JPH0445037A - Paper size detector for image former - Google Patents

Abstract

PURPOSE:To detect various paper sizes with one sensor as well as to make whether a sheet of paper is set normally or not detectable by attaching a sensor, detecting an edge of the paper, to a movable body shiftable in the longitudinal direction or cross direction of the paper in a paper feed cassette. CONSTITUTION:In a while till a photosensor 21 of a movable body (turning arm) 20 detects a rear end edge 14b in the longitudinal direction of paper 14 since it has detected one end edge 14a in the cross direction of the paper 14, output of the photosensor 21 comes to be high. Size of the paper 14 is discriminated by a period of this high setting, while whether the paper 14 is normally set up or not is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a paper size detection device for detecting the size of paper in a paper feed cassette loaded in a main body of an image forming apparatus such as a copying machine or a printer.

2. Description of the Related Art Conventionally, in a printer, a paper feed cassette 2 is removably loaded into a main body 1, as shown in FIG. 6, for example, and the paper in the paper feed cassette 2 is automatically fed by an automatic paper feeder. Inside the main body 1, as shown in FIG. 7, for example, there is a sensor board 3.
For example, five transmissive photosensors 4 are installed in the paper feed cassette 2.
are arranged at intervals in the insertion direction. The paper feed cassette 2 has a shielding plate 5 corresponding to each paper size, as shown in FIG. 8, for example. In the example shown in FIG. 8, the shielding plate 5 has a recess 6 corresponding to a certain paper size.

Then, among the five photosensors 4, only one photosensor corresponding to the recess 6 is turned on, and the others remain off, thereby detecting the paper size. FIG. 9 shows the detection circuit, in which symbol C is a light receiving element of the photosensor 4, and S is a Schmidt circuit.

However, according to this method, a photo sensor 4 corresponding to each paper size and a shielding plate 5 corresponding to it in a one-to-one relationship are used, and when resetting paper of a different size, the shielding plate 5 is used. Plate 5 must also be replaced.

Apart from this, there were methods that used a button switch (this method also involved replacing the detection plate for each paper size in the same way as above), and methods that allowed the user to input the size from the operation panel, but the paper cassette It was difficult to make it universal.

As a countermeasure, a method was adopted in which bush switches, reed switches, etc. were arranged side by side in the width direction and length direction of the paper, and these switches were moved when the side guides and end guides of the paper feed cassette were moved. .

However, with this method, for example, in the case of an image forming apparatus capable of printing up to A3 size, a wide variety of paper sizes must be detected. For this reason, the number of switches must be increased accordingly, resulting in complicated control and high costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper size detection device that can detect various paper sizes with a single sensor, and can also detect whether or not the paper has been properly set.

The present invention provides an image forming apparatus in which a paper feed cassette is removably loaded into a main body and the paper in the paper feed cassette is automatically fed by an automatic paper feeder. The present invention is characterized in that a sensor for detecting the edge of the paper is attached to a movable body that can move in the length direction or width direction of the paper.

Operation When the moving body is moved, the sensor attached to it detects the edge of the paper. The size of the paper can be determined based on the time interval from when the movable body starts moving until the edge of the paper is detected, or the amount of movement of the movable body, and it is also possible to detect whether the paper is set in a specified position.

Example Next, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 3, a paper feed cassette 1o is removably loaded into a cassette loading port 12 of an image forming apparatus main body 11 along a cassette guide 13. The paper feed cassette 10 includes:
A pair of side plates 15 that determine the positions of both side edges of the paper 14 and an end plate 16 that determines the position of the trailing edge are slidably mounted.

1 and 2, a motor 18 is installed on a frame 17 within the image forming apparatus main body 11, and the motor 18
A base end of a swing arm 20 is fixed to a rotating shaft 19 of the swing arm 20 . The pivot arm 20 is pivoted horizontally on the paper feed cassette lo by rotation of the rotating shaft 19. A reflective photosensor 21 is attached to the tip of the rotating arm 20.

The photosensor 21 scans the paper feed cassette 10 in an arc shape through the arc-shaped window hole 17a of the frame 17 as the swing arm 20 rotates.

On the other hand, on the upper end surface of one side wall 10a of the paper feed cassette 10,
A starting point mark 22 and a reversal mark 23 that are detected by a photosensor 21 are provided.

The turning arm 20 has a photosensor 21 as a starting point mark 2.
2 is detected as the home position, and is normally stopped at this position. In this state, paper cassette 1
When o is pulled out from the image forming apparatus main body 11, the photosensor 21 no longer detects anything, but at this time the rotating arm 20 does not move.

When the paper feed cassette 10 is set in the image forming apparatus 11, the photosensor 21 detects the starting point mark 22, and it is detected that the paper feed cassette 10 is set. After the detection, the motor 8 rotates forward in a short period of time (for example, 200 to 400 m5ec), and the swing arm 20 swings clockwise in FIG. 1. At this time, if the paper 14 is set in the paper cassette 10, the photo sensor 21
The period from when one side @ 14a in the width direction of the paper 14 is detected until the rear end l#14b in the longitudinal direction is detected.

As shown in FIG. 4, the output becomes HIGH. Therefore, H
The size of the paper 14 can be determined based on the time that the IGH is set, and the presence or absence of the paper 14 can also be detected. When the photosensor 21 detects the reversal mark 23, the motor 18 is reversed. and.

The turning arm 20 has a photosensor 21 as a starting point mark 2.
It is rotated counterclockwise until 2 is detected again.

Note that the rotation control of the rotation arm 21 may be such that when the photosensor 21 detects the trailing edge 14b of the paper 14, the motor 18 is reversed to return the rotation arm 21. Alternatively, as shown in FIG. 5, the photo sensor 21 may be attached to a moving body 25 that moves in the width direction of the paper 14 along the track 24, and the size of the paper 14 may be determined based on the width of the paper 14.

According to the present invention, various paper sizes can be detected with one sensor, and the sensor can also detect whether or not the paper has been properly set, making it possible to make the paper feed cassette universal at low cost. can be realized.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a sectional view thereof, FIG. 3 is a perspective view of the main body of the image forming apparatus and the paper feed cassette in a separated state, and FIG. 4 is a method of determining paper size. The timing chart shown in FIG. 5 is a schematic plan view of another embodiment of the present invention. Fig. 6 is a perspective view for explaining the conventional example, Fig. 7 is a front view of the sensor board used therein, Fig. 8 is a partially enlarged view of the paper feed cassette in Fig. 6, and Fig. 9 is the paper sheet. It is a size detection circuit diagram. 10... Paper feed cassette 11... Image forming apparatus main body 14...
...Paper 2o...Swivel arm 21...Photo sensor

Claims (1)

[Claims] In an image forming apparatus in which a paper feed cassette is removably loaded in the main body and the paper in the paper feed cassette is automatically fed by an automatic paper feeder, the paper in the paper feed cassette is moved in the length direction or the width direction. A paper size detection device for an image forming apparatus, characterized in that a sensor for detecting the edge of paper is attached to a movable body.