Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1997-04-22
1999-05-25
Weiss, John G.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820512, 12820418, 12820125, A62B 710
Patent
active
059062037
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a fan-forced positive pressure breathing apparatus of the kind in which filtered air is pumped to a face piece or mask covering at least the nose or mouth of the wearer, the air being pumped by means of a fan driven by an electric motor which is usually battery powered.
BACKGROUND ART
Breathing apparatus of the kind of which the present invention is concerned is well known and a variety of different constructions have been proposed and the advantages and disadvantages of such apparatus are discussed in many patent specifications. Among the requirements of a satisfactory apparatus are that it supplies adequate quantities of air when the user takes a deep breath which, testing shows, necessitates the supply of a substantially higher flow rate than normally anticipated. It is desirable to minimise power consumption by the motor driving the fan consistent with the requirements set out above to increase battery life.
It is also highly desirable that the air pressure within the face piece or mask is never allowed to fall below the ambient atmospheric pressure. If this happened air may be drawn into the space within the piece or mask drawing environmental contaminants into that space.
The present invention is directed to providing an alternative form of forced air breathing apparatus that, at least in preferred embodiments, allows these desired ends to be achieved.
SUMMARY OF THE INVENTION
In a first aspect the present invention consists in a forced air breathing apparatus comprising a face piece or mask covering at least the nose or mouth of a wearer, a pump unit arranged to supply air to a space within the face piece or mask, an electric motor within the pump unit arranged to drive a fan forming part of the pump unit, a filter to filter air entering the face piece or mask and a valve means controlling the flow of air from the pump unit to the face piece or mask during inhalation and from the face piece or mask during exhalation, the valve means including an air inlet valve and an air outlet valve, the air outlet valve being maintained in a closed position during inhalation through the air inlet valve by air pressure from the pump unit and being opened by exhaled air which also acts on the inlet valve to prevent the entry of exhaled air to the pump unit.
It has been found that it is desirable to control the speed of the motor driving the fan so that it runs at a substantially constant speed. This is in contrast to previous proposals which have required the speed of the fan to be accelerated when more air flow is required. It has been found that operating at constant speed results in a saving of power consumed as compared with letting the fan slow down and then speeding it up again.
In a second aspect the present invention therefore consists in a forced air breathing apparatus comprising a face piece or mask for covering at least the nose or mouth of a wearer, a pump unit arranged to supply air to a space within the face piece or mask, an electric motor within the pump unit arranged to drive a centrifugal fan, means for monitoring and controlling the speed of the motor so that the fan rotates at a substantially constant speed during its operation, a filter to filter air entering the face piece or mask and a valve controlling exhalation of air from the face piece or mask by a user.
It has also been found that the functioning of such apparatus can be improved by the provision of a valve controlling the inlet of air to the pump unit, the valve being arranged upstream or downstream of the fan and being arranged to close when a defined air pressure is present within the pump unit. With apparatus according to this third aspect of the invention it is easier to ensure that there shall always be a positive pressure within the face piece or mask at all times thus avoiding the existence of the negative pressure which could give rise to the entry of contaminated air.
In a third aspect the present invention therefore consists in a forced air breathing apparatus co
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Berndtsson Goran Bertil Claes
Jervmo Bengt Yngve Roland
Klockseth Martinus Oliver
Safety Equipment Sweden AB
Srivastava Virendra
Weiss John G.
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