Abstract:
An ink cartridge for ink jet use is provided with an aperture for filling in the cartridge with ink. The circumference of the aperture and a part of a plug pressed in the aperture are fused and welded to be formed integrally to airtightly close the aperture, and obtain an integrated structure without any interface. Hence, it is made possible to reliably prevent ink from leaking therefrom, even if some scratches and cracks are present on both of them. This contributes to eliminating inspection steps to find ink leakage in the course of manufacture, and also, contributes to improving the yield of production. As a result, a significant reduction of costs is possible, while enhancing the reliability of the ink cartridge.

Description:
This application is a division of application Ser. No. 08/721,205, filed Sep. 26, 1996, still pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink cartridge for ink jet use having an aperture serving as an opening for ink filling, which is sealed, and the invention relates to a method for sealing such aperture. 
     2. Related Background Art 
     As an ink cartridge suitable for use in the technical field of ink jet printing, the one having a structure shown in FIGS. 3A to  3 C is known, for example. FIG. 3A is a cross-sectional view showing such ink cartridge. FIG. 3B is an enlarged sectional view showing the ink filling opening thereof. FIG. 3C represents FIG. 3B, observed from below in the direction indicated by an arrow in FIG.  3 B. 
     In FIG. 3A, a reference numeral  300  designates an ink cartridge formed by polypropylene (PP) or the like, for example. The ink cartridge  300  substantially comprises a container  302  for a member that generates negative pressure, which is partitioned by a partitioning wall  301 , and an ink container  303 . The container  302  for a member that generates negative pressure and the ink container  303  are conductively connected through a conductive aperture  304 . For the container  302  for a member that generates negative pressure, an ink supply port  305  is formed to supply ink to an ink jet head (not shown) that can be mounted on an ink cartridge. On one wall of the container  302  for a member that generates negative pressure, where the ink supply port  305  is formed, an air conduit hole  305  is arranged away from the ink supply port. In the interior of the container  302  for a member that generates negative pressure, a negative pressure generating member  307  formed by a porous element or the like is contained to absorb and hold ink, while ink is contained directly in the interior of the ink container arranged adjacent to it. For this ink container  303 , an ink filling port  309  is formed as an aperture to fill in the container with ink directly. 
     As shown in FIG. 3D, the ink filling port  309  substantially comprises a recessed portion  309   a  where a plug, to be described later, is inserted under pressure to airtightly close the ink filling port  309 ; and an aperture  309   b  formed on the bottom of the recessed portion  309   a  and arranged to be conductively connected with the ink container  303 . A plug  310  that can be inserted into the recessed portion  309   a  is usually a metallic ball of SUS or the like or a plastic ball of PP or the like. Then, a ball of the kind is inserted into the ink filling port  309  under pressure after the ink container is filled with ink, thus keeping the ink filling port in a state of being sealed. 
     Ink is filled into the ink cartridge structured as described above from the aperture  309   b  of the ink filling port  309 . As a method therefor, it is possible to adopt any one of the known methods, such as applying pressure or reducing pressure, among others. 
     After ink is filled, ink cartridges are often distributed on the market individually. In this case, all the apertures of the ink cartridge including the ink filling port  309  (and the ink supply port  305  and the air conduit hole  306 , for example) should be closed by sealing material as a preventive measure against the evaporation of ink and the expansion of air in the container. (Here, the ink filling port  309  is sealed by the plug  310  as described above.) 
     As a sealing material to be used preferably for closing such apertures as described above, it is possible to use a compound material produced by combining a single layered barrier, which is called a “barrier material” in the field of packaging industry, and a multi-laminated plastic film, or a compound barrier material produced by combining this compound material and a reinforcing material, such as paper or fabrics or by combining it with aluminum foil or the like. Particularly, using the same material as that of an ink cartridge as an adhesive layer, it becomes possible to maintain a higher airtightness when the sealing material is thermally welded to the ink supply port  305 , and the air conduit hole  306 , which also provide apertures for an ink cartridge. 
