Patent Publication Number: US-7213903-B2

Title: Liquid-discharge-head recovering device

Description:
This application claims priority from Japanese Patent Application No. 2003-203982 filed Jul. 30, 2003, which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to image recording apparatuses, and more particularly to a liquid-discharge-head recovering device. 
   2. Description of the Related Art 
   Liquid discharge heads, such as inkjet print heads, are widely used in, for example, inkjet printers and have been researched for many years. There are problems existing in conventional liquid discharge heads in that the nozzles disposed in the discharging surface cannot properly discharge liquid or that the discharging direction of the liquid may deviate from the intended direction. This can be caused when the liquid (for example, an ink solvent) in the nozzles evaporates, increasing the viscosity of the liquid in each nozzle, or when foreign matter, such as paper dust, becomes attached to the nozzles. 
   For these reasons, inkjet printers are generally provided with a liquid-discharge-head recovering device which includes, for example, a liquid-discharge-head cap for preventing the evaporation of the liquid (ink solvent) in the nozzles; a suction unit for sucking out and removing the thickened liquid (ink) from the nozzles; and a wiping unit for wiping off the liquid remaining on the discharging surface and any foreign matter, such as paper dust, attached to the discharging surface. 
     FIG. 10  is a schematic plan view of a conventional liquid-discharge-head cap  410 .  FIG. 11  is a cross-sectional view of a discharge head  300  and the cap  410  taken along line XI—XI in  FIG. 10 . Specifically, the plan view of  FIG. 10  is viewed from a direction indicated by an arrow V shown in  FIG. 11 . Referring to  FIGS. 10 and 11 , the discharge head  300  is an inkjet print head having a discharging surface  301  in which nozzles are disposed. The liquid-discharge-head cap  410  is generally formed of an elastic material, such as rubber, so that the contact between the cap  410  and the discharging surface  301  can be properly maintained. Moreover, the cap  410  has a base  411 . 
   The cap  410  is driven by a known cap-driving unit, such as a cam or a motor, and is movable in directions indicated by an arrow G in  FIG. 11 . Specifically, the cap  410  is capable of moving back and forth to come into and out of contact with the discharging surface  301 , that is, between a capping position and a non-contact position, which is not shown in  FIG. 11 . 
   The base  411  of the cap  410  is provided with a suction opening  412 , and this suction opening  412  is connected with a suction tube  420 . Moreover, the suction tube  420  is connected with a suction pump  425  which functions as a pressure-reducing source. When the cap  410  is in the capping position, the suction pump  425  performs a suction process via the suction opening  412  to reduce the pressure in a space  450  formed between the cap  410  and the discharging surface  301 . 
   Furthermore, the base  411  is provided with an air-communication opening  413 , and this air-communication opening  413  is connected with an air-communication tube  430 . Moreover, the air-communication tube  430  is connected with an air-communication valve  435  which functions as an air-communication controlling element. The valve  435  is for controlling whether to open or close the communication between the space  450  and the atmosphere via the air-communication opening  413 . As shown in  FIGS. 10 and 11 , the space  450  of the cap  410  includes an absorber  440  formed of an ink-absorptive porous material. 
   A suction process of a typical liquid-discharge-head recovering device provided with the liquid-discharge-head cap  410  described above will now be described. 
   For performing the suction process, the cap  410  is first set at the non-contact position, and the discharge head  300  is moved to a position where it faces the cap  410 . The cap  410  is then moved to a capping position by means of the cap-driving unit. Subsequently, the air-communication valve  435  is closed. The suction pump  425  then operates so as to reduce the pressure in the space  450 . 
