WO1990000435A1

WO1990000435A1 - Method of cleaning particles from a filter and a filter for use hereby

Info

Publication number: WO1990000435A1
Application number: PCT/DK1989/000173
Authority: WO
Inventors: Tage Christoffer Hansen
Original assignee: Tage Christoffer Hansen
Priority date: 1988-07-14
Filing date: 1989-07-11
Publication date: 1990-01-25
Also published as: AU3974589A; DK394888D0; DK394888A

Abstract

A method and a filter are indicated which filter is cleaned periodically, preferably during continuous running of the filter, by rotating the filter element (26) placed in the filter housing (1) around its axis of symmetry (12) which is congruent with a rotatable axle (16). Means are provided for periodically rotating the axle (16), for collecting separated particles from the filter housing (1), and means (22-25, 34-39) are provided to produce a releasable pressure cushion seal between a first part (5) and a second part (6) of the filter housing (1), said parts (5, 6) being placed on each end of the filter element (26), whereby the pressure cushion seal can be formed by the flow of the purified medium. In an embodiment the pressure cushion seal can be produced by moving the filter element (26) away relatively from contact with a contact surface (4), which devides the filter housing (1) into said first part (5) and second part (6).

Description

METHOD OF CLEANING PARTICLES FROM A FILTER AND A FILTER FOR USE HEREBY.

The invention relates to a method of cleaning a filter comprising a filter housing with an inlet and at least one annular filter element placed in the filter housing for filtering a medium containing particles, said medium be¬ ing conducted in a flow through the filter element from the inlet to the outlet.

During the filtering particles, which contaminate the said medium, are deposited in the filter element to the effect that the flow through the filter will be gradually diminished and eventually be completely cut off so that the filter element has to be replaced in order that the filter may regain the intended capacity.

Such replacement is inexpedient, partly because filter elements are expensive, and partly because the replacement in itself is expensive as a result of the necessary work and the service stop, which is caused by the replacement.

Therefore, various methods have been developed to clean the filter element of particles deposited in order that the filter element may regain its original capacity.

From US patent specification no. 4.133.657 describes a filter of the above mentioned kind consisting of several concentrically arranged filter elements, in which the cleaning of the filter element is provided by gas which is made to flow through the filter element in a direction opposite the direction of the flow of the medium in question during filtration. The cleaning gas is provided under pressure through nozzle pipes extending into the spaces between the concentrically placed filter elements, and the gas flushes or blows the deposited particles out of the filter elements so that the particles can be remo- ved from the filter. The said nozzle pipes are mounted like the teeth of a comb on two supply tubes forming a cross above the filter elements, and in this way the nozzle pipes are separated by an angle of 90° in the in- terspaces.

To achieve flushing or blowing through the entire radial surface of the filter elements these are supported swivel- lingly in the filter housing, and means have been provided to turn them forwards and back through an angle of 90°.

The disadvantage of this known filter is that the filter has to be stopped during the cleaning, which means that if continous purification of the contaminated medium is needed, at least two filters have to be used alterna¬ tively.

This drawback has been avoided in a filter known from SE printed specification no. 372.892. In this filter a clean- ing arm with a single nozzle pipe is used, said arm ex¬ tending axially along the radial inner surface of the fil¬ ter element. The cleaning arm rotates continuously so that a flow through the arm and the nozzle pipe of the medium, which is being purified in the filter, is flushed or blown through the filter element as a counterflow after a com¬ plete revolution of the filter.

As a result of this cleaning by counterflow the filter ca¬ pacity is constantly smaller as compared to the capacity without the mentioned cleaning. Furthermore, a part of the medium is drained together with the suspended particles whereupon this part of the medium has to be filtered to remove the particles in a sunbsequent operation.

It is therefore an object of this invention to show a method of cleaning a filter in such a way that it can be_. used continuously while preserving the capacity of the filter.

This object will be achieved by a method of the above men¬ tioned description which method is characteristic accord- ing to the invention in that the filter element is placed rotatably around an axle congruent with its axis of symmetri, that the filter element is cleaned periodically, preferably during continuous running of the filter, of particles deposited on its influx side by rotating the filter element around the axle, and that the particles se¬ parated by the rotation are collected from the filter housing.

By cleaning the filter element periodically its maximum capacity is not reduced during the cleaning, and through the rotation the particles deposited in the filter element are subjected to a centrifugal force which can be made far greater than the force, to which the particles has been subjected in the known filters by circulating a cleaning medium in counterflow through the filter element.

If the inlet, the filter element and the outlet are placed in such a way relative to one another that the said medi¬ um, which is to be purified, is passed radially inwards through the filter element, it is preferable, as indicated in claim 2, that a wall, which is impermeable to the medi¬ um, is provided in the filter housing, said wall extending at least partly around the filter element and dividing the filter housing in a first part and a second part, and that the particles are collected from the wall and/or from the second part of the filter housing.

By means of the wall an advantageous division of the said medium into a purified part, which can be removed from the first part of the housing through the outlet, and an un- purified part, which remains in the second part of the housing from which the separated particles can be removed, is achieved.

It is especially advantageous to place the filter in such a way that the axle of the filter element is substantially 5 vertical, and so that the first and the second part con¬ sists of an upper and a lower space in the filter housing, as indicated in claim 3.

By this arrangement of the filter the gravitational effect 0 on the particles is taken advantage of in such a way that they can descend to the bottom of the filter housing, and from there they can be removed by adequate means.