     As described above, the ink filling port  309 , ink supply port  305 , and air conduit hole  306  are airtightly sealed. Therefore, there is no ink leakage or the like, and extremely high reliability is obtainable when the ink cartridge  301  is distributed on the market individually. 
     Now, in this respect, the SUS ball used for pressurized insertion to the ink filling port of an ink cartridge of the kind is prepared for the intended process only after a severe selection so that the acceptable ball should have no scratches or cracks on the surface or any other defects. Therefore, it is required to take many steps when selecting the balls, leading to a disadvantage that the costs become inevitably high. Also, the SUS balls, which are made available after a severe selection process, may sometimes present the scratches or cracks that cannot be discriminated by eye-sight. If such SUS balls should be used, it is conceivable that the provision of any perfect durability is hindered or there may be produced ink tanks, which are unable to fit for use in the environments subjected to changes. A problem that scratches and the others cannot be discriminated perfectly by eye-sight is equally encountered when using PP balls. The scratches and others may exist in the interior of the ink filling port, too. 
     Here, the following is regarded as causes of the generation of these scratches and others: 
     As the causes of scratches in the interior of the ink filling port are: 
     1) Welded lines created when forming an ink tank. 
     2) Scratches created by rubbing when the ink filling port is being pressed by the ink filling mouth of an ink filling machine. 
     Also, for the causes of scratches on the surface of the plug: 
     1) Scratches created by rubbing of one plug with another when being distributed on the market. 
     2) Welded lines created when forming a plug. 
     If a plug having such scratches and others is pressed in the ink filling port described above, ink may leak from the ink filling port or it becomes impossible to keep the ink container airtightly closed. As a result, the performance of an ink cartridge cannot be anticipated as desired, and then, conceivably, ink is caused to shift into a negative pressure generating member in the container for such member. Therefore, ink may leak from the ink supply port. In order to prevent such ink cartridge from being distributed on the market, it should be necessary to exercise an inspect by leaving the ink tank for a period of 8 to 24 hours with the ink filling port being placed downward after the ink filling port, ink supply port, and air conduit hole are sealed or to adopt an inspection method in which the ink tank is left in a dry preservation equipment at 45° C. or at 60° C. With an inspection of the kind, ink leakage from the ink filling port is noticed if any fine leakage takes place in the ink filling port or a phenomenon is observable that the portion of the negative pressure generating member, which is not wet by ink usually, is wet by ink sucked up by means of capillary force of the negative pressure generating member. Thus, those cartridge presenting ink leakage can be checked and excluded while still in the manufacturing stage. However, the execution of these inspecting steps to find ink leakage from the ink filling port not only results in the elongated production tact, but also, results in the reduced yield due to the defective products thus excluded. The costs of manufacture rises inevitably. 
     Therefore, it has been studied to apply a thermal welding method to a PP ball after it is pressed in the filling port for sealing it. However, with the usual thermal welding method, heat cannot be concentrated in the vicinity of the ink filling port for the intended thermal welding. The heat tends to affect the other portions of the ink cartridge, leading to the thermal influence exerted on the ink that has been contained. Also, there is a possibility that an adverse effect is produced on the reliability of the airtightness of the ink tank itself eventually. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a welding method capable of performing a welding locally within a limited range so as not to produce any adverse effect on the entire body of a product. 
     It is another object of the invention to provide a method for sealing the apertures of the ink cartridge for ink jet use to reliably prevent ink from leaking from the apertures of ink filling ports and others, and also, to provide an inexpensive ink cartridge for ink jet use formed by the application of such method. 
     It is still another object of the invention to provide an ink cartridge for ink jet use having a larger amount of ink that can be filled in it by making the aperture space smaller for the ink filling port and others. 
     It is a further object of the invention to provide a method for sealing the aperture of an ink cartridge for ink jet use having the aperture arranged therefor, including the steps of inserting a plug under pressure into the aperture; compressing a welding horn to the upper part of the plug to exert twisting vibration around the axis of the aperture in order to fuse the plug to be integrated with the inner wall of the aperture; and cooling the integrally fused portion after retracting the welding horn from such portion. 
     It is still a further object of the invention to provide a method for sealing the aperture of an ink cartridge for ink jet use by fusing a plug positioned in an inserted state in order to airtightly close the outer aperture. 
