JPH1020416A - Original falling preventive device for image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an original falling preventive device for a copying machine capable of preventing the original from slide falling on the copying machine rear side at the time of opening the original press-contacting plate, and dealing with the original of a large size. SOLUTION: The original falling preventive device for the image reader provided with the original mounting plate 2 on a top surface of the image reader main body 1 and an original pressing plate 3 for covering the original mounting plate 2 in freely open-closing attached on the top surface of the image reader main body 1 by a hinge mechanism 4 in permitting rocking, is provided with a projection 5 retractable from the top surface of the image reader main body 1 associating with open-closing of the original pressing plate 3 as the original falling preventive device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used in a copying machine, a facsimile, and the like.
The present invention relates to a document drop prevention device that prevents a document placed on a document placing plate of an image reading device from dropping when opening and closing a document pressing plate.

[0002]

2. Description of the Related Art For example, an image reading apparatus of a copying machine is provided with a document placing plate for placing a document thereon. It is attached to the upper surface of the reading device in a tiltable manner by a hinge mechanism.

When copying an original in a copying machine,
A document is placed on a document placing plate, the back of the document is covered with a document pressing plate, and the image surface of the document is scanned from below the document placing plate.

When the original cover is closed, the air between the original placing plate and the original cover is pushed outward.
An air flow is generated from the hinge mechanism side of the image reading apparatus, that is, from the base end side of the original cover to the free end side of the original cover. For this reason, even if the original is placed at the correct position on the original placing plate, the original may move from the correct placing position due to the airflow generated when the original cover is closed.

In order to prevent such movement of the original,
As described in Japanese Utility Model Publication No. 6-36901,
The document cover may be composed of two rigid bodies connected by a center folding hinge, or a paper pressing member interlocking with the opening / closing operation of the document pressing plate may be provided as described in Japanese Patent Application Laid-Open No. 4-186334. JP-A-5-173262
As described in Japanese Patent Application Laid-Open Publication No. H11-209, it has been proposed that a document pressing plate for preventing the document from floating due to wind pressure is rotatably attached to a peripheral portion of the document table.

[0006]

The prior art described in each of the above publications is effective for preventing the original from moving when the original cover is closed, but is effective for opening the original when the original cover is opened. Can not be prevented. Hereinafter, the reason will be described.

When removing the original after copying, the original cover is lifted. At this time, static pressure is generated between the back of the original cover and the original, and the original may be lifted together with the original cover. . In this case, as time passes, air flows in from the surrounding space between the back surface of the document pressing plate and the document, so that the static pressure disappears and the document starts to fall by its own weight. At this time, since the original cover is inclined, the original is also inclined. For this reason, the original slides down along the surface of the original cover toward the hinge mechanism of the original cover. For this reason, the document may fall through the gap formed between the base edge of the document pressing plate and the upper surface of the image reading device and fall to the rear of the copying machine.

[0008] However, the above-mentioned Japanese Utility Model Publication No. 6-369.
No. 01, JP-A-4-186334, the document cannot be pressed down unless the original cover is closed to a certain degree, and the original is not pressed when the original cover is opened. Movement cannot be prevented. Also,
In the configuration described in JP-A-5-173262, since it is necessary to rotate the document pressing plate for each document,
The operation becomes very complicated, and there is a problem that large-format originals cannot be handled.

Japanese Unexamined Patent Publication No. Hei 5-289433 discloses an image forming apparatus in which an upper main body can be tilted and opened with respect to a lower main body when an upper main body is tilted open due to a trouble such as a paper jam. In order to prevent a document set on a glass surface from dropping by its own weight, a document drop prevention step portion slightly higher than the document glass surface is provided along a side edge of the document glass surface.

However, the document drop prevention step described in Japanese Patent Application Laid-Open No. Hei 5-289433 is for preventing the document from dropping under its own weight, and the document is prevented from falling by the static pressure generated when the document pressure plate is opened. In the case where the document can be lifted from the surface of the document placing plate, the movement of the document cannot be prevented.

Therefore, the present invention provides an apparatus for preventing a document from dropping in a copying machine which does not slide down to the rear of the copying machine when the document pressing plate is opened and which can cope with a large-sized document. The task is to

[0012]

According to the present invention, a document placing plate is provided on an upper surface of an image reading device main body, and a document pressing plate for opening and closing the document placing plate is provided on the image reading device main body. A document drop prevention device in an image reading device that is tiltably attached to an upper surface by a hinge mechanism,
An original falling prevention member is provided which is protruded and retracted from the upper surface of the image reading apparatus main body in conjunction with opening and closing of the original pressing plate.

