JPH065178Y2 - Thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a thermal printer for pressing and releasing a print head to a platen.

<Prior Art> Conventionally, there is a printer that performs printing using a thermal head. In such a printer, as shown in FIG. 8, a head-up lever 3 is supported by a guide shaft 1 and is rotated by a head spring 2 fixed to a frame (not shown). It rotates according to the rotation of the cam 5 attached to the source 4, and pushes and moves the head holder 7 carrying the head 6 pivotally supported by the guide shaft 1 to press the head 6 against the platen 8 side. Further, there is known an up / down mechanism of a printer print head that lifts the head holder 7 according to the rotation of the cam 5 by a carriage 9 and a head-up spring 10 attached to the head holder 7 to release the pressure contact.

<Problems to be solved by the invention> However, in such a conventional head up-down mechanism, since the pressure contact is gradually released by the rotation of the cam at the time of head-up, the thermal transfer printing using the ink ribbon is performed. However, there is a drawback in that unnecessary transfer occurs when the pressure contact is released and the print quality is remarkably reduced. Further, in the conventional head up / down mechanism, the pressure contact force of the head is fixed, and the difference between thermal transfer printing and thermal paper printing or
Since the pressure contact force of the head cannot be changed to the optimum value due to the difference in paper quality of the recording paper, printing was performed with the maximum required pressure contact force, but as a result of using an unnecessarily large pressure contact force, deterioration of print quality, There are drawbacks such as a decrease in printing speed, a decrease in durability, and an increase in power consumption.

The present invention eliminates such drawbacks and provides a high-quality and high-speed printing and a durable and power-saving printer printhead up-down mechanism.

<Means for Solving Problems> The present invention relates to a thermal printer for recording image information on a recording medium while repeating head-up and head-down of a thermal head arranged facing a platen surface.
A head holder on which the thermal head is mounted, a cam member for operating the thermal head in an up / down state with respect to the platen, one end of the head holder, and the other end of the cam member engaged with the cam member. A first lever that swings in response to rotation in one direction, a first elastic member that biases the head holder to bring the thermal head up, and a swing in response to rotation in one direction of the cam member. A second lever that moves, an incomplete gear formed in the cam member and a part of the second lever so that at least two types of head pressing force can be set when the head is down, and the first lever And a second elastic member which is stretched by a second lever and causes the first lever to follow the swing of the second lever when the imperfect gears are meshed with each other.

<Example> Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a printer to which the mechanism of the present invention is applied, and FIG. 2 is a perspective view of an up-down mechanism of a printer print head according to the present invention, FIGS. 3, 4, 5, and 6. The figure is
FIG. 7 is a diagram illustrating the operation of the up-down mechanism of the printer print head according to the present invention, and FIG. 7 is a tooth profile diagram of the up-down mechanism of the printer print head according to the present invention.

In FIG. 1, a head holder 7 is mounted on a guide shaft 1 so as to be movable left and right and rotatably mounted with a head 6. The carriage 9 is axially supported by the guide shaft 1 and is restricted in rotational movement by the guide rail 22 so that it can be moved only left and right.
The head holder 7 is sandwiched and an ink ribbon winding mechanism is built in. The head holder 7 moves left and right with respect to the platen 8 together with the carriage 9 when the belt 11 partially fixed to the carriage 9 is driven by the motor 12. The head holder 7 and the carriage 9 are connected by a head-up spring 10.

