JP2003103866A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer in which the position of a thermal head to a platen roller can be easily adjusted by a user level and a stable printing quality can be achieved. SOLUTION: An aligning face 28 is formed to the center in a width direction of an oscillation end of the thermal head 21. The aligning face 28 is pressed in contact with a cam body 102 of an eccentric cam 101 by the action of a coil spring 81. A thermal head unit 20 is thus aligned and a heating unit 22 presses into contact with the platen roller 31 by a uniform pressure. The thermal head unit 20 oscillates when the eccentric cam 101 is rotated, and the position of the heating unit 22 moves in a tangential direction of the platen roller 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention sandwiches a heat-sensitive paper between a heating element of a thermal head and a platen roller,
The present invention relates to a thermal printer that prints on a sheet while conveying the sheet by rotating a platen roller.

[0002]

2. Description of the Related Art In this type of thermal printer, the thermal head is of a swinging type that can be brought into and out of contact with a platen roller so that it can flexibly cope with paper of various thicknesses, and the thermal head is provided by a spring. In many cases, the head is biased toward the platen roller so that the heating element is always in pressure contact with the platen roller when there is no paper.
In such a thermal printer, when the thickness of the paper is different, the density of the image may be modulated due to the change in the color development sensitivity, but this modulation causes the position of the heating element with respect to the platen roller to be changed. It has been found that this can be corrected by moving the platen roller tangentially. Therefore, there is provided a heating element whose position can be adjusted so that the heating element is pressed against the platen roller at an appropriate position according to the thickness of the sheet.

A device capable of adjusting the position of the heating element in this way is disclosed in Japanese Patent Application Laid-Open No. 9-131945. According to the publication, when the screw which is screwed into the rear end of the thermal head and the tip of which is in contact with the fixing member (arm support shaft) is rotated, the thermal head swings, whereby the tangent line of the heating element with respect to the platen roller. It is said that the position in the direction can be adjusted.

[0004]

By the way, in the heating element of the thermal head, it is desirable that the pressure distribution in the longitudinal direction of the contact surface with respect to the platen roller is uniform without being biased to one side. There is a device provided with a centering mechanism for uniformly pressing the plate against the platen roller. The centering mechanism supports the thermal head so that it can be tilted in the left-right direction of the paper conveyance direction, and the heating element press-contacts the platen roller with the centering surface provided at the center part in the left-right direction at the swinging end of the thermal head. There is a configuration of pushing in the direction of doing. It is impossible to apply such an aligning mechanism to the thermal printer described in the above publication because a screw for adjusting the position of the heating element is attached to the swing end of the thermal head. That is, although the thermal head oscillates due to the rotation of the screw, the oscillating action only serves to adjust the position of the heating element, and the thermal head is restrained from tilting in the left-right direction by the screw, so the centering of the heating element is You can't. Therefore, if a centering mechanism is provided, another means must be taken, which may lead to problems such as complication of the device and increase in the number of parts.

Therefore, an object of the present invention is to provide a thermal printer which can realize the position adjustment of the heating element with respect to the platen roller and the alignment of the heating element with a simple structure.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a thermal head unit comprising a thermal head having a heating element extending in a width direction orthogonal to a sheet conveying direction is fixed to a support, and the thermal head unit is disposed so as to face the heating element. A platen roller that sandwiches the paper to be fed between the heating element, a swinging shaft portion that is parallel to the heating element and that swingably supports the thermal head unit, and this swinging shaft portion is tilted toward the platen roller. A tilting mechanism that supports the thermal head unit, an urging member that urges the thermal head unit toward the platen roller to press the heating element against the platen roller, and an adjustment member that is provided in the center of the swinging end of the thermal head unit in the width direction. A head adjusting member that causes the thermal head unit to oscillate with the oscillating shaft portion as a fulcrum by being pressed against the core surface by the action of the urging member and operated by the urging member. It is characterized by having a.

