Abstract:
A docking system may repeatedly dock a movable sensor module relative to another module with high precision. The docking system may move with minimal constraints and several degrees of freedom. The docking system may be particularly useful for precisely locating a movable sensor module relative to another module, such as a full width array sensor relative to a photoreceptor module within an image forming apparatus. A high degree of freedom may be achieved through use of a series of at least three spherical bearing connections that enable freedom of movement about X, Y and Z axes.

Description:
BACKGROUND 
       [0001]    This disclosure generally relates to a docking system for repeatedly docking a movable sensor module relative to a module with high precision. Such a docking system may move with fewer constraints and more degrees of freedom. Such a docking system may be particularly useful for precisely locating a movable sensor module relative to another module, such as a full width array sensor relative to a photoreceptor module within an image forming apparatus. 
       SUMMARY  
       [0002]    Cross-process non-uniformities, commonly referred to as streaks, are considered to be one of the biggest customer complaints with digital production presses. Current architectures and technology sets contain a number of different streak sources that often cannot be satisfactorily controlled via design or system optimization. To achieve image quality demands of current and future customers, there is a need for systems that automatically correct for streaks and cross-process non-uniformities that may otherwise be produced. 
         [0003]    One approach to address the streaks is a service tool for a digital production press. The tool enables correction for stable sources of spatial low-frequency non-uniformities in prints, such as the raster output system (ROS) fast-scan spot size profile. A print non-uniformity is sensed using an offline spectrophotometer connected to a Portable Work Station (PWS). Corrections are made through a ROS intensity profile via a rolloff correction curve. While extremely successful in correcting for some problems, this solution does not address or help with time-varying and/or narrower streaks, which may still be present. 
         [0004]    To address the troublesome streaks, many of which are found in the developed image on a photoreceptor (P/R) belt, another approach has been attempted. This second approach relies on a closed-loop system that senses non-uniformities of developed images on the photoreceptor belt using a full width array (FWA) sensor. The system corrects for sensed non-uniformities by applying of spatial Tone Reproduction Curves (TRC) in a Contone Rendering Module (CRM). 
         [0005]    In the existing architecture, the FWA sensor is provided in a right X-Tower of the digital production press. This allows necessary patch measurements to be taken while printing (in inter-print zones), allowing corrections to be made without disrupting the printing of customer jobs. 
         [0006]    For the FWA sensor to take appropriate measurements, the FWA sensor must be mounted and located accurately in relation to the photoreceptor belt. However, because the belt must be accessible for replacement, adjustment or maintenance, it is desirable for the photoreceptor module to be movable to provide complete access to the belt. 
         [0007]      FIG. 1  shows a photoreceptor module  200  and an X-tower module  300  on which is mounted a full width array sensor  600 . To provide access to the photoreceptor belt  220  driven by drive roll  210 , the photoreceptor module  200  and/or adjacent modules, such as the X-tower  300 , must be relatively moved out of the way. In an exemplary system, the X-tower module moves in the X-direction up to 228 mm while the photoreceptor module moves up to 114 mm. Photoreceptor module  200  may then be extracted in the Z-direction to provide access to the photoreceptor belt  220 . However, because this movement alters the alignment of the FWA sensor, upon completion of the repair or replacement operation, it may become necessary to reposition the various modules so that the sensor  600  is again precisely located. 
         [0008]    In the case of an exemplary fall width array sensor, the sensor spans the entire width of the belt and has a length of about 15″. To achieve a high degree of accuracy in measurement, the sensor should maintain placement tolerances of ±0.6 mm with an angular orientation of less than ±1.5°. Because of the need to use movable modules, the placement tolerances must be repeatable upon every return of the modules to an operating position after a repair or maintenance procedure. Also, because of the large length of the sensor, this also requires precise control of the angle of the sensor about several axes to ensure that the accuracy is maintained along the entire length of the sensor. Thus, providing a precise, repositioning of the sensor has been difficult to achieve. 
         [0009]    Aspects of the disclosure describe a system that removably mounts and locates a sensor, such as a full width array (FWA) sensor, within an image forming apparatus with a desirable degree of freedom (compliance) to locate the sensor to a reference surface or module, such as the photoreceptor belt, with a desired accuracy. 
