EP0380565A1

EP0380565A1 - A processing chamber and a method of preventing escape of a contaminating substance therefrom

Info

Publication number: EP0380565A1
Application number: EP19880908946
Authority: EP
Inventors: Jorgen Kurt Andersen; Erik Herforth Larsen
Original assignee: H MOLDOW AS
Current assignee: H. MOLDOW A/S
Priority date: 1987-09-30
Filing date: 1988-09-30
Publication date: 1990-08-08
Also published as: WO1989002788A1; DK514587D0

Abstract

Dans une chambre de traitement dans laquelle est utilisée une peinture ou une laque liquide pulvérisée ou atomisée, les parois internes de la chambre sont recouvertes d'un revêtement intérieur en forme de sac (40) constitué par du papier ou par un film plastique. Le bord du revêtement intérieur en forme de sac qui définit l'ouverture du sac est monté sur une unité filtrante (23) et le revêtement intérieur est maintenu de façon libérable en contact avec les parois internes de la chambre de traitement (10), par exemple par vide d'air, pendant qu'une pression subatmosphérique est maintenue à l'ntérieur de la chambre de traitement par aspiration d'air à travers l'unité filtrante (23). Lorsque la couleur de la peinture ou de la laque utilisée doit être modifiée, le revêtement intérieur peut être dégagé des parois de la chambre et être replié sur le côté supérieur de l'unité filtrante (23), puis cette dernière et le revêtement intérieur replié peuvent être remplacés par une nouvelle unité.In a treatment chamber in which a sprayed or atomized liquid paint or lacquer is used, the internal walls of the chamber are covered with a bag-shaped interior covering (40) consisting of paper or a plastic film. The edge of the bag-shaped inner lining which defines the opening of the bag is mounted on a filter unit (23) and the inner lining is releasably held in contact with the internal walls of the treatment chamber (10), by example by vacuum, while a subatmospheric pressure is maintained inside the treatment chamber by suction of air through the filter unit (23). When the color of the paint or lacquer used has to be changed, the interior lining can be released from the walls of the chamber and folded over the upper side of the filter unit (23), then the latter and the interior lining folded can be replaced with a new unit.

Description

A PROCESSING CHAMBER AND A METHOD OF PREVENTING ESCAPE OF CONTAMINAT¬ ING SUBSTANCES THEREFROM

The present invention relates to a method of preventing escape of contaminating powdered or atomized substances from an enclosure or a processing chamber.

In connection with industrial processes it is well-known to apply paints and other protective or decorative coatings on to the surfaces of the manufactured objects by spraying powdered solid or atomized liquid surface protecting substances on to the objects by means of a spray gun or another suitable spraying device. In order to reduce spreading of the powdered or atomized substances to the environment and also to reduce loss of such substances the spraying process normally takes place within a cabin or chamber. Normally, the objects to be treated are transported into and out from the chamber by means of a conveyor, and, consequently, the processing chamber or cabin must be provided with an entrance opening through which the untreated objects may pass into the chamber and exit opening through which the coated objects may leave the chamber. Furthermore, the conveyor is preferably arranged outside the cabin or chamber in order to avoid contamination thereof, and the upper wall of the chamber or cabin may therefore define a slit or slot through which elongated object suspending members carried by the conveyor may extend. Frequently, the chamber or cabin is also provided with an opening through which an operator may operate the spraying device. The powdered or atomized substance may be guided to the surfaces of the objects being treated by an electrostatic field. Thus, the particles of the substance being applied may be charged oppositely to the charging of the objects being treated. In order to prevent the powdered or atomized substance sprayed in the processing chamber or cabin from escaping through the openings of the cabin and thereby contaminating the environment, air is withdrawn from the chamber so as to create a subatmospheric pres¬ sure therein, and the withdrawn air. is passed through a cyclone or a filter for separating the contaminating substance from the air which is exhausted into the atmosphere. Despite all these measures it cannot be avoided that deposits of the sprayed substance are formed on the inner walls of the cabin or chamber. Such deposits may be spread to- the environment when use of the processing chamber is terminated and withdrawal of air therefrom is stopped. The deposits may also create problems when it is desired to shift from one kind of surface protective or decorative substance to another, for example from one colour of paint material to another, because particles from the deposits of the previously used substance may be whirled into and mixed with the new substance which is sprayed into the chamber or cabin. This problem is solved by the method according to the invention.

