JPH04251036A - Sheet feeding device - Google Patents

Abstract

PURPOSE:To control the position of an upper surface of a loaded sheet material to a specified level by a method wherein a middle plate 5 on which sheet materials are loaded is supported by a pressure spring 22 the length of which is changed in proportion to a change amount of the sheet material owing to the feed of sheets, and a one-way rotation mechanism rotatable only in a direction in which the free end of the middle plate is raised is located to a support axle around which the middle plate is rotated. CONSTITUTION:With the decrease of sheet material loaded on a middle plate 5 through sheet feed operation of a sheet feed roller 12, the middle plate 5 is pushed up in proportion thereto through the force of a pressure spring 22 and an upper surface Pa of a sheet material P is controlled to a specified level. This constitution controls the upper surface Pa of the sheet material P at a specified level without especially providing a back sensor to detect the position of the upper surface Pa and a motor to raise the middle plate 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device for feeding regular size sheet materials in image forming apparatuses such as copying machines and laser beam printers.

0002

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and laser beam printers, the front end of an intermediate plate loaded with sheet materials of a standard size is urged upward by a pressure member, and the uppermost sheet is One or more sheets of sheet material are fed by rotating the paper feed roller while the material is in pressure contact with the paper feed roller, and one sheet material is further separated by a separating means provided downstream of the paper feed roller. They were separated and sent separately. A control means is provided for controlling the position of the uppermost sheet material to a predetermined height. An example of a conventional paper feeding device of this type will be explained with reference to FIG.

[0003] In the figure, a paper feed cassette 2 of a paper feed device 1a is detachably attached to an apparatus main body 3 of an image forming apparatus such as a copying machine. A plurality of sheets P of a standard size are loaded in a middle plate 51 disposed in the paper feed cassette 2, and the middle plate 51 rotates around a support shaft 52 to which a base is fixed. It is free to move. The middle plate 51 is biased so that its free end (the right end in the figure) rises by a pressure arm 53 disposed between the middle plate 51 and the paper feed cassette 2, and the rear end of this pressure arm 53 A support shaft 55 to which a portion is fixed is rotated by a predetermined amount by a motor 57 controlled by a control portion (CPU) 56.

A paper feed roller 12 rotatably mounted on the free end of a support member 11 is disposed above the front end of the paper feed cassette 2, and an arm portion 11a integral with the support member 11 is provided. A solenoid 15 controlled by the control section 56 is connected to the solenoid 15 . A drive roller 17a of a separation roller pair 17 connected to a drive source (not shown) is attached to a support shaft 16 to which the base of the support member 11 is pivotally mounted. A driven roller 17 that is freely reversible and forward-reversible is connected to a drive source (not shown) via a limiter.
b is in contact. Reference numeral 19 indicates a guide plate.

[0005] Furthermore, the free end of a sensor arm 61 rotatably supported by a support shaft 60 is in contact with the uppermost sheet material P of the sheet materials P.
The protrusion 61a provided at the base of the sheet member 1 opens and closes the optical path of the light transmission type sensor 62 to detect the height of the upper surface Pa of the sheet material P.

The paper feed roller 12 comes into contact with the sheet material P due to its own weight to obtain a predetermined paper feed pressure, and the solenoid 1
By operating 5, the sheet material P is fed by contacting and separating from the sheet material P. This is the driven roller 17
This is to avoid hindering the retreat of the sheet material P that is separated and returned by b, and normally the paper feed roller 12 is moved to the sheet material P only when the paper feed roller 12 feeds the sheet material P to the separation roller pair 17. It is controlled so that it makes contact. One sheet material P separated by the separation roller pair 17 is further conveyed to an image forming section (not shown) in the apparatus main body 3.

Next, a lifting mechanism for keeping the upper surface of the sheet material P constant will be explained. When the feeding of the sheet material P is repeated and the upper surface Pa of the sheet material P decreases,
The sensor lever 61 and sensor 62 that follow this detect this, and the information is sent to the control section 56. As a result, a drive signal is sent from the control unit 56 to the motor 57,
The motor 57 rotates in a direction that lifts the sheet material P. The sheet material P is lifted by the rotation of the motor 57,
When the upper surface Pa reaches a predetermined height, the upper surface Pa of the sheet material P is detected by the sensor arm 61 and the sensor 62 in the same way as in the above case, and the rotation of the motor 57 is stopped by a command from the control section 56. By repeating this operation, the upper surface Pa of the sheet material P is maintained at a generally constant position.

[0008]

However, in the conventional sheet feeding device described above, in order to control the upper surface Pa of the sheet material P to a constant height, the pressure arm 53
A motor 57 for rotating the sheet material P, a sensor arm 61, a sensor 62 for detecting the position of the upper surface Pa of the sheet material P, etc. are required, which increases the complexity and size of the paper feed device and increases the cost. There were issues such as increased cost.

