JPH0429B2 - - Google Patents

Description

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

Technical background of the invention and its problems Conventional dot printers impact pressure-sensitive paper along a platen with a needle, or impact plain paper through an ink ribbon. In any case, the collision between the needle and the platen causes a lot of printing noise.

For this reason, a printing method has been considered in which magnetic ink in an ink tank is attracted by magnetic force between opposing magnetic poles, and a needle wetted with the magnetic ink is slid toward the recording paper. However, there is a problem in that the amount of magnetic ink transferred from the tip of the needle to the recording paper varies, resulting in inconsistent print density.

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a dot printer that can reduce printing noise and freely vary printing density.

Summary of the Invention This invention forms a magnetic ink layer by attracting magnetic ink in an ink tank between opposing magnetic poles,
Slide the needle and transfer the magnetic ink attached to the tip of the needle to the recording paper to form a dot.
As a result, printing pressure can be significantly reduced and printing noise can be significantly reduced.Furthermore, the excitation voltage of the magnetic ink suction coil can be varied by the control unit to change the strength of the magnetic field between the magnetic poles. The structure is such that printing density can be freely selected by adjusting the thickness of the magnetic ink layer between the magnetic poles.

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 on both sides of the guide frame 10 there are magnetic plates 1 connected to both poles of a magnetic ink attraction coil 16.
7 are fixed, magnetic poles 19 facing each other with a slit 18 in between are continuously formed at the tips of these magnetic plates 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. A permanent magnet 26 facing the lower end of the magnetic pole 19 is fixed to the lower surface of the ink tank 20. A tube 27 that fits into the opening 25 is formed on the lower surface of the cartridge 21. An opening 28 is formed at the lower end of the tube 27 to discharge the magnetic ink 24 inside. A plug 29 that closes the opening 28 is urged downward by a spring 30 and is fitted so as to be vertically movable. 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 larger than the radius of the opening 28.

Further, in front of the print head 2, a recording paper 34 is supported by a permanent magnet 35 and is fed by a paper feed roller 33.

A variable resistor 36 serving as a control section is attached to the front surface of the casing 1. This variable resistor 36 is connected between the power source and the magnetic ink attraction coil 16, and has an adjustment knob 37.

In such a configuration, when 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 a magnetic ink layer is formed along the slit 18, and the tip of the needle 9 is is wetted with magnetic ink 24. Therefore, by exciting the specified electromagnet 7 and causing the needle 9 to fly toward the recording paper 34, the magnetic ink 24 at the tip of the needle 9 comes into contact with the recording paper 34 to form a dot. In this case, needle 9
When the leading edge of the dot 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 permanent magnet 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 bring it into contact with the recording paper 34. It is also possible to further reduce printing 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.

FIG. 6 shows the relationship between the strength of the magnetic field between the magnetic poles 19 and the excitation voltage to the magnetic ink attraction coil 16.
Even if the excitation voltage is increased above a certain level, a saturated state will occur, so the excitation voltage is adjusted in a region where the strength of the magnetic field changes linearly. That is, by adjusting the variable resistor 36, the thickness D of the magnetic ink layer 38 can be selected in proportion to the strength of the magnetic field between the magnetic poles 19, as shown in FIG. As shown in FIG. 8, the thickness D is the dimension in the direction perpendicular to the spacing between the opposing magnetic poles 19. By increasing the thickness D, the amount of magnetic ink 24 sprayed onto the recording paper 34 is increased, and the print density is increased. On the other hand, by reducing the thickness D, the amount of magnetic ink 24 transferred to the recording paper 34 can be reduced, and the print density can be reduced. Therefore, by turning the adjustment knob 37 of the variable resistor 36, the desired print density can be freely selected.

Note that the magnetic ink 24 transferred to the recording paper 34
Detect the concentration of, for example, with an optical sensor,
The signal from this sensor may be input to the control circuit to change the excitation voltage of the magnetic ink attraction coil 16. This also allows automatic adjustment of print density.

Effects of the Invention Since the present invention is configured as described above, the printing pressure of the needle on the recording paper can be significantly reduced, thereby making it possible to significantly reduce printing noise.Furthermore, the excitation voltage of the magnetic ink attraction coil can be reduced significantly. The strength of the magnetic field between the magnetic poles can be varied by the control unit, and therefore the thickness of the magnetic ink layer between the magnetic poles can be adjusted to freely select the printing density. be.

[Brief explanation of drawings]

The drawings show one embodiment of the invention.
The figure is a perspective view showing the overall configuration with a reduced size and a part cut away, Figure 2 is a plan view, Figure 3 is a longitudinal side view, and Figure 4 is a perspective view showing the overall configuration.
The figure is an exploded perspective view, Figure 5 is a partially cutaway and enlarged front view, Figure 6 is a graph showing the relationship between magnetic field strength and excitation voltage, and Figure 7 is magnetic field strength and thickness of magnetic ink layer. FIG. 8 is a partially enlarged plan view showing the state of formation of the magnetic ink layer between the magnetic poles. 9...Needle, 16...Magnetic ink attraction coil, 18...Slit, 19...Magnetic pole, 20...
Ink tank, 24...Magnetic ink, 34...Recording paper, 36...Variable resistor (control unit).

Claims (1)

[Claims] 1. Magnetic poles are magnetically coupled to a magnetic ink suction coil and face each other with slits made, and the lower ends of these magnetic poles are inserted into an ink tank containing magnetic ink and immersed in the magnetic ink. A plurality of needles that capture the magnetic ink attracted between the magnetic poles and transfer it to recording paper are slidably provided between the magnetic poles, and a control unit that varies the excitation voltage of the magnetic ink attraction coil is provided. A dot printer with special features.