Thus, the present invention provides a method of preventing escape of contaminating powdered or atomized substances from .an enclosure or a chamber defined within a structure, which includes substantially stiff wall parts and defines at least one first access opening there¬ in, said method comprising inflating a bag-like lining member of a flexible material within said enclosure or chamber into contact with said stiff wall parts to make the flexible material adhere thereto, providing at least one second access opening in the flexible material at a position opposite to the first access opening, exhausting air from an exhaust opening of the lining member so as to establish a subatmospheric pressure within the enclosure or chamber, and suspend¬ ing the powdered or atomized substance in the air within the enclo¬ sure or chamber. Thus, the inner surfaces of the stiff wall parts of the structure may be provided with a replaceable lining merely by inflating the bag-like lining member therein and releasably adhering the flexible walls of the lining member to the stiff wall parts. When the necessary openings have been provided in the inflated lining member, a subatmospheric pressure may be provided by exhausting air from the inner space of the lining member. This means that a powdered or atomized substance which is suspended in the air within the inner space of the bag-like lining member for the purpose of forming a protective or decorative coating on objects of any kind, or for any other purpose, cannot escape through the openings provided in the lining member because air from the ambient atmosphere will flow through these openings into the inner space of the lining member because of the subatmospheric pressure provided therein. This flexible lining material may be adhered or releasably fastened to the stiff wall parts of the structure in any suitable manner, for example by means of fastening means of the velvet type, releasable glue, magnetic means, mechanical fastening means, or the like. In the preferred embodiment, however, the flexible lining material is ad¬ hered to the adjacent stiff wall parts by establishing a subatmos¬ pheric pressure in a space defined between the lining material and the stiff wall parts. The latter pressure must then be substantially lower than the subatmospheric pressure provided within the inner space of the bag-like lining member.

The air exhausted from the exhaust opening of the lining member inevitably entrains powdered or atomized substance from the enclosure or processing chamber. Therefore, such exhaust air is preferably passed through a separating device, such as a cyclone or a filtering device, for separating the powdered or atomized substance from the exhausted air flow. In case the separated substance is a solid pow¬ dered material, the separated substance may be recirculated into the processing chamber or enclosure, for example through a spraying device or a spray gun. It should be understood that the powdered or atomized substance suspended in the air of the processing chamber or enclosure may be of any kind used in connection with some kind of process, such as a disinfectant or a pesticide, which may contaminate the environment if spread thereto. However, as mentioned above, the powdered or atomized substance is preferably a paint or another coating or surface covering material which is applied to the surface of an object for protective or decorative purposes.

It cannot be prevented that the powdered or atomized substance will to some extent deposit on the inner side of the flexible walls of the lining member. However, when it is desired to stop the operation of the processing chamber or to shift from one kind of product to a- nother, any residues of the paint or substance previously used may be removed together with the flexible bag-like lining member. In such case the lining material is released from the stiff wall parts, and the openings formed in the lining material are at least partly closed while exhausting of air from the exhaust opening is maintained so as to deflate the flexible lining member, which may thereafter be remo¬ ved together with the substance residues contained therein. There¬ after, a new bag-like lining member may be mounted and inflated in the structure as described above, whereafter operation may be con- tinued with another kind of substance, If desired.

The rim portion of the flexible lining member encircling the exhaust opening thereof may be fastened to the separating device, and the separating device may then be removed together with the deflated lining member so as to prevent that powdered substance from a previ- ous process may spread from the separating device into the enclosure or processing chamber and contaminating the new processing substance used.

The present invention also provides a bag-like lining member for use in the carrying out of the method described above and made of a flexible plastic material, the lining member having closable slits or openings formed therein. Such slits or openings may be closable for example by means of adhesive tape, fastening means of the velvet type, or by means of a slide fastener.

According to another aspect the present invention provides a process- ing chamber comprising a structure including substantially stiff wall parts defining at least one access opening therein, an inflatable bag-like lining member having an exhaust opening and being made of a flexible material and being arranged within said chamber, releasable fastening means for fastening the lining member to the stiff wall parts in its inflated condition, means for suspending a powdered or atomized substance in an inner space defined by the bag-like lining member, a substance separating device communicating with the exhaust opening of the lining member, and air exhausting means for exhausting air from the inner space of the lining member through the separating device.

