Abstract:
An ink tank including a casing having a front wall provided with a coupling, and a bag disposed in said casing and connected to said coupling, wherein the casing comprises a first shell including said front wall, and a second shell welded to the first shell.

Description:
This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 02078188.6 filed in Europe on Jun. 28, 2002, which is herein incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an ink tank comprising a casing having a front wall formed with a coupling, and a bag disposed in the casing and connected to the coupling. 
   2. Background Art 
   Several ink jet printers comprise an ink tank that has a comparatively large volume and is arranged to be stationary in the frame of the printer and is connected to a movable ink jet device through a flexible tube. In operation, ink supply to the ink jet device is achieved either by drawing ink out of the tank or by supplying air into the space inside of the casing but outside of the bag, so that the bag can be collapsed and the ink can be squeezed out. The supply of ink from the tank to the ink jet device may be assisted by gravitational forces. As an alternative, ink supply might be achieved through gravitational forces alone, provided that the casing can be vented. In any case, the bag prevents the ink from leaking out of the casing and/or from being dried out through contact with the air in the casing, whereas the casing prevents the bag from being damaged or squeezed and facilitates the handling of the ink tank. An example of an ink tank of this type is described in U.S. Pat. No. 6,264,318. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an ink tank that is easy to manufacture, and a method of manufacturing the same. 
   The ink tank according to the present invention comprises a first shell including a front wall, and a second shell welded to the first shell. 
   A method of manufacturing the ink tank of the present invention includes the steps of:
     molding a first and a second shell, the first shell having a front wall with a coupling formed therein, and an open end opposite to the front wall;   connecting a bag to the coupling such that a rear portion of the bag projects out of the open end of the first shell;   fitting the second shell over the projecting portion of the bag; and   welding the first and second shells together.   

   Since the first shell has an open end opposite to the front wall, it is possible to mold the coupling in the front wall, even when this coupling has a rather complicated structure, without causing any problems in withdrawing the molded shell from the mold. This greatly facilitates the manufacture of the casing formed with the coupling. Further, the bag may easily be connected to the coupling which is accessible through the open end of the first shell. Since the casing is completed and closed-off by welding the two shells together, with the second shell being fitted over the rear end of the bag, it is not necessary to provide any additional means for closing the casing. 
   The resulting ink tank has an integrated structure and cannot be re-opened, so that it is not possible to get access to the interior of the casing and to manipulate the bag. Since the two shells of the casing may be molded in almost any desired shape, it is possible to provide an ink tank which has an appealing design and one that satisfies practical needs. 
   When the two shells of the casing are connected by a continuous weld seam, it is possible to obtain an air-tight casing in which an elevated pressure can be generated for squeezing the ink out of the bag. In this case, a supply port for compressed air may preferably be molded in the second shell of the casing. On the other hand, when the ink is to be drained out of the bag by gravitational forces and, to this end, the casing has to be vented, the two shells may be welded together by spot-welding, so that minor gaps, which may serve as vent holes, remain at the seam between the two shells. 
   The bag is preferably accommodated in the casing in a U-shaped configuration, with both lateral portions of the bag being bent upwardly. In order to assist the bag in collapsing in the desired U-shape without forming undesired wrinkles, a wall-shaped collapsing induction fitment may be provided at the top wall of the first shell so as to extend into the interior of the casing. Then, when the bag is expanded, its top wall will fit around this fitment, so that the bag retains its U-configuration even in the expanded state, although it then almost fills the entire volume of the casing. When the bag collapses, it will reliably retain the U-shaped configuration which it already had in the expanded state. 
   Since the expansion and collapsing behavior of the bag is controlled by the walls of the casing and, as the case may be, by the collapsing induction fitment, the bag may be filled and emptied multiple times without any need for obtaining access to the interior of the casing, once the bag has been accommodated in the casing. 
   Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is a perspective view of an ink tank according to the present invention; 
       FIG. 2  is a longitudinal section through the casing of the ink tank; and 
       FIG. 3  is an exploded side elevation showing two shells forming a casing of the ink tank. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The ink tank shown in  FIG. 1  has a box-like casing  10  made of a synthetic resin. The casing comprises a first shell  12  and a second shell  14  which are both obtained through injection molding and are fitted together at a seam  16  which passes substantially vertically through the side walls  18  of the casing and bisects the casing into approximately two halves. 
