Title of Invention: CYCLONE SEPARATOR AND POWDER

RECOVERY EQUIPMENT FOR A POWDER COATING

FACILITY COMPRISING A CYCLONE SEPARATOR

[1] The present invention relates to a cyclone separator defined in the preamble of claim

1. Accordingly the present invention relates in particular to powder recovery equipment in a powder coating facility. Furthermore the invention relates to powder recovery equipment including such a cyclone separator in a powder coating facility.

[2] Cyclone separators are widely known in the field of exhaust-gas purification and separation of solid particulates contained in a flow of a mix of powder and air. Contrary to the case of a centrifuge, the mixed flow to be processed within a cyclone separator is made to rotate on account of its own speed and of an appropriate design of the separating equipment. The centrifugal forces acting on the mixed flow's powder particles accelerate said particles radially outward and in this manner are separated from the gas flow which in the cyclone separator is guided inward and exhausted.

[3] Substantially a cyclone separator consists of an intake zone in the form of a cylindrical receptacle, a separation zone fitted with a conical end region being configured underneath the intake zone, the centrifugal separation of at least a fraction of the powder contained in the mixed flow taking place in said end region. The powder/air mix flow to be processed is fed to the intake zone of the cyclone separator. Various intake structure geometries are applicable, for instance helical, tangential, axial or spiral intakes.

[4] These intake geometries generate a rotational flow of the mixed flow inside the cyclone separator. The resulting swirling flow causes centrifugal forces acting on the particles to be separated from the mixed flow toward the outer wall of the separation zone and to be moved with the wall boundary layer in spiraling paths along the cone subtended in the lower end region downward into a powder collection zone. The gas flow is constrained thereby to flow back upward. The gas leaves the cyclone separator in the form of a radial flow from the outside to the inside and passes upward through a so-called dip pipe at the top of the cyclone separator. The dip pipe is an important component of the cyclone separator because its diameter determines the centrifugal force arising in the cyclone separator and therefore the separation efficiency and the pressure drop. The other dimensions of the regions of the cyclone separator are matched to the dip pipe.

[5] The designs of the different cyclone separators differ substantively by their intake geometries. The most conventional intake geometries are the spiral intake, further the tangential intake which is also called the slotted intake. Both designs offering similar results regarding separation efficiency, the simpler tangential intake design being frequently preferred. The axial intake is required in many ways for its compactness. It is also suitable for large gas transmissions at somewhat lower separation efficiencies.

[6] A cyclone separator of the initially cited kind is known for instance from the German patent document DE 10 2007 005 312 Al. In this state of the art, the cyclone separator is used to separate the coating powder from a powder/air mix. In this design, the powder separated in the cyclone separation zone is fed back as recovery powder into the powder spraycoating equipment. Before the powder that was separated and hence before it was recovered from the powder/air mix flow can be used as recovery powder in powder coating equipment — whether in pure form or mixed with fresh powder- such recovered powder may require reprocessing to be of adequate quality. Such a procedure includes sifting the recovered powder on a sieve to eliminate from it coarse- grain contaminants. It is known already in the state of the art to configure upstream or downstream of the cyclone separator a sifting apparatus in the form of a separate sieve. Basically too, a sieve may be inserted into the cyclone separator itself to sift the powder separated from powder/air mixed flow.

[7] However it was found in practice that a sieve inserted into a cyclone separator in at least some regions of said operational separator is exposed to extreme mechanical loads. Because of the flow geometry arising in the cyclone separator, looses of material are incurred at the sieve surface due to and generated by the flow of the powder/air mix prevailing in the cyclone separator. Depending on the powder content of the mixed flow to be processed, the sieve is bound sooner or later to wear due to abrasion, and consequently it requires regular replacement. Operating costs are incurred if a sieve is used inside the cyclone separator to process the separated powder.

[8] In the light of this problem, it is the objective of the present invention to create a cyclone separator characterized by its very simple design, its compactness, high operational reliability and resulting low capital and operational costs.

