Note: Descriptions are shown in the official language in which they were submitted.
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Air Treatment
The subject invention relates to air treatment at a
table.
There are many examples of air treatment means in
combination with tables. For example DE 3410288 and U.S.
4,248,162 both disclose tables comprising an air inlet in
the table top and air filtration means attached to the
underside of the table top. JP 6-344519 and JP 7-184723
both disclose tables comprising central ducts projecting
above the surface of the table, through which ducts air
flows, and an air filtration means located below the table
top.
Furthermore, there are many examples of filter units
suitable for use in such tables. For example, U.S.
4,886,526 discloses a removable filter cartridge comprising
an inner electrically conductive screen sandwiched between
two sheets of dielectric filtration material with
electrically conductive screens on either side of the
cartridge. The inner electrically conductive screen has
smaller dimensions than the outer electrically conductive
screens.
The present invention aims to provide a table in
combination with air treatment means which provides improved
air filtration efficiency. The present invention also aims
to provide a table in combination with air treatment means
with greater commercial viability.
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The present invention provides a table in combination
with air treatment means, said table comprising a table top
and said air treatment means comprising air inlet means in
communication with the environment above said table top, air
induction means, housing means, air filtration means, an air
distribution space within said housing means, bounded by
said filtration means, and air outlet means of said housing
means, the air induction means being operable to draw air
from said environment via said air inlet means into said air
distribution space, and thence through said air filtration
means and through said air outlet means, and the air flow
cross-section of said filtration means being at least 10
times greater than the minimum air flow cross-section at
said air inlet means.
The air filtration means is preferably electrical air
filtration means, for example, polarising air filtration
means. Alternatively, or in addition, the air filtration
means may comprise chemical air filtration means, a carbon
filter for example.
Preferably, the air flow cross-section of the
filtration means is at least 15 times greater than the air
flow cross-section at the air inlet means. More preferably,
the air flow cross-section of the filtration means is at
least 20 times greater than the air flow cross-section at
the air inlet means.
The air filtration means may comprise a plurality of
polarising filter units, each of which units lies along a
respective portion of a periphery of said air distribution
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space and a number of said units, providing a group of said
units, being electrically connected such that the units of
said number of said units of said group are operable as a
unitary electrical air filter.
There may be a plurality of groups of the filter units,
the units of each group being electrically connected such
that the units of each group are operable as a unitary
polarising filter. Preferably though, the totality of the
units are electrically connected so as to form a single
unitary filter.
Advantageously, the air flow cross-section of the
totality of the filtration units is at least 10 times
greater than the air flow cross-section at the air inlet
means. More preferably, the air flow cross-section of the
totality of the filtration units is at least 15 times
greater than the air flow cross-section at the air inlet
means. More preferably still, the air flow cross-section of
the totality of the filtration units acting as a unitary
filter is at least 20 times greater than the air flow cross-
section at the air inlet means.
The table may be a dining table, a coffee table, a
desk, a work bench, a bar, a counter, a consul or similar.
In plan view, the table may be round, square, rectangular,
polygonal, L-shaped, oval or of other shape.
Suitably, the outer periphery of the air inlet means is
located at no more than one metre from the outer edge of the
table top or from the position occupied by a person when
seated at the table. Preferably, the air inlet means is
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located no more than 0.6m from the outer edge of the table
top.
The air inlet means may comprise a grille or gauze
mesh. The holes in the air inlet grille or mesh should be
of large enough dimensions as to ensure that the flow of air
through the inlet means is not impeded, but are of small
enough dimensions as to ensure that objects such as
cigarette butts cannot pass through the air inlet means.
The air inlet means preferably comprises a continuous
wall, which extends upwards of the table top. The wall acts
to raise the effective capture zone of the air inlet to a
location above the surface of the table top. The location
of the effective capture zone depends upon the height above
the table top to which the protective wall extends.
Furthermore, the wall acts to deter users from accidentally
blocking the air inlet means as a result of, say, placing an
object on top of the air inlet means.
Suitably, the air induction means comprises a fan.
A major proportion of the total surface area of the
upwardly extending wall(s) of the housing preferably
comprises the air outlet means. The air flow cross-section
at the air outlet means is preferably not less than, or not
substantially less than, that of the air filtration means.
