Abstract:
An image forming apparatus has a liquid discharge head to discharge droplets of a recording liquid to form an image on a recording medium and a maintenance-and-recovery mechanism to perform a maintenance and recovery operation on the liquid discharge head. The maintenance-and-recovery mechanism includes a suction device, a control unit, a drain tube, and a drain reservoir. The suction device suctions droplets of the recording liquid from the liquid discharge head. The suctioned droplets are not used for an image forming operation. The control unit controls a suction speed of the suction device. The drain reservoir stores the suctioned droplets drained from the drain tube. The drain tube is inclined relative to an opening portion of the drain reservoir. The control unit controls the suction speed of the suction device to change a drain speed of the suctioned droplets drained from the drain tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application claims priority under 35 U.S.C. §119 from Japanese Patent Application No. 2007-046354 filed on Feb. 27, 2007 in the Japan Patent Office, the entire contents of which are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     This disclosure generally relates to image forming apparatuses, and more specifically, to an image forming apparatus capable of preventing waste liquid from accumulating at a certain place in a drain reservoir. 
     2. Description of the Background 
     An image forming apparatus used as a printer, facsimile machine, copier, multi-functional device thereof, or plotter may have a recording head configured as, for example, a liquid discharge head for discharging liquid droplets of a recording liquid such as ink. Such image forming apparatuses discharge liquid droplets of a recording liquid from nozzles of the liquid discharge head to form a desired image on a recording medium, for example, a paper sheet. 
     However, in such image forming apparatuses, standby operation, high-temperature and/or low-humidity environment, and low printing frequency may increase the viscosity of the recording liquid, thereby resulting in clogging of the nozzles. Accordingly, such image forming apparatuses generally have a function to maintain and recover the discharge performance of the recording head. 
     As one example of such a maintenance and recovery function, a conventional image forming apparatus performs an idle discharge operation to discharge liquid droplets not contributing to image recording from nozzles at certain intervals or as needed, thus removing such viscosity-increase liquid from the recording head. 
     Such a conventional image forming apparatus may also have an idle discharge receiver to receive liquid droplets discharged from the nozzles during such an idle discharge operation. In such an idle discharge receiver, color materials, for example, pigment or dye, contained in a recording liquid may accumulate and grow over time. If such growth of accumulated color materials is not removed, the accumulated color materials may come into contact with a nozzle formation face of the recording head, thereby resulting in an operation failure of the recording head. 
     Hence, several measures have been proposed to deal with such accumulated materials. 
     In one example, a conventional inkjet image forming apparatus has a cleaning unit to prevent overflow or contamination of waste liquid. The cleaning unit includes a suction device to suction ink from discharge orifices, an ink passage tube through which to pass the suctioned ink, a drain reservoir to store the ink drained through the ink passage tube, and a shifting unit to shift a position of an end opening of the ink passage tube. When performing a cleaning operation using the cleaning unit, the conventional inkjet image forming apparatus shifts the position of the end opening of the ink passage tube so that such waste ink is relatively uniformly distributed over substantially an entire floor area of the drain reservoir. 
     In one example, a waste-liquid removal structure is proposed for a conventional inkjet image forming apparatus. The conventional image forming apparatus has a tube to guide waste liquid into a waste liquid tank, and an end opening of the tube is disposed at a certain height relative to the waste liquid tank. In order to remove the waste liquid accumulated below the end opening of the tube, the waste-liquid removal structure has a belt conveyor horizontally disposed in the waste liquid tank and a scraper uprightly disposed on a bottom portion of the waste liquid tank. 
     However, the above-described conventional inkjet image forming apparatuses have certain disadvantages, for example, relatively large size or highly complex configuration. 
     In one example, a conventional inkjet recording apparatus has a configuration in which an end opening for pigment waste liquid and an end opening for dye waste liquid are positioned adjacent each other. Such a configuration allows the two types of waste liquids to mix, thereby dissolving a solid deposit of the pigment waste liquid or suppressing solidification and accumulation of such pigment waste liquid. However, in such a conventional inkjet recording apparatus, pigment component may not be fully dissolved and therefore may result in the fixation and accumulation of such pigment waste liquid. 