         [0010]    In accordance with aspects of the disclosure, the repositionable mounting structure may not be overly constrained, allowing an image module frame module containing the sensor to move with several degrees of freedom and contact various locating features on, the photoreceptor module without any undesirable part deflections. This freedom and minimal deflection may result in an efficient mechanical mechanism, a minimal amount of force to keep the image module in its operating position, and highly accurate positioning. 
         [0011]    In accordance with an exemplary embodiment, various modules within the image forming apparatus include the photoreceptor module, the FWA sensor, a docking module, a loading module, and a right X-tower. 
         [0012]    In accordance with aspects of the disclosure, desired degrees of freedom may be achieved through the use of a series of spherical bearings that allow limited movements about several planes and axes. 
         [0013]    In accordance with aspects of the disclosure, a docking system for repeatedly and precisely docking a full width array sensor relative to an image forming apparatus module may be provided. The docking system includes: an image forming apparatus module; inboard and outboard docking blocks fixedly mountable to the image forming apparatus near inboard and outboard sides thereof; a second module adjacent to the image forming apparatus module that is movable relative to the image forming apparatus module between a first docked position and a second undocked position; a loading module fixedly mounted within the adjacent second module; a docking module provided between the image forming apparatus module and the loading module, the docking module including a sensor fixedly mounted thereon and inboard and outboard protrusions that mate with the inboard and outboard docking blocks when the second module is in the docked position and release from the docking blocks when the second module is in the undocked position; and at least one biased plunger mounted to the loading module that applies an urging force to the docking module to retain the inboard and outboard protrusions against the docking blocks at least when the second module is in the docked position. The docking module is preferably loosely constrained with multiple degrees of freedom by three spherical bearings that are configured to allow the docking module to at least rotate about X, Y and Z axes with limited mobility when the second module is moved between the docked position and the undocked position, 
         [0014]    In accordance wit further aspects of the disclosure, an image forming apparatus may include a docking system for docking, preferably repeatedly a full width array sensor relative to the image forming apparatus. The image forming apparatus may include: a photoreceptor module including a photoreceptor belt; inboard and outboard docking blocks fixedly mounted to the photoreceptor module near inboard and outboard sides of the photoreceptor belt; a second module adjacent to the photoreceptor module that is movable relative to the photoreceptor module between a docked position and an undocked position; a loading module fixedly mounted within the adjacent second module; a docking module provided between the photoreceptor belt and the loading module, the docking module including a front plate having a full width array sensor fixedly mounted thereon, inboard and outboard side frame plates, and a back side load plate, the front plate also including inboard and outboard protrusions that mate with the inboard and outboard docking blocks when the second module is in the docked position and release from the docking blocks when the second module is in the undocked position; and at least one biased plunger mounted to the loading module that applies an urging force to the docking module to retain the inboard and outboard protrusions against the docking blocks at least when the second module is in the docked position. The image module may be loosely constrained with multiple degrees of freedom by a series of at least three spherical bearings. A first spherical bearing connection is between the docking module back side load plate and the loading module, a second spherical connection is between the inboard side surface and the back side surface of the docking mechanism, and a third spherical connection between the outboard side plate and the load plate so that the image module can at least rotate about the X, Y and Z axes with limited mobility. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Exemplary embodiments will be described with reference to the accompanying drawings, in which like numerals represent like parts, and wherein: 
           [0016]      FIG. 1  shows a side partial view of an exemplary image forming device with two relatively movable modules in the form of a photoreceptor module and an X-tower module, one of which includes a high precision sensor module; 
           [0017]      FIG. 2  shows a side view of the sensor module precisely located relative to a photoreceptor belt surface of the photoreceptor module; 
           [0018]      FIG. 3  shows a side view of a docking module on which the sensor module is precisely located with limited constraints between the photoreceptor module and the X-tower module in a docked position; 
           [0019]      FIG. 4  shows a side view of  FIG. 3  in an undocked position in which the photoreceptor module and the X-tower module are relatively moved away from each other; 
           [0020]      FIG. 5  shows a perspective view of  FIG. 3 ; 
           [0021]      FIG. 6  shows a partial side view of the photoreceptor module of  FIG. 1  showing image module rolls, a docking frame, and docking blocks; 
           [0022]      FIG. 7  shows a perspective view of  FIG. 6  showing inboard and outboard docking blocks; 
           [0023]      FIG. 8  shows a side view of an exemplary docking module on which the sensor is mounted; 
           [0024]      FIG. 9  shows a perspective view of  FIG. 8 ; 
           [0025]      FIG. 10  shows a side view of an exemplary loading module mounted within the X-tower (X-tower omitted for clarity); 
           [0026]      FIG. 11  shows a perspective view of  FIG. 10 ; 
           [0027]      FIG. 12  shows a partial perspective view of the docking module of  FIG. 9  with a rear plate omitted for clarity; 
           [0028]      FIG. 13  slows another partial perspective view of the docking module of  FIG. 9  showing the rear plate; and 
           [0029]      FIG. 14  shows a side view of the docking module of  FIG. 4  including illustrations for the degrees of freedom. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0030]    An exemplary embodiment of the disclosure will be described with reference to  FIGS. 1-14 , which show components of an exemplary docking system for use in an image forming apparatus. In this disclosure, left/right movement is referred to as “X” direction movement, up/down movement is referred to as “Y” direction movement, and in/out movement is referred to as “Z” direction movement. 
