Abstract:
Discrete disturbance features are included in a process member drive train coupling mechanism to prevent the mechanism from remaining in a disengaged position. The mechanism may include a rotatable drive receiver operative to rotate an electrophotographic imaging process member and a coupler including a driver. The driver and drive receiver may include respective mating drive features to transmit rotary drive forces to the process member. The coupling mechanism includes one or more disturbance features located at discrete radial positions relative to a rotation axis of the coupler at an interface between the driver and the drive receiver. As the coupler rotates, the disturbance feature disrupts the position of the coupler to align the driver and drive receiver and move the coupler towards an engaged position in which the first and second drive features are engaged.

Description:
BACKGROUND 
       [0001]    Process cartridges in image forming devices are typically consumable items that may be removed and/or replaced by the end user. The process cartridges often include rotating process members (e.g., photoconductive drums, developer rollers, toner paddles) that are driven by motors that are located elsewhere within the image forming device. Since the process cartridge is removable, the drive train that couples the motors and the rotating process members may include gears and/or couplers that disengage upon removal of the process cartridge. The gears and/or couplers are also configured to re-engage the process cartridge upon insertion of the process cartridge. 
         [0002]    In certain instances, the respective gears/couplers on the process cartridge may not engage the mating gears/couplers in the image forming device upon insertion of the process cartridge. This faulty engagement may be caused by several factors, including tolerance stack up, product variation, manufacturing defects, and the like. Additional problems arise in that the point of engagement of the drive train is not always readily visible or accessible to correct the engagement. As a consequence, the rotating process members may not be driven in the desired manner, rendering the process cartridge ineffective in image formation. 
       SUMMARY 
       [0003]    Embodiments of the present invention are directed to discrete disturbance features in a process member drive train coupling mechanism to prevent the mechanism from remaining in a disengaged position. The mechanism may include a rotatable drive receiver operative to rotate an electrophotographic imaging process member and a coupler including a driver The driver and drive receiver may include respective mating drive features to transmit rotary drive forces to the process member. The coupling mechanism includes one or more disturbance features located at discrete radial positions relative to a rotation axis of the coupler at an interface between the driver and the drive receiver. The disturbance feature may be formed on the driver or the drive receiver. The disturbance features may be formed as notches, protrusions, or other features that disturb the position of the coupler. As the coupler rotates, the disturbance feature disrupts the position of the coupler to align the driver and drive receiver and move the coupler towards an engaged position in which the first and second drive features are engaged. 
         [0004]    The coupler may be moveable along a rotation axis from a disengaged position in which the driver an drive receiver are not coupled and an engaged position in which the driver and drive receiver are coupled to rotate the process member. The disturbance feature engaged the drive receiver to disrupt the position of the coupling in a direction transverse to the rotation axis to move the coupling from an intermediate equilibrium position between the engaged and disengaged positions and towards the engaged position under the influence of a biasing force. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic diagram of a representative image forming apparatus having a plurality of pairs of detachable developer units and photoconductor units; 
           [0006]      FIG. 2  is a schematic diagram of a representative image forming apparatus having an openable and closable subunit; 
           [0007]      FIG. 3  is a perspective view of a pivoting coupling retraction plate assembly; 
           [0008]      FIG. 4A  is a top view of the pivoting coupling retraction plate assembly in an engaged position; 
           [0009]      FIG. 4B  is a top view of the pivoting coupling retraction plate assembly in a retracted position; 
           [0010]      FIG. 5  is a side view of an exemplary process member drive train coupling according to one embodiment; 
           [0011]      FIG. 6  is an exploded perspective view of an exemplary process member drive train coupling according to one embodiment; 
           [0012]      FIG. 7  is a perspective view of an improperly engaged process member drive train coupling according to one embodiment; 
           [0013]      FIG. 8  is a side view of an improperly engaged process member drive train coupling according to one embodiment; 
           [0014]      FIG. 9  is a graphical representation of multiple equilibrium positions for a process member drive train coupling according to one embodiment; 
