GB2280624A

GB2280624A - Method of and apparatus for cleaning a centrifugal separator

Info

Publication number: GB2280624A
Application number: GB9414627A
Authority: GB
Inventors: Uwe Heitmann
Original assignee: Koerber AG
Current assignee: Koerber AG
Priority date: 1993-07-20
Filing date: 1994-07-20
Publication date: 1995-02-08
Anticipated expiration: 2014-07-20
Also published as: GB9414627D0; DE4324280A1; GB2280624B

Description

Method of and apparatus for cleaning a centrifugal separator The invention

relates to a method of cleaning a centrifugal separator acted upon by at least one air Stream containing dust ' om fr a machine of the tobacco-processing industry, having a plurality of individual cyclones operating in parallel, of dust which has settled in ffie centrifugal separator.

The invention also relates to an apparatus for cleaning a centriflUgal separator acted upon by at least one air stream containing dust from a machine of the tobacco-processing industry, having a plurality of individual cyclones operating in parallel, of dust which has settled in the centrifugal separator.

The term "machine of the tobacco-processing industry" is intended within the context of the invention to mean in particular cigarette machines, filter attaching machines and filter making machines in which flowing air which contains dust to a greater or lesser extent and therefore has to be freed of the dust is used. The invention is also suitable for use in other machines of the tobaccoprocessing industry in which flowing air or gases which contain dust and have to be freed of the dust are used.

The term "cyclone" is intended to mean rotating separation vortices.

The term "dusC is understood to mean dust from tobacco, silicates or filter material, but also small particles of tobacco, silicates such as sand or filter material.

Tobaccoprocessing machines of the type mentioned above are operated using air streams in order to convey tobacco fibres or to hold them firmly against a conveyor (by means of suction air). Cigarettes or filter sections are also conveyed by air streams or held firmly against a conveyor (by means of suction air). Since the air streams contain dust or small particles which in the case, of air guided in circulation accumulate in the air and can cause disruptions, the dust has to be separated out. Centrifugal separators of the type mentioned at the outset, in which an air stream containing dust is divided up into individual air streams which are made to rotate by guiding devices, i.e. form rotating separation vortices, so-called 2 cyclones, are suitable for this purpose. Here, the dust particles accumulate in the outer regions of the cyclones and are separated from the inner regions of the separation vortices which contain the majority of the air streams containing only a small amount of dust. The smaller outgoing air streams charged with a large amount of dust are combined and conveyed away through an Outlet of the centrifugal separator. The same thing happens with the larger sifted air streams which contain small quantities of dust and which after being combined leave the centrifugal separator through another opening and are returned for example to the corresponding tobacco -pro c essing machine again.

The centrifugal separators described have the disadvantage that not all the dust is conveyed away by the outgoing air streams. A certain quantity of dust settles in the centrifugal separator, particularly in the case of sticky dusts, as are not infrequent in tobacco processing, and can clog it over time. A t irm e -consuming and unpleasant cleaning is then necessary.

The object of the invention is to lengthen the time intervals of a centrifugal separator between two cleaning procedures (operating time).

According to the invention, this is achieved in that brief cleaning air streams or, in the case of differing operating states (e.g. operation stoppages), ones of longer duration which at least partially remove the settled dust are periodically supplied to the centrifugal separator during normal operating states of the machine.

Further embodiments of the method according to the invention can be inferred from the dependent method claims.

The apparatus mentioned at the outset is characterized by a supply arrangement for cleaning air entraining dust which has settled in the centrifugal separator.

Further embodiments of the apparatus according to the invention can be inferred from the dependent apparatus claims.

The advantage of the solution according to the invention consists in the fact that the time-consuming (machine stoppage) and unpleasant dirty work of cleaning the centrifugal separato.- manually is eliminated completely or is at least required a-c far longe.- time intervals.

3 The invenEion will be described in detail with reference to the embodiment illustrated in the drawing. Figures 1 and 2 must here be contemplated together.

Figure 1 shows a section through a part of a distributor VE of a cigarette extrusion machine of the known PROTOS type which is widely used in the tobacco -processing industry. The tobacco supply, which is arranged upstream of the illustrated part of the distributor, to a supply and the removal of the tobacco from the tobacco supply, e.g. by means of a steep conveyor, are widely known and do not need to be described here.

Figure 2 shows a centrifugal dust separator according to t.-.e invention.

