Photosensitive member cartridge

ES 2 178 982 T3

DESCRIPTION

Photosensitive member cartridge.

Field and background of the invention

The present invention relates to a photosensitive member cartridge and a process cartridge for use in an electrostatographic imaging apparatus.

For example, Japanese Patent Publications 8-54786 and 9-319285, corresponding to US Patents 5,845,176 and 5,805,959, respectively, show some electrostatographic imaging apparatus in which a visible image is obtained by supplying toner to the electrostatic latent image formed on a photosensitive drum.

The first publication shows such structures, in which a photosensitive member cartridge includes a photosensitive drum and a developer cartridge includes a developer roller, located separately in a housing.

The second publication shows such structures, in which a photosensitive member cartridge and a developer cartridge are movably connected to one part by a pin, whereby the photosensitive member and the developer roller are pushed together.

Normally, the surface of the photosensitive drum is coated with a photosensitive material. To prevent the surface of the photosensitive drum from being scratched or contaminated, some measures have to be taken. When a part of the photosensitive surface is scratched or contaminated with, for example, dust, as could happen if the surface of the photosensitive drum is touched, the photosensitive characteristics of the photosensitive surface will be changed and the image quality will be affected significantly. unfavorable.

Consequently, in the apparatuses shown in the publications described above, a structure is employed in which the photosensitive drum is covered by a shutter.

However, it is necessary to construct the shutter to open when the photosensitive member cartridge is placed in a body (housing), and to close when the photosensitive member cartridge is separated from the body (housing). This makes the structure of the photosensitive member cartridge complicated. Furthermore, there may be a possibility that the user accidentally opens the shutter and touches the surface of the photosensitive member cartridge.

Also, when the photosensitive member cartridge is placed on a table, the shutter may be accidentally opened, thereby exposing the photosensitive drum.

From EP-A-0 530 491, an electrophotographic imaging apparatus is known comprising a detachable imaging cartridge provided with a photosensitive drum, a developing device and a charging roller. The charging roller pushes the photosensitive member to transfer the image to the sheet as it passes through the apparatus. Both the photosensitive member and the transfer roller are substantially covered with a box.

Furthermore, from EP-A-0 437 097 an imaging apparatus is known which includes a cartridge comprising a photosensitive member and a corotron-shaped transfer medium. The cartridge constitutes a box that pivots on an articulated mechanism.

Brief description of the invention

One of the objects of the present invention is to provide a photosensitive member cartridge that eliminates the danger of the photosensitive member being fouled or contaminated. This is achieved by the features of claim 1. Further advantageous improvements are the subject of the dependent claims.

The photosensitive member cartridge of the invention includes a case, and a photosensitive member and a transfer roller rotatably arranged in the case. The box covers the photosensitive member and the transfer roller. Especially, a lower wall of the case covers a lower part of the transfer roller, and upper and rear walls cover the photosensitive member.

The bottom wall extends below the transfer roller. In the extensible part of the bottom wall, there is located a developer cartridge that includes a developer roller. Such structures prevent the photosensitive member and transfer roller from being accidentally touched, which improves image quality.

Furthermore, it is also not necessary to provide complicated components such as a shutter, thereby simplifying the structures of the photosensitive member.

Also, support bases that are located on the underside of the bottom wall stabilize the photosensitive member cartridge when it is placed on a table.

Brief description of the drawings

A preferred embodiment of the invention is described below with reference to the following figures in which:

- Figure 1 is a schematic side sectional view of a printer that includes the imaging apparatus of the invention.

- Figure 2 is a side view of the printer, where a situation is illustrated in which the insertion of a processing unit in a casing of a body begins.

- Figure 3 is a plan view of a photosensitive member cartridge.

- Figure 4 is a side sectional view of the photosensitive member cartridge taken along plane IV-IV in Figure 3.

- Figure 5 is a right side view of the photosensitive member cartridge.

- Figure 6 is a left side view of the photosensitive member cartridge.

- Figure 7 is a front view of the photosensitive member cartridge.

- Figure 8 is a sectional view illustrating a pushing part of a transfer roller.

ES 2

- Figure 9 is a sectional view taken along plane IX-IX in figure 8.

- Figure 10 is a perspective view of a pushing device and a part that receives the action.

- Figure 11 (a) is a plan view of a locking device.

- Figure 11 (b) is a sectional view taken along the line Xlb-XIb in Figure 11 (a).

- Figure 12 (a) is a left side view of a developer cartridge.

- Figure 12 (b) is a right side view of a developer cartridge.

- Figure 13 is a plan view of the developer cartridge.

- Figure 14 is a view of the developer cartridge taken as indicated by arrows XIV in figure 13.

- Figure 15 is a sectional view of the developer cartridge, illustrating the structure of the shaft bearings arranged on the right and left sides of the developer cartridge.

- Figure 16 is a plan view of a processing unit.

- Figure 17 is a right side view of the processing unit.

- Figure 18 is a left side view of the processing unit.

- Figure 19 is a view of the processing unit taken as indicated by arrows XIX in Figure 17.

- Figure 20 (a) illustrates a situation in which the processing unit is being introduced into the body casing.

- Figure 20 (b), illustrates a situation in which the process unit is being inserted more.

- Figure 21 illustrates a situation in which the processing unit has been placed in the body casing.

- Figure 22 is an illustration of a printer drive system.

- Figure 23 is a plan view of the processing unit showing the upper registration roller 12a provided to expose its surface to the lower opening 300a of the box.

- Figure 24 is an enlarged view of the circular part B of figure 23.

- Figures 25A to 25F are views showing the registration roller 12a and the bearings 700, 710.

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Figures 26A to 26D are views showing the bearings 700, 710 and the support part 300b of the box 30.

Figures 27A to 27F are views showing the bearing 700.

Figures 28A to 28E are views showing the bearing 710.

- Figure 29 is a view showing the bearing 700 with a chamfered part 700f and a side wall 300c with a hollow space

300e.

- Figure 30 is a view showing the registration roller 12a and the bearings 700, 710.

- Figure 31 is a view showing the registration rollers 12a, 12b, the bearing 700 and a spring 45.

- Figure 32 and the last one, is an illustration of a force that pushes a developer roller against a photosensitive drum and of other forces involved.

Description of the preferred embodiments

Hereafter, a preferred embodiment in which the invention includes a laser beam type printer is described in detail with reference to the drawings. Figure 1 is a schematic side sectional view of a printer including the imaging apparatus. Figure 2 is a partially cutaway side view of the printer, illustrating a situation in which insertion of a processing unit 2 into a housing 1 of the body begins.

