Abstract:
An ink jet printer having an improved print head cleaning apparatus includes an ink cartridge provided with a print head on a lower portion thereof and performs a linear reciprocating movement in a predetermined direction by means of a carriage. A housing is disposed below a lower side of the carriage. A wiper is provided in the housing and cleans the print head in contact with the print head. A wiper variable position unit moves the wiper to change a contact position between the print head and the wiper.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 2004-437, filed on Jan. 5, 2004, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an ink jet printer with an improved print head cleaning apparatus and method of operating the same. More particularly, the present invention relates to an ink jet printer with an improved print head cleaning apparatus and method of operating the same, in which a contact position between a print head and a wiper is periodically changed, thereby preventing abrasion of the wiper and enhancing a wiping effect of the wiper. 
   2. Description of the Related Art 
   As a general rule, ink jet printers are designed so that a carriage with an ink cartridge is movably installed to a main frame. The carriage is reciprocated by a moving unit, with support on a timing belt and a guide shaft. 
   The ink cartridge is provided with a print head on a lower side thereof. The print head sprays ink on printing paper fed by a feeding roller, thereby generating an image. The print head sprays the ink on one side of the printing paper through an injection nozzle, and thus the ink transferred into the printing paper forms an image. Operation of spraying the ink through the injection nozzle is appropriately controlled according to image information received at a controller of the printer. 
   After printing, residual ink is found in the injection nozzle. Sometimes, especially after the printer has been idle for a long time, the residual ink in the injection nozzle becomes solidified. In this case, the injection nozzle is entirely or partly clogged by the solidified ink. As a result, a proper amount of ink is not sprayed during printing, which results in poor print quality. 
   The ink injection nozzle may be clogged by the ink as well as by a foreign material such as dust. Dust will also negatively affect print quality. Therefore, to prevent the ink injection nozzle from being clogged, a device for cleaning the print head is required. 
   Such a print head cleaning apparatus is disclosed in Japan Patent Publication No. 2001-18407 (publication date: Jan. 23, 2001; title: INK JET PRINTER), the entire contents of which are incorporated herein by reference. 
   As for its configuration, a nozzle head wiper holding member is mounted to a wiper carrier capable of reciprocating in the main scanning direction of a nozzle head in such a manner that the nozzle head wiper holding member can be vertically moved through a predetermined range. A spring for upwardly urging the nozzle head wiper holding member is provided between the wiper carrier and the nozzle head wiper holding member. Both elastically deformable nozzle head wipers, and a wiper contact angle adjusting roller rotatably engaged with the nozzle head side are attached to the nozzle head wiper holding member. The nozzle head is capable of being wiped by holding a contact angle of each of the nozzle head wipers with respect to the lower surface of the nozzle head to a constant level. 
   One example of the conventional print head cleaning apparatus is shown in  FIG. 1 . As shown, the device includes a housing  10  installed on the lower side of a cartridge  1 , a plate  11  slidably mounted in the housing  10 , and a wiper  13  vertically provided on the plate  11 . The wiper  13  cleans a print head of the ink cartridge at a home position while it is reciprocated by the plate  11 . 
   The conventional print head cleaning apparatus brings the print head into contact with the wiper at a single position at all times. For this reason, the wiper is subjected to concentrated abrasion at only that single position, thus decreasing wiping efficiency. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an objective of the present invention to provide an ink jet printer with an improved print head cleaning apparatus, capable of changing a contact position with a print head by periodically moving a wiper which performs cleaning in contact with the print head. 
   In order to accomplish this objective, according to an aspect of the present invention, there is provided an ink jet printer having an improved print head cleaning apparatus. The ink jet printer comprises an ink cartridge provided with a print head on a lower portion thereof and reciprocating in a predetermined direction by means of a carriage, a housing provided on a lower side of the carriage, a wiper provided in the housing and cleaning the print head in contact with the print head, and a wiper variable position unit moving the wiper so as to change a contact position between the print head and the wiper. 
   The wiper variable position unit according to an embodiment of the present invention comprises a movable plate reciprocating in a direction substantially perpendicular to a motion direction of the carriage, a wiper slider supporting the wiper on an upper surface thereof and provided on one side of the movable plate and moving along the motion direction of the carriage, and a slider transfer unit moving the wiper slider. 
   The slider transfer unit according to an embodiment of the present invention comprises a first elastic member, a rack, a stopper and a moving unit. The first elastic member is provided to exert an attraction force on the slider transfer unit with one end connected to one side of the wiper slider and with the other end connected to one side of the movable plate. The rack is formed on a bottom surface of the wiper slider. The stopper is rotatably hinged on one side of the housing, having one end caught onto the rack, and coupled to exert a repulsive force on the rack via a second elastic member. The moving unit releases the stopper from the rack. 
