Patent Publication Number: US-6209982-B1

Title: Ink jet recording device capable of reliably discharging air bubble during purging operations

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink jet recording device having a manifold fluidly connecting an ink cartridge with an ink jet head, and more specifically to the ink jet recording device capable of reliably discharging air bubbles from the manifold by purging operations. 
     2. Description of the Related Art 
     A conventional ink jet recording device includes an ink jet head having actuators. The actuators are formed from an electromechanical converting element or electrothermal converting element, and define a plurality of ink chambers aligned in a row. An ink cartridge storing ink is detachably attached to the ink jet head by a manifold. The manifold is formed with an ink supply path that normally broadens from the ink cartridge side to the ink jet head side so as to encompass the entire row of ink chambers. Ink in the ink cartridge is supplied through the ink supply path of the manifold into the ink chambers. When the actuators are energized, ink is ejected from the ink chambers through nozzles to form an image on a recording medium. 
     Normally, purging operations are performed when the ink cartridge is exchanged for a new one. Specifically, during the purging operations, suction force is applied to the nozzles of the ink jet head so as to introduce fresh ink from the new ink cartridge into the ink chambers. At the same time, air that was introduced into the manifold during exchange of the ink cartridge is discharged out of the ink jet head along with some ink. 
     However, when the air forms a single spherical air bubble that floats freely in the broad portion of ink supply path, ink flows around the air bubble during the purging operations. As a result, a sufficient pressure for discharging the air bubble may not be generated within the manifold. As a result, the air bubble remains in the ink supply path without being ejected during the purging operations. Also, because the air bubble itself has a relatively large volume, by coupling with micro-air bubbles dissolved in the ink, the air bubble can quickly grow to a sufficient extend to clog up the inlets to the ink chambers. As a result, shortly after the ink cartridge is exchanged, printing can become defective due to improper ejection of ink from the ink chamber. 
     Also, air introduced into the ink supply path during exchange of the ink cartridge may remain in the ink supply path without being discharged, because of changes in ink viscosity by temperature, variation in suction force generated by the purging operation, or other indefinite reasons. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to solve the above-described problems and also to provide an ink jet recording device having a manifold capable of efficiently ejecting air bubbles, which are introduced during exchange of ink cartridge, by using purging operations performed directly after exchange of ink cartridge. 
     In order to achieve, the above and other objectives, there is provided an ink jet recording device including an ink jet head, a manifold, and a cartridge. The ink jet head has a first surface and a second surface opposite from the first surface. The ink jet head is formed with a plurality of ink channels each extending from the first surface to the second surface, and each having an inlet port opened at the first surface and a nozzle opened at the second surface. The manifold is mounted on the first surface of the ink jet head, and is formed with an ink inlet path and an ink supply path fluidly connecting the ink inlet path with the plurality of the ink channels. The cartridge is replaceable and detachably mounted on the manifold. The cartridge is formed with an outlet port for supplying ink to the plurality of ink channels through the outlet port, the ink inlet path, the ink supply path, and the inlet port. When the cartridge is replaced, and air is introduced as a single air bubble into the ink supply path from the ink inlet path, the single air bubble is supported within the ink supply path while contacting the first surface of the ink jet head. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The particular features and advantages of the invention as well as other objects will become more apparent from the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing an ink jet recording device according to an embodiment of the present invention; 
     FIG. 2 is a partial cross-sectional view of the ink jet recording device of FIG. 1; 
     FIG. 3 is an exploded view showing a manifold and an ink jet head of the ink jet recording device; 
     FIG. 4 is a plan view showing the manifold; 
     FIG. 5 is a cross-sectional view of the manifold and the ink jet head taken along a line V—V of FIG. 4; and 
     FIG. 6 is a cross-sectional view of the manifold and the ink jet head taken along a line VI—VI of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An ink jet recording device  1  according to a preferred embodiment of the present invention will be described while referring to the accompanying drawings. In the following description, the expressions “upper”, “lower”, and “horizontal” are used throughout the description to define the various parts when the ink jet recording device is disposed in an orientation in which it is intended to be used. 