   On the outer surfaces of the side walls  18 , the first and second shells  12 ,  14  are formed with mating flanges  20  which extend along the seam  16  and engage each other in the plane of the seam  16 . These flanges  20  serve to improve the rigidity of the side walls  18  and each flange has two outwardly projecting ears  22  which are fixed to one another by spot-welding so as to form the two shells  12 ,  14  into an integral structure. 
   The first shell  12  has guide rails  24  projecting from its top and bottom surfaces. These guide rails  24  serve to guide the casing  10  when the same is inserted into a socket (not shown) of an ink jet printer in order to connect the ink tank to the ink supply system of the printer. 
   In the second shell  14 , the rear wall  26  of the casing is provided with a lens-shaped depression  28 . In order to disengage the casing  10  from the socket of the printer, the casing  10  must be pushed forwardly and upwardly. To this end, a user may engage his finger into the depression  28 . 
   On the top side, the second shell  14  has a roof-shaped portion  30  which is limited on the top side by an upwardly sloping wall  32  and a downwardly sloping wall  34 . A shallow rectangular recess  36  in the upwardly sloping wall  32  is intended for accommodating a tag which may be used for example for indicating the type and color of the ink contained in the tank. 
   As is shown in  FIG. 2 , the casing  10  accommodates a bag  38  made of flexible liquid-tight material and filled with ink. A spout  40  formed in the front lower edge of the bag  38  is connected to a coupling  42  which penetrates a front wall  44  of the first shell  12  and is molded integrally with the first shell. Thus, when the ink tank has been inserted in the socket of the printer, the coupling  42  connects to the ink supply system of the printer, so that the ink may be withdrawn from the bag  38 . This will cause the bag  38  to collapse, and since the seam  16  is not air-tight, the interior of the casing  10  is vented through minor gaps formed at the seam  16 . 
   As is further shown in  FIG. 2 , the first shell  12  is formed with an internal wall  46  which extends from the top wall into the interior of the casing and is arranged in a longitudinal median plane of the casing. The wall  46  forms a fold in the bag  38 , so that the lateral portions of the bag  38  are bent upwardly around the wall  46 . When the ink is withdrawn from the bag, the bag collapses into a sheet-like configuration, and the wall  46  induces the collapsing of the bag in such a manner that it will retain a U-shaped configuration with the lateral portions of the bag  38  being bent upwardly. When the bag  38  is refilled with ink through the coupling  42 , the bag is expanded again so that it fills the interior of the casing  10  around the wall  46 . 
   Coupling  42  comprises a valve mechanism that prevents the leaking out of the ink when bag  38  is filled with ink and enables the bag  38  to be refilled again with ink. The coupling only has one connection for ink and due to the construction of the ink tank and casing no extra coupling for the inlet or outlet of air is needed. When, during the process of filling, the bag  38  expands and the air from the interior of the casing  10  is pressed out through the non-airtight seam  16 . 
   As is shown in  FIG. 3 , the downwardly sloping wall  34  of the roof-shaped portion  30  is formed integrally with the first shell  12 , so that the top leg of the seam  16  extends along the top corner between the walls  32  and  34 . As a result, the second shell  14  has an open end facing towards the front side of the casing  10  without forming any undercuts, so that the second shell may readily be removed from the mold in the injection molding process. Similarly, the first shell  12  is flared towards an open end opposite to the front wall  44 . Thus, both shells  12 ,  14  can easily be formed by injection molding. 
   When the first and second shells  12 ,  14  have been molded, the bag  38  is inserted into the first shell  12  from the open rear end thereof and is connected to the coupling  42 . Then, the second shell  14  is fitted over the projecting rear end of the bag  38 , as is shown in  FIG. 3 . Finally, the shells  12 ,  14  are fixedly connected with one another by spot welding at the ears  22 , e.g. by means of an ultrasonic welding tong. 
   The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.