JP2607512Y2 - Thermal printer - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a thermal printer for printing paper by the heat of a thermal head, and an improved pressing mechanism for uniformly pressing a thermal head attached to a frame toward a platen in order to obtain uniform printing. Thermal printer.

[0002]

2. Description of the Related Art A conventional thermal head holding and pressing mechanism is disclosed in Japanese Patent Application Laid-Open Nos. 62-11670 and 1-294081.

Japanese Patent Application Laid-Open No. Sho 62-11670 discloses a method in which a thermal head is supported by a head holder attached to a ball bearing fixed to a hinge shaft spanned between both frames. JP-A 1-294081
The thermal head disclosed in the publication is fixed to a pressing lever by a threaded connecting member via an elastic body.

[0004] Of these, Japanese Patent Application Laid-Open No. 1-294081 requires a connecting member particularly as a fixing member, and in all other cases, another holding bracket is attached to a heat sink portion of a thermal head, and a through shaft is attached thereto. It is supported on a frame as a rotating shaft and is pressed against a platen. Also,
JP-A-62-1670 and JP-A-1-29408
No. 1 presses the thermal head using the elasticity of the spring.

A conventional head pressing spring has been constituted by a single or a plurality of leaf springs or a single or a plurality of compression coil springs. If a single leaf spring is used, a leaf spring with a width approximately corresponding to the longitudinal length of the head must be used.
The pressing force in the longitudinal direction of the head becomes non-uniform, so that the adhesion between the head and the paper becomes non-uniform, and the printing quality is degraded. Further, when a leaf spring having a width corresponding to the longitudinal direction of the head is used, the weight becomes heavy and the cost is high. Further, when a plurality of springs are used, the pressing force is non-uniform due to variations in spring constant due to manufacturing variations of each leaf spring. Further, the spring constant varies depending on the variation when each leaf spring is attached to the frame, and a uniform pressing force cannot be obtained. On the other hand, when a compression coil spring is used, it is difficult to reduce the thickness of the device because a certain space for accommodating the compression coil spring is required.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it has been proposed to increase the weight and the device by a leaf spring or a compression coil spring conventionally used for pressing a thermal head. It is an object of the present invention to provide a thermal printer which can be made thinner, can uniformly press the thermal head toward the platen, and can easily attach a head pressing spring.

[0007]

To achieve the above object, according to the Invention The thermal printer according to the present invention includes a frame, a platen rotatably provided on the frame, the full
Motor fixed to the frame and driving the platen to rotate
When a thermal head is capable of contacting and separating from the said platen by swings around the pivot shaft relative to the frame, the frame for pressing the thermal head to said platen side fixing And a head pressing spring, wherein the head pressing spring has a head pressing portion formed of a linear member and
At least two coil portions, wherein the head pressing portion
Connects the two coil portions and the platen
The two coil portions are formed substantially parallel to the rotation axis of
By fixing the opposite end of the pressing portion to the frame, the two coil portions act as a torsion coil spring, and press the thermal head with this spring force. A spring is fixed to the frame by a member formed separately from the frame, and a linear pressing portion of the head pressing spring is formed integrally with the two coil portions. It has a substantially U shape.

[0008]

The protrusions formed at both ends of the heat sink of the thermal head are fitted into the locking portions formed on both sides of the frame, and when the thermal head is tilted down to the platen side, the protrusions of the heat sink are prevented from falling off, and the thermal head is prevented from falling off. Hold it securely to the frame. In addition, by locking the ends of the two coil portions formed at both ends of the linear pressing portion in contact with the head to the frame on which the thermal head is attached, the two coil portions are connected. Acting as a torsion coil spring, the thermal head can be uniformly pressed toward the platen by the linear pressing portion. Further, in order to easily attach the head pressing spring to the frame,
A head pressing spring is unitized, a sleeve is provided at an end of the unitized head pressing spring, a plate having a square hole is provided, and the sleeve is inserted into a receiving window provided in a frame. Then, after sliding down the slit portion of the receiving window and pushing it down, the whole is shifted toward the front to fit the square hole into the projection of the frame to perform positioning. For this reason, the head pressing spring is securely fixed to the frame and simultaneously presses the thermal head toward the platen.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall exploded perspective view showing one embodiment of the present invention. FIG. 2 is a sectional view of a main part showing a printing state in which a thermal head is attached to a printer main body. FIG. 3 is a cross-sectional view of a main part showing a state where the pressing of the thermal head against the platen is released.

First, the configuration will be described. Reference numeral 1 denotes a frame of the printer main body on which a rotatable platen 2 is pivotally supported. Reference numeral 3 denotes a thermal head having a heat sink unit 4. Reference numeral 5 denotes a holder in which a head pressing spring for pressing the thermal head 3 held on the frame 1 toward the platen is unitized.

Protrusions 6, 6 are formed below both ends of the heat sink portion 4 of the thermal head 3 in the longitudinal direction.
The bush 7, 7 is fitted into the bush. The bush 7 has a D-shaped cross section obtained by cutting off one side of the outer periphery.
And press fit. Locking portions 8, 8 for fitting the bushes 7, 7 are formed below both ends of the frame 1. The locking portion 8 includes a groove 8a below the hole 8b and a hole 8b having a diameter above which the cross section D of the bush 7 can rotate.

The width of the groove 8a is determined by the thermal head 3
When attaching the thermal head 3 to the frame 1, the bush 7 slides, and the attached thermal head 3 is attached to the platen 2.
The diameter of the bush 7 is smaller than the diameter of the D-shaped portion so that the bush 7 is prevented from falling off when the bush 7 is tilted down.