[9] The basic problem of the present invention is solved by a cyclone separator characterized by the features of the independent claim 1.

[10] Accordingly the present invention relates to a cyclone separator, in particular one for powder recovery equipment in a powder coating facility, containing an intake zone fitted with a powder intake for powder/air mix flow, further a separation zone situated at the lower end of said intake zone to centrifugally separate at least a fraction of the powder contained in said mix flow, also a powder collection zone connected or con- nectable to the lower end region of the separation zone to collect the powder having been separated in it, and a dip pipe issuing centrally from above into the separation zone to evacuate air from the mix flow, the lower end region of the separation zone being frustoconical and tapering in the direction to the powder collection zone, in particular being fitted with a conically tapering lateral surface, and a sieve to sift the powder separated in the separation zone. In particular the sieve is situated in a horizontal plane between the lower end region of the separation zone and a plane containing the intersection of the surface lines of the frustrum of cone constituted by the separation zone's lower end region.

[11] Using a sieve integrated into the cyclone separator offers the advantage that large- grain contaminants can already be separated inside the cyclone separator from the powder separated in the separation zone, as a result of which this powder illustratively can be directly used as recovered powder in a powder coating facility without the need for additional sieves upstream or downstream of the cyclone separator. This design offers an especially compact and simple powder recovery equipment.

[12] It must be borne in mind moreover that when a sieve is inside the cyclone separator, the sieve cleaning required for instance when changing colors shall be considerably easier and quicker without the danger of contaminating the ambience with powder. Illustratively the sieve may be pivoted into or out of the lower end region and the powder collecting zone by a preferably horizontally pivoting motion. In a merely partly pivoted-in displacement, the sieve already may be reached effortlessly by the cyclone separator's operator for purposes of cleaning, any powder dropping off the sieve during the cleaning process being aspirated by the flow adjusted in the cyclone separator and accordingly not reaching the ambience.

[13] Again the special configuration of the sieve between the lower end region of the separation zone and the powder collection zone assures that the sieve shall be configured in a horizontal plane directly at the reversal site of the main flow formed during operation within the cyclone separator. Though in principle the sieve may well be situated in a horizontal plane passing through the reversal site, efficiency of sifting preferably situates the sieve slightly above the reversal site in order that the main flow's axial speed components be used within the cyclone separator to move the powder particles through the sieve bottom respectively the sieve lining.

[14] Equally as well, the sieve might be configured in a horizontal plane passing through the reversal site of the main flow being generated in operation within the cyclone separator. Then sieve also might be situated underneath the reversal point. This feature is especially applicable when for instance the sieve meshes are large relative to the powder's grain size, as a result of which there shall be no need for reinforced sifting, to move the powder particles through the sieve bottom respectively the sieve lining, where said reinforcement is in the form the main flow's axial speed components in the direction to the powder collection zone. It is essential that the sieve be mounted in the reversal site or near it (above or below) in order to avert or at least significantly reduce the mechanical loads generated by the powder particles in the mix flow on the sieve surface and thus avert /reduce abrasion and loss of material at that surface.

[15] The sieve -positioning characteristic reversal point at the main flow forming inside the cyclone separator during operation is determined by the natural swirling length. Regarding a cyclone separator of which the separation zone comprises a lower end region in the form of a frustrum of cone, the swirl which arises in operation inside the cyclone separator is approximately a point corresponding to the intersection of the generating lines of the frustoconical lower end region.

[16] It is essential that the circumferential speed assume the value zero or be substantially reduced relative to the circumferential flow above the reversal point. Because the sieve of the present invention is situated at or directly near the main flow's reversal point, the mechanical load applied to the sieve surface and hence the abrasion and loss in material generated by friction and by powder particles contained in the mix flow can be significantly reduced. Consequently the cyclone separator of the present invention is characterized by requiring less maintenance and entail fewer shutdowns of the cyclone separator than the conventional ones.

