Ink cartridge

An ink cartridge includes a cartridge case having a partition in it, which partitions its interior into an ink chamber and a storage chamber. The ink chamber contains ink, and the storage chamber contains a member impregnated with ink. The partition has an ink passage formed through it. The relationship between the width "w" of the passage and the width "d" of the storage chamber meets the expression w.ltoreq.d/2. Even if gaps remain along edges of the storage chamber around the member, air bubbles are restrained from flowing from the gaps through the passage into the ink chamber.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an ink cartridge having an ink chamber 
filled with ink and a storage chamber containing a porous member 
impregnated with ink. In particular, the invention relates to improvements 
in the ink passage between the ink chamber and the storage chamber. 
2. Description of Related Art 
In an ideal ink cartridge of this type, the ink in the storage chamber is 
first consumed through the ink passage and the ink chamber. Then, air is 
supplied from the storage chamber to the ink chamber, while ink in the ink 
chamber is consumed. The cartridge is connected to a recording head 
mounted on the carriage of a printer. Because the carriage reciprocates at 
high speed, the air in an upper portion of the ink chamber is formed into 
bubbles, which are liable to mix with the ink in this chamber. If air 
mixes with the ink, the recording performance of the printer lowers. 
It is preferable that the porous member be fitted in close contact with the 
inner surfaces of the storage chamber without gaps. Actually, however, 
gaps or spaces remain along edges of the storage chamber around the porous 
member. The gaps are liable to be air passages. 
Japanese Patent Laid-Open Publication No. H.6-238908 discloses a 
conventional ink cartridge in practical use for supplying ink to a 
recording head of an ink jet recorder. The cartridge includes a case 
partitioned into a liquid chamber and a storage chamber by a partition 
formed therebetween. The liquid chamber contains ink, and the storage 
chamber contains a porous member impregnated with ink. The liquid chamber 
has an ink supply hole, through which ink can be supplied to the head. The 
storage chamber has an air vent formed through its top wall. The partition 
between the chambers has a short ink passage formed through it at a 
predetermined height from its bottom. The passage is fitted with a filter 
on its side adjacent to the storage chamber. The filter can remove fine 
foreign substances produced mainly from the porous member. 
The size, the shape, the position, etc. of the ink passage in this 
cartridge are neither disclosed nor suggested to prevent air from flowing 
from the storage chamber through the passage into the liquid chamber. The 
ink being sucked from the porous member into the liquid chamber is 
resisted higher than the air being sucked through the gaps along edges of 
the storage chamber, and through the passage into the liquid chamber. 
Therefore, if the passage is wide, air is liable to flow into the liquid 
chamber when ink in the cartridge is consumed and negative pressure 
develops in the liquid chamber. As a result, the ink in the porous member 
is difficult to supply to the liquid chamber. This lowers the ink 
consumption rate (ink consumption/amount of filled ink) of the cartridge. 
Besides, air may mix with the ink in the liquid chamber, thereby lowering 
the recording performance of the recording head. In particular, when the 
filter is clogged, and/or when the ink viscosity resistance is high at low 
temperature, the negative pressure in the liquid chamber may be high. If 
the negative pressure is high, a remarkable amount of air may flow into 
the liquid chamber. 
Japanese Patent Laid-Open Publication No. H.6-255122 discloses another ink 
cartridge for supplying ink to a recording head of an ink jet recorder. 
The cartridge includes a case partitioned into a main ink storage chamber 
and an auxiliary ink storage chamber by a partition formed therebetween. 
The main chamber contains ink, and the auxiliary chamber contains a porous 
member impregnated with ink. The main chamber has an ink supply hole 
formed through its bottom wall. The auxiliary chamber has an air vent 
formed through its top wall. The partition between the chambers has an ink 
passage formed through its bottom. The passage connects the chambers and 
is fitted with a filter. 
When ink is supplied from the main ink storage chamber of this cartridge 
through the supply hole to the recording head, some negative pressure 
develops in this chamber. In the meantime, ink is supplied from the porous 
member in the auxiliary chamber through the passage to the main chamber, 
and air is introduced through the vent into the auxiliary chamber. While 
ink is flowing through the fine porous passages in the porous member, the 
ink is subjected to viscous (viscosity) resistance, capillary 
(capillarity) resistance, etc. If foreign substances stick to the filter, 
they resist the ink flowing through it. As a result, the negative pressure 
develops in the main chamber. 
