JPH09141969A - Head up mechanism for thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a ribbon from sagging due to pull out of a paper by providing a drive means for changing the rotational direction of a motor through a planetary gear provided in the motor gear and switching transmission of power between platen roller and lever. SOLUTION: At the time of printing, a motor gear 21 fixed to a motor is turned in the direction of an arrow and power is transmitted through a planetary gear 22 and gears 24, 25 to a platen roller gear 26. The platen roller gear 26 is fixed with a platen roller which rotates upon rotation of the motor. Upon finishing the printing, rotation of the motor is reversed. When the motor gear 21 is turned, the planetary gear 22 is disengaged from the gear 24 and engages a head up gear 23 which is thereby turned. The head up gear 23 is fixed with a head up shaft which is also turned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for separating a head of a thermal printer from a platen roller by utilizing a driving force for feeding a sheet.

[0002]

2. Description of the Related Art A thermal printer for recording using thermal paper or transfer ribbon is widely used as a recording device. The thermal printer uses a thermal head in which heating elements are arranged in a row as a recording head, and selectively energizes the heating elements of the thermal head to record a desired pattern. Further, in the thermal printer, the platen roller is provided at a position where the platen roller is in uniform contact with the heating element of the thermal head. The printer is provided with a mechanism for pressing the thermal head to apply a pressing force suitable for printing to the platen roller. Recording paper is passed between the platen roller and the thermal head, and recording and paper feeding are performed while rotating the platen roller. The mechanism that supports the thermal head is equipped with a mechanism that lifts the thermal head using a lever to release the pressure on the platen roller (hereinafter referred to as "head-up"). Insert paper. After setting the paper, operate the lever to return the thermal head to the print position and print. In a thermal transfer printer using a transfer ribbon, a sheet of paper and an ink ribbon are passed between a thermal head and a platen roller, and the heat of a thermal head heating element transfers the ink of the ink ribbon to the sheet for printing.

[0003]

In order to take out the paper after printing, the head is raised and the paper is taken out. In the thermal transfer printer, when the thermal head is pressed against the platen roller at the end of printing and the paper is pulled out, the ink ribbon is pulled out from the ribbon cassette together with the paper. If printing is performed with the ink ribbon pulled out, wrinkles occur on the ink ribbon, and print fading occurs and the print quality deteriorates. When the ink ribbon was pulled out, the ribbon cassette had to be removed from the printer body and the reel of the ribbon cassette had to be wound to wind up the ink ribbon, and measures were taken to prevent the ink ribbon from being pulled out. . When the ink ribbon is pulled out, a mechanism is provided to reversely rotate the ink ribbon to loosen it, but a sensor for detecting the ink ribbon and a power transmission mechanism for rewinding the ink ribbon are required.

An object of the present invention is to prevent the occurrence of slack in the ribbon due to the pulling out of the paper by providing a mechanism for raising the head at the end of printing.

[0005]

In order to achieve the above object, the present invention provides a thermal head provided on a support frame, a platen roller provided at a position where the thermal head heating element portion is in contact, and the platen roller. In a thermal printer having a driving means for driving the thermal head, a pressing means for pressing the thermal head against the platen roller, and a lever for pressing and releasing the thermal head against the platen roller. And a drive means for switching the power transmission to the platen roller and the power transmission to the lever by changing the rotation direction of the motor by a planet gear provided on the motor gear.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. 1A is a front view showing a thermal head supporting portion of the present invention, FIG. 1B is a perspective view of a side surface of a thermal head carriage in a printing state, and FIG. 1C is a thermal head carriage in a head-up state. It is a perspective view of a side surface. As shown in the figure, the platen roller 2 is attached to the printer body 9.
And the carriage 7 is attached by the shaft 8. The carriage 7 is provided so as to be movable along the shaft 8, and the printing position can be changed. The carriage 7 is provided with a thermal head 1, a lever 3, a pressure spring 4, and a ribbon cassette (not shown). The thermal head 1 is provided on the carriage 7 so as to be rotatable by the shaft 6 and the heating element of the thermal head uniformly contacts the platen roller 2.
A pressure spring 4 is provided between one end of the thermal head 1 and the lever 3, and the thermal head 1 can be pressed against the platen roller 2 or released by operating the lever 3. The head-up shaft 5 is the printer body 9
Is provided over the moving direction of the carriage. The head-up shaft 5 is configured to engage with the protrusion 3a of the lever 3 in a printing state, and the protrusion 3a is lifted upward in the drawing by the rotation of the head-up shaft 5. There is. A head-up gear 23 is attached to the printer drive unit side 10 of the head-up shaft 5 as shown in FIG.

