EP0106382B1 - Working table with laminar air flow protection - Google Patents
Working table with laminar air flow protection Download PDFInfo
- Publication number
- EP0106382B1 EP0106382B1 EP83201301A EP83201301A EP0106382B1 EP 0106382 B1 EP0106382 B1 EP 0106382B1 EP 83201301 A EP83201301 A EP 83201301A EP 83201301 A EP83201301 A EP 83201301A EP 0106382 B1 EP0106382 B1 EP 0106382B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- space
- air
- working table
- filter
- upstream
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
- F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
- F24F3/16—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by purification, e.g. by filtering; by sterilisation; by ozonisation
- F24F3/163—Clean air work stations, i.e. selected areas within a space which filtered air is passed
Definitions
- the invention relates to a working table, especially for biological tasks, provided with an air circulation system having a first filter for filtering air from a space upstream of said first filter, the air being fed downstream of said first filter to a space above the working surface of the working table, and a second filter mounted between the space above said working surface and the suction side of a fan, the pressure side of the fan being connected via a duct to an exhaust and to the said space upstream of said first filter.
- filters are used with a very high filtering performance for small particles, it being not unusual to let pass no more than 3.10- 5 of all particles above 0,3 pm.
- This high degree of filtering out of these particles not only an almost complete protection against bacteria passing said filter is obtained, but the same holds also for viruses, which in practice cannot exist independently but only on a matrix or such like, which may be a bacterium for instance.
- the invention aims to improve the security of working tables with a constructively simple means which also can be applied directly to working tables that already exist.
- the invention provides that the circulation of the air towards the exhaust and through both filters is generated solely by said fan, said duct being bifurcated at a location to provide branches, one branch leading to the exhaust and the other branch leading to the said space upstream of said first filter, said location being provided with an adjustable flap, controlling the proportion between the air quantities streaming towards the respective branches.
- the flap has a pivot which is located at the downstream side of the flap.
- a location of an air control flap per se is known from the cited Dutch Patent Specification 76.698. With the invention this feature enables an effective possibility to modify the division of the air current without influencing the total flow resistance of the system in a considerable degree.
- said other branch to the space upstream of said first filter is obliquely oriented with respect to the duct portion upstream of the location.
- this feature per se has been shown in the cited Dutch Patent Specification 76.698. Also is this position of the passage per se known in working tables without flap.
- a further important aspect of the invention is, that in order to increasingly safeguard the room in which the working table is present, it is desired that the duct from the fan towards the location and the branch leading to the space upstream of the first filter are hermetically sealable from the room that contains the working table. Because in the duct and the space upstream of the first filter one has air directly coming from the space above the working surface but having been filtered only once, it is possible that this air contains some infectious germs. Because a slight over pressure has to reign in this space with respect to the room containing the working table, a high guarantee is important that this hermetical seal is maintained.
- the flap has no mechanically movable control members extending outside said hermetically sealed parts.
- FIG. 1 indicates a Work sheet that serves the purpose of working surface and at its edges is provided with vent openings, for instance in the shape of a grid or sieve structure 2, by which the space 3 above the working surface is connected to the space 4 below this working surface.
- a pre-filter 6 At the lower side of this space 4, which at its right side forms a leakage pan 5 a pre-filter 6 has been mounted the lower side of which is connected to a space 7, which at its lower side is closed by a so-called absolute filter 8.
- Such a filter has the capacity to retain particles of 0,3 pm or larger with a perviousness of 3.10- 5 .
- the space 9 below the absolute filter 8 is connected to the suction side 9' of a fan 10 with an exit 11 which opens into a duct 12.
- This duct has at 13 an enlargement towards the right, which opens into an obliquely oriented passage opening 14 and at the other side a deviation 15 towards the left, which opens into a vertical exhaust duct 16 with at the upper side an exhaust 17, which preferably is connected to a non shown exhaust channel which debouches outside the building containing the working table.