For the size, the shape, the position, etc. of the ink passage in this 
cartridge as well, nothing is disclosed to prevent air from flowing 
through the passage into the main ink storage chamber. In addition, the 
passage is positioned at the bottom of the partition, and extends nearly 
over the whole width of the auxiliary chamber. Therefore, air which has 
entered the gaps along edges of the auxiliary chamber flows easily into 
the main chamber. This prevents the ink in this cartridge, too, from being 
consumed ideally, thus lowering the ink consumption rate of the cartridge. 
The recording performance of the recording head is lowered by air mixing 
with the ink in the main chamber. 
The inventors made an experiment with an ink cartridge of the type 
mentioned first. The experiment has proved that, if the distance between 
the ink passage and each of the edges of the storage chamber is too short, 
air is liable to flow from the gaps along edges into the passage. In 
addition, if the ink chamber is excessively large in comparison with the 
storage chamber, air is liable to mix with the ink in the ink chamber. 
This is not preferable in terms of recording performance. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an ink cartridge of this type 
in which air is restrained from flowing into the ink chamber before a 
sufficient amount of ink in the storage chamber is consumed. 
It is another object to provide an ink cartridge of this type which can 
supply a recording head stably with ink. It is a further object to provide 
an ink cartridge of this type which has a high ink consumption rate. 
In accordance with the invention, an ink cartridge is provided, which 
includes a cartridge case. The case includes a partition therein which 
partitions the interior of the case into an ink chamber and a storage 
chamber. The partition has an ink passage formed therethrough. The 
relationship between the width "w" of the passage and the width "d" of the 
storage chamber satisfies the expression w.ltoreq.d/2. The case has an ink 
supply hole through which the ink chamber communicates with the outside of 
the case. The case also has an air vent through which the storage chamber 
communicates with the outside of the case. The ink chamber is filled with 
ink. The storage chamber contains a member impregnated with ink. 
The impregnated member in the storage chamber may be a foamed porous 
member. The ink cartridge may be used with an ink jet printer, which 
includes a carriage supporting a recording head. When mounted on the 
carriage, the cartridge is connected to the head. While ink is consumed at 
the head connected to the cartridge, ink in the ink chamber is supplied 
through the supply hole to the head. When ink is supplied from the ink 
chamber to the head, with the porous member impregnated with ink, some 
negative pressure develops in the ink chamber. In the meantime, ink is 
supplied from the porous member through the passage to the ink chamber, 
and air is introduced through the vent into the storage chamber. 
As further ink is supplied through the supply hole to the recording head, 
ink in the porous member is consumed. When the ink level in the storage 
chamber has reached the ink passage, air in this chamber is introduced 
through the passage into the ink chamber, while ink in the ink chamber is 
consumed. Thus, the ink in the storage chamber is consumed through the 
passage and the ink chamber before the ink in the ink chamber is consumed. 
Thereafter, air in the storage chamber is supplied to the ink chamber, 
while ink in the ink chamber is consumed. 
The porous member should be fitted in close contact with the inner surfaces 
of the storage chamber. Actually, however, gaps or spaces remain along 
edges of the storage chamber around the porous member. The gaps are liable 
to be air passages. 
As stated above, the storage chamber is "d" in width. The ink passage is 
d/2 or less in width as also stated, and may be positioned near the bottom 
of the partition. Therefore, even though there are gaps along edges of the 
storage chamber, air (bubbles) is restrained from moving from the edges to 
the passage. As a result, less air is introduced through the gaps into the 
ink chamber by the negative pressure in this chamber before a sufficient 
amount of ink in the storage chamber is consumed. 
It is therefore possible to consume ink in the cartridge ideally by 
consuming the ink in the storage chamber prior to the ink in the ink 
chamber. This can raise the ink consumption rate (ink consumption/amount 
of filled ink) of the cartridge. It is also possible to prevent a large 
amount of air from mixing with the ink in the ink chamber. This can supply 
ink stably to the recording head, thereby preventing the recording 
performance of the head from lowering. 
