GB718355A - Improvements in or relating to sealed air-purifying canisters - Google Patents

Abstract

718,355. Respiratory devices. MINE SAFETY APPLIANCE CO. Dec. 18, 1952, No. 32091/52. Class 81(2) An air-purifying canister for a respirator in which the inner end of the canister is inaccessible comprises a can containing an air-purifying unit and having inlet and outlet openings surrounded by seats engaged by sealing covers and a pin arranged axially through the can and slidably mounted with one end projecting from the outer end of the unit so that it may be pushed inwardly to remove the outlet cover when the inlet cover has been removed. A respirator, having a mouthreceiving flange 13 with lugs 14 to be gripped by the teeth, is provided with a cup 1 of impervious flexible material such as rubber in which an air-purifying canister 4 is mounted so that a chamber for purified air is left between the inner end of the canister and the end wall 2 of the cup 1. The canister 4 is held in the cup 1 by a band 7 tightened around the cup 1. The canister 4 has a cylindrical side wall 32 integral with an outer end wall 33 and an inner end wall 37 each having annular corrugations which provide seats 35, 39 around an inlet opening 34 and an outlet opening 38 respectively. The inlet and outlet openings 34, 38 are sealed by covers 60, 61 which are secured to the seats 35, 39 by layers of plastic sealing material 62. An air-purifying unit is disposed in the canister 4, the unit comprising perforated end plates 41, 42 and a perforated centre plate 43 between which an air-drying chemical 47 and an air-purifying chemical 49 are disposed, filtering layers 46, 48 lining the end plates 41, 42. An inhalation valve is arranged between the inner perforated plate 42 and the outlet cover 61, the valve comprising a seating plate 51 which is solid at the centre and a diaphragm 54 which has a central aperture 56. An exhalation valve is provided in the end wall 2 of the cup 1 and comprises a shallow cup 25 having a central opening 27 which is surrounded by a valve seat 28 for a flexible diaphragm 29 having circumferentially arranged holes 31. A perforated cuplike cover 30 is provided for the exhalation valve. When the respirator is to be used, the inlet cover 60 is removed from the canister 4 by a lever 63. A slidable pin 66 passing axially through the air-purifying unit and projecting from a depression 72 in the outer perforated plate 41 is then pushed inwardly to press against the outlet cover 61 and thus remove it from the outlet opening 38. Bosses 73 projecting from the end wall 2 of the cup 1 prevent the exhalation valve being obstructed by the removal of the outlet cover 61.