JPS5995164A - Printing head for wire dot printer - Google Patents

Abstract

PURPOSE:To obtain high printing quality free from the disturbance of alignment or the irregularity of printing density, in a printing head taking a two-stage structure, by using a wire with higher specific gravity in a front stage as compared with the wire used in a rear stage. CONSTITUTION:When a current is supplied to a coil 5 toward a direction for negating the magnetic field of a permanent magnet 1, a printing wire 9 is protruded through a lever 8 by the elastic force of a leaf spring T and, after dots are formed on recording paper, a plunger 6 is attracted to a core 2 by the attraction force of the permanent magnet 1 to finish one process in dot formation. The material quality of the wire is adjusted so that the wire in a rear stage has specific gravity about 1/2 as compared with the wire in a front stage and, for example, a tungsten wire (specific gravity 19.3) is used in the front stage printing wire 9f while a piano wire (specific gravity 7.9) is used in the post stage printing wire 9r to make the inertias of movable parts almost equal in the front and the rear stages and, in a same driving condition, printing energy and response speed are made equal and good printing quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a print head for a wire dot printer.

Conventional devices of this type include multi-bin wire dots such as 24-bin heads and 18-bin heads that enable fine dot matrix printing for printing kanji characters, etc., but these heads have been made smaller. For this reason, a fine wire dot head having a two-layer structure in which wire driving devices are arranged in two stages, a front stage and a rear stage, is known as disclosed in Japanese Patent Application Laid-open No. 56-11273 and Japanese Utility Model Publication No. 57-36437. Furthermore, in order to construct such a fine dot matrix, wires with a small wire diameter must be used. As the diameter of the wire becomes smaller, the wire may pierce through the ink ribbon or printing paper if excessive printing energy is applied, so the permissible range of printing energy becomes narrower. By the way, in the above-mentioned two-stage print head, the wire lengths in the front and rear stages were different, and the wire material was the same for both the front and rear stages, so the mass of the movable parts of the wire drive device, including the wires, was The rear stage becomes larger, and as a result, the front stage 9
If the wires were driven under the same driving conditions in both the latter stages, the response speeds would be different between the former and latter stages, resulting in disturbances in dot alignment and a deterioration in print quality. If the driving conditions of the front and rear stages are changed so that both the front and rear stages respond at the same response speed, the wire drive circuit becomes complicated, and the printing energy of the rear stage wire becomes larger than that of the front stage, resulting in an energy difference. However, there is a drawback that the printing energy does not fall within the allowable range of appropriate printing energy, and a difference occurs in printing density between the first and second stages, resulting in a decrease in printing quality.

The present invention eliminates these drawbacks, and its object is to provide a print head for wire dot printers that provides high print quality without alignment disturbances or print shading.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the 24-pin wire dot head of the present invention.The wire drive device at the front stage is explained as follows: permanent magnet 1, upper yoke 4. The lower yoke 6 and the presser plate 10 are connected to the fixed shaft 1
2 and a nut 27. Printing wire 9
f is fixed to the tip of the lever 8, and the lever 8 and the leaf spring 7
is fixed by caulking with the plunger 6. The core 2 is fixed to a lower yoke 6, and a coil 5 is attached around the core. The printing wire 9f at the front stage is a tungsten wire (specific gravity: 19°3).

The wire drive device in the rear stage is also configured in the same way as the front stage.
The difference from the previous stage is that the printing wire 9r is a piano wire (specific gravity 7.
9).

Next, the driving device described above can be operated by passing a current through the coil 5 to cancel the magnetic attraction force of the permanent magnet 1. That is, normally, the plate spring 7 is deflected by the magnetic attraction force of the permanent magnet 1, and the plunger 6 is attracted to the core 2. When a current is applied to the coil 5 in a direction to cancel the magnetic field of the permanent magnet 1, the plunger 6 is released from the core 2 by the elastic force of the leaf spring 7, and its motion is transmitted to the printing wire 9 via the lever 8. The printing wire 9 protrudes and is filled with ink (not shown in the figure).

After forming a dot on the recording paper through the plunger, the plunger 6 is again attracted to the core 2 by the force of the permanent magnet 1, and in the present invention, the wire material has a specific gravity in the subsequent stage. Since different materials are used in the front and rear stages so that the specific gravity is approximately 1/2 of the specific gravity of the front stage, the inertia of the moving parts is almost equal in the front and rear stages, and under the same driving conditions, the printing energy - response speed is The printing quality is the same in the front and rear stages, making it possible to obtain good printing quality.

As explained above, in a head with a two-stage structure,
By changing the materials of the wires in the front and rear stages and using a wire with a higher specific gravity in the front stage than in the latter stage, the printing energy of the front and rear wires can be reduced.

The response speeds are about the same, and good print quality can be obtained.

Note that the present invention can be widely used in addition to the spring-charge type heads described in the embodiments, as well as electromagnetic suction types and others.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the two-stage structure head of the present invention. 1...Permanent magnet 9f　、9r・・・Wire

Claims (1)

[Claims] A print head for a wire dot printer, which has a two-stage structure in which a plurality of wire drive devices are arranged in a front stage and a rear stage, and is characterized in that the specific gravity of the rear stage wire is smaller than the specific gravity of the front stage wire.