JPH04308767A - print head - Google Patents

Abstract

PURPOSE:To provide a printing head not generating the lowering of printing quality and a printing impossible state even during long-term use. CONSTITUTION:A printing head is equipped with the projection 1b provided to the upper surface of the yoke 1 holding an electromagnetic coil at every predetermined angle in the peripheral direction of the yoke 1, the armature 3 supported in a freely revolvable manner around the contact part with said projection 1b and attracted by the electromagnetic coil, the printing wire fixed to the armature 3 at one end thereof and provided so as to extend along the attraction direction of the electromagnetic coil and the elastic member coming into contact with the armature 3 and energizing the part opposed to the electromagnetic coil of the armature 3 in the direction separated from the electromagnetic coil and the first fulcrum 21 coming into contact with the armature 3 to become a fulcrum and the second fulcrum 22 coming into contact with the armature 1 in place of the first fulcrum 1 when the first fulcrum 21 is abraded to become a fulcrum are provided to the projection 1b of the yoke 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head for a dot matrix printer.

0002

2. Description of the Related Art Conventionally, print heads used in dot matrix printers are broadly classified into clapper type and spring charge type. In recent years, clapper-type print heads have been widely used because they have a small number of component parts and are inexpensive to manufacture.

[0003] A conventional print head will be explained below. FIG. 4 is a partial cross-sectional view of a conventional clapper type print head. Reference numeral 1 denotes a yoke that holds a plurality of electromagnetic coils 2 at predetermined angles in the circumferential direction, and has a hole 1a for wire insertion in the center. Projections 1b are provided on the upper surface of the yoke 1 at predetermined angles in the circumferential direction, and an armature 3 that is attracted in the direction a by the electromagnetic coil 2 is pressed against the projections 1b. It is designed to rotate about a corner 9 (see FIG. 5) at one end of 1b as a fulcrum. A printing wire 4 is attached to one end of the armature 3, and this printing wire 4 extends through the hole 1a of the yoke 1 along the attraction direction of the electromagnetic coil 2. 5 is a wire guide that guides the tip of the printing wire 4; 6 is a nose that holds the wire guide 5;
7 is a flexible printed circuit board.

[0004] A presser spring 8 as an elastic member is in contact with the other end of the armature 3 located on the outer peripheral side of the protrusion 1b of the yoke 1. side (b direction) to urge the portion of the armature 3 facing the electromagnetic coil in a direction (anti-a direction) away from the electromagnetic coil 2. An armature guide 10 is disposed on the outer peripheral side of the armature 3 so as to surround the armature 3, and regulates the position of the armature 3. Note that 11 is an armature stopper that restricts rotation of the armature 3 about the protrusion 1b by a stopper portion 11a, and 12 is a cover.

The operation of the conventional print head configured as described above will be explained below. Figures 4 and 5
By energizing the electromagnetic coil 2 from the initial state shown by the solid line, the armature 3 is attracted to the electromagnetic coil 2, and the printing wire 4 is moved toward the printing medium using the corner 9 of the protrusion 1b as a fulcrum to the attraction position (Fig. Printing is performed by moving to the dotted line section in 5) and contacting the print medium. Thereafter, by de-energizing the electromagnetic coil 2, the armature 3 is moved to the corner portion 9 of the protrusion 1b due to the compressive load of the presser spring 8.
is used as a fulcrum to return to the initial position.

[0006]

However, in the above-mentioned conventional configuration, as the usage time increases, the stepped portion 9 of the protrusion 1b, which serves as the fulcrum of the armature 3, wears out, causing the operation of the armature 3 to become unstable, making it difficult to print. There have been problems in that the quality deteriorates, and furthermore, the stepped portion 9 becomes abraded beyond a certain amount, making it impossible to print.

The present invention solves the above-mentioned problems, and aims to provide a print head that does not deteriorate print quality or become unable to print even after long-term use.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a yoke for holding an electromagnetic coil, protrusions provided at predetermined angles in the circumferential direction on the upper surface of the yoke, and the protrusions. an armature that is rotatably supported using a contact portion as a fulcrum and is attracted by the electromagnetic coil; a printing wire that is fixed to one end of the armature and extends along the attraction direction of the electromagnetic coil; In the print head, the print head includes an elastic member that contacts the armature and biases a portion of the armature facing the electromagnetic coil in a direction away from the electromagnetic coil, wherein a protrusion of the yoke contacts the armature and serves as a fulcrum. It is provided with a first fulcrum and a second fulcrum that comes into contact with the armature and becomes a fulcrum in place of the first fulcrum when the first fulcrum wears out.

