Patent Publication Number: US-2006001695-A1

Title: Inkjet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application Serial No. 10-2004-0051010, filed on Jul. 1, 2004, the entire disclosure of which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an inkjet printer. More particularly, the present invention relates to an inkjet printer with a printing head having a nozzle that is as wide as the paper being printed on.  
      2. Description of the Related Art  
      In general, an inkjet printer is a device for forming an image on paper by projecting ink onto the upper surface of the paper from a printing head. The printing head is generally spaced apart from the upper surface of the paper at a desired interval and reciprocates in a direction perpendicular to the feeding direction of the paper. The printing head includes a nozzle unit with a plurality of nozzles. If the nozzle unit is exposed to the atmosphere for a long time, the ink dries and clogs the nozzle. Also, dust in the air adheres to the nozzle and clogs the nozzle. The inkjet printer therefore includes a capping unit to shield the nozzle unit from the air when the printer is not in operation. The capping unit prevents the nozzle unit from drying or becoming contaminated by pollutants. Examples of capping units are disclosed in U.S. Pat. No. 6,467,872 and Korean Unexamined Patent Publication No. 1998-925, both of which are incorporated by reference in their entirety.  
      Recently, there have been attempts to achieve high-speed printing by using a printing head having a nozzle unit that is as wide as the paper being printed on, instead of a reciprocating printing head. In inkjet printers employing such a nozzle unit, the printing head is basically stationary while the paper is transferred. As such, the drive unit of the inkjet printer can be simplified and high-speed printing can be achieved. The length of the nozzle unit for the printing head is about 210 mm to correspond to a paper such as A4 size paper, without including any margins. To accommodate these wider printing nozzle units, there is a need for a new capping unit.  
     SUMMARY OF THE INVENTION  
      An aspect of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an inkjet printer employing a printing head having a nozzle unit with a length that corresponds to the width of a paper being printed on and a capping unit for capping the nozzle unit.  
      According to an aspect of the present invention, an inkjet printer includes a printing head with a nozzle unit having a length corresponding to the width of a paper being printed on, the printing head printing an image on the paper by projecting ink onto the paper from a stationary position, the nozzle unit being divided into a plurality of nozzle sections, a plurality of cap members each corresponding to at least one nozzle section, a cap drive unit for moving the plurality of cap members between a capped position and an uncapped position, and a motor for driving the cap drive unit.  
      The plurality of cap members may be divided into a plurality of cap groups including at least one cap member, and the cap drive unit may sequentially move the cap groups to the uncapped position one by one.  
      The cap drive unit may move the cap groups to the uncapped position starting from the cap group located at one side of the paper being printed. Alternatively, the cap drive unit may move the cap groups to the uncapped position starting from the cap group located at the center of the paper being printed.  
      The cap drive unit may include a plurality of rotary cams corresponding to the plurality of cap members, with each rotary cam including a first cam supporting the cap member at the capped position, a second cam supporting the cam member at the uncapped position and spirally engaged to the first cam, and a ramp for selectively allowing the first and second cams to be engaged depending upon the direction of rotation of the cam; a plurality of resilient members for applying a resilient force to the plurality of cap members to force the cap members toward the capped position; an uncapping unit for rotating the rotary cam in a third direction to move the plurality of cam members in a direction opposite the resilient force when the motor rotates in a first direction; and a capping unit for rotating the rotary cam in a fourth direction to allow the plurality of cam members to move in the same direction as the resilient force when the motor rotates in a second direction.  
      The inkjet printer may further comprise locking means for locking the rotary cam in the capped position or the uncapped position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features, and advantages of certain embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a perspective view of an inkjet printer according to an embodiment of the present invention;  
       FIGS. 2 and 3  are top views of exemplary nozzle units;  
       FIGS. 4A, 4B  and  4 C are top views of exemplary cap members;  
       FIGS. 5A and 5B  are top views showing examples of divided cap groups;  
       FIG. 6  is a top view of an embodiment of a cap drive unit;  
       FIG. 7  is a perspective view of an embodiment of a cap member;  
       FIGS. 8 and 9  are top views of an embodiment of a rotary cam;  
       FIG. 10  is a cross-sectional view of a ramp;  
       FIGS. 11 and 12  are top views showing the interrelationship between a gear of a rotary cam and a first gear;  
       FIG. 13  is a top view of an embodiment of an uncapping unit;  
       FIG. 14  is a top view showing the operation of a first delaying means;  
       FIG. 15  is a top view of an embodiment of a capping unit;  
       FIG. 16  is an exploded perspective view of an embodiment of the capping unit in  FIG. 15 ;  
       FIG. 17  is a side view showing the operation of a capping unit;  
       FIG. 18  is a top view showing the operation of a second delaying means;  
       FIG. 19  is an exploded perspective view of another embodiment of a capping unit;  
       FIG. 20  is a top view of an embodiment of a first delaying means;  
       FIG. 21  is a top view of another embodiment of a first delaying means;  
       FIG. 22  is a top view of another embodiment of a first delaying means;  
       FIG. 23  is a top view of another embodiment of a cap drive unit;  
       FIG. 24  is a top view of another embodiment of a cap drive unit; and  
       FIG. 25  is a top view of another embodiment of a cap drive unit. 
