Patent ID: 7931415

Claim:
A knock-type writing instrument comprising a refill having a writing portion at a front end thereof, a spring for urging the refill backward, and a knock rod that is arranged at the back of said refill and is linked to said refill and protrudes beyond the rear end of a holder, wherein upon depressing said knock rod, the refill is brought to a writing position protruding beyond the front end of said holder and an engaging nub of a clip is engaged with an engaging protuberance of a slide body to maintain said writing position; and wherein a rotor is provided between said knock rod and the refill to support the refill, the knock rod and said rotor have tilted cam surfaces for rotation corresponding to each other, and the rotor rotates in only one direction by only a predetermined angle each time due to the reactive force of said spring and responsive to the knocking operation forward and backward in the axial direction; when the knocking operation is effected in a state where the refill has been drawn back into the holder, a tilted cam surface for positioning formed on the side surface of a cylindrical portion of the rotor comes in contact with a first tilted surface of the cam formed in an inner cylinder corresponding thereto and with a tilted cam surface formed on the slide body successively, and a vertical surface of the cam for positioning of the rotor comes in contact with a vertical wall of a cam formed in the holder and maintains the refill at a writing position being supported by the load in the axial direction and by the rotational force; when the knocking operation is effected in a state where the refill is at the writing position, said tilted cam surface for positioning of the rotor comes in contact with a tilted cam surface formed in the holder and, further, rotates upon coming in contact with a second tilted surface of the cam formed in the inner cylinder, and moves to a retreated limit position to maintain the refill at the holding position; the slide body that can move in the lengthwise direction has an inward protuberance in a cut-away portion of the holder and when the refill is at the writing position, said inward protuberance is brought into engagement with a rear end of the cam for positioning of the rotor, and an engaging protuberance formed on the slide body engages with an engaging step formed in a clip body to maintain the refill at the writing position; when the engagement is released between said engaging protuberance of the slide body and said engaging step of the clip body, the refill is returned by the spring back to the retreated position together with the slide body, and the positioning cam of the rotor moves to the retreated limit position passing through a gap formed at the back of the tilted cam surface of the holder to maintain the refill at the holding position; wherein the second tilted surface of said cam formed in the inner cylinder has a step in the axial direction.