Patent Document

TECHNICAL FIELD 
       [0001]    This disclosure relates to the field of inkjet printing systems, and more particularly, to inkjet printheads configured to eject drops of inks having different colors. 
       BACKGROUND 
       [0002]    Drop-on-demand ink jet printing systems eject ink drops from printhead nozzles in response to pressure pulses generated within the printhead by either piezoelectric devices or thermal transducers, such as resistors. The printheads typically include a manifold that receives ink from an external ink supply and supplies ink to a plurality of pressure chambers. Each pressure chamber is fluidly coupled to the manifold by an inlet and to a nozzle, which is an opening in an external surface of the printing system, by an outlet. On a side of the pressure chamber opposite the fluid path to the nozzle, a flexible diaphragm layer overlies the pressure chamber and a piezoelectric or thermal transducer is positioned over the diaphragm layer. 
         [0003]    To eject an ink drop from a nozzle, an electric pulse activates the piezoelectric device or thermal transducer, which causes the device or transducer to bend the diaphragm layer into the pressure chamber. This movement urges ink out of the pressure chamber through the outlet to the nozzle where an ink drop is ejected. Each piezoelectric device or thermal transducer is individually addressable to enable the device or transducer to receive an electrical firing signal. Each structure comprised of a piezoelectric or thermal transducer, a diaphragm, a pressure chamber, and nozzle is commonly called an inkjet or jet. When the diaphragm rebounds to its original position, the ink volume in the pressure chamber is refilled by capillary action of the inlet from the manifold. 
         [0004]    Many ink jet printing systems eject drops of various colored inks. The inkjets in the system are configured to enable the differently colored drops to form color images on an image receiving member that is positioned opposite the printing system. In a common embodiment, an inkjet printer is configured to emit drops of a predetermined number of different ink colors onto the image receiving member. Combinations of the various ink colors on the image receiving member generate images with a wide range of colors. Common examples of such systems include cyan, magenta, yellow, black (CMYK) printing systems, as well as systems that use different numbers and colors of inks to generate color images. In some multicolor printing systems, separate printheads exclusively eject ink having only one of the predetermined colors. Other printing systems include a multicolor printhead with separate groups of inkjet ejectors. Each group of inkjet ejectors in the multicolor printhead is fluidly coupled to a manifold that supplies only one of the predetermined colors to the pressure chambers in the group of inkjet ejectors. The added complexity of supplying multiple ink colors to the inkjet ejectors and ensuring that ink of one color does not contaminate ink of another color presents a challenge to the design of multicolor printheads. Consequently, improvements to inkjet ejector isolation in multicolor printheads are desirable. 
       SUMMARY 
       [0005]    In one embodiment, an inkjet array has been developed. The inkjet array includes a body layer defining at least portions of a plurality of pressure chambers, an inlet layer having a plurality of inlets formed through the inlet layer, the inlet layer being bonded to the body layer at a position that enables each inlet in the inlet layer to communicate fluidly with only one pressure chamber in the plurality of pressure chambers, an offset channel layer having a plurality of offset channels formed through the offset channel layer, each offset channel having a first end and a second end, each first end of each offset channel being laterally offset from each second end of each offset channel in the offset channel layer, the offset channel layer being bonded to the inlet layer to position each inlet in the inlet layer proximate only one first end of one offset channel formed in the offset channel layer, and an offset inlet layer having a plurality of offset inlets formed through the offset inlet layer. The offset inlet layer is bonded to the offset channel layer to position each offset inlet in the offset inlet layer proximate only one second end in the offset channel layer to form a continuous fluid path from each offset inlet to only one pressure chamber through only one offset channel and only one inlet. 
