Integrated apparatus for supplying ink and regulating pressure

Disclosed is an integrated apparatus for supplying ink and regulating pressure, which comprises a chamber accommodating ink, a main chamber preliminarily storing ink to be supplied to the chamber, a nozzle communicating with the chamber and jetting ink transferred from the chamber to an outside, a first valve blocking or letting flow of ink between the main chamber and the chamber, a second valve blocking and letting flow of ink between the chamber and the nozzle, a piston placed above ink accommodated in the chamber and reciprocating rectilinearly while sealing ink inside the chamber, a piston driver providing a driving force to the piston, a sensor installed in the chamber and sensing pressure due to weight of ink, and a controller receiving a sensed signal from the sensor and outputting a signal for controlling the piston to the piston, wherein the piston moves down as a level of ink accommodated in the chamber is lowered when ink is discharged to the outside through the nozzle, and the piston moves up and the first valve and the second valve are respectively opened and closed when ink is filled in the chamber.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0048189 filed in the Korean Intellectual Property Office on Jun. 1, 2009, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an integrated apparatus for supplying ink and regulating pressure, and more particularly, to an integrated apparatus for supplying ink and regulating pressure, in which proper negative pressure can be kept in a chamber accommodating the ink to stably form a meniscus in a nozzle.

(b) Description of the Related Art

In general, an inkjet printer is an apparatus that prints an image with predetermined colors by discharging a minute droplet of ink to a desired position on recording paper. The inkjet printer is provided with an ink transfer system for discharging the ink. The ink transfer system is broadly classified into two types according to methods of discharging the ink. One is a thermal driving type that uses a heat source to generate bubbles in ink and discharges the ink by the expansive force of the bubbles. The other one is a piezoelectric type that uses transformation of a piezoelectric body to discharge ink by pressure applied due to the transformation.

FIG. 1is a schematic view showing an example of a conventional ink transfer system.

Referring toFIG. 1, an ink transfer system includes a main chamber10preliminarily accommodating a large amount of ink1, a remote chamber20accommodating the ink1to be used in a printing job, and a nozzle30communicating with the remote chamber20and jetting the ink transferred from the remote chamber20to the outside. The ink1is transferred from the main chamber10to the remote chamber20via a control valve12and a filter24. The amount of ink1accommodated in the remote chamber20is sensed by a level sensor22installed in the remote chamber20so that the amount of ink1transferred from the main chamber10to the remote chamber20can be controlled.

Even while the printing job is not performed, the ink1is remained in the remote chamber20, the nozzle30and a channel26connected between the remote chamber20and the nozzle30. To prevent the ink1in the nozzle30from being discharged to the outside while the printing job is not performed, the remote chamber20has to internally keep negative pressure lower than the atmospheric pressure. To this end, a vacuum pump40or the like is connected to the remote chamber20and keeps the remote chamber20in the negative pressure lower than the atmospheric pressure.

However, the conventional ink transfer system additionally needs the vacuum pump or the like for keeping the remote chamber in the negative pressure, so that it is inconvenient to separately install the additional device. Further, vibration generated when the vacuum pump operates is transmitted to the system, so that there is a problem in precisely controlling the discharge of the ink. Also, the vacuum pump is so distant from the remote chamber that a problem arises in response time delay. Furthermore, a separate pump is needed to supply ink from the main chamber to the remote chamber.

SUMMARY OF THE INVENTION

Accordingly, the present invention is conceived to solve the foregoing problems, and an aspect of the present invention is to provide an integrated apparatus for supplying ink and regulating pressure, in which a piston is directly installed in a chamber to keep the chamber in negative pressure, thereby efficiently controlling the negative pressure inside the chamber in real time and easily supplying the ink from an outside to an inside of a chamber.

