Document guide roller assembly in a scanner

A scanner comprising:

• an upper unit consisting of a cover shell made through a molding process, a document guide roller assembly, two spring pressers, and a lid, said cover shell having a document feed port, a document outlet port, a plurality of locating elements to hold said document guide roller assembly, and a plurality of internally threaded posts to hold said spring pressers and said lid by screws, said document guide roller assembly comprising two axles retained to said locating elements by said spring pressers and covered by said lid, and rollers protruded through openings on said lid, each spring presser having two opposite ends respectively pressed on either axle at either end said ends formed into two opposite sloping strips respectively pressed on either axle of said document guide roller assembly to hold down said document guide roller assembly and prevent the inserted document from being biased;
• and
• a bottom unit comprised of a casing, a motor drive, a transmission gear set, a transmission roller assembly, a spring switch, a LED lightsource, a reflector, a focus lens assembly, a cover board, and a control circuit board, said casing having mounting boards to which said motor drive and transmission gear set and transmission roller assembly are respectively fastened, said spring switch, said LED light source, said reflector, said focus lens assembly and said control circuit being incorporated into a scanning control circuit system for scanning control, said cover board having screw holes at two opposite ends respectively fastened to internally threaded posts on said casing by screws, and openings through which rollers on said transmission roller assembly protrude.