Patent Publication Number: US-2011058003-A1

Title: Image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of application Ser. No. 11/619,715 filed Jan. 4, 2007, the entire contents of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image forming apparatus for printing an image on a medium such as a print sheet, and, more particularly to an image forming apparatus that has a recording head of an ink jet system. 
     2. Description of the Related Art 
     As an image forming apparatus of this type, for example, as disclosed in JP-A-2005-125675, there is known an image forming apparatus that has a sheet conveying path for conveying a sheet in an apparatus body thereof and ejects an ink from a recording head to the sheet conveyed by this sheet conveying path to form an image. 
     Usually, a sheet guide (a media guide) is spaced apart from and opposed to the recording head and the ink is ejected to a sheet guided along this sheet guide. 
     At the time of a printing operation, ink mist is generated around the recording head and, in particular, the sheet guide is stained by this ink mist. When the sheet guide is stained by the ink mist, it is likely that, when following sheets are guided, the sheets are stained. 
     Thus, conventionally, the sheet guide is cleaned periodically. 
     However, conventionally, since the sheet guide is fixedly provided in the apparatus body, in cleaning the sheet guide, it is necessary to insert a cleaning tool into the apparatus body and perform work in a small space. Therefore, there is a problem in that workability is low and it is difficult to check a cleaning effect. 
     As other means for cleaning the sheet guide, paper (e.g., white paper) for cleaning is passed through the sheet guide to clean the stain of the sheet guide with this paper. 
     However, in this case, there is a problem in that this is uneconomical because paper is used wastefully. 
     BRIEF SUMMARY OF THE INVENTION 
     An aspect of the invention has been devised in view of such a point and it is an object of the invention to provide an image forming apparatus that makes it possible to take out a media guide to the outside of an apparatus body and clean the media guide. 
     An image forming apparatus according to the aspect of the invention includes an apparatus body, a conveying device that is provided in this apparatus body and conveys a medium, a recording device that ejects an ink to a medium conveyed by this conveying device and records an image on the medium, and a media guide that is spaced apart from and opposed to this recording device, guides the medium, and is provided to be freely inserted into and taken out from the apparatus body. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is an external perspective view showing an image forming apparatus according to a first embodiment of the invention; 
         FIG. 2  is a diagram showing an internal structure of the image forming apparatus in  FIG. 1 ; 
         FIG. 3  is a perspective view showing a moving mechanism and a cleaning mechanism for a recording head in  FIG. 2 ; 
         FIG. 4  is a perspective view showing a driving mechanism for a conveying roller in  FIG. 2 ; 
         FIG. 5  is a plan view showing a sheet guide in  FIG. 2 ; 
         FIG. 6  is a perspective view showing the sheet guide in  FIG. 2 ; 
         FIG. 7  is a perspective view showing a state in which the sheet guide in  FIG. 2  is taken out from an apparatus body; 
         FIG. 8  is a perspective view showing a state in which an ink absorbing member is removed from the sheet guide in  FIG. 7 ; 
         FIG. 9  is a diagram showing an image forming apparatus according to a second embodiment of the invention; 
         FIG. 10  is a diagram showing a state in which a sheet guide is taken out from the image forming apparatus in  FIG. 9 ; and 
         FIG. 11  is a diagram showing a state in which the sheet guide in  FIG. 10  is taken out to the outside. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention will be hereinafter explained in detail with reference to the drawings. 
       FIG. 1  is an external perspective view showing an image forming apparatus according to a first embodiment of the invention. 
     An image forming apparatus  10  includes an apparatus body  11 . A first feed tray  13  is disposed on a rear side of this apparatus body  11 , a discharge tray  14  is disposed on a front side of the apparatus body  11 , and a second feed tray  15  is provided on a lower side of the apparatus body. 
       FIG. 2  schematically shows an internal structure of the image forming apparatus  10 . 
     In the apparatus body  11 , a sheet conveying mechanism  21  serving as a conveying device, a sheet guide  22  serving as a media guide that has a guide surface  22   a  in the horizontal direction, and a head cleaning mechanism  24  shown in  FIG. 3  are included. The sheet guide  22  and the head cleaning mechanism  24  will be explained in detail later. 
