JPH0428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention This invention relates to a dot printer.

Technical Background and Problems of the Invention Conventional dot printers impact pressure-sensitive paper along a platen with a needle, or impact plain paper with an ink ribbon. In either case, printing is caused by collision between the needle and the platen, which causes a lot of noise.

For this reason, magnetic poles are placed opposite to each other on the front surface of the platen, and the magnetic ink in the ink tank is attracted between these magnetic poles by magnetic force. A needle is passed through this magnetic ink layer, and the magnetic ink is applied from the tip of the needle to the recording paper. A method is being considered in which the image is transferred to However, when the magnetic field between the magnetic poles is removed at the end of printing, the magnetic ink returns to the ink tank due to its own weight, but as it diffuses, the surrounding area becomes dirty. Enlarging the holes in the ink tank is inconvenient because the magnetic ink may evaporate and dust may enter. In order to collect magnetic ink between the magnetic poles to a certain width due to surface tension, it is necessary to reduce the distance between the magnetic poles, but at the end of printing, it becomes difficult for the magnetic ink between the magnetic poles to return to the ink tank, and there is a risk that the magnetic ink may solidify on the spot. There are problems that make it difficult to put it into practical use.

Purpose of the Invention This invention has been made in view of the above-mentioned points, and is aimed at reducing printing noise, and in particular, by quickly returning the magnetic ink between the magnetic poles to the ink tank at the end of printing, and preventing the magnetic ink from clumping between the magnetic poles. The object of the present invention is to provide a dot printer that can prevent this.

Summary of the Invention This invention attracts magnetic ink in an ink tank between opposing magnetic poles, causes a needle to penetrate the magnetic ink layer between the magnetic poles, and transfers the magnetic ink at the tip of the needle onto recording paper. The printing pressure on the recording paper can be reduced to extremely reduce printing noise, and the ink between the magnetic poles can be quickly returned to the ink tank by a magnet when printing is completed.

Embodiment of the Invention An embodiment of the invention will be described based on the drawings.
Reference numeral 1 denotes a housing, and a carrier 3 on which a printing head 2 is mounted is slidably provided in the housing 1 and held by a carrier shaft 4 and a guide shaft 5. A cover 6 is provided on the upper surface of the housing 1, although only a portion thereof is shown. The print head 2 is comprised of a magnet case 8 containing a plurality of electromagnets 7 arranged in a ring shape and a guide frame 10 holding a plurality of needles 9. The armature 11 of each electromagnet 7 comes into contact with the needle 9, is urged in the return direction by the needle spring 12, and is pressed against the stopper 13. Needle guides 14 and 15 for aligning the needles 9 are fixed to the guide frame 10, and magnetic plates 17 magnetically coupled to both poles of a magnetic ink attraction coil 16 are fixed to both sides of the guide frame 10. Magnetic poles 19 facing each other with a slit 18 in between are continuously formed at the tip of the needle 17, and the tip of the needle 9 projects from the slit 18.

Furthermore, a flat ink tank 20 and a cartridge 21 are detachably attached to the print head 2. A magnetic pole 19 is provided on the top surface of the ink tank 20.
A small slit-like hole 22 into which the lower end of the slit is inserted and a through hole 23 located in the center are formed continuously, and
An opening 25 for replenishing magnetic ink 24 is formed. An electromagnet 26, which is a magnet facing the lower end of the magnetic pole 19, is fixed to the lower surface of the ink tank 20. A cylinder 27 that fits into the opening 25 is formed on the lower surface of the cartridge 21.
An opening 28 for discharging the internal magnetic ink 24 is formed at the lower end of the cylinder 27, and a plug 29 that closes the opening 28 when the cylinder 27 is in close contact with the cylinder 27 is fitted into the cylinder 27 so as to be able to move up and down while being biased downward by a spring 30. ing. Further, a rod 31 is formed protruding from the lower surface of this plug 29, and a plurality of notches 32 are formed on the outer periphery.
The radius of the circle connecting the bottoms of these notches 32 is the opening 28
It is made larger than the radius of

Furthermore, a paper feed roller 3 is provided in front of the print head 2.
A recording paper 34, which is fed by the magnet 3, is supported by a permanent magnet 35.

As shown in FIG. 6, magnetic ink suction coil 1
6, a changeover switch 36, and a battery 37 are connected in series, and a coil of an electromagnet 26, a changeover switch 36, a battery 37, and a timer 38 are connected in series. In addition, the magnetic ink suction coil 16 and the battery stone 2
A capacitor 39 is connected to both poles of the coil 6, respectively.
40 are connected.

In such a configuration, when the changeover switch 36 is switched to the terminal a side and the magnetic ink attraction coil 16 is energized, the magnetic ink 24 in the ink tank 20 is attracted by the magnetic flux generated between the magnetic poles 19, and the magnetic ink is drawn along the slit 18. A layer is formed and the tip of the needle 9 is wetted with magnetic ink 24. Therefore, by exciting the specified electromagnet 7 and making the needle 9 fly toward the recording paper 34, the needle 9
The magnetic ink 24 at the tip contacts the recording paper 34 to form a dot. In this case, if the tip of the needle 9 lightly touches the recording paper 34, a dot is formed, so there is no collision sound as in the conventional case, and the noise is extremely low. According to this embodiment, when the tip of the needle 9 approaches the recording paper 34, the magnetic pole 35 attracts the magnetic ink 24 at the tip of the needle 9, so the stroke of the needle 9 is set to a small stroke that does not contact the recording paper 34, and printing is performed. It is also possible to further reduce the noise.

