Note: Descriptions are shown in the official language in which they were submitted.
CA 02485327 2004-11-18
Description of the Invention
One embodiment of the invention includes a stable base (1) containing a fan or
blower (2),
an air intake opening (3), and a rigid passageway or air duct (4) for
directing the air to a
plenum (5). The passageway (4) is of a telescopingly adjustable length, making
use of a
sliding arrangement to adjust the height of the plenum above the floor and a
set screw to fix
the height (6). The plenum provides two functions: a partition that stops air
movement
horizontally and a support for a mechanical air filter (7) that also functions
as a diffuser of
air flow. During operation, air is drawn by the fan (2) into the air intake
(3) and blown
through the passageway (4) leading to the plenum (5). The air flow causes a
uniform
pressure to build-up uniformly inside the plenum (S) and consequently across
the
diffuser/mechanical air filter (7) installed on the open side of the plenum.
The cleaned air
exits perpendicularly to the face of the diffuser/mechanical air filter with
or without
activated charcoal (7) in a laminar flow pattern as a column of clean air (8)
emanating from
the face of the air filter, displacing the ambient air in the direction normal
to the face of the
diffuser/mechanical filter (?). The back of the plenum is solid and provides a
partition that
stops the movement of room air in the vicinity of the diffuser/mechanical air
filter.
The invention is shown in a sketch on Figure 1. The invention incorporates a
stable base( 1 ),
permitting the unit to stand adjacent to the side of a bed or at the head of a
bead, or beside a
desk or a chair, where the subject would normally spend a lot of time. The
height (above
the floor) of the plenum (5) with its diffuser/filter (7) attached is
adjustable to permit lining
up the centre of the outlet of the filter with the same height as the user's
face, so that the
face will intercept the column of filtered air emanating from the
diffuser/filter surface. In
this manner, the air cleaner effectively displaces the ambient air in the
subject's breathing
zone with filtered air. The filtered air emanates from the diffuser filter at
a velocity low
enough to prevent discomfort from drafts, yet high enough to cause a laminar
flow that
displaces ambient air in the breathing zone with little or no mixing. This
effect is achieved
at a velocity of the air emanating from the filter face (8) ranging between 2
and 5 inches per
second. In this range, air speed is sufficiently low to create a laminar flow
without causing
Saul Stricken November 19, 2004
CA 02485327 2004-11-18
Patent Application
for a Portable Breathing Zone Air Cleaner
the sensation of a draft within the space 6 inches to 36 inches in front of
the diffuser/filter.
A throughput of air of 10 to 25 cu ft per sq. ft of surface area of
diffuser/filter would result
in air flow velocity in the desired range of 2-5 inches/second. By trial and
error, this
velocity range was found to be acceptable to most subjects, yet permit, while
the fan or
blower is running, the formation of a moving column of air perpendicular to
the face of the
diffuser/filter with little mixing with ambient room air within a 36 inch
distance from the
face of the diffuser/filter. Higher velocities can cause the sensation of a
draft and
discomfort, especially for sedentary or supine subjects. Lower velocities may
not achieve
sufficiently uniform displacement of ambient air with filtered air to
significantly reduce
exposure of occupants to airborne contaminants in the local ambient air.
Construction
One embodiment of the invention is composed of four main components: a housing
(made
of coated wood or plastic producing no material emissions) that doubles as a
base with a
fan or blower with an air inlet and an air duct outlet, a plenum with an inlet
and with a large
outlet opening, and an air diffuser/filter covering the outlet opening of the
plenum.
Figures 2 and 3 illustrate one possible embodiment of the invention. Exploded
views with
typical dimensions of the base unit and of the plenum which holds the
diffuser/filter
element are shown. The length of the air duct outlet of the base is used to
adjustably join
the base unit to the plenum by a sliding telescoping connection, fixed by a
set-screw. The
telescoping connection is useful for adjusting (raising and lowering the
height of) the
diffuser/filter to optimize the flow of cleaned air into the subject's
breathing zone. All
materials used are selected for their low emission characteristics and where
necessary, are
coated with impervious low emission surface coatings such as shellac and
odorless paint
The resistance to air flow of the diffuser/filter is selected to cause a build-
up of pressure in
the plenum behind the diffuser/filter that is uniform across the entire face
of the filter. A
typical filter medium configuration is a 1" thickness of fibrous non-woven
fabric with a
covering on the front and back surfaces of non-woven single layer porous
fabric for
support of the filter medium. The fabric must be of a non-allergenic type of
material such
as polyester fiber. The combined resistance of the filter medium and the front
and rear
layers of fabrics is necessary to produce the required static pressure build
up in the plenum
to produce a uniform flow of air emanating perpendicularly from the surface of
the filter.
The Diffuser/filter element captures airborne particulates by mechanical
entrapment and
by adsorption to the fiber surfaces. The smallest particles may be attracted
to the fiber and
held there by Van der VVaal forces because of the low air velocity through the
filter medium.
The filter may also include adsorbing material such as activated charcoal to
remove
volatile organic compounds from the air. The filter has to be replaced
regularly in order to
maintain the air cleaner operating effectively.
CA 02485327 2004-11-18
Background
It has been established from field testing in houses that there is a strong
correlation between
indoor particulate levels and occupancy~2. The research showed that exposure
of house
occupants to airborne particles appears to be directly linked to their
activities when they are
in the home as a result of their movements. The furnace filter appears to have
only a small
to moderate effect on the exposure of an individual to respirable particles in
the home.
When occupants are moving around, they stir up the dust, and the dust cloud
"follows"
them around as they generate new clouds of dust. The dust in this cloud is
usually not
affected by the quality of the furnace filter or room air filter because the
filter is far away
from where the dust is being generated, and it normally takes several hours
for the dust to
be removed from most of the volume in the room, once all occupants have left
the room.
A certain percentage of the population have sensitivities to certain solid
particles such as
micro flora, micogens and mould spores and to gaseous chemicals dissolved in
the air in a
building such as volatile organic compounds (VOCs) from perfumes, from moulds
or
materials on their own skin and hair, as well as from chemicals and solvents
such as
formaldehyde. Individuals who are hypersensitive to long-term exposure to some
of these
materials and chemicals may exhibit certain reactions such as an immune
response to
respiratory exposure to the allergen, with resulting symptoms such as such as
asthma,
bronchitis, allergic rhinitis, nasal congestion, sleep disturbance and in
extreme cases, if
uncorrected, altered brain function.
Humans, pets and materials such as carpeting generate airborne particulates
such as
allergens, molds, bacteria, viruses and chemicals that spread out into the
occupied space.
The rate of production of particles associated with human activities and
occupancy indoors
is normally much higher than the rate of removal of particles from the air by
room-by-room
or central air cleaners. The result is that conventional mechanical air
cleaners produce a
small or insignificant reduction in the level of air contaminants surrounding
a person, and
thus produce a small reduction in human exposure to indoor levels of
particulates or
chemicals in the air that the person breathes indoors.
