JPH05289202A - Image forming device - Google Patents

Abstract

PURPOSE:To enable a user to perform the attaching/detaching work of an overlay by one hand with a simple structure by providing a fixing device for fixing an original platen at a fixed position at the time of attaching/detaching the overlay. CONSTITUTION:In a state where the original platen 6 is at a copying starting position(when a cam follower 17 exists at a flat part 26), the attachment/ detachment of the overlay is performed. At the time of attaching the overlay, the original platen 6 has a tendency to move in the left direction, but it keeps the fixed position because a non return member 38 prevents the progress of the cam follower 17. Since the member 38 is in a resin-integrated shape and can rotate centering around a pin 39, the cam follower 17 pushes up the member 38 when it moves from an inclined part 25 to the flat part 26. However, when the cam follower 17 reaches the flat part 26, the member 38 is restored to a home position by gravity. The overlay is attached/detached by one hand without fixing the original platen 6 with hands by means of the member 38 provided on a regulating member engaging with the cam follower 17 provided on a pressure plate 16 as the original platen 6 moves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to attachment / detachment of an overlay in an image forming apparatus such as a copy table movable type copy machine and fixing of the copy platen at that time.

[0002]

2. Description of the Related Art A manuscript table such as a manuscript table moving type copying machine has a movable range larger than the scanning process, and is moved to the outside of the scanning process manually during maintenance inspection and paper jam processing. .. A stopper is provided at the movement limit position of the maximum movable range. A guide rail to which an overlay can be attached and an overlay fixing device are provided on the document table, and the overlay can be attached to and detached from the guide rail.

[0003]

When a manuscript table moving type copying machine or the like is operated with an overlay being attached to and detached from the manuscript table, for example, in the case of a manuscript table using rails, the manuscript table hits stoppers at both ends. Since it will move up to and down, one side will grab the platen and immobilize it, and the other hand will attach and detach the overlay to the platen, making it difficult to attach and detach.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a device having a simple structure and allowing a user to perform the attaching / detaching work with one hand.

[0005]

A first aspect of the present invention is a movable document table, and an overlay that is detachable from the table.
The image forming apparatus is provided with a fixing device that fixes the document table at a fixed position when the overlay is attached and detached.

A second invention of the present invention has a restricting member for restricting the movement of the original platen, the restricting member being held on the main body of the apparatus, and a fixing device for fixing the original table to a fixed position on the restricting member. The image forming apparatus according to the first aspect of the invention is characterized in that.

According to a third aspect of the present invention, the regulating member is a cam portion fixed to the main body of the apparatus, and the fixing portion for fixing the original table at a fixed position by engaging the cam portion with a cam follower provided on the original pressure plate is a cam portion. A non-return member rotatably attached to the back end by a pin, wherein the non-return member engages the cam follower and the non-return member in a state where the document table is in the original position.
The image forming apparatus according to the invention.

According to a fourth aspect of the present invention, a document table fixing device is provided in the main body of the apparatus and is inserted into and removed from the document table in a direction intersecting with the movement direction of the document table, and one of the document table when engaged with the document table. The image forming apparatus according to the first aspect of the present invention is provided with a non-return member for stopping the movement of the non-return member and a driving unit for driving the non-return member.

[0009]

EXAMPLES The present invention will be described below with reference to specific examples.

[First Embodiment] FIG. 1 is a longitudinal sectional view of a copying machine according to an embodiment of the present invention. The sheet 2 stacked in the sheet feeding cassette 1 is sent out by the sheet feeding roller 3, conveyed by the slip roller 4, and reaches the registration roller 5. The registration roller 5 makes the sheet 2 stand by for a certain period of time, and conveys the sheet 2 in synchronism with document exposure. The document table 6 is configured to be movable in the left-right direction.
The original placed on the surface is illuminated by the illumination lamp 7 and projected onto the photosensitive drum 9 via the SELFOC lens 8. Around the photosensitive drum 9, known charging means, developing means, and cleaning means (not shown) are provided, and after the latent image is formed, transfer is performed on the sheet 2 conveyed from the resist roller 5 by known transfer means. The transferred sheet 2 is guided by the fixing inlet guide 11 via the conveying unit 10 and is conveyed to the fixing device 12 and then to the fixing device 12. The sheet 2 fixed by the fixing device 12 passes through the paper discharge roller 13 and is discharged to the outside of the machine.

