GB855728A - Air saving arrangement in breathing apparatus for submarine use - Google Patents

Abstract

855,728. Respiratory appliances. LUNDGREN, C. E. G., and ARBORELIUS, M. M. March 11, 1957 [March 12, 1956], No. 7938/57. Class 81(2) Open circuit submarine breathing apparatus in which air is supplied by a demand valve only on inhalation, has an air chamber the maximum volume of which allows receipt on exhalation of the total volume of air in the trachea, mouth and nasal cavity of a normal user, and an exhalation valve loaded so that it opens during exhalation only after the chamber has received the aforesaid maximum volume of air. A mouthpiece 6 is connected to a supply of compressed gas by way of a diaphragm-operated demand valve 3 and an inhalation channel 7 and to an expiration valve 9 by an expiration channel 8. A bladder 10 is connected to the inhalation channel 7. When the bladder 10 is full of gas its pressure loading is higher than the opening pressure of the demand valve 3 so that on inhalation air is inspired from the bladder 10 before the demand valve 3 is opened. The closing pressure of the expiration valve 9 is equal to the pressure loading of the bladder 10 when full so that, on expiration, air first expired fills the bladder 10, further expired air being exhausted by the expiration valve 9. The bladder 10 may be replaced by a chamber in the housing of the demand valve, one side of the chamber being bounded by the diaphragm which operates the demand valve 3 and is extensible. Alternatively the bladder 10 may be replaced by a bellows which operates the demand valve. The expiration valve may be of the duck bill type and subjected to the gas pressure within the bellows. Specification 829,646 is referred to.