In FIG. 2, the guide shaft 1 includes a right guide bearing 13 and a left guide bearing 14 provided on a frame (not shown).
Is pivotally supported by. The head-up lever 3, which is a first lever, is sandwiched between the left guide bearing 14 and the right guide bearing 13, is loosely inserted into the groove 9a of the carriage 9 provided behind the head holder 7, and is rotatably attached to the guide shaft 1. It is supported. The guide shaft 1 and the head-up lever 3 are arranged on the left guide bearing 14 side via a sector lever 15 fixed to the guide shaft 1, and on the right guide bearing 13 side via a second sector gear 16 fixed to the guide shaft 1. The head springs 2 are engaged with each other. Sector gear 16
Is a second incomplete gear barrel gear A1 as shown in FIG.
6a, a gear B16b, a gear C16c, a sector imperfection 17 which is a first imperfect gear fixed to the cam 5 and rotationally driven by the head-up drive source 4 has a gear A17a and a gear B17b. It meshes with 17. The head-up lever 3 has a roller 19 rotatably attached by a pin 18,
The roller 19 is in pressure contact with the cam 5 provided coaxially with the sector pinion 17. The right guide bearing 13 has a stopper A20 for restricting the rotation of the sector gear 16, and the head-up lever 3 has a stopper A20.
Is provided with a stopper B21 for restricting the relative position thereof. Here, when the rigidity of the guide shaft 1 and the head-up lever 3 is high, at least one head spring 2 and one set of stoppers 20 and 21 may be provided on either the left or right bearing side. If the rigidity is low, head springs 2 and stoppers may be provided on both left and right sides.

Hereinafter, the operation will be described in detail with reference to operation diagrams.

FIG. 3 shows a head-up standby state, in which the head holder 7 having the head 6 mounted thereon has a head-up spring up 10
The state in which the head 6 is lifted up and the pressure contact of the head 6 is released is shown. At this time, since the head up lever 3 is lifted by the cam 5, the head holder 7 is
Head up. The head holder 7 is constantly pressed against the head-up lever 3 by the pulling force of the head-up spring 10. At this time, the sector gear 16 and the sector pinion 17 are in a state where meshing is started, and the stopper B21 and the sector gear 16 are separated from each other. Therefore, the sector gear 16 is moved to the stopper A20 by the spring force of the head spring 2, and the head up lever 3 is moved to The cams 5 are in pressure contact with each other and stand by in a stable state. Where cam 5
When is rotated in the direction of arrow A, it engages with the sector pinion 17 and starts a series of head up / down operations.

First, as the sector pinion 17 rotates, the sector pinion gear A17a and the sector gear gear B16b mesh with each other, and the sector gear 16 separates from the stopper A20 and rotates in the direction of arrow B. On the other hand, despite the rotation of the cam 5, the head-up lever 3 has a cam surface that holds its position, so that the head spring 2 gradually expands to store a pulling force. Further, as the rotation progresses, the roller 19 drops at the cam step portion A5a, and the stored spring force instantly
The head-up lever 3 rotates in the direction of arrow B to press the head 6 into pressure contact with the platen 8 via the head holder 7, and the head-down state shown in FIG. 4 is obtained. At this time, the cam surface is set so that a gap is opened between the cam 5 and the roller 19 in a state where the head 6 is pressed against the platen 8, and the pulling force of the head spring 2 is applied to a predetermined head pressing force. By setting the value to which the pulling force of the head-up spring 10 is added, a predetermined head pressure contact force can be obtained. Further, as shown by the solid line in FIG. 7, by providing the gear B16b with an imperfect gear that allows the gear A17a to ride up, the tensile force of the head spring 2 causes the sector gear 16 to move.
Rotation torque is generated in the sector pinion 17 via the, and the head-up drive source 4 is prevented from reversing. The state shown in FIG. 4 is a head-down state in which the head pressure contact force is small.

Further, when the sector pinion 17 rotates in the direction of arrow A, the gear C16c and the gear B1 smoothly move as shown by the broken line in FIG.
The meshing of 7b starts. At this time, the cam surface is the fourth
Similarly to the state shown in the figure, since the cam 5 and the roller 19 rotate with a gap maintained, the pulling force of the head spring 2 increases again and the head pressure contact force increases. Further, as the rotation advances, as in the case of FIG. 4, an incomplete gear is provided on the gear C16c so that the gear B17b runs on the gear C16c. Therefore, the head-up drive source 4 is reversed by the pulling force of the head spring 2. In a stable state, a head pressure contact force larger than that in FIG. 4 is generated. The above is the fifth
The head-down state shown in the figure has a large head contact force.