FIG. 2 is a rear view of FIG. 1 showing a drive system of a copying machine which is a specific example of the present invention. A part of the document table 6 for placing the document has a rack 6a, and the rack 6a
Engages with the pinion gear 14 to transmit drive. The pinion gear 14 is driven by the main motor 15 via a plurality of gears.

Further, by providing a clutch mechanism (not shown) in the intermediate path from the output gear fixed to the main motor 15 to the pinion gear 14, the pinion gear 14 can be rotated normally or reversely. .. Therefore,
The document table 6 can be moved rightward or leftward by rotating the pinion gear 14.

The original table 6 is provided with cams A, B and C,
Document position detecting means a and b operated by these cams are provided on the main body side. The detection means a, b and the cam A,
Arms d and e are provided between B and C, respectively. These arms d and e are in the form of arms pivotally attached to the main body by a pin 41, the middle of the arms are in contact with actuators attached to the detection means a and b, and the tips of the arms are rollers followers that engage with cams A, B and C. 42 are provided. Therefore, when the cams A, B, C are moved by the movement of the document table 6, the roller follower 42 is pushed and the arms d, e rotate around the pin 41 down to activate the detecting means a, b. ing. When the copy button is turned on while the rack 6a and the pinion gear 14 are in mesh with each other, the original table 6 turns on the original position detecting means a with the cam A and the original position detecting means b with the cam B from the state shown in FIG. After moving to the right so as to be in the state, it is synchronized with the fed sheet 2. At this time, by switching a clutch (not shown), the pinion gear 14 reversely rotates, and the document table 6 moves leftward to start exposure of the document. When the exposure of the original document is completed and the cam C turns on the original document position detecting means a, the original document table 6 is reversed by a clutch (not shown) to move rightward again to the state of FIG.

Next, the pressure plate 1 for pressing the document on the document table 6
The switchgear 6 (FIG. 1) will be described.

A pressure plate rotating shaft 22 fixed to the edge of the pressure plate 16.
Is rotatably supported on the document table 6. As shown in FIGS. 3 and 4, one end of the pressure plate rotating shaft 22 is provided with a lever member (a) 18 which is rotatable with respect to the shaft 22. A lever member (b) 19 fixed by a shaft 22 and a spring pin 23 is provided. The tip end member of the lever member (a) 18 is the cam follower 17, and the cam follower 17 moves by being guided by the cam portion 24 fixed to the main body (details will be described later). Considering this, the angle with respect to the pressure plate rotating shaft 22 changes with the movement of the document table 6.

The lever member (b) 19 is engaged with the V groove 18a of the lever member (a) 18 (V groove perpendicular to the lever member (a) 18) via the notch 20 pressed by the spring 21. Accordingly, the lever member (a) 18 and the lever member (b) 19 are integrally swung in conjunction with the movement of the cam follower 17, and the pressure plate 16 is turned. That is, when the cam follower 17 is raised, the lever plate (a) 18 and the lever member (b) 19 are engaged with the notch 20 and the pressure plate rotating shaft 22 is rotated in the direction in which the pressure plate 16 moves away from the document table 6 to press the pressure plate. 16 opens, and when the cam follower 17 descends, the pressure plate 16 closes contrary to the above.

If the pressure plate 16 is forcibly closed by hand when the pressure plate 16 is released, the pressure plate rotating shaft 22 rotates and the V groove 18a of the lever member (a) 18 pushes the notch 20 and the notch 20 springs. By compressing 21 (see FIG. 4), the lever member (a) 18 is disengaged, and the pressure plate 16 can be manually opened and closed at any position.

The movements of the cam portion 24 and the cam follower 17 fixed to the main body will be described. The cam portion 24 is the pressure plate 1.
It is a restricting member that restricts the interlocking of 6.

When the document table 6 in FIG. 1 is in the original position and is moved to the left copying start position, the cam follower 17 engages with the cam groove 24 of the cam groove 24.
To reach the flat portion 26 while pushing up the rotatable check member 38 (detailed later) pivotally attached to the cam portion 24 by the pin 39 (FIG. 10).

