JP2004098699A - Pressing mechanism for thermal head and printer equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structurally inexpensive thermal printer with good printing quality, which facilitates the attachment/detachment of a printhead and stabilizes a head pressing force. <P>SOLUTION: The printhead 39, into which a head supporting shaft 40 is pressed, is inserted into a supporting groove part 50, whose upper part is opened, in a state wherein a platen is removed from a head pressing mechanism part; and a head pressing plate 41 is moved along a guide rail part 50b and attached to the groove part 50, so that the printhead 39 can be urged by a pressing force. In the supporting part 50a, the other side of the platen is opened, and a spring receiving part 48 is provided between the supporting shaft 40 and a position, wherein the platen abuts on the printhead 39, on the backside of the printhead 39. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a thermal printer used in a POS system, a cash register, a copying machine, a facsimile, and the like, and more particularly, to a pressing mechanism that supports a thermal head on a frame and presses the thermal head against a platen roller.

Conventionally, this type of printer has a structure in which a shaft is passed through a head support member, supported on a main body frame, an elastic member is disposed between a head pressing member and the head support member, and a thermal head is urged in a platen direction. Is generally known. When a thermal head is incorporated in a printer, it is necessary to dispose a head pressing member against the resilience of the elastic member, so that the assembling work is complicated and the productivity of the device is reduced.

Therefore, as described in Japanese Patent Application Laid-Open No. H5-24308 (Patent Document 1) and the like, a state in which the head support member and the head pressing member (the support arm 19 and the pressing arm 21 in the gazette) are connected before the main assembly. A method has been proposed in which a sub-assembly is made and then assembled to a main body frame.

In particular, in the case of a line thermal printer having a long width, if the pressing force in the line direction does not become uniform, the pressing force becomes insufficient at the end of the print line, resulting in a problem that the printing becomes thin. Therefore, an automatic centering mechanism for a thermal head has been proposed. For example, as described in Japanese Patent Application Laid-Open No. 6-336069 (Patent Document 2) or the like, a plurality of springs are provided on the back surface of the head support member by setting the rotation fulcrum of the head support member fixed to the thermal head to a long hole. Even if the head support shaft and the platen roller are not exactly parallel or the cylindricity of the platen roller is not exactly cylindrical due to the variation in component accuracy, the thermal head can follow the platen roller. There is a mechanism that moves and applies a uniform pressing force in the line direction. In both of the above-mentioned conventional examples, the thermal head is attached to the head support member, and the shaft is passed through the pivot point.
JP-A-5-24308 JP-A-6-336069 JP-A-7-242038 CD-ROM of Japanese Utility Model No. 7-5745

However, the conventional head pressing mechanism described above has the following problems. First, in the configuration described in Japanese Patent Application Laid-Open No. H5-24308 (Patent Document 1), although the productivity is certainly improved, it is at the time of the main assembly, and In the group, it is necessary to assemble the thermal head against the resilience of a spring or the like as in the related art. Overall productivity improvement is modest. Conversely, in addition to the support member and the pressing member, a member that locks the pressing member (the stopper arm 26 in the publication of Patent Document 1) is required, which increases the number of parts and increases the cost.

Further, in the configuration described in JP-A-6-336069 (Patent Document 2), since the hole through which the shaft passes is a long hole, the pressing force of the head becomes uniform, and the printing quality is improved. , The head support member must be passed through the shaft. This structure is the same in Japanese Patent Application Laid-Open No. H5-24308 (Patent Document 1). That is, in the related art, in a printer in which a thermal head is rotatably supported, a method of passing a shaft through a head support member is generally used. In this case, the thermal head is detached, or the shaft is pulled out, and the thermal head is detached together with the head supporting member. Therefore, not only the productivity of the printer is poor, but also the exchangeability in the event of a head failure is poor, and the maintenance time is long. Further, the configuration of the printer has become complicated, which has hindered cost reduction.

Therefore, the present invention has been made in consideration of such conventional problems, and has as its object to provide excellent productivity, easy exchangeability of the thermal head, and stable head pressing force. Another object of the present invention is to provide a thermal printer with good printing quality.

Another object of the present invention is to provide a low-cost thermal printer by reducing the number of components in the pressing mechanism of the thermal head and adopting a simple configuration in which fastening members such as screws are eliminated. is there.

