Abstract:
An inkjet printer is provided having a filter that is replaceable efficiently and quickly and capable of reducing the possibility of contamination of an operator&#39;s hands and ambient surroundings. The filter includes a pipe connecting port which is connected in a channel through which ink or solvent flows and communicates with a primary side and a secondary side of an element of the filter. A channel block is provided with a housing cavity. A filter case is accommodated in the housing cavity and holds the filter element. The filter case is not connected with a pipe to the channel block. The filter case is detachable from the channel block, and a securing unit secures the filter case to the channel block.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority from Japanese Application No. JP-2009-230159 filed on Oct. 2, 2009 entitled “Inkjet Recording Apparatus,” the disclosure of which also is entirely incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present discussion relates to an inkjet printers having filters with characteristic structures for use in removing particulates in ink and solvent circulating channels. 
       BACKGROUND 
       [0003]    An inkjet printer produces printed output by ejecting ink from a nozzle having a diameter of from 40 μm to 100 μm to transform the ink into droplets. If such a small-diameter nozzle is clogged with particulates, proper ejection of the ink from the nozzle is hindered and the inkjet printer cannot continue printing. To avoid nozzle clogging, multiple filters are placed on channels, through which ink and solvent circulate, in the inkjet printer. 
         [0004]    Typical filters include a main ink filter located on a channel used to supply ink to the nozzle, a solvent filter located on a solvent supply channel, and a recovery filter located on a recovery channel that collects ink droplets ejected from the nozzle but not used. 
         [0005]    Filters may gradually become clogged over time and block the flow of liquid, and hence require periodical replacement. 
         [0006]    Various types of filters have been developed in consideration of installability and replaceability. Examples include: a filter in a housing with a primary side, which liquid flows into, and a secondary side, from which the liquid flows out, connected with pipes; a filter with one of the primary and secondary sides connected with a pipe to a housing and the other side directly connected to a manifold having a channel therein provided with multiple components; and a filter with primary and secondary sides directly connected to a manifold. 
         [0007]    Filter replacement is done by replacing a housing including a filter or by replacing only a filter from a disassembled housing (e.g., see JP-A-2001-146020A). 
       SUMMARY 
       [0008]    Since the inkjet printer in this description is a printing apparatus which produces printed output on products that are continuously mass-manufactured on a production line, filter replacement involving an operation halt of the apparatus causes a downtime for the production line. The more time is required to replace the filter, the greater the production efficiency is compromised. 
         [0009]    In addition, for inkjet printers often used on a production line of products, which require to be manufactured under strictly-controlled, hygienic conditions, such as food, beverages, chemical agents and cosmetics, contamination of the interior of the inkjet printer, peripheral facilities, floors and an operator&#39;s hands with ink and diffusion of ink odor to ambient surroundings, represent problems that may be caused by filter replacement. 
         [0010]    More specifically, in many cases, when a pipe is pulled off from a housing including a filter, ink is spilled from the end of the pipe or the pipe connecting port of the housing, ink is spilled from the housing that was disassembled to remove the filter embedded therein, or ink adheres to the hands of an operator removing the filter from a disassembled housing. 
         [0011]    The present subject matter has been made to provide an inkjet printer including a filter that can be replaced effectively in a short time. 
         [0012]    In addition, the present subject matter has been made to provide an inkjet printer including a filter that can reduce the possibilities of contaminating an operator&#39;s hands or ambient surroundings with ink. 
         [0013]    For the purpose of solving the above described problems, a filter is provided in an example of an inkjet printer. The exemplary apparatus produces a printed output on an object being printed by ejecting pressurized ink from a nozzle, transforming the ink into droplets at a constant frequency by vibrating the nozzle at a constant frequency, applying an electric charge to ink droplets corresponding to dots to be printed in the transformed ink droplets by applying a charge voltage in synchronization with the frequency of the droplet transformation to a charging electrode based on output information to be printed, deflecting the ink droplets applied with the electric charge in an electric field produced by applying a direct voltage to deflection electrodes, collecting ink droplets, which correspond to dots not to be printed and are not charged, by a gutter, and relatively moving the object being printed approximately orthogonal to a deflected direction of the charged ink droplets. The inkjet printer includes a pipe connecting port which is placed on a channel through which ink or solvent flows and communicates with a primary side and a secondary side of the filter. A channel block which is provided with a housing cavity. A filter case, is accommodated in the housing cavity, holds a filter element. The filter case is not connected with a pipe to the channel block and is detachable from the channel block. A securing unit secures the filter case to the channel block. 