By raising the cam follower 17 at this time, the pressure plate 16 is opened at a predetermined angle, and the original can be set. When a copy button (not shown) is turned on in this state, the cam follower 17 is pivotally attached to the cam portion 24 by a pin 29, gets over the non-return pawl 27 biased by the spring force in the clockwise direction, reaches the flat portion 28, and then is conveyed. The sheet 2 is instantaneously stopped to synchronize with the sheet 2. Thereafter, the document table 6 is reversed and moves rightward, so that the cam follower 17 is guided by the check claw 27 and slides down the inclined portion 30. Similar to the check member 38, the check claw 27 has a resin-integral shape and is rotatable about a pin 29. The rear part of the check claw 27 has a shape of a leaf spring 27a. A spring force is applied to the rotation of the claw 27.

When the cam follower 17 slides down the inclined portion 30, the pressure plate 16 is closed and the original is pressed against the original table 6. When the cam follower 17 reaches the flat portion 31, the illumination lamp 7 is turned on, and the exposure of the original document on the already exposed photosensitive drum 9 is started. The cam follower 17 moves to the right of the document table 6 and the flat portion 3
1 is moved to the right, and document exposure is continued. The cam follower 17 that has moved to the right on the flat portion 31 further moves to the right while pushing up the switching cam member 32 pivotally attached to the cam portion 24 by the pin 33. The switching cam member 32 also has a resin-integral shape similar to the check member 38, is rotatable around the pin 33, and has a rear end shaped like a leaf spring 32a. The leaf spring 32a is planted in the cam portion 24. It is stopped by the pin 32b and the switching cam member 32 is biased clockwise by a spring force so that the cam follower 17 can move smoothly. When the document exposure is completed and the document table 6 is turned over to the left, the cam follower 17 is provided with the inclined portion 25.
, The check member 38 is pushed up and stopped at the flat portion 26. Along with this, the cam follower 17 rises, and the pressure plate 16 rotates around the pressure plate rotation shaft 22 and opens. At this time, since the pressure plate 16 is in the open state, it is possible to replace or set the original document as it is. In the case of the present embodiment, the process cartridge system in which the photosensitive drum, the developing means and the cleaning means are integrated is adopted, and when the process cartridge is replaced or the jam processing is performed, the document table 6 is set to the left end. It is configured to move and open the upper side of the machine in an alligator shape. It is a so-called clam shell type.

When the document table 6 is manually moved to the left end, the flat portion 28 is guided by the cam member 35 and goes down the inclined portion 34 to reach the flat portion 36. When the document table 6 is moved to the right from this state, the cam follower 17 moves the flat portions 37, 3
It smoothly returns to the state of Fig. 1 through 1.

As described above, it is possible to set a document and perform a copying operation without manually opening and closing the pressure plate by the regulating member that engages with the pressure plate as the platen moves.

The attachment / detachment device 44 for attaching / detaching the overlay 43 to / from the document table 6 will be described. 8 and 9 are plan views of the inside of the overlay attaching / detaching device 44. A hook member 44A is fitted to the guide member 44B fixed to the document table 6 so as to be movable in the attachment / detachment direction of the overlay 43. The hook member 44A is composed of a pair of hook portions 44a and a body portion 4 which are opposed to each other by a reverse claw capable of gripping the fixed portion 43a of the overlay 43.
4d, and a lock member 44b is rotatably attached to the main body portion 44d by a pin 44e. Lock member 4
The position 4b is vertically long in the moving direction of the hook member 44A in FIG. 8, and the abdomen 44b of the lock member 44b is provided.
The tip end of a square locking portion 44f provided on the guide member 44B is in contact with -1. The locking member 44b has a locking portion 44f.
There is provided a groove portion 44b-2 which engages with the corner of the hook to prevent the hook member 44A from moving downward in the drawing. The hook portion 44a is elastically opened so as to maintain the position shown in FIG. Further, the compression spring 44c is connected to the rear end of the hook member 44A and the guide member 44B.
It is contracted between the two and urges the hook member 44A downward in the drawing. In FIG. 8, the step portion 44g of the hook member 44A is in contact with the stopper 44h provided on the guide member 44B.
Following the stopper 44h, an inclined portion 44i for pressing the back portion of the hook portion 44a is provided. The inclined portions 44i on both sides are in the shape of a letter "H", with a facing distance from the mouth to the inner side.

