JPH0462542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a printing apparatus that forms an image by selectively ejecting ink droplets using electrostatic means.

Prior Art Conventionally, ink dot printers that form images by ejecting ink droplets from nozzles have had a fatal defect in that the nozzles become clogged.

Therefore, in order to prevent ink clogging, there are conventional devices in which an image is formed by ejecting ink held in a slit instead of a nozzle. As an example of such a thing, as shown in FIG.
There is one described in Publication No. 42664.
That is, a large number of recording electrodes 2 are arranged within a slit 1 that holds ink, and a counter electrode 4 is arranged to face these recording electrodes 2 with a recording paper 3 interposed therebetween. A power source 6 is connected between the recording electrode 2 and the counter electrode 4, with a switching element 5 interposed between each electrode to generate a potential difference sufficient to cause ink to fly between the two. ing.

With such a configuration, when the switching element 5 is selectively turned on in response to a print signal, a potential difference is generated between each recording electrode 2. Then, the ink in the portion where the voltage is applied flies toward the counter electrode 4, thereby performing printing. At this time, since the ink is held within the slit 1, clogging of the ink is prevented. However, in this type of device, the distance between slit 1 and recording paper 3 is
Unless the distance is about 200 μm, stable ink flight cannot be achieved, and if the position of the slit 1 and the recording paper 3 is out of alignment, the recording paper 3 will be significantly stained.

For this reason, the applicant has applied for a printing device as shown in FIG. Such a device is described in Japanese Patent Application No. 60-69485. That is, the counter electrode 11 is connected via the recording paper 10.
A recording electrode 12 with a tapered tip disposed opposite to
is formed into a member or shape that is impregnated with ink. This recording electrode 12 has an ink 13
The tip is inserted into an electrode hole 15 and the rear end is fixed to a wire 16 to be held. and,
A power source 18 is connected between the recording electrode 12 and the counter electrode 11 via a switching element 17 to generate a potential difference sufficient to cause ink to fly between them. Here, the details of the recording electrode 12 are that it is formed to have ink-impregnating property and conductivity.
That is, a fibrous material integrally formed into a bundle so as not to lose air permeability in the fiber direction, a rod-shaped member having a through hole or an outer circumferential groove in the axial direction,
The recording electrode 12 is formed of a sintered compact, a cast compact, a foam compact, or the like. The recording electrode 12 is imparted with conductivity by being mixed with a conductive substance or by being formed with a metal thin film.

In such a configuration, the ink 13 impregnates the recording electrode 12 and wraps around the tip thereof. Therefore, when the switching element 17 is turned on, a potential difference is generated between the recording electrode 12 and the counter electrode 11, and the ink 13 is ejected from the tip of the recording electrode 12. At this time, since the tip of the recording electrode 12 is protruding, the electric field is concentrated on that part, improving the flying condition of the ink 13, and it is possible to arrange the recording electrode 12 and the counter electrode 11 with some distance from each other. become. Therefore, even if the positional relationship between the recording electrodes 12 and the recording paper 10 becomes out of alignment, the recording paper 10 will not be soiled.

However, such a method in which the recording electrode 12 is impregnated with the ink 13 has a drawback that positioning of the recording electrode 12 is difficult. This is because if the center point of the tip of the recording electrode 12 and the center of the electrode hole 15 do not match, it is not possible to form a dot at an accurate position. This is because it is difficult in terms of component precision and manufacturing.

Therefore, in a patent application filed on September 26, 1985, the applicant has filed a patent application that allows for easy accurate positioning of the recording electrode 12. Such a device will be explained based on FIG. 12 (portions that are the same as or correspond to those in FIG. 11 are denoted by the same reference numerals and explanations will be omitted). That is, the electrode hole 15 becomes a tapered holding hole 20.
This holding hole 20 has a tapered shape whose diameter decreases as it approaches the counter electrode 11.
The tip of the recording electrode 12 is held in the holding hole 20, and only the apex portion of the tip is exposed to the outside.

In such a configuration, the recording electrode 12 fitted into the holding hole 20 and fixed is positioned in all the X, Y, and Z directions. Therefore, the recording electrode 12 can be easily positioned by simply fitting the recording electrode 12 into the holding hole 20.