         [0014]    Accordingly, the present teaching can provide an inkjet printer that enables quicker and more efficient filter replacement. 
         [0015]    Furthermore, according to the present teaching, an inkjet printer can be provided that enables filter replacement less chance of ink contamination of the operator&#39;s hands and ambient surroundings. 
         [0016]    Additional advantages and novel features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The advantages of the present teachings may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities and combinations set forth in the detailed example discussed below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements. 
           [0018]      FIG. 1  is a perspective view of the main body and printhead of an inkjet printer; 
           [0019]      FIG. 2  is a perspective view showing the use of the inkjet printer; 
           [0020]      FIG. 3  is a channel diagram of an inkjet printer according to an example; 
           [0021]      FIG. 4  is a perspective view illustrating basic operations of the inkjet printer; 
           [0022]      FIG. 5  is a functional block diagram of the inkjet printer; 
           [0023]      FIG. 6  is a front view showing a filter structure of the inkjet printer according to the example; 
           [0024]      FIG. 7  is an exploded perspective view showing the filter structure of the inkjet printer according to the example; 
           [0025]      FIG. 8  is another exploded perspective view showing the filter structure of the inkjet printer according to the example; 
           [0026]      FIG. 9  is a cross-sectional view of a channel block of the inkjet printer according to the example; and 
           [0027]      FIG. 10  is a cross-sectional view showing the filter structure of the inkjet printer according to the example. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    While we have shown and described an example in accordance with our subject matter below, it should be understood that disclosed example is susceptible of changes and modifications without departing from the scope of the subject matter. Therefore, we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications a fall within the ambit of the appended claims. 
         [0029]    With reference to an illustrated example, an example will be described below; however, the present subject matter is not limited to the illustrated example. 
         [0030]      FIG. 1  is an overall view of an inkjet printer  100  according to an example. The inkjet printer  100  includes a main body  1  provided with an externally mounted operation display  3  and a printhead  2 . The main body  1  is connected to the printhead  2  with a cable  4 . 
         [0031]      FIG. 2  shows an example when the inkjet printer  100  is actually being used. The inkjet printer  100  is installed on a production line in a factory that manufactures, for example, food products and beverages. The main body  1  is situated in a range where a user can operate the apparatus, while the printhead  2  is placed adjacent to a print object  6  conveyed on the production line such as a belt conveyer  5 . 
         [0032]    At the production line or belt conveyer  5 , an encoder  7  outputs signals to the inkjet printer  100  in accordance with a conveying speed; and a print sensor  8 , which detects the print object  6  and outputs signals instructing to print characters to the inkjet printer  100 . The encoder  7  and print sensor  8  are used in order to print the characters at a constant width irrespective of the conveying speed, and both are connected to a controller  200  (shown in  FIG. 5 ) in the main body  1 . 
         [0033]    In response to the signals from the encoder  7  and print sensor  8 , the controller  200  controls the amount of charge and timing for charging the ink droplets  10  propelled from the nozzle  9  so that the charged and deflected ink droplets  10  adhere to the print object  6  while the print object  6  passes in the vicinity of the printhead  2 . In this manner, the inkjet printer performs printing operations. 
         [0034]      FIG. 3  shows the entire channel structure of the inkjet printer  100 . The main body  1  includes a main ink reservoir  20  containing ink that circulates through channels. The main ink reservoir  20  is provided with a level sensor  21  that senses whether the fluid in the main ink reservoir  20  reaches the reference fluid level which reflects that there is a proper amount of fluid in the reservoir  20 . Extending from the main ink reservoir  20  is a channel  101  that is opened and closed by a solenoid valve  22 . The ink is generally sucked by a supply pump  23  through the channel  101 . However, only when ink viscosity measurement is required, the ink is sucked by the supply pump  23  through a bypass channel  102  on which a viscometer  24  is placed in order to refresh the ink being measured. The viscometer  24  may be a falling type viscometer for measuring the viscosity of the ink. 