According to the thermal printer of the present invention, the thermal head unit swings about the swing shaft portion as a fulcrum and can tilt in the left-right direction which is the axial direction of the platen roller together with the swing shaft portion. The thermal head unit is urged toward the platen roller by the urging member, so that the heating element presses the platen roller and the alignment surface presses the head adjusting member in the absence of paper. When the head adjusting member is actuated in this state, the thermal head unit swings around the centering surface as a force point and the swing shaft portion as a fulcrum, and the heating element serving as an action point moves in the tangential direction of the platen roller. Since the alignment surface is located at the center of the thermal head unit in the width direction, the thermal head unit whose alignment surface is in pressure contact with the head adjustment member is
The tilted state is balanced. For this reason, the pressure distribution in the longitudinal direction of the heating element pressed against the platen roller becomes uniform without being biased to one side, and the heating element presses against the platen roller with a uniform pressure.

As described above, in the present invention, the head adjusting member acting on the centering surface adjusts the position of the heat generating element in the tangential direction to the platen roller and aligns the heat generating element with the platen roller with a uniform pressure. It also has two functions.
Therefore, the configuration is simple in mounting these two functions, and the increase in the number of parts can be suppressed.

In the present invention, it is preferable that the head adjusting member can be directly operated by hand and that the adjusting position within the operating range can be selected stepwise. With this configuration, the head adjustment member can be easily operated without using a dedicated tool or the like. In addition, since the adjustment position can be selected stepwise, the position of the heating element can be accurately adjusted without being forced to perform a delicate operation, and the adjustment time can be shortened.

Further, according to the present invention, it is preferable that the head adjusting member is arranged at a position operable from a paper storage space provided on the paper feeding side of the paper. According to this aspect, there is no need to provide a dedicated space for operating the head adjusting member, and there is an advantage that the head adjusting member can be easily operated.

The head adjusting member according to the present invention may be of any type as long as it is an operating element that swings the thermal head unit through the centering surface.
A cam that causes the thermal head unit to swing by contacting the peripheral surface with the aligning surface and rotating is preferably used. When a cam is adopted, as a mechanism capable of selecting the adjustment position stepwise, for example, an engaging portion is formed on the cam, and the engaging portion of the cam is engaged with a fixed member that supports the cam. There is a form in which a plurality of engaged parts to be fitted are provided and the cam is rotated to engage the engaging parts with one engaged part.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a front perspective view of a thermal printer according to an embodiment, and FIG. 2 is a vertical sectional view of the printer. As shown in FIG. 2, this thermal printer uses a heat-sensitive paper S supplied from a rear side (right side in FIG. 2) guide 10 and a platen held by a heating element 22 of a thermal head 21 and a panel 30. By sandwiching the sheet S with the roller 31 and rotating the platen roller 31 counterclockwise in FIG. 2, the sheet S is conveyed to the front side which is the left side in FIG.
Printing is performed on the paper S by the heating element 22 that is energized. The printed sheet S is discharged forward from the discharge port 42 and cut at the discharge port 42.

Reference numeral 40 in FIG. 1 is a cutter unit, 50
Is a gear cover, and 60 is a blade cover fixed to the front surface of the panel 30, and a state in which these parts are removed is shown in FIG. Further, FIG. 4 is an exploded perspective view excluding the panel 30, the cutter unit 40, and the gear cover 50. 1 to 4, reference numeral 70 is a frame. As shown in FIG. 4, the frame 70 includes upper and lower back plate portions 71, 7
2 and a pair of left and right side plate portions 73, 74 are substantially U-shaped in a plan view. The guide 10 is provided on the lower rear side of the frame 70. As shown in FIG.
Is inclined forward and upward, and the supply port 11 for the paper S is opened at the rear end thereof. On the rear side of the frame 70, a paper storage space 75 in which a paper roll is stored is provided by a case (not shown). As shown in FIGS. 2 and 5, between the upper and lower back plate portions 71 and 72 of the frame 70, the sheet storage space 75 to the supply port 11 of the guide 10 is provided.
An opening 76 is provided through which the sheet S passes.

The panel 30 is hinged to the front portion of the lower end of the frame 70 so that the upper side is tilted. Figure 2
As shown in, a platen roller 31 extending in the left-right direction is rotatably supported inside a top end, which is a rotating end of the panel 30, via a platen holder 32. In the platen roller 31, when the panel 30 is closed as shown in FIG.
Bearing groove 77 formed in each side plate portion 73, 74 (see FIG. 4).
(Refer to FIG. 2), the platen roller 31 is attached to the frame 7
It is positioned rotatably with respect to zero. Panel 3
The opening and closing of 0 is performed by the lever 33 shown in FIG.