According to another aspect of the present invention, a document placing plate is provided on an upper surface of the image reading device main body, and a document pressing plate for opening and closing the document placing plate is provided on the upper surface of the image reading device main body with a hinge mechanism. A document drop-prevention device in an image reading device attached to be tiltable by suctioning a document to a rear side of the device from a side edge of a rear surface of the document mounting plate on an upper surface of the main body of the image reading device. The air intake port is provided. Further, according to the present invention, a document placing plate is provided on an upper surface of the image reading device main body, and a document pressing plate for opening and closing the document placing plate can be tilted to the upper surface of the image reading device main body by a hinge mechanism. And a detachable document drop prevention member is provided on an upper surface of the image reading device main body.

According to another aspect of the present invention, a document placing plate is provided on the upper surface of the image reading device main body, and a document pressing plate for opening and closing the document placing plate is provided on the upper surface of the image reading device main body with a hinge mechanism. The document reading prevention device in the image reading device attached to be tiltable by the above, characterized in that a document falling prevention member which can be protruded and retracted is provided on the upper surface of the image reading device main body.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 24, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Detailed description of the invention

[Correction method] Change

[Correction contents]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used in a copying machine, a facsimile, and the like.
The present invention relates to a document drop prevention device that prevents a document placed on a document placing plate of an image reading device from dropping when opening and closing a document pressing plate.

[0002]

2. Description of the Related Art For example, an image reading apparatus of a copying machine is provided with a document placing plate for placing a document thereon. It is attached to the upper surface of the reading device in a tiltable manner by a hinge mechanism.

When copying an original in a copying machine,
A document is placed on a document placing plate, the back of the document is covered with a document pressing plate, and the image surface of the document is scanned from below the document placing plate.

When the original cover is closed, the air between the original placing plate and the original cover is pushed outward.
An air flow is generated from the hinge mechanism side of the image reading apparatus, that is, from the base end side of the original cover to the free end side of the original cover. For this reason, even if the original is placed at the correct position on the original placing plate, the original may move from the correct placing position due to the airflow generated when the original cover is closed.

In order to prevent such movement of the original,
As described in Japanese Utility Model Publication No. 6-36901,
The document cover may be composed of two rigid bodies connected by a center folding hinge, or a paper pressing member interlocking with the opening / closing operation of the document pressing plate may be provided as described in Japanese Patent Application Laid-Open No. 4-186334. JP-A-5-173262
As described in Japanese Patent Application Laid-Open Publication No. H11-209, it has been proposed that a document pressing plate for preventing the document from floating due to wind pressure is rotatably attached to a peripheral portion of the document table.

[0006]

The prior art described in each of the above publications is effective for preventing the original from moving when the original cover is closed, but is effective for opening the original when the original cover is opened. Can not be prevented. Hereinafter, the reason will be described.

When removing the original after copying, the original cover is lifted. At this time, static pressure is generated between the back of the original cover and the original, and the original may be lifted together with the original cover. . In this case, as time passes, air flows in from the surrounding space between the back surface of the document pressing plate and the document, so that the static pressure disappears and the document starts to fall by its own weight. At this time, since the original cover is inclined, the original is also inclined. For this reason, the original slides down along the surface of the original cover toward the hinge mechanism of the original cover. For this reason, the document may fall through the gap formed between the base edge of the document pressing plate and the upper surface of the image reading device and fall to the rear of the copying machine.

[0008] However, the above-mentioned Japanese Utility Model Publication No. 6-369.
No. 01, JP-A-4-186334, the document cannot be pressed down unless the original cover is closed to a certain degree, and the original is not pressed when the original cover is opened. Movement cannot be prevented. Also,
In the configuration described in JP-A-5-173262, since it is necessary to rotate the document pressing plate for each document,
The operation becomes very complicated, and there is a problem that large-format originals cannot be handled.

Japanese Unexamined Patent Publication No. Hei 5-289433 discloses an image forming apparatus in which an upper main body can be tilted and opened with respect to a lower main body when an upper main body is tilted open due to a trouble such as a paper jam. In order to prevent a document set on a glass surface from dropping by its own weight, a document drop prevention step portion slightly higher than the document glass surface is provided along a side edge of the document glass surface.