     As shown in FIG. 1, the ink jet recording device  1  includes a carriage  11 , a carriage shaft  12 , a guide plate  13 , a pair of pulleys  14 ,  15 , a belt  16 , a motor  17 , a platen roller  18 , a head unit  30 , and four ink cartridges  50 . Each of the ink cartridges  50  stores one of four different colored inks, that is cyan ink, magenta ink, yellow ink, and black ink. The head unit  30  includes four ink jet heads  31  and four manifolds  40  (FIG.  2 ). The manifolds  40  fluidly connect the ink cartridges  50  with corresponding ink jet heads  31  so that ink is supplied from the ink cartridge  50  to the corresponding ink jet heads  31 . The head unit  30  and the ink cartridges  50  are both mounted on the carriage  11 . 
     The carriage shaft  12  and the guide plate  13  are both supported by a frame (not shown) and extend in horizontal directions indicated by an arrow H. The carriage  11  is freely slidably supported on the carriage shaft  12  and the guide plate  13 . The belt  16  is wound around and spans between the pair of pulleys  14 ,  15 , and is connected to the carriage  11 . When the motor  17  drives the pulley  14 , the belt  16  reciprocally moves the carriage  11  along with the head unit  30  and ink cartridge  50  in the horizontal direction H. 
     The platen roller  18  is freely rotatable and extends in the horizontal direction H below the head unit  30  so as to be in facing confrontation with the lower surfaces of the ink jet heads  31 . A print sheet P is fed by a feed mechanism (not shown) in a direction indicated by an arrow F. When the print sheet P is provided between the ink jet heads  31  and the platen roller  18 , the ink jet heads  31  selectively eject ink onto the print sheet P to form an image on the print sheet P. The print sheet P formed with the image is, then, discharged out of the ink jet recording device  1 . 
     Next, detailed description of the ink jet heads  31  will be described. As shown in FIGS. 2 and 3, each ink jet head  31  includes an actuator  32  formed from a piezoelectric ceramic material and a nozzle plate  34  attached to the lower end of the actuator  32 . The actuator  32  is formed with two rows of a plurality of ejection channels  33 . The rows of ejection channels  33  extend longitudinally along the ink jet head  31  in directions indicated by an arrow L, and each ejection channel  33  extends from the lower end to the upper end of the actuator  32 . The nozzle plate  34  is formed with a plurality of nozzles (not shown) in correspondence with the ejection channels  33 . 
     Each ejection channel  33  has an ink inlet port  33   a  opened at an upper surface  31   a  of the ink jet head  31 . Ink from the ink cartridge  50  is supplied into the ejection channels  33  through the ink inlet ports  33   a.    
     When the actuator  32  is energized to deform during printing operations, the volume of the ejection channel  33  decreases, so that the ink is ejected from the ejection channel  33  through the nozzle, thereby forming an image on the print sheet P. Then, when the actuator  32  returns to its initial condition, the volume of the ejection channel  33  increases to its initial volume, thereby introducing ink from the ink cartridge  50  into the ejection channel  33 . It should be noted that the ink jet head  31  can be designed such that ink is introduced into the ejection channel  33  when the actuator  32  deforms, and ink is ejected when the ejection channels  33  returns in its normal condition. 
     Next, the ink cartridge  50  will be described. As shown in FIG. 2, the ink cartridge  50  includes a joint member  50   a  by which the ink cartridge  50  is freely detachably attached to the upper end of the manifold  40 . The ink cartridge  50  is formed with a first ink chamber  51 , a second ink chamber  52 , a connection hole  51   a,  and ink supply port  53 . The first ink chamber  51  houses a porous ink absorption member  54  formed form polyurethane foam, for example. The ink absorption member  54  is impregnated with ink. The connection hole  51   a  fluidly connects the first ink chamber  51  with the second ink chamber  52 . Ink impregnating the ink absorption member  54  in the first ink chamber  51  is supplied through the connection hole  51   a,  the second ink chamber  52 , and the ink supply port  53  into the manifold  40 . A mesh filter  53   a  is provided at the ink supply port  53 . 
