Patent Publication Number: US-6981755-B2

Title: Print head position adjusting apparatus of ink-jet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Korean Application No. 2002-56612, filed Sep. 17, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an ink-jet printer, and more particularly, to a print head position adjusting apparatus of an ink-jet printer capable of adjusting an orientation of a print head mounted in a carrier, thereby preventing a stitching problem. 
   2. Description of the Related Art 
   There are many types of printers printing data or a file created by a user using a computer. For example, an ink-jet printer performs a printing process in a manner that a bubble, which is generated by heating ink stored in an ink cartridge constituting a print head (Hereinafter, it is referred to as “print head”), causes the ink to be ejected onto a sheet of paper through a nozzle in a predetermined pattern. 
   As shown in  FIGS. 1 and 2 , a conventional ink-jet printer  10  includes a paper feeding device  20  on which sheets of paper P are stacked, a conveying device  30  conveying the paper P from the paper feeding device  20 , a printing device  40  having a print head  41  mounted in a carrier moving along a carrier shaft  42  in left and right directions to perform printing with respect to the paper P conveyed by the conveying device  30 , and a discharging device  60  discharging the printed paper P from the printing device  40  to an outside of the ink-jet printer  10 . 
   As shown in  FIGS. 3 and 4 , the ink jet printer  10  is provided with a balancing shaft  44  disposed at a lower portion of the carrier  46  to allow the print head  41  seated on a lower supporting portion  45  of the carrier  46  to be secured in position, in this instance, a position where a lower securing surface  23  of the print head  41  is in a parallel relationship with a carrier shaft  42 , so that the ink can be precisely ejected onto the paper P while the print head  41  moves along the carrier shaft  42  to perform the printing. 
   Operations of the ink jet printer  10  having the above structure are described hereinbelow in conjunction with  FIGS. 1 through 4 . The paper P is stacked on the paper feeding device  20  and resiliently supported by a rock-up spring  21 , is picked-up by a pickup roller  22 , and then is supplied to the conveying device  30 . 
   Next, the paper P is transferred to the printing device  40  by rotations of a feed roller  31  and a friction roller  32  of the conveying device  30 . As the paper P is transferred from the conveying device  30  to the printing device  40 , a carrier driving motor  47  is driven to activate a belt  43 . Accordingly, while the carrier  46  moves along the carrier shaft  42  together with the print head  41 , which is contained in the carrier  46  and has a nozzle  41   a  attached thereto to eject the ink, the print head  41  ejects the ink onto the paper P conveyed from the conveying device  30  to print data on the paper P. 
   The paper onto which the data is printed by the ink ejected from the nozzle  41   a  of the print head  41 , moves on a base frame  50 , gradually reaches the discharging device  60 , and then is discharged through a discharging roller  61  and a star-shaped wheel  62 . 
   However, in the conventional ink jet printer  10 , the balancing shaft  44  allowing the print head  41  to be in position is secured to the carrier  46  and thus is not movable with respect to the carrier  46 . Accordingly, when the securing surface  23  of the print head  41  is positioned with an improper orientation due to errors of fabrication and assembly of the ink jet printer  10 , for example, when the securing surface  23  is not parallel to the balancing shaft  44  attached to the carrier  46  or when there occurs a misalignment, such as an unparallel relationship, between the balancing shaft  44  and the carrier shaft  42 , there is no way to adjust the improper orientation of the printing head  41 . 
   Also, even though the print head  41  is precisely positioned initially, the print head  41  becomes deviated from an initial position by a mechanical abrasion and a work load during a long time printing work and thus cannot maintain the parallel relationship with the balancing shaft  44  or the carrier shaft  42 . 
   As described above, if the print head  41  cannot maintain the parallel relationship with the balancing shaft  44  or the carrier shaft  42 , there occurs a stitching problem so that the ink ejected from the nozzle  41   a  of the print head  41  onto the paper P is skewed at each swath-to-swath boundary in a printed image, and thus a printing quality deteriorates. The stitching problem more seriously affects the image quality deterioration when the data to be printed relates to a perpendicular line or image. 
   SUMMARY OF THE INVENTION 
   The present invention has been developed in order to solve the above and/or other problems. Accordingly, an aspect of the present invention is to provide a print head position adjusting apparatus of an ink jet printer of a relatively simplified structure, which is capable of adjusting an orientation of a print head mounted in a carrier to prevent a stitching problem caused by a misalignment of the print head. 
   Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
   The above and/or other aspects of the present invention is achieved by providing a print head position adjusting apparatus of an ink jet printer which includes at least one print head performing printing by ejecting ink and a carrier containing the print head therein and moving along a carrier shaft. The print head position adjusting apparatus includes at least one stitching adjustment unit disposed at the carrier to adjust an orientation of the print head, and at least one resilient pressing unit resiliently pressing the print head toward the stitching adjustment unit. 
   The stitching adjustment unit includes a supporting knob movably disposed at a wall of the carrier to press a surface of the print head facing the wall of the carrier, and an adjusting knob disposed at the wall of the carrier to push or release the supporting knob toward or from the surface of the print head. 
   The supporting knob includes a contacting member having a contacting surface contacting the surface of the print head, and a supporting hook being supported by the wall of the carrier to move the contacting member within a predetermined range. 
   Also, the supporting knob further includes a resilient spring disposed between the contacting member and the wall of the carrier to press the contacting member toward the surface of the print head. It is possible that the resilient spring includes a coil spring. 
   The adjusting knob includes a screw bar that is screwed into a screw hole formed on the wall of the carrier and has one end rotatably contacting the contacting member and the other end having a gripper. The gripper includes a plurality of rips to be easily held by a user hand. 
   According to another aspect of the invention, the adjusting knob includes a screw bar that has one end rotatably and securely supported by the contacting member and the other end having a gripper. At this point, the resilient spring disposed between the contacting member and the wall of the carrier to press the contacting member toward the surface of the print head is not required. 
   The resilient pressing unit includes at least one resilient spring disposed between a second surface of the print head opposite to the surface of the print head and a second wall of the carrier facing the second surface of the print head to resiliently press the print head toward the supporting knob. 
   It is possible that the resilient spring includes a plate spring having one end fastened to and supported on the second wall of the carrier and the other end contacting the second surface of the print head. 
   In a case that the supporting knob includes the coil spring disposed between the contacting member and the wall of the carrier and winding around the screw bar so that the end of the coil spring rotatably contacts the contacting member, it is possible that the plate spring of the resilient pressing unit has a greater resilient force than that of the coil spring of the supporting knob. Accordingly, when the adjusting knob is released from the wall of the carrier, the plate spring of the resilient pressing unit is enabled to push the print head toward the supporting knob. 
   Also, the stitching adjustment unit includes a securing member securing the adjusting knob at an adjustment position after an orientation of the print head is adjusted by the adjusting knob. 
   The securing member includes either a plurality of first screw holes or pin holes formed on the adjusting knob and a plurality of second screw or pin holes formed on the wall of the carrier, and either screws or pins inserted into corresponding ones of the first screw holes or pin holes of the adjusting knob and the second screw holes or pin holes of the wall of the carrier, thereby preventing a rotation of the adjusting knob with respect to the wall of the carrier. 
   According to another aspect of the present invention, a print head position adjusting apparatus of an ink jet printer includes a carrier shaft and a carrier moving along the carrier and having first, second, and intermediate sidewalls to contain a mono print head between the first and intermediate sidewalls and a color print head between the intermediate and second sidewalls to perform printing on a sheet of paper, a first stitching adjusting unit formed on the first sidewall to push the mono print head toward a first side of the intermediate sidewall facing the first sidewall, a second stitching adjusting unit formed on the second sidewall to push the color print head toward a second side of the intermediate sidewall facing the second sidewall, a first resilient member disposed on the first side of the intermediate sidewall to push the mono print head toward the first sidewall, and a second elastic member disposed on the second side of the intermediate sidewall to push the color print head toward the second sidewall. 
   According to another aspect to the present invention, a print head position adjusting apparatus of an ink jet printer includes a carrier shaft and a carrier moving along the carrier and having first and second sidewalls to contain a print head between the first and second sidewalls to perform printing on a sheet of paper, a stitching adjusting unit formed on the first sidewall to push the print head toward the second sidewall, and a resilient member disposed on an inside of the second sidewall facing the first sidewall to push the print head toward the first sidewall. 
