Patent Publication Number: US-7585048-B2

Title: Print head cap

Description:
This is a Divisional of application Ser. No. 10/809,341 filed Mar. 26, 2004, now U.S. Pat. No. 7,419,240. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a print head cap for covering a nozzle surface therewith at the time of recovering a print head for ejecting ink droplets onto printing paper or at the time of keeping the print head moist. 
   2. Background Art 
   In the related art, as disclosed in JP-A-5-193150, there has been known a cap having a box-like sealing portion, a thick portion formed in the outer circumference of the sealing portion and a thin portion coupling the sealing portion with the thick portion. In order to improve the sealing performance of the cap pressed onto the nozzle surface of a print head, the cap is adapted so that the thin portion is deformed when the sealing portion is pressed onto the nozzle surface, so that the sealing portion is equalized and brought into tight contact with the nozzle surface. 
   In addition, as disclosed in JP-A-10-211711, the cap is formed into a rectangular box-like shape corresponding to the shape of the nozzle surface. 
   SUMMARY OF THE INVENTION 
   In such a related-art rectangular cap, particularly in such a cap for use in a full-line type print head in which a plurality nozzles are arrayed all over the width-direction area of printing paper, precision in flatness, dimensions and the like has to be high enough when the size of the print head in the direction in which the nozzles are arrayed is large and the cap is brought into tight contact with the nozzle surface uniformly. However, since the cap is formed out of an elastic body of rubber or the like, it is difficult to manufacture the cap particularly into such a high-precision shape. Thus, it is difficult to retain air-tightness required in the cap. In addition, since defective caps are often manufactured, there is also a problem that the yield in manufacturing deteriorates. 
   A print head cap is disclosed herein, in which air-tightness can be retained while the yield in manufacturing can be improved. 
   According to one aspect of the invention, a print head cap includes: a bottom surface; and a ring-like lip surrounding the bottom surface like a ring and protruding toward a nozzle surface of a print head of an ink jet printer and being elastically deformable, the ring-like lip to be pressed onto the nozzle surface to cover the nozzle surface therewith. The ring-like lip has corners that change a direction of surrounding the bottom surface. The corners are more elastically deformable than the other portion of the ring-like lip. 
   According to another aspect of the invention, a print head cap includes: a bottom surface; and an elastically deformable lip surrounding the bottom surface like a ring and protruding toward a nozzle surface of a print head of an ink jet printer, the lip to be pressed onto the nozzle surface to cover the nozzle surface therewith. The lip has a plurality of side lips and a plurality of corner lips connecting the side lips with each other and changing a direction of surrounding the bottom surface. At least one of the plurality of corner lips is formed into an arc-like shape swelling outward and is formed to be lower in height than the side lips. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be more readily described with reference to the accompanying drawings: 
       FIG. 1  is a configuration diagram of a printer using a print head cap according to a first embodiment of the invention. 
       FIG. 2  is a plan view of a capping mechanism using the print head cap according to the embodiment. 
       FIG. 3  is a sectional view taken on line  3 - 3  in  FIG. 2 . 
       FIG. 4  is a plan view of the print head cap according to the embodiment. 
       FIG. 5  is a sectional view taken on line  5 - 5  in  FIG. 4 . 
       FIG. 6  is a sectional view taken on line  6 - 6  in  FIG. 4 . 
       FIG. 7  is a sectional view taken on line  7 - 7  in  FIG. 4 . 
       FIG. 8  is a plan view of a print head cap according to a second embodiment of the invention. 
       FIG. 9  is a sectional view taken on line  9 - 9  in  FIG. 8 . 
       FIG. 10  is a sectional view taken on line  10 - 10  in  FIG. 8 . 
       FIGS. 11A and 11B  are explanatory views showing the falling of a lip of the print head cap according to the second embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the invention will be described below in detail with reference to the drawings. 
   As shown in  FIG. 1 , a printer according to this embodiment has a full-line type print head  1 , and a large number of not-shown nozzles are formed in the print head  1  in a direction perpendicular to the direction of feeding printing paper. A nozzle surface  2  in which the nozzles are opened is disposed to be opposed to the printing paper. 
   In addition, the print head  1  is of an ink jet system for ejecting ink droplets onto the printing paper. For example, such a print head  1  is provided for respective colors of yellow, magenta, cyan and black. Incidentally, each part of the print head  1  is supplied with its corresponding color ink from an ink cartridge  4  through an ink supply mechanism  6 . 
   The printing paper is fed in tight contact with the surface of a belt  10  laid between a pair of rollers  8  (only one of which is shown). Each print head  1  is disposed in a body case  11  movably in a direction perpendicular to the surface of the belt  10  on which the paper is mounted. At the time of carrying out printing, the print head  1  is moved to an ink ejection position close to the printing paper. At the time of maintenance, the print head  1  is moved to a standby position in which a predetermined space is formed between the print head  1  and the printing paper and which is more distant from the belt  10  than the ink ejection position, as shown in  FIG. 1 . 
