Patent ID: 7708398

Claim:
A printing apparatus comprising: (A) a transport mechanism transporting a medium in a forward direction and a backward direction; (B) a head printing dots on the medium; (C) a sensor sensing existence of the medium in a non-contact manner; (D) a reversion mechanism reversing the medium; and (E) a controller controlling the sensor to sense an end of the medium when the transport mechanism transports the medium in the forward direction so as to allow the head to print the dots on a surface of the medium and controlling the sensor to sense the end of the medium when the transport mechanism transports the medium in the backward direction so as to allow the reversion mechanism to reverse the medium after the dots are printed on the surface thereof wherein the sensor includes a light-emitting portion and a light-receiving portion, and wherein the printing apparatus further comprises a lower guide and an upper guide for guiding the medium between the light-emitting portion and the light-receiving portion; and wherein the sensor includes an upper protrusion portion and a lower protrusion portion, wherein the upper protrusion portion includes one of the light-emitting portion and the light-receiving portion and the lower protrusion portion includes the other thereof, wherein the lower guide includes a base surface, ribs protruding upward from the base surface so as to come in contact with the medium, and an insertion portion in which the lower protrusion portion is inserted, and wherein an opening is provided at a position of an optical axis of the sensor in the lower guide and the opening is formed in the base surface between the ribs.