     On an upper side of the sheet guide  22 , a carriage  30 , a carriage driving mechanism  31  for driving this carriage  30 , a recording head  32  serving as a recording device of an ink-jet system mounted on the carriage  30 , and the like are arranged. A replaceable ink cartridge (not shown) is housed in the recording head  32 . 
     As shown in  FIG. 2 , the recording head  32  has a nozzle section  32   a  opposed to the guide surface  22   a  of the sheet guide  22  and an ink ejecting mechanism (not shown) that ejects an ink from this nozzle section  32   a . The recording head  32  forms an image on a sheet S (shown in  FIG. 3 ) with this ink. An arrow A in  FIG. 3  indicates a conveying direction of the sheet S. 
     An example of the ink ejecting mechanism is a thermal type. The thermal type applies heat to the ink with a heater built in the recording head  32  to film-boil the ink. A pressure change is caused in the ink by growth or contraction of air bubbles due to this film boiling. An image is formed on the sheet S by ejecting the ink from the nozzle section  32   a  according to this pressure change. Other than the thermal type, for example, an ink ejecting mechanism that uses an element (e.g., a piezoelectric element) having a piezoelectric effect may be adopted. For example, the piezoelectric element is deformed by an electric current and an ink is ejected from a nozzle section according to a pumping action based on the deformation. 
     As shown in  FIG. 3 , the carriage driving mechanism  31  includes a carriage guide  40  extending in the horizontal direction, a motor  41  such as a stepping motor, power transmitting members such as a timing belt  42  and sprockets  43  and  44 , and a sensor unit  45  for controlling a position of the carriage  30 . The carriage guide  40  extends in a direction B orthogonal to the conveying direction of the sheet S. The carriage guide  40  is supported by a frame of the apparatus body  11 . The recording head  32  is reciprocatingly moved in a direction (the arrow B direction) orthogonal to the conveying direction of the sheet S together with the carriage  30  along the carriage guide  40 . 
     The rotation of the motor  41  is transmitted to the carriage  30  via the timing belt  42 . Therefore, the recording head  32  reciprocatingly moves along the carriage guide  40 . The sensor unit  45  for controlling a position of the carriage  30  includes, for example, an encoder sensor  46  and a ladder plate  47  serving as a section to be detected. The ladder plate  47  extends in a direction parallel to the carriage guide  40 . The ladder plate  47  has a ladder pattern formed at equal pitches. The ladder pattern of the ladder plate  47  is optically detected by the encoder sensor  46  according to the position of the carriage  30 , whereby the position of the carriage  30  is detected. A signal of the position detected is inputted to a control unit  50  via a flexible harness  48 . 
     As shown in  FIG. 2 , the sheet conveying mechanism  21  includes a first conveying unit  61 , a second conveying unit  62 , a duplex-printing conveying unit  63  used in performing duplex printing, and a discharging mechanism  64 . 
     The first conveying unit  61  conveys a sheet taken out from the first feed tray  13  to the recording head  32 . The second conveying unit  62  conveys a sheet taken out from the second feed tray  15  to the recording head  32 . The discharging mechanism  64  has a function of discharging a sheet having an image printed thereon onto the discharge tray  14 . 
     It is possible to place plural sheets (e.g., print sheets) on the first feed tray  13  stacking the sheets in the thickness direction. As shown in  FIG. 1 , a movable guide  65  is provided in the first feed tray  13 . The movable guide  65  is movable in the width direction of the sheet S according to a size of the sheet S. It is possible to regulate a position in the width direction of the sheet S on the first feed tray  13  by moving the movable guide  65  in the width direction of the sheet S. 
     The first conveying unit  61  includes a feed roller  70 , a separation roller  71  located below the feed roller  70 , and a separation unit  72  including a separation pad. The feed roller  70  feeds a sheet taken out from the lower end of the first feed tray  13  to the recording head  32 . 
     A torque limiter is provided in the separation roller  71 . The separation roller  71  rotates in a direction identical with a direction of rotation of the feed roller  70  according to a function of the torque limiter when only one sheet is present between the separation roller  71  and the feed roller  70 . When two or more sheets are present between the feed roller  70  and the separation roller  71 , the separation roller  71  rotates in a direction opposite to the direction of rotation of the feed roller  70 . Therefore, when plural sheets are taken out from the first feed tray  13  and fed into a space between the feed roller  70  and the separation roller  71 , an uppermost sheet and the other sheets are separated and only the uppermost sheet is fed to the recording head  32 . A sheet separating mechanism for taking out sheets from the first feed tray  13  one by one is constituted by the feed roller  70 , the separation roller  71 , the separation unit  72 , and the like. 
