US 4,055,904 AGranted

Automatic critical point drying apparatus

AssigneeTousimis Research Corporation

InventorJohn E. Horne

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Abstract

A critical point drying apparatus for sample preparation in electron microscopy is automated to proceed in order through multiple operational modes in drying the specimen. These modes are: precooling, in which a specimen chamber is cooled; starting, in which the specimen chamber is filled with liquid CO.sub.2 : purging, in which a limited amount of CO.sub.2 passes through the specimen chamber; heating, in which the specimen chamber is heated to elevate pressure to the critical pressure and heat the specimen to the critical temperature; bleeding, in which the specimen chamber is depressurized to atmospheric pressure at a very slow rate; and finishing, in which the chamber is vented and an indicator signals the end of the drying operation. These steps are automatically activated in sequence when desired mode conditions are met or can be selectively controlled in a manual mode.

Claims19

Dependent claims

In a critical point dryer for specimen preparation in electron microscopy, said specimen being dehydrated in a dehydrating fluid, said dryer including a specimen chamber in which said dehydrating fluid containing specimen is inserted, cooling means for cooling said chamber, filling means for filling said chamber with a transitional fluid having a critical temperature and critical pressure, purging means for purging said chamber of said dehydrating fluid, heating and pressurizing means for heating said transitional fluid above said critical temperature and pressurizing said transitional fluid above said critical pressure, bleeding means for controllably equalizing said chamber to atmospheric pressure, venting means for venting said chamber directly into the atmosphere, the improvement comprising:

automatic means for automatically and sequentially controlling said cooling means, said filling means, said purging means, said heating and pressurizing means, said bleeding means and said venting means.

Dependencies are inferred from the claim text.