Helium gas liquefying apparatus

Claim 1

A helium gas liquefying apparatus, comprising: (a) a liquefied helium reservoir (4); (b) a compressor (2) with inlet means receiving a helium gas stock and connected to said reservoir; (c) a plurality of heat exchangers (9 1 , 9 2 ) connected in series with each other via a series liquefying line (11); (d) a plurality of expansion engines (10, 10 2 ), connected in parallel with corresponding heat exchangers; (e) a Joule-Thompson valve (5) connected from the outlet of said liquifying line to said reservoir; (f) a series return line (12) with an inlet (12' ), said series return line being disposed in reverse flow of said heat exchangers to said liquefying line and connected to said compressor inlet means; (g) a return valve (6) connected to said reservoir; (h) means for eliminating a temperature rise in the helium gas exhausted from a series liquefying line to the Joule-Thompson valve including a three-way valve having one passage connected to said return line inlet (12' ) from said return valve, and a second passage branched therefrom connected to the inlet of said compressor inlet means; and, (i) an additional line connected from the inlet of said compressor to said three-way valve.