In the overlay attaching / detaching device 44, when the hook member 44A is pushed against the compression spring 44c at the tip of the fixed portion 43a of the overlay, the hook member 44A faces upward in FIG. When the lock member 44b passes over the upper left corner of the locking portion 44f of the guide member 44B while being hooked to the overlay fixing portion 43a as shown in FIG. 9, the portion rotates counterclockwise about the pin 44e. Then, the hook member 44A returns to the original state and the state shown in FIG. 9 is obtained. When the overlay fixing portion 43a is pushed slightly upward in the state of FIG. 9, the hook member 44A moves a little in the same direction, and the lock member 44b turns clockwise around the pin 44e to be disengaged from the locking portion 44f. .. Then, due to the spring force of the compression spring 44c, the hook member 44A faces downward in the drawing and the space between the hooks 44a expands, so that the overlay fixing portion 43a is released. FIG. 8 is a drawing of the overlay 43 slightly in the escape direction.

As shown in FIG. 5, the overlay 43 is fixed to the document table 6 by a fixed portion 43a of the overlay 43 and an overlay attaching / detaching device 44 fixed to the document table 6 side. Further, as shown in FIG. 7, the pressing portion 4 of the overlay 43 is fixed by the spring member 46 screwed to the document table 6.
By pressing 3b, the backlash of the overlay 43 is eliminated and the overlay 43 is securely fixed.

With respect to the attachment / detachment device 44, any means such as a magnet and an embossing latch may be selected as long as the overlay 43 can be attached / detached to / from the document table.

As for the spring member 46, any means such as a compression spring, a tension spring, a torsion spring, a leaf spring or the like may be selected as long as the overlay 43 can be pressed.

The operation of attaching / detaching the overlay 43 will be described. 5 and 7 are plan views of the document table showing a state when the overlay is attached and detached, and FIG. 6 is a cross-sectional view taken along the line AA of FIG. 5. In FIG. 5, the overlay 43 is a guide rail for overlay attachment and detachment of the document table 6. It is in a state of being plugged into 47.
When this overlay 43 is moved in the direction of the arrow in FIG. 5, the fixed portion 43a of the overlay 43 engages with the overlay attaching / detaching device 44 fixed to the document table side as shown in FIG. 7, and the overlay 43 is fixed to the document table 6. It will be in the state of being. At this time, the spring member 46 fixed to the document table side presses the pressing portion 43b of the overlay 43.

When the overlay 43 is removed from the original table 6, when the overlay 43 is pushed in the set direction, the lock member 44 in FIG.
b is released, and the overlay 43 is pulled out by pressing the compression spring 44c. After that, pull out in a direction opposite to the direction in which the overlay 43 is set, and the overlay 43
Can be removed by sliding the guide rail 47.

The movement of the non-return member 38 and the cam follower 17 provided as a document table fixing device at the time of overlay attachment / detachment when the document table is fixed at a fixed position by a mechanical means at the time of overlay attachment / detachment will be described. The check member 38 is also one of the regulating members for regulating the movement of the document table 6.

When the document table 6 in FIG. 10 is in the copy start position (when the cam follower 17 is on the flat portion 26), the overlay is attached and detached. When the overlay 43 is attached, the document table 6 tries to move to the left, but the check member 38
Since the cam follower 17 interferes with the progress of the cam follower 17, the document table 6 can be maintained at a fixed position. Since the non-return member 38 is made of resin and can rotate around the pin 39, the cam follower 17 pushes up the non-return member 38 when the cam follower 17 moves from the inclined portion 25 to the flat portion 26.
When reaches the flat portion 26, the check member 38 returns to its original position by its own weight.

As described above, the overlay attaching / detaching operation is performed with one hand without fixing the document table by hand by the non-return member provided on the regulating member which engages with the cam follower provided on the pressure plate as the document table is moved. It became possible to do.

[Embodiment 2] A non-return device at the time of attaching / detaching an overlay in the case of fixing an original plate at a fixed position by an electric means at the time of attaching / detaching an overlay will be described with reference to FIGS. In this example, the non-return member 3 used in Example 1
8 is unnecessary.

The check device is an electrical means such as a solenoid 5.
2 is a mechanism for moving the check member 49, and is fixed to the main body side. That is, the solenoid 52 is fixed to the main body of the apparatus, and the vertical movable rod 52a of the solenoid is connected to the check member 49 and the pin 56.
The non-return member 49 is slidably engaged with the guide box 50 so as to be vertically movable, and is brought into contact with the top plate of the guide box 50 by the flange portion 49a to determine a rising position. A spring member 51 is contracted to the check member 49 between the flange 49a and the bottom of the guide box 50.
Is always biased upward. The upper end of the check member 49 is provided with an inclination toward the upper right as shown. The guide box 50 is fixed to the apparatus body near the top plate 48 of the apparatus body.