However, the document drop prevention step described in Japanese Patent Application Laid-Open No. Hei 5-289433 is for preventing the document from dropping under its own weight, and the document is prevented from falling by the static pressure generated when the document pressure plate is opened. In the case where the document can be lifted from the surface of the document placing plate, the movement of the document cannot be prevented.

Therefore, the present invention provides an apparatus for preventing a document from dropping in a copying machine which does not slide down to the rear of the copying machine when the document pressing plate is opened and which can cope with a large-sized document. The task is to

[0012]

According to the present invention, a document placing plate is provided on an upper surface of an image reading device main body, and a document pressing plate for opening and closing the document placing plate is provided on the image reading device main body. A document drop prevention device in an image reading device that is tiltably attached to an upper surface by a hinge mechanism,
An original falling prevention member is provided which is protruded and retracted from the upper surface of the image reading apparatus main body in conjunction with opening and closing of the original pressing plate.

According to another aspect of the present invention, a document placing plate is provided on an upper surface of the image reading device main body, and a document pressing plate for opening and closing the document placing plate is provided on the upper surface of the image reading device main body with a hinge mechanism. A document drop-prevention device in an image reading device attached to be tiltable by suctioning a document to a rear side of the device from a side edge of a rear surface of the document mounting plate on an upper surface of the main body of the image reading device. The air intake port is provided. Further, according to the present invention, a document placing plate is provided on an upper surface of the image reading device main body, and a document pressing plate for opening and closing the document placing plate can be tilted to the upper surface of the image reading device main body by a hinge mechanism. And a detachable document drop prevention member is provided on an upper surface of the image reading device main body.

According to another aspect of the present invention, a document placing plate is provided on the upper surface of the image reading device main body, and a document pressing plate for opening and closing the document placing plate is provided on the upper surface of the image reading device main body with a hinge mechanism. The document reading prevention device in the image reading device attached to be tiltable by the above, characterized in that a document falling prevention member which can be protruded and retracted is provided on the upper surface of the image reading device main body.

[0015]

FIG. 1 is a schematic perspective view of an image reading apparatus to which a document drop prevention device according to the present invention is applied. FIG. 2 is a schematic sectional view of the image reading apparatus shown in FIG.

On the upper surface of the image reading apparatus main body 1, there is provided a transparent original placing plate 2 for placing an original, and a light shielding member for covering the original placing plate 2 so as to be openable and closable. An original cover 3 is attached to an upper surface of the image reading apparatus main body 1 by a hinge mechanism 4 so as to be tiltable. The hinge mechanism 4 can be detached from the image reading apparatus main body 1 together with the original cover 3 so that a large original can be read.

In this embodiment, the upper surface of the image reading apparatus main body 1 can be protruded and retracted near the side edge of the original placing plate 2 on the rear side of the apparatus, that is, near the side edge on the hinge mechanism 4 side. The projection 5 is provided as a document drop prevention member.

As shown in FIG. 2, the projections 5 are provided in a housing 6 provided on the upper surface of the image reading apparatus main body 1 so as to be movable in the vertical direction. I have. A stopper 5a is formed at an intermediate portion of the protrusion 5 in the vertical direction, and the upper limit position of the protrusion 5 is determined when the stopper 5a abuts on the upper surface of the image reading apparatus main body 1.

When an original is read by the image reading apparatus shown in FIG. 1, as shown in FIG. 2, the original pressing plate 3 is opened, the original D is placed on the original placing plate 2, and then the original D is placed. The back surface of the document D is covered with the document pressing plate 3, and the image surface of the document D is scanned from below the document placing plate 2. At this time,
Since the top of the protrusion 5 is pressed by the lower surface of the original cover 3, the protrusion 5 is pushed into the housing 6 and the spring 7 is compressed. As described above, when the original cover 3 is closed, the projections 5 are housed inside the image reading apparatus main body 1, so that there is no problem in closing the original cover 3.

Next, in order to remove the original D from the original placing plate 2, when the original cover 3 is opened, the original D is lifted by the static pressure, and is moved along the surface of the original cover 3 toward the rear side of the image reading apparatus. Trying to slide down. However, at this time, since the projection 5 is not in contact with the original pressing plate 3, the projection 5 is pushed up by the spring 7 and projects from the upper surface of the image reading apparatus main body 1. Since it hits and stops there, it does not slide down to the rear side of the image reading device.

