Driving apparatus for a flatbed scanner

A driving apparatus located inside a housing of a double carriage scanner for driving a lamp carriage and an optical carriage in tandem, wherein said double carriage scanner having at least a housing, a glass table on top of said housing, a photoelectric converting means mounted on the inner bottom of said housing, a lamp carriage, and an optical carriage, comprising:

• a plurality of slave pulleys circumscribing a longitudinal side of said housing;
• a pair of reduction pulleys mounted on the same side of said optical carriage;
• two idle pulleys disposed parallel to each other and at opposite sides of said housing;
• closed-loop conveying means having a first portion connecting said lamp carriage, engaging one of said pair of reduction pulleys and one of said idle pulleys through a first substantial arc of 180.degree. in a first direction, and second portion engaging the other one of said pair of reduction pulleys and the other one of said idle pulleys through a second substantial arc of 180.degree. in a second direction, a third portion connecting said two idle pulleys, a fourth portion connecting to said first portion, a fifth portion connecting to said second portion, and a sixth portion connecting to said fourth portion and said fifth portion;
• and
• a master gear connected to a portion of said closed-loop conveying means for driving said lamp carriage one unit distance and said optical carriage one half unit distance in synchronism and in the same direction.