     In one example, a conventional liquid discharge apparatus has a controller to change the rotation speed of a tube pump. In the conventional liquid discharge apparatus, the controller controls the tube pump to rotate at a relatively high speed for a given time period and then rotate at a relatively low speed for a given time period. However, such a configuration may need a relatively complex control operation to change the rotation speed of the tube pump. Moreover, repeating such a relatively complex speed change may adversely affect the durability of the tube pump. 
     In one example, for a conventional image forming apparatus, an idle discharge receiver is proposed that removes deposits of waste liquid accumulated at a slope portion that is provided to receive a recording liquid. The idle discharge receiver has a swing member including a plurality of swing plates coupled with coupling ribs. The swing plates are reciprocated parallel to a surface of the slope portion while keeping away from the slope portion. However, such a configuration has a disadvantage that, as the amount of ink attached to the swing member increases over time, such ink may intrude into gaps among components, so that the movement of the swing member may be prevented. 
     Thus, there is still a need for an image forming apparatus having a simple configuration and capable of relatively uniformly draining of waste liquid into a drain reservoir while maintaining stable operation without an increase in overall size. 
     BRIEF SUMMARY OF THE INVENTION 
     In an aspect of this disclosure, there is provided an image forming apparatus capable of preventing waste liquid from accumulating at a certain place in a drain reservoir. 
     In another aspect, an image forming apparatus has a liquid discharge head and a maintenance-and-recovery mechanism. The liquid discharge head discharges droplets of a recording liquid to form an image on a recording medium. The maintenance-and-recovery mechanism performs a maintenance and recovery operation on the liquid discharge head. The maintenance-and-recovery mechanism includes a suction device, a control unit, a drain tube, and a drain reservoir. The suction device suctions droplets of the recording liquid from the liquid discharge head. The suctioned droplets are not used for an image forming operation. The control unit controls a suction speed of the suction device. The drain tube drains the suctioned droplets suctioned by the suction device. The drain reservoir stores the suctioned droplets drained from the drain tube. The drain tube is inclined relative to an opening portion of the drain reservoir. The control unit controls the suction speed of the suction device to change a drain speed with which the suctioned droplets are drained from the drain tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant aforementioned and other features, aspects and advantages will be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a schematic view illustrating a general configuration of maintenance-and-recovery mechanisms used in image forming apparatuses according to exemplary embodiments of the present invention; 
         FIGS. 2A to 2C  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a first exemplary embodiment; 
         FIG. 3  is a schematic view illustrating a configuration of a maintenance-and-recovery mechanism used in an image forming apparatus according to a second exemplary embodiment; 
         FIGS. 4A to 4C  are wave form diagrams illustrating input pulses generated when a stepping motor is used in the maintenance-and-recovery mechanism of  FIG. 3 ; 
         FIG. 5  is a schematic view illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a third exemplary embodiment; 
         FIGS. 6A and 6B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a fourth exemplary embodiment; 
         FIGS. 7A and 7B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a fifth exemplary embodiment; 
         FIGS. 8A and 8B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a sixth exemplary embodiment; and 
         FIGS. 9A and 9B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a seventh exemplary embodiment. 
     
    
    
     The accompanying drawings are intended to depict exemplary embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In describing exemplary embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner and achieve the same results. For the sake of simplicity, the same reference numerals are used in the drawings and the descriptions for the same materials and constituent parts having the same functions, and redundant descriptions thereof are omitted. 
     Exemplary embodiments of the present disclosure are now described below with reference to the accompanying drawings. It should be noted that, in a later-described comparative example, exemplary embodiment, and alternative example, the same reference numerals are used for the same constituent elements such as parts and materials having the same functions, and redundant descriptions thereof are omitted. 
       FIG. 1  is a schematic view illustrating a general configuration of maintenance-and-recovery mechanisms used in image forming apparatuses according to exemplary embodiments of the present invention. 
