Exhalation valve for use in an underwater breathing device

An underwater breathing device configured to produce positive end-expiratory pressure in the airway of a user of the underwater breathing device, the underwater breathing device comprising:

• a chamber comprising a breathing port and an exhalation port, the chamber being configured such that when air is being exhaled through the breathing port into the chamber in a manner that restricts air from simultaneously escaping through the breathing port, there is no unrestricted passageway out of the chamber through which air can exit the underwater breathing device and, as a result, the exhaled air creates an exhalation pressure within the chamber;
• and
• a valve for restricting airflow from the chamber through the exhalation port, the valve comprising:
• a plate defining the exhalation port;
• an exhalation conduit connected to the exhalation port, a lower portion of the exhalation conduit being divided by a septum which divides the exhalation conduit and the exhalation port into a first exhalation port connected to a first exhalation conduit and a second exhalation port connected to a second exhalation conduit;
• and
• a flexible membrane that is sealable against a surface of the plate and is sized and positioned to be capable of sealing the first exhalation port and the second exhalation port, the flexible membrane being configured such that an opening force, comprising any exhalation pressure within the chamber, biases the flexible membrane in a first direction and a closing force biases the flexible membrane in a second direction, the first direction being substantially opposite the second direction, the flexible membrane comprising:
• a fully-sealed position in which the flexible membrane seals the first and second exhalation ports such that substantially no air nor water can flow through the first nor second exhalation ports;
• a partially-sealed position in which the flexible membrane seals the second exhalation port but does not seal the first exhalation port such that air and water can flow from the chamber through the first exhalation port and substantially no water can flow from the second exhalation conduit through the second exhalation port;
• and
• an unsealed position in which the flexible membrane does not seal the first and second exhalation ports such that air and water can flow from the chamber through the first and second exhalation ports.

An underwater breathing device configured to produce positive end-expiratory pressure in the airway of a user of the underwater breathing device, the underwater breathing device comprising:

• a chamber including a breathing port and an exhalation port, the chamber being configured such that when air is being exhaled through the breathing port into the chamber in a manner that restricts air from simultaneously escaping through the breathing port, there is no unrestricted passageway out of the chamber through which air can exit the underwater breathing device and, as a result, the exhaled air creates an exhalation pressure within the chamber;
• and
• a valve for restricting airflow from the chamber through the exhalation port, the valve being configured such that, when the chamber is submerged in water, any exhalation pressure within the chamber combined with a biasing pressure of the valve biases the valve in a first direction and ambient water pressure biases the valve in a second direction, the first direction being substantially opposite the second direction, the valve comprising:
• a fully-sealed position in which substantially no air nor water can flow through the exhalation port, the valve being disposed in the fully-sealed position when any exhalation pressure within the chamber combined with a biasing pressure of the valve is substantially less than the ambient water pressure;
• and
• an unsealed position in which air and water can flow from the chamber through the exhalation port, the valve being disposed in the unsealed position when any exhalation pressure within the chamber combined with a biasing pressure of the valve is substantially greater than the ambient water pressure;
• wherein the valve further comprises:
• an exhalation conduit connected to the exhalation port, a lower portion of the exhalation conduit being divided by a septum which divides the exhalation conduit and the exhalation port into a first exhalation port connected to a first exhalation conduit and a second exhalation port connected to a second conduit.