Problems to be Solved by the Invention However, in the case where the recording electrode 12 is held in the holding hole 20 as described above, there is a possibility that the supply of ink 13 to the tip of the recording electrode 12 may not be sufficient depending on the conditions. be. for example,
This is the case when high-speed printing or solid printing is performed.

Furthermore, when the amount of ink 13 consumed is low, the ink 13 swells at the outlet of the holding hole 20 due to surface tension, so there is a risk that more ink 13 than necessary may fly due to changes in the atmosphere around the location. .

For this reason, there is a possibility that the printing density etc. may change depending on changes in surrounding conditions, making it difficult to perform uniform printing.

The present invention has been developed in view of the above, and is capable of ejecting ink droplets from the tip of a recording electrode impregnated with ink by electrostatic means, and is capable of ejecting ink droplets uniformly regardless of changes in surrounding conditions. An object of the present invention is to obtain a printing device capable of printing.

Means for Solving the Problems In the present invention, a counter electrode and a recording electrode with ink attached to the tip thereof are arranged facing each other with a recording body interposed therebetween, and the electric field between the recording electrode and the counter electrode is set to a predetermined level. In a printing device in which ink is ejected from the tip of a recording electrode to form an image on a recording medium when a value exceeds a certain value, the recording electrode is formed into a member or shape that is impregnated with ink, and the tip of the recording electrode is A holding plate is provided which has a tapered holding hole whose diameter decreases as it approaches the counter electrode, and an ink outflow groove is formed on the inner peripheral surface of the holding hole to communicate both ends of the holding plate. The tip of the recording electrode was held in the hole.

Function: Ink is supplied to the tip of the recording electrode not only from the recording electrode itself, which has ink-impregnating properties, but also from the ink outflow groove of the holding hole. Therefore, the amount of ink supplied to the tip of the recording electrode increases, and a sufficient amount of ink is always supplied to the tip of the recording electrode. Further, since the ink outflow groove exists, the ink holding area at the outlet of the holding hole becomes large, and the swelling of the ink in that part due to surface tension becomes small. Therefore, the amount of ink ejected from the tip of the recording electrode is less affected by changes in surrounding conditions, and uniform printing is performed.

Embodiment of the Invention An embodiment of the present invention will be described based on FIGS. 1 to 9. Two guide shafts 31 are disposed horizontally within the housing-like case 30, and a carrier 32 is attached to these guide shafts 31 so as to be able to reciprocate in the left-right direction. A printing head 33 is placed on this carrier 32. A horizontally long counter electrode 34 is installed horizontally in the center of the case 30 so as to face the printing head 33. A tractor 36 is provided behind the counter electrode 34 to feed a recording paper 35 as a recording medium guided between the counter electrode 34 and the printing head 33. These tractors 36 are coupled with operating knobs 37 that protrude outward.

Here, the details of the printing head 33 are shown in FIG.
This will be explained based on FIGS. 3 and 4. A housing-like case 38 is provided, and an ink holding portion 40 for storing ink 39 is formed within the case 38 . The top surface of this ink holding portion 40 is covered with a lid 41 attached to the case 38.
Further, the front wall of the case 38 is connected to the counter electrode 34.
The holding plate 42 is opposed to the holding plate 42, and the rear wall is a thick supporting body 43. Then, the holding plate 42
A plurality of holding holes 44 are formed at equal intervals in the horizontal direction and communicate with the lower part of the ink holding section 40 . These holding holes 44 are formed in a tapered shape whose diameter decreases as it approaches the counter electrode 34. Here, a plurality of ink outflow grooves 46 are formed on the inner peripheral surface 45 of the holding hole 44 . These ink outflow grooves 46 are formed in the axial direction of the holding hole 44 and have a length that allows both ends of the holding plate 42 to communicate with each other. On the other hand, a plurality of support holes 47 are formed in the support body 43 at positions facing each of the holding holes 44 . Conductive terminals 48 are fitted and fixed at the rear ends of these support holes 47 . Thus, a plurality of recording electrodes 50 each having a conductive coil spring 49 wound and fixed at its rear end are provided. These recording electrodes 50 are made of a member that is endowed with electrical conductivity and is impregnated with ink, and have tapered tips.
And those recording electrodes 50 are connected to the coil spring 4
9 is inserted into the support hole 47, and the tip is pressed against the holding hole 44 by the force of the coil spring 49 and held. Moreover, the holding plate 4
The front surface of 2 is sloped in a direction away from the counter electrode 34 from below the holding hole 44, and this sloped portion forms an inclined surface 51. The starting portion of this inclined surface 51 is marked with an R. Further, an ink escape groove 52 is formed on the front surface of the holding plate 42, hanging down from the lower end of the holding hole 44 and reaching the lower end of the inclined surface 51.

