Improvements relating to filters and purifiers employed for conditioning air, for example for respiration, by freeing it from poisonous gases and other injurious or undesired constituents

摘要

445,457. Respiratory appliances. SOC. ITALIANA PIRELLI, 21, Via Fabio Filzi, Milan, Italy. Sept. 9, 1935, No. 25057. Convention date, Sept. 21, 1934. [Class 81 (ii)] In air or gas purifying apparatus, particularly individual and collective filters employed in removing noxious constituents from respired gases, the exhaust of moisture absorbing materials employed is indicated by causing the gases during passage through or after emergence from the materials, to traverse one or more elements which, in the presence of moisture, close the circuit of an electric signalling device or generate current for such a circuit. As shown applied to a respiratory filter containing a moisture absorbing mass 4, and an active filter mass 2 such as a catalytic carbon monoxide filter, an oxygen-generating peroxide, alkali hydroxide, or silica gel, a pair of metal plates 6 enclosing between them dry hygroscopic material 7 such as potassium hydroxide or calcium chloride, are embedded in the upper part of the mass 4 and are connected, by wires 11 passing through an insulated plug 8, to a battery 12, and to a lamp 14 and ammeter 15 either of which may be placed in circuit by a switch 13. The material 7 acts as an insulator when dry but completes the circuit when moistened. The plates 6 may be perforated. In an alternative construction the plates 6 are replaced by pairs of plates of different metals such as copper and zinc set parallel to the gas-path, the plates having dry hygroscopic material between them and being connected in series to form a battery energizing an external signal circuit when the material is moistened. Glass wool or like insulating material is packed between the pairs of plates. The filter container has an outlet 3 and an inlet closed by a plug 10. The signal device may comprise a glass phial containing a substance changing its colour on passage of current such as an aqueous solution of methyl orange containing an ionizable salt such as sodium chloride, or of decomposing so as to break the phial, such as acidulated water. The hygroscopic material between the signal plates may constitute the sole moisture-absorbing element of the filter.