Patent Publication Number: US-8983321-B2

Title: Fluid delivery system and method thereof

Description:
BACKGROUND 
     Fluid delivery systems for image forming apparatuses such as liquid electrophotography printing apparatuses include providing liquid toner to fluid applicators. Subsequently, the fluid applicators provide the charged liquid toner to an image transfer member that receives images formed by the image forming apparatuses and transfer the images onto substrates such as print media. Generally, the liquid toner includes charge directors to electrically charge the liquid toner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary non-limiting embodiments of the present disclosure are described in the following description, read with reference to the figures attached hereto and do not limit the scope of the claims. In the figures, identical and similar structures, elements or parts thereof that appear in more than one figure are generally labeled with the same or similar references in the figures in which they appear. Dimensions of components and features illustrated in the figures are chosen primarily for convenience and clarity of presentation and are not necessarily to scale. Referring to the attached figures: 
         FIG. 1  is a schematic view illustrating a fluid delivery system in communication with an exemplary liquid electrophotography printing apparatus according to an example of the present disclosure. 
         FIG. 2A  is a block diagram illustrating a fluid delivery system according to an example of the present disclosure. 
         FIG. 2B  is a partial side view illustrating the fluid delivery system of  FIG. 2A  according to an example of the present disclosure. 
         FIGS. 3A and 38  are perspective views of charge reducing units of the fluid delivery system of  FIG. 2B  according to examples of the present disclosure. 
         FIG. 4A  is a block diagram illustrating a fluid delivery system of  FIG. 2A  according to an example of the present disclosure, 
         FIG. 4B  is a partial side view illustrating the fluid delivery system of  FIG. 4A  according to an example of the present disclosure. 
         FIG. 5  is a flowchart illustrating a method of controlling a charge level of fluid in a fluid chamber of a fluid delivery system according to an example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is depicted by way of illustration specific embodiments in which the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. 
     Fluid delivery systems for image forming apparatuses such as liquid electrophotography printing apparatuses provide charged liquid toner including charge directors and a carrier fluid to fluid applicators such as binary ink developers (BIDS) of the liquid electrophotography apparatuses. A fluid chamber receives each of the charge directors and carrier fluid forming the charged liquid toner and subsequently provides the charged liquid toner to a respective BID. The BID provides the charged liquid toner to a latent image on a photo imaging member, which in turn provides the image to an image transfer member such as an image transfer blanket. The image transfer blanket transfers the image onto a substrate such as print media. The fluid delivery system may include multiple fluid chambers in fluid communication with corresponding BIDS in which each fluid chamber with its corresponding BID may correspond to a different color fluid to enable color printing. 
     At times, however, a charge level of the liquid toner in the fluid chamber may change in a manner in which the charge level is no longer within a range recommended, for example, for the liquid toner to be sufficiently transferred to and from the intermediate transfer member. The charge level may rise above the recommended range due to, for example, an accumulation of charge directors on the photo imaging member as a result of periodic cleaning processes thereof, an accumulation of charge directors remaining in fluid chamber, and/or printing side effects such as electrical fatigue. Such a rise in charge level may contribute to printing defects resulting in printed images of an inferior image quality. In examples of the present disclosure, a fluid delivery system is disclosed to prevent inferior quality images from being printed and stabilize optical density. A fluid delivery system is disclosed to maintain the charge level of the fluid in the fluid chamber within a predetermined range, for example, by changing a concentration of an amount of charge directors in the fluid. A charge reducing unit is configured to decrease the charge level of the fluid of the fluid chamber and a charge increasing unit is configured to increase the charge level of the fluid based on based on a detection of at least one fluid parameter corresponding to the charge level of the fluid of the fluid chamber. 