    
    
      Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features, and structures.  
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.  
       FIG. 1  is a perspective view showing an inkjet printer according to an embodiment of the present invention. Referring to  FIG. 1 , a paper P is transferred by a pair of rollers  20  which mate with one another and rotate together. A printing head  10  is located above the paper P and includes a nozzle unit  11  having a length corresponding to the width of the paper P. The printing head  10  prints an image on the paper P by projecting ink from the stationary nozzle unit  11  onto the paper P while the paper P is transferred by the pair of rollers  20 .  
       FIGS. 2 and 3  are top views showing exemplary embodiments of the nozzle unit  11 . Referring to  FIG. 2 , the nozzle unit  11  in this embodiment is divided into three nozzle sections  12 - 1 ,  12 - 2  and  12 - 3 . Each of the nozzle sections  12 - 1 ,  12 - 2  and  12 - 3  has a plurality of nozzles (not shown) for projecting ink. Referring to  FIG. 3 , the nozzle unit  11  has a plurality of nozzle sections  13  across the width of the paper P. Each of the nozzle sections  13  is angled with respect to the direction of the width of the paper P. Each of the nozzle sections  13  has a plurality of nozzles (not shown) for projecting ink. While  FIGS. 2 and 3  show exemplary nozzle units, it should be understood that any suitable nozzle unit can be used, and the scope of the present invention is not limited to the particular embodiments shown in  FIGS. 2 and 3 .  
      An inkjet printer employing the nozzle unit  11  in  FIG. 3  will now be described. Referring to  FIG. 4A , the inkjet printer includes a plurality of cap members  40  to prevent the nozzle unit  11  from drying out or becoming polluted. In  FIG. 4A , one nozzle section  13  is allocated to one cap member  40 . Alternatively, as shown in  FIG. 4B , two nozzle sections  13  may be allocated to one cap member  40 . The number of cap members  40  does not need to be identical with the number of nozzle sections  13 , and various combinations in addition to those shown in  FIGS. 4A and 4B  may be used. The exemplary embodiment using the same number of cap members as nozzle sections  13  will be now described with reference to  FIG. 4A .  
      The inkjet printer includes a cap drive unit  100  for moving a plurality of cap members  40  between a capped position and an uncapped position and a motor  30  for driving the cap drive unit  100 . In a conventional cap drive unit, the motor  30  needs to produce enough torque to move the plurality of cap members  40  en masse, and that requires a large and expensive motor. In the illustrated embodiment, the cap members are not moved en masse, however. To explain further, the nozzle unit  11  may be long enough to cover a letter-sized paper. The inkjet printer may print an image on a paper P smaller than the letter-sized paper, such as A4-sized, B5-sized or A6-sized paper. When an image is printed on smaller sized paper, such as A6-sized paper, only the nozzle section  13   a  is utilized, and the remaining nozzle section  13   b  is not utilized, as shown in  FIG. 4A . If the nozzle section  13   b  is exposed to the atmosphere when an image is printed, the nozzles may dry out. To prevent this, in the illustrated embodiment, it is possible to uncap only the nozzle section  13   a  used for printing and to cap the remaining nozzle section  13   b . To this end, the cap drive unit  100  of this embodiment sequentially moves a plurality of cap members  40  to the uncapped position one by one, such that only cap members  40  covering the nozzle section  13   a  used for printing can be moved to the uncapped position. When the paper P is aligned to one side of the printing unit regardless of the width of the paper, as illustrated in  FIG. 4A , the cap members  40  are sequentially uncapped starting from the cap member  40   a  located at the one side of the paper and proceeding across the width of the paper. When the paper P is aligned at the center of the printer, as shown in  FIG. 4C , the cap members  40  are sequentially uncapped starting at the center and moving outward. To move the cap members  40  into the capped position, the cap members  40  are moved in the reverse sequence.  
