JPH04355173A - Paper feed device in printer - Google Patents

Abstract

PURPOSE:To feed paper in a forward line-feed direction and a reverse line-feed direction without the occurrence of a failure of paper, such as slack and skew. CONSTITUTION:The following two states are set correspondingly to a change of a rotating direction of a drive gear 21 by changing over a change arm 15: in one state, a first planetary gear 24 engages with one of two gears of a two- speed follower gear 13 and the drive gear 21, and in the other state, a second planetary gear 14 engages with the other gear of the two-speed follower gear 13 and the drive gear 21. In this manner, a paper feed speed of a paper discharge roller 11 can be set higher than that of a platen 20 at the time of a forward line feed and lower than that of the platen 20 at the time of a reverse line feed. Therefore, a slack of printing paper can be eliminated from on the platen 20 onto the paper discharge roller 11, a line feed accuracy is improved, and a printing contamination can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feed device for a printer, and more particularly to a paper feed device for a dot serial printer that feeds paper in a forward line feed direction or a reverse line feed direction.

0002

2. Description of the Related Art Conventionally, in a printer, as shown in FIG. The driven gear 25 of the discharge roller 11 is rotated by the provided drive gear 21, and the paper 1 is
9 is being sent out. A one-way clutch bearing (not shown) was provided between the shaft portion of the discharge roller 11 and the driven gear 25 so that the discharge roller 11 rotates only in the forward direction.

In this paper ejection unit, only when the driving gear 21 is rotating in the direction A, the driven gear 25
After that, the discharge roller 11 rotates forward and feeds the paper. When the drive gear 21 is rotating in the direction B, the discharge roller 11 does not rotate.

[0004] In addition, as another type of conventional paper ejection unit, the shaft portion of the ejection roller 11 and the driven gear 25 are directly connected and fixed without having the above-mentioned one-way clutch bearing. The changing operation of the rotational direction of the drive gear 21 which is meshed with the drive gear 21 is directly transmitted to the discharge roller 11, and the discharge roller 11 can rotate forward or backward. At this time, the absolute value of the rotational speed of the discharge roller 11 during forward rotation and the rotational speed during reverse rotation was the same.

In the figure, 10 is a roller cover, 16 is a platen bushing, and 18 is a pressure roller assembly that presses the paper 19 against the platen 20.

[0006]

[Problems to be Solved by the Invention] By the way, in this conventional paper ejection unit, in which the ejection roller rotates even when performing a reverse line feed, the paper feed speed of the paper ejection roller is changed to Since the paper feed speed is set higher than the paper feed speed of the platen or tractor, as shown in Fig. 3, the slack portion 1 of the paper 19 on the platen is
9a occurs, resulting in poor line feed accuracy. In addition, printing smudge defects may also occur.

On the other hand, in the case where the ejection roller does not rotate when performing a reverse line feed, the paper holding force in the paper ejection unit is large, causing problems such as skewed paper feeding and paper jams. Ta.

The present invention has been made in view of the above-mentioned problems, and provides a printer that can feed paper in the normal line feed direction and reverse line feed direction without causing paper defects such as sagging or skewed paper. The purpose is to provide a paper feeding device for

[0009]

[Means for Solving the Problems] In order to achieve the above object, the paper feeding device of the printer of the present invention winds paper between a platen facing a print head and a paper ejection roller provided parallel to the platen. In a paper feed device for a printer that rotates a paper ejection roller in conjunction with a platen to feed the paper, a planetary gear mechanism is provided between the platen and the ejection roller to change the rotational speed of the ejection roller according to the rotational direction of the platen. The configuration includes the following.

If necessary, the planetary gear mechanism includes a drive gear provided on the drive shaft of the platen, a two-stage driven gear provided on the shaft of the ejecting roller, and a second gear that meshes with one of the drive gear and the driven gear. a second planetary gear that meshes with the other of the drive gear and the driven gear; a second planetary gear that supports the first and second planetary gears and is rotatably provided on the drive shaft of the platen; The configuration includes a change arm that switches and engages the first and second planetary gears by operation.

[0011]

[Operation] According to the paper feeding device for a printer having the above structure, the rotational speed of the ejection roller is changed according to the rotational direction of the platen by the planetary gear mechanism.

According to the paper feeding device of the printer according to the second aspect, the change arm is switched in response to a change in the rotational direction of the drive gear, so that one of the two gears of the driven gear and the drive gear are connected to each other. The second planetary gear is set when the first planetary gear meshes with both the second gear of the driven gear and the drive gear. Therefore, it is possible to change the absolute value of the rotation speed of the paper ejection roller depending on the rotation direction of the drive gear.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a paper delivery device including a paper delivery unit including a mechanical section of a dot serial printer according to an embodiment of the present invention.

In the figure, 20 is a platen facing a print head 23 supported by a carriage 22. As shown in FIG. 11 is a paper ejection roller provided parallel to the platen 20. The printing paper 19 is fed by the platen 20 and the pressure roller assembly 18, but is also sandwiched between the roller cover 10 and the paper ejection roller 11, which are part of the paper ejection unit.
The printing paper 19 is also sent by the paper discharge roller 11.

Further, while a drive gear 21 is provided on the drive shaft (platen shaft 17) of the platen 20,
A two-stage driven gear 13 is provided on the roller shaft 12 of the discharge roller 11.

24 is a first planetary gear (F) that meshes with one of the drive gear 21 and the driven gear 13; 14 is a second planetary gear (B) that meshes with the other of the drive gear 21 and the driven gear 13. . These first and second planetary gears 24,
14 is rotatably provided outside the platen bush 16 of the platen 20 and connects the first and second planetary gears 24.
, 14 are supported by a change arm 15 that switches and engages them.

Further, the drive gear 21 fixed to the platen shaft 17 always includes a first planetary gear (F) 24.
and the second planetary gear (B) 14 are engaged with each other. Furthermore, the driven gear 13 is a two-stage gear, with the smaller gear meshing with the first planetary gear (F) 24 and the larger gear meshing with the second planetary gear (B) 14.

The change arm 15 is connected to the platen 20.
It is possible to rotate by a certain angle with respect to the axis of the This certain angle means that the change arm 15 rotates from the point where the first planetary gear (F) 24 meshes with the driven gear 13 without any problem, and the second planetary gear (B) 14 engages with the driven gear 1.
This is the angle required to mesh with 3 without any problem, and this angle is made as small as possible. Also, the first planetary gear (F)
24 and the driven gear 13, and the second planetary gear (B) 14 and the driven gear 13, a convex portion is formed on the platen bush 16, and a convex portion is formed on the change arm 15.
A groove corresponding to this is provided to limit rotation to a certain angle at all times.

Therefore, according to the paper feeding device according to the embodiment, when feeding the printing paper 19 in the direction of the arrow x (normal line feed), the drive gear 21 is driven by the LF motor (not shown) and rotates. At the same time, the second planetary gear (B) 14 supported by the change arm 15 shifts to the driven gear 1.
3, the first planetary gear (F) 24 is separated from the driven gear 13
Move to the side and engage. Then, the paper discharge roller 11 sends the paper in the same x direction as the direction in which the platen 20 sends the printing paper 19. At this time, the gear ratio is set so that the paper feed speed of the paper discharge roller 11 is higher than the paper feed speed of the platen 20.

When the printing paper 19 is sent in the direction of the arrow y (reverse line feed), the drive gear 21 is driven by the LF motor and rotates, and at the same time the first planetary gear supported by the change gear 15 (F) 24 separates from the driven gear 13, and the second planetary gear (B) 14, which was not engaged with it until then, moves toward the driven gear 13 and engages with it. Then, the paper discharge roller 11 sends the paper in the same y direction as the direction in which the platen 20 sends the printing paper 19. At this time, the gear ratio is set so that the paper feed speed of the paper ejection roller 11 is slightly smaller than or the same as the paper feed speed of the platen 20.

[0021] For this reason, when performing a reverse line feed, the platen 2
It is possible to prevent the paper from sagging between the paper output roller 11 and the paper discharge roller 11, and the line feed accuracy is improved.

[0022]

As explained above, according to the paper feed device of the present invention, the paper feed speed of the paper ejection roller is made higher than the paper feed speed of the platen at the time of a normal line feed.
At the time of reverse line feed, the paper feed speed of the paper ejection roller can be made smaller than the paper feed speed of the platen, so it is possible to eliminate slack in the printing paper from the top of the platen to the top of the paper ejection roller, and improve line feed accuracy. This has the effect of preventing print stains.

Furthermore, the paper tension between the paper ejection roller and the platen, which takes up the slack in the printing paper at the time of reverse line feed, can be made smaller than before, making it possible to prevent paper jams and skew feeding. It also has the effect of being able to do so.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a paper feeding device of a printer according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a paper feeding device of a conventional printer, and shows a normal line feed of printing paper.

FIG. 3 is a cross-sectional view showing a conventional problem, illustrating a slack portion of the printing paper that occurs when the printing paper is reversely line-feeded.

[Explanation of symbols]

10 Roller cover 11 Paper discharge roller 12 Paper discharge roller shaft 13 Driven gear 14 Second planetary gear (B) 15 Change arm 16 Platen bush 17 Platen shaft 18 Pressure roller assembly 19 Print paper 20 Platen 21 Drive gear 22 Carriage 23 Print head 24 First planetary gear (F) x Forward line feed direction y Reverse line feed direction 25 Driven gear

Claims (2)

[Claims] 1. Paper for a printer in which paper is wound between a platen facing a print head and a paper ejection roller provided parallel to the platen, and the paper ejection roller is rotated in conjunction with the platen to send out the paper. A paper feeding device for a printer, characterized in that a planetary gear mechanism is provided between the platen and the ejecting roller to change the rotational speed of the ejecting roller according to the rotational direction of the platen. 2. The planetary gear mechanism includes a drive gear provided on the drive shaft of the platen and a drive gear provided on the shaft of the discharge roller.
a driven gear of the stage, a first planetary gear that meshes with one of the drive gear and the driven gear, a second planetary gear that meshes with the other of the drive gear and the driven gear, and the first and second planetary gears. 2. The change arm according to claim 1, further comprising a change arm that supports the platen and is rotatably provided on the drive shaft of the platen, and switches and engages the first and second planetary gears by the rotational action. Printer's paper feed device.