The air outlet means may comprise a grille or gauze mesh.
The housing may comprise, for example, three or more
upwardly extending walls, or it may be of upwardly extending
cylindrical conformation. The table top may form the upper
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wall of the housing and the base of the housing may be
paralleI to the table top.
The housing is preferably secured either directly or
indirectly to the table top. Advantageously, the housing is
secured to the underside of the table top. It is also
advantageous that the housing is removably secured to the
table top.
Suitably, the filtration means is arranged so that the
air flow entering the air distribution space does not pass
through the filtration means without first being subject to
a change of direction. The change of direction may be, for
example, through 90 degrees or thereabouts and may be from
generally downwards to generally horizontal.
The hereinabove mentioned polarising filter units are
preferably arranged substantially parallel to the upwardly
extending walls of the housing. Advantageously, the filter
units abut one another so as to form a substantially
continuous wall of filtration units about the periphery of
the air distribution space. Suitably, the periphery in
respect of which the filter units lie is the periphery of
the, or a horizontal cross-section of the air distribution
space. The filtration means may provide the air outlet
means.
A polarising filter provided for use in accordance with
the present invention preferably comprises a first
electrically conductive mesh screen sandwiched between two
sheets of dielectric filtration material in combination with
a second electrically conductive mesh screen. In operation
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of the filter the first screen is held at a DC high voltage
potential, preferably a positive potential, relative to the
second screen, which second screen is preferably earthed or
held at a ground potential. The potential difference
between the first screen and the second screen may be in the
range of 4-lOkV. Preferably, the potential difference
between the first screen and the second screen is in the
range of 4-7kV.
Advantageously, the first screen and the two dielectric
material sheets are interattached, thus to provide a
tripartite, unitary cartridge, which cartridge may be
removed, and disposed of, when required, and replaced by a
fresh such cartridge. Similarly, if the filter is comprised
of a number of electrically connected filter units, it is
preferable that each of the units comprises a removable
cartridge, which cartridge again may comprise a first screen
sandwiched between dielectric material sheets.
An air filtration means comprising a polarising filter
may also comprise a chemical filter, a carbon filter for
example. These carbon filters are preferably positioned
downstream of the polarising filter units so that the air
flows consecutively through the polarising filter and then
the carbon filter.
In order that the subject invention may be clearly
understood and readily carried into effect, reference will
now be made, by way of example, to the diagrammatic drawings
hereof, in which:
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Figure 1 shows a cross-section of a table and air
treatment means in combination therewith which combination
provides a smokers' ventilated table;
Figure 2 shows an underside plan view of the air
treatment means of Figure 1; and
Figure 3 shows an underside plan view of air treatment
means with alternative filtration means from that shown in
Figures 1 and 2.
With reference to Figure 1, reference numeral
generally designates a table top and reference numeral 5
generally designates air treatment means. Supported on the
table top is a protective wall 2. The protective wall 2,
which is suitably of circular cross-section in plan view,
surrounds the air inlet 3, which air inlet 3 comprises a
grille 3'. The protective wall 2 may extend about lOcm
above the upper surface of the table top 1.
The air treatment means 5 comprises a housing 4, the
major area of the upwardly extending walls of the housing 4
taking the form of a grille thus providing air outlet means
sa, 9b, 9c and 9d. The base 12 of the housing 4 is
substantially non air-permeable and comprises no air outlet.
The air treatment means 5 further comprises a fan 6
providing air induction means, an air distribution space 7,
and polarising filtration means 13 taking the form of a
unitary polarising filter. The filter is provided by
tripartite unitary cartridges 8a, 8b, 8c and 8d, each
cartridge comprising a first metal mesh screen 14 sandwiched
between two sheets of dielectric filtration material 15 and
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15', in combination with a second earthed metal mesh screen
11. The air flow cross-section of the filtration means is
the sum of the cross-sectional areas of the faces of the
filters 8a-d which faces bound the air distribution space 7,
i.e. for a tripartate filter unit only the cross-sectional
area of a single layer of the unit is taken into account.
The first screens 14 of each of the cartridges 8a-d are
connected together by means of electrical connections.