         [0031]    Various components shown in  FIG. 3-13  include a docking module  500  that supports a full width array (FWA) sensor  600  (shown in  FIG. 9 ) and a loading module  400  mounted within X-tower  300  that supports portions of the docking module  500 . 
         [0032]    Due to the mechanical architecture of such an image forming apparatus, it is desirable to locate the docking module  500  within the right X-tower  300  rather than entirely on the photoreceptor module  200 . This is because the external surface of the photoreceptor should be free of external obstacles to enable removal of the belt  220  from the photoreceptor module  200 . 
         [0033]    For the FWA sensor  600  to perform correctly, sensor  600  should be located to the photoreceptor belt  220  on photoreceptor module  200  in a specific position and attitude. For example, the focal point  602  of the sensor lens should be positioned at the photoreceptor belt surface to within a tolerance of 0.0±0.6 mm. The lens centerline should be positioned at an angle of 22.5±1.5° from perpendicular to the photoreceptor belt plane ( FIG. 2 ). The FWA lens of FWA sensor  600  also should be aligned parallel to the photoreceptor module drive roll  210  within 0.9 mm over the length of the maximum image to be read. This may include an image length of over 14 inches. 
         [0034]    However, certain maintenance or repair procedures require access to various modules. For example, a Customer Service Engineer (CSE) may require changing of a photoreceptor belt or perform maintenance to the photoreceptor module or right X-tower module. To achieve this, it may be desirable for the various modules to move relative to the imaging device or various other modules for access. In the illustrative example, the photoreceptor module  200  moves 114 mm to the right and 3 mm down and the right X-tower  300  moves 228 mm to the right and 2 mm down from a “machine operating position” to a “P/R Module undocked position.” Thus, upon completion of the necessary repair or maintenance, there is a need to efficiently return the sensor module to the desired precise position and attitude for optimal sensing. 
         [0035]      FIG. 3  shows the docking module  500  and a loading module  400  in a docked position in which a FWA sensor  600  within the module is precisely located relative to the photoreceptor belt  220  of photoreceptor module  200 . Thus, any mounting structure used for the FWA sensor  600  should be capable of allowing movement, including non-linear movement, of the modules while being capable of returning the FWA sensor  600  back to desired positioning. Preferably, this alignment is reliable and repeatable for each movement of the modules between docked and undocked positions. Although not shown in this figure, docking module  500  and loading module  400  are mounted within X-tower  300 . 
         [0036]      FIG. 4  shows the docking module  500  and loading module  400  in an undocked position upon movement of the X-tower relative to the photoreceptor module for a maintenance or repair operation. As can be seen from the drawings, docking module  500  may be loosely constrained relative to loading module  400  and photoreceptor belt  220  to allow limited movement about several axes relative to loading module  400  and photoreceptor module  200 . This ensures that the components can freely move apart yet precisely align without binding upon return to the docked position. This loose constraint also assists in movement of the various modules to the undocked separation stations while also allowing flexibility to return to the precise desired position and attitude upon return to the docked position. Additional details of the docking and alignment will be described after the following discussion of individual components. 