   Consequently, the ink is sucked out from the nozzles of the discharge head  300 . The ink removed from the nozzles is absorbed by the ink absorber  440 , but is immediately drawn into the suction pump  425 . Subsequently, the air-communication valve  435  opens and connects the space  450  with the atmosphere. In most recovering devices, the suction pump  425  remains in an operative state after the air-communication valve  435  is opened so that the ink remaining in the space  450 , especially the ink absorbed in the ink absorber  440 , can be drawn into the suction pump  425 . The cap  410  is then driven to the non-contact position, i.e. an unsealing position, by means of the cap-driving unit. The suction pump  425  is drained by an ink drainage process such that the ink drawn into the suction pump  425  is emitted out of the recovering device in a direction indicated by an arrow W in  FIG. 11 . 
   In most cases, after performing such a suction process, some of the ink sucked out from the nozzles remains on the discharging surface  301 . This may be problematic if the ink remaining on the discharging surface  301  covers the nozzles since it may lead to improper discharging of liquid or deviation of the discharging direction of liquid, as described previously. To prevent such problems, most inkjet printers are provided with a wiping unit for wiping off the ink remaining on the discharging surface  301  after the suction process. This effectively prevents the problems described above, such as the improper discharging of liquid and the deviation of the discharging direction of liquid. 
   In recent years, small-sized inkjet printers have been widely manufactured. Such small-size inkjet printers are mainly used for printing images taken by, for example, digital cameras, on relatively small-size paper, such as A6-size paper. For reducing the size of such printers, the ink capacity of the printer must be relatively reduced as much as possible. For this reason, the amount of ink to be sucked out from the nozzles during the suction process must also be reduced to the greatest extent possible. 
   To fulfill such demands, a negative-pressure valve may be disposed in a section of the suction tube  420  between the suction opening  412  and the suction pump  425 . This negative-pressure valve is an on-off valve that allows the pressure in the space  450  to be reduced by means of the suction pump  425 . In detail, in a state where the negative-pressure valve is closed, the suction pump  425  begins its operation so as to reduce the pressure in a space in the suction tube  420  between the negative-pressure valve and the suction pump  425 . Thus, the pressure in this space in the suction tube  420  is highly reduced with respect to the ambient pressure. This highly-reduced pressure will be referred to as high negative pressure hereinafter. Subsequently, when the high negative pressure reaches a predetermined value and the negative-pressure valve opens, the pressure in the space  450  in the cap  410  is reduced at once. Shortly after the negative-pressure valve is opened, the air-communication valve  435  is opened. This suction process, which utilizes high negative pressure, is effective due to the fact that the pressure in the space  450  is greatly reduced in an extremely short period of time. Specifically, this reduces the amount of ink sucked out from the nozzles, and moreover, effectively removes, for example, thickened ink attached around each nozzle and bubbles formed inside the nozzles. 
   However, when performing the suction process using high negative pressure in the conventional liquid-discharge-head recovering devices, the amount of ink remaining on the discharging surface  301  may increase due to the following reasons. Because the air-communication valve  435  opens shortly after the negative-pressure valve is opened, an extremely high negative pressure still remains in the space  450  just before the air-communication valve  435  is opened. For this reason, when the air-communication valve  435  opens, atmospheric gas enters the space  450  at an extremely high rate through the air-communication opening  413 . The ink present in the space  450  when the air-communication valve  435  is opened, that is, the ink previously sucked out from the nozzles when the negative-pressure valve opened, spatters in various directions in the space  450  due to the fast-flowing gas. 
   In a case where a large amount of ink is present in the vicinity of the air-communication opening  413 , the amount of ink spattering is relatively large and may even reach the contact section between the discharging surface  301  and the cap  410 . Thus, even if the suction pump  425  continues to operate in this state, the suction pump  425  may be able to suck in the ink absorbed in the ink absorber  440  but not the ink present in other regions within the space  450  of the cap  410 . For this reason, the ink attached to the discharging surface  301  may remain even after the cap  410  is moved to the non-contact position. Of all the ink remaining in the contact section between the discharging surface  301  and the cap  410 , the amount of ink remaining in the contact section near the air-communication opening  413  is especially large. 