To achieve the above objectives,
The thermal head pressing mechanism according to the present invention includes:
It is rotatably supported on a rotation support shaft as a fulcrum,
A heating element that contacts the opposing platen roller;
A spring for pressing a heating element toward the platen roller,
With
A spring receiver for receiving the spring is formed in a groove shape.

In addition, the thermal head of the present invention
It is rotatably supported on a rotation support shaft as a fulcrum,
A heating element that contacts the opposing platen roller;
A spring receiver for receiving a spring pressing the heating element toward the platen roller is formed in a groove shape.

Further, the printer of the present invention
Comprising the platen roller,
The thermal head is made detachable.

に よ り By adopting these configurations, the position of the spring is correctly determined, the pressing force is stabilized, and the printing quality is improved. Further, assemblability is improved.

Hereinafter, a preferred embodiment of the printer according to the present invention will be described in detail with reference to FIGS.

FIG. 3 is a perspective view showing an external configuration of the embodiment of the printer according to the present invention.

The printer 1 according to the present embodiment is applied to, for example, a receipt printer used in a POS system or the like.

The printer 1 of the present embodiment performs recording such as printing on a roll-shaped recording paper S by using a recording head of a heat-sensitive method, and generally includes a recording section and a paper cutting section in front and a recording paper in rear. And a roll paper storage unit for storing and holding S.

The internal printer mechanism 8 is fixed to the lower case 4 made of resin, the side and rear portions are covered by the upper case 3, and the front portion is covered by the panel 2. Further, a printing unit is arranged inside the panel 2, and a paper cutting unit is arranged above the panel 2. The paper cut portion is covered with a cutter cover 6, and the cutter cover 6 can be slid in the direction of arrow A and pulled out.

An open button 7 is provided on one side of the upper case 3 for driving the internal cover open lever 9 to rotate the internal cover frame 10 when the recording paper S is taken out. Here, the cover frame 10 is connected to the upper cover 5. When the open button 7 is pressed in the direction of arrow B, the cover open lever 9 is rotated clockwise to release the lock mechanism, and the upper cover 5 is opened in the direction of arrow C to expose the roll paper storage unit. Is done.

1 and 2 are perspective views showing a printer mechanism 8 inside the printer 1 according to the present embodiment. FIG. 1 is an external view of the printer mechanism 8 with a cover frame 10 opened, as viewed from the left side. FIG. 2 is an external view of the right side of the printer mechanism 8 with the cover frame 10 closed.

The printer mechanism has a cover frame 10 that can be freely opened and closed on a main body frame 13 made of metal or the like, and an automatic cutter unit 11 that houses the movable blade 32 and its driving means. In this case, when printing, that is, when the recording paper S is not cut, the movable blade 32 is housed inside the automatic cutter unit 11, and the blade portion of the movable blade 32 is not exposed. In this state, the movable blade 32 is at the standby position.

The fixed blade 33 that intersects the movable blade 32 in a scissor shape is disposed on the cover frame 10 so as to face the automatic cutter unit 11. A blade shutter 34 is provided above the fixed blade 33. The blade shutter 34 is urged by a shutter spring 35 in a direction to cover the blade portion of the fixed blade 33. As shown in FIG. 2, when the cover frame 10 is closed, a part of the blade shutter 34 The blade shutter 34 is lifted in a slightly opening direction in contact with the engaging portion provided on the blade 13. Therefore, the blade portion of the fixed blade 33 is exposed, and the movable blade 32 is configured to be able to cross in a scissor shape when the movable blade 32 moves.
A hole 37 for confirming the position of the movable blade 32 and a knob 36 for manually moving the movable blade 32 are provided on the upper surface of the automatic cutter unit 11, and the operator slides the cutter cover 6 described above. Then, a part of the upper surface of the automatic cutter unit 11 is exposed, and the hole 37 and the knob 36 are visible. As described above, in the embodiment of the present application, in the event of any abnormality such as a power failure, the movable blade 32 is manually crossed with the fixed blade 33 so as not to return to the standby position. Is provided for moving the.

