JP2577814Y2 - Printer paper feed mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a paper feeding mechanism of a printer, and particularly has paper feeding rollers on a loading side and a loading side of a platen and a print head, respectively. The present invention relates to a paper feed mechanism of a printer that transports paper linearly.

[Conventional technology]

Generally, paper feed rollers are provided on a carry-in side and a carry-out side of a platen and a print head mounted on a carriage so as to be opposed to the platen, and the respective paper feed rollers are driven to rotate, whereby the desired paper is formed. 2. Description of the Related Art A paper feed mechanism of a printer that linearly conveys between a platen and a print head is often used.

FIG. 5 shows a paper feeding mechanism of a conventional printer, in which a platen 1 in the form of a flat plate is provided, and a carriage 2 is provided near the platen 1 in the longitudinal direction of the platen 1 (perpendicular to FIG. 5). Direction). A print head 3 is mounted on the upper surface of the carriage 2 so as to face the platen 1, and an ink ribbon (not shown) is wound between the platen 1 and the print head 3 on the upper surface of the carriage 2. A ribbon cassette 4 for guiding while taking is mounted.

Above the platen 1, a loading paper feed roller 6 for transporting the paper 5 between the platen 1 and the print head 3 is rotatably disposed. , A carry-in side auxiliary roller 7 for holding the paper 5 is pressed. An unloading paper feed roller 8 for discharging the printed paper 5 is provided below the platen 1.
The discharge side paper feed roller 8 is pressed against a discharge side auxiliary roller 9 for holding the sheet 5 with a pressing force stronger than the pressing force of the load side auxiliary roller 7. ing.

Also, a discharge motor 8 for rotating the discharge paper feed roller 8 and the discharge paper feed roller 8 is provided. The output pinion 11 of the drive motor 10 has a two-stage load transmission gear 12 and The idle gear 13 meshes with a carry-in paper feed drive gear 14 fixed to the carry-in paper feed roller 6. Further, the output pinion 11 of the drive motor 10 has a two-stage unloading-side transmission gear 15 and an idle gear
The gear 16 is meshed with a carry-out paper feed drive gear 17 fixed to the carry-out paper feed roller 8 via the same.

In the conventional paper feed mechanism, the drive motor 10
To rotate the carry-in paper feed roller 6 and the carry-out paper feed roller 8 via the transmission gears 12 and 15 and the idle gears 13 and 16, and move the carry-in paper feed roller 6 to the carry-in auxiliary roller. 7 by inserting the paper 5
The sheet 5 is conveyed between the platen 1 and the print head 3, and the lower end of the sheet 5 is moved to the unloading side paper feed roller 8.
And the discharge-side auxiliary roller 9. In this state, the carriage 2 is moved along the platen 1 and the print head 3 is driven based on a desired print signal while the ink ribbon of the ribbon cassette 4 is being wound up. The desired printing is performed. In this case, when the leading end of the paper 5 does not reach the carry-out side paper feed roller 8 and the carry-out side auxiliary roller 9, the carry-in side paper feed roller 6 and the carry-in side auxiliary roller 7
As a result, printing is performed on the leading end of the sheet while feeding the sheet 5. When the trailing end of the paper 5 is disengaged from the carry-in paper feed roller 6 and the carry-in auxiliary roller 7, the paper 5 is fed by the carry-out paper feed roller 8 and the carry-out auxiliary roller 9, Printing is performed.

At this time, since the carry-out paper feed roller 8 is driven at a slightly higher speed than the carry-in paper feed roller 6, as shown in FIG. Since the pulling force F1 of the carry-in paper feed roller 6 and the pulling force F2 of the carry-in paper feed roller 8 are applied, and the press-contact force between the carry-in paper feed roller 6 and the carry-in auxiliary roller 7 is weak, The paper 5 slips and is conveyed to the carry-in paper feed roller 6 and the carry-in auxiliary roller 7, and the tensile forces F 1 and F 2 with respect to the paper 5 are mutually disturbed so as not to affect the conveyance of the paper 5. They are canceling each other out. As a result, a constant tension is applied to the paper 5, and it is possible to prevent the print quality from being degraded due to the slack of the paper 5.

[Problems to be solved by the invention]

However, in the paper feed mechanism of the conventional printer, the discharge paper feed roller 8 is connected to the input paper feed roller 6.
Since the paper 5 is driven at a slightly higher speed than that, the printing of the paper 5 proceeds, and at the moment when the rear end of the paper 5 comes off the carry-in paper feed roller 6 and the carry-in auxiliary roller 7, Tensile force F1 by the carry-in side paper feed roller 6
Becomes zero, and the carry-out paper feed roller 8 rotates excessively by the amount of backlash of the carry-out paper feed drive gear 17 of the carry-out paper feed roller 8, and the conveyance pitch of the paper 5 is disturbed. However, there is a problem that the printing cannot be performed properly and the printing quality is deteriorated. This is particularly noticeable when the paper 5 is a thick paper.

The present invention has been made in view of these points, and even when the end of the paper comes off the paper feed roller on the loading side, it is possible to perform proper printing with a constant paper conveyance pitch and to achieve a high print quality. It is an object of the present invention to provide a paper feeding mechanism of a printer which can improve the paper feeding.