Referring to Fig. 1, the processing unit 2 having a photosensitive member cartridge 3 and a developer cartridge 4 was detachably disposed in a substantially central part of the housing 1 of the printer body. As shown in the left part of figure 1, a clamp 5 is arranged next to the processing unit 2. A sheet feeder 6 was located below the processing unit 2. A sheet drawer 6 can be attached to the bottom of the body shell 1 by moving the sheet drawer 6 from a front surface of the body shell 1 (as indicated by arrow A).

A laser scanner 7 was mounted on the lower surface of a sheet discharge tray 1a made of synthetic resin, through a frame. The sheet discharge tray 1a also serves as a cover.

When printing data is transmitted to the printer from an external device, for example a personal computer, with printing instructions, a sheet P (recording medium) is separated from a pile of sheets P placed on a support plate 9 of the sheet drawer 8 by a separator pad 11, so that one sheet is separated at a time as a sheet feed roller 10 rotates. The separated sheet P is transferred to a contact part that is between a photosensitive drum 13 (photosensitive element) located in the unit.

ES 2 178 982 T3 process 2 and a transfer roller 14 (transfer device) which bears against the lower surface of the photosensitive drum 13, via a pair of registration rollers 12a, 12b.

A laser beam is emitted from the laser scanner 7 having a laser light emitting part, a polygonal mirror 18, a lens 19, a plurality of reflecting mirrors 20 and the like, through a light emitting hole that is formed. at the bottom of the armazoan that holds the laser scanner 7. The laser beam travels to the upper peripheral surface of the photosensitive drum 13, via a light input portion 31 which is formed in a case 30 of the photosensitive member cartridge 3, that is, a case of the processing unit 2. The peripheral surface of the photosensitive drum 13 is thus exposed in correspondence to the printing data, to thereby form an electrostatic latent image.

The developer (toner) that is supplied from a developer roller (22) of the developer cartridge 4 is deposited in the electrostatic latent image that is in the photosensitive drum 13, thus making the image visible. After the visible image formed by the developer (toner) is transferred from the photosensitive drum 13 to the sheet P, the sheet P is transferred between a thermal roller 15 and a press roller 16 to the fixer 5, where the sheet P undergoes a heat setting process. The sheet P is then discharged into the sheet discharge tray 1a via a sheet discharge chute 17.

In this embodiment, the process unit 2 includes the cartridge of a photosensitive element 3 that has at least the photosensitive drum 13, and the developer cartridge 4 that has at least the developer roller 22 (developer device) that is located in a box 21 . The developer cartridge 4 is designed so that it can be detachably attached to the photosensitive member cartridge 3, and also so that the developer roller 22 is prevented from being separated by a locking device 46 described later.

The structures of the photosensitive member cartridge 3 and the developer cartridge 4 are described in detail. As shown in Figures 3 to 7, the synthetic resin box 30 that is in the photosensitive member cartridge 3 is integrally formed by a bottom wall 30a, a pair of side walls 30c extending upward from the right sides and left of the lower wall 30a, an upper wall 30b that contacts the upper edges of the pair of side walls 30c, and a rear wall 30e that is connected to one side of the upper wall 30b, at one end of each of the right and left side walls 30c, and at one side of the bottom wall 30a. The photosensitive drum 13 is secured in the box 30 near one side thereof, that is, in an area that is surrounded by the upper wall 30b, the rear wall 30e, the right and left side walls 30c, and the lower wall. 30a. The photosensitive drum 13 is rotatably articulated on the right and left side walls 30c. The right and left side walls 30c and the bottom wall 30a extend towards the front of the photosensitive drum 13.

As shown in figure 4, the lower part of the transfer roller 14 which is arranged below the photosensitive drum 13 is covered by the bottom wall 30a of the case 30. The transfer roller 14 is hinged so that it can be moved vertically. , whereby it can be separated from the lower surface of the photosensitive drum 13 due to the weight of the transfer roller 14. When the process unit 2 is secured in the body casing 1, the transfer roller 14 is brought into contact with the lower surface of the photosensitive drum 13. More specifically, upwardly open U-shaped bearings 35, secured at both ends of the shaft 14a of the transfer roller 14, are raised by shaft bearing lifters 34 (see Figures 8 and 9) which are pushed upwards by means of springs 33 which are arranged on the right and left internal side surfaces of the body casing 1, whereby the transfer roller 14 is moved upward to push the lower surface (transfer region) of the photosensitive drum 13. On the other hand, when the process unit 2 is removed from the body casing 1, the transfer roller 14 it separates from the photosensitive drum 13 without receiving the action of the springs 33.

The upper wall 30b of the box 30 covers an upper part of the photosensitive drum 13. The light input part 31, which allows irradiation of an upper surface of the photosensitive drum 13 with laser light emitted from the laser scanner 7, is formed on the upper wall 30b, and elongates in the direction of the axis of the photosensitive drum 13. Near the light input portion 31 is a charger 36, such as a corotron or the like, which charges a photosensitive surface of the photosensitive drum 13. An electrostatic latent image is formed on the photosensitive drum surface 13 by scanning a laser light at the surface of the same photosensitive drum 13 that is evenly loaded with the magazine 36. After the electrostatic latent image is made visible (developed) by the deposition of a thin layer of toner that is supplied by the developer roller 22, the image is transferred to the sheet P which is moved between the photosensitive drum 13 and the transfer roller 14, which are squeezed together and come into contact with each other.

A part of the box 30, any but the top wall 30b, opens upward. The part is defined by the left and right side walls 30c, and by the bottom wall 30a which has a curved surface of substantially a quarter of a carcase. The part that opens upwards is a housing part 32 in which the developer cartridge 4 can be secured at an angle from above.

With the structures described, almost all surfaces of the photosensitive drum 13 are covered by the casing 30 formed integrally and rigidly, thereby increasing stability when an operator manipulates the photosensitive drum 13.

Since the bottom wall 30a of the box 30 extends outward from the photosensitive drum 13, the circumference of the photosensitive drum is not touched.

ES 2 178 982 T3 ble 13, even though the operator holds the extended part of the bottom wall 30a. Therefore, when the operator holds the photosensitive member cartridge 3 by hand, the photosensitive surface of the photosensitive drum 13 remains untouched, whereby the surface of the photosensitive drum 13 is not contaminated but instead always remains clean.

In particular, when the developer cartridge 4 is brought into contact with the photosensitive member cartridge 3, the bearings 23a, 23b contact and move through a first section of the guide grooves 37 in a direction that includes a vertical component. . The bearings 23a, 23b are then contacted and moved through a second section of the guide grooves 37 in a direction that is substantially horizontal. The difference in the direction of movement of the bearings 23a, 23b is due to the arcuate shape of the guide grooves 37. Furthermore, due to this arcuate shape, the bearings 23a, 23b move faster through the first section of the grooves. guide and then through the second section.