Further, as shown in FIG. 3, a long groove 5b having an L-shaped cross section may be formed at the tip of the projection 5 to constitute a lock mechanism for the document drop prevention member. In the steady state, FIG.
As shown in (a), the protrusion 5 can be projected from the upper surface 1a of the image reading apparatus main body 1. When reading a large-sized original, the hinge mechanism 4 together with the original pressing plate 3 is detached from the image reading apparatus main body 1, and the projection 5 is manually pushed into the image reading apparatus main body 1. By pressing the projection 5 in the direction, the long groove 5b of the tip of the projection 5 is engaged with the edge 1b of the opening of the upper surface 1a of the image reading apparatus main body 1 and fixed so that the projection 5 does not project upward. Is not in the way. Further, from this state, by pushing the tip of the projection 5 by hand in the direction opposite to the arrow P, the engaged state is released, and the projection 5 can protrude from the upper surface 1a of the image reading apparatus main body 1 again. .

FIG. 4 is a view showing another specific example of the lock mechanism. FIG. 4A is a sectional view showing a protruding state, and FIG.
(B) is sectional drawing which shows a storage state. FIG.
FIG. 4C is a sectional view taken along line AA of FIG. The base 5 c of the projection 5 is provided with a pin 5 d protruding laterally. The housing 6 that houses the projection 5 has a shaft 8
The movable hook 8b is swingably mounted in two directions by a. In the vicinity of the free end of the movable hook 8b, a locking claw 8c
Is formed to form a notch 8d.
A first inclined surface portion 8e is formed extending from the upper end of the first inclined surface in the direction of the shaft 8a. The free end of the movable hook 8b is formed with a second inclined portion 8f that becomes lower toward the opening of the notch 8d. Further, a spring 8h is wound around a shaft 8a between a locking portion 8g formed at an intermediate portion of the movable hook 8b and a fixed portion 6a on the housing 6 side.

FIG. 5 is an explanatory diagram showing the operation of the lock mechanism shown in FIG. In the initial state, FIG.
As shown in (c), the projection 5 is pushed up by the spring 7 and is in a protruding state. When the projection 5 is pressed down, the pin 5d is lowered as shown in FIG. 5A, and the movable hook 8b is pressed against the force of the spring 8h to push down the second inclined portion 8f of the movable hook 8b. It turns in the direction of arrow R. As shown in FIG. 5B, when the pin 5d passes through the tip of the locking claw 8c as shown by the arrow S, the pin 5d
Falls into the notch 8d and abuts against the side surface of the first slope portion 8, so that the movable hook 8b rotates in the direction opposite to the arrow R by the force of the spring 8h. In this state, the pin 5d
Is locked by the locking claw 8c, so that the projection 5 is maintained at the lowered position. Next, when the protrusion 5 is pressed down again by hand, the pin 5 d descends along the side surface of the first slope portion 8,
As shown in FIG. 5C, the tip of the pin 5 d sinks below the first slope 8. When the hand is released from the projection 5 in this state, as shown in FIG. 5D, the pin 5d moves in the direction of the arrow U along the lower surface of the slope portion 8, and the movable hook 8b moves to the tip of the pin 5d. It is pushed and tilts in the direction of arrow V. Therefore, the pin 5d comes out of the movable hook 8b without being locked by the locking claw 8c, and the projection 5 returns to the protruding state.

FIG. 6 is a perspective view showing another embodiment of an image reading apparatus to which the document drop prevention device of the present invention is applied.
FIG. 7 is a schematic sectional view of a main part of the image reading apparatus shown in FIG. Members corresponding to those in the embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals.

Generally, the inside of an image reading apparatus main body 1 used in a copying machine contains ozone, heat,
An exhaust duct 9 is provided for discharging dust and the like outside the machine. In the embodiment shown in FIGS. 6 and 7, a branch duct 11 is provided upstream of the fan 10 of the exhaust duct 9, and the tip of the branch duct 11 is located near the side edge of the document placing plate 2 on the rear side of the apparatus. Is connected to the slit 12 provided in the first position.

According to the embodiment shown in FIG.
The original is lifted when the original cover 3 is opened, and even when the original slides down,
The original is attracted to the slit 12 and does not move any further. Therefore, it is possible to prevent the document from dropping to the rear of the apparatus.