      The plurality of cap members  40  may be divided into multiple cap groups  40 - 1 ,  40 - 2  and  40 - 3 , as shown in  FIG. 5A . Each of the cap groups  40 - 1 ,  40 - 2  and  40 - 3  includes at least one cap member  40 . For example, the cap group  40 - 1  covers the A6-sized paper, while the cap groups  40 - 1  and  40 - 2  cover the B5-sized paper. The cap groups  40 - 1 ,  40 - 2  and  40 - 3  collectively cover A4-sized paper and letter-sized paper. The division of the cap groups shown in  FIG. 5A  may be used when the paper is aligned to one side of the printer regardless of the width of the paper. The plurality of cap members  40  may be divided into cap groups  40 - 1   a ,  40 - 2   b  and  40 - 3   c  as shown in  FIG. 5B  when the paper P is aligned at the center of the printer. For example, the cap group  40 - 1   a  covers A6-sized paper, while the cap groups  40 - 1   a  and  40 - 2   a  cover the B5-sized paper. The cap groups  40 - 1   a ,  40 - 2   b  and  40 - 3   c  collectively cover A4-sized paper and letter-sized paper. Of course, any suitable grouping of caps can be provided to cover any desired paper widths, in addition to the above embodiments shown in  FIGS. 5A and 5B .  
      Referring to  FIG. 6 , the cap drive unit  100  includes a plurality of rotary cams  60  positioned under the plurality of cap members  40 , an uncapping unit  110  and a capping unit  120 . The uncapping unit  110  and capping unit  120  rotate the plurality of rotary cams  60  to move the plurality of cam members  40  between the capped and uncapped positions.  
      Referring to  FIG. 7 , the cap member  40  includes a cap  41 , a frame  42 , and an arm  43 . The cap  41  tightly contacts the nozzle unit  11  and is preferably made of rubber. The cap  41  is coupled to the frame  42 , and the arm  43  extends downwardly from the frame  42 .  
      The rotary cam  60  includes first and second cams  61  and  62 , as shown in  FIG. 8 . The first cam  61  is located nearer the outer diameter of the rotary cam  60 , while the second cam  62  is located towards the interior of the rotary cam  60 . The first and second cams  61  and  62  are divided by a partition  64  that has an opening  64   a . The first and second cams  61  and  62  are spirally coupled to each other through the opening  64   a . The first and second cams  61  and  62  are selectively coupled by a ramp  63 , depending on the direction of rotation of the rotary cam  60 .  
      Referring to  FIG. 8 , the cap  41  contacts the nozzle unit  11 . The first cam  61  supports the arm  43 , thereby supporting the cap member  40  in the capped position. To move the cap member  40  to an uncapped position, the rotary cam  60  is rotated in a third direction C 3 .  FIG. 10  is a cross-sectional view of a section taken along the line A-B in  FIG. 8 . Referring to  FIG. 10 , the ramp  63  includes an upward stepped portion  63   a  formed on the first cam  61  to guide the arm  43  from the first cam  61  to the second cam  62  through the opening  64   a  when the rotary cam  60  is rotated in the third direction C 3 . When the rotary cam  60  is rotated in the third direction C 3 , for example, at an angle of 180 degrees, the second cam  62  supports the arm  43 , and the cap  41  is spaced apart from the nozzle unit  11 , as shown in  FIG. 9 . The second cam  62  supports the cap member  40  in the uncapped position. Even though the rotary cam  60  is continuously rotated in the third direction C 3 , with the arm  43  being supported by the second cam  62 , the arm  43  is guided by the partition  64  and the stepped portion  63   a  so that it is continuously supported by the second cam  62 .  
      The rotary cam  60  is rotated in a fourth direction C 4  to move the cap member  40  back to the capped position. When the rotary cam  60  is rotated in the fourth direction C 4 , the stepped portion  63   a  guides the arm  43  from the second cam  62  to the first cam  61  through the opening  64   a . When the rotary cam  60  is rotated in the fourth direction C 4  and the cam member  40  is being supported by the first cam  61 , it is necessary to continuously support the cap member  40  by the first cam  61 . To accomplish this, as shown in  FIG. 10 , the ramp  63  includes an upward inclined portion  63   c  that extends from the first cam  61  and a downward inclined portion  63   b  that extends from the upward inclined portion  63   c  to the stepped portion  63   a . Preferably, the upward inclined portion  63   c  has a top lower than the partition  64 . With such a construction, when the cap member  40  is being supported by the first cam  61  and the rotary cam  60  is rotated in the fourth direction C 4 , the arm  43  is sequentially supported by a section A of the first cam  61 , the upward inclined portion  63   c , the downward inclined portion  63   b , the stepped portion  63   a , and a section B of the first cam  61 . Thus, the cap member  40  is continuously supported by the cam  61 . Preferably, the arm  43  is mounted so that it slightly moves in the direction indicated by the arrow D in  FIG. 7 .  