         [0006]    In another embodiment, a printhead has been developed. The printhead includes a body layer defining at least portions of a plurality of pressure chambers, the pressure chambers being arranged in an array of columns and rows, an inlet layer having a plurality of inlets formed through the inlet layer, the inlets being arranged in an array of columns and rows corresponding to the array of columns and rows in which the pressure chambers are arranged, the inlet layer being bonded to the body layer at a position that enables each inlet in the inlet layer to communicate fluidly with only one pressure chamber in the plurality of pressure chambers, an offset channel layer having a plurality of offset channels formed through the offset channel layer, each offset channel having a first end and a second end, each first end of each offset channel being laterally offset from each second end of each offset channel in the offset channel layer, the offset channel layer being bonded to the inlet layer to position each inlet in the inlet layer proximate only one first end of one offset channel formed in the offset channel layer, and an offset inlet layer having a plurality of offset inlets formed through the offset inlet layer, the offset inlets being arranged in columns and rows, the offset inlet layer being bonded to the offset channel layer to position a first column of offset inlets on a first side of each column of inlets in the inlet layer and a second column of offset inlets on a second side of each column of inlets in the inlet layer. Each offset inlet is proximate only one second end of an offset channel in the offset channel layer to form a continuous fluid path from each offset inlet to only one pressure chamber through only one offset channel and only one inlet. The offset inlets on each side of one of the columns of inlets in the inlet layer are aligned in a plurality of rows that are perpendicular to the column of inlets and the rows of the offset inlets are offset from the rows of inlets formed by parallel columns of inlets in the array of inlets in the inlet layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The foregoing aspects and other features of a multicolor inkjet ejector array and printhead are explained in the following description, taken in connection with the accompanying drawings. 
           [0008]      FIG. 1  is a partial view of an array of inkjet ejectors with a first set of inkjet ejectors in the array configured to receive ink having a first color, and a second set of inkjet ejectors in the array configured to receive ink having a second color. 
           [0009]      FIG. 2  is a plan view of inkjet ejectors and inlet openings depicted in  FIG. 1 . 
           [0010]      FIG. 3  is a plan view of offset inlet channels depicted in  FIG. 1  that are positioned over inlets to the inkjet ejectors depicted in  FIG. 2 . 
           [0011]      FIG. 4  is a plan view of offset inlet channel openings depicted in  FIG. 1  that are positioned over the offset inlet channels depicted in  FIG. 3 . 
           [0012]      FIG. 5  is a cross-sectional view of a portion of the inkjet ejectors in the inkjet ejector array of  FIG. 1  taken along line  160 . 
           [0013]      FIG. 6  is a plan view of another configuration of offset channel inlets and offset channels. 
           [0014]      FIG. 7  is a cross-sectional view of a portion of the offset channel inlets and offset channels of  FIG. 6  taken along line  620 . 
           [0015]      FIG. 8  is a cross-sectional view of an offset channel and inkjet ejector with an inlet to the offset channel positioned on one side of a manifold wall, and an inlet to the inkjet ejector positioned on an opposite side of the manifold wall. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the term “image receiving member” refers to a print medium, such as paper, or may be an intermediate imaging member, such as a print drum or endless belt, which holds ink images formed by inkjet printheads. As used herein, the term “process direction” refers to a direction in which an image receiving member moves relative to one or more printheads during an imaging operation. The term “cross-process direction” refers to a direction that is perpendicular to the process direction along the surface of the image receiving member. As used herein, the term “fluid resistance” refers to a property of a fluid path that resists a flow of fluid through the fluid path. The fluid resistance of the fluid path may be identified by dividing a measured pressure of fluid in the fluid path by the volumetric flow rate of fluid through the path. The fluid resistance of a fluid path may be altered by changing one or more physical dimensions, including length, width, and depth, of the fluid path. 
         [0017]      FIG. 1  and  FIG. 5  depict two inkjet ejector groups that are configured to be fluidly coupled to two ink manifolds that supply different colors of ink.  FIG. 1  depicts a top-view of the inkjet ejector groups  102 A and  102 B that include multiple layers extending into the page that form the inkjet ejectors. The multiple layers depicted in  FIG. 1  are shown separately in  FIG. 2-FIG .  4 .  FIG. 2  depicts an array of inkjet ejectors forming ejector groups  102 A and  102 B.  FIG. 3  depicts a layer  208  of inlet offset channels formed above the inkjet ejectors.  FIG. 4  depicts a layer  204  of inlet offset openings formed above the inlet offset channels. The inlet offset openings and inlet offset channels enable two or more ink reservoirs to supply different colors of ink to the inkjet ejector groups  102 A and  102 B. 