One end of a high voltage switch 54 is connected to the terminal 48 via a connector 53, and the other end of the high voltage switch 54 is connected to the terminal 48 via two divided high voltage power supplies 55 and 56. It is connected to the counter electrode 34. the high voltage power supply 55,
The middle point of connection 56 is grounded.

In such a configuration, the ink 39 in the ink holding section 40 impregnates the recording electrode 50 and flows out from the ink outflow groove 46 to be supplied to the tip of the recording electrode 50. Therefore, when the high voltage switch 54 is selectively turned on in accordance with the print signal, a potential difference is generated between each recording electrode 50, and the ink 39 at the tip of the recording electrode 50 to which the voltage is applied flies toward the counter electrode 34. do. As a result, dots are formed on the recording paper 35, and printing is performed by a collection of these dots.

During printing, the dots formed on the recording paper 35 are always formed at accurate positions. This is because the positions of the recording electrodes 50 are regulated by the holding holes 44, so that all the recording electrodes 50 are positioned at preset correct positions. Moreover, such positioning of the recording electrode 50 can be easily performed by simply pressing the tip of the recording electrode 50 against the holding hole 44. In addition, in this embodiment, the holding hole 4
Since the recording electrode 50 is pressed against the holding hole 44 by the coil spring 49, there is no problem such as excessive force being applied from an undesirable direction, and the recording electrode 50 is naturally pressed against the holding hole 44.

On the other hand, the ink 39 on the tip of the recording electrode 50
The ink is also supplied from the ink outflow groove 46. Therefore, the ink 39 on the tip of the recording electrode 50
The amount of ink 39 supplied increases, and a sufficient amount of ink 39 is supplied to the tip of the recording electrode 50 even when high-speed printing or solid printing is performed.
In addition, since the ink outflow groove 46 exists, the holding hole 4
The holding area of the ink 39 at the outlet 4 becomes larger, and the swelling of the ink 39 at that part due to surface tension becomes smaller. Therefore, the recording electrode 5
The amount of ink 39 ejected from the tip of the 0 is not easily affected by changes in surrounding conditions, and uniform printing is performed.

Therefore, even if an excessive amount of ink 39 flows out to the outlet of the holding hole 44, the ink 39 flows down from the ink escape groove 52 and does not stagnate around the outlet of the holding hole 44. Further, since the inclined surface 51 is inclined in the direction away from the counter electrode 34, the ink 39 is prevented from flying from this portion. Furthermore, since the starting part of the inclined surface 51 is marked with R, the electric field will not be concentrated here, and the ink 3 from that part will be prevented from concentrating.
9 is prevented from flying. In this manner, from the above-mentioned aspects, printing is made uniform, and unnecessary flying of the ink 39 is prevented, thereby preventing accidents such as staining the recording paper 35.

It should be noted that those shown in FIGS. 6 to 9 are modified examples of the holding hole 44, respectively. First, in the one shown in FIG. 6, ink outflow grooves 46 that coincide with the axial direction of the holding hole 44 are formed in a cross shape with a length that communicates both ends of the holding plate 42, and these ink outflow grooves 46 are communicated with each other. An ink outflow groove 46 is formed on the circumference inside the holding hole 44. What is shown in Figure 7 is
A star-shaped ink outflow groove 46 is formed in the holding hole 44 so as to communicate both ends of the holding plate 42. The one shown in FIG. 8 is one in which ink outflow grooves 46 long enough to communicate with both ends of the holding plate 42 are formed radially, and these ink outflow grooves 46 are inclined to be offset from the axial direction of the holding hole 44. It is. In the case shown in FIG. 9, both ends of the holding plate 42 are connected through a spiral ink outflow groove 46.

