JPH02112973A - Sheet jam preventing device for printer - Google Patents

Abstract

PURPOSE:To prevent a sheet jam by detecting no sheet by sheet detecting means when the end of the sheet is displaced out of feed rollers of supply side sheet feeding means to become a free state, and operating a roller releasing mechanism by driving means on the basis of its signal. CONSTITUTION:When a reverse sheet feed signal is, if a sheet detection sensor 37 is turned ON and some sheets are detected, input, the reverse sheet feeding operation of designated distance is executed. The sensor 37 is turned OFF, and if no sheet is detected, a drive signal is applied to a drive motor 34, the lower feeding roller 9 of supply side sheet feeding means 7 is retreated to a roller releasing position, and then the reverse sheet feeding operation of the designated distance is performed. Thereafter, the drive signal is again applied to the motor 34 to move the roller 9 of the means 7 to a sheet feeding position.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a paper jam prevention device for a printer, specifically,
Paper jam prevention to prevent paper jams that occur when paper is transported in the reverse direction in printers that can transport paper in the opposite direction to the normal paper transport direction (this is called reverse transport). This is related to H.

[Prior Art] An example of a conventional printer capable of reverse paper feeding will be briefly described with reference to FIG. 4, which shows a sectional view of the area around the printing section.

A printing section 1 of the printer includes a print head 2 and a platen 3. The print head 2 is installed on a carriage that is arranged to be movable back and forth in the left and right directions (front and back directions of the page) with respect to a printer frame (not shown), and the platen 3 is rotatably supported on the frame via a plate 4. , and is actively rotated in both forward and reverse directions using a paper feeding drive motor (not shown) which can rotate in forward and reverse directions as a drive source.

On the paper supply side (lower right in the figure) of the printing section 1, there is provided a supply-side paper feed means 7 consisting of a pair of upper and lower feed rollers 8 and 9 capable of transporting the paper 5 in both forward and reverse directions. Further, on the paper ejection side of the printing section 1, there is provided an ejection side paper feeding means 11 consisting of a pair of upper and lower feed rollers 12 and 13 capable of transporting the paper 5 in both forward and reverse directions. Feed rollers 8, 9 and 12.13 of both paper feed means 7.11 are rotatably supported on the frame via shafts 8a, 9a and 12a, 13a, respectively. Therefore, both paper feeding means 7.11
On the other hand, in this example, each lower feed roller 8.12 is actively rotated in both forward and reverse directions together with the platen 3 using the paper feed drive motor as a drive source.

Further, in FIG. 4, reference numeral 14 denotes a cover 15 of the printer, and the paper outlet of the cover 14 is made smaller.

Other prior art for printers includes Japanese Patent Laid-Open No. 5
6-60985, JP-A-57-84885, and JP-A-50-16206.

[Problems to be Solved by the Invention] However, in the printer described above, as printing is performed on the paper 5, mainly cut paper, the paper 5 is moved in the forward direction (
When the process (see arrow A in FIG. 4) is performed for a predetermined 44 times, the trailing edge 5a, which is the lower edge of the paper 5, comes off from between the feed rollers 8 and 9 of the paper feeding means 7 on the supply side, and becomes free (see arrow A in FIG. 4). 4
(see figure).

A path for the paper 5 is formed by a pair of upper and lower guide plates (not shown) lying between the supply side paper feed lower stage 7 and the discharge side paper feed means 11. Align the guide plate with the contact point of the feed roller 8゜9.
．． 9 is in a state of protruding beyond the guide plate. For this reason,
Even if the trailing edge 5a of the paper 5 exists between the guide plates, the end portion 5a of the paper 5 may be moved by the feed roller 8 depending on the beginning or end or curling of the paper 5.
It does not point in the direction of the contact point of 9.

In this state, when performing special printing such as double printing, multicolor printing, enlarged character printing, graph printing, etc., if the paper 5 is transferred in the reverse direction (see arrow B in Figure 4), the ejection side As the paper 5 is transported in the opposite direction by the reverse rotation of the feed rollers 12 and 13 of the first paper feed stage 11, the terminal end 5a of the paper 5 is transferred to the feed roller of the supply side paper feed means 7, especially the lower feed roller 9. There was a problem in that the paper interfered with the paper, causing paper jams. Note that this paper jam causes problems such as line feed errors and paper breakage, so there is a strong need for an improvement measure.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to prevent the trailing edge of the paper generated during reverse direction transport from reaching the feed roller of the paper feed means on the supply side in a printer capable of reverse paper feed. To provide a paper jam prevention device capable of preventing paper jams by avoiding interference.