[17] Advantageous embodiment modes of the cyclone separator are defined in the dependent claims.

[18] The present invention also relates to powder recovery equipment for a powder coating facility, where said recovery equipment includes a cyclone separator of the present invention.

[19] The invention is elucidated below in relation to the appended drawings and with respect to an illustrative embodiment mode.

[20] Fig. 1 is a schematic of a powder spraycoating facility which is illustrative of a plurality of different spraycoating facilities that may use a cyclone separator of the present invention acting as powder recovery equipment,

[21] Fig. 2 is a side view of the front side of the lower end region of a cyclone separator of one embodiment of the invention shown in longitudinal section,

[22] Fig. 3 is a sideview of the lower end region of the cyclone separator of Fig. 2 in longitudinal section,

[23] Fig. 4 is a perspective view of the lower end region of a cyclone separator of Fig. 1, the sieve housing being pivoted out,

[24] Fig. 5 is a top view of the lower end region of the cyclone separator of Fig. 1, the sieve housing being in its pivoted out position, the powder collection zone being directly communicating with the separation zone, and

[25] Fig. 6 is a sideview of the sieve housing for application in a cyclone separator of the present invention.

[26] Fig. 1 schematically shows an embodiment mode of a powder spraycoating facility to spray coat objects 2 with coating powder, said powder being molten onto the objects subsequently in an omitted heating oven. The powder spraycoating facility shown in Fig. 1 comprises a cyclone separator 100 of the present invention.

[27] One or more electronic controls 3 drive the functions of the powder spraycoating facility. Powder pumps 4 pneumatically convey the coating powder. Said pumps may be injectors aspirating, from a powder receptacle, compressed air serving as feed air, whereafter the mixture of feed air / coating powder flows jointly into a receptacle or a spray device.

[28] The powder pumps also may be pumps that consecutively feed small powder portions by means of compressed air, each small powder portion (quantity) being stored in a powder chamber and then being expelled from it using compressed air. The compressed air remains behind the powder portion and pushes it ahead of itself. Such kinds of pumps may also be called compressed thrust pumps or plug-conveying pumps because the compressed air moves the stored powder portion like a plug before it through a pump outlet conduit.

[29] A compressed air source 6 generates compressed air for the pneumatic feed and flu- idization of the coating powder, and it is connected by means of corresponding pressure setting implements 8, for instance pressure regulators and/or valves to the various components.

[30] Fresh powder from a powder supplier is fed from a supplier-provided receptacle, for instance a small receptacle 12 or a large receptacle 14, by means of a powder pump 4 or 18 to a sieve 10,

[31] The coating powder sifted by the sieve 10 is moved by gravity or preferably by a powder pump 4 through one or several powder feed conduits 20 and through powder intake apertures 26 into a buffer container chamber 22 of a buffer container 24. The volume of the buffer container chamber 22 preferably is substantially less than that of the small fresh powder receptacle 12.

[32] In one preferred embodiment of the invention, the powder pump 4 of the minimum of one powder feed conduit 20 to the buffer container 24 is a compressed air thrust pump. In this design the initial segment of the powder feed conduit 20 may serve as a pump chamber receiving powder sifted by the sieve 10 through a valve such as a pinch valve. Once said pump chamber holds a given quantity of powder, the powder feed conduit 20 is separated flow- wise from the sieve 10 by closing said valve. Thereafter the given powder quantity is expelled by compressed air through the powder feed conduit 20 into the buffer container chamber 24.

[33] Preferably the powder intake apertures 26 are fitted into a sidewall of the buffer container chamber 24 preferably near the bottom of the buffer container chamber 22, so that, when flushing said chamber with compressed air, even powder residues at the bottom can be expelled through the powder intakes 26, for which purpose the powder feed conduits 20 preferably are kept separate from the sieve 10 and aligned to point into a waste bin as indicated by a dashed arrow 28 in Fig. 1. A dip pipe 30 fitted with compressed air nozzles illustratively is used to clean the buffer container chamber 22 and is displaceable through it.