At the time of printing, the motor gear 21 attached to the motor (not shown) is rotated in the direction of the arrow in FIG. 2, and the power is applied to the platen roller gear 26 via the planetary gear 22, gears 24, 25. introduce. The platen roller 2 is attached to the platen roller gear 26, and the platen roller 2 is rotated by the rotation of the motor. At the end of printing, the motor is rotated as shown in FIGS. When the motor gear 21 rotates in the direction shown in the figure, the planet gear 22 separates from the gear 24 and meshes with the head-up gear 23 to rotate the head-up gear 23. The head-up shaft 5 is attached to the head-up gear 23, and the head-up shaft 5 rotates. Head up shaft 5
When is rotated, as shown in FIG. 1B, the protrusion 3a provided on the lever 3 engaged with the head-up shaft 5 is pushed, the lever 3 is rotated, and the head is raised. A pressure spring 4 is provided between the lever 3 and the thermal head 1.
Is provided and the pressure spring 4 is pulled in the printing state. Therefore, when the protrusion 3a of the lever 3 is slightly moved upward by the head-up shaft 5, this spring force causes the lever 3 to move to the head open side. Pulled back, Figure 1
The state shown in FIG. Head down is performed by operating the lever 3.

Since the head-up shaft 5 is provided over the range in which the carriage 7 moves even if the carriage 7 moves, the head-up gear 23 can be rotated by rotating the motor in the reverse direction regardless of the position of the carriage 7. If
The lever 3 rotates so that the thermal head 1 can be separated from the platen roller 2. When printing is restarted, when the motor is rotated in the printing direction, the planetary gear 22 separates from the head-up gear 23, meshes with the gear 24, and transmits power to the platen roller gear 26. The head-up gear 23 is returned to the standby position shown in FIG. 2 by the spring 27 when the planet gear 22 is separated. In this way, the thermal head can be separated from the platen roller simply by reversing the motor when printing is completed, and the motor can be rotated normally when printing is started.

[0008]

According to the present invention, since the thermal head can be separated from the platen roller 2 at the end of printing,
The ribbon is no longer pulled out by mistake while pulling out the paper while the thermal head is being pressed against the platen roller 2. Further, since the head-up can be completed by simply rotating the paper feed motor in the reverse direction, power for head-up is not required.

[Brief description of the drawings]

1A is a front view showing a thermal head support portion of the present invention, FIG. 1B is a perspective view of a side surface of a thermal head carriage in a printing state, and FIG. 1C is a side view of a side surface of the thermal head carriage in a head-up state. It is a perspective view.

FIG. 2 is a diagram showing a platen roller drive unit.

FIG. 3 is a diagram illustrating an operation of a drive unit at the start of head-up.

FIG. 4 is a diagram illustrating an operation of a drive unit when head up.

[Explanation of symbols]

 1 Thermal Head 2 Platen Roller 3 Lever 4 Pressure Spring 5 Head Up Shaft 21 Motor Gear 22 Planetary Gear 23 Head Up Gear

Claims (1)

[Claims] A thermal head provided on a support frame, a platen roller provided at a position where the thermal head heating element portion is in contact, a driving means for driving the platen roller, and a thermal head applied to the platen roller. In a thermal printer having a pressing means for pressing and a lever for pressing and releasing the thermal head on the platen roller, a driving means for moving the lever is provided, and the driving means is provided on a motor gear. A head-up mechanism for a thermal printer, characterized in that the transmission of power to the platen roller and the transmission of power to the lever are switched by changing the rotation direction of a motor by the planet gears.