The ink passage may be spaced at a distance which is d/4 or longer from 
each side wall of the storage chamber. The distance may be 2 mm or longer, 
and the passage may be 4 mm in width or narrower. 
If the ink passage is positioned at the bottom of the partition, it is 
possible to raise the ink consumption rate for the following reason. When 
the ink in the cartridge has been consumed, the ink level in the storage 
chamber reaches the ink passage, and air is introduced from this chamber 
through the passage into the ink chamber. Therefore, by positioning the 
passage at the partition bottom, it is possible to consume ink in the 
storage chamber to the maximum. 
The ink passage may otherwise be positioned at a predetermined height from 
the bottom of the partition. In this case, the passage is positioned away 
from the edge between the partition and the bottom of the storage chamber. 
As a result, air (bubbles) is restrained from flowing from the edge into 
the passage. The passage may be positioned at a height of about 1.5 mm 
from the partition bottom. 
The ink passage may be rectangular in section in parallel to the partition, 
and greater in width than in height. In this case, it is possible to 
shorten the distance between the top of the passage and the bottom of the 
storage chamber. It is therefore possible to improve the ink consumption 
rate. 
The ink passage may be positioned substantially in the middle of the 
partition between both side walls of the storage chamber. In this case, 
the passage is spaced at equal distances from the edges each between the 
partition and one of both side walls of the storage chamber. Consequently, 
air is restrained from flowing from both of the edges into the passage. 
The ink chamber may be 0.5 cc or smaller in volume to restrain the ink in 
it from bubbling even while the carriage which supports the ink cartridge 
is moving at high speed. The volume ratio of the ink chamber to the 
storage chamber may be about 1/13 or less. 
The partition may have an extension to the ink passage. The extension 
protrudes into the storage chamber. In this case, air can flow from the 
storage chamber through the extension and the passage into the ink 
chamber. Because the extension presses the member impregnated with ink, 
air is restrained from flowing into the pressed portion of the member 
around the extension. This restrains air from being introduced into the 
passage. 
The ink cartridge is suitable for an ink jet printer. If the cartridge is 
used with an ink jet printer, the member impregnated with ink also 
functions to maintain the meniscuses of the printing head. Because all the 
ink in the member can be consumed, the cartridge is useful for this type 
of printer, and can stably supply ink to the recording head. In 
particular, the invention is suitable for a disposable cartridge.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
With reference to FIGS. 1 and 2, an ink jet recorder 1 according to an 
embodiment of the invention can print color images on recording paper P or 
another recording medium by ejecting a cyanogen ink (C: blue-green), a 
magenta ink (M), a yellow ink (Y) and a black ink (K). The recorder 1 
includes a body frame 3 covered with a body cover 2. The frame 3 includes 
a vertical rear plate and vertical plates 3a, 3b and 3c extending 
perpendicularly to the rear plate. The frame 3 supports a paper feeder 10, 
a carriage drive 20 and a recording mechanism 30 for recording color 
images on a recording paper P. 
The recording mechanism 30 includes a carriage 21, which supports a holder 
31 fixed to its top and shaped like a box. Four ink cartridges 50-53 can 
be mounted removably on the holder 31. The cartridges 50-53 contain a 
cyanogen ink, a magenta ink, a yellow ink and a black ink, respectively. 
The paper feeder 10 includes a platen 11 made of rubber. The platen 11 is 
fixed to a laterally extending horizontal shaft 11a, both ends of which 
are supported rotatably by the frame plates 3a and 3b. The plate 3b 
supports a feed motor 12, which can be driven by a control unit (not 
shown) to rotate the platen shaft 11a through a gear mechanism 13 
consisting of gears 14-17. 
The carriage drive 20 includes a guide rod 22 extending in front of and in 
parallel to the platen 11. Both ends of the rod 22 are fixed to the frame 
plates 3a and 3c. The frame 3 also includes a guide rail 3d formed at its 
front end in front of and in parallel to the rod 22. The carriage 21 is 
supported slidably on and along the rod 22 and the rail 3d. 
The carriage drive 20 also includes a driven pulley 25 supported rotatably 
on the right (left in FIG. 2) end of the frame 3. The drive 20 further 
includes a stepping motor 26 mounted on a left end portion of the frame 3, 
and a drive pulley 27 fixed to the output shaft of this motor 26. An 
endless timing belt 28 runs between the pulleys 25 and 27, and is 
connected to the carriage 21. The control unit (not shown) can drive the 
motor 26 to move the carriage 21 right and left. 