      The cap drive unit  100  also includes a locking means for locking the rotary cam  60  in the capped position and the uncapped position. Referring to  FIG. 8 , the locking means includes first and second recessed locking portions  65  and  66  formed at an outer periphery  67  of the rotary cam  60 , and a resilient engaging member  70  resiliently contacted with the outer periphery  67  of the rotary cam  60 . The first and second locking portions  65  and  66  are spaced apart from each other at a distance corresponding to the phase difference between the first and second cams  61  and  62 . In other words, in the illustrated embodiment, since the first and second cams  61  and  62  are spaced apart from each other at an angle of 180 degrees, the first and second locking portions  65  and  66  are spaced apart from each other at an angle of 180 degrees. As shown in  FIG. 8 , when the cap member  40  is in the capped position, the resilient engaging member  70  resiliently engages the first locking portion  65 . During the rotation of the rotary cam  60 , the resilient engaging member  70  resiliently contacts the outer periphery  67  of the rotary cam  60 . As shown in  FIG. 9 , when the cap member  40  is located in the uncapped position, the resilient engaging member  70  resiliently engages the second locking portion  66 .  
      The cap drive unit  100  also includes a plurality of resilient members  50  that apply a resilient force to the cap member  40  in a direction towards the capped position as shown in  FIGS. 7 and 8 . The uncapping unit  110  rotates the rotary cam  60  in the third direction C 3  to cause the cap member  40  to move in a direction against the resilient force of the resilient member  50  when the motor  30  rotates in the first direction C 1 . The capping unit  120  rotates the rotary cam  60  in the fourth direction C 4  to cause the cap member  40  to move in a direction toward the resilient force of the resilient member  50  when the motor  30  rotates in the second direction C 2 . With this construction, the load applied to the motor  30  is very small when the cap member  40  is moved to the capped position.  
      Referring to  FIGS. 6, 11 ,  12  and  13 , the uncapping unit  110  includes a plurality of geared portions  68  corresponding to the plurality of rotary cams  60 , a plurality of first gears  80  corresponding to the plurality of rotary cams  60 , and a plurality of first delaying means  89  disposed between the first gears  80 . As shown in  FIG. 11 , a first gear  80  meshes with a geared portion  68 . The geared portion  68  has an idle portion  69  with no teeth. The idle portion  69  is located at a position that corresponds to the uncapped position of the cap member  40 , as shown in  FIG. 12 . Thus, in that position, when the first gear  80  is rotated, the rotary cam  60  does not rotate. Preferably, the geared portion  68  of the rotary cam  60  has the same number of teeth as that of the first gear  80 .  
      The plurality of rotary cams  60  are axially aligned with one another. Also, the plurality of first gears  80  are axially aligned with one another. To accomplish this, the rotary cams  60  and the first gears  80  are rotatably mounted to the first shaft  101  and the second shaft  102 , respectively, as shown in  FIG. 13 .  
      Referring to  FIG. 13 , a gear  103  is mounted on the second shaft  102 . The gear  103  has a recessed portion  104  engaged with a second protrusion  82  of the first gear  80   a . With the arrangement, when the motor  30  rotates in the first and second directions C 1  and C 2 , the first gear  80   a  is rotated in the fifth and sixth directions C 5  and C 6 . Alternatively, although not shown in the figures, the motor  30  may be directly coupled to the first gear  80   a.    
      The rotary cam  60   a  is rotated in the third direction C 3  to move the cap member  40   a  to the uncapped position. In this situation, the rotary cam  60   b  should not be rotated. Accordingly, the first gear  80   b  should not be rotated when the first gear  80   a  rotates the rotary cam  60   a . To accomplish this, the first delaying means  89  allows a preceding first gear  80   a  to be coupled to a subsequent first gear  80   b  after a delay corresponding to the phase difference between the first and second cams  61  and  62  of the rotary cam  60 . As described above, the phase difference between the first and second cams  61  and  62  is set to 180 degrees.  
