Patent Publication Number: US-7905562-B2

Title: Liquid guiding device and liquid ejecting apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a liquid guiding device in a liquid ejecting apparatus, such as an ink jet recording apparatus, that discharges liquid from its head to spray a medium. 
     Liquid ejecting apparatuses are not limited to recording apparatuses, such as printers, copying machines, and facsimiles, in which an ink jet recording head is used and that discharge ink from the recording head to perform recording on a recording medium. Liquid ejecting apparatuses include apparatuses that eject, instead of ink, liquid corresponding to their uses from a liquid ejecting head corresponding to the recording head onto a medium to be sprayed corresponding to the recording medium so as to attach the liquid to the medium. 
     Other than the recording head, liquid ejecting heads include a color material ejecting head used for manufacturing color filters of, for example, liquid crystal displays, an electrode material (conductive paste) ejecting head used for forming electrodes of, for example, organic EL displays and field emission displays (FEDs), a bioorganic matter ejecting head used for manufacturing biochips, and a sample ejecting head used as a precision pipette. 
     2. Related Art 
     In ink jet recording apparatuses, ink is discharged from a recording head. In order to remove ink dumped outside the edges of a recording medium on a platen, a depressed portion is formed in a region of the platen facing the recording head, an ink absorber is provided therein, and ink is absorbed in the ink absorber. As shown in  FIG. 10 , in a known platen  101 , the upstream side of a downstream portion  101   a  of the platen located on the downstream side of an ink dumping region  103  in the traveling direction of a recording medium is straight and has a rectangular cross section (see the portion shown by reference numeral  105 ) and an ink absorber  107  is provided up to this portion. 
     Therefore, even if ink is dumped at a position adjacent to the upstream side of the downstream portion  101   a  of the platen, ink is not attached on the downstream portion  101   a  of the platen, and ink is dumped onto the ink absorber  107 . A platen having such a configuration is disclosed in, for example, Patent Document 1. 
     However, when the entire surface of a recording medium is sprayed with ink, the front end of the recording medium bends downward due to a large amount of attached ink, and the front end of the recording medium can collide with the upstream end of the downstream platen  101   a  (the portion shown by reference numeral  105 ). In such a case, as shown in  FIG. 9 , it is possible to extend part of the upstream side of the downstream platen  101   a  into the liquid dumping region  103 , to form a guiding surface portion  109  that slopes down toward the liquid dumping region  103 , and to upward guide the front end of a recording medium that is bent downward as described above. 
     However, in such a configuration, since the sloping guiding surface portion  109  is located in the ink dumping region  23 , ink  111  remains dumped on the guiding surface portion  109  and can contaminate the underside of the recording medium. 
     In Patent Document 2, as shown in  FIG. 11 , there is disclosed a configuration in which a sloping surface  113  is formed on the upstream side of a most upstream platen  101   b , and arc-shaped grooves  115  successively arranged in the vertical direction and ridges  117  between the grooves  115  are formed in this sloping surface  113 . Due to such a configuration, even if ink is sprayed onto the sloping surface  113 , ink accumulates in the grooves  115 , and the underside of a recording medium is guided by the ridges  117 , goes over the ink, and is therefore not contaminated by contact with the ink. However, the amount of ink that accumulates in the arc-shaped grooves  115  is limited. When this amount is exceeded, ink overflows the grooves  115  and can contaminate the vicinity of the platen. 
     JP-A-2002-86821 
     JP-A-7-285251 
     SUMMARY 
     It is an object of the invention to provide a liquid guiding device in a liquid ejecting apparatus such that, when liquid is dumped onto a sloping guiding surface portion located in a region where liquid such as ink is dumped, the liquid is easily guided to an ink absorber and no liquid remains on the guiding surface portion. In addition, it is another object of the invention to provide a liquid ejecting apparatus having such a liquid guiding device. 
     To attain the above objects, a liquid guiding device in a liquid ejecting apparatus according to a first aspect of the invention includes: a platen located so as to face a liquid ejecting head; a liquid dumping region provided in a portion of the platen that faces the liquid ejecting head and that extends beyond a liquid discharge region of the liquid ejecting head, the liquid dumping region having a liquid absorber; a guiding surface portion provided on an edge of the platen defining the downstream end of the liquid dumping region, the upper surface of the guiding surface portion sloping down toward the upstream side, the guiding surface portion being protruded into the liquid discharge region; and a guiding structure portion provided in the guiding surface portion and guiding liquid attached to the guiding surface portion to the liquid absorber. 
