Patent Publication Number: US-9409387-B2

Title: Adjustable printhead

Description:
CLAIM FOR PRIORITY 
     The present application claims the benefit of priority to European patent application number 14275018.1 having a filing date of Jan. 30, 2014, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     A printhead assembly may include a printbar beam member and a plurality of printheads. The printheads may be spaced apart from each other along the printbar beam member. The printbar beam member may extend across a print zone including a width of media. The printheads may apply fluid onto the media to form images thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting examples are described in the following description, read with reference to the figures attached hereto and do not limit the scope of the claims. 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 block diagram illustrating a printhead assembly according to an example. 
         FIG. 2A  is a top view illustrating a printhead assembly according to an example. 
         FIG. 2B  is a schematic side view illustrating the printhead assembly of  FIG. 2A  according to an example. 
         FIG. 3  is a top view illustrating a printbar beam member of the printhead assembly of  FIG. 2A  according to an example. 
         FIGS. 4A and 4B  are side views of a first eccentric pin and a second eccentric pin, respectively, of the printhead assembly of  FIG. 2A  according to examples. 
         FIG. 5  is a block diagram illustrating a printhead assembly according to an example. 
         FIG. 6  is a top view illustrating a printhead assembly of  FIG. 5  according to an example. 
         FIGS. 7 and 8  are flowcharts illustrating methods of calibrating a printhead assembly according to examples. 
     
    
    
     DETAILED DESCRIPTION 
     Printers such as inkjet page wide printers may include printhead assemblies that include a printbar beam member and a plurality of printheads disposed thereon. The printbar beam member extends across a print zone including a width of media. The printheads apply fluid such as ink onto media to form images thereon. The printheads are spaced apart from each other along the printbar beam member. Accurate spacing between printheads assists in reducing print quality defects such as visible strikes and line artifacts. As the span of the printhead assembly increases, for example, to accommodate wider media, the number of printheads on the printbar beam member may also increase. For example, the spacing between end nozzles of adjacent printheads should be within an acceptable range to prevent visible strikes and line artifacts. Thus, errors in the respective spacing between some of the printheads may increase resulting in an increase in print quality defects. Further, the number of defective printheads manufactured outside of acceptable manufacturing tolerances may increase. 
     In examples, a printhead assembly includes a printbar beam member, a printhead, and a first eccentric pin. The printbar beam member includes a beam surface and a first cavity disposed through the beam surface. The printhead includes a printhead surface and a second cavity disposed through the printhead surface. The first eccentric pin may be inserted into the first cavity and the second cavity to couple the printhead to the printbar beam member. The first eccentric pin may rotate to adjust a position of the printhead relative to the printbar beam member along a first axis along the beam surface. The adjustment of printheads with respect to the printbar beam member may enable accurate spacing between printheads on the printbar beam member. The adjustment of printheads with respect to the printbar beam member may also decrease the number of defective printheads to be used for the printhead assembly. Thus, adjustable printhead and/or printhead assemblies may decrease print quality defects and the cost of the printheads. 
       FIG. 1  is a block diagram illustrating a printhead assembly according to an example. Referring to  FIG. 1 , in some examples, a printhead assembly  100  includes a printbar beam member  10 , a printhead  11 , and a first eccentric pin  12 . An eccentric pin, for example, may have its axis of revolution displaced from its center so that it is capable of imparting reciprocating motion. That is movement of an offset portion ( FIG. 4A ) of the respective eccentric pin  11  from one position to another position within a respective cavity may provide linear movement to the respective printhead  11 . The printbar beam member  10  includes a beam surface  10   a  and a first cavity  13  disposed through the beam surface  10   a . The printhead  11  includes a printhead surface  11   a  and a second cavity  14  disposed through the printhead surface  11   a . The printhead surface  11   a , for example, may be configured to oppose and/or contact the printbar beam member surface  10   a . The first eccentric pin  12  may be inserted into the first cavity  13  and the second cavity  14  to couple the printhead  11  to the printbar beam member  10 . 