      Referring to  FIG. 13 , the first delaying means  89  includes a first protrusion  81  formed at the preceding first gear  80   a  and a second protrusion  82  formed at the subsequent first gear  80   b . The first gear  80   a  is rotated in the fifth direction C 5  to cause the rotary cam  60   a  to rotate in the third direction C 3 . Preferably, the second protrusion  82  is spaced apart from the first protrusion  81  in the fifth direction C 5  at an angle greater than 180 degrees. In this embodiment, the second protrusion  82  initially contacts a side of the first protrusion  81  facing the sixth direction C 6  of the first protrusion  81 . Accordingly, when the first gear  80   a  is rotated in the fifth direction C 5 , the first protrusion  81  is spaced apart from the second protrusion  82 , so that the first gear  80   b  is not rotated. If the rotary cam  60   a  is rotated at an angle of 180 degrees, the cap member  40   a  is moved to the uncapped position, as shown in  FIG. 9 . Since the first gear  80   a  meshes with the idle portion  69 , as shown in  FIG. 12 , the rotary cam  60   a  stops rotating. If the first gear  80   a  is continuously rotated in the fifth direction C 5 , as shown in  FIG. 14 , the first protrusion  81  of the first gear  80   a  contacts a side of the second protrusion  82  of the first gear  80   b  facing to the sixth direction C 6 . If the first gear  80   a  is further rotated in the fifth direction C 5 , the first protrusion  81  pushes the second protrusion  82 , so that the first gear  80   b  starts rotating. Accordingly, the rotary cam  60   b  is rotated, and the cap member  40   b  is moved to the uncapped position.  
      With the above described uncapping unit  110 , if the motor  30  continuously rotates in the first direction C 1 , the cap member  40   a  located at one end of the nozzle unit  11  is uncapped first and the rest of the cap members  40  are sequentially moved to the uncapped position. Thus, the proper number of cap members  40  can be moved to the uncapped position in line with a predetermined or detected size of paper P, and the motor  30  can then be stopped. For example, the number of cap members  40  moved to the uncapped position can be calculated by detecting the amount of rotation the motor  30 . The paper P is transferred by a pair of carry rollers  20 , and the nozzles of the uncapped nozzle section  13  project the ink onto the paper to print the image. After completing the print, the nozzle section  13  is again capped by actuating the capping unit  120 .  
      Referring to  FIGS. 15 and 16 , the capping unit  120  includes a second gear  92 , a transmitting means  90 , and a second delaying means  79 . The second gear  92  is installed on the first shaft  101 , and rotates the rotary cam  60   z  spaced farthest from the rotary cam located at the far end of the nozzle unit  11  (in other words, the rotary cam  60   a ). The transmitting means  90  transmits the rotational force of the motor  30  to the second gear  92  when the motor  30  rotates in the second direction C 2 . When the second gear  92  is rotated in the fourth direction C 4 , the driving force is transmitted from the rotary cam  60   z  to the rotary cam  60   a  through the second delaying means  79 . The subsequent rotary cam  60   b  should not be rotated by the preceding rotary cam  60   a  in the uncapping process. Specifically, the second delaying means  79  keeps the subsequent rotary cam  60   b  in a stopped state while the rotary cam  60   a  rotates in the third direction C 3  by at least the phase difference between the first and second cams  61  and  62  in the uncapping process.  
      The transmitting means  90  includes a third gear  93 , a swing arm  95 , and coupling gears  94   a  and  94   b . The third gear  93  is axially aligned with the plurality of first gears  80 . The third gear  93  is installed towards the end of the second shaft  102 , and is rotated by the first gear  80   z  that is spaced farthest from the first gear located at the far end of the nozzle unit  11  (in other words, the first gear  80   a ). The swing arm  95  is pivotally engaged to the second shaft  102 , and the coupling gears  94   a  and  94   b  are installed on the swing arm  95 . The coupling gear  94   a  meshes with the third gear  93 , while the coupling gear  94   a  meshes with the coupling gear  94   b . A first delaying means  89  may be interposed between the first gear  80   z  and the third gear  93 .  
      The second delaying means  79  includes a fourth protrusion  74  provided at the preceding rotary cam  60   y  and a fifth protrusion  75  provided at the subsequent rotary cam  60   z . The fifth protrusion  75  is spaced apart from the fourth protrusion  74  in the third direction C 3  at a distance corresponding to the phase difference between the first and second cams  61  and  62 . A plurality of rotary cams  60  is rotated in the third direction C 3  to uncap the cam member  40 . In this embodiment, the fifth protrusion  75  contacts the side of the fourth protrusion  74  that faces the fourth direction C 4 . Since the cap members  40   a  through  40   x  are already moved to the uncapped position, each of the rotary cams  60   a  through  60   x  is rotated in the third direction C 3  at an angle of 180 degrees.  
