JP3064307U - Thermal printer - Google Patents

Abstract

(57) [Abstract] [Purpose] A head pressing spring can be easily held on a frame of a printer body, and a head pressing spring can be easily united and held with one touch by unitizing the head pressing spring. Without the need for special components for
An object of the present invention is to provide a thermal printer capable of reducing the weight and thickness of a printer main body. The head pressing spring comprises a linear pressing portion that contacts the head and two coil portions formed at both ends of the pressing portion, and whether the ends of the two coil portions are fixed to the frame. Or a thermal printer in which a head pressing spring is unitized and this unit is detachably engaged with the frame.

Description

[Detailed description of the invention]

[0001]

[Industrial applications]

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

[0002]

[Prior art]

 Conventional thermal head holding and pressing mechanisms include JP-A-62-1670 and JP-A-1-294081.

Japanese Patent Application Laid-Open No. 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. The thermal head disclosed in Japanese Patent Application Laid-Open No. 1-294081 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 as a fixing member, and all the other members are provided with another holding bracket on a heat sink portion of a thermal head and penetrate therethrough. The shaft is supported on the frame as the axis of rotation and is pressed against the platen. Japanese Patent Application Laid-Open Nos. 62-11670 and 1-294081 both use the elasticity of a spring to press a thermal head.

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, the pressing force in the longitudinal direction of the head will be uneven unless a leaf spring with a width approximately corresponding to the longitudinal length of the head is used. The adhesion was also uneven, and the print quality was degraded. When a leaf spring having a width corresponding to the longitudinal direction of the head was used, the weight was heavy and the cost was high. Further, when a plurality of springs are used, the pressing force is non-uniform due to variations in spring constants due to manufacturing variations of each leaf spring. Furthermore, the spring constants also differ due to variations in mounting each leaf spring 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 amount of space is required to accommodate the compression coil spring.

[0006]

[Problems to be solved by the invention]

 The present invention has been made in view of such a conventional problem, and it is possible to increase the weight and reduce the thickness of the device by using a leaf spring or a compression coil spring conventionally used for pressing the thermal head. SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal printer which can uniformly press a thermal head toward a platen and can easily mount a head pressing spring.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, a thermal printer according to the present invention includes a frame, a platen rotatably provided on the frame, and a pivot about a pivot shaft with respect to the frame. And a head pressing spring fixed to the frame for pressing the thermal head toward the platen side. The head pressing spring comprises a linear pressing portion contacting the head and two coil portions formed at both ends of the pressing portion, and ends of the two coil portions on the opposite side of the pressing portion are the frame. The two coil portions act as a torsion coil spring by being fixed to the frame, and press the head with this spring force. Also, the head pressing spring is separate from the frame. Composed And holder - the frame via a - characterized in that it is fixed to the arm, further, the linear pressing portion of the head pressing spring, characterized in that has a substantially U-shape.

[0008]

[Action]

When the protrusions formed on both ends of the heat sink part of the thermal head are fitted into the locking parts formed on both sides of the frame, and the thermal head is tilted toward the platen, the protrusions on the heat sink part are prevented from falling off and the thermal head is attached to the frame. Hold securely. Further, by locking the ends of the two coil portions formed at both ends of the linear pressing portion in contact with the head with the frame on which the thermal head is mounted, two coils are formed. The portion acts as a torsion coil spring, and the thermal head can be uniformly pressed toward the platen by the linear pressing portion. Further, in order to facilitate attachment of the head pressing spring to the frame, the head pressing spring is unitized, a sleeve is provided at an end of the unitized head pressing spring, and a plate having a square hole is provided. After inserting the sleeve into the receiving window provided on the frame, sliding down the slit portion of the receiving window and pushing down, the whole is shifted forward and the square hole is inserted into the frame. It fits into the projection and performs positioning. For this reason, the head pressing spring is securely fixed to the frame and simultaneously presses the thermal head toward the platen.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described 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 by the frame 1 toward the platen is unitized.