     Next, detailed description of the manifold  40  will be described. As shown in FIGS. 2 to  5 , the manifold  40  includes a frame  41  and a main portion  42 . The frame  41  has a pair of fixing ribs  41   a  and a pair of positioning ribs  41   b.  The pair of fixing ribs  41   a  are fixed to side surfaces of the ink jet head  31  by adhesive. The pair of positioning ribs  41   b  are for positioning the manifold  40  when fixed to the ink jet head  31 . The main portion  40  is disposed interior of the frame  41  and partially connected to inner surfaces of the frame  41 . A space S is defined between the frame  41  and the main portion  42 . When the fixing rib  41   a  is fixed to the side surfaces of the ink jet head  31 , adhesive is introduced to fill the space S, so that ink is prevented from leaking from the upper surface  31   a  of the ink jet head  31 . 
     The lower end of the manifold  40  is fixed to the upper surface  31   a  of the ink jet head  31  so as to cover the upper surface  31   a.  The main portion  42  is formed with an ink supply path  43  fluidly connecting the ejection channels  33  with the ink cartridge  50 . The ink supply path  43  includes a connection path  44  having a small diameter and a broad portion  45  connecting the connection path  44 . The connection path  44  has an ink inlet  43   a  that is connected to the ink cartridge  50 . A mesh filter  40   a  is provided at the ink inlet  43   a.    
     As shown in FIGS. 5 and 6, the connection path  44  is substantially centered between the rows of ejection channels  33 . The broad portion  45  broadens from the connection path  44  toward the ends of the rows of ejection channels  33  in an enlarging tapering manner, and has an ink outlet  43   b  encompassing the ink inlet ports  33   a  of the ejection channels  33 . The broad portion  45  has a substantially symmetrical configuration with respect to a central axis, extending in the vertical direction, of the connection path  44 . 
     As shown in FIG. 2, a space A is defined between the mesh filter  53   a  and the mesh filter  40   a.  The size and shape of the broad portion  45  is designed so that the volume of the space A is the same or larger than the volume of an imaginary spherical shape B, which is inscribed, in the geometric sense, by a ceiling surface of the broad portion  45  and the upper surface  31   a  of the ink jet head  31  and which closes up the connection path  44 . 
     As shown in FIG. 1, the ink jet recording device  1  further includes an ink suction unit  21 , a wiper unit  26 , a protection cap unit  27 , and an ink support member  28 . The ink suction unit  21 , the wiper unit  26 , and the protection cap unit  27  are disposed in a reset position of the ink jet heads  31 , that is, at a position at the side of the platen roller  18 . The ink suction unit  21  is for performing purging operations. The wiper unit  26  is for wiping the nozzle plates  34  of the ink jet heads  31 . The protection cap unit  27  is for covering the nozzle plate  34  when printing is not being performed so that ink in the nozzles will not dry out. The ink support member  28  is disposed in a forced ejection position which is at the opposite end of the platen roller  18  from the reset position. The ink support member  28  is for absorbing and maintaining ink that was forcibly ejected from the ink jet heads  31 . The forcible ink ejection is performed periodically for preventing the nozzles of the nozzle plate  34  from clogging. The ink suction unit  21 , the wiper unit  26 , the protection cap unit  27 , and the ink support member  28  together configure a recovery maintenance mechanism for recovering and maintaining good ejection condition of the ink jet heads  31 . 
     The ink suction unit  21  includes a suction pump  22 , a suction portion  23 , a waste ink tank  24 , and a cam  25 . The suction pump  22  and the suction portion  23  are driven by the drive force transmitted from a drive force transmission mechanism (not shown) and the cam  25 . The ink suction unit  21  performs the purging operations regularly or when needed during the printing operations, and also right after the ink cartridge  50  is exchanged so as to introduce fresh ink from a new ink cartridge  50  into the ink supply path  43  and the ejection channels  33 . 
     During the purging operations, the suction portion  23  covers the nozzle plate  34  of the ink jet head  31 . In this condition, the suction pump  22  generates a negative purging pressure in the suction portion  23 , so that defective ink with air bubbles is sucked out from the ejection channels  33  and the ink supply path  43 . As a result, fresh ink is introduced from the ink cartridge  50  into the ink supply path  43  and the ejection channels  33 . In this way, the ink jet head  31  becomes ready for printing. The defective ink sucked form the ink jet head  31  in this manner is conveyed to and held in the waste ink tank  24 . 
