A METHOD OF AND AN ARRANGEMENT FOR PROVIDING A CIRCULATING AIR FLOW IN A TREATMENT SPACE

Abstract: A method of providing a circulating air flow in a treatment space for a working area, whereby inlet air (A) is blown into the treatment space (1) to form a circulating air flow (A') in the treatment space, which flow provides an air curtain (A'') at an access opening (5) to the treatment space. In order to eliminate the disturbing influence of a workpiece (4) within the working area (3) on the circulating flow and to improve the working conditions, at least a part (B) of the circulating air flow (A') is deflected from the working area in such a way that the working area remains essentially within the circulating air flow. An arrangement for carrying out the method comprises a duct (7) formed in the treatment space (1) and passing the working area (3) for at least a part (B) of the circulating air flow.

Description: A method of and an arrangement for providing a cir¬ culating air flow in a treatment space The present invention relates to a method of providing a circulating air flow in a treatment space separated from the surroundings for a production line, a working area or the like, whereby inlet air is blown into the treatment space to form a circulat¬ ing air flow in the treatment space, which flow pro- vides an air curtain at an open access opening to the treatment space to prevent entrance of ambient air. From Finnish Patent Application 911968 is pre¬ viously known a method of obtaining an air change i.i a treatment space, in which the condition of the air is kept divergent from that of the ambient air by means of an air flow circulating in the treatment space, which air flow forms an air curtain at an ac¬ cess opening to the treatment space tc prevent en¬ trance of ambient air. The circulating air flow is thereby created by means of an air jet to be blown into the treatment space. The method saves a con¬ siderable amount of energy and improves the working conditions. However, some drawbacks are associated with the arrangement. Disturbances are easily caused in the circulating flow by workpieces positioned within the working area, on account of which a mixing with am¬ bient air takes place and the conditions in the treatment space remain worse than in case of an un- disturbed flow. A strong blow from the outer edge of the working area efficiently prevents the air from escaping from the lower part of the treatment space, but is unpleasant for the worker, and therefore, the improvement in the working conditions remains smaller than could be concluded on the basis of the mere tern- perature. The object of the present invention is to pro¬ vide a method by means of which flow losses caused by a workpiece in the treatment space are eliminated al- most entirely and the working conditions are improved remarkably. This object is achieved by means of the method according to the invention, which is charac¬ terized in that at least a part of the circulating air flow is deflected from the working area in such a manner that the working area remains essentially within the circulating air flow. The basic idea of the invention is that a part of the circulating air flow directed towards the workpiece in the treatment space is caused to flow past the workpiece outside the actual working area in such a way that the workpiece remains in the middle of the circulating flow or at least within the range of a low flow rate. In this manner it is possible to eliminate essentially the disturbing influence of the workpiece on the circulating flow, which improves the working conditions. At the same time, the rate of the air flow is reduced within the working area to a fraction of the respective rate in the known systems. The invention also relates to an arrangement for carrying out the method described above, in which the treatment space comprises means for blowing inlet air supplied ' from outside the space or from the very space into the treatment space in such a manner that the inlet air forms an air flow circulating in the treatment space, which flow provides an air curtain at the access opening to prevent entrance of ambient air. The arrangement is characterized in that a duct passing the working area is formed in the treatment space at least for a part of the circulating air flow. All the advantages mentioned in connection with the method are achieved by means of an arrangement of this kind. The invention will be described in the follow- ing in greater detail referring to the enclosed draw¬ ing, in which Figure 1 shows schematically a sectional eleva¬ tion of a treatment space, comprising a circulating air flow according to an embodiment of the method of the invention, and Figure 2 shows in the same way a treatment space, in which the circulating air flow has been provided according to an alternative embodiment of the invention. Figure 1 shows a treatment space 1 surrounded by a cabinet 2 having a roof, walls and a bottom 2a, above which there is a working level 3 for a work¬ piece 4 to be treated. The front wall of the cabinet has a passage, i.e. an access opening 5. The walls of the cabinet are shaped to be suitable fcr a convec¬ tion flow. At the lower edge of the access opening of the cabinet there are nozzles 6, through which inlet air A is blown horizontally into the treatment space to- wards the back wall of the cabinet. The inlet air flows along the back wall of the cabinet to the upper part of the treatment space and towards the front wall and further downwards along the front wall of the cabinet so that a vertical air curtain A' ' is formed at the access opening. The initial rate of the inlet air is so high that a circulating