[34] Powder pumps 4, for instance injectors, are connected to one or preferably several powder outlets 36 to feed coating powder through powder conduits 38 to spray devices 40. The spray devices 40 may be spray nozzles or rotary atomizers to spray the coating powder 42 onto the object(s) 2 to be coated which preferably are situated in a coating cabin 43. The powder outlet apertures 36 preferably are situated in a wall opposite that wall fitted which is fitted with the powder intake apertures 26. The powder outlet apertures 36 preferably are also configured near the bottom of the buffer container chamber 22.

[35] Coating powder 42 not adhering to the object(s) 2 is aspirated as excess powder through an excess powder conduit 44 by means of a the suction air from a blower 46 into a cyclone separator 100. To the extent possible said excess powder shall be separated in the cyclone separator 100 from the flow of suction air. The separated powder fraction is then fed as recovery powder from the cyclone separator 100 through a powder recovery conduit 50 back into the buffer container chamber 22.

[36] Depending on the kind of powder and/or the degree of powder soiling, the powder recovery conduit 50 also may be separated from the buffer container chamber 22 by means of the control 3 and the recovery powder may be fed into a waste bin as indicated schematically in Fig. 1 by a dashed line 51.

[37] The buffer container 24 may be fitted with one or several, illustratively two sensors

S 1 and/or S2 to control the feed of coating powder into the buffer container chamber 22 by means of the control 3 and by means of the powder pumps 4 in the powder conduits 20. Illustratively the lower sensor S 1 detects a lower powder level limit and the upper sensor S2 an upper powder level limit.

[38] The lower end region of the cyclone separator 100 acts as the powder collecting zone

104 and can be designed as recovery powder supply silo and be used as such, and for that purpose it is fitted with one or more sensors, which in the shown embodiment modes of the cyclone separator 100, is one sensor S3 functionally connected to the control 3. In this manner, illustratively, the fresh powder supply through the fresh powder feed conduits 16 and 18 may then be stopped automatically as long as enough recovery powder remains in the cyclone separator 100 to sufficiently supply enough recovery powder to the buffer container chamber 22 for spraycoating by means of the spray devices 40. When the cyclone separator 100 no longer holds an adequate quantity of recovery powder, the supply of fresh powder through the fresh powder conduits 16 or 18 may be switched ON automatically. The present invention also allows the further procedure of simultaneously feeding fresh powder and recovery powder to the buffer container chamber 22, in this manner mixing the two kinds of powder.

[39] The exhaust air of the cyclone separator 100 passes through a dip pipe (not shown in further detail) — which runs from above to issue centrally into the intake zone 101 — and an exhaust air conduit 54 into a post-filtering system 56 and one or more filters 58 therein to the blower 46, and beyond said blower, into the atmosphere. The filters 58 may be filter bags or filter cartridges or filter plates or the like. The powder separated from the air flow by the filters 58 typically is waste powder and drops by gravity into a waste bin or it may be moved, as shown in Fig. 1, through one or more waste exhaust conduits 60 each fitted with one powder pump 4, into a waste bin 62 at a waste station 63.

[40] Depending on the kind of powder and powder coating conditions, the waste powder may be recovered for the sieve 10 in order to be fed again into the coating circuit. This condition is schematically shown in Fig. 1 by switches 59 and shunts 61 of the waste conduits 60.