Figure 1 shows a pile-up shaft 1 having a tobacco supply 5 and a removal apparatus 2 which comprises a rotating removal roller 3 and a beater roller 4 rotating more quickly. The shower 6 of tobacco fibres removed by the removal apparatus 2 from the pile-up shaft 1 and containing light tobacco fibres 12 and heavier tobacco fibres (ribs) 13 passes into a supply chute tapering in the manner of a funnel and in the form of a channel 7 in which a blowing air nozzle 11 arranged in a deflection zone 8 in the pressure chamber lla blows a sifted air stream transversely with respect to the conveying direction of the tobacco shower 6. The sifted air stream separates the light tobacco fibres 12 from the heavier tobacco fibres 13 (tobacco ribs) and conveys them away transversely in the direction of the arrow 14. Some light tobacco fibres 12a fall downwards along with the heavier tobacco ribs 13. They pass through a bucket wheel sluice 16 into a sifting shaft 17 in which the heavier tobacco ribs 13 fall further downwards and are discharged, while the lighter tobacco fibres 12a, as a result of the injector action of a blowing air jet from a blowIng air nozzle 18 arranged in a pressure chamber 18a, rise upwards and are returned to the stream of the light fibres 12. Aided by a further blowing air nozzle 19 in a pressure chamber 19a, the tobacco fibres are transferred in the example illustrated to a guide track in the form of a curved guide surface 21 on which they form a thin tobacco stream 22 (illustrated in exaggerated manner in the drawing) of loosened and spreadout tobacco fibres, blowing air and tobacco fibres forming a wall flow moving closely along the guide surface 21. To aid the 4 further conveyance of the spread-out loosened tobacco stream 22 along the guide surface 21 a blowing air nozzle 23 in a pressure chamber 23a and, if appropriate, further blowing air nozzles arranged in the course of the guide surface 21 and not illustrated in the drawing are provided.

The loosened and spread-out tobacco stream 22 passes in an extrusion formation zone 24 to a suction extrusion conveyor 26 to which a suction force for forming and holding a tobacco extrusion 30 is applied by the suction action of an underpressure chamber 27 from the rear side, suction air flowing through the extrusion 30 and the airpermeable suction extrusion conveyor 26. Excess blowing air escapes through a screen 28 into a relaxation space 29.

The suction extrusion conveyor 26 constructed as an air permeable conveyor belt runs in a tobacco channel 31 which is laterally delimited by two channel cheeks 32. The end sec-Lion 21a of the guide surface 21 is aligned with respect to. one of the channel cheeks 32. so that a gap-free smooth transition of the guide surface to the tobacco channel 31 is ensured. The end section 21a of the guide surface 21 is constructed as a deflection body 34 whú-ch can be pivoted away about a pivot axis 33 in order to ensure better accessibility to the apparatus during disruptions.

The suction extrusion conveyor 26 is raised by a raising and lowering mechanism, which is known per se and which is therefore not illustrated, during operation stoppages in the direction of the arrow 36, and lowered in the direction of the arrow 37 during operation of the machine.

The tobacco fibres 12 supplied through the channel 7 are deflected by the blowing air stream from the nozzle ll, ribs 33 being separated out. By means of blowing air streams from the nozzles 18 and 19, the deflected fibre stream is conveyed, while drawing to it the undeflected light tobacco fibres 12a. to the guide surface 21 along which it is conveyed, aided by the blowing air stream from the nozzle 23, into the tobacco channel 31 and to the suction extrusion conveyor 26. As a result of the suction air flowing through the sucked tobacco extrusion 30 and the suction extrusion conveyor 26 into the underpressure chamber 27, the tobacco fibres are securely held as an -ion extrusion conveyor 26 and extrusion 30 against the moving suct conveyed away perpendicular to the plane of the drawing. Subsequently, the tobacco extrusion is wrapped in cigarette paper in an extrusion unit SE (not illustrated) of the PROTOS machine and adhesive is applied to the cigarette paper in an edge region. Cigarettes are then continuously cut off from the thus formed endless cigarette extrusion, and to which filter sections can be attached to them in an adjacent filter attaching device, e.g. of the MAX type of the PROTOS machine.

The underpressure chamber 27 is connected by way of an air line 41 to the suction side 42 of a ventilator 43 which maintains the underpressure.

The blowing air flowing from the nozzles 11, 18, 19 and 23 passes, insofar as it does not flow into the underpressure chamber 27, through an air line 44 to a centrifugal separator 46 according to Figure 2, in which the dust (comprising tobacco or silicates such as sand) extracted from the tobacco and small particles are separated out. The centrifugal separator 46 has a central supply space 47 for the air which is supplied through the air line 44, contains dust and is supplied through an inlet 50. The air is then divided into a plurality of part air streams which are preferably made to rotate by preferably stationary helical or propeller-shaped guide surfaces 48a... 48n in pipe sections 51a... 51n, and therefore form separation vortices, also called cyclones, which are designated 49a... 49n and are indicated by corresponding arrows. A centrifugal separator 46 of the type described can contain even more individual cyclones than illustrated in the drawing, but these have been omitted for the sake of clarity. As a result of the rotation of the part air streams, the dust becomes concentrated in the outer regions of the separation vortices. These outer regions are separated by conical pipes 52a... 52n from the main 1: dust, which quantities in the centre containing only small amounts o are guided off through the inner spaces 53a... 53n of the conical pipes 52a... 52n. The ratio of low-dust main quantity (sifted air) and dustcharged secondary quantity (outgoing air) of a separation vortex can for example be 90% to 10%.