(4) The cover frame 10 is mounted to be swingable, that is, openable and closable about a support shaft 14 provided at an upper end portion on both sides of the main body frame 13. Note that the cover frame 10 is provided with an arc-shaped lid portion 15 for avoiding contact with the recording paper S when the cover frame 10 is closed. When the installation angle of the printer is changed, the lid 15 also functions as a holding member for receiving the recording paper S.

カ バ ー A cover detector 44 for detecting the closed state of the cover frame 10 is provided on the right side surface of the main body frame 13. The cover detector 44 is a transmission type optical detector, and detects whether or not the cover frame 10 is properly closed depending on whether or not a part of the cover frame 10 blocks the optical axis of the detector.

As the detector, a paper detector 30 and a near-end detector 24, which will be described later, are provided in addition to the cover detector 44. These various detectors, the automatic cutter unit 11, and a lead wire group 12 of a paper feed motor 23, which will be described later, are connected to a relay board 16 fixed to the right side of the main body frame 13. The relay board 16 and a main circuit board (not shown) for controlling the printer are connected by an FFC or the like.

FIG. 1 is an external view of the left side of the printer mechanism 8, showing a state in which the cover frame 10 is opened. The blade shutter 34 covers and covers the fixed blade 33. Care is taken to prevent the operator from touching the fixed blade and causing injury when the cover frame 10 is opened. The movable blade 32 is housed in the automatic cutter unit 11, and there is no safety problem.

ロ ー ル A resin roll paper holder 17 is arranged inside the cover frame 10 opened. The roll paper holder 17 is provided with a paper detector 30 for detecting the presence or absence of paper immediately before the printing section. The paper detector 30 is a reflection-type optical detector, and a hole 31 is provided upstream of the paper detector 30 for dropping foreign substances and paper dust attached to the recording paper S downward. As a result, the detector does not malfunction. Furthermore, the roll paper holder 17 is provided with a slit groove 27 that engages with the left and right side plates of the main body frame 13. The width direction is regulated, so that an appropriate width is maintained inside the recording paper storage portion with respect to the recording paper.

The platen 18 made of a cylindrical rubber roller is rotatably supported by the cover frame 10 via a platen bearing 20. A platen gear 19 is press-fitted into one of the platens 18. The body frame 13 is provided with a groove 21. When the cover frame 10 is closed, the platen bearing 20 comes into contact with the groove 21 and the platen 18 is positioned downward. When the cover frame 10 is closed, a downward force acts on the cover frame 10 by the pressing force applied to the platen by the print head, and the position of the platen 18 is determined. When the cover frame 10 is closed, the platen gear 19 and the paper feed transmission gear 22 mesh with each other, and the power from the paper feed motor 23 is transmitted to the platen 18.

Further, a near-end detector 24 for detecting that the remaining amount of the recording paper S is running low is attached to the left side surface of the main body frame 13 so as to be rotatable about a support shaft 25. This is for setting the near-end detector 24 to the optimum position in accordance with the change of the installation angle of the printer. For example, as shown in FIG. 1, when the main body frame 10 is installed with the bottom surface 28 facing down, the actuator 26 of the near-end detector 24 is fixed at a position where it can enter the hole 32a provided in the frame main body 10. On the other hand, when the main frame 10 is installed with the back surface 29 facing down, the actuator 26 is fixed at a position to enter the hole 32b.
The left and right side surfaces of the main body frame 13 are provided with support grooves 50 for supporting a print head 39 and a head pressing plate 41 described later.
FIG. 4 is a side sectional view of the printer mechanism 8, showing a state in which the recording paper S is held by the roll paper holder 17 and the paper is fed. FIG. 4 shows a state in which the recording paper S has a large diameter. When the recording paper S is fed and becomes smaller in diameter, the recording paper S falls into the groove 38. Then, the near-end detector 24 detects that the recording paper S has become small in diameter.
The recording paper S is sandwiched between the platen 18 and the print head 39 and is fed by the frictional force when the platen 18 rotates. Head support shafts 40 are provided on both side surfaces of the print head 39, and the head support shafts 40 are supported by a part of a support groove 50 provided in the main body frame 13. The back surface of the print head 39 is urged toward the platen 18 by a spring 42. The spring 42 is fixed to the head pressing plate 41, and the head pressing plate 42 is supported by a part of a support groove 50 provided in the main body frame 13.

