Abstract:
The ink cartridge is provided with a pressure controller to regulate the inner pressure therein by atmospheric pressure while the ink stored in the ink cartridge is gradually drained off. The ink is stored in a container with negative pressure therein, and at least one through hole formed on the container is used to connect to the atmosphere, and at least one recess is formed on the inner wall of the through hole. The pressure controller has a plug movably disposed on the through hole and the recesses. The recesses are used as a channel to allow the entrance of the atmospheric air, and the plug can be automatically moved so as to enlarge the clearance between the plug and the through hole while the ink stored in the ink cartridge is gradually drained off. The inputted air can effectively reduce the negative pressure in the container, and therefore the printing process of the ink cartridge can be proceeding steadily.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an ink cartridge. More particularly, this invention relates to an ink cartridge provided with a pressure controller so as to precisely control ink pressure therein. 
     2. Description of Prior Art 
     In the field of the printing device, “Drop-On-Demand” is a general control method used to control the flow rate of the ink dropping on the printing surface. For example, thermal bubble type printhead and piezoelectric type printhead are two classic outputting devices designed by “Drop-On-Demand”. 
     Thermal bubble type printhead has a film resistor. The ink droplet is immediately vaporized and the expansion effect is generated as the film resistor is energized, and then parts of ink droplet is jetted out off the nozzle, and finally dropping on the printing surface. The thermal bubble type printhead controlled by the “Drop-On-Demand” will cause the ink oozing through the nozzle if it is not taken a control mechanism—to generate a predetermined negative pressure in the ink cartridge while the printing procedure is stopped. 
     Some of ink cartridges are provided with a “regulator”, disposed in the ink container to generate negative pressure therein. In general, a regulator such as air bag is used to change the volume of the ink container by expansion or contraction so that the adequate negative pressure can be generated. 
     However, the volume in the ink container cannot be further increased once the maximum degree of the expansible air bag is limited. When this occurs the air bag cannot be further expanded and the ink stored in the container continues draining out, the negative pressure is relatively increased over the predetermined value. Then, the ink supply of the printhead will be abnormally terminated and then the remaining ink cannot be used. 
     For solving the above problem, some printing devices are applied with “bubble generator” to control the negative pressure in the cartridge. The bubble generator is provided with a designed through hole which is connected the inner space of cartridge to the ambient atmosphere and used to generate “liquid seal” with capillary forces so as to keep the ink remaining in the cartridge. 
     When the negative pressure is raising up to a preset value and it is larger than the capillary forces, the atmospheric air from the ambient atmosphere is quickly sucked into the ink cartridge via the through hole and scrubbed into bubbles dispersing in the ink. Then, the negative pressure can be immediately decreased by the generation of these bubbles, and then the liquid seal can be rebuild as the negative pressure is smaller than the capillary forces. 
     There are several crucial functions for the bubble generator. First, the negative pressure has to be precisely controlled as the bubbles are generated. Second, the variation of negative pressure in the cartridge has to be precisely controlled within a predetermined range, and the generation of the bubbles has to be terminated when the negative pressure is lower to a predetermined value. Third, “self-wetting capability” has to be provided. As the ink is about to be used up or the position of the cartridge is altered, for example, resulting in the bubble generator is not merged in the ink, the self-wetting capability of the bubble generator can effectively prevent the ambient air from entering into the cartridge. 
     U.S. Pat. No. 5,526,030 discloses the bubble generator provided with a through hole and a packing member. Several ribs are protruded from the inner wall of the through hole and used to position the packing member within the through hole. The packing member cannot be moved or rotated within the through hole and the gaps between the packing member and the inner wall are used to generate bubbles. The &#39;030 case further comprises a liquid sealing device and is configured with the ability of self-wetting. For generating desirable negative in the ink pen, the annular orifice between the fixed sphere and the inside of the boss must be precisely calculated and manufactured. This increases the production cost and difficulty of fabricating the device. 