         [0018]    The inkjet ejector groups  102 A and  102 B shown in  FIG. 1-FIG .  5  are suitable for use in a multicolor inkjet printhead.  FIG. 5  is a cross-sectional view of some of the inkjet ejectors depicted in  FIG. 1  taken along line  160 .  FIG. 1  and  FIG. 5  depict openings  112 A- 112 D and  142 A- 142 D formed in an offset inlet layer  204 . The offset inlet layer  204  is bonded to an offset channel layer  208 , that includes offset channels  108 A- 108 D and  138 A- 138 D. The offset channel layer  208  is bonded to an inlet layer  212  that includes inlet openings  104 A- 104 D and  134 A- 134 D. The inlet layer is in fluid communication with the inkjet ejectors  116 A- 116 D and  146 A- 146 D in the ejector groups  102 A and  102 B, respectively.  FIG. 5  depicts the offset inlet layer  204 , offset channel layer  208 , and inlet layer  212 . The reader should understand that some layers, walls, and other opaque structures have been omitted from selected portions of  FIG. 1  and  FIG. 5  to clarify the structures and fluid paths described below. 
         [0019]      FIG. 1  and  FIG. 2  depict a plan view of two inkjet ejector groups  102 A and  102 B that are configured to receive ink from two different ink reservoirs. Each of the inkjet ejectors in the inkjet ejector groups  102 A and  102 B is fluidly coupled to an ink reservoir, referred to as an ink manifold, with inkjet ejector groups  102 A and  102 B being fluidly coupled to separate ink manifolds that hold inks having different colors. Each of the inkjet ejector groups  102 A and  102 B includes a plurality of inkjet ejectors arranged in a predetermined number of rows. The rows are arranged next to one another in process direction  162  and each row extends along the cross-process direction as indicated by line  174 .  FIG. 1  and  FIG. 2  depict inkjet ejector group  102 A including inkjet ejectors  116 A- 116 B in one row, with inkjet ejectors  116 C- 116 D in an adjacent row. Similarly, inkjet ejector group  102 B includes inkjet ejectors  146 A- 146 B in one row with inkjet ejectors  146 C- 146 D in a second row. While  FIG. 1  and  FIG. 2  depict inkjet ejector groups that each have two rows of inkjet ejectors, various printhead embodiments may also include one row or three or more rows of inkjet ejectors in each group. The number of inkjet ejectors in each row may vary with respect to the width and density of the inkjet ejector arrays in each printhead. 
         [0020]      FIG. 5  depicts a cross-sectional view of a portion of a printhead including inkjet ejectors  116 B,  116 D,  146 B and  146 D. The inkjet ejectors are formed from a plurality of layers, including an ink inlet layer  212 , an actuator layer  216  that surrounds a plurality of piezoelectric transducer elements  256 , a diaphragm layer  220 , body layers  224  and  228 , an outlet layer  232 , and an aperture layer  236 . The various layers are bonded to each other in the arrangement shown in  FIG. 5  to form the inkjet ejectors. 
         [0021]    Referring to inkjet ejector  146 D in more detail, fluid ink enters the inkjet ejector through inlet opening  134 D. A fluid path formed through the actuator layer  216 , diaphragm layer  220 , body layers  224  and  228 , and outlet layer  232  enables the fluid ink to flow into a pressure chamber  260 . The pressure chamber  260  is formed by the body layers  224  and  228  under the piezoelectric transducer  256  and diaphragm layer  220 . In operation, an electrical firing signal is transmitted through a flexible, electrically conductive adhesive  252  that is electrically connected to the piezoelectric transducer  256 . Piezoelectric transducer  256  is rigidly attached to the diaphragm layer  220 . Both the piezoelectric transducer  256  and diaphragm layer  220  deflect the direction of the pressure chamber  260  in response to the electric firing signal. The motion of the diaphragm layer  220  urges ink in the pressure chamber  260  through an outlet  264  and aperture, or nozzle,  268 . The ink leaves the inkjet ejector  146 D in the form of a drop. After the ink drop is ejected, ink from the manifold  240 B flows through inlet  134 D to replenish ink in the pressure chamber  260 . Each inkjet ejector depicted in  FIG. 1  and  FIG. 5  has substantially the same structure and operates in the same manner as ejector  146 D. 
