Abstract:
A recording apparatus includes a first recording head. The first recording head includes a first nozzle plate. The first nozzle plate includes a first group of nozzle holes and a first positioning hole configured to position the first recording head. A second recording head is adjacent to the first recording head in a first direction. The second recording head includes a second nozzle plate. The second nozzle plate includes a second plurality of nozzle holes and a second positioning hole configured to position the second recording head. The first positioning hole and the second positioning hole are aligned in a straight line extending in the first direction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2008-064012, which was filed on Mar. 13, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates generally to a recording apparatus for recording an image on a recording medium by ejecting droplets and a method for manufacturing the recording apparatus. 
         [0004]    2. Description of Related Art 
         [0005]    A known inkjet printer includes a plurality of inkjet heads arranged, such that the inkjet heads partially overlap one another in the conveying direction, e.g., staggered in a scanning direction perpendicular to the conveying direction. In the known inkjet printer, the inkjet heads are positioned with reference to the positions of the nozzles arranged in the overlapping regions of the inkjet heads, or, with reference to alignment marks formed in the ink ejection surfaces of the inkjet heads. 
         [0006]    In the known inkjet printer, the nozzles formed in the inkjet heads are spaced apart from one another by a distance equal to the print resolution in the scanning direction. Therefore, the nozzles formed in overlapping regions of the inkjet heads are not arranged in a straight line extending in the conveying direction. Thus, it is difficult to position adjacent inkjet heads in the conveying direction with reference to the positions of their nozzles. 
       SUMMARY OF THE INVENTION 
       [0007]    A need has arisen for a recording apparatus capable of accurately and easily positioning the recording heads. 
         [0008]    According to an embodiment of the invention, a recording apparatus comprises a first recording head and a second recording head. The first recording head comprises a first nozzle plate. The first nozzle plate comprises a first plurality of nozzle holes and a first positioning hole configured to position the first recording head. The second recording head is adjacent to the first recording head in a first direction. The second recording head comprises a second nozzle plate. The second nozzle plate comprises a plurality of nozzle holes and a second positioning hole configured to position the second recording head. The first positioning hole and the second positioning hole are aligned in the first direction. 
         [0009]    According to another embodiment of the invention, a recording apparatus comprises a plurality of recording heads arranged adjacent to one another in a first direction. Each of the recording heads comprises a nozzle plate. Each nozzle plate comprises a plurality of nozzle holes and at least one positioning hole configured to position the plurality of recording heads. A first positioning hole formed in a first nozzle plate of a first recording head and a second nozzle hole formed in a second nozzle plate of a second recording head adjacent to the first recording head are aligned in the first direction. 
         [0010]    According to yet another embodiment of the invention, a recording apparatus manufacturing method comprises the steps of arranging a first recording head and a second recording head adjacent to the first recording head in a first direction. Each of the first and the second recording heads comprises a nozzle plate which comprises a plurality of nozzle holes, at least one detection hole, and at least one positioning hole configured to position the recording heads. The manufacturing method further comprises the steps of attaching the first and the second recording heads to the recording apparatus, determining the positions of a first positioning hole of the first recording head and a second positioning hole of the second recording head, detecting the positions of the first and the second positioning holes with reference to the at least one detecting hole of each of the first and the second recording head, confirming the positions of the first and the second positioning holes, and positioning the first and the second inkjet heads, such that the first and the second positioning holes are aligned in the first direction. 
         [0011]    Other objects, features, and advantages of the invention will be apparent to persons of ordinary skill in the art in view of the foregoing detailed description of the invention and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of the invention, the needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following description taken in connection with the accompanying drawings. 
           [0013]      FIG. 1  is a side view of an inkjet printer according to an embodiment of the invention. 
           [0014]      FIG. 2  is a plan view of inkjet heads according to an embodiment of the invention. 
           [0015]      FIG. 3  is a plan view of a head body according to the embodiment of  FIG. 2 . 
           [0016]      FIG. 4  is an enlarged view of a region enclosed by a dashed-line in  FIG. 3 . 
           [0017]      FIG. 5  is a cross-sectional view along line V-V in  FIG. 4 . 
           [0018]      FIG. 6A  is an enlarged partial view of regions in which two of the ink jet heads overlap each other according to the embodiment of  FIG. 2 . 
           [0019]      FIG. 6B  is an enlarged view of a region enclosed by a dashed-line in  FIG. 6A . 
           [0020]      FIG. 7  is an enlarged plan view of positioning holes according to the embodiment of  FIG. 2 . 