     It is another object of the invention to provide a method for sealing the aperture of an ink cartridge for ink jet use having the aperture arranged therefor, including the steps of inserting a plug under pressure into the aperture so that the upper part of the plug is exposed from the aperture; compressing a welding horn to the upper part of the plug to exert twisting vibration around the axis of the aperture in order to fuse the plug to be integrated with the circumference of the aperture; and cooling the integrally fused portion after retracting the welding horn from such portion. 
     It is still another object of the invention to provide a method for sealing the aperture of an ink cartridge for ink jet use by fusing the circumference of the aperture integrally with a part of a plug inserted into the aperture under pressure. 
     It is a further object of the invention to provide an ink cartridge for ink jet use having an aperture therefor wherein the aperture is arranged to fill in it with ink; 
     or to provide an ink cartridge for ink jet use wherein the material of the plug is the same as the material of the circumference of the aperture; 
     or to provide an ink cartridge for ink jet use wherein the melting point of the material of the plug is the same as that of the material of the circumference of the aperture; 
     or to provide an ink cartridge for ink jet use wherein the aperture is formed for an ink container that contains ink directly; 
     or to provide an ink cartridge for ink jet use wherein a container for a member that generates negative pressure is arranged adjacent to the ink container, which contains a negative pressure generating member to absorb and hold ink in it, and then, the ink container and the container for such member are conductively connected by use of gas-liquid exchanging means; 
     or to provide an ink cartridge for ink jet use wherein the plug positioned in the inserted condition is fused, and then, the outer aperture is airtightly closed. 
     With the structure described above, it is possible to provide an integrated structure without any interface by the utilization of friction heat to fuse and weld the plug to the ink filling port after the plug is pressed in it unlike the conventional structure where an interface exists because of the fitting of a plug that is just pressed in the ink filling port. Hence, the airtightness of the ink filling port can be held reliably, while the production yield is improved, making it possible to reduce the costs of manufacture significantly. 
     Also, with the structure described above, the ink container provided with the ink filling port is fixed by means for fusing the plug to be welded to the ink filling port by the utilization of friction heat, and then, only a part of the plug is fused by the friction heat to make the plug integrally formed with the circumference of the ink filling port or with its inner face by use of resin thus fused in order to airtightly close the ink filling port. Therefore, the portion integrally formed by fusion welding can be made smaller. Accordingly, it is possible to increase the amount of ink to be filled in the container to the extent that such portion needed for ink filling is made smaller, and to enhance the efficiency of ink consumption per ink cartridge. 
     Also, with this method, only the limited portion is fused to be welded. Therefore, there is no possibility that the other structural parts of the ink tank, and ink filled in the container are affected by such fusion welding. 
     Ink may be present in the vicinity of an ink filling port if the ink filling rate inside the container so as to improve an using efficiency of ink for an ink jet cartridge and prevent ink from jetting out caused by the expansion of internal air when the package is opened at the change of environment (particularly, when the atmospheric pressure decreases and the temperature rises). When the ink filling port is closed, a plug is inserted into the port under pressure and the port is preliminarily sealed and then the fusion bonding is performed by the frictional heat. Accordingly, the frictional force and the vibration is not applied without the preliminary sealing so that ink is not splattered in the vicinity of the ink filling port, thus remarkably improving the productivity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A,  1 B,  1 C,  1 D and  1 E are views illustrating each operation of a method for sealing the aperture of an ink cartridge for ink jet use until a plug is fused and welded to the ink filling port in accordance with one mode embodying the present invention; 
     FIGS. 2A,  2 B,  2 C,  2 D and  2 E are views illustrating each operation of a method for sealing the aperture of an ink cartridge for ink jet use until a plug is fused and welded to the ink filling port in accordance with another mode embodying the present invention; 
     FIGS. 3A,  3 B and  3 C are cross-sectional views showing one example of the ink cartridge for ink jet use to which the method of present invention is applicable for sealing the aperture thereof; 
     FIGS. 4A,  4 B and  4 C are views showing the contour of the other, ink cartridge for ink jet to which the opening sealing method according to the present invention may be applied; and 
     FIG. 5 is a cross-sectional view showing the contour of the other ink cartridge for ink jet to which the opening sealing method according to the present invention may be applied. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (Embodiment 1) 
     FIGS. 1A to  1 E are cross-sectional views showing a method for sealing the aperture of an ink cartridge for ink jet use in accordance with one mode embodying the present invention, respectively. FIG. 1A is a cross-sectional view showing the state where an ink filling port is plugged, and also, a welding horn. FIG. 1B is a cross-sectional view showing the operation to fuse the plug by use of the leading end of the welding horn. FIG. 1C is a cross-sectional view showing the operation to fuse and weld the plug and the ink filling port by use of the intermediate section of the welding horn. FIG. 1D is a cross-sectional view showing the state where the plug is fused and welded to the ink filling port. FIG. 1E is a view showing FIG. 1D, observed in the direction indicated by an arrow in FIG.  1 D. Here, in the present mode embodying the invention, the same reference marks are applied to the same elements as those represented in FIGS. 3A to  3 C, and the description thereof will be omitted. 