   A mounting base  12  which can be inserted into this space is provided. As shown in  FIG. 2 , the mounting base  12  is supported on a pair of guide bars  14  and  16  through a plurality of sliding members  18  so that the mounting base  12  can move forward/backward linearly. The guide bars  14  and  16  are disposed perpendicularly to the direction of feeding the printing paper (direction perpendicular to the paper surface of  FIG. 1 ). A belt  19  is laid in parallel with the guide bars  14  and  16 . The mounting base  12  and the belt  19  are fastened to each other through a lock member  20 . 
   When the belt  19  is driven by a motor, the mounting base  12  slides along the guide bars  14  and  16  so that the mounting base  12  can move forward/backward between a maintenance position (position designated by the solid line in  FIG. 1 ) in which the mounting base  12  is inserted into the space between the print head  1  and the printing paper and a retraction position (position designated by the chain double-dashed line in  FIG. 1 ) in which the mounting base  12  is retracted from the space to the upper side of the ink cartridge  4  at the time of printing. 
   A capping mechanism  22  is mounted on the mounting base  12 . The capping mechanism  22  has a plurality of links  24  one ends of which are supported swingably on the mounting base  12 , and a cap base  26  on which the other ends of the plurality of links  24  are supported swingably. The cap base  26  is configured as follows. That is, when the mounting base  12  is moved to the maintenance position, each engagement portion  28  integrated with the cap base  26  abuts against a fixed side provided in the print head  1  so as to keep the cap base  26  parallel with the nozzle surface  2  while being moved toward the nozzle surface  2  so as to describe an arc. 
   A swinging base  30  is supported on the cap base  26  swingably around a pin  32  as shown in  FIG. 3 . On each of opposite sides of the pin  32 , a coil spring  33   a ,  33   b  is disposed between the cap base  26  and the swinging base  30 . Four print head caps  34  (hereinafter referred to as “caps  34 ”) are attached to the swinging base  30  correspondingly to the respective colors of the print head  1  in this embodiment. The caps  34  are formed out of an elastically deformable material, particularly a material resistant to ink, such as butyl rubber or EPDM. 
   A bottom surface  36  opposed to the nozzle surface  2  is formed in the cap  34  as shown in  FIG. 3 . The bottom surface  36  is substantially flat, and an exhaust hole  38  opened in the bottom surface  36  is formed in the cap  34 . The exhaust hole  38  is designed to be connected to a not-shown exhaust duct so as to be able to exhaust ink. 
   In each cap  34 , a lip  40  is provided to surround the bottom surface  36  like a ring. The lip  40  protrudes toward the nozzle surface  2  of the print head  1 . In this embodiment, the lip  40  has a pair of side lips  40   a  and  40   b  provided linearly along the long sides of the bottom surface  36 , and a pair of side lips  40   c  and  40   d  provided linearly along the short sides of the bottom surface  36 . 
   Each side lip  40   a - 40   d  is formed into a tapered shape having a sectional shape thicker on the bottom surface  36  side and thinner gradually as the location goes toward the front end of the side lip  40   a - 40   d , as shown in  FIGS. 5 and 6 . Incidentally, the shape of the side lip  40   a - 40   d  is not limited to the linear shape, but it may be a curved shape describing a gentle arc or the like. 
   Of the corners of the lip  40  in which the direction of surrounding the bottom surface  36  changes, in this embodiment, each corner in which the direction changes at the angle of 90 degrees from the side lip  40   a ,  40   b  along the long side to the side lip  40   c ,  40   d  along the short side connects the side lips  40   a - 40   d  with each other through a corner lip  40   e - 40   h  formed out of an arc. The corner lip  40   e - 40   h  is formed to have the same height from the mounting surface S as the height of the side lip  40   a - 40   d . In this embodiment, the corner lip  40   e - 40   h  is formed to have the same thickness in its sectional shape as that of the front end of the side lip  40   a - 40   d  as shown in  FIG. 7 . The corner lip  40   e - 40   h  is formed to be easier to be elastically deformable than the side lip  40   a - 40   h .  FIGS. 4 and 6  shows the state of the lower side than the center line where the cap  34  has been pressed onto the nozzle surface  2  and thereby deformed. Incidentally, if the corner lip  40   e - 40   h  is thinner than the side lip  40   a - 40   d , it will be easier to be elastically deformed, and then the embodiment can be carried out. 