     SUMMARY OF THE INVENTION 
     To solve the above problem, the primary object of this invention is to provide an ink cartridge comprising a pressure controller so as to adjust the inner pressure therein by atmospheric pressure while the ink stored in the ink cartridge is gradually drained off. The ink cartridge has a container used to store ink with negative pressure therein. At least one through hole is formed on the container and used to connect to the atmosphere, and at least one recess is formed on the inner wall of the through hole. The pressure controller has a plug movably disposed on the through hole and the recess. The recess is designed to regulate the pressure difference between the ink in the container and the atmosphere, and the plug can be automatically shifted to enlarge the clearance between the plug and the through hole while the ink stored in the ink cartridge is gradually drained off. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reading the subsequent detailed description and examples with reference made to accompanying drawings in which: 
     FIG. 1A is a plane view showing the inner structure of an ink cartridge ( 1 ) according to a first embodiment of the present invention; 
     FIG. 1B is an enlarged view showing the structure of a pressure controller (R 1 ) of FIG. 1A; 
     FIG. 1C is a cross-sectioned view according to the line A—A of FIG. 1B; 
     FIG. 2A is a plane view showing the inner structure of the ink cartridge ( 1 ′) according to a second embodiment of the present invention; 
     FIG. 2B is an enlarged view showing the structure of a pressure controller (R 1 ′) of FIG. 2A; 
     FIG. 3A is a plane view showing the inner structure of the ink cartridge ( 1 ″) according to a third embodiment of the present invention; 
     FIG. 3B is an enlarged view showing the structure of a pressure controller (R 2 ) of FIG. 3A; 
     FIG. 3C is a plan view showing the pressure controller (R 2 ) being actuated of FIG. 3B; 
     FIG. 4 is a plan view showing another derivative example according to FIG. 1C; 
     FIG. 5A is a plan view showing the structure of a pressure controller (R′) according to a fourth embodiment of the present invention; 
     FIG. 5B is a plan view showing the structure of a pressure controller (R″) according to a fifth embodiment of the present invention; and 
     FIG. 5C is a plan view showing the structure of a pressure controller (R′″) according to a sixth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1A, a plane view shows the inner structure of an ink cartridge  1  according a first embodiment of the present invention. 
     The ink cartridge  1  comprises a container  10 , an expansible chamber  11 , a movable plate  12 , a spring  13  and a pressure controller R 1 . The ink W is in the container  10  with negative pressure, and a guiding path  103 H is formed on the bottom of the container  10 . A printhead  2  located outside of the container  10  is connected to the guiding path  103 H, wherein the ink W can be drained out by the printhead  2  through the guiding path  103 H. The expansible chamber  11 , the movable plate  12  and the spring  13  are partially immersed in the stored ink W, and the pressure controller R 1  located at the bottom of the container  10  is fully immersed in the stored ink W. 
     The container  10  comprises a body  10 - 1  and a cover  10 - 2 . The cover  10 - 2  is used to connect the body  10 - 1  on the top and is formed with a hole  104 H which can be sealed by a cap  104 P. The ink W is loaded into the container  10  through the hole  104 H. The body  10 - 1  is composed of two side plates  101 ,  102  and a bottom plate  103 . The expansible chamber  11  is installed in the container  10  and communicated to a gas source  3  (such as atmospheric gas) by a conduit  110 . The movable plate  12  is disposed between the spring  13  and the expansible chamber  11 , and the spring  13  is disposed between the side plate  101  and the movable plate  12 . The movable plate  12  is attached on the expansible chamber  11 , and one end of the spring  13  is connected to the side plate  101 , and the another end of the spring  13  is connected to the movable plate  12 . Therefore, the expansible chamber  11  can be used to move the movable plate  12 , and the movement of the .movable plate  12  is limited by the spring  13 . 
     Referring also to FIG. 1B, an enlarged view shows the inner structure of the pressure controller R 1  of FIG.  1 A. 