[41] In multi-color operation, where different colors are sprayed only for a short time, typically the cyclone separator 100 and the post-filtering system 56 are used, and the waste powder of said post- filtering system reaches the waste bin 62. While in general the powder separation efficiency of the cyclone separator 100 is less than that of the post-filtering system 56, said cyclone separator on the other hand may be cleaned faster than said post-filtering system. As regards mono-chrome operation, where the same powder is used for a long time, the cyclone separator 100 may be dispensed with and the excess powder conduit 44 may be connected instead of the waste air conduit 54 to said post-filtering system 56 and the waste conduits 60 — which in this instance contain powder to be recovered — may be connected as recovery powder conduits to the sieve 10. In general, regarding monochrome operation, the cyclone separator 100 is only used in combination with the post-filtering system 56 when the coating powder is problematical. In that case only the recovery powder of the cyclone separator 100 is fed through the powder recovery conduit 50 to the buffer container chamber 22 while the waste powder of the post-filtering system 56 arrives as waste in the waste bin 62 or into another waste receptacle, the latter being positionable without any waste conduits 60 directly underneath an outlet aperture of the post-filtering system 56.

[42] An outlet valve 64, for instance a pinch valve, may be configured at the lower end of the powder collection zone 104 of the cyclone separator 100. Furthermore a fluidizing system 66 to fluidize the coating powder may be configured above said outlet valve 64, in or at the lower end of the powder collecting region 104 — of the cyclone separator 100 — acting as a supply receptacle. The fluidizing system 66 contains at least one fluidizing wall 80 made of an open-pore material or one fitted with narrow boreholes, said material being permeable to air but not to coating powder. The fluidizing wall 80 is configured between the powder path and a fluidizing compressed air chamber 81. Said fluidizing compressed air chamber 81 can be connected by means of a pressure setting element 8 to the compressed air source 6.

[43] At its upstream end, the fresh powder conduit 16 and/or 18 may be connected flow- wise directly or by means of a powder pump 4 to a powder feed pipe 70 which can be dipped into supplier-provided container 12 or 14 to aspirate fresh coating powder. The powder pump 4 may be configured at the beginning of, the end of, or in-between in the fresh powder conduit 16 respectively 18 or at the upper or lower end of the powder feed pipe 70.

[44] Fig. 1 shows a small fresh powder receptacle in the form of a fresh powder bag 12 in a bag-receiving hopper 74. The powder bag is received by the hopper 74 in a predetermined manner, the bag's opening being situated at the upper bag end. The bag- receiving hopper 74 may be mounted on a scale or on weight sensors 76. Depending on their kind, said scale or weight sensors may generate an optical and/or an electrical signal which, following deduction of the bag's weight, denotes the weight and hence the quantity of coating powder in the small receptacle 12. At least one vibrator 78 driving the bag-receiving hopper 72 is mounted on latter.

[45] As regards the powder spraycoating facility of Fig. 1, it is essential that the powder fraction separated by the suction air flow in the cyclone separator 100 can be fed by means of a powder pump 4 and act as the recovery powder from the cyclone separator 100 by mans of powder recovery conduit 50 directly to the buffer container chamber 22 without being required, on its path from the powder collecting region 104 of the cyclone separator 100 to the buffer container chamber 22, to pass through a sieve, for instance the sieve 10. This feature is made possible as elucidated further below because a sieve 121 already is configured inside the cyclone separator to sift the powder that was separated in the separation region 103 of said cyclone separator 100. Another option is obviously that in spite of the sieve 121 configured in the cyclone separator 100, the powder fraction separated by air suction in said cyclone separator may be guided as recovery powder by means of the powder pump 4 as recovery powder first into the sieve and from there into the buffer container chamber 22.

[46] A cyclone separator 100 according to one embodiment of the invention is elucidated as follows in relation to the Figures 2 and 3. Fig. 2 shows a top view of a longitudinal section of the lower end region of the cyclone separator of one embodiment mode of the present invention, Fig. 3 showing a sideview, in longitudinal section, of the lower end region of the cyclone separator of Fig. 2. [47] In the shown embodiment mode of the cyclone separator 100 of the invention, at least the lower end region 103a of the separation zone 103 is frastoconical, having a tapering, in particular a conically tapering lateral outside geometry. Though not shown in Figs. 2 and 3, the upper end region 103b of the separation zone 103 also may be tapering in slightly conical manner, though it also may be cylindrical as indicated for the cyclone separator 100 of Fig. 1. An intake zone 101 which is also cylindrical and fitted with the powder intake 102 adjoins the upper end of the separation zone. An air flow outlet constituted by the upstream of the waste air conduit 54 or optionally connected to the waste conduit 54 is situated at the radial center of the intake zone

