A liquid ink instrument, including: a pen body, a writing element mounted on the head of the pen body, an ink absorber mounted at the rear end of the writing element; a fiber ink feeder mounted in the body penetrates the ink absorbing body, the front end in contact with the writing element, the rear end communicated with the ink cartridge; at least one air-liquid balancer in the axial direction, the air-liquid balancer installed between the recited fiber ink feeder and the body; having one or more air-liquid exchange grooves penetrating through the outer circumferential surface; having an overflow groove on a radial surface of the air-liquid balancer, one end contacted to fiber ink feeder, and the other end communicating with air-liquid exchange groove; a gas-free fit or an interference fit adopted between the outer circumferential surface of the fiber ink feeder and the inner wall of the air-liquid balancer.

A pressure regulating device for a writing tool has a deformable member. Minor air pressure variations in a pen tube of the writing tool can be regulated by deformation of the deformable member. Major air pressure variations in the pen tube can also be regulated by movement of the pressure regulating device. Thus, the pen tube of the writing tool can avoid internal air pressure imbalance caused by external high temperature or low air pressure. Before the writing tool is shipped from a manufacturer, the deformable member is pressurized in advance, such that the minor air pressure variation formed when a pen cap caps the writing tool offsets the air pressure pre-applied to the deformable member. Accordingly, ink inside an internal chamber does not spout out upon removal of the pen cap and the ink will not be overly dispensed or leak during writing.

A pressure regulating device for a writing tool has a deformable member. Minor air pressure variations in a pen tube of the writing tool can be regulated by deformation of the deformable member. Major air pressure variations in the pen tube can also be regulated by movement of the pressure regulating device. Thus, the pen tube of the writing tool can avoid internal air pressure imbalance caused by external high temperature or low air pressure. Before the writing tool is shipped from a manufacturer, the deformable member is pressurized in advance, such that the minor air pressure variation formed when a pen cap caps the writing tool offsets the air pressure pre-applied to the deformable member. Accordingly, ink inside an internal chamber does not spout out upon removal of the pen cap and the ink will not be overly dispensed or leak during writing.

A compensation membrane for compensating a pressure difference between the outside and the inside of a free ink reservoir of a pen or the equivalent, the membrane comprising a first portion having a first rigidity, and a second portion having a second rigidity, the first rigidity being less than the second rigidity. A pen or the equivalent comprising a free ink reservoir provided with such a compensation membrane.

A compensation membrane for compensating a pressure difference between the outside and the inside of a free ink reservoir of a pen or the equivalent, the membrane comprising a first portion having a first rigidity, and a second portion having a second rigidity, the first rigidity being less than the second rigidity. A pen or the equivalent comprising a free ink reservoir provided with such a compensation membrane.

A pressure regulating device for a writing tool has a deformable member. Minor air pressure variations in a pen tube of the writing tool can be regulated by deformation of the deformable member. Major air pressure variations in the pen tube can also be regulated by movement of the pressure regulating device. Thus, the pen tube of the writing tool can avoid internal air pressure imbalance caused by external high temperature or low air pressure. Before the writing tool is shipped from a manufacturer, the deformable member is pressurized in advance, such that the minor air pressure variation formed when a pen cap caps the writing tool offsets the air pressure pre-applied to the deformable member. Accordingly, ink inside an internal chamber does not spout out upon removal of the pen cap and the ink will not be overly dispensed or leak during writing.

A writing instrument includes: a replacement ink cartridge including a bottomed cylindrical container that has an opened front end and a closed rear end and a plug fitted into an inner circumferential surface of an opening of the container; and a projection inserted into the opening of the container to press the plug rearward, thereby opening the plug of the ink cartridge, wherein the projection and the plug are fitted when the plug is press opened, and when the cartridge is replaced, the fitting between the projection and the plug is released and the plug is locked again in the opening of the container.

A writing instrument includes: a replacement ink cartridge including a bottomed cylindrical container that has an opened front end and a closed rear end and a plug fitted into an inner circumferential surface of an opening of the container; and a projection inserted into the opening of the container to press the plug rearward, thereby opening the plug of the ink cartridge, wherein the projection and the plug are fitted when the plug is press opened, and when the cartridge is replaced, the fitting between the projection and the plug is released and the plug is locked again in the opening of the container.

A thermochromic writing instrument including a writing body, storing a thermochromic ink therein, stored in a barrel; an operation body provided in the barrel to be operated to longitudinally move the writing body; a nib of the writing body configured to be capable of appearing from a front end of the writing instrument, wherein the writing instrument 1 further includes a friction unit, for rubbing handwriting in the thermochromic ink and capable of thermally changing the color of the handwriting by frictional heat generated at that time, and at least one clip body as the operation body, the friction unit 10 is provided at a rear end of the barrel, and the clip body is provided in an area other than the rear end of the barrel.

A thermochromic writing instrument including a writing body, storing a thermochromic ink therein, stored in a barrel; an operation body provided in the barrel to be operated to longitudinally move the writing body; a nib of the writing body configured to be capable of appearing from a front end of the writing instrument, wherein the writing instrument 1 further includes a friction unit, for rubbing handwriting in the thermochromic ink and capable of thermally changing the color of the handwriting by frictional heat generated at that time, and at least one clip body as the operation body, the friction unit 10 is provided at a rear end of the barrel, and the clip body is provided in an area other than the rear end of the barrel.