         [0022]    The layers seen in  FIG. 5  are illustrative of one inkjet ejector embodiment, and alternative configurations may include a different number of layers and different configurations of fluid paths. For example, while  FIG. 5  depicts two body layers  224  and  228 , an alternative inkjet ejector configuration may include one body layer or three or more body layers. The fluid path may be arranged in a different configuration than shown in  FIG. 5  and may pass through different layers than the example of  FIG. 5 . Alternative inkjet ejectors including thermal ejectors may also be used. A thermal ejector includes a thermal actuator configured to heat ink in a pressure chamber such as pressure chamber  260 . The thermal actuator includes a resistive thermal element, which heats ink in response to an electrical current. The heating forms an expanding gas bubble in the pressure chamber. As the gas bubble expands, ink in the pressure chamber is urged through an inkjet ejector nozzle as an ink drop. 
         [0023]      FIG. 5  depicts two ink reservoirs, seen here as manifolds  240 A and  240 B, which are placed in fluid communication with different groups of inkjet ejectors. While  FIG. 5  depicts two manifold reservoirs, various multicolor printheads may include four or more ink reservoirs that are configured to supply inks of various colors to inkjet ejectors. With particular reference to  FIG. 4  and  FIG. 5 , the ink manifolds  240 A and  240 B are positioned over an offset inlet layer  204  that includes an offset inlet opening corresponding to each inkjet ejector. For example, inlet offset openings  112 A and  112 B correspond to inkjet ejectors  116 A and  116 B, respectively. 
         [0024]    As seen in  FIG. 1 ,  FIG. 3 , and  FIG. 5 , the offset inlet layer  204  is bonded to an offset channel layer  208  that includes a plurality of fluid channels. Each fluid channel in the offset channel layer  208  is fluidly coupled to an offset inlet opening and an ejector inlet opening of a corresponding inkjet ejector. For example, offset inlet opening  142 D is fluidly coupled to one end of offset channel  138 D, and another end of offset channel  138 D is fluidly coupled to the ink inlet  134 D of inkjet ejector  146 D. Ink from manifold  240 B flows through the offset channel  138 D and into the inkjet ejector  146 D. The embodiment of  FIG. 5  further depicts filters  244 B,  244 D,  248 B, and  248 D that are positioned over and across offset inlet openings  112 B,  112 D,  142 B, and  142 D, respectively. In alternative embodiments, the filters  244 B,  244 D,  248 B and  248 D are positioned across and within the corresponding inlet openings to be flush with the offset inlet opening layer  204 . The filters enable ink to pass through the respective offset inlet openings while preventing particulates and other solid contaminates from entering inkjet ejectors. 
         [0025]    As seen in  FIG. 1 ,  FIG. 4  and  FIG. 5 , a manifold wall  150  separates manifold  240 A from manifold  240 B. The manifold wall  150  is bonded to the offset inlet layer  204 . The surface area of the manifold wall  150  that contacts the offset inlet layer  204  is sufficient to form a seal between manifolds  240 A and  240 B that prevents an exchange of ink between the manifolds. The manifold wall  150  in the embodiment of  FIG. 1  and  FIG. 5  has a thickness that extends above of some of the ink inlet openings, including ink inlet openings  104 D and  134 A.  FIG. 1  and  FIG. 4  depict an outline of the base of manifold wall  150  to indicate the location where the manifold wall  150  contacts the offset inlet layer  204 .  FIG. 5  depicts the thickness of the wall  150 . As described below, the configuration of the offset inlet layer  204  and offset channel layer  208  enables manifolds  240 A and  240 B to provide ink to the inkjet ejectors in ejector groups  102 A and  102 B, respectively, including inkjet ejectors having inlet openings positioned under the manifold wall  150 . 
         [0026]    Referring to  FIG. 1 ,  FIG. 2 , and  FIG. 5 , the inlet layer  212  includes plurality of inlet openings that each enable ink to flow into a body layer in a single inkjet ejector. In  FIG. 1 , inlet openings  104 A,  104 B,  104 C  104 D in inkjet ejector group  102 A are fluidly coupled inkjet ejectors  116 A,  116 B,  116 C, and  116 D, respectively. In inkjet ejector group  102 B, the inlet openings  134 A,  134 B,  134 C, and  134 D are fluidly coupled to the inkjet ejectors  146 A,  146 B,  146 C, and  146 D, respectively. As seen in  FIG. 1  and  FIG. 2 , the inlet openings  104 A- 104 D and  134 A- 134 D are arranged in a column that is parallel to the process direction  162  as indicated by line  172 . Two adjacent inkjet ejectors in each row, such as inkjet ejectors  116 A and  116 B, have corresponding inlet openings  104 A and  104 B arranged along the column. This arrangement is repeated in the cross process direction for adjacent pairs of inkjet ejectors in each row. 
