Electrophotographic process cartridge and image forming apparatus with such process cartridge

Abstract: The present invention provides a process cartridge (B) mountable to an image forming apparatus, comprising a frame, an image bearing member, process means acting on the image bearing member, and a gripper (12d) for gripping the process cartridge (B). The gripper portion is provided on said frame to be offset toward a position where the frame is subjected to a greater mounting resistance generated by engagement between the process cartridge (B) and a member on the main body, when the process cartridge (B) is mounted to the image forming apparatus.

Description: The present invention relates to an electrophotographic process cartridge for use in an electrophotographic image forming apparatus (such as a laser beam printer, an electrophotographic copying machine, a facsimile machine, a word processor or the like), to a combination of such a cartridge and apparatus, to a method of assembling the cartridge, and to a method of recycling the cartridge. Process cartridges are known in which a photosensitive drum, a charger, a developing device, a cleaning device and the like are integrally contained in a cartridge casing which can be removably mounted in an image forming apparatus, whereby the replenishment of toner or the exchange of parts whose service lives have expired can be permitted and maintenance can be facilitated, by the user of the apparatus. Many early laser beam printers using replaceable process cartridges were of the so-called "clam-shell" type, in which substantial upper and lower parts of the printer are hinged together. In order to replace a process cartridge the upper part is hinged open, the old cartridge is removed and replaced by a fresh cartridge, and the upper part is then hinged closed. In one example of a clam-shell printer, operating parts of the printer are disposed in the upper part of the printer. Consequently, the upper part is bulky and heavy, and strong hinges and counterbalancing springs are required. Furthermore, the operating parts in the upper part of the printer are liable to be upset with the opening and closing of the printer to replace a cartridge or clear a paper jam. Recently, a "monocoque" printer has been proposed in which, rather than hinging substantial parts of the printer open in order to replace a cartridge or clear a paper jam, the printer has a monocoque body with a cavity. A fresh cartridge is inserted into the cavity by a general sliding movement with guides being provided on the cavity wall and cartridge, and a lightweight cover is then closed over the inserted cartridge. To remove a cartridge, the cover is opened, and the cartridge is pulled out with a general sliding movement. Examples of such printers are described in patent applications EP-A-0 538 479, JP-A-3-252665, JP-A-3-252667, JP-A-3-252668 and JP-A-4-070767. In some process cartridges an openable drum shutter is provided for covering an exposed portion of a photosensitive drum to prevent deterioration of the drum when the process cartridge is dismounted from the image forming apparatus. The drum shutter is automatically opened by engaging a link portion of the drum shutter by a cam portion of the image forming apparatus when the process cartridge is inserted into the image forming apparatus, and is automatically closed by a biasing force of a spring when the process cartridge is dismounted from the image forming apparatus. In a process cartridge having a drum shutter, since the drum shutter is opened in opposition to the biasing force of the spring when the cartridge is inserted into the apparatus, a load is generated in a cartridge inserting direction. If the link portion for opening the drum shutter is provided on a longitudinal end of the process cartridge, an unbalanced load may be applied to the process cartridge. The present invention is more particularly concerned with facilitating insertion of a process cartridge into an image forming apparatus of the monocoque type described above. In accordance with the present invention, there is provided an electrophotographic process cartridge comprising a casing containing a rotatable photosensitive drum, a driven gear coaxial with the drum and charging, developing and cleaning means cooperating with the drum, the casing having a first opening for passing light to the drum for forming a latent image thereon and a second opening for transferring developed images from the drum to transfer material, said cartridge being adapted to be removably inserted in a direction transverse to the axis of the drum into an image forming apparatus having an arrangement for guiding the cartridge to an operative position in the apparatus and supporting the cartridge in said operative position with said driven gear engaged with a driving gear of the apparatus, wherein said drum is mounted in said casing at a front portion thereof relative to the direction of insertion, outwardly protruding guide means are provided on said casing at opposite sides of said front portion for cooperation with said guiding arrangement for effecting said guiding, and a rear portion of said casing relative to the direction of insertion is constructed so that it may be gripped by an operator for inserting the cartridge into and removing it from the apparatus, and wherein the cartridge has a drum shutter mounted on the casing for movement between a closed position in which the drum shutter closes said second opening and protects the drum and an open position, and a shutter actuating mechanism having a portion which is provided at one of the sides of the casing and which is engagable with the image forming apparatus to move the shutter from the closed position to the open position upon insertion of the cartridge into the apparatus; characterised in that: the drum shutter is biased by a spring towards its closed position; and the grippable portion of the casing comprises a surface formation which is configured to facilitate gripping of the formation by an operator, said surface formation having a centre which is offset from a centre plane of the cartridge bisecting the drum, the offset being towards said one side of the casing. Accordingly, upon insertion of the cartridge into the apparatus, the operator when gripping the grippable portion centrally will provide an offset insertion force on the cartridge which will tend to counteract the offset reaction provided by the spring bias of the shutter actuating mechanism. Other preferred features of the cartridge are defined in the subsidiary claims. Fig. 1 is an elevational sectional view of an image forming apparatus to which a process cartridge is mounted; Fig. 2 is a perspective view of the image forming apparatus; Fig. 3 is a cross-sectional view of the process cartridge; Fig. 4 is a perspective view of the process cartridge; Fig. 5 is a partial view showing a left guide member; Fig. 6 is a partial view showing a right guide member; Fig. 7 is an exploded view of the process cartridge showing frames thereof; Fig. 8A is a longitudinal sectional view of a photosensitive drum, and Fig. 8B is a cross-sectional view of the photosensitive drum; Fig. 9 is a perspective view of a conductive member contacting with a metal shaft; Fig. 10 is a view showing a charger roller and bearings therefor; Fig. 11 is an exploded perspective view showing an overlapping relation between a blow sheet and toner leak preventing seals; Fig. 12 is a view showing a positional relation between a developing blade and the toner leak preventing seals and the blow sheet; Fig. 13A is a sectional view taken along the line A - A in Fig. 11, and Fig. 13B is a sectional view taken along the line B - B in Fig. 11; Figs. 14A and 14B are views showing a case where a blow sheet is bent; Fig. 15 is an enlarged sectional view showing a condition that a sharp rib is penetrated into a developing blade; Fig. 16 is a sectional view showing a condition that an adhesive for an antenna wire is swollen; Fig. 17A is a view showing a condition that the adhesive is swollen by fitting the antenna wire, Fig. 17B is a view showing a condition that the swelled adhesive is averaged, and Fig. 17C is a view showing a condition that a seal is attached; Fig. 18A is a view showing the antenna wire which is not bent, and Fig. 18B is a view showing the antenna wire which is bent; Fig. 19 is a perspective view of a cartridge showing a condition that a cover film is drawn obliquely; Fig. 20 is a view showing a relation between the cover film and the toner leak preventing seal when the cover film is drawn obliquely; Fig. 21 is a perspective view showing a condition that a tear preventing sheet is secured to the toner leak preventing seal in spaced relation to an edge of the toner leak preventing seal; Fig. 22 is a view showing various dimensions of a photosensitive drum, a developing sleeve and a charger roller; Fig. 23 is a view showing various dimensions of the charger roller; Fig. 24 is a plan view showing toner leak preventing seals and screens disposed on both ends of a cleaning blade; Fig. 25 is a perspective view showing the toner leak preventing seal and the screens disposed on the end of the cleaning blade; Fig. 26 is an explanatory view for explaining a method for attaching the toner preventing seal on the end of the cleaning blade; Fig. 27 is a view showing a method for demolding a developing frame; Fig. 28 is a view showing a method for demolding a cleaning frame; Fig. 29 is a view showing a process for bonding a toner frame and a developing frame by ultrasonic welding; Fig. 30 is a view showing positioning bosses and fitting holes formed on and in the toner frame and the developing frame in a widthwise direction thereof; Fig. 31 is a perspective view showing a plurality of positioning bosses and fitting holes formed on and in the toner frame and the developing frame in a longitudinal direction thereof; Fig. 32A is a view showing a condition that the toner developing frame is rested on an assembling tray, and Fig. 32B is a view showing a condition that the cleaning frame is rested on an assembling tray; Fig. 33 is a view showing assembling steps through which the toner developing frame is assembled by an automatic machine; Fig. 34 is a view showing assembling steps through which the cleaning frame is assembled by an automatic machine; Figs. 35 and 36 are views showing a construction or arrangement wherein the photosensitive drum is not contacted with a table when the cleaning frame is rested on the table; Fig. 37 is a view showing a construction wherein a developing sleeve is not contacted with a table when the toner developing frame is rested on a table; Fig. 38 is an exploded partial perspective view showing a method for connecting the toner developing frame and the cleaning frame by connecting members; Fig. 39A is a perspective view showing a condition that the connecting members are attached, and Fig. 39B is a sectional view showing a condition that the connecting members are attached; Fig. 40 is a partial perspective view showing a left end surface of a process cartridge; Fig. 41 is an elevational sectional view showing a condition that the process cartridge is mounted to an image forming apparatus; Figs. 42 to 45 are enlarged partial sectional views showing a condition that the process cartridge is mounted to the image forming apparatus; Fig. 46 is an enlarged partial sectional view showing a condition that the process cartridge is dismounted from the image forming apparatus; Fig. 47 is a perspective view showing a mechanism for opening and closing a laser shutter; Fig. 48 is a view showing a gripper portion on which lateral ribs are formed; Fig. 49 is a perspective view showing a condition that the gripper portion of the cartridge is gripped by hand; Fig. 50 is a perspective view showing a gripper portion in which a recess is formed; Fig. 51 is a perspective view showing a gripper portion on which a projection is formed; Fig. 52 is a partial perspective view showing the arrangement of various contacts provided on a process cartridge; Fig. 53 is a plan view showing the arrangement of various contacts provided on an image forming apparatus; Fig. 54 is a sectional view showing a relation between the contacts and contact pins; Fig. 55 is a detection circuit for detecting a toner remaining amount; Fig. 56 is a graph showing a relation between a toner amount and a toner remaining amount detection voltage; Fig. 57 is a circuit according to an embodiment wherein the cartridge mount is detected by an inverter; Fig. 58 is a circuit according to an embodiment wherein the cartridge mount is detected by a digital signal; Fig. 59 is a function block diagram of a control means; Fig. 60 is an exploded perspective view of a cleaning frame showing an inner construction thereof; Figs. 61 and 62 are views showing a bearing for a charger roller according to another embodiment; Fig. 63 is a perspective view of a bearing for a charger roller according to a further embodiment; Fig. 64 is a view showing a mechanism for preventing the deformation of a contact member, according to another embodiment; Fig. 65 is a view showing a mechanism for preventing the deformation of a contact member, according to a further embodiment; Fig. 66 is a view showing an embodiment wherein a second rib on a developing frame is sharpened; Fig. 67A is an explanatory view showing a condition that an antenna wire is bent to a semi-circular shape, and Fig. 67B is an explanatory view showing a condition that the antenna wire is bent to a trapezoidal shape; Fig. 68 is a view showing an embodiment wherein a cut-out is formed in a developer frame and the floating of an antenna wire is prevented by inserting the antenna wire into the cut-out; and Fig. 69 is a view showing an embodiment wherein a round hole is formed in a developer frame and the floating of an antenna wire is prevented by inserting the antenna wire into the round hole. First of all, a process cartridge and an image forming apparatus using such process cartridge, according to a first embodiment, will be explained with reference to the accompanying drawings. {General Explanation of Process Cartridge and Image Forming Apparatus Having Such Process Cartridge Mounted thereto}: The whole construction of an image forming apparatus is firstly explained. Incidentally, Fig. 1 is an elevational sectional view of a laser beam printer having a process cartridge mounted thereto, according to one aspect of the present invention, Fig. 2 is a perspective view of the laser beam printer, Fig. 3 is a cross-sectional view of the process cartridge, and Fig. 4 is a perspective view of the process cartridge. As shown in Fig. 1, the image forming apparatus A is so designed that a latent image is formed on a photosensitive drum (as an example of an image bearing member) by illuminating light image from an optical system 1 onto the drum in response to image information, and the latent image is developed with developer (referred to as "toner" hereinafter) to form a toner image. In synchronism with the formation of the toner image, a recording medium 2 is fed by a convey means 3 to an image forming station of a process cartridge B, and, in the image forming station, the toner image formed on the photosensitive drum is transferred onto the recording medium 2 by a transfer means 4. Then, the recording medium 2 is sent to a fixing means 5, where the transferred toner image is fixed to the recording medium. Thereafter, the recording medium is discharged to a discharge portion 6. As shown in Fig. 3, in the process cartridge B providing the image forming station, the rotating photosensitive drum (an example of an image bearing member) 7 is uniformly charged by a charger means 8. The latent image is formed on the photosensitive drum 7 by illuminating the light image from the optical system 1 through an exposure portion 9, and then the latent image is developed by a developing means 10 to visualize the image as a toner image. The toner image is then transferred onto the recording medium 2. On the other hand, after the transferring operation, the residual toner remaining on the photosensitive drum 7 is removed by a cleaning means 11. Incidentally, the process cartridge B comprises a toner frame 12 as a first frame having a toner reservoir, a developing frame 13 as a second frame having a developing sleeve, and a cleaning frame 14 as a third frame having the photosensitive drum 7 and the cleaning means 11 and the like. In Fig. 2, the reference numeral 15a denotes an operation portion on which a recording copy number setting button, a density setting button, a test print button, a lamp for informing of the exchange of the cartridge which will be described later, and the like are provided. Next, various parts of the image forming apparatus A and the process cartridge B mounted thereto will be fully explained. {Image Forming Apparatus}: First of all, regarding the various parts of the image forming apparatus A, the optical system, convey means, transfer means, fixing means and cartridge mounting means will be described in order. (Optical System): The optical system 1 serves to illuminate the light image onto the photosensitive drum 7 in response to the image information sent from an external device and the like. As shown in Fig. 1, the optical system comprises an optical unit 1a in which a polygon mirror 1b, a scanner motor 1c, a focusing lens 1d, a reflection mirror 1e and a laser diode 1f are accommodated and which is disposed within a frame 15 of the apparatus A. When an image signal is given from an external device such as a computer, a word processor and the like (refer to host 62 (Fig. 59)), the laser diode 1f emits the light in response to the image signal, which light is sent to the polygon mirror 1b as image light. The polygon mirror 1b is rotated at a high speed by the scanner motor 1c, and the image light reflected by the polygon mirror 1b is illuminated onto the photosensitive drum 7 via the focusing lens 1d and the reflection mirror 1e, thereby selectively exposing the surface of the photosensitive drum 7 to form a latent image corresponding to the image information on the photosensitive drum 7. (Recording Medium Convey Means): Next, the convey means 3 for conveying or feeding the recording medium (for example, an OHP sheet, thin film or the like) 2 will be explained. The convey means 3 according to the illustrated embodiment permits both the manual sheet supply and the cassette sheet supply. As shown in Fig. 1, in the manual sheet supply, one or more recording medium 2 is set on a sheet supply tray 3a and then the image forming operation is started. As