     Referring to  FIG. 1 , in some examples, the first eccentric pin  12  may rotate to adjust a position of the printhead  11  relative to the printbar beam member  10  along a first axis along the beam surface  10   a . For example, the first axis may be transverse to a printing direction. In some examples, the printhead  11  may remain on the printbar beam member  10  during rotation of the first eccentric pin  12 . Alternatively, the printhead  11  may be removed from the printbar beam member  10  prior to the rotation of the first eccentric pin  12  and placed back on the printbar beam member  10  after completion of the rotation of the first eccentric pin  12 . That is, after completion of the rotation of the first eccentric pin  12 , the first eccentric pin  12  disposed through the second cavity  14  of the printhead  11  may be reinserted back into the corresponding first cavity  13  of the printbar beam member  10  to place the printhead  11  in a new position (e.g., an alignment state) on the printbar beam member  10 . In some examples, the first cavity  13  may include a first hollow sleeve and the second cavity  14  may include a second hollow sleeve. 
       FIG. 2A  is a top view illustrating a printhead assembly according to an example.  FIG. 2B  is a schematic side view illustrating the printhead assembly of  FIG. 2A  according to an example.  FIG. 3  is a top view illustrating a printbar beam member of the printhead assembly of  FIG. 2A  according to an example. In some examples, the printhead assembly  200  may include the printbar beam member  10 , the printhead  11 , and the first eccentric pin  12  previously described with respect to the printhead assembly  100  of  FIG. 1 . The first eccentric pin  12  may be rotated to adjust the printhead  11  along the first axis  20   a  of the printbar beam member  10 . In doing so, at times, the printhead  11  may also unintentionally be adjusted along the second axis as well (e.g., the printing direction). Referring to  FIGS. 2A-3 , in some examples, the printhead assembly  200  may also include a second eccentric pin  22 . The second eccentric pin  22 , for example, may be provided to adjust the printhead  11  along the second axis  20   b  of the printbar beam member  10  (e.g., a printing direction). Additionally, the printbar beam member  10  may also include a third cavity  23  disposed through the beam surface  10   a , a printhead receiving area  29 , and printbar fluid ports (not illustrated). 
     In some examples, the printbar beam member  10  may include an extrusion beam. Also, the printhead  11  may include a fourth cavity  24  disposed through the printhead surface  11   a , nozzles  26 , and printhead fluid ports (not illustrated). For example, the printhead fluid ports and the printbar fluid ports may be placed in fluid communication with each other when the printhead  11  is installed on the printbar beam member  10  to pass fluid therebetween. Fluid in the printhead  11  may be selectively passed through the respective nozzles  26  of the printhead  11 , for example, to form an image on media. In some examples, the fluid is ink. 
     Referring to  FIGS. 2A-3 , in some examples, the first eccentric pin  12  may be inserted into the first cavity  13  and the second cavity  14  to couple the printhead  11  to the printbar beam member  10 . The first eccentric pin  12  may rotate to adjust a position of the printhead  11  relative to the printbar beam member  10 , for example, along a first axis  20   a  along the beam surface  10   a . In some examples, the first eccentric pin  12  may have eccentricity in a range from −30 microns to 30 microns. That is, the linear range of movement of the printhead  11  imparted by a full rotation of the first eccentric pin  12  may be about sixty microns. Additionally, in some examples, the second eccentric pin  22  may be inserted into the third cavity  23  and the fourth cavity  24  to couple the printhead  11  to the printbar beam member  10   a.    
     In some examples, the first cavity  13  may be a first hollow sleeve, the second cavity  14  may be a second hollow sleeve, the third cavity  23  may be a third hollow sleeve, and a fourth cavity  24  may be a fourth hollow sleeve. For example, hollow sleeves may be used to accurately set the distance between a first nozzle of the respective printhead and a center of the hollow sleeve to enable the respective eccentric pins therein to freely rotate. In some examples, the first, second and fourth hollow sleeves may have a circular-shaped opening and the third hollow sleeve may have an oval-shaped opening. For example, the third cavity  23  and/or third hollow sleeve of the printbar beam member  10  may be shaped as an oval such as a slit. The slit may be arranged to direct movement of the printhead  11  in a cross-print direction (along the first axis  20   a ). The slit may also enable the second eccentric pin  22  to adjust the printhead  11  along the second axis  20   b  without unintentionally adjusting it along the first axis  20   a.    
     Referring to  FIGS. 2A-3 , in some examples, the second eccentric pin  22  may rotate to adjust the position of the printhead  11  relative to the printbar beam member  10 , for example, along a second axis  20   b  along the beam surface  10   a . The second axis  20   b  may be different than the first axis  20   a . In some examples, the second axis  20   b  may be in a printing direction and the first axis  20   a  may be traverse to the printing direction (e.g., cross-print direction). The printhead receiving area  29  may include an oversized compartment to receive the printhead  11  and include space, for example, for it to move in respective directions corresponding to movement of the respective eccentric pins  12  and  22 , as desired. 
