JPH078221Y2 - Printer platen mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a platen mechanism of a printer.

(Prior Art) A platen mechanism of a printer according to the prior art will be described with reference to the drawings.

FIG. 6 is a plan view showing a schematic configuration of a printer according to the prior art, and FIG. 7 is a side view seen from the direction A in FIG. In FIG. 6, the platen mechanism 1 includes a platen 2 and a bearing.
3 and 4, a platen pulley 5, an LF belt 8 as a drive belt, an LF motor 6 and a drive pulley 7 as a platen drive unit. The platen 2 is composed of a roll portion 2a, a shaft portion 2b at one end and a shaft portion 2c at the other end, and the shaft portions 2b and 2c are fitted into side frames 12 and 13 as frames located on both left and right sides of the printer. It is rotatably supported by bearings 3 and 4. A platen pulley 5 is fixed to an extension portion of the shaft portion 2b penetrating the bearing 3. The LF motor 6 is fixed to the side frame 12, and the drive pulley 7 is fixed to the motor shaft 6a of the LF motor 6. An LF belt 8 that transmits a driving force is wound between the drive pulley 7 and the platen pulley 5. A carriage 10 to which the print head 9 is fixed is located in front of the roll portion 2a of the platen 2, and slides in the direction of arrow BC along the main shaft 11 fixed to the side frames 12 and 13 in parallel with the platen 2. . Platen 2
Pin tractors 14 and 15 for conveying the print medium 16 are provided behind the roll portion 2a, and slide along a shaft (not shown) rotatably supported by the side frames 12 and 13. The platen 2 and the pin tractors 14 and 15 are connected by a driving force transmission mechanism (not shown).

Next, the operation will be described.

When the carriage 10 slides along the main shaft 11 in the direction of arrow C by a drive source (not shown), the print head 9 moves to the medium.
Print on 16. After printing one line, the platen 2 and the pin tractors 14 and 15 are rotated by one line by the LF motor 6, and the medium 16 is fed. Subsequently, the carriage 10 slides in the direction of arrow B, and the print head 9 prints on the medium 16. After that, this printing operation is repeated. These printing operations are performed based on commands from a control unit (not shown).

(Problems to be Solved by the Invention) However, in the platen mechanism of the printer having the above-described configuration, the tension of the drive belt exerts a force of pulling each other in the direction connecting the centers of the drive pulley and the platen pulley. By the way, there is a play due to fitting between the frame and the bearing and between the bearing and the shaft portion of the platen. Therefore, the shaft and the bearing of the platen near the drive belt move toward the center of the drive pulley and are biased.
On the other hand, the movement of the shaft and bearing of the platen farther from the drive belt is in the same direction as the movement of the shaft and bearing of the platen closer to the drive belt but in the opposite direction. As a result,
The distance between the platen and the main shaft varies between frames.
A difference of 0.03 mm to 0.06 mm is produced. When printing, the gap between the roll of the platen and the tip of the print head (hereinafter referred to as the head gap) is determined. This head gap is determined by abutting the leading end of the print head against the roll portion of the platen at, for example, the 13th character position from the print start position provided at the position closest to the drive belt within the movement range of the print head. When printing is performed in this state, when the print head is closer to the drive belt, printing is performed on the print paper with an appropriate head gap. However, when the print head moves farther from the drive belt, the head gap becomes narrower, so that the axial compression load on each dot pin of the print head from the roll side of the platen gradually increases. Since the tip of the dot pin collides with the printing paper and the roll portion at a high speed, it receives a shock of several times the static axial compression load and buckles. As a result of the axial compressive load due to this repeated impact, the pin guide and the dot pin at the tip of the print head cause abnormal wear, and the life of the print head is shortened. In extreme cases, the pin may break.

In addition, there is a gap of about 0.05 mm between the print paper and the ink ribbon, but when the print head moves toward the narrower head gap, the ink ribbon and print paper come into contact with each other, and There was a problem that dirt was generated.

This invention considers the platen as a lever and uses the principle of lever,
A force of equal magnitude in the same direction as the tension of the drive belt is applied to the other end of the platen. As a result, the inclination of the platen with respect to the main shaft is eliminated, and the leading end of the print head prints on the print paper with an appropriate head gap with respect to the roll of the platen.

(Means for Solving the Problems) In order to solve the above problems, the platen mechanism of the printer according to the present invention applies a force having the same magnitude in the same direction as the tension of the drive belt between the other end of the platen and the frame. A force generating means for generating is generated.

According to the present invention, in the platen mechanism of the printer in which both ends of the platen are pivotally supported by the frame and one end of the platen and the platen drive unit are connected by the drive belt, the same direction as the tension of the drive belt is applied. Since the force generating means for generating a force having the same magnitude is provided between the other end of the platen and the frame, both ends of the platen, which are pivotally supported, are brought to the frame by the same force in the same direction, and the main shaft There is no tilt of the platen with respect to. Therefore, a proper head gap can be obtained.