           [0015]      FIG. 10  is a perspective view of an output of a process member drive train coupling including a plurality of disturbing features according to one embodiment; 
           [0016]      FIG. 11  is a side view of an output of a process member drive train coupling including a disturbing feature according to one embodiment; 
           [0017]      FIG. 12  is a side view of an output of a process member drive train coupling including a plurality of disturbing features according to one embodiment; 
           [0018]      FIG. 13  is a side view of an output of a process member drive train coupling including a plurality of disturbing features according to one embodiment; 
           [0019]      FIG. 14  is a perspective view of a process member drive train coupling including a plurality of disturbing features according to one embodiment; and 
           [0020]      FIG. 15  is a perspective view of a properly engaged process member drive train coupling according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The various embodiments disclosed herein are directed to a technique for promoting the proper engagement of a process member drive train. Embodiments disclosed herein include disturbance features that prevent a drive train coupling from remaining in a disengaged position. The embodiments may be implemented in an image forming device to improve the likelihood of properly engaging rotating process members in a removable process cartridge. To that end,  FIG. 1  depicts a representative image forming apparatus, indicated generally the numeral  10 . The image forming apparatus  10  comprises a body  12  with a top portion  11 , subunit  13  and a media tray  14 . The media tray  14  includes a main media sheet stack  16  with a sheet pick mechanism  18 , and a manual input  20 . The media tray  14  is preferably removable for refilling, and in the embodiment shown, is located on a lower section of the device  10 . One example of an image forming device including these and other features described herein is the Lexmark C52X or the C53X series of color laser printers available from Lexmark International. 
         [0022]    Within the image forming apparatus body  12  and/or in the subunit  13 , the image forming apparatus  10  includes registration rollers  22 , a media sheet transfer belt  24 , one or more removable developer units  26 , a corresponding number of removable photoconductor units  28 , an imaging device  30 , a fuser  32 , reversible exit rollers  34 , and a duplex media sheet path  36 , as well as various rollers, actuators, sensors, optics, and electronic (not shown) as are conventionally known in the image forming apparatus arts, and which are not further explicated herein. 
         [0023]    The internal components of the developer units  26  and photoconductor units  28  are briefly described (these components are not all explicitly depicted in the drawings). Each developer unit  26  is a removable cartridge that includes a reservoir holding a supply of toner, paddles to agitate and move the toner, a toner adder roll for supplying toner to a developer roll  27 , a developer roll  27  for applying toner to develop a latent image on a (separate) photoconductive drum  29 , and a doctor blade to regulate the amount of toner on the developer roll  27 . Each photoconductor unit  28  is a separate removable cartridge that includes a photoconductive (PC) drum  29 . The PC drum  29  may comprise, for example, an aluminum hollow-core drum coated with one or more layers of light-sensitive organic photoconductive materials. The photoconductor unit  28  also includes a charge roll for applying a uniform electrical charge to the surface of the PC drum  29 , a cleaner blade for removing residual toner from the PC drum  29 , and an auger to move waste toner out of the photoconductor unit  28  into a waste toner container (not shown). 
         [0024]    Each developer unit  26  mates with a corresponding photoconductor unit  28 , with the developer roll  27  of the developer unit  26  developing a latent image on the surface of the PC drum  29  of the photoconductor unit  28  by supplying toner to the PC drum  29 . In a typical color printer, four colors of toner—cyan, yellow, magenta, and black—are applied successively (and not necessarily in that order) to a print media sheet to create a color image. Correspondingly,  FIG. 1  depicts four pairs of developer units  26  and photoconductor units  28 . Each of the developer units  26  and photoconductor units  28  include rollers, drums, augers, paddles, and/or similar generally cylindrical elements that are rotationally driven from a single rotational drive input by a drive train, such as a network of gears within or appended to the respective cartridge housing. 
         [0025]    The operation of the image forming apparatus  10  is conventionally known. Upon command from control electronics, a single media sheet is “picked, ” or selected, from either the primary media stack  16  or the manual input  20 . Alternatively, a media sheet may travel through the duplex path  36  for a two-sided print operation. Regardless of its source, the media sheet is presented at the nip of a registration roller  22 , which aligns the sheet and precisely controls its further movement into the print path. 
