JPS59184801A - Original size detecting device - Google Patents

Abstract

PURPOSE:To obtain a titled device by simple constitution having no sensor by detecting an insertion of an original to a gap between a registration guide and a plate electrode, by a capacity variation. CONSTITUTION:Plate electrodes 17A, 17B opposed to a platen 12 side and a registration 13 side are provided respectively so that air becomes a dielectric. In this state, the size of various originals PA which are placed on the platen 12 and inserted into the gap is detected by a capacity variation between the opposed plate electrodes, based on a size of an area of the part inserted into the gap of these originals PA. This method utilizes a theory by which the larger the size of paper is, the larger the electrostatic capacity becomes, and no matter how many kinds of originals there may be, they can be discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document size detection device used in a copying machine or a fufufu-miri device, and detects the size of a special document to determine the paper to be supplied or the scanning width of a reading optical system. The present invention relates to a device for selecting a document corresponding to the size of the document.

In general, conventional document size detection devices include (1) a plurality of light emitting elements provided at appropriate positions under a platen in response to various sizes of originals, and receiving light from the plurality of light emitting elements; A method in which a plurality of photosensors are provided on the back side of a platen cover, and the size of the document is detected by the difference in the light reception mode by the plurality of photosensors when the document is placed on the platen and the platen cover is closed. 2) A plurality of light emitting elements and a plurality of photosensors are provided at appropriate positions under the platen in accordance with the sizes of various originals, and a plurality of photosensors are provided to receive light reflected from the plurality of light emitting elements by the originals on the platen. In some cases, the size of the document is detected based on the difference in the light reception mode by the plurality of photosensors.

However, since all of the conventional devices described above use a plurality of photosensors, this becomes a major obstacle in reducing the cost of the device. Further, since the photosensor or the light emitting element is placed under the platen, it is difficult to arrange it in a position where the operation of the document scanning mechanism or the like is not prevented. Sara[,! Additionally, in method (1) above, when copying is performed with the platen cover closed, one of the multiple photosensors overlaps the original, making it difficult to copy translucent originals such as tracing paper. In some cases, the image of the photosensor appears on the copy, making it impossible to make high-quality copies.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a document size detection device that is inexpensive and has a simple configuration without using a photosensor.

That is, the present invention provides a gap between the platen and the 1/' strain guide disposed along the platen (and uses the gap, that is, air, as a dielectric material), so that the platen side and the AfJ Flat plate electrodes are provided facing each other on the registration side, and the sizes of various originals placed on the platen and inserted into the gap are determined based on the size of the area of the portion of these originals inserted into the gap. This is intended to be detected by changes in capacitance between electrodes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The document size detection device according to the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a perspective view showing an example of a copying machine equipped with a document size detection device according to the present invention, and FIG. This is the view from arrow I in the figure. Further, FIG. 3 shows a state in which FIG. 2 is viewed from the arrow ■ in FIG. 1.

1 to 3, the upper table 11 of the main body 10 of the copying machine has a platen 1 on which a document PA is placed.
2 is provided. This platen 12 has four types of copy areas AI to accommodate four types of original sizes.
Be CPD is provided, and these copy areas A.

It is assumed that B, O, and D correspond to the sizes of row 8, number 5, row A, number 4, row B, and number 3, row A, respectively, of the Japanese Industrial Standards. Further, at one end of the platen 12, the platen 1
2, a registration guide C (hereinafter simply referred to as "guide") 13 is provided. Further, the platen cover 14 is rotatably supported by support members 15A and 15B in the direction of arrow F in FIG. On the top of the main unit are 16A of items necessary for operating switches, etc.

16B are provided as appropriate.

Now, as shown in FIG. 2, a gap of an appropriate width (corresponding to the shaded area in FIG. 3) is provided between the platen 12 and the guide 13, and the guide is inserted across this gap. An electrode 17A is provided on the lower surface of platen 13, and an electrode 17B is provided on the upper surface of platen 12. In other words, this configuration is an opposed plate electrode capacitor in which the above-mentioned gap is air as a dielectric. Therefore, when the capacitance of a capacitor using air as a dielectric is used as a reference, the capacitance increases when the document PA is inserted into the gap. This is because the dielectric constant of paper is greater than that of air. Naturally, this capacitance also changes depending on the size of the paper inserted between the opposing flat electrodes. For example, as shown in FIG. 3, in a state in which a 5-size document PA (corresponding to area A) is inserted and a state in which a document FA of A4 size (corresponding to area B) is inserted (not shown), Of course, the capacitance is greater when an A4-sized original PA is inserted, that is, the size of the inserted paper is larger.

Therefore, if this capacitance change is detected by an appropriate capacitance detection means 18 corresponding to a current change, for example, the size of the document PA can be easily determined.

In the above-described embodiment, the guide 13 was arranged along the platen 12 so as to be parallel to the arrow ■ in FIG. If so, they may be arranged in a direction perpendicular to that shown in FIG.

Further, in the above-described embodiment, the sharpness of four types of originals can be identified, but it goes without saying that the object to be detected may be any type of original.

According to the document size detection device that performs BAK as described above, l) it is inexpensive and has a simple configuration;

2) The photo sensor image will no longer appear on the copy.

It has excellent effects such as

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a copying machine equipped with a document size detection device according to the present invention, FIG. 2 is an enlarged view of the main part of the present invention, and FIG. 3 is a plan view of FIG. 2. It is a diagram. lO...copy machine, 11...upper table, 12...
・Platen, 13...Registry storage guide, 1
4...Platen cover, 16A, 16B...Switch, 17A, 17B...Opposing flat plate electrode, 18...Capacitance detection means, FA...Document

Claims (1)

[Claims] Flat plate electrodes are arranged to face each other with a predetermined gap between a platen and a registration guide provided above the platen, and a gap between these flat plate electrodes is based on the insertion of a document into the gap. A document size detection device, comprising: a capacitance detection means for detecting a capacitance change, and detects the size of the document based on the detected capacitance change.