The hole 8b is desirably slightly larger than the bush 7 so that the printing surface of the thermal head 3 is in close contact with the outside of the platen 2. A head pressing spring 9 for pressing the thermal head 3 attached to the frame 1 is attached to the front of the holder 5, sleeve pieces 10 are provided at both ends as stopper portions, and the frame 1 is positioned on the rear plate portion 11. A square hole 13 to be fitted into the projection 12 is formed. On the other hand, 14 is a head-up lever for releasing the pressing of the thermal head 3 toward the printing side, and 15 is a holder-up lever.
5 are receiving windows into which the sleeves 10 enter, and are provided on the frame 1 side, respectively. The projections 12 and the receiving windows 15 are provided at positions corresponding to the square holes 13 and the sleeves 10 when the holder 5 is fixed to the frame 1. The head pressing spring 9 has substantially the same size as the width of the thermal head 3 in order to uniformly press the entire thermal head 3 from above. The head pressing spring 9 is preferably linear so that the entire thermal head 3 can be pressed uniformly and the weight can be reduced.

The actual use of the thermal head holding / pressing mechanism of the present invention having the above-described structure will be described. FIG.
As shown in FIG.
And the bushes 7, 7 are inserted into the grooves 8a, 8a of the locking portions 8, 8 and slid upward. With the entire bushes 7, 7 inserted into the holes 8b, 8b, the thermal head 3 is removed. Push down to the platen 2 side. As a result, the thermal head 3 is held by the frame 1 without the bush 7 falling out of the locking portion 8. Next, the plate portion 11 behind the holder 5 is placed on the positioning protrusions 12, 12 of the frame 1, and the sleeves 10, 10, which are stopper portions, are inserted into the receiving windows 15, 15 of the frame 1 and pushed down, so that Holes 13, 1
3 so that the holder 3 can be inserted into the positioning protrusions 12 and 12.
The holder 5 is attached to the frame 1 by shifting the.

As described above, the printer main body in which the thermal head 3 and the holder 5 are incorporated in the frame 1 with the head-up lever 14 pulled forward as shown by an arrow in FIG. After the paper is supplied, the head-up lever 14 is moved down to the platen 2 as shown in FIG. 2 to start printing. Note that pulling the head-up lever 14 toward the user as shown in FIG. 3 is not limited to only when the paper is supplied. If the print head is pulled forward when printing is not performed, unnecessary load is not imposed on the heat sink portion of the thermal head, and disorder due to distortion can be prevented.

The removal of the thermal head 3 from the frame 1 is performed in the reverse procedure. That is, the square holes 13, 13 of the holder 5 are removed from the positioning protrusions 12, 12, and the sleeves 10, 10, which are stopper portions, are attached to the frame 1.
When the holder is displaced from the receiving windows 15, 15, the holder
5 comes off. Further, assuming that the width of the straight portion that is a cut portion of D, which is the maximum diameter of the circular portion of the bushes 7, 7, is set to the minimum diameter d, the minimum diameter d and the linear surface of the groove portion 8a are drawn. When they match, the heat sink part 4 falls down and the thermal head 3
Get off.

In the above embodiment, the heat sink 4
Although the bush 7 is press-fitted into the protruding piece 6 as the projection formed at both ends of the heat sink portion 4, the same shape as the bush 7 can be directly formed at both ends of the heat sink portion 4. However, the method in which the bush is fitted as in this embodiment has an advantage that the heat sink portion can be easily manufactured.

[0018]

As described above, the head pressing spring of the thermal printer according to the present invention can be made lighter than when a single wide leaf spring is used, and the cost can be reduced. Can be. In addition, space can be saved as compared with the case where a compression coil spring is used, and the device can be made thinner. Furthermore, the holder is accurately positioned on the frame by the square hole of the plate portion, and the sleeve can be detachably and securely attached to the frame simply by fitting it into the receiving window and pressing down firmly. In this case, not only is there no trouble such as incorporating only the springs at the same time, but also the pressing force of the thermal head can be appropriately adjusted by changing the springs.

[Brief description of the drawings]

FIG. 1 is an overall exploded perspective view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing a printing state in which a thermal head is attached to a printer main body.

FIG. 3 is a cross-sectional view of a main part showing a state in which pressing of a thermal head against a platen is released.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame 2 Platen 3 Thermal head 4 Heat sink part 5 Holder 6 Projection piece 7 Bush 8 Locking part 8a Groove part 8b Hole part 9 Head pressing spring 10 Sleeve piece 11 Plate part 12 Projection 13 Square hole 14 Head-up lever 15 Receiving window

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 25/312 B41J 2/32 B41J 25/316

Claims (3)

(57) [Scope of request for utility model registration] 1. A frame, a platen rotatably provided on the frame, and a platen fixed to the frame.
A motor for rotating the Ten, a thermal head is capable of contacting and separating from the said platen by swings around the pivot shaft relative to the frame, pressing the thermal head to said platen side And a head pressing spring fixed to the frame, wherein the head pressing spring is a head formed of a linear member.
A pressing portion and at least two coil portions;
The pad pressing portion connects the two coil portions and
The two cores are formed substantially parallel to the rotation axis of the platen.
The thermal head is characterized in that the two coil portions act as a torsion coil spring by fixing an end on the opposite side of the pressing portion to the frame, and press the thermal head with this spring force. Printer. 2. The thermal printer according to claim 1, wherein said head pressing spring is fixed to said frame by a member formed separately from said frame. 3. A linear pressing portion of the head pressing spring, before
Serial two coil portions and the thermal printer according to claim 1 or claim 2, that said that a substantially U-shape are integrally formed.