JPH0582828B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention provides a support for a thermal head in a line-end type thermal printer in order to bring the thermal head into pressure contact with the platen when in use and to separate it from the platen when not in use. The thermal head support is moved by a polygonal cylindrical cam that is rotatably mounted and rotated in one direction by a drive motor.

[Industrial application field]

The present invention relates to a thermal printer using a lined thermal head.

Thermal printers are fast, low noise, low cost,
This printer has many features such as being maintenance-free, and its configuration is simple, lightweight, and compact, making it widely used. Especially measuring instruments,
The field of use is expanding to include medical machines, office machines, etc., and it is also attracting attention as an on-board printer.

As the field of use expands, simplicity in structure and operation method is increasingly desired, and so-called "one-button operation" is required, and thermal printers are advantageous in meeting this demand. It's in a good position.

[Conventional technology]

High speed is now required of thermal printers, and it is effective to use a line-end thermal head to achieve this. In order to guarantee printing with line dot thermal heads,
This is carried out by using a relatively low-hardness platen (for example, a rubber platen) and placing thermal paper or the like in the gap between them, but at this time it is necessary to maintain the pressure applied to the thermal paper above a certain value.

A constant pressure is required during printing, but that pressure is not required when not printing.If pressure is left unattended, the low hardness rubber platen will undergo more or less permanent deformation, causing problems during the next printing. It will have a defect that causes In order to avoid such troubles, various mechanisms have been proposed to keep the platen and thermal head apart. For example, in order to separate the thermal head from the platen, a cam provided on the platen shaft is manually brought into contact with the thermal head support plate, and a similar cam rotation shaft is provided separately from the platen shaft. These mechanisms are in most cases manual. Some devices use a motor to drive the cam, but they utilize the reciprocating motion of the cam.
Therefore, in order to keep the thermal head pulled out, it is necessary to constantly supply current to the motor to ensure the holding force, and it is also necessary to feed the paper at the same time when the thermal head is returned to its original position. This may cause inconveniences such as Of course, it would be possible to use a motor or solenoid that works only for the operation of this mechanism, but such an idea would result in an expensive product.

[Problem that the invention seeks to solve]

The basic problem is automating the mostly manual actuation of the cam used in conventional thermal printers to separate the lined thermal head from the platen.

Some devices use a motor to drive the above-mentioned cam, but in this case, there are disadvantages and drawbacks as pointed out above.

[Means for solving problems]

The above-mentioned problems can be solved by the following thermal printer according to the present invention, which includes a head support which is attached with a dot thermal head and is rotatable around a head rotation axis parallel to the dot line. a pressurizing elastic body attached to the head support for pressing the lined thermal head against the platen; and a pressurizing elastic body disposed on the opposite side of the lined thermal head with respect to the head rotation axis and in contact with the head support and driven. It consists of a polygonal cylindrical cam that is rotated by a motor, and the rotation of the polygonal cylindrical cam presses the line dot thermal head against the platen or moves it away from the platen, and the drive motor 8 moves the thermal paper to the platen. The drive motor 8 is the same as the drive motor 1, and is a one-way clutch that rotates only the platen 1 when the drive motor 8 rotates in one direction, and rotates only the polygonal cam 5 when the drive motor 8 rotates in the other direction. It is characterized by comprising a transmission device 13 including.

The polygonal cylindrical cam is rotated by the reverse rotation of the motor, using the torque of the motor that is sufficient to rotate the platen against the head pressure (pressure force that presses the thermal paper against the platen by the thermal head) during printing. In order to overcome head pressure, it is preferable to locate the polygonal cylindrical cam at a distance from the head axis of rotation close to or further from the attachment point of the pressurizing elastic body (eg, a spring).

The polygonal columnar cam that causes the rotatable head support to make reciprocating angular movements is preferably trigonal to pentagonal because the difference in height is 1/2 of the diameter between the circumscribed circle and the inscribed circle of the polygon. .

Furthermore, since it is desirable to have a printer structure that allows the characters or figures printed by the line-dot thermal head to be viewed as quickly as possible, the position of the polygonal cylindrical cam is set at the opposite side of the thermal head, that is, the platen, with respect to the head rotation axis. It is set as.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail by way of embodiments with reference to the accompanying drawings.

The thermal printer according to the present invention illustrated in FIGS. 1 and 2 basically consists of a low-hardness platen (rubber platen) 1, a lined thermal head 2, a rotatable head support 3, and a pressurized elastic body. (spring) 4, and a polygonal columnar cam 5. The platen 1 has a rotating shaft 6 connected to a gear transmission 7 (second
(Fig.) by motor (e.g. pulse motor) 8
is connected to. In addition, a one-way clutch is employed in the gear transmission 7 so as not to transmit the rotation to the platen 1 when the motor rotates in reverse (for example, a one-way clutch is installed between the platen rotating shaft 6 and the gear attached to it). ). The head support 3 is rotatable (actually, swinging or reciprocating angular movement) about the head rotation axis 9, and the line head thermal head 2 is attached to the position corresponding to the platen 1, and the line head thermal head 2 is attached to the opposite side. A pressurizing elastic body 4 is attached to the end portion 11. This pressurizing elastic body (spring) 4 acts to pull the head support end 11 upward, so that the thermal head 2 is pressed against the platen 1 with the pressure necessary for printing.

