Ink-jet cartridge with a negative pressure ink reservoir

An ink-jet cartridge with a negative pressure ink reservoir includes a rigid body provided with an ejecting device; an ink reservoir provided within the rigid body, the ink reservoir including two relatively movable plates and a plate body having resilience. The plate body is provided between the two flat plates, and is sealed with the circumferences of the two flat plates to form an enclosed ink reservoir. During ink-jet printing, the pressure within the ink reservoir decreases and the two plates move closer to each other to compress the plate body and the resilience of the plate body causes a negative pressure within the ink reservoir that prevents ink leakage from the ink-jet cartridge.

FIELD OF THE INVENTION
 The present invention relates to an ink-jet cartridge for an ink-jet
 printing apparatus, and in particular, to an ink-jet cartridge with a
 negative pressure ink reservoir that provides a negative pressure by the
 resilience of the ink reservoir itself to prevent ink leakage from the
 ink-jet cartridge.
 BACKGROUND OF THE INVENTION
 An ink cartridge structure for a conventional ink-jet printing apparatus,
 as disclosed in U.S. Pat. No. 5,409,134, provides a fluid pressure
 regulating element in the ink reservoir for controlling the back pressure
 within an operating range that is suitable for preventing ink leakage
 while permitting the ejecting device to eject ink drops during printing.
 As shown in this prior patent, the fluid pressure regulation in the rigid
 ink reservoir can be controlled by flexible bags that are mounted to a
 curved spring. The pressure within the rigid ink reservoir drops instantly
 as the ink is ejected from the rigid ink reservoir via the ejecting
 device. At this moment, the atmosphere pressure is larger than the
 pressure within the rigid ink reservoir. Thus, ambient air will flow into
 the flexible bag so that the ink can be ejected smoothly while printing.
 Moreover, the expansion of the bag causes the deflection of the adjacent
 springs and thus decreases the ink pressure in the ink reservoir so that
 the zero ink leakage effect during printing can be achieved.
 In another ink cartridge for an ink-jet printing apparatus, for example,
 the ink cartridge disclosed in U.S. Pat. No. 5,767,882, in order to avoid
 ink leakage in the process of ink-jet printing, a pressure regulating
 element is usually provided in the ink reservoir for keeping the pressure
 within the ink reservoir at a negative pressure so that there is no ink
 leakage in the printing process.
 However, in both of these prior art ink-jet cartridges, a pressure
 regulating means has to be provided in the ink-jet cartridge and this
 causes the complexity in structure and assembly of the ink-jet cartridge.
 SUMMARY OF THE INVENTION
 It is accordingly an object of the invention to provide an ink-jet
 cartridge with a negative pressure ink reservoir that is simple in
 structure and easy to assemble. Thereby, the manufacturing cost of the
 ink-jet cartridge can be reduced.
 Another object of the invention is to provide an ink-jet cartridge with a
 negative pressure ink reservoir that generates a negative pressure during
 ink-jet printing so that ink leakage from the ink-jet cartridge can be
 prevented.
 To achieve the above objects, an ink-jet cartridge with a negative pressure
 ink reservoir of the invention comprises: a rigid body provided with an
 ejecting device; an ink reservoir provided within the rigid body, the ink
 reservoir including two relatively movable plates and a negative pressure
 means. The negative pressure means is embodied as a plate body having
 resilience, is provided between the two flat plates, and is sealed with
 the circumferences of the two flat plates to form an enclosed ink
 reservoir.
 Thus, during ink-jet printing, the pressure within the ink reservoir
 decreases and the two plates move closer to each other to compress the
 plate body and the resilience of the plate body causes a negative pressure
 within the ink reservoir that prevents ink leakage from the ink-jet
 cartridge.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to FIGS. 1 and 2, an ink-jet cartridge with a negative pressure
 ink reservoir in accordance with a preferred embodiment of the invention
 comprises a rigid body 12 having an output port 10 on which is mounted an
 ejecting device 14 for ejecting the ink from the ink-jet cartridge during
 printing. The ejecting device 14 can be either of the hot vapor bubble
 type or of the piezoelectric type.
 The rigid body 12 includes a hollow frame 16 and two cover plates 18 that
 cover the two sides of the hollow frame 16 respectively to form an
 enclosed space.
 An ink reservoir 20 for holding ink is provided in the rigid body 12 and is
 in communication with the output port 10 so that the ejecting device 14
 can eject the ink from the ink reservoir 20. The ink reservoir 20 includes
 two relatively movable flat plates 22 and a negative pressure means that
 is embodied as a plate body 28 having at least a crease 26. The plate body
 28 is positioned between the two flat plates 22 and is sealed with the
 circumferences of the two flat plates to form an enclosed ink reservoir
 20. Thus, when the ink reservoir 20 is compressed and then released, a
 negative pressure is generated in the ink reservoir 20 by the resilience
 thereof. The two flat plates 22 and the plate body 28 can also be
 integrally formed, for example by a plastic injection molding process.
 Referring to FIG. 3, when the ink within the ink reservoir 20 is ejected
 for printing, the ambient pressure pushed the two flat plates 22 closer
 and the plate body 28 having at least a crease is deformed. A negative
 pressure is generated within the ink reservoir 20 by the resilience of the
 plate body 28. The negative pressure prevents ink leakage from the ink-jet
 cartridge. Moreover, the plate body 28 can have an arc-shaped surface as
 shown in FIG. 4 and has resilience when it is deformed.
 Referring to FIG. 5, a plate body 28 is assembled between two flat plates
 22 and the crease on the plate body 28 extends outward beyond the
 circumferences of the two flat plates 22. With respect to this structure,
 when the ink within the ink reservoir 20 is about to be exhausted, the two
 flat plates 22 can be substantially pressed together and all the ink
 within the ink reservoir 20 can be ejected without any ink left.
 Therefore, an ink-jet cartridge with a negative pressure ink reservoir of
 the invention can generate a negative pressure within the ink reservoir by
 the resilience of the ink reservoir itself to prevent ink leakage from the
 ink-jet cartridge. Moreover, no additional negative pressure is needed in
 the ink-jet cartridge. Obviously, this helps to reduce the manufacturing
 cost and assembling cost. An ink reservoir integrally formed by plastic
 injection molding is even easier to manufacture.
 While the invention has been described by way of example and in terms of
 three preferred embodiments, it is to be understood that the invention is
 not limited to the disclosed embodiments. To the contrary, it is intended
 to cover various modifications. Therefore, the scope of the appended
 claims should be accorded the broadest interpretation so as to encompass
 all such modifications.