Apparatus and methods for improving the safety and efficiency and decreasing the cost of producing liquid oxygen with a small-scale use liquefaction device, according to various embodiments of the present invention. In one embodiment, a switch is electrically coupled to a storage dewar pressurizing means, the switch positioned to be activated by a portable dewar upon engagement of portable dewar with storage dewar. Cryocooler and/or cooling fan enter low power mode when dewar liquid level reaches a predetermined level, and to return to a fall power mode when dewar liquid level drops to another predetermined level. A cold finger of the cryocooler extends within the dewar and may prevent overfilling of the dewar. The cold finger has a temperature gradient. As the gas liquefies and fills the dewar, the liquid level rises only to a level on the cold finger at which the temperature exceeds the boiling point of oxygen.
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of U.S. Provisional Patent Application No. 60/622,483, entitled "Liquefying and Storing a Gas" and filed on Oct. 26, 2004. The present application also claims the benefit of U.S. Provisional Patent Application No. 60/677,661, entitled "Liquefying and Storing a Gas" and filed on May 2, 2005. The aforementioned applications are hereby incorporated by reference herein in their entirety for all purposes.
The present application is further related to U.S. patent application Ser. No. 11/131,071 entitled "Liquefying and Storing a Gas," filed on a date even herewith and assigned to an entity common hereto, the contents of which are herein incorporated by reference in their entirety for all purposes.