         [0035]    The viscometer  24  is connected to a solenoid valve  25  via the channel  102 . The solenoid valve  25  closes and opens the channel  102 . The secondary side of the solenoid valve  25  is connected to the pump  23 , which sucks and feeds the ink with pressure, via the channel  101 . The pump  23  is connected via a channel  103  to an ink chamber  27  in which the pressurized ink applies pressure to a solvent through a diaphragm  26 . The ink applied, with pressure by the supply pump  23  pressurizes the solvent in a solvent chamber  63  through the diaphragm  26 , thereby supplying the solvent to the printhead  2 . The ink chamber  27  is connected to an ink filter  28 , which removes particulates in the ink, via a channel  104 . 
         [0036]    The ink filter  28  is connected to a pressure-reducing valve  29 , which adjusts the pressure of the ink pushed out by the pump  23  to a pressure suitable for printing, via a channel  105 . The pressure-reducing valve  29  is connected to the primary side of a three-port solenoid valve  30  in the printhead  2  via an ink supply channel  106  running in the cable  4 . The secondary side of the three-port solenoid valve  30  is connected to a nozzle  9 , which has a discharge orifice from which the ink is discharged, via a channel  107 . The three-port solenoid valve  30  has two ports on the primary side and one port on the secondary side and is designed to selectively switch back and forth between the primary ports to communicate with the secondary port. An ink supply channel  106  is connected to the normally closed port, while a solvent supply channel  122  is connected to the normally open port. 
         [0037]    The channel  107  on the secondary side of the three-port solenoid valve  30  branches off before the nozzle  9  to connect with a suction channel  112 . The suction channel  112  passes through inside the cable  4  and a pressure gauge  40  for measuring the pressure of the ink and is connected to a solenoid valve  41 . The secondary side of the solenoid valve  41  is connected to a recovery pump  50  that fills up ink through the suction channel  112  and performs sucking operations when the discharge orifice of the nozzle  9  is clogged. 
         [0038]    Along the direction where the ink is discharged from the nozzle  9  placed is a charging electrode  11  that applies electric charge to the ink droplets  10  ejected from the nozzle  9  in an amount according to character information to be printed. In the direction where the ink droplets  10  charged by the charging electrode  11  are flying, deflection electrodes  12  are placed which create an electric field that deflects the charged ink droplets  10 . 
         [0039]    Ahead of the deflection electrodes  12  in the direction in which the ink flies, a gutter  14  is placed that captures the ink droplets  10  that are not used for printing and fly straight without being charged and deflected. 
         [0040]    The gutter  14  is connected to a recovery filter  51 , which is placed in the main body  1  and used to remove particulates contained in the ink, via a recovery channel  108  running through the cable  4 . The recovery filter  51  is connected to a solenoid valve  15 , which opens and closes the recovery channel, via a channel  109  and further is connected to a recovery pump  50 , which sucks the ink droplets  10  captured by the gutter  14 , via a channel  110 . The recovery pump  50  feeds the sucked ink to the main ink reservoir  20  through a channel  111 . 
         [0041]    In addition, the main body  1  includes a solvent reservoir  60  containing solvent used to clean the nozzle  9  at stop time and to adjust the viscosity of the ink. The solvent reservoir  60  is connected to a solvent filter  61 , which removes particulates in the solvent channel, via a channel  120  and is further connected to a solvent chamber  63 , which sucks the solvent in and feeds the solvent with pressure, via a check valve  62 , which prevents backflow of the solvent. The solvent chamber  63  is connected to a solenoid valve  64  via a channel  121 . The secondary side of the solenoid valve  64  is connected to the primary port of the three-port solenoid valve  30  via the solvent supply channel  122  running through the cable  4 . The channel  120  through which the solvent is sucked from the solvent reservoir  60  is connected to a solenoid valve  65  via a channel  123 . The solenoid valve  65  is connected to the recovery pump  50  via a channel  124 . 
         [0042]    The main body  1  further includes an auxiliary ink reservoir  80  containing refill ink. The auxiliary ink reservoir  80  is connected to a solenoid valve  81  via a channel  130 . The solenoid valve  81  is used to open and close the channel  130 . The solenoid valve  81  is connected to the supply pump  23  via a channel  131 . 
         [0043]    Descriptions now will be made about the operating principles of the inkjet printer  100 . The inkjet printer  100  illustrated in  FIG. 4  is identical to the inkjet printer  100  shown in  FIG. 1 , but  FIG. 4  shows only components necessary to this description of the operating principles. 