The polygonal prism-shaped cam 5 is shown as a regular square prism in FIG. 1 and as a regular triangular prism in FIG. 2, and each corner is chamfered. The polygonal columnar cam 5 is connected to its cam rotation shaft 1.
2, and is connected to the platen drive motor 8 by a gear transmission 13. Gear transmission device 1 for polygonal columnar cam
3 and the gear transmission for the platen have some overlap, and when the motor 8 rotates in reverse, the rotation is transmitted to the polygonal columnar cam 5, but during normal rotation (motor rotation for platen rotation), the rotation is transmitted to the polygonal columnar cam 5. A one-way clutch is employed to prevent transmission (e.g., mounted between the cam rotation shaft 12 and the gear attached thereto). A head rotation shaft 9 is supported by a thermal printer housing 14, a portion of which is shown in FIG.
Motor 8, gear transmission 7, 13, pressurized elastic body 4
The other end is supported by a casing (not shown). A connector 15 (see Figure 2) is used to transmit electrical signals to the lined thermal head 2.
is attached to the head support 3.

In the above-mentioned thermal printer, thermal paper (not shown) is placed between the thermal head 2 and the platen 1, and the thermal head 2, head support 3, and polygonal cam 5 are arranged in the printing state. This is shown by the solid line in FIG. At this time, the head support 3 is moved around the head rotation axis 9 so that the head support end 11 is pulled up by the spring 4, and as a result, the thermal head 2 presses the thermal paper against the platen 1. The platen 1 is rotated by the motor 8 via the gear transmission 7 in the direction of arrow A (the direction in which the thermal paper is sent out), and the polygonal cylindrical cam 5 is stopped at the rotation position shown by the solid line and the head support 3 It is in a state where it is not in contact with.

When the printing operation is completed, a reverse rotation signal is sent to the motor 8 to rotate the polygonal columnar cam 5 via the gear transmission 13 in the rotational direction B to the position shown by the broken line in FIG. 1 and stop at that position. For example, if the motor 8 is a pulse motor, a predetermined rotational position can be controlled by a predetermined pulse, and if it is a DC motor, a stop switch that is braked by a polygonal cam 5 is installed to control the predetermined rotational position. The rotation direction of the polygonal columnar cam 5 is determined by connecting the one-way clutch to the motor 8.
Since it is provided between the cam rotation shaft 12 and the cam rotation shaft 12, it can only be directed in a certain direction, for example, the B direction (FIG. 1). On the other hand, when the motor 8 is rotated in the reverse direction, the platen 1 is also rotated in the reverse direction via the gear transmission 7, which is undesirable as it may cause the thermal paper to return. 1, and the platen 1 is in a stopped state. In this way, the polygonal columnar cam 5
By rotating 45 degrees in the figure (or 60 degrees in FIG. 2), the chamfered corners of the polygonal columnar cam 5 come into contact with the head support 3 and push it down. Therefore, the head support 3
is the force that overcomes the tensile force of the spring 4, and the head rotation shaft 9
The thermal head 2 is rotated slightly clockwise in FIG. 1 around , and the thermal head 2 is separated from the platen 1.

Next, when printing, the motor 8 is reversely rotated to rotate the polygonal columnar cam 5 as described above.
is further rotated in direction B so that the cam 5 does not push down the head support 3. Therefore, the thermal head 2 presses the platen 1.
Then, the motor 8 is normally rotated to rotate the platen 1 in the A direction.

In the thermal printer shown in FIG. 2, the head support 3 on which the thermal head 2 is fixed is connected to a second head rotation axis which is arranged at right angles to the rotation center axis of the platen 1 when viewed from the top. 16
(Fig. 2).
Although this rotation is limited by the housing 14, it is effective in making the pressure between the thermal head 2 and the platen 1 uniform over the entire contact area.

〔Effect of the invention〕

When the platen driving motor is not used to drive the platen, it is reversely rotated to rotate a polygonal columnar cam that reciprocates the support body of the thermal head. In this manner, by controlling the rotation of the motor, it is possible to easily maintain the thermal head separated from the platen. Moreover, the reverse rotation control of the motor can be performed without affecting the feeding of the thermal paper.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic structure of a thermal printer according to the present invention, and FIG. 2 is a perspective view of essential parts of the thermal printer according to the present invention. DESCRIPTION OF SYMBOLS 1...Platen, 2...Line dot thermal head, 3...Head support, 4...Pressure elastic body, 5...Polygonal columnar cam, 8...Motor, 9...
Head rotation axis.

Claims (1)

[Claims] 1 A head support 3 on which the line dot thermal head 2 is attached and rotatable around a head rotation axis 9 parallel to the dot line; and a head support 3 attached to the head support 3 for pressing the line dot thermal head 2 against the platen 1. a polygonal columnar cam 5 disposed on the opposite side of the linear head thermal head 2 with respect to the head rotation axis 9, in contact with the head support 3, and rotated by a drive motor 8; The rotation of the polygonal columnar cam 5 forces the lined thermal head 2 against or away from the platen 1, and the drive motor 8 serves as a drive motor for the platen 1 for feeding thermal paper. The transmission device 13 includes a one-way clutch that rotates only the platen 1 when the drive motor 8 rotates in one direction, and rotates only the polygonal cam 5 when the drive motor 8 rotates in the other direction. A thermal printer characterized by comprising: