JPH05124279A - Pressure switching mechanism for paper convey roller - Google Patents

Abstract

PURPOSE:To make a structure small in size and reduce irregularity of pressing force, in a mechanism for switching the pressing force of a pinch roller against a feed roller. CONSTITUTION:A mechanism for switching pressing force of a pinch roller 2b against a feed roller 2a comprises a cam, a follower lever, racks 10a, 10b, a gear 12, a connecting shaft 16, a flame 14, a pressing member 15, and a compression spring 17. The pinch roller 2b is moved slidably to the feed roller 2a so as to switch the pressing force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure switch mechanism for a paper feed roller, which is used in printers and the like, and which comprises a feed roller for feeding paper and a pinch roller for feeding the paper in pressure contact with the feed roller.

[0002]

2. Description of the Related Art Conventionally, the pressure of a sheet conveying roller in a printer of this type is switched to weaker for continuous sheets and stronger for single-cut sheets, for example, because the pressure required for conveying differs depending on the type of sheet. There is. As shown in, for example, Japanese Utility Model Laid-Open No. 1-146959, that is, as shown in FIGS. 4 and 5, this switching mechanism has a pinch roller 52 which is in pressure contact with the feed roller 51 and one end of which is fixed to a rotary shaft 53. It is rotatably arranged at the tip of the leaf spring 54,
A cam 55 and a link 56 connected to the rotary shaft 53 are provided as a mechanism for switching the roller pressure by a spring force. The rotary shaft 53 is rotated by the rotation of the cam 55 to rotate the leaf spring 54 with respect to the pinch roller 52. The pressing force can be variably set and the pinch roller 52 can be opened. The sheet 57 is conveyed while being sandwiched between a feed roller 51 and a pinch roller 52 provided on the upstream side and the downstream side in the sheet feeding direction, and printed by a print head 58 located between them.

[0003]

However, in the above structure, the rotary shaft 53 is used to switch the roller pressure.
Since the plate spring 54 is used, the structure becomes large, especially in the sheet conveying direction, and waste is likely to occur between the printed pages of continuous paper. Further, due to the flatness of the leaf spring 54, there is a problem that the pressing force tends to vary and the required pressing force may not be obtained. The present invention has been made in order to solve the above-mentioned problems, and provides a pressure switching mechanism for a paper transport roller, which can have a more compact structure and can reduce variations in the pressing force of the roller. The purpose is to

[0004]

In order to achieve this object, the present invention is a mechanism for switching the nip pressure of a pair of rollers for conveying a sheet, and a feed roller disposed along the printing direction, and the feed roller. A pinch roller that is in pressure contact with the roller and that conveys a sheet; a frame member that extends parallel to the pinch roller; pressing means that is attached to the frame member and that presses the pinch roller into contact with the feed roller; and the pinch roller. Rack movably supported in the press contact direction, coupled to the frame member, a gear meshing with the rack, a connecting shaft that rotates the gears in synchronization, and one of the racks. And a power transmission means for moving in the press contact direction.

[0005]

According to the above construction, by driving the power transmission means, the rack engaged with the power transmission means is moved in the press contact direction of the pinch roller. The movement of the rack is transmitted to the other rack by the gear and the connecting shaft, and as a result, the racks on both sides slide in synchronization.
The frame member to which the pressing means is attached is connected to the rack and moves integrally with the rack. The pressure contact force of the pinch roller with respect to the feed roller by the pressing means attached to the frame member can be changed by the movement amount of the rack. Further, the pressure contact of the rollers can be released depending on the amount of movement of the rack.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic side sectional structure of a printer embodying the present invention, FIG. 2 shows its plane structure, and FIG. 3 shows a structure of a pressing means for a feed roller and a pinch roller. The first continuous paper transporting path is provided between the feed roller 1a and the pinch roller 1b forming the first transporting means from the front tractor 20 arranged on the upstream side in the paper transporting direction, between the print head 12 and the platen 7, and It is formed by a path that passes between the feed roller 2a and the pinch roller 2b that form the second conveying means. In addition, the second continuous form paper transport path is
It is formed by a path from the rear tractor 21 between the feed roller 3 and the paper pan 6 forming the third conveying means, between the print head 12 and the platen 7, and between the feed roller 2a and the pinch roller 2b forming the second conveying means. The discharge path of the continuous paper transport path is configured to be switchable between the feed roller 2a and the pinch roller 2b of the second transport means and between the feed roller 4a and the pinch roller 4b which constitute the fourth transport means. ..

Further, the cut sheet transport path has a feed roller 5a and a pinch roller 5b, which form a fifth transport means, from a feed roller 1a and a pinch roller 1 of the first transport means.
b, between the print head 12 and the platen 7, and between the feed roller 2a and the pinch roller 2b of the second conveying means. The print head 12 has a guide shaft 19
It is held by a carriage 18 supported by a and 19b. The arrow shown in the figure indicates the sheet conveyance direction. A cam 8 and a follower lever 9 are provided as power transmission means for switching the roller pressure. The follower lever 9 is urged to a cam 8 by a pulling spring 11 attached to the tip of the follower lever with a shaft 9a as a fulcrum, and the cam 8 is rotationally driven by a drive motor (not shown). The node lever 9 is swung. This drive motor is operated by a switch for switching the transmission of power to each of the transport devices that can switch the paper path. The drive shaft 2c of the feed roller 2a has the left and right side plates 2 at both ends thereof.
It is rotatably supported by 2a and 22b. Pinch roller 2b
Although not shown in the drawings, the shaft 2d of the side plates 22a, 22
It is rotatably supported by a bearing movably provided by being guided by the long hole of b.

The rack 1 is placed close to the side plates 22a and 22b.
0a and 10b are provided so as to be slidable in the pressure contact direction of the pinch roller 2b, and a shaft 9b fixed to the tip of the follower lever 9 engages with an elongated hole formed at the lower end of one rack 10a. Therefore, the rack 10a is moved in the pressure contact direction by the swing of the follower lever 9. In addition, rack 1
The drive shaft 2c is inserted through a long hole formed in the middle portion of 0a. A gear 13 meshes with a pinion formed on an end surface of the rack 10a, and the rotation of the gear 13 is transmitted to a gear meshing with the rack 10b on the opposite side via a connecting shaft 16. As a result, the racks 10a and 10b slide in synchronization. A frame 14 is attached to the ends of the racks 10a and 10b, and the racks 10a, 10b and the frame 14 move integrally. In FIG. 2, the follower lever 9, the gear 13,
Illustration of the connecting shaft 16 and the like is omitted.

Feed roller 2a and pinch roller 2b
As shown in FIG. 3, a plurality of drive shafts are arranged in the moving direction of the print head 12, and both ends of the drive shaft 2c and the shaft 2d are rotatably supported by the side plates 22a and 22b.
The drive shaft 2d is movable in the pressure contact direction. Print head 1
A plurality of pressing members 15 are provided on a frame 14 extending in parallel to the moving direction of 2 so as to be movable in parallel to the moving directions of the racks 10a and 10b. It is biased toward the feed roller 2a. Gears are fixed to the ends of the drive shaft 2c and the feed roller 1a, and a timing belt circulates around these gears and the gears attached to the drive shaft of the conveyance motor. Then, the feed rollers 1a and 2a rotate at the same peripheral speed by the rotation of the transport motor.

In the above structure, for example, when continuous form paper is fed from the front tractor 20, the cam 8 is rotated by a motor (not shown) and the rack 10a is pinched by the follower lever 9 into a pinch roller. 2b is a feed roller 2a
When the rack 10b is moved further away, the other rack 10b also moves in the same direction via the gear 13 and the connecting shaft 16. As a result, the frame 14 integrated with the rack 10a and the rack 10b moves, and the compression amount of the compression spring 17 decreases,
The pressing member 15 weakens the pressure contact force for pressing the drive shaft 2d. Therefore, the pressure contact force of the pinch roller 2b becomes weak. In this state, the continuous form paper is conveyed. On the other hand, when the cut sheet is fed from the feed roller 5a and the pinch roller 5b of the fifth conveying means, the cam 8 is rotated in the opposite direction to move the racks 10a and 10b in the opposite direction, The compression amount of the compression spring 17 is increased and the pressure contact force of the pinch roller 2b is increased to convey the single-cut sheet.

When the sheet is sucked, the cam 8 is rotated to move the racks 10a and 10b largely in the direction in which the pinch rollers 2b are separated from the feed rollers 2a, and the edges of the long holes formed in the racks 10a and 10b are moved. Both ends of the drive shaft 2d of the pinch roller 2b are supported, the pinch roller 2b is opened, and the paper is fed to the feed roller 2a and the pinch roller 2b.
After guiding in between, the cam 8 is rotated in the opposite direction to move the rack 10
After a and 10b are moved in the opposite direction to sandwich the paper, the paper is conveyed. As described above, since the pressure of the paper transport roller is switched by the sliding movement of the shaft, the dimension in the paper transport direction is shorter than that of the conventional mechanism by the rotation of the spring plate, and the space between the pages of the paper can be reduced. With less waste,
The variation in the sandwiching force in the width direction of the paper is also reduced.
In this embodiment, the pressure contact force of the feed roller 2a and the pinch roller 2b is changed in association with the selection of the paper, but a mechanism for setting the pressure contact force, that is, the rotation amount of the drive motor is provided on the operation panel. It may be provided.

[0012]

As is apparent from the above description, according to the present invention, the roller pressing means is attached to the frame member extending in the roller axial direction, and the rack is moved in the pressure contact direction by the power transmission means. By moving the frame member by, the roller pressure contact force can be changed,
The structure can be made smaller than the conventional one, and the variation of the pressing force can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of a printer according to an embodiment of the present invention.

FIG. 2 is a plan view showing a roller structure according to the present embodiment.

FIG. 3 is a sectional view showing a pressure contact structure of a roller according to the present embodiment.

FIG. 4 is a side view showing a schematic configuration of a conventional printer.

FIG. 5 is a perspective view showing a schematic configuration of a conventional printer.

[Explanation of symbols]

 2a feed roller 2b pinch roller 2c drive shaft 2d drive shaft 8 cam 9 follower lever 10a rack 10b rack 13 gear 14 frame 15 pressing member 16 connecting shaft 17 compression spring

Claims (1)

[Claims] 1. A mechanism for switching a nip pressure between a pair of rollers for conveying a sheet, a feed roller arranged along a printing direction, and a pressure roller being in contact with the feed roller.
A pinch roller that conveys a sheet, a frame member that extends parallel to the pinch roller, pressing means that is attached to the frame member and presses the pinch roller to the feed roller, and moves in the press contact direction of the pinch roller. A rack that is movably supported and is coupled to the frame member, a gear that meshes with the rack, a connecting shaft that rotates the gear in synchronization, and one of the racks that engages with each other.
A pressure switching mechanism for the sheet conveying roller, comprising: a power transmission means for moving the rack in a pressure contact direction.