A pusher device 42 which pushes the developer roller 22 against the photosensitive drum 13 via the developer cartridge 4 is pivotally and extensibly mounted on the inner surface of each of the right and left side walls 30c. As shown in Figures 4 and 10, each thrust device 42 has a pivoting articulation element 39 provided with pivots 39a 39b projecting entirely from the left and right sides thereof, a frame-type sliding support element 40 which extends connected with and supports the pivotal articulation element 39 that facilitates sliding movements and a thrust spring device 41, such as a helical spring or the like, which is arranged on the arm of the sliding support element 40 to push the pivotal articulation element 39 towards one end. The sliding bearing member 40 has a laterally extending cylindrical movement actuator portion 43. The motion actuator part 43 of each pusher device 42 is arranged so that the part 43 projects outwardly from a guide hole 44 formed in one of the corresponding left and right side walls 30c.

The locking device 46 that prevents the developer cartridge 4, secured in the housing part 32, from moving upward out of the housing part 32, is arranged on the inner side of one of the left and right walls 30c (the right side wall in the embodiment) of the photosensitive member cartridge 3. As shown in Figures 4, 5, 11 (a) and 11 (b), the locking device 46 is designed so that a rotary shaft 48 extending through the side wall 30c axially supports a locking lever. 47 so that it can pivot in correspondence to a lateral surface of the same locking lever 47.

A resin spring 49 extending downwardly from a lower end of the locking lever 47 is arranged so that a lower part of the resin spring 49 contacts a restriction piece 30d projecting upwardly from the wall. bottom 30a of box 30. A lower surface of the locking lever 47 has an arcuate contact portion 47 that limits upward movement of one of the action receiving portions 61 (the one on the right) protruding outward from the right and left side surfaces of the lock. the case 21 of the developer cartridge 4, contacting an upper surface of the part receiving the action 61. In side view, the parts receiving action 61 are generally in the shape of an inverted triangle.

The parts receiving the action 61 are arranged to communicate with the locking device 46 and, furthermore, with the pushers 42 that push the developer roller 22 against the photosensitive drum 13.

The rollers 50 are arranged, as receiving members, in a plurality of positions (two positions in the embodiment, namely, right and left) in the bottom wall 30a of the case 30, in the housing part 32 of the photosensitive member cartridge. 3 (see figures 3 and 4). The rollers 50 project from the inner surface of the bottom wall 30a. When the developer cartridge 4 is inserted into the housing part 32, the rollers 50 (receiving device) receive a part of the weight of the developer cartridge 4, in a part running side-to-side of the axis 22a of the developer roller 22 from the drum photosensitive 13, that is, one side of the axis 22a of the developer roller 22 opposite the photosensitive drum 13. Specifically, rollers 50 are brought into contact with the lower portions of a downwardly curved convex surface of a toner-containing compartment 24 (see Figures 1, 12 (a), and 12 (b)) formed in the case 21 of the developer cartridge 4, and rollers 50 reduce the noise that box 21 makes during setting or separating operation.

The upper roller 12a of the pair of registration rollers is mounted on the lower wall 30a of the case 30 of the photosensitive member cartridge 3 so as to prevent the upper roller 12a from detaching. The lower wall 30a has an introduction opening 51a extending laterally adjacent to the upper roller 12a, to introduce the sheet P, coming from the pair of registration rollers 12a, 12b, into a transfer portion 52 that lies between the photosensitive drum. 13 and transfer roller 14. The upper surface of a part of the lower wall 30a extending between the insertion opening 51 and the transfer part 52 has flanges 53 which extend from the insertion opening 51a to the transfer part 52. The flanges 53 are designed so that the sheet P moves smoothly with reduced contact resistance on the lower surface of the sheet P.

A discharge opening 51b is formed between the bottom wall 30a and the rear wall 30e of the box 30, to transfer the sheet P between a heat roller 15 and a press roller 16, through the transfer part 52 (see figure 4 ).

The structure of the developer cartridge 4 is described with reference to Figures 1, 12a, 12b and 13 to 15. After a driven stirrer rotates5

ES 2 178 982 T3 tionally 27 agitates and discharges the toner that is in the downward convex compartment 24 that contains toner and that in turn is in the box21, the toner is brought to the outer peripheral surface of the developer roller 22 via a feed roller 25. A paddle 26 is provided to prevent the toner layer on the developer roller 22 from thickening (see Figure 1). The parts that receive the action 61 and that are normally in the shape of an inverted triangle, protrude from the left and right lateral outer ends of the compartment 24 that contains the toner and which is in the box 21.

The shaft bearings 23a, 23b, which are rotatably secured at the right and left ends of the developer roller shaft 22a, will be formed of a material whose coefficient of friction is small, for example, acetal resin or the like. Each of the bearings 23a, 23b has a driver 62 which engages in an annular groove 63 whereby the bearing does not separate from the end of the shaft. Each of the shaft bearings 23a, 23b has, at its base end, an umbrella-shaped shaft diameter adjusting portion 64 whose diameter gradually increases.

A spring device 65 pushes at least one of the shaft bearings 23a, 23b (the right bearing 23b in the embodiment) (see figure 15). Therefore, when the developer cartridge 4 is secured in a certain position in correspondence with the photosensitive member cartridge 3, the axis 22a of the developer roller 22 rests, noiselessly, on the guide grooves 37 formed in the right side walls. and left 30c of the photosensitive member cartridge 3.

As shown in Figures 16 and 19, the case 21 of the developer cartridge 4 has, in a part of the upper surface and in a part of the lower surface thereof, holding parts 70, 66, respectively, which facilitate the manipulation of the developer cartridge 4 by the operator.

Furthermore, as shown in Figures 17 and 18, the case 30 of the photosensitive member cartridge 3 has support bases 69a, 69b at the lower parts thereof, whereby the photosensitive member cartridge 3 can be positioned so that stable on table 67 either alone or in combination with developer cartridge 4. It is necessary to position the support bases 69a, 69b diagonally in at least two positions and, preferably, in four positions in each corner of the box 30, as in the embodiment. Additional support bases 69a, 69b can be provided if space is available in box 30.

As shown in Figures 5-7, 17 and 18, in the embodiment, when looking at the photosensitive member cartridge 3 from the side, the support bases 69a, 69b are provided, extending outwardly, at the lower portions of the box 30 near both ends of the front and rear sides thereof. The support bases 69a, 69b bring the table 67 into contact with the center of gravity of the photosensitive member cartridge 3 that is positioned between the support bases 69a, 69b, whereby the photosensitive element cartridge 3 is stabilized when it is positioned. on the table 67.

The box 30 is formed with an upwardly open housing portion 32 near one side thereof. The developer cartridge 4 can be detachably secured in the housing part 32 from above, when the photosensitive member cartridge 3 is placed on the flat surface of the table 67 in a stable posture via the support bases 69a, 69b. Therefore, the developer cartridge 4 can be easily replaced.