         [0027]    The distance between each of the ink inlets  104 A- 104 D and  134 A- 134 D is uniform for the ejector groups  102 A and  102 B. In particular, the distance between inlet port  104 D in color group  102 A and inlet port  134 A in color group  102 B is the same as the distances between adjacent ink inlet ports within each of the two color groups. In one example embodiment, the edges of adjacent inlet openings positioned in a column are separated by a distance of approximately 170 μm. The distance between the corresponding inkjet ejectors  116 D and  146 D is also the same as the distance between adjacent inkjet ejectors in each of the two ejector groups  102 A and  102 B. 
         [0028]    Referring to  FIG. 1  and  FIG. 5 , the offset inlet layer  204  includes a plurality of offset inlet openings exemplified by offset openings  112 A,  112 B,  112 C,  112 D,  142 A,  142 B,  142 C, and  142 D. A single offset inlet opening is configured to enable ink from a corresponding manifold to enter the offset inlet layer  204 , pass through a corresponding ink offset channel, and flow into a corresponding inlet opening for an inkjet ejector. For example, offset inlet opening  112 B enables ink in manifold  240 A to enter offset channel  108 B and flow through inlet opening  104 B of inkjet ejector  116 B.  FIG. 1  and  FIG. 5  depict offset inlet openings having a diameter that is approximately equal to the diameter of the inkjet inlet openings, but alternative offset inlet openings may have a different diameter. The offset inlet openings for each row of inkjet ejectors in the ejector groups  102 A and  102 B are arranged in a row along the cross-process direction  174  and perpendicular to the columns of ink inlets for the inkjet ejectors as indicated by line  172 . 
         [0029]    The position of each row of offset inlet openings is selected to place the offset inlet openings at a predetermined distance from the manifold wall  150 . As seen in  FIG. 1  and  FIG. 4 , the rows of offset inlet openings in inkjet ejector groups  102 A and  102 B that are closest to the manifold wall  150  are both aligned in parallel to the manifold wall  150  along the cross-process direction parallel to line  174 . The distance between each row of offset inlet openings, shown as distance  180  for inkjet ejector group  102 A and distance  182  for inkjet ejector group  102 B, are substantially equal for both inkjet ejector groups. The distance between the two rows of offset inlet openings is more than twice the distance that separates adjacent ink inlets that are fluidly coupled to inkjet ejectors in different inkjet ejector groups, such as ink inlets  104 D and  134 A. 
         [0030]    As seen in  FIG. 1  and  FIG. 5 , the manifold wall  150  has a thickness that would partially or fully occlude ink inlet openings near the manifold wall, such as ink inlet openings  104 D and  134 A, if the manifold wall  150  were bonded to the inlet layer  212 . The arrangement of the inlet offset openings enables the manifold wall  150  to be bonded to the offset inlet layer  204  without blocking the offset inlet openings such as openings  112 D and  142 A. The positions of the offset inlet openings and offset channels enable ink to flow from reservoir  240 A through opening  112 D, offset channel  108 D and into inlet opening  104 D for printhead  116 D. Similarly, offset inlet opening  142 A enables ink to flow from reservoir  240 B through channel  138 A and into inlet opening  134 A for printhead  146 A. 
         [0031]    The offset inlet openings that correspond to each pair of inlet openings in a single column of inlet openings are spaced at substantially equal linear distances from the corresponding inlet openings. For example, offset channels  108 A and  108 B fluidly couple offset inlet openings  112 A and  112 B to corresponding inlet openings  104 A and  108 B, respectively. The linear distance, and consequently the length of the corresponding offset channel, between offset inlet opening  112 A and inlet opening  104 A is substantially equal to the linear distance between offset inlet opening  112 B and inlet opening  104 B. The offset channels have substantially equal lengths that enable the offset channels to provide a uniform fluid resistance to ink flowing from a manifold to each inkjet ejector fluidly coupled to the manifold. 
