Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink cartridge used in an ink jet printing device, and more particularly, to an ink cartridge with an ability to adjust internal fluid pressure automatically. 
     2. Description of the Prior Art 
     As personal computers become more popular, ink jet printing devices are becoming a most common computer output/printing device used by people, families, and companies, because a price and a quality of the ink jet printers attract customers to buy. 
     A typical ink jet printing device has a printing head that moves along a track, back and forth, to print on a document. The printing head usually has at least an ink cartridge, and the ink cartridge comprises a housing with an ink reservoir for storing ink, and a print head connected to the ink reservoir to control the ink jetting. In a typical ink jet printing device, flow control is usually employed to control the ink jetting out to the document from the ink reservoir. Typical print head flow control mechanisms are divided into two types: thermal-bubbles and pressure-waves. 
     The thermal-bubbles print head comprises a thin-film resister. When the resistor is heated, a trace of ink vaporizes immediately, quickly expanding to make ink pass through the print head, and print on the document. Although the print head using the flow control can get ink from the ink reservoir and jet ink effectively, the flow control needs a controlling mechanism, so that the print head does not seep ink when not in use. The controlling mechanism usually provides a light negative pressure to prevent ink from seeping onto the print head. The negative pressure is partial vacuum in the ink cartridge, so that the external atmospheric pressure is slightly higher than the fluid pressure us in the ink cartridge. The negative pressure is indicated by a positive value, so an increase in the negative pressure means an increased vacuum of the ink cartridge, and a greater difference between the external atmospheric pressure and the fluid pressure in the cartridge. By increasing the negative pressure, ink is prevented from seeping from the print head. 
     Although increasing the negative pressure prevents ink from seeping out of the print head, the negative pressure has an upper limit. If the negative pressure is too high, ink cannot overcome the negative pressure and jet from the print head. On the other hand, the ink cartridge must be able to adjust the negative pressure in the ink reservoir automatically by changing the pressure of the surrounding environment to maintain a suitable range. For example, when the pressure of the surrounding environment decreases, the negative pressure causing ink not to seep through the print head is higher. Furthermore, the “operating-effect” of the ink reservoir also affects the negative pressure of the ink reservoir. For example, when the ink in the ink reservoir is continually consumed, the negative pressure of the ink reservoir increases. At this time, unless the negative pressure is adjusted appropriately, the print head ejects less ink, which affects the printing quality, such that the print head may not even jet ink any more. 
     In the prior art, the negative pressure of the ink reservoir is controlled by a “regulator” in the ink reservoir. The regulator is usually an elastic air bag. By stretching the elastic air bag between a maximum volume and a minimum volume, the volume of stored ink in the ink reservoir also changes to adjust to changes of the negative pressure. For example, when the pressure of the surrounding environment decreases, the negative pressure of the ink reservoir also decreases. At this time, the regulator starts to increase the volume used for storing ink in the ink reservoir. Therefore, the negative pressure is increased, and the ink does not seep. 
     A major shortcoming of the prior art elastic air bag regulator is that the maximum volume of the elastic air bag has limits. When ink is consumed to a predetermined degree, and the elastic air bag expands to the maximum volume, the volume of stored ink in the ink reservoir does not change any more. Continued reduction of ink volume causes the negative pressure to exceed the range, and the ink does not overcome the negative pressure to jet from the print head, such that the ink in the ink trough is not used completely and is wasted. 
     Another kind of prior art used to control the negative pressure in the ink trough is a bubble generator. As disclosed in U.S. Pat. No. 5,526,030, the bubble generator is set in the ink reservoir and has a jet hole through the housing of the ink cartridge. With the jet hole, external air can enter into the ink reservoir. The controlling mechanism in the bubble generator designed appropriately makes ink gather in the jet hole and utilizes the capillarity of ink to form a liquid seal. When the negative pressure of the ink reservoir rises to a predetermined degree, external air overcomes the liquid seal and enters into the ink reservoir as a bubble. Thus, the negative pressure of the ink reservoir decreases. Furthermore, as a result of the bubble entering into the ink reservoir and negative pressure reducing, the liquid seal of the jet hole rebuilds to prevent bubbles from continuing entering. 