     In FIGS. 1A to  1 E, a reference numeral  101  designates an ink filling port to fill in the ink cartridge with ink;  102 , a plug to be pressed in the ink filling port  101 ; and  103 , a welding horn to fuse and weld the plug  102  with the inner face of the ink filling port  101 . 
     Here, the description will be made of an ink filling and a closing operation thereafter. 
     At first, an ink injection outlet (not shown) is pressed in the ink filling port  101  of an ink cartridge to inject a given amount of ink into the cartridge under pressure. Then, after the ink injection, the ink supply port  305  and the air conduit hole  306 , which are the other apertures of the ink container than the ink filling port  101 , are airtightly closed by a sealing material such as silicon rubber. In this state, the ink injection outlet is removed from the ink filling port  101 . 
     Subsequently, immediately after the removal of the ink injection outlet, the plug  102  is pressed in as shown in FIG. 1A to fit it with the ink filling port  101 . It is preferable to make the plug  102  spherical in consideration of the convenience of a pressure-in device and handling. Also, it is most preferable to use the same material of the ink container for the plug  102 . 
     Then, As shown in FIG. 1B, the welding horn  103  is arranged in a position facing the center line of the ink filling port  101 , and allowed to descend along the center line of the ink filling port  101  in the direction indicated by an arrow A. Immediately before the horn abuts upon the upper portion of the plug  102 , oscillation begins in the twisting directions (indicated by arrows B). The amplitude of this oscillation can be variable within a range of 0.05 to 0.1 mm. The frequency thereof is within 10 kHz to 30 kHz. Thus, the plug  102  is fused by the leading end of the welding horn  103 . In this respect, the most preferable condition of the fusion welding is: the amplitude is 0.08 mm at an oscillating frequency of 18 kHz, which is optimal. 
     Since the leading end  104  of the welding horn  103  oscillates in the twisting directions (indicated by arrows B), friction heat is generated on the portion where the plug  102  and the leading end  104  of the welding horn  103  are in contact to fuse the plug  102 . 
     Then, as shown in FIG. 1C, the plug  102  is fused by the leading end  104  of the welding horn  103 . The resin thus fused is blocked by the intermediate section  105  of the welding horn, and welded to the inner face portion of the ink filling port  101  by the application of friction heat being generated by the intermediate section  105  of the welding horn  103 . In this way, the ink filling port  101  and the plug  102  are formed integrally without any interface between them. 
     Lastly, as shown in FIGS. 1D and 1E, the welding horn  103  shifts upward to complete the fusion welding. Thus, the plug  102  is fused and welded to the ink filling port  101  to form an integral structure without any interface. Therefore, it is possible to reliably prevent ink from leaking due to the scratches or cracks that may exist on the plug  102  and the ink supply port  101 . Further, there is no need for any steps of inspection to find ink leakage, thus making it possible to reduce the costs of manufacture. 
     Also, the welding is locally possible only on the portion that needs it. Hence, there is no adverse effect to be produced on any other portions of the structure. 
