Valve anti - return device of breath, a mask, a helmet and protective suit

摘要

The valve (13) has a valve flap (33) to fit hermetically against a seat (34) and prevent circulation of fluid passing through the passage (35) in a direction opposite the closure movement. The gas can flow when its pressure is greater than the closure force of springs (36) that close the valve flap against the seat. There are two seating faces for the end of the return springs. One is movably mounted on the valve closure and the other is fixed in place. At least one of the seating faces is inclined with respect to the direction of travel or with respect to an axis along which the closure moves. The return springs drive the valve closure. There is a hysteresis effect in the ration between the force of the return springs and their size between the two seating faces.