JP3046520B2 - Thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer for printing on recording paper by a thermal head.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional example of a thermal printer. 1 is a side cover 1. The side cover 1 has a recording paper supply shaft 3 for holding a recording paper 2 (label paper as an example) wound in a roll shape, and a ribbon supply shaft 5 for holding an ink ribbon 4 wound in a roll shape. When,
One end on the back side of the ribbon winding shaft 6 for winding the ink ribbon 4 is held in a cantilevered state. The side cover 1 has a platen 7 and a label releaser 8 disposed near the platen 7 and bending the recording paper 2 at an acute angle.
And one end of a rewinder 9 for winding the recording paper 2 folded by the label releaser 8, and the other end of the platen 7 and the label releaser 8 are connected to a side plate (not shown) facing the side cover 1. ). Further, the side plate and the side cover 1 have a paper guide 10 facing the upper surface of the recording paper 2 and an edge guide 11 disposed below the paper guide 10 and guiding the side edge of the recording paper 2. , And a pair of transport rollers 12 are held.

Further, a head frame 14 which faces the platen 7 with the recording paper transport path 13 interposed therebetween is held on the side cover 1 in a cantilevered state. The path of the ink ribbon 4 is defined by ribbon guides 15 and 16 provided on the head frame 14 and the side cover 1. A head support 18 rotatably held by a fulcrum shaft 17, a thermal head 19 mounted on the head support 18, and a head support 18 mounted on the back surface of the head support 18 opposite to the platen 7. Slender leaf spring 2
With 0, a head assembly 21 is formed. A plurality of leaf springs 20 are arranged in a straight line along the axial direction of the platen 7, and both ends are supported such that the center is curved. The head assembly 21 is urged by a head-up spring 22 in a direction away from the platen 7, and the cam 100 presses the head assembly 21 toward the platen 7 against the urging force of the head-up spring 22.
Is provided.

As shown in FIG. 3, both ends of the head-up spring 22 are fixed to spring hook pieces 23 and 24 provided on the head frame 14 and the head support 18, respectively. The cam 100 rotates integrally with a rotary shaft 101 having a knob (not shown) at one end, and its outer periphery is in contact with the leaf spring 20 to separate the head assembly 21 from the platen 7. A pressing surface 103 whose radius from the rotation shaft 101 is gradually increased to include a stopper surface 102 that determines the position is formed.

A side cover 1 is provided with a top cover (not shown) for covering an upper space of the recording paper transport path 13 so as to be freely opened. The thermal head 19
Uses a line thermal head in which heating elements are arranged in the width direction of the recording paper 2.

In such a thermal printer,
As shown in FIG. 2, the leaf spring 20 is pressed by the pressing surface 103 of the cam 100 against the urging force of the head-up spring 22 to lower the head support 18, and the elasticity of the leaf spring 20 deformed at this time. As a result, the thermal head 19 is pressed against the recording paper 2 and the ink ribbon 4 on the platen 7.

In this state, the transport roller 12 and the platen 7
In this process, the recording paper 2 is transported one pitch at a time, and the ribbon winding shaft 6 transports the ink ribbon 4 at a speed equal to the transport speed of the recording paper 2.
9 prints desired data on the recording paper 2. Then, the printed recording paper 2 is discharged outside the thermal printer. Alternatively, the recording paper 2 can be bent at an acute angle by the label peeling member 8 and only the backing paper 2a after the label has been peeled off can be wound up by the rewinder 9.

Further, when the ink ribbon 4 is passed between the platen 7 and the thermal head 19 or during maintenance, as shown in FIG.
00 is rotated counterclockwise together with the rotating shaft 101, and the head assembly 21 is rotated in a direction away from the platen 7 by the urging force of the head-up spring 22.

[0009]

As described above, when the cam 100 is rotated counterclockwise and the head assembly 21 is rotated upward about the fulcrum shaft 17 by the urging force of the head-up spring 22. 3, the head-up spring 22 is connected to the stopper surface 10 of the cam 100.
In the state where the head assembly 21 is in contact with the platen 2, the position at which the head assembly 21 is separated from the platen 7 is determined. In this state, the cam 100
Since the whole is located above the uppermost part of the leaf spring 20, the distance between the cam 100 and the head assembly 21 becomes longer, which causes an increase in the size of the apparatus. Also, the head assembly 21 cannot be pressed against the platen 7 unless the rotation angle of the cam 100 is increased by the length of the distance.
When the rotation angle of the cam 100 is restricted, the head assembly 21
Cannot be widened. In this case,
Since the space between the platen 7 and the thermal head 19 is reduced, the workability of the setting or maintenance of the ink ribbon 4 is deteriorated.