[48] To collect the powder separated in the separation zone 103, the powder collection zone 104 is connected or connectable to the lower end region 103a of the said separation zone 103. In the embodiment mode of Fig. 2 or Fig. 3 the lower end region 103a of the separation zone 103 communicates, through a cylindrical sieve housing 20 containing the sieve 121, with the powder collection zone 104.

[49] The powder collection zone 104 is characterized in the direction of the lower powder outlet 105 at its lower end by a tapering, especially a conically tapering surface geometry, so that the recycled powder in the powder collection zone 104 drops by gravity toward the powder outlet 105. This powder outlet 105 is fitted with the powder outlet valve 64 which preferably is a pinch valve, which can alternatively open or close the powder outlet 105.

[50] A fluidizing system 66 can be configured in the lower part of the powder collection zone 104 to fluidize the recovery powder in this powder collection zone. Said fluidizing system 66 may project into the powder collection zone 104 or preferably be designed in a manner that the fluidizing wall 66 shall be at least part of the wall of the powder collection zone 104.

[51] The expression "fluidizing" here denotes that the compressed fluidizing air flows through the recovery powder and in this process converts the recovery powder into a fluid (fluidized) state or improves the fluidity of the recovery powder.

[52] As already indicated above, the powder collection zone 104 may be fitted with at least one sensor S3. Such a sensor may be a level sensor or a switch generating a signal depending on the recovery powder in the powder collection zone 104 having reached or not the powder level to be detected by the sensor S3. Illustratively the sensor S3 is mounted a predetermined distance above the powder outlet valve 64 and may serve to define a predetermined reserve quantity of recovery powder.

[53] Using the minimum of sensor S3 allows controlling the powder outlet valve 64 as a function of a signal from said sensor S3 by means of the control 3. Where desired, the powder outlet valve 64 also may be driven by the control 3 as a function of other criteria, for instance depending on the sensor S 1 of the buffer container 24 displaying a shortage of powder and/or depending on sensors or weighing cells 76 and thereby whether sufficient fresh powder is or is not present in the fresh powder receptacle 12.

[54] Preferably a device generating mechanical vibrations is used in the powder collection zone 104 to allow mechanically vibrating the powder collection zone 104 to detach any deposited powder material from the sensor S3.

[55] Preferably the powder outlet valve 64 shall be opened only when recovery powder is being removed from the powder collection zone 104, whereas the powder outlet valve 64 preferably always shall remain closed when no power is removed from the cyclone separator 100 respectively the powder collection zone 104. In this manner air is prevented from entering the cyclone separator 100 and from interfering with the centrifugal separation.

[56] In the preferred embodiment mode shown in the drawings, the outlet side of the powder outlet valve 64 is connected to the powder recovery conduit 50. Preferably a powder pump 4 is configured in the powder recovery conduit 50, more preferably still at its upstream or downstream end, to feed recovery powder from the powder collection zone 104 to the buffer container chamber 22.

[57] In one preferred embodiment mode of the present invention, said powder pump 4 shall be turned ON by a control 3 only when the powder outlet valve 64 is also opened by the control 3. As a result and depending on the kind of powder pump 4, the compressed air is precluded from being aspirated out of the cyclone separator 100 or from being moved into the cyclone separator 100, that is from interfering with the proper operation of the cyclone separator 100.