a result, the recording medium 2 on the sheet supply tray 3a is sent into the image forming apparatus by the rotation of a pick-up roller 3b. Incidentally, a plurality of recording media 2 are set on the sheet supply tray, the recording media are separated one by one by a pair of separation rollers 3c1, 3c2, and the separated recording medium is conveyed until a leading end of the recording medium is abutted against a nip between a pair of regist rollers 3d1, 3d2. The paired regist rollers 3d1, 3d2 are rotated in response to the image forming operation to feed the recording medium 2 to an image forming station. Further, after the image formation, the recording medium 2 is conveyed to the fixing means 5, and then is discharged onto the discharge portion 6 by a pair of intermediate discharge rollers 3e and a pair of discharge rollers 3f1, 3f2. Incidentally, guide members 3g for guiding the recording medium 2 are arranged between the fixing means and the intermediate discharge rollers and between the intermediate discharge rollers and the paired discharge rollers. Further, the sheet supply tray 3a comprises an inner member 3al and an outer member 3a2. In an inoperative condition, the inner member 3a1 is contained in the outer member 3a2, and, as shown in Fig. 2, the outer member 3a2 constitutes a portion of the frame 15 of the apparatus. On the other hand, for the cassette sheet supply, as shown in Fig. 1, a mounting portion for a cassette 3h is provided at a lower portion within the frame 15. When the manual sheet supply is not effected, the recording media 2 in the cassette 3h mounted in the mounting portion are sent to the paired regist rollers 3d1, 3d2 one by one from the uppermost one by the rotation of a pick-up roller 3i and a feed roller 3j. At a downstream side of the paired regist rollers 3d1, 3d2, the recording medium is conveyed in the same manner as the manual sheet supply. Incidentally, a sensor 3k serves to detect the presence/absence of the recording medium 2 in the cassette 3h. (Transfer Means): The transfer means 4 serves to transfer the toner image formed on the photosensitive drum 7 onto the recording medium 2, and, as shown in Fig. 1, comprises a transfer roller 4. More particularly, the recording medium 2 is urged against the photosensitive drum 7 of the process cartridge B mounted on a mounting means (described later) by the transfer roller 4, and, by applying a voltage having the polarity opposite to that of the toner image formed on the photosensitive drum 7 to the transfer roller 4 (in the illustrated embodiment, by effecting the constant current control with DC voltage of about 1000 V), the toner image on the photosensitive drum 7 is transferred onto the recording medium 2. (Fixing Means): The fixing means 5 serves to fix the toner image transferred to the recording medium 2 by the application of the voltage to the transfer roller 4 onto the recording medium 2. As shown in Fig. 1, the fixing means comprises a rotating drive roller 5a, and a driven fixing roller 5b having a heater 5c therein and urged against the drive roller 5a. More particularly, while the recording medium 2 to which the toner image was transferred at the image forming station is being passed between the drive roller 5a and the fixing roller 5b, the recording medium is subjected to pressure due to the abutment between the rollers 5a, 5b and heat due to the heating of the fixing roller 5b, thereby fixing the transferred toner image to the recording medium 2. (Cartridge Mounting Means): The cartridge mounting means for mounting the process cartridge B is provided in the image forming apparatus A. After an opening/closing cover 16 is opened, the mounting or dismounting of the process cartridge B is effected. More particularly, the opening/closing cover 16 is pivotally mounted on an upper part of the frame 15 via hinges 16a. On the other hand, as shown in Figs. 5 and 6, a left guide member 17 and a right guide member 18 are attached to inner side walls. The guide members 17, 18 have first guide portions 17a, 18a which are inclined forwardly and downwardly, and second guide portions 17b, 18b which are disposed above the first guide portions. The guide portions 17a, 17b and 18a, 18b are arranged with left/right symmetry. Bearing portions 17c, 18c (described later) for supporting drum bearings of the process cartridge B are formed on ends of the first guide portions 17a, 18a, respectively, and intermediate stepped portions 17b1, 18b1 are formed on the second guide portions 17b, 18b, respectively. Further, the left guide member 17 has a cartridge rocking movement regulating guide portion 17d which is disposed above the second guide portion 17b. The right guide member 18 has a shutter cam portion 18d for opening and closing a drum shutter 35 of the process cartridge B, which cam portion is disposed above the second guide portion 18b. Further, pressure members 19 are disposed above the rocking movement regulating guide portion 17d and the shutter cam portion 18d, which pressure members serve to bias the mounted process cartridge B downwardly via torsion coil springs 19a. Further, abutment members 20 for positioning the process cartridge B are arranged at front sides of the left and right guide members 17, 18 (front sides in a cartridge inserting direction). After the opening/closing cover 16 is opened, the process cartridge B can be mounted within the image forming apparatus while being guided by the first and second guide portions 17a, 18a and 17b, 18b of the left and right guide members 17, 18. The mounting operation for the process cartridge will be explained after the construction of the process cartridge is described. {Process Cartridge}: Next, various parts of the process cartridge B which is to be mounted to the image forming apparatus A will now be described. The process cartridge B includes an image bearing member, and at least one process means. The process means may be, for example, a charger means for charging a surface of the image bearing member, a developing means for developing a latent image formed on the image bearing member to form a toner image, a cleaning means for removing residual toner remaining on the image bearing member, and the like. As shown in Fig. 3, the process cartridge B according to the illustrated embodiment comprises a charger means 8, exposure portion 9, developing means 10 for performing a developing operation with toner and cleaning means 11 which are arranged around an electrophotographic photosensitive drum 7 as an image bearing member and which are enclosed by a housing comprising a toner frame 12, developing frame 13 and cleaning frame 14 to form a unit which can removably be mounted to the frame 15 of the image forming apparatus as a process cartridge B. Next, regarding the various parts of the process cartridge B, the photosensitive drum 7, charger means 8, exposure portion 9, developing means 10 and cleaning means 11 will be fully explained in order. (Photosensitive Drum): The photosensitive drum 7 according to the illustrated embodiment comprises a cylindrical drum base 17a made of aluminium, and an organic photosensitive layer 7b coated on an outer peripheral surface of the drum base. As shown in Fig. 7, when the photosensitive drum 7 is attached to the cleaning frame 14 and a driving force of a drive motor 71 (refer to Fig. 59) of the image forming apparatus is transmitted to a helical gear 7c (refer to Fig. 8A) secured to one longitudinal end of the photosensitive drum 7, the drum 7 is rotated in a direction shown by the arrow in Fig. 1 in response to the image forming operation. Incidentally, as shown by the longitudinal sectional view in Fig. 8A, the photosensitive drum 7 is rotatably attached to the cleaning frame 14 by fitting a boss 7d1 of a gear flange 7d attached to one longitudinal end of the photosensitive drum into a bearing portion 14a of the frame 14 and by inserting a metal (iron in the illustrated embodiment) shaft 21 into a hole formed in a resin helical gear 7c attached to the other end of the drum and by securing the shaft 21 to the frame 14. Further, the shaft 21 has an integral shaft portion 21a and flange 21b and is secured to the frame 14 by securing the flange 21b to the frame 14 by screws. Further, the gear flange 7d comprises a spur wheel and serves to transmit the rotational force of the photosensitive drum 7 rotated via the helical gear 7c receiving the driving force from the image forming apparatus to the transfer roller 4, thereby rotating the latter. Further, the metal shaft 21 is a conductive member, and another conductive member 22 (made of bronze phosphide in the illustrated embodiment) is arranged to contact with an inner surface of the aluminium drum base 7a of the photosensitive drum at the end thereof into which the metal shaft 21 is inserted, so that,- when the metal shaft 21 is inserted, it is contacted with the conductive member 22. Consequently, the photosensitive drum 7 is earthed to the image forming apparatus through the conductive member 22 and the metal shaft 21 as will be described later. That is to say, as shown in Fig. 9, the conductive member 22 is fitted on and secured by bosses 7c2 formed on a side surface of the flange portion 7c1 of the helical gear 7c, and has a hole or opening 22a into which the metal shaft 21 is to be inserted. Further, a contact portion 22b having a spring feature is also provided to extend into the opening 22a. When the metal shaft 21 is inserted into the opening, it is contacted with the contact member 22b while urging the latter. Further, the conductive member 22 is provided with bifurcated pawl portions 22c protruding in the left and right direction, so that, when the flange portion 7c1 is inserted into the photosensitive drum 7, the pawl portions 22c are contacted with the inner surface of the photosensitive drum 7. In the image forming operation, the photosensitive drum 7 is rotated, and the surface of the photosensitive drum 7 is uniformly charged by applying the DC voltage and AC voltage in an overlapped fashion to the charger roller 8. Incidentally, in this case, in order to charge the surface of the photosensitive drum 7 uniformly, it is preferable that the DC voltage and AC voltage are applied to the charger roller 8 in the overlapped fashion and the frequency of the AC voltage is increased. However, if the frequency of the AC voltage exceeds about 200 Hz, it is feared that a so-called "charging noise" due to the vibration of the photosensitive drum 7 and the charger roller 8 is increased. More particularly, when the AC voltage is applied to the charger roller 8, an electrostatic attraction force is generated between the photosensitive drum 7 and the charger roller 8, and the attraction force is strong at the maximum and minimum values of the AC voltage, whereby the charger roller 8 is attracted toward the photosensitive drum 7 while deforming elastically. On the other hand, the attraction force is relatively weak at the intermediate value of the AC voltage, with the result that the charger roller 8 tends to separate from the photosensitive drum 7 by the restoring force due to the elastic deformation. Consequently, the photosensitive drum 7 and the charger roller 8 are vibrated at the frequency greater than the frequency of the applied AC voltage by twice. Further, when the charger roller 8 is attracted to the photosensitive drum 7, the rotations of the roller and the drum are braked, thereby generating the vibration due to the stick slip (generated as if a wet glass is rubbed by a finger); this vibration causes the charging noise. Thus, according to the illustrated embodiment, in order to reduce the vibration of the photosensitive drum 7, as shown by the sectional views in Figs. 8A and 8B, a filler 7e formed from a rigid body or elastic body is arranged in the photosensitive drum 7 at a central portion in the longitudinal direction thereof. The material of the filler 7e may be metal such as aluminium or brass, or ceramics such as cement or gypsum, or rubber such as natural rubber or the like. In consideration of the productivity, workability, and effect of weight and cost, the material of the filler may be appropriately selected among them. Incidentally, in the illustrated embodiment, the filler 7e is made of aluminium having a weight of about 120 grams. The shape or configuration of the filler 7e may be solid cylindrical or hollow cylindrical (in the illustrated embodiment, as shown in Fig. 8B, the filler is formed as the solid cylinder). For example, the filler 7e having an outer diameter smaller than an inner diameter of the photosensitive drum 7 by about 100 µm is inserted into the hollow drum base 7a, thus attaching the filler to the photosensitive drum. That is to say, the gap between the drum base 7a and the filler 7e is kept to 100 µm at the maximum, and an adhesive (for example, cyanoacrylate group, epoxy resin group or the like) is applied to an outer surface of the filler or the inner surface of the drum base 7a, thereby adhering the filler 7e to the inner surface of the drum base 7a. As mentioned above, by providing the filler 7e in the photosensitive drum 7, the photosensitive drum 7 is rotated stably, thereby suppressing the vibration due to the rotation of the photosensitive drum 7 during the image forming operation. As a result, even when the frequency of the AC voltage applied to the charger roller 8 is increased, it is possible to suppress the charging noise. (Charger Means): The charger means serves to charge the surface of the photosensitive drum 7. In the illustrated embodiment, a charging method of a so-called contact type as disclosed in the Japanese Patent Laid-open No. 63-149669 is used. More particularly, as shown in Fig. 10, the charger roller 8 is rotatably mounted on the cleaning frame 14. The charger roller 8 comprises a metal roller shaft 8a, an elastic conductive layer around the roller shaft, a high resistive elastic layer around the conductive layer, and a protection film around the high resistive layer. The elastic conductive layer is formed from an elastic rubber layer made of EPDM or NBR dispersing carbon powder therein, and acts to direct the bias voltage to the roller shaft 8a. Further, the high resistive elastic layer is made of urethane rubber dispersing a small amount of conductive fine powder (for example, carbon powder), and acts to prevent the abrupt reduction of the bias voltage by limiting the leak current to the photosensitive drum 7 even when the charger roller having high conductivity such as a pin hole is opposed to the photosensitive drum 7. Further, the protection film is made of N-methyl methoxyl nylon and acts to prevent the deterioration of the surface of the photosensitive drum 7 if the plastic material of the conductive elastic layer and/or the high resistive elastic layer is contacted with the photosensitive layer. The roller shaft 8a is attached to the frame 14 via bearings 23, 24 slidable slightly toward the photosensitive drum 7, which bearings are biased toward the photosensitive drum 7 by springs 25, thereby contacting the charger roller 8 with the photosensitive drum 7. In the image forming operation, the charger roller 8 is rotatingly driven by the rotation of the photosensitive drum 7 while applying the DC voltage and AC voltage in the overlapped fashion to the charger roller 8 as mentioned above, thereby uniformly charging the surface of the photosensitive drum 7. To this end, a metal contact member 26 having a spring feature is contacted with one end of the metal roller shaft 8a, thereby permitting the application of the voltage from the image forming apparatus to the charger roller 8. Further, a regulating member 14b for suppressing the deformation of the contact member 26 is formed on the cleaning frame 14 so that, even if any force directing toward the left in Fig. 10 is applied to the roller shaft 8a resulting from the dropping of the process cartridge B or the like, the contact member 26 is prevented from being deformed plastically by contacting the contact member 26 against the regulating member 14b. Further, since the regulating member 14b limits the axial movement (toward the left in Fig. 10) of the charger roller 8, the charger roller 8 is always maintained on the photosensitive drum 7. On the other hand, the positioning of the other end of the charger roller 8 is effected by the bearing 24. That is to say, as shown in Fig. 10, the bearing 24 has a hooked abutment portion 24a integrally formed therewith. By abutting the other end of the roller shaft 8a of the charger roller 8 against the abutment portion 24a, the right (Fig. 10) axial movement of the charger roller 8 is limited. The bearing 24 is made of polyacetal (POM) which has the good anti-wear feature and provides the good slidability with respect to the metal roller shaft 8a. As mentioned above, the both ends of the roller shaft 8a are abutted against the anti-wear bearing 24 and the contact member 26 to limit the axial movement of the charger roller 8, thereby preventing the roller shaft 8a from contacting with the frame 14. If the axial movement of the charger roller 8 is limited by abutting the ends of the roller shaft 8a against the frame 14 directly, the frame 14 must be made from material such as polyphenylene oxide resin (PPO) having the good anti-wear feature with respect to the metal roller shaft 8a. To the contrary, as in the illustrated embodiment, when the roller shaft 8a is not directly contacted with the frame 14, it is not required to increase the anti-wear ability of the frame 14. Thus, in the illustrated embodiment, the frame 14 can be made of polystyrene resin (PS) which is more cheap, rather than PPO, thereby reducing the manufacturing cost of the process cartridge B. Incidentally, the material of the bearing 24 is not limited to polyacetal, but may be other material such as nylon, so long as the material has the high anti-wear ability with respect to the metal roller shaft 8a. According to the illustrated embodiment, the voltage applied to the charger roller 8 to charge the photosensitive drum 7 has an AC component Vpp of about 1800 V and DC component VDC1 of about -670 V, and the constant current control is effected. (Exposure Portion): The exposure portion 9 serves to form an electrostatic latent image on the photosensitive drum 7 uniformly charged by the charger roller 8, by exposing the light image from the optical system 1 onto the photosensitive drum. As shown by the perspective view in Fig. 4, the exposure portion is constituted by an opening portion 9 which is formed in an upper surface between the developing frame 13 and the cleaning frame 14 and through which