| 摘要 |
1,243,765. Reciprocating pumps. PYE Ltd. March 18, 1970, No.13064/70. Heading F1A. [Also in Division A5] A medical respirator, in which a predetermined quantity of gas is stored at higher than atmospheric pressure in a known volumn during an expiratory period of a respiratory cycle and discharged to a patient in the next inspiratory period, includes a liquid injector for discharging a quantity of liquid stored therein into said quantity of gas, the injector comprising a variable volume container for the liquid, driving means operable by the stored gas pressure to reduce the container volume to discharge liquid therefrom, and a spring 33 having an increasing restitution force with increasing deflection acting on the driving means in a direction to oppose movement thereof caused by the gas whereby the quantity of liquid discharged into said quantity of gas is proportional to the stored gas pressure. The known volume is the maximum of a variable volume V1 defined between a wall 75, rigid diaphragm and flexible surround 73, diaphragm 72 being connected to a smaller diaphragm 70 which together with a surround 71 and wall 74 defines a variable volume V2. During inspiration gas passes from a port 36 via regulator 38 to volume V2 and expels a gas-liquid mixture in volume V1 via valve 40 and flow control 57 to a patient. During expiration gas passes via valve 40 into volume V1 and the gas pressure is applied via a valve 39 to move a bellows 30 connected to a piston to thereby expel liquid from a cylinder 32A via one-way valve D2 to volume V1. Cylinder 32A is connected via a one-way valve D1 to a liquid reservoir, and the movement of bellows 30 and piston 32 is opposed by the spring 33. For a given gas pressure the displacement of piston 32 depends on the location of a movable fulcrum 33B, the position of which may be calibrated in terms of the ratio of gas/liquid supplied to the patient which ratio is substantially independent of gas pressure. Spring 33 may be replaced by a variable effective length leaf spring, bellows 30 by a piston, and diaphrams 70, 72 by a piston with unequal area end-faces. In an alternative embodiment, Fig.2 (not shown), the liquid is injected into the stored gas volume during inspiratory periods. |