[58] The cyclone separator 100 of the preferred embodiment mode of the invention partly shown in Figs. 2 through 5 is characterized in that on one hand the lower end region 103a of the separation zone 103 is frustoconical with a lateral surface geometry that in particular is conical and tapers toward the powder collection zone 104 and that on the other hand the powder collection zone 104 also is frustoconical, its lateral surface geometry tapering conically toward the powder outlet 105, where the lateral surface generating lines Ml, M2 of the lower, frustoconical end region 103a of the separation zone 103 and the lateral surface generating lines M3, M4 of the conical powder collection zone 104 may subtend in each case approximately the same angle with the longitudinal axis of the cyclone separator 100.

[59] A cylindrical intermediate portion, constituted in this instance of the embodiment mode of the cyclone separator 100 by the sieve housing 120, is configured between the lower end region 103a of the separation zone 103 and the powder collection zone 104. Said sieve housing 120 supports the sieve 121 and preferably is configured in in- sertable/removable manner in the space between the lower end region 103a of the separation zone 103 and the powder collection zone 104. [60] When the sieve housing 120 is inserted into the space between the lower end region

103a of the separation zone 103 and the powder collection zone 104, the sieve 121 received in said sieve housing is configured in a way to be situated in a horizontal plane between the lower end region 103a of the separation zone 103 and a plane containing the intersection point S of the lateral surface generating lines Ml, M2 of the frustoconical lower end region 103a of the separation zone 103. In this design, the aperture at the upper end of the cylindrical sieve housing 120 coincides with the outlet aperture at the lower end region 103a of the separation region 103 and the aperture at the lower end of the cylindrical sieve housing 120 coincides with the intake aperture at the upper end of the powder collection zone 104.

[61] In one preferred embodiment mode of the cyclone separator 100 of the present invention, the powder collection zone 104 is displaceable, preferably in pneumatic, hydraulic, electric or manual manner, in the longitudinal direction of the cyclone separator 100 relative to the separation zone 103, as a result of which, in the event the cylindrical sieve housing 120 is not inserted between the lower end region 103a of the separation zone 103 and the powder collection zone 104, the outlet aperture of the separation zone 103 shall coincide with the intake aperture of the collection zone 104 and can be connected to it as may be inferred from Figs. 4 and 5.

[62] As a result, and as shown in Fig. 5, as called for or in an emergency, the cyclone separator 100 also may be operated in the absence of a sieve 121 respectively a sieve housing 120.

[63] Figs. 4 and 5 moreover indicate with respect to the preferred embodiment of the cyclone separator 100 of the present invention that by means of a horizontal pivoting motion, the cylindrical sieve housing 120 may be pivoted in-between the lower end region 103a of the separation zone 103 and the powder collection zone 104.

[64] Fig. 6 shows the sieve housing 120 in a detailed side view. The sieve housing 120 comprises the sieve 121 and a frame 122, further a compressed air vibrator 123 which is affixed to the frame 122 and hence able to vibrate this frame 122 together with the sieve 121. The vibrations may be linear, though preferably they are peripherally circular, arcuate or advancing and retracting.

[65] Compressed air to drive the vibrator 123 is fed to it by means of a corresponding hookup 124. Though vibrators in principle may be electrical, the compressed-air vibrators offer the advantage that they are less vulnerable to the dust and powders present at the sieve when the cyclone separator is operating. Moreover compressed-air vibrators do not require operating with electrical power at the lower region of the cyclone separator, hence are safer.

[66] As indicated especially clearly in Figs. 4 and 5, the noise damping of the vibrator 123 makes it desirable to acoustically insulate the space between the lower end region 103a of the separator zone 103 and the powder collection zone 104. Such noise insulation/ damping may be in the form of a housing 125 fitted with closable openings in the form of doors 126 to allow as needed removing respectively pivoting the sieve housing out of the space between the lower end region 103a of the separation zone 103 and the powder collection zone 104.

[67] The present invention is not restricted to the illustratively discussed embodiments of the cyclone separator of this invention. The present invention on the contrary is based on expert perspective of the patent claims and of the description of the illustrative embodiments.