JPS60135981A - Electrophotographic copying device - Google Patents

Abstract

PURPOSE:To prevent failure of insertion by providing a device body with a photosensitive body positioning member turnably so that it is placed in the front side of a drum unit and setting an endless sheet-shaped photosensitive body to a prescribed insertion position in accordance with the turning operation of this member. CONSTITUTION:When a tension release lever 31 is rotated in case that an endless photosensitive body 4 is removed from between drums 16 and 17, a connecting plate 58 is rotated around a shaft 54, and a tension plate 52 is moved in accordance with movement of a guide pin 59, and the inter-shaft length is shortened to release the tension of the photosensitive body 4. In this state, the tension release lever 31 is turned counterclockwise after insertion of the photosensitive body 4 to bring closely the photosensitive body 4 into contact with each drum. Next, when an upper frame unit 21 is depressed and is joined with a lower frame unit 23 in the state where application of tension to the photosensitive body 4 is foregotton, the tip part of a projecting member 60 of the lower frame unit 23 is brought into contact with the right end of the tension release lever 31, and the small-diameter drum 17 is moved from a position C to a position D, and thus, tension acts automatically.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an improvement in an electrophotographic copying apparatus using an endless sheet-like photoreceptor, and more specifically relates to the improvement of an electrophotographic copying apparatus using an endless sheet-like photoreceptor. The present invention relates to an electrophotographic copying apparatus that has been improved in the insertion positioning of a sheet-like photoreceptor into a drum unit that is movably supported along a drum unit.

<Technical background of the invention and its problems> An electrophotographic copying apparatus using a conventional endless sheet-like photoreceptor is disclosed in, for example, Japanese Patent Laid-Open No. 55-93184. In such a conventional electrophotographic copying device using an endless sheet-like photoreceptor, copying quality deteriorates due to deterioration of the characteristics and life of the sheet-like photoreceptor used, so a certain number of copies are made. The sheet-like photoreceptor is replaced every time, but the operator only has to check whether the new photoreceptor has been inserted into the correct position. If the sheet-like photoreceptor is replaced without inserting the photoreceptor all the way to its normal position, it may not be possible to make copies due to the shift in the insertion position of the sheet-like photoreceptor. Furthermore, in the case where the sheet-like photoreceptor is provided with holes for process control, there have been problems such as signal irregularities for process control.

<Object of the Invention> The present invention has been made with the object of providing an electrophotographic copying apparatus equipped with a novel sheet-like photoreceptor insertion and positioning mechanism that eliminates the problems of the conventional art. In order to achieve the object, a drum unit for movably supporting the light body of the present invention along a predetermined path, and a photoconductor positioning member rotatably provided on the main body of the apparatus so as to be located in front of the drum unit are provided. The endless sheet-like photoreceptor inserted into the drum unit is set at a predetermined insertion position by the photoreceptor positioning member in accordance with the rotational movement of the photoreceptor positioning member.

<Embodiment of the Invention> Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view showing the entire internal structure of a specific example of an electrophotographic copying apparatus in which the present invention is implemented.

In FIG. 1, reference numeral 2 indicates a document table which is movably provided on the main body of the copying machine and holds the document; 2 is an illumination device which illuminates the document on the document table 1; This is an optical means including a SELFOC lens, etc., which projects the image onto the photoreceptor 4. The photoreceptor 4 is formed into an endless sheet as described later, and the optical means 3
Prior to the image projection (exposure) process, the corona discharger 5 installed opposite the photoreceptor 4 uniformly charges the photoreceptor 4 to a specific polarity, and by exposing the image to the photoreceptor 4, An electrostatic latent image corresponding to the original to be copied is formed on the photoreceptor 4. This latent image is then transferred to a developing/cleaning device 6.
The film is developed and toner is applied. Note that the image is developed in a developing/cleaning device 6 and toner is attached thereto. Note that a cartridge 7 for replenishing toner is attached to the developing/cleaning device 6.

