Patent ID: 6981647

Claim:
A foreign matter detection mechanism for detecting a foreign matter other than a carriage object, comprising: a foreign matter detection member having a foreign matter engagement portion and being able to move closer to or away from a traveling path of the object; a movement mechanism for moving the foreign matter detection member in a direction crossing the traveling path; and detecting means for detecting presence/absence of foreign matter detection by the foreign matter detection member, wherein the foreign matter detection member is attached to the movement mechanism so as to thoroughly cut across an area through which the foreign matter can pass when the object does not exist in the traveling path and move while sliding on a lower surface of the object when the object exists in the traveling path; the foreign matter engagement portion of the foreign matter detection member being constituted by a tabular portion, a concave portion which the tabular portion can enter is provided to the detecting means, and the concave portion being formed to have a width which allows passage of the tabular portion with which the foreign matter is not engaged and does not allow passage of the tabular portion with which the foreign matter is engaged.