Counterlung form

Counterlung form and mechanism

Counter lungs are in most cases made of flexible materials. In some special cases the designer chooses for a more rigid material.  Sometimes counterweights are used to compensate the hydrostatic pressure difference. This technique was patented way before Halcyon patented big Hall! AGA’s patent US 2,896,616

The development of the counterlung is mainly linked to the technique of dosing the gas. The position of the counterlung also largely determines the breathing resistance experienced by the user. The pressure in the lung is generally equal to the ambient pressure. This means that on land only the atmospheric pressure will play a role unless an overpressure system is used.

However, the pressure difference can be significant underwater. Because the breathing resistance of a human being can only absorb small differences, a diver with a counterlung on his back will have more difficulty breathing than if the counterlung were as close as possible to his own lungs. This is explained in the accompanying article.

Counter lungs have also been developed that regulate the gas supply. These techniques have been further developed for both land and underwater use. A special technique is that applied in the Halcyon rebreather. The counterlungs consist of a bellows. In the large bellows there is a small bellows that is pushed in by the diver when he breathes in. The small bellows will release a certain percentage of the gas content of the large bellows to the environment, after which, when breathing out, new gas is supplied to the large bellows. This mechanism causes a gas refreshment and makes it possible to dive up to 60 metres deep with this system. However, this requires gas of a different composition than pure oxygen. The system is now called semi-closed because a small part of the gas is released into the environment each time.