Apparatus for regulating air pressure in ink tank and ink-supplying system having the same

An apparatus for regulating air pressure in an ink tank, comprising:

• a vacuum pump configured for providing a pressure below atmospheric pressure in the ink tank;
• a first regulating unit, a second regulating unit, and a third regulating unit disposed between the vacuum pump and the ink tank, and in communication with each other, the second regulating unit being connected between the first regulating unit and the third regulating unit, wherein the first regulating unit and the third regulating unit each comprise a pressure regulating valve and a buffer tank connected with the pressure regulating valve, and the second regulating unit comprises a closed-loop pressure regulating valve and a buffer tank connected with the closed-loop pressure regulating valve.

An ink-supplying system, comprising:

• an ink tank for receiving ink therein;
• a vacuum pump configured for providing a pressure below atmospheric pressure in the ink tank;
• a first regulating unit, at least one second regulating unit, and a third regulating unit disposed between the vacuum pump and the ink tank, and in communication with each other, wherein the first regulating unit and the third regulating unit each comprise a pressure regulating valve and a buffer tank connected therewith, and the at least one second regulating unit comprises a closed-loop pressure regulating valve and a buffer tank connected with the closed-loop pressure regulating valve.