Security bar transfer mechanism assembly

A security bar assembly has a plurality of bars that extend across an opening and have ends joined to drive chains. The bars may extend between two channels positioned on opposite faces of the opening, and may be slidable within the channels. The ends of the bars may be retained in the channels and the ends may have connections to chain links in opposing drive chains which are spaced apart a predetermined number of links to keep the bars a predetermined distance apart. A drive mechanism may be provided for moving the drive chains to slide the bars in the channels and a storage area adjacent the opening associated with the channels to retain the bars when they are not in place over the opening. Transfer mechanisms are provided for moving the security bars between a stored position and a position in which the bars engage the bar drive chain.