FIG. 8 shows a modification of the embodiment shown in FIGS. In the example shown in FIG. 8, the backflow duct 1 is located between the downstream side of the fan 10 of the exhaust duct 9 and the branch duct 11.
3 are connected. Further, a partition plate 16 for selectively closing the opening 14 from the exhaust duct 9 to the branch duct 11 and the opening 15 from the backflow duct 13 to the branch duct 11 to switch the flow path of the exhaust is provided. This partition plate 16
Can be tilted about a shaft 16a, and the position thereof is controlled in conjunction with opening and closing of the original cover 3. That is, when the original cover 3 is opened, the partition plate 16 opens the opening 14 from the exhaust duct 9 to the branch duct 11 and moves from the backflow duct 13 to the branch duct 11 as shown by a solid line in FIG. Is moved to a position that closes the opening 15 of the. As a result, similarly to the embodiment shown in FIG. 7, ozone, heat, dust, and the like generated inside the apparatus are discharged out of the apparatus through the exhaust duct 9 and the air is sucked from the slits 12 so that the original is transferred to the apparatus. It is prevented from falling backward. When the original cover 3 is closed, the partition plate 16 opens the opening 15 from the backflow duct 13 to the branch duct 11, as shown by the broken line in FIG. It is moved to a position to close the opening 14. As a result, a part of the air downstream of the fan 10 flows into the branch duct 11 and is exhausted outside the machine through the slit 12, thereby preventing the slit 12 from being clogged with dust.

As a means for controlling the position of the partition plate 16 in conjunction with the opening and closing of the original cover 3, an open / close state of the original cover 3 is detected by an optical sensor or a mechanical switch, and the detection result is obtained. A mechanism for driving the partition plate 16 by controlling a motor, a plunger, and the like, and a link mechanism between the original cover 3 and the partition plate 16 are provided. A mechanism for mechanically driving can be employed. However, the present invention is not limited to these mechanisms, and any interlocking mechanism can be adopted.

In the embodiment shown in FIGS. 6 to 8 described above, the mechanism for preventing the document from dropping to the rear of the apparatus does not protrude upward from the upper surface of the image reading apparatus main body 1. There is no hindrance when reading large format documents.

FIG. 9 is a perspective view showing still another embodiment of an image reading apparatus to which the document drop prevention device of the present invention is applied. In the embodiment shown in FIG. 9, a tiltable projection 17 is provided on the upper surface of the image reading device behind the hinge mechanism 4 so as to take a storage position and an upright position. A base end of the projection 17 is rotatably supported by a shaft 17 below the upper surface of the image reading device, and is provided below the upper surface of the image reading device.
8 are provided.

In the embodiment shown in FIG. 9, when reading an original of a normal size, the original is lifted when the original cover 3 is opened by setting the projection 17 in an upright state. Even when the document slides down along the surface of the pressure-bonding plate 3, the document abuts on the projection 17 and does not move any further. Therefore, it is possible to prevent the document from dropping to the rear of the apparatus. At this time, since the projections 17 are provided on the rear side of the apparatus with respect to the hinge mechanism 4, the original that slides down along the surface of the original cover 3 always moves along the upper surface of the image reading apparatus. The document does not jump over the projection 17. When reading a large-format original, the hinge mechanism 4 together with the original compression plate 3 is detached from the image reading apparatus main body 1 and the projection 17 is stored in the storage section 18 so that the large-format original can be read without any trouble. .

FIG. 10 is a perspective view showing still another embodiment of an image reading apparatus to which the document drop prevention device of the present invention is applied. In the embodiment shown in FIG. 10, a detachable projection 19 is provided on the upper surface of the image reading apparatus, on the rear side of the hinge mechanism 4 with respect to the apparatus. Base 19a of this projection 19
Is detachably fitted in a concave portion 20 formed on the upper surface of the image reading device, and a top portion 19b of the projection 19 projects upward from the upper surface of the image reading device.

In the embodiment shown in FIG. 10, when reading a normal-size original, the original is lifted when the original cover 3 is opened by fitting the projection 19 into the concave portion 20, and thereafter the original is lifted. Even when the original slides down along the surface of the original cover 3, the original abuts on the top 19 b of the projection 19 and does not move any further. Therefore, it is possible to prevent the document from dropping to the rear of the apparatus. When reading a large-format original, the hinge mechanism 4 and the original cover 3 are detached from the image reading apparatus main body 1 and the projection 19 is detached from the concave portion 20, so that the large-format original can be read without any trouble. Sign 1
9 'denotes a projection in a detached state.

[0034]

According to the present invention, since the document drop prevention member is provided so as to be able to protrude and retract from the image reading surface in conjunction with opening and closing of the document pressure plate, the document drops to the rear of the apparatus when the document pressure plate is opened. Can be prevented with a simple configuration, and there is no hindrance when reading a large-format original.