     In some examples, the printhead  11  may remain on the printbar beam member  10  during rotation of the first eccentric pin  12  and second eccentric pin  22 . Alternatively, the printhead  11  may be removed from the printbar beam member  10  prior to the rotation of the first eccentric pin  12  and the second eccentric pin  22 , and placed back on the printbar beam member  10  after completion of the rotation of the respective eccentric pins  12  and  22 . For example, after completion of the rotation of the first eccentric pin  12 , the first eccentric pin  12  disposed through the second cavity  14  of the printhead  11  may be reinserted back into the corresponding first cavity  13  of the printbar beam member  10  to place the printhead  11  in a new position (e.g., alignment state) on the printbar beam member  10 . 
       FIGS. 4A and 4B  are side views illustrating a first eccentric pin and a second eccentric pin, respectively, of the printhead assembly of  FIG. 2A  according to examples. Referring to  FIGS. 4A and 4B , in some examples, the first eccentric pin  11  and the second eccentric pin  22  may include a shaft portion  42   a , an intermediate portion  42   b , an offset portion  42   c , and an axis of rotation  42   d . The shaft portion  42   a  may be an elongated portion to be placed into the respective cavity such as a respective hollow sleeve of the printhead  11 . The intermediate portion  42   b  may be disposed between the shaft portion  42   a  and the offset portion  42   c . The offset portion  42  may be connected to the shaft portion  42   a  in an offset manner in which an axis of revolution  42   d  of the eccentric pin is displaced from its center so that it is capable of imparting reciprocating motion, for example, to the respective printhead  11 . 
     In some examples, the respective eccentric pin  12  and  22  may be rotated such that the shaft portion  42   a  is rotated, for example, from being biased toward one side of a respective cavity, for example, to being biased toward the other side of the respective cavity by an amount to enable the printhead  11  to move a displacement distance to place the printhead  11  in an aligned state. In some examples, the respective eccentric pins  12  and  22  may be rotated by hand, a tool, and the like. For example, the misaligned state of a printhead  11  may be determined by a calibration image. Additionally, in some examples, a displacement distance to place the printhead  11  in an aligned state may be determined by open loop calibration methods, closed loop calibration methods, and the like. For example, a closed loop calibration method may include physically measuring the displacement distance (e.g., amount of misalignment) by a jig, and the like). 
       FIG. 5  is a block diagram illustrating a printhead assembly according to an example.  FIG. 6  is a top view illustrating a printhead assembly according to an example. In some examples, a printhead assembly  500  may correspond to the printhead assemblies  100  and  200  as previously discussed with respective to  FIGS. 1-4B  and also include a plurality of printheads  11 . Referring to  FIGS. 5 and 6 , in some examples, the printhead assembly  500  includes a printbar beam member  10 , a plurality of printheads  11 , and a plurality of first eccentric pins  12 . The printbar beam member  10  may include a beam surface  10   a  and a plurality of first cavities  13  disposed through the beam surface  10   a . Each one of the plurality of printheads  11  includes a printhead surface  11   a  and a second cavity  14  disposed through the respective printhead surface  11   a . Each one of the plurality of first eccentric pins  12  may be inserted into the respective first cavity  13  and the corresponding second cavity  14  to couple the respective printhead  11  to the printbar beam member  10 . Each one of the first eccentric pins  12  may be configured to rotate to adjust the respective position of the respect printhead  11  relative to the printbar beam member  10 , for example, along a first axis  20   a  along the beam surface  10   a.    
     Referring to  FIGS. 5 and 6 , in some examples, the printbar beam member  10  may also include a plurality of third cavities  23  disposed through the beam surface  10   a . Each one of the printheads  11  may also include a fourth cavity  24  disposed through the respective printhead surface  11   a . The printhead assembly  500  may also include a plurality of second eccentric pins  22 . Each one of the second eccentric pins  22  may be inserted into the respective third cavity  23  and the corresponding fourth cavity  24  to couple the respective printhead  11  to the printbar beam member  10 . In some examples, the first cavity  13  may be a first hollow sleeve, the second cavity  14  may be a second hollow sleeve, the third cavity  23  may be a third hollow sleeve, and a fourth cavity  24  may be a fourth hollow sleeve. In some examples, the first, second and fourth hollow sleeves may have a circular-shaped opening and the third hollow sleeve may have an oval-shaped opening. 