An exemplary embodiment of the present invention provides an integrated apparatus for supplying ink and regulating pressure, which comprises a chamber accommodating ink, a main chamber preliminarily storing ink to be supplied to the chamber, a nozzle communicating with the chamber and jetting ink transferred from the chamber to an outside, a first valve blocking or letting flow of ink between the main chamber and the chamber, a second valve blocking and letting flow of ink between the chamber and the nozzle, a piston placed above ink accommodated in the chamber and reciprocating rectilinearly while sealing ink inside the chamber, a piston driver providing a driving force to the piston, a sensor installed in the chamber and sensing pressure due to weight of ink, and a controller receiving a sensed signal from the sensor and outputting a signal for controlling the piston to the piston, wherein the piston moves down as a level of ink accommodated in the chamber is lowered when ink is discharged to the outside through the nozzle, and the piston moves up and the first valve and the second valve are respectively opened and closed when ink is filled in the chamber.

The piston may move down as a level of ink accommodated in the chamber is lowered while being spaced from a top surface of ink accommodated in the chamber.

The piston may comprise a facing unit that faces ink, the facing unit comprising a horizontal part formed substantially parallel with a top surface of ink, and a protruding part formed protruding from the horizontal part toward ink.

The integrated apparatus may further comprise an ink inlet through which the chamber is filled with ink supplied from the main chamber, wherein the ink inlet is placed below the piston in the chamber.

The sensor may be installed on a bottom surface of the chamber.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of an apparatus for supplying ink and regulating pressure according to the present invention will be described with reference to accompanying drawings.

FIG. 2is a schematic view showing an integrated apparatus for supplying ink and regulating pressure according to a first exemplary embodiment of the present invention.

Referring toFIG. 2, an integrated apparatus100for supplying ink and regulating pressure in this exemplary embodiment uses a piston as a means for keeping an inside of a chamber in negative pressure and supplying the ink to the inside of the chamber, which includes a chamber110, a main chamber172, a nozzle120, a first valve174, a second valve178, a piston130, a piston driver140, a sensor150, and a controller160.

The chamber110accommodates ink2. The chamber110communicates with the main chamber172preliminarily storing the ink2to be filled in the chamber110if the chamber110lacks the ink2, and the amount of ink2transferred from the main chamber172to the chamber110is adjusted by the first valve174installed on a channel connected between the main chamber172and the chamber110.

The first valve174blocks or let the flow of ink between the main chamber174and the chamber110. The ink2passed by the first valve174experiences the filter176before being introduced into the chamber110, so that impurities can be removed from the ink2.

To fill the inside of the chamber110with the ink2, the chamber110is provided with an ink inlet112through which the ink2supplied from an exterior, particularly, from the main chamber172is provided to the chamber110. In this exemplary embodiment, the ink inlet112may be formed in a lateral wall or a bottom surface of the chamber110. For example, to maintain sealing between the piston130and the chamber110, the ink inlet112may be placed on the lateral wall of the chamber110below the piston130.

The nozzle120communicates with the chamber110and jets the ink2transferred from the chamber110to the outside. While the operation of jetting the ink is not performed, the ink2is remained in the chamber110, the nozzle120and a channel connected between the chamber110and the nozzle120, and the ink2in the nozzle120at a part being in contact with external air has a meniscus shape, i.e., an inwardly curved shape.

The second valve178blocks or lets the flow of ink between the chamber170and the nozzle120.

The piston130is placed above the ink2accommodated in the chamber110and seals the ink2inside the chamber110. The piston130can rectilinearly reciprocate in a vertical direction along an inner wall of the chamber110while being in nearly contact with a top surface of the ink2accommodated in the chamber110.

The piston driver140gives a driving force to the piston130so that the piston130can rectilinearly reciprocate in the vertical direction. In this exemplary embodiment, the piston driver140includes a linear motor providing a linear driving force, and a linear moving guide connected to a rod132of the piston130and guiding the piston130to move rectilinearly. Combination of the linear motor and the linear moving guide to achieve the rectilinear movement of the piston130is well known to a person having an ordinary skill in the art, and thus repetitive descriptions thereof will be avoided. Alternatively, the piston driver140may be achieved by combination of a rotation motor providing a rotation driving force, a ball screw, and a linear moving guide.

