Abstract: The present invention is directed to a seal crossover system which includes two seal plates adjacent to slot crossover portions of separate respective conveyor loops as they diverge (or converge) past a switch in a power and free conveyor system. The seal plates are driven by respective pneumatic cylinders which are pneumatically linked to a switch cylinder such that the seal plates are automatically extended or retracted depending upon the condition of the switch. Thus a respective slot crossover portion of each conveyor loop is selectively and alternately sealed or opened to allow unimpeded passage of a load carriage and a drive trolley, respectively.

Abstract: A power and free conveyor transfer system includes a number of drive trolleys operating within a free track and being selectively propelled by endless drive chains within a vertically aligned power track. Each drive trolley includes a trolley housing body to which are rigidly attached a pair of downwardly extending lateral arms, each with a rearward facing drive surface. A pivotable drive member is attached to the front end of the trolley housing and extends backward and downward between the lateral arms with a drive dog forming a portion thereof. The drive trolley design facilitates transfer of each drive trolley between non-synchronous delivering and receiving power tracks in a conveyor transfer zone. Within the transfer zone, the delivering and receiving power tracks are at different elevations and approach each other from a relatively large angle to minimize the potential for mechanical interference or jamming.