Further, a cassette 8 containing a large number of sheets of paper is removably installed in the main body of the copying apparatus, and a paper feed roller 9 is provided facing the sheets of the cassette. The paper feed roller 9 is driven in response to a paper feed signal from a control means (tQ+not shown) for controlling copying of the copying apparatus, and the paper in the cassette 8 is fed one by one. This feed paper is sent to a conveyance roller 10 and a conveyance timing control plate 11, and the conveyance timing control plate 11 rotates the photoconductor 4 so that the leading edge of the image on the photoconductor 4 and the leading edge of the paper coincide in the transfer process. The conveyed paper is conveyed to the transfer process in synchronization with the position. A corona discharger 12 emits a corona from the back side of the paper at the position where the paper is fed (transfer position), coinciding with the leading edge of the image formation on the photoconductor 4.
Through this transfer process, the toner image formed on the photoconductor 4 is transferred to the paper 2, and the paper supporting the toner image is peeled off from the photoconductor 4 and transferred from the photoconductor 4. After the toner image is fixed by passing through a fixing roller 13 arranged in the direction away from the paper, the paper is discharged from the apparatus.

On the other hand, a static eliminator 14 and a static eliminator 15 are provided behind the transfer process position to face the photoreceptor 4.
In the second rotation after the transfer process, after the static electricity has been removed, the toner remains on the surface of the developing and cleaning device 6 which is cleaned and prepared for the next image formation.

This photoreceptor 4 is different from one that is formed or supported by a normal cylindrical drum, and is located between a large diameter drive roller (large diameter drum) 16 and a small diameter roller (small diameter drum) +7 that constitute a drum unit. An endless sheet-like photoreceptor is held under tension. The drive roller 16 is identified at a fixed position with respect to the main body of the copying apparatus, and is rotated by the rotational force of the drive means (main morph 18) being transmitted thereto. Further, the roller 17 provided opposite to the drive roller I6 is normally held at the position shown in the figure (rotatable), but is moved in the direction of the arrow when the photoreceptor 4 is replaced, as will be described later. It is.

Therefore, if the roller 17 is moved in the direction of the arrow, the roller 1
The tension state of the photoreceptor 4 held between 6 and 17 is released, and the photoreceptor 4 can be replaced easily.

In particular, the photoreceptor 4 is formed into an endless shape by fixing the front and rear ends of the sheet-like photoreceptor with fixtures 19, as shown in FIG. Such a photoreceptor is deformable to some extent, and since the photoreceptor 4 has an endless shape, it is very easy to take out the photoreceptor 4 or insert it between the rollers 16 and 17. If the roller I7 is returned to its normal position after insertion, appropriate tension will be applied to the photoreceptor 4 itself.
For example, it goes without saying that the photoreceptor 4 may be lifted up from the drive roller 16.

FIG. 3 is an external perspective view showing the open state of the copying apparatus embodying the present invention, which is structured to be able to be divided into a first main body and a second main body, and is configured to be openable and closable.

In FIG. 3, the upper frame unit 2+ constituting the first body is rotatably supported by the lower frame unit 1 which rotates around a shaft 22 and regenerates the second body. by a spring (not shown) or the like in the open position shown.
It is held in its open position.

On the first main body side, there is a document table 1, an illumination device 2, and an optical means 3.
, a corona discharger 5, a developing/cleaning device 6, a cartridge 7, a static eliminator lamp I4, a static eliminator 5, and a photoreceptor 4 are installed. Paper roller 9, conveyance roller 10, conveyance timing control board 11, corona discharger 12
, a fixing roller 3, and a paper discharge tray 25 are provided, and the length is 494 m so that the first body and the second body can be opened along the paper conveyance path.

26 is a protective cover for the drum unit 24, and this drum unit protective cover 26 is attached to the upper frame unit 21.
It is rotatably supported by a protrusion provided at the lower part of the opening 28. Reference numeral 27 denotes a front cabinet opening/closing lid of the main body of the copying apparatus, and this opening/closing lid 27 is rotatably supported on the upper part of the lower frame unit book.

According to the embodiment of the present invention, when replacing the endless sheet-like photoreceptor 4 (master M), first open the front cabinet opening/closing lid 27 of the copying apparatus main body, and then remove the upper frame unit 21 and the lower frame. The unit 23 is opened up and down, and the tension release lever 3I is rotated in the direction of the arrow A about the shaft 32 as shown in FIG. 4, and moved from the position a to the position b.

This operation releases the tension state of the photoreceptor 4, as will be described later. Next, the drum unit protective cover 26
Grasp the lock release lever 33 provided at the top of the outside and pull it toward you to open the drum unit protective cover 26 for preventing the photoreceptor 4 (master M) from being exposed before it is exposed (at this time, the device is in the state shown in FIG. 3). Become.).