   A groove  42  is formed all over the circumference outside the side lips  40   a - 40   d  and the corner lips  40   e - 40   h . When each front end of the side lips  40   a - 40   d  and the corner lips  40   e - 40   h  is pressed onto the nozzle surface  2 , the front end is urged to be deformed due to the groove  42  as shown in  FIG. 6 . Incidentally, protrusions  44  and  46  for positioning the cap  34  when it is attached to the swinging base  30  are formed on the back surface of the cap  34 . 
   Next, description will be made on the operation of the print head cap according to this embodiment. 
   At the time of printing, the belt  10  is driven by the rotations of the rollers  8  so that printing paper passes under the printhead  1  at a fixed speed. Then, ink droplets are ejected from the print head  1  so that printing is performed line by line. 
   At the time of maintenance for recovering the nozzles of the print head  1  from clogging or keeping the nozzles of the print head  1  moist, the print head  1  is moved from the ink ejection position to the standby position as shown by the arrow in  FIG. 1  so that a predetermined space is formed between the print head  1  and the belt  10 . Then, driven by the belt  19 , the mounting base  12  is guided along the guide bars  14  and  16  and inserted into the space between the print head  1  and the belt  10 . 
   When each engagement portion  28  abuts against the fixed side of the printer, and the mounting base  12  is moved further, the cap base  26  is moved to describe an arc from the separation position shown in  FIG. 3  toward the nozzle surface  2  by the plurality of links  24  while retaining its parallelism with the nozzle surface  2 . Then, the cap  34  is pressed onto the nozzle surface  2 . In that event, the swinging base  30  swings around the pin  32  so as to press the cap  34  onto the nozzle surface  2  by uniform pressing force. 
   When the cap  34  is pressed onto the nozzle surface  2 , each side lip  40   a - 40   d  is elastically deformed as if the front end thereof falls down to the inside of the groove  42  as shown in  FIG. 6 . Then, each corner lip  40   e - 40   h  is elastically deformed as if the front end of the corner  40   e - 40   h  falls down to the inside of the groove  42  similarly. At the same time, the arc-like circumferential length of the corner lip  40   e - 40   h  connecting the front ends of the side lips  40   a - 40   d  on the opposite sides of the corner lip  40   e - 40   h  is elongated because the front ends of the side lips  40   a - 40   d  fall down to expand outward. Since the corner lip  40   e - 40   h  is formed to be easy to be elastically deformed, the corner lip  40   e - 40   h  expands in its circumferential direction. 
   Accordingly, when the cap  34  is pressed onto the nozzle surface  2 , as shown in  FIGS. 4 and 6 , the front ends of the side lips  40   a - 40   d  fall down outward, and the front ends of the corner lips  40   e - 40   h  fall down outward while expanding in their circumferential directions respectively. Thus, the front ends of the side lips  40   a - 40   d  and the corner lips  40   e - 40   h  are brought into tight contact with the nozzle surface  2  so as to cover the nozzle surface  2  air-tightly with the bottom surface  36 , the side lips  40   a - 40   d  and the corner lips  40   e - 40   h.    
   After that, ink is ejected from the print head  1  for the sake of recovery of the nozzles or the like. In that event, since the nozzles are covered air-tightly with the bottom surface  36 , the side lips  40   a - 40   d  and the corner lips  40   e - 40   h , there is no fear that the ink leaks out. Incidentally, not only at the time of recovery but also at any time when printing is not carried out, the cap  34  is pressed onto the nozzle surface  2  so as to keep the nozzle surface  2  moist. 
   Since the corner lips  40   e - 40   h  are formed to be easy to be elastically deformed in such a manner, it is possible to retain air-tightness. In addition, since the corner lips  40   e - 40   h  are elastically deformed to retain the air-tightness, the tolerance for dimensional accuracy is so large that the number of caps  34  defective in dimensions can be reduced. Thus, the yield in manufacturing can be improved. 
   Next, description will be made on a printhead cap according to a second embodiment different from the aforementioned embodiment, with reference to  FIGS. 8 to 10 ,  11 A and  11 B. Members the same as those in the aforementioned embodiment are denoted by the same reference numerals correspondingly, and their detailed description will be omitted. 
   As shown in  FIG. 8 , in a cap  50 , a bottom surface  36  is formed to be opposed to the nozzle surface  2 . The cap  50  is provided with a lip  52  surrounding the bottom surface  36  like a ring. The lip  52  protrudes toward the nozzle surface  2  of the print head  1 . In this embodiment, the lip  52  has a pair of side lips  52   a  and  52   b  provided linearly along the long sides of the bottom surface  36 , and a pair of side lips  52   c  and  52   d  provided linearly along the short sides of the bottom surface  36 . Also in this case, the shape of the side lip  52   a - 52   d  is not limited to the linear shape, but may be a curved shape. 