Preferably, the support bases 69a, 69b are provided on the front and rear sides of the box 30, to position the centers of gravity of both the developer cartridge 4 and the photosensitive member cartridge 3 between the support bases 69a, 69b. With such arrangements, the developer cartridge 4 can be secured in the photosensitive member cartridge 3, which is located on the table 67, without destabilizing actions being transmitted to the photosensitive member cartridge 3, such as rocking.

Furthermore, Figure 7 shows the support bases 69a, 69b provided at the left and right side ends of the lower surface of the box 30. The support bases 69a, 69b can be provided in the lowermost parts of the box 30 to protruding to the left and right sides.

Next, the operation of securing the developer cartridge 4 relative to the photosensitive member cartridge 3. To secure the developer cartridge 4 relative to the photosensitive member cartridge 3, an operator holds with one hand the holding parts 70, 66 that They are formed in a part of the upper surface and in a part of the lower surface of the case 21 of the developer cartridge 4. When the developer cartridge 4 is inserted, with the developer roller 22 side as the front side, into the housing part 32 of the box 30 (inserting operation), one of the parts receiving the action 61 of the developer cartridge 4 becomes in contact with the locking lever 47 and causes it to rotate to a position indicated by a dashed line and two dots in Figure 4, facing the force of the resin spring 49. When the developer cartridge 4 is inserted (the inserting operation is completed), the part receiving action 61 is lowered, and therefore contact between the part receiving action 61 and the locking lever 47 ceases. Therefore, the locking lever 47 returns to the position indicated by a solid line in FIG. 4, restoring the force of the resin spring 49, whereby the contact portion 47a of the locking lever 47 is oriented toward an upper surface of the part receiving action 61, establishing a blocking state. The process unit 2, which is part of the developer cartridge 4 and the photosensitive member cartridge 3, can be lifted with one hand by holding the holding parts 70. 66. That is, the operator can successively secure the process unit 2 in a determined part of the body casing 1 and simultaneously holding the clamping parts 70, 66 after securing the developing cartridge 4 with respect to the photosensitive member cartridge 3.

During insertion of the developer cartridge 4 into the housing part 32, the bearings 23a,

ES 2 178 982 T3

23b of the shaft that are arranged at the left and right side ends of the developer roller 22 slide down the guide grooves 37 formed in the upper edges of the left and right side walls 30c of the box, to approach the shaft 13a of the photosensitive drum 13. The housing 21 of the developer cartridge 4 can pivot about the bearings 23a, 23b of the shaft 22a of the developer roller 22 when the bearings 23a, 23b rest on the guide grooves 37. Therefore, when the bearings 23a, 23b are located in the guide grooves 37 in a position that is close to the axis 13a of the photosensitive drum 13 ("U" shaped parts of the guide grooves 37) one side of the compartment 24 containing toner from the housing 21 of the developer cartridge 4 is introduced into the housing portion 32 of the photosensitive member cartridge 3 by pivoting about the axis 22 of the developer roller 22. Thus, the developer cartridge 4 is fixedly secured in the housing part 32.

In this state, the rollers 50 provided on the inner surface of the housing part 32 are brought into contact, by sliding, with a part of the lower surface of the box 21 which is on the side of the compartment 24 containing toner, and the bearings 23a, 23b move through the guide grooves 37 to a position where the developer roller 22 is located substantially as close as possible to the photosensitive drum 13. When the locking lever 47 is pivoted clockwise to return from the position indicated by the broken line and colon to the position indicated by the solid line in Figure 4, the contact part 47a of the locking lever 47 is oriented towards the upper surface (projection 61a) of the action receiving part 61, thereby preventing the developer cartridge 4 from slipping out of the photosensitive member cartridge 3.

Figures 16 to 19 are a plan view, a right side view, a left side view, and a rear view (a leaf discharge opening side view) of the process unit 2 with the developer cartridge 4 secured. with respect to the photosensitive member cartridge 3. Since the parts receiving the actuator 61 push down the pushers 42 as the developer cartridge 4 is pushed down towards the process unit 2, each pusher 42 normally assumes an orientation such that it causes the part motion actuator 43 is lowered slightly, as shown in figures 2 and 4.

The processing unit 2 is designed so that it can be secured in and detached from the body casing 1 when a cover 1b, provided at the right end, in figure 1 (front surface), of the body casing 1, rotates down to form a large opening (see figure 2).

That is, as shown in Figures 2, 20 (a), 20 (b) and 21, a pair of guiding devices 55, made with resin or the like, are secured on the internal surfaces of the left and right side parts of the the body casing 1 (in the drawings only the right side guiding device 55 is shown). Each guiding device 55 has an upward sloping surface open upwardly extending inwardly from the right end of the body casing 1, and an upper side guide surface 55a extending inwardly descending from the top 55d of the surface. upward sloping, and a lower side guide surface 55b which is disposed below the upper side guide surface 55a and extends inwardly descending from the right end of the body casing 1, and terminates in a position close to the lower roller 12 (b). of the pair of registration rollers.

Figure 2 indicates a position in which the insertion of the processing unit 2 into the housing 1 of the body begins. The process unit 2 is inserted into the body casing 1 whereby the axis 13a of the photosensitive drum 13 approaches an upper inner end 55c of the upper side guide surface 55a. Subsequently, as shown in Fig. 20 (a), the motion actuator portion 43 of each pusher device 42 is brought into contact with the upward sloping surface of the upper side guide surface 55a, and each of the guiding members 56, protruding laterally from the lower parts of the right and left sides of the process unit 2 (photosensitive member cartridge 3), fits into the lower side guide surface 55b (only one of the guide members 56 is shown in the drawings), thereby preventing the process unit 2 from moving upward in correspondence with the body casing 1, and Only it is allowed to move a little further inward along the lower side guide surface 55b.

In this state, as the process unit is pushed inward, the corresponding upper side guide surface 55a pushes the movement actuator part 43 of each pusher device 42, whereby the sliding support member 40 of each device thrust 42 pivots upward about pivots 39a, 39b. Thus, the sliding bearing member 40 of each pushing device 42 stops the corresponding action receiving part 61 of the developer cartridge 4 in a direction such that the distal end of the sliding bearing element 40 pushes the action receiving portion 61 . When the movement actuating part 43 of each pusher 42 reaches the top 55d of the upper side guide surface 55a, the sliding bearing element 40 of each pusher 42 pivots to the most upward orientation. In this orientation, the distal end of the sliding bearing element 40 of each thrust device 42 is held by stopping the corresponding part that receives the actuator 61 (see figure 20 (b)).