Further, the drum unit protective cover 26 is structured so that it cannot be opened unless the tension state of the photoreceptor 4 is released. That is, in a state where the tension acting on the photoreceptor 4 (master M) is not released, the tension release lever 31 is in the state a (see fourth step), and in this state, the tip of the tension release lever 31 is 31-a engages with a restraining member 34 provided on the back surface of the drum unit protective cover 26 as shown in FIG. The structure is such that

Therefore, when the drum unit protection cover 26 is opened, the tension state of the photoconductor 4 is released, and the old photoconductor 4 (master M) is pulled out from the opening 28 of the upper frame unit 21 and a new endless photoconductor is inserted. 4 (master M) to replace the photoreceptor 4.

Further, as an embodiment of the present invention, a photoreceptor positioning member 35 is provided at the lower part of the back surface of the drum unit protective cover 26 at a position facing the side edge of the photoreceptor 4 when the cover 26 is closed.

Therefore, if you close the drum unit protection cover 26 that was opened after replacing the old and new photoconductors 4, even if the new photoconductor 4 has not been moved to its normal position, the tram unit ('4 m The photoreceptor 4 is pushed in the insertion direction by the photoreceptor positioning member 35 provided on the back surface of the cover 26, and the photoreceptor 4 is inserted and set at a fixed position.That is, as shown in FIG. When the protective cover 26 is closed by rotating it in the direction indicated by the arrow around the shaft 36, the photoconductor positioning unit assembly provided so as to face the one end 4-a of the photoconductor 4 will open as a result of this closing operation. 35 moves in the direction of arrow C, for example, the photoreceptor 4
Even if the photoreceptor 4 is not inserted into the predetermined position, the photoreceptor 4 is pushed in the direction of the arrow C by the photoreceptor positioning member 35, and the photoreceptor 4 is inserted and positioned at the predetermined position H.

Note that if the tension release lever 31 is returned from the b position to the a position before closing the drum unit protection cover 26, the drum unit protection cover 26 cannot be closed. That is, if the tension release lever 31 is rotated counterclockwise and moved from position b to position a before closing the drum unit protection cover 26, and then the drum unit protection cover 26 is closed, the tension will be reduced as shown in FIG. The distal end portion 31-a of the release lever 31 is the stopper 34.
The drum unit protective cover 26 is configured so as not to be closed when it comes into contact with the photoconductor 4. With this configuration, when the photoconductor 4 is positioned by the photoconductor positioning member 35, a state in which tension is applied to the photoconductor 4 is prevented. In fg, photoreceptor 4
When the insertion position is shifted without being inserted and moved to the normal position,
This prevents the inconvenience of remaining in that location and causing defects on the copied image, and the tension release lever 31 is
In other words, the drum unit protective cover 26 can be closed only when the photoreceptor 4 is in the position where no tension is applied to the photoreceptor 4 and is movable in the insertion direction.

Further, as the photoreceptor positioning member 35 which functions as described above, it is suitable to use, for example, polyethylene terephthalate (P, E, T) having a thickness of about 0.2 mm.

With the tension release lever 31 at position b, the drum unit protective cover 26 is closed, and then the tension release lever 3I is rotated back from position b to position a to apply tension to the photoreceptor 4.

Next, the upper frame unit 21 is pushed down to integrate with the lower frame unit, and the front cabinet opening/closing lid 27 is closed to complete the replacement of the photoconductor 4. According to this example, the drum unit protective cover 26 If you forget to close the tension release lever 31 (even if you forget to keep an eye on the photoreceptor 4, the upper frame unit) 2]
By pressing down to combine with the lower frame unit 23, the drum unit protective cover 26 is automatically closed and the tension release lever 31 is rotated from position b (tension released state) to position a (tension applied state). It is configured to be restored.

The specific structure will be explained below.

As shown in FIG. 8, a suppressing member 41 is provided upright on the lower frame unit 23 in correspondence with the drum unit protective cover 26, and an inclined portion 41-a is formed at the upper end portion of this suppressing member 4I. There is.