   The first elastic member preferably is a tension coil spring. 
   The moving unit according to an embodiment of the present invention comprises an actuating bar integrally extending from the stopper, and an actuator forcing the stopper to be momentarily released from the rack in contact with the actuating bar, wherein the actuator is a solenoid shaft. 
   According to another aspect of the present invention, there is provided a method for operating an ink jet printer having an improved print head cleaning apparatus. The method of operating an ink jet printer comprises moving an ink cartridge provided with a print head in a linear reciprocating manner in a predetermined direction, cleaning the print head by wiping a wiper in contact with the printhead in a direction perpendicular to the predetermined direction, and moving the wiper so as to change a contact position between the print head and the wiper. 
   The step of moving the wiper so as to change the contact position between the print head and the wiper according to another embodiment of the present invention comprises moving the wiper by a wiper variable position unit. Furthermore, the step of moving the wiper further comprises moving the wiper in a direction parallel to the predetermined direction. 
   The step of moving the wiper by the wiper variable position unit according to another embodiment of the present invention comprises reciprocating a movable plate in a direction substantially perpendicular to a motion direction of the carriage, and moving a wiper slider adapted to support the wiper on an upper surface thereof and provided on one side of the movable plate. Movement of the wiper slider is along the motion direction of the carriage and is performed by a slider transfer unit. 
   The step of moving the slider transfer unit according to another embodiment of the present invention comprises exerting an attraction force on the slider transfer unit by a first elastic member with one end connected to one side of the wiper slider and with the other end connected to one side of the movable plate, exerting a repulsive force on a rack, the rack formed on a bottom surface of the wiper slider, via a second elastic member. The exerting is performed by a stopper adapted to be rotatably hinged on one side of the housing and having one end caught on the rack, and releasing the stopper from the rack by a moving unit. 
   The step of exerting an attraction force on the slider transfer unit by a first elastic member according to an embodiment of the present invention comprises exerting the attraction force on the slider transfer unit by a tension coil spring, and the step of exerting the repulsive force on the rack comprises exerting the repulsive force on the rack by a torsion spring having one end connected to the stopper and the other end connected to one side of the housing. The step of releasing the stopper by the moving unit comprises forcing the stopper to be momentarily released from the rack by an actuator, the actuator in contact with an actuating bar, wherein the actuating bar is adapted to integrally extend from the stopper. 
   The step of forcing the stopper to be momentarily released from the rack actuator according to an embodiment of the present invention comprises forcing the stopper to be momentarily released from the rack by a solenoid shaft. 
   The method for operating an ink jet printer according to another embodiment of the present invention further comprises shifting the wiper after a predetermined period of time. 
   The method for operating an ink jet printer according to still another embodiment of the present invention further comprises shifting the wiper after a predetermined number of print operations. 
   The method for operating an ink jet printer according to a further embodiment of the present invention further comprises shifting the wiper after a predetermined number of linear reciprocations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
       FIG. 1  illustrates construction of a print head cleaning apparatus of a conventional ink jet printer; 
       FIG. 2  illustrates construction of a print head cleaning apparatus of an ink jet printer according to an embodiment of the present invention; 
       FIG. 3  is a cross-sectional view taken along the line  2 A- 2 A′ of  FIG. 2 ; 
       FIG. 4  is a cross-sectional view taken along the line  2 B- 2 B′ of  FIG. 2 ; and 
       FIG. 5  is an enlarged view of the area D circled in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, description will be made in more detail with regard to the configuration and operation of a print head cleaning apparatus according to an exemplary embodiment of the present invention with reference to  FIGS. 2 to 5 . 
   As shown in  FIG. 2 , an ink jet printer is provided with an ink cartridge  110  on its lower side, wherein the ink cartridge  110  is provided with a print head  111  and is received in a carriage  130 . The carriage  130  is installed to be capable of reciprocating along a guide shaft  131  in a Y-axis direction. 
   To prevent solidification of ink or introduction of foreign materials around a nozzle of the print head  111  in a printing standby state or a printer power-off state, a head cleaner  200  according to an embodiment of the present invention is provided on a service area. 
   The head cleaner  200  is generally composed of a housing  201 , a wiper  203 , and a wiper variable position unit  210 . 
   The housing  201  is installed on the service area, and the wiper  203  is installed in the housing  201  and performs wiping in contact with the print head  111 . 