As the processing unit 2 is pushed further inward, the shaft 13a of the photosensitive drum 13 is secured in a certain position at the inner end 55c of the upper side guide surface 55a. In this position, the operator releases the process unit 2, whereupon the developer cartridge 4 side of the process unit 2 is lowered and secured by the weight of the process unit 2 in such a state that the registration roller top 12a located on one side

ES 2 178 982 T3 of the lower surface of the case 30 of the photosensitive member cartridge 3 is placed on the lower registration roller 12b arranged in the body case 1, and is urged by a spring 45 shown in figure 2 and, at the same time, the guide members 56 rest in suitable positions on the guide devices 55 (see figure 21).

When the process unit 2 is secured as described above, the distal end of the sliding support member 40 of each pusher device 42 pushes the corresponding part receiving the action 61. Therefore, the pusher devices 41 and the parts receiving the action 61 push the developer roller 22 against the photosensitive drum 13 via the developer cartridge 4.

As shown in Figure 21, it is preferred that the contact part 72a between the photosensitive drum 13 and the developer roller 22, that is the parts compressed in the closest positions, (the contact part 72a lies in a straight interaxial line). 72 passing through the axis of the axis 13a of the photosensitive drum 13 and the axis of the axis 22a of the developer roller 22), stretches above or on a line of compressive action 71 of the action of one of the thrust devices 42 towards the corresponding part that receives the action 61 (that is, a straight line that passes through the pivot 39a (39b) and a point of compression in which the distal end of the sliding bearing element 40 is brought into contact with the part receiving the action 61), The straight interaxial line 72 coincides substantially with or extends substantially parallel to the line of compressive action 71.

As shown in Fig. 22, a transmission mechanism 74 that transmits force from a drive motor 73 is disposed on the inner surface of one side (the left side in the embodiment) of the body casing 1. The drive mechanism 74 causes the sheet feed roller 10 of the sheet feeder 6, the lower registration roller 12b, the developer roller 22, the photosensitive drum 13, the heat roller 15 and the transport rollers that are in rotation to rotate. the sheet discharge chute. The developer roller 22 and the photosensitive drum 13 rotate in opposite directions, as indicated in Figures 1 and 21, that is, the developer roller 22 rotates counterclockwise and the photosensitive drum 13 rotates counterclockwise. clockwise. Furthermore, the mechanism is designed so that the circumferential speed of the developer roller 22 is greater than that of the photosensitive drum 13.

Therefore, as shown in Fig. 32, during the imaging operation, the compressive force F1 of each thrust device 42 acting on the contact portion 72a is parallel to the compressive action line 71, and the force Compressive F1 is divided into a component F1V in the direction of the tangent of the circumferences of the developer roller 22 and the photosensitive drum 13 and into a component F1H in the direction of the interaxial straight line 72.

The circumferential speed difference between the developer roller 22 and the photosensitive drum 13 creates a frictional resistance force F2 upward in Figure 32 relative to the developer roller 22 and downward relative to the photosensitive drum 13, the friction resistance force F2 having a value equal to the product of the coefficient of friction and the component F1H of the compressive force in the direction of the interaxial straight line 72 of the photosensitive drum 13 and the developer roller 22. Therefore, the moment of The rotation produced by the friction resistance force F2 acting on the developer cartridge 4 acted around the axis 22a of the developer roller in a clockwise direction in FIG. 32.

If the compressive action line 71 extends above the developer roller axis 22a, a moment of rotation acted on the developer cartridge 4 about the developer roller axis 22a in the counterclockwise direction in Fig. 32, and reduces or counteracts the moment of rotation produced by the frictional resistance force F2. In such a case, the developer cartridge 4 tends to rise, which is unfavorable. In this invention, however, the position of the axis 22a of the developer roller is above or on the compressive action line 71, or the interaxial straight line 72 coincides substantially with, or extends substantially parallel to the compressive action line 71. Therefore, during imaging, the developer roller 22 is substantially prevented from rising, and a stable compressive action can be achieved.

Furthermore, the compressive structure is formed by the pusher devices 42 for compressing the developer roller 22 against the photosensitive drum 13, and the parts receiving the action 61 provided in the developer cartridge 4. The parts receiving the action 61 are arranged in one side of the developer roller 22, the side being away from the photosensitive drum 13. Therefore, the photosensitive drum 13, the developer roller 22 and the transmission mechanism are not impediments, and the compressive action line 71 and the interaxial straight line 72 can be established substantially parallel to each other and adjacent.

If the developer cartridge 4 is pivoted about the axis 22a of the developer roller 22 while the imaging operation is in progress, with the developer cartridge 4 positioned in correspondence with the photosensitive member cartridge 3, that is, If the mount is positioned so that during the imaging operation, the bearings 23a, 23b which are at both ends of the shaft 22a of the developer roller 22 are locked on the inner sides of the guide grooves 37 of the photosensitive member cartridge 3 and thus further inward movement is prevented, and the weight Wo of the developer cartridge 4 is supported sparsely in two positions in a side view, that is, the position of the bearing 23a (23 (b) of the shaft, and a position on one side of the axis 22a of the developer roller away from the photosensitive drum 13, for example , a position in which the bottom of the toner-containing compartment 24 is in contact with the rollers 50, or the like, whereby the divided loads W1, W2 of the weight Wo are supported in two positions (see figure 32), then, the direction of the moment of rotation around the axis (the axis 22a of the rodi8

ES 2 178 982 T3 (developer roller) of the developer roller 22 produced by the frictional resistance force F2 received by the developer roller 22 from the photosensitive drum 13 becomes the same as the direction of the rotation moment about the axis (the axis 22a of the developer roller) of the developer roller 22 produced by the weight (load Wo at the center of gravity G) of the developer cartridge 4, that is, clockwise in Fig. 32. Therefore, during the imaging operation, the aforementioned frictional resistance force F2 did not act as a moment in a direction such as to lift the developer cartridge 4 against the weight (load Wo at the center of gravity G) of the developer cartridge. 4, thereby stabilizing the operation of cartridge 4.

In the aforementioned structure, the pusher devices 42 are located at positions within the housing part 32 that was in the photosensitive member cartridge 3, and away from the developer roller 22 of the developer cartridge 4 when the developer cartridge 4 was located in the accommodation 32. The action receiving parts 61 protrude outward from the outer walls of the compartment 24 containing developer (toner), which is disposed on a side away from the developer roller 22. Therefore, these component parts are unlikely to interfere with operations. developer cartridge insertion or detachment 4.

