Abstract:
A capping device for capping a print head of a printer includes a cap for capping the print head, a supporting structure for mechanically engaging and disengaging the cap with the print head, and an elastic structure installed inside the cap. The top of the cap is lower than the top of the elastic structure. Before the supporting structure engages the cap with the print head, the top of the elastic structure bends outward and contacts the print head in an incomplete sealed manner.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a capping device and more particularly, to a capping device capable of preventing a sudden capping pressure generated during the capping process from destroying the surface tension of ink.  
         [0003]     2. Description of the Prior Art  
         [0004]     Ink jet print systems are used for fax machines, printers, photocopiers, or other office appliances. The ink jet print system includes a capping device for capping a print head so as to ensure normal operation of the print head. When the inkjet print system is not used, the capping device is capable of capping the print head to prevent the ink in the nozzles from drying so as to jam the print head.  
         [0005]     Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  is a schematic drawing of a conventional capping device  10 , and  FIG. 2  is a schematic drawing of a cap  12  of the capping device  10 . The capping device  10  includes the cap  12 , a cap sled  14 , and a cap housing  16 . The cap sled  14  is capable of carrying the cap  12 , and the cap housing  16  is installed on a print track (not shown in  FIG. 1 ) in a slidable manner for carrying the cap sled  14 . When a carrier of an ink cartridge (not shown in  FIG. 1 ) moves to the capping device  10 , the cap sled  14  can be driven upward for driving the cap  12  upward to cap a print head of the ink cartridge. When the cap  12  caps the print head, the air system outside the print head and covered by the cap  12  will be transformed from an open system to a closed system. This results in air volume compression so as to generate a sudden increase in pressure. The sum of the sudden pressure and a back pressure of the ink cartridge must be less than surface tension of the ink so that the pressure does not destroy the surface tension of the ink. However in the prior art, the common method for preventing the capping device from generating the excess sudden pressure is by forming a hole on the surface of the cap  12  so as to promote circulation between the air inside and outside of the cap  12  because this prevents the volume of the air from decreasing suddenly and the sudden pressure will not be generated. Unfortunately, the design mentioned above has a disadvantage of drying the nozzle.  
         [0006]     Furthermore, the movement of the carrier of the ink cartridge might deform the outer sides of the cap  12  so that a gap between the cap  12  and the print head will be generated, and the nozzle will dry due to unsealed combination of the cap  12  and the print head.  
       SUMMARY OF INVENTION  
       [0007]     It is therefore a primary objective of the claimed invention to provide a capping device capable of preventing a sudden capping pressure generated during the capping process from destroying the surface tension of ink for solving the above-mentioned problem.  
         [0008]     According to the claimed invention, a capping device for capping a print head of a printer includes a cap for capping the print head, a supporting structure for mechanically engaging and disengaging the cap with the print head, and an elastic structure installed inside the cap. The top of the cap is lower than the top of the elastic structure. Before the supporting structure engages the cap with the print head, the top of the elastic structure bends outward and contacts the print head in an incomplete sealed manner.  
         [0009]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]      FIG. 1  is a schematic drawing of a conventional capping device.  
         [0011]      FIG. 2  is a schematic drawing of a cap of the capping device shown in  FIG. 1 .  
         [0012]      FIG. 3  is a perspective drawing of a printer of the present invention.  
         [0013]      FIG. 4  is a schematic drawing of a capping device shown in  FIG. 3  of the present invention.  
         [0014]      FIG. 5  is a schematic drawing of a cap shown in  FIG. 3  of the present invention.  
         [0015]      FIG. 6  is a lateral view of the cap.  
         [0016]      FIG. 7  is a diagram illustrating that an elastic structure shown in  FIG. 5  contacts with an ink cartridge shown in  FIG. 3  and deforms during the capping process.  
         [0017]      FIG. 8  is a diagram that illustrates the cap contacting the ink cartridge. 
     
    
     DETAILED DESCRIPTION  
       [0018]     Please refer to  FIG. 3 .  FIG. 3  is a perspective drawing of a printer  20  of the present invention. The printer  20  includes an ink cartridge  22  installed on a carrier  24 . The ink cartridge  22  contains ink for printing. The carrier  24  can carry the ink cartridge  22  to move on a print track  26 , and a print head (not shown in  FIG. 3 ) on the bottom of the ink cartridge  22  can print images on a print medium (not shown in  FIG. 3 ). The print head includes at least one nozzle (not shown in  FIG. 3 ) to jet out ink onto the print medium. The printer  20  further includes a capping device  28  installed on one side of the print track  26 . When the ink cartridge  22  finishes printing, the carrier  24  can drive the ink cartridge  22  to the capping device  28  for capping the print head.  