      Accordingly, the fourth protrusions  74  of the rotary cams  60   a  through  60   w  contact the sides of the fifth protrusions  75  of the rotary cams  60   b  through  60   x  that face the fourth direction C 4 . The second delaying means  79  may be interposed between the second gear  92  and the rotary cam  60   z.    
      The operation of the mechanism described above will now be described. To facilitate the description, an exemplary case where the cap members  40   a  through  40   x  are moved to the uncapped position by the uncapping unit  110  is described. The motor  30  is rotated in the second direction C 2  to perform the capping operation. A plurality of first gears  80  are rotated in the sixth direction C 6 . In the process of moving the cap members  60   a  through  60   x  to the uncapped position, the first protrusions  81  of the first gears  80   a  through  80   x  contact the sides of the second protrusions  82  of the first gears  80   b  through  80   y  facing the sixth direction C 6 . Accordingly, when the motor  30  is rotated: in the second direction C 2 , the first gear  80   a  is immediately rotated, but the first gear  80   b  is not rotated until the first protrusion  81  of the first gear  80   a  contacts the side of the second protrusion  82  of the first gear  80   b  facing to the fifth direction C 5 . Thus, if the motor  30  continuously rotates, the first gears  80   b  through  80   x  are sequentially rotated in the sixth direction C 6  by the action of the first delaying means  89 . Since the first gears  80   a  through  80   x  mesh with the idle portions  69  of the rotary cam  60   a  through  60   x , the rotary cams  60   a  through  60   x  are not rotated. If the first protrusion  81  of the first gear  80   x  is in contact with the side of the second protrusion  82  of the first gear  80   y  facing the fifth direction C 5 , the first gear  80   y  is rotated. Since the first protrusion  81  of the first gear  80   y  contacts the side of the second protrusion  82  of the first gear  80   z  facing the fifth direction C 5 , the first gears  80   y  and  80   z  are simultaneously rotated in the sixth direction C 6  by the first gear  80   z . The third gear  93  is rotated in the sixth direction C 6  by the first gear  80   z . Since the third gear  93  meshes with the coupling gears  94   a  and  94   b , the rotational force is transmitted from the third gear  93  to the swing arm  95 . The swing arm  95  is pivotally moved in the sixth direction C 6 , as shown in  FIG. 17 , so that the coupling gear  94   b  meshes with the second gear  92 . The second gear  92  rotates the rotary cam  60   z  in the fourth direction C 4 .  
      Referring to  FIG. 15 , the fifth protrusion  75  of the rotary cam  60   z  contacts the side of the fourth protrusion  74  of the rotary cam  60   y  facing the fourth direction C 4 . Accordingly, after the fifth protrusion  75  of the rotary cam  60   z  contacts the side of the fourth protrusion  74  of the rotary cam  60   y  facing the third direction C 3 , as shown in  FIG. 18 , the rotary cam  60   y  starts rotating. Without considering the thickness of the fourth and fifth protrusions  74  and  75 , the fifth protrusion  75  of the rotary cam  60   y  is spaced apart from the fourth protrusion  74  of the rotary cam  60   x  in the fourth direction C 4  at a distance corresponding to the results obtained by subtracting the phase difference between the first and second cams  61  and  62  from 360 degrees. Accordingly, the rotary cam  60   x  is delayed with respect to the rotary cam  60   y  by the value obtained by subtracting the phase difference between the first and second cams  61  and  62  from 360 degrees. At this stage, the cap members  40   z  and  40   y  are capped. Although the rotary cams  60   z  and  60   y  are rotated in the fourth direction C 4 , the cap members  40   z  and  40   y  are continuously supported by the first cam  61  to keep them in the capped position, due to the operation of the ramp  63  shown in  FIG. 10 . When the rotary cam  60   x  starts rotating, the rotary cams  60   x  through  60   a  are sequentially rotated, and the cap members  40   x  through  40   a  are sequentially moved to the capped position. When the cap member  60   a  is moved to the capped position, the motor  30  is stopped. After the cap members  40   z  through  40   a  are sequentially moved to the capped position, although the motor  30  continuously rotates in the second direction C 2 , the cap members  40   z  through  40   a  are maintained in the capped position due to the operation of the ramp  63  shown in  FIG. 10 . Since the cap drive unit  100  of the present invention includes a plurality of resilient members  50  for resiliently biasing the plurality of cap members  40  towards the capped position, a plurality of rotary cams  60  allows the cap members  40  to move in the direction of the resilient force of the resilient members  50 . Accordingly, little load is applied to the motor  30  during the capping operation.  