In the embodiment of the invention, the pusher devices 42, which have a relatively complicated structure, are arranged in the photosensitive member cartridge 3, which does not need such frequent replacement. The parts receiving the action 61, which have a more simple structure, are arranged in the developer cartridge 4, which needs to be replaced more often. Therefore, the production costs of the process unit 2 and the developer cartridge 4 can be reduced, and the operating costs can also be reduced. Furthermore, as the projecting parts receiving the action 61, provided in the developer cartridge 4, form part of the side surfaces of the box 21, the part receiving the action 61 can be formed together with the box 21, thus reducing costs. production and, furthermore, making it easier to compress the parts receiving the action 61 by means of the sliding support elements 40 of the pusher devices 42 provided in the photosensitive member cartridge 3.

The left and right thrust devices 42 are arranged on the inner surfaces of the right and left sides of the photosensitive member cartridge 3, and are connected thereto such that they can change the orientation between a thrust direction and a no-thrust direction. . Thus, if the developer cartridge 4 was simply positioned on or near the photosensitive member cartridge 3, the developer roller 22 is not pushed against the photosensitive drum 13. For this reason, the photosensitive member cartridge 3 and the developer cartridge 4 can be combined as a process unit 2 for packaging and shipping, while avoiding the danger of permanent deformation of the outer peripheral surface of the process unit 2, or the danger of contamination of the photosensitive drum 13 with components coming from the developer roller 22.

But furthermore, as each thrust device 42 was substantially formed by the pivoting articulation element 39, the sliding support element 40 that can be slidable in correspondence with the pivoting articulation element 39 and the thrust spring device arranged between the two. elements, the thrust devices 42 increase their degree of freedom by changing the orientation between the thrust direction and the no-thrust direction, Compared to a conventional device that employs a thrust spring to directly push a part receiving the action and interrupt the thrust. The advantage can also be achieved that the pushing and non-pushing operations of the parts receiving the action 61 can be carried out by the sliding support elements 40.

In addition, since the pivotal articulation member 39 of each pusher device 42 is rotatably connected with the inner surface of the right or left side of the case 30 of the photosensitive member cartridge 3, most of the component parts of the devices thrust 42 are not exposed on the outside of the box 30, regardless of whether the photosensitive member cartridge 3 is independent or combined with the developer cartridge 4 in the process unit 2. Thus, the danger that any component part of the pusher devices may be accidentally hit and broken 42 and ease of handling is improved.

The sliding bearing element 40 of each pushing device 42 was integrally provided with a laterally projecting pin-type actuating part 43 to guide the sliding bearing element 40 towards the pushing direction and the non-pushing direction. The movement actuation portions 43 of the pushers 42 protrude outwardly from the guide openings 44 on the right and left sides of the case 30 of the photosensitive member cartridge 3. Thus, most of the component parts of the pushers are not exposed on the outside of the case 30. Thus, the danger that any component parts of the pushers 42 can be struck and broken facilitates its handling.

The action receiving parts 61 protruding outward from the right and left sides of the case 21 of the developer cartridge 4 perform the function of being pushed by the pusher devices 42 and the function of cooperating with the locking lever 47. of the locking device 46 to prevent the developer cartridge 4 from rising in correspondence with the photosensitive member cartridge 3. Since the parts receiving the action 61 carry out these two functions, the predetermined costs of the developer cartridge 4 can be greatly reduced.

The processing unit 2 is designed to be removably positioned in the housing 1 of the body of the imaging apparatus. The

ES 2 178 982 T3 body casing 1 is provided with the guiding devices 55 which guide the thrust devices 42 and switch the thrust devices 42 between the thrust state and the no-thrust state. Therefore, the orientation of the pushers 42 and the operation thereof is changed simply by placing the process unit 2 in the body casing 1 or by detaching the same from the body casing 1. Thus, the ease of operation is greatly improved.

The upper wall 30b of the box 30 covers the upper part of the photosensitive drum 13. The back wall 30e, extending downward from the upper wall 30b, covers the back of the photosensitive drum 13. The lower wall 30a covers the lower part of the transfer roller 14 that was arranged below the photosensitive drum 13. Therefore, the parts of the photosensitive drum 13 that are exposed are very small. The left and right side walls 30c cover each end of the transfer roller 14 and the photosensitive drum 13. The box 30 is rigidly and integrally formed of synthetic resin, whereby the operator does not touch the surface of the photosensitive drum 13. The The box also prevents it from sticking to the photosensitive drum 13. The operator can safely handle the photosensitive drum 13.

In addition, the bottom wall 30a of the box 30 extends outward from the photosensitive drum 13. By holding the extension of the bottom wall 30a and the rear wall with the hands, the operator does not touch the photosensitive drum 13 and can safely manipulate photosensitive member cartridge 3. While the operator was holding the bottom wall extension 30a and the rear wall 30e, the bottom wall 30a does not bend as the box 30 is a rigid body with a substantially concave transverse profile, with the bottom wall 30a connected to the right and left side walls 30c of the box 30. Thus, the box can be handled safely.

Furthermore, the light input part 31, which allows irradiation of the upper surface of the photosensitive drum 13 with laser light emitted from the laser scanner 7, and the charger 36 which charges a photosensitive surface of the photosensitive drum 13 provided on the wall. upper 30b, make the box 30 solid.

Since the upwardly open housing part 32 is formed by extending the bottom wall 30a and the right and left side walls 30c to house the developer cartridge 4, the photosensitive member cartridge 3 can be easily manipulated with the developer cartridge 4 positioned inside.

The housing portion 32 covers the lower surface and the peripheral surfaces of the developer cartridge 4 when the latter is positioned therein. In addition, the housing part 32 was open upwards, whereby the housing 21 of the developer cartridge 4 that was inside the housing part 32 is separated from there in such a direction that the developer roller 22 moves away from the photosensitive drum. 13. Thus, the operation of placing the developer cartridge 4 in the housing part 32, or separating the developer cartridge 4 from the housing part 32, can be easily performed.

The bottom wall 30a has an introduction opening 51a for inserting a sheet P. The upper surface of a part of the bottom wall 30a has extendable flanges 53 to smoothly transport the sheet P from the introduction opening 51a to the contact part, between the lower surface of the photosensitive drum 13 and the upper surface of the transfer roller 14. The flanges 53 guide the sheet P and increase the rigidity towards the lower wall 30a. When the developer cartridge 4 is located in the housing part 32, the tabs 53 are facing the bottom surface of the developer cartridge.

Four. The space remaining between the tabs 53 and the lower surface of the developer cartridge 4 becomes the path of the sheet P. In this way the sheet transport structures are simplified.

If the area of ​​the lower wall 30a covering the lower part of the transfer roller 14 is increased, the larger parts of the exposed surfaces of the transfer roller 14 and the photosensitive drum 13 are covered, without increasing the resistance when the Sheet is being translated as the introduction opening 51a and discharge opening 51b are provided.