[Means for Solving the Problems 1] In order to achieve this object, the paper jam prevention device for a printer of the present invention includes a marking section 7 including a print head and a platen, and a paper jam prevention device provided on the paper supply side of the printing section to prevent paper jams. Can be transferred in both forward and reverse directions.1
In the printer capable of reverse paper feeding, the printer is equipped with a supply side paper feeding means consisting of a pair of feed rollers, and an ejection side paper feeding means provided on the paper ejection side of the printing section and capable of transporting the paper in both forward and reverse directions. a roller release gate mechanism for changing the position of the feed roller of the supply side paper feed means between a paper feed position where the paper is nipped and a roller release position where the paper is released; a paper detecting means for detecting the presence or absence of paper between or on the side of the printing unit; and a paper detecting means that is driven based on a paper out detection signal from the paper detecting means to release the roller release mechanism when the paper is transferred in the reverse direction. and a drive means for operating the device.

[Operation] According to the present invention having the above-described configuration, when the paper is transported in the reverse direction, if the trailing edge of the paper comes off between the feed rollers of the supply side paper feed means and is in a free state, the paper is detected. The means detects that there is no paper, and the drive means operates the roller release mechanism based on the signal, whereby the feed roller of the supply side paper feed means is changed to a roller release position,
As a result of the gap between the feed rollers being released, the trailing edge of the paper that is transported in the opposite direction due to the reverse rotation of the feed roller of the paper feed means on the discharge side quickly intervenes between the feed rollers of the paper feed means on the supply side.

[Practical example] Hereinafter, an example embodying the present invention will be described with reference to FIGS. 1 to 3. Since this example is implemented in the printer capable of reverse paper feeding described in the conventional example above, the same parts will be given the same reference numerals and their explanation will be omitted, and only the different structures will be described in detail. Make it.

In FIG. 1, which is a sectional view showing the vicinity of the printing unit of a printer capable of reverse paper feeding, both ends of the shaft 9a of the lower feed roller 9 of the supply side paper feeding means 7 are different from the conventional paper feeder, and are not attached to the frame of the printer. It is rotatably supported by a roller holder 21 of a roller release mechanism 20 which will be described next.

The roller holder 21 is rotated via a holder @ 22 at a position between the platen 3 of the printing unit 1 and the upper feed roller 8 of the supply side paper feed means 7 with respect to the frame of the printer (more specifically, the left and right side plates). movably supported. The roller holders 21 are disposed symmetrically on the left and right side plates of the frame, and both ends of the shaft 9a of the lower feed row 59 of the paper feed means 7 are connected to the lower ends of both roller holders 21. Each is rotatably supported. It is assumed that the left and right roller holders 21 are connected so that they can rotate synchronously.

A spring attachment hole 23 is provided in the lower half of the roller holder 21, and the spring attachment hole 23 is provided in the side plate of the frame.
A spring mounting pin 24 located diagonally above is protruded. A spring member 26 made of a coil spring is installed in the spring mounting hole 23 and the spring mounting pin 24 . Due to the elasticity of the spring member 26, the lower feed roller 9 is always urged in a direction in which it comes into pressure contact with the side feed roller 8, that is, in a direction in which it cooperates with the upper feed roller 8 to nip the paper 5. The paper is held at the paper feed position shown by the solid line in .

A cam follower section 27 is set at the upper end of the roller holder 21. This cam follower portion 27 is brought into contact with the outer circumferential surface of the cam 30 via the elasticity of the spring member 26 .

The cam 30 is fixed to a camshaft 290 rotatably supported by the side plate of the frame, and together with the roller holder 21 constitutes a roller assembly 111 mechanism 20.

On the outer peripheral surface of the cam 30, a first cam surface 31 having a shape corresponding to the contact edge of the cam follower section 27 and a second cam surface 32 having a substantially semicircular shape on the opposite side are continuously formed. has been done. Note that the cam follower section 27 and the first cam surface 31
The contact portion with the cam surface 31 has a substantially flat V-shape with a recess on the cam surface 31 side.

