GB1483299A - Breathing apparatus - Google Patents

Abstract

1483299 Respiratory appliances WESTINGHOUSE ELECTRIC CORP 4 Nov 1974 [6 Nov 1973[ 47572/74 Heading A5T Breathing apparatus includes means for capturing an automatically variable portion of the user's exhaled breath and for releasing the captured breath for rebreathing, said means comprising a gas collection for receiving only an initial portion of each exhalation, sensing means for automatically determining the magnitude of a parameter of the gas breathed by the user, and automatic control means connected to said sensing means for automatically varying said initial portion of exhaled breath in accordance with variations in the sensed parameter. The parameter sensed may be inspired volume, or carbon dioxide content of exhaled breath. The gas collector 50 may comprise an outer wall 51 and an internal wall formed by a bellows 53 biassed to its extended position by a spring 54. The downward stroke of the bellows is limited by a sensor actuator 58 also comprising a bellows. Actuator 58 communicates through an aperture 61 controlled by a spring-loaded button 63, with a passage 60 communicating with a sensor 67 comprising chambers 69-71 defined by interconnected diaphragms 73, 74. A plate 80 of diaphragm 73 is spring-loaded against the opening of passage 60. When inhalation commences gas in collector 50 passes to an oronasal mask 42 positioned in a head cover 40 through a one-way valve 100. As inhalation continues bellows 53 expands to a position such that a disk 102 at the top thereof actuates a lever 104 to open valve 46 for supply of fresh breathing gas to the mask 42 by way of a venturi passage 48 which communicates with the sensor through orifice 82. The resultant pressure drop (P 4 -P 1 ) across orifice 82 results in gas flow from actuator 58 via passage 60 at a rate substantially equal to the flow rate of breathing gas through the venturi so that the volume change in actuator 58 is indicative of the amount of breathing gas inhaled. When exhalation commences the exhaled gas passes initially through a one-way valve 120 to collector 50 until the downward stroke of bellows 53 is stopped by disk 102 seating button 63 against aperture 61 so that no more exhaled gas is accepted by collector 50, the remaining exhaled gas flowing to atmosphere through relief valve 95. When the next inhalation commences a pressure drop occurs in oro-nasal mask 42 so that pressure therein becomes less than that in head cover 40 and therefore that in chamber 70. Diaphragms 73, 74 therefore move against the action of spring 78 to allow air to flow into actuator 58 to reset it to its maximum length. In a modification collector 50 comprises two compartments one of which has a fixed maximum volume and the other of which has a variable maximum volume and is connected to the sensor actuator. The apparatus may be used in diving, space work, fire-fighting or other rescue work.