Even though the photosensitive member cartridge 3 remains separated from the housing 1 from the body for a long time, the danger that the outer peripheral surface of the transfer roller 14 is permanently deformed, or the danger that the photosensitive drum 13 is contaminated with chemicals coming from the transfer roller 14, since the photosensitive member cartridge 3 has the rigid case 30 on its peripheral surface.

When the case 30 is positioned in a certain position with respect to the body casing 1, the bearings 35 that are secured at both ends of the transfer roller 14 are raised by the action of the axle bearing lifters 34 and the springs 33 , whereby the transfer roller 14 moves upward to compress the photosensitive drum 13. By the simple operation of placing the box 30 in the body casing 1, or removing the casing box 1 from the body, pressure can be applied to or withdrawn pressure from the transfer portion 52.

When the photosensitive member cartridge 3 is removed from the body casing 1, the transfer roller 14 is separated from the lower surface of the photosensitive drum 13 due to the weight of the transfer roller 14. Therefore, even if the sheet P gets stuck in the transfer part 52, the sheet P which is stopped in the transfer part 52 can be released by only pulling the photosensitive member cartridge 3 out of the body casing 1 and then pulling out the sheet P From the transfer part 52 through the introduction opening 51a, or the discharge opening 51b, the paper can be easily unblocked.

The registration rollers 12a, 12b are a pair of rollers for translating the sheet P supplied by the sheet feeder 6 to the contact part between the photosensitive drum 13 and the transfer roller 14, while timing10

ES 2 178 982 T3 tracing time. The upper registration roller 12a is located on the side of the processing unit.

two. The lower registration roller 12b is located on the casing 1 side of the body. In this embodiment, the processing unit 2 is designed to be removably positioned in the body casing 1 by the front surface thereof. When both registration rollers 12a and 12b are provided in the body casing 1 as in conventional apparatus, a part of the case 30 covering the transfer roller 14 contacts the upper registration roller 12a when the transfer unit Process 2 is removed from the front surface of the body shell 1, as can be seen in Figure 1. This makes it difficult to separate the process unit 2 from the body shell 1.

By placing the upper registration roller 12a on the side of the processing unit 2, the detachment of the processing unit 2 from the front surface of the casing 1 of the body can be facilitated. The process unit 2 can be placed in the body casing 1 while it is moving into the body casing 1 in a direction substantially parallel to the feeding direction of the sheet P which is being translated by the pair of registration rollers 12a, 12b.

However, when the upper registration roller 12a and the lower registration roller 12b are positioned on the sides of the process unit 2 and the body casing 1, respectively, to facilitate the positioning of the process unit 2 in the casing. 1 from the body or the separation of the processing unit 2 from the casing 1 from the body, it is important to maintain the positions, Appropriate pushing pressures and angles of the upper and lower registration rollers 12a and 12b relative to each other to translate the sheet P evenly.

Even if Process Unit 2 is replaced with a new one, it is necessary to place the new Process Unit 2 into Body Casing 1 while maintaining the proper positions, angles and thrust pressures of the upper and lower registration rollers 12 and 12b with each other.

In the embodiment, the registration roller pair positioning mechanism 12a, 12b is constructed as described below.

As shown in Figure 23, the upper registration roller 12a is provided so that its surface is exposed to the lower opening 300a of the box 30. Unlike a conventional roller hinged on the side surfaces of the body of an apparatus or the box, the registration roller 12a is positioned as follows. As shown in Figure 24, which is an enlarged view of the circular portion B of Figure 23, the projections 700a of the bearing 700 that is secured to the registration roller 12, are in contact with the bearing portions 300b that will be integrally formed with box 30. The registration roller 12a is arranged to move vertically in the directions indicated by the arrow in FIG. 24 (the direction in which the registration roller 12a is pushed against the registration roller 12b and the opposite direction).

As shown in FIG. 25B, the registration roller 12a is a shaft formed of coated iron or stainless steel. The length of the registration roller 12a is greater than the width of the sheet P. The resin made bearings 700, 710 are arranged at each end of the registration roller 12a. As shown in Figures 25A and 27A to 27F, the bearing 700 is provided with an integrally formed cylindrical part 700b having an insert opening 700c for inserting an end of the registration roller 12a and a bearing part 700d formed with protrusions. 700a.

Bearing 710 is located at the other end of registration roller 12a. As shown in Figures 25C and 28A through 28E, bearing 710 has substantially the same shape as bearing 700, except that it has a cavity 710e. That is, the bearing 710 is provided with an integrally formed cylindrical part 710b having an insert opening 710c for inserting an end of the registration roller 12a and a bearing part 710d formed with projections 710a and cavity 710e, as shown in Figure 28D. Thanks to the cavity 710e, the bearing part 710d can be easily bent inwards (towards its central part), as shown with arrows in Fig. 28D.

After securing the bearings 700, 710 described above at each end of the registration roller 12a, as shown in FIG. 25B, the registration roller 12 is mounted in the housing 30 as described below.

As shown in Figure 29, the bearing 700 is first inserted into a hollow space 300e that is defined between a side wall 300c of the case 30 and a bottom wall 300d that covers one end of the registration roller 12a, at an angle that is indicated in figure 29. Next, the bearing 700 is pushed in the direction of the arrow G. As shown in Fig. 29, a chamfered part 700f having an inclined surface is formed at the upper end of the abutment part 700d above the protrusions 700a. The chamfered part 700f makes a smooth contact with the corner of the bottom wall 300d, whereby the bearing 700 can be adjusted smoothly in the hollow space 300e.

As shown in Figures 24 and 27D, an inclined surface 720 is formed on the boss 770a. The inclined surface 720 makes a smooth contact with the bearing portions 300b, whereby the bearing 700 can be easily fitted into the hollow space 300a. The bearing 700 fitted in this way in the hollow space 300e is shown in FIG. 30.

To fit the bearing 710 in the hollow space 300e, the bearing portion 710d is bent inward (toward its center portion) as indicated by the arrows in Figure 28D. While the bearing portion 710d is being bent, to reduce the width thereof, the bearing 710 is pushed into the hollow space 300e. The flexible bearing part 710d easily carries out the insertion of the bearing 710 into the hollow space 300e. An inclined surface 730 is also formed on the protrusions 710a of the bearing 710, as shown in FIG. 28D. The inclined surface 730 makes a smooth contact with the bearing portions 300b, whereby the bearing 710 can be easily fitted into the hollow space 300e.