     (Embodiment 2) 
     FIGS. 2A to  2 E are cross-sectional views showing a method for sealing the aperture of an ink cartridge for ink jet use in accordance with another mode embodying the present invention, respectively, and illustrating each of the operations until a plug is fused and welded to an ink filling port. Here, the welding position of the plug to the ink filling port is modified to be outside the ink container. FIG. 2A is a cross-sectional view showing the state where an ink filling port is plugged, and also, a welding horn. FIG. 2B is a cross-sectional view showing the operation to fuse the plug by use of the leading end of the welding horn. FIG. 2C is a cross-sectional view showing the operation to fuse and weld the plug and the ink filling port by use of the intermediate section of the welding horn. FIG. 2D is a cross-sectional view showing the state where the plug is fused and welded to the ink filling port. FIG. 2E is a view showing FIG. 2D, observed in the direction indicated by an arrow in FIG.  2 D. Here, in the present mode embodying the invention, the same reference marks are also applied to the same elements as those represented in FIGS. 1A to  1 E and FIGS. 3A to  3 C, and the description thereof will be omitted. 
     In FIGS. 2A to  2 E, a reference numeral  201  designates an ink filling port to fill in the ink cartridge with ink;  202 , a plug to be pressed in the ink filling port  201 ; and  203 , a welding horn to fuse and weld the plug  202  with the inner face of the ink filling port  201 . 
     Unlike the previous mode embodying the present invention, the upper part of the plug  202  pressed in the ink filling port  201  is protruded from the ink filling port  201  in this mode. Also, the intermediate section  205  of the welding horn  203  is configured to extrude it largely outward. These aspects characterize this mode embodying the present invention. 
     Here, after the ink injection is conducted as in the previous mode, the welding horn  203  descends as shown in FIG.  2 A and FIG. 2B in the same manner as in the previous mode to fuse the protruded upper part of the plug  202  by the leading end  204  of the welding horn  203 . 
     Then, as shown in FIG. 2C, the resin, which is fused by the leading end  204  of the welding horn  203 , is blocked by the intermediate section  205  of the welding horn, and welded on the circumference of the upper portion of the ink filling port  201  by the application of friction heat being generated by the intermediate section of the welding horn. In this way, the ink filling port  201  and the plug  202  are formed integrally without any interface between them. 
     Lastly, as shown in FIGS. 2D and 2E, the welding horn  203  shifts upward to complete the fusion welding. Thus, the plug  202  is fused and welded on the upper circumference of the ink filling port  201  to form an integral structure without any interface. Therefore, it is possible to reliably prevent ink from leaking due to the scratches or cracks that may exist on the plug  202  and the ink supply port  201 . Further, there is no need for any steps of inspection to find ink leakage, thus making it possible to reduce the costs of manufacture. Moreover, since the plug  202  can be fused and welded in the state where it protrudes upward from the ink filling port  201 , the space provided for the ink filling port that occupies the ink container is made smaller, hence increasing the filling amount of ink accordingly. 
     FIGS. 4A to  4 C are three-side views showing the appearance of an ink cartridge according to other embodiment to which the present invention may be applied, and FIG. 5 is a cross-sectional view typically showing its inside. 
     As shown in FIGS. 4A to  5 , the ink cartridge  100  of this embodiment presents an appearance almost like a U-shaped character, with a constant width. Provided at one end of the U-shaped character shape on the bottom is an ink supply port  100 A, which is thereby connected with an ink supply tube of an ink-jet head (not shown) for the supply of the ink. Also, provided above the U-shaped character shape is an atmosphere communication opening  100 B, thereby relieving pressure variations within the ink cartridge to maintain its internal pressure substantially constant. An ink inlet port  100 C is provided to fill the ink via this ink inlet port when manufacturing the ink cartridge. 
     As shown in FIG. 5, the ink cartridge of this embodiment is largely divided into two chambers. That is, formed inside this ink cartridge is a partition wall  111  which is substantially at an angle in an upper portion of the cartridge, and runs substantially like a crank in the lower portion, the ink cartridge  100  being divided into two chambers, an ink containing portion  114  and a negative pressure generating receiving portion  112 , and spaces  106 ,  107 . A communication channel  110  is provided at the lower end of the partition  111 , and a gas and liquid exchanging groove (not shown) is provided on the partition  111  in the vicinity thereof. 