The holder 31 on the carriage 21 includes a rear wall 31a. Four recording 
heads 35-38 are fixed to the rear side of the wall 31a, and arranged 
horizontally side by side. The heads 35-38 are associated with the ink 
cartridges 50-53, respectively. Each of the heads 35-38 has jet nozzles 
(not shown) formed in it, which may be 64 in number. Each of the heads 
35-38 includes a jet mechanism (not shown), which has piezoelectric 
elements, for ejecting ink out through the nozzles. Four ink supply pipes 
40-43 are fixed to the holder wall 31a, extend through it and protrude 
forward from it. The pipes 40-43 are connected to the heads 35-38, 
respectively. As shown with the two dot chain lines in FIG. 3, the front 
end of each of the pipes 40-43 is fitted with a seal adapter 45. The rear 
end of each of the ink cartridges 50-53 is fitted with an adapter 85. When 
each of the cartridges 50-53 is mounted on the holder 31, the associated 
adapters 45 and 85 are connected together. 
Because the ink cartridges 50-53 are basically identical in structure, only 
the cartridge 50 will be described below, representing all the cartridges. 
Exceptionally, because the cartridge 53 for the black ink is used more 
frequently, it is somewhat wider than the other cartridges. 
As shown in FIGS. 3-6, the ink cartridge 50 includes a cartridge case 60 
made of synthetic resin. The case 60 includes a body 61 which is open at 
its top and a lid 62 covering the top. The case body 61 includes a 
partition wall 63 extending perpendicularly to, and formed integrally 
with, both its side walls 61a and its bottom. The partition wall 63 
partitions the interior of the case 60 into a rear chamber 65 and a front 
chamber 66. The volume ratio of the rear chamber 65 to the front chamber 
66 is about 1:13 or less. 
The rear chamber 65 is filled with ink I, and the front chamber 66 contains 
a porous member 68 impregnated with ink I. The porous member 68 may be 
sponge or other material having a mass or aggregation of air bubbles. The 
volume of ink with which the member 68 can be impregnated may be about 75% 
of the volume of this member. As shown in Table 1, the rear chamber 65 may 
contain 1.1 cc of ink, which is similar in volume to this chamber. The 
front chamber 66 (porous member 68) may be 14.5 cc in volume. As also 
shown, the front chamber 66 may contain 10.7 cc of ink, which is about 75% 
by volume of this chamber. In total, the cartridge 50 may contain 11.8 cc 
of ink. 
TABLE 1 
______________________________________ 
AMOUNT OF CONTAINED INK (cc) 
______________________________________ 
REAR CHAMBER 1.1 
FRONT CHAMBER 10.7 (14.5) 
REAR CHAMBER + 11.8 
FRONT CHAMBER 
______________________________________ 
The partition wall 63 has an ink passage 67 formed through it at its bottom 
to connect the chambers 65 and 66. Ink can flow through the passage 67 
between the chambers 65 and 66. 
With reference to FIGS. 6 and 3, the width "d" of the chambers 65 and 66 
may be 8 mm. As shown in FIG. 6, the ink passage 67 takes the form of a 
laterally wide rectangle in section in parallel with the wall 63. The 
rectangle is d/2 in width, which may be 4 mm, and d/8 in height, which may 
be 1 mm. The passage 67 is positioned in the middle of the partition wall 
63 between the side walls 61a, and spaced at a distance of d/4 from each 
side surface 66a of the front chamber 66. 
As shown in FIG. 3, the cartridge case 60 includes a handle 70 protruding 
forward from the top of its front end. The handle 70 can be held by one's 
fingers when the ink cartridge 50 is mounted on and removed from the 
holder 31. The handle 70 has an air passage 71 formed in it in the form of 
a maze and an air vent 72 formed through its front wall. The front chamber 
66 communicates with the atmosphere through the passage 71 and the vent 
72. Even if the side walls 61a of the case 60 are pressed, or the interior 
of the case 60 is pressurized otherwise, with the cartridge 50 filled with 
ink, it is possible to prevent the ink from leaking out by causing the ink 
in the front chamber 66 to flow into the air passage 71. 