(4) The heating element position 43 of the print head 39 is located so as to be substantially in contact with the platen 18 and the print head 39. A guide slope 45 is provided in a portion of the print head 39 downstream of the heating element position 43. On the other hand, the cover frame 10 is provided with an introduction portion 47 for guiding the recording paper S to the cutter portion so as to face the guide slope portion 45 of the print head 39. The recording paper S that has passed through the print head 39 passes between the movable blade 32 and the fixed blade 33 and is discharged in the direction of arrow D. The print head 39 includes a connector 46, and is connected to a main circuit board (not shown) for controlling the printer by an FFC or the like.

The outline of the basic configuration of the entire printer according to the present embodiment has been described above. Next, the pressing mechanism of the thermal head will be described in more detail with reference to FIGS.

FIG. 5 shows a cross section of the recording section before the print head 39 and the head pressing plate 41 are assembled. The auto cutter unit 11 is detached from the main body frame 13 and the cover frame 10 is open. The print head 39 engages with the support groove 50 provided on the main body frame 13 and is positioned. The platen 18 (not shown) is also engaged with the groove 21 provided on the main body frame 13 and positioned.
Therefore, since the print head 39 and the platen 18 are positioned on the same plane of the main body frame 13, which is the same component, the positional accuracy is improved. The print head 39 and the head pressing plate 41 are assembled before the platen 18 is assembled in the recording unit. First, the print head 39 is inserted into a support groove 50 provided in the main body frame 13. As shown in the figure, since the support groove 50 is open at the top, the print head 39 can be easily inserted from above. Then, the head support shaft 40 is substantially aligned with the head support portion 50a. Next, a head pressing plate 41, which is a pressing member for urging the print head 39 in the direction of the platen 18, is attached to the support groove 50. This assembling method will be described with reference to FIG.
FIG. 6 is a side view showing the manner in which the head pressing plate 41 is assembled to the support groove 50. The head pressing plate 41 is formed to have a width slightly smaller than the inner dimension between the main body frames 13 except for the wide portion 41a. As shown in the drawing, first, a spring 42 is applied to a spring receiving portion 48 on the back of the print head 39, the lower end of the head pressing plate 41 is positioned in the lower groove 50 c of the support groove 50, and the wide portion 41 a on the upper side of the head pressing plate 41. To the guide rail portion 50b. At this time, although there is no platen 18, the print head 39 comes into contact with the head engaging portion 49 provided on the main body frame 13, and the rotation of the print head 39 is restricted. Next, the head pressing plate 41 is pressed from the back in the direction of arrow E. Since the shape of the guide rail portion 50b is an arc shape with the lower groove 50c substantially at the center, the head pressing plate 41 rotates around the position of the lower groove 50c substantially as a fulcrum, and the upper wide portion 41a It moves along the guide rail portion 50b, moves downward at the opening, and stays at a predetermined position. Thus, in the invention of the present application, the provision of the guide rail portion 50b makes it extremely easy to assemble the head pressing plate 41.

FIG. 7 shows a perspective view of the state in which the head pressing plate 41 is assembled to the main body frame 13 as described above. A plurality of springs 42 are arranged on the head pressing plate 41 in the print line direction. This is to make the applied force uniform in the print line direction. The main body frame 13 is provided with a cutter receiving portion 53 for fixing the automatic cutter unit 11. When the automatic cutter unit 11 is not disposed, the head pressing mechanism is exposed. Therefore, the replacement of the print head 39 is facilitated, but on the other hand, there is a possibility that the operator may touch it unnecessarily and cause a failure. That is, during normal use, it is not preferable that the head pressing mechanism is exposed.

