JPH0977288A - Paer feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeder which can secure the number of paper feeding stages as before while the height of the feeder is held down and is simple in structure. SOLUTION: A paper feeder comprises plural paper feed cassettes 5 which respectively store paper sheets of plural sizes and are disposed, in a stacking state, and pick-up rollers 8, feed rollers 7 and reverse rollers 10 which are provided on the above paper feed cassettes, respectively, wherein as the paper feed cassette is positioned lower, the size thereof is increased, and a paper feed means is disposed in a space produced due to a difference in size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device equipped with a plurality of sheet feeding cassettes, which is mounted to convey a sheet to an image forming unit of an image forming apparatus.

[0002]

2. Description of the Related Art A sheet feeding device for conveying sheets to an image forming section is provided with a sheet stacking section having a relatively large capacity, and the sheets are stacked on an elevating plate which is vertically movable in the stacking section. In addition to the configuration in which the lift plate is lifted by the drive motor according to the paper feeding and the storage amount of the paper is displayed based on the moving amount of the lift plate, it is also possible to select the desired size from multiple sizes of paper. There is known a configuration in which a plurality of paper cassettes respectively accommodating papers of different sizes are provided in advance so that papers of different sizes can be selected and image formation can be performed. FIG. 4 shows an example. First to fourth trays 1, 2, 3, 4 respectively accommodating sheets of different sizes are arranged one above the other, and from one of the trays accommodating sheets of the desired size, using the attached paper feed mechanism, The sheet is fed to an image forming unit (not shown) arranged above. Regarding the sheet feeding mechanism, a corner claw method, a back rubbing separation method (FRR sheet feeding method), and the like are known, but in the illustrated example, the FRR sheet feeding mechanism is attached to each tray.

To explain the details, as shown in FIG. 5, when it is detected that the cassette 5 is set in the cassette receiver, the lever 6 interlocked with the bottom plate raising mechanism
The upper surface of the paper is raised so as to come to the proper feeding position, and the position is controlled to be maintained. The feed roller 7 and the pickup roller 8 are rotationally driven in the clockwise direction by the paper feed signal, and at the same time, the pickup arm 9 is rotated in the clockwise direction to press the rollers against the upper surface of the sheet with a predetermined pressure. Therefore, the paper is sent out to the left in the figure.

The pickup roller 8 is released from the paper surface after a set time sufficient to feed the paper to the nip between the feed roller 7 and the reverse roller 10. On the other hand, the reverse roller shaft is also rotationally driven in the clockwise direction at the same time as the paper feed signal. The reverse roller 10, which is axially supported by this shaft via a torque limiter, is given an initial pressure by a pressure spring 11 and an operating pressure obtained as a reaction force of the torque limiter torque, and is pressed against the feed roller 7.

The torque limiter slides when the reverse roller 10 comes into contact with the feed roller 7 (when there is no paper between the nips) and when one paper is fed into the nip.
Turn around counterclockwise.

Further, when two or more sheets are fed into the nip, the torque limiter torque overcomes the frictional force between the sheets, the reverse roller 10 is rotated clockwise, and the lower sheet is pushed back toward the cassette side. It is designed to prevent feeding.

[0007]

Recently, digital image forming apparatuses have been rapidly spread, but unlike analog apparatuses, parts such as optical writing, which are not present in conventional image forming apparatuses, are required, and the entire apparatus is required. It tends to increase in size. Therefore, especially in a digital device, the height tends to be higher than in the past, which is difficult to use. As described above,
Providing a plurality of paper feed cassettes to accommodate a large number of paper sizes has a negative effect on this height. However, if the number of cassette stages is reduced, the frequency of cassette attachment / detachment work increases, which causes annoying drawbacks.

Therefore, conventionally, some proposals have been made to suppress the total height of the apparatus. For example, JP-A-60-1533
According to Japanese Patent Laid-Open No. 5 publication, for example, A3, B4, A4 and B5 size cassettes are provided at intervals in the vertical direction on the side surface of the copying machine body having a paper feed section, which is placed on a movable desk. A multi-stage cassette unit is set, and this unit 16 is configured such that each cassette can be moved up and down. It is disclosed that each cassette is screwed into a plurality of screw shafts extending in the direction at a nut portion, and the cassette shafts are vertically moved by the rotation of the screw shafts driven by a drive motor. . However, the unit having such a configuration has a problem that the area occupied by the apparatus is increased, the system is complicated, and it is not possible to instantaneously cope with the case of changing the paper feed size.