the image light passes. That is to say, by providing a rectangular notch 9a in an upper surface 13r of the developing frame 13 and by arranging an upper wall portion 14n of the cleaning frame 14 to cover a portion of the notch 9a, the exposure portion 9 is formed. (Developing Means): Next, the developing means will be explained. The developing means serves to visualize the electrostatic latent image formed on the photosensitive drum 7 by the aforementioned exposure with toner to form a toner image. Incidentally, although the image forming apparatus A can utilize both magnetic toner and non-magnetic toner, in the illustrated embodiment, an example that a process cartridge B containing magnetic toner as one-component magnetic developer is mounted to the image forming apparatus is shown. The magnetic toner used in the developing operation utilizes polystyrene resin as the binding resin, and preferably utilizes styrene acrylic resin. Coloring material which can be added to the magnetic toner may be conventional carbon black, copper phthalocyanine, iron black or the like. Further, magnetic fine particles included in the magnetic toner are made from material which can be magnetized in the magnetic field and which may be ferromagnetic metal powder such as iron, cobalt, nickel, or alloy or compound such as magnetite or ferrite. As shown by the sectional view in Fig. 3, the developing means 10 for forming the toner image with the magnetic toner has a toner reservoir 10a for containing toner, and a toner feed member 10b for feeding out the toner is disposed in the toner reservoir 10a, which feed member is rotated in a direction shown by the arrow. Further, by using the fed out toner and by rotating a developing sleeve 10d having a magnet 10c therein, a thin toner layer is formed on the developing sleeve. When the toner layer is formed on the developing sleeve 10d, the friction charging charge sufficient to develop the electrostatic latent image on the photosensitive drum 7 can be obtained due to the friction between the toner and the developing sleeve 10d. Further, a developing blade 10e for regulating a thickness of the toner layer is provided to abut against the surface of the developing sleeve 10d. In the illustrated embodiment, as the developing bias, the AC component Vpp of about 1600 V and the DC component VDC2 of about -500 V are applied. Incidentally, in a relation between the DC component VDC2 of this developing bias and the DC component VDC1 of the aforementioned charging bias, if a value (VDC1 - VDC2) becomes greater than -50 V (becomes greater toward the plus side), it is feared that the fog occurs. Incidentally, the toner reservoir 10a and the toner feed member 10b are formed in the toner frame 12; whereas, the developing sleeve 10d and the developing blade 10e are attached to the developing frame 13. Longitudinal abutment portions of the frames 12, 13 are bonded to each other by ultrasonic welding, thereby integrally connecting these frames. The developing sleeve 10d on which the toner layer is formed and the photosensitive drum 7 are positioned to be spaced apart from each other with a small gap (about 250 µm). To this end, in the illustrated embodiment, as shown by the exploded perspective view in Fig. 11, abutment rings 10f each having an outer diameter greater than an outer diameter of the developing sleeve 10d by a value corresponding to the above-mentioned gap are arranged in the vicinity of both axial ends of the developing sleeve 10d and out of a toner forming area on the developing sleeve, which abutment rings are abutted against the photosensitive drum 7 out of a latent image forming area thereon. Further, a gear (helical gear) 10g is attached to one axial end of the developing sleeve 10d so that the gear 10g can be rotated together with the developing sleeve 10d. When the developing frame 13 is bonded to the cleaning frame 14, the gear 10g is meshed with the helical gear 7c of the photosensitive drum 7 so that the developing sleeve 10d can be rotated by the rotation of the photosensitive drum 7. Further, the gear 10g is meshed with a gear (not shown) connected to the toner feed member 10b, thereby transmitting the rotational force of the photosensitive drum 7 to the toner feed member 10b. With this arrangement, in the image forming operation, by the rotation of the toner feed member 10b, the toner in the toner reservoir 10a is sent to the developing sleeve 10d, where the toner layer having a constant thickness is formed on the developing sleeve 10d by the developing blade 10e, and then the toner on the developing sleeve is transferred onto the electrostatic latent image formed on the photosensitive drum 7. Incidentally, the formation of the toner layer on the developing sleeve 10d is effected by supplying the toner to only a carbon coating area of the developing sleeve 10d, and a relation between (a) the photosensitive layer area on the photosensitive drum 7 along its longitudinal (axial) direction and (b) the charging area affected by the charger roller 8 and (c) the toner layer forming area (developing area) on the developing sleeve 10d is so selected to become (a) > (b) > (c). Incidentally, the toner in the toner reservoir 10a must be prevented from leaking between the developing sleeve 10d and the developing frame 13. To this end, in the illustrated embodiment, as shown in Fig. 11, toner leak preventing elastic seals 10h are arranged on both longitudinal end portions of an opening 13a which is formed in the developing frame 13 and through which the toner is fed toward the developing sleeve 10d, and an elastic blow sheet 10i is arranged along a lower edge of the opening 13a to contact with the whole length of the developing sleeve 10d. Now, a thickness of each toner leak preventing seal 10h is equal to a thickness of a stepped portion formed on a lower edge 130 of the developing frame 13 so that, when the toner leak preventing seals 10h are adhered to the developing frame 13, upper surfaces of the seals 10h become flush with the lower edge 13o. The blow sheet 10i is adhered to an upper surface of the lower edge portion 130 by a both-sided adhesive tape (not shown). A (longitudinal) length of the blow sheet 10i is longer than a (longitudinal) length of the opening 13a, and both longitudinal end portions of the blow sheet are overlapped with the toner leak preventing seals 10h, and a (widthwise) free edge of the blow sheet is urged against the peripheral surface of the developing sleeve 10d along its length with an appropriate urging force. The overlapped relation between the blow sheet and the toner leak preventing seals will now be fully described. Since the thickness of the developing blade 10e is about 13 mm, as shown in Fig. 12, both longitudinal end portions of the developing blade 10e and the toner leak preventing seals 10h cannot be overlapped, with the result that a small gap 10k is created between the end of the developing blade and each toner leak preventing seal. And, the toner leak preventing seals 10h are overlapped with the blow sheet 10i at areas axially outwardly of the gaps 10k. Thus, when the toner layer is formed on the developing sleeve 10d, the toner tm passing through the gaps 10k is adhered to the developing sleeve 10d in a swelled condition. However, since there is no toner leak preventing seals 10h in the rotating areas of the toner tm, the toner tm is collected to the toner reservoir 10a through the blow sheet 10i, thereby preventing the toner from leaking out of the cartridge. Further, Fig. 13A shows a section taken along the line A - A in Fig. 11, and Fig. 13B shows a section taken along the line B - B in Fig. 11. As shown in Fig. 13A, the toner leak preventing seals 10h and the blow sheet 10i are closely contacted with each other without bending at the overlapped areas, and they become in parallel with each other. If the blow sheet 10i is bent and not closely contacted with the toner leak preventing seals 10h as shown in Figs. 14A and 14B, it is feared that the toner leaks between a gap between the seals and the sheet. However, in the illustrated embodiment, since the blow sheet 10i is not bent and is closely contacted with the toner leak preventing seals 10h, the risk of the leakage of toner can be avoided. Further, in the illustrated embodiment, an abutment angle between the free edge portion of the blow sheet 10i and the peripheral surface of the developing sleeve 10d is defined by the upper surfaces of the toner leak preventing seals 10h, and there is no dispersion in the accuracy of the upper surfaces of the toner leak preventing seals. Thus, there is substantially no dispersion in the initial setting accuracy of the abutment angle. Further, since the blow sheet 10i is used in the straight condition, the abutment angle of the blow sheet 10i is difficult to change for a long time. Thus, the toner contained in the toner reservoir 10a is hard to leak between the blow sheet 10i and the developing sleeve 10d. Incidentally, regarding the leakage of toner, it is feared that the toner is leaked between the developing blade 10e and the developing frame 13. To avoid this, in the illustrated embodiment, as shown by the sectional views in Figs. 3 and 15, three longitudinal ribs 13b, 13c, 13d are formed on a portion of the developing frame 13 against which the developing blade 10e is abutted, so that the first and second ribs 13b, 13c are abutted against the developing blade 10e and the third rib 13d is abutted against a blade attachment member 10j such as a metal plate for attaching the developing blade 10e. Further, a free edge of the second rib 13c abutted against the developing blade 10e is sharpened so that, when the first rib 13b is abutted against the developing blade 10e and the third rib 13d is abutted against the blade attachment member 10j, the sharpened edge of the second rib 13c is penetrated into the developing blade made of rubber having a thickness of about 1.3 mm. Further, the sharpened edge of the second rib 13c is curved so that a central portion of the edge in the longitudinal direction is convexly protruded slightly more than both end portions of the edge. Now, when the developing blade 10e is attached to the developing frame 13, since portions of the blade attachment member 10j near both longitudinal edges are secured by screws, the longitudinal central portion of the developing blade attached to the blade attachment member may be deflected. However, according to the above arrangement, even if the central portion of the blade is deflected, since the edge of the second rib 13c is curved so that the central portion is protruded more than both end portions (in a process cartridge capable of recording an image on A4 size sheet, it is preferable to protrude by 0.1 - 0.5 mm), the rib 13c can be surely penetrated into the developing blade 10e along its whole longitudinal edge. Accordingly, there is no gap between the developing frame 13 and the blade 10e, thus preventing the toner from leaking between the blade and the developing frame. If a gap is created between the second rib 13c and the developing blade 10e and the toner is leaked therebetween, since the third rib 13d is abutted against the blade attachment member 10j, the leakage of toner is prevented by the third rib. Particularly, since the abutment area between the second rib 13c and the developing blade 10e is offset (i.e. not aligned) with respect to the abutment area between the third rib 13d and the blade attachment member 10j by an amount corresponding to the thickness of the developing blade 10e, the toner is hard to leak out of the cartridge through both the abutment area between the second rib 13c and the developing blade 10e and the abutment area between the third rib 13d and the blade attachment member 10j. Further, in the developing means 10 according to the illustrated embodiment, there is provided a toner remaining amount detection mechanism for detecting the toner remaining in the toner reservoir 10a. As shown in Figs. 11 and 15, this mechanism comprises a metallic antenna wire 27 arranged at a jointed zone between the toner frame 12 and the developing frame 13 and in a toner passage from the toner reservoir 10a to the developing sleeve 10d. By acting the antenna wire 27 as a first electrode and the developing sleeve 10d as a second electrode, the voltage is applied between the first and second electrodes. In this case, if there is any toner between the electrodes, the electrostatic capacity therebetween will be increased; whereas, if there is no toner between the electrodes, the electrostatic capacity will be decreased. Accordingly, by detecting the change in the electrostatic capacity by a control portion 60 (refer to Fig. 59), it is possible to detect the toner remaining amount. By comparing an electric signal representative of the electrostatic capacity with a predetermined reference value, it is possible to detect a "no toner" condition. When the "no toner" condition is detected by the control portion 60, for example, a lamp (alarm for process cartridge exchange) is lightened to inform an operator of the need for exchanging the process cartridge B. Incidentally, a concrete circuit for detecting the toner remaining amount will be described later. Regarding the jointed zone between the toner frame 12 and the developing frame 13, since the longitudinal jointed area is welded, the toner cannot leak through this jointed area. However, the widthwise jointed areas cannot be welded, because, as shown in Fig. 11, an opening 12e formed in the toner frame 12 is sealingly covered by a cover film 28 to prevent the leakage of the toner in the toner reservoir 10a of the process cartridge B and a free end of the cover film 28 is exposed outwardly through the widthwise jointed area (between the frames 12, 13) so that in use the operator can pull the free end of the cover film 28 to open the opening 12e. Therefore, in order to prevent the toner from leaking through the widthwise jointed areas between the toner frame 12 and the developing frame 13, toner leak preventing seals 29 are disposed at the widthwise jointed areas. However, as mentioned above, since the voltage is applied to the antenna wire or line 27, one end of the antenna line 27 must be protruded outwardly through the jointed zone between the frames 12, 13 and a contact portion 27a is formed on the end of the antenna line. To this end, the antenna line 27 must be protruded outwardly through the widthwise jointed area (between the toner frame 12 and the developing frame 13) where the toner leak preventing seal 29 is adhered. In order to attach the antenna line 27 in this way, as shown in Fig. 16, a recess 13e is formed in the developing frame 13 at its jointed zone, and an adhesive 30 such as silicone is coated on the surface of the recess 13e, and then the antenna line 27 is adhered to the developing frame 13 by inserting the antenna line into the recess. When the antenna line 27 is inserted into the recess 13e, as shown in Fig. 16, the adhesive 30 coated on the surface of the recess 13e is projected from the recess and swollen. If the adhesive 30 is cured in the swelled condition, even when the toner leak preventing seal 29 is adhered to the frame 13, the seal 29 cannot be closely contacted with the developing frame 13 completely, thereby often creating a clearance 31. Although such clearance 31 is small, since the toner comprises fine particles, it is feared that the toner is leaked through the clearance 31. To avoid this, in the illustrated embodiment, as shown in Fig. 17A, after the antenna line 27 is inserted into the recess 13e having the adhesive 30 therein, the adhesive swollen from the recess 13e is flattened or averaged along and on the antenna line 27 (as completely covering the antenna line 27) by a rod member or the like as shown in Fig. 17B. Thereafter, as shown in Fig. 17C, when the toner leak preventing seal 29 is adhered to the frame 13, the seal 29 can be closely contacted with the surface (to be jointed) of the developing frame 13 without any clearance, thereby preventing the leakage of toner completely. Incidentally, when the swelled adhesive 30 is averaged as shown in Fig. 17B, new adhesive may be added to average the adhesive and completely cover the antenna line 27. Further, the contact portion 27a of the antenna line 27 is exposed outwardly. Therefore, it is feared that the exposed portion of the antenna line 27 is erroneously struck against any body by the operator during the handling of the process cartridge B. Since the toner leak preventing seal 29 is made of foam urethane having a thickness of about 4 mm and is elastic, if the exposed portion of the antenna line 27 is struck against any body, as shown in Fig. 18A, it is feared that the antenna line 27 is floated from the developing frame 13. Also in this case, a small clearance 32 is created between the frame 13 and the antenna line 27, resulting in the leakage of toner. To avoid this, in the illustrated embodiment, as shown in Fig. 18B, a bent portion 27b bent in an L-shape directing from the developing frame 13 to the toner frame 12 is formed on the antenna line 27 disposed in the jointed zone between the toner frame 12 and the developing frame 13. At this bent portion 27b, since the seal 29 having the thickness of about 4 mm is compressed up to about 1 mm, the elastic deformation does not occur. Accordingly, if the shock acts on the exposed portion of the antenna line 27 as mentioned above, the antenna line 27 does not float from the recess 13e of the developing frame 13. Thus, since the clearance as shown in Fig. 18A is not created, the risk of the leakage of the toner can be avoided. (Toner Leak Preventing Seal): Next, the toner leak preventing seal 29 will be explained. The toner leak preventing seals 29 are adhered to both longitudinal end portions of the opening 12e of the toner frame 12 by both-sided tapes. As shown in Fig. 11, on the upper surface of the toner leak preventing seal 29 disposed at a side where the operator draws out the cover film 28, a tear preventing sheet 29a having a width narrower than a width of the seal 29 and a thickness of about 0.01 - 1 mm is adhered. The reason why the tear preventing sheet 29a is provided is as follows. That is to say, in use, the operator must draw out the cover film 28 by hand to open the opening 12e of the process cartridge B. In this case, there is no problem when the operator pulls the cover film 28 in a film draw-out direction (corresponding to the longitudinal direction of the opening 12e). However, as shown in Fig. 19, when the cover film is pulled in a direction inclined with respect to the film draw-out direction by an