Abstract: A rack for holding dental impression trays includes a rectangular block having apertures therein to receive the handles or tubes extending from the trays and to cantilever the trays from the rack. A paired arrangement of apertures can accommodate a tray having both a handle and tubes. A base supporting the rack upright has wells therein for holding water which, together with a dome enclosing the rack, provide a moist atmosphere for the impression material, where needed. The rack can be free-standing or wall-mounted. One embodiment of the rack adapted for wall-mounting can be inexpensively manufactured of plastic by extrusion.

Abstract: The system includes a plurality of material discharge spouts combined with a blending device for use with a hoppered bin. Each spout opens to the hopper at a location selected to draw material into the hopper from substantially one predetermined portion of a horizontal bin cross sectional plane in a first in -- first out segregation free manner. The blending device combines the material discharge streams formed by the spouts in proportion to the areas of the portions of the horizontal bin cross sectional plane from which they are drawn, respectively, to form a common discharge stream of uniform composition. The principles of the invention are applicable to conversion of existing bins or bin bottoms, or to a bin withdrawal system or process. Also disclosed is a blending unit which includes a mass flow hopper, the blending unit being particularly suited for bin or bin bottom conversion application.