A stopper hole 6b is provided on the lower surface of the document table 6. In the stopper hole 6b, a right side wall 6b-1 of the document table 6 in the left-right direction in the drawing is orthogonal to the document table movement direction, and a left side thereof is an inclined portion 6b-2 following the upper end of the check member 49.

As shown in FIG. 11, when the overlay is attached / detached, the non-return member 49 interferes with the side wall 6b-1 of the stopper hole 6b, so that the document table 6 does not move leftward.

When replacing the process cartridge,
Or, when performing jam (paper jam) processing, the document table 6
Must be moved to the right end in FIG.
First, when the document table 6 is pushed rightward from the position shown in FIG. 11, the left portion (inclined portion 6b-2) of the stopper hole 6b comes into contact with the check member 49. When pushed further, the check member 49 is held by the spring member 51, so that the check member 49 moves in the direction in which the spring member 51 is compressed (downward).

Non-return member 49 slipped out of the stopper hole 6b
Is pressed against the bottom surface of the document table 6 by the force of the spring member 51. (FIG. 12) In order to return the document table 6 from the right end to the current position of FIG.
When the stopper hole 6b reaches right above, the non-return member 49, which is pressed by the force of the spring member 51, automatically engages with the stopper hole 6b, resulting in the state of FIG.

Since the document table 6 moves to the left when copying is being performed, the solenoid 52 of the electric means is pulled at a certain timing to eliminate the effect of the check member 49. This allows the document table 6 to move freely in the left-right direction.

Incidentally, as the electrical means, any means other than the solenoid 52, such as a motor and an electromagnetic clutch, may be selected as long as the check member 49 can be moved.

The movements of the non-return device and the document table 6 at the time of attaching / detaching the overlay in the case where the document table 6 is fixed at a fixed position by electric means during the attachment / detachment of the overlay will be described.

The copy start position of the document table 6 is shown in FIG. 13. When the copy button is turned on in this state, the solenoid 52 of the check device is actuated when the document table starts moving, and the check member 49 is pulled. When the position of the stopper hole 6b moves to the left of the position of the check member 49 due to the movement of the document table 6, the solenoid 52 is de-energized and the check member 49 is deenergized by the spring force of the spring member 51. It contacts the bottom of the document table 6. In this state (FIG. 14), the document table 6 is moved for exposure scanning.

A cam D is provided on the document table 6, and a document position detecting means f operated by the cam is provided on the apparatus main body side.
Is provided. An arm g is provided between the detecting means f and the cam D. This arm g has a pin 53 on the main body.
A roller follower 54 that is pivotally attached to the actuator is attached to the actuator attached to the detecting means f at the middle of the arm, and a roller follower 54 that engages with the cam D is provided at the tip of the arm g. Therefore, when the cam D moves due to the movement of the document table 6, the roller follower 54 is pushed and the arm g rotates around the pin 53 to move down to activate the detecting means f. The distance between the cam D and the stopper hole 6b and the roller follower 54
And the non-return member 49 have the same interval.

After the exposure is completed, when the document table 6 moves to the right and returns to the copy start position (the state shown in FIG. 13), the moving cam D pushes the roller follower 54 to operate the document position detecting means f. Along with this, the original table 6 stops, and the check member 49 engages with the stopper hole 6b to fix the original table 6.

In this state, the overlay is attached / detached, but the overlay can be attached / detached easily and in a short time, as in the case of fixing the document table by a mechanical means.

[Third Embodiment] FIG. 1 shows another example of this embodiment.
As shown in FIG. 5, a method may be considered in which the document table 6 is not provided with a stopper hole and the document table 6 is fixed to the rear end of the document table 6 by a non-return device E using an electric means. The non-return device E is similar to the non-return device of the previous embodiment, but the non-return member 55, which replaces the non-return member 49, has a flat top surface. In this example, when the process cartridge is replaced, or when jamming (paper jam) is performed, the check device E is at the rear end of the document table 6 and is not related to the right movement of the document table 6.

