Note: Descriptions are shown in the official language in which they were submitted.
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PROTECTIVE RESPIRATOR'S AIR GUIDANCE SYSTEM AND PROTECTIVE
RESPIRATOR
This invention concerns an air guidance system for a protec-
tive respirator and a protective respirator.
Protective respirators have conventionally been used mainly
in industrial work and agricultural work in order to protect
the user against harmful dust and gases. Protective respira-
tors are being used increasingly in the home as well; e.g. in
order to avoid pollen allergy. The following is a description
of some alternative solutions concerning the valve arrange-
ment of protective respirators.
In accordance with FI patent application 833006, the exhala-
tion valve of a filter bridge type of a half mask is located
at an angle in the upper part of the mask's visor to enable
the exhaled air to exit. In accordance with EP patent appli-
cation 258508, the exhalation valve and the inhalation valve
have been located concentrically in the face section of the
respirator's fore part. The exhalation air is conveyed di-
rectly into the surrounding air from the face section.
One of the major problems with protective respirators is the
formation of condensated water on the sealing surface of the
face section. The excess moisture causes powerful bacterial
growth on the surfaces in contact with the skin and thus
leads to skin infections and hypersensitiveness. Further, the
mask is extremely unhygienic should more than one person take
turns in wearing it. The formation of condensated water is
caused by the air temperature outside the face section of the
device being lower than inside the face section. The warm and
moist exhalation air condensates on the surfaces of the face
section when the temperature of these surfaces falls below
what is referred to as the dewpoint temperature.
Another significant problem is encountered when breathing in
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WO 92/19322 PCT/FI92/00137
cold inhalation air in sub-zero temperatures. Since breathing
through the. protective respirator always causes some degree
of breathing resistance, the person using the respirator is
generally forced to breath in the air using such a breathing
technique as will cause the cold air to pass (especially when
working reasonably hard) directly into the person's respira-
tory organs. Person's afflicted by asthma run a definite
health risk in such a situation.
Often, sub-zero temperatures also lead to the formation of
ice in the exhalation valve. When this happens, non-filtered
air may leak via the exhalation valve in the wrong direction
into the face section.
A common shortcoming in protective respirators is that the
exhalation air leaves the respirator too close to the inhala-
tion inlet. This leads to the risk that the carbon dioxide
concentration of the air breathed in may rise to an excessive
level. High carbon dioxide levels causes headache, fatigue,
and even loss of consciousness in extreme cases. According to
the authorities, a carbon dioxide concentration limit of ca.
1 % is still safe when breathing in.
A shortcoming in several currently available masks that redu-
ces work safety and wearing comfort is that the user's spec-
tacles and protective goggles tend to fog up because of the
warm and moist exhalation air. This is generally due to the
exhalation air having the possibility of being guided unobst-
ructed from the exhalation valve directly onto the user's
spectacles or goggles.
Since the exhalation valve on conventional protective respi-
rators is on the outside of the mask in the immediate vi-
cinity of the surrounding non-filtered air,.a leak in the
exhalation valve may result in the unfiltered air outside the
valve and in its immediate vicinity being admitted in small
amounts along with the inhalation air because of the suction
...
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produced during the inhalation stage.
The air guidance system of the respirator in accordance with
the invention brings about a decisive improvement to the
above shortcomings. In order to implement these improvements,
the air guidance system of the respirator of the protective
breathing apparatus type in accordance with the invention is
characterised by an air guidance system for a respirator
protecting the user against air impurities, the said
respirator being formed of a face sealing section (7) made of
a rubber type substance, of inhalation and exhalation valves
(5, 6) connected onto a frame section (3) and a valve frame
(4), of a filter (2), through which air is breathed into the
face section (7), characterized in that the air that passes
through the exhalation valve (6) is guided into an enclosure
(11) between the frame and face sealing sections (3, 7). The
respirator is characterised by a protective respirator for
the purpose of protecting the wearer against air impurities,
the said respirator being formed of a face sealing section
(7) made of a rubber-like substance, of inhalation and
exhalation valves (5, 6) connected onto a frame section (3)
and a valve frame (4), of a filter (2), through which air is
breathed into the face section (7), characterized in that the
air that the outlet aperture of the exhalation valve (6) is
between the frame and face sealing sections (3, 7) and the
inlet aperture of the inhalation valve (5) is in the frame
section (3) underneath the filter surface.
The foremost advantage of the invention may be seen in that
the formation of condensated water on the sealing surfaces of
the face section is markedly reduced. This is accompanied by
the warming up of the inhalation air and the respirator is
safe to use even in sub-zero temperatures. Further, the
mixing up of exhalation air into the inhalation air is
minimised.
