Process Cartridge Having Removable Drive Means

The present invention relates generally to a process kit for image-forming apparatus and more particularly to the driving system for a photosensitive member or drum contained in the process kit.

Process cartridges which are detachably mounted in copying apparatus are well known in the art. Some such cartridges are disclosed in U.S. Pat. Nos. 4,588,280; 4,591,258; 4,575,221; and 4,566,777. These cartridges typically include a photosensitive drum rotatably mounted in the cartridge housing, and generally a more or less clearance is provided between the housing or casing in order to allow smooth rotation of the photosensitive drum in the process cartridge housing. Such clearance generally results in a small longitudinal shift of the drum when the photosensitive drum is driven. One manner in which the sideways thrust is created is disclosed in U.S. Pat. No. 4,829,335, wherein longitudinal movement is created by the helical gear, and the cartridge continues to move against the main frame of the image- forming apparatus even after the initial engagement between the cartridge and the main frame. To provide the structure to permit this limited longitudinal movement, the cartridge in U.S. Pat. No. 4,829,335 is provided with a photosensitive drum having a helical gear formed on the annulus of an end member having a central opening therein to receive a shaft which is fixed to and extends from the main assembly of the copying appartaus and into the drum. The end member of the drum and the helical gear is made integral with each other and with the end of the photosensitive drum, and the drum rotates freely on the shaft.

It is, therefore, an object of the present invention to provide a process kit for use in an image-forming apparatus wherein the photosensitive drum in the process cartridge is provided with a gear for rotation thereof, the gear and the photosensitive drum cooperating in such a manner which will prevent frictional contact between the end of the photosensitive drum and the process cartridge housing and the cartridge housing and the main frame of the image-forming apparatus.

According to an embodiment of the present invention, applicant provides a structure wherein the photosensitive drum is provided with an end member made integral therewith. A helical gear is loosely mounted on the end member and is keyed thereto for longitudinal movement across the end member responsive to the initial rotation of the helical gear and the end member. The keyed gear and end member imparts rotational movement to the drum.

FIG. 1 is a partial longitudinal sectional view illustrating a process cartidge including a rotatable photosensitive drum mounted in an image-forming apparatus.

FIG. 2 is an end elevational view illustrating a helical gear mounted on an end member of the photosensitive drum assembly.

FIGS. 3-8 illustrate various configurations of keyways provided in the end member of FIG. 2 to recieve correspondingly configured keys of the gear of FIG. 2 for mating engagement.

As seen in FIG. 1, a photosensitive drum 10 is shown rotatably mounted on a shaft 12 affixed to the main frame 14 of a copying apparatus and extending into a processing cartridge housing 16 which is removably carried in the main frame 14. To support the drum at its end 17, an end member 18 having a central shaft receiving opening 20 therein is secured to the drum (as by gluing, etc.) and mounted on shaft 12. A second end member 22 is secured to drum 10 at the opposite end 24 thereof and is provided with a central shaft reciving opening 26 therein to recieve a second shaft 28 extending from an end wall 29 of cartridge housing 16.

To impart rotation to drum 10, a helical gear 30 is mounted on end member 18. Gear 30 includes a projection or key 32 (FIG. 2) extending imwardly from an annular surface 34 which forms a central opening 36 into which end member 18 fits. Key 32 extends into and is loosely received in a slot 38 provided in annular surface 40 of end member 18.

FIGS. 3-8 illustrate various configurations of the keyways. FIG. 3 illustrates a straight slot or keyway 38 with substantially straight, parallel sides 42 and 44 which extend across the width of end member 18. FIG. 4 illustrates an angled slot 38 having substantially parallel sides 45 and 46 which extend in angled relation substantially across the width of end member 18. FIG. 5 illustrates an angled slot 38 having substantially parallel sides 48 and 50 which are angled in the opposite direction from that illustrated in FIG. 4. The angled slots of members 18 shown in FIGS. 4 and 5 provide for either clockwise or counterclockwise rotation of the gear. FIG. 6 illustrates slot 38 as having a pair of sides 52 and 54 which extend across the width of member 18 in converging-diverging relationship. This arrangement provides for key 32 to ride in the slot during clockwise or counterclockwise rotation of the gear. FIG. 7 illustrates slot 38 extending across the width of member 18 and provided with a straight side 56 and an angled side 58. FIG. 8 illustrates slot 38 extending across the width of member 18 and provided with a straight side 60 and an angled side 62 which is angled in a direction opposite to the angled surface of the slot shown in FIG. 7. The slots of member 18 as shown in FIGS. 7 and 8 accommodate clockwise or counterclockwise rotation of the gear.

It is to be understood that while the drawings illustrate projection (key) 32 being on the gear and slot 38 as being on end member 18, these may be reversed, with the projection on member 18 and the key being provided on the gear.

As seen in FIG. 1, grounding spring 66 is shown and provides an electrical ground between the internal surface of the OPC drum and shaft 28. Of course, other types of ground connections may be used, such as making end member 22 of electrically conductive plastic.

It can be seen that the applicant has provided a process cartridge for an image-forming apparatus which utilizes the smooth, efficient operation provided by a helical gear for rotation of a photosensitive drum in the cartridge. The sliding gear arrangement provided by the applicant provides for discarding of the drum once the drum is no longer usable (because of scratches, etc., or because its lifetime has ended) without the necessity of discarding the helical driving gear. Additionally, it should be obvious that as a result of the sliding gear arrangement which prevents longitudinal movement of the drum, frictional contact between the gear and cartridge housing and the cartridge housing and the main frame is substantially eliminated, thus resulting in a more efficient operation of the apparatus.

It is to be understood that while the above description has been directed to rotating an OPC drum of a process cartridge, the invention should not be limited only to such use as, obviously, the structure may be also usable in the rotating mechanism for belt OPC systems. It is to be further understood that the OPC drum substrate may be comprised of metal or conductive plastics.