   Accordingly, for performing the suction process using high negative pressure in the conventional recovering devices, the amount of ink remaining on the discharging surface  301  is large in comparison with performing the suction process without using the high negative pressure. The larger amount of ink left on the discharging surface  301  may be problematic for the subsequent wiping process, which is generally performed after the suction process, in that the ink may spatter to various parts of the inkjet printer during the wiping process, and moreover, that the ink may attach to, for example, a wiper blade used for the wiping process and may thicken when the wiper blade is left unused. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a capping unit for use with a liquid-discharge-head that minimizes liquid spatter during a suction process so that after the suction process, liquid spatter during a wiping process is minimized and thickening of the liquid remaining on a wiper blade used during a wiping process is prevented. The present invention is also directed to a recovering device incorporating the capping unit and directed to an image forming apparatus incorporating the recovering device. 
   In one aspect of the present invention, the capping unit includes a cap having a periphery, the cap defining a cavity with the liquid discharge head, a suction opening defined in the cap, and an air-communication opening defined at about the periphery of the cap, the air-communication opening connecting the cavity with an atmosphere. In another aspect of the present invention, a recovering device includes a wiping unit operable to wipe the discharge surface, and a cap selectively moving into and out of contact with the discharge surface, the cap including a base having a corner, a space defined by the base and the discharge surface, a suction opening defined in the base and communicating with the space, an air-communication opening defined at about the corner, the air-communication opening communicating with the space. 
   Further features and advantages of the present invention will become apparent from the following description of the embodiments (with reference to the attached drawings). 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic perspective view of an inkjet printer which includes a liquid-discharge-head recovering device provided with a liquid-discharge-head cap according to one of embodiments of the present invention; 
       FIG. 2  is a schematic perspective view of the recovering device in  FIG. 1 ; 
       FIG. 3  is a schematic plan view of the cap according to a first embodiment of the present invention; 
       FIG. 4  is a cross-sectional view of the recovering device including the cap taken along line IV—IV in  FIG. 3 ; 
       FIG. 5  is a cross-sectional view of the recovering device including the cap taken along line V—V in  FIG. 3 ; 
       FIG. 6  is a schematic plan view of the liquid-discharge-head cap according to a second embodiment of the present invention; 
       FIG. 7  is a cross-sectional view of the recovering device including the cap taken along line VII—VII in  FIG. 6 ; 
       FIG. 8  is a cross-sectional view of the recovering device including the cap taken along line VIII—VIII in  FIG. 6 ; 
       FIG. 9  is a cross-sectional view of the recovering device including the cap taken along line IX—IX in  FIG. 6 ; 
       FIG. 10  is a schematic plan view of a typical liquid-discharge-head cap; and 
       FIG. 11  is a cross-sectional view of a typical liquid-discharge-head recovering device including the cap of  FIG. 10  taken along line XI—XI of  FIG. 10 . 
   

   DESCRIPTION OF THE EMBODIMENTS 
   Embodiments of the present invention will now be described with reference to the drawings. In the drawings, the same reference numerals are used to indicate the same components or to indicate corresponding components having similar functions. 
     FIG. 1  is a schematic perspective view of an inkjet printer  15  which includes a liquid-discharge-head recovering device  5  provided with a liquid-discharge-head cap  2100  according to one of the embodiments of the present invention.  FIG. 2  is a schematic perspective view of the recovering device  5  in  FIG. 1 .  FIG. 3  is a schematic plan view of the cap  2100  according to a first embodiment of the present invention.  FIG. 4  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line IV—IV in  FIG. 3 .  FIG. 5  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line V—V in  FIG. 3 . 
   The inkjet printer  15  in  FIG. 1  is provided with a feeder  1  for feeding a recording medium, such as paper, to a recording position; a sender  2  for pulling the recording medium from the feeder  1 ; a liquid discharge head (an inkjet print head)  100  functioning as a printing element; a carriage  4  which carries the discharge head  100  and moves horizontally with respect to the recording medium for scanning; the recovering device  5  for recovering the liquid discharging performance of the discharge head  100 ; a guide shaft  6  for guiding the carriage  4  such that the carriage  4  is capable of oscillating along the guide shaft  6 ; and a carriage motor  7  functioning as a driving source for the carriage  4  such that the carriage  4  is movable in two directions indicated by an arrow A in  FIG. 1 . 