Electrical supply means (not shown) are provided
respectively for the cartridges 8a-d and for the fan 6. The
electrical supply to the screens 14 of the cartridges 8a-d
provides a positive charge of 6kV. Screen 11, which is
electrically continuous, and may be mechanically continuous,
is held at earth potential.
With the fan 6 in operation and with the electrical
supply established to the aforesaid screens 14, and when a
person is seated at the table smoking a cigarette,
sidestream smoke from the smouldering of the cigarette and
exhaled mainstream smoke will be drawn via the air inlet 3
into the air distribution space 7 by means of the fan 6.
The air passes through the cartridges 8a-d and earthed
screen 11 and out of the air treatment means 5 as filtered
air via the air outlet means 9a-d.
With reference to Figure 3, the air treatment means 5
is essentially as that shown in Figures 1 and 2 excepting
that additional filters lOa, lOb, lOc and lOd comprising
granular carbon are located parallel and adjacent to the
polarising filter units provided by cartridges 8a-d and
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earthed screen 11. In operation, the smoke entrained in air
passes via the air inlet 3 into the air distribution space 7
by means of the fan 6. Filtered air then passes out of air
outlet means 9a-d via cartridges 8a-d, earthed screen 11 and
granular carbon filters lOa-d.
The following examples are illustrative of the
operation of a smokers' ventilated table in accordance with
the present invention.
EXAMPLE 1
The smokers' ventilated table as illustrated in Figure
3 was utilised. The air flow cross-section of the air inlet
3 was 0.018mZ. The air flow cross-section of the cartridges
8a-d of the polarising filter was 0.270mZ. The air flow
cross-section of the filtration means was therefore lS times
greater than the air flow cross-section of the air inlet
means.
The smokers' ventilation table was located in a closed
room of known volume. Without the air treatment means in
operation, four cigarettes were lit and allowed to smoulder
at a distance of approximately 0.2m from the outer periphery
of the air inlet means 3. The mean peak concentration of
particulate matter in the air of the closed room was found
to be approximately 1150~gm~3.
This process was repeated with the air treatment means
in operation. The mean peak concentration of particulate
matter in the atmosphere was then found to be approximately
546~gm~'. The air treatment means therefore effected an
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approximate 53% reduction in the particulate matter in the
closed room.
EXAMPLE 2
The apparatus as described in relation to Example l was
used in order to determine the time taken for the
concentration of particulate matter in the air of the closed
room to decrease from the peak value to half of the peak
value, i.e. the half-life of the concentration of
particulate matter in the air.
The peak value was obtained by lighting four cigarettes
and allowing them to smoulder in the closed room. The mean
peak value was again found to be approximately llSO~gm~3.
Without the air treatment means of the table in
operation it was found that the control half-life was 55-60
minutes. With the air treatment means of the table in
operation the half-life was found to be 13-15 minutes.
The mean velocity of the air entering the air treatment
means of Example 1 was measured and found to be 3.25ms~1.
The mean velocity of the air leaving the air treatment means
was measured and found to be approximately 0.26ms~1. The
air residence time of the polarising filter was calculated
therefrom to be approximately 0.1 seconds.
In comparison, the residence time of air passing
through a standard ceiling mounted air filtration means was
calculated to be approximately 0.01 seconds. The standard
ceiling mounted filtration means tested was a Colt
ConditionAir (Trade Name) filter, which Colt filtration
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means comprised an air flow cross-section at the air inlet
in the region of that of the air flow cross-section of the
filtration means. The Colt ConditionAir filter is as that
as generally described in EP 0 585 054.
The ratio of the cross-section of the filtration means
to that of the air inlet means in accordance with an aspect
of the present invention facilitates a greater residence
time of the air flow in the filtration means. Such a
greatly increased residence time effects a significantly
higher filtration efficiency.
As will be appreciated by those skilled in the art,
that the air distribution space 7 serves the purpose of
ensuring an even air distribution over the full air flow
cross-section of the filtration means.
An advantage deriving from the nature of the second
aspect of the invention is that although the polarising
filter units are electrically connected so that the units
operate as a unitary polarising filter, being separate units
each unit can be removed and replaced individually and the
units can be packed flat for storage and transit.