     For a maintenance-and-recovery mechanism  10  illustrated in  FIG. 1 , when viscosity-increased ink or bubbles appear in a recording head  11 , the recording head  11  may become unable to discharge ink normally. Hence, a nozzle formation face of the recording head  11  is sealed with a cap  12 , and such viscosity-increased ink or bubbles are suctioned from a drain tube  13 , communicating with the cap  12 , by using a suction device, for example, a pump  15  driven by a motor  14  serving as a drive source. The viscosity-increased ink or bubbles suctioned by the pump  15  are drained to a drain reservoir  16 , thus maintaining the recording head  11  in a normal state. 
     However, when a highly viscous ink, for example, a pigmented ink, is used, such a highly viscous ink may accumulate in a solid state in the drain reservoir  16 . Particularly in a low-humidity environment, such solid accumulation may occur due to air drying. 
     Hence, image forming apparatuses according to exemplary embodiments of the present invention are configured as follows. 
       FIGS. 2A to 2C  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a first exemplary embodiment. In  FIGS. 2A to 2C , reference characters identical to those of  FIG. 1  refer to identical components. 
     In a maintenance-and-recovery mechanism  20  illustrated in  FIGS. 2A to 2C , a drain tube  13  is inclined relative to an opening face of a drain reservoir  16 , and the suction speed of a pump  15  is controlled to change the speed at which waste ink is drained from an end opening of the drain tube  13 . 
     For example, as illustrated in  FIG. 2A , when the suction speed of the pump  15  is increased, the drain speed of the waste ink from the end opening of the drain tube  13  is increased, and thereby such waste ink is drained to a distal end side of the drain reservoir  16  that is distal relative to the drain tube  13 . 
     Further, as illustrated in  FIG. 2B , when the suction speed of the pump  15  is moderate, the drain speed of waste ink from the end opening of the drain tube  13  is moderated, and thereby such waste ink is drained to an intermediate portion of the drain reservoir  16 . 
     Furthermore, as illustrated in  FIG. 2C , when the suction speed of the pump  15  is decreased, the drain speed of waste ink from the end opening of the drain tube  13  is decreased and thereby such waste ink is drained to a proximal end side of the drain reservoir  16  relative the drain tube  13 . Thus, the maintenance-and-recovery mechanism  20  is capable of draining waste ink over substantially an entire floor area of the drain reservoir  16 . 
       FIG. 3  is a schematic view illustrating a configuration of a maintenance-and-recovery mechanism used in an image forming apparatus according to a second exemplary embodiment. In  FIG. 3 , reference characters identical to those of  FIG. 2  refer to identical components. 
     In a maintenance-and-recovery mechanism  20  illustrated in  FIG. 3 , a drain tube  13  is inclined relative to an opening face of a drain reservoir  16 . The maintenance-and-recovery mechanism  20  has a motor driver  21 , serving as a control unit, to control a motor  14  to change the suction speed of a pump  15 . 
     For example, when the motor  14  is a DC (direct current) motor, the motor driver  21  changes the speed of the motor  14  by current control. Alternatively, when the motor  14  is a stepping motor, the motor driver  21  changes the speed of the motor  14  by pulse control. 
     More specifically, as illustrated in  FIG. 4A , in a case in which a stepping motor is used as a drive source of the pump  15 , a triangular wave is used as the frequency of input pulse to continuously change the drain speed of waste ink. In such a case, as illustrated in  FIG. 4B , every time the number of suctioning attempts reaches a first number, the frequency of input pulse may be changed to change the drain speed of waste ink. Alternatively, as illustrated in  FIG. 4C , every time the number of suctioning attempts reaches a second number, the frequency of input pulse may be reduced to decrease the drain speed of waste ink. 
       FIG. 5  is a schematic view illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a third exemplary embodiment. In  FIG. 5 , reference characters identical to those of  FIG. 2  refer to identical components. 