   Referring to  FIGS. 2 to 5 , the recovering device  5  functions as a recovering element and includes a capping unit  20 . The capping unit  20  includes the cap  2100  for covering a discharging surface  101  of the discharge head  100  when the inkjet printer  15  is in a non-recording state. The recovering device  5  also includes a wiping unit  30  for wiping the discharging surface  101 , and a suction unit  40  for drawing in liquid from nozzles disposed on the discharging surface  101  when the discharging surface  101  is being covered with the capping unit  20 . The units  20 ,  30 , and  40  are disposed on a base  10  of the recovering device  5 . 
   The discharge head  100  of the present invention performs the printing operation in the following manner. First, an electric-heat transferring element (not shown) in the discharge head  100  applies heat energy to ink contained in the discharge head  100 . The heat vaporizes the ink to create a bubble. The bubble expands and shrinks to generate a pressure change. This pressure change induces discharge of ink from each of the nozzles for performing printing. 
   Referring to  FIGS. 1 and 2 , the arrow A indicates the moving direction of the carriage  4  carrying the discharge head  100 . The cap  2100  is preferably formed of an elastic material, such as rubber or elastomer, and is for hermetically sealing the discharging surface  101  of the discharge head  100 . Moreover, the cap  2100  is mounted on a cap holder  22  having a rigid body. When a printing operation is not being performed or when a suction process for recovering the discharging performance of the discharge head  100  is being performed, the cap  2100  is moved to a position where it comes into contact with the discharging surface  101  by means of a cap-driving unit. 
   Referring to  FIG. 2 , the wiping unit  30  is for wiping the discharging surface  101  of the discharge head  100  to remove liquid, i.e. ink, or foreign matter, such as paper dust, attached to the discharging surface  101 . The wiping unit  30  is provided with a wiper holder  32  for holding a wiper  31 , which can be rubbed against the discharging surface  101 . Thus, the wiping unit  30  is capable of performing the wiping process by moving the wiper holder  32  in the rubbing direction and also by moving the wiper holder  32  toward and away from the discharging surface  101 . 
   Referring to  FIG. 2 , the suction unit  40  includes a suction pump  225  and a suction tube  220 . The suction pump  225  is connected to the cap  2100  via the suction tube  220 . 
   As described above,  FIG. 3  is a schematic plan view of the cap  2100  according to the first embodiment.  FIG. 4  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line IV—IV in  FIG. 3 , and  FIG. 5  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line V—V in  FIG. 3 . The cap  2100  is formed of an elastic material, such as rubber, and has a substantially rectangular base  2110  whose four corners are curved. 
   When the cap  2100  faces the discharging surface  101  of the discharge head  100 , the cap  2100  is capable of moving towards and away from the discharging surface  101  for sealing and unsealing the discharging surface  101 , respectively. Here, the cap  2100  is driven by means of a cap-driving unit, which is not shown in the drawings.  FIGS. 4 and 5  illustrate a state in which the cap  2100  is in contact with the discharging surface  101 , that is, a sealed state. In this sealed state, a space/cavity  250  is formed between the cap  2100  and the discharging surface  101 . 
   Referring to  FIGS. 3 and 5 , the base  2110  of the cap  2100  is provided with air-communication openings  2103  and  2104 . The air-communication openings  2103  and  2104  are disposed at about a periphery of the cap  2100 , such as at corners  2113  and  2114 . Specifically, the two opposite ends of one of the shorter sides  2111  of the substantially rectangular base  2110  respectively have the two neighboring corners  2113  and  2114 , and the openings  2103  and  2104  are disposed adjacent to the corners  2113  and  2114 , respectively. Furthermore, the openings  2103  and  2104  are connected to air-communication tubes  2303  and  2304 , respectively. As shown in  FIG. 5 , the tubes  2303  and  2304  are joined together at position J to become a single air-communication tube  2300 . 