Therefore, the present invention provides a paper feeding device that maintains the upper surface of the sheet material P constant without using a special motor 57 for driving the loading means or a sensor 62 for detecting the upper surface Pa of the sheet material. The purpose is to provide the following.

0010

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances. For example, as shown with reference to FIG. A loading means (5) rotatable about a supporting shaft (6), a paper feeding means (12) for feeding the sheet material (P), and a paper feeding means (12) disposed downstream of the paper feeding means (12). a separation means (17) for separating the sheet material (P) being fed one by one; and a separating means (17) for separating the sheet material (P) that is fed one by one; A paper feeding device (1) comprising: a pressure means (22) for applying pressure to the stacking means (5);
and a control means (20) for releasing the restriction on the rotation of the one-way rotation means (10). Features.

[0011] Furthermore, the amount of change in the pressure means (22) is
It is characterized in that it is approximately proportional to the amount of change in height of the stacked sheet materials (P) due to paper feeding.

0012

[Operation] Based on the above structure, the sheet materials (P) on the stacking means (5) are separated and fed one by one by the rotation of the paper feed roller (12) and the separation roller pair (17).

As the sheet material (P) is fed, the sheet material (
As P) decreases, loading means (5) correspondingly decreases.
is pushed up by the pressure means (22), and the sheet material (
The upper surface of P) is held at a constant height. In addition, by releasing the rotation restriction on the loading means (5) by the one-way rotation means (10) by the control means (20), the loading means (5) can freely rotate in the direction in which the free end descends. Thus, the sheet material (P) can be supplied to the loading means (5).

[0014] Furthermore, when the paper feed roller (12) is feeding, the stacking means (5) is rotatable in one direction in which the free end (5a) thereof is upward. (12) is pressed against the upper surface (Pa) of the sheet material (P), the position of the upper surface (Pa) does not fall, and as a result, the paper feeding operation of the paper feed roller (12) is performed stably. .

Note that the above-mentioned symbols in parentheses are shown for reference to the drawings and do not limit the structure of the present invention in any way.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Components having the same functions as those in FIG. 4 are denoted by the same reference numerals, and their explanation will be omitted.

In FIG. 1, a plurality of sheets P of a standard size are stacked on a stacking means (hereinafter referred to as an intermediate plate) 5. As shown in FIG. A base of a ratchet gear 7 is fixed to a support shaft 6 to which a rear end (left end in the figure) of the intermediate plate 5 is fixed. The teeth 7a of the ratchet gear 7a have
A hook 9 rotatably supported by a support shaft 9a is engaged. The ratchet gear 7 and the hook 9 constitute a one-way rotation means (one-way rotation mechanism) 10 that restricts rotation of the middle plate 5 in one direction.

The hook 9 is rotatable between a first position 9A in which it engages with the ratchet gear 7 and a second position 9B in which it disengages from the ratchet gear 7. is a control unit (C) connected to the support shaft 9a.
PU) 20.

When the hook 9 is engaged with the ratchet gear 7, rotation is restricted so that the free end 5a of the middle plate 5 can only rotate in the upward direction due to the tooth shape of the engagement portion. has been done. Further, when the hook 9 is separated from the ratchet gear 7, the ratchet gear 7 is free to rotate, and the middle plate 5 is free to rise and fall.

[0020] A pressure means (hereinafter referred to as a pressure spring) 22 for urging the middle plate 5 upward is provided below the free end of the middle plate 5.
is provided. Due to the elasticity of the pressure spring 22, the upper surface of the sheet material P loaded on the intermediate plate 5 is pressed against the paper feed roller 12.
biased toward the side.

Next, the setting of the pressure spring 22 will be explained.

FIG. 3 is a graph showing the characteristics of the pressure spring 22. The load supported by the pressure spring 22 is
It is almost proportional to the number of sheet materials P loaded on the board. Therefore, as shown in Fig. 3(b), the sheet material P
The height of the pressure spring 22 gradually decreases in proportion to the number of sheets loaded.

Therefore, the pressure spring 22 is set so that the amount of change in the height of the pressure spring 22 when the sheet material P decreases is the same as the amount of change in the height of the stacked sheet material P. As a result, the stacking height of the sheet materials P on the intermediate plate 5 is always kept constant as shown in FIG. 3(a).

Next, the operation of the present invention will be explained.