         [0037]    As shown in  FIGS. 3-5 , loading module  400  includes a U-shaped frame  410 . Frame  410  is fixedly mounted within X-tower  300  by suitable means (unshown). A pivot shaft  420  (better shown in  FIGS. 10-11 ) is centrally located on a front surface of frame  410  and receives a first spherical bearing  562  ( FIG. 13 ) provided within a load plate  560  ( FIG. 13 ). 
         [0038]    A pair of plunger pivot blocks  440  are provided on a top surface of frame  410  and connected to the frame through second and third spherical bearings  430 . Pivot blocks  440  each include a spring-loaded plunger  445  on a front surface. Plungers  445  provide an urging force against docking module  500  to urge module  500  towards photoreceptor module  200  to retain the docking module  500  in the docked position. These features are better shown in  FIGS. 10-11 . 
         [0039]    Docking module  500  includes several components loosely mounted to loading module  400  and several docking components fixedly mounted to the photoreceptor module  200 . As best shown in  FIGS. 6-7 , photoreceptor module  200  includes an image module isolation roll  230  and an image module backup roll  240 . Docking frames  530  that include docking blocks  540 ,  550  are located on inboard and outboard sides of the photoreceptor belt  220  in the vicinity of the rolls  230 ,  240 . One of the docking blocks ( 540 ) is provided on the outboard side while the other ( 550 ) is provided on the inboard side. Preferably, at least one of the docking blocks is shaped to accurately locate the docking frame  500  in at least one different direction than the other block. In the exemplary configuration shown, docking block  540  is a V-block in a V-shape that locates the sensor in X and Y directions while docking block  550  is in the form of a countersunk hole that locates the sensor in X, Y and Z directions. 
         [0040]    Additional components of docking module  500  are shown in  FIG. 9 and 12  and include a front housing  510  on which FWA sensor  600  is fixedly mounted, back side load plate  560 , inboard frame plate  570 , and outboard frame plate  580 . The front housing is a casting so that when connected to frame plates  570 ,  580 , the module becomes relatively rigid. A rear end of inboard frame plate  570  includes a fourth spherical bearing  572  while a rear end of outboard frame plate  580  includes a fifth spherical bearing  582 . These spherical bearings receive load plate  560  and define an axis A ( FIG. 12 ). Due to the bearings  572 ,  582  being of the spherical type, the inner race of each bearing can rotate so that the axis of each bearing can align to the other along axis A. 
         [0041]    A front end of inboard frame plate  570  includes a spherical protrusion  574  while a front end of outboard frame plate  580  includes a similar spherical protrusion  584 . Protrusions  574 ,  584  are provided to mate with and precisely align with docking blocks  540  and  550  to control position and orientation of sensor  600 . 
         [0042]    As best shown in  FIG. 13 , the load plate  560  has several features that enable movement of the module with several degrees of freedom. In particular, docking module load plate spherical bearing  562  is located at the bottom center of the plate and mounts on pivot shaft  420 . This allows rotation about axis D. Pivot shafts  564  and  566  are provided for mating with spherical bearings  582  and  572 , respectively, of the inboard and outboard frame plates  570 ,  580 . This structure allows rotation of plate  560  about axis B/C. Moreover, because of spherical bearing  562 , limited B/C axis rotation may also be possible. Spring loaded plungers  445  are received by spring loaded plunger receptacles  568  near outer top edges of the plate to urge the module  500  against docking blocks  540 ,  550 . As shown in  FIG. 13 , the vertical axis originating from the pivot point of the spherical bearing  562  is axis F and the horizontal axis originating from the pivot point of the spherical bearing  562  is axis G. 
         [0043]    For the FWA sensor  600  to be located properly to the photoreceptor belt  220 , the image module  500  should be aligned to the photoreceptor module  200  while accommodating specific linear and/or non-linear movements of the modules  200 ,  300  necessary for separation. For the docking module  500  to make proper contact with its locating features on the photoreceptor module  200 , docking module  500  needs at least the following degrees of freedom: rotation around the X, Y and Z axes. 