   The tube  2300  is connected with an air-communication valve  235 , which functions as a controlling element for controlling the communication between the space  250  and the atmosphere via the openings  2103  and  2104 . 
   An imaginary line H—H in  FIG. 3  extends substantially through the center of the base  2110  of the cap  2100  and substantially bisects the base  2110 . In detail, the imaginary line H—H is parallel to an imaginary line extending between the openings  2103  and  2104 , namely, line V—V in  FIG. 3 . The base  2110  is provided with a suction opening  2102  in one of the two imaginary-bisected regions not having the air-communication openings  2103  and  2104 . The suction opening  2102  is connected to the suction tube  220 . 
   Referring to  FIG. 4 , the suction tube  220  is connected to a negative-pressure valve  223  and the suction pump  225 . The negative-pressure valve  223  is an on-off valve that allows the pressure in the space  250  in the cap  2100  to be reduced by means of the suction pump  225 . The suction pump  225  is, for example, a piston pump. In other words, the cap  2100  is connected with the suction pump  225  included in the suction unit  40  via the suction opening  2102 , and the suction pump  225  functions as a pressure-reducing source for the suction of the space  250 . Furthermore, the interior of the cap  2100  defined by the space  250  is provided with a liquid absorber  2400 , such as an ink absorber, formed of a liquid-absorptive porous material. In the first embodiment, the liquid absorber  2400  is disposed over the suction opening  2102  but not over the air-communication openings  2103  and  2104 . 
   Referring to  FIGS. 3 to 5 , the suction process performed by the recovering device  5  provided with the cap  2100  will now be described. Firstly, the discharge head  100 , i.e. the inkjet print head, is moved to a position where the discharge head  100  faces the cap  2100 . Secondly, the cap  2100  is moved to the capping position so that the cap  2100  comes into contact with the discharging surface  101  by means of the cap-driving unit. Then, the negative-pressure valve  223  and the air-communication valve  235  are closed. As described previously, the negative-pressure valve  223  is an on-off valve that controls the communication between the suction pump  225  and the space  250 . On the other hand, the air-communication valve  235  is also an on-off valve that controls the communication between the space  250  and the atmosphere. 
   The suction pump  225  then begins the suction operation and reduces the pressure in a space in the suction tube  220  between the negative-pressure valve  223  and the suction pump  225 . The negative-pressure valve  223  is opened as soon as the pressure in the space is reduced to a predetermined level so that the pressure in the space  250  in the cap  2100  can be reduced at once. Consequently, this high negative pressure sucks out the ink from the nozzles of the discharge head  100 . Even though the ink may spatter in the space  250  including the liquid absorber  2400 , the odds of the ink spatter reaching the vicinity of the four corners of the substantially rectangular base  2110  are low, and in most cases, the ink does not reach the vicinity of the four corners. 
   Subsequently, the air-communication valve  235  opens shortly after the negative-pressure valve  223  is opened. Since there is still an extremely high negative pressure in the space  250  as the air-communication valve  235  is being opened, atmospheric gas enters the space  250  at an extremely high rate through the air-communication openings  2103  and  2104 . 
   Although this fast-traveling gas flows toward the discharging surface  101  in a direction indicated by arrows S 10  and S 20  in  FIG. 5 , the gas cannot flow in a direction indicated by an arrow R in  FIG. 3  since the air-communication openings  2103  and  2104  are disposed adjacent to the respective neighboring corners  2113  and  2114 . Furthermore, because the gas flows into the space  250  from both the openings  2103  and  2104 , only a small amount of gas flows in directions indicated by arrows T 1  and T 2  in  FIG. 3 . Moreover, as indicated by arrows S 11  and S 21  in  FIG. 3 , according to the suction effect by the suction pump  225  via the suction opening  2102 , the gas flows substantially parallel to the discharging surface  101  towards the suction opening  2102  so as to be drawn into the suction pump  225 . 