       FIG. 1  is a schematic view illustrating a fluid delivery system in communication with an exemplary liquid electrophotography printing apparatus according to an example of the present disclosure. Referring to  FIG. 1 , a fluid deliver system  100  is usable with an image forming apparatus such as a liquid electrophotography printing apparatus (LEP)  110 . As illustrated in  FIG. 1 , the LEP  110  includes an image forming unit  120  that receives a substrate S such as a print media from an input unit  140  and outputs the substrate S to an output unit  160 . The image forming unit  120  includes a photo imaging member (PIP)  180  that defines an outer surface on which images can be formed. The outer surface may be charged with a suitable charger (not illustrated), such as a charge roller, and portions of the outer surface that correspond to features of the image can be selectively discharged by a laser writing unit  119  to form an electrostatic image on the outer surface. 
     Referring to  FIG. 1 , a fluid delivery system  100  may supply fluid such as liquid toner, for example, Electroink, trademarked by Hewlett-Packard Company, to fluid development units of the LEP  110  such as BIDs  130 . The BIDs  130  apply the fluid to the electrostatic image to form a fluid image on the cuter surface of the PIP  180  to be transferred to an intermediate transfer member (ITM)  150 . The ITM  150  is configured to receive the fluid image from the PIP  180 , heat the image, and transfer the image to the substrate S. During the transfer from the ITM  150  to the substrate S, the substrate S is pinched between the ITM  150  and an impression member  190 . Once the fluid image has been transferred to the substrate S, the substrate S can be transported to the output unit  160 . 
       FIG. 2A  is a block diagram illustrating a fluid delivery system according to an example of the present disclosure. Referring to  FIG. 2A , a fluid delivery system  100  includes a fluid chamber  111 , a charge reducing unit  112 , and a charge control unit  113 . In an example, the fluid delivery system  100  may be disposed within the image forming apparatus  110 . In other examples, the fluid delivery system  100  may be external to the image forming apparatus  110 . In the present example, the fluid chamber  111  is configured to store fluid having at least charge directors and a carrier liquid. In examples, the fluid chamber  111  may be a reservoir, ink tank, or the like. In an example, the fluid may also be supplied to a LEP  110  to print images on a substrate S ( FIGS. 1 and 2B ) and/or used as a cleaning fluid for the PIP  180 , or the like. The charge reducing unit  112  is in fluid communication with the fluid chamber  111 . The charge reducing unit  112  is configured to decrease a charge level of the fluid of the fluid chamber  111 . The charge control unit  113  is in communication with the fluid chamber  111  and is configured to control the charge level of the fluid based on a detection of at least one fluid parameter corresponding to the charge level of the fluid of the fluid chamber  111 . In an example, the charge reducing unit  112  reduces a concentration of an amount of the charge directors in the fluid of the fluid chamber  111 . In an example, the charge directors, that is, charge control agents, may include one or more of lecithin, barium sulfocuccinate, or the like. 
       FIG. 2B  is a partial side view illustrating the fluid delivery system of  FIG. 2A  according to an example of the present disclosure. Referring to  FIGS. 2A and 2B , in an example, the charge reducing unit  112  includes a filter unit  112   a  configured to remove charge directors from the fluid by adsorption with the fluid f p  entering the filter unit  112   a  to form a filtered fluid f f , and provide the filtered fluid f f  to the fluid chamber  111 . As illustrated in  FIG. 2B , the charge control unit  113  includes a fluid parameter detector  113   a  configured to detect the at least one fluid parameter corresponding to the charge level of the fluid. For example, the at least one fluid parameter may be conductivity. In an example, the charge control unit  113  may also include a selector unit  113   b  configured to place the charge reducing unit  112  such as the filter unit  112   a  in or out of fluid communication with the fluid chamber  111  based on the detection of the at least one fluid parameter such as the conductivity of the fluid. 