According to a third aspect the present invention provides a gas filtering device comprising a gas inlet, at-least one hollow filter¬ ing element defining an inner space, which communicates with a gas outlet for filtered gas, and a gas deflecting member covering the filtering member opposite to said gas inlet. Gas with entrained particulate impurities flowing from the gas inlet towards the inner space of the filtering element is deflected by the deflecting member. The consequent change of flow direction will cause separation of part of the entrained particles, whereby an outer layer of particles filtered from the gas flow builds up at a reduced rate.

The gas inlet of the filtering device is preferably positioned at a higher level than the filtering element or elements which means that the deflecting member covers the upper surface of the associated filtering element or elements, and the deflecting member may have downwardly sloping upper surfaces so that particulate solid materials or impurities to be filtered do not tend to collect on these upper surfaces. Furthermore, each of the deflecting members may form a cover enclosing at least one filtering element and defining a down- wardly directed inlet opening, the inner walls of the cover being spaced from the filtering element or elements. The flow direction of gas flowing in a downward direction from the gas inlet will then have to be changed about 180". Due to inertia a substantial part of parti¬ culate foreign matter entrained with the gas flow will continue its movement in a downward direction, so that only a fraction of particu¬ late materials or impurities entrained with the gas will deposit on the filtering element or elements.

The preferred embodiment of the filtering device according to the invention comprises at least one tubular filtering element with an axis extending substantially horizontally, whereby all parts of the outer surface of the filtering element may be arranged rather close to the inlet opening of the cover.

In order to obtain an increased capacity of the filtering device it may comprise an arrangement of a plurality of filtering elements and of a plurality of deflecting members arranged at substantially the same level, and the deflecting members may then be mutually horizon¬ tally spaced so as to defined gas flow passages therebetween. Fur¬ thermore, the filtering device may comprise at least two superposed, substantially horizontal arrangements of filtering elements and deflecting members, and adjacent arrangements may be vertically spaced. Preferably, in operation of the filtering device the gas flow velocity in the gas flow passages defined between the mutually spaced deflecting members or covers substantially exceeds the flow velociti¬ es in the spacings between the outer surfaces of the filtering ele- ments and the inner surfaces of the associated deflecting members or covers, whereby the tendency of entrained foreign matters to continue in a downward direction is augmented.

Fine particles or dust which may follow the gas flowing into the house-like covers through the inlet openings thereof will deposit on the outer surface of the filtering elements. Therefore, from time to time such deposit of dust must be removed so as to regenerate the filtering elements. Therefore, the filtering device according to the invention may further comprise means for selectively supplying pulses of compressed gas into the inner space of the filtering element or elements so as to remove a dust deposit on the outer surface thereof. The pulses of compressed gas may have a relatively short duration. However, the duration should be sufficient to ensure that the dust removed from the filtering element or elements has been substantially discharged from the inner space of the associated cover. As soon as the dust or foreign matter has been blown out from the house-like cover through the inlet opening thereof, it will be entrained by the gas flowing at a relatively high velocity in the flow passages defi¬ ned between adjacent deflecting members or covers.

The invention will now be further described with reference to the drawings, wherein

Fig. 1 is a perspective view of a spray painting or powder coating plant,

Fig. 2 is a side view and partially sectional view of the plant of

Fig. 1 shown in an enlarged scale, Fig. 3 is a perspective view of a detachable filter unit of the plant,

Fig. 4 is an end view and partially sectional view of the plant shown in Figs. 1 and 2,

Fig. 5 is a perspective view of another embodiment of a filter unit, where certain wall parts have been removed, and Fig. 6 is a perspective view of a further embodiment of a filter unit formed by a plurality of filter modules.