     The separation roller  71  is held by a holder  73 . The holder  73  is movable in the up-to-down direction around a shaft  74  extending in the horizontal direction. The separation roller  71  is brought into contact with the feed roller  70  at a predetermined load by a spring and separated from the feed roller  70  by a not-shown cam. It is possible to move the separation unit  72  in a direction toward and away from the feed roller  70  with a not-shown cam. 
     After the sheet is fed, the separation roller  71  and the separation unit  72  are separated from the feed roller  70 , moved to standby positions, and put on standby until the next sheet feed time, respectively. A return lever  75  is rotatably arranged near the lower end of the first feed tray  13 . When the sheet taken out from the first feed tray  13  is conveyed to the feed roller  70 , the return lever  75  is retracted by a spring to a position where the return lever  75  does not hinder the conveyance of the sheet. This return lever  75  rotates in synchronization with the movement of the separation roller  71  and the separation unit  72  to the standby positions and feeds a remaining sheet back to the first feed tray  13 . 
     The first conveying unit  61  includes a conveying roller  80 , a pinch roller  81  opposed to this conveying roller  80 , a sheet sensor  82 , a media sensor  83 , and a switching member  84 . The conveying roller  80  feeds a sheet to a space between the sheet guide  22  and the recording head  32 . The sheet sensor  82  has a sensor arm that is capable of detecting positions of the leading end and the trailing end of the sheet. 
     The media sensor  83  has a function of detecting a quality (e.g., paper quality) of a sheet. For example, when the surface of the sheet is made of a material having moisture-absorption characteristics, the media sensor  83  outputs a signal for increasing a quantity of ink ejected from the recording head  32  to the control unit  50 . In the case of a sheet having glossiness on the surface thereof, for example, coat paper, the media sensor  83  performs control for outputting a signal for reducing a quantity of ink ejected from the recording head  32  to the control unit  50 . In the case of color printing, a ratio of ejection of plural color elements may be adjusted on the basis of a signal from the media sensor  83 . 
     As shown in  FIG. 4 , the conveying roller  80  is attached to a shaft  90 . The shaft  90  is rotated by a controllable motor  91  such as a stepping motor. The pinch roller  81  opposed to the conveying roller  80  is set in contact with the conveying roller  80  by a not-shown spring. A ladder wheel  92  of a disc shape is attached to the shaft  90  of the conveying roller  80 . A ladder pattern is formed in a circumferential direction at fixed pitches in the ladder wheel  92 . This ladder wheel  92  is detected by a sensor  93  and inputted to the control unit  50 . Consequently, the rotation of the conveying roller  80  is controlled and conveyance of a sheet is controlled at the time of image formation. 
     A sheet taken out from the first feed tray  13  by the feed roller  70  is conveyed to a space between the conveying roller  80  and the pinch roller  81  through the first conveying unit  61  as indicated by an arrow F 1  in  FIG. 2 . The leading end of the sheet is detected by the sheet sensor  82  and positioning for image formation is performed. This sheet passes between the upper surface (the guide surface  22   a ) of the sheet guide  22  and the recording head  32  according to the rotation of the conveying roller  80 . When the sheet passes, an image is formed on the sheet S by the recording head  32 . Ribs functioning as a conveyance reference surface are rormed on the guide surface  22   a  of the sheet guide  22 . These ribs keep the height of the sheet proper and prevent the sheet from heaving. The sheet having the image formed thereon is conveyed to the discharging mechanism  64 . 
     The second conveying unit  62  includes rollers  100  and  101  for taking out a sheet from the second feed tray  15  of a cassette type, a switching member  102 , guide members  103  and  104  for guiding the sheet taken out, a conveying roller  105  provided along the guide members  103  and  104 , and a pinch roller  106  opposed to the conveying roller  105 . The pinch roller  106  is pressed against the conveying roller  105  by a spring. It is possible to store plural sheets (e.g., print sheets) in the second feed tray  15  stacking the sheets in the thickness direction. The rollers  100  and  101  of the second conveying unit  62  function as sheet separating mechanisms for taking out sheets from the second feed tray  15  one by one. 
