Patent ID: 8468839

Claim:
A portable liquid oxygen (PLOX) unit comprising: a liquid oxygen (LOX) container having an interior; an inlet line having a first inlet end portion disposed outside the interior of the LOX container and a second inlet end portion disposed in the interior of the LOX container, wherein the inlet line is adapted to communicate LOX from a LOX supply to the interior of the LOX container; an outlet line having a first outlet end portion disposed outside the interior of the LOX container and a second outlet end portion disposed in the interior of the LOX container, wherein the outlet line is adapted to communicate LOX from the interior of the LOX container; a vent line having a first vent end portion disposed outside the interior of the LOX container and a second vent end portion disposed in the interior of the LOX container, the vent line further having an interior, wherein the vent line is adapted to communicate the interior of the LOX container to ambient atmosphere; a vent valve operatively coupled to the vent line to selectively communicate the interior of the LOX container to the ambient atmosphere; and an auto shutoff assembly associated with the vent line, wherein the auto shutoff assembly includes: a valve seat defined in the vent line between the first vent end portion and the second vent end portion, a movable valve element that is buoyant in LOX and is configured such that buoyancy of the valve element in LOX and a rising level of LOX in the interior of the LOX container during filling cause the valve element to engage the valve seat and substantially block the vent line responsive to LOX in the interior of the LOX container reaching a predetermined level of LOX in the interior of the container, wherein the valve element and/or the valve seat are configured such that, during engagement of the valve element and the valve seat, the interior of the vent line communicates with the interior of the LOX container, wherein such communication between the interior of the vent line and the interior of the LOX container causes a pressure differential between different sides of the movable valve element to be gradually reduced to unblock the vent line, and wherein the interior of the vent line communicates with the interior of the LOX container through one or more pathways provided by one or more nodules formed on a surface of the valve element and/or on a surface of the valve seat.