Fountain pen with quick-filling coupling

A fountain pen comprising:

• a housing with a main tank and a writing tank formed therein;
• a nib assembly disposed on a first end of the housing;
• a rotatable finial disposed on a second end of the housing opposite from the first end;
• a coupling configured to couple the housing with an ink feed device;
• a first sealing unit arranged between the writing tank and the main tank to provide fluid communication therebetween, wherein the first sealing unit is operable to open and close for selectively filling the writing tank via the main tank;
• a second sealing unit arranged between the writing tank and the nib assembly to provide fluid communication therebetween, wherein the second sealing unit is operable to open and close for selectively supplying ink from the writing tank to the nib assembly;
• and
• a third sealing unit arranged between the main tank and the coupling for providing fluid communication therebetween, wherein the third sealing unit is operable to open and close for selectively filling the main tank when coupled to the ink feed device, and
• wherein the finial is operably coupled to the first and second sealing units for controlling the opening and closing thereof.