     A sheet taken out from the second feed tray  15  passes between the guide members  103  and  104  of the second conveying unit  62  through the switching member  102  as indicated by an arrow F 2  in  FIG. 2 . This sheet is further conveyed to the conveying roller  80  by the rollers  105  and  106  and fed to the space between the recording head  32  and the sheet guide  22 . 
     The duplex-printing conveying unit  63  includes guide members  110  and  111 , a conveying roller  112  provided along the guide members  110  and  111 , and a pinch roller  113  opposed to the conveying roller  112 . The pinch roller  113  is pressed against the conveying roller  112  by a spring. The guide members  110  and  111  are arranged between the switching member  84  of the first conveying unit  61  and the switching member  102  of the second conveying unit  62 . At the time of duplex printing, a sheet is fed in an arrow F 3  direction in  FIG. 2 . The conveying rollers  80 ,  105 , and  112  are obtained by providing rubber-like resin such as EPDM (ethylene propylene diene rubber) on a metal shaft and have a function of conveying the sheet S with friction. 
     When duplex printing is performed, after an image is printed on one side of a sheet by the recording head  32 , the trailing end of this sheet is detected by the sheet sensor  82 . Immediately after the detection, the conveying roller  80  rotates reversely and a position of the switching member  84  is switched. Consequently, the sheet is sent to the duplex printing conveying unit  63  as indicated by the arrow F 3  in  FIG. 2 . Moreover, this sheet is conveyed by the rollers  112  and  113  and passes between the guide members  103  and  104  of the second conveying unit  62  through the switching member  102 . In this way, the front and the back of the sheet are reversed and this sheet is sent to the recording head  32  again by the conveying roller  80 , whereby an image is printed on the other side of the sheet. 
     The discharging mechanism  64  has a discharge roller  120 , a star wheel  121 , a transmitting mechanism (not shown) for transmitting the rotation of the conveying roller  80  to the discharge roller  120  and the star wheel  121 , and the like. The star wheel  121  is a wheel of a gear shape made of a thin plate of stainless steel or the like. A sheet having an image printed thereon by the recording head  32  is conveyed in a direction indicated by an arrow F 4  to the discharge tray  14  while being pressed against the discharge roller  120  by the star wheel  121 . The sheet after printing is prevented from floating from the discharge roller  120  by this star wheel  121 . 
     The head cleaning mechanism  24  shown in  FIG. 3  includes a suction pump  140  for performing cleaning of the recording head  32 , a cap  141  for preventing the recording head  32  from drying, and a blade member  142  for cleaning the nozzle section  32   a  of the recording head  32 . An example of the suction pump  140  strokes a tube  144  in a direction indicated by an arrow C with a body of rotation  143  to generate a negative pressure on the inner side of the cap  141 . 
     It is possible to move the cap  141  in an up-to-down direction (an arrow D direction in  FIG. 3 ) with a driving mechanism  145 . The driving mechanism  145  moves the cap  141  up and down with an electric actuator  146  such as a solenoid as a driving source. The rotation of a motor may be converted into a linear motion by a cam, a link mechanism, or the like to move the cap  141  up and down. In maintaining the recording head  32 , the cap  141  is lifted to the recording head  32  to bring the cap  141  into close contact with the recording head  32 . In this state, the suction pump  140  is actuated to suck an excess ink adhering to the nozzle section  32   a  of the recording head  32 . The waste ink sucked is discharged into a waste ink tank  146 . Thereafter, the cap  141  moves away from the recording head  32  and the nozzle section  32   a  of the recording head  32  is cleaned by the blade member  142 . 
     On the other hand, the sheet guide  22  arranged below the recording head  32  to be opposed to the recording head  32  is provided to be freely inserted into and taken out from the apparatus body  11 . As shown in  FIG. 2 , both sides of a bottom surface of the sheet guide  22  are slidably supported by guide rails  151 . The guide rails  151  are disposed along a direction orthogonal to the conveying direction of the sheet, i.e., the moving direction of the recording head  32 . The guide rails  151  can guide the sheet guide  22  along the moving direction of the recording head  32 . A knob section  22   b  is provided at one end of the sheet guide  22 . The sheet guide  22  is pulled out by grabbing the knob  22   b  with a hand. An opening  11   a  is formed on one side of the apparatus body  11  as shown in  FIG. 1 . The sheet guide  22  is inserted in and taken out from this opening  11   a.    
