| 摘要 |
The risk of lung "squeeze" in use of diving headgear in return-line diving systems arises through the need to subject the exhaust hose to suction pressure in order to withdraw the used gas from the helmet. The usual exhaust regulating valve can quite readily jam, needs considerable servicing, and can only provide the desired high flow rates at the expense of the mechanical advantage which must however be kept high to avoid rendering the valve unduly sensitive to across-the-valve fluctuations. According to one aspect of the invention, all of these difficulties are met by using on the helmet a novel exhaust regulating valve comprising a collapsible and expansible housing including a hinged flap and a peripheral bellows wall on the flap, an orificed seat in the housing covering an outlet opening in the housing, and a flexible membrane adjacent to the seat and connected to the flap so that hingeing movements of the flap in response to pressure variations in the helmet effect progressive laying of the membrane on to and progressive lifting of the membrane from the orificed seat. A further safety feature is a shut-off valve whereof the seating is at an inlet opening in the housing and the closure member is on the hinged flap. According to another aspect of the invention, superior lung ventilation is obtained by using demand-type supply and exhaust valves, and spring-loading them both to the open position. It is found that the work of opening one is done by the other and vice versa, rather than by the user of the equipment.
|