As shown in FIG. 3, the rear wall 61b of the cartridge case 60 has a recess 
74 formed on its rear side near its bottom. As shown in FIGS. 3 and 5, the 
rear wall 61b also has an ink supply hole 73 formed through it in the 
center of the recess 74 to supply ink to the supply pipe 40. The outer end 
of the hole 73 is covered with a filter 80 made of stainless steel. The 
filter 80 is fixed by the adapter 85 being engaged with and welded to the 
recess 74. The microporous meshes of the filter 80 are finer than the 
cellular pores of the porous member 68. Therefore, when the cartridge 50 
filled with ink is removed from the holder 31, the surface tension of the 
ink on the filter 80 prevents the ink in the cartridge 50 from leaking 
through the hole 73. 
The rear wall 61b of the cartridge case 60 includes an ink rectifier 75 
formed integrally with it for blocking a lower portion of the inner end of 
the ink supply hole 73. The rectifier 75 has a guide slope 76 formed on 
its rear side. When the cartridge 50 is made, the porous member 68 
impregnated with no ink is squeezed into the case body 61, and then ink is 
supplied through the hole 73 to the rear chamber 65. The ink being 
supplied through the hole 73 is guided or directed by the rectifier slope 
76 to an upper portion of the rear chamber 65. It is therefore possible to 
fill the rear chamber 65 with ink without air remaining in this chamber. 
When the ink cartridge 50 is mounted on the holder 31, the adapter 85 
around the ink supply hole 73 is engaged and connected with the seal 
adapter 45 on the supply pipe 40. Then, when ink is sucked from the 
cartridge 50 through the pipe 40 and the recording head 35 by a suction 
device (not shown), the ink fills both sides of the filter 80. As a 
result, no surface tension acts on the ink on the filter 80 any longer. 
This allows the ink in the rear chamber 65 to be supplied through the pipe 
40 to the head 35. As ink is consumed at the head 35, ink is supplied from 
the rear chamber 65 through the hole 73, filter 80 and pipe 40 to the head 
35. 
When ink is supplied from the rear chamber 65 to the recording head 35, 
with the porous member 68 impregnated with ink, some negative pressure 
develops in the rear chamber 65. In the meantime, ink is supplied from the 
member 68 through the passage 67 to the rear chamber 65, and air is 
introduced through the vent 72 and the passage 71 into the front chamber 
66. Because the front chamber 66 is exposed to the atmospheric pressure, 
the ink level in it lowers as ink is consumed. Because the top of the rear 
chamber 65 is closed with the lid 62, this chamber 65 is kept filled with 
ink while ink is consumed until the ink level in the front chamber 66 
reaches the ink passage 67. 
When the ink level in the front chamber 66 has reached the ink passage 67, 
air in this chamber 66 is introduced through the passage 67 into the rear 
chamber 65, while ink in the rear chamber 65 is consumed. In other words, 
the ink in the front chamber 66 is consumed through the passage 67 and the 
rear chamber 65 prior to the ink in the rear chamber 65. Thereafter, air 
in the front chamber 66 is supplied to the rear chamber 65, while ink in 
the rear chamber 65 is consumed. 
The porous member 68 impregnated with ink should be fitted in close contact 
with the inner surfaces of the front chamber 66. Actually, however, gaps 
or spaces remain along edges 66c of the front chamber 66 around the member 
68. The gaps are liable to be air passages. 
It is ideal and most preferable that the ink in the front chamber be 
consumed prior to that in the rear chamber. However, because the ink in 
the conventional cartridges is not consumed in such an ideal manner, their 
ink consumption rates (ink consumption/amount of filled ink) are very low 
for the following reason. 
Although the porous member in the front chamber of each conventional 
cartridge is impregnated with ink, air in this chamber flows into the rear 
chamber. Consequently, ink in the rear chamber is consumed and the ink 
remaining in this chamber decreases. In the meantime, ink is difficult to 
supply from the porous member to the rear chamber and remains in the front 
chamber. 