   Each side lip  52   a - 52   d  is formed to have a sectional shape protruding obliquely from the bottom surface  36  side toward the nozzle surface  2 , and to have a front end opened to the outside so as to overhang the bottom surface  36 , as shown in  FIGS. 9 and 10 . The side lip  52   a - 52   d  is formed to have a substantially uniform thickness between the bottom surface  36  side and the front end side or a thickness reduced slightly as the location goes toward the front end. 
   Of the corners of the lip  52  in which the direction of surrounding the bottom surface  36  changes, in this embodiment, each corner in which the direction changes at the angle of 90 degrees from the side lip  52   a ,  52   b  along the long side to the side lip  52   c ,  52   d  along the short side connects the side lips  52   a - 52   d  with each other through each corner lip  52   e - 52   h . The corner lip  52   e - 52   h  is formed into an arc-like shape swelling outside the corner where the extensions of the side lips  52   a - 52   d  cross each other, as shown in  FIG. 8 . As shown in  FIGS. 9 and 11A , the corner lip  52   e - 52   h  is formed to protrude obliquely further outside the side lip  52   a - 52   d  between the bottom surface  36  and its front end. 
   In addition, the corner lip  52   e - 52   h  is formed to be lower in height (height from the mounting surface S) than the side lip  52   a - 52   d . The corner lip  52   e - 52   h  is formed to be the lowest at the intermediate point of its arc and to be inclined toward the front end of the side lip  52   a - 52   d  on either side so as to be equal in height to the side lip  52   a - 52   d . The height of the corner lip  52   e - 52   h  may be determined by experiment or the like so that the height of the corner lip  52   e - 52   h  becomes equal to that of the side lip  52   a - 52   d  due to the deformation of the cap  50  when the cap  50  is pressed onto the nozzle surface  2 . Incidentally,  FIGS. 8 and 10  show the state of the lower side than the center line where the cap  50  has been pressed onto the nozzle surface  2  and deformed. 
   Next, description will be made on the operation of the print head cap according to this second embodiment. 
   When the cap  50  is pressed onto the nozzle surface  2 , each side lip  52   a - 52   d  is elastically deformed as if it falls down outward as shown in  FIGS. 8 ,  10  and  11 B. Thus, the height of the side lip  50   a - 50   d  is lowered. On the other hand, each corner lip  52   e - 52   h  falls down outward similarly together with the side lip  52   a - 52   d  on either side on the side lip  52   a - 52   d  side. The corner lip  52   e - 52   h  does not fall down very much in its intermediate portion. Thus, the height of the corner lip  52   e - 52   h  is not lowered. 
   Accordingly, when the cap  50  is pressed onto the nozzle surface  2 , the height of the side lip  52   a - 52   d  and the height of the corner lip  52   e - 52   h  become substantially equal to each other so as to be brought into tight contact with the nozzle surface  2  with no space therebetween. Thus, the nozzle surface  2  is covered air-tightly with the bottom surface  36 , the side lips  52   a - 52   d  and the corner lips  52   e - 52   h.    
   In such a manner, the cap  50  is formed so that the side lips  52   a - 52   d  are deformed to be equal in height to the corner lips  52   e - 52   h . Thus, it is possible to retain air-tightness. In addition, since the air-tightness is retained due to deformation of the side lips  52   a - 52   d , the tolerance for dimensional accuracy is so large that the number of caps  50  defective in dimensions can be reduced. Thus, the yield in manufacturing can be improved. 
   The invention is not limited to the embodiments described above, but it can be carried out in various modes without departing from the gist of the invention. 
   As has been described in detail above, the print head cap  34  and  52  according to embodiments of the invention is formed so that the corner lips  40   e - 40   h  and  52   e - 52   h  are easy to be elastically deformed. Thus, it is possible to retain air-tightness. In addition, since the air-tightness is retained due to the elastic deformation of the corner lips  40   e - 40   h  and  52   e - 52   h , the tolerance for dimensional accuracy is so large that the number of defective caps in dimensions can be reduced. Thus, there is an advantage that the yield in manufacturing can be improved. Particularly, when a groove  42  is formed outside the lip  40 , the elastic deformation is urged so that the air-tightness can be retained more surely. 
   In addition, in the print head cap  52 , the side lips  52   a - 52   d  are deformed to have the same height as the corner lips  52   e - 52   h , so that the air-tightness can be retained. In addition, since the air-tightness is retained due to the deformation of the side lips  52   a - 52   d , the tolerance for dimensional accuracy is so large that the number of defective caps in dimensions can be reduced. Thus, there is an advantage that the yield in manufacturing can be improved. 
   While the invention has been described in conjunction with the specific embodiments described above, many equivalent alternatives, modifications and variations may become apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention as set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.