Automatic apparatus for grinding and polishing samples

A sample preparation system for grinding and polishing metallurgical and other samples prior to microscopic examination thereof, said system including, in combination, a platen rack having a plurality of shelves arranged vertically one above the other, each shelf having a support surface for supporting a polishing platen thereon in a horizontal position, platen exchange means for selecting one platen from said rack and transferring the same to a platen drive plate for conjoint rotation with said drive plate for a polishing operation, and a polishing head which is movable between a polishing position where it is located over said platen drive plate and a wash position where it is located over a wash station, said polishing head having means to support a sample holder therebeneath so that said sample holder may be positioned down against a platen on said drive plate for polishing samples held in said sample holder, means associated with said polishing head for raising and lowering said sample holder and for rotating the same, and said platen exchange means being operated when said polishing head is positioned over said wash station, said platen exchange means including a transfer arm which is movable both vertically and horizontally, said transfer arm being movable vertically to align with a platen to be transferred from said rack, and being movable horizontally from a position behind said rack so as to move directly through said rack between a pair of adjacent shelves thereof to remove and transfer a selected platen to said platen drive plate, said transfer arm including an arm member having two lift arms extending horizontally therefrom, said lift arms serving to carry a selected platen, and said arm member including means for engaging and pushing a selected platen off its rack support surface and onto said lift arms for transfer of said platen, said platen rack including an upright support plate and one side of each of said shelves being attached to said support plate in cantilever fashion so that said transfer arm may move horizontally in either direction between the free ends of said shelves, and said platen rack being disposed on one side of said platen drive plate and said wash station being disposed on the opposite side of said platen drive plate.