   According to another aspect of the present invention, a method in a print head position adjusting apparatus of an ink jet printer which includes a carrier shaft and a carrier moving along the carrier and having first, second, and intermediate sidewalls to contain a mono print head between the first and intermediate sidewalls and a color print head between the intermediate and second sidewalls to perform printing on a sheet of paper, includes causing a first stitching adjusting unit to be formed on the first sidewall, causing a second stitching adjusting unit to be formed on the second sidewall, causing a first resilient member to be disposed on a first side of the intermediate sidewall facing the first sidewall to push the mono print head toward the first sidewall, causing a second resilient member to be disposed on a second side of the intermediate sidewall facing the third sidewall to push the color print head toward the second sidewall, moving the first stitching adjusting unit to push the mono print head toward the intermediate sidewall, and moving the first stitching adjusting unit to push the color print head toward the intermediate sidewall. 
   According to another aspect of the present invention, a method in a print head position adjusting apparatus of an ink jet printer which includes a carrier shaft and a carrier moving along the carrier and having first and second sidewalls to contain a print head between the first and second sidewalls to perform printing on a sheet of paper, includes causing a stitching adjusting unit to be formed on the first sidewall, causing a resilient member to be disposed on an inside of the second sidewall facing the first sidewall to push the print head toward the first sidewall, and controlling the moving the stitching adjusting unit to push the print head toward the second sidewall. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a partial perspective view showing a conventional ink jet printer; 
       FIG. 2  is a schematic cross-sectional view showing the conventional ink jet printer shown in  FIG. 1 ; 
       FIG. 3  is a side view showing a carrier assembly of the ink jet printer of  FIG. 1 ; 
       FIG. 4  is a partial perspective view showing the carrier assembly of  FIG. 3 ; 
       FIG. 5  is a perspective view showing a carrier assembly employing a print head position adjusting apparatus according to an embodiment of the present invention; 
       FIG. 6  is a partial perspective view showing a stitching adjustment unit of the print head position adjusting apparatus of  FIG. 5 ; 
       FIG. 7  is a partial cross-sectional view showing the stitching adjustment unit of the print head position adjusting apparatus of  FIG. 5 ; and 
       FIGS. 8A and 8B  are partial plane views showing operations of the print head position adjusting apparatus of FIG.  5 . 
       FIG. 9  is a top view illustrating particularly the stitching adjusting units. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the present preferred embodiment of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiment is described below in order to explain the present invention by referring to the figures. 
   Hereinafter, a print head position adjusting apparatus of an ink jet printer according to an embodiment of the present invention will be described in greater detail with reference to the accompanying drawings. 
     FIG. 5  shows a carrier assembly  80  mounted in the ink jet printer to transfer a mono print head  241  and a color print head  242 , each employing the print head position adjusting apparatus. 
   The carrier assembly  80  includes a carrier  246  containing the mono and color print heads  241  and  242  therein, a carrier shaft guide  248  supportably holding a carrier shaft (not shown) to allow the carrier  246  to move along the carrier shaft, and two print head position adjusting apparatuses  200  and  200 ′ respectively adjusting orientations of the mono and color print heads  241  and  242 , which are illustrated in FIG.  6  through  FIG. 9  by way of an example. 
   As shown in  FIGS. 8A and 8B , the print head position adjusting apparatus  200  for the mono print head  241  includes a stitching adjustment unit  201  disposed at a front portion of the mono print head  241 , i.e., at a sidewall  246   a  of the carrier  246 , to adjust the orientation of the mono print head  241 , and a resilient pressing unit  249  disposed at an intermediate wall  246   b  of the carrier  246  to resiliently press the mono print head  241  toward the stitching adjustment unit  201 . 
   Referring to  FIGS. 6 and 7 , the stitching adjustment unit  201  includes a supporting knob  210  movably disposed on the sidewall  246   a  of the carrier  246  to press a side surface  241   a  of the mono print head  241 , and an adjusting knob  220  disposed on the sidewall  246   a  of the carrier  246  to push or separate the supporting knob  210  toward or from the side surface  241   a  of the mono print head  241 . 
   The supporting knob  210  includes a contacting member  211  having a contacting surface contacting the side surface  241   a  of the print head  241 , and a first supporting hook  217   a  and a second supporting hook  217   b  respectively supported on a first slide groove  218   a  and a second slide groove  218   b  formed on the sidewall  246   a  of the carrier  246  to slidably move the contacting member  211  within a predetermined range. 