Therefore, in the present printer, in normal use, a part of the bottom of the automatic cutter unit 11 is engaged with a part of the cutter receiving portion 53, and the automatic cutter unit 11 is fixed to the cutter receiving portion 53 by a screw or the like. . In this manner, since the auto cutter unit 11 is disposed above the head pressing mechanism, the head pressing mechanism is covered and concealed, so that the structure is normally not touched by the operator, and there is no safety problem and good reliability. It becomes. Further, the auto cutter unit 11 is firmly fixed to the main body frame 13 with screws or the like, whereby the width direction of the main body frame 13 is regulated, the position of the print head 39 is stabilized, and the printing position accuracy is improved. In addition, the strength of the head pressing mechanism is increased. In the embodiment, an example in which the auto cutter unit 11 is fixed with a screw or the like has been described. However, the auto cutter unit 11 does not necessarily need to be fixed with a screw or the like, and the auto cutter unit 11 pivots on the main body frame 13 at a hinge portion. When the auto-cutter unit 11 is set in a proper position, it can be engaged with a part of the main body frame 13 to increase the strength.
FIG. 8 is a side view showing a state where the platen 18 is mounted on the head pressing mechanism shown in FIG. By mounting the platen 18, the print head 39 moves against the elastic force of the spring 42 and separates from the head engaging portion 49. Therefore, the print head 39 is pressed against the platen 18 by the spring force of the spring 42. As described above, in this printer, when the head pressing plate 41 is assembled, since the platen 18 is separated from the head pressing portion, the length for compressing the spring 42 against the elastic force of the spring 42 has a predetermined length. It is not necessary to shorten the length to the set length at which the pressing force can be obtained, and therefore, the force required for assembling the head pressing plate 41 may be small. This also facilitates the assembly of the head pressing plate 41.

The point to be noted here is that the spring 42 urges the position between the contact position where the print head 39 contacts the platen 18 and the head support shaft 40 which is the rotation fulcrum of the print head 39. That is. Thus, even if the rear side of the head supporting portion 50a, that is, the back direction of the print head 39 is open, the head support shaft 40 of the print head 39 is urged toward the platen 18 and the head support shaft 40 does not come off. There is no. Therefore, conventionally, the support hole of the head support shaft 40 is generally a long hole, and a method of passing the shaft through the long hole is adopted. It is possible to do.
As shown in FIG. 8, the spring a is a distance between the contact position between the platen 18 and the print head 39, which is a printing position, and the biasing position of the spring 42, and the distance between the head support shaft 40 and the biasing position of the spring 42. When b is set, b is urged so that a <b. Thus, for example, the cylindricity of the platen 18 can be accurately determined even though the line connecting the contact surface between the platen 18 and the print head 39 and the left and right head support shafts 40 is set in parallel as in the present embodiment. If the parts are not parallel and are not parallel due to variations in the precision of the parts and twists occur, one of the left or right of the contact surface between the platen 18 and the print head 39, or the right or the left or right of the head support shaft 40, Since the position of the spring 42 is a <b, the force for urging the contact surface between the platen 18 and the print head 39 is strong, so that the print head 39 moves following the platen 18 and the print position floats. Instead, one of the head support shafts 40 floats on the opening side of the head support portion 50a. Therefore, in the present printer, since the rear of the head support portion 50a is open, the head is automatically aligned in the same manner as the conventional long hole head support portion, and the printing side is securely pressed. The printing quality and reliability are improved without the problem that printing is not performed due to insufficient pressure or no contact, and that the printing is not sharp.
Further, as shown in FIG. 8, since the spring receiving portion 48 is provided on the back surface of the print head 39, the position of the spring 42 is correctly determined, and the pressing force is stabilized. Therefore, the printing quality is improved. Also, when the head pressing plate 41 is attached to and detached from the main body frame, there is an advantage that the spring 42 is hard to come off. In the present embodiment, as the head pressing means, a method in which a projection such as burring is provided on a head pressing plate 41 made of a sheet metal and a spring 42 of a compression coil spring is fitted. However, the head pressing means is not limited to this method, and the spring and the head pressing plate can be made into one part by using a leaf spring material.
As described above, the head pressing mechanism of the present invention facilitates the printer assembling operation while maintaining the function of uniformly and stabilizing the head pressing force that greatly affects the print quality. Next, details of cost reduction of the print head itself used for the head pressing mechanism will be described below.
FIG. 9 is a perspective view of the print head 39 of this printer, and the heat radiating plate 51 is a drawn aluminum material. Reference numeral 52 denotes a head chip, which is attached to the heat sink 51 with a double-sided adhesive tape. Since the width of the head chip 52 is shorter than the width of the heat radiating plate 51, a locking surface 51 b, which is a part of the heat radiating plate 51, protrudes from the head chip 52 to the left and right of the head chip 52. When the print head 39 is mounted on the main body frame 13, the locking surface 51b and the head engaging portion 49 provided on the main body frame 13 are engaged. Above the head chip 52 of the heat radiating plate 51, a guide slope 45 is formed in the print line direction. After the print head 39 is mounted on the main body frame 13 and the cover frame 10 is closed and the platen 18 is mounted on the recording section, first, the guide slope 45 and the platen 18 come into contact with each other, and the print head 39 is moved to the head pressing plate 41. Therefore, the impact of the platen 18 hitting the head chip 52 is reduced by the guide slope 45.
The head support shaft 40 is a spring pin having a wavy slit portion, and is press-fitted into holes provided on the left and right side surfaces of the heat sink 51. The corrugated spring pins are elastically changed in diameter according to the holes of the radiator plate 51 and do not deform the radiator plate 51. When the heat radiating plate 51 is deformed, a stress is applied to the head chip 52, which causes disconnection of the internal wiring of the substrate and shortens the service life. However, this printer does not have such a problem, and high reliability can be secured.
Conventionally, the support shaft of the print head is provided with a head support member that is a separate part from the print head, and the shaft is passed through it, or the heat sink is manufactured by die casting and the support shaft is projected. was there. However, these methods have a large number of parts and cost increase. Therefore, as shown in the present embodiment, the method of press-fitting the shaft material into the heat-dissipating plate made of the drawn aluminum material can reduce the number of parts and reduce the cost. Further, if the shaft of the spring pin is press-fitted, it is not necessary to increase the precision of the component in the shaft hole portion of the aluminum extraction material, which also reduces the cost.

