BACKGROUND 
       [0001]    Some types of printing systems (e.g., liquid electro photographic printers) include one or more binary ink developers. Printing systems that use binary ink developers are structurally complicated machines and the binary ink developer itself is a complicated and expensive device. Binary ink developers eventually must be replaced and replacement of such developers may not be easy, particularly in the face of tight tolerance requirements between the roller and other components in the printing system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]    For a detailed description of various examples, reference will now be made to the accompanying drawings in which: 
           [0003]      FIG. 1  shows a printing system in accordance with an example; 
           [0004]      FIG. 2  shows a binary ink developer (BID) assembly with its clamps in a locked position in accordance with an example; 
           [0005]      FIG. 3  shows a BID assembly with its clamps in an unlocked position in accordance with an example; 
           [0006]      FIG. 4  shows a BID assembly with its clamps in an unlocked position and the developer roller removed from the BID assembly in accordance with an example; 
           [0007]      FIG. 5  shows a close-up view of one end of the BID assembly with a clamp in an unlocked position in accordance with an example; 
           [0008]      FIG. 6  shows a close-up view of one end of the BID assembly with a clamp in a locked position in accordance with an example; 
           [0009]      FIG. 7  shows a side view of one end of the BID assembly with a clamp in locked position in accordance with an example; and 
           [0010]      FIG. 8  shows a side view of one end of the BID assembly with a clamp in an unlocked position in accordance with an example. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    One component of a binary ink developer is a developer roller. The lifespan of the developer roller may be shorter than the lifespan of the rest of the binary ink developer. The implementations described herein are directed to binary ink developer with a replaceable developer roller. The structure included in the binary ink developer roller to facilitate its removal and replacement avoids the need for tools to be used when replacing the developer roller. Further, the disclosed structure enables the developer roller to be precisely located within the binary ink developer. Precise location of the developer roller relative to a main electrode ensures proper operation of the binary ink developer. 
         [0012]      FIG. 1  illustrates an example of a printing system  10 . In the example shown in  FIG. 1 , the printing system  10  represents a liquid electro-photographic (LEP) printing system, although printing system  10  may be representative of other types of printers. As shown, the printing system  10  includes a photoconductor  12 , a charging device  14 , a photo imaging device  16 , an intermediate transfer member  20 , and an impression cylinder  24 . One or more binary ink developer (BID) assemblies  30  are also provided adjacent the photoconductor  12 . The example of  FIG. 1  includes multiple BIDs  30 , one for each color including, for example, cyan, magenta, yellow, and black as well as other colors as desired such as orange, green, violet, white, light cyan, and light magenta. The number of different colors and the particular colors can be varied as desired. 
         [0013]    In printing system  10  a uniform electrostatic charge may be applied to a photoconductive surface such as the outer surface of a photoconductor  12  by a scorotron, charge roller, or other suitable charging device  14 . The photoconductor  12  used for liquid electro photography (LEP) printing may be referred to as a photo imaging plate (PIP). A scanning laser or other suitable photo imaging device  16  exposes selected areas on photoconductor  12  to light in the pattern of the desired printed image to dissipate the charge on the areas of photoconductor  12  exposed to the light. In discharge area development (DAD), for example, the discharged areas on photoconductor  12  form an electrostatic image which corresponds to the image to be printed. This electrostatic image is a “latent” image because it has not yet been developed into a toner image. A thin layer of liquid toner is applied to the patterned photoconductor  12  using the various BID assemblies  30 . Each BID assembly  30  includes a developer roller  32  that supplies ink to the photoconductor  12  as the developer roller  32  rotates against the photoconductor  12 . 
