Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
37
Medical Breathing APparatus.
This invention: relates to breathing apparatus for medical
purposes.
It has been found that humid air at around ga~ relative
humidity and a critical temperature of 43C, when breathed by a
patient for periods up to around 20 ~inutes, is effective in
rendering groups of viruses in the upper respiratory tract
inactive, which results in the body being able to counteract
colds, allergies, etc ef~iciently, and thereby reduce dramatic-
ally the patient's recovery time.
Although breathing apparatus has been proposed for such
treatment, the arrangement of the apparatus, particularly the
temperature control, has not been well designed. ~ence, the
temperature of the heatea, moist air has varied widely from the
critical temperature, thereby reducing the effectiveness of the
apparatus.
An object of the invention is to provide breathing
apparatus incorporating an efficient temperature control
arrangement by which air drawn through the apparatus is
supplied to the user - in a heated, moist condition at or close
to the critical temperature.
, According to this invention such breathing apparatus is
characterised by a water chamber, heating means for the water,
means for drawing air over the water to an outlet, a face mask
for the outlet, and temperature sensor means located at or
adjacent said outlet adapted to control either the heating
means and hence the water temperature, or the speed at which
the air is drawn o~er the water, or both, to maintain the air
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at or close to a re~uired elevated temperature.
Preferably, the apparatus is designed to deliver air to
the face mask in a volume substantially greater than that
required for breathing, and the face mask is formed with vents
through which excess air together with air exhaled by the user
can pass to atmosphere.
Preferably the means for drawing air is a fan driven by an
electric motor, which may be powered by the mains or a battery.
Conveniently, the heating means is either an electrical
resistance, or positive temperature co-efficient tPTC) elements
and is controlled by the temperature sensor, and temperature
adjustment is effected via an electrical control circuit, e.g.
a solid state circuit, designed to regulate the power supplied
to said heating means and/or to the fan motor.
In order that the invention may be readily understood,
four embodiments of breathing apparatus in accordance there-
with will now be described, with reference to the accompanying
drawings in which:-
Figures 1 and 2 are half-sectional views of the first and
second embodiments, respectively,
Figure 3 is an exploded perspective view of the third
embodiment,
Figure ~ is a part sectional rear view showing the
interior of the third embodiment,
Figure 5 is a part sectLonal side view of the third
embodiment, and
Figure 6 is a part sectional side view of the fourth
embodiment.
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Referring to Figure 1, in this embodiment the a~paratus is
free-standing and comprises a rectangular housing 1 which may
be moulded from plastics material, eg ABS. The housing has an
aii inlet opening ~ leading to an inlet chamber 3 in which a
fan 4 driven by a motor 5 is located, a water chamber 6 in the
lower part of the housing, and a mixing chamber 7 leading to an
outlet 8 which is preferably a flexible pipe to which a face
mask 15 can be removably fitted.
The water chamber 6 is ~illed with water via a filler 9
and has an associated sight glass 10 to indicate the level of
water therein. An electric resistance heating element 11 is
located within the water chamber 6 and power is fed thereto
frorn the mains or a battery, in a regulated manner, via an
electric control circuit, e.g. a solid-state printed circuit
12, in response to a temperature sensor probe 13 located in the
outlet 8. The mixing chamber 7 is insulated, in this
embodiment by a surrounding sealed cavity wall 14 which
provides an air pocket, so that the temperature in the mixing
chamber is substantially unaffected by external changes in
temperature.
In use, ambient air is drawn into the inlet chamber via
the fan 4 and is guided downwardly towards the water surface,
where it passes along said surface to abstract heat and water
droplets therefrom, thereby to heat and humidif~ the air. The
heated, humid air then flows upwardly to co].lect in the mixing
chamber 7 from where it is supplied, in use, to the face mask
15.
The temperature and, if required, the humidity of the air
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passing through the outlet 8 is sensed b~ an appropriate
device, such as the temperature probe 13, and if the air is
found to be outside a re~uired range, e.g. a temperature range
between 40 - 45C, it initiates the control circuit 12 to
regulate the power supplied to the heating element 11 and, if
desired, to the fan motor 5 so as to adjust appropriately the
temperature of the water and possibly the air flow speed.
For electrical safety, and prevention of corrosion, the
fan motor 5 is preferably encapsulated and oeerates at a low DC
voltage. The circuit board 12 is also encapsulated for safety
and reliability of operation in humid conditions. For
additional safety, the apparatus can be powered from an
external A.C. or D.C. voltage supply using a double isolation
transformer.