When the first cam 31 of the cam 30 collides with the cam follower section 27, as shown by the solid line in FIG.
Also, from this state, the cam 30 is rotated approximately 180 degrees,
When the center portion of the second cam surface 32 of the cam 30 abuts against the cam follower portion 27, the roller holder 21 resists the elasticity of the spring member 26 and moves against the holder shaft 2, as shown in FIG.
2 in the clockwise direction, the lower feed roller 9 is brought to the U-ra release position where the paper 5 is released from being held (see the dotted chain line in Figure 1).

The camshaft 29 of the cam 30 has an output shaft 35 of a roller release drive motor 34 consisting of a stepping motor.
are connected. This drive motor 34 is appropriately installed on the frame.

Further, since the drive motor 34 corresponds to a driving means in the present invention, it is operated based on a detection signal indicating the presence or absence of paper from a paper detection sensor 37, which will be described later.

Near the supply side paper feeding means 7, for example both feeding rows 58.9
A paper detection sensor 9--37, which is a paper detection means such as a photo sensor, supported on the frame via a suitable bracket is disposed on a straight line connecting the axes of the paper.

The paper detection sensor 37 detects the presence or absence of the paper 5 between the feed rollers 8 and 9 of the supply side paper feed means 7, and outputs the detection signal to the microcomputer 39. The microcomputer 39, when transporting paper in the reverse direction,
A drive signal is given to the drive motor 34 based on the detection signal of the paper detection sensor 37. In response to this drive signal, the drive motor 34 rotates the camshaft 29 intermittently by about 180 degrees. That is, the drive motor 34 is
Based on the paper-out detection signal from the paper detection sensor 37, the camshaft 29 is simultaneously moved 180 degrees. Note that the paper detection sensor +j-37 is located not only between the feed rollers 8 and 9 of the paper feed means 7 on the supply side, but also between the printing unit 1
It may be possible to detect the presence or absence of paper 5 on the side. Further, it is arranged further on the paper supply side (lower right in the figure) than the supply side paper feeding means 7, and the feed amount after the paper trailing edge 5a passes the paper detection sensor 37 is counted as 4, and the paper trailing edge is It may be determined that the roller 5a is between the feed rollers 8 and 9 or closer to the printing section than the feed rollers 8 and 9.

In the paper jam prevention device of the printer described above, as printing is performed on the cut paper 5, the paper 5 is transported in the forward direction (the first
When the movement (see arrow A in the figure) is carried out for a predetermined period, the trailing edge 5a, which is the lower edge of the paper 5, comes off from between the feed rollers 8 and 9 of the paper feeding means 7 on the supply side, and becomes free (see the arrow A in the figure). reference).

In this state, when performing special printing such as double printing, multicolor printing, enlarged character printing, and graph printing, use 1;
, 5 are transferred in the reverse direction (see arrow B in FIG. 1), the trailing edge of the paper 5 comes off from between the feed rollers 8 and 9 of the paper feed means 7 on the supply side and becomes free. If so, the paper detection sensor 37 detects the absence of paper and outputs a detection signal to the microcomputer 39. The microcomputer 39 provides a drive signal to the roller release drive motor 34 based on the detection signal of the paper detection sensor 37. The drive motor 34 receiving this drive signal rotates the camshaft 29 by about 180 degrees. Then, cam 3
As a result of the 00 rotation, the roller holder 21 is rotated in the clockwise direction in FIG. It is evacuated to the release position.

For this reason, the feed roller of the discharge side paper feed means 11, 12.
The end portion 5a of the sheet 5, which is transported in the opposite direction by the reverse rotation of the sheet 13, is quickly interposed between the feed rollers 8.9 of the supply side sheet feed means 7.

When the camshaft 29 is further rotated by approximately 180 degrees, the roller holder 21 is rotated counterclockwise in FIG. 2 about the holder shaft 22 due to the elasticity of the spring member 26 as the cam 30 is rotated. As a result, the lower feed roller 9 of the supply side paper feed means 7 is moved to the paper feed position as shown in FIG.

Regarding the operation of the microcomputer 39,
Referring to the flowchart of FIG. 3, the flowchart of FIG. 3 starts from a state in which paper 5 has already been inserted into the printing position, and in step 101,
When a forward paper feed signal is input, step 107
Then, the presence or absence of the paper 5 is determined based on the detection signal (on/off signal) from the paper detection sensor 37. If the paper detection sensor 37 is turned on and it is determined that there is paper, the process proceeds to step 108, where forward line feeding by the specified length is executed.