     In an example, a predetermined range for the conductivity may be 70 to 110 picoseimens per centimeter (pS/cm). Thus, for example, when the fluid parameter detector  113   a  detects the conductivity of the fluid exceeding 110 pS/cm, the selector unit  113   b  may place the filter unit  112   a  in fluid communication with the fluid chamber  111  to reduce the charge level of the fluid. For example, the selector unit  113   b  may open an automated control valve  113   c , or the like, disposed between the filter unit  112   a  and the fluid chamber  111  to enable the filter unit  112   a  to remove the charge directors from the fluid passing therethrough. The fluid parameter detector  113   a  may be a conductivity sensor disposed on the fluid chamber  111 . The fluid chamber  111  may further include a pump (not illustrated), additional sensors (not illustrated) such as a density sensor, level sensor and temperature sensor, and a fluid temperature controller such as a heater or a cooler. As illustrated in  FIG. 2B , the fluid delivery system  100  may also include an ink tank  211  configured to receive fluid from the fluid chamber  111  and toner concentrate  115   a  ( FIG. 4B ) to form a printing fluid. The ink tank  211  may also be in fluid communication with the LEP  110 , to provide the printing fluid to a respective BID  130  ( FIG. 1 ) of the LEP  110  to print images therewith. 
       FIGS. 3A and 3B  are perspective views of charge reducing units of the fluid delivery system of  FIG. 2B  according to examples of the present disclosure. Referring to  FIGS. 3A and 3B , the filter unit  112   a  may include at least one of silica gel  310  ( FIG. 3A ) and a mono-directional membrane  350  ( FIG. 3B ). Referring to  FIG. 3A , in an example, the filter unit  112   a  may include a silica gel  310  and a housing unit  312  to store the silica gel  310 . The housing unit  312  may include a removable portion  314  in which the silica gel  310  can be removably stored, and a stationary portion  316  having an inlet  316   a  and outlet  316   b  in fluid communication with the removable portion  314  and the silica gel  310  stored therein. The silica gel  310  may be replaced as needed. In an example, the fluid f p  from the fluid chamber  111  enters the inlet  316   a  of the stationary portion  316  of the filter unit  112   a . Subsequently, the fluid f p  flows into the removable portion  314  of the filter unit  112   a  and comes in contact with the silica gel  310 . The silica gel  310  filters the fluid by attracting to its surface solids such as charge directors. The filtered fluid f f  having a reduced amount and/or no charge directors therein, flows out of the outlet  316   b  of the stationary portion  316  of the filter unit  112   a , and into the fluid chamber  111 . In the fluid chamber  111 , the filtered fluid f f  mixes together with the rest of the fluid therein resulting in a reduction of the concentration of the amount of charge directors in the fluid stored in the fluid chamber  111 . 
     In other examples, the housing unit  312  may include a mono-directional membrane  350  stored therein in which the mono-directional membrane  350  and/or the housing unit  312 , or a portion thereof, is replaceable as illustrated in  FIG. 3B . Referring to  FIG. 3B , the fluid f p  from the fluid chamber  111  is directed through the mono-directional membrane  350  in order to remove charge directors therefrom resulting in the filtered fluid f f . The filtered fluid f f  having a lower concentration of the amount of the charge directors than the fluid in the fluid chamber  111  is directed into the fluid chamber  111 . 
       FIG. 4A  is a block diagram illustrating a fluid delivery system of  FIG. 2A  according to an example of the present disclosure. Referring to FIG.  4 A, in an example, a fluid delivery system  100  includes a fluid chamber  111 , a charge reducing unit  112 , a charge increasing unit  114 , and a charge control unit  113 . In the present example, the fluid chamber  111  is configured to store fluid having at least charge directors and a carrier liquid. The charge reducing unit  112  is in fluid communication with the fluid chamber  111 . The charge reducing unit  112  is configured to decrease a charge level of the fluid of the fluid chamber  111 . In an example, the charge reducing unit  112  reduces a concentration of an amount of the charge directors in the fluid of the fluid chamber  111 . The charge control unit  113  is in communication with the fluid chamber  111 , the charge reducing unit  112 , and the charge increasing unit  114 . 