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In the arrangements in accordance with the invention, due to
the location of the exhalation valve, the air leaked by the
exhalation valve is noticeably cleaner than the air surroun-
ding the respirator, because the unclean surrounding air is
not in the immediate vicinity of the exhalation valve, the
leaked air has, in the main, composed of air that has been
filtered once and then exhaled. As an example, air containing
particles as impurities is cleaner between the frame and face
sealing section than on the outer surface of the mask,
because the exhaled air stays around the exhalation valve in
between the user's breaths and the pressure of the exhaled
air forces unclean air away through the valve opening.
In the following, the invention is explained in detail with
references being made to the appended drawings.
Figure 1 is an exploded presentation of the protective
respirator.
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Figure 2 shows the protective respirator from above and
partially as a sectional presentation.
Figure 3 shows a side view of the protective respirator and
partly as a sectional view along the line C-C in fig. 2.
Figures 4a and 4b show two different implementations of the
heat exchange surfaces.
Figure 5 is an isometric assembly drawing of a respirator in
accordance with the invention.
Fig. 1 is a schematic exploded presentation of a protective
respirator in accordance-with the invention. The respirator
is composed of a lattice section 1 protecting the filter, a
filter 2, a frame section 3 made up of supporting ribbing
with a hole for the inhalation air, a valve frame 4 onto
which the inhalation and exhalation valves are mounted, and a
face sealing section 7 that is connected to a valve frame 4
by means of the respirator's mounting straps, these straps
not being shown in fig. 1. The top of the respirator's frame
section 3 houses an air guidance plate 8.
Fig. 2 shows the protective respirator as seen from above and
partially as a sectional view of it. The mounting straps 3
are indicated by dashed lines in the drawing.
Fig. 3 shows the assembled mask placed over the user's face:
The presentation is a side view partially as a sectional
presentation along the line C-C shown in fig. 2. The drawing
shows how the warm exhalation air is guided through the exha-
lation valve 6 into the air enclosure 11 between the frame
section 3 and the face sealing section 7. Due to convec-
tional force, the warm exhalation air rises upward in the air
enclosure 11 until it meets the air guidance plate 8. The air
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guidance plate 8 guides most of the warm air to the rear and
up toward the ears of the person wearing the protective
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WO 92/19322 ~ ~ ~ ~ ~ ~ ~ PGT/F192/00137
respirator. This being the case, a flow of warm air is gene-
rated in the air enclosure formed between the protective
respirator's frame section and the face sealing section, the
said flow of warm air keeping the temperature in the said air
5 enclosure essentially higher than that of the outside air.
The number 16 indicates a removable protective visor.
The warm exhalation air in the air enclosure maintains the
temperature of the face sealing section's outside surface
above the dewpoint temperature and thereby the formation of
condensated water on the inner surfaces of the face sealing
section is significantly reduced.
The warm exhalation air in the air enclosure also warms up
the heat exchange surface 12 forming the rear surface of the
frame section 3. Heat is transmitted by conduction from the
heat exchange surface to the supporting ribbing 13. On being
warmed up, the supporting ribbing releases heat into the
filtered inhalation air flowing between the ribbing. Thus,
the temperature of the inhalation air is not dangerously cold
even for persons afflicted by asthma.
Since the exhalation air rich in carbon dioxide flows in its
own air enclosure and exits essentially via the ends of the
respirator, there is little chance of it finding its way back
to be breathed in once again. This enhances the respirator's
operational safety.
Due to the guiding plate 8 the warm air is prevented from
causing fogging up of spectacles or goggles.
Figs. 4a and 4b shows another possible solution for the
structure of the heat exchange surface 12. The ribbing 13 is
thus formed that the frame section 3 is essentially of the
same thickness at the points of the ribs as it is next to the
transfer channels 10. The said construction facilitates a
more efficient exchange of heat because of the greater surfa-
WO 92/19322 PCT/FI92/00137
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s
ce area and more even thickness of the frame section.
Fig. 5 shows a fastening stud 15 by means of which the latti-
ce section 1 is fastened onto the frame section. The pressure
equalising apertures 14 can be executed, for example, into
the section of the lattice 1 curving underneath the respira-
tor. When this is done, the said pressure equalising apertu-
res converge with the apertures made into the corresponding
parts of the frame section 3 when the respirator is assem-
bled.
It should be noted that the respirator in accordance with the
invention has been described with reference having been made
to only one of its advantageous implementation examples. This
is in no way intended to restrict the invention to only this
one example. Instead, all modifications of the inventive idea
within the scope defined in the patent claims are, naturally,
possible.