[0009]

[Function] With the above structure, a second fulcrum is provided that comes into contact with the armature and becomes a fulcrum in place of the first fulcrum when the first fulcrum wears out. , the armature is stably rotated by the second fulcrum, thereby preventing deterioration of print quality and occurrence of a print failure state.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial sectional view of a print head according to an embodiment of the present invention, and FIGS. 2 and 3 are enlarged views of the vicinity of a protrusion of the same print head. In Figure 1, 2 is an electromagnetic coil, 3 is an armature, 4 is a printing wire, and 5
is a wire guide, 6 is a nose, 7 is a flexible printed circuit board, 8
10 is a presser spring, 10 is an armature guide, 11 is an armature stopper, and 12 is a cover, which are the same as those in the conventional example, so they are given the same numbers and their explanation will be omitted.

The difference from the conventional method is that, as shown in FIG. 2, a step 1c is formed on the outer circumference of the protrusion 1b of the yoke 1,
In addition to the first fulcrum 21 formed at the outer peripheral end of b, a second fulcrum 22 is provided at a diagonally upper position closer to the center than the first fulcrum 21. At the initial stage of use of the print head, the armature 3 is positioned at a position lower than the suction posture (indicated by the dotted line in FIG. 2) of the armature 3 at the initial stage of use, so that the armature 3 contacts the first fulcrum 21 and rotates. A second fulcrum 22 is provided at .

The operation of the print head of this embodiment constructed as described above will be explained below. When the electromagnetic coil 2 is energized from the initial state (return position) shown in FIG. 1, the armature 3 is attracted by the electromagnetic coil 2 and rotates, and the wire 4 comes into contact with the printing medium to print. After that, when the electromagnetic coil 2 is de-energized, the armature 3
is rotated to the return position by the biasing force of the presser spring 8.

At the beginning of use of the print head, as shown in FIG.
However, due to the friction between the first fulcrum 21 and the abutting part of the armature 3, wear of the first fulcrum 21 progresses depending on the usage time, and the first fulcrum 21 wears out by a certain amount. As shown in FIG. 3, the armature 3 contacts the second fulcrum 22 and rotates about the second fulcrum 22. Therefore, even if the first fulcrum 21 is worn out, the armature 3 can be stably rotated by the second fulcrum 22, thereby preventing deterioration in print quality or the occurrence of a printing impossible state.

[0014]

As described above, according to the present invention, when the first fulcrum wears out, a second fulcrum is provided which comes into contact with the armature and becomes a fulcrum in place of the first fulcrum. 1
Even if the second fulcrum is worn out, the armature can rotate stably by the second fulcrum while minimizing stroke fluctuations, preventing deterioration of print quality or the occurrence of a non-printing state, and extending the life of the head compared to the conventional one. It can be expanded to about twice its size.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a print head according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the vicinity of the yoke protrusion, illustrating the operation of the armature at the initial stage of use of the print head.

FIG. 3 is an enlarged view of the vicinity of the yoke protrusion for explaining the operation of the armature when the first fulcrum of the print head is worn out.

FIG. 4 is a partial cross-sectional view of a conventional print head.

FIG. 5 is an enlarged view of the vicinity of a yoke protrusion of a conventional print head.

[Explanation of symbols]

1 Yoke 1b Projection 1c Stepped portion 2 Electromagnetic coil 3 Armature 4 Printing wire 8 Holding spring (elastic member) 11a
Stopper part 21 First fulcrum 22 Second fulcrum

Claims (1)

[Claims] 1. A yoke for holding an electromagnetic coil; protrusions provided at predetermined angles in the circumferential direction on the upper surface of the yoke;
It is rotatably supported using the contact part with this protrusion as a fulcrum,
An armature attracted by the electromagnetic coil, a printing wire fixed to one end of the armature and extending along the attraction direction of the electromagnetic coil, and a part of the armature facing the electromagnetic coil that comes into contact with the armature. The print head includes an elastic member biased in a direction away from the electromagnetic coil, and a first fulcrum that contacts the armature and serves as a fulcrum on the protrusion of the yoke; The print head is provided with a second fulcrum that comes into contact with the armature and becomes a fulcrum in place of the first fulcrum when worn.