     The pressure controller R 1  can be a set or module, which can be separably installed on the container  10  or directed or formed on the container  10  as this preferred embodiment. The pressure controller R 1  comprises a base  14 - 1 , a plug  15 , a plate  16 - 1 , a connector  17  and a resilient element  18 . 
     The base  14 - 1  provided with a through hole  140 - 1  is integrally formed on the bottom plate  103 . The through hole  140 - 1  is used to connect the ink W in the container  10  and the atmosphere, as showed in FIG.  1 A. One opening near the inner space of the container  10  of the through hole  140 - 1  is shaped with a semispherical space  140 U. 
     The plate  16 - 1  is fixed on the bottom plate  103  by the connector  17  and used as a cantilever arm extending above the through hole  140 - 1  of the base  14 - 1 . The resilient element  18  is a spring used to connect to the plate  16 - 1  and provided with a contacting end  180  faced toward the semispherical space  140 U. The plug  15  is a ball disposed between the contacting end  180  of the resilient element  18  and the base  14 - 1 , wherein the plug  15  is pushed by the resilient element  18  and uniformly pressed on the protrusions  141 P. 
     Referring to FIG. 1C, the cross-sectional view by the line A—A of FIG. 1B shows the geometrical relationships between the plug  15  and the base  14 - 1 . Three recesses  141 V are formed on the inner wall of the through hole  140 - 1  and separated by the protrusions  141 P. Thus, three clearances G (recesses  141 V) are formed among the base  14 - 1 , the plug  15  and the protrusions  141 P at the present situation. 
     When the printing process is underway and the ink W in the container  10  is gradually drained off, the negative pressure in the container  10  is gradually increased and the back pressure located at the plug  15  is relatively elevated. Once the negative pressure in the container  10  is increased over a critical value, the atmospheric air can be immediately sucked into the container  10  via the through hole  140 - 1  and the clearances G and it is dispersed into the ink W in the form of bubbles. Then, the negative pressure in the container  10  can be immediately increased. 
     Once the negative pressure in the container  10  is greatly larger than the pressure of the atmospheric air and it cannot be effectively increased by the aforementioned method, the negative pressure pushes the plug  15  pressing on the resilient member  18  toward the plate  16 - 1 . Then, the clearance between the plug  15  and the through hole  140 - 1  is enlarged and it allows more air entering the container  10  to reduce the negative pressure in the container  10 . 
     In addition, owing to the expansible chamber  11  is connected to the atmospheric gas source  3 , the pressure in the expansible chamber  11  is decreased when the ink cartridge  1  is moved from a lower altitude to a higher altitude such as transported by flight. Thus, the pressure in the expansible chamber  11  is decreased by the atmospheric gas source  3  and the expansible chamber  11  is relatively contracted. With the decreasing of the inner pressure of the container  10 , the air can be immediately sucked into the container  10  by passing the clearance G, and then the negative pressure in the container  10  can be immediately reduced and there is no ink oozed from the printhead  2 . With the regulation of the clearances G between the inside and outside of the container  2 , therefore, the printing process can be proceeded with stable, and the negative pressure can be precisely controlled within a designed range by regulating the inflow rate of air outside. 
     Referring to FIG.  2 A and FIG. 2B, FIG. 2A shows the inner structure of the ink cartridge  1 ′ according to a second embodiment of the present invention, and FIG. 2B shows the structure of a pressure controller R 1 ′ of FIG.  2 A. 
     The second embodiment differs from the first embodiment in that the spring  18  in FIG. 1A is removed, and a reed  16 - 2  replaces the plate  16 - 1 . The same elements in FIG.  2 A and FIG. 2B are denoted the same symbols as the first embodiment. The reed  16 - 2 , a resilient element, has a contacting end  160  used for pressing the plug  15  on the protrusions  141 P 1  of the base  14 - 1  and limiting the plug  15  at the semispherical space  140 U. 
