Shelf arrangement for freeze drying apparatus

Abstract

A shelf arrangement is disposed within the vacuum drying chamber of a freeze dryer. The shelf arrangement has multiple vertically-movable shelves that are suspended by stops on flexible wires stretched between upper and lower brackets of a frame assembly. Each shelf has four flanges extending from the edge thereof which comprise arms that straddle corresponding wires thereby engaging the stops so that the shelves are positioned in a vertical arrangement. The slots between the arms of the flanges allow the shelves to slide vertically along the wires when multiple screw members which engage following threaded nuts attached to the lower most shelf of the group of shelves are rotated. Thus, as the lower most shelf is raised, it engages the next highest shelf and so forth until all of the shelves are elevated vertically against the upper bracket. The power to elevate the shelves is supplied by a drive system mounted externally of the vacuum chamber of the freeze dryer which has a shaft that extends into the freeze drying chamber. The drive assembly includes a plate mounted for rotation about the output shaft that extends into the drying chamber. A motor and gear reduction are mounted on the plate and adjustable limits are mounted adjacent to the plate to limit the rotation of the plate and to sense the amount of torque being delivered through the output shaft. A microswitch can be mounted to turn off the motor when a predetermined torque is sensed. The plate may be connected to a hydraulic damper which dampens out excessive transient forces produced by the motor thereby preventing premature motor stoppage. A latching mechanism is also provided to latch certain shelves in an elevated position against the upper bracket so that the remaining shelves can be repositioned in the remaining space by spacers attached to the wires.