The spray painting or powder coating plant shown in the drawings comprises a housing or cabin 10 supported by legs 11 and having entrance and exit openings 12 and 13. A conveyor rail 14 extends longitudinally within a downwardly open channel 15 formed in the upper wall of the housing 10, and objects 16 (Fig. 4) to be painted or coated are suspended from the conveyor rail 14 by means of suspen¬ sion members 17 slidable along the conveyor rail 14. Thus, the ob- jects 16 may successively be moved into the inner space of the hous¬ ing 10 through the entrance opening 12 and out from the housing through the exit opening 13 after treatment within the housing. The objects 16 may be moved along the rail 14 manually, but are preferab¬ ly moved by mechanical means, such as a driving chain or the like not shown. Lamps 18 are mounted in the upper wall of the housing 10, and the wall of the housing is a hollow double wall defining a space 19 therein. This space 19 may be connected to a vacuum source (not shown) via a connecting tube 20 extending upwardly from the top wall of the housing.

An operator access opening 21 formed in one of the side walls of the housing allows an operator to operate a spraying device, such as a spray gun 22, arranged within the housing. A processing chamber defi¬ ned within the housing 10 communicates with a filter unit 23 through an air exhaust opening 24 defined in the bottom wall of the housing 10. The filter unit 23, which is detachably mounted below the housing 10 and supported by castor wheels 25, comprises an upwardly open filter housing 26 and a plurality of spaced, parallelly and substan¬ tially horizontally extending tubular filter elements 27. One end of each filter element is closed while the other end communicates with an air exhaust passage 28 extending upwardly along the side wall of the housing 10 opposite to the access opening 21. Each of the filter elements 27 contains a centrally arranged core member or filler member 29 pointed at its free end adjacent to the open end of the tubular filter elements 27. In operation air is exhausted from the processing chamber defined within the housing 10 through the exhaust opening 24, through the walls of the filter elements 27 and out through the exhaust passage 28 by means of air exhaust means, such as a pump or ventilator, not shown. This pump or ventilator may also be the above-mentioned vacuum source to which the space 19 is connected. Each of the filter ele¬ ments 27 are embraced by downwardly open flow deflecting members 30 causing a sudden change of flow direction of the air flowing down¬ wardly through the filter unit 23 as indicated by arrows, vide espe- cially Fig. 2. This sudden change of flow direction tends to separate powdered and particulate material 31 so that it will fall down through a sieve 32 positioned below the filter elements 27. Remaining powdered or particulate product entrained by the air flows will deposit on the outer surface of the filter elements 27. From time to time each of the filter elements 27 may be freed from powdered or particulate material deposited on the outer surface thereof. This may be done by actuating a corresponding magnet valve 33, whereby pres¬ surized air is blown from a corresponding air nozzle 34 through a funnel member 35 and into the inner space of the filter elements 27. The spraying device or spray gun 22 may be operated through the access opening 21 for spraying a powdered painting or coating materi¬ al on to the objects 16 arranged within the process chamber of the housing 10, and the powder may be deposited on the outer surfaces of the objects 16 by electrostatic forces in a manner known per se„ Due to the exhaust of air through the air exhaust opening 24 a subat¬ mospheric pressure is created within the processing chamber of the housing 10 causing air to flow into the processing chamber through the entrance and exit openings 12 and 13 and through the access opening 21. The inflow of air through these openings tends to keep the powdered product within the processing chamber, and in the filter unit 23 excessive painting or coating powder is separated from the air exhausted through the exhaust passage 28 as described above. The separated powder 31 may be fluidized on a bed plate 36 sloping down¬ wardly to a powder pump 37 driven by a pneumatic or electric motor 38, or the pump 37 may be an ejector pump. The powder pump 37 may recirculate the painting or coating powder to the spraying device 22 through a return tube 39. When operation of the spraying plant described above is stopped, residues of the powdered painting or coating material remain on the inner walls of the housing 10 and in the filter unit 23. Such resi¬ dues of a coloured powdered painting or coating material are very disadvantageous and problematic when it is desired to change to another colour. To solve this problem the inner walls of the process¬ ing chamber defined within the housing 10 are lined with a sheet or film material of plastic, paper or a similar flexible material imper¬ vious to the powdered product used. According to the present inven- tion the processing chamber of the housing 10 may be lined with the sheet or film material as follows:

A bag-shaped flexible lining material having an opening surrounded by a rim or flange 41 is mounted in a frame 44 arranged at the upper end of the filter unit 23 at the top of the filter housing 26. The frame 44 may also comprise a grounded protective grid 45, which is prefera¬ bly made of copper or another highly conductive metal. Such grid may serve to discharge the electrostatically charged powder flowing into the filter unit 23 and to catch possible objects, such as high vol¬ tage objects, which are unintentionally dropped within the housing 10. Furthermore, the frame 44 may comprise a flexible cover 46, which is wound into a roll and which may selectively be unwound like a blind so as to substantially cover the bottom side of the grid 45. The filter unit 23 with the frame 44 and the liner 40 as shown in Fig. 3 is now positioned below the housing 10 as shown in Figs. 1, 2 and 4. The bag-shaped liner 40 is now inflated by passing pressurized air upwardly through the filter unit and into the liner bag 40 where¬ by the flexible plastic film is pressed into contact with the inner walls of the housing 10. The plastic film material of the bag-shaped liner 40 is kept in this position by applying vacuum to the inner space 19 defined in the double wall of the housing 10 through the connecting tube 20. Because of openings 42 formed in the inner wall of the housing 10 the flexible material of the bag-shaped liner 40 is sucked into engagement with this inner wall. The parts of the bag-- shaped liner 40 covering the openings 12, 13, and 21 of the housing 10 may now be cut away or slit so as to allow objects to be treated to pass through the openings 12 and 13, and so as to allow the opera¬ tor to operate the spraying device 22 through the opening 21. The liner 40 may be provided with a slit 43, which may be opened and closed in a slide fastener-like manner. The slit is closed while the liner 40 is inflated and is opened when suction as been applied to the inner space 19, so as to allow the suspension members 17 to pass through the slit. A subatmospheric pressure may now be created within the processing chamber by exhausting air through the exhaust passage 28 as previously described, and a coloured, powdered painting or coating material may now be sprayed on to the objects 16 by means of the spraying device 22 as previously described. When it is desired to change the colour of the powdered paint, the slit 43, the inlet and exit openings 12 and 13, and the access opening 21 are closed, while the subatmospheric pressure within the processing chamber is maintained. When these openings have been closed the supply of vacuum to the inner space 19 of the hollow wall of the housing 10 is ter- minated, whereby the bag-shaped liner 40 is caused to deflate to a position on top of the filter unit 23 as shown in Fig. 3. The filter unit 23 may now be removed from the plant, and another filter unit with a new bag-shaped liner 40 mounted thereon may be placed in position below the housing 10, and the procedure described above may be repeated.

It should be understood that the inflatable bag-shaped liner 40 need not necessarily be mounted on a filter unit as described above. Alternatively, the filter unit could be replaced by a cyclone, and the liner 40 could then be mounted on a removable frame arranged below the housing 10 and forming part of a passage connecting the processing chamber with the cyclone. In such case an atomized liquid paint could be applied to the objects 16 within the processing cham¬ ber, and the paint separated from the exhaust air in the cyclone need not be recirculated.

Figs. 5 and 6 illustrate further embodiments of a filter unit accor¬ ding to the invention, which includes filtering elements 27 housed in deflecting members 30 of the type described above with reference to Figs. 1 and 2, and the inner space of each of these filtering ele¬ ments 27 is connected to a common gas exhaust passage 28. Each of the filtering elements 27 may contain a filler member 29, and pressurized gas may be blown into funnel members 35 from air nozzles 34 control- led by a magnet valve 33 as described above. Each of the filter units illustrated in Figs. 5 and 6 comprises superposed, substantially horizontally extending layers of the tubular filtering elements each housed in an associated deflecting member 30. Adjacent deflecting members 30 in each layer are mutually horizontally spaced so as to define gas flow passages 50 therebetween, and in the embodiments illustrated these flow passages defined in adjacent horizontal layers of filtering elements 27 are vertically aligned, and the gas deflec¬ ting members 30 in the adjacent layers are vertically spaced, so that gas may flow from the passages into the inner space of the deflecting members 30 through a downwardly directed inlet opening 51.

