JP3069429B2 - Thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer.

[0002]

2. Description of the Related Art As shown in Japanese Patent Application Laid-Open No. Hei 3-182380, a conventional thermal printer is configured such that a platen roller which is rotatably supported by being fixed at a fixed position between body frames is supported by a fulcrum shaft between the body frames. The thermal head unit, which is swingable around
By providing a coil spring in a compressed state between the thermal head unit and the head cover fixed on the main body frame, the thermal head is pressed toward the platen roller. There is also a type in which a leaf spring is attached to a metal fitting similar to a head cover, and the thermal head is pressed by the leaf spring.

[0003]

In this conventional thermal printer, a head cover for receiving a spring or a metal fitting similar to the head cover is indispensable. Since the head cover and the like is a member for receiving the repulsive force of the spring, a certain degree of the head cover is required. It is necessary to firmly fix a strong sheet metal or the like to the main body frame, which complicates the frame structure consisting of the main body frame and the head cover, increases the size and weight, and increases the number of parts, which increases assembly labor and costs. There is also a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and aims at reducing the size and weight of a thermal printer, reducing the number of parts, and assembling easiness by simplifying a spring mounting structure. It is the purpose.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a platen roller which is rotatably driven by being supported between main body frames.
In a thermal printer in which a thermal head unit swingable about a fulcrum shaft provided between main body frames is opposed to the thermal head unit and the thermal head unit is pressed toward a platen roller by a spring, the spring is
A pressing portion engaged with the upper surface of the distal end portion of the thermal head unit by a single wire and integrally formed on both sides of the pressing portion and projecting inward from both sides of the main body frame on the fulcrum shaft side from the pressing portion. A pair of torsion springs fitted to the pair of convex portions, and a pair of torsion springs integrally protruding from the pair of torsion springs to the opposite side to the pressing portion and engaged on both side portions of the main body frame. This is a thermal printer having a series of engagement ends.

[0006]

According to the present invention, the space between the pair of torsion springs is narrowed, the torsion springs are fitted to the pair of projections, and the pair of engagement ends are engaged on both sides of the main body frame. The spring can be easily attached to the body frame. The spring presses the thermal head unit toward the platen roller via the pressing portion by the repulsive force in the torsional direction stored in the torsion spring portion.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings.

FIG. 1 shows a thermal line printer, in which a main body frame 11 mainly composed of a bottom plate 11a, a side plate 11b and a back plate 11c is integrally formed of synthetic resin, and is rotatably supported between the side plates 11b of the main body frame. A thermal head unit 14 is swingably opposed to a platen roller 12 around a fulcrum shaft 13 fitted between the side plates 11b of the main body frame behind the platen roller 12, and the thermal head unit 14 It is pressed toward the platen roller 12 by a wire spring 15 described in detail below.

The spring 15 is formed by a single wire.
A pressing portion 15a engaged with the upper surface of the distal end portion of the thermal head unit 14, and a pair of pressing members 15a formed integrally on both sides of the pressing portion 15a behind the pressing portion and projecting inward from the side plates 11b of the body frames on both sides. And a pair of torsion spring portions 15b fitted to the projections 16 of the main body frame. And a pair of engagement ends 15c engaged from above are formed in series.

The rotating shaft 21 of the platen roller 12 is driven by a motor 22 mounted on the main body frame 11 by a reduction gear mechanism.
Driven via 23.

A push-up cam 24 for rotatably separating the thermal head unit 14 from the platen roller 12 is rotatably fitted to the opposite side of the rotary shaft 21. By rotating the cam 24 by pushing up as shown by the two-dot chain line in FIG.
From 27, the pressing of the thermal head 14a against the paper inserted between the platen roller 12 and the thermal head 14a is released. This released state is sensed by a limit switch 28 attached to the back plate 11c of the main frame.

As shown in FIG. 2, the thermal head unit 14 has a thermal head 14a integrated with a lower surface of a heat radiating plate 14b, and an inverted U-shaped groove 14c provided at a rear end of the heat radiating plate 14b. Are fitted to the fulcrum shaft 13.

The thermal printer is assembled by inserting a platen roller into a cut groove 29 provided in the side plate 11b of the main frame.
12 rotary shaft 21 is fitted, and the fulcrum shaft 13
Finally, the space between the pair of torsion spring portions 15b of the wire spring 15 is narrowed, the torsion spring portion 15b is fitted to the pair of projections 16, and the pair of engagement end portions is formed. It is only necessary to engage 15c with the notch 17 on the side plate of the main body frame.

The wire spring 15 is pressed by the pressing portion 15a by the repulsive force in the torsion direction stored in the torsion spring portions 15b on both sides.
Is uniformly pressed against the thermal head unit 14 and the thermal head 14a is pressed evenly over the entire width of the platen roller 12, so that a uniform printing pressure can be secured over the entire width.

[0015]

According to the present invention, as a spring for pressing the thermal head unit toward the platen roller, a pressing portion, a pair of torsion spring portions, and a pair of engagement ends are formed in series by a single wire. Therefore, the spring can be mounted with an extremely simple mounting structure simply by using a pair of protrusions provided integrally with the main body frame, and it is not necessary to attach a head cover or a similar bracket for receiving the spring as in the conventional case. . For this reason, the thermal printer can be reduced in size and weight, the number of parts can be significantly reduced, the assembling is easy, and the cost can be significantly reduced. Further, a uniform pressing force can be applied to the entire surface of the thermal head by the entire length of the pressing portion formed of the wire material, and excellent printing quality can be secured.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a thermal printer according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

[Description of Signs] 11 Body frame 12 Platen roller 13 Support shaft 14 Thermal head unit 15 Spring 15a Pressing part 15b Torsion spring part 15c Engagement end part 16 Convex part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/32 B41J 25/34

Claims (1)

(57) [Claims] 1. A thermal head unit, which is swingable about a fulcrum shaft provided between main body frames, is opposed to a platen roller which is rotatably supported by being supported between main body frames. In the thermal printer pressed to the platen roller side by a spring, the spring is formed by a single wire and a pressing portion engaged with an upper surface of a distal end portion of the thermal head unit, and integrally formed on both sides of the pressing portion to be pressed. A pair of torsion springs fitted to a pair of protrusions protruding inward from both sides of the main body frame on the fulcrum shaft side from the portion, and from the pair of torsion springs to a side opposite to the pressing portion. A thermal printer, wherein a pair of engaging end portions which are integrally protruded and engaged on both side portions of a main body frame are formed in series.