- a flap 18 is pivotable about a pivot 19. With non shown means the flap. can be fixed in a certain position. If the flap in figures 1 is swayed towards the left an important part of the air passes through the passage opening 14 and when the flap 18 is swayed towards the right a more important part passes through the exhaust 17.
- the passage opening 14 opens into a space 20 (vide fig. 1) which by means of a baffle 21 is separated from the space 3 above the working surface. At its upper end the baffle 21 is somewhat bent wherewith it is connected with little flow resistance with the space 22 above filter 23. Consequently the air enters the space 3 from above through filter 23 and through the front side 24 of the space 3 from the right above the work sheet 1 and forms therein a constant air down flow, which goes toward the vents 2, wherewith also a continuous airflowthrough the front side 24 of the space 3 occurs in the direction towards the working table. Both these air currents prevent suspended particles to remain permanently in space 3 or to migrate to the outside.
- the air sucked in byfan 10 passes through ducts 12 and 16, which latter duct is located in a space 20, which towards the outer side is closed by a shutter 25.
- This shutter can be mounted air tightly and normally is controlled with respect to its seal by means of soaping.
- the proportionality between the air current which passes through the filter 23 and the one that is sucked in through the front side 24 can be controlled by adjusting flap 18.
- the rotational speed of the fan 10 can be adjusted for maintaining certain desired flow velocities. With both these adjustment facilities the possibility exists to adjust the working table to an optimum air flow velocity and air current distribution for a certain use. Then, when small variations occur during use, for instance because filters get a higher flow resistance, by a just choice of the starting condition it can be seen to it that one works amply within safe application limits.
- the filter which firstly may show a tendency to clog is the pre-filter, in which most of the coarse particles suspended in the air are caught. Naturally this filter will be replaced if this is necessary or desired.
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Ventilation (AREA)
- Accommodation For Nursing Or Treatment Tables (AREA)
- Workshop Equipment, Work Benches, Supports, Or Storage Means (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
Abstract
Description
- The invention relates to a working table, especially for biological tasks, provided with an air circulation system having a first filter for filtering air from a space upstream of said first filter, the air being fed downstream of said first filter to a space above the working surface of the working table, and a second filter mounted between the space above said working surface and the suction side of a fan, the pressure side of the fan being connected via a duct to an exhaust and to the said space upstream of said first filter.
- Such working tables are known in practice. The publication "Nouvelle Gamme", (Sofiltra), no. R. C. Seine 67B3072, 4-70 shows working tables having an air flow system with an adjustable fan, which tables, however, create an almost dust free atmosphere above the working surface but do not prevent that air from the table enters the room in which the table is located. In the first mentioned working table a so-called laminar air current fulfils the double task at the one hand to prevent that the micro particles, such as aerosol particles, bacteria or other particles may come from the space above the working surface into the space in which the working table is located and at the other hand to see to it that any particles in the space above the working surface are steadily carried off. Con- sequentlythey have to comply with very stringent reliability requirements, specially if biological activities are involved. With bacteriological experiments or processes a minor escape may lead to serious consequences, which naturally may be even more so with certain so-called biological manipulations for instance with hereditary material.
- For this reason filters are used with a very high filtering performance for small particles, it being not unusual to let pass no more than 3.10-5 of all particles above 0,3 pm. By this high degree of filtering out of these particles not only an almost complete protection against bacteria passing said filter is obtained, but the same holds also for viruses, which in practice cannot exist independently but only on a matrix or such like, which may be a bacterium for instance.
- With such working tables it is of great importance that the air current complies always with the requirement, that a good air curtain is present, such that particles present above the working surface will be carried off steadily and no such particles may migrate to the outside. The air circuit of such a working table contains a suction from the space above the working surface and an exist through the exhaust and further two filters. For complying with all requirements under varying conditions it is possible to equip the fan with an adjustable rotational speed, but even then adaptation to changed conditions, for instance other experiments or such like is not always possible in such a way that optimum security can be guaranteed. The same is true also when the flow resistances of the filters change during use, which mostly means that they increase.