[Means for solving the problem]

In order to achieve the above object, a first invention is to dispose a paper feed roller rotatably on a paper loading side and a paper loading side with a platen and a print head arranged opposite to the platen interposed therebetween, and each of these paper feed rollers is provided. A paper feed mechanism for a printer, wherein a drive motor is connected to each of the rollers via a rotation transmission mechanism, and the output side paper feed roller is driven to rotate at a slightly higher speed than the input side paper feed roller. It is characterized in that a friction member that constantly applies a frictional force that is a rotational load to the rotation shaft of the carry-out paper feed roller is disposed on the rotation shaft. Paper feed rollers are rotatably arranged on the paper loading side and the paper output side, respectively, with the platen and the print head arranged opposite to the platen interposed therebetween,
A paper feed mechanism for a printer, wherein a drive motor is connected to each of the paper feed rollers via a rotation transmission gear, and the output paper feed roller is driven to rotate at a slightly higher speed than the input paper feed roller. Wherein a back crush removing mechanism is provided in a rotation transmission gear to the discharge side paper feed roller.

[Action]

According to the first aspect of the present invention, the driving motor is driven to rotate the output paper feed roller at a slightly higher speed than the input paper feed roller via the rotation transmission mechanism so that the paper is fixed to the paper. While applying a tension between the platen and the print head. And
At the moment the trailing edge of the paper comes off the paper feed roller on the loading side,
Although the tension on the paper is lost, the discharge paper feed roller attempts to rotate instantaneously, but the load on the discharge paper feed roller is caused by the frictional force of the friction member provided at the rotating portion of the discharge paper feed roller. Therefore, it is possible to surely prevent the unloading-side paper feed roller from rotating unnecessarily and changing the sheet conveyance pitch.

According to the second aspect of the present invention, a back is formed by joining two thin gears which are urged in circumferentially opposite directions to a rotation transmitting gear to a discharge side paper feed roller. Since the lash removing mechanism is provided, the gears with which the teeth of the thin gears are meshed are meshed with the gear with which the backlash is removed, and when the tension on the paper is lost, the unloading side It is possible to reliably prevent unnecessary rotation of the paper feed roller.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
5 and 6 will be described with the same reference numerals.

FIG. 1 shows an embodiment of the present invention. In the vicinity of a flat platen 1, a carriage 2 on which a print head 3 is mounted on the upper surface is arranged in the longitudinal direction of the platen 1 (perpendicular to FIG. 1). The carriage 2 is provided with a ribbon cassette 4 for guiding an ink ribbon (not shown) between the platen 1 and the print head 3 on the upper surface of the carriage 2.

Above the platen 1, a loading paper feed roller 6 for transporting the paper 5 between the platen 1 and the print head 3, and a loading auxiliary roller 7 pressed against the loading paper feed roller 6 are provided. Each of them is rotatably disposed, and is pressed below the platen 1 with a pressing force stronger than the pressing force of the unloading side paper feed roller 8 for discharging the paper 5 after printing and the loading side auxiliary roller 7. The carry-out side auxiliary rollers 9 are rotatably arranged.

Further, a carry-in paper feed drive gear fixed to the carry-in paper feed roller 6 and the carry-out paper feed roller 8, respectively.
The output side paper feed drive gear 14 and the output side paper feed drive gear 17 are connected to the output pinion 11 of the drive motor 10 via idle gears 13 and 16 and a two-stage input side transmission gear 12 and output side transmission gear 15, respectively. Each gear ratio is set so that the carry-out paper feed roller 8 is driven to rotate at a slightly higher speed than the carry-in paper feed roller 6.

As shown in FIG. 2, in the present embodiment, the rotation shaft 18 of the unloading side paper feed roller 8 is rotatably held by a bearing 20 mounted on a frame 19 of the printer. A stopper 21 such as a washer is attached to a middle portion of the rotation shaft 18 of the discharge paper feed roller 8. On the outside of the frame 19 of the rotating shaft 18, the unloading side paper feed drive gear 17 is coaxially fixed,
A felt 22 as a friction member is interposed between the outer surface of the frame 19 and the carry-out paper feed drive gear 17. Further, an urging spring is provided between the bearing 20 and the stopper 21 of the rotary shaft 18 to urge the discharge-side paper feed drive gear 17 in a direction of pressing the frame 19 through the felt 22.
The rotating shaft 18, that is, the unloading paper feed roller 8, is provided by a frictional force generated when the discharge-side paper feed drive gear 17 is pressed against the felt 22 by the biasing spring 23. When the external load is applied to the output side paper feed roller 8, the output side paper feed roller 8 is not easily rotated.

 Next, the operation of the present embodiment will be described.

In the present embodiment, the drive motor 10 is driven to rotate the carry-in side paper feed roller 6 and the carry-out side paper feed roller 8 via the transmission gears 12 and 15 and the idle gears 13 and 16, respectively. The paper 5 is transported between the platen 1 and the print head 3. In this state, the carriage 2 is moved along the platen 1 and the print head 3 is driven based on a desired print signal while the ink ribbon of the ribbon cassette 4 is being wound up. The desired printing is performed. At this time, since the rotation speeds of the carry-in paper feed roller 6 and the carry-out paper feed roller 8 are different, a constant tension is applied to the paper 5 and the print quality is deteriorated due to the slack of the paper 5 or the like. Is to be prevented.

