A method for manufacturing a writing instrument includes inject molding a cushion spring of the writing instrument to form the cushion spring as one piece, and axially pushing out the cushion spring from a molding die set. The cushion spring elastically supports a tip of the writing instrument in an axial direction to a barrel of the writing instrument. The forming of the cushion spring includes forming a plurality of apertures in the cushion spring, one of the apertures being relatively arranged with another one of the apertures by rotations of angles at 90 degrees about the axial direction on an outer peripheral surface thereof, and forming a plurality of displacement regulating protrusions, one of the protrusions being relatively arranged with another one of the protrusions by rotations of angles at 90 degrees about the axial direction.

A method for manufacturing a writing instrument includes inject molding a cushion spring of the writing instrument to form the cushion spring as one piece, and axially pushing out the cushion spring from a molding die set. The cushion spring elastically supports a tip of the writing instrument in an axial direction to a barrel of the writing instrument. The forming of the cushion spring includes forming a plurality of apertures in the cushion spring, one of the apertures being relatively arranged with another one of the apertures by rotations of angles at 90 degrees about the axial direction on an outer peripheral surface thereof, and forming a plurality of displacement regulating protrusions, one of the protrusions being relatively arranged with another one of the protrusions by rotations of angles at 90 degrees about the axial direction.

A knocking-type writing instrument has a writing refill, such as a pencil lead or an ink cartridge, that is advanced by knocking a knocking member, and an eraser held by an eraser holder disposed at a rear part of the knocking member. When the writing instrument is inclined so that the eraser side faces downward, a control pin provided in the eraser holder and a movable stopper drop by their own weights along a sliding groove of the knocking member. When the control pin drops a predetermined distance and enters a circumferential locking groove provided at a rear end of the sliding groove, detachment of the control pin is prevented by the stopper, and the eraser holder is unable to retract to the inside of the knocking member. In this state, a radial projection on the control pin abuts a rear end face of the knocking holder, whereby the knocking member is locked and can no longer be knocked, and feeding of the writing refill is prevented.

A knocking-type writing instrument has a writing refill, such as a pencil lead or an ink cartridge, that is advanced by knocking a knocking member, and an eraser held by an eraser holder disposed at a rear part of the knocking member. When the writing instrument is inclined so that the eraser side faces downward, a control pin provided in the eraser holder and a movable stopper drop by their own weights along a sliding groove of the knocking member. When the control pin drops a predetermined distance and enters a circumferential locking groove provided at a rear end of the sliding groove, detachment of the control pin is prevented by the stopper, and the eraser holder is unable to retract to the inside of the knocking member. In this state, a radial projection on the control pin abuts a rear end face of the knocking holder, whereby the knocking member is locked and can no longer be knocked, and feeding of the writing refill is prevented.

A mechanical pencil includes a writing lead, a chuck unit for chucking the writing lead, and a cushion spring configured to elastically support the chuck unit in such a manner that the chuck unit is retractable with a writing pressure. An output of the cushion spring, in response to a cushion stroke, is non-linear, and a slope of a spring constant, in a region where the cushion stroke is relatively small, is smaller than a slope of a spring constant in a region where the cushion stroke is relatively large.

A mechanical pencil includes a writing lead, a chuck unit for chucking the writing lead, and a cushion spring configured to elastically support the chuck unit in such a manner that the chuck unit is retractable with a writing pressure. An output of the cushion spring, in response to a cushion stroke, is non-linear, and a slope of a spring constant, in a region where the cushion stroke is relatively small, is smaller than a slope of a spring constant in a region where the cushion stroke is relatively large.

A writing instrument includes a barrel, a tip, and a cushion spring that elastically supports the tip in the axial direction to the barrel. The cushion spring is formed as one piece by injection molding, the cushion spring includes an aperture on its outer peripheral surface, and a displacement regulating protrusion that protrudes and extends into the aperture along the axial direction. The protrusion prevents the cushion spring from compression beyond a prescribed length.

A writing instrument includes a barrel, a tip, and a cushion spring that elastically supports the tip in the axial direction to the barrel. The cushion spring is formed as one piece by injection molding, the cushion spring includes an aperture on its outer peripheral surface, and a displacement regulating protrusion that protrudes and extends into the aperture along the axial direction. The protrusion prevents the cushion spring from compression beyond a prescribed length.

A mechanical pencil includes a barrel extending in a longitudinal direction, a lead-propelling mechanism, a lead reservoir, a side button, and an eraser-propelling mechanism having a helical cam. The lead-propelling mechanism, the lead reservoir, the eraser-propelling mechanism, and the side button are at least partly housed inside the barrel. The lead-propelling mechanism, the lead reservoir, and the eraser-propelling mechanism are prevented from rotating about the longitudinal direction relative to one another and relative to the side button, and the side button is prevented from rotating about the longitudinal direction relative to the barrel.

A mechanical pencil includes a barrel extending in a longitudinal direction, a lead-propelling mechanism, a lead reservoir, a side button, and an eraser-propelling mechanism having a helical cam. The lead-propelling mechanism, the lead reservoir, the eraser-propelling mechanism, and the side button are at least partly housed inside the barrel. The lead-propelling mechanism, the lead reservoir, and the eraser-propelling mechanism are prevented from rotating about the longitudinal direction relative to one another and relative to the side button, and the side button is prevented from rotating about the longitudinal direction relative to the barrel.