The low-dust sifted air streams from the inner spaces 53a... 53n are combined in a central removal space 54 to form a total sifted air stream which leaves the centrifugal separator 46 through the outlet 6 56 and is supplied by way of an air line 57 to the suction side 58 of a ventilator 59.

The dust-charged outgoing air streams flow out of the vortex chamber 61 through an outlet 62 for the combined dust-charged outgoing air which, as above, constitutes quantitywise only a fraction of the sifted air, even expressed numerically. The dust-charged outgoing air passes by way of an air line 63, together with the suction air stream from the underpressure chamber 27 in air line 41, to the suction side 42 of the ventilator 43 which it passes through. The air stream which is charged with dust leaving the ventilator 43 can be freed of dust by means of filters or by means of a centrifugal separator similar to the centrifugal separator 46 described, before it is returned to the machine or is released into the atmosphere.

A suitable centrifugal separator of the type described by 46 is -ers LTD, Abergavenny, sold for example by the company Coopers Fill, Gwent, NP7 9LW, GB, under the type designation 1102 DR 41. It is particularly advantageous constructionally for use for the invention, since the inlet 50 for the air containing dust and the outlet 56 for the sifted air substantially freed of dust run in the direction of the separation vortices 49, i.e. axially.

The sifted air stream passes from the pressure side of the ventilator 59 to an air box 64 and from there by way of air lines 65... 68 to the pressure chambers 23a, 18a and lla, 19a respectively. Of course, further pressure chambers (not illustrated) can also be supplied with air from the air box 64 by way of further air lines. Moreover, the air from the air box 64 can be returned to the distributor VE by way of a single line which.;s only there divided into individual lines 65... 68. M are motors for the ventilators 43 and 59.

Over time, despite continuous suction of a certain quantity of dustcharged outgoing air from the outlet 62, dust can settle in the vortex chamber 61, especially if the dust, as is not infrequent in tobacco processing, is sticky. If a considerable quantity of dust has settled, then the centrifugal separator has to be cleaned by hand, which owing to the machine stoppage associated therewith is costly and is unpleasant for the operator owing to the unavoidable dirt.

According to the invention, the time intervals between cleanino's are lengthened very considerably if brief cleaning air streams (blowing c 7 air pulses) from a cleaning air source 71 under pressure which blow away the dust from the vortex chamber 61 are periodically supplied, preferably centrally, to the centrifugal separator 46. To this end, there is supplied to the centrifugal separator 46 from the cleaning air source 71 by way of an air line 72 compressed air which flows into the vortex chamber 61 at the inlet 73 for the cleaning air. To this end, the vortex chamber does not have in its centre a pipe section 51 nor a conical pipe 52, but only a supply pipe 74. The cleaning blowing air flowing periodically but briefly out of the pipe 74 entrains the dust and conveys it to the outlet 62, where the cleaning air charged with dust leaves the centrifugal separator together with the normal dustcharged outgoing air derived from the individual separation vortices. It has been found that the cleaning air acting periodically but briefly does not disrupt, at least not substantially, the operation of the centrifugal separator.

To generate the cleaning air pulses there serves an electrical clock generator 76 which supplies control pulses to an electromagnetic valve 77 arranged in a part air line 72a such that it opens periodically, e.g. every 100 secs., for a short time, e.g. 2 secs., and then closes again. A further electromagnetic valve 78 arranged in a parallel part air line 72b is closed during this. If ithe machine, along with the distributor VE, is stopped, the suction extrusion conveyor 26 being raised in the direction of the arrow 36, then in conjunction therewith a control pulse is sent by way of a switch 79 to the electromagnetic valve 78, which opens, so that a cleaning air stream of longer duration can flow from the cleaning air source 71 to the inlet 73 and into the vortex chamber 61 and can intensively remove the settled dust. After the end of machine stoppage and lowering of the main extrusion conveyor 26 in the direction of the arrow 37, the switch 79 switches the electromagnetic valve 78 off again, so that only the periodic short air pulses released lby the clock generator 26 blow away the settled dust from the vortex chamber 61.

The air line 63 for the dust-charged outgoing air is divided into two parallel part lines 63a and 63b. An air throttle 81 is arranged in the part line 63b, and an electromagnetic valve 82 which receives an electrical opening pulse from the switch 79, when a long-lasting cleaning air stream is supplied during machine stoppages and raising 8 of the suction extrusion conveyor 26, is arranged in part line 63a. In the air line 57 of the sifted air stream there is located an electromagnetic valve 83 which receives an electrical closing pulse from the switch 79 when the machine is stationary, the suction extrusion conveyor 26 is raised and the centrifugal separator 46 receives a long- lasting cleaning stream. Instead of a complete closure of the air line 57, it can be advantageous to also adni it a small residual air stream through line 57 to the distributor VE.

