Portable cryogenic power system for pneumatically operated tools

Claim 1

A portable cryogenic power system for use with pneumatic tools, said system comprising: insulative tank means for storing a cryogenic fluid in a liquid state at relatively low pressure, said tank means having an interior with a bottom surface and an aperture providing fluid communication with said interior, said tank means including an inner vessel and an outer vessel each provided with an aperture, neck means for providing a fluidtight connection between said inner vessel aperture and said outer vessel aperture, and lossy insulation means positioned between said inner vessel and said outer vessel for hindering the flow of heat from ambient to said interior of said tank means, said tank means further including an outer wall surface and a top surface joined to the upper periphery of said outer wall surface to define an upper peripheral edge thereof; manifold means coupled to said tank means for providing a fill path and a vent path to said interior of said tank means, said manifold means being fabricated from a material having a relatively high coefficient of thermal conductivity and including a fill inlet, a vent outlet, a cryogenic working fluid outlet and a bottom surface portion in fluid communication with said interior of said tank means; fill tube means having a first end coupled to said fill path of said manifold means and a second end extending into said interior of said tank means; vent tube means having a first end coupled to said vent path of said manifold means and a second end extending into said interior of said tank means, said second end of said vent tube means terminating at a distance above said interior bottom surface of said tank means to provide a maximum fill capacity less than the total internal volume of said tank means; first relief valve means coupled to said vent path of said manifold means for providing pressure relief to said interior to said tank means at a first release pressure; vent valve means coupled to said vent outlet of said manifold means for enabling said interior to be vented to ambient; check valve means coupled to said fill path for preventing fluid flow from said interior of said tank means to said fill inlet; heat exchanger means for vaporizing cryogenic fluid flowing therethrough, said heat exchanger means having an inlet portion and an outlet portion; economizer check valve means coupled to said cryogenic working fluid outlet of said manifold means and said inlet portion of said heat exchanger means for enabling one-way flow of said cryogenic fluid from said interior of said tank means to said heat exchanger means; pneumatic circuit breaker valve means for limiting the flow of cryogenic fluid therethrough to a relatively low predetermined maximum rate, said pneumatic circuit breaker valve means having an inlet coupled to said heat exchanger outlet portion and an outlet adapted to be coupled to a pneumatic hose; second relief valve means coupled to said heat exchanger outlet portion for providing pressure relief to said heat exchanger at a second release pressure greater than said first release pressure; means including said bottom surface portion of said manifold means for vaporizing a portion of said cryogenic fluid in said interior of said tank means to provide a relatively low working pressure to said interior of said tank means for causing flow of cryogenic fluid from said interior through said economizer check valve means to said heat exchanger means; and shroud means having a lower end coupled to said insulative tank means adjacent said upper peripheral edge for providing a protective enclosure for said manifold means, said fill tube means, said vent tube means, said first and second relief valve means, said vent valve means, said check valve means and said economizer check valve means, said lower end of said shroud means being spaced from said top surface and said outer wall surface of said insulative tank means to provide communication between ambient and said heat exchanger means.