angle α, as shown in Fig. 20, the width of the cover film 28 is shortened or wrinkled by gathering the sheet in one direction (upward direction in Fig. 20), with the result that the creases of the sheet are rubbed against the toner leak preventing seal 29, thereby often tearing a portion (hatched area) of the seal 29. If the toner leak preventing seal 29 is torn or broken, the toner is leaked through the broken portion of the seal, thus smudging the operator's hand or often dropping into the image forming apparatus to smudge the recorded recording medium. However, as in the illustrated embodiment, when the tear preventing sheet 29a is adhered to the toner leak preventing seal 29 through which the cover film 28 is drawn out, if the creases are created during the pulling of the cover film 28, since the tear preventing sheet 29a protects the seal 29, the seal 29 is prevented from tearing. Accordingly, regardless of the direction along which the operator draws out the cover film 28, the leakage of the toner can be prevented. Further, by providing the tear preventing sheet 29a along the width of the seal 29 at a side of the opening 12e, while the cover film 28 is being drawn out, the toner adhered to the film 28 is scraped by the tear preventing sheet 29a, thereby eliminating the possibility that the operator's hand is smudged by the drawn-out film 28. Incidentally, when the toner frame 12 and the developing frame 13 are welded to each other, since the toner leak preventing seal 29 and the tear preventing sheet 29a are firmly pinched between and secured by the frames 12, 13 at both longitudinal ends thereof (upper and lower ends in Fig. 11), the sheet 29a is not deviated from the seal 29. The tear preventing sheet 29a is preferably made from material which is strong against the rubbing to the cover-film 28, for example, such as polyethylene terephthalate or high dense polyethylene. Further, when the tear preventing sheet 29a having the width smaller than the width of the toner leak preventing seal 29 is adhered to the seal 29, as shown in Fig. 21, the adhering position of the sheet 29a is spaced apart from an edge 29b of the toner leak preventing seal 29 in the film draw-out direction by a distance U. By doing so, while the cover film 28 is being drawn out, the toner adhered to the film 28 is scraped by the edge 29b more effectively. And, when the distance is selected to be about 5 mm or less, the tear preventing effect regarding the toner leak preventing seal 29 is not worsened during the draw-out of the cover film 28. Incidentally, as mentioned above, the tear preventing sheet 29a may have a width not small than the width of the toner preventing seal 29 so that the sheet are adhered to the whole surface of the seal 29. (Various Sizes of Photosensitive Drum and the like): Next, various sizes of the photosensitive drum 7, charger roller 8 and developing sleeve 10d according to the illustrated embodiment, and the positional relation between these elements will be explained with reference to Figs. 22 and 23. However, the present invention is not limited to such example, but other sizes and positional relation may be adopted appropriately. (1) Number of teeth of helical gear 7c 32; (2) Diameter (D1) of helical gear 7c about 31.85 mm; (3) Width (W1) of helical gear 7c about 9.8 mm; (4) Number of teeth of gear flange 7d 43; (5) Diameter (D2) of gear flange 7d about 32 mm; (6) Width (W2) of gear flange 7d about 5.6 mm; (7) Length (L1) of photosensitive drum 7 about 254 mm; (8) Length (L2) of photosensitive body coating area on photosensitive drum 7 about 250 mm (9) Diameter (D3) of photosensitive drum 7 about 30 mm; (10) Diameter (D4) of metal shaft 21 of photosensitive drum 7 about 10 mm; (11) Length (L3) of developing sleeve 10d about 246 mm; (12) Length (L4) of carbon coating area on developing sleeve 10d about 216 mm; (13) Diameter (D5) of developing sleeve 10d about 16 mm; (14) Outer diameter (D6) of ring member 10f about 16.5 mm; (15) Length (L5) of ring member 10f about 12 mm; (16) Length (L6) of ring member 10f about 9 mm; (17) Outer diameter (D7) of drum abutment portion of ring member 10f about 16.7 mm; (18) Thickness (El) of drum abutment portion of ring member 10f about 0.3 mm; (19) Width (W3) of drum abutment portion of ring member 10f about 4 mm; (20) Number of teeth of developing gear 10g 17; (21) Diameter (D8) of developing gear 10g about 18.1 mm; (22) Width (W4) of developing gear 10g about 8.3 mm; (23) Length (L7) of charging bias contact 49 about 7 mm; (24) Width (W5) of charging bias contact 49 about 7.8 mm; (25) Length (L8) of charging bias contact 48 about 6 mm; (26) Width (W6) of charging bias contact 48 about 9.4 mm; (27) Diameter (D9) of contact portion 27a of antenna line 27 about 2 mm; (28) Width (W7) of contact portion 27a of antenna line 27 about 15.5 mm; (29) Length (L8) of charger roller 8 about 251 mm; (30) Length (L9) of charging portion (rubber portion) of charger roller 8 about 225 mm; (31) Diameter (D10) of charger roller 8 about 12 mm; (32) Length (L10) of roller shaft 8a about 12 mm; and (33) Diameter (Dll) of roller shaft 8a about 6 mm. Incidentally, here, the helical gear 7c and the developing gear 10g are so-called helical gears, so that, when the gear 7c is subjected to the driving force from the image forming apparatus, the photosensitive drum 7 mounted with play is subjected to the thrust force directing to the gear 7c. Thus, the photosensitive drum 7 is shifted in the thrust direction by the thrust force, with the result that the photosensitive drum is abutted against the cleaning frame 14, thus positioning the photosensitive drum in the thrust direction. (Cleaning Means): The cleaning means 11 serves to remove the toner remaining on the photosensitive drum 7 after the toner image on the photosensitive drum 7 is transferred onto the recording medium 2 by the transfer means 4. As shown in Fig. 3, the cleaning means 11 comprises a cleaning blade 11a contacted with the surface of the photosensitive drum 7 and adapted to scrape off the toner remaining on the drum 7, a dip sheet 11b disposed below the blade 11a to receive and scraped toner and contacted with the surface of the photosensitive drum 7, and a waste toner reservoir 11c for collecting the received waste toner. Incidentally, the dip sheet 11b is lightly contacted with the surface of the photosensitive drum 7 so that it permits the passage of the waste toner on the photosensitive drum 7 and directs the toner removed from the photosensitive drum 7 by the blade 11a toward a direction away from the surface of the photosensitive drum 7 (i.e., toward the waste toner reservoir 11c). Similar to the developing blade 10e, the cleaning blade 11a is made of rubber and the like and is adhered to a blade attachment member 11d by a both-sided adhesive tape, which blade attachment member is attached to the cleaning frame 14 by screws. Further, the dip sheet 11b is adhered to a dip sheet adhesion surface (edge portion) 11c1 of the waste toner reservoir 11c by a both-sided adhesive tape. Now, it is necessary to prevent the waste toner collected in the waste toner reservoir 11c from leaking between both longitudinal ends of the cleaning blade 11a and the opposed cleaning frame 14. To this end, toner leak preventing seals are adhered to both longitudinal end portions of the blade 11a. However, if the toner leak preventing seals are not closely contacted with the cleaning blade 11a completely, it is feared that the toner is leaked through a gap between the seal and blade. Similarly, if the toner leak preventing seals are not closely contacted with the dip sheet adhesion surface 11c1 of the waste toner reservoir 11c, it is feared that the toner is leaked through a gap between the seal and the adhesion surface. To avoid this, in the illustrated embodiment, as shown in Fig. 24, toner leak preventing seals 11e are provided on both longitudinal ends of the cleaning blade 11a. The portions where the seals 11e are provided will be further fully described. As shown in Figs. 24 and 25, the seals 11e are adhered to both end portions of the waste toner reservoir 11c, and the both longitudinal end portions of the cleaning blade 11a are adhered to the seals 11e. Further, screen members 11c3 are formed on an upper surface 11c2 of the waste toner reservoir 11c to contact with inner surfaces of the corresponding seals 11e. Now, a method for attaching the toner leak preventing seals 11e will be explained. First of all, the cleaning blade 11a is attached to the cleaning frame 14, and then the seals 11e are attached in such a manner that edges S2 of the seals are closely contacted with both longitudinal edges S1 of the cleaning blade 11a shown in Fig. 26. In this case, if the width W1 of the seal 11e is longer than a distance L0 between the dip sheet adhesion surface 11c1 and the cleaning blade 11a, a clearance is created between a lower edge T1 of the seal 11e and the dip sheet adhesion surface 11c1, thus causing the leakage of toner. In order to prevent this, in the illustrated embodiment, the distance L0 is selected to be greater than the width L1 (L0 >L1) in tolerance and an compression amount X is given to the seal 11e. In this case, the seal 11e must be adhered to the dip sheet adhesion surface 11c1 while urging the lower edge T1 of the seal against a hatched portion T2 of the adhesion surface; however, in the illustrated embodiment, since the screen members 11c3 are provided, the waste toner is prevented from leaking while sliding laterally along the dip sheet adhesion surface. Thus, it is possible to make the compression amount X of the seal 11e substantially zero in tolerance. (Frames): Next, the frames constituting the housing of the process cartridge B will be explained. As shown in Fig. 7, the housing of the process cartridge B is constituted by the toner frame 12, developing frame 13 and cleaning frame 14. The toner frame 12 and the developing frame 13 are integrally welded to each other to form a toner developing frame C. The toner developing frame C is connected to the cleaning frame 14 in a manner as described later to form the housing of the process cartridge B. Incidentally, the frames 12, 13, 14 according to the illustrated embodiment are formed from polystyrene resin by injection molding. When the frames 12, 13, 14 are made of material having the charging feature near that of the toner component, even if the toner is rubbed against the frames during the image forming operation, the abnormal charge is not generated due to the frictional charging, thereby preventing the deterioration of the image quality. In this respect, in the illustrated embodiment, as shown in the following Table 1 (literature "Surface Polymer and Electrostatics" Surface Film Molecule Design Series 5, published from Japan Surface Science Associates, written by Yuji Murata), since the polystyrene which is material for the frames and the styren acryl which is toner component are both same styren group and have the similar charging feature, even if the toner is rubbed against the frames, the abnormal charge is not generated. Incidentally, "styren group" means a base material including styrene of 60% or more. By the way, as shown in Fig. 7, the toner reservoir 12a and the toner feed member 10b is provided in the toner frame 12. Further, as shown in Figs. 3 and 4, a plurality of longitudinal ribs 12d are formed on an outer surface of the toner frame 12, which ribs constitute a gripper portion. The widths of the ribs 12d formed on the outer surface of the toner frame 12 are gradually changed to form the R configuration wholly. Thus, when the process cartridge B is mounted or dismounted with respect to the image forming apparatus A, since the operator can easily grip the toner frame 12 without slipping, the mounting and dismounting operability is improved. Further, as shown in Fig. 7, the developing sleeve 10d and the developing blade 10e are provided on the developing frame 13. As shown in Fig. 11, although the developing blade 10e is mounted by attaching both longitudinal end portions of the blade attachment member 10j to which the blade is adhered to the frame 13 by screws, in the illustrated embodiment, prior to the attachment by the screws, the blade attachment member 10j is positioned with respect to the developing frame 13. To this end, positioning bosses 13g are uprightly formed on a blade attachment surface 13f of the developing frame 13, and holes formed in the blade attachment member 10j are fitted onto the positioning bosses 13g, thereby positioning the attachment member with respect to the frame 13. Further, as shown in Figs. 7 and 11, positioning bosses 13i are uprightly formed on an interface 13h of the developing frame 13 which is to be joined to the toner frame 12 (these positioning bosses are disposed on both longitudinal end portions of the developing frame 13, as shown in Fig. 11), and these bosses 13i are fitted into fitting holes 12c formed in the toner frame 12, thereby positioning the joint position between the developing frame 13 and the toner frame 12. In the illustrated embodiment, as shown in Fig. 27, it is so designed that the blade attachment surface 13f and the joint interface 13h of the developing frame 13 are in parallel with each other. Thus, when the developing frame 13 is formed by injection molding, since the bosses 13g for positioning the blade and the bosses 13i for positioning the toner frame are in parallel with each other, after the molding operation, only by separating molds 33 from each other in the left and right direction, the molded frame can easily be separated from the molds. Further, as shown in Fig. 7, the photosensitive drum 7, the charger roller 8, and the cleaning blade 11a, dip sheet 11b and waste toner reservoir 11c of the cleaning means 11 are provided on the cleaning frame 14. Incidentally, when the cleaning blade 11a is attached to the cleaning frame 14, similar to the attachment of the developing blade 10e as mentioned above, both longitudinal end portions of a blade attachment member 11d to which the cleaning blade is adhered are attached to the frame 14 by screws. However, prior to the attachment by the screws, the blade attachment member 11d is positioned with respect to the frame 14. To this end, as shown in Fig. 28, positioning bosses 14d are uprightly formed on a blade attachment surface 14c of the frame 14, and holes (not shown) formed in the blade attachment member 11d are fitted onto the bosses 14d, thereby positioning the attachment member with respect to the cleaning frame. In this case, it is so designed that the blade attachment surface 14c becomes perpendicular to a mold releasing direction (as shown by the arrow in Fig. 28) for molds 34. With this arrangement, since the protruded direction of the positioning bosses 14d formed on the blade attachment surface 14c is aligned with the mold releasing direction for the molds 34, the design of the molds 34 can be facilitated. Incidentally, the drum shutter 35 shown in Fig. 3 is pivotably mounted on the cleaning frame 14. The drum shutter 35 serves to open and close an opening through which the photosensitive drum 7 faces the transfer roller 4. As will be described later, the drum shutter is automatically opened when the process cartridge B is mounted to the image forming apparatus A and is automatically closed when the process cartridge is dismounted from the image forming apparatus A. (Welding between Toner Frame and Developing Frame): Now, the welding between the toner frame 12 and the developing frame 13 will be explained. The frames 12, 13 are joined to each other by ultrasonic welding. That is to say, after the opening 12e of the toner frame 12 is closed by the cover film 28, as shown in Fig. 29, the toner frame 12 is set in a recessed portion 75a of a receiving tool 75, and then a separable cover film draw-out grip 12f formed integrally with the frame 12 is bent downwardly. Then, the developing frame 13 is overlapped with the toner frame 12, and the developing frame 13 is pressed from above by a press (hold-down) tool 76. In this condition, when the ultrasonic waves are applied to the toner frame 12 and the developing frame 13, ribs 13s (Fig. 7) formed on the joint interface of the toner frame 12 are welded, thereby interconnecting the frames 12, 13. By the way, when the ultrasonic waves are applied to the frames, the frames 12, 13 are apt to deform in their widthwise directions (shown by the arrows J in Fig. 29). However, in the illustrated embodiment, since longitudinal ribs 13t are formed on the developing frame 13 as shown in Fig. 11 and the blade attachment member 10j made of a metal plate is attached to the developing frame, the developing frame has the sufficient strength to resist the deformation thereof. Furthermore, since the toner frame 12 has no reinforcement rib, the toner frame has poor strength and is generally apt to deform. However, in the illustrated embodiment, as shown in Figs. 7 and 11, flanges 12g are formed on the toner frame 12 at both lengthwise edges (upper and lower ends along lengthwise direction of opening 12e) thereof. A distance between the flanges 12g is substantially equal to the widthwise length L13 of the interface 13h of the developing frame 13, so that the interface 13h of the developing frame 13 can be fitted between the flanges 12g. Thus, when the frames 12, 13 are joined together by the ultrasonic welding, the interface 13h of the developing frame 13 is fitted between the flanges 12g of the toner frame 12 and the positioning bosses 13i of the developing frame 13 are fitted into the fitting holes 12c of the toner frame 12. Therefore, the toner frame 12 is hard to deform by the vibration generated during the ultrasonic welding operation, thereby preventing the deviation between the frames 12, 13. That is to say, since the interface 13h of the developing frame is fitted between the flanges 12g formed on the toner frame 12 along their upper and lower edges, even if the up-and-down vibration is applied to the widthwise direction of the toner frame 12, the movement of the toner frame 12 is regulated by the developing frame 13, thus preventing the formation of the toner frame and the deviation between the frames 12, 13. Further, when the frames 12, 13 are welded together, in the illustrated embodiment, since all of the frames are formed from the same material (polystyrene resin), the welding and bonding strength between the frames 12, 13 is increased extremely. Incidentally, since the developing frame 13 is not welded to the cleaning frame 14, from the view point of the improvement of the welding and bonding strength, it is not necessary to make the