Therefore, the inventors speculated that the ink consumption rate of the 
ink cartridge 50 might be related to the distance between the ink passage 
67 and each edge 66c of the front chamber 66. Then, the inventors made 
sample cartridges like the cartridge 60. The width "d" of the front 
chamber (66) of each sample cartridge was 8 mm. The ink passages (67) of 
the partition walls (63) differed in width. Ink consumption rates P (ink 
consumption/amount of filled ink.times.100) were measured for these 
cartridges. 
Table 2 shows the results of the experiment. For the passage width of 8 mm, 
the ink consumption rates P were as very low as 30-45%. Even for the 
widths of 7 mm and 5 mm, the rates P were as not very high as 50-65% and 
55-70%, respectively. For the widths of 4 mm, 2.5 mm and 2 mm, the rates P 
were as high as 70-85%, 75-85% and 75-85%, respectively. For the widths of 
2.5 mm and 2 mm, the remaining 15-25% of the filled ink was the ink 
dispersed finely in the porous member (68) and remaining there due to 
capillarity. 
TABLE 2 
______________________________________ 
INK PASSAGE WIDTH (mm) 
INK CONSUMPTION RATE P (%) 
______________________________________ 
8 30-45 
7 50-65 
5 55-70 
4 70-85 
2.5 75-85 
2 75-85 
______________________________________ 
This experiment has proved that, if the distance between the ink passage 
and each edge of the front chamber is too short, air is liable to flow 
through the gaps along the edges into the passage, thereby lowering the 
ink consumption rate P. It has also been proved that, if the passage width 
is 4 mm or narrower, that is to say, if the passage is spaced at a 
distance of d/4 (2 mm) or farther from each side surface of the front 
chamber, air does not easily flow through the gaps along the edges into 
the passage, thereby raising the consumption rate P. 
As stated already, the ink passage 67 of this embodiment is d/2 in width, 
and spaced at a distance of d/4 from each side surface 66a of the front 
chamber 66. 
As stated above, the ink cartridge 50 has a rear chamber 65 and a front 
chamber 66 on both sides of a partition wall 63. The wall 63 has an ink 
passage 67 formed through it at its bottom. The front chamber 66 has a 
width "d" between both its side surfaces 66a. The passage 67 is spaced at 
a distance of d/4 from each side surface 66a. This makes it possible to 
restrain air from flowing through the gaps 95 (FIG. 6) along the edges 66c 
into the passage 67 and being supplied to the rear chamber 65 before a 
sufficient amount of ink in the front chamber 66 is consumed. 
It is therefore possible to consume ink in the cartridge 50 ideally by 
consuming ink in the front chamber 66 prior to the ink in the rear chamber 
65. This can raise the ink consumption rate P (ink consumption/amount of 
filled ink) of the cartridge 50. It is also possible to prevent a large 
amount of air from mixing with the ink in the rear chamber 65. This can 
supply ink stably to the recording head 35, thereby preventing the 
recording performance of the head from lowering. 
The ink passage 67 is positioned at the bottom of the partition wall 63. 
Therefore, when the ink level in the porous member 68 has reached the 
passage 67, so that air in the front chamber 66 is introduced through the 
passage 67 into the rear chamber 65, a sufficient amount of ink in the 
front chamber 66 has been consumed. This can remarkably raise the ink 
consumption rate P. 
The ink passage 67 is laterally wide and rectangular. Therefore, the 
passage 67 can have a proper width, which depends on conditions such as 
the flow velocity of the ink flowing through the passage. In addition, it 
is possible to lower the height of the passage 67, which is the distance 
between the bottom 66b of the front chamber 66 and the top of the passage 
67. It is therefore possible to raise the ink consumption rate P. 
The rear chamber 65 is sufficiently small in volume as compared with the 
front chamber 66. The volume ratio of the rear chamber 65 to the front 
chamber 66 may be 1:13 or less. Accordingly, the front chamber 66 contains 
much more ink than the rear chamber 65. Therefore, most of the ink in the 
cartridge 50 is supplied to the recording head 35 in such condition that 
ink can be supplied from the front chamber 66 to the rear chamber 65, that 
is to say, such condition that the rear chamber 65 is filled with ink. It 
is consequently possible to supply ink stably to the head 35, without air 
mixing with the ink in the rear chamber 65. 