           [0021]      FIG. 8  is an enlarged partial view of nozzles holes and positioning holes according to another embodiment of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]    Embodiments of the invention and their features and technical advantages may be understood by referring to  FIGS. 1-8 , like numerals being used for like corresponding portions in the various drawings. References to the “right” or “left” side refer to opposite sides consistent with the orientation of the referenced figure. 
         [0023]    Referring to  FIG. 1 , an inkjet printer  101 , e.g., a color inkjet printer, may comprise a plurality of inkjet heads  1 , e.g., eight, inkjet heads  1 . Inkjet printer  101  may comprise a sheet feeding part  11  on the left side, a sheet discharging part  12  on the right side, and a sheet conveying path extending from sheet feeding part  11  to sheet discharging part  12  for conveying a sheet P, as shown in  FIG. 1 . 
         [0024]    A plurality of feed rollers, e.g., feed rollers  5   a  and  5   b , may nip and convey sheet P, and may be disposed at the downstream side of sheet feeding part  11  in a sheet conveying direction. Feed rollers  5   a  and  5   b  may feed sheet P from sheet feeding part  11  in the sheet conveying direction, e.g., toward the right in  FIG. 1 . A conveying mechanism  13  may be disposed in sheet conveying path  11 . Conveying mechanism  13  may comprise a plurality of belt rollers, e.g., belt rollers  6  and  7 ; an endless conveying belt  8  that wraps and moves around belt rollers  6  and  7 ; and a platen  15  positioned in a region surrounded by conveying belt  8 . Platen  15  may support conveying belt  8  at a position opposite to the positions of inkjet heads  1  to prevent conveying belt  8  from sagging downward. A nip roller  4  may be disposed at a position opposite belt roller  7 . Nip roller  4  may press sheet P fed from feed rollers  5   a  and  5   b  onto an outer circumference  8   a  of conveying belt  8 . 
         [0025]    When a conveying motor (not shown) rotates belt roller  6 , conveying belt  8  may convey sheet P from nip roller  4  to sheet discharging part  12 , and may hold sheet P with a weak adhesive force on the surface of conveying belt  8  during the sheet conveying process. The surface of conveying belt  8  may comprise a weak-adhesive, silicon resin layer. 
         [0026]    A separating mechanism  14  may be disposed on the downstream side of conveying belt  8  in the sheet conveying direction. Separating mechanism  14  may separate sheet P from outer circumference  8   a  of conveying belt  8  and may guide sheet P to sheet discharging part  12 . 
         [0027]    Referring to  FIG. 2 , inkjet heads  1  may have a substantially rectangular-parallelepiped shape, elongated in a direction, e.g., main scanning direction, perpendicular to the sheet conveying direction, e.g., the direction from the bottom to the top in  FIG. 2 . A plurality of inkjet heads  1 , e.g., eight inkjet heads  1 , may be arranged, such that the inkjet heads alternately reverse orientation in the sheet conveying direction. Inkjet heads  1  may be arranged in an alternately reversed manner in the sheet conveying direction. Two adjacent inkjet heads  1  in the sheet conveying direction may comprise an inkjet head pair. A plurality of inkjet head pairs, e.g., four inkjet head pairs, may be arranged in the sheet conveying direction. Each of the plurality of inkjet head pairs may correspond to one of a plurality of colors of ink, e.g., magenta, yellow, cyan, and black. Each inkjet head  1  may eject ink droplets of its corresponding color. 
         [0028]    Two inkjet heads  1  of each inkjet head pair may be disposed, so that the pair of inkjet heads partially overlap each other in the sheet conveying direction and are offset from each other in the main scanning direction. The length of the ejection area of an inkjet head pair in the main scanning direction may be greater than the width of sheet P. Inkjet printer  101  may be a line printer. In another embodiment, a plurality of inkjet heads  1  may be aligned linearly in the sheet conveying direction, without offset from each other in the main scanning direction. 
         [0029]    Referring to  FIGS. 1 and 2 , inkjet heads  1  may comprise head bodies  2  at their lower ends, e.g., the portion of the inkjet heads closest to the conveying belt. The lower surfaces of head bodies  2  may comprise ink ejection surfaces  2   a  which are disposed opposite from outer circumference  8   a . Ink ejection surfaces  2   a  may be disposed at the lower surfaces of nozzle plates  130 . Each of ink ejection surfaces  2   a  may comprise a plurality of nozzle holes  108 . Nozzle holes  108  may be arranged at a pitch of 600 dpi in the main scanning direction. When the sheet P conveyed by conveying belt  8  passes below the plurality of head bodies  2 , ink droplets of various colors may be ejected from ink ejection surfaces  2   a  onto a top surface, e.g., print surface, of sheet P. In this way, a desired color image may be formed on the print surface of sheet P. 