When the drum unit protection cover 26 is now open (Fig. 8) and the upper frame unit 2 is pushed down in the direction of the arrow to close it, the drum unit protection cover 26 will be tilted as shown in Figs. 8 to 10. The pressing member 4 is attached to the portion 26-a.
While the inclined portion 41-a of No. 1 comes into contact first (Fig. 9),
The drum unit protection cover 26 is closed, and finally it is reliably pressed in the direction of arrow E by the vertical portion 41-b of the pressing member 41, and the drum unit protection cover 26 is closed (FIG. 10). At this time, the lock portion 83-a of the lock release lever 38 provided on the protective cover 26 fits into the lock hole 42 provided on the drum unit 24 as shown in FIG. 11 and is locked.

The lock release lever 33 is attached to the drum unit protective cover 26 so as to be rotatable about a shaft 43, and a force is applied in the direction of arrow F by a spring-like pressing material 33-b.

As shown in FIG. 11, the drum unit protection cover 26 is always held in the open state by the lock release lever 33, and will be locked unless the lock release lever 33 is pushed down and rotated counterclockwise. 4 portraits are made to prevent it from being lifted. Therefore, the drum unit protective cover 26 is opened by pushing down the lock release lever 33 to remove the lock hole 42 formed in the drum unit 24 and then pulling it toward the front.

Next, a configuration for applying and releasing tension to the photoreceptor 4 will be described with reference to FIGS. 12 and 13.

In this example, as a method for applying and releasing tension on the photoreceptor 4, a large diameter drum (large diameter drive roller) 16 and a small diameter drum (
This is done by changing the distance between the shafts of the small diameter roller) 17, and FIG. 12 is a perspective view showing an example of this.

The large diameter drum 16 is connected to the upper frame unit 2 as described later.
1 is held in place. On the other hand, small diameter roller 1
7, the other end (not shown) of the rotating shaft 51 is slidably supported through an elongated hole as will be described later. Further, the tip of a rotating shaft 51 shown in FIG. 12 is rotatably attached to a tension plate 52. The tension play 1/52 has a new L-shaped long hole 5 as shown in the figure.
3 is formed, and one end of a shaft 54 passes through this elongated hole 53. Also, the tension plate 52 has a pin 5.
5 is provided, and a spring 57 for applying tension by the small diameter drum 17 is attached between this pin 55 and a hook plate 56 attached to the side plate of the drum unit.

This spring ring 57 serves to bias the tension plate 52 in the direction of arrow G in the state shown in FIG. Z12, and to apply tension by the small diameter drum 17. A connecting plate 58 is fixed to the tip of the shaft 54 passing through the deformed elongated hole 53 of the tension plate 52, and the tension release lever 3
I is attached to the tip of the shaft 54 in the relationship shown in FIG. Additionally, a tension plate 52 is attached to the connecting plate 58.
A guide pin 59 passing through the L hand hole 53 is fixed.

The other end of the drum 17 is provided with the same structure as described above except for the tension release lever 31.

In the structure as described above, when removing the endless photosensitive book 4 from between the drums 16 and 17, rotating the tension release lever 3I in the direction of arrow H as shown in FIG. The connecting plate 58 rotates around the shaft 54. At this time, the tension plate 52 moves rightward in the drawing while the L hand hole 53 is guided by the shaft 54 due to the movement of the guide pin 59, and is held in the state shown in FIG. 14. Note that the amount of movement of the small diameter drum 17 at this time is the distance X between the shaft 54 and the guide pin 59. In this way, the inter-shaft side 11 between the shaft 54 and the guide pin 59
The tension plate 52 is attached to the guide pin 5 only by flI x.
9 and the deformed elongated hole 53 as guides, the distance between the axes of the large-diameter drum 16 and the small-diameter drum 17 is reduced, and the tension on the photoreceptor 4 is released.

In the state shown in FIG. 14 above, the endless photoconductor 4 inserted between the drums 16 and 17 can be easily removed, and a new endless photoconductor 4 is inserted between the drums 16 and 17. Body 4 is exchanged. After the insertion of the new photoreceptor 4 is completed, if the tension release lever 3■ is rotated counterclockwise in the opposite direction to the above, as the connecting plate 58 is rotated,
The tension plate 52 moves to the left while being guided by the shaft 54 and reaches the state shown in FIG. 13, and the drum 16.1
Appropriate tension is applied to the endless photoreceptor 4 inserted between the drums 7 and 7, and the photoreceptor 4 is brought into close contact with each drum.

