 4 is opened to start ink jetting, the ink pressure inside the inkjet head 5 is rapidly increased from atmospheric pressure to the jetting pressure (2 to 5 to 9/d).
The ejection direction of the ink is momentarily disturbed, or the ink is scattered, contaminating the charging electrode 6, the detection electrode 7, the deflection electrode 8, etc. with the ink. Further, even when ink jetting is stopped, ink drips and contamination occurs due to the transient characteristic of a decrease in jetting pressure. The contamination of the electrodes by this ink not only seriously impedes normal operation but also impedes safety because the ink has conductivity.

For example, since the detection electrode 7 detects the electrical charge generated on the detection electrode 7 when a charged ink droplet passes nearby, a shield is provided to prevent it from being affected by the electric field of the charging electrode 6 or the deflection electrode 8. However, this detection electrode 7
If conductive ink adheres to the surface, the shielding effect will decrease and the detection function will deteriorate. Additionally, if ink builds up on these electrodes, it will obstruct the flight path of the ink droplets and, because the ink is conductive, will substantially change the dimensions of each electrode, making it difficult to maintain the proper amount of charge. It is not possible to obtain the desired amount of deflection or deflection, and the printing position shifts, significantly impairing the printing quality.
Furthermore, the insulation of the electrodes etc. is reduced, and in particular, since a high voltage (2 to 4 k) is applied to the deflection electrode 8, safety is impaired. Therefore, in order to prevent the various failures mentioned above, with conventional equipment, the contamination status of the electrodes due to ink must be constantly monitored and cleaning and maintenance performed as appropriate, but this work is extremely difficult due to the multi-head system. The drawback was that it was complicated and required a lot of time and effort. In order to eliminate the drawbacks of the conventional example, the present invention provides a plurality of inkjet heads at one end of a head base member.
A gutter is provided at the other end, and a plurality of charges corresponding to each inkjet head are connected between the inkjet head and the gutter! An electrode block consisting of an electrode, a detection electrode, and a deflection electrode is provided so as to be movable in the horizontal direction, and the high-voltage side electrode of the deflection electrode is provided except for a portion that requires a deflection electric field to deflect charged ink droplets. The surface is coated with an insulating coating film, and when ink droplet jetting starts or stops, the electrode blocks are slid to move each electrode between the inkjet heads, thereby preventing contamination of the electrodes by ink. There is also a multi-head inkjet printing device with high performance.

Hereinafter, embodiments will be explained in detail with reference to the drawings. FIG. 2 shows one embodiment of the present invention, in which 12 is a head base, 13 is a gutter, 14 is an inkjet head, 15 is a head holder for fixing the inkjet head 14 to the head base 12, 16 is a charging electrode, 17 is a detection electrode, 1
8 is a deflection electrode, 19 is an electrode base which also serves as the ground side electrode plate of the deflection electrode 18 and is loaded with a charging electrode 16 and a detection electrode 17 to form an electrode block; 20 is a gutter 13 for storing non-imprinted ink droplets; This is a discharge port for guiding the ink collected in the ink reservoir 12a to the ink tank through the tube 21.

Note that 9 is a drum, and 10 is a recording paper attached to the drum 9. Further, 31 is a feed screw for moving the head base 12 loaded with an inkjet head, an electrode block, etc. in parallel to the axis of the drum 9, and is rotationally driven by a pulse motor (not shown). Reference numeral 32 denotes a main guide shaft, and rollers 33a and 33b arranged above and below the main guide shaft rotate to move the head base 12.

FIG. 3 is an exploded perspective view of FIG. 2.

A gutter 13 is attached to one end of the head base 12, and an ink reservoir 12a for storing non-printing ink droplets captured by the gutter 13 is provided. A plurality of inkjet heads 14 are fixed on the head base 12 by head holders 15 facing the gutter 13 . The head holder 15 is provided with an adjustment device that adjusts the direction of ink jetting from the inkjet head. The deflection electrode (high-voltage side electrode plate) 18 and the ground side electrode part of the electrode base 19 are held by insulating electrode holding plates 22a and 22b so as to face each other, and the charging electrode 16 and the detection electrode 17 are fixed to each other. - Detection electrode units are fixed on the electrode base 19 in correspondence with the inkjet heads 14, respectively, to constitute an electrode block. This electrode block is supported on an ink reservoir 12a provided on the head base 12 so as to be movable in a direction parallel to the gutter 13. That is, the guide shafts 2 of the electrode block support plates 23a and 23b fixed to the head base 12
4 are loosely inserted into the through holes provided in the electrode holding plates 22a and 22b of the electrode block, so that the electrode block is attached to the guide shaft 24.
You can move horizontally by sliding. The deflection electrode 18 and the ground side electrode portion of the electrode base 19 include an electrode portion 18a facing the inkjet head 14,
19a is provided, and notches 18b and 19b are provided between adjacent electrode portions, respectively, and in particular, the notch 19b on the ground side is inclined.

Further, as shown in FIG. 4, the deflection electrode 18 has all its surfaces covered with an insulating coating 18c, except for only the portion that requires a deflection electric field to deflect the printed ink droplets. As shown in FIG. 5, the charging/detection electrode unit in which the charging electrode 16 and the detection electrode 17 are fixedly connected is connected to the ink droplet passage 25.
The detection end 2 of the detection electrode 17 is located above and below this passage 25.
6, and a shield 27 is provided to surround the detection end 26 so as not to be affected by external electric fields. Next, the operation of this embodiment will be explained.