The rear chamber 65 is very small in volume (1.1 cc). Therefore, even if 
air in the front chamber 66 is introduced into the rear chamber 65 after 
the ink in the front chamber 66 is consumed or even before it has been, 
the ink in the rear chamber 65 is restrained from bubbling even when the 
carriage 21, on which the cartridge 50 is mounted, reciprocates at high 
speed. As a result, air is not liable to mix with the ink in the rear 
chamber 65. It is therefore possible to supply ink stably to the recording 
head 35. 
Thus, air is prevented from flowing into the rear chamber 65 before a 
sufficient amount of ink in the front chamber 66 is consumed. Therefore, 
by applying the ink cartridges 50-53 to an ink jet recorder for printing a 
sheet of recording paper by ejecting ink onto the sheet, it is possible to 
supply ink stably to the recording heads of the printer, and to raise the 
ink consumption rate. 
FIGS. 7, 8 and 9 show modified ink cartridges according to the invention, 
which are substantially identical in shape and size with the cartridge 50. 
In FIGS. 7-9, parts which are equivalent to those of the cartridge 50 are 
assigned the same numerals to avoid repeating the descriptions. 
The ink cartridge 50A shown in FIGS. 7 and 8 includes a partition wall 63A, 
which has an ink passage 67A formed through it. The passage 67A is spaced 
at a predetermined height "h", which may be 1.5 mm, from the bottom of the 
wall 63A. The front chamber 66 has a width "d". The passage 67A takes the 
form of a laterally wide rectangle in section in parallel with the wall 
63A. The passage 67A is d/2 in width, d/8 in height, and spaced at a 
distance of d/4 from each side surface 66a of the front chamber 66. 
The ink cartridge 50A has functions and effects which are similar to those 
of the cartridge 50. In addition, the ink passage 67A can be positioned 
away from the lower edge of the front chamber 66 which is adjacent to the 
partition 63A. It is therefore possible to restrain air securely from 
flowing through the gap 96 between the lower edge and the porous member 68 
into the passage 67A. 
The ink cartridge 50B shown in FIG. 9 includes a partition wall 63B, which 
is similar to the wall 63A of FIGS. 7 and 8. The wall 63B has an ink 
passage 67B formed through it. The passage 67B is positioned and sized the 
same as the passage 67A of the cartridge 50A. In addition, the wall 63B 
includes a port 90 protruding slightly from it into the front chamber 66. 
The port 90 has a passage 90a formed through it and communicating with the 
passage 67B. The passage 90a is equal in height and width to the passage 
67B, and aligned with it. 
The ink cartridge 50B has functions and effects which are similar to those 
of the cartridge 50A shown in FIGS. 7 and 8. Ink flows from the porous 
member 68 through the passages 90a and 67B into the rear chamber 65. 
Because the port 90 is in close contact with the member 68, air is 
restrained securely from flowing into the passages 90a and 67B through the 
gaps 95 and 96 where the member 68 is out of close contact with the edges 
of the front chamber 66. 
The invention has been described in the specific forms, but may be embodied 
in other forms without departing from the spirit or essential 
characteristics thereof. For example, the ink cartridges 50, 50A and 50B 
may be modified further as follows: 
1) Each of the ink passages 67, 67A and 67B might be narrower than d/2 (for 
example, 2.5 or 2 mm), and spaced at a distance longer than d/4 from each 
side surface 66a of the front chamber 66. 
2) Each of the partitions 63, 63A and 63B might have two or more ink 
passages spaced at a distance longer than d/4 from both side surfaces 66a 
of the front chamber 66. 
3) The ink passages 67, 67A and 67B might not be rectangular, but might be 
circular, oval or shaped otherwise in section in parallel with the 
partitions 63, 63A and 63B, respectively. 
4) The edges of at least the front chamber 66 might be rounded or curved so 
that the porous member 68 might closely contact the whole inner surface of 
this chamber. In this case, no gap is formed between the member 68 and the 
inner surface of the chamber 66. Therefore, with the member 68 impregnated 
with ink, the air in the front chamber 66 is prevented securely from 
flowing through the passage 67, 67A or 67B into the rear chamber 65. 
5) Each of the ink cartridges 50, 50A and 50B is shown and has been 
described as positioned with the axis of its ink supply hole 73 
horizontal, but might be used with the hole axis vertical or at an angle 
of about 45 degrees between the horizontal and vertical.