Next, with the tension release lever 31 forgetting to apply tension to the photoreceptor 4, the upper frame unit 4 is pushed down to combine with the lower frame unit, and the tension release lever 31 is automatically rotated back. The configuration for doing this will be explained.

As shown in FIG. 15, the lower frame unit 23 is provided with a projection member 60 at a position facing the tension release lever 31. Therefore, before applying tension to the photoreceptor 4,
When the upper frame unit 21 is pushed down, the projection member 60 provided on the lower frame unit 23
As the upper frame unit 21 moves during the opening process, the tip of the protruding member 60 comes into contact with the right end of the tension release lever 31, and the tension release lever 31 rotates in the direction of arrow I as shown in Figure H+16, releasing the small diameter drum. 17, tension is automatically applied to the photoreceptor 4 in response to the closing operation of the lower frame unit 21.

Also, in this specific example, the deflection is -☆ii! in the direction of the rotation axis of the drum unit! The (rear side) is supported by the apparatus main body as a fixed end, and the other end (front side) is configured to become a free end or a fixed end depending on whether the drum unit protection cover 26 is opened or closed.

A specific example of how to support the drum unit will be explained below.

As shown in FIG. 17, the drum unit 24 has a drum support body consisting of a drum unit support frame 61, a drum unit front cover 62, and a top plate 63 connected between them, on which a large diameter drum I6 and a small diameter drum 17 can rotate. On the rear side of the drum unit 24, as shown in FIG. It is inserted through the hole 64.
It is rotatably attached to the side tension plate 65 and slides using the elongated hole 64 as a guide.

It is composed of The rear tension plate 65 has an L
A deformed elongated hole 66 is formed in the shape of a letter, and the shaft 54 that has passed through the drum unit support frame 61 is inserted into this elongated hole 66.
The other end is inserted. A splinter (not shown) is installed between the rear tension plate 65 and the drum unit support frame 61 of the drum unit 24 to apply tension from the small diameter drum 17. Further, one end of a connecting plate 67 is fixed to the tip of the shaft 54 passing through the deformed elongated hole 66 of the rear tension plate 65, and the other end of the rear tension plate 61 is fixed to the other end of the connecting plate 67. A guide pin 68 passing through the L hand hole 66 is fixed.

One end of the shaft 69 for supporting the large diameter drum 16 is supported by a bearing 70 provided on the drum unit support frame 61, and the other end of the shaft 69 is rotated by the drum unit front cover 62 as shown in FIG. It is pivoted on functionality.

Each member related to the rear tension plate 65 is located outside the drum unit support frame 61, and an opening 72 is formed in the rear frame 71 of the upper frame unit 21 to correspond to this protrusion. .

Bearing 7 that supports the shaft 69 for supporting the large diameter drum 16
0 is fixed to the drum unit support frame 61 as described above, and this bearing 70 is further fixed to the rear frame 71 of the upper frame unit 2+ as shown in FIG. It has become a supported voltage test. In this state, the drum unit support frame 61 may be cantilever-supported by the rear frame 71 via the shaft 69, or the drum unit support frame 61 may be supported by the shaft 69 alone. B. It is fixed by screws 3 at several places, and the entire rear side of the drum unit is cantilevered by the rear frame 71 of the two-frame unit layer.

On the other hand, the drum unit protective cover 26 attached to the upper frame unit 21 has a large-diameter drum 1
Bearings 74 and 75 are provided corresponding to the supporting shafts 69 and 54 of the large-diameter drum 16, respectively, and when the drum unit protection cover 26 is closed, the supporting shafts 69 and 54 of the large-diameter drum 16 are They are fitted into bearings 74 and 75 provided on the drum unit protective cover 26, respectively.

Therefore, during a copying operation, that is, when the drum unit protective cover 26 is closed, the drum unit is reliably supported by the upper frame unit 21 at both ends. In addition, when the drum unit protection cover 26 is open, the rear side of the drum unit 24 is cantilever-supported by the upper frame unit 21, and the front side becomes the free end of the photoreceptor 4.
This makes it possible to exchange items smoothly.

Note that the bearing portions 74, 75 and the shafts 69, 54 are tapered as shown in FIG. 19 so that they can be easily fitted together.