         [0014]    The latent image on photoconductor  12  is developed through the application of liquid toner from the developer rollers  32 . The liquid toner adheres to the discharged areas of photoconductor  12  in a uniform layer of toner on photoconductor  12 , thereby developing the latent electrostatic image into a toner image. The toner image is transferred from photoconductor  12  to the intermediate transfer member  20  and then from the intermediate transfer member  20  to print medium  22  as the print medium passes through a nip  23  between intermediate transfer member  20  and the impression cylinder  24 . Print medium  22  represents generally any suitable print medium (e.g., paper) and may be delivered to printing system  10  as a continuous web dispensed from a roll or as individual sheets. A discharging device  26  (e.g., a laser) removes residual charge from photoconductor  12  and toner residue is removed at a cleaning station  28  in preparation for developing the next image or for applying the next toner color plane. 
         [0015]    Intermediate transfer member  20  may include a removable, replaceable blanket wrapped around a drum. The comparatively soft, compliant blanket is heated to drive off most of the carrier fluid component of the liquid toner. The thin layer of toner is then transferred, and simultaneously fused, to print medium  22  through the application of pressure at the nip  23  between the intermediate transfer member  20  and the impression cylinder  24 . 
         [0016]      FIG. 2  illustrates an example of a BID assembly  30 . As shown in the example, the BID assembly  30  includes a base assembly  36  which includes end caps  40  at opposing ends of the base assembly. The base assembly  36  receives the developer roller  32  at an upper end of the base assembly  36  as shown. The developer roller includes a gear, bearing, and handle assembly  48 . Each end cap  40  includes a clamp  45  that locks the developer roller  32  in place on the base assembly  36 . In  FIG. 2 , the clamps  45  are shown in a locked position. 
         [0017]      FIG. 3  shows the clamps  45  in an unlocked position. The clamps  45  are hinged to the end caps  40  and are rotated between locked and unlocked positions to remove and replace the developer roller  32 .  FIG. 4  shows the developer roller  32  removed from the base assembly  36  of the BID assembly  30 . Once the developer roller  32  is removed, a new developer roller  32  can be installed in the BID assembly  30  and locked in place by rotating the clamps to the locked position.  FIGS. 3 and 4  also show rotary bearings  47  provided on opposing ends of the developer roller  32 . The clamps  45  engage the rotary bearings  47  and apply sufficient force on the bearings to hold the developer roller in place. 
         [0018]      FIGS. 5 and 6  provide close-up views of one end of the BID assembly  30 . The developer roller  32  is not shown in  FIGS. 5 and 6 . The clamp  45  is in an unlocked position in  FIG. 5  and in a locked position in  FIG. 6 . Referring to  FIG. 5 , in one implementation the clamp  45  comprises three components—a bearing race clamp  50 , a handle  52 , and a spring member  54 . The bearing race clamp  50  is pinned to the end cap  40  as shown thereby permitting the bearing race clamp  50  to rotate between the locked and unlocked positions. The handle  52  is pinned to the bearing race clamp  50  by way of a pin  51 . As such, the handle is able to rotate about pin  51  relative to the bearing race clamp  50 . The spring member  54  in some implementations comprises a curved spring metal (e.g., steel) member. One end  57  of the spring member  54  is pinned to the handle  52  at a center portion of the handle by way of pin  59 . The opposing end  55  of the spring member  54  is formed into a hook shape that engages a retaining pin  66  provided in the end cap  40 .  FIG. 6  shows the clamp  45  in a closed position with the hook shaped end  55  of the spring member  54  engaged at the retaining pin  66 .  FIGS. 5 and 6  also illustrate a seal  72  provided at the end cap. The seal is discussed below. 
         [0019]      FIG. 7  shows a side view of an end cap  40 . The BID base assembly  36  includes a number of components. In some embodiments, the BID base assembly  36  includes a cleaning roller  100 , a sponge roller  102 , a squeezer roller  104 , a wiper  110 , a main electrode  112 , a squeegee roller  114 , and other possible components. A potential bias between the main electrode  112  and the developer roller  32  initially transfers ink to the developer roller  32 . The squeegee roller  114  regulates the ink film thickness on the developer roller  32 . Ink is then selectively transferred from the developer roller  32  to the discharged portions of the surface of the photoconductor  12  ( FIG. 1 ). 