      After the above-described uncapping/capping operation is completed, the plurality of first delaying means  89  are arranged in the state shown in  FIG. 13 , while the plurality of second delaying means  79  are arranged in the same state as the second delaying means  79  between the rotary cams  40   y  and  40   z  shown in FIG.  15 . With the above construction and process, the cap members  40  are sequentially moved to the uncapped position across the width of the paper P, and after completion of the printing, the cap members  40  are sequentially moved to the capped position.  
       FIG. 19  shows an alternative embodiment of the capping unit  120  in  FIG. 16 . Referring to  FIG. 19 , an end of a first shaft  101  is provided with a D-shaped cut portion  106 . The second gear  92  is inserted into the D-shaped cut portion  106 , and a pin  107  is inserted into a first shaft  101 . With the above arrangement, when the motor  30  rotates in the second direction C 2 , the first shaft  101  is rotated in the fourth direction C 4 . The pin  107  pushes the fourth protrusion  74  of the rotary cam  60   z  to rotate the rotary cam  60   z  in the fourth direction C 4 . The capping operation is identical to that described above.  
      The first delaying means  89  shown in  FIG. 13  has a delay angle of less than 360 degrees, because of the thickness of the first and second protrusions  81  and  82 . If the first gear  80  has the same number of teeth as the geared portion  68  of the rotary cam  60  and the delay angle due to the first delaying means  89  is 360 degrees, it is very easy to control the cap drive unit  100 . Specifically, whenever the first gear  80  is rotated once in the fifth direction C 5 , the cap members  40  are moved to the uncapped position one by one. Thus, if the revolutions of the first gear  80  are detected, it is possible to know how many cap members  40  are moved to the uncapped position. Reference is now made to  FIGS. 20 through 22  which illustrate three embodiments of the first delaying means  89  where the delay angle is 360 degrees. Of course, the present invention is not limited to that delay angle.  
      Referring to  FIGS. 20 through 22 , the first gear  80   a  is provided with a first protrusion  81 , while the second gear  80   b  is provided with a second protrusion  82 . A sleeve  85  is interposed between the first and second gears  80   a  and  80   b . The sleeve  85  is provided with a third protrusion  83  and a first recessed portion  84  for receiving the first protrusion  81 . The third protrusion  83  contacts the end of the second protrusion  82  facing to the third direction C 3 . Referring to  FIG. 20 , the first and second protrusions  81  and  82  are located at the third and fourth directions C 3  and C 4  around a rotational axis X, respectively. In this case, the width W 1  of the first recessed portion  84  relative to the rotation direction is identical to the sum total of the thickness of the first, second and third protrusions  81 ,  82  and  83  relative to the direction of rotation. Referring to  FIG. 21 , the first and second protrusions  81  and  82  are located at the fourth direction C 4  around the rotational axis X. In this case, the width W 2  of the first recessed portion  84  relative to the direction of rotation is identical to the sum of the thickness of the first and third protrusions  81  and  83  relative to the direction of rotation. Referring to  FIG. 22 , the first and second protrusions  81  and  82  are located on the rotational axis X. In this case, the width W 3  of the first recessed portion  84  relative to the rotation direction is identical to the sum of one half of the thickness of the first and second protrusions  81  and  82  and the thickness of the third protrusion  83 .  
      Referring to  FIGS. 6 through 22 , the cap drive unit  100  sequentially moves the cap members  40  to the uncapped position, starting from the cap member  40   a  located at one side of the paper P. Preferably, the cap drive unit  100  is used in printers where the paper P is aligned on one side of the printer irrespective of the width of the paper.  FIG. 23  shows an embodiment of the cap drive unit  100  used where the paper P aligned at the center of the printer regardless of the width of the paper. Referring to  FIG. 23 , a gear  103   a  is interposed between a first gear  80 L and a first gear  80   m . Both sides of the gear  103   a  are provided with recessed portions.  104   a  and  104   b . The recessed portions  104   a  and  104   b  respectively receive a second protrusion  82  of the first gear  80 L and a second protrusion  82  of the first gear  80   m . The motor  30  rotates the gear  103   a . A first delaying means  89  is interposed between the first gears  80 L and  80   k  and between the first gears  80   m  and  80   n , respectively. Of course, the motor  30  may be directly coupled to the first gear  80   m . The first and second shafts  101  and  102  are provided with the same capping unit  120  as those shown in  FIGS. 15 through 18 . With this arrangement, when the motor  30  rotates in the first direction C 1 , the plurality of cap members  40  are sequentially moved to the uncapped position, starting from the cap members  80   m  and  80 L and progressing across the width of the paper P. When the motor  30  rotates in the second direction C 2 , the cap members  40  are sequentially moved to the capped position, starting from the cap members  80   a  and  80   z  and progressing towards the center of the paper P.  
