Chain driven linkage assemblies for room extensions

The invention relates to a linkage arrangement for moving members together or apart in a substantially linear motion without a substantial shift in a direction perpendicular to the desired linear motion. Typical linkages that are commonly used for a variety of purposes involve a pair of parallel members attached pivotally to a pair of parallel linkage members to form a parallelogram. If one of the parallel members is fixed, then motion of the parallelogram linkage results in an angular motion-in or out and up or down rather than simply in or out. The present invention relates to a linkage arrangement of the "X" or scissors type for moving members relative to one another in a substantially linear motion. A push-pull drive chain mechanism and scissors linkage assembly powered by a hydraulic cylinder to affect the coordinated, linear movement of an expandable room in a recreational vehicle. The drive chain moves generally vertically along a first structural member, such as a vehicle frame member, as the hydraulic cylinder extends or retracts to move the expandable room relative to the vehicle frame. The drive chain is pivotally connected at the proper place on the scissors-type linkage assembly, the links that form the scissors extending and crossing for pivotal attachment to a structural member of the vehicle body and a structural member of the expandable room. The drive chain is constructed and guided to provide the required force for opening and closing the scissors assembly.