     Additionally, each one of the second eccentric pins  22  may be configured to rotate to adjust the respective position of the respective printhead  11  relative to the printbar beam member  10 , for example, along a second axis  20   b  along the beam surface  10   a . The second axis  20   b  may be different than the first axis  20   a . In some examples, the second axis  20   b  may be in a printing direction and the first axis  20   a  may be traverse to the printing direction. In some examples, a rotation of the respective first and second eccentric pins  12  and  22  of the respective printhead  11  may be configured to move the respective printhead  11  along the printbar beam surface  10   a  relative to other printheads thereon. 
       FIG. 7  is a flowchart illustrating a method of calibrating a printhead assembly according to an example. In some examples, the modules and/or assemblies implementing the method may be those described in relation to the printhead assemblies  100 ,  200  and  500  of  FIGS. 1-6 . In block S 710 , a calibration image is formed based on respective positions of printheads coupled to a printbar beam member of the printhead assembly such that the printbar beam member includes a first set of cavities and the printheads include a second set of cavities to correspond to the first set of cavities. In some examples, the first cavity may include a first hollow sleeve and the second cavity may include a second hollow sleeve. The calibration image may be printed onto a media by each one of the printheads. In block S 712 , the calibration image is analyzed to identify which of the printheads are in a misaligned state with respect to the respective positions of the printheads along the printbar beam member. 
     In block S 714 , the misaligned printheads are removed from the printbar beam member. In block S 716 , respective first eccentric pins corresponding to the misaligned printheads and disposed through respective ones of the second set of cavities are rotated to enable the misaligned printheads, for example, to be placed in an aligned state. In some examples, the method may also include engaging respective ones of the first set of cavities of the misaligned printheads by the respective first eccentric pins to place the misaligned printheads in the aligned state. 
       FIG. 8  is a flowchart illustrating a method of calibrating a printhead assembly according to an example. In some examples, the modules and/or assemblies implementing the method may be those described in relation to the printhead assemblies  100 ,  200  and  500  of  FIGS. 1-6 . In block S 810 , a calibration image is formed based on respective positions of printheads coupled to a printbar beam member of the printhead assembly such that the printbar beam member includes a first set of cavities and the printheads include a second set of cavities to correspond to the first set of cavities. In some examples, the first cavity may include a first hollow sleeve and the second cavity may include a second hollow sleeve. The calibration image may be printed onto a media by each one of the printheads. In block S 812 , misaligned printheads are identified by analyzing the calibration image to determine which of the printheads are in a misaligned state with respect to the respective positions of the printheads along the printbar beam member. In block S 814 , respective first eccentric pins corresponding to the misaligned printheads and disposed through respective ones of the first set of cavities are rotated to move the misaligned printheads along the printbar beam member by the respective amount of misalignment, for example, into an aligned state. In some examples, the method also includes determining an amount of misalignment (e.g., displacement distance) for each one of the misaligned printheads by performing an open loop calibration. Alternatively, in some examples, the method may include performing a closed loop calibration by physically measuring an amount of misalignment for each one of the misaligned printheads. 
     It is to be understood that the flowcharts of  FIGS. 7 and 8  illustrate architecture, functionality, and/or operation of examples of the present disclosure. If embodied in software, each block may represent a module, segment, or portion of code that includes one or more executable instructions to implement the specified logical function(s). If embodied in hardware, each block may represent a circuit or a number of interconnected circuits to implement the specified logical function(s). Although the flowcharts of  FIGS. 7 and 8  illustrate a specific order of execution, the order of execution may differ from that which is depicted. For example, the order of execution of two or more blocks may be rearranged relative to the order illustrated. Also, two or more blocks illustrated in succession in  FIGS. 7 and 8  may be executed concurrently or with partial concurrence. All such variations are within the scope of the present disclosure. 
     The present disclosure has been described using non-limiting detailed descriptions of examples thereof that are not intended to limit the scope of the general inventive concept. 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 have all of the features and/or operations illustrated in a particular figure or described with respect to one of the examples. Variations of examples described will occur to persons of the art. Furthermore, the terms “comprise,” “include,” “have” and their conjugates, shall mean, when used in the disclosure and/or claims, “including but not necessarily limited to.” 
     It is noted that some of the above described examples may include structure, acts or details of structures and acts that may not be essential to the general inventive concept and which are described for illustrative purposes. 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 general inventive concept is limited only by the elements and limitations as used in the claims.