As shown in FIG. 4, the thermal head 21
Is fixed to the lower side of the head holder 23 with a screw 24, and the thermal head 21, the heating element 22, and the head holder 23 are integrated to form the thermal head unit 20. Shaft pieces (swinging shaft portions) 25 projecting laterally are formed at both ends of the front portion of the head holder 23, and these shaft pieces 25 are vertically long formed above the bearing groove 77 of the frame 70. Is inserted in the bearing hole 78 of the.
The bearing hole 78 allows the shaft piece 25 to move in the vertical direction, but has a dimension that restricts the movement in the front-back direction.
Therefore, the thermal head unit 20 is swingable around the laterally extending shaft piece 25 as a fulcrum and is tiltable to the left and right while the movement in the front-rear direction is restricted.

As shown in FIG. 2, the thermal head unit 20 is urged downward by a plurality of compressed coil springs (urging members) 81 mounted on a spring holder 80 fixed to the frame 70. Due to
The heating element 22 of the thermal head 21 is a platen roller 31.
It is pressed with a proper pressure. As shown in FIG. 4, a slit 82 is formed at the center of the rear end of the spring holder 80, and a pair of left and right holding pieces 83 is formed at the lower front end. The spring holder 80 has a slit 8
2 is hooked on a positioning piece 71a protruding from the center of the upper back plate portion 71 of the frame 70, and each holding piece 83 is attached to the bearing hole 7
It is held by the coil spring 81 while being pressed by the rod 84 that is bridged between the eight.
When the panel 30 is closed, the platen roller 31 comes into pressure contact with the heating element 22 of the thermal head 21, and in that state, the left and right shaft pieces 25 of the head holder 23 are in a state of floating in the bearing hole 78. Therefore, when the panel 30 is opened, the platen roller 31 is disengaged from the heating element 22, so that the thermal head unit 20 moves downward by the force of the coil spring 81, but each shaft piece 25 contacts the lower end edge of the bearing hole 78. As a result, the position of the thermal head unit 20 is regulated there.

As shown in FIG. 3, the driven gear 51 is attached to the shaft end protruding from the left side plate portion 73 of the platen roller 31.
Is fixed. On the other hand, a motor 90 that drives the platen roller 31 is fixed inside the left side plate portion 73. The drive shaft of the motor 90 penetrates the side plate portion 73, and the pinion 91 is fixed to the protruding end thereof. The pinion 91 and the driven gear 51 are connected via the reduction gears 52, 53 supported by the side plate portion 73, and when the motor 90 is driven, the rotation thereof passes through the reduction gears 52, 53 and the driven gear 51. The platen roller 31 rotates in both forward and reverse directions. When the platen roller 31 rotates in the normal direction (counterclockwise in FIG. 2), the paper S sandwiched between the platen roller 31 and the heating element 22 is conveyed forward by friction.

As shown in FIG. 2, a discharge port 42 for the paper S is provided between the cutter unit 40 and the panel 30, and inside the cutter unit 40, it moves forward and backward with respect to the discharge port 42 (not shown). A movable blade is provided. The cutter unit 40 is equipped with a drive mechanism (not shown) that reciprocates the movable blade and normally stores the movable blade in the cutter unit 40. On the other hand, a fixed blade 61 that cuts the sheet S in cooperation with the movable blade is fixed to the front surface of the panel 30. When the movable blade advances into the discharge port 42, the movable blade intersects with the fixed blade 61, whereby the sheet S is cut. Fixed blade 6
No. 1 is covered with the blade cover 60 so that it cannot be touched carelessly. As shown in FIGS. 1 and 2, the paper S is attached to the front of the cutter unit 40.
A cutter 41 that can be turned by hand and cut is fixed.

As shown in FIG. 4, the head holder 23 constituting the thermal head unit 20 has a rear end which is a swinging end, and an aligning piece 27 which rises upward is formed over the entire length in the width direction. A rectangular through hole 23a reaching the aligning piece 27 is formed at the center of the rear portion of the head holder 23, and the through hole 23a is provided at the lower center of the aligning piece 27.
A notch 27a having a trapezoidal shape that communicates with is formed. A horizontal upper edge forming the notch 27a serves as an alignment surface 28 for pressing the heating element 22 against the platen roller 31 with a uniform pressure.