     However, the bubble generator above uses surface tension of ink and static water pressure of ink to control bubbles entering into the ink reservoir. Therefore, the primary shortcomings of the prior art above are: 1.) When using different ink, the surface tension of ink is different, and the bubble generator needs to be redesigned; 2.) When remaining ink is reduced, static water pressure of the ink changes, and an pressure adjusting capability of the bubble generator is limited. 3.) For a negative pressure of the ink reservoir as bubbles enter being the designed value, the bubble generator must be designed precisely, increasing the difficulties of manufacturing and assembling. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary objective of the present invention to provide an ink cartridge with an ability to adjust pressure automatically, regardless of atmospheric pressure effects. 
     According to the claimed invention, the ink cartridge comprises a housing with an ink reservoir for storing ink. The housing has a first vent, a second vent and an opening. The opening is installed at a bottom end of the housing and is connected to the ink reservoir. The ink cartridge further comprises an air bag installed in the ink reservoir and connected to the first vent. The first vent enables external air to enter the air bag, and the air bag adjusts pressure within the ink reservoir. An elastic restricting device is installed in the ink reservoir for restricting air in the air bag, to prevent the ink in the ink reservoir from seeping through the opening. An elastic plugging device elastically plugs the second vent of the housing. And, an active shaft is movably installed in the ink reservoir for pushing the elastic plugging device. Consumption of the ink in the ink reservoir causes the air bag to expand. When the air bag expands to a predetermined degree, the air bag moves the active shaft, the active shaft pushes the elastic plugging device, and air enters into the ink reservoir through the second vent to reduce the volume of the air bag. When the air bag stops moving the active shaft, the elastic plugging device elastically plugs the second vent. 
     It is an advantage of the claimed invention that the ink cartridge can adjust internal pressure within the ink reservoir. 
     These and other objectives and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an overhead view of the present invention ink cartridge. 
     FIG. 2 is a cross-sectional diagram of the ink cartridge along a tangent  2 — 2  shown in FIG.  1 . 
     FIG. 3 is a structural diagram of an elastic plugging device and an active shaft shown in FIG.  2 . 
     FIG. 4 is a diagram of the elastic plugging device operated by an active shaft to open a second vent of the present invention cartridge. 
     FIG. 5 is a diagram of the elastic plugging device of a second preferred embodiment of the present invention cartridge. 
     FIG. 6 is a diagram of the elastic plugging device of a third preferred embodiment of the present invention cartridge. 
     FIG. 7 is a diagram of the elastic plugging device of a fourth preferred embodiment of the present invention cartridge. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to FIG.  1 . FIG. 1 is an overhead view of the present invention ink cartridge  11 . The ink cartridge  11  comprises a housing  10  with an ink reservoir  20 . A top  12  of the housing  10  has a first vent  30  and a ink-pour opening  16 , and a bottom  14  of the housing  10  has a second vent  50  and an ink-exit opening  200 . Ink stored in the ink cartridge  11  is poured in through the ink-pour opening  16 . When the ink cartridge  10  is full of ink, there is a seal-up cover  18  to seal up the ink-pour opening  16 . The ink cartridge  11  provides ink through the ink-exit opening  200 . Additionally, the ink-exit opening  200  connects to an ink jet printing head and other relative circuitry used to control the ink jetting to print. 
     Please refer to FIG.  2 . FIG. 2 is a cross-sectional diagram of the ink cartridge  11 . As above, the present invention ink cartridge  11  uses the housing  10  to cover the ink reservoir  20  and provides ink through the ink-exit opening  200 . To prevent ink seeping from the ink-exit opening  200  when not supplying ink, the ink reservoir  20  must keep a predetermined negative pressure. As mentioned above, although there are several prior art mechanisms to keep negative pressure, they all have shortcomings. To overcome the shortcomings of the prior art, the present invention ink cartridge  11  uses a new negative pressure control mechanism. The negative pressure control mechanism comprises an air bag  32 , an elastic restricting device  34 , an active shaft  40 , and an elastic plugging device  100 . The air bag  32  is a seal-up hollow bag and is isolated from the fluid in the ink reservoir  20 . It connects to a first vent  30  of the top  12  of the housing  11  only by a first ventilated pipe  33 , so that external air can pass in and out of the air bag  32 . The elastic restricting device  34  comprises a press board  36  and a first spring  38 . One end of the first spring  38  is fixed on a wall of the housing  10 , and the other end is fixed on the press board  36 , so that the spring  38  presses the air bag  32  through the press board  36 . The active shaft  40  is fixed on the bottom of the housing  14 , and it is an elastic element. The detailed structure of the elastic plugging device  100  is shown in FIG.  3 . 
