Document stream merging method and apparatus

A collation control mechanism is used to transfer a collation from a dual accumulator to an exit nip of a collation machine. The collation control mechanism has a middle drum and two side rollers to form an upper nip and a lower nip. The drum is caused to rotate alternately in a clockwise direction and in a counter-clockwise direction for transferring a collation from the upper bay and the lower bay, respectively, to the exit nip. A motor is used to drive the drum in both the clockwise and counter-clockwise direction. A coupling mechanism including two sets of one-way clutches is used to engage the motor to the upper and lower rollers of the exit nip so that the upper roller is caused to rotate only in the counter-clockwise direction while the lower roller is cause to rotate only in the clockwise direction.