Further, when the sector pinion 17 rotates in the direction of arrow A, the sector pinion 17 has no gear to be meshed next. , The sector gear 16 is pressed against the stopper B21, and at the same time,
The head-up spring 10 rotates the head-up lever 3 and the sector gear 16 in the direction of arrow C via the head holder 7 by the pulling force until the sector gear 16 contacts the stopper A20. At this time, at the same time, the head 6 also rotates in the arrow direction, and the head pressure contact force is instantly released. This head-up state is shown in FIG.

After that, the sector pinion 17 further rotates in the direction of arrow A from the head-up state of FIG. 6 and returns to the head-up standby state of FIG. The above is a series of head up / down operations, and the head up / down operation is repeated thereafter. The selection of the pressure contact force controls the rotational position of the head-up drive source 4 and designates whether the pressure contact state at the time of printing is the state shown in FIG. 4 or the state shown in FIG. 5 depending on the printing method and paper quality. Then do.

When the printing of one line is completed with the specified pressure contact force, the head is raised and the carriage returns to the initial position and a line feed is performed at the same time.
Printing is repeated with the specified pressure contact force.

In this embodiment, the second lever is rotatable on the guide shaft 1, but the second lever does not necessarily have to be attached to the guide shaft 1, and a separate shaft may be provided.

Further, in the head-down state where the head pressure contact force is small as shown in FIG. By providing a (imperfect) gear that allows normal meshing instead of the gear A17a riding on the head, the head pressure contact force can be set continuously according to the rotational position of the sector pinion 17 as well as the large and small binary values. Can be set to the value of.

<Advantages of Device> As described above, according to the present invention, since the pressure contact force of the head can be changed, the print quality and the print speed can be improved even if the thermal transfer printing and the thermal paper printing are different or the recording paper quality is different. Good, durability of head is good, and power consumption can be saved. Further, since the head pressure contact force can be maintained without the need for a holding force due to the rotational torque from the outside, the driving source can be switched to be shared with the power of the paper feeding mechanism or the like, and a strong holding force can be applied to the driving source. It is also possible to dispense with the power supply for providing.

As described above, the present invention is extremely useful for providing high-quality and high-speed printing and a printer with high durability and power saving.

[Brief description of drawings]

1 is a plan view of an embodiment of a printer to which the mechanism of the present invention is applied, FIG. 2 is a perspective view of the printer according to the present invention, FIG. 3, FIG. 4, FIG. FIG. 7 is an operation explanatory view of an embodiment of a printer print head up / down mechanism according to the present invention, FIG. 7 is a tooth profile of an embodiment of a printer print head up / down mechanism according to the present invention, and FIG. FIG. 11 is a perspective view of an up-down mechanism of a printer print head of a conventional example. 1 is a guide shaft, 2 is a head spring, 3 is a head-up lever (first lever) 4, is a head-up drive source, 5 is a cam, 6 is a head, 7 is a head holder, 8 is , Platen, 10 is a head-up spring, 16 is a sector gear (second lever) 17, and 17 is a sector pinion (first incomplete gear).

Claims (1)

[Scope of utility model registration request] 1. A thermal printer for recording image information on a recording medium by repeating head-up and head-down of a thermal head arranged facing a platen, comprising a head holder equipped with the thermal head and the thermal head. A cam member that acts on the platen in an up / down state, one end engages with the head holder, and the other end engages with the cam member,
A first lever that swings in response to one-direction rotation of the cam member; a first elastic member that biases the head holder to bring the thermal head up; and a one-way rotation of the cam member. A second lever that oscillates accordingly; an incomplete gear formed in the cam member and a part of the second lever so that at least two or more head pressing forces can be set in the head-down state; And a second elastic member which is stretched between the first lever and the second lever, and which makes the first lever follow the swing of the second lever when the imperfect gears are meshed with each other. And a thermal printer.