EP0888073B1

EP0888073B1 - Air treatment

Info

Publication number: EP0888073B1
Application number: EP97903501A
Authority: EP
Inventors: Michael Arthur John Bevan; Anthony Craig Claringbould; Nigel David Warren
Original assignee: British American Tobacco Investments Ltd; British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 1996-03-07
Filing date: 1997-02-19
Publication date: 2000-01-05
Anticipated expiration: 2017-02-19
Also published as: WO1997032504A1; AU1804697A; PT888073E; ES2141596T3; CA2247934A1; GB9605115D0; EP0888073A1; GR3032700T3; AU714592B2; ATE188353T1; ID16767A; NZ331584A; JP2000506042A; CN1217636A; DE69701087D1; DE69701087T2; AR006144A1

Abstract

A table (1) in combination with air treatment means (5) which exhibits improved air filtration efficiency, particularly in respect of removal of particulate matter, such as tobacco smoke, from the environment about the top of the table. The table in combination with air treatment means of the present invention is furthermore, a combination with improved practical application and commercial viability.

Description

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.
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 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.
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 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 wall of the housing and the base of the housing may be parallel 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 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 4-10kV. 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:
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 1 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 10cm 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 9a, 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 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 10a, 10b, 10c and 10d comprising granular carbon are located parallel and adjacent to the polarising filter units provided by cartridges 8a-d and 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 10a-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 0.018m². The air flow cross-section of the cartridges 8a-d of the polarising filter was 0.270m². The air flow cross-section of the filtration means was therefore 15 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 1150µgm^-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 546µgm^-3. The air treatment means therefore effected an approximate 53% reduction in the particulate matter in the closed room.

EXAMPLE 2

The apparatus as described in relation to Example 1 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 1150µgm^-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 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.

Claims

A table in combination with air treatment means (5), said table comprising a table top (1) and said air treatment means (5) comprising air inlet means (3) in communication with the environment above said table top (1), air induction means (6), housing means (4), air filtration means (13), and air outlet means (9) of said housing means (4), characterised in that it further comprises an air distribution space (7) within said housing means (4) bounded by said air filtration means (13), the air induction means (6) being operable to draw air from said environment via said air inlet means (3) into said air distribution space (7), and thence through said air filtration means (13) and through said air outlet means (9), and the air flow cross-section of said filtration means (13) being at least 10 times greater than the minimum air flow cross-section at said air inlet means (3).
A combination in accordance with claim 1, wherein the direction of air flow through said air filtration means (13) is transverse the direction of air drawn through said air inlet means (3).
A combination in accordance with Claim 1 or 2, wherein said air inlet means (3), comprises a continuous wall means (2), said wall means extending upwardly of said table top(1).
A combination in accordance with any one of claims 1 to 3, wherein the air flow cross-section of the filtration means (13) is at least 15 times greater than the air flow cross-section of the air inlet means (3).
A combination in accordance with Claim 4, wherein the air flow cross-section of the filtration means (13) is at least 20 times greater than the air flow cross-section of the air inlet means (3).
A combination in accordance with any one of the preceding claims, wherein said air filtration means (13) comprises a plurality of filter units (8), each of which units lies along a respective portion of the periphery of said air distribution space (7) and a number of said units (8), providing a group of said units (8), being electrically connected such that the units (8) of said group are operable as a unitary electrical air filter.
A combination in accordance with Claim 6, wherein said plurality of filter units (8) abut one another so as to form a substantially continuous wall of filtration units about the periphery of said air distribution space (7).
A combination in accordance with any one of the preceding claims, wherein said air filtration means (13) comprises polarising air filtration means.
A combination in accordance with any one of the preceding claims, wherein said air filtration means (13) comprises chemical air filtration means.