JPH0672573A - Sheet separation method - Google Patents

Abstract

PURPOSE:To provide a sheet separation method by which sheets, which are stacked and stored on a plate of a sheet feeding cassette, are surely separated into an individual sheet. CONSTITUTION:A sheet separation method consists of a process in which a pick up roller 6 is driven so as to deliver a sheet stored in a sheet feeding part 5 to the contact part between the pick up roller 6 and a friction pad 8, a process in which driving of the pick up roller 6 is stopped after the pick up roller 6 is rotated by the predetermined number of rotation, and a process in which the pick up roller 6 is driven again so as to deliver a sheet touching the pick up roller 6 toward a printing part, after driving of the pick up roller 6 is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet separating method for separating sheets stored in a sheet feeding section (hereinafter referred to as a sheet feeding cassette) of a printer and stored in the sheet feeding section to convey them to a printing section.

[0002]

2. Description of the Related Art A friction pad system is known as one of the methods for separating the sheets stacked and accommodated in a paper feed cassette of a printer one by one. Generally, this friction pad system is shown in FIG. The configuration is as shown in. The configuration of the friction pad system will be described below with reference to this figure.

In the figure, reference numeral 5 indicates a sheet feeding cassette, and the sheet feeding cassette 5 is provided with a plate 2 on which, for example, A1 size sheets 1 are stacked. The plate 2 is urged by urging means (not shown) so that the uppermost sheet comes into contact with the pickup roller 6. The sheet stacked on the plate 2 has its end surface supported by the support portion 3, and the sheet contacting the pickup roller 6 is rotated between the support portion 3 and the pickup roller 6 by the rotation of the pickup roller 6. It is fed out from the gap. A friction pad 8 urged by an urging means 9 is in contact with the pickup roller 6, and the friction pad 8 is the uppermost sheet fed by the pickup roller 6 and the sheet taken out together with this sheet. Serves to separate the.

Then, the sheet separated into one sheet by the friction pad 8 is further conveyed by the rotation of the pickup roller 6, and thereafter, the front end of the sheet is detected by the sensor 20. Based on the detection signal from the sensor 20, the pickup roller 6 is rotated by a predetermined amount and stopped. At this time, as shown in the figure, the platen 1
Bending is formed by abutting the contact portion between 0 and the pinch roller 12, and the skew of the sheet is removed.
After that, the paper is set on the platen 10 and the pinch roller 12
Is conveyed along the paper pan 14 and is printed by the print head 16. The principle of separating the sheet into one sheet at the friction pad 8 in the above configuration will be described in detail.

FIG. 2 is an enlarged view of the pickup roller 6 shown in FIG. 1 and the friction pad 8 abutting on the pickup roller 6. In the friction pad type separation, when the friction coefficient between the pickup roller and the paper is μ1, the friction coefficient between the friction pad and the paper is μ2, and the friction coefficient between the paper and the paper is μ3, μ1> The materials of the pickup roller 6 and the friction pad 8 are selected so that μ2> μ3. In this case, μ2 is considerably larger than μ3.

When the pickup roller 6 feeds a sheet, the next sheet P2 may be taken out together with the uppermost sheet P1 depending on the state of the sheet as shown in FIG. The pick-up roller 6 is driven at a constant speed, and the taken-out sheet P2 together with the uppermost sheet P1 has a nip portion between the pickup roller 6 and the friction pad 8 (the elastic pickup roller and the pad are in elastic contact, The contact portion is referred to as a nip portion). At this nip portion, the taken-out paper P2 is stopped by the dynamic frictional force generated between the paper and the friction pad, and the uppermost paper P1 slides on the taken-out paper P2 as the pickup roller 6 rotates.

As described above, the sheet can be separated into one sheet at the nip portion because the friction coefficient between the pickup roller, the sheet and the friction pad is μ1>μ2> μ3. , The static friction force between the pickup roller 6 and the uppermost sheet P1> the dynamic friction force between the taken-out sheet P2 and the friction pad 8> the static friction force between the sheets P1 and P2. is there.

As described above, the pickup roller 6
Even if the sheet is taken out when is driven, the uppermost sheet of the stacked sheets is separated into one sheet at the nip portion of the friction pad 8 and conveyed toward the printing section.

[0009]

The above-mentioned friction coefficient μ3 between the sheets is not constant among all the sheets, and may vary between certain sheets due to the following reasons, for example.