         [0044]    The image module inboard and outboard docking blocks  550 ,  540  are fixedly located in the photoreceptor module  200  so that when the spherical protrusions  574 ,  584  on side plates  570 ,  580  locate into them the lens of FWA sensor  600  is then correctly located relative to the photoreceptor belt  220 . Also, the lens of FWA sensor  600  is correctly aligned relative to the photoreceptor drive roll  210 . 
         [0045]    The “Y” relationship between the inboard and outboard docking blocks  550 ,  540  located in the photoreceptor module and the load plate pivot shaft  420 , located in the right X-tower  300 , sets the suitable angle of the lens of the FWA sensor  600 . 
         [0046]    When all of the subsystems are in the machine operating position they are located correctly. When the machine is placed into the photoreceptor module undocked position ( FIG. 4 ), the photoreceptor module  200 , tight X-tower  300 , and the docking module  500  lose their accurate location. The photoreceptor module  200  moves away from what locates it into a print engine. The right X-tower  300  moves away from the photoreceptor module that locates it. The docking module  500  moves away from the photoreceptor module, which locates part of it. The only subsystem that will be addressed as to how it gets its operating position back again is the docking module  500 . 
         [0047]    When the docking module  500  moves to its undocked position it rotates around the “Z” Axis (axes A and G). Once docking module  500  moves away from the photoreceptor module  200  docking module  500  is free to move (with limited movement) through all of its degrees of freedom, limited by the travel of the spherical bearings. Movement may also be limited by two image module stop blocks  700  that are mounted on the right X-tower  300 . These blocks may limit movement of the sensor side of docking module  500  (front side containing sensor  600 ). The movement limit is designed to position the inboard and outboard spherical protrusions  574  and  584  within the acceptable receiving range of docking blocks  540 ,  550  when the right X-tower  300  moves to the left (into its operating position) and makes contact with the photoreceptor module  200 . That is, the motion may be controlled to ensure that the spherical protrusions  574 ,  584  will mate with and align relative to docking blocks  540 ,  550 . In particular, stop blocks  700  may include a window  710  that receives a dowel pin  576  protruding outward from side frame plates  570 ,  580  ( FIGS. 3-4 ). Window  710  may define the boundaries of movement of the dowel pin, which controls movement of the front side of the docking module  500 . Alternatively, the stop blocks  700  may include a dowel pin and the side frame plates could include the window. In an exemplary embodiment, movement is constrained to only a few millimeters, preferably ±5 mm of left to right movement (X axis) and ±3 mm up to down movement (Y axis). 
         [0048]    As the docking module  500  moves to its operating position (docked position) it is free to move through all of its degrees of freedom as shown in  FIG. 14 . The spherical protrusions  574 ,  584  move into the respective docking blocks  540 ,  550  to precisely position the image module  500  in the X, Y and Z directions. In an exemplary embodiment, inboard docking block  550  has a conical shape and the corresponding spherical protrusion  574  has a spherical shape that interfaces therewith. The outboard docking block  540  in an exemplary embodiment has a V-shape and the corresponding spherical protrusion  584  has a complementary shape that interfaces therewith. Throughout all of the movements the spring-loaded plungers  445  apply a sufficient force to the docking module  500  to ensure proper positioning in all of its positions. Moreover, because each spring-loaded plunger mechanism  445  has a spherical bearing associated with it (bearings  430 ), the impedance that the plungers may have on the docking module  500  is minimized. 
         [0049]    A tolerance analysis of the parts involved in the disclosure indicates that if all of the piece parts are within their drawing specifications, the FWA sensor  600  will be located within its positional requirements. 
         [0050]    Docking module  500  has all of the necessary degrees of freedom to locate the FWA sensor  600  to the photoreceptor module  200  and right X-tower  300  through use of three (3) and preferably five (5) spherical bearings. This results in no undesirable deflections and no undesirable impedances to module  500  motions. Moreover, only a minimal amount of force is needed to ensure proper positioning of FWA sensor  600 . 
         [0051]    Although described with reference to a full width array sensor, the disclosure is applicable to other types of sensors that have a criticality to their placement. It is particularly applicable to sensors having any substantial width or height that requires accuracy in positioning along the entire dimension. 
         [0052]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, and are also intended to be encompassed by the following claims.