         [0020]    The cleaning roller  100  electrically removes substantially all remaining ink from the developer roller  32 . The wiper  110  cleans the cleaning roller  100 , and the sponge roller  102  cleans the wiper  110  and remixes the ink. The squeezer roller  104  then cleans the sponge roller  102 . 
         [0021]    Referring still to  FIG. 7 , the clamp  45  in  FIG. 7  is shown in the locked position thereby locking the developer roller  32  in place. As noted above, both ends of the developer roller  32  include a rotary bearing  47 . Each rotary bearing  47  includes a bearing outer race  82  which rotates relative to a bearing inner race  80 . The bearing inner race  80  is locked to the developer roller  32  and thus rotates with the developer roller. The bearing outer race  82  can rotate independent of the bearing inner race  80  and developer roller  32 . The bearing race clamp  50  is forced into contact with the bearing outer race  82  as a result of the force created by the spring member  54 . The bearing race clamp  50  has a substantially planar portion  83  that contacts the bearing outer race  82 . 
         [0022]    The force applied by the bearing race clamp  50  on the bearing out race  82  causes the bearing outer race into contact with developer roller datum pins  60  and  62 . These pins are also shown in  FIG. 5 . As a result of the force on the developer roller&#39;s bearing outer race  82  as well as the location of the datum pins  60  and  62 , the developer roller  32  is restrained in precisely the correct position. A small gap  89  (e.g., about  500  microns in one example) between the developer roller  32  and the main electrode  142  is needed for proper operation of the developer roller. The position of the developer roller relative to the main electrode  112  is tightly controlled by the datum pins  60  and  62  and the clamp&#39;s bearing race clamp  50 . The developer roller datum pins  60  and  62  are positioned so that, when the bearing outer race  82  is clamped in place, the datum pins are approximately 120 degrees apart about the outer circular perimeter of the bearing outer race. In some implementations, the datum pins are spaced about  117  degrees apart, and the center point of contact of the bearing race clamp  50  may be spaced about 121 degrees from each datum pin  60 ,  62 . The combination of the bearing race clamp  50  and the two datum pins  60  and  62  function as a V-block clamp. 
         [0023]    The spring member  54  facilitates the correct amount of force to be applied to the developer roller&#39;s outer bearing race  82 , and thus to the developer roller itself. In some implementations, force in the range of 50-600 Newtons is generated by the action of the spring member  54 . 
         [0024]    Referring again to  FIG. 6 , developer roller datum pin  60  is shown, but datum pin  62  is hidden from view. Each datum pin is installed in the end cap  40 . In some implementations, each datum pin  60 ,  62  comprises a solid cylindrical member (circular cross sectional area) made from a suitable material such as a metal (e.g., aluminum). Each datum pin has a longitudinal dimension that extends in a direction generally orthogonal to the rotational direction of the clamps  45 . Each datum pin  60 ,  62  has a head portion  63 ,  65  that sits in a retaining portion  91  of the end cap  40 . The retaining portion  91  sits on top of seal  72 . When the clamp  45  is rotated to the locked position, the downward force on the developer roller&#39;s bearing  47  also causes the retaining portion  91  to engage the seals  47  which prevent toner fluid from penetrating from the main electrode  112  and developer  32  into the area of the end cap  40 . 
         [0025]      FIG. 8  is a similar view to that of  FIG. 7  but shows the clamp  45  in an unlocked position. With the clamp in this position, the developer roller  32  can be removed from the BID assembly  30  and replaced with a different developer roller  32 . 
         [0026]    The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.
An apparatus to receive a developer roller for a printing device. The apparatus comprises a base assembly including end caps at opposing ends. The base assembly includes a receptacle for a developer roller having rotary bearings. Each end cap includes first and second datum pins and a clamp containing a spring member. Each clamp, when locked in place in part by action of the spring member, is to push against a corresponding rotary bearing when the developer roller is installed in the base assembly. The rotary bearing being forced by the clamp into contact with the first and second datum pins to position the developer roller in the base assembly.