GB733473A - Improvements relating to breathing apparatus - Google Patents

Abstract

733,473. Respiratory appliances. NATIONAL RESEARCH DEVELOPMENT CORPORATION. April 10, 1952 [Jan. 10, 1951], No. 693/51. Class 81 (2). Closed cycle breathing apparatus comprising an air or oxygen supply bottle, a purifier, a breathing-bag, a cooler and a face mask is provided with a liquid or solid cooling agent which is evaporated by heat from expired gas or the ambient atmosphere and cools the expired gas during its evaporation or subsequent thereto, the expired gas after being purified circulating through a tube contiguous with a tube or vessel containing the cooling agent in liquid, solid or gaseous form, a supplementary supply of air or oxygen being mixed with the expired gas before it enters the contiguous tube. A face mask is connected with closed circuit apparatus (Fig. 1) comprising an oxygen bottle 2, a breathing-bag 1, cooling means 5 for the air which is to be inhaled and carbon dioxide filtering means 8 which receives exhaled air. The cooling means 5 (Fig. 2) comprises a casing of synthetic resin e.g. a substance known under the Registered Trade Mark " Bakelite," the interior of which casing is divided by baffles 18, 19 into passages through which air to be inhaled passes so that it is cooled by solid carbon dioxide contained in a cylinder 13 and passages for the venting of evaporated carbon dioxide to the atmosphere through an outlet 24. Water condensing in the passages is collected in a sump 22. An alternative cooling means 5 (not shown) utilises liquid oxygen or air in place of solid carbon dioxide. In another form of the apparatus (Fig. 4) liquid air or oxygen provides the gas to be inhaled and also serves to cool recirculated gas. A liquid air or oxygen container 32 is connected with a breathing-bag 33 by way of a heat exchanger 35 and exhaled air reaches the breathing-bag 33 through a carbon dioxide absorber 34. The heat exchanger 35 (Fig. 5) consists of a tube 38 through which gas passes from the breathing- bag 33 to the face mask and is cooled by evaporated air or oxygen from the container 32 which passes through a cylinder 37 surrounding the tube 38. The face mask 41 (Fig. 6) is made from moulded rubber and is provided with a T-piece 46 for the supply and discharge of gas. Air to be inhaled passes to the mask 41 through a one-way valve 51, enters channels 53 in the mask 41 and is discharged over the eyepieces into a space between the mask and the face, misting of the eyepieces thus being prevented. Exhaled gas passes into a tube 50 in the T-piece 46 and returns to the closed circuit apparatus through a one-way valve 52. A microphone may be incorporated in the mask.