     Referring to  FIG. 4A , in an example, the charge increasing unit  114  of the fluid delivery system  100  is in fluid communication with the fluid chamber  111  and in communication with the charge control unit  113 . In an example, the charge increasing unit  114  is configured to increase the charge level of the fluid of the fluid chamber  111 . In an example, the charge increasing unit  114  increases a concentration of the amount of the charge directors in the fluid of the fluid chamber  111 . For example, the charge increasing unit  114  may provide a supplemental fluid  114   a  ( FIG. 4B ) to the fluid of the fluid chamber  111  such that the concentration of the amount of charge directors of the supplemental fluid  114   a  is greater than the concentration of the amount of the charge directors of the fluid in the fluid chamber  111  at the time of the detection of the at least one fluid parameter. In an example, the charge increasing unit  114  may include the supplemental fluid  114   a  and a supplemental fluid receptacle  114   b  configured to removable receive the supplemental fluid  114   a  as illustrated in  FIG. 4B . In an example, the supplemental fluid  114   a  may be primarily imaging oil such as ISOPAR, trademarked by Exxon Corporation, having a charge director compound dispersed therein, a toner concentrate  115   a  having charge directors and toner particles mixed therein, and/or primarily a charge director compound  116   a  in a solution. The supplemental fluid  114   a  may be replaced as needed. 
     Referring to  FIG. 4A , in an example, the charge control unit  113  is in communication with the fluid chamber  111 , the charge reducing unit  112  and the charge increasing unit  114 . In the present example, the charge control unit  113  is configured to control the charge level of the fluid based on a detection of at least one fluid parameter corresponding to the charge level of the fluid of the fluid chamber  111 .  FIG. 4B  is a partial side view illustrating the fluid delivery system of  FIG. 4A  according to an example of the present disclosure. Referring to  FIGS. 4A and 4B , in an example, the charge reducing unit  112  includes a filter unit  112   a  configured to remove charge directors from the fluid by adsorption with the fluid f p entering the filter unit  112   a  to form a filtered fluid f f  having a lower concentration of an amount of charge directors than the fluid in the fluid chamber  111 . Subsequently, the filtered fluid f f  is directed from the filter unit  112   a  to the fluid chamber  111 . As illustrated in  FIG. 4B , the charge control unit  113  includes a fluid parameter detector  113   a  configured to detect the at least one fluid parameter such as conductivity corresponding to the charge level of the fluid. 
     Referring to  FIG. 4B , the charge control unit  113  may also include a selector unit  113   b  configured to place the charge reducing unit  112  such as the filter unit  112   a  and the charge increasing unit  114  such as the supplemental fluid  114   a  in or out of fluid communication with the fluid chamber  111  based on the detection of the at least one fluid parameter. For example, when the fluid parameter detector  113   a  detects the conductivity of the fluid below 70 pS/cm, the selector unit  113   b  may place the fluid chamber  111  in fluid communication with the supplemental fluid  114   a  having a higher concentration of the amount of the charge directors than the fluid in the fluid chamber  111  to mix with the fluid therein. For example, the selector unit  113   b  may open an automatic control valve  113   d , or the like, disposed between the supplemental fluid  114   a  and the fluid chamber  111 . Thus, in the fluid chamber  111 , the filtered fluid f f  mixes together with the rest of the fluid resulting in a reduction of the concentration of the amount of charge directors in the fluid stored in the fluid chamber  111 . Accordingly, the supplemental fluid  114   a  may be primarily imaging oil such as ISOPAR having a charge director compound dispersed therein, a toner concentrate  115   a  having charge directors and toner particles mixed therein, and/or primarily a charge director compound  116   a  in solution. In an example, the supplemental fluid  114   a  includes the imaging oil having a concentration of an amount of charge directors of approximately 0.075%. 