         [0026]    The media sheet passes the registration roller  22  and electrostatically adheres to transport belt  24 , which carries the media sheet successively past the photoconductor units  28 . At each photoconductor unit  28 , a latent image is formed by the imaging device  30  and optically projected onto the PC drum  29 . The latent image is developed by applying toner to the PC drum  29  from the developer roll  27  of the corresponding developer unit  26 . The toner is subsequently deposited on the media sheet as it is conveyed past the photoconductor unit  28  by the transport belt  24 . 
         [0027]    The toner is thermally fused to the media sheet by the fuser  32 , and the sheet then passes through reversible exit rollers  34 , to land facedown in the output stack  35  formed on the exterior of the image forming apparatus body  12 . Alternatively, the exit rollers  34  may reverse motion after the trailing edge of the media sheet has passed the entrance to the duplex path  36 , directing the media sheet through the duplex path  36  for the printing of another image on the back side thereof. 
         [0028]      FIG. 2  depicts an image forming apparatus  10  wherein a subunit  14  is separated from the main housing  12  by pivoting about a hinge point  15 . At least the media sheet transport belt  24  and the photoconductor units  28  are mounted to the subunit  13 . To allow the photoconductor units  28  to clear the housing  12  when the subunit  13  is opened, the photoconductor units  28  must first be decoupled from the drive mechanism couplings  44  within the housing  12  that supply rotary power to the photoconductor units  28 . Additionally, to remove or insert a developer unit  26  from or into the housing  12 , at least the developer unit  26  of interest must be decoupled from the drive mechanism coupling (not shown) that supplies rotary power to it. Furthermore, since the developer units  26  are inserted and removed from the housing  12  in a direction at right angles to the axes of the rollers within the cartridges, the drive mechanism couplings must be decoupled to provide mechanical clearance for the removal or insertion of the developer unit  26  cartridges. 
         [0029]    In one implementation, all of the drive mechanism couplings to all developer units  26  and photoconductor units  28  may be decoupled, or retracted, simultaneously, allowing any cartridge to be removed and/or replaced without the necessity of individually retracting its drive mechanism coupling. In the illustrated embodiment, the drive mechanism couplings are retracted automatically from the cartridges whenever the subunit  13  is opened to allow access to the cartridges, without requiring conscious action on the part of the operator. According to various embodiments of the present invention, all of the drive couplers supplying rotary power to the developer units  26  and the photoconductor units  28  are retracted simultaneously, by actuation of a retraction plate  46  within a coupling retraction mechanism  40 ,  60 , as described herein. 
         [0030]    In particular, a pivoting coupling retraction mechanism according to one embodiment of the present invention is depicted in  FIG. 3 , indicated generally by the numeral  40 . The pivoting coupling retraction mechanism  40  comprises a gearbox frame  49  housing various drive components such as motors, gears, and the like, and a pivoting retraction plate  46 . Mounted to the gearbox frame  49 , and axially retained by the pivoting retraction plate  46 , is a plurality of developer unit couplers  42 , which mate with and provide rotational power to a corresponding plurality of developer units  26 . In this embodiment, the developer unit couplers  42  comprise Oldham couplings, which are capable of transferring rotary power between two parallel, but not necessarily radially aligned, shafts. Additionally mounted to gearbox frame  49 , and axially retained by the pivoting retraction plate  46 , is a plurality of photoconductor unit couplers  44 , each of which couples with and provides rotary power to a corresponding photoconductor unit  28 . 
         [0031]    The developer unit couplers  42  and photoconductor unit couplers  44  are biased in the positive z-direction (out of the page as depicted in  FIG. 3 ), such as by springs  54  (see  FIGS. 4A ,  4 B). The couplers  42 ,  44  mate with their respective input members on the removable cartridges when the pivoting retraction plate  46  is in an engaged position, and are constrained in the positive z-direction by the pivoting retraction plate  46  when it is in a retracted position. According to the present invention, all developer unit couplers  42  and photoconductor unit couplers  44  (four of each in the embodiment depicted in  FIG. 3 ) are simultaneously retracted in the negative z-direction (i.e., in an axial direction of the coupler shafts) as the pivoting retraction plate  46  moves from an engaged to a retracted position. 