         [0019]     Please refer to  FIG. 4 .  FIG. 4  is a schematic drawing of the capping device  28  of the present invention. The capping device  28  includes two caps  30 , and a supporting structure  32 . The supporting structure  32  includes a cap sled  34 , and a cap housing  36 . The cap sled  34  is capable of carrying the cap  30 , and the cap housing  36  is installed on the print track  26  in a slidable manner for carrying the cap sled  34 . The left and right movement of the carrier  24  can be transformed into upward and downward movement. When the carrier  24  of the ink cartridge  24  moves to the capping device  28 , the cap sled  34  will be driven upward so as to drive the cap  30  to cap the print head of the ink cartridge  22 .  
         [0020]     Please refer to  FIG. 5  and  FIG. 6 .  FIG. 5  is a schematic drawing of the cap  30  of the present invention.  FIG. 6  is a lateral view of the cap  30 . The capping device  28  further includes an elastic structure  38  installed inside the cap  30 . A room is formed inside one side of the cap  30 , and the elastic structure  38  is positioned inside the room. The top of the cap  30  is lower than the top of the elastic structure  38 . The elastic structure  38  includes four inclined planes extending outwardly to the outer sides of the cap  30 , and the elastic structure  38  is a petal structure. The elastic structure  38  can be connected to the cap  30  to create a monolithic structure.  
         [0021]     When the carrier  24  of the ink cartridge  22  moves to the capping device  28 , the cap sled  34  can be driven upward. Because the elastic structure  38  is higher than the cap  30 , during the capping process the elastic structure  38  can contact the ink cartridge  22  first. And during the contact process of the elastic structure  38  and the ink cartridge  22 , the inclined planes of the elastic structure  38  will be deformed by the compression of the print head. Please refer to  FIG. 7 .  FIG. 7  is a diagram illustrating that the elastic structure  38  contacts with the ink cartridge  22  and deforms during the capping process. The elastic structure  38  is compressed and the top of the elastic structure  38  will bend outward so that the elastic structure  38  cannot be combined with the print head  23  of the ink cartridge  22  tightly and a gap between the elastic structure  38  and the print head  23  of the ink cartridge exists. That is, the elastic structure  38  caps the print head in an unsealed manner. At this time the difference between the ambient pressure and the pressure of the air covered by the elastic structure  38  is small because the elastic structure  38  can not cap the print head tightly. The pressure outside and inside the elastic structure  38  will balance, and it will not cause the great sudden capping pressure. If the sum of the sudden capping pressure and the back pressure of the ink cartridge is greater than the surface tension of the ink, the air will flow into the nozzle so that there are bubbles in the nozzle and the print quality will decrease.  
         [0022]     Please refer to  FIG. 8 .  FIG. 8  is a diagram that illustrates the cap  30  contacting the ink cartridge  22 . When the capping device  28  rises to a predetermined position, the elastic structure  38  is compressed by the print head  23  to extend outward. At the same time, the cap  30  having a trapezoid shape outside the elastic structure  38  contacts the ink cartridge  22  afterward to provide the second protection layer. Because the cap  30  is composed of four planes perpendicularly to the print head  23  instead of four inclined planes extending outwardly of the elastic structure  38 , the cap will not bend out when contacting the ink cartridge  22  so that the print head  23  can be properly sealed.  
         [0023]     The purpose of the present invention is to pre-cap the print head  23 . That is, during the capping process the elastic structure  38  contacts the ink cartridge  22  first and then caps the print head  23  in an incomplete sealed manner, so the difference between the ambient pressure and the pressure of the air covered by the elastic structure  38  is small so as to prevent the sudden capping pressure from destroying the surface tension of the ink. Finally the capping device  28  rises to the predetermined position, and the cap  30  can cap the print head  23  completely to prevent the print head  23  from drying.  
         [0024]     In the present invention the cap  30  and the elastic structure  38  can be made of rubber material. Because rubber is elastic, it is easy to create these parts from a mold and to mass produce these parts.  
         [0025]     Compared to the conventional capping device, the capping device of the present invention not only can avoid the problem of a sudden capping pressure generated during the capping process destroying the surface tension of the ink but also can seal the print head tightly to prevent the print head from drying. Furthermore, the present invention merely modifies the structure of the capping device instead of applying additional devices for capping, and the manufacture is very easy. Therefore the present invention provides a low cost and effective solution to solve the problems of the conventional capping mechanism.  
         [0026]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.