Further, as shown in FIG. 4, on the lower end of the upper back plate portion 71 of the frame 70 and on the front surface side at the center in the width direction thereof, an eccentric cam 101 (via an axially extending cam shaft 100) is provided. A head adjusting member) is rotatably attached. As shown in FIGS. 6 and 7, the eccentric cam 101 includes a disc-shaped cam body 102 and an elastically deformable lever portion 103 extending from the circumferential surface of the cam body 102 in the radial direction of the cam body 102. The camshaft 100 is equipped with
It eccentrically penetrates through the cam body 102. A hook 104 protruding rearward is formed at the tip of the lever portion 103.

On the other hand, on the lower end portion of the upper back plate portion 71 of the frame 70, grooves 79 into which the hooks 104 of the eccentric cam 101 are fitted and engaged are arranged in an arc shape at equal intervals. The tip of the hook 104 that engages with the groove 79 projects from the groove 79. When the protruding end of the hook 104 is pushed forward to elastically deform the lever and the engagement of the hook 104 with the groove 79 is released, the eccentric cam 101 is rotated. Can
The hook 104 can be engaged with another groove 79. The eccentric cam 101 can be manually operated from the rear sheet storage space 75.

As shown in FIG. 2, the head holder 23 of the thermal head unit 20 is provided on the peripheral surface of the cam body 102 of the eccentric cam 101 by the action of the coil spring 81.
The aligning surface 28 of is in pressure contact. Therefore, the eccentric cam 101
When is rotated, the peripheral surface of the cam main body 102 is brought into sliding contact with the centering surface 28, so that the thermal head unit 20 swings with the centering surface 28 as a power point and the shaft piece 25 as a fulcrum, and following this, The heating element 22 serving as the point of action moves in the tangential direction of the platen roller 31. In this case, as shown in FIG. 4, when the hook 104 is engaged with the groove 79 on the rightmost side when viewed from the front, as shown in FIG.
And the peripheral surface of the cam body 102 that abuts on the centering surface 28 has the largest thickness (radial distance), and the rear end of the thermal head unit 20 is in the most floating state. Also,
When the hook 104 is engaged with the leftmost groove 79 when viewed from the front, as shown in FIG. 8B, the gap between the cam shaft 100 and the peripheral surface of the cam body 102 that abuts on the centering surface 28 is provided. The thickness is the smallest, and the rear end of the thermal head unit 20 is located at the bottom.

As described above, when the eccentric cam 101 is rotated, the thermal head unit 20 swings and the hook 104
The position of the thermal head unit 20 is determined by engaging with any of the grooves 79. Further, in this case, the shaft piece 25, which is the swinging shaft portion of the thermal head unit 20, is arranged above the contact position between the platen roller 31 and the heating element 22 in FIG.
As shown in (a), when the thermal head unit 20 swings in the arrow A direction in which the rear end floats, the heating element 22 moves rearward. Further, as shown in FIG. 8B, when the thermal head unit 20 swings in the direction of the arrow B where the rear end descends, the heating element 22 moves forward. The position of the heating element 22 that can be moved in this way is determined by the eccentric cam 1
By engaging the hook 104 of No. 01 with one of the grooves 79, the selection can be made stepwise.

The above is the configuration of the thermal printer of the present embodiment. According to this thermal printer, the hand is inserted into the paper storage space 75 and the lever portion 103 of the eccentric cam 101 is operated by the finger to rotate the eccentric cam 101. By doing so, the pressure contact position of the heating element 22 with respect to the platen roller 31 can be adjusted in the front-back direction (tangential direction). Specifically, the front portion of the heating element 22 is connected to the platen roller 3
When it is desired to press the lever 1, the lever 1
03 to the right (left side when viewed from the front) to move the eccentric cam 10
Rotate 1. Then, the thermal head unit 20 swings in the direction of arrow A shown in FIG. 8A, and the heating element 22 moves rearward as shown by arrow A ′. Therefore, the heating element 2
The front part of 2 is pressed against the platen roller 31. On the contrary, when it is desired to press the rear portion of the heating element 22 against the platen roller 31, the lever portion 103 is moved to the left side (right side when viewed from the front) as viewed from the operator, and the eccentric cam 101 is rotated. Then, the thermal head unit 20 swings in the direction of arrow B shown in FIG. 8B, and the heating element 22 moves forward as shown by arrow B ′. Therefore, the rear portion of the heating element 22 is pressed against the platen roller 31.