ES 2 178 982 T3

Figures 25D to 25I show the bearings 700, 710 secured in the hollow spaces 300e in the manner described above. As shown in Figures 25D to 25I, when the registration roller 12a rises to the highest position where the cylindrical parts 700b, 710b of the bearings 700, 710, respectively, will be in contact with the lower ends of the side walls 300c. , the bearings 700, 710 extending outward from the side wall 300c prevent the registration roller 12a from rising further. As shown in Figures 26A to 26D, which are enlarged views of the bearings 700, 710 and their periphery shown in Figures 25G to 25I, when the registration roller 12a is lowered to the lowest position due to its weight, the contact of the projections 700a 710a with the bearing portions 300b prevents the registration roller 12 from descending further.

The described structure allows the registration roller 12a to freely rise and fall in the direction in which the registration roller 12a moves away from and pushes the registration roller 12b.

As shown in FIG. 1, the registration roller 12b has a shaft 12c formed from coated iron or stainless steel and an elastic layer 12d formed from urethane rubber located on the shaft 12c. The shaft 12c is rotatably supported in the housing 1 of the body. Shaft 12c is connected to a motor via a transmission mechanism (not shown). A controller (not shown) calculates the time for registration roller 12b to start rotating and controls its speed.

As described above, the registration roller 12a is provided to move vertically. The registration roller 12a is positioned to maintain the proper position, angle and push pressure with respect to the registration roller 12b, when the process unit 2 is located in the body casing 1.

With reference to Figures 2, 9, 20A, 20B, 21 and 31, the operation of placing the processing unit 2 in the body casing 1 and the positioning mechanism of the registration roller 12a are described below.

The processing unit 2 is placed in, and removed from, the housing 1 of the body, when a cover 1b, which is positioned on the far right, in Figure 1 front surface, of the housing 1 of the body is rotated downwards. body, to form a large opening. As shown in Fig. 2, a pair of left and right guide devices 55, made of resin, are secured to the inner surfaces of the left and right sides of the body casing 1. Each guiding device 55 has an upward sloping surface that is open upwardly and extends inwardly from the right end of the body casing 1, and an upper side guide surface 55a that extends inwardly downward from a top 55d of the body. upward sloping surface, and a lower side guide surface 55b which is disposed below the upper side guide surface 55a, it extends inwardly descending from the right end of the body casing 1 and ends at a position close to the lower roller 12b.

Figure 2 indicates the position in which the insertion of the processing unit 2 in the housing 1 of the body begins. When the process unit 2 is inserted into the body casing 1 from a position shown in figure 2 to a position shown in figure 20A, the process unit 2 is pushed inwards whereby the shaft 13a of the photosensitive drum 13 approaches an inner end 55c which is located on the upper side guide surface 55a. Subsequently, as shown in Fig. 20A, the motion actuator portion 43 of each pusher device 42, mounted on the process unit 2, is brought into contact with the upward sloping surface of the guiding device 55, and each of the guiding members 56, (Only one of the guide members is shown in the drawings) protruding laterally from the lower parts of the right and left sides of the process unit 2 fits into the lower side guide surface 55b, thereby preventing the process unit 2 is moved upward in correspondence with the body casing 1, and is only allowed to move a little further inward by the lower side guide surface 55b.

At that time, the registration roller 12a lowers due to its own weight as shown in FIGS. 20A, and approaches the registration roller 12b by slidingly contacting the lower guide surface 55b.

When the process unit 2 is thus pushed inward, the corresponding upper guide surface 55a raises the motion drive part 43 of each thrust device 42, whereby the sliding support member 40 of each thrust device 42 pivots. upward around pivots 39a, 39b. Therefore, the sliding bearing element 40 of each thrust device 42 stops the corresponding part receiving the action 61 in a direction in which the distal end of the sliding bearing element 40 pushes the part receiving the action 61, as shown. shown in Figure 20B. When the movement actuating part 43 of each pusher 42 reaches the top 55d of the upward inclined surface, the sliding bearing member 40 of each pusher 42 pivots to the uppermost position. In this position, the distal end of the sliding support element 40 of each thrust device 42 stops the corresponding part that receives the action 61.

At that time, the registration roller 12a contacts the registration roller 12b. As the processing unit is pushed further inward, the registration rollers 12a, 12b move together as they come into contact with each other.

When the processing unit 2 is pushed further inward, the shaft 13a of the photosensitive drum 13 is placed in a determined position at the inner end 55c. In this position, the operator releases the process unit 2, whereupon the latter stops under its own weight in a state in which the registration roller 12a is positioned on the registration roller 12b, as shown in the figure 21. As shown in figure 31, the springs 45 push the bearings 700, 710 which

ES 2 178 982 T3 are secured at each end of the registration roller 12a. Consequently, the registration roller 12a urges the registration roller 12b at the proper push position, angle, and pressure.

When the process unit 2 is located in the body casing 1, as shown in Figure 21, the distal end of the sliding bearing element 40 of each pusher device 42 pushes the corresponding part that receives the action 61. Therefore , the pushers 42 and the acting parts 61 push the developer roller 22 against the photosensitive drum 13.

In this state, shown in Figures 21 and 9, the springs 33 lift the bearings 35 that movably and vertically support the axis 14a of the transfer roller 14, whereby the transfer roller 14 rises to push the drum. photosensitive 13 with a determined pressure.

As described above, when the processing unit 2 is removed from the body casing 1, the registration roller 12a is not fixed but is freely ascending and descending. The registration roller 12a is positioned to push the registration roller 12b into the proper position, angle and pressure only after the process unit 2 is positioned in the body casing 1. The precision of the position, angle and thrust pressure of the registration roller 12a with respect to the registration roller 12b is determined by the springs 45 located in the housing 1 of the body. Therefore, even though the processing unit 2 can be replaced, the relationship between the registration rollers 12a, 12b can be properly maintained. Consequently, the blade

P can move steadily and uniformly.

The positioning of the registration rollers 12a and 12b is carried out in correspondence with the bearings 700, 710. The bearings 700, 710 are secured in the registration roller 12a so that they are spaced from each other a distance that is greater than the width of process unit 2, and tin provided to extend outward from the side surface of process unit 2. Therefore, the positioning of the registration roller 12a is carried out on each side surface of the body casing 1. When processing unit 2 is attached to or detached from casing 1 from the body at the front surface of the casing, it is unlikely that the springs 45 for positioning the registration roller 12a will interfere with the positioning or detachment of the processing unit 2, whereby the processing unit 2 can easily be placed in and removed from the body casing 1.

The registration roller 12a is a metal shaft. While the rigidity of the registration roller 12a is suitably maintained, this roller, which is longer than the width of the sheet P, is mounted in the process unit 2 through a simple structure. Therefore, costs can be reduced.

As shown in figure 1, a guide opening 80 is provided, to guide the sheet P towards the contact part that is between the photosensitive drum 13 and the transfer roller 14, in the case 30 near the registration roller 12a. . With the sheet guide opening 80, the sheet is smoothly conveyed towards the contact part that is between the photosensitive drum 13 and the transfer roller 14.