cleaning frame 14 by the material same as the material of the toner frame 12 and the developing frame 13. Further, in the illustrated embodiment, as mentioned above, while an example that the positioning bosses 13i of the developing frame 13 are disposed only at one lengthwise edge of the developing frame was explained, such positioning bosses 13i may be formed on both lengthwise edges of the developing frame 13. If do so, it is possible to prevent the deformation of the toner frame 12 and the developing frame 13 more positively during the welding operation and to prevent the deviation between the frames 12, 13 more positively. Further, as shown in Fig. 31, when a plurality of positioning bosses (not seen) of the developing frame and the fitting holes 12c (into which the bosses are fitted) of the toner frame 12 are arranged side by side in the longitudinal directions of the frames, the deformation of the frames and the deviation between the frames can be prevented more positively. If do so, the flanges 12g arranged on both widthwise edges of the toner frame 12 as mentioned above can be omitted. (Construction for Facilitating Assembling of Process Cartridge): In assembling the process cartridge B, the toner feed member 10b is mounted on the toner frame 12, and the opening 12e of the toner reservoir 10a containing the toner is closed by the cover film 28, and the antenna line 27 is attached. Thereafter, the developing frame 13 is welded to the toner frame. Then, the developing sleeve 10d and the like are assembled to the developing frame 13. In this case, the toner developing frame C comprising the integral developing frame 13 and toner frame 12 is securely rested on the assembling tray, and the various parts are assembled to the frame C (refer to Fig. 33). In the illustrated embodiment, as shown in Fig. 32A, a fitting hole 12a is formed in the toner frame 12 at a predetermined position, and a bottom 12b of the toner frame 12 is made flat. Thus, by inserting a member 36a formed on the assembling tray 36 into the fitting hole 12a, the toner frame 12 can easily be fixed, thereby facilitating the assembling of the parts such as the developing sleeve 10d, developing blade 10e and the like, which results in the improvement of the assembling operability. Similarly, the parts such as the cleaning blade 11a and the like are assembled to the cleaning frame 14. In the illustrated embodiment, as shown in Fig. 32B, a bottom of the cleaning frame 14 is made flat, and a fitting hole 14e is formed in the bottom of the cleaning frame. Accordingly, when the parts such as the blade 11a and the like are assembled to the cleaning frame 14, by inserting a fitting projection 37a formed on the assembling tray 37 into the fitting hole 14e, the cleaning frame 14 can easily be fixed, thereby facilitating the assembling of the parts such as the cleaning blade 11a and the like, which results in the improvement of the assembling operability. Now, the automatic assembling will be explained with reference to the accompanying drawings. First of all, regarding the assembling of the toner developing frame C, as shown in Fig. 33, with respect to the assembling tray 36 shifting in a direction shown by the arrow via conveyor rollers 36b, at a step 1 ○ the fitting hole 12a of the toner frame 12 is fitted onto the projection 36a of the assembling tray 36, at a step 2 ○ the developing blade 10e is mounted, and at a step 3 ○ the developing blade 10e is secured by screws. Then, at a step 4 ○ the developing sleeve 10d is assembled, at a step 5 ○ the developing sleeve is fixed, and at a step 6 ○ the toner developing frame C is picked up to bring it to a next step. Further, after the toner developing frame C is picked up, the assembling tray 36 is returned through a lower auxiliary line, and the step 1 ○ is repeated again. As mentioned above, by providing the fitting portion (for fitting into the assembling tray 36) in the toner frame 12, it is possible to omit a clamping step for clamping the toner frame, thereby facilitating the assembling of the toner frame 12. Next, regarding the assembling of the cleaning frame 14, as shown in Fig. 34, with respect to the assembling tray 37 shifting in a direction shown by the arrow via conveyor rollers 37b, at a step 1 ○ the fitting hole 14e of the cleaning frame 14 is fitted onto the projection 37a of the assembling tray 37, at a step 2 ○ the dip sheet 11a is adhered, at a step 3 ○ the cleaning blade 11a is mounted, and at a step 4 ○ the cleaning blade 11a is secured by screws. Further, at a step 5 ○ the photosensitive drum 7 is mounted, and at a step 6 ○ the photosensitive drum is fixed. And, at a step 7 ○ the assembled cleaning frame 14 is picked up to bring it to a next step. Further, after the cleaning frame 14 is picked up, the assembling tray 37 is returned through a lower auxiliary line, and the step 1 ○ is repeated again. Accordingly, similar to the toner developing frame C, by providing the fitting portion (for fitting into the assembling tray 37) in the cleaning frame 14, it is possible to omit a clamping step for clamping the cleaning frame 14, thereby facilitating the assembling of the cleaning frame 14. Incidentally, as shown in Fig. 4, the cleaing frame 14 is provided with locking recessed portions 140 which are gripped by the assembling machine to shift the cleaning frame between the stations during the automatic assembling operation. Incidentally, the assembling of the toner frame 12 and the cleaning frame 14 can be effected by any means other than the automatic assembling machines. For example, in simple assembling lines where the frames are assembled manually by using simple tools, by utilizing the assembling trays 36, 37, the working efficiency can be improved. After the various parts are assembled to the toner developing frame C comprising the integral toner frame 12 and developing frame 13 and to the cleaning frame 14, the toner developing frame C is joined to the cleaning frame 14. In this regard, the frames are often rested on a table. In this case, before the toner developing frame C is joined to the cleaning frame 14, the photosensitive drum 7 assembled to the cleaning frame 14 and the developing sleeve 10d assembled to the developing frame 13 are exposed outwardly. Thus, it is feared that such elements are contacted with the table to damage such elements. Particularly, the photosensitive drum 7 is a most important element for performing the image forming operation, and, even if the surface of the drum is damaged more or less, the image will be distorted or deteriorated, thereby worsening the image quality. Therefore, in the assembling operation and the like, when the frame to which the photosensitive drum 7 is assembled or the frame to which the developing sleeve 10d is assembled is rested on the table, the operator must take care not to contact the photosensitive drum 7 or the developing sleeve 10d with the table. In the illustrated embodiment, as shown in Fig. 35, protruded portions 14f are formed on edges of an open end of the cleaning frame 14 to which the photosensitive drum 7 is assembled. The photosensitive drum 7 is arranged so that the photosensitive drum is positioned inwardly (toward the cleaning frame 14) from a line connecting between tip ends of the protruded portions 14f. With this arrangement, as shown in Figs. 35 and 36, when the cleaning frame 14 is rested on the table, the protruded portions 14f are contacted with the table and the photosensitive drum 7 is not contacted with the table, thereby preventing the damage of the surface of the photosensitive drum 7. Similarly, as shown in Fig. 37, protruded portions 13j are formed on edges of an open end of the toner developing frame C to which the developing sleeve 10d is assembled. And, the developing sleeve 10d is arranged so that the developing sleeve is positioned inwardly (toward the developing frame 13) from a line connecting between tip ends of the protruded portions 13j. With this arrangement, when the developing frame 13 integrally joined to the toner frame 12 is rested on the table, the protruded portions 13j are contacted with the table and the developing sleeve 10d is not contacted with the table. In this way, since the developing sleeve 10d or the photosensitive drum 7 is not contacted with the table even when the developing frame 13 or the cleaning frame 14 is rested on the table, the inadvertent damage of the photosensitive drum 7 and the like can be prevented, thus improving the assembling operability. After the various parts are assembled to the toner frame 12, developing frame 13 and cleaning frame 14 in this way, the developing frame 13 is joined to the cleaning frame 14 to assemble the process cartridge B. The connection between the frames 13, 14 is effected by connection members 38 shown in Fig. 38. Next, the connection between the frames 13, 14 will be explained. In Fig. 38, the connection member 38 comprises a base member 38a having a threaded hole 38b through which a screw 39 is threaded, a vertical portion 38c, and a spring attachment portion 38d, which portions 38c, 38d are disposed on both sides of the threaded hole 38b. The vertical portion 38c protrudes downwardly from the base member 38a to prevent a connection projection (described later) of the developing frame 13 from falling out. The spring attachment portion 38d is disposed in parallel with the vertical portion 38c and is provided at its free end portion with a spring 38e which is protruded downwardly more than the vertical portion 38c. Arm portions 13k are provided on both longitudinal ends of the developing frame 13, and a connection projection 13m is protruded laterally from each arm portion 13k. Further, a spring receiving recessed portion 13n is formed on an upper surface of each arm portion 13k. On the other hand, connection recessed portions 14g into which the connection projections 13m are fitted are provided in the cleaning frame 14. And, a fastening portion 14h is formed on each recessed portion 14g. The fastening portion 14h has a fitting hole 14i into which the vertical portion 38c of the connection member 38 is fitted, a female threaded portion 14j into which the screw 39 is threaded, and a through hole 14k through which the spring 38e extends. To join the toner developing frame C and the cleaning frame 14, as shown in Figs. 39A and 39B, the connection projections 13m of the developing frame 13 are deeply fitted into the corresponding connection recessed portions 14g of the cleaning frame 14, and then the connection members 38 are fastened to the fastening portions 14h. That is to say, each vertical portion 38c of the connection member 38 is fitted into the hole 14i, and the spring 38e is passed through the through hole 14k and is compressed against the spring receiving recessed portion 13n of the developing frame 13. In this condition, the screw 39 is threaded into the threaded hole 38b and is fastened to the female threaded portion 14j. In this way, the toner developing frame C and the cleaning frame 14 are connected to each other for relative pivotal movement around the connection projections 13m, thereby completing the assembling of the process cartridge B. In a condition that the frames 13, 14 are interconnected, the ring members 10f are abutted against the peripheral surface of the photosensitive drum 7, thereby determining the positions of the photosensitive drum 7 and the developing sleeve 10d. Further, by spring forces of the compressed springs 38e, the developing sleeve 10d is biased toward the photosensitive drum 7 (Incidentally, in the illustrated embodiment, the spring force of the spring 38e is selected to about 2 kg to urge the developing sleeve 10d with a force of about 1 kg). Further, when the toner developing frame C is joined to the cleaning frame 14, the helical gear 7c provided at the end of the photosensitive drum 7 is meshed with the gear 10g provided at the end of the developing sleeve 10d. In the joint construction between the toner developing frame C and the cleaning frame 14 according to the illustrated embodiment, since the toner developing frame C can be mounted in a direction of the connection recessed portions 14g, the connection projections 13m can be extended outwardly (these may be extended inwardly). Thus, the frames 13, 14 can be positioned with respect to the longitudinal direction (thrust direction), thereby eliminating the need for providing thrust stoppers. Further, since the connection members 38 are inserted from the above and are fastened, the toner developing frame C can be pressurized at the same time when the connection members 38 are fastened. In this respect, conventionally, after the toner developing frame was joined to the cleaning frame, it was requried for hooking a tension spring to the frames to urge the frames against each other, with the result that a space for arranging the tension spring was required and the spring hooking operation was troublesome. However, according to the illustrated embodiment, it is possible to eliminate the provision of such tension spring and save the installation space for the tension spring. Further, when the frames are disconnected from each other, by loosening the screws 39, the compression forces of the compressed springs 38e are released, thereby permitting the very easy disassembling of the frames because of no thrust stopper. (Cartridge Mounting Construction): Next, the construction for mounting the process cartridge B to the image forming apparatus A will be explained. As shown in Figs. 5 and 6 and as mentioned above, the left guide member 17 having the first and second guide portions 17a, 17b and the right guide member 18 having the first and second guide portions 18a, 18b are formed on the frame 15 of the image forming apparatus. In correspondence to these guide members, as shown in Fig. 4 (showing the right side surface of the process cartridge B) and Fig. 40 (showing the left side surface of the cartridge), the bearing portion 14a and the shaft 21 (which are guided along the first guide portions 17a, 18a) are protruded from the left and right side surfaces of the cleaning frame 14 of the process cartridge B substantially in left/right symmetry. Further, protruded ribs 40 which are to be guided along the second guide portions 17b, 18b are arranged above the bearing portion 14a and the shaft 21 in left/right symmetry. Further, pressure surfaces 41 are formed on the upper surface of the cleaning frame 14 at both longitudinal ends thereof, which pressure surfaces are pressurized by pressure members 19 attached to the frame 15 of the image forming apparatus. Furthermore, there are provided positioning recesses 42 for receiving the abutment members 20 and for positioning the abutment members. In addition, an auxiliary rib 43 is protruded from the right side surface of the cleaning frame 14 above the protruded rib 40, as shown in Fig. 4. Further, there is provided a link portion 35a for opening and closing the drum shutter 35. The link portion 35a is pivoted in response to the mounting and dismounting movement of the process cartridge B, thereby opening and closing the drum shutter 35 connected to the link portion. Incidentally, the opening and closing of the drum shutter 35 will be described later fully. Now, the mounting and dismounting of the process cartridge B with respect to the image forming apparatus A will be explained with reference to Figs. 41 to 44. Incidentally, although the left and right sides of the process cartridge B are similarly guided by the left and right guide members 17, 18, to clarify and simplify the explanation, only the right guide member 18 will be explained. First of all, as shown in Fig. 41, after the opening/closing cover 16 of the frame 15 of the image forming apparatus is opened, the shaft 21 of the process cartridge B is rested on the first guide portion 18a, and the protruded rib 40 is rested on the second guide portion 18b. Then, as shown in Fig. 42, the shaft 21 and the protruded rib 40 are slid along the guide portions 18b, 18a to insert the process cartridge into the frame 15 of the apparatus. As a result, the pressure surfaces 41 of the process cartridge B are pressurized by the pressure members 19 of the frame 15, whereby the process cartridge B is inserted into the frame while being urged against the second guide portion 18b. Then, as shown in Fig. 43, when the protruded rib 40 exceeds the second guide portion 18b, the process cartridge B is rotated slightly in an anticlockwise direction by the urging forces of the pressure members 19, thereby supporting the shaft 21 on the first guide portion 18a. When the process cartridge B is further inserted, as shown in Fig. 44, the process cartridge B is further rotated in the anti-clockwise direction, with the result that the abutment members 20 of the frame 15 are engaged by the positioning recesses 42 of the process cartridge B. Thereafter, when the operator releases the process cartridge, as shown in Fig. 45, the shaft 21 of the process cartridge B is dropped into the bearing portion 18c by its own weight. In this case, the abutment members 20 are completely engaged by the positioning recesses 42, with the result that the process cartridge B is mounted to the frame 15 of the image forming apparatus while being pressurized by the pressure members 19. Further, in this case, the helical gear 7c of the photosensitive drum 7 is meshed with the drive gear (refer to Fig. 6) in the frame 15, thereby permitting the transmission of the driving force. Further, when the process cartridge B is mounted, the urging forces of the pressure members 19 against the process cartridge B are relieved by the lowering movement of the process cartridge B. Thus, the operator who has mounted the process cartridge B feels the "click" feeling to easily recognize the fact that the process cartridge B was positioned at the mounting position. Incidentally, the abutment members 20 of the apparatus frame 15 and the positioning recesses 42 of the process cartridge B are so arranged that abutment surfaces 20a, 42a thereof are substantially in parallel with each other. Thus, the abutment members 20 may be assembled to the frame 15 in such a manner that the abutment surfaces 20a are disposed substantially horizontally. Therefore, the design of the abutment members 20 and the assembling of the abutment members to the frame 15 can be simplified or facilitated, with the result that the dimensional error is hard to occur. Accordingly, it is easy to mount the process cartridge B to the frame 15 of the image forming apparatus correctly. Incidentally, a roller 19b is mounted on each pressure member 19, so that the sliding resistance