         [0032]    In the embodiment depicted in  FIG. 3 , the pivoting retraction plate  46  moves from an engaged to a retracted position by pivoting about a pivot rod  48 . For instance, the pivoting retraction plate  46  pivots through an angle between about 5° and 10°.  FIGS. 4A and 4B  depict the coupling retraction operation of the pivoting coupling retraction mechanism  40 . In  FIG. 4A , the mechanism  40  is in an engaged position, with the developer unit coupler  42  coupled to a developer unit drive receiver  50 , which is affixed to the developer unit  26  (not shown). In this engaged position, the biasing spring  54  urges the developer unit coupler  42  into engagement with the developer unit drive receiver  50 . Additionally, the photoconductor unit coupler  44  is coupled to a photoconductor unit drive receiver  52 , attached to a photoconductor unit  28  (not shown). Note that all (e.g., four) pairs of developer unit couplers  42  and photoconductor unit couplers  44  are simultaneously engaged. 
         [0033]      FIG. 4B  depicts the pivoting coupling retraction mechanism  40  in a retracted position, wherein the pivoting retraction plate  46  has rotated about the pivot pin  48 . The pivoting retraction plate  46  retracts both the developer unit coupler  42  and the photoconductor unit coupler  44  laterally, in an axial direction, thus disengaging the couplers  42 ,  44  from the developer unit and photoconductor unit drive receivers  50 ,  52 , respectively. The biasing spring  54  is compressed in this disengaged position. With the couplers  42 ,  44  thus retracted, the subunit  13  holding the photoconductor units  28  may be opened (to facilitate the removal or installation of a photoconductor units  28 ), and the developer units  26  may be freely removed from, or inserted into, the housing  12  of the image forming apparatus  10 . 
         [0034]    The developer unit couplers  42  comprise Oldham couplings to improve the likelihood of properly engaging the developer unit drive receivers  50 .  FIG. 5  depicts a detail side view of a developer unit coupler  42  at a point of initial engagement with a developer unit drive receiver  50 .  FIG. 6  depicts an exploded view of the same developer unit coupler  42  and the drive receiver  50 . The developer unit coupler includes a floating intermediate member  56  that is loosely coupled between an input member  58  and an output member  60 . The developer unit coupler  42  includes a plurality of rollers  62  that are secured to the input  58  or output  60  members. The rollers  62  roll within slots  64  in the intermediate member. With this configuration, the output member  60  is free to float in the X-Y plane to account for radial misalignment between the developer unit coupler  42  and drive receiver  50 . Splines  61  on the output member  60  mate with similar features on the inside of the drive receiver  50 . The biasing spring  54  (see  FIGS. 4A ,  4 B) urges the developer unit coupler  42  in the negative Z direction and in the direction indicated by arrows B into engagement with the developer unit drive receiver  50 . The leading end  65  of the output member  60  further includes chamfers  63  to further promote engagement of the output member  60  into the drive receiver  50 . 
         [0035]    Regardless of the biasing force Band the chamfers  63 , reliable engagement between the output member  60  and the drive receiver  50  may not be guaranteed.  FIGS. 7 and 8  depict possible scenarios where the output member  60  and the drive receiver  50  are not properly engaged. In  FIG. 7 , the developer unit coupler  42  is misaligned a sufficient amount that the output member  60  rests on the outer lip  51  of the drive receiver  50 . In  FIG. 8 , the misalignment between the developer unit coupler  42  and the driver receiver  50  is less severe. However, an internal defect  53  within the drive receiver  53  prohibits further engagement of the output member  60  into the drive receiver  50 . Some examples of defects  53  that may cause this situation include machine burrs, casting flash, parting lines, wear defects, and the like. The defect  53  may be minimal, but since the developer unit coupler  42  is urged into engagement with the defect  53 , the output member  60  becomes locked against the defect  53 . Further, the defect  53  need not be isolated to the drive receiver  50 . Defects  53  located on the output member  60  may cause a similar lack of engagement. 