Further, Japanese Patent Laid-Open No. 4-121329 discloses that
Rotatable paper feed rollers that come into contact with the uppermost paper leaf of each paper feed cassette, friction pads pressed against each of these paper feed rollers, and paper sheets pulled out from the paper feed rollers are automatically fed The casing is provided with a rotatable conveying roller that conveys to the passage and a vertically rotatable pressing body that faces the lower surface of each paper sheet stacking plate, and the pressing body is urged downward by its own weight. It is disclosed that a worm gear passing through the side of the paper feed cassette is rotatably provided inside with a vertical axis, and the upper end of the worm gear is connected to one motor. With this configuration, a single drive device for pushing up the pressing body is provided, and the space between the upper and lower paper feed cassettes is narrowed to reduce the overall height dimension. JP-A-4-2
In Japanese Patent No. 43737, an arbitrary paper feed cassette is pulled out from a standby position to a paper feed position by driving a cassette drive unit, then the paper feed means is lowered by the drive of a paper feed drive unit, and the paper feed cassette is pulled out. A configuration is shown in which the position is stopped, and thereafter, the uppermost sheet in the sheet feeding cassette and the sheet feeding roller are kept in a pressurized state by the pressing unit, and the sheet is fed from the sheet feeding cassette by the sheet feeding roller.

The technique disclosed in Japanese Patent Laid-Open No. 4-121329 suppresses the overall height by using a common drive device, but there is a restriction due to the fact that a paper feed roller and a friction pad are attached to each paper feed cassette. It has been left behind. For example, in the case where the paper feed roller has an outer diameter of about 24 mm, a total space of about 30 mm is inevitable in consideration of the space for its movement. According to the technique of Japanese Patent Laid-Open No. 4-243737, the dimensional height of the entire apparatus can be suppressed considerably, but since the paper feeding operation is performed after the paper feeding means is moved up and down, the pressure contact pressure of the paper feeding roller is constant. It is not easy to adjust to
Similar to No. 0-15335, there is a problem in that the paper feed size cannot be instantaneously dealt with. Further, if the paper feeding means becomes out of order, the paper cannot be fed at all.

Therefore, the present invention has been made in view of the drawbacks of the above-mentioned respective prior arts, and its object is to secure the number of paper feed stages as in the conventional manner while suppressing the height of the apparatus, and structurally. It is to provide a simple paper feeding device.

[0012]

In order to solve the problem, according to the present invention, a plurality of paper feed cassettes each accommodating paper of a plurality of sizes and arranged in a stack, and a plurality of paper feed cassettes In a paper feeding device provided with a paper feeding means attached to each, the paper feeding means is arranged in a space caused by the size difference of each paper feeding cassette as the size of the paper feeding cassette becomes lower. .

The above problem can be solved by arranging the sheet feeding cassettes so as to be offset from each other and arranging the sheet feeding means in the space resulting from the shifting. The sheet feeding cassettes may be staggered, but it is also preferable that the sheet feeding cassettes are staggered and the sheet feeding positions from the sheet feeding cassettes are alternately reversed.

[0014]

The details of the present invention will be described based on the embodiments shown in the drawings. FIG. 1 shows a sheet feeding device having a four-stage cassette structure according to the present invention. The plurality of cassettes 5 arranged vertically have not only the size of the sheets to be stored but also the cassette size itself gradually increasing from the upper stage to the lower stage. For example, the uppermost cassette is for A4 horizontal or less, the second cassette is A4 vertical or less, the third cassette is B4 vertical or less, and the fourth cassette is A3 vertical or less. Each cassette 5
Incorporates the FRR mechanism. The FRR mechanism has already been described, and it is omitted here to avoid duplication of description, but in the cassette selected by the paper feed instruction, the stored paper is lifted by the bottom plate 12 and picked up. The rollers 8 are pressed against each other, separated one by one by the rotation of the feed roller 7 and the reverse roller 10, and are conveyed via a conveying roller 13 to an image forming unit (not shown) arranged above the sheet feeding device. Since the rear ends of the respective cassettes are aligned and supported by the accuride 14 and have different sizes, the pickup roller 8 and each sheet conveying path can be arranged in a space caused by a difference in cassette size. As can be seen from the drawing, the overall height of the device can be suppressed by narrowing the interval between the cassettes.

