Liquid container for ink jet head

Details Liquid container for ink jet head Liquid container for ink jet head

1998-02-18

2001-09-25

Nguyen, Judy (Department: 2861)

Incremental printing of symbolic information

Ink jet

Fluid or fluid source handling means

Reexamination Certificate

active

06293660

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a liquid container for accommodating liquid to be used for recording by an ejection head(ink jet head) which forms images by ejection of droplets onto sheets.
In conventional printers, an ejection head for image formation by ejection of droplets onto sheets, can be carried on a carriage which makes reciprocal movement in a direction perpendicular to the sheet feeding direction in a plane parallel to the sheet.
In such a scanning type apparatus, the carriage is moved on a line in response to instructions, and simultaneously, the droplets are ejected in response to ejection signals to effect the image formation on the sheet, and thereafter, the sheet is fed through a predetermined distance by a feeding device, and these operations are repeated. As for the droplet ejecting type, there are a type using an electrothermal transducer element(heater) and a type using a piezoelectric element(piezoelectric), in either of which the ejections of the ink droplets are controllable by an electrical signals. In the liquid droplet ejecting method using the electrothermal transducer element, an electric signal is supplied to the electrothermal transducer element so that ink adjacent the electrothermal transducer element is instantaneously boiled, and the droplet is ejected at a high speed by an abrupt growth of a bubble caused by the instantaneous of the ink by the boiling.
Since the liquid is consumed during the image formation, the ejection head has to be always supplied with the liquid. To accomplish this there is a system, for example, wherein an ink container is provided in a main assembly of the ink jet recording apparatus, and an ink supply tube is extended from the ink container to the recording head to supply the ink with negative pressure provided by a static head difference between the ink jet head and the ink container. Such a type, however, results in bulky structure, and therefore, it is unsuitable to a popular type machines from the standpoint of the size and the price.
As another system, there is a so-called liquid container carrying type wherein a liquid container which is detachably mountable relative to the ejection head carried on the carriage, an is connected to a liquid supply port of the ejection head. In this system, the liquid container is exchanged with a new one after the liquid therein is consumed up.
In such a liquid container carrying type, the ejection head is usually disposed below the liquid container. Therefore, if the liquid container has an open-to-ambience structure, a means has to be provided to produce a predetermined negative pressure to prevent the liquid from leaking out through the droplet ejection outlet(orifice) of he ejection head. Additionally, in order to stabilize the ejection property, a stable meniscus should be maintained at the droplet ejection outlet of the ejection head. In such a liquid container, the negative pressure is adjusted to a predetermined level in consideration of the static head difference between the ejection portion of the ejection head and the liquid surface in the container so as to maintain the stabilized meniscus at the ejection outlet. Therefore, the state of the liquid in the liquid container is influential to the liquid droplet ejection performance from the ejection head.
In order to generate such negative pressure, Japanese Laid-open Patent Application No. SHO- 56-67269 and Japanese Laid-open Patent Application No. SHO- 59-98857, for example, proposes a spring urged bladder ink container type using an ink bladder urged by a spring in an ink container. With such a type, the manufacturing step is complicated, and therefore, the manufacturing cost is high, and in addition the ink content per unit volume of the ink container, i.e., the ink holding rate is smaller if the thickness of the container is smaller, with the result of higher running cost.
For example, Japanese Laid-open Patent Application No. HEI- 2-21466 discloses a container, the inside of which is divided into a plurality of ink chambers, which in turn are communicated through a fine hole which is capable of producing a negative pressure. In this type, however, the ink does not exist at the fine hole portion depending on the orientation of the ink container, with the result of no negative pressure, or the negative pressure tends to reduce by the expansion of the air in the ink chamber due to the ambient temperature or the like, so that ink leaks relatively easily.
There is a further known system wherein an absorbing material occupies the entire inside space of the ink container, and the ink is retained by the absorbing material. The absorbing material is a liquid absorbing material in the form of a porous material such as a sponge, and it is ordinary that absorbing material has originally a size larger than the inside volume of the container, and is compressed when it is placed therein.
With such a system, the ink amount which can be actually used from the container is smaller than the total volume of the ink container since the ink amount which can be contained in the absorbing material is limited to provide the stable negative pressure to avoid the ink leakage or the like, and since the ink in the absorbing material sometimes cannot be completely used up since the absolute value of the negative pressure increases with the consumption of the ink retained in the absorbing material.
There is a further system, which is a so-called half-sponge ink container type which increases the amount of the ink which can be consumed. An example of this is disclosed in Japanese Laid-open Patent Application No. HEI- 6-40043 wherein the container includes a liquid retaining member accommodating portion accommodating a liquid retaining member for negative pressure production, and an ink accommodating portion accommodating the ink next to the liquid retaining member accommodating portion and communicating therewith through a passage. This container for ink jet printer, therefore, is provided with a liquid retaining member accommodation chamber for accommodating the liquid retaining member and the ink accommodation chamber for accommodation the ink, so that ink holding rate is improved while stabilizing the negative pressure, with a simple structure, thus accomplishing the low manufacturing cost, low running cost, highly reliable and the downsizing of the apparatus.
A detailed description will be made as to the structure of liquid containers.
FIGS. 15 and 16
show conventional liquid containers.
The container of
FIG. 15
supplies the recording liquid to a wire dot head, and the liquid absorbing material
101
has a thicknesses which is different at the front side portion and the rear side portion, wherein when it is placed in the main body
102
of the container, the front side portion is compressed by the cap
103
. With this structure, the capillary force provided by the liquid absorbing material
101
increases toward the liquid supply port
104
so that ink can be concentrated at the ink supply port side efficiently.
In
FIG. 16
, the container is integral with an ink jet head, and three chambers of the container accommodates the liquid absorbing materials
201
, respectively, wherein an ejection head
203
is provided at the bottom portion of the main body
202
. The liquid absorbing material
210
is press-contacted to the supply pipe
205
which is in communication with the orifices
204
of the ejection head
203
((Japanese Laid-open Patent Application No. SHO- 63-87242). With such a structure, the portion of the liquid absorbing material
210
which is contacted to the supply pipe
205
is compressed, and therefore, the capillary force of the portion is larger so that ink is efficiently collected to the supply pipe
205
. Japanese Laid-open Patent Application No. SHO- 55-161661 discloses a structure using fiber as the absorbing material, and the configuration of the container per se is reduced toward the connecting portion to improve the supply of the ink.
FIG. 17
shows another liquid container. T

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