     Please refer to FIG.  3 . FIG. 3 is a detailed structural diagram of the elastic plugging device  100 . The elastic plugging device  100  is set in the ink reservoir  20  and on the bottom of the housing  14  of the present invention ink cartridge  11  to control the switch of the second vent  50 . The elastic plugging device  100  comprises a flat panel  102 , a second spring  104 , and a spherically shaped plug  106 . The flat panel  102  is fixed on the housing  10  and has a round hole  103 . The second spring  104  is fixed on the flat panel  102  to elastically support the spherically shaped plug  106 . The housing  10  forms a projective edge  110  around the second vent  50 . The projective edge  110  surrounds the second vent  50  to form around hole  111  smaller than the spherically shaped plug  106  to limit the position of the spherically shaped plug  106 . Please note that the spherically shaped plug  106  is not fixed on the projective edge  110 , and it is only pasted tightly on the projective edge  110  by the upward thrust of the second spring  104 . FIG. 3 also shows relative positions of the active shaft  40  and the elastic plugging device  100 . The active shaft  40  is fixed on the housing  10  with a fixing latch and extends to the spherically shaped plug  106  of the elastic plugging device. In a situation where the active shaft  40  lacks an external force, the horizontal section  46  of the active shaft keeps a fixed distance with the spherically shaped plug  106 , and both do not make contact. Therefore, the spherically shaped plug  106  is only pasted tightly on the projective edge  110  by the upward thrust of the second spring  104 , and thus seals up the second vent  50 . 
     The working principle of keeping the negative pressure in the present invention ink cartridge  11  is described below. Please refer to FIG. 2 again. When the ink cartridge  11  is full of ink, the air bag  32  is pressed to the right wall of the ink reservoir  20  along a direction  54  (i.e. the right direction of the figure) by the first spring  38  of the elastic restricting device  34 . Please note that the press board  36  is not in contact with the active shaft  40 . By transferring the ink in the ink cartridge  11  to the printing head through the opening  200 , the vacuum degree of the ink reservoir  20  also raises. At this time, the air bag  32  expands because of inhaling external atmosphere through the first vent  30  to make up for the vacuum left by consumed ink in the ink reservoir  20 . As the air bag  32  expands along a direction  52  (i.e. the left direction of the figure) by ink consumption, the first spring  38  of the elastic restricting device  34  continuously exerts pressure upon the air bag  32  through the press board  36  along a direction  54  to appropriately restrict the expansion of the air bag  32 , so that the ink reservoir  20  keeps an appropriate negative pressure. 
     By consuming more ink of the ink reservoir  20 , the air bag  32  expands along the direction  52  and pushes the press board  36  toward the left of the figure. When the air bag  32  expands to a predetermined degree, the press board  36  contacts and pushes the active shaft  40  to trigger the elastic plugging device  100 . Please refer to FIG. 4 for more detailed information. FIG. 4 is a diagram of the elastic plugging device  100  being triggered by the active shaft  40 . When the air bag  32  expands to a predetermined degree, the press board  36  is pushed to the left of the figure along the direction  52  until the active shaft  40  is contacted and pushed. At this time, the elastic active shaft  40  composed of reeds is bent downward by the thrust of the press board  36  along the direction  52 , and the horizontal section  46  of the active shaft  40  presses the spherically shaped plug  106  downward. After the spherically shaped plug  106  is pressed downward to leave the projective edge  110 , the spherically shaped plug  106  and the projective edge  110  are not closely contacted anymore, and a channel allowing external atmospheric air to enter appears. The external atmospheric air enters the ink reservoir  20  from the second vent  50  through the round hole  103  of the flat panel  102  and the round hole  111  of the projective edge  110  to fill in the vacuum of the ink reservoir  20  because of ink consumption. By the external atmospheric air entering into the ink reservoir  20  through the second vent  50 , the fluid pressure in the ink reservoir (i.e. the total pressure of the air and ink in the ink reservoir) gradually increases, and the resistance of the air bag  32 , which expands along the direction  52 , against the press board is higher. Finally, the force generated by the gradually increasing fluid pressure, as external atmospheric air enters, and by the elastic restricting device  34  in the ink reservoir  20 , along the direction  54 , exceeds the expanding force of the air bag  32 , along the direction  52 , and the press board  36  is pushed to the right of the figure, along the direction  54 , and leaves the active shaft  40 . After the force acting on the active shaft  40  by the press board  36  disappears, the elasticity of the active shaft restores the horizontal section  46  of the active shaft to horizontal, and stops pressing the spherically shaped plug  111  downward. The upward elasticity of the second spring  104  presses the spherically shaped plug  106  to tightly seal the projective edge  110  again, to seal the second vent  50 . The entire elastic plugging device  100  is also restored to the status in FIG. 3, i.e. the active shaft  40  does not receive any force, and the spherically shaped plug  106  tightly seals the projective edge  110  to seal the second vent  50 . If ink is consumed, such that the air bag  32  expands to a predetermined degree again, the above process of opening/closing the second vent happens repeatedly until the ink is exhausted. 
