Pumps – By heating of pumped fluid
Reexamination Certificate
1999-07-28
2002-09-17
Freay, Charles G. (Department: 3746)
Pumps
By heating of pumped fluid
C417S208000, C417S209000, C347S065000
Reexamination Certificate
active
06450776
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid discharging device which produces a bubble by exerting a heat energy to a liquid and discharges the liquid utilizing the bubble, and more specifically a liquid discharging device which comprises a movable member displaced by utilizing production of a bubble.
A term of “recording” used in this specification means impairment of not only a significant image such as a character or a figure but also of an insignificant image such as a pattern to a recording medium.
2. Related Background Art
This is conventionally known an ink-jet recording method, or the so-called bubble-jet recording method, which produces a bubble by exerting an energy such as heat to liquid ink contained in a flow path of a recording apparatus such as a printer and discharges the ink through a discharging port utilizing a force generated by an abrupt volumetric change caused by the production of the bubble, thereby allowing the ink to adhere to a recording medium so as to form an image. A recording apparatus which uses the bubble-jet recording method generally comprises a discharging port to discharge ink, a flow path communicated with the discharging port and an electrothermal converting element as energy generating means as disclosed by U.S. Pat. No. 4,723,129.
Such a recording method permits not only recording a high quality image at a fast speed and with low noise but also arranging discharging ports to discharge ink at a high density in a head adopted to carry out the method, thereby having a lot of merits such as a capability to record a high resolution image and even a color image easily with a compact apparatus. Accordingly, the bubble-jet recording method has recently been utilized for many kinds of office appliances such as printers, copying machines and facsimiles, and further for industrial systems such as printing machines.
Demands which are mentioned below have recently been stronger as a bubble jet method has been utilized for products in many fields.
There have been proposed driving conditions to provide a liquid discharging method which permits stable production of a bubble for favorable discharge of ink at a fast speed, thereby obtaining a high quality image as well as improvement in a shape of a flow path for a liquid discharging head which refills a discharged liquid into a flow path at a fast speed in terms of high speed recording.
Speaking apart from such a head, Japanese Patent Application Laid-Open No. 6-31918 pays attention to a back wave (a pressure applied in a direction reverse to a direction toward discharging ports) which is produced when a bubble is produced and discloses an invention of a structure to prevent the back wave due to which a liquid discharging energy is lost. In the structure according to this invention, a triangular plate like member is opposed to a heater which produces a bubble. This invention suppresses the back wave with the triangular plate like member temporarily and slightly. However, the patent makes no reference to correlation between growth of the bubble and the triangular member nor has a conception of this correlation, whereby the invention mentioned above poses problems which are below.
The invention disclosed by the patent cannot stabilize a forms of a liquid drops due to a fact that the heater is located at a bottom of a cavity and cannot the communicated linearly with a discharging port and allows the bubble to grow within an entire range from a side to an opposite side of the triangular plate like member due to a fact that the bubble is allowed to grow from surroundings of a vertex portion of a triangle, thereby providing a result that the bubble is grown as usual in a liquid as if the plate like member were not used. Accordingly, existence of the plate like member has not relation to a grown bubble. Inversely, the plate like member is surrounded as a whole by the bubble, and allows a refilling liquid to the heater located in the cavity to produce a turbulent flow at a contraction stage of the bubble and constitutes a cause for accumulation of minute bubbles in the cavity, thereby disturbing a principle itself to discharge the liquid on the basis of growth of the bubble.
On the other hand, EP Publication Laid-Open No. 436047A1 proposes an invention which alternately opens and closes a first valve which shields a section in the vicinity of discharging ports from a bubble producing section, and a second valve which shields the bubble producing section and an ink supplying section (FIGS. 4 through 9 in EP No. 436047A1). However, this invention partitions these three sections into two, thereby allowing ink which follows a liquid drop to remarkably tail at a discharging stage, thereby producing satellite dots in a number prettily larger than that of satellite dots produced by the ordinary discharging method which grows, contracts and breaks a bubble (assumed to be incapable of utilizing an effect of retreat of a meniscus caused by breaking the bubbles). Furthermore, the invention allows discharged liquid drops to be remarkably variable and provides an extremely low discharge response frequency which is not a practically usable level since it is incapable of supplying the liquid to a region in the vicinity of a discharging port until a next bubble is produced through it allows the liquid to be supplied into the bubble producing section as the bubble is broken at a refilling stage.
The applicant has proposed a large number of inventions using movable members (a plate like member which has a free end on a side of discharging ports from a fulcrum or the like) which can effectively contribute to discharge of liquid drops quite differently from the prior art described above. Out of the inventions, Japanese Patent Application Laid-Open No. 9-48127 discloses an invention which restricts an upper limit of displacement of the movable member described above to prevent a behavior of the movable member from being slightly disturbed. Furthermore, Japanese Patent Application Laid-Open No. 9-323420 discloses an invention which enhances a refilling capability by shifting a common upstream liquid chamber toward a free end, or downstream, relative to the movable member utilizing a merit of the movable member described above. These inventions are based on a conceptional premise that growth of bubbles is open at a breath toward a side of discharging ports from a condition where the bubble is enwrapped by the movable member temporally and pay no attention to individual factors of the bubbles as a whole which relate to formation of liquid drops or correlation among these factors.
At a next step, the applicant disclosed an invention which partially opens a bubble producing region from the movable member described above as an invention which pays attention to a growth of bubbles due to propagation of a pressure wave as a factor related to liquid discharge (acoustic wave) in Japanese Patent Application Laid-Open No. 10-24588. However, even this invention pays attention only to the growth of the bubbles at a liquid discharging stage, but not to the individual factors of the bubbles as a whole which relate to the formation of the liquid drops themselves nor correlation among the factors.
Though it is conventionally known that discharge of a liquid is largely influenced by a front portion (edge chutter type) of bubbles produced by film boiling, no one has ever paid attention to this portion which may effectively contribute to formation of liquid drops to be discharged and the inventor et al. eagerly made researches to accomplish an invention which solves these technical problems.
Paying attention to the displacement of the movable member described above and produced bubbles, the inventor et al. obtained useful knowledge which is described below.
Paying attention to “a form of an inter-flow path wall” which is effective also for restriction of growing bubbles as a new structure to restrict the movable member, the inventor et al. conceived to restrict an upper limit of displacement of the m
Ishinaga Hiroyuki
Shimazu Satoshi
Sugama Sadayuki
Sugiyama Hiroyuki
Taneya Yoichi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Freay Charles G.
Gray Michael K.
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