     According to the first aspect of the invention, when part of liquid on the guiding surface portion reaches the guiding structure portion, the liquid is easily guided to the liquid absorber through the guiding structure portion, and the liquid on the guiding surface portion is quickly absorbed by the liquid absorber. Therefore, even in the case of a platen that has a guiding surface portion extending into the liquid discharge region of the liquid ejecting head, liquid on the upper surface of the guiding surface portion is removed through the guiding structure portion. Therefore, when a medium to be sprayed goes over the platen, liquid can be prevented from being attached to the underside of the medium to be sprayed. 
     A liquid guiding device in a liquid ejecting apparatus according to a second aspect of the invention is as follows. In the first aspect, the guiding structure portion includes an edge portion guiding liquid by capillary action, and the edge portion extends to the liquid absorber. 
     According to this aspect, when part of liquid on the guiding surface portion reaches the edge portion or its vicinity, the liquid is quickly guided to the liquid absorber by capillary action in the edge portion. Once a flow from the edge portion to the liquid absorber is formed, as long as liquid is continuous, all liquid is guided to the liquid absorber through this channel of flow. Therefore, the liquid on the guiding surface portion decreases rapidly. 
     A liquid guiding device in a liquid ejecting apparatus according to a third aspect of the invention is as follows. In the second aspect, the edge portion is located at the vertex of a V-shaped opening that opens toward the upstream end of the sloping surface of the guiding surface portion. 
     According to this aspect, when part of liquid on the guiding surface portion reaches the vertex of the V-shaped opening, the liquid is quickly guided to the liquid absorber by capillary action in the edge portion. Once a flow from the edge portion to the liquid absorber is formed, liquid can be quickly guided to the liquid absorber because the width of the flow can be increased in the V-shaped opening. 
     A liquid guiding device in a liquid ejecting apparatus according to a fourth aspect of the invention is as follows. In the third aspect, the V-shaped opening extends over substantially the entire length of the sloping surface in the direction between the upstream and downstream sides. 
     According to this aspect, the liquid on the sloping surface can be more effectively removed because the region where liquid begins to be guided is extended. 
     A liquid guiding device in a liquid ejecting apparatus according to a fifth aspect of the invention is as follows. In the second aspect, the edge portion is located at the lower end of an elongated groove having a V-shaped cross section and extending from the downstream side to the end on the upstream side of the sloping surface of the guiding surface portion. 
     According to this aspect, when part of liquid on the guiding surface portion reaches the elongated groove, the liquid flows into the edge portion. Once such a channel for liquid flow is formed, liquid is quickly guided from the upstream end of the elongated groove to the ink absorber by capillary action in the edge portion. 
     A liquid guiding device in a liquid ejecting apparatus according to a sixth aspect of the invention is as follows. In any one of the second to fifth aspects, the radius of curvature of the corner of the edge portion is 0.05 mm or less. 
     According to this aspect, since the radius of curvature of the edge portion is about 0.05 mm, the capillary action in the edge portion acts effectively, and the efficiency of guiding liquid to the liquid absorber is increased. 
     A liquid guiding device in a liquid ejecting apparatus according to a seventh aspect of the invention is as follows. In any one of the third to fifth aspects, the vertex angle of the shape of a V is 20° to 60°. 
     According to this aspect, the capillary action in the edge portion acts effectively, and the efficiency of guiding liquid to the liquid absorber is increased. 
     A liquid ejecting apparatus according to an eighth aspect of the invention includes: a liquid ejecting head; a platen located so as to face the liquid ejecting head; and a liquid dumping region provided in a portion of the platen that faces the liquid ejecting head and that extends beyond a liquid discharge region of the liquid ejecting head, the liquid dumping region having a liquid absorber. The liquid ejecting apparatus further includes: a sloping guiding surface portion provided in at least part of the upper surface of the edge of the platen that abuts the liquid dumping region of the platen or the upper surface of the edge of a rib that abuts the liquid dumping region of the platen; and a guiding structure portion provided in the guiding surface portion and guiding liquid attached to the guiding surface portion to the liquid absorber. According to this aspect, a high-quality sprayed matter can be obtained because the underside of a medium to be sprayed can be prevented from being contaminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional view of an ink jet recording apparatus to which is applied an ink guiding device according to the invention. 
         FIG. 2  is an upper perspective view of the vicinity of a platen. 
         FIG. 3  is an enlarged perspective view of the vicinity of the platen. 
         FIG. 4  is a perspective view showing an exemplary embodiment of an ink guiding device. 
         FIG. 5  is a side sectional view of the vicinity of the ink guiding device. 
         FIG. 6  is a perspective view showing another exemplary embodiment of an ink guiding device. 
