Description
Class F17B : GAS-HOLDERS OF VARIABLE CAPACITY
Subclass 1/007: Gas-holders of variable capacity (large containers in general B65D 88/00; storing fluids in natural or artificial cavities or chambers in the earth B65G 5/00) with telescopically movable ring-shaped parts (F17B 1/1 takes precedence; sealing of rings F17B 1/04)