Marker pen

摘要

In a marking pen, the body of the marking pen containing the cartridge is made air tight except for the opening on the distal end to receive the marker nib and a vent hole. The walls of the pen body are made flexible and the vent hole is provided through the flexible walls near the distal end so that the cavity containing the cartridge can be pressurized by squeezing the body between the thumb and index finger, with the index finger covering the vent hole. The pressuring of the cartridge cavity applies hydraulic pressure to the nib to flush the nib with ink or unclog it.