Further, the magnetic force of the magnetic ink attraction coil 16 is constant, and the magnetic ink 24 in the ink tank 20 is replenished from the cartridge 21 according to the amount consumed, so it is maintained at a constant level. The layer level is also constant, and there is no situation where the magnetic ink 24 does not reach the upper needle 9. Further, due to the presence of the cartridge 21, there is no need to manually replenish the ink tank 20, which saves time and effort.

When printing is finished, switch 36 to terminal B.
switch to the side. At this moment, the magnetic ink attraction coil 16 is disconnected from the battery 37 and is excited only by the discharge current of the capacitor 39, and the electromagnet 26 is activated by the timer 3.
It is excited by the battery 37 for a certain period of time set to 8. FIG. 7A shows the change in the current to the magnetic ink attraction coil 16, where t ₁ is when the connection to the battery 37 is cut off by the changeover switch 36, and from t ₁ to t ₃ , the current is applied to the magnetic ink attraction coil 16 by the capacitor 39. This is the excitation period.
FIG. 7B shows the excitation operation of the electromagnet 26.
During the timer 38 set period from t ₁ to t ₂ , battery 3
7 and is excited by the discharge current of the capacitor 40 from t ₂ to t ₄ . FIG. 7C shows the level change of the magnetic ink 24 between the magnetic poles 19.

That is, the strength of the magnetic field of the electromagnet 26 immediately after printing is completed is strong enough to push the magnetic ink 24 to the level _h1 . By gradually decreasing the strength of the magnetic field between the magnetic poles 19 using the capacitor 39 instead of reducing it to zero all at once, the magnetic ink 2 between the magnetic poles 19
4 is returned to the ink tank 20 through the through hole 23 by its own weight. At time t ₂ when the magnetic ink 24 between the magnetic poles 19 has dropped from the level h ₂ to the level h ₁ , the strength of the magnetic field of the electromagnet 26 is gradually lowered by the capacitor 40 as shown in FIG. 8 to increase the pushing force. By making it smaller,
The magnetic ink 24 between the magnetic poles 19 is transferred to the ink tank 20.
to be collected. Since a weak magnetic field exists between the magnetic poles 19 until time t ₃ during this recovery period, the magnetic ink 24 enters the through hole 23 without being diffused.
Therefore, the magnetic ink 24 does not remain on the magnetic pole 19 and harden, nor does it overflow from the through hole 23 and stain the surrounding area. If the timing of disconnecting between the battery 37 and the electromagnet 26 is delayed from _t2 , as shown by the dashed line in _FIG . Adjust accurately.

In the embodiment described above, when collecting the magnetic ink 24 between the magnetic poles 19, the initial stage is performed by gradually decreasing the strength of the magnetic field of the magnetic ink attraction coil 16, and the latter stage is performed by gradually decreasing the strength of the magnetic field of the electromagnet 26. However, at the end of printing, the strength of the magnetic field of the electromagnet 26 is increased, and at the end of printing, the strength of the magnetic field of the magnetic ink suction coil 16 is set to zero, and from this moment on, the magnetic field of the electromagnet 26 is increased. The magnetic ink 24 may be collected into the ink tank 20 only by controlling the electromagnet 26 during the entire collection period by gradually decreasing the strength of the magnetic ink 24 . In addition, the direction of the magnetic field lines of the electromagnet 26 is reversed, and the magnetic ink 24 between the magnetic poles 19 is transferred to the ink tank 2 by the attractive force of the electromagnet 26.
Recovery to zero is also included in this invention. In this case, a permanent magnet may be used as the magnet.

Effects of the Invention Since the present invention is configured as described above, the magnetic ink between the magnetic poles can be quickly collected into the ink tank by the magnet at the end of printing, thereby preventing the magnetic ink from remaining on the magnetic poles and hardening. This has effects such as being able to prevent printing noise and further suppressing printing noise.

[Brief explanation of drawings]

The drawings show one embodiment of the invention.
The figure is a perspective view of the whole with a part cut out and reduced.
The figure is a plan view, Figure 3 is a vertical side view, Figure 4 is an exploded perspective view, Figure 5 is a partially enlarged and cutaway front view, Figure 6 is an electrical circuit diagram, and Figure 7 is a magnetic ink drawing. A graph showing the recovery operation, FIG. 8, is a graph showing changes in the strength of the magnetic field of the electromagnet. 9...Needle, 16...Magnetic ink attraction coil, 18...Slit, 19...Magnetic pole, 20...
Ink tank, 23...through hole, 24...magnetic ink, 26...electromagnet (magnet), 34...recording paper,
40... Capacitor.

Claims (1)

[Claims] 1. Magnetic poles that are magnetically coupled to a magnetic ink attraction coil and face each other with slits are provided, and the lower ends of these magnetic poles are inserted into an ink tank to absorb the magnetic ink in the ink tank. A plurality of needles are slidably provided between the magnetic poles for capturing the magnetic ink that is immersed in the magnetic ink and being attracted between the magnetic poles by magnetic force and transferring it to recording paper, and a magnet facing the lower end of the magnetic poles is provided in the ink tank. A dot printer characterized by: 2. The dot printer according to claim 1, characterized in that an electromagnet is used as the magnet. 3. The dot printer according to claim 2, characterized in that the electromagnet is excited by gradually lowering the energizing current for a certain period of time from the end of printing. 4. The dot printer according to claim 3, wherein the current flowing to the electromagnet is gradually reduced by a capacitor.