   The wiper variable position unit  210  is also installed in the housing  201 , and includes a movable plate  211  reciprocating in an X-axis direction, a wiper slider  213  provided on one side of the movable plate  211  and moving along a motion direction of the carriage  130  with the wiper  203  supported on the upper surface of the wiper slider, and a slider transfer unit  230  moving the wiper slider  213 . 
   The slider transfer unit  230  includes a first elastic member  231  provided to exert an attraction force on the wiper slider  213  with one end connected to one side of the wiper slider  213  and with the other end connected to one side of the movable plate  211 , a rack  233  formed on a bottom surface of the wiper slider  213 , a stopper  235  rotatably hinged on one side of the housing  201  and having one end caught onto the rack  233  and coupled to exert a repulsive force on the rack  233  via a second elastic member  234 , and a moving unit  237  releasing the stopper  235  from the rack  233 . 
   In one exemplary embodiment, the first elastic member  231  is comprised of a tension coil spring. In order to fix the first elastic member  231 , a fixing piece  211   a  is further provided on one side of the movable plate  211 . 
   The second elastic member  234 , in one embodiment of the present invention, makes use of a torsion spring. In this case, a separate bracket  201   a  is further provided on the inner surface of the housing  201  in order to fix the torsion spring  234 , so that the torsion spring  234  is connected to the stopper  235  on one end thereof and fixed to the separate bracket  201   a  on the other end thereof. 
   The wiper slider  213 , as shown in  FIG. 4 , is inserted into a sliding slot  211   b  of the movable plate  211  so that it can move in a Y-axis direction which is substantially perpendicular to the movable plate  211  (i.e., substantially perpendicular to the sheet of  FIG. 4 ). In order to avoid interfering with the stopper  235  caught on the rack  233  when the movable plate  211  reciprocates in the X-axis direction, there is an extension  213   c  in contact with the bottom surface of the movable plate  211 . In one embodiment of the present invention, a length of the extension  213   c  can be set in consideration of a movable length of the movable plate  211 , and a bottom surface of the extension  213   c  is provided with the same profile as that of the rack  233 . 
   The moving unit  237  includes an actuating bar  237   a  integrally extending from the stopper  235 , and an actuator  237   b  forcing the stopper  235  to be released from the rack  233  in contact with the actuating bar  237   a . In one embodiment of the present invention, the actuator  237   b  makes use of a solenoid shaft which is electrically driven. Further, the actuator  237   b  is periodically operated to move the wiper  203  for a predetermined period of time. The predetermined period of time refers to an interval which it takes the number of printed sheets of paper processed through the ink cartridge  110  to reach a predetermined number. 
   Operation of the print head cleaning apparatus constructed as set forth above will now be described in greater detail. 
   After completing a predetermined printing process, the ink cartridge  110  is transferred to a service area by the carriage  130 . Then, the movable plate  211  installed in the housing  201  performs linear reciprocating movement in the X-axis direction, and thus comes into contact with the print head  111  provided on the bottom surface of the ink cartridge  110  to perform cleaning. 
   When the ink cartridge  110  processes the printing paper more than a predetermined number of times, an operation signal is transmitted to the actuator  237   b  or the solenoid shaft through a controller (not shown). The solenoid shaft  237   b  then pushes the actuating bar  237   a  (see  FIG. 3 ), so that the stopper  235  engaged with one gear tooth of the rack  233  is released to the next gear tooth of the rack  233 . Thereby, the stopper  235  is caught on the next gear tooth of the rack  233  (see  FIG. 5 ). 
   Simultaneously, the tension spring  231  pulls the wiper slider  213  in the Y-axis direction, and thus the wiper slider  213  is shifted by one pitch. The solenoid shaft  237   b  does not continuously press the actuating bar  237   a , but it only does so momentarily. As a result, the stopper  235  is caught on the next gear tooth of the rack  233  by the restoring force of the second elastic member  234 , so that the wiper slider  213  is no longer shifted. 
   This operation causes the wiper  203  to move in a predetermined period of time. 
   In this manner, the wiper  203  changes its contact position with the nozzle portion of the print head  111  through the wiper variable position unit  210 . 
   As can be seen from the foregoing, the invention is designed so that the wiper is capable of changing its contact position with the print head. Consequently, the drawback of abrasion taking place at a particular part of the wiper is substantially decreased, so that it is possible to enhance the wiping effect. 
   Although a preferred embodiment of the present invention has been described for illustrative purposes, it is apparent to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.