         [0044]    As shown in  FIG. 4 , the ink in the main ink reservoir  20  is sucked and applied with pressure by the pump  23  and is ejected in the form of an ink column from the nozzle  9 . The nozzle  9  includes an electrostriction element  18  that vibrates the ink at a predetermined frequency to transform the ink column  17  ejected from the nozzle  9  into droplets. The number of generated ink droplets  10  in this manner is dependent on the frequency of the excitation voltage applied to the electrostriction element  18 , resulting in the same number as the frequency. The ink droplet  10  is charged by applying voltage in an amount according to character information to the charging electrode  11 . While an ink droplet  10  charged by the charging electrode  11  is flying in the electric field between deflection electrodes  12 , the ink droplet  10  is deflected by the force in proportion to the amount of electric charge. Then, the ink droplet  10  flies and lands on the print object  6 . The amount of charge determines the deflection direction of the ink droplet  10 , and therefore the position where the ink droplet  10  lands varies in accordance with the amount of charge. Moving the print object  6  by the production line in a direction orthogonal to the deflection direction allows ink droplets to land in the direction orthogonal to the deflection direction, thereby forming a character with the multiple landed droplets. 
         [0045]    The ink droplets  10  that were not used for printing fly straight between the deflection electrodes  12  and are captured by the gutter  14 . Then the ink droplets  10  pass through the recovery channel  108  and are collected in the main ink reservoir  20 . 
         [0046]      FIG. 5  is a functional block diagram of the inkjet printer  100 . The inkjet printer  100  includes a controller  200  provided with, for example, a master processing unit (MPU). The controller  200  controls components including the operation display  3 , nozzle  9 , charging electrode  11 , deflection electrodes  12 , encoder  7 , print sensor  8 , viscometer  24 , solenoid valves  15 ,  22 ,  25 ,  41 ,  64 ,  65 ,  81 , pumps  23 ,  50 , three-port solenoid valve  30 , level sensor  21 , pressure gauge  40  and a storage unit  202  via a bus line  201 . 
         [0047]    The storage unit  202  stores a program for controlling the inkjet printer  100 , and therefore the controller  200  controls each component included in the inkjet printer  100  based on the program. 
         [0048]    Following are descriptions about effects of the present teaching according to the example. 
         [0049]      FIG. 6  shows a channel block  90  having a recovery filter  51  and a solvent filter  61  integrally connected to the top face thereof and a pressure-reducing valve  29  integrally connected to the front face thereof. The recovery filter  51  and solvent filter  61  are identical in structure, and descriptions hereinafter will be made for only the recovery filter  51 . 
         [0050]    Projecting upwardly from the top face of the channel block  90 , as shown in  FIG. 7 , is a wall that defines a housing cavity  91  for housing a filter case  150  therein. That wall also has a thread  92  on the outside, for engaging with a securing nut  160 . 
         [0051]    The filter case  150  having an outer circumference slightly smaller than the inner circumference of the housing cavity  91  is placed in the housing cavity  91 . The filter case  150  is fixed with the securing nut  160  so as to be pushed against the channel block  90 , but can be detached in the upward direction from the channel block  90  by disengaging the securing nut  160 . The filter case  150  is integrally provided with a grip  151  that allows a user&#39;s hand to handle the filter case  150  without touching the ink-contact area of the filter case  150 . 
         [0052]    As shown in  FIG. 8 , the filter case  150  has an opening  152  that houses a holder  170 , a filter  180  and an O-ring  190 . 
         [0053]    The holder  170  includes a through hole  171  and a projection  172  at the center, a circular groove  173  and four through holes  174  penetrating from the bottom of the groove  173  to the back side of the holder  170 . The outer face  175  and inner face  176  defining the groove  173  are flush with each other and abut against the filter  180 . The outside diameter of the holder  170  is designed so that a clearance between the holder  170  and the opening  152  of the filter case  150  becomes small for easy assembly; however, the holder  170  is properly press-fitted in the opening  152 . 
         [0054]    The filter  180  is a flat metal mesh filter and achieves a filter rating of 75 μm. The outer circumference of the filter  180  fits in the filter case  150  so that the clearance between the filter  180  and opening  152  becomes small. At the center provided is a through hole  181  through which the projection  172  of the holder  170  passes. 