When the copy button is turned on during copying, the check member 55 causes the solenoid 5 to move before the document table 6 moves.
It is pulled by 2 and there is no check action. When the image is exposed in this state (shown in FIG. 16) and returns to the copy start position (the state shown in FIG. 15) after completion of copying, the cam D pushes the roller follower 54, and the document position detecting means f operates. Along with that, the non-return member 55 again projects when the power of the solenoid 52 is turned off. The overlay is attached and detached in this state.

Although the solenoid 52 is used as the electric means, any means such as a motor or an electromagnetic clutch may be selected as long as the check member 55 can be moved.

Of course, the drive means for the non-return member in the embodiment may be a hydraulic cylinder such as hydraulic pressure or pneumatic pressure.

[0051]

According to the first aspect of the present invention, an image forming is provided with a movable document table, an overlay which can be attached to and detached from the document table, and a fixing device which fixes the document table in a fixed position when the overlay is attached and detached. Since it is a device, the overlay can be attached to and detached from the platen with one hand, improving operability.

A second invention of the present invention has a restricting member for restricting the movement of the original platen, the restricting member being held on the main body of the apparatus, and a fixing device for fixing the original table to a fixed position on the restricting member. Since the image forming apparatus according to the first aspect of the present invention is characterized in that the apparatus main body is easily manufactured as an apparatus for facilitating attachment / detachment of the overlay to / from the document table. it can.

According to a third aspect of the present invention, in the second aspect of the present invention, the regulating member of the original pressure plate is a cam, and the check member with which the cam follower attached to the pressure plate is engaged is provided in the cam portion. The structure is simple because it can be attached to the cam portion only by connecting the pins, and when the original platen is in the original position, it is not necessary to perform any operation, and a member for controlling the check member is not required.

According to the fourth aspect of the present invention, since the apparatus main body is provided with the non-return member which goes in and out toward the document table, it has flexibility to be applied to the image forming apparatus which does not have the regulation member for regulating the movement of the document pressure plate. is there.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a rear view of FIG.

FIG. 3 is a horizontal sectional view showing the structure of a pressure plate.

FIG. 4 is a horizontal sectional view showing the operation of FIG.

FIG. 5 is a plan view showing a configuration of a document table.

6 is a cross-sectional view taken along the line AA of FIG.

FIG. 7 is a plan view showing the operation of FIG.

FIG. 8 is a partially enlarged view of FIG. 5 showing the overlay attaching / detaching device.

9 is an enlarged view of a part of FIG. 7, showing the overlay attaching / detaching device.

FIG. 10 is a front view showing the operation of FIG. 1 of the document table reverse locking device using mechanical means.

FIG. 11 is a vertical cross-sectional view showing the configuration of a document table reverse-turning device using electrical means.

12 is a vertical cross-sectional view showing the operation of FIG.

FIG. 13 is a vertical cross-sectional view showing the configuration of a document table reverse-turning device using electrical means and the document table.

FIG. 14 is a vertical cross-sectional view showing the operation of FIG.

FIG. 15 is a vertical sectional view showing another embodiment.

16 is a vertical sectional view showing the operation of FIG.

[Explanation of symbols]

 6 Document Plate 16 Pressure Plate 17 Cam Follower 24 Cam Part 38 Check Member 43 Overlay 49 Check Member

Claims (4)

[Claims] 1. An image forming apparatus comprising: a movable document table, an overlay that can be attached to and detached from the document table, and a fixing device that fixes the document table in a fixed position when the overlay is attached and detached. 2. A regulating member for regulating the movement of a document pressure plate, wherein the regulating member is held on the apparatus main body side, and a fixing device for fixing the document table at a fixed position is provided on the regulating member. The image forming apparatus according to claim 1. 3. The restricting member is a cam portion fixed to the main body of the apparatus, a cam follower provided on the original pressure plate is engaged with the cam portion, and a fixing device for fixing the original table at a fixed position is rotatable by a pin on the cam portion. 3. The image forming apparatus according to claim 2, wherein the non-return member is attached to the non-return member, and the non-return member engages with the cam follower and the non-return member in a state where the document table is in the original position. 4. The platen fixing device is provided in the main body of the apparatus and moves in and out of the platen in a direction intersecting with the direction of movement of the platen and restrains movement to one side of the platen when engaged with the platen. The image forming apparatus according to claim 1, further comprising a check member and a driving unit for driving the check member.