     In short, the main spirit of the present invention ink cartridge  11  is controlling the elastic plugging device  100  to open or close the second vent  50  with the air bag  32  through the press board  36  and the active shaft  40  to maintain the negative pressure of the ink reservoir  20 . In the prior art method of maintaining the negative pressure of the ink reservoir with the air bag, the vacuum in the ink reservoir because of the ink being consumed is filled up with the air bag. However, the volume of the air bag is limited. When the air bag expands to the maximum volume, the function of adjusting the negative pressure cannot be produced any longer. In the present invention ink cartridge  11 , the vacuum in the ink reservoir due to the ink consumption is not only filled up by the air bag  32 , but opening the second vent  50  by the elastic plugging device  100  to import external atmospheric air also balances the vacuum in the ink reservoir  20 . Therefore, the present invention ink cartridge can continuously maintain the stability of the negative pressure until ink is exhausted. 
     The prior art bubble-generator as disclosed in U.S. Pat. No. 5,526,030 also uses a controlling mechanism to control an import air vent opening to import external atmospheric air to maintain the negative pressure of the ink reservoir. However, the operating key of the controlling mechanism relates to the surface tension and the static water pressure of the ink. The structure is precise and complicated, and increases the difficulty of production and manufacturing. If the types of ink filled in the ink cartridge are different, the controlling mechanism must be redesigned because the surface tensions of the ink are also different. Furthermore, as ink is consumed, the static pressure of the ink decreases. Once reduced to a particular degree, the controlling mechanism loses efficacy. In contrast with the negative pressure maintaining mechanism of the prior art ink cartridge, the air bag  32  engages with the active shaft  40  through the press board  36  to control the elastic plugging device  100  to open or prevent the external atmospheric air entering into the ink reservoir  20  through the second vent  50 . The key of the controlling mechanism is the fluid pressure of the ink reservoir. Therefore, the negative pressure mechanism of the present invention ink cartridge can continuously work until ink is exhausted, and it does not need to be redesigned or remanufactured depending on the type of ink used. Furthermore, the structure of the negative pressure keeping mechanism of the present invention ink cartridge is simple, small, and easy to produce, manufacture,and assemble. It is better than the prior art. 
     The negative pressure maintaining mechanism of the present invention ink cartridge further includes a double protecting mechanism to maintain the closed state of the second vent. Please refer to FIG. 3 again. Please note that the negative pressure maintaining mechanism of the present invention ink cartridge comprises two elastic components, one is the active shaft  40 , and the other elastic component is the second spring  104  pressing the spherically shaped plug  106  to tightly seal the projective edge  110 . If the external atmosphere changes frequently, in the process of maintaining the negative pressure by the active shaft  40 , the press board  36  pushes repeatedly. If the active shaft  40  is worn down because of the repeated operations, or the external atmosphere changes violently, so that the press board  36  pushes the active shaft  40  violently, the active shaft may be deformed forever and lose elasticity. Even if the press board  36  leaves the active shaft  40 , the horizontal section  46  of the active shaft  40  still cannot restore a horizontal state, and continuously contact with the spherically shaped plug. At this time, the second spring  104  supporting the spherically shaped plug  106  functions to double protect and push the spherically shaped plug  106  upward to tightly seal the projective edge  110  and seal up the second vent  50 . If not for the second spring  104 , the active shaft, losing elasticity, continuously presses the spherically shaped plug  106  downward, and the second vent  50  cannot be sealed to let the external atmosphere enter continuously. Finally, the negative pressure cannot be kept, and the ink seeps from the second vent  50 . The second spring  104  of the elastic plugging device  100  in the present invention ink cartridge  11  avoid this shortcoming completely. 