As ment-oned hereinbefore, it is preferable to limit use
of the apparatus to periods up to approximately 20 mins, for
which an appropriate timing/alarm mechanism could conveniently
be built into the apparatus.
Referring to Figure 2, the second embodiment shown therein
is also free standing and like parts have been given the same
reference numerals.
In this embodiment, the housing 1 is in three parts,
preferably moulded from a plastics material such as ABS, and
comprises a one part base 16, which incorporates the water
chamber 6, and a two part cover 17, 18. The lower cover part
17 has a shaped wall l9 which carries most of the associated
equipment, including the fan 4 and motor 5, the heating element
ll, and circuit board 12.
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The motor 5 is mounted on a sloping part of the wall 19
immediately beneath the inlet opening 2, which is formed in the
top cover part 18. The fan a is coupled to the motor beneath
the wall 19 and draws air through openings in said wall and
directs it across the surface of the water in chamber 6 towards
the outlet 8, which is formed in the lower cover part 17.
The heating element 11 in this embodiment is of the
electric resistance type and has an aluminium shell which is
encased within a coating of PTFE to prevent oxidation of the
casing and to facilitate cleaning. The element is located
vertically beneath the wall lg and is mounted at its upper end
within a boss 20 formed in said wall with its terminal above
tne latter.
The clrcuit board 12, which is preferably encapsulated for
safety and reliability of operation, is mounted directly above
the heating element 20 and is appropriately connected to the
associated equipment, including the temperature sensor 13
located within the outlet 8. The apparatus can be conveniently
sited on a worktop, or floor, and the height of the face mask
15, which is designed to fit over the nose and mouth of the
user, can be adjusted by one, or more, or even a telescopic
~xtension tube 21, which is connected to the face mask via a
ball joint 22 so that the mask can be pivoted and/or rotated to
a comEortable position for the user.
It will be noted that the arrangement of the equipment,
a~d in particular the heating e1ement, is such that all
electrical connections are well above the fill level of the
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chamber 6, and indeed are separated therefrom by the wall 19,
thereby enhancing safety.
A pair of supports are provided in the base part 16, one
(not shown) in front of, and one 23 to the rear of, the heating
element 11 as seen in the drawing. These supports ensure that
the lower part of the heating element 11 is not damaged when
the cover part 17 is removed and laid upon a work surface for
cleaning or service. Conveniently, at least one of the supports
incorporates a water probe over its height which, by means of
an electrical connection via the circuit board 12, indicates
the level of water in the chamber 6.
It will be noted that the two part cover 17, 18 can be
lifted clear of the base part 16 to provide ready access to the
chamber 6 for filling, whilst access to the associated
equipment for repair of servicing is obtained by removing the
top cover part 18.
The apparatus is designed to produce an air speed of
approximately 5 metres/sec across the water surface, and to
retain the critical temperature of the air, the water is
maintained substantially constant at an appropriate temperature
depending upon the fill volume and ambient conditions, eg
between 65 to 75C. Thus, moist air is produced at or close to
the critical temperature of 43C, which is delivered at a
pressure above atmospheric to the face mask (15), in a volume
of approximately 40 litres/min. This volume is, of course, far
in excess of that required by the user and, hence, vents 22 are
provided in the mask so that the excess air, toge~her with the
air exhaled by the user, can vent to atmosphere. This is
important since, when air at 43C is inhaled it is cooled
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substantially, perhaps to arouna 37C, due to vascular cooling
in the bronchii. This reducea temperature, when exhaled, could
otherwise affect the constancy of the temperature of the
heated, moist air being producea by the apparatus. It will be
appreciated that, by provi~ing a mask lS which covers the nose
and mouth, the heated, moist air not inhaled and venting to
atmosphere nevertheless acts to warm the outside of the nose
and mouth and, therefore, ensures the minimum of heat
dissipation around this area.
Referring to Figures 3 to 5 the third embodiment is
portable and like parts are again given the same reference
numerals.
In this embodiment the housing is in two parts comprising
a base 24 and a cover 25.
The base 24 incorporates the water chamber 6, and most of
the associated e~uipment including the fan 4 which is inclined
to direct air towards the chamber 6, motor 5, heating element
ll, and circuit board 12. The cover ~5 incorporates a baffle
wall 26 to guide air from the fan towards and over the water
sur~ace in the chamber 6 into the mixing area 7 and outlet 8 to
the face mask 15.