The sheets stacked on the plate are, for example, 5 sheets.
Cut into A4 size, B5 size, etc. on a sheet-by-sheet basis, and stack 50 sets of this into a 250-sheet unit (500 in some cases.
It is packed in units of sheets. Therefore, the paraffin for preventing moisture absorption of the paper may move to the outermost layer of the paper, and the paper in this portion may have a lower friction coefficient than the paper on the inner side. That is, due to the decrease in the coefficient of friction,
Friction coefficient between outermost paper and friction pad μ
It can be as small as 2.

Alternatively, when the sheet is replenished with the sheet, the sheet having a different condition such as humidity and temperature from the sheet on the plate is taken out from the package and placed on the sheet on the plate, so that the sheet on this portion is placed. It is possible that the coefficient of friction may be high between the two.

In such a case, as shown in FIG. 2, when two sheets of paper are conveyed to the nip portion, the sheets cannot be separated at this portion and double feeding may occur. That is,
If μ2 becomes too small or μ3 becomes too large, the static friction force between the sheets at the nip portion may become larger than the dynamic friction force between the sheets and the friction pad. It is possible that, as a result, the second sheet is not stopped at the friction pad portion, and is taken out together with the uppermost sheet, causing a double feed.

The present invention has been made in order to solve the above-mentioned problems, and it is a method of separating sheets, which always and surely separates one sheet regardless of changes in the state of sheets stacked and accommodated. The purpose is to provide.

[0014]

In order to solve the above-mentioned problems, a paper separating method of the present invention drives a pickup roller based on a paper feed start signal to pick up a paper stored in a paper feeding section. A step of transporting the pickup roller toward a contact portion between the roller and the friction pad, a step of stopping the driving of the pickup roller after the pickup roller is driven for a predetermined rotation, and a step of stopping the driving of the pickup roller and then picking up again. Drive the rollers,
And a step of transporting the sheet in contact with the pickup roller toward the printing section.

[0015]

[Operation] By driving the pickup roller,
The sheet accommodated in the sheet feeding section is conveyed toward the contact section between the pickup roller and the friction pad. After the conveyed paper is caught at least in the contact portion,
The drive of the pickup roller is once stopped and then driven again. When the drive of the pickup roller is stopped, a static friction force larger than the dynamic friction force is generated between the friction pad and the paper. By thus generating the static frictional force between the friction pad and the paper, one sheet of paper is reliably achieved at the friction pad.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the present invention is characterized by the method of driving the pickup roller, and the friction pad is used to load the paper 1
The structure of the apparatus for separating the sheet and feeding it to the printing unit is the same as that in FIGS. Therefore, these drawings will be used in describing the embodiment of the present invention.

As shown in FIG. 3, the uppermost sheet P1 of the sheets 1 stacked on the plate 2 of the sheet feeding cassette 5 is in contact with the pickup roller 6 by the biased plate 2. A friction pad 8 is elastically contacted with the pickup roller 6 by an urging spring 9, and the elastic pickup roller 6 and the friction pad 8 are in contact with each other to form a nip portion.

The material of the pickup roller 6 and the friction pad 8 is such that the friction coefficient between the pickup roller and the paper is μ1, the friction coefficient between the friction pad and the paper is μ2, and the friction coefficient between the paper and the paper is the friction coefficient. When μ3 is selected, it is selected so that μ1>μ2> μ3. In this case, μ2 is a sufficiently large value with respect to μ3.

Further, the pickup roller 6 is driven to rotate by a paper feed start signal, but after being rotated by a predetermined amount, it is temporarily stopped and then driven again. Specifically, the pickup roller 6 is temporarily stopped when the sheet placed on the plate 2 is conveyed by the pickup roller 6 and the leading edge of the sheet is within the nip width range. In this case, the rotation angle of the pickup roller from the drive of the pickup roller 6 to the sheet reaching the nip portion can be calculated in advance from the arrangement state of the paper feed cassette 5, the friction pad 8 and the like. Therefore, the drive control system of the pickup roller 6 may be programmed to stop once when the pickup roller rotates by the rotation angle calculated in advance. The operation of this embodiment will be described below with reference to FIGS.

When the pickup roller 6 is rotated by the sheet feed start signal, the uppermost sheet P1 is fed from the gap between the support portion 3 and the pickup roller 6 toward the nip portion. However, as described above, the coefficient of friction between the stacked sheets P1, P2, P3, ... Is not constant due to humidity or the packaging state of the sheets, and is, for example, more than the friction force between the sheets P2 and P3. The frictional force between the sheets P1 and P2 may be extremely large (the friction coefficient between the sheets is μ3a). In this case, as shown in FIG. 4, the paper P1 and the paper P2 overlap and are sent out.