     In  FIG. 5 , a maintenance-and-recovery mechanism  20  has a cap  12 , a drain tube  13 , a motor  14 , a pump  15 , a drain reservoir  16 , a speed changer  22 , and a control unit  30 . The drain tube  13  is inclined relative to an opening face of a drain reservoir  16 , and the motor  14  is driven at a substantially constant speed. The speed changer  22  is provided between the motor  14  and the pump  15 . The control unit  30  controls the drive speed of the pump  15  via the speed changer  22  to change the speed at which waste ink is drained from an end opening of a drain tube  13 . 
       FIGS. 6A and 6B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a fourth exemplary embodiment. In  FIGS. 6A and 6B , reference characters identical to those of  FIG. 2  refer to identical components. 
     In a maintenance-and-recovery mechanism  20 , a fixed member  24 - 1  and a moving member  24 - 2  sandwiches an end opening of a drain tube  13 , with the moving member  24 - 2  moved by a solenoid  23 . A control unit  30  controls the solenoid  23  to move the moving member  24 - 2 . Thus, the fixed member  24 - 1  and the moving member  24 - 2  serve as an adjustment unit to adjust a cross-sectional area of the end opening of the drain tube  13 , so as to change the speed with which waste ink is drained from the end opening of the drain tube  13 . 
     For example, as illustrated in  FIG. 6A , when the solenoid  23  moves the moving member  24 - 2  so as to open the end opening of the drain tube  13 , the cross sectional area of the end opening of the drain tube  13  is increased, thereby reducing the drain speed of waste ink from the end opening of the drain tube  13 . By contrast, as illustrated in  FIG. 6B , when the solenoid  23  moves the moving member  24 - 2  so as to press the end opening of the drain tube  13 , the cross-sectional area of the end opening of the drain tube  13  is decreased, thereby increasing the drain speed of waste ink from the end opening of the drain tube  13 . Thus, the maintenance-and-recovery mechanism  20  is capable of relatively uniformly draining waste ink over substantially an entire floor area of the drain reservoir. 
       FIGS. 7A and 7B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a fifth exemplary embodiment. In  FIGS. 7A and 7B , reference characters identical to those of  FIG. 2  refer to identical components. 
     In a maintenance-and-recovery mechanism  20 , as illustrated in  FIG. 7B , a drain tube  13  is moved by a solenoid  25  laterally from side to side relative to a lateral face of a drain reservoir  16 . Thus, the maintenance-and-recovery mechanism  20  is capable of relatively uniformly draining waste ink over a substantially entire floor area of the drain reservoir. 
       FIGS. 8A and 8B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a sixth exemplary embodiment. In  FIGS. 8A and 8B , reference characters identical to those of  FIG. 2  refer to identical components. 
     As illustrated in  FIG. 8B , in a maintenance-and-recovery mechanism  20 , a drain reservoir  16  is moved by a solenoid  26  laterally from side to side relative to a lateral face of the drain reservoir  16 . Thus, the maintenance-and-recovery mechanism  20  is capable of relatively uniformly draining waste ink over a substantially entire floor area of the drain reservoir. 
       FIGS. 9A and 9B  are schematic views illustrating a configuration of a maintenance-and-recovery mechanism of an image forming apparatus according to a seventh exemplary embodiment. In  FIGS. 9A and 9B , reference characters identical to those of  FIG. 2  refer to identical components. 
     As illustrated in  FIG. 9B , in a maintenance-and-recovery mechanism  20 , a drain tube  13  is an elastic member, for example, a silicone tube. Two vibrators  27  are provided, one at either side, at an end opening of the drain tube  13 . It should be noted that the number of vibrators  27  is not limited to two and may be any other suitable number. The vibrators  27  vibrate the drain tube  13  laterally from side to side relative to a lateral face of the drain reservoir  13 . Thus, the maintenance-and-recovery mechanism  20  is capable of relatively uniformly draining waste ink over a substantially entire floor area of the drain reservoir. 
     Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this application may be practiced otherwise than as specifically described herein. 
     Further, elements and/or features of different exemplary embodiments and/or examples may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.