         [0032]    As seen in  FIG. 1  and  FIG. 3 , the offset inlet openings are positioned on opposite sides of each column of inlet openings. For example, offset inlet opening  112 A is laterally offset to the right of inlet opening  104 A along line  174  and offset inlet opening  112 B is laterally offset to the left of inlet opening  104 B along line  174 . The arrangement of offset inlet openings provides a larger magnitude of separation in between adjacent offset inlet openings in each row than between adjacent inlet openings in each column. For example, the separation between offset inlet openings  112 A and  112 B in a single row seen along line  174  is approximately twice the distance that separates the corresponding inlet openings  104 A and  104 B in a single column seen along the transverse line  172 . The selected arrangement of offset inlet openings that correspond to each row of inkjet ejectors may separate adjacent offset inlet openings in a row by a factor two or more times the distance that separates adjacent inlet openings in each column of inlet openings. 
         [0033]    Each pair of corresponding offset inlet openings in the offset inlet layer  204  and inlet openings in the inlet layer  212  are fluidly coupled via an offset channel formed in the offset layer  208 . In inkjet ejector group  102 A, offset channels  108 A,  108 B,  108 C, and  108 D place inlet openings  104 A,  104 B,  104 C, and  104 D in fluid communication with manifold  240 A via offset inlet openings  112 A,  112 B,  112 C, and  112 D, respectively. In inkjet ejector group  102 B, offset channels  138 A,  138 B,  138 C, and  138 D place inlet openings  134 A,  134 B,  134 C, and  134 D in fluid communication with manifold  240 B via offset inlet openings  142 A,  142 B,  142 C, and  142 D, respectively. Each offset channel includes two ends, with an offset inlet opening positioned at one end and the corresponding inlet opening positioned at the other end. The length and angular offset of each offset channel corresponds to the relative positions of the corresponding offset inlet openings and inlet openings. The offset channels have a width that is wider than the diameters of the offset inlet openings and inlet openings, with the offset channels depicted herein having a width of approximately 200 μm. 
         [0034]    Each offset channel presents a fluid resistance to the flow of ink through the offset channel to a corresponding ink inlet. The amount of fluid resistance that the offset channel presents is determined, at least in part, by the length, width, and thickness of the offset channel. As described above, the length and width of the fluid channels are dictated by the relative positions and sizes of corresponding offset inlet openings and inkjet inlet openings. Consequently, the thickness of offset layer  208  may be varied to change the level of fluid resistance through the flow channel. The selected thickness of the offset layer  208  and offset channels changes the level of fluid resistance that each offset channel presents to fluid ink, with the level of fluid resistance being inversely related to the thickness of the fluid channel. 
         [0035]    As seen in  FIG. 5 , the path leading from an ink manifold to each inkjet ejector presents a level of fluid resistance to the fluid as the fluid flows from the manifold to the inkjet ejector. Using inkjet ejector  146 D as an example, the inlet path in the inkjet ejector through the ink inlet  134 D to pressure chamber  260  presents a predetermined amount of fluid resistance to ink as the ink flows through the inkjet ejector  146 D. The offset channel  138 D forms a portion of the length of the fluid path from the manifold  240 B to the inkjet ejector  146 D, and consequently contributes fluid resistance to ink supplied to the inkjet ejector  146 D. 
         [0036]    A certain degree of fluid resistance aids the operation of the inkjet ejector  146 D by preventing ink from flowing through the aperture  268  in the ejector  146 D in the absence of a firing signal. If the magnitude of flow resistance is too great, however, the inkjet ejector  146 D may not receive a sufficient quantity of ink to eject during an imaging operation, leading to a reduction in image quality and potential damage to the inkjet ejector. Thus, the offset channel  138 D is configured to add an amount of flow resistance to the fluid path through ejector  146 D that enables the ejector  146 D to receive ink at a sufficient rate to eject ink drops during imaging operations. 
         [0037]    The thickness of the offset layer  208  is selected so that the proportion of fluid resistance that the offset channel contributes to the fluid path from the manifold  240 B to the inkjet ejector  146 D is below a predetermined proportion of the total fluid resistance for the fluid path. In the embodiment of  FIG. 1  and  FIG. 5 , the offset channel is configured to contribute less than ten percent of the total fluid resistance of the fluid path. In the selected configuration, the thickness of the offset channel layer is 125 μm. In general, the flow channel contributes a smaller portion of the fluid resistance in the fluid path as the thickness of the flow channel increases. Various other configurations of the flow channel may have different thicknesses to provide a higher or lower proportion of the total fluid resistance. 
