Abstract: A coupling device for establishing a detachable connection for a tube system is to be improved so that while simple detachability of the pipe socket and tube is guaranteed, the pulling-off force is equivalent to firm clamping. To accomplish the task, a sleeve-like coupling box 7 is provided, which surrounds the tube 5 in a clamp-like manner and, for fixation on the pipe socket 2, it has, on the inside, a circumferential notch 8, into which two oppositely arranged projecting parts 4 of the pipe socket 2 snap. The coupling box 7 expands under the effect of a force acting laterally, so that the projecting parts 4 will disengage from the notch 8.

Abstract: A closed-cycle breathing equipment and gas mask for operation under pressure with a pressurized air source for respiratory air and with an air bag being under prestress during the inspiration phase includes an arrangement where the prestress is decreased by a control element recognizing the expiratory phase and so as to support respiration during the expiration phase. A pneumatic control valve is used which can switch connections between the inspiration and the expiration phase and which is directly controlled by the difference between the exhalation pressure and the pressure in the air bag. The control valve connects the pressurized air source with the air bag during the inspiration phase and during the expiration phase it interrupts the connection due to the occurring dynamic pressure of the pressurized air from the pressurized air source and thus actuates a pneumatic adjusting element so that the mechanical prestress at the air bag is reduced.