   In order for the supporting knob  210  to be in contact with the side surface  241   a  of the mono print head  241  with a predetermined pressure, the supporting knob  210  further includes a coil spring  215 . The coil spring  215  is disposed between the contacting member  211  and an inner surface of the sidewall  246   a  of the carrier  246  to press the contacting member  211  toward the side surface  241   a  of the print head  241 . 
   The adjusting knob  220  is shaped in a screw bar  221  so that it is screwed into a screw hole  227  formed on the sidewall  246   a  of the carrier  246 , and has one end rotatably contacting the contacting member  211 and the other end having a gripper  223 . The gripper  223  has a plurality of ribs  225  formed on an outer side thereof to be easily gripped by a user hand. 
   Accordingly, as the adjusting knob  220  rotates in a fastening direction to advance into the screw hole  227  formed on the sidewall  246   a  of the carrier  246 , the contacting member  211  of the supporting knob  210  is pressed in an arrow direction “A” of  FIG. 8A , i.e., to the left side of  FIGS. 6 and 8A . Then, a front portion of the side surface  241   a  of the print head  241  is pushed to the left side against the resilient pressing unit  249 , and accordingly, the orientation of the mono print head  241  is adjusted. 
   Also, as the adjusting knob  220  rotates in a releasing direction from the screw hole  227 , an end of the adjusting knob  220  is separated from the contacting member  211  of the supporting knob  210  in an arrow direction “B” of FIG.  8 B. Then, a front portion of the side surface  241   a  of the print head  241  moves in the arrow direction “B” due to a resilient force of the resilient pressing unit  249  that is greater than that of the coil spring  215 , and accordingly, the orientation of the mono print head  241  is adjusted. 
   Selectively, the adjusting knob  220  may have a screw bar shape so that one end thereof is inserted into the supporting hole  227  formed on the contacting member  211  and is rotatably and supportably secured in the supporting hole  227  and the other end thereof has the gripper  223 . In this embodiment, since the adjusting knob  220  moves together with the contacting member  211  of the supporting knob  210  as a single body, it does not require the coil spring  215  that is disposed between the contacting member  211  and an inner surface of the sidewall  246   a  of the carrier  246  to press the contacting member  211  toward the side surface  241   a  of the mono print head  241 . 
   The resilient pressing unit  249  is a plate spring that is disposed between the other side surface  241   b  disposed opposite to the side surface  241   a  of the mono print head  241  and the intermediate wall  246   b  of the carrier  246  facing the other side surface  241   b  of the mono print head  241  to resiliently press the print head  241  toward the contacting member  211  of the supporting knob  210 . 
   One end of the plate spring  249  is securely supported by the intermediate wall  246   b  through a spring fixing hole  250  formed on the intermediate wall  246   b  of the carrier  246 , and the other end of the plate spring  249  contacts the other side surface  241   b  of the mono print head  241 . 
   In a case that the supporting knob  210  includes the coil spring  215  disposed between the wall  246   a  of the carrier  246  and the contacting member  211 and winding around the screw bar so that one end of the coil spring  215  rotatably contacts the contacting member  211 , it is possible that the plate spring  249  has a greater resilient force than that of the coil spring  215 . Accordingly, when the adjusting knob  220  is released from the screw hole  227 , the plate spring  249  is enabled to push the mono print head  241  and the contacting member  211  in the direction “B” against the resilient force of the coil spring  215 . 
   Also, the stitching adjustment unit  201  includes a securing member (not shown) securing the adjusting knob  220  at an adjustment position after the orientation of the mono print head  241  is adjusted by the adjusting knob  220 . 
   The securing member may include a plurality of first screw holes or pin holes (not shown) formed on the gripper  223 , a plurality of second screw holes or pin holes (not shown) formed on the sidewall  246   a  of the carrier  246  in a circular shape, and screws or pins (not shown) screwed (inserted) into corresponding ones of the first and second screw holes or the pin holes not to rotate the adjusting knob  220  with respect to the carrier  246 . 
   Another print head position adjusting apparatus ( 200 ′) for the color print head  242  has another stitching adjustment unit  201 ′ disposed at a second sidewall  246   c  of the carrier  246  and another resilient pressing unit  249 ′ disposed between the intermediate wall  246   b  of the carrier  246  and the color print head  242 . 
