GB1358303A - Breathing apparatus - Google Patents

Abstract

1358303 Breathing apparatus AGA AB 18 Aug 1971 [24 Aug 1970] 38821/71 Heading A5T Breathing apparatus comprises a rebreathing system from which exhalation to the ambient medium is possible, connected to a fresh gas supply 46, and a control for maintaining the breathing system closed with respect to the ambient medium during a series of breaths, and opening the system for exhalation to the ambient medium after the series of breaths. Control is effected by a valve device which operates in dependence on a parameter determined by the breathing of the user e.g. volume of gas breathed, number of breaths. Air is supplied to a mouthpiece 41 from a bellows type breathing bag 39 through an inhalation valve 43, and is returned to the breathing bag via a filter 40 for carbon dioxide removal, and an exhalation valve 44. On inhalation the upper wall 47 of the bag pivots about an axis 48 to which it is hinged, Fig. 6, and swings a lever 50 downwardly whereby a pawl 51 on the lever abuts the periphery of a toothed ratchet wheel 52 Fig. 7 and turns the wheel. On exhalation a stem 55 of the opening exhalation valve 44 engages slots 56 in the wheel, and the wheel is prevented from rotating back with the now upwardly pivoting lever 50 and wall 47, by a fixed pawl 53. As the wheel is turned by successive inhalations, a position comes in which the stem 55 abuts a land between the slots 56 and prevents exhalation through the valve 44, and exhaled breath is forced out of valve 42 to the ambient medium. A subsequent inhalation turns a handle 45 and admits fresh air to the bag. Abutments 57A may be provided at the ends of a slot 57 through which the lever 50 projects Fig. 7, to limit the movement of the wheel per breath, whereby fresh air may be admitted to the bag after a preselected number of breaths. In a further embodiment, Fig. 8 (not shown) the toothed wheel is replaced by two toothed wheels (58) and (59) on a shaft (60) the latter wheel being toothed at only diametrically opposed parts of its periphery and an arm (61) replaces the lands between slots in a wheel. A pawl (62) attached to a hinged bar (67) turns the wheels when the bar is pivoted by a push rod (66) due to compression of the bag. The push rod is slidable on the bar and its position on the bar is determined by bellows 68, which contract at high pressure and expand to the position shown in broken lines at atmospheric pressure. A pawl (63) engages the toothed portions of the wheel (59) when the arm (61) prevents the valve (44) from opening, and the air is exhaled to the ambient medium. A demand valve (71) Fig. 9, (not shown) may be connected to the fresh gas supply to cause gas to be supplied to the breathing bag if its pressure drops to a predetermined level, and when exhalation to the ambient medium takes place the bag is completely implied through a relief valve (8). The storage container may be replenished during exhalation to the ambient medium, Fig. 10 (not shown).