      A plurality of cam members  40  are divided into many cap groups  40 - 1 ,  40 - 2  and  40 - 3  including at least one cap member  40 , as shown in  FIG. 5A . The cap drive unit  100   a  sequentially moves the cap groups  40 - 1 ,  40 - 2  and  40 - 3  to the uncapped position one by one. In this case, the rotary cams  60  and the first gears  80  are divided into three rotary cam groups and three first gear groups each corresponding to each of the cap groups  40 - 1 ,  40 - 2  and  40 - 3 . The first gears  80  associated with the same group are engaged in series to each other such that the first gears  60  are rotated at the same time, and the first delaying means  89  is interposed only between the first gear groups. The rotary cams  60  associated with the same group are engaged in series to each other such that the rotary cams  60  rotate at the same time, and the second delaying means  79  is interposed only between rotary cam groups.  FIG. 24  shows rotary cam groups  60 - 1  and  60 - 2  and first gear groups  80 - 1  and  80 - 2  corresponding to the cap groups  40 - 1  and  40 - 2 . A first gear  80   g  and a first gear  80   i  associated with the first gear group  80 - 1  are simultaneously rotated by connection of the protrusion  86  and the recessed portion  87 . A first gear  80   k  and a first gear  80   j  area associated with the first gear group  80 - 2 . A first delaying means  89  is interposed between the first gear  80   i  and the first gear  80   j  (which are associated with the first gear groups  80 - 1  and  80 - 2 ). A rotary cam  60   g  and a rotary cam  60   i  associated with the rotary cam group  60 - 1  are simultaneously rotated by connection of the protrusion  71  and the recessed portion  72 . A rotary cam  60   k  and a rotary cam  60   j  are associated with the rotary cam group  60 - 2 . A second delaying-means  79  is interposed between the rotary cam  60   i  and the rotary cam  60   j  which are associated with the rotary cam groups  60 - 1  and  60 - 2 . The capping unit  120  described with respect to  FIGS. 16 through 19  may be used. With this arrangement, the cap groups  40 - 1 ,  40 - 2  and  40 - 3  can be sequentially moved to the capped/uncapped positions.  
      A cap drive unit  100   b  shown in  FIG. 25  is an alternative embodiment of the cap drive unit  100   a  shown in  FIG. 24 , and includes the same number of first gears  80  as that of the rotary cam groups. The cap drive unit  100   b  may include three first gears  80 , in the case of dividing the cap groups  40 - 1 ,  40 - 2  and  40 - 3 , as shown in  FIG. 5A . For example, the first gear  80   g  meshes with the geared portion  68  of the rotary cam  60   g  of the rotary cam group  60 - 1 , while the first gear  80   j  meshes with the geared portion  68  of the rotary cam  60   j  of the rotary cam group  60 - 2 . The second delaying means  79  is interposed between the rotary cam  60   i  and the rotary cam  60   j  each pertaining to the rotary cam groups  60 - 1  and  60 - 2 , while the first delaying means  89  is interposed between the first gear  80   g  and the first gear  80   j , as shown in  FIG. 20 . With the above arrangement, the cap groups  40 - 1 ,  40 - 2  and  40 - 3  are sequentially moved to the capped/uncapped positions.  
      It would be understood to one skilled in the art that embodiments of the cap drive units shown in FIGS.  23  to  25  may be suitably modified to drive the divided cap groups shown in  FIG. 5B .  
      An inkjet printer built in accordance with these above described exemplary embodiments of the invention is advantageous in that it is possible to uncap only the nozzle section used for printing in accordance with the width of the paper being printed on. In addition, it is possible to reduce a drive load of the motor driving the cam drive unit by moving the cap members to the capped/uncapped positions one by one.  
      While the present invention has been particularly shown and described with reference to exemplary embodiments, it will be understood by those of ordinary skill in the art that various changes and modifications in form and details may be made therein without departing from the spirit and scope of the present invention. as defined by the following claims.