     Referring to  FIG. 4B , the fluid delivery system  100  may also include an ink tank  211  configured to receive fluid from the fluid chamber  111  and toner concentrate  115   a  to form a printing fluid. The ink tank  211  may also be in fluid communication with the LEP  110 , to provide the printing fluid to a respective BID  130  ( FIG. 1 ) of the LEP  110  to print images therewith. In an example, the fluid delivery system  100  may include other fluid receptacles  115   b  in addition to the supplemental fluid receptacle  114   b  to receivable mount, for example, the toner concentrate  115   a . In an example, the toner concentrate  115   a  supplies color pigments to the fluid to correspond with a desired color. In an example, the toner concentrate  115   a  may include 21.5% solids. 
     In other examples, the selector unit  113   b  may additionally place the filter unit  112   a  out of fluid communication with the fluid chamber  111  in response to the detection of the conductivity below 70 pS/cm. For example, the selector unit  113   b  may close an automated control valve  113   c , or the like, disposed between the fluid chamber  111  and the charge reducing unit  112 . In an example, the selector unit  113   b  may select the charge reducing unit  112  to be in fluid communication with the fluid chamber  111  when the conductivity is greater than 110 pS/cm, and select the charge increasing unit  114  to be in fluid communication with the fluid chamber  111  when the conductivity is less than 70 pS/cm. As illustrated in  FIG. 4B , the fluid chamber  111  of the fluid delivery system  100  may also be in fluid communication with the LEP  110 , for example, through the ink tank  211 , to provide the fluid to a respective the BID  130  ( FIG. 1 ). 
       FIG. 5  is a flowchart illustrating a method of controlling a charge level of fluid in a fluid chamber of a fluid delivery system  100  according to an example of the present disclosure. Referring to  FIGS. 4A ,  4 B and  5 , in block  510 , at least one fluid parameter corresponding to a charge level of a fluid having at least charge directors and carrier liquid in a fluid chamber is detected. In an example, the at least one parameter may be conductivity and a predetermined range of the conductivity of the fluid may be in a range of 70 pS/cm to 110 pS/cm. 
     In block  520 , the charge level of the fluid in the fluid container is controlled by changing a concentration of an amount of the charge directors in the fluid based on the detected fluid parameter. For example, a charge control unit may control the charge level of the fluid by selecting at least one of a charge reducing unit and a charge increasing unit to be in fluid communication with the fluid chamber based on the detected at least one fluid parameter of the fluid. In an example, the charge reducing unit may reduce the concentration of the amount of the charge directors in the fluid and the charge increasing unit may increase the concentration of the amount of the charge directors in the fluid. In an example, the charge control unit may select the charge reducing unit when the detected fluid parameter is greater than 110 pS/cm and may select the charge increasing unit when the detected fluid parameter is less than 70 pS/cm. The concentration of the amount of the charge directors in the fluid may be reduced by a filter unit removing respective charge directors from the fluid by adsorption. In examples, the filter unit  112   a  may include at least one of a silica gel and a mono-directional membrane ( FIGS. 3A and 3B ). 
     The present disclosure has been described using non-limiting detailed descriptions of example embodiments thereof that are provided by way of example and are not intended to limit the scope of the present disclosure. It should be understood that features and/or operations described with respect to one example may be used with other examples and that not all examples of the present disclosure have all of the features and/or operations illustrated in a particular figure or described with respect to one of the embodiments. Variations of embodiments described will occur to persons of the art. Furthermore, the terms “comprise,” “include,” “have” and their conjugates, shall mean, when used in the present disclosure and/or claims, “including but not necessarily limited to.” 
     It is noted that some of the above described embodiments may describe examples contemplated by the inventors and therefore may include structure, acts or details of structures and acts that may not be essential to the present disclosure and which are described as examples. Structure and acts described herein are replaceable by equivalents, which perform the same function, even if the structure or acts are different, as known in the art. Therefore, the scope of the present disclosure is limited only by the elements and limitations as used in the claims.