   Since the another stitching adjustment unit  201 ′ and the another resilient pressing unit  249 ′ of the another print head position adjusting apparatus  200 ′ for the color print head  242  are identical to the stitching adjustment unit  201  and the resilient pressing unit  249  of the print head position adjusting apparatus  200  for the mono print head  241 , respectively, descriptions thereof are omitted. 
   Although the stitching adjustment unit  201  and the resilient pressing unit  249  are respectively disposed between the intermediate wall  246   b  and the sidewall  246   a  of the carrier  246  or the second sidewall  246   c  in this embodiment, it should not be considered as limiting. Accordingly, it is understood that the stitching adjustment unit  201  and the resilient pressing unit  249  are disposed at any positions if they adjust the orientation of the print head  241 , for example, at a front wall and a rear wall of the carrier  246 . 
   A method of adjusting the orientation of the mono and/or color print heads  241  and/or  242  using the print head position adjusting apparatus  200  of the ink jet printer having the above structure is described with reference to  FIGS. 5  to  8 . 
   When there occurs “stitching” during printing, an orientation of the mono or color print head  241  or  242  is adjusted based on a stitching angle of the mono and/or color print heads  241  and/or  242 . The stitching angle is formed between the side surface  241   a  of the mono print head  241  and a plane perpendicular to the carrier shaft. 
   For example, when the mono print head  241  is slightly tilted to the left side with respect to a center line of the carrier as shown in  FIG. 8A , i.e., when the stitching angle is tilted to the left side, the adjusting knob  220  is rotated in one direction, e.g., a clockwise direction with respect to the screw bar  221 , to be inserted into the screw hole  227  of the sidewall  246   a  of the carrier  246 , thereby pushed by the front portion of the side surface  241   a  of the print head  241  in the direction “A”, i.e., to the left side of the drawing. Thus, the side surface  241  of the mono print head  241  becomes parallel to a plane of the carrier  246  perpendicular to the carrier shaft, thereby arranging a moving direction of nozzles of the mono print head  241  to be parallel to the carrier shaft or to be perpendicular to a feeding direction of a sheet of paper. 
   As the adjusting knob  220  is inserted into the screw hole  227 , the contacting member  211  of the supporting knob  210  contacting the one end of the adjusting knob  220  pushes the front portion of the side surface  241   a  of the mono print head  241 against the resilient force of the plate spring  249 . 
   As described above, when the mono print head  241  is positioned uprightly by being pushed to the left side at the front portion thereof, the ink jet printer performs a test printing. 
   As a result of the test printing, if there does not occur the “stitching,” the adjusting knob  220  is secured to the sidewall  246   a  of the carrier  246  by the securing members, such as a pin, a screw or the like, and adjusting work is finished. 
   However, if there still occurs the stitching where the stitching angle is tilted to the left side, the above-described procedure is repeated. 
   Also, if there occurs the stitching where the stitching angle is tilted toward the right side of the drawing due to an excessive rotation of the adjusting knob  220  in a clockwise direction, the adjusting knob  220  is rotated in the other direction, i.e., in a counter clockwise direction, to be released from the screw hole  227  of the sidewall  246   a  of the carrier  246 , thereby moving the front portion of the side surface  241   a  of the print head  241  in the direction of “B”, i.e., to the right side of the drawing. 
   As the adjusting knob  220  is released from the screw hole  227 , the contacting member  211  of the supporting knob  210  contacting the one end of the adjusting knob  220 , and the front portion of the side surface  241   a  of the print head  241 are pushed by the plate spring  249  to the right side against the coil spring  215 . 
   As described above, when the mono print head  241  is positioned upright by being pushed to the right side at the front portion thereof, the ink jet printer performs the test printing. According to the result of the test printing, the adjusting knob  220  is secured to the adjustment position and the adjusting work is completed. Otherwise, the above-described operation is repeated. 
   As described above, the print head position adjusting apparatus  200  of the ink jet printer according to the present invention is capable of adjusting the orientations of the mono and color print heads  241  and  242  mounted in the carrier  246  with a relatively simplified structure, thereby preventing the stitching problem that is caused by the misalignment of the mono and color print heads  241  and  242 . 
   The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and structural equivalents.