         [0030]    Referring to  FIG. 3 , in each head body  2 , a plurality of actuator units  21 , e.g., four actuator units  21 , may be coupled to an upper surface  9   a  of a channel unit  9 . Referring to  FIG. 4 , each channel unit  9  may comprise ink channels with pressure chambers  110  and the like formed therein. Each actuator unit  21  may comprise a plurality of actuators, and each of the plurality of actuators may correspond to one or more of a plurality of pressure chambers  110 . Each actuator may be driven by a driver IC (not shown) and selectively may apply ejection energy to the ink in the corresponding pressure chamber. 
         [0031]    Each channel unit  9  may have a substantially rectangular-parallelepiped shape. Upper surface  9   a  of channel unit  9  may comprise a plurality of ink supply ports  105   b  corresponding to ink discharge channels (not shown) of a reservoir unit. Referring to  FIGS. 3 and 4 , channel unit  9  may comprise manifold channels  105 , and manifold channels  105  may communicate with ink supply ports  105   b  and sub-manifold channels  105   a , which branch off from the manifold channels  105 . Ink ejection surface  2   a  may comprise a plurality of nozzle holes  108  which are arranged in a matrix and may be disposed at the lower surface of channel unit  9 . A plurality of pressure chambers  110  may be arranged in a matrix in a surface of channel unit  9 , to which actuator units  21  are coupled. 
         [0032]    A plurality of rows of pressure chambers  110 , e.g., sixteen rows, may be arranged in the longitudinal direction of channel unit  9  and spaced equal distances apart from one another, and each of the plurality of rows may be arranged parallel to one another in the main scanning direction. Actuator units  21  may have a substantially trapezoidal shape. The number of pressure chambers  110  in each pressure chamber row gradually may decrease from the longer-side end to the shorter-side end of actuator units  21 . Nozzle holes  108  also may be arranged in similar manner. 
         [0033]    Referring to  FIG. 5 , channel unit  9  may be comprise a plurality of plates, e.g., nine plates  122  to  130 , made of metal, e.g., stainless steel. Each of plates  122  to  130  may be a rectangular, flat plate elongated in the main scanning direction. 
         [0034]    Through holes may be formed in plates  122  to  130 . Through holes may be connected by aligning and stacking plates  122  to  130 . Consequently, manifold channels  105 , sub-manifold channels  105   a , and multiple individual ink channels  132  extending from the outlets of sub-manifold channels  105   a  through pressure chambers  110  to nozzle holes  108  may be formed in channel unit  9 . The lower surface of nozzle plate  130  may comprise nozzle holes  108  and may function as ink ejection surface  2   a.    
         [0035]    Ink supplied from the reservoir unit through ink supply ports  105   b  to channel unit  9  may flow from manifold channels  105  to sub-manifold channels  105   a . The ink in sub-manifold channels  105   a  may flow in individual ink channels  132 . The ink may pass through apertures  112  which may function as throttles and pressure chambers  110 , before reaching nozzle holes  108 . 
         [0036]    Referring to  FIGS. 2 ,  6 A and  6 B, each nozzle plate  130  may comprise nozzle holes  108  and a plurality of positioning holes  109 , e.g., four positioning holes  109 . Positioning holes  109  may have the same shape as nozzle holes  108 . 
         [0037]    As shown in  FIGS. 2 and 6A , two of the plurality of positioning holes  109  may be disposed near two edges of nozzle plate  130  in the sheet conveying direction. As shown in  FIG. 6B , the two of the plurality of positioning holes  109  also may be disposed at the midpoint, in the main scanning direction, between two particular nozzle holes  108 . Two particular nozzle holes  108  may be formed in the overlapping regions of two nozzle plates  130 , adjacent to each other in the sheet conveying direction. Each of the two particular nozzle holes  108  may be one of the plurality of nozzle holes in its corresponding nozzle plate  130  and may be the nozzle hole disposed closest to the edge of its corresponding nozzle plate  130  in the main scanning direction. The other two positioning holes  109  may be arranged point-symmetrically to the aforementioned positioning holes  109  with respect to the center of the nozzle plate  130 . 
         [0038]    Each nozzle plate  130  may comprise positioning holes  109  arranged in a plurality of pairs, e.g., two pairs. The pairs of positioning holes  109  may be disposed point-symmetrically to each other with respect to the center of nozzle plate  130 . One of the two pairs of positioning holes  109 , e.g., the pair formed in the overlapping region, may be disposed along a straight line X, extending generally in the sheet conveying direction. In the nozzle plates  130  of two inkjet heads  1  adjacent to each other in the sheet conveying direction, positioning holes  109  formed in one nozzle plate  130  and positioning holes  109  formed in another nozzle plate  130  may be aligned along the straight line X. 