         [0038]      FIG. 6  and  FIG. 7  depict an alternative configuration of offset inlet channels. In  FIG. 6 , an offset inlet opening layer  604  is depicted with offset inlet openings  644  and  648  formed over one end of offset channels  636  and  638 , respectively. Another end of offset channel  636  is positioned over an inlet opening  606  formed in an inlet layer  612 . The inlet opening  606  is fluidly connected to an inkjet ejector. Similarly, offset channel  638  is positioned over ink inlet  634  that is formed through the inlet layer  612 . The offset inlet openings  644  and  648  have an approximately quadrilateral shape and are larger in area than corresponding inlet openings  606  and  634  that are positioned at another end of each offset channel. The offset channel inlets  644  and  648  are filled with filters  642  and  646 , respectively. The filters  642  and  646  enable ink to flow into a corresponding offset channels and inkjet ejectors and block contaminants suspended in ink from passing through the offset inlet openings. 
         [0039]    A wall  650  is positioned between the offset inlet openings  644  and  648  and over a portion of ink inlets  606  and  610 . As seen in  FIG. 7 , the wall  650  is bonded to the offset inlet layer  604  and separates two manifolds  640 A and  640 B that hold inks having two different colors.  FIG. 7  also depicts the filters  642  and  646  as being positioned across the corresponding offset inlet opening  644  and  648  coextensive with the offset inlet layer  604 . In one embodiment, the filters  642  and  646  are formed by ablation of a plurality of openings through the offset inlet layer  604  in locations corresponding to the offset inlet openings  644  and  648 , respectively. 
         [0040]    In operation, the offset inlet opening  644  enables ink in the ink supply  640 A to pass through filter  642 , flow through offset inlet channel  632 , and enter an inkjet ejector through inlet opening  606 . The offset inlet opening  648  enables ink in the ink supply  640 B to pass through filter  646 , flow through offset inlet channel  638 , and enter another inkjet ejector through inlet opening  634 . The offset inlet openings and offset channels enable the wall  650  to have a sufficient width to separate the inks held in manifolds  640 A and  640 B while also enabling ink to flow through inlet openings, such as inlet opening  606  and  610  that are positioned under the wall  650 . The size and shape of the offset inlet openings and offset channels are selected to enable each of the offset channels to provide a uniform fluid resistance to ink flowing from a manifold to each inkjet ejector fluidly coupled to the manifold. 
         [0041]      FIG. 8  depicts another alternative configuration of an offset inlet channel  808  and an inkjet ejector  816 . Inkjet ejector  816  includes the ink inlet layer  212 , actuator layer  216 , piezoelectric transducer elements  256 , diaphragm layer  220 , body layers  224  and  228 , outlet layer  232 , and aperture layer  236  as described above. In the configuration of  FIG. 8 , a manifold wall  850  separates two ink manifolds  840 A and  840 B. The manifold wall  850  is bonded to one side of an offset inlet layer  804 , and an opposite side of the offset inlet layer  804  is bonded to an offset channel layer  806 . An offset inlet opening  812  formed in the offset inlet layer  804 , offset channel  808  formed in the offset channel layer, and inlet opening  814  places the ink manifold  840 B in fluid communication with the inkjet ejector  816 . The offset inlet opening  812  is positioned on one side of the wall  850  under ink manifold  840 B, while the inlet opening  814  that is in fluid communication with the inkjet ejector  816  is positioned on the opposite side of the manifold wall  850  under ink manifold  840 A. The offset inlet channel  808  passes under the manifold wall  850  to place the ink manifold  840 B in fluid communication with the ink ejector  816  even though the corresponding inlet opening  814  is positioned under the ink manifold  840 A. 
         [0042]    It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. For example, the positions and sizes of the offset inlets described herein may be varied to accommodate different sizes and configurations of inkjet arrays and manifold designs. Various offset inlet placement configurations may be employed that provide ink to the inkjet ejectors while enabling a manifold wall to seal adjacent ink manifolds. Similarly, the dimensions and angular configurations of the offset channels may be altered to accommodate different inkjet ejector array configurations. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Technology Category: b