is minimized by pressurizing the process cartridge by the rollers 19b when the process cartridge B is being shifted while pressurizing the pressure surfaces 41 by the pressure members 19. Further, in the illustrated embodiment, while the pressure surfaces 41 of the process cartridge B pressurized by the rollers 19b were formed as surface configuration, such process surfaces may be ribbed-shape to reduce the contacting area, thereby further reducing the sliding resistance. Further, as apparent from the sectional view in Fig. 1 and the perspective view in Fig. 4, the upper portion of the process cartridge B is made substantially flat, and the flat upper surface of the process cartridge is substantially in parallel with the cartridge mounting direction. Thus, the cartridge mounting space in the frame 15 of the image forming apparatus can be minimized, and the space in the process cartridge B (for example, spaces for the toner reservoir and the waste toner reservoir) can be used efficiently. On the other hand, when the process cartridge B is dismounted, as shown in Fig. 46, the process cartridge B is rotated in the anti-clockwise direction (shown by the arrow a) slightly, thereby permitting the riding of the protruded rib 40 over the stepped portion 18b1 of the second guide portion 18b, with the result that the process cartridge can be dismounted by drawing out the process cartridge as it is. Incidentally, when the process cartridge B is rotated in the anti-clockwise. direction, if the cartridge is rotated excessively, the auxiliary rib 43 (refer to Fig. 4) is abutted against the shutter cam portion 18d (and, regarding the left guide member 17, the protruded rib 40 is abutted against the rocking movement regulating guide portion (refer to Fig. 5)), thereby regulating anti-clockwise rotation of the process cartridge. Further, when the process cartridge is mounted, the auxiliary rib 43 provided at the right side of the process cartridge is inserted between the second guide portion 18b and the shutter cam portion 18d, and the protruded rib 40 provided at the left side of the cartridge is inserted between the second guide portion 17b and the rocking movement regulating guide portion 17d. Thus, the moving paths when the process cartridge B is mounted and dismounted are further regulated, thereby mounting and dismounting the process cartridge B more smoothly. (Drum Shutter Opening/Closing Construction): The drum shutter 35 is opened and closed in response to the mounting and dismounting movement of the process cartridge. Now, the opening/closing operation of the drum shutter will be explained. As shown in Fig. 4, the drum shutter 35 has the arm portion 35b pivotally mounted around a shaft 35c, and the link portion 35a is pivotally mounted on the shaft 35c for movement together with the arm portion 35b. Thus, when the link portion 35a is pivoted, the arm portion 35b is also pivoted, thereby opening and closing the drum shutter 35. Further, a link boss 35d is protruded from the arm portion 35b. By engaging the link portion 35a and the link boss 35d by the shutter cam portion 18d, the drum shutter 35 is opened and closed. The opening and closing of the drum shutter will be explained in connection with the mounting of the process cartridge B to the image forming apparatus A with reference to Figs. 41 to 45. As shown in Figs. 41 to 45, the shutter cam portion 18d provided on the right guide member 18 has a first cam portion 18d1 engaged by the link portion 35a, and a second cam portion 18d2 engaged by the link boss 35d. An inclined angle of the first cam portion 18d1 is substantially the same as that of the second guide portion 18b for guiding the protruded portion 40 of the process cartridge B, and an inclined angle of the second cam portion 18d2 is greater than that of the first cam portion 18d1. As shown in Fig. 41, when the process cartridge B is inserted and is pushed, the link portion 35a is engaged by the first cam portion 18d1 of the shutter cam portion 18d as shown in Fig. 42, thereby rotating the link portion 35a around the shaft 35c. As a result, the arm portion 35b is rotated to open the drum shutter 35; however, in this case, the drum shutter is not completely opened but is in a so-called half open condition. When the cartridge B is further pushed, as shown in Fig. 43, the rotation of the arm portion 35b causes the disengagement between the link portion 35a and the first cam portion 18d1 and at the same time the engagement between link boss 35d and the second cam portion 18d2. And, when the mounting of the process cartridge B is completed as shown in Fig. 45, the drum shutter 35 is completely opened so that the recording medium 2 fed below the cartridge does not interfere with the drum shutter. Incidentally, when the process cartridge B is drawn from the condition shown in Fig. 45 to dismount the process cartridge B from the image forming apparatus A, by a spring force of a torsion coil spring 35e locked to the arm portion 35b, the shutter cam portion 18d is engaged by the link boss 35d and then by the link portion 35a in an order opposite to the aforementioned order, thus closing the drum shutter 35. The above-mentioned drum shutter 35 serves to protect the photosensitive drum 7. In the illustrated embodiment, other than the drum shutter 35, the laser shutter is provided in the image forming apparatus A. The laser shutter constitutes a laser light path blocking means to prevent the laser light emitted from the optical system 1 to the photosensitive drum 7 from leaking from the optical unit 1a (of the image forming apparatus) in an inoperative condition of the apparatus. (Laser Light Path Blocking Means): Next, the construction of the laser light path blocking means will be explained. As shown in Fig. 47, the optical unit 1a is provided with an opening 1a1 through which the laser light is illuminated onto the photosensitive drum 7, and the laser shutter 46 is formed from a metal plate bent to cover the opening 1a1. That is to say, the laser shutter 46 has a shutter portion 46a comprising the bent metal plate, and a link portion 46b disposed at the left of the shutter portion and integrally formed therewith. The laser shutter 46 is pivotally mounted on the frame 15 of the image forming apparatus via shafts 46c. Further, in the vicinity of the left guide member 17 for guiding the process cartridge B, an arm member 47 is pivotally mounted around a shaft 47a. The arm member 47 has a free end engageable by the link portion 46b of the laser shutter 46 and is positioned to abut against the end of the process cartridge B when the cartridge B is mounted to the frame 15 of the apparatus. With this arrangement, when the process cartridge B is inserted while being guided by the left and right guide members 17, 18, an opening/closing member of the cartridge B pushes the arm member 47 in a direction shown by the arrow a in Fig. 47. As a result the free end of the arm member 47 urges the link portion 46b of the laser shutter 46, thereby rotating the shutter portion 46b in a direction shown by the arrow b. Consequently, the opening lal of the optical unit 1a is opened, thus permitting the illumination of the laser light onto the photosensitive drum 7. Further, by a biasing force of a tension spring attached to the link portion 46b of the laser shutter 46, the laser shutter 46 is always biased toward a direction to close the opening lal. Thus, when the operator dismounts the process cartridge B from the image forming apparatus A, since the urging force of the arm member 47 is released, the laser shutter 46 automatically closes the opening lal by the spring force of the spring 47b. Accordingly, other than the case where the process cartridge B is mounted to the image forming apparatus to permit the image recording operation, the laser light is prevented from illuminating onto the photosensitive drum 7 and the like from the optical unit 1a. Further, since the link portion 46b and the arm member 47 for opening and closing the laser shutter 46 are positioned in the vicinity of the left guide member 17 and opposite to the right guide member 18, the space for installing these elements can be used effectively. Accordingly, the effective use of the space can be achieved, and, thus, the apparatus can be made small-sized. Incidentally, in the illustrated embodiment, as shown in Fig. 48, the position where the projection 14m is abutted against the arm member 47 is spaced apart from the longitudinal end of the cartridge by a distance Y1 of about 5 - 6 mm. (Offset of Gripper Portion): As shown in Fig. 48, when the operator mounts the process cartridge B to the image forming apparatus A, the projection 14m (acting as an opening member) provided at the left (in longitudinal or thrust direction) shoulder portion of the process cartridge B urges the arm member 47 (for opening and closing the laser shutter 46) provided on the frame of the apparatus. Substantially at the same time, the metal shaft 21 (having a diameter X1 of about 10 mm and a protruding amount X2 of about 5 mm) protruded from the right side of the process cartridge B and acting as a drum earth is contacted with an earthing contact member (electric contact) 51 having a spring feature and provided on the frame of the apparatus. Further, the link portion provided on the right side of the cartridge B is abutted against the shutter cam portion 18d of the frame to open the drum shutter 35. Accordingly, when the cartridge B is mounted, the left side of the cartridge B in the longitudinal direction is subjected to a load for resisting to the biasing force of the spring 47b, in order to open the laser shutter 46. On the other hand, the right side of the process cartridge B is subjected to a load for deforming the contact member 51 having the spring feature due to the contact between the metal shaft 21 and the earthing contact member 51, and a load for resisting to the biasing force of the torsion coil spring 35e in order to open the drum shutter 35. In the illustrated embodiment, among the above loads, the load for opening the drum shutter 35 is greatest. As a result, when the cartridge B is inserted, the cartridge is subjected to the load offset from a longitudinal center C2 of the cartridge. Thus, in the illustrated embodiment, as shown in Fig. 48, the ribs 12d are arranged so that the longitudinal center C1 of the ribs (constituting the gripper portion of the cartridge B) is offset from the longitudinal center C2 of the process cartridge B toward a side where the link portion 35a of the drum shutter 35 and the metal shaft (conductive member) 21 are provided. That is to say, in the illustrated embodiment, the longitudinal center C1 of the ribs 12d is offset from the center C2 of the longitudinal length L11 (about 300 mm) of the process cartridge B by about 10 mm (The longitudinal center C1 of the ribs 12d is offset from a center of a recording medium convey path when the process cartridge B is mounted to the image forming apparatus A by about 10 mm or is offset from a longitudinal center of the photosensitive drum 7 of the process cartridge B by about 10 mm). With this arrangement, when the cartridge B is mounted to the image forming apparatus A, as shown in Fig. 49, the operator grips the right side from the longitudinal center C2 of the cartridge B, i.e., a side where the link portion 35a of the drum shutter 35 is provided to insert the cartridge into the frame of the apparatus. To do so, in the longitudinal direction of the cartridge B, the side where the link portion 35a is provided is subjected to a force slightly greater than the other side. Due to the offset of force, the load for opening and closing the drum shutter 35 is cancelled, whereby the cartridge B can be smoothly inserted into the image forming apparatus A without any play, as a whole. Further, since the ribs 12d are disposed in parallel with the photosensitive drum 7 arranged in the longitudinal direction of the cartridge B, when the cartridge is inserted while gripping the ribs 12d, the longitudinal direction of the cartridge can easily be maintained in perpendicular to the cartridge inserting direction, thereby easily eliminating any plays at both longitudinal ends of the cartridge during the insertion of the cartridge. Incidentally, although the gripper portion can be constituted by the ribs 12d as shown in Fig. 48, it may be constituted by a recess 73 formed in the frame as shown in Fig. 50 or may be constituted by a projection or ridge 74 formed on the frame as shown in Fig. 51. That is to say, the gripper portion may have any configuration so long as the operator can easily grip it. Further, in the illustrated embodiment, while an example that the gripper portion is arranged offset toward the side where the link portion 35a of the drum shutter 35 and the metal shaft 21 are provided was explained, the present invention is not limited to this example. For example, when the spring force of the spring 47b of the laser shutter 46 is strong and the load for resisting to the biasing force of the coil spring 35e is stronger than the load for resisting to the biasing force of the spring 47b and the load for deforming the contact member 51, the gripper portion is arranged offset toward a side where the projection 14m is provided. In this way, the gripper portion is arranged offset toward a side where the frame is subjected to the greater mounting resistance generated due to the abutment between the parts of the image forming apparatus and the frame when the process cartridge is mounted to the image forming apparatus. (Explanation of Electric Contacts): Next, the electric connection between various parts when the process cartridge B is mounted to the image forming apparatus will be explained. When the process cartridge B is mounted to the image forming apparatus A, various contact portions provided on the process cartridge B are contacted with various contact portions provided in the frame 15 of the image forming apparatus, thereby electrically connecting the process cartridge B to the image forming apparatus. That is to say, as shown in Fig. 52, the contact portion 27a (made of stainless steel in the illustrated embodiment) as the conductive member provided on the end of the antenna line 27 for detecting the toner remaining amount is exposed from the lower portion of the developing frame 13, and the developing bias contact portion 48 (made of stainless steel in the illustrated embodiment) as the conductive member for applying the developing bias to the develoing sleeve 10d is also exposed. Further, the charging bias contact portion 49 (made of stainless steel in the illustrated embodiment) as the conductive member for applying the charging bias to the charger roller 8 is exposed from the lower portion of the cleaning frame 14. More particularly, with respect to the photosensitive drum 7, the contact portion 27a of the antenna line 27 and the developing bias contact portion 48 are arranged at one side, and the charging bias contact portion 49 is arranged at the other side. Incidentally, the charging bias contact portion 49 is integrally formed with the contact member 26 (Fig. 10). In correspondence to these contacts, as shown in Fig. 53, with respect to the transfer roller 4, an antenna line contact member 50a to which the contact portion 27a of the antenna line 27 is contacted when the process cartridge B is mounted and a developing bias contact pin 50b to which the developing bias contact portion 48 is contacted are arranged at one side in the recording medium feeding direction, and a charging bias contact pin 50c to which the charging bias contact portion 49 is contacted is arranged at the other side. Incidentally, as shown in Fig. 54, the contact pins 50b, 50c are attached to respective holder covers 50d not to slip out of the holder covers and can be protruded from the holder covers. The contact pins are biased upwardly by springs 50f and are electrically connected to the wiring pattern on an electric substrate 50e to which the holder covers 50d are attached via the springs 50f. Further, among the contact portions 48, 49 to which the contact pins 50b, 50c are abutted, the charging bias contact portion 49 is configured as an arcuated shape having straight portions and a curved portion connecting between the straight portions so that the curvature is formed at a side of the pivot hinge 16a of the opening/closing cover 16. Thus, when the opening/closing cover 16 is closed around the hinge 16a toward a direction shown by the arrow c after the process cartridge B is mounted, the charging bias contact portion 49 nearest the hinge 16a and having the minimum radius of rotation can be smoothly and effectively contacted with the contact pin 50c. Further, the shaft 21 for supporting one end of the photosensitive drum 7 is made of metal, and the photosensitive drum 7 is earthed via the metal shaft 21. To this end, as shown in Figs. 6 and 48, an earthing contact member 51 comprising a leaf spring earthed via a chassis of the frame 15 and the like is provided at the bearing portion 18a of the right guide member 17 on which the shaft 21 is disposed when the process cartridge B is mounted, and, in the condition that the cartridge is mounted, the shaft 21 is contacted with the earthing contact member 51. Now, the arrangement of the electric contacts will be explained with reference to Fig. 22 and Fig. 52. As seen in Fig. 22, the contacts 48, 49 are arranged at the side of the photosensitive drum 7 opposite to the side where the helical gear 7c is provided, and at the other side (where the helical gear 7c is provided) of the photosensitive drum 7, the metal shaft 21 as the drum earthing contact is arranged. In a direction perpendicular to the longitudinal direction of the photosensitive drum 7, i.e., in the recording medium feeding direction, the developing bias contct member 48 is arranged at one side of the drum (side toward the developing means 10), and the charging bias contact member 49 is arranged at the other side (side toward the cleaning means 11). Incidentally, the metal shaft 21 as the drum earthing contact is protruded outwardly of the frame 14 and is positioned on a rotational centerline of the photosensitive drum 7. Further, the developing bias contact member 48 and the charging bias contact member 49 are arranged along a line with respect to the longitudinal direction of the photosensitive drum 7 and are disposed on both sides of the gear flange (spur gear) 7d and the photosensitive drum 7. In addition, the contact members 48, 49 are positioned inwardly of the outer end surface of the gear flange 7d of the longitudinal direction of the photosensitive