Gas tight shut off valve for a material charging or discharging lock

Gas-tight shut-off valve for a material charging or discharging lock, comprising:

• a valve housing;
• an annular valve seat connected to said valve housing, said valve seat surrounding a discharge opening;
• a valve closing element associated, in said valve housing, with said valve seat, said valve closing element being movable between a first position, in which said valve closing element and said annular valve seat can be axially pressed together, and a second position, in which said valve closing element is located laterally of said discharge opening;
• means for axially pressing said valve closing element and said annular valve seat together when said valve closing element in its first position;
• and
• a soft sealing means associated either with said annular valve seat or with said valve closing element, said soft sealing means having an exposed sealing surface to be pressed against a sealing means contact surface on said valve closing element, respectively on said valve seat, for providing gas-tightness when said valve seat and said valve closing element are pressed together;
• characterised by
• a heat protecting element that is movable in said valve housing between a first position, in which it covers said exposed sealing surface when said valve closing element is in its second position, and a second position, in which it uncovers said exposed sealing surface, so as to enable again a gas-tight contact between said exposed sealing surface and said sealing means contact surface.