Self-venting cap for a neck of a dewar vessel

Abstract

A self-venting cap for a neck of a dewar vessel with a lower component having a first plurality of apertures, an upper component with a second plurality of apertures, a seal held between the lower and upper components, and a third component releasably secured to the upper component. The cap forms a compression seal about an inner circumference of the neck of a dewar vessel when the lower and upper components are matingly engaged in a sealing position, creating a plurality of tortuous vapor paths through the cap. When the cap is in the sealing position, a first chamber is formed between the lower and upper components and a second chamber and a vent opening are formed between the upper and third components. In this position, vapor inside the dewar vessel can travel in a plurality of tortuous paths beginning within the neck and then sequentially travelling up through the first plurality of apertures, the first chamber, the second plurality of apertures, the second chamber and then out the vent opening. There can also be a plurality of shorter tortuous paths beginning within the first plurality of apertures, travelling through the first chamber, and then up through at least two of the second plurality of apertures. A semi-permeable membrane, which can be incorporated in the cap, prevents moisture from entering into the dewar vessel while still allowing vaporous cryogen to exit from the dewar vessel.

What is claimed is:  
     
         1 . A self-venting cap for a neck of a dewar vessel, comprising: 
 a lower component with a first plurality of apertures;    an upper component with a second plurality of apertures, a second chamber and a vent opening;    a seal held between the lower and upper components that can form a compression seal about an inner circumference of the neck when the lower and upper components are matingly engaged in a compression seal position; and    a first chamber located between the lower and upper components;    wherein vapor inside the dewar vessel can travel in a plurality of tortuous paths when the cap is in the compression seal position, the plurality of tortuous paths beginning within the neck and then sequentially travelling up through the first plurality of apertures, the first chamber, the second plurality of apertures, the second chamber and then out the vent opening.    
     
     
         2 . A self-venting cap as recited in  claim 1 , further comprising: 
 a third component secured to the upper component so as to define the second chamber and vent openings between the upper and third components.    
     
     
         3 . A self-venting cap as recited in  claim 2 , wherein the lower and upper components are matingly engaged by a male and a female thread.  
     
     
         4 . A self-venting cap as recited in  claim 2 , wherein the upper component contains a positioning device on a lower surface capable of engaging with a second positioning device located in a fixed position relative to the neck such that once the first and second positioning devices are engaged, rotation of the third component in a tightening direction will cause the seal to be squeezed between the lower and upper components to form the compression seal.  
     
     
         5 . A self-venting cap as recited in  claim 2 , wherein the lower component, the upper component and the third component are made of cryogenically compatible material that is non-metallic and non-conductive.  
     
     
         6 . A self-venting cap as recited in  claim 2 , wherein the third component is releasably secured to the upper component.  
     
     
         7 . A self-venting cap as recited in  claim 1 , wherein the vent opening is comprised of a plurality of vent openings.  
     
     
         8 . A self-venting cap as recited in  claim 1 , wherein the plurality of tortuous paths include a plurality of shorter tortuous paths beginning within the first plurality of apertures, travelling through the first chamber, and then up through the second plurality of apertures.  
     
     
         9 . A self-venting cap as recited in  claim 1 , wherein there is a plurality of shorter tortuous paths beginning within each of the first plurality of apertures, travelling through the first chamber, and then up through at least two of the second plurality of apertures.  
     
     
         10 . A self-venting cap as recited in  claim 1 , wherein the seal is comprised of a silicone material.  
     
     
         11 . A self-venting cap as recited in  claim 1 , wherein the lower component has an outer circumference that is less than the inner circumference of the neck and the first plurality of apertures is located inside of the outer circumference.  
     
     
         12 . A self-venting cap as recited in  claim 10 , wherein the vent opening is located outside of the inner circumference.  
     
     
         13 . A self-venting cap as recited in  claim 10 , wherein the compression seal is strong enough to support the weight of the dewar vessel when it is not charged with a cryogen.  
     
     
         14 . A self-venting cap as recited in  claim 10 , wherein the upper component has an upper outer circumference that is located outside of the inner circumference.  
     
     
         15 . A self-venting cap as recited in  claim 14 , wherein the vent opening is located outside of the upper outer circumference.  
     
     
         16 . A self-venting cap for a neck of a dewar vessel, comprising: 
 a lower component having an outer circumference that is less than the inner circumference of the neck and a first plurality of apertures that is located inside of the outer circumference;    an upper component having an upper outer circumference and a second plurality of apertures, the upper outer circumference being located outside of the inner circumference;    a seal held between the lower and upper components that forms a compression seal with an inner circumference of the neck when the lower and upper components are matingly engaged in a compression seal position; and    a third component secured to the upper component;    wherein a first chamber is formed between the lower and upper components when the lower and upper components are matingly engaged in the compression seal position;    wherein a second chamber and a vent opening located outside of the upper outer circumference are formed between the upper and third components when the lower and upper components are matingly engaged in the compression seal position; and    wherein vapor inside the dewar vessel can travel in a plurality of tortuous paths when the cap is in the compression seal position, the plurality of tortuous paths beginning within the neck and then sequentially travelling up through the first plurality of apertures, the first chamber, the second plurality of apertures, the second chamber and then out the vent opening.    
     
     
         17 . A self-venting cap as recited in  claim 16 , wherein the lower component, the upper component and the third component are made of cryogenically compatible material that is non-metallic and non-conductive.  
     
     
         18 . A self-venting cap as recited in  claim 17 , wherein there is a plurality of shorter tortuous paths beginning within each of the first plurality of apertures, travelling through the first chamber, and then up through at least two of the second plurality of apertures.  
     
     
         19 . A self-venting cap as recited in  claim 16 , further comprising: 
 a semi-permeable membrane that prevents moisture from passing through the first plurality of apertures while still allowing vaporous cryogen to pass through the first plurality of apertures.    
     
     
         20 . A capped dewar vessel assembly, comprising: 
 a dewar vessel having an outer casing and an inner vessel with each having openings at their tops connected together by a neck portion forming an evacuable space between the outer casing and the inner vessel and a dewar opening into the inner vessel;    a specimen chamber connected to the inner vessel that extends inside the inner vessel and is accessed through the dewar opening; and    a self-venting cap that restricts access to the specimen chamber when it is in a compression seal position that forms a compression seal with an inner circumference of the neck;    wherein vapor inside the dewar vessel can travel in a plurality of tortuous paths when the cap is in the compression seal position, the plurality of tortuous paths beginning within the dewar opening and then sequentially travelling up through a first plurality of apertures, a first chamber, a second plurality of apertures, a second chamber and then out a vent opening.    
     
     
         21 . A capped dewar vessel assembly as recited in  claim 20 , wherein there is a plurality of shorter tortuous paths beginning within each of the first plurality of apertures, travelling through the first chamber, and then up through at least two of the second plurality of apertures.  
     
     
         22 . A capped dewar vessel assembly as recited in  claim 20 , further comprising: 
 a semi-permeable membrane that prevents moisture from entering into the dewar vessel while still allowing vaporous cryogen to exit from the dewar vessel.    
     
     
         23 . A capped dewar vessel assembly as recited in  claim 22 , wherein the semi-permeable membrane is incorporated into the self-venting cap.