The use of the invention is not restricted to machines having suction extrusion conveyor. It can also be used advantageously in machines known per se, e.g. of the PROTOS 2 type of the Applicant, in which tobacco 22 is conveyed to two parallel 7 two guide surf aces 21.

suction extrusion conveyors 26 by way o1L only one 1 9

Claims

C 1 a i m s

1. Method of cleaning a centrifugal separator acted upon by at least one air stream containing dust from a machine of the tobaccoprocessing industry, having a plurality of individual cyclones operating in parallel, of dust which has settled in the centrifugal separator, characterized in that brief cleaning air streams or, in the case of differing operating states (e.g. operation stoppages), ones of longer duration which at least partially remove the settled dust are periodically supplied to the centrifugal separator during normal operating states of the machines.

2. Method according to Claim 1, characterized in that the individual cyclones divide the air streams supplied to them in each case and containing dust into in each case larger sifted air streari-,s charged with small amounts of dust and smaller outgoing air streams charged with large amounts of dust, in that sifted air streams and outgoing air streams are combined with one another and are conveyed away, and in that at least one cleaning air stream is supplied to the centrifugal separator in a central region such that it leaves the centrifugal separator entraining the settled dust on the path of the outgoing air streams.

3. Method according to Claim 2, characterized in that the cleaning air supplied in a central region of the centrifugal separator flows to the outside at least approximately symmetrically, during which it entrains settled dust.

4. Method according to one or more of the preceding claims, characterized in that the air containing dust is supplied from the distributor of a cigarette extrusion machine in which it conveys tobacco fibres along a conveying surface, and in that an air stream formed from the combined sifted air streams is returned to the distributor.

5. Method according to Claim 4, characterized in that an air stream formed from the combined outgoing air streams and the cleaning air is supplied to the suction side of a ventilator to which suction air holding tobacco fibres against a moving air-permeable conveyor belt is also supplied.

6. Method according to Claim 5, characterized in that a cleaning air stream of longer duration is supplied to the centrifugal separator when the suction air against the conveyor belt is switched off.

7. Apparatus for cleaning a centrifugal separator acted upon by at least one air stream containing dust from a machine of the tobaccoprocessing industry, having a plurality of individual cyclones operating in parallel of dust which has settled in the centrifugal separator, characterized by a supply arrangement (71, 72) for cleaning air entraining dust which has settled in the centrifugal separator (46).

8. Apparatus according to Claim 7, characterized by a supply arrangement (72a, 76, 77) for a periodic brief supply of cleaning air streams during normal operating states of the machine (VE).

9. Apparatus according to Claim 7 and/or 8, characterized by a supply arrangement (72b, 79, 78) for a cleaning air stream of longer duration during operating states, in particular stoppages, differing from normal operating states of the machine (VE).

10. Apparatus according to one or more of Claims 7 to 9, characterized in that the cleaning air is supplied at least approximately centrally (73) to the centrifugal separator (46) with its individual cyclones (49a... 49n) dividing the supplied part air streams in each case into larger sifted air streams charged with small amounts of dust and into outgoing air streams charged with large amounts of dust and leaves it through an outlet (62) for the outgoing air charged with large amounts of dust.

11. Apparatus according to one or more of Claims 7 to 10, characterized by a connection line (44) between the distributor (VE) of a cigarette extrusion machine and the centrifugal separator (46) for supplying the air conveying tobacco fibres (22) along a guide surface (21) in the distributor and containing dust, and by a connection line (57, 59, 64... 68) between the centrifugal separator and the distributor for conveying the sifted air substantially cleaned of dust back to the distributor.

12. Apparatus according to one or more of Claims 7 to 11, characterized by a connection line (63) between an outlet (62) of the centrifugal separator (46) for the outgoing air charged with large amounts of dust and the suction side (42) of a ventilator (43) which is connected to an air-permeable conveyor belt (26) for accumulated tobacco fibres by way of a connection line (41).

13. Apparatus according to one or more of Claims 7 to 12, characterized by a circuit arrangement (76, 77) for the periodic brief connection of the centrifugal separator (46) to a cleaning air source (71).

14. Apparatus according +Go one or more of Claims 7 to 13, characterized by a switch (79) for a connection of longer duration of the centrifugal separator (46) to a cleaning air source (71) during operational interruptions of the distributor (VE).

15. A method of cleaning a centrifugal separator substantially as herein described with reference tO the accompanying drawings.

16. Apparatus for cleaning a centrifugal separator substantially as herein described with reference to the accompanying drawings.