The arrangement of superposed layers of filtering elements 27 and deflecting members 30 is arranged in an outer housing 52 having a gas inlet 53 arranged at the upper end thereof. The housing 52 has a funnel-shaped lower part 54 leading into a discharge channel 55 in which particulate material or dust separated from the gas is collec¬ ted and discharged by suitable means, for example by a screw conveyor or other suitable discharge means not shown. Filtered gas may be sucked from the gas exhaust passage 28 through a gas outlet 56 by means of a gas pump or fan, not shown.

In the embodiment shown in Fig. 6, each filtering element 27 with its corresponding deflecting member 30 is arranged in a box-like casing 57 formed like a short tube section with a vertically extending axis and having a rectangular cross-section. The filtering elements 27 and the associated deflecting member 30 extend between opposite end walls of the box-like casing 57, and the outer side walls of the deflecting member 30 are spaced from the adjacent inner side walls of the casing 57 so as to define the above mentioned flow passages 50. A plurality of similar filtering modules each comprising a casing 57 with a filtering element 27 and a deflecting member 30 arranged therein, may be arranged in superposed layers as shown in Fig. 6. Thus, the ca¬ sings 57 may define a number of chimney-like vertical flow passages.

Any of the filtering units illustrated in Figs. 2", 4, 5 and 6 may be used in connection with a painting plant of the type shown in Figs. 1-4. However, these- filtering units may also be used in connection with any other plant or system in which powdered or particulate material should be separated from a gas flow, such as combustion gas or flue gas. It should also be noted that the tubular filtering elements 27 shown in the drawings need not necessarily have a cylin- drical shape. Thus, the hollow filtering elements may have any other spherical or elongate shape.

EXAMPLE

A filter unit 23 as shown in Figs. 1-4 is used for filtering exhaust air from a powder coating plant as that described above. The exhaust air entrains large amounts of epoxy lacquer powder. The filter unit comprises a single horizontal layer of five mutually spaced, parallel tubular filtering elements 27 which are arranged in a rectangular housing which is 1925x1000 mm. Each filtering element which is made from a plated layer of polyester, has an outer diameter of 220 mm, and a length of 1000 mm. The filter area of each filtering element is approximately 5 m . Each filtering element 27 is arranged within a gas deflecting member 30 having sloping upper surfaces defining an angle of 70° therebetween and vertically extending, oppositely arran¬ ged side walls extending below the lower part of the filtering ele- ment. The spacing of the opposite inner side surfaces of the side walls of each deflecting member is 300 mm. An amount of 3500 m^ air was passed through the filter unit per hour, and the pressure drop across the filter elements was less than 50 mm column of water. The. velocity of the downwardly flowing air varies between 5 and 1.5 m/sec. from the upper to the lower part of the filter unit, and the velocity of the air flowing upwardly into the deflecting members 30 is about 0.5 m/sec.

.The operation of the magnet valve 33 is controlled by a differential pressure switch triggering the magnet valve when the pressure drop across the filtering elements 27 exceeds 50 mm column of water. When the magnet valve 33 is triggered, pressurized air at 5.5 bar is supplied to the air nozzles 34 for a short time period of about 0.25 second. The pressure pulse which is thereby generated in the inner space of each filtering element 27 causes the dust collected on the outer surface of each filtering element to be blown therefrom and out from the inner space of the surrounding deflecting member 30 when the pressure pulse has been terminated, the dust or the particulate material removed from the filtering element will be entrained by the downwardly directed air flow. The pressure switch will trigger the magnet valve 33 at time intervals of approximately 10 minutes.

The embodiments of the filter units shown in Figs. 5 and 6 may be operated similarly as described above in the example, and the air or gas will flow through the unit as indicated by arrows in Fig. 5.

Claims

1. A method of preventing escape of contaminating powdered or atomi¬ zed substances from an enclosure defined within a structure, which includes substantially stiff wall parts and defines at least one first access opening therein, said method comprising inflating a bag-like lining member of a flexible material within said enclosure into contact with said stiff wall parts to make the flexible material adhere thereto, providing at least one second access opening in the flexible material at a position opposite to the first access opening, exhausting air from an exhaust opening of the lining member so as to establish a subatmospheric pressure within the enclosure, and suspending the powdered or atomized substance in the air within the enclosure.

_* 2. A method according to claim 1, wherein the flexible lining materi¬ al is adhered to the adjacent stiff wall parts by establishing a subatmospheric pressure in a space defined between the lining mate¬ rial and the stiff wall parts.