The sensor150is installed in the chamber110and senses pressure due to the weight of the ink2. The pressure of the ink2accommodated in the chamber110varies depending on ink levels, which calculated as follows.
p=ρgh

where, p indicates the pressure based on the weight of the ink2, ρ indicates the density of the accommodated ink2, g indicates the acceleration of gravity, and h indicates a level from a bottom surface114of the chamber110to the top surface of the ink2.

As the ink2is discharged to the outside through the nozzle120, the amount of ink2in the chamber110decreases and thus the level of the ink2in the chamber110is lowered. If the level of the ink2is lowered, the pressure due to the weight of the ink2decreases and the sensor150senses such a change in the pressure. In this exemplary embodiment, the sensor150is installed on the bottom surface114of the chamber110. Alternatively, the sensor150may be installed on the lateral wall adjacent to the bottom surface114of the chamber110.

The controller160receives a sensed signal from the sensor150and outputs a control signal to the piston driver140so as to control the piston130. That is, the controller160controls the piston driver140to move the piston130down on the basis of the sensed signal received from the sensor150that senses a lowered level of the ink2accommodated in the chamber110. if the ink2is discharged to the outside through the nozzle120, the level of the ink2accommodated in the chamber110is lowered, and the sensor150senses corresponding decrease of the pressure. The sensed signal is input to the controller160, and the controller160outputs the control signal for controlling the piston driver140to move the piston130down.

In this exemplary embodiment configured as described above, an operating principle of the integrated apparatus for supplying the ink and regulating the pressure will be schematically described with reference toFIG. 2.

First, if the ink20starts being discharged to the outside through the nozzle120at the operation of jetting the ink2, the amount of ink2accommodated in the chamber110is reduced and the level of the ink2in the chamber110is lowered. As the level of the ink2is lowered, the pressure due to the weight of the ink2is decreased and the sensor150installed on the bottom surface114of the chamber110senses such a pressure change in real time.

A signal of pressure sensed by the sensor150is input to the controller160, and the controller160outputs a signal for controlling the piston driver140so as to move the piston130down (in a direction of “A”). At this time, a moving-down speed of the piston130is controlled to maintain a state that the piston130is not dipped into the ink2and there is no airspace between the piston130and the ink2, that is, a state that the piston130and the top surface of the ink2are in nearly contact with each other.

In the state that the down movement of the piston130is controlled depending on the level of the ink2accommodated in the chamber110, if the operation of outwardly jetting the ink is stopped, the inside of the chamber110accommodating the ink2is kept in negative pressure lower than the atmospheric pressure of the outside. Thus, the ink2inside the nozzle120is not outwardly discharged any more and has a stable meniscus in a boundary where the nozzle120meets the outside. This is based on the same principle that no more injection is discharged to the outside of a cylinder when a piston stops moving in a syringe having the cylinder and the piston.

Meanwhile, if the ink2in the chamber110is used up and there is a need of filling the chamber110with the ink2, the second valve178is first closed not to have an effect on the ink2remained in the nozzle120and the channel connected between the chamber110and the nozzle120, thereby blocking the flow of the ink2between the chamber110and the nozzle120. Next, the first valve174placed between the main chamber172and the chamber110is opened to let the ink flow between the main chamber172and the chamber110. Then, the piston driver140drives the piston130to move up (in a direction of “B”), so that the ink2remained in the main chamber172can be transferred to the inside of the chamber110.

In the integrated apparatus for supplying ink and regulating pressure, configured as described above according to an exemplary embodiment of the present invention, the piston directly installed inside the chamber is used to keep the inside of the chamber in the negative pressure and to supply the ink to the inside of the chamber if necessary, and it is thus effective in simplifying the whole system.

Also, in the integrated apparatus for supplying ink and regulating pressure, configured as described above according to an exemplary embodiment of the present invention, a vacuum pump for keeping the inside of the chamber in the negative pressure, a pump for supplying the ink to the inside of the chamber, etc. are not used to thereby isolate vibration to be transmitted to the system and thus precisely control the discharge of the ink.