     The ink containing portion  114  which is one chamber of the ink cartridge  100  is filled with the ink  116  at the initial time of use. Along with the ink consumption the gas (air) is introduced from the negative pressure generating member receiving portion which is the other chamber via the communication channel  110  by the exchange between gas and liquid, as will be described later, so that the air  115  gradually increases in volume. 
     The negative pressure generating member receiving portion  101  which is the other chamber and the spaces  106 ,  107  are constituted as follows. The negative pressure generating member receiving portion  101  is densely packed with an ink holding member  113  by conforming with the shape of its receiving portion. This ink holding member  113  is formed of a porous material like sponge to generate an apparent negative pressure relative to atmospheric pressure owing to its capillary force. Provided on the upper portion of the negative pressure generating member receiving portion  112  is a space  107  having a member  107 A for regulating the displacement of the ink holding member  113  disposed along the upper portion of the member  113  packed. Further, a space  106  in communication with this space  107  and leading to an atmosphere communication opening  100 B is provided. This space  106  has a substantially triangular shape with its volume gradually increasing toward the atmosphere communication opening  100 B. 
     In the ink cartridge with the above constitution, if the ink is consumed by e.g. being discharged by an ink-jet head (not shown), the ink is supplied via the supply port  100 A to the ink-jet head, but there may occur a non-uniform pressure distribution within the ink holding member  113 . And to make up for this non-uniform pressure distribution, the ink is moved from the ink containing portion  114  via the communication channel  110  to the ink holding member  113 . Then, the air  115  within the ink containing portion  103  undergoes a decrease in pressure (an increase in volume) corresponding to the above movement of the ink, but this decrease in pressure can be offset as the air introduced via the atmosphere communication opening  100 B into the ink cartridge  100  is finally conducted via the gas and liquid exchanging groove (not shown) of the partition  111  in contact with the ink holding member and the communication channel  110  to the ink containing portion  103 . 
     With the constitution of gas and liquid exchange as above described, if the ink within the ink containing portion  114  is used up, the ink held by the ink holding member  113  is then gradually consumed. 
     As described above, in accordance with the present invention, the plug is fused and welded in the ink filling port. Therefore, it is possible to reliably prevent ink from leaking due to the scratches or cracks that may exist on the plug and the ink supply port. Further, there is no need for any steps of inspection to find ink leakage, thus making it possible to reduce the costs of manufacture. 
     Also, since the plug can be fused and welded on the upper circumference of the ink filling port to form the structure integrally without any interface, the space provided for the ink filling port that occupies the ink container can be made smaller thereby to increase the amount of ink usable in the ink container accordingly, and also, improve the efficiency of ink consumption. 
     Also, the welding is locally effectuated only on the portion that needs it. There is no adverse effect to be produced on any other portions of the structure of an ink cartridge. 
     After the plug is inserted into the port under pressure and the port is preliminarily sealed and then the fusion bonding is performed by the frictional heat. Accordingly, the frictional force and the vibration is not applied without the preliminary sealing so that ink is not splattered in the vicinity of the ink filling port, thus improving the sealing properties. 
     The plug of the embodiments is a resin ball. However, the plug may be a flat disk as the ink filling port  100 C shown in FIG.  5 . If the sealing properties can be improved, other shapes such as rectangular may be also used. The material of the plug may be other material which may be fused and sealed other than the resin. In addition, the plug may be made not only a single member but also with a plug made by a core with the periphery thereof covered with the fusible material. The core is made from the different material. 
     Furthermore, the plug may be preferably fused and integral with a part of the container so as to improve the sealing properties. However, the plug may be partially integral with the container with a border surface. Either of the plug and the container may be fused. Even in this case, the sealing method as mentioned above according to present invention may be also applied. In the preceding embodiments, the torsion vibration fusion bonding is used. However, the ultrasonic fusion bonding in which the material itself generates the friction heat may be also used.