A pump assembly for a high pressure cryogenic fluid generator of a type including a container assembly for containing a cryogenic fluid and at least one external check valve in fluid communication with said pump assembly housing outlet for maintaining the fluid pressure provided by the at least one pump assembly, said pump assembly, comprising:
- a) an actuator mounted to said container assembly;
- b) a pump assembly housing having a housing opening and being securely attached at a first end thereof to said container assembly, said pump assembly housing including at least one longitudinal positioning opening, said pump assembly housing having a pressurization cavity formed therein at a distal end terminating with a pump assembly outlet;
- c) an internal check valve assembly operatively associated with said pump assembly housing, said internal check valve assembly, comprising:
- i. a shaft positioned within said housing opening of said pump assembly housing and having a distal end thereof, said shaft extending into said pressurization cavity, said shaft being fixedly attached at a first end to said actuator, said shaft including a longitudinal guidance slot, said shaft having a fluid passageway formed therein that extends from said longitudinal guidance slot to said distal end, said distal end of said shaft having an internal sealing surface;
- ii. a positioning bar assembly operatively positioned within said longitudinal guidance slot;
- iii. a biasing element supported at a first end by said pump assembly housing and supported at a second end by said positioning bar assembly;
- and,
- iv. a connecting rod assembly securely connected at a first end to said positioning bar, said connecting rod assembly being positioned within said fluid passageway, said connecting rod assembly terminating with a flow inhibiting element;
- and,
- and,
- d) a seal element positioned between said pump assembly housing and said internal check valve assembly to provide a closure for said pressurization cavity,
- wherein,
- i) at an initial fill position, said actuator positions said shaft at an upper position in which said positioning bar assembly is biased by said biasing element against a stop portion of said pump assembly housing, and a flow passage is formed allowing cryogenic fluid to flow from said container assembly, through said longitudinal positioning opening of said pump assembly housing, through said longitudinal guidance slot of said shaft, through said fluid passageway of said shaft, through a space formed between said flow inhibiting element and said internal sealing surface, and into said pressurization cavity;
- ii) at intermediate fill positions said shaft moves in a first direction longitudinally through said pressurization cavity toward said flow inhibiting element;
- iii) at a shutoff position, said internal sealing surface of said shaft contacts said flow inhibiting element creating a seal therebetween;
- iv) in a pressurization cycle, said shaft moves longitudinally further through said pressurization cavity compressing the fluid within said pressurization cavity and displacing said fluid through said fluid generator outlet;
- v) at the beginning of an upstroke, said internal check valve assembly moves in a second, reverse direction in said pressurization cavity until said positioning bar assembly contacts said stop portion of said pump assembly housing;
- vi) at intermediate parts of the upstroke, said shaft continues to move in said second direction while other portions of said internal check valve assembly remain stationary, thus creating an expanding gap between said flow inhibiting element and said internal sealing surface and allowing fluid to flow into said pressurization cavity;
- and,
- vii) at the end of an upstroke, said shaft moves to said initial fill position,
- wherein filling is provided without loss of sealing engagement of said shaft and said seal element.