         [0036]    These engagement problems are depicted graphically in  FIG. 9 . In essence, the output member  60  has come to rest at a point of unstable equilibrium.  FIG. 9  shows two points of unstable equilibria that may be caused by the misalignment shown in  FIG. 7  or by the defect  53  shown in  FIG. 8 . In either case, the biasing spring  54  includes some amount of potential energy that would tend to cause the output member  60  to further engage the drive receiver  50  but for the engagement defects illustrated in  FIGS. 7 and 8 . However, in the absence of some disturbance to cause the output member  60  to move in the direction of arrow D from the unstable equilibrium to the stable equilibrium, the developer unit coupler  42  may remain engaged to the drive receiver  50  at the unstable equilibrium. 
         [0037]    To account for these possible engagement problems, one or more disturbance features  70  are incorporated into the output member  60  as shown in  FIG. 7 . The disturbance features  70  are incorporated into the leading end  65  of the output member  60 . In the illustrated embodiment, the disturbance features  70  include notches that extend through the chamfered end  63  of the output member. The disturbance features  70  may be implemented with or without the aid of a chamfer  63  at the leading end  65  of the output member  60 . The disturbance features  70  are discrete and located at a particular radial position on the output member  60 . Thus, the disturbance features  70  may contact the drive receiver  50  once per revolution of the output member  60  to disrupt the position of the output member  60  and promote engagement with the drive receiver  50 . The exemplary output member  60  includes three disturbance features that are spaced apart approximately 120 degrees about the rotation axis A of the output member  60 . In other embodiments, multiple disturbance features  70  may be spaced apart an unequal distance. Further, while  FIG. 10  depicts three disturbance members  70 , a greater or lesser number of disturbance features  70  may be incorporated into the output member  60 . 
         [0038]    Furthermore, as  FIG. 11  shows, the output member  60  may include a single disturbance feature  70 . Other types and shapes of disturbance features  70  may be used. For example,  FIG. 12  depicts a plurality of disturbance features  70  implemented as U-shaped notches in contrast with the V-shaped notches in  FIGS. 10 and 11 . Other notch shapes may be used, including for example, diamond, pyramid, circular, elliptical, round, square, trapezoidal, or other shapes that would occur to one skilled in the art. In addition, the disturbance features  70  need not be limited to notches. In one embodiment shown in  FIG. 13 , the disturbance features  70  comprise protrusions extending outward from the leading end  65  of the output member  60 . The disturbance features  70  may further include teeth, knurls, slots, grooves, undulations, or other features conceivable by those skilled in the art. Also, the disturbance features  70  need not be limited to the output member  60 .  FIG. 14  depicts an engagement between exemplary output member  60  and drive receiver  50 , where each includes respective disturbance features  70 ,  70 A. The disturbance features  70 A on the drive receiver  50  may be appropriate when the drive receiver  50  rotates itself or rotates at a mismatched speed from the output member  60 . Thus, the disturbance features  70 A on the drive receiver  50  are not necessary in all embodiments and may not be preferable in some embodiments. 
         [0039]    Upon rotation of the output member  60  from an associated drive motor (not shown) the disturbance features  70 ,  70 A on one or both of the output member  60  and drive receiver  50  may disturb the relative position of the output member  60  in the X-Y plane. The amount of disturbance is sufficient to cause the output member  60  to move into alignment with the drive receiver  50 . Consequently, the output member  60  moves from the unstable equilibrium point ( FIG. 9 ) towards the stable equilibrium point where the output member  60  becomes positively engaged with the drive receiver  50  as shown in  FIG. 15 . 
         [0040]    The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. For example, embodiments described above have contemplated an Oldham coupling implemented at the developer unit coupler  42  to engage a corresponding developer unit drive receiver  50 . Those skilled in the art should appreciate that Oldham couplings may be used to engage different process members, including but not limited to a photoconductive member, a toner adder roller, and toner agitators. Thus, the disturbance features described herein may be implemented on Oldham couplings used to drive other process members besides a developer roller. Further, the disturbance features need not be limited to use with Oldham couplings. The disturbance features may product significant opportunity for engagement of other types of drive train couplings that permit limited or significant amounts of radial play. Furthermore, the disturbance features are certainly applicable in other types of image forming devices besides the examples provided herein. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.