drum 7. With this arrangement, it is possible to reduce the longitudinal size of the process cartridge B, and, thus, to make the process cartridge small-sized. Further, as mentioned above, the charging bias contact member 49 is arcuated outwardly. That is to say, the contact member 49 has the straight portion which becomes a leading end when the process cartridge is mounted, and is arcuated from the straight portion. With this arrangement, when the process cartridge B is mounted to the image forming apparatus A, even if there arises the dispersion in the abutment angle between the charging bias contact member 49 and the charging bias contact pin 50c of the image forming apparatus, such dispersion can be absorbed, thereby abutting the charging bias contact member 49 against the charging bias contact pin 50c surely and effectively. Although the charging bias contact member 49 is positioned forwardly when the process cartridge B is mounted to the image forming apparatus A, the contact member 49 and the contact pin 50c are not damaged during the cartridge mounting operation. Furthermore, the contact portion 27a of the antenna line 27 for detecting the toner remaining amount of the toner in the toner reservoir 10a of the developing means 10 at the side of the image forming apparatus is disposed at the same side as the developing bias contact member 48 with respect to the longitudinal direction of the photosensitive drum 7, and is spaced apart from the photosensitive drum 7 more than the developing bias contact member 48 at one lateral side (toward the developing means 10) of the photosensitive drum 7. By arranging the contacts as mentioned above, since the charging bias contact member 49 is spaced apart from the metal shaft 21 as the earthing contact, there is no risk of generating the floating capacity between the contacts, thereby stabilizing the charging voltage to avoid the charging discrepancy. That is to say, if the drum earthing contact is arranged near other contacts, the floating capacity will be generated between the wiring and contacts arranged around the drum earthing contact and such other contacts, with the result that the AC voltages used to the developing, charging and toner remaining amount detection tend to go wrong. Particularly, in the case of the charger roller that is contacted with the photosensitive drum 7 to charge the latter, since the constant current control is effected, if the AC voltage is fluctuated due to the floating capacity, it is feared that the image is deteriorated. To the contrary, by arranging the contacts as in the illustrated embodiment, the floating capacity can be eliminated, thus maintaining the AC voltage stably or normally, thereby eliminating the charging discrepancy. Further, since the developing bias contact member 48 and the charging bias contact member 49 are arranged on both sides with respect to the photosensitive drum 7, the electric interference between these contacts can be avoided. In view of the above, in the present embodiment, upon assembling the process cartridge B, the metal shaft 21 is attached to the cleaning frame 14 which supports the photosensitive member 7 in the direction protruding outwardly from the drum 7 with respect to the axial direction of the drum 7, and the contact member for charge bias 49 is attached at opposite side of the metal shaft 21 with respect to the axial direction of the drum. Furthermore, to the toner developing frame member C which supports developing means 10 the contact member for developing bias 48 is attached. This contact member 48 is located in the axial direction of the photosensitive drum 7 when the cleaning frame member 14 and the toner developing frame member C are connected to each other. Afterthen, the frame members 14 and C are connected to assemble the process cartridge B. (Toner Remaining Amount Detection and Cartridge Mount Detection Circuits): Next, the toner remaining amount detection and the process cartridge mount detection in this apparatus will be explained. In this apparatus, as mentioned above, the remaining amount of toner in the process cartridge B is detected on the basis of the change in the electrostatic capacity between the antenna line 27 provided on the cartridge and the developing sleeve 10d. To this end, a circuit shown in Fig. 55 is provided. In the circuit shown in Fig. 55, the developing sleeve 10d and the antenna line 27 constitute the equivalent capacitors. A high voltage power source HV applies a rectangular wave AC voltage (Vpp = about 1600 V) to the developing sleeve 10d. The high voltage from the high voltage power source HV has the rectangular building-up and the rectangular building-down, and is detected as the derivative wave form ANT by the electrostatic capacity between the developing sleeve 10d and the antenna line 27 and resistors R1, R2. Incidentally, a diode D1 is a clamp diode having the minus output. The derivative wave form ANT is voltage-divided by the resistors R1, R2 and is peak-detected by a first peak hold circuit comprising an operation amplifier OA1, a diode D2 and a capacitor C1, and is converted into a DC signal. Incidentally, a resistor R3 serves to discharge the capacitor C1. The electrostatic capacity between the developing sleeve 10d and the antenna line 27 depends upon an amount of toner exsisting between the developing sleeve 10d and the antenna line 27. That is to say, when the toner exists between both conductors, since the dielectric constant between the conductors increases, the electrostatic capacity between the conductors is increased. Accordingly, as the amount of the toner is decreased, since the dielectric constant between the conductors is decreased and the electrostatic capacity is also decreased, the voltage detected by the first peak hold circuit is decreased as the amount of the toner is reduced. On the other hand, the output from the high voltage power source HV is supplied to the developing sleeve 10d and is also -supplied to a derivative circuit comprised of a reference capacitor C2, a resistor R4, a resistor R5 (volume resistor) and a resistor R6. Incidentally, a diode D3 is a clamp diode having the minus output. The derivative wave form detected through the volume resistor R5 is converted into a DC signal by a second peak hold circuit comprising an operation amplifier OA2, a diode D4, a capacitor C3 and a discharging resistor R7. The volume resistor R5 is adjusted so that the output from the second peak hold circuit becomes a desired reference value (about 2.7 V in the illustrated embodiment). The output (potential of the capacitor C1 → value corresponding to the toner remaining amount) of the first peak hold circuit and the output (potential of the capacitor C3 → reference value) of the second peak hold circuit are compared by a comparator CO1, and is outputted as a signal representative of the toner remaining amount. Accordingly, when the adequate amount of toner remains between the developing sleeve 10d and the antenna line 27, the potential of the capacitor C1 is higher than the potential of the capacitor C3, and the output of the comparator CO1 becomes a high level. As the amount of toner between the developing sleeve 10d and the antenna line 27 is reduced, the potential of the capacitor C1 is decreased. When the potential of the capacitor C1 is lowered below the potential of the capacitor C3, the output of the comparator becomes a low level. Therefore, it is possible to detect the toner remaining amount on the basis of the output of the comparator CO1. Incidentally, in the illustrated embodiment, it is also detected whether the process cartridge B is mounted to the image forming apparatus A or not. That is to say, in the circuit shown in Fig. 55, when the potential of the capacitor C1 becomes smaller than a reference potential E (about 1 V in the illustrated embodient), the output of a comparator CO2 becomes the low level, thereby judging that the process cartridge B is not mounted to the image forming apparatus A. For example, when the power source is turned ON, the controller for controlling the apparatus outputs the rectangular wave form alternate current from the high voltage power source HV to the developing sleeve 10d. However, if the process cartridge B is not mounted to the image forming apparatus, since the photosensitive drum 7, developing sleeve 10d and antenna line 27 do not exist in the circuit of Fig. 55, the signal is not inputted to the operation amplifier OA1. Accordingly, in this case, the potential of the capacitor C1 becomes zero. Thus, by setting the reference potential E to the plus voltage having some margin regarding the zero level and to the potential lower than the potential of the capacitor C1 when the toner in the cartridge is empty, it is possible to detect the presence/absence of the process cartridge B. A voltage relation between the detection level of the presence of the toner remaining amount and the detection level of the presence of the cartridge mount is shown in Fig. 56. In Fig. 56, a detection reference voltage (potential of the capacitor C3) for the presence/absence of the toner remaining amount may be set to an alarm level for informing of the toner amount insufficient to perform the recording. Incidentally, in the illustrated embodiment, the reference voltage is adjusted by adjusting the volume resistor R5 (at the manufacture thereof) to the electrostatic capacity (about 7.5 pF) corresponding to the case where the toner of about 20 grams exists between the develoing sleeve 10d and the antenna line 27. Further, the detection reference voltage for the presence/absence of the cartridge mount may be obtained by voltage-dividing the voltage of the power source by resistor(s). Incidentally, in the circuit of Fig. 55, while the comparator CO2 was used to detect the presence/absence of the cartridge mount, in place of this comparator, as shown by a circuit in Fig. 57, inverters IN1, IN2 having the appropriate slice level may be used. Also in this case, it is necessary to adjust the detection voltage level from the antenna line 27 by the resistors R1, R2, R4, R5, R6 so that the outputs of the inverters IN1, IN2 do not become the low levels when there is no toner in the cartridge. Further, regarding the detection of the presence/absence of the cartridge mount, as shown in Fig. 58, when the output of the capacitor C1 is sent to the controller via a buffer amplifier BA and the A/D conversion is effected, the detection becomes more reliable. (Control Portion): Next, the control system of the image forming apparatus A will be briefly described with reference to a function block diagram shown in Fig. 59. In Fig. 59, a control portion 60 for controlling the whole image forming apparatus comprises a CPU such as a microcomputer, a ROM for storing a control program for the CPU and various data, and a RAM used as a work area for the CPU and adapted to temporarily store various data. The control portion 60 receives signals from a sensor group 61 including a sheet jam sensor and the like. Further, the control portion receives a signal from a toner remaining amount detection mechanism 61a for detecting the remaining amount of the toner in the cartridge on the basis of the change in the electrostatic capacity between the developing sleeve 10d and the antenna line 27. Further, the control portion receives an image signal from a host 62 such as a computer, a word processor or the like. On the basis of such information, the control portion 60 controls various processes such as exposure 63, charge 64 (charger roller 8 and the like), development 65 (developing sleeve 10d and the like), transfer 66 (transfer roller 4 and the like) and fixing 67 (fixing roller 5b and the like), and the feeding 68 of the recording medium (regist rollers 3d1, 3d2, discharge rollers 3f1, 3f2 and the like). Further, the control portion controls the drive of a main drive motor 71 via a counter 70 for counting the number of pulses to be applied from the control portion to a driver 69. Further, in the illustrated embodiment, the control portion 60 receives a signal representative of no toner generated as a result of the toner remaining amount detection, and performs the alarm 72 for the process cartridge exchange (for example, turning lamp or buzzer ON). (Image Forming Operation): Next, the image forming operation effected after the process cartridge B is mounted to the image forming apparatus A will be explained. When the recording medium 2 is set on the sheet supply tray 3a shown in Fig. 1 and the setting of the recording medium is detected by a sensor (not shown) or when the cassette 3h containing the recording medium 2 is set and the copy start key is depressed, the pick-up roller 3b or 3i starts to rotate, and the paired separation rollers 3c1, 3c2 and the paired regist rollers 3d1, 3d2 are rotated to feed the recording medium 2 to the image forming station. In registration with the feeding timing of the paired regist rollers 3d1, 3d2, the photosensitive drum 7 is rotated in the direction shown by the arrow in Fig. 1, and, by applying the charging bias to the charger roller 8, the surface of the photosensitive drum 7 is uniformly charged. Then, the laser light corresponding to the image signal is illuminated from the optical system 1 through the exposure portion 9 onto the photosensitive drum 7, thereby forming a latent image on the drum in response to the light illumination. At the same time when the latent image is formed, the developing means 10 of the process cartridge B is driven to rotate the toner feed member 10b, thereby feeding out the toner in the toner reservoir 10a to the developing sleeve 10d where the toner layer is formed on the sleeve 10d. By applying the voltage having the same polarity and potential as the charging polarity of the photosensitive drum 7 to the developing sleeve 10d, the latent image on the photosensitive drum 7 is visualized as the toner image. The recording medium 2 is fed between the photosensitive drum 7 and the transfer roller 4, and, by applying the voltage having the polarity opposite to that of the toner to the transfer roller 4, the toner image on the photosensitive drum 7 is transferred onto the recording medium 2. After the transferring operation, the photosensitive drum 7 is further rotated in the direction shown by the arrow in Fig. 1; meanwhile, the residual toner remaining on the photosensitive drum 7 is scraped off by the cleaning blade 11a, and the scraped toner is collected into the waste toner reservoir 10c. On the other hand, the recording medium 2 to which the toner image was transferred is sent to the fixing means 5, where the toner image is fixed to the recording medium 2 with heat and pressure. Thereafter, the recording medium 2 is discharged onto the discharge portion 6 by the discharge rollers 3e, 3f1, 3f2. Incidentally, regarding the fixing means, in the illustrated embodiment, while the so-called heat fixing type was used, other fixing means such as pressure fixing type may be used. (Recycle of Process Cartridge): Next, the recycle of the process cartridge according to the illustrated embodiment will be explained. In the past, when the toner in the process cartridge was consumed or used up, the process cartridge was dumped. Thus, the reusable parts such as rollers were also dumped together with the process cartridge. However, recently, in consideration of the protection of the earth environment, various electric equipments and electronic equipments are not dumped as conventionally, but parts of such equipments have been recycled (regenerated or reused) from the view point of the saving of resources, the saving of energy and the reduction of dust. Thus, in the process cartridge according to the illustrated embodiment, since the parts such as the charging members, developing members or cleaning members have the long service lives, such parts can be still used after the toner in the cartridge is consumed. Therefore, recently, the cartridges wherein the toner was consumed have been collected and the reusable parts have been recycled. Now, the procedure of the recycle of the process cartridge will be described. The procedure of the recycle of the process cartridge includes the following steps; that is, (1) collection, (2) sorting, (3) decomposition, (4) selection, (5) cleaning, (6) check and (7) re-assembling. These steps will be fully explained hereinbelow. (1) Collection: The used process cartridges are collected to a collection center with the aid of users and service men. (2) Sorting: The used process cartridges collected to the various collection centers are transported to a cartridge recycle factory. And, the collected process cartridges are sorted on the basis of the types. (3) Decomposition: The sorted process cartridges are decomposed to pick up parts. (4) Selection: The picked-up parts are checked to select or divide them into reusable parts and non-reusable parts which were damaged or service lives of which were expired. (5) Cleaning: Only the parts which pass the selection are cleaned to reuse new parts. (6) Check: After the cleaning, the parts are checked whether they restore their functions sufficiently and can be reused. (7) Re-assembling: A new process cartridge is assembled by using the parts which pass the check. In the recycle, the charger roller 8 and the developing sleeve 10d and the like are reused by reassembling them, and the frames 12, 13, 14 are crushed to reuse as material. In this case, if the frames 12, 13, 14 are formed from different materials, when these frames are crushed together, the different materials are mixed, thus deteriorating the mechanical feature of the material which is reused. Thus, each frame 12, 13, 14 must be crushed separately or independently. However, since the toner frame is welded to the developing frame, these frames must be separated from each other by cutting, thereby making the recycle process troublesome. To the contrary, according to the illustrated embodiment, as mentioned above, since the toner frame 12, developing frame 13 and cleaning frame 14 are formed from the same material (polystyrene resin), even when these frames 12, 13, 14 are crushed together to obtain pellets, the mechanical feature of the material is not worsened, thereby improving the recycle process. Further, in the illustrated embodiment, since the polystyrene resin which is material for the frames is the similar material to the component of the toner (both styrene group), even when the frames are crushed in a condition that the cleaning of the used cartridge is incomplete and the toner is adhered to the frames, the mechanical feature of the material is not deteriorated, unlike to the