A freeze dryer (10) comprises a chamber (12) having a rectangular slot through which vials (86) are inserted into the chamber (12). An assembly for loading and/or unloading the chamber (12) comprises a transfer bar (42) extending across the slot. The bar (42) is pivotally attached at each end to first and second flat springs (46, 48), each spring being wound on a respective rotatably mounted spool (50, 52) located proximate the slot. Drive means are provided for synchronously rotating the spools (50, 52) to effect movement of the bar (42) into or out from the chamber (12) and for selectively rotating the spools (50, 52) to raise or lower the bar (52).