GB867597A - Improvements in apparatus for mixing gases - Google Patents

Abstract

867,597. Mixing gases in flow. ANãSTHETIC EQUIPMENT Ltd. July 14, 1959 [July 19, 1958], No. 23260/58. Class 86 [Also in Group VI] In an apparatus for supplying a mixture of two gases, particularly anaesthetic gases, in predetermined proportions, the pressure of the constituent gases is first equalized. Nitrous oxide and oxygen are respectively admitted through inlet ports 10, 11 and inlet valves 13, 23 into chambers 14, 24 having bellows portions 15, 25. The pressure in the chambers is equalized by levers 18, 28 having projections 19, 29 bearing on the extensible portions of the chambers. The outer ends of the levers are connected by the adjustable tension spring 32 and their inner ends have members 20, 30 bearing on the inlet valves 13, 23 to actuate them in a closing direction as pressure rises in the corresponding gas chamber. The pressure equalized gases pass from chambers 14, 24 to the mixing valve 12. Nitrous oxide from duct 40 enters the annular chamber 50 which communicates with upper cavity 47 in the hollow valve spindle 44; oxygen enters the lower cavity 48 in spindle 44 via duct 41 and chamber 51. The spindle has an arcuate oxygen port 65 and two arcuate nitrous oxide ports 67 co-operating with ports 66, 68 respectively in the valve sleeve 45, whereby the gases are admitted to the mixing chamber 42. The angular disposition of the arcuate ports is such that any desired proportion of nitrous oxide to oxygen may be pre-selected by manually rotating the hollow spindle 44 by means of the knob 52, see Figs. 4-7 (not shown). One wall of the mixing chamber 42 is formed as a flexible diaphragm 60 which controls the rate of flow of the mixed gases by actuating the bell crank 59 to displace the valve sleeve 45 axially in such a direction that when the pressure of the mixed gas in the mixing chamber 42 is at a maximum or is excessive, the gas ports in spindle 44 and sleeve 45 are axially out of register. The mixing chamber 42 communicates with a delivery chamber 72 by means of a valve 70 upon which the gas pressure in the mixing chamber acts in a closing direction. The wall 73 of delivery chamber 72 is flexible and acts upon valve 70 to open it when flexed as the patient inspires. Alternatively any desired gas pressure may be provided in the delivery chamber (and hence in the breathing tube) by manually rotating the knob 80 which acts through cam 82, lever 74, pressure pad 75 and wall 73 to hold valve 70 open.