- Moreover the flow conditions with a single fan, a suction and a exhaust and two principally not completely constant flow resistances are not always sufficiently controllable.
- It is remarked that from the Dutch Patent Application 7215495 a working table of the discussed down-flow type is known, having two fans. Apart from the complicated construction, with two fans the risk exists that if one of the fans drops out, very abnormal flow conditions may arise, even with the effect of blowing particles into the space outside the working table.
- The invention aims to improve the security of working tables with a constructively simple means which also can be applied directly to working tables that already exist.
- Accordingly the invention provides that the circulation of the air towards the exhaust and through both filters is generated solely by said fan, said duct being bifurcated at a location to provide branches, one branch leading to the exhaust and the other branch leading to the said space upstream of said first filter, said location being provided with an adjustable flap, controlling the proportion between the air quantities streaming towards the respective branches.
- By giving the flap an adjustment, which complies with conditions corresponding to a determined application of the working table and again doing so within the reach in which these conditions may change, for instance by change of the filter resistances, a very important improvement is obtained with very simple means.
- It is remarked that from Dutch Patent Specification 76.698 an air conditioning system is known having a flap that controls the recirculation air flow directly towards a space which is the fan room of a main fan or indirectly via a space to which also the fresh air is admitted and which via a cooling means and an auxiliary fan discharges into said fan room.
- According to a further elaboration of the invention it is preferably provided that the flap has a pivot which is located at the downstream side of the flap. Such a location of an air control flap per se is known from the cited Dutch Patent Specification 76.698. With the invention this feature enables an effective possibility to modify the division of the air current without influencing the total flow resistance of the system in a considerable degree.
- According to still a further elaboration of the invention it is preferably provided that said other branch to the space upstream of said first filter is obliquely oriented with respect to the duct portion upstream of the location. Herewith is pointed to the fact that this feature per se has been shown in the cited Dutch Patent Specification 76.698. Also is this position of the passage per se known in working tables without flap.
- A further important aspect of the invention is, that in order to increasingly safeguard the room in which the working table is present, it is desired that the duct from the fan towards the location and the branch leading to the space upstream of the first filter are hermetically sealable from the room that contains the working table. Because in the duct and the space upstream of the first filter one has air directly coming from the space above the working surface but having been filtered only once, it is possible that this air contains some infectious germs. Because a slight over pressure has to reign in this space with respect to the room containing the working table, a high guarantee is important that this hermetical seal is maintained.
- For this reason it is according a further elaboration of the invention provided that the flap has no mechanically movable control members extending outside said hermetically sealed parts.
- The invention in the following is further elucidated on hand of the drawing, in which:-
- Figure 1 shows a cross-section through a working table according the invention.
- Figure 2 shows a cross-section over the line II-II of figure 1.