         [0055]    The O-ring  190  not only enhances sealing performance between the channel block  90  and filter case  150 , but also plays a role in holding the holder and filter in the filter case  150 . The outside circumference dimension of the O-ring  190  is designed so as to be greater than the circumference of the opening  152  of the filter case  150  by a few percent. When the O-ring  190  is housed, the dimension allows the O-ring  190  to retain the housed components on its own elasticity causing the O-ring  190  to stretch outwardly. 
         [0056]    As shown in  FIG. 9 , inside the housing cavity  91  of the channel block  90  there are a slanting seal face  93 , which abuts against the O-ring  190 , a flat portion  94 , a projecting portion  95  raised from the flat portion  94 , a first channel hole  97 , which is formed in the center of the projecting portion  95 , receives the projection  172  of the holder  170  and is connected to a primary externally-connecting pipe joint  96 , and a second channel hole  99 , which is formed in the flat portion  94  and is connected to a secondary externally-connecting pipe joint  98 . 
         [0057]    With reference to  FIGS. 9 and 10 , an exemplary liquid flow is illustrated. Liquid enters the channel block  90  from the primary externally-connecting pipe joint  96 , goes up the first channel hole  97 , passes through the through hole  171  of the holder, goes through a cylindrical channel  195  between the filter case  150  and holder  170 , falls into the four through holes  174  and the groove  173  to reach the top face (primary side) of the filter  180 , and passes through the filter  180  with particulates removed. The liquid having reached the filter  180  always passes through the filter  180  toward the secondary side, because the filter  180  is in close contact with the O-ring  190  at the outer side and abuts against both the inner face  176  of the holder  170  and the top face of the projecting portion  95  of the channel block  90  at the inner side. After passing through the filter  180 , the liquid reaches the secondary externally-connecting pipe joint  98  via the second channel hole  99 . 
         [0058]    Next, description of a filter replacement procedure will be made, with reference to  FIGS. 7 and 8 . The securing nut  160  secured to the channel block  90  is loosened and removed by hand. Then, the filter case  150  released from the secured state is pulled up with the grip  151  by hand to remove the filter case  150  from the housing cavity  91  of the channel block  90 . At this time, as shown in  FIG. 8 , the filter case  150  is removed together with the filter  180 , holder  170  and O-ring  190  from the housing cavity  91  of the channel block  90 . 
         [0059]    Even in a state where the securing nut  160 , filter case  150  and filter  180  are removed, the liquid will not spill from the housing cavity  91  of the channel block  90  thanks to the upward-facing opening at the top of the housing cavity  91 . 
         [0060]    Subsequently, a new filter case  150  is placed in the housing cavity  91  of the channel block  90 . The new filter case  150  holding a filter  180 , holder  170  and O-ring  190  is attached all together in the channel block  90 . 
         [0061]    At last, the new filter case  150  is secured in the channel block  90  by tightening the removed securing nut  160  by hand. The O-ring  190  compressed between the channel block  90  and filter case  150  ensures sealing performance. 
         [0062]    Although the filter has a primary side and secondary side in the example, the liquid can be set to flow in any direction, either of the externally-connecting pipe joints can be the primary or secondary. 
         [0063]    As shown and described, each filter case with the filter element and O-ring is detachably mounted to the respective housing cavity on the channel block by a securing nut and a thread on the respective housing. However, neither filter case is directly connected to any of the pipes for the ink or solvent channels of the inkjet printer. As a result, each filter case is configured for attachment in and detachment from the respective housing cavity, without the need for attachment and detachment of the filter case to the pipes of the respective ink or solvent channel of the inkjet printer. Consequently, it is not necessary to disconnect and connect any pipe to remove and replace a filter. 
         [0064]    According to the above-described structure, production line downtime required to replace a filter can be reduced, thereby improving production efficiency. 
         [0065]    In addition, the example of the teaching eliminates the necessity of pipe disconnection and disassembly of filter housings during filter replacement operations, thereby significantly reducing ink contamination of the interior of the inkjet printer, peripheral facilities, floors and an operator&#39;s hands. 
         [0066]    Furthermore, reduction of replacement time and ambient contamination with ink can decrease diffusion of ink odor to ambient surroundings. 
         [0067]    While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.