Further, in the present invention, since the means for sucking air is provided on the upper surface of the image reading apparatus, the original does not move due to the wind pressure regardless of the position of the original pressing plate. Also, there is no problem when reading a large-format original. Further, since there is no projecting portion on the upper surface of the image reading apparatus, the appearance is not impaired.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an image reading apparatus to which a document drop prevention device of the present invention is applied.

FIG. 2 is a schematic sectional view of the image reading apparatus shown in FIG.

FIG. 3 is an explanatory view showing a lock mechanism for a document drop prevention member.

FIG. 4 is a diagram showing another specific example of the lock mechanism.

FIG. 5 is an explanatory view showing the operation of the lock mechanism shown in FIG.

FIG. 6 is a perspective view showing another embodiment of the image reading apparatus to which the document drop prevention device of the present invention is applied.

FIG. 7 is a schematic sectional view of a main part of the image reading apparatus shown in FIG. 6;

FIG. 8 shows a modification of the embodiment shown in FIGS.

FIG. 9 is a perspective view showing still another embodiment of the image reading apparatus to which the document drop prevention device of the present invention is applied.

FIG. 10 is a perspective view showing still another embodiment of the image reading apparatus to which the document drop prevention device of the present invention is applied.

[Description of Signs] 1... Image reading device main body, 1a.
Document placement plate, 3 ... Document press plate, 4 ... Hinge mechanism, 5 ... Protrusion, 5a ... Stopper, 5b ... Long groove, 6 ... Housing, 7
... spring, 8a ... shaft, 8b ... movable hook, 8c ... locking claw,
8d: notch, 8e: first slope portion, 8f: second slope portion, 8g: locking portion, 8h: spring, 9: exhaust duct, 10
... Fan, 11 ... Branch duct, 12 ... Slit, 13 ...
Backflow duct, 14 ... opening, 15 ... opening, 16 ... partition plate, 16a ... shaft, 17 ... projection, 18 ... storage, 19 ... projection, 20 ... recess

Claims (9)

[Claims] An original mounting plate is provided on an upper surface of an image reading device main body, and an original pressing plate that opens and closes the original mounting plate so as to be openable and closable by a hinge mechanism on the upper surface of the image reading device main body. An image reading prevention device in an attached image reading device, comprising: a document falling prevention member that protrudes and retracts from an upper surface of the image reading device main body in conjunction with opening and closing of the document pressing plate. Document fall prevention device in the device. 2. The image reading device according to claim 1, wherein the document drop prevention member protrudes from an upper surface of the image reading apparatus body further rearward than a side edge of the document placing plate on a rear side of the apparatus when the document pressing plate is opened. 2. The document drop prevention device in the image reading device according to claim 1, wherein 3. The document according to claim 2, wherein the document drop prevention member is retracted from an upper surface of the image reading device main body when the document pressing plate is closed. Fall prevention device. 4. A document drop prevention device in an image reading apparatus according to claim 3, further comprising lock means for fixing said document drop prevention member in a retracted state. 5. A document placing plate is provided on an upper surface of the image reading device main body, and a document pressure plate for opening and closing the document placing plate is opened and closed by a hinge mechanism on the upper surface of the image reading device main body. A document drop prevention device in an attached image reading device, wherein an air suction port for sucking a document is provided on the upper surface of the image reading device main body at a position closer to the rear of the device than a side edge of the document placing plate on the device rear side. A document drop prevention device in an image reading device, comprising: 6. An apparatus according to claim 5, wherein said air intake port is connected to an exhaust duct provided in said image reading apparatus main body. 7. The document drop prevention device in the image reading apparatus according to claim 6, wherein the air suction port is configured to suction air when the document pressure plate is open. 8. A document placing plate is provided on an upper surface of the image reading device main body, and a document pressure plate for opening and closing the document placing plate is opened and closed by a hinge mechanism on the upper surface of the image reading device main body. A document drop prevention device for an attached image reading device, wherein a detachable document drop prevention member is provided on an upper surface of the image reading device main body. 9. A document placing plate is provided on an upper surface of the image reading device main body, and a document pressure plate for opening and closing the document placing plate is tiltably movable on the upper surface of the image reading device main body by a hinge mechanism. An apparatus for preventing a document from dropping in an attached image reading device, wherein a document drop-preventing member is provided on an upper surface of the image reading device main body so as to be retractable.