- In the drawing reference 1 indicates a Work sheet that serves the purpose of working surface and at its edges is provided with vent openings, for instance in the shape of a grid or
sieve structure 2, by which thespace 3 above the working surface is connected to thespace 4 below this working surface. At the lower side of thisspace 4, which at its right side forms a leakage pan 5 a pre-filter 6 has been mounted the lower side of which is connected to aspace 7, which at its lower side is closed by a so-calledabsolute filter 8. Such a filter has the capacity to retain particles of 0,3 pm or larger with a perviousness of 3.10-5. - The
space 9 below theabsolute filter 8 is connected to the suction side 9' of afan 10 with anexit 11 which opens into aduct 12. This duct has at 13 an enlargement towards the right, which opens into an obliquely oriented passage opening 14 and at the other side adeviation 15 towards the left, which opens into avertical exhaust duct 16 with at the upper side an exhaust 17, which preferably is connected to a non shown exhaust channel which debouches outside the building containing the working table. - A
flap 18 is pivotable about a pivot 19. With non shown means the flap. can be fixed in a certain position. If the flap in figures 1 is swayed towards the left an important part of the air passes through the passage opening 14 and when theflap 18 is swayed towards the right a more important part passes through the exhaust 17. - The passage opening 14 opens into a space 20 (vide fig. 1) which by means of a
baffle 21 is separated from thespace 3 above the working surface. At its upper end thebaffle 21 is somewhat bent wherewith it is connected with little flow resistance with thespace 22 above filter 23. Consequently the air enters thespace 3 from above through filter 23 and through thefront side 24 of thespace 3 from the right above the work sheet 1 and forms therein a constant air down flow, which goes toward thevents 2, wherewith also a continuous airflowthrough thefront side 24 of thespace 3 occurs in the direction towards the working table. Both these air currents prevent suspended particles to remain permanently inspace 3 or to migrate to the outside. - The air sucked in
byfan 10 passes throughducts space 20, which towards the outer side is closed by ashutter 25. This shutter can be mounted air tightly and normally is controlled with respect to its seal by means of soaping. - The proportionality between the air current which passes through the filter 23 and the one that is sucked in through the
front side 24 can be controlled by adjustingflap 18. Moreover the rotational speed of thefan 10 can be adjusted for maintaining certain desired flow velocities. With both these adjustment facilities the possibility exists to adjust the working table to an optimum air flow velocity and air current distribution for a certain use. Then, when small variations occur during use, for instance because filters get a higher flow resistance, by a just choice of the starting condition it can be seen to it that one works amply within safe application limits. - The filter which firstly may show a tendency to clog is the pre-filter, in which most of the coarse particles suspended in the air are caught. Naturally this filter will be replaced if this is necessary or desired.
- Summarizing it can be putthatthe application of the
flap 18 forms an extremely simple means for enlarging the adjustment possibilities of the table and consequently adjust it better to the current velocities allowable with different applications. This adjustability is obtained without the complications and dangers tied up with two fans connected in series or parallel, giving flow circuits which often are very sensible for relatively small changes, as is well known.
Claims (5)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT83201301T ATE21165T1 (en) | 1982-09-10 | 1983-09-09 | WORKPLACE WITH ''CLEAN ROOM'' THROUGH LAMINAR AIR FLOW. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL8203523A NL8203523A (en) | 1982-09-10 | 1982-09-10 | WORKBENCH WITH LAMINARY AIRFLOW AS SECURITY. |
NL8203523 | 1982-09-10 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0106382A1 EP0106382A1 (en) | 1984-04-25 |
EP0106382B1 true EP0106382B1 (en) | 1986-07-30 |
Family
ID=19840256
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP83201301A Expired EP0106382B1 (en) | 1982-09-10 | 1983-09-09 | Working table with laminar air flow protection |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0106382B1 (en) |
AT (1) | ATE21165T1 (en) |
DE (1) | DE3364965D1 (en) |
NL (1) | NL8203523A (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2243800A (en) * | 1990-05-07 | 1991-11-13 | Hortotec | A safety cabinet. |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL76698C (en) * | ||||
NL7215945A (en) * | 1972-11-24 | 1974-05-28 | ||
DE2723503A1 (en) * | 1977-05-25 | 1979-01-11 | Eberle Hans | Insulated building air conditioning plant - has auxiliary heating system for water and air heating |
-
1982
- 1982-09-10 NL NL8203523A patent/NL8203523A/en not_active Application Discontinuation
-
1983
- 1983-09-09 AT AT83201301T patent/ATE21165T1/en not_active IP Right Cessation
- 1983-09-09 EP EP83201301A patent/EP0106382B1/en not_active Expired
- 1983-09-09 DE DE8383201301T patent/DE3364965D1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
DE3364965D1 (en) | 1986-09-04 |
EP0106382A1 (en) | 1984-04-25 |
NL8203523A (en) | 1984-04-02 |
ATE21165T1 (en) | 1986-08-15 |
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