According to the embodiment described above, the means for setting the endless photoreceptor inserted into the drum unit at a predetermined insertion position is a pre-exposure means for the photoreceptor, which is provided in the main body of the apparatus so as to be openable and closable so as to be located in front of the drum unit. Although the present invention is not limited to this, it may be configured by a photoreceptor positioning member provided on the drum unit protection cover for preventing rotation.

The structure is such that the photoconductor is placed in a predetermined insertion position by opening/closing or moving back and forth to rotate the support assembly of the photoconductor positioning unit attached to the main body of the device to a desired position, opening/closing or moving back and forth. Needless to say, that's a good thing.

<Effects of the Invention> As described above, the electrophotographic copying apparatus of the present invention uses an endless sheet-like photoreceptor, and uses a drum unit to move this sheet-like photoreceptor along a predetermined path. In an electrophotographic copying apparatus configured to support a drum unit, a photoreceptor positioning member is provided on the body of the apparatus so as to be positioned on the njJ side of the drum unit, and the photoreceptor positioning member is rotated in response to the rotational movement of the photoreceptor positioning member. The endless sheet-like photoreceptor pushed into the drum unit is set at a predetermined push-in position by the photoreceptor position θ reducing member. It can be set by pushing it into the specified position, which eliminates problems that occur when replacing the photoconductor, such as poor end copying and process control signal generation caused by incorrectly inserting the photoconductor into the specified position. It can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the internal structure of an embodiment of an electrophotographic copying apparatus embodying the present invention, FIG. 2 is a W1 side view showing a specific example of an endless photoreceptor, and FIG. FIG. 4 is a perspective view of an embodiment of the electrophotographic copying apparatus in an open state;
FIG. 5 is a diagram showing the I-I disconnection r@ in FIG. 4, FIG. 6 is a diagram showing the positioning operation of the photoreceptor by the drum unit protective cover, and FIG. 7 is a diagram showing the closing prohibition mechanism of the drum unit protective cover. , Figures 8 to 10 are diagrams showing the locking mechanism of the drum unit protective cover of the Niframe unit,
FIG. 12 is a perspective view showing a specific example of the attachment mechanism for the endless photoreceptor, and FIGS. 13 and 14 are side views for explaining the movement of the side release lever, respectively, to explain the operation of the photoreceptor attachment mechanism. , FIG. 17 is a perspective view showing an example of a photosensitive drum unit, FIG. 18 is a side view showing a mounting machine 1 of the drum unit, and FIG. 19 is an example of a tapered shaft and bearing part. This is a side view. 4...Photoconductor, I6...Large diameter drum, 17...Small diameter drum, shadow''...Upper frame unit, 23 ・Lower frame Unino l-124-・Drum unit, 26.
・Drum unit protective cover, 31... Tension release lever, 33... Lock release lever, 34... Stopping member,
35... Photoreceptor positioning member, 41... Suppressing member, 6o
・Protrusion member, 69, 74.75...Bearing part. Agent Patent attorney Aihiko Fukushi (2 others) $7 Figure 1/4 2/6 1! 39 Figure 10 Figure 11

Claims (1)

[Claims] (1) An electrophotographic copying apparatus using an endless sheet-like photoreceptor, comprising: a drum unit/nod that supports the endless sheet-like photoreceptor so as to be movable along a predetermined path; and the drum unit. a photoreceptor positioning member rotatably provided on the apparatus main body so as to be located in front of the apparatus body, and the endless endless member is inserted into the drum unit by the photoreceptor positioning member in accordance with the rotational movement of the photoreceptor positioning member. 1. An electrophotographic copying apparatus characterized in that a sheet-like photoreceptor is set at a predetermined insertion position. 2. The photoconductor positioning member is provided on an opening/closing member that is freely openable and closable in the main body of the apparatus so as to be located in front of the drum unit, and the photoconductor positioning member is adjusted in accordance with the closing operation of the opening/closing member. 2. The electrophotographic copying apparatus according to claim 1, wherein said endless sheet-like photoreceptor inserted into said drum unit is set at a predetermined insertion position. 3. The electrophotographic copying apparatus according to claim 2, wherein the opening/closing member is constituted by a drum unit protective cover for preventing pre-exposure of the photoreceptor.