Medical respirator

Claim 1

In a medical respirator comprising a cylinder for containing patient gas at a storage pressure which is higher than atmospheric pressure, a piston having opposite end faces thereof of unequal areas movable within said cylinder and dividing said cylinder into first and second volumes, first connection means connected to a source of gas and to said first volume for supplying patient gas thereto during an expiratory period of said respirator, second connection means connected to said first volume for passing patient gas therefrom to a patient during an inspiration period of the respirator, switching means for connecting said first volume to said first or second connection means during expiration or inspiration periods, means connected to said switching means for cyclically operating said switch, means connected to said second volume for supplying gas thereto the pressure of which acts on said piston to expel the gas within said first volume, a liquid injector means for injecting an adjustably predetermined quantity of liquid into the patient gas to be passed to the patient comprising a variable volume container for the liquid, driving means connected to said variable volume liquid container and operable by said storage pressure of said gas to reduce the volume of said liquid container to cause liquid to be discharged therefrom into the said quantity of gas, means connecting said driving meanS to said switch for applying said gas at storage pressure to said driving means to cause operation thereof so that the quantity of liquid discharged is proportional to the said storage pressure of the gas, and a spring control means for adjustably controlling said driving means having increasing restitution force with increasing deflection from an unstressed position acting on the driving means in such a direction as to tend to oppose movement thereof, caused by the gas for reducing the volume of said liquid.