US Patent 7823880 Stepper mechanism

A stepper mechanism for transporting a substrate along a linear transport path, which includes a stationary member and first and second transport members, extending widthwise across the transport path, the stationary member and transport members each being adapted to alternatively grip and release the substrate, and independent drive units are arranged on either side of the transport path for moving the respective ends of the transport members in a transport direction (X), wherein the transport members are movable independently of one another, and at least one of the drive units is adapted to move one end of the first transport member independently of the corresponding end of the second transport member.