(Embodiment) An embodiment of the present invention will be described with reference to the drawings.

The elements common to the drawings are given the same reference numerals. 1 is a plan view of a platen mechanism of a printer according to the present invention, FIG. 2 is a partial perspective view as seen from the direction E of FIG. 1, and FIG. 3 is a sectional view taken along the line GG of FIG. It is a figure.

In FIG. 1, the difference from the prior art is that a platen lever 17 as a force generating means is provided between the other end of the platen 2 and the side frame 13. As shown in FIG. 2, the platen lever 17 is a substantially L-shaped elastic body (eg, polyurethane rubber). One end 17a is rotatably attached to a shaft 2c at the other end of the platen 2. Also, the other end 17
b is the platen pulley 5 provided at one end of the platen 2 and the LF
The notch 13 of the side frame 13 is formed so as to be substantially aligned with the direction connecting the center of the drive pulley 7 provided on the motor 6.
Lock to a. At this time, the central portion 17c of the platen lever 17
The contact portion 18 between the cutout portion 13a and the other end portion 17b due to the bending of the
A tensile force H is generated between a and the contact portion 18b of the shaft portion 2c and the one end portion 17a. This thrust force H can be decomposed into a component force I in the axial direction of the platen 2 and a component force J in the direction connecting the center between the platen pulley 5 and the drive pulley 7 provided in the LF motor. The component force J is made equal to the pulling force K of the LF belt 8 as shown in FIG. Therefore, the shaft portions 2a and 2b of the platen 2 and the bearings 3 and 4 are pressed in the same direction with the same force. Therefore, the head gap F between the roll portion 2a of the platen 2 and the tip portion 9a of the print head 9 is equal at any position within the print range. According to this embodiment, since the platen lever is engaged with the platen shaft portion between the roll portion and the bearing of the platen, the platen side may be the same as the prior art.

Alternatively, the shaft portion 2c at the other end of the platen may be extended and the platen lever may be engaged with the portion through which the bearing passes.

In this case, since the position where the tension force of the platen lever acts is far from the contact portion between the shaft portion at one end of the platen and the bearing, the action force may be smaller than that of this embodiment due to the lever principle. Therefore, the force for attaching and detaching the platen lever is small, and the bending force applied to the central portion of the platen lever is also small.

FIG. 4 is a plan view of a platen mechanism of a printer according to another embodiment, and FIG. 5 is a side view seen from the L direction in FIG. In FIG. 4, the spring post 20 may be fixed to the side frame 13 in parallel with the platen 2, and a tension spring may be provided between the shaft portion 2c of the platen 2 and the spring hook 20a of the spring post 20 as a tension generating means.

In this case, since the tension spring can be provided in parallel with the LF belt as shown in FIG. 5, the tension of the tension spring and the tension direction of the LF belt can be made the same.
In addition, since the tension can be accurately calculated and set for both the LF belt and the tension spring, it is possible to apply a balanced tension to the platen.

(Advantages of the Invention) In the present invention, in the platen mechanism of a printer in which both ends of a platen are pivotally supported by a frame, and one end of the platen and the platen drive unit are connected by a drive belt, the platen mechanism is mounted in the same direction as the tension of the drive belt. Since the tension generating means for generating a force by bending is provided between the other end of the platen and the frame, the inclination of the platen with respect to the main shaft is eliminated, and the dot pin of the print head is on the platen roll side during printing. Since the axial compressive load received from the device is kept within the proper load range to eliminate unnecessary buckling, abnormal wear and dot pin breakage between the pin guide and dot pin at the tip of the print head are eliminated, and the life of the print head is improved. I can keep it. In addition, since the gap between the printing paper and the ink ribbon can be maintained at a proper gap, unnecessary contact between the printing paper and the ink ribbon does not occur, and printing stain does not occur.

[Brief description of drawings]

FIG. 1 is a plan view of a platen mechanism of a printer according to the present invention, FIG. 2 is a partial perspective view seen from the direction E, and FIG.
FIG. 4 is a plan view of a platen mechanism of a printer according to another embodiment, FIG. 5 is a side view seen from the L direction in FIG. 4, and FIG. FIG. 7 is a plan view showing a schematic configuration of the printer, and FIG. 7 is a side view seen from the direction A in FIG. 1,19,22 …… Platen mechanism, 2 …… Platen, 8 …… LF
Belts, 12, 13 …… Side frames, 17 …… Platen levers, 21 …… Tension springs.

Claims (1)

[Scope of utility model registration request] 1. A platen having both ends thereof pivotally supported by a frame,
In a platen mechanism of a printer in which one end of the platen and a platen drive unit are connected by a drive belt, force generating means for generating a force having the same magnitude in the same direction as the tension of the drive belt is connected to the other end of the platen. A platen mechanism for a printer provided between the frame and the frame.