In order to increase the rotation angle of the head assembly 21, the pressing force of the cam 100 must be efficiently transmitted to the leaf spring 20. From this point of view, the cam 100
When the cam 100 pushes the head assembly 21 toward the platen 7 from a state in which the leaf spring 20 is horizontal with respect to the stopper surface 102, the leaf spring 20 The inclination angle of the cam 20 becomes large, and the cam 100 easily slides on the leaf spring 20. Therefore, the leaf springs 20 are mounted so as to be substantially horizontal in the middle of the rotation range of the head assembly 21, and the leaf springs at both ends of the rotation range of the head assembly 21 with respect to the horizontal line in the middle. 20 inclinations are sorted. For this reason, when the head assembly 21 is farthest from the platen 7, the leaf spring 20 is inclined to the stopper surface 102 of the cam 100, and the edge contacts the stopper surface 102. As a result, the edge of the hard leaf spring 20
Bites into the stopper surface 102. Thereby, the cam 10
0 and the operation of the head assembly 22 becomes dull.

[0011]

According to the present invention, a head assembly having a thermal head is rotatably held by a fulcrum shaft, and the head assembly is biased by a head-up spring in a direction away from a platen. A plate spring supported on the back surface of the head assembly opposite to the platen is pressed by a rotatable cam to rotate the head assembly against the urging force of the head-up spring. In a thermal printer in which the thermal head is resiliently contacted with the platen by the elasticity of the leaf spring, the cam is in contact with a flat surface of the leaf spring to separate the head assembly from the platen. And a protrusion adjacent to the protrusion when the head assembly is most separated from the platen. A pressing recess which is continuous with the protrusion from the side opposite to the clearance recess and whose radius from the center of rotation of the cam is gradually increased as the distance from the protrusion increases, and which presses the flat surface of the leaf spring. Face and
Is provided on the outer periphery of the thermal printer.

[0012]

When the head assembly is separated from the platen by the urging force of the head-up spring, the position of the head assembly is determined by the contact between the flat surface of the leaf spring and the projection of the cam. In this state, the edge of the leaf spring is located in the escape recess of the cam, so that the leaf spring does not bite into the cam. When the cam is turned and the leaf spring is pressed by the pressing surface, the head assembly turns to the platen side, and the thermal head is pressed against the platen by elastic deformation of the leaf spring.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. 2 and 3 are denoted by the same reference numerals, and description thereof is omitted. Cam 2 used in this embodiment
5 is fixedly fitted to a rotating shaft 26 having a knob (not shown) at one end. As shown in FIG. 1B, the outer peripheral surface of the cam 25 is provided with a projection 27 which abuts on a flat surface 20 a which is not an edge of the leaf spring 20 and determines a position where the head assembly 21 is separated from the platen 7. An escape recess 28 that is adjacent to the projection 27 and avoids interference with the edge of the leaf spring 20 when the head assembly 21 is most separated from the platen 7, and a cam that is continuous from the opposite side of the escape recess 28 of the projection 27 A pressing surface 29 that presses the flat surface 20 a of the leaf spring 20, with the radius from the rotation center (the center of the rotation shaft 26) of the plate spring 20 gradually increasing as the distance from the protrusion 27 increases.
Are provided on the outer periphery. The projection 27 is provided on the platen 7.
Not only determines the separation position of the head assembly 21 with respect to, but also functions as a pressing portion that presses the leaf spring 20 to press the head assembly 21 toward the platen 7. The shape of the adjacent relief recess 28 is determined so that the intermediate portion of the flat surface 20 a of the leaf spring 20 is pressed without interfering with the edge of the leaf spring 20.

In such a configuration, when the cam 25 is rotated counterclockwise together with the rotating shaft 26 from the state shown in FIG. 1A, as shown in FIG. The urging force causes the head assembly 21 to rotate clockwise about the fulcrum shaft 17 to rotate the platen 7.
Depart from. In this state, the flat surface 20 of the leaf spring 20 is
a and the projection 27 of the cam 25 contact the head assembly 2
1 is determined. Thus, it is not necessary to form a stopper for stopping the head assembly 21 at the head-up position against the urging force of the head-up spring 22 by a separate member. Accordingly, it is possible to reduce the number of parts and reduce costs.