   Although the atmospheric gas traveling at a high rate may further cause the ink to spatter in the space  250 , because the air-communication openings  2103  and  2104  are respectively disposed adjacent to the neighboring corners  2113  and  2114 , the amount of ink remaining on the discharging surface  101  after the completion of the suction process can be reduced due to the following three reasons. 
   The first reason is that there is only a small amount of ink present in the vicinity of the air-communication openings  2103  and  2104  when the air-communication valve  235  is opened. 
   The second reason is that the gas entering the space  250  when the air-communication valve  235  opens does not flow in the direction indicated by the arrow R in  FIG. 3 , and moreover, only a small amount of gas flows in directions indicated by the arrows T 1  and T 2  in  FIG. 3 . This implies that there is only an extremely small amount of ink left in a contact section between the discharging surface  101  and the cap  2100  adjacent to the openings  2103  and  2104 . 
   The third reason is that the gas entering the space  250  when the air-communication valve  235  opens flows substantially parallel to the discharging surface  101  towards the suction opening  2102  at an extremely high rate, as indicated by the arrows S 11  and S 21  in  FIG. 3 . This implies that, when the valve  235  is opened, most of the ink spattered in the space  250  is directed towards the suction opening  2102  and is carried with the fast-traveling gas flowing substantially parallel to the discharging surface  101  without being left on the discharging surface  101 . Thus, the ink is drawn into the suction pump  225  with the gas through the suction opening  2102 . 
   According to the three reasons described above, the ink remaining on the discharging surface  101  after the suction process can be reduced to a small amount. In a case where a piston pump is used for the suction pump  225 , the piston of the suction pump  225  moves continuously as the suction process is started for pressure reduction, and continues to move after the air-communication valve  235  is opened. Thus, the ink absorbed by the liquid absorber  2400  in the space  250  is effectively drawn into the suction pump  225 , i.e. the piston pump. Finally, the cap-driving unit drives the cap  2100  to an unsealing position, i.e. the non-contact position. Furthermore, the suction pump  225 , i.e. the piston pump, is drained by a known ink drainage process such that the ink drawn into the suction pump  225  is emitted out of the recovering device  5 . 
   Due to the cap  2100  and the recovering device  5  provided with the cap  2100 , the liquid (ink) remaining on the discharging surface  101  after the suction process can be reduced to a small amount. Moreover, the recovering device  5  of the present invention can prevent the problems occurring in the previously-described conventional recovering device. To achieve an effective suction process using high negative pressure, the pressure in the space  250  after opening the negative-pressure valve  223  is reduced by about 30 kPa or more, and moreover, the pressure in the space  250  after opening the air-communication valve  235  is reduced by about half the amount of the reduced pressure after opening the negative-pressure valve  223 , that is, about 15 kPa or more. Furthermore, the pressure in the space  250  after opening the negative-pressure valve  223  can be reduced to about 50 kPa or more, and to reduce the pressure in the space  250  after opening the air-communication valve  235  by about 70% of the amount of the reduced pressure after opening the negative-pressure valve  223 , that is, about 35 kPA or more. 
   Furthermore, according to the first embodiment described above, the pressure level in the space  250  after opening the negative-pressure valve  223  and the pressure level in the space  250  after opening the air-communication valve  235  may respectively be controlled by adjusting, for example, the time period between the starting point of the suction by the suction pump  225  and the opening point of the negative-pressure valve  223 , and between the opening point of the negative-pressure valve  223  and the opening point of the air-communication valve  235 . 