     Please refer to FIG.  5 . FIG. 5 is a diagram of the elastic plugging device  100  of a second preferred embodiment of the present invention. Specifically, the bottom panel  102  and the second spring  104  are replaced with a monolithically elastic bottom panel  180  in the preferred embodiment. Like the second spring  104  of the first preferred embodiment, the elastic bottom panel  180  elastically supports the spherically shaped plug  106 . In the situation of the elastic plugging device  100  not exerting force, the second vent  50  is sealed. 
     Please refer to FIG.  6 . FIG. 6 is a diagram of the elastic plugging device  100  of a third preferred embodiment of the present invention. In the preferred embodiment, the spherically shaped plug  208  is an elastic, spherically shaped plug that tightly presses against the projective edge  110  to seal the second vent  50  with a hard bottom panel  282 . When the active shaft pushed by the press board  36  presses the spherically shaped plug  208  downward, the spherically shaped plug  208  maintains a gap to allow the external atmospheric air to enter the ink reservoir from the round hole  111  of the projective edge  110  as a result of deformation. 
     Please refer to FIG.  7 . FIG. 7 is a diagram of the elastic plugging device  100  of a fourth preferred embodiment of the present invention. In this preferred embodiment, the active shaft, which seals up the spherically shaped plug of the second vent  50  and triggers the plastic plugging device, is replaced by a monolithically plugging cover  700 . The plugging cover has a rotating axis  720 , in which is installed a shearing stress spring  730  (not shown in FIG.  7 ), through a hole of the projective edge  710  corresponding to the axis  720 , to elastically connect the plugging cover  700  to the housing  10 . When the plugging cover  700  is not triggered by the press board  36 , the shearing stress spring  730  adds a shearing stress on the plugging cover  700  in a clockwise direction, with  720  acting as the axis, so that the plugging cover  700  tightly presses the second vent  50  and seals it. When the press board  36  is pushed to the left (relative to the figure) by expansion of the air bag  32 , the press board  36  causes the plugging cover  700  to rotate anticlockwise around the axis  720 , so that the external atmospheric air enters from the second vent  50  to adjust the negative pressure of the ink reservoir  20 . 
     The basic spirit of the above mentioned preferred embodiments of the present invention is using the air bag  32  to control the elastic plugging device  100  to open or close the second vent  50  through the active shaft and adjust the negative pressure of the ink reservoir  20 . When the elastic plugging device  100  is not triggered by the active shaft, the elastic design of the elastic plugging device  100  can force sealing of the second vent. When ink is consumed in the well  20 , the air bag  32  expands. When the air bag  32  expands to a predetermined degree, the air bag  32  triggers the elastic plugging device  100 , through the press board  36  or the active shaft  40 , and opens the second vent  50  to import the external atmospheric air to increase the fluid pressure in the well and keep the stability of the negative pressure. After the prior art air bag expands to a predetermined degree, it is no longer able to develop the function of keeping the negative pressure. 
     After the present invention air bag expands to a predetermined degree, importing the external atmospheric air to help maintain the negative pressure. This overcomes the shortcoming of the prior art air bag. Furthermore, with the prior art bubble generator, the triggering mechanism relates to the surface tension and the static water pressure of the ink. The structure is too complex and increases the difficulty of producing and manufacturing. The design lacks of elasticity and has to change with different kinds of ink. The operations are unavoidably affected by the operation of the ink cartridge. In contrast, the present invention ink cartridge uses the expanding of the air bag to trigger the elastic plugging device. The design is succinct, well-executed, easy to produce, assemble, and manufacture. Different kinds of ink and operation effects of the ink cartridge do not influence operation of the present invention. Finally, the elastic design of the elastic plugging device  100  of the present invention ink cartridge maintains sealing of the second vent  50 , even if the active shaft  40  loses efficacy and continuously triggers the elastic plugging device  100 . Operation is not affected by errors of the active shaft  40 . 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device 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.

Technology Category: 7