Thermal insulation device for a very low-temperature line

Claim 1

In a thermal insulation device for a very low-temperature line and comprising; a thermal screen in the form of a metal cylinder surrounding said line, said screen consisting of at least two parts assembled along two generatrices of the formed cylinder, an outer water and air tight cylindrical, metal case surrounding said screen, a thermally insulating powder occupying the space between the screen and the outer case, means for suspending the line in the screen and means for suspending the screen in the outer case, at least one intermediate part disposed along each of said generatrices for the mechanical assembly of the parts of said screen while insulating them thermally from each other, the two parts of said screen each bearing in good thermal contact at least one cooling conduit, means for circulating a cooling fluid in a forward direction in the cooling conduit borne by one of the parts and in a return directioN in the cooling circuit borne by the other part, the improvement wherein: means including said intermediate parts define openings to allow communication between the space inside and outside the screen without permitting the passage of the powder therethrough but allowing the degassing of the powder from the inside of the screen.