         [0039]    Nozzle holes  108  formed in one inkjet head pair may be arranged at a pitch of 600 dpi in the main scanning direction by aligning the positioning holes  109  along the straight line X. A configuration in which nozzle holes  108  are arranged at equal distances apart in the main scanning direction may be provided even when inkjet heads  1  are arranged, such that the inkjet heads alternately reverse orientation. Therefore, the center of each nozzle plate  130  also may be the center of nozzle holes  108  formed in each inkjet head  1 . In various shapes of nozzle plates  130 , positioning holes  109  may be formed with respect to the center of nozzle holes  108  which are formed in each inkjet head  1 . An inkjet head pair with a predetermined resolution in the main scanning direction may be provided by aligning positioning holes  109  in two nozzle plates  130  along the straight line X. 
         [0040]    Nozzle holes  108  may be arranged to conform to the trapezoidal shape of actuator units  21 . As shown in  FIG. 3 , the plurality of actuator units  21 , e.g., four actuator units  21 , may be arranged in a staggered manner in the longitudinal direction of channel unit  9 . Moreover, the center of nozzle holes  108  may coincide with the center of actuator units  21 . 
         [0041]    Referring to  FIG. 7 , a plurality of detection holes  109   a , e.g., four detection holes  109   a , with the same shape as nozzle holes  108  may be formed in a circle C centered at positioning hole  109  in nozzle plate  130 . The plurality of detection holes  109   a  may be evenly spaced apart from one another in circle C. Thus, positioning holes  109  may be detected readily with reference to detection holes  109   a.    
         [0042]    Nozzle holes  108 , positioning holes  109 , and detection holes  109   a  may be formed simultaneously by a punching member of a processing machine in the fabrication process of nozzle plates  130 . In the fabrication process, the relative positions of nozzle holes  108 , positioning holes  109 , and detection holes  109   a  may be maintained precisely. 
         [0043]    Inkjet heads  1  may be mounted to inkjet printer  101  during an assembling process of inkjet printer  101 . First, a plurality of inkjet heads  1 , e.g., eight inkjet heads  1 , may be attached temporarily to inkjet printer  101 . Second, a high-magnification camera may determine the overlapping regions of ink ejection surfaces  2   a , e.g., nozzle plates  130 , of inkjet heads  1  adjacent to one another in the sheet conveying direction. Third, with reference to detection holes  109   a , the positions of positioning holes  109  near the edges of ink ejection surfaces  2   a  which are adjacent to one another in the sheet conveying direction may be confirmed. Subsequently, inkjet heads  1  may be arranged, such that positioning holes  109  of adjacent ink ejection surfaces  2   a  are disposed along the same straight line X extending in the sheet conveying direction. By aligning positioning holes  109  along the same straight line X, inkjet heads  1  may be accurately and readily positioned. 
         [0044]    Because the plurality of positioning holes  109  are arranged point-symmetrically with respect to the center of ink ejection surface  2   a , the positional relationship of the plurality of positioning holes  109  may not change even when one or more of the plurality of inkjet heads  1  are mounted to inkjet head  1  in a reverse orientation. Thus, despite various mounting orientations, inkjet head  1  may use one type of nozzle plates  130 . Accordingly, the cost of producing inkjet heads  1  for various mounting orientations may be reduced. 
         [0045]    Two positioning holes  109  may be disposed near both edges in the width direction of nozzle plate  130  and at the midpoint, in the main scanning direction, between the particular nozzle holes  108  closest to the end edges, in the main scanning direction, of the nozzle plates  130  adjacent to each other in the sheet conveying direction. Accordingly, adjacent inkjet heads  1  may be positioned accurately with respect to one another in the sheet conveying direction by aligning the plurality of positioning holes  109 . 
         [0046]    Referring to  FIG. 8 , in nozzle plates  130  of two inkjet heads  1  adjacent to each other in the sheet conveying direction, a positioning hole  109  formed in one nozzle plate  130  and a particular nozzle hole  108  formed in the other nozzle plate  130  may be aligned along a straight line X′ extending in the sheet conveying direction. 
         [0047]    While the invention has been described in connection with various exemplary structures and illustrative embodiments, it will be understood by those skilled in the art that other variations and modifications of the structures and embodiments described above may be made without departing from the scope of the invention. Other structures and embodiments will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and the described examples are illustrative with the scope of the invention being defined by the following claims.