Cryogenic device selectively operable in a continuous freezing mode, a continuous thawing mode or a combination thereof

A cryogenic device is described that utilizes pressurized coolant gas and is provided with a single control easily manipulatable by finger pressure to selectively furnish either continuous freezing or continuous thawing, each alone or in sequence. The expansion chamber is pressurized only when the control lever is deliberately held depressed and, in consequence, either the expansion chamber or the coolant inlet subassembly can be detached or exchanged without risk to the operator or the equipment and without need for closing off the coolant supply. A pressure regulator forming a part of the device limits the maximum possible pressure in the expansion chamber and exhaust passages to a safe value. The device is substantially noiseless in operation and the control is operable through first and second stages by movement in the same direction to provide freezing or warming modes at the user's option and is self-locking in the freezing mode but is automatically disengaged therefrom upon movement into the thawing mode