case where the different materials are mixed. Incidentally, since the cleaning frame 14 can be separated from the toner developing frame C, it is not necessary to form the cleaning frame from the same material as that of the toner developing frame so long as these frames are crushed independently; however, the cleaning frame is preferably formed from the same material as that of the toner developing frame C when these frames are formed from the material similar to the material of the toner component. However, the cleaning frame 14 must have the mechanical strength sufficient to support the photosensitive drum 7 and the like. But, as in the illustrated embodiment, when the cleaning frame 14 is formed from polystyrene resin which is material same as that of the toner developing frame C, the mechanical strength of the cleaning frame is weaker than that of a cleaning frame which is formed from polyphenylene oxide (PPO) or polyphenylene ether (PPE). Thus, as shown in Fig. 60, the cleaning frame 14 according to the illustrated embodiment is provided with an upper wall portion 14n (Figs. 4, 7 and 47 - 51) for covering an upper portion of the photosensitive drum 7 between both side walls 14p (of the frame 14) for supporting the rotary shaft of the photosensitive drum 7, thereby reinforcing the side walls 14p. Further, partition walls 14q are provided in the waste toner reservoir 11c to divide the interior of the waste toner reservoir into a plurality of chambers, and reinforcing ribs 14r are formed on the walls of each chamber at that side, thereby reinforcing the cleaning frame. Incidentally, the partition walls 14q limits the inadvertent longitudinal movement of the toner contained in the waste toner reservoir 11c, thereby preventing the waste toner from leaking from the waste toner reservoir 11c. By reinforcing the cleaning frame 14 as mentioned above, even when the cleaning frame 14 is formed from the same material (polystyrene resin) as that of the toner developing frame C, the sufficient mechanical strength can be obtained. [Other Embodiments] Next, other embodiments of various parts of the aforementioned process cartridge and image forming apparatus will be explained. (Charger Means): In the above-mentioned embodiment, while an example that the axial shifting movement of the charger roller 8 is regulated by abutting one end of the roller shaft 8a against the abutment portion 24a of the bearing 24 was explained, as another embodiment, as shown in Figs. 61 and 62, one end of the roller shaft 8a may be supported by a bearing 52 having a cylindrical bore 52a. In this arrangement, when the roller shaft 8a is biased toward a direction shown by the arrow in Fig. 61, an end face of the roller shaft 8a is abutted against a bottom 52b of the bore 52, thereby positioning the roller shaft. Accordingly, this arrangement can achieve the same advantage as that of the previous embodiment. Incidentally, the bearing 52 is preferably formed from material such as polyacetal having the good sliding feature to the metal, silimar to the bearing 24 in the previous embodiment. Further, as shown in Fig. 63, a side notch 52c may be formed in the bearing 52, and the roller shaft 8a may be forcibly inserted into the bearing while deforming the notch 52c elastically. With this arrangement, the assembling ability of the charger roller 8 is improved. Further, when the notch 52c is oriented to direct downwardly as the process cartridge B is mounted, even if a small amount of cutting debris remains in the cylindrical bore 52a, since such cutting debris drops through the notch 52c and is removed from the bore 52a, it is possible to stably rotate the roller shaft 8a in the bore 52a. Further, in the aforementioned embodiments, while an example that one end of the roller shaft 8a is supported by the bearing 24 or bearing 52 was explained, the rotary shaft of the developing sleeve 10d and the like may be supported by the bearing 24 or 52. Furthermore, in the first embodiment, while the regulating member 14b was provided for preventing the plastic deformation of the contact member 26 when the roller shaft 8a was shifted, as another embodiment, as shown in Fig. 64, a rib 53 as a regulating member may be provided on the cleaning frame 14 and the contact member 26 may be secured to the rib 53 by heat caulking and the like. With this arrangement, even when the changer roller 8 is subjected to a force P shown by the arrow in Fig. 64, the contact member 26 is abutted against the rib 53, thereby preventing the further deformation of the contact member. Thus, in use, even if the cartridge B is dropped to generate the force P during the transportation of the cartridge, it is possible to prevent the damage of the contact member 26. Further, as shown in Fig. 65, a buffer 54 made of rubber or the like may be adhered to a side surface of the rib 53 by a both-sided adhesive tape so that the buffer is interposed between the rib 53 and the contact member 26. With this arrangement, even when the charger roller 8 is subjected to a force P shown by the arrow, the plastic deformation of the contact member 26 can be prevented by the buffer 54. Further, if the end portion of the contact member 26 is not contacted with an end face of the rotating roller shaft 8a in parallel, the contact member 26 will be eccentrically contacted with the end face of the roller shaft 8a, thus causing the vibration and/or noise. However, in this embodiment, since the buffer 54 is provided, the vibration can be suppressed, thereby preventing the generation of the noise. (Developing Means): In the aforementioned first embodiment, while the three ribs 13b, 13c, 13d were formed on the developing frame 13 and the sharp wedged end of the second rib 13c was penetrated into the developing blade 10e as shown in Fig. 15, the end of the second rib may not necessarily be wedged, and, as for example, shown in Fig. 66, the edge of the second rib 13c may be sharpened as an arrow shape, and the tip end of the rib 13c may be strongly urged against the developing blade 10e. Further, in the first embodiment, as shown in Fig. 18, the bent portion 27b was formed in the antenna line 27 so that the antenna line 27 did not float from the recessed portion 13e of the developing frame 13 when the shock is applied to the exposed portion of the antenna line 27. However, the configuration of the bent portion 27b is not limited to that shown in Fig. 18, but may be semi-circular as shown in Fig. 67A or trapezoidal as shown in Fig. 67B. Further, in order to prevent the floating of the antenna line 27, other than the provision of the bent portion 27b, as shown in Fig. 68, a cut-out 13p may be formed in the developing frame 13 and the antenna line 27 may be passed through the cut-out 13p. With this arrangement, even when the antenna line 27 is subjected to an external force shown by the arrow in Fig. 68, the antenna line 27 does not float from the developing frame 13, thereby preventing the generation of the clearance or gap between the developing frame 13 and the toner leak preventing seals 29. Further, in place of the cut-out 13p, as shown in Fig. 69, a round bore 13q having a diameter which permits the passage of the antenna line 27 may be formed in the developing frame 13 and the antenna line 27 may be passed through the cylindrical bore 13q. Also with this arrangement, similar to the cut-out 13p, even when the antenna line 27 is subjected to an external force shown by the arrow in Fig. 69, the antenna line 27 does not float from the developing frame 13. Further, in the first embodiment, while the positioning of the developing sleeve 10d in the rotational direction thereof was not explained, such positioning may be effected by abutting one end of the rotary shaft of the developing sleeve against a bearing member, similar to the charger roller 8, and the bearing member may be cylindrical as shown in Figs. 61 to 63. In addition, when not only the developing sleeve 10d but also non-magnetic toner are used, the toner layer is formed on the developing sleeve 10d by a coating roller. In this case, the coating roller may be positioned by abutting one end of a roller shaft of the coating roller against a bearing member having the same construction as mentioned above. (Cleaning Means): In the aforementioned embodiment, as shown in Figs. 12, 13A and 13B, while an example that the blow sheet 10i is overlapped with the toner leak preventing seals 10h was explained, the arrangement shown in Figs. 12, 13A and 13B may be taken into consideration on the basis of the relation between the cleaning means (cleaning blade 11a, dip sheet 11b, toner leak preventing seals 11e) and the photosensitive drum 7. That is to say, the dip sheet 11b may be overlapped with the toner leak preventing seals 11e outwardly of both longitudinal ends of the cleaning blade 11a. (Others): The process cartridge according to the present invention can be suitably applied to form not only a mono-color image as mentioned above, but also a plural color image (for example, two-color image, three-color image or full-color image) by providing a plurality of developing means 10. Further, as a developing method, a conventional two-component magnetic brush developing method, cascade developing method, touch-down developing method or cloud developing method may be used. Further, regarding the charger means, in the first embodiment, while a so-called contact charging type was used, a conventional charging arrangement wherein three walls formed from tungsten wires are enclosed by a metal shield such as aluminium and positive or negative ions generated by applying high voltage to the tungsten wires are transferred onto the photosensitive drum 7 thereby to uniformly charge the surface of the photosensitive drum 7 may be used. Incidentally, the charger means may be of blade (charger blade) type, pad type, block type, rod type or wire type, other than the aforementioned roller type. Further, the cleaning means for cleaning the residual toner remaining on an image bearing member such as the photosensitive drum 7 may be constituted by a blade, a fur brush and/or a magnet brush. Further, regarding the image bearing member, as a photosensitive body, for example, organic semiconductor (OPC), amorphous silicone (A-Si), selenium (Se), zinc oxide (ZnO), or cadmium sulfide (CdS) can be used, and the shape of the image bearing member is not limited to the drum, but may be a belt. Furthermore, the process cartridge B includes an electrophotographic photosensitive body as an image bearing member, and at least one process means. Accordingly, the process cartridge may integrally incorporate therein an image bearing member and a charger means as a unit which can be removably mounted to an image forming apparatus, or may integrally incorporated therein an image bearing member and a developing means as a unit which can be removably mounted to an image forming apparatus, or may integrally incorporate therein an image bearing member and a cleaning means as a unit which can be removably mounted to an image forming apparatus, or may integrally incorporate therein an image bearing member and two or more process means as a unit which can be removably mounted to an image forming apparatus, as well as the above-mentioned one. That is to say, the process cartridge integrally incorporates therein an electrophotographic photosensitive body, and a charger means, a developing means or a cleaning means as a unit which can be removably mounted to an image forming apparatus, or integrally incorporates therein an electrophotographic photosensitive body, and at least one of a charger means, a developing means and a cleaning means as a unit which can be removably mounted to an image forming apparatus, or integrally incorporates therein an electrophotographic photosensitive body, and at least a developing means as a unit which can be removably mounted to an image forming apparatus. Further, in the aforementioned embodiments, while the laser beam printer was explained as the image forming apparatus, the present invention is not limited to the laser beam printer, but may be applied to other image forming apparatuses such as an LED printer, an electrophotographic copying machine, a facsimile system or a word processor. As mentioned above, according to the present invention, since the frames constituting the housing of the process cartridge are formed from the same material, the welding between the frames can be effected positively and strongly. Further, since the frames are formed from material similar to that of the toner, in the recycle, even when the frames having the toner adhered thereto are crushed, the mechanical feature of the material is not deteriorated, unlike to the case where different materials are mixed. Accordingly, in the recycle, it is not required for separating the frames independently, and the cleaning operation can be facilitated. Furthermore, since the frames are formed from material having the charging feature similar to that of the developer, even when the developer is rubbed against the frames during the image forming operation, the abnormal charging does not occur, thus obtaining an image with high quality. As mentioned above, according to the present invention, since the gripper portion of the cartridge is provided in such a manner that it is offset toward the position where the greater mounting load is applied to the cartridge, when the cartridge is mounted to the image forming apparatus while gripping the gripper portion by hand, it is possible to eliminate the occurrence of any play, thereby permitting the smooth mounting of the cartridge. Further, since the gripper portion is provided in parallel with the image bearing member positioned within the frame, the longitudinal direction of the cartridge can easily be aligned with a direction perpendicular to the cartridge inserting direction when the cartridge is mounted to the image forming apparatus while gripping the gripper portion by hand, thereby further reducing any play at both longitudinal sides of the cartridge during the mounting of the cartridge.

Claims: An electrophotographic process cartridge comprising a casing (12, 13, 14) containing a rotatable photosensitive drum (7), a driven gear (7c) coaxial with the drum and charging, developing and cleaning means (8, 10, 11) cooperating with the drum, the casing having a first opening (9) for passing light to the drum for forming a latent image thereon and a second opening for transferring developed images from the drum to transfer material, said cartridge being adapted to be removably inserted in a direction transverse to the axis of the drum into an electrophotographic image forming apparatus having an arrangement (17, 18) for guiding the cartridge to an operative position in the apparatus and supporting the cartridge in said operative position with said driven gear engaged with a driving gear of the apparatus, wherein said drum is mounted in said casing at a front portion thereof relative to the direction of insertion, outwardly protruding guide means (40) are provided on said casing at opposite sides of said front portion for cooperation with said guiding arrangement for effecting said guiding, and a rear portion (12a) of said casing relative to the direction of insertion is constructed so that it may be gripped by an operator for inserting the cartridge into and removing it from the apparatus, and wherein the cartridge has a drum shutter (35) mounted on the casing for movement between a closed position in which the drum shutter closes said second opening and protects the drum and an open position, and a shutter actuating mechanism having a portion (35a) which is provided at one of the sides of the casing and which is engagable with the image forming apparatus to move the shutter from the closed position to the open position upon insertion of the cartridge into the apparatus; characterised in that: the drum shutter is biased by a spring towards its closed position; and the grippable portion of the casing comprises a surface formation configured to facilitate gripping of the formation by an operator, said surface formation having a centre (C1) which is offset from a centre plane (C2) of the cartridge bisecting the drum, the offset being towards said one side of the casing. A cartridge according to claim 1, wherein said surface formation is defined by one or more ribs, recesses, ridges or projections. A cartridge according to claim 1 or 2, wherein the offset is approximately 10mm. A cartridge according to any preceding claim, wherein said gripper portion is provided on an outer surface of a portion of the casing which encases the developing means (10). A cartridge according to any one of the preceding claims and formed as a first unit (14) housing the photosensitive drum (7) and a second unit (13) housing the developing means (10). A cartridge according to claim 5, wherein the first and second units are connected together for rocking movement with respect to each other about an axis (13m) parallel to the axis of the drum. A cartridge according to claim 5 or 6, wherein the first unit contains the charging means (8) and cleaning means (11), and the second unit contains the reservoir (12) for toner for use by the developing means. A cartridge according to any preceding claim, and including a conductive member (21) for earthing said photosensitive drum by engagement with a contact on said apparatus, said conductive member being located at said one side of the casing. A cartridge according to claim 8, wherein the conductive member is arranged at an axial end of the drum. A cartridge according to claim 9, wherein said driven gear is a helical gear provided at an end of said drum, a spur gear (7d) being provided at the other end of the drum, said conductive member protruding outwardly of said helical gear in the axial direction of said drum. A cartridge according to any preceding claim, wherein said charging means comprises a roller (8) contacting the drum. A combination of a cartridge according to any preceding claim and a complementary image forming apparatus.

Inventors: IKEMOTO ISAO, KARAKAMA TOSHIYUKI, MIURA KOJI, NUMAGAMI ATSUSHI, SASAKI SHINICHI, YASHIRO MASAHIKO, IKEMOTO, ISAO, KARAKAMA, TOSHIYUKI, MIURA, KOJI, NUMAGAMI, ATSUSHI, SASAKI, SHINICHI, YASHIRO, MASAHIKO, IKEMOTO, ISAO, C/O CANON KABUSHIKI KAISHA, KARAKAMA, TOSHIYUKI, C/O CANON KABUSHIKI KAISHA, Miura, Koji, c/o Canon Kabushiki Kaisha, Numagami, Atsushi, c/o Canon Kabushiki Kaisha, SASAKI, SHINICHI, C/O CANON KABUSHIKI KAISHA, YASHIRO, MASAHIKO, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1993
Main classification: G03G15
IPC codes: G03G15, G03G21