Retractable writing instrument

A retractable writing instrument comprising:

• a barrel;
• a writing element that is accommodated in the barrel and is movable in a longitudinal direction;
• a push member that is disposed on a rear end portion of the barrel;
• and
• a protruding and retracting mechanism that causes a pen point of the writing element to protrude from and retract into a front end of the barrel at a frontward press on the push member,
• the protruding and retracting mechanism including:
• a plurality of cam teeth and a plurality of cam grooves that are formed on and in an inner face of the barrel, are arranged alternately along a circumferential direction, and extend in the longitudinal direction;
• a rotary member that is rotatably disposed rearward of the writing element and includes a plurality of protuberances engageable alternately with the cam teeth or the cam grooves;
• a cam member that is connected to the push member and includes a plurality of cam projections rotating the rotary member, and a plurality of engagement projections engaged with the cam grooves in the inner face of the barrel so as to be movable in the longitudinal direction;
• and
• a resilient element that biases the writing element rearward,
• wherein
• the push member and the cam member are in detent engagement with each other.

A retractable writing instrument comprising:

• a barrel;
• a writing element that is accommodated in the barrel and is movable in a longitudinal direction;
• a push member that is disposed on a rear end portion of the barrel and includes a prominence formed on an outer face of the push member and extending outward in a radial direction;
• and
• a protruding and retracting mechanism that causes a pen point of the writing element to protrude from and retract into a front end of the barrel at a frontward press on the push member,
• the protruding and retracting mechanism including:
• a plurality of cam teeth and a plurality of cam grooves that are formed on and in an inner face of the barrel, are arranged alternately along a circumferential direction, and extend in the longitudinal direction;
• a rotary member that is rotatably disposed rearward of the writing element and includes a plurality of protuberances engageable alternately with the cam teeth or the cam grooves;
• a cam member that is connected to the push member and includes a plurality of cam projections rotating the rotary member, and a plurality of engagement projections engaged with the cam grooves in the inner face of the barrel so as to be movable in the longitudinal direction;
• and
• a resilient element that biases the writing element rearward,
• wherein
• the push member and the cam member are in detent engagement with each other.