FIG. 2 shows a sheet feeding device according to another structure.
The plurality of cassettes 5 arranged in the upper and lower sides have the same outer size of each cassette, and are models capable of supporting up to A3 portrait, for example. These cassettes 5 are stacked in a stepwise manner, and the pickup roller 8 and the sheet conveying path are arranged in the space generated by the horizontal displacement of the cassettes, so that the distance between the cassettes can be minimized.

FIG. 3 shows a sheet feeding device according to still another structure. The plurality of cassettes 5 stacked vertically are arranged in a staggered manner in the horizontal direction. The pickup roller 8, the feed roller 7, and the reverse roller 10 are arranged in the space between the cassettes, which is created by being staggered in this way. Since the positions of drawing out the papers from the respective cassettes 5 are staggered for each stage, the paper carrying paths provided with the carrying rollers 13 are provided on both sides inside the apparatus housing, and the paper feeding paths are provided upward through a single paper feeding port 14. In order to convey the paper to the image forming unit (not shown) arranged, a conveyance guide 15 for keeping the paper conveyance paths uniform is arranged above the cassette stage. This transport guide can also be used as a transport unit in the double-sided image forming mechanism.

Although each of the above-described embodiments has been described with respect to the FRR paper feed mechanism, it is needless to say that the present invention can be implemented with other paper feed methods such as a corner pawl method.

[0018]

According to the first aspect of the present invention, a plurality of sheet feeding cassettes each accommodating sheets of a plurality of sizes are arranged in a stacked state, and sheet feeding cassettes attached to each of these sheet feeding cassettes. In the paper feeding device provided with the paper means, the size of each paper feeding cassette becomes larger as it goes down, and the paper feeding means is arranged in the space caused by the size difference, so that the overall height of the device is minimized. You can keep it to the limit.

According to the second aspect of the invention, the sheet feeding cassettes are arranged so as to be offset from each other, and the sheet feeding means is disposed in the space resulting from the shifting, so that the overall height of the apparatus is minimized. Since the size of the paper feed cassette in the upper stage is not limited, it can be set to a position close to the image forming part due to the paper size that is frequently used, and it can be used for speeding up image formation. be able to. Moreover, when the sheet feeding cassettes are staggered and the sheet feeding positions from the sheet feeding cassettes are alternately set to opposite positions as in the invention described in claim 3, the installation space of the apparatus is suppressed. It is possible.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a sheet feeding device according to a first configuration example of the present invention.

FIG. 2 is a schematic sectional view of a paper feeding device according to a second configuration example of the present invention.

FIG. 3 is a schematic sectional view of a sheet feeding device according to a third configuration example of the present invention.

FIG. 4 is a schematic sectional view illustrating a conventional paper feeding device.

FIG. 5 is a conceptual diagram showing a schematic configuration of an FRR paper feed mechanism.

[Explanation of symbols]

 5 Cassette 7 Feed Roller 8 Pickup Roller 10 Reverse Roller 12 Bottom Plate 13 Transport Roller 14 Acculide

Claims (3)

[Claims] 1. A sheet feeding device comprising a plurality of sheet feeding cassettes for accommodating sheets of a plurality of sizes and arranged in a stacked state, and a sheet feeding means attached to each of these sheet feeding cassettes. A sheet feeding device, in which the sheet feeding cassette is increased in size as it goes down, and a sheet feeding unit is disposed in a space generated by the size. 2. A sheet feeding device comprising a plurality of sheet feeding cassettes each accommodating sheets of a plurality of sizes and arranged in a stacked state, and a sheet feeding means attached to each of these sheet feeding cassettes. A sheet feeding device, wherein the sheet feeding cassettes are arranged so as to be offset from each other, and a sheet feeding means is disposed in a space resulting from the shifting. 3. The paper feeding device according to claim 2, wherein the paper feeding cassettes are staggered so that the paper feeding positions from the paper feeding cassettes are alternately different.