flow A' is preserved in the treatment space and no warmer am¬ bient air can enter the cabinet as a convection air flow through the upper edge of the access opening. The nozzles are positioned according to the in- vention below the working level 3 to blow inlet air into a passing duct 7 between the working level and the bottom 2a, so that air flows horinzontally below the working level and the workpiece supported by it. An air jet from the nozzles sucks a part B of the air flow A' ' circulating in the treatment space and in¬ duction air from the surroundings of the cabinet through an inlet 8 at the lower edge of the access opening 5 into the passing duct. This prevents the air from escaping through the lower edge of the ac¬ cess opening into the surroundings and draws the main part of that part of : the circulating flow which otherwise flows horizontally along the working level towards the workpiece down into the passing duct. At the rear end of the passing duct, at the back wall of the cabinet, there is an outlet 9 at the height of the working level, through which outlet the circulat¬ ing flow is directed upwards again. If the distance between the working level and the bottom of the treatment cabinet is sufficient, the rate of the flow in the passing duct is not so high as to disturb the circulating flow. It is found that the peripheral part of the circulating flow can be caused to move away from the workpiece by means of the arrangement of the invention and to pass the workpiece from below without this disturbing the cir¬ culating flow in the treatment space. This reduces the disturbing influence of the workpiece on the cir¬ culating flow and lowers the rate of the remaining circulating flow towards the workpiece above the working level. On the other hand, this improves the working conditions on the working level. Disturbances can be reduced further by extend¬ ing the passing duct 7 and its upwards directed dis- charge outlet 9 above the working level 3, as is pre- sented by broken lines in Figure 1. This is especial¬ ly useful when two adjacent production lines are com¬ bined in one cabinet with access openings 5 and noz¬ zles 6 on the opposite sides of the cabinet. The part of the passing duct 7 directed upwards and situated in the middle of the cabinet then forms a common passing duct, by means of which the air can be di¬ rected upwards through the common discharge outlet 9. Figure 1 shows a treatment space, in which the duct passing the circulating flow is formed between the bottom of the treatment space and the working level elevated from the bottom. Figure 2 shows a sit¬ uation in which the passing duct is formed outside the treatment space below the bottom thereof. Figure 2 shows an airtight plate 10 mounted at a distance below the bottom 2a of the treatment space, which plate prevents the circulating flow from flowing into the whole lower space 11 below the bot¬ tom 2a. The front part of the bottom is provided with an inlet 8 into a passing duct 12 between the bottom and the plate and the rear part with an outlet 9 from the passing duct, respectively. With respect to the circulating flow, this arrangement works in the same way as described in connection with Figure 1, so that the main part of the circulating flow is caused to move through the passing duct and only a small part of the flow passes via the workpiece. By means of plates 10 it is possible to form vertical or horizon¬ tal guide channels also elsewhere in the treatment space, as shown by broken lines in Figure 2. In the arrangement of Figure 2, nozzles 13 for inlet air A are positioned inside the passing duct itself. The nozzles draw also in this case the same amount of induction air through the lower edge of the access opening of the cabinet into the passing duct as in the previous embodiment. Such an arrangement sometimes facilitates the problems with the position¬ ing of the equipments. In the above case, for in¬ stance, in which two production lines are positioned in the same cabinet with access openings 5 on both sides of the cabinet, it is possible to manage with one inlet air equipment and with nozzles 13, which are positioned between both working levels 3 in order to blow upwards, in which case they suck air below both working levels. The inlet and outlet openings 8, 9 can be made smaller by providing them with guide plates 14, 15, Figure 2, when the plates are formed in such a way that they reduce the flow resistance of the openings. The outer dimensions of the treatment space will then become smaller. Guide plates can be placed also else¬ where. The drawing and the specification attached thereto are only intended to illustrate the idea of the invention. As far as details are concerned, the method and the arrangement according to the invention may vary within the scope of the claims. Even if the invention has been described above applied to a ca¬ binet, in which the air circulating therein is colder than that in the surroundings, the invention can also be applied when overheated air circulates in the treatment space. Then the flow direction of the air is opposite with respect to the flows indicated by arrows in Figures 1 and 2. The nozzle 13 blows to- wards the access opening side of the cabinet and the nozzle at the upper edge of the access opening 5 blows air towards the roof of the treatment space. It is also possible to mount at desired places in the treatment space small auxiliary nozzles, in the cases presented in Figure 1 and 2, for instance, at the upper edge of the access opening 5 nozzles blowing downwards to support the circulating flow. The lower bottom of the treatment space can naturally also be the floor level of a room.