The spring pin used in the present embodiment has a wave portion bent inward as shown in FIG. Accordingly, the slit portion does not protrude in the circumferential direction, the head support portion 50a and the slit portion of the spring pin are not caught at any position of the wave portion, and the print head 39 can be smoothly rotated. Movement becomes possible. Therefore, at the time of press-fitting the spring pin, there is no need to control the position of the slit portion, and assembly is easy.

1 is a perspective view illustrating an internal configuration of an embodiment of a printer according to the present invention, in a state where a cover frame is opened. FIG. 2 is a perspective view showing an internal configuration of the embodiment, showing a state in which a cover frame is closed. It is a perspective view which shows the external appearance structure of the embodiment. FIG. 2 is a side sectional view showing an internal configuration of the same embodiment. FIG. 4 is a partial cross-sectional view for explaining the assembling of the recording unit according to the embodiment, showing a state before assembling. FIG. 4 is a partial cross-sectional view illustrating the assembling of the recording unit according to the embodiment, showing a state after the assembling. FIG. 3 is a partial perspective view illustrating a recording unit according to the embodiment. FIG. 2 is a side sectional view of a main part showing a recording unit of the embodiment. FIG. 2 is a perspective view illustrating an appearance of the print head according to the embodiment. FIG. 3 is a sectional view of a spring pin used in the print head according to the embodiment.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Printer 5 Upper cover 8 Printer mechanism 9 Cover open lever 10 Cover frame 11 Auto cutter unit 13 Main body frame 16 Relay board 17 Roll paper holder 18 Platen 20 Platen bearing 21 Groove part 23 Paper feed motor 39 Print head 40 Head spindle 41 Head press Plate 42 Spring 43 Heating element position 45 Guide slope section 48 Spring receiving section 49 Head engaging section 50 Support groove section 50a Head supporting section 50b Guide rail section 50c Lower groove 51 Heat radiating plate 53 Cutter receiving section

Claims (3)

It is rotatably supported on a rotation support shaft as a fulcrum,
A heating element that contacts the opposing platen roller;
A spring for pressing a heating element toward the platen roller,
With
A pressing mechanism for a thermal head, wherein a spring receiver for receiving the spring is formed in a groove shape. It is rotatably supported on a rotation support shaft as a fulcrum,
A heating element that contacts the opposing platen roller;
A thermal head, wherein a spring receiver for receiving a spring pressing a heating element toward the platen roller is formed in a groove shape. Comprising the platen roller,
A printer in which the thermal head according to claim 2 is detachable.

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