   According to the first embodiment, a liquid-discharge-head cap and a liquid-discharge-head recovering device that prevents problems occurring in a wiping process, which is generally performed after a suction process, are provided. Specifically, the liquid-discharge-head cap  2100  and the liquid-discharge-head recovering device  5  of the first embodiment perform an effective suction process that can reduce the liquid remaining on the discharging surface  101  of the discharge head  100  after the suction to a small amount. Accordingly, this prevents problems occurring in a wiping process caused by spattering of liquid remaining on the discharging surface  101  and also by thickening of liquid remaining on, for example, a wiper blade used for the wiping process caused when the wiper blade is left unused. 
     FIG. 6  is a schematic plan view of the liquid-discharge-head cap  2100  according to a second embodiment of the present invention.  FIG. 7  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line VII—VII in  FIG. 6 .  FIG. 8  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line VIII—VIII in  FIG. 6 .  FIG. 9  is a cross-sectional view of the recovering device  5  including the cap  2100  taken along line IX—IX in  FIG. 6 . 
   Referring to  FIGS. 6 to 9 , similar to the first embodiment, the cap  2100  of the second embodiment is formed of an elastic material, such as rubber, and has the substantially rectangular base  2110  whose four corners are curved. The base  2110  is provided with the air-communication openings  2103  and  2104 . Like the first embodiment, the two opposite ends of one of the shorter sides  2111  of the substantially rectangular base  2110  respectively have neighboring corners  2113  and  2114 , and the openings  2103  and  2104  are disposed adjacent to the corners  2113  and  2114 , respectively. In the second embodiment, the openings  2103  and  2104  are joined together at position K in the base  2110 , and this joint section is connected to an air-communication tube  230 . Furthermore, the air-communication tube  230  is connected to the air-communication valve  235 , which functions as a controlling element for controlling the communication between the space  250  and the atmosphere via the openings  2103  and  2104 . 
   The base  2110  is provided with the suction opening  2102  in the same position as the first embodiment, and the suction opening  2102  is connected to the suction tube  220 . The suction tube  220  is connected to the negative-pressure valve  223  and the suction pump  225 . The suction pump  225 , which is included in the suction unit  40 , functions as a pressure-reducing source for the suction of the space  250  via the suction opening  2102 . Furthermore, the interior of the cap  2100  defined by the space  250  is provided with the liquid absorber  2400  formed of a liquid-absorptive (ink-absorptive) porous material. Similar to the first embodiment, the liquid absorber  2400  is disposed over the suction opening  2102  but not over the air-communication openings  2103  and  2104 . 
   The cap  2100  and the recovering device  5  of the second embodiment shown in  FIGS. 6 to 9  perform a similar suction process to that of the first embodiment. Consequently, the ink remaining on the discharging surface  101  after the suction process can be reduced to a small amount. Similar to the advantages of the first embodiment, the cap  2100  and the recovering device  5  of the second embodiment prevents problems occurring in a wiping process, which is generally performed after the suction process. As described previously, the liquid remaining on the discharging surface  101  of the discharge head  100  after the suction can be reduced to a small amount, preventing spattering of liquid during the wiping process and also preventing thickening of liquid remaining on, for example, a wiper blade used for the wiping process caused when the wiper blade is left unused. 
   On the other hand, in comparison with the first embodiment, the cap  2100  of the second embodiment contributes to the size reduction of the recovering device  5 . Specifically, the length of the cap  2100  in the direction indicated by the arrow R in  FIG. 3 , and the width of the cap  2100  in the direction indicated by the arrows T 1  and T 2  in  FIG. 3  can both be reduced while still achieving a lesser amount of ink remaining on the discharging surface  101  after the suction process. Accordingly, this is advantageous for small-size inkjet printers used mainly for printing on relatively small-size paper, such as A6-size paper. 