Even after detecting no paper in step 107,
The line feed in the forward direction of step 108 is executed until the paper 5 is fed a certain distance smaller than the distance from the paper detection sensor 37 to the print head 2 (step 109).

Further, in step 101, when a reverse paper feed signal is input, the process proceeds to step 102, and the paper detection sensor 3
7 is turned on and it is determined that there is paper, the process proceeds to step 103, where a reverse paper feed operation by a specified amount is executed.

Further, if the paper detection sensor 37 is turned off in step 102 and it is determined that there is no paper, then step 10
Step 4 proceeds to step 105, where a drive signal is applied to the drive motor 34, so that the lower feed row 59 of the supply side paper feeding means 7 is retracted to the roller release position. A paper feed operation is performed. Thereafter, in step 106, a drive signal is again given to the drive motor 34, so that the supply side paper feeding means 7
The lower feed roller 9 is moved to the paper feed position.

As mentioned above, the feed row 58.9 of the supply side paper feed means 7
When the paper 5 is present in between, the paper 5 is moved by the cooperation between the reverse rotation of the feed rollers 12 and 13 of the paper feed means 11 on the discharge side and the reverse rotation of the feed rollers 8 and 9 of the paper feed means 7 on the supply side. It is smoothly transferred in the opposite direction.

After the paper 5 passes between the feed rollers 8 and 9, the paper 5
The interference of the paper end portion 5a with the lower feed roller 9 of the first paper feed stage 7 on the supply side during the reverse direction transport is avoided, and occurrence of paper jam is prevented.

This prevents problems such as line break errors and paper breakage.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and the sheath enclosure can be changed without deviating from the gist of the present invention.

For example, as the discharge side paper feeding means 11, in addition to a feeding roller, a bin tractor may also be used.

Furthermore, if the paper detection sensor 37 is activated only when the paper is reversely fed, the drive of the roller release drive motor 34 can be directly turned on and off based on the on/off detection signal from the detection sensor 37. It is possible.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, when paper is transported in the reverse direction by a printer capable of reverse paper feeding, the trailing edge of the paper is moved between the feed rollers of the paper feeding means on the supply side. If the sheet is removed from the sheet and is in a free state, the drive means operates the roller release mechanism based on the paper-out signal from the paper detection means, and as a result, the space between the feed rollers of the paper feed means on the supply side is released, and as a result, the paper is ejected. The trailing edge of the paper being transferred in the opposite direction due to the reverse rotation of the feed roller of the side paper feed means is quickly moved between the feed rollers of the supply side paper feed means without interfering with the feed roller of the supply side paper feed means. Because of this intervention, it is possible to prevent paper jams during reverse direction transport.

[Brief explanation of drawings]

1 to 3 show an embodiment embodying the present invention. FIG. 1 is a sectional view of a paper jam prevention device of a printer, FIG. 2 is a sectional view of its operating state, and FIG. 3 is a micro It is a flowchart of a computer. FIG. 4 is a sectional view of the vicinity of the printing section of a conventional printer. 1... Printing section 2... Print head 3... Platen 5... Paper 7... Supply side paper feeding means 8.9... Feed roller 11... Discharge side paper feeding means 12. 13... Feed roller 20... Roller release mechanism 34... Drive motor (driving means) 37... Paper detection sensor (paper detection means) Application
People Brother Industries, Ltd.

Claims (1)

[Scope of Claims] A printing unit including a print head and a platen; a supply-side paper feeding means provided on the paper supply side of the printing unit and comprising a pair of feed rollers capable of transporting paper in both forward and reverse directions; A printer capable of reverse paper feeding, which is equipped with a discharge side paper feeding means provided on the paper ejection side of the printer and capable of transporting the paper in both forward and reverse directions, wherein a feed roller of the supply side paper feeding means is configured to nip the paper. a roller release mechanism that changes the position between a paper feed position and a roller release position where paper is released from being held; and a paper that detects the presence or absence of paper between the feed rollers of the supply side paper feed means or closer to the printing unit. A paper jam prevention device for a printer, comprising: a detection means; and a drive means that operates based on a paper-out detection signal from the paper detection means to release the roller release mechanism when the paper is transported in the reverse direction.