First, the steady operation will be explained with reference to FIG. The ink droplets are deflected and printed on the recording paper 10, while uncharged ink droplets travel straight and are collected by the gutter 13 and collected in the ink reservoir 12a.
The ink in the ink reservoir 12a is sent to the ink tank through the tube 21. Here, the drum 9 rotates at a constant speed in the direction of the arrow, thereby performing vertical main scanning, while the inkjet head 14 moves parallel to the axis of the drum 9 by rotation of the feed screw 31. Then, sub-scanning in the horizontal direction is performed, so that printing is performed on the recording paper 10 in a two-dimensional manner. Note that the movement of the head base 12 in the sub-scanning direction covers the entire printing width of the drum 9 by moving by the distance between adjacent heads. The driving method is to rotate the feed screw 31 using a pulse motor (not shown). Next, FIG. 6 shows the state at the time of starting or just before stopping the ejection of ink droplets from the inkjet head.

That is, when starting ink droplet ejection from the inkjet head 14, the electrode block consisting of the charging electrode 16, the detection electrode 17, and the deflection electrode 18 is moved in a horizontal direction perpendicular to the ink droplet ejection direction. Notch 18
b, 19b are placed at the ink droplet passage position. That is, each electrode is positioned midway between the trajectories of the flying ink droplets. A cross-sectional view of the electrode block along the ink droplet flight trajectory at that time is shown in FIG. 7a. Ink droplet ejection is started in this state, and after a few seconds, when the ink droplet ejection operation stabilizes, the electrode block is moved to the normal position, that is, the electrode parts 18a and 19a of the deflection electrode are at the ink droplet passing position. Therefore, the charging electrode 16 and the detection electrode 17 are also set to their normal positions, and the printing operation is started. Figure 7b shows a cross-sectional view of the electrode block at this time.
Shown below. Further, when the printing operation is completed and the ejection of ink droplets is to be stopped, the electrode block is moved to the state shown in FIG. 7a. Note that the electrode block may be moved manually, or may be moved using a separate driving means such as a solenoid. In this embodiment configured as described above, when starting and stopping the ejection of ink droplets, the electrode blocks are moved to form ink droplet paths of the electrode parts 18a and 19a of the deflection electrodes and the corresponding charging electrodes 16 and detection electrodes 17. Since it is retracted from the front surface of the inkjet head 14, it is possible to prevent this portion from being contaminated by ink, and the notches 18b and 19b of the deflection electrode and the corresponding portions of the charging electrode 16 and the detection electrode 17 are contaminated. Even if something happens, the electrode block can be moved to a normal position during the printing operation, and normal charging, detection, and deflection operations can be performed using the uncontaminated electrode section.

The notches 18b, 19b of the deflection electrodes reduce contamination by ink when ink droplets are ejected, and prevent ink from flowing into the electrodes 18a, 19a even if it adheres and accumulates, and the notches 19b are inclined. Therefore, the ink adheres to this portion and flows into the ink reservoir 12a. Furthermore, since the entire surface of the deflection electrode (high-voltage side electrode plate) 18 except for the portion that requires a deflection electric field is covered with an insulating coating 18c, insulation is ensured and extremely safe.
As described above, according to the present invention, the charging electrodes, detection electrodes, and deflection electrodes corresponding to a plurality of inkjet heads are divided into blocks, and the electrode blocks 7 are moved at the start and stop of ink droplet ejection, and each By retracting the electrodes from the front of the inkjet head, it is possible to prevent contamination due to ink scattering and dripping, so it is possible to always perform stable printing operations without deteriorating the function of each electrode. There are advantages.

In addition, the surface of the high-voltage side electrode of the deflection electrode is covered with an insulating film except for the part that requires the deflection electric field, increasing safety.Furthermore, each electrode is made into a block, and the multi-head is integrated. This has the advantage of simplifying parts, improving maintainability, and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional charge deflection type inkjet printing device, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is an exploded perspective view of FIG. 2, and FIGS. FIG. 5 is an explanatory diagram of the portion shown in FIG. 3, and FIGS. 6 and 7 are explanatory diagrams of the operation of FIG. 2. 12...Head base, 13...Gutter,
14...Inkjet head, 16...Charging electrode, 17...Detection electrode, 18...
Deflection electrode, 19...electrode base.

Claims (1)

[Claims] 1. In a charge deflection type multi-head inkjet printing device, a head base member, a plurality of inkjet heads disposed on one end of the head base member, and a plurality of inkjet heads disposed on the other end of the head base member. A plurality of sets of electrodes are arranged between a provided gutter and the inkjet head and the gutter, and each set includes a charging electrode, a detection electrode, and a deflection electrode, each of which is provided corresponding to each of the inkjet heads. It includes an electrode block and a support mechanism that supports the electrode block so as to be movable in a horizontal direction perpendicular to the ink jetting direction of the inkjet head, and the high-voltage side electrode member of the deflection electrode is provided with a deflection electric field that deflects charged ink droplets. The surface of the block is coated with an insulating film except for the parts that require it, and when ink droplet ejection is started or stopped, the electrode block is moved so that each of the electrodes is located between the trajectories of the flying ink droplets. to prevent contamination of each of the electrodes due to ink scattering or dripping, and move the electrode block so that each of the electrodes is positioned on the ink droplet flight trajectory when the ink droplet ejection operation reaches a steady state. A multi-head of an inkjet printing device, which is characterized by printing.