     Next, detailed description of the purging operations performed directly after exchange of the ink cartridge  50  will be provided. When the ink cartridge  50  is replaced, ink is supported in the new ink cartridge  50  by surface tension at the mesh filter  53   a,  but no ink exists in areas external from the mesh filter  53   a.  Accordingly, when the new ink cartridge  50  is mounted on the small diameter connection path  44  of the manifold  40 , air fills the space A although some ink can remain in the ink supply path  43 . In this condition, the ink suction unit  21  is driven to generate a negative purging pressure in the ink supply path  43 . As a result, the air bubble is sucked from the space A into the broad portion  45 . At this time, because the volume of the space A is set to the same or larger than the volume of the spherical shape B, the air bubble forms substantially the spherical shape B, which, as mentioned previously, is inscribed by the ceiling surface of the broad portion  45  and the upper surface  31   a  of the ink jet head  31  and which closes off the connection path  44 . Therefore, the purging pressure will effectively operate both on the air bubble and ink in the broad portion  45  without the ink flowing around the air bubble. Therefore, the air bubble can reliably pulled into the ejection channels  33  and discharged out of the ink jet head  31  into the ink suction unit  21 . 
     It should be noted that when ink in the ink supply path  43  has been consumed, that is, so that air exists on both sides of the mesh filter  40   a,  then, the volume of air that must be discharged by the purging operations after replacement of the ink cartridge  50  is greater than the volume of the space A. Therefore, the air bubble in the broad portion  45  may not have the substantially spherical shape B. However, regardless of the shape of the air bubble, the air bubble will be inscribed by the ceiling surface of the broad portion  45  and the upper surface  31   a  of the ink jet head  31 , and will close up the connection path  44 . Therefore, the air bubble will be reliably discharged by the purging operations. 
     Also, because the manifold  40  is mounted on the ink jet head  31  so as to cover the ink inlet port  33   a  of the ejection channels  33  from the above, the air bubble introduced into the broad portion  45  attempts to float upward, so that the connection path  44  will be reliably covered up by the air bubble. 
     As described above, according to the present invention, when air that has been introduced into the ink supply path  43  during exchange of the ink cartridge  50  forms a substantially spherical air bubble in the broad portion  45 , the air bubble blocks off the connection path  44 . Therefore, the negative purging pressure generated during the purging operations will operate effectively on the air bubble. As a result, the air bubble can be easily drawn into the ink chambers  33 , so that the ability of the ink jet recording device  1  to discharge the air bubble during the purging operations is increased. 
     While the invention has been described in detail with reference to specific embodiments thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the attached claims. 
     For example, in the above described embodiment, the size and shape of the broad portion  45  are designed so that the air bubble forms the substantial spherical shape B, and so is inscribed by the upper surface  31   a  of the ink jet head  31  and blocks off the small diameter connection path  44 . However, the air bubble need not have the substantially spherical shape B as long as the air bubble is maintained in contact with the upper surface  31   a  of the ink jet head  31 . 
     Also, the air bubble needs not block off the connection path  44 . However, it is desirable that the broad portion  45  be designed with size and shape that induces the air bubble to block off the connection path  44  for the reasons described above. 
     Also, in the above described embodiment, the mesh filter  53   a  is provided to the ink supply port  53  of the ink cartridge  50  for preventing ink from leaking from the ink cartridge  50  when the cartridge  50  is being exchanged. However, in the case when the ink absorption member  54  is provided adjacent to the inner surface of the ink supply port  53 , the mesh filter  53   a  can be dispensed with. In this case, a space defined between the ink absorption member  54  and the mesh filter  40   a  is considered as the space A. 
     Further, in the above-described embodiment, purging operations are performed by the ink suction unit  21  by sucking ink from the ejection channels  33  of the ink jet head  31 . However, purging operations can be performed by pushing fresh ink from the ink cartridge  50  into the ink jet head  31 .