Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1998-04-14
2001-07-24
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06264315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink tank for use in the field of ink jet recording, and an ink jet cartridge made up of the ink tank and an ink jet recording head which are combined into a one-piece structure. More particularly, the present invention relates to an ink tank and an ink jet cartridge in which a negative pressure generating member is used as an ink absorbing member.
The present invention also relates to a method of filling ink into the ink tank or the ink jet cartridge.
It is to be noted that the term “ink” used in this specification means a liquid containing, in addition to ink of a type ejected from an ink jet recording head, a printing property improving liquid such as a treatment liquid used for improving permeability of a sheet of recording paper to ink.
2. Description of the Related Art
In the field of ink jet recording, an ink jet cartridge, which is made up of a recording head and an ink tank combined into a one-piece structure and which is detachably mounted onto a recording apparatus, has been employed to render the recording apparatus smaller in size and relatively free from maintenance. Known ink jet cartridges are constructed, for example, by permanently combining a recording head and an ink tank into a one-piece structure, or by separately fabricating a recording head and an ink tank and then combining them into a one-piece structure when used.
In any of the above conventional constructions of ink jet cartridges, the ink tank is required to have a mechanism for generating a back pressure (negative pressure) with respect to an ink flow supplied to the recording head so that ink is stably held in the tank and is supplied to the recording head in a stable manner during the recording process.
One of the simplest known methods of generating such a negative pressure is to employ a porous body, e.g., a urethane foam, as a negative pressure generating member (ink absorbing member) so as to utilize capillary attraction developed in the porous body. An ink tank for use in the above method generally comprises a receiving portion in which the ink absorbing member for storing ink is placed, an ink supply opening through which the ink is supplied to the ink absorbing member, and an open-air communication port through which air is taken into the receiving portion for allowing the ink to be smoothly supplied during the printing process.
As disclosed in Japanese Examined Patent Publication No. 5-23954, for example, one known ink tank of the above-described type is constructed by providing a rib to form a gap between an inner wall surface of the receiving portion and a corresponding surface of the ink absorbing member, and then communicating the gap with open air through an open-air communication port so that an air layer enclosed by the ink does not exist in the receiving portion.
The ink absorbing member to be placed in the receiving portion of the ink tank is preferably formed of a member that has been subjected to heat treatment and compression beforehand (referred to as a heat-compressed absorber hereinafter). When filling ink into an ink tank in which such a heat-compressed absorber is already placed, a depressurizing filling method is generally used to fill the ink. According to this filling method, ink is filled into the heat-compressed absorber by first depressurizing an inner space of the receiving portion of the ink tank which is not yet filled with ink. Next, ink is filled into the inner space of the receiving portion through the ink supply opening, and the ink spreads all over an entire surface of the heat-compressed absorber while maintaining a depressurized state in the receiving portion is maintained. Then, the inner space of the receiving portion is opened to communication with the open air after the injection of the ink is stopped.
Some ink tanks for use with ink jet cartridges are designed such that the ink tank is detachably mounted onto a carriage of the recording apparatus and has a narrow width in the scan direction of the carriage, so as to increase an amount of ink that can be stored in a limited space inside the recording apparatus. This type of ink tank therefore has a thin and flat outer configuration in a direction perpendicular to the scan direction of the carriage.
As a result of experiments, the inventors found that when ink is filled into the above-mentioned flat, thin ink tank by the depressurizing filling method, there may occur a phenomenon below.
Specifically, when the ink tank is depressurized, walls of a receiving portion of the ink tank, which are relatively weak in strength, may be deformed inward or toward a porous body (ink absorbing member) in the receiving portion such that the inner wall surfaces of the receiving portion come into contact with the ink absorbing member. For ink tank
301
that is flat and thin as shown in
FIG. 16
, in particular, those ones
302
W (referred to as maximum area wall surfaces hereinafter) of inner wall surfaces defining receiving portion
302
a
in housing
302
, which have a maximum surface area, are apt to deform or warp inward (i.e., in respective directions of arrows X), whereupon
302
a
maximum area wall surfaces
302
W of receiving portion
302
a
are brought into contact with corresponding surfaces of ink absorbing member
303
over large regions. If ink is injected into the ink tank while the tank is in the above contact state between maximum area wall surfaces
302
W and ink absorbing member
303
, the ink cannot infiltrate to the surfaces of ink absorbing member
303
located within the contact regions. If receiving portion
302
a
is then released from the depressurized state to be communicated with the open air in the above condition, the ink cannot evenly permeate into the ink absorbing member. In the worst case, the ink jet cartridge may suffer from a trouble in its ability of supplying the ink from the ink tank
301
to a recording head.
Such a phenomenon is more marked especially for an ink tank of the type wherein the maximum area wall surfaces of the receiving portion have a larger area than the total area of other wall surfaces adjacent to each of the maximum area wall surfaces. This problem was recognized for the first time by the inventors.
As a result of conducting further experiments, the inventors also found that, even with a single rib simply provided on each of the maximum area wall surfaces of the receiving portion as practiced in the prior art, the rib was buried in the ink absorbing member, and the contact region between the inner wall surface of the receiving portion and the corresponding surface of the ink absorbing member was not significantly reduced in size.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ink tank, an ink jet cartridge, and an ink filling method which can overcome the above-described problems encountered when ink is filled into an ink tank under depressurization.
As a result of conducting intensive studies with a view to achieve the above object, the inventors found that an area of contact between inner wall surfaces of a receiving portion of the ink tank and corresponding surfaces of an ink absorbing member in the receiving portion that occurred when filling ink into the ink tank under depressurization was reduced by providing a projection comprising a set of at least two ribs on, for example, each of those ones of the inner wall surfaces of the receiving portion, which have a maximum surface area, with a narrow spacing between the ribs. With this construction the ink was satisfactorily filled into the ink tank and permeated into the ink absorbing member efficiently.
In other words, the present invention provides an ink tank including a receiving portion having a polyhedral shape and receiving an ink absorbing member to store ink therein, an ink supply opening formed in part of the receiving portion for supplying the ink stored in the ink absorbing member to the outside, and an open-air communication port formed in part of the receiving portion apart fro
Nozawa Minoru
Tsukuda Keiichiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Le N.
Nghiem Michael
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