Further, in the integrated apparatus for supplying ink and regulating pressure, configured as described above according to an exemplary embodiment of the present invention, the piston installed inside the chamber is employed instead of the vacuum pump installed distantly from the chamber, thereby quickly responding to change in a level of the ink.

FIG. 3is a schematic view showing an integrated apparatus for supplying ink and regulating pressure according to a second exemplary embodiment of the present invention.

InFIG. 3, numerals similar to those shown inFIG. 2refer to elements having similar structures and functions, and thus repetitive descriptions thereof will be avoided.

Referring toFIG. 3, an integrated apparatus200for supplying ink and regulating pressure in this exemplary embodiment is characterized in that the piston130moves down corresponding to a lowered level of the ink while being spaced apart from the top surface of the ink2accommodated in the chamber110.

Since the fluid ink2is generally incompressible, a volume change of the ink2inside the chamber110directly affects the amount of ink discharged to the outside through the nozzle120. Therefore, if the piston130repeatedly reciprocates in the state that the piston130and the top surface of the ink2are in nearly contact with each other like the first exemplary embodiment, even a little error generated in the up and down movement of the piston130directly makes an abnormal amount of ink2be discharged to the outside through the nozzle120and causes an object, onto which the ink2is applied, to be defective.

Accordingly, an airspace3having a certain thickness is provided between the ink2and the piston130, and it is controlled that the airspace3is maintained constantly when the piston130moves down as the level of the ink2is lowered. In other words, the gaseous airspace3provided between the ink2and the piston130serves as a kind of buffer.

In the integrated apparatus for supplying ink and regulating pressure, configured as described above according to an exemplary embodiment of the present invention, there is provided the airspace capable of decreasing an error that may occur while the piston moves and functioning as a kind of buffer, thereby preventing an abnormal amount of ink from being discharged when jetting the ink.

FIG. 4is a schematic view showing an integrated apparatus for supplying ink and regulating pressure according to a third exemplary embodiment of the present invention.

InFIG. 4, numerals similar to those shown inFIG. 2refer to elements having similar structures and functions, and thus repetitive descriptions thereof will be avoided.

Referring toFIG. 4, an integrated apparatus300for supplying ink and regulating pressure in this exemplary embodiment is characterized in that the piston130includes a facing unit134facing the ink2, the facing unit134having a horizontal part136formed substantially parallel with the top surface of the ink2and a protruding part138protruding from the horizontal part136toward the ink2.

In this exemplary embodiment, the piston130moves down inside the chamber110while an end part of the protruding part138is kept in nearly contact with the top surface of the ink2. Also, the airspace3is formed around the protruding part138between the horizontal part136and the top surface of the ink2, and serves as a kind of buffer like that according to the second exemplary embodiment of the present invention. Although malfunction due to the contact between the protruding part138and the ink2when jetting the ink may cause the ink to be excessively discharged, an area of the contact is minimized to thereby have a minimum effect on the amount of ink discharged through the nozzle120.

As described above, according to an exemplary embodiment of the present invention, there is provided an integrated apparatus for supplying ink and regulating pressure, which uses a piston directly installed inside a chamber to keep an inside of the chamber in negative pressure and to supply ink from an outside to the inside of the chamber, thereby simplifying the system.

Also, according to an exemplary embodiment of the present invention, there is provided an integrated apparatus for supplying ink and regulating pressure, which does not use a vacuum pump for keeping the inside of the chamber in the negative pressure or a pump for supplying ink to the inside the chamber, thereby isolating vibration to be transmitted to the system and thus precisely controlling discharge of ink.

Further, according to an exemplary embodiment of the present invention, there is provided an integrated apparatus for supplying ink and regulating pressure, which employs the piston installed inside the chamber instead of the is vacuum pump installed distantly from the chamber, thereby quickly responding to change in a level of the ink.

Furthermore, according to an exemplary embodiment of the present invention, there is provided an integrated apparatus for supplying ink and regulating pressure, which moves the piston with an airspace between the piston and the ink, thereby preventing the ink from being excessively jetted or the like due to malfunction of the piston when jetting the ink.