         FIG. 7  is a perspective view showing still another exemplary embodiment of an ink guiding device. 
         FIG. 8  is a perspective view showing yet another exemplary embodiment of an ink guiding device. 
         FIG. 9  is a perspective view showing a comparative example of the invention. 
         FIG. 10  is a perspective view showing a known art. 
         FIG. 11  is a perspective view showing another known art. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments of the invention will now be described with reference to the drawings.  FIG. 1  is a side sectional view of an ink jet recording apparatus that is an example of a liquid ejecting apparatus to which is applied an ink guiding device that is an example of a liquid guiding device according to the invention.  FIG. 2  is an upper perspective view of the vicinity of a platen.  FIG. 3  is an enlarged perspective view of the vicinity of the platen.  FIG. 4  is a perspective view showing an exemplary embodiment of an ink guiding device.  FIG. 5  is a side sectional view of the vicinity of the ink guiding device. 
       FIG. 6  is a perspective view showing another exemplary embodiment of an ink guiding device.  FIG. 7  is a perspective view showing still another exemplary embodiment of an ink guiding device.  FIG. 8  is a perspective view showing yet another exemplary embodiment of an ink guiding device.  FIG. 9  is a perspective view showing a comparative example of the invention. 
     The ink jet recording apparatus  1  (hereinafter simply referred to as recording apparatus) shown in  FIG. 1  has a feeding cassette  5  that is detachable from a main body  3  of the recording apparatus. Recording media P that are stacked in the feeding cassette  5  and that correspond to media to be sprayed are pressed against the outer circumferential surface of a feeding roller  7  by a hopper  9  that rocks toward the feeding roller  7 , and are separated and automatically fed to a transporting roller  11  one at a time by driving and rotating of the feeding roller  7 . Reference numeral  8  denotes a known retard roller. The retard roller  8  and the feeding roller  7  separate double-fed recording media from one another in cooperation with each other. 
     A recording head  13  is an example of a liquid ejecting head that performs recording by ejecting ink onto a recording medium P. The main body  3  of the recording apparatus includes a carriage  15  for causing the recording head  13  to scan the recording medium P in the width direction thereof. The carriage  15  is loaded with a detachable ink cartridge (not shown) filled with each color of ink. The ink cartridge supplies the recording head  13  with each color of ink. The recording head  13  reciprocates, facing a platen  17 , in the width direction of the recording media P. A line of nozzles are arranged in the surface of the head parallel to the transporting direction of the recording medium P. Ink is discharged from each nozzle hole of the line of nozzles onto the recording medium P being transported on the platen  17 , and recording is thereby performed. A range within which the line of nozzles exists in the above transporting direction is an ink (liquid) discharge region. After completion of recording, the recording medium P is output by an output roller  19  in the sub-scanning direction. 
     As shown in  FIG. 2 , on the upper surface of the platen  17 , which faces the recording head  13 , are formed many protrusion-like ribs  21  and a liquid dumping region  23 . The ribs  21  support a recording material P and define a distance between the recording medium P and the recording head  13 . The liquid dumping region  23  receives ink that is sprayed outside the edges of the recording medium P and that is dumped. The ribs  21  include upstream ribs  21   a  formed in an upstream portion  22  of the platen located upstream in the traveling direction of the recording medium P, downstream ribs  21   b  formed in a downstream portion  24  of the platen located downstream in the traveling direction of the recording medium P, and intermediate ribs  21   c  located in an intermediate region between the upstream ribs  21   a  and the downstream ribs  21   b . The liquid dumping region  23  is located between the downstream edge of the upstream portion  22  of the platen and the upstream edge of the downstream portion  24  of the platen. Therein are located the intermediate ribs  21   c  like islands. 
     During recording on the leading edge of the recording medium P, waste ink sprayed on the downstream side of the leading edge of the recording medium P is dumped in a corresponding downstream portion of the liquid dumping region  23 . During recording on the trailing edge of the recording medium P, waste ink sprayed on the upstream side of the trailing edge of the recording medium P is dumped in a corresponding upstream portion of the liquid dumping region  23 . 
     As shown in  FIG. 5 , in the liquid dumping region  23  is provided an ink absorber  25  (corresponding to a liquid absorber) that absorbs and holds dumped ink and that is formed of a polyether based material. Under the ink absorber  25  is provided an absorber  26  (corresponding to a liquid absorber) that is formed of a polyvinyl alcohol based material. A guiding portion  27  is provided on the bottom surface of the liquid dumping region  23 . One end of the absorber  26  is guided by the guiding portion  27  so as to be communicated with an ink absorber having a larger capacity. Since the ink absorber  25  and the ink absorber  26  are layers formed of different materials, dumped ink can be guided to the guiding portion  27  more efficiently than in the case of a single material. 