[0011] Protrusions 6, 6 are formed below both ends in the longitudinal direction of the heat sink portion 4 of the thermal head 3, and bushes 7, 7 are fitted into the respective protruding pieces 6, 6. The bush 7 has a D-shaped cross section obtained by cutting off one side of the outer periphery, and is press-fitted into the protruding piece 6 and attached. 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.

When the thermal head 3 is mounted on the frame 1, the bush 7 slides when the thermal head 3 is mounted on the frame 1, and when the mounted thermal head 3 is tilted down to the platen 2 side, the bush 7 is prevented from falling off. As described above, the diameter is smaller than the diameter of the D-shaped portion of the bush 7.

The hole 8 b 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, so that the hole 8 b has a slight play to avoid being over-constrained. 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, sleeves 10 as stoppers are provided at both ends, respectively, and the rear plate 11 is attached to the rear. A square hole 13 to be fitted to the positioning projection 12 of the frame 1 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 receiving window into which the sleeve 10 of the holder 5 enters, each of which is provided on the frame 1 side. These projections 12 and 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 and pressing mechanism of the present invention having the above configuration will be described. As shown in FIG. 1, the heat sink 4 is inserted from below the frame 1, and the bushings 7, 7 are inserted into the grooves 8a, 8a of the locking portions 8, 8 and slid upward. The thermal head 3 is tilted toward the platen 2 with the entirety of the head having entered the holes 8b. Thus, 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, and The holder 5 is attached to the frame 1 by shifting the holder 5 so that the holes 13 are inserted into the positioning projections 12.

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 from the printer, the head-up lever 14 is moved down to the platen 2 side as shown in FIG. Note that pulling the head-up lever 14 toward the user as shown in FIG. 3 is not limited to the time of paper supply. If it is pulled forward when printing is not performed, unnecessary load is not applied to the heat sink portion of the thermal head, and irregularity 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, when the square holes 13 and 13 of the holder 5 are removed from the positioning projections 12 and the sleeves 10 and 10 serving as stopper portions are displaced from the receiving windows 15 and 15 of the frame 1, the holder 5 is removed. Further, assuming that the width of the straight portion, which 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 portion 4 falls down, and the thermal head 3 comes off the frame 1.

In the above-described embodiment, as the protrusions formed on both ends of the heat sink portion 4, the protrusions 6 in which the bushes 7 are press-fitted are shown. Can also be formed. However, the one in which the bush is fitted as in this embodiment has an advantage that the heat sink portion can be easily manufactured.

[0018]

[Effect of the invention]

 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. Further, space can be saved as compared with the case where a compression coil spring is used, and the device can be made thinner. In addition, the square hole in the plate of the holder allows accurate positioning on the frame, and the sleeve can be detachably and securely attached to the frame simply by fitting it into the receiving window and pushing down strongly. Not only is there no trouble such as incorporating only the spring at the time of mounting, but also the pressing force of the thermal head can be adjusted appropriately by changing the spring.

[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 Protrusion 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

Claims (3)

[Utility model registration claims] 1. A frame, a platen rotatably provided on the frame, and a platen that can be brought into contact with and separated from the platen by swinging about a swing axis with respect to the frame. In a thermal printer having a thermal head and a head pressing spring fixed to the frame for pressing the thermal head toward the platen, the head pressing spring has a linear contact with the head. It comprises a pressing portion and two coil portions formed at both ends thereof, and the two coil portions are fixed to the frame at opposite ends of the pressing portion to the two coil portions. Act as a torsion coil spring and press the head with this spring force. 2. The thermal printer according to claim 1, wherein said head pressing spring is fixed to said frame via a holder formed separately from said frame. . 3. The linear pressing portion of the head pressing spring,
3. The thermal printer according to claim 2, wherein the thermal printer has a substantially U-shape.