Claims: Claims: 1. A method of providing a circulating air flow in a treatment space separated from the surroundings for a production line, a working area or the like, whereby inlet air (A) is blown into the treatment space (1) to form a circulating air flow (A') in the treatment space, which flow provides an air curtain (A' ' ) at an open access opening (5) to the treatment space to prevent entrance of ambient air, c h a r¬ a c t e r i z e d in that at least a part (B) of the circulating air flow (A' ) is deflected from the work¬ ing area (3) in such a manner that the working area remains essentially within the circulating air flow. 2. A method according to claim 1, c h a r a c¬ t e r i z e d in that the part (B) of the circulat¬ ing air flow (A' ) to be deflected is removed from the working area (3) on the access opening (5) side of the treatment space and returned to the working area at a bottom of the treatment space on a back wall side (9) of the treatment space. 3. A method according to claim 1 or 2, c h a r¬ a c t e r i z e d in that the part (B) of the circu¬ lating air flow (A* ) to be deflected is removed from the working area (3) by means of a suction effect of an inlet air jet (A) blown below the working area. 4. An arrangement for providing a circulating air flow in a treatment space separated from the sur¬ roundings for a production line, a working area or the like, which treatment space (1) is provided with an access opening (5) to the surroundings, the treatment space comprising means (6; 13) for blowing inlet air (A) into the treatment space in such a way that the inlet air forms an air flow (A' ) circulating in the treatment space, which flow provides an air curtain (A' ' ) at the access opening to prevent en¬ trance of ambient air, c h a r a c t e r i z e d in that a duct (7; 12) passing the working area (3) is formed in the treatment space (1) at least for a part (B) of the circulating air flow. 5. An arrangement according to claim 4, c h a r a c t e r i z e d in that the passing duct is a flow duct (7) between a working level, forming the working area (3), and a bottom plate (2a) of the treatment space (1). 6. An arrangement according to claim 4, c h a r a c t e r i z e d in that the passing duct is a flow duct (12) positioned below a bottom plate (2a) of the treatment space (1), whereby the duct comprises an inlet (8) positioned adjacent to the access opening (5) of the treatment space and an out¬ let (9) positioned adjacent to a back wall of the treatment space. 7. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d in that the means (6) for blowing inlet air (A) into the treatment space (1) and for providing the circulating air flow (A' ) are positioned within the area of the passing duct (7; 12). 8. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d in that the passing duct (7; 12) is provided with guide plates (14, 15) or the like for directing the air flow. 9. An arrangement according to claim 5, c h a r a c t e r i z e d in that the outlet (9) of the passing duct (7; 12) extends above the working level (3). 10. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d in that the treatment space (1) is provided with plates (10) to form a guide channel or guide channels within the walls of the treatment space. AMENDED CLAIMS [received by the International Bureau on 2 July 1993 (02.07.93); original claims 1, 2, 4 and 6 amended; other claims unchanged (3 pages)] 1. A method of providing a circulating air flow in a treatment space separated from the surroundings for a production line, a working area or the like, whereby inlet air (A) is blown into the treatment space (1) to form a circulating air flow (A 1 ) in the treatment space, which flow provides an air curtain (A 11 ) at an open access opening (5) to the treatment space to prevent entrance of ambient air, c a r¬ a c t e r i z e d in that at least a part (B) of the circulating air flow (A') is deflected from the work¬ ing area (3) on the access opening side of the treat¬ ment space and returned on the opposite side with respect to the access opening in such a manner that the working area remains essentially within the cir¬ culating air flow. 2. A method according to claim l, c h a r a c¬ t e r i z e d in that the deflected part (B) of the circulating air flow (A') is returned to the working area at a bottom of the treatment space on a back wall side (9) of the treatment space. 3. A method according to claim 1 or 2, c h a r¬ a c t e r i z e d in that the part (B) of the circu- lating air flow (A 1 ) to be deflected is removed from the working area (3) by means of a suction effect of an inlet air jet (A) blown below the working area. 4. An arrangement for providing a circulating air flow in a treatment space separated from the sur- roundings for a production line, a working area or the like, which treatment space (1) is provided with an access opening (5) to the surroundings, the treatment space comprising means (6; 13) for blowing inlet air (A) into the treatment space in such a way that the inlet air forms an air flow (A 1 ) circulating in the treatment space, which flow provides an air curtain (A 11 ) at the access opening to prevent en¬ trance of ambient air, c h a r a c t e r i z e d in that a duct (7; 12) passing the working area (3) is formed in the treatment space (1) at least for a part (B) of the circulating air flow, whereby the duct comprises an inlet (8) positioned adjacent to the access opening (5) of the treatment space and an out¬ let (9) positioned on the opposite side of the treat- ment space with respect to the access opening. 5. An arrangement according to claim 4, c h a r a c t e r i z e d in that the passing duct is a flow duct (7) between a working level, forming the working area (3) , and a bottom plate (2a) of the treatment space (1) . 6. An arrangement according to claim 4, c h a r a c t e r i z e d in that the passing duct is a flow duct (12) positioned below a bottom plate (2a) of the treatment space (1) , whereby the duct comprises an outlet (9) positioned adjacent to a back wall of the treatment space. 7. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d in that the means (6) for blowing inlet air (A) into the treatment space (1) and for providing the circulating air flow (A 1 ) are positioned within the area of the passing duct (7; 12) . 8. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d in that the passing duct (7; 12) is provided with guide plates (14, 15) or the like for directing the air flow. 9. An arrangement according to claim 5, c h a r a c t e r i z e d in that the outlet (9) of the passing duct (7; 12) extends above the working level (3). 10. An arrangement according to claim 5 or 6, c h a r a c t e r i z e d in that the treatment space (1) is provided with plates (10) to form a guide channel or guide channels within the walls of the treatment space.

Inventors: JAERVINEN TYTTI KATARIINA, LESKINEN SEPPO JUHANI, JAERVINEN, TYTTI, KATARIINA, LESKINEN, SEPPO, JUHANI
Applicants: FLAEKT OY, ABB FLAEKT OY
Application year: 1993
Main classification: F24F9
IPC codes: F24F3