As shown in Figures 3 to 5, the apparatus is provided with
a wedge shaped fro~t wall to provide stability when placed
upright on a worktop. In this position, the user would tend to
press his mouth and nose down into the face mask 15 as shown in
dashed outline "x" in Figure 5. However, in most cases, the
user would probably press the ~ace mask manually against his
nose and mouth and perhaps strap it in place~ For this, it
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would be ~ore comfortable for the user to adopt the position
shown in dotted outline "y'. To cater for these different user
positions, the face mask 15 is pivotally mounted to the top of
the cover 25 so that it can rotate from the position shown in
solid lines in Figure 5 to the position shown chain dotted.
Referring again to Figure g, in more detail, the heating
element 11 comprises a number of positive temperature co-effic-
ient (PTC) elements 27 spaced across the bottom wall o-f the
chamber 6 which are regulated to operate at a working
temperature which will maintain the water at an appropriate
temperature, eg appro~imately 80C, depending upon the normal
fill volume of water used in the chamber 6 and ambient
conditions. The fill level line ~z" for the apparatus is
controlled by an overflow pipe 28 which can drain into the
sealed air space provided around the chamber 6 for insulation.
This water can be subsequently removed via a drain plug 28a.
Because of the relatively high temperature required for the
heating element, safety is extremely important, and PTC
elements are especially advantageous since they are inherently
safe against overheating. However, if a conventional electr-
ical resistance element such as described for the first and
second embodiments is used, a thermal cut-out would be included
in the heating element to prevent overheating. In either case
a thermal cut-out could be used in the circuit board 12 for
additional safet~l.
The circuit board 12 is solid state and preferably
encapsulated for reliability of operation. It would be
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aesigned to include the following control features:-
a) a water level sensing circuit including water sensingprobes 29,
b) a temperature control sub-circuit, for controlling the
temperature of the heating element ll, and hence the water
temperature, in dependence upon the water level sensed, and/or
for adjusting the fan speed, and hence the air flow over the
water surface This control circuit is preferably in the form
of a proportional band, zero voltage switch for providing
pulsed or continuous voltage to the heating element so as to
provide accurate control and to reduce the possibility of
electrical interference in use.
c) a comparator sub-circuit for comparing the output
resistance from the sensor 13, which is preferably a thermistor
wlth a basic pre-set value, this sub-circuit being connected to
the temperature control sub-circuit for providing a correcting
signal for finely adjusting the water temperature, or fan
speed.
d) a mercury tilt switch connected so as to cut-off power
to the heating element 11 if the apparatus moves beyond a
predetermined angle from its upright position so as to ensure
e'lectrical sa~ety.
To re~uce to a minimum the possibility of scalding the
user should the apparatus fall over, an anti-spill cover 30
(see Figure 3) is provided for the water chamber 6 having
sloping front and rear side walls 31, 32 to act as a dam to
retain the water.
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Referring to Figure 6, this embodiment is ~lso of a
convenient design to be portable. It cornprises an elongate
tubular housing 1 which, in use, is orientated to be generally
upright. The housing comerises an upper end portion 33 and a
lower end portion 34 of smaller dimensions, enabling it to be
conveniently held by the hands of the user. The motor 5 is
supported centrally within the portion 34, to leave an air
passage around it (âS shown), above the air inlet opening 2,
which is defined by the bottom of the casing 1. The fan 4 is
mounted above the motor near the junction between the portions
33 and 3a. The water chamber 6 is supported centrally within
the portion 33 to leave an air passage around it (as shown),
the water chamber having â suitable heating element 11
associated therewith. A face mask 15 is mountea on the top of
the portion 33, which would be generally as described above
with reference to the third embodiment, and the temperature
sensor 13 is apgropriately located therein. The circuit board
17 is mounted in a convenient position, e.g. as shown.
In use, as shown by the arrows, air is drawn upwardly
through the opening 2 and through the air passages around the
motor 5 and tank 6, whereafter it is deflected by sloping walls
34 defining the face mask 15 across the water in the tank 6 and
then upwardly through an outlet 8 to pass into and through the
face mask. As described in respect of the foregoing
embodiments, the heated, moist, air delivered to the face mask
15 is in a volume far greater than body requirements and the
e~cess air would be vented to atmosphere.
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