     Referring to FIG. 3A, a plan view shows the inner structure of the ink cartridge  1 ″ according to a third embodiment of the present invention. The third embodiment differs from the first and the second embodiments in that the movable plate  12  is used to replace the spring  18  (FIG. 1A) or reed  16 - 2  (FIG. 2A) to control the movement of the plug  15 . 
     Referring to FIG.  3 B and FIG. 3C, FIG. 3B shows the detailed structure of a pressure controller R 2  of FIG. 3A, and FIG. 3C shows the pressure controller R 2  being actuated by the movable plate  12 . 
     As shown in FIG. 3B, the pressure controller R 2  has a base  14 - 2  formed with a through hole  140 - 2 , and the through hole  140 - 2  is provided with a space  140 U- 2  and a plurality of protrusions  141  P 2  therein. A plate  16 ′ is used as a cantilever disposed above the through hole  140 - 2  and it is composed of two portions  16 ′- 1  and  16 ′- 2 . The portion  16 ′- 1  has a contacting end  160 ′ faced toward the through hole  140 - 2  and is fixed on the bottom plate  103  by the connector  17 , so that the plug  15  can be uniformly pressed on the protrusions  142 P 2  by the portion  16 ′- 1 . 
     In FIG. 3C, as the expansible chamber  11  is inflated with gas supplied from the gas source  3 , the movable plate  12  is moved toward the plate  16 ′ and then contacts the portion  16 ′- 2  of the plate  16 ′. Then, the inflating expansible chamber  11  causes the moving plate  12  pressing on the plate  16 ′ and results in the plate  16 ′ substantially rotated above the fixed connector  17 . The portion  16 ′- 1  is shifted with a slant angle away from the base  14 - 2  and the space between the plate  16 ′ and the base  14 - 2  is enlarged. Then, the plug  15  is not fixedly pressed by the plate  16 ′ and it can locally move between the plate  16 ′ and the base  14 - 2 , and the clearance between the plug  15  and the through hole  140 - 2  can be enlarged. Although the plug  15  can freely move within the space  140 U 2 , the plug  15  is still constrained between the plate  16 ′ and the base  14 - 2 . Therefore, the atmospheric air can be immediately sucked into the container  10  via the enlarged clearances G and it is dispersed into the ink W in the form of bubbles. 
     Once the plug  15  is stuck as the plate  16 ′ is pressed, the atmospheric air still can be sucked into the container  10  via the minimum clearances among the plug  15  and the protrusions  141 P 2  and dispersed itself into the ink W in the form of bubbles. 
     Referring to FIG. 4, a plan view shows another derivative example according to FIG.  1 C. In FIG. 4, three grooves  141 R, instead of the protrusions  141 P, are formed on the inner wall of the through hole  140 - 1 , and therefore three clearances G 2  are formed between the base  14 - 1  and the plug  15  as the plug  15  is pressed on the base  14 - 1 . 
     Referring to FIGS.  5 A˜ 5 C, three plan views respectively show the structure of three different types of pressure controller R′, R″, R′″ according to a fourth, fifth and sixth embodiment of the present invention. Three spaces  140 U′,  140 U″,  140 U′″ with different shapes are respectively provided in a through hole  140 ′ of a base  14 ′, a through hole  140 ″ of a base  14 ″ and a through hole  140 ′″ of a base  14 ′″. Protrusions  141 P′,  141 P″,  141 P′″ are respectively formed on the spaces  140 U′,  140 U″,  140 U′″. 
     In FIG. 5A, the plug  15  is pressed on the protrusion  141 P′and located in the space  140 U′ by the plate  16 . In a FIG. 5B, the plug  15  is pressed on the protrusion  141 P″ and located in the space  140 U″ by the plate  16 . In FIG. 5C, the plug  15  is pressed on the protrusions  141 P′″ and located in the space  140 U′″ by the plate  16 . Once the negative pressure in the container  10  is increased, the clearances between the plug  15  and the through hole  140 ′ ( 140 ″ or  14 ′″) allow the atmospheric air to enter the container  10 . 
     While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.