     As shown in  FIGS. 5 and 6 , an ink absorbing section  130  is formed on the upper surface side of the sheet guide  22 . The ink absorbing section  130  is opposed to the nozzle section  32   a  (shown in  FIG. 2 ) of the recording head  32  and formed in a position lower than the guide surface  22   a . The width of the ink absorbing section  130  is larger than the width of the sheet S. For example, a sponge-like ink absorbing member  131  is housed in this ink absorbing section  130 . When rimless printing on a sheet is performed, an excess ink ejected on the outside of the edge of the sheet is absorbed by this ink absorbing member  131 , whereby following sheets are prevented from being stained. The ink absorbing member  131  is provided detachably attachable. It is possible to remove the ink absorbing member  131  as shown in  FIG. 8 . 
     At the time of the printing operation, since the ink is ejected from the recording head  32  and ink mist is generated around the recording head  32 , in particular, the sheet guide  22  is stained by the ink mist. When the sheet guide  22  is stained, following sheets are stained when the sheet passes through the sheet guide  22 . Thus, it is necessary to periodically clean the sheet guide  22 . 
     A method of cleaning the sheet guide  22  will be explained. 
     In this case, first, a user inserts a hand into the opening  11   a  on one side of the apparatus body  11  and grabs the knob section  22   a  of the sheet guide  22  with the hand to pull the sheet guide  22  forward. Consequently, the user moves the sheet guide  22  forward along the guide rails  151  and, as shown in  FIG. 7 , takes out the sheet guide  22  to the outside from the opening  11   a  of the apparatus body  11 . After taking out the sheet guide  22 , the user performs cleaning of the sheet guide  22  and the ink absorbing member  131 . 
     When it is necessary to replace the ink absorbing member  131 , as shown in  FIG. 8 , the user removes the ink absorbing member  131  from the sheet guide  22  and attaches a new ink absorbing member to the sheet guide  22 . 
     After cleaning the sheet guide  22  and the ink absorbing member  131  or replacing the ink absorbing member  131  in this way, the user inserts the sheet guide  22  from the opening  11   a  of the apparatus body  11  again and sets the sheet guide  22  in a predetermined position. 
     As described above, since it is possible to take out the sheet guide  22  to the outside of the apparatus body  11  and clean the sheet guide  22 , cleaning work is easily performed. 
     Since it is also possible to perform cleaning and replacement work for the ink absorbing member  131  on the outside of the apparatus body  11 , workability is high and it is possible to prevent the user from touching the ink absorbing member  131  and being smeared with the ink as much as possible. 
       FIG. 9  shows a second embodiment of the invention. 
     In the first embodiment, the sheet guide  22  is inserted and taken out along the traveling direction of the recording head  32 . However, in the second embodiment, the sheet guide  22  is inserted and taken out along a direction orthogonal to the traveling direction of the recording head  32 , i.e., the conveying direction of a sheet. 
     In this second embodiment, when the sheet guide  22  is simply pulled out along the conveying direction of a sheet, it is likely that the sheet guide  22  comes into contact with the discharge roller  120  and scratches the discharge roller. 
     Thus, in this second embodiment, after the sheet guide  22  is once moved downward and away from the recording head  32 , the sheet guide  22  is pulled out. 
     Vertical guide members  155  and a horizontal guide member  156  are disposed below the sheet guide  22 . The sheet guide  22  is moved in the up-to-down direction along the vertical guide members  155  and moved in the horizontal direction along the horizontal guide member  156 . 
     In cleaning the sheet guide  22 , as shown in  FIG. 10 , a user once moves the sheet guide  22  downward along the vertical guide members  155  and places the sheet guide  22  on the horizontal guide member  156 . Subsequently, the user inserts a hand from an opening  11   b  on the front side of the apparatus body  11  to take out the sheet guide  22  to the outside of the apparatus body  11  as shown in  FIG. 11 . 
     After taking out the sheet guide  22  in this way, the user cleans the sheet guide  22  and the ink absorbing member  131  as explained in the first embodiment. When it is necessary to replace the ink absorbing member  131 , the user replaces the ink absorbing member  131 . 
     According to this second embodiment, as in the first embodiment, it is easy to clean the sheet guide  22  and clean and replace the ink absorbing member  131 . 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.