As a writing tool, the pen is widely used in our daily life. It can be used to draw, write, decorate and so on. Its wide range of categories, there are neutral pens, water pens, markers, fountain pens, pencils, watercolor pens and so on. The neutral pen is one of the writing instruments with high market share at present. The common structure types of the neutral pen are insert and pull. The pen head selected by the snap type is the spring pen head, which is self-tightness of the ball and bead (the internal spring withstands the ball and bead, with high processing accuracy and much higher cost than the ordinary pen head). When the spring withstands the ball and bead, it plays a timely sealing and protection role when the writing stops, and the pen head is sealed by wax wrapping in the final use state.
The cartridge type can be divided into front-end positioning cartridge type and back-end positioning cartridge type according to the fixed way of the pen. Front-end positioning refers to the positioning of the pen core through the outer round step of the pen core connector and the front end of the inner hole of the pen rod, so that the stability of the distance between the pen tip and the tip sleeve of the pen core is improved, and the error of the length of the core is relatively small. Back end positioning refers to the fixation of the oil pipe through the outer circle of the oil pipe and the tail groove of the pen rod or the tail cap (back plug) through the interference or limit mode, the oil pipe is fixed. Due to the large number of parts involved in this method, the accumulated error is large, which affects the accuracy and consistency of the pen tip exposure length.
Compared with ink ballpoint pen, neutral pen requires large amount of ink (the amount of ink is about 10 times that of ink ballpoint pen), large tip gap, and neutral ink is water-based ink, and the dry resistance of ink (oily ink) is poor. Under normal temperature conditions, compared with the intermittent writing time of the two kinds of ballpoint pens (the time that the pen can write normally under normal temperature environment after the pen sleeve is pulled out), the intermittent writing time of ink ballpoint pen can be maintained for about two years, which is equivalent to the shelf life of the whole pen, while the interval writing time of neutral pen can generally reach 20 days to 3 months. In addition, the viscosity of neutral ink is lower than that of ink, and the hole in the tubing is larger, so the ink is easier to produce backflow phenomenon. Therefore, a rubber or silicone sealing ring is designed in the neutral pen sleeve. After the cover of the pen sleeve, the sealing ring will be squeezed and sealed with the pen tip to prevent the ink from drying up between the pen tip and the ball, and prevent the air from entering the pen tip into the pen core, resulting in ink backflow and writing break. Therefore, the depth of the pen tip into the sealing ring has certain tolerance requirements. Different shapes of pen tip, ball diameter size and with different shapes of sealing ring, the depth of the pen tip into the sealing ring is different.