   Alternatively, the substantially rectangular base  2110  of the cap  2100  may be longer in the longitudinal direction of the drawings so that, instead of being disposed adjacent to the corners at the two respective ends of one of the shorter sides, the air-communication openings  2103  and  2104  may respectively be disposed adjacent to the corners at the two respective ends of one of the longer sides. Such a structure is included within the scope of the present invention. However, in a case where there is a significant difference in length between the longer sides and the shorter sides of the substantially rectangular base  2110  of the cap  2100 , if the openings  2103  and  2104  are disposed in such a manner described above, the atmospheric gas entering the space  250  through the openings  2103  and  2104  may flow in the directions indicated by the arrows T 1  and T 2  in  FIG. 3  and create turbulence. This can cause the ink in the space  250  to become attached to the discharging surface  101 . For this reason, in a case where there is a significant difference in length between the longer sides and the shorter sides of the substantially rectangular base  2110  of the cap  2100 , the openings  2103  and  2104  are disposed adjacent to the corners at the two respective ends of one of the shorter sides. 
   Furthermore, although the air-communication openings  2103  and  2104  are provided in the base  2110  of the cap  2100  in the above embodiments, the openings  2103  and  2104  do not necessarily have to be disposed in the base  2110 . Alternatively, the openings  2103  and  2104  may be disposed in the corresponding sides of the cap  2100 . Similarly, the suction opening  2102  does not necessarily have to be provided in the base  2110  of the cap  2100 , and may alternatively be disposed in one of the corresponding sides of the cap  2100 . Accordingly, such alternative structures related to the position of the air-communication openings  2103  and  2104  and the suction opening  2102  are included within the scope of the present invention. 
   Furthermore, although the suction opening  2102  is disposed in one of the two imaginary-bisected regions not having the air-communication openings  2103  and  2104  in the above embodiments, the suction opening  2102  may alternatively be disposed in the other imaginary-bisected region that has the air-communication openings  2103  and  2104 . Such a structure is included within the scope of the present invention. However, disposing the suction opening in the other imaginary-bisected region may lower the effectiveness of the present invention to some extent since the suction opening  2102  is near one of the sides whose two opposite ends, i.e. the two neighboring corners, respectively have the air-communication openings  2103  and  2104  adjacent thereto. 
   Furthermore, although only a single suction opening  2102  is provided in the above embodiments, a plurality of suction openings  2102  may alternatively be provided. In such a case, a plurality of suction pumps  225  may be provided for the corresponding suction openings  2102  for reducing the pressure in the space  250 , or a single suction pump  225  may be connected to the suction openings  2102  for reducing the pressure in the space  250 . 
   Furthermore, although a single air-communication valve  235  is provided in the above embodiments, a plurality of air-communication valves  235  may alternatively be provided such that, for example, the air-communication tubes  2303  and  2304  shown in  FIG. 5  are each provided with a corresponding air-communication valve  235 . 
   Furthermore, although the liquid absorber  2400  provided in the space  250  is not disposed over the air-communication openings  2103  and  2104  in the above embodiments, substantially the same effect can be achieved by alternatively disposing the liquid absorber  2400  over the air-communication openings  2103  and  2104 . Furthermore, the liquid absorber  2400  may alternatively cover about half the opening area of each of the air-communication openings  2103  and  2104 . Accordingly, such alternative structures are included within the scope of the present invention. 
   However, if the liquid absorber  2400  in the space  250  is formed of a material having low porosity, the liquid absorber  2400  should not completely cover the air-communication openings  2103  and  2104  since the rate at which the atmospheric gas enters the space  250  may diminish. 
   Furthermore, although high negative pressure is used for performing the suction process in the above embodiments and the application of such high negative pressure exhibits the distinguishable advantage of the present invention, a similar effect can be obtained without using the high negative pressure. Accordingly, the present invention does not necessarily depend upon the magnitude of pressure used. 
   According to the embodiments of the present invention, a liquid-discharge-head cap that is capable of preventing problems occurring in a wiping process, which is generally performed after a suction process, is provided. Specifically, the liquid remaining on the discharging surface after the suction process can be reduced to a small amount so as to prevent spattering of liquid during the wiping process, and also to prevent thickening of liquid remaining on, for example, a wiper blade used for the wiping process caused when the wiper blade is left unused. 
   While the present invention has been described with reference to what are presently considered to be the embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.