As described above, when the paper P1 and the paper P2 are delivered in an overlapping manner, the static frictional force between the papers is the dynamic friction between the paper P2 and the friction pad 8 when the pickup roller 6 is driven as it is. It can be greater than force.

However, as described above, the pickup roller 6 is configured to stop once when the leading edge of the paper is within the nip width range. That is, as shown in FIG. 4, the pickup roller 6 is configured to temporarily stop when it is rotated by θ after being driven, and then is rotationally driven (α indicates that the leading edge of the sheet is caught in the nip portion). It is the angle when it is inserted). Therefore, when the pickup roller 6 is driven, a static friction force acts between the paper P2 and the friction pad 8. The static friction force is considerably larger than the dynamic friction force, and unless μ3a is equal to or larger than μ2, the static friction force between the pickup roller 6 and the sheet P1> the static friction force between the sheet P2 and the friction pad 8>
The relationship of static friction force between the paper P1 and the paper P2 is established. Therefore, when the pickup roller 6 is driven again, as shown in FIG. 2, the sheet can be separated into one sheet at this nip portion.

Of course, even if one sheet is conveyed to the nip portion, this sheet is not affected by the temporarily stopping operation of the pickup roller 6 and is conveyed to the printing section as it is.

FIG. 5 is a time chart showing the relationship among the pickup roller 6, the sensor 20 and the platen 10 in the above embodiment. Hereinafter, these relationships will be described with reference to FIGS. 1 and 5.

When the sensor 20 detects the trailing edge of the previously conveyed sheet, the pickup roller 6 is driven to convey the next sheet. When the pickup roller 6 rotates by θ, its driving is stopped for a time T1. When the pickup roller 6 is driven again and the leading edge of the sheet is detected by the sensor 20, the drive of the pickup roller 6 is stopped after a predetermined time T2. At this time, the sheet is bent as shown in FIG. 1, and the sheet is skewed. After that, the platen 10 is driven after a lapse of a predetermined time T3 after the leading edge of the paper is detected by the sensor 20, and the printing process is started. Then, the rear end of the printed sheet is detected by the sensor 20 again, and one step is completed. In this way, by including the step of temporarily stopping the pickup roller 6, it becomes possible to almost eliminate the double feeding of the sheets.

In the above structure, the pickup roller 6
5 may be stopped anywhere within the range R in the time chart shown in FIG.
Further, in this embodiment, the pickup roller 6 is
Although it is configured to stop when it rotates by a predetermined amount, for example, another sensor is provided between the friction pad 8 and the sensor 20, and when this sensor detects the leading edge of the paper, the pickup roller 6 may be temporarily stopped. In this way, the detection of the temporarily stopped position of the pickup roller 6 can be appropriately modified.

[0027]

As described above, according to the sheet separating method of the present invention, one sheet of paper is always and reliably separated regardless of the state change of the sheets stacked and accommodated on the plate of the sheet feeding cassette. Can be fulfilled.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a friction pad system for separating one sheet of paper.

FIG. 2 is a diagram showing a state in which a sheet is separated into one sheet at a friction pad portion.

FIG. 3 is a diagram showing a contact state between a pickup roller and a friction pad.

FIG. 4 is a diagram showing a state where two sheets of paper have been conveyed to a nip portion between a pickup roller and a friction pad.

FIG. 5 is a diagram showing a time chart of the paper separating method according to the present invention.

[Explanation of symbols]

1 ... Paper, 2 ... Plate, 5 ... Paper feeding cassette (paper feeding unit), 6 ... Pickup roller, 8 ... Friction pad, 10 ... Platen, 16 ... Print head.

Claims (3)

[Claims] 1. A paper separating device for separating a laminated paper sheet housed in a paper feeding unit into one sheet by using a friction pad pressed and biased by a pickup roller, and conveying the separated paper sheet to a printing unit. In the method, a step of driving the pickup roller based on a sheet feed start signal to convey the sheet accommodated in the sheet feed section toward a contact portion between the pickup roller and a friction pad, and the pickup roller A step of stopping the driving of the pickup roller after being driven for a predetermined rotation, and driving the pickup roller again after the driving of the pickup roller is stopped so that the paper contacting the pickup roller is directed to the printing section. Transporting process,
A method for separating a sheet, comprising: 2. The pickup roller is driven for a predetermined rotation at least until the pickup roller is driven until the sheet accommodated in the sheet feeding section reaches a contact section between the pickup roller and the friction pad. The paper separating method according to claim 1, wherein 3. The sheet separating method according to claim 1, wherein the driving of the pickup roller is stopped based on a detection signal of a sensor that detects the leading edge of the sheet.