GB475440A - Improvements in or relating to apparatus for determining the flow resistance of breathing apparatus elements - Google Patents

Abstract

475,440. Respiratory appliances ;determining flow-resistance. MINE SAFETY APPLIANCES CO. Sept. 1, 1936, No. 23933. Convention date, Sept. 23, 1935. [Class 81 (ii)] [Also in Group XIX] The flow - resistance of gas - mask canisters or other respiratory appliance elements is determined by periodically passing air or other gas by a bellows 10 through the canister or the like 33, in one direction only, or alternately in one direction and then in the other, and measuring the pressure or suction above the canister as bv a manometer 39. The volume of gas passed is adjusted to that of breathing under various conditions by adjusting the stroke of the bellows, and the frequency by regulating the driving motor 13 by a rheostat 14. The pipe 27 connecting the bellows with the element 33 contains a branch-pipe 34 with a cock 35 and non- return valve 36 used in single-direction determinations, a regulating valve 26 and a cock-controlled branch 29 for a pressure gauge. The bellows is driven through a connecting rod 22 with turn-buckle length adjustment 23, a crank 18 with a crank-pin 18a adjustable in throw by a screw 19, and reducing gearing 16 driven by the motor 13. The manometer 39 comprises a U-tube, of the differential type (containing two liquids of differing densities), the limbs of the tube being connected through reservoirs 52, 53 to a common two-way tap 40. The tube has a constriction 46 at its lowest point and one limb 42 contains a non-return valve 45. The tap 40, in one position, connects the limb 42 to a pipe 58 leading to the pipe 27 close to the element 33, and the other limb to atmosphere through a pipe 59. The manometer is then unaffected by pressure and registers steady maximum suction only, liquid passing the valve 45 being unable to return. In the other position of tap 40, limb 42 is connected to atmosphere and the other limb to pipe 58, a steady maximum pressure reading being obtained. The limbs are connected by a byepass tube controlled by a cock 47 to re-set the manometer after each reading. The manometer 39 may be replaced by two manometers connected permanently to the pipe 27 and each provided with a non-return valve in one limb, a constriction, and a controlled byepass, whereby, when the valve 36 is cut off, steady readings are obtained respectively of the maximum pressure and maximum suction in pipe 27 due to the bellows strokes. The manometers may be of the differential or the single liquid type.