3. A method according to claim 1 or 2, wherein the air exhausted from the exhaust opening of the lining member is passed through a separat¬ ing device for separating the powdered or atomized substance from the exhaust air.

4. A method according to claim 3, wherein said separating device is a filtering device.

5. A method according to claim 3 or 4, wherein the separated sub¬ stance is recirculated into the enclosure.

6. A method according to any of the claims 1-5, wherein the powdered or atomized substance is a paint or another surface covering materi¬ al.

7. A method according to any of the claims 1-6, wherein the lining material is released from the stiff wall parts, and the second access openings are at least partly closed while exhaust of air from the exhaust opening is maintained so as to deflate the flexible lining member.

8. A method according to any of the claims 3-7, wherein a rim portion of the flexible lining member encircling the exhaust opening thereof is fastened to the separating device.

9. A bag-like lining member for use in carrying out the method ac¬ cording to any of the claims 1-8 and being made of a flexible plastic material, the lining member having closable slits or openings formed therein.

10. A processing chamber comprising a structure including substan¬ tially stiff wall parts defining at least one access opening therein, an inflatable bag-like lining member having an exhaust opening and being made of a flexible material and being arranged within said chamber, releasable fastening means for fastening the lining member to the stiff wall parts in its inflated condition, means for suspending a powdered or atomized substance in an inner space defined by the bag-like lining member, a substance separating device communicating with the exhaust opening of the lining member, and air exhausting means for exhausting air from the inner space of the lining member through the separating device.

11. A processing chamber according to claim 10, wherein said separating device is a filtering device.

12. A processing chamber according to claim 10 or 11, further comprising releasable fastening means for fastening a rim portion of the lining member surrounding said exhaust opening to the separating device.

13. A processing chamber according to claim 12, wherein the separat¬ ing device is releasably fastened to said structure.

14. A processing chamber according to any of the claims 11-13, wherein the filtering device comprises at least one hollow filtering member arranged below the exhaust opening of the lining member and having an inner space communicating with the air exhausting means, and an air deflecting member covering the upper side of the filtering member.

15. A processing chamber according to claim 14, wherein the air de¬ flecting member has downwardly sloping upper surfaces.

16. A gas filtering device comprising a gas inlet, at least one hollow filtering element defining an inner space, which communicates with a gas outlet for filtered gas', and a gas deflecting member covering the filtering element opposite to said gas inlet.

17. A gas filtering device according to claim 16, wherein the gas inlet is positioned above the filtering element, the gas deflecting member having downwardly sloping upper surfaces.

18. A gas filtering device according to claim 16 or 17, wherein the gas deflectin member forms a cover enclosing at least one filtering element and defining a downwardly directed inlet opening, the inner walls of the cover being spaced from the filtering element or ele- ments.

19. A gas filtering device according to any of the claims 16-18, wherein the filtering element is a tubular filtering element with an axis extending substantially horizontally.

20. A gas filtering device according to claim 19 and comprising an arrangement of a plurality of filtering elements and a plurality of deflecting members arranged at substantially the same level, the deflecting members being mutually horizontally spaced so as to define gas flow passages therebetween.

21. A gas filtering device according to claim 20 and comprising at least two superposed, substantially horizontal arrangements of fll- tering elements and deflecting members, adjacent arrangements being vertically spaced.

22. A gas filtering device according to claim 21, wherein in the horizontal spacings of the deflecting members in adjacent superposed arrangements are aligned.

23. A gas filtering device according to any of the claims 16-22, and including a plurality of filtering elements and deflecting members housed in a common housing defining the gas inlet in the upper part thereof.

24. A gas filtering device according to claim 23, wherein the inner spaces of the filtering elements are communicating with a common gas outlet.

25. A gas filtering device according to any of the claims 16-24, further comprising means for selectively supplying pulses of compres- sed gas into the inner space of the filtering element or elements so as to remove dust deposited on the outer surface thereof.

26. A gas filtering device according to claim 25, wherein the com¬ pressed gas supplying means are adapted to supply compressed gas pulses of a time duration sufficient to ensure that dust removed from the filter element has substantially been discharged from the inner space of the associated cover.