At the moment when the paper 5 is conveyed and the rear end of the paper 5 is disengaged from the carry-in paper feed roller 6 and the carry-in auxiliary roller 7, the tension on the paper 5 is lost. 8 tries to rotate by the backlash of the discharge paper feed drive gear 17, but in this embodiment, the load is applied to the discharge paper feed roller 8 by the frictional force of the felt 22, so that The unloading side paper feed roller 8 does not rotate unnecessarily, and it is possible to reliably prevent a change in the transport pitch of the paper 5.

Therefore, in the present embodiment, when the paper 5 comes off the carry-in paper feed roller 6, unnecessary rotation of the carry-out paper feed roller 8 can be prevented, and the transport pitch of the paper 5 is disturbed. Therefore, printing can be performed properly and the printing quality can be significantly improved.

FIGS. 3 and 4 show a backlash removing mechanism according to another embodiment of the present invention. For example, the paper feed drive gear 17 on the discharge side is coaxially connected to two thin gears 24a, 24b having the same diameter. These thin gears are formed by joining
Arc-shaped spring accommodating grooves 25, 25 are formed at positions corresponding to the mutually facing surfaces of 24a, 24b, respectively. Locking projections 26, 26 are formed at opposite ends of each of the spring housing grooves 25, 25, respectively.
Inside the 5, both ends are locked by the locking projections 26,
A spring 27 biased in a contracting direction is housed. Then, in this state, the unloading side paper feed gear 17 is formed by joining the thin gears 24a, 24b, and the thin gears 24a, 24b are circumferentially moved by the urging force of the spring 27. In the opposite direction.

In the present embodiment, the discharge-side paper feed gear 17 having the above-described configuration is used.
By meshing the gear with the idle gear 16, each thin gear
Since the teeth of 24a and 24b sandwich the teeth of the idle gear 16 from opposite directions, the carry-out paper feed drive gear 17 is meshed with the idle gear 16 in a state where backlash is removed. Will be. Therefore, when the paper comes off the carry-in paper feed roller 6 and the tension on the paper is lost, the carry-out paper feed drive gear 17 has no backlash.
Can be prevented from rotating unnecessarily.

Therefore, in the present embodiment, as in the above-described embodiment, printing can be performed properly without disturbing the paper conveyance pitch, and the printing quality can be significantly improved.

The present invention is not limited to the above-described embodiment, but can be variously modified as needed.

[Effect of the invention]

As described above, the paper feed mechanism of the printer according to the present invention is configured such that when the tension on the paper is lost due to the friction member or the backlash removing mechanism disposed on the paper feed roller section on the discharge side, the paper feed mechanism on the discharge side is fed. Unnecessary rotation of the roller can be reliably prevented. As a result, it is possible to perform printing properly without disturbing the paper conveyance pitch, and to achieve effects such as remarkable improvement in printing quality.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of a part of the discharge side paper feed roller of FIG. 1, and FIGS. 3 and 4 show other embodiments of the present invention. Example 3
FIG. 4 is an exploded perspective view of the unloading side paper feed roller, FIG. 4 is a perspective view of the unloading side paper feed roller, FIG. 5 is a schematic configuration diagram showing a conventional paper feed mechanism, and FIG. It is explanatory drawing which shows the applied pulling force. DESCRIPTION OF SYMBOLS 1 ... Platen, 2 ... Carriage, 3 ... Print head, 5 ... Paper, 6 ... Carry-in side paper feed roller, 7 ... Carry-in side auxiliary roller, 8 ... Carry-out side paper feed roller, 9 ... Unloading-side auxiliary roller, 10 ... Drive motor, 17 ... Unloading-side paper feed drive gear, 18 ... Rotary shaft, 19 ... 20, ... Bearing, 22 ...
... felt, 24 ... thin gear.

Claims (2)

(57) [Scope of request for utility model registration] 1. A paper feed roller is rotatably disposed on a paper carry-in side and a paper carry-out side with a platen and a print head disposed opposite to the platen interposed therebetween, and a rotation transmitting mechanism is respectively provided to each of the paper feed rollers. And a drive motor connected to the paper feed roller of the printer at a speed slightly higher than that of the paper feed roller on the input side. A paper feed mechanism for a printer, wherein a friction member that constantly applies a frictional force that is a rotational load to a shaft is disposed on the rotation shaft. 2. A paper feed roller is rotatably disposed on a paper loading side and a paper discharge side with a platen and a print head disposed opposite to the platen interposed therebetween, and a rotation transmission gear is provided for each of the paper feed rollers. And a drive motor connected to the paper feed roller of the printer, wherein the paper feed roller of the discharge side is rotated at a slightly higher speed than the paper feed roller of the input side. A paper feed mechanism for a printer, wherein a backlash removing mechanism is provided on the rotation transmission gear.