According to the position adjusting mechanism for the heating element 22 by the eccentric cam 101, the eccentric cam 101 can be directly operated by hand, and therefore can be easily operated without using a dedicated tool or the like. In addition, the hook 104 is attached to one of the grooves 7
9 to fix the position of the eccentric cam 101,
The position of the heating element 22 can be accurately adjusted without being forced to perform a delicate operation, and the adjustment time can be shortened. In addition, the eccentric cam 10 moves from the paper storage space 75.
1 is operated, there is no need to provide a dedicated space for operating the eccentric cam 101, and the eccentric cam 10
1 is easy to operate.

In the present embodiment, the centering surface 28 provided on the thermal head unit 20 is located at the center in the width direction of the thermal head unit 20, and therefore the centering surface 28 is pressed against the eccentric cam 101. The thermal head unit 20 that operates is kept in an equilibrium in a tilted state. Therefore, the pressure distribution in the longitudinal direction of the heat generating element 22 that is in pressure contact with the platen roller 31 is uniform without being biased to one side, and the heat generating element 22 is in pressure contact with the platen roller 31 with a uniform pressure.

As described above, in the present embodiment, the aligning surface 2
The eccentric cam 101 that acts on the heat generating element 22 adjusts the tangential position of the heat generating element 22 with respect to the platen roller 31.
Also has the two functions of aligning the platen roller 31 with a uniform pressure. Therefore, the configuration is simple in mounting these two functions, and the increase in the number of parts can be suppressed.

[0028]

As described above, according to the present invention,
The head adjusting member acting on the aligning surface has two functions of adjusting the position of the heating element in the tangential direction of the platen roller and aligning the heating element with the platen roller with a uniform pressure. The effect is that the configuration is simplified when mounting the, and the increase in the number of parts can be suppressed.

[Brief description of drawings]

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

FIG. 2 is a vertical cross-sectional view of the thermal printer according to the embodiment of the present invention.

FIG. 3 is a front perspective view of the thermal printer according to the embodiment of the present invention with some components removed.

FIG. 4 is an exploded perspective view of the thermal printer according to the embodiment of the present invention.

FIG. 5 is a rear perspective view of the thermal printer according to the embodiment of the present invention.

FIG. 6 is a perspective view of an eccentric cam according to an embodiment of the present invention.

FIG. 7 is a front view of an eccentric cam according to an embodiment of the present invention.

8A and 8B are side views showing the operation of the eccentric cam according to the embodiment of the present invention.

[Explanation of symbols]

21 ... Thermal head 22 ... Heating element 25 ... Shaft piece (swing shaft) 28 ... Aligning surface 31 ... Platen roller 75 ... Paper storage space 81 ... Coil spring (biasing member) 101 ... Eccentric cam (head adjusting member)

Claims (4)

[Claims] 1. A thermal head unit including a thermal head having a heating element extending in a width direction orthogonal to a sheet conveying direction, the thermal head unit being fixed to a support, and a sheet to be fed which is disposed so as to face the heating element. A platen roller sandwiched between the heating element, a swinging shaft portion which is parallel to the heating element and which swingably supports the thermal head unit, and a swinging shaft portion which is tiltably supported in the platen roller direction. An inclining mechanism, an urging member for urging the thermal head unit in the platen roller direction to press the heating element against the platen roller, and a center in the swing direction of the thermal head unit in the width direction. An aligning surface, and the thermal head unit is pressed against the aligning surface by the action of the biasing member and is operated to make the thermal head unit the swing shaft portion as a fulcrum. A thermal printer having a head adjusting member for rocking the head. 2. The thermal printer according to claim 1, wherein the head adjustment member can be directly operated by hand, and the adjustment position within its operating range can be selected stepwise. 3. The thermal printer according to claim 1, wherein the head adjustment member is arranged at a position operable from a paper storage space provided on the paper feed side of the paper. 4. The head adjusting member is a cam which has a peripheral surface in contact with the aligning surface and rotates to swing the thermal head unit. The thermal printer described in.