Patent ID: 8011845

Claim:
A marking instrument configured for use in filling an answer blank on an answer sheet, the marking instrument comprising: an upper body portion having an internal cavity disposed therein; a depressor element disposed at least partially within the upper body portion; a depressor spring that is mechanically coupled to the depressor element to provide an elastic force thereto at least while the depressor element is displaced linearly; a spirally-grooved circular shaft that is configured to cooperate with the depressor element such that the spirally grooved circular shaft rotates about its longitudinal axis in response to the depressor element being displaced linearly; a marking platform having at least one marking element disposed thereon, and being configured such that at least a portion of the marking platform rotates in response to rotation of the spirally grooved circular shaft; a cap element having an opening that corresponds to a geometric shape of the answer blank; and wherein the cap element and the marking platform are configured such that, during at least a portion of the rotation of at least a portion of the marking platform, at least one of the marking elements protrudes though said opening and moves relative to the cap as the cap guides the motion of at least one of the protruding marking elements in accordance with the shape of opening.