chain drive is substantially rigid and in a linear orientation and pivotally connected chain links may not substantially rotate relative to each other and may not be deflected substantially from the linear orientation the chains may be engaged and disengaged by rotating around sprockets which deliver the force to the chain drive the chain drive may be utilized as a garage door system for raising or moving laterally a garage door or movable barrier with the chain drive in compression application_number US 36522803 A description referring initially to fig1 and 2 a head unit 10 of a garage door system 11 is shown attached to an outer wall 12 of a structure such as a garage and attached to a movable barrier such as a garage door 14 as depicted in fig1 the garage door 14 is in a closed position in fig2 the garage door 14 is in an intermediate partially open position the garage door 14 includes a plurality of door sections 16 which span vertically from a ground level not shown to a point below the outer wall 12 each door section 16 is connected to any abutting door section with a hinge 17 a rubber seal 18 is provided attached to the outer wall 12 or preferably to the top of the garage door 14 when the garage door 14 is in a closed.