As shown in FIG. 1, the position of the upper surface Pa of the sheet material P loaded on the intermediate plate 5 maintains a state in which the pressure force of the pressure spring 22 is balanced. At this time, the hook 9 is engaged with the ratchet gear 7 as shown in the figure, and its teeth 7a
The ratchet gear 7 can only rotate in one direction as shown by the arrow A. That is, the middle plate 5 is in a locked state with respect to the direction in which the free end 5a descends, and even if paper feeding pressure is applied to the sheet material P by the paper feeding roller 12 in this state, the upper surface Pa of the sheet material P will not move up or down. The paper feed roller 12 can stably feed the sheet material P without moving.

From this state, as the paper feeding operation by the paper feeding roller 12 is repeated and the sheet material P on the intermediate plate 5 decreases, as shown in FIG. Since the pressure spring 22 is expanded, the upper surface Pa of the sheet material P is always at the same height. In addition, the ratchet gear 7 is
Since the free end 5a of the middle plate 5 is rotatable only in one direction in the upward direction, the hook 9 engages with the tooth 7a corresponding to its position, and the middle plate 5 is locked in the downward direction. in a state. As a result, even when paper feeding pressure is applied to the sheet material P by the paper feeding roller 12, the middle plate 5 does not move up and down.
Stable paper feeding pressure can be obtained.

When the paper feed roller 12 feeds paper, a slight vertical difference may occur in the upper surface Pa of the sheet material P due to factors such as the pitch of the ratchet gear 7 and the difference in specific gravity of the sheet material P depending on the condition of the sheet material P. However, since there is a certain tolerance in the set height of the paper feed roller 12, by taking measures such as reducing the pitch of the ratchet gear 7, the vertical difference in the upper surface Pa of the sheet material P can be adjusted to reduce the paper feeding performance. can be kept at a level without any problems. Incidentally, in the experiment in this example, there was a tolerance of about 10 mm for the vertical difference in the upper surface Pa of the sheet material P.

After the sheet feeding operation has been carried out as described above, when replenishing the sheet material P onto the intermediate plate 5, an operation button (not shown) is operated and the control unit 20 receives a signal from the control section 20. Replenishment becomes possible by releasing the engagement of the hook 9 using a solenoid (not shown), freeing the ratchet gear 7, and lowering the middle plate 5.

In the above embodiment, the height of the sheet material P on the intermediate plate 5 was maintained by a combination of the one-way rotation mechanism 10 consisting of the ratchet gear 7 and the hook 9, and the pressure spring 22. However, instead of the one-way rotation mechanism 10, a combination of an appropriate one-way rotation mechanism and another elastic member may be used.

As described above, according to the paper feeding device of the present invention, the simple combination of the pressure spring 22 that presses and supports the sheet material P and the one-way rotation mechanism 10 that acts on the intermediate plate 5 allows The upper surface Pa of the sheet material P loaded on the intermediate plate 5 can be kept constant, and the sensor that detects the position of the upper surface of the sheet material P, as in conventional paper feeding devices, and the intermediate plate can be raised by driving it. It is possible to eliminate the use of a motor, etc., which causes the oscillation, and to simplify and downsize the device.

[0031]

[Effects of the Invention] As explained above, according to the present invention,
The loading means (middle plate) on which sheet materials are loaded is pressed by pressing means
By providing a one-way rotation mechanism (one-way rotation mechanism) on the support shaft at the rear end of the loading means, the sensor that detects the top surface of the sheet material and the loading means can be raised. With a simple configuration that does not require a special motor or the like, it is possible to control the upper surface position of the sheet material on the loading means at a constant level.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal side view of a paper feeding device showing an embodiment of the present invention.

[Figure 2] Same operation diagram

[Figure 3] Characteristic diagram of the pressure means (pressure spring)

[Figure 4]
FIG. 2 is a longitudinal side view showing an example of a conventional paper feeding device.

[Explanation of symbols]

P...Sheet material, Pa...Top surface of sheet material,
A... Rotating direction of the loading means (middle plate), 1... Paper feeding device, 2... Paper feeding cassette, 5... Loading means (middle plate), 6... Support shaft, 12... Paper feeding means (
paper feed roller), 17... separation means (separation roller pair), 10... one-way rotation means (one-way rotation mechanism)
, 20...control unit, 22...pressurizing means (pressurizing spring).

Claims (2)

[Claims] Claim 1: A stacking means for stacking a plurality of sheet materials and rotatable about a support shaft provided at a rear end, a paper feeding means for feeding the sheet materials, and a downstream side of the paper feeding means. a separation means that is arranged on the side and separates the fed sheet materials one by one, and a pressure means that urges the sheet materials loaded on the stacking means toward the paper feeding means side. The paper feeding device is characterized by having a one-way rotation means that allows the free end of the loading means to rotate freely in an upward direction, and a control means that releases rotation restriction of the one-way rotation means. Paper feeding device. 2. The paper feeding device according to claim 1, wherein the amount of change in the pressure means is approximately proportional to the amount of change in height of the stacked sheet materials due to paper feeding.