Effects of the Invention In the present invention, a counter electrode and a recording electrode having ink attached to the tip thereof are arranged opposite to each other with a recording medium interposed therebetween, and when the electric field between these recording electrodes and the counter electrode exceeds a predetermined value, In a printing device in which ink is ejected from the tip of a recording electrode to form an image on a recording medium, the recording electrode is formed into a member or shape that is impregnated with ink, and the tip of the recording electrode is formed into a tapered shape. A holding plate having a tapered holding hole whose diameter becomes smaller as it approaches the counter electrode is provided, and an ink outflow groove is formed on the inner peripheral surface of the holding hole to communicate both ends of the holding plate, and the recording electrode is connected to the holding hole. Since the tip is held, the amount of ink flying is less affected by changes in surrounding conditions, making it possible to perform uniform printing and high-speed printing. If an ink escape groove is formed on the surface of the retaining plate that exits downward from the bottom end of the hole, excess ink around the outlet of the retaining hole can flow downward, which contributes to more uniform printing. If the part of the holding plate below the holding hole is tilted in a direction away from the counter electrode, ink will be prevented from flying from that part, thereby preventing accidents such as staining the recording medium. Furthermore, if the holding plate is sloped and a radius is added at the beginning of the slope, the electric field will no longer be concentrated in that area, and the recording material will be affected by the ink flying from that area. This has effects such as preventing staining accidents.

[Brief explanation of drawings]

Fig. 1 is a partially sectional perspective view of a printing head showing an embodiment of the present invention, Fig. 2 is an overall perspective view, Fig. 3 is a longitudinal side view of a holding hole, and Fig. 4 is a rear view thereof. 5 is a longitudinal side view showing the electrical connection state between the printing head and the counter electrode, FIG. 6 is a rear view showing a modified example of the holding hole, and FIG. 7 is a rear view showing another modified example. Figure 8 is a rear view showing another modification;
The figure is a rear view showing another modified example, FIG. 10 is a perspective view showing a conventional example, FIG. 11 is a longitudinal side view showing another example, and FIG. 12 is a longitudinal side view showing another example. . 34... Counter electrode, 35... Recording paper (recording body),
39... Ink, 42... Holding plate, 44... Holding hole, 46... Ink outflow groove, 50... Recording electrode,
52...Ink escape groove.

Claims (1)

[Scope of Claims] 1. When a counter electrode and a recording electrode having ink attached to the tip thereof are arranged facing each other with a recording body interposed therebetween, and the electric field between these recording electrodes and the counter electrode exceeds a predetermined value. In a printing device in which ink is ejected from the tip of the recording electrode to form an image on the recording medium, the recording electrode is formed into a member or shape that is impregnated with ink, and the tip of the recording electrode is A holding plate having a tapered holding hole whose diameter becomes smaller as it approaches the counter electrode is provided, and an ink outflow groove is formed on the inner circumferential surface of the holding hole to communicate both ends of the holding plate. . A printing device, wherein the holding hole holds a tip of the recording electrode. 2. A counter electrode and a recording electrode with ink attached to the tip thereof are arranged opposite to each other with a recording body interposed therebetween, and when the electric field between these recording electrodes and the counter electrode exceeds a predetermined value, the tip of the recording electrode In a printing device in which ink is ejected from a portion to form an image on the recording medium, the recording electrode is formed into a member or shape having ink impregnating property, and the tip of the recording electrode is formed into a tapered shape, A holding plate having a tapered holding hole whose diameter decreases as it approaches the counter electrode is provided, an ink outflow groove is formed on the inner peripheral surface of the holding hole to communicate both ends of the holding plate, and a lower end of the holding hole is provided. A printing device characterized in that an ink escape groove that escapes further downward is formed on the surface of the holding plate, and the tip of the recording electrode is held in the holding hole. 3. The printing device according to claim 2, wherein a portion of the holding plate below the holding hole is inclined in a direction away from the counter electrode. 4. The printing device according to claim 3, wherein the holding plate is rounded at the beginning of the slope.