In this state, the edge of the leaf spring 20 is located in the escape recess 28 of the cam 25.
Biting of the leaf spring 20 with respect to. further,
In this state, since a part of the cam 25 is located closer to the platen 7 than the edge of the leaf spring 20, the interval between the rotation center of the cam 25 and the rotation center of the head assembly 21 can be reduced. As a result, the head assembly 21 can be largely rotated with a small rotation angle of the cam 25, and the space occupied by the head assembly 21 and the cam 25 can be reduced, thereby contributing to downsizing of the apparatus.

In addition, the fact that a part of the cam 25 is located closer to the platen 7 than the edge of the leaf spring 20 is as shown in FIG.
When the cam 25 is rotated clockwise from the state shown in (b) to press the head assembly 21 toward the platen 7,
The head assembly 21 can be largely rotated at a small rotation angle of the cam 25. In this case, as described above, since the edge of the leaf spring 20 is prevented from biting into the cam 25, the cam 25 and the head assembly 21 can be smoothly rotated. In this case, the thermal head 19 is pressed against the recording paper 2 and the ink ribbon 4 on the platen 7 by the pressure of the leaf spring 20 curved by the pressing force of the cam 25.

The present invention is also applied to a case where printing is performed using thermosensitive coloring paper without using the ink ribbon 4.

[0018]

According to the present invention, a leaf spring supported on the back of a head assembly urged in a direction away from a platen by a head-up spring is pressed by a cam, and the elasticity of the leaf spring at this time causes thermal In a thermal printer in which a head is resiliently brought into contact with a platen, a projection which comes into contact with a flat surface of the leaf spring to determine a separation position of the head assembly with respect to the platen; A relief recess that avoids interference with the edge of the leaf spring when the assembly is most separated from the platen; and a radius from the center of rotation of the cam that is continuous with the projection from the opposite side of the relief recess. A hook-shaped cam provided on the outer periphery with a pressing surface that is gradually larger as it moves away from the plate spring and presses the flat surface of the leaf spring is used. In the state where the head assembly is separated from the platen by the urging force of the head-up spring, the position of the head assembly is determined by the contact between the flat surface of the leaf spring and the projection of the cam. By locating the edge in the recessed portion of the cam, it is possible to prevent the leaf spring from biting into the cam and smoothly rotate the cam and the head assembly. Further, when the head assembly is separated from the platen, a portion of the cam is located closer to the platen than the edge of the leaf spring, so that the distance between the rotation center of the cam and the rotation center of the head assembly is reduced. be able to. As a result, the head assembly can be largely rotated at a small rotation angle of the cam, and the space occupied by the head assembly and the cam can be reduced, thereby contributing to downsizing of the apparatus.

[Brief description of the drawings]

FIGS. 1A and 1B show an embodiment of the present invention, in which FIG. 1A is a longitudinal side view showing a state where a head assembly is pressed against a platen by a cam, and FIG. It is a longitudinal side view which shows a state.

FIG. 2 is a vertical sectional side view showing an internal structure of a conventional thermal printer.

FIG. 3 is a vertical sectional side view showing a state where the head assembly is separated from a platen.

[Explanation of symbols]

 Reference Signs List 7 platen 17 fulcrum shaft 19 thermal head 20 leaf spring 20a flat surface 21 head assembly 22 head-up spring 25 cam 27 protrusion 28 escape recess 29 pressing surface

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 25/312 B41J 2/32 B41J 2/325 B41J 25/316

Claims (1)

(57) [Claims] A head assembly having a thermal head rotatably held by a fulcrum shaft, and a head-up spring for urging the head assembly in a direction away from a platen, and The leaf spring supported on the opposite side is pressed by a rotatable cam to rotate the head assembly against the urging force of the head-up spring, and the thermal action is performed by the elasticity of the leaf spring. In a thermal printer in which a head is resiliently brought into contact with the platen, the cam abuts on a flat surface of the leaf spring to determine a separation position of the head assembly with respect to the platen; An escape recess that is adjacent to avoid interference with the edge of the leaf spring when the head assembly is most separated from the platen; A pressing surface which is continuous with the protrusion from the side opposite to the escape concave portion, and which has a radius from the center of rotation of the cam gradually increased as the distance from the protrusion is increased and presses the flat surface of the leaf spring; A thermal printer.