     As shown in  FIG. 4 , the upstream edge of the downstream portion  24  of the platen, which defines the downstream end of the liquid dumping region  23 , has guiding surface portions  29  that extend into the liquid dumping region  23  with their upper surfaces sloping down toward the upstream side. Each guiding surface portion  29  has edge portions  31  formed therein. The edge portions  31  serve as guiding structure portions that guide ink attached to the guiding surface portion  29  to the ink absorbers  25  and  26 . The edge portions  31  guide ink to the ink absorbers  25  and  26  by capillary action. 
     Each edge portion  31  is located at the vertex of a V-shaped opening  35  that opens toward the upstream end  33  of the guiding surface portion  29 . The radius of curvature of the corner  37  of each edge portion  31  is 0.05 mm or less. Due to such a small radius of curvature, when part of ink on the guiding surface portion  29  reaches any one of the edge portions  31  or its vicinity, the ink is quickly guided to the ink absorbers  25  and  26  by capillary action in the edge portion  31 . 
     The vertex angle of the V-shaped openings  35  is 60° in the exemplary embodiment shown in  FIG. 4  but is preferably within a range of 20° to 60°. As shown in  FIG. 7 , the V-shaped openings  35  may extend over substantially the entire length of the guiding surface portion  29  in the direction between the upstream and downstream sides. In the exemplary embodiment shown in  FIG. 7 , the vertex angle of the V-shaped openings  35  is 20°, and the depth of the openings  35  is 2 mm. 
       FIG. 6  shows still another exemplary embodiment of the invention. In this exemplary embodiment, each sloping guiding surface portion  29  has elongated grooves  37  formed from the downstream side (the upper side of  FIG. 6 ) to the end on the upstream side (the lower side of  FIG. 6 ) thereof. The elongated grooves  37  have a V-shaped cross section. An edge portion  31  is formed at the lower end of the V-shaped cross section along each elongated groove  37 . A terminal end portion  39  cut out in a triangular shape is formed on the downstream side of each elongated groove  37 . The terminal end portion  39  also has a V-shaped cross section, at the lower end of which an edge portion  31  is also formed. In each edge portion  31  in this exemplary embodiment, the vertex angle of the lower end of the shape of a V is 60°. The radius of curvature of the corner  37  of each edge portion  31  is 0.05 mm or less. The length of the elongated grooves  37  is 2.2 mm. 
     In this exemplary embodiment, when part of ink on the guiding surface portion  29  reaches any one of the elongated grooves  37 , the ink flows into the edge portion  31 . Once such a channel for ink flow is formed, the ink is continuously guided from the upstream end of the elongated groove  37  to the ink absorbers  25  and  26  by capillary action in the edge portions  31 . 
     In the exemplary embodiment shown in  FIG. 8 , each guiding surface portion  29  has ink guiding structure portions in which slit-like gap portions  39  that penetrate to the underside are formed from the downstream side (the upper side of  FIG. 8 ) to the end on the upstream side (the lower side of  FIG. 8 ). A terminal end portion  41  cut out in a triangular shape is formed on the downstream side (the upper side of  FIG. 8 ) of each slit-like gap portion  39 . The terminal end portion  41  has a V-shaped cross section, at the lower end of which an edge portion  31  is formed. In this exemplary embodiment, when part of ink on the guiding surface portion  29  reaches any one of the terminal end portions  41 , the ink flows into the edge portion  31 . Once such a channel for ink flow is formed, the ink is continuously guided through the gap portion  39  to the ink absorbers  25  and  26  by capillary action in the edge portion  31  and the slit-like gap portion  39 . 
     Although edge portions  31  are shown only on the upper surfaces of the guiding surfaces  29  of the downstream ribs  21   b  in  FIG. 2 , edge portions  31  may be provided on the edges other than those of the downstream ribs  21   b  in order to obtain the above-described advantages. Edge portions may be provided, for example, in the upper surface of the edge of the platen  17  that abuts the liquid dumping region  23  of the platen or in the upper surface of the edge of the upstream rib  21   a  or the intermediate rib  21   c  that abuts the liquid dumping region  23  of the platen, as long as at least part of the upper surface of the edge is a sloping guiding surface. By providing edge portions in the guiding surface, liquid can be prevented from being attached to the underside of a medium to be sprayed. It goes without saying that the same advantages can be obtained by capillary action when separate protrusions are provided in each guiding surface as a modification of edge portions of each guiding surface.