The method according to the invention can also be carried 5 out in such a way that the filter housing, as indicated in claim 4, is separated into the upper part and the lower part by an annular intermediate bottom, which is tight- fittingly connected with the inner side of the wall of the filter housing, and a rotor consisting of the axle, the 0 filter element and parts of the impermeable wall, the ra¬ dially outer edge of which is made to co-operate tightly and releasably with the edge of the intermediate bottom, preferably by means of a pressure pad.

25 Hereby the possibility is created of rotating the filter element so that the particles, by means of the centrifugal force created by the rotation, can be flung outwards to¬ wards parts of the impermeable wall and from there glide or fall down into the lower part of the filter housing,

30. from where the particles can be collected. The releasable seal makes disengagement during the rotation of the rotor possible, so that the power necessary to rotate it needs to be minimal only and so that the upper and lower parts will be mutually tightly connected when the rotor stops.

35

The invention also concerns a filter for use in connection with the implementation of the method according to the in- vention, and this filter is of the kind in which the fil¬ ter comprises a filter housing with an inlet and an outlet and at least one annular filter element placed in the filter housing for filtering a medium containing particles, which medium can be passed in a flow through the filter element from the inlet to the outlet, and which filter is characteristic according to the invention in that the filter element is connected to a rotatable axle which is congruent with the axis of symmetri of the filter element, in means for periodically rotating said axle, preferably during continuous use of the filter, and in that the filter has means for collecting particles sepa¬ rated from the filter housing by the rotation.

Other embodiments of the filter according to the invention will appear from the subclaims, and the advantages of these embodiments will appear from the following detailed description of the filter,

The said medium can be a gas or a liquid.

If the medium is a gas, it may for example be air from factory premises in which work processes take place in¬ volving dust nuisances and where the air is exhausted lo- cally from the work place and subsequently passed through the filter, whereby it is purified of floating dust par¬ ticles and other contaminants.

The contaminated air also be air containing droplets of various kinds. As an example it can be mentioned that in connection with cutting tools, cutting oils are used which are sprayed on the cutting tool for cooling and lubrica¬ tion. Such cutting oils are quite expensive and should be collected after use, because they also cause environmen- tal inconveniences. The machines in question are usually enclosed to keep in the cutting oils of which a substan¬ tial part is transformed during the work process to drop- lets of such size that the droplets will float in the air, whereupon the oil droplets will be ventilated into the open whereby the cutting oils are lost with the re¬ sulting expenses and environmental inconveniences.

In both cases the filter according to the invention has been found to be superior in relation to the known filters as regards effective purification of a gaseous medium and collection of the particles or droplets.

However, it has become apparent that for example the above mentioned cutting oils, which have been collected as drop¬ lets, together with the liquid cutting oil, can also ad¬ vantageously be purified in the filter, since the cutting oil is usually also contaminated with metal shavings, which can be filtered from the cutting oil by being passed through the filter, naturally after an appropriate change of the filter element.

The method according to the invention will be further ex¬ plained in the following with reference to the drawings, which illustrate various embodiments of a filter for use with the implementation of the method, and in which

Fig. 1 shows schematically a first embodiment of a fil¬ ter for use with the method according to the in¬ vention.

Fig. 2 shows a second embodiment of a filter according to the invention.

Fig. 3 is a diametrical section of a rotor.

Fig. 4 is a bottom view of the rotor shown in fig. 3.

Fig. 5 is a section through the connection between the rotor shown in fig. 3 and an intermediate bottom in a filter housing.

Fig. 6 is a bottom view of the connecting passage shown in fig. 5.

Fig. 7 shows an circumferential ring on the rotor shown in fig. 3.

Fig. 8 shows a further embodiment of a filter according to the invention.

Fig. 9 shows a preferred third embodiment of a filter according to the invention.

Fig. 10 shows in a larger scale the shape of the connection shown in fig. 9.

Fig. 11 shows in larger scale the shape of means for height adjustment of a rotor in the filter shown in fig. 9.

Fig. 12 shows schematically the construction of a rotor comprising two concentric filter cylinders in the filter shown in fig. 9.

A self-cleaning filter according to the invention for filtering of a medium may, in a first and very simplified embodiment, be shaped as shown in fig. 1.

The filter element 26 is contained in a housing 1, which can be made of a plate of a suitable material and according to the circumstances can be metal, plastic, glass or similar materials which in a tight manner and in an appropriate shape can contain the filter.

The housing 1 is dismountable to permit access to the se¬ parate parts of the filter for change of filter elements as required. The dismantling can be achieved by one or more of the walls being attached with screws and nuts, clasps, catches or similar connecting means.

The housing 1 can as a minimum be provided with a top plate 2 and a dismountable bottom 3. The housing is supported in relation to the environment by a frame, which is not illustrated in the drawing.

The filter housing has an inlet 40 and an outlet 41, arid in the housing is placed an annular filter element 26 be¬ tween the inlet and the outlet so that a medium will be forced through the filter elememt 26 by a suitable diffe¬ rential pressure.

The annular filter element 26 may in a diametrical section be shaped as two truncated cones, the tips of which face opposite directions, whereby the largest diameter of the radially innermost cone corresponds to the smallest dia- meter of the radially outermost cone so that the diametri¬ cal section by and large has the shape of an M. From the radially outermost rim of the outermost cone the filter element continues into an edge which extends radially out¬ wards from the axis of symmetri of the filter element 26. This edge has a largest diameter, which is only slightly smaller than the inner diameter of the filter housing 1, which has a circular section.

The filter element 26 is mounted on an axle 16, the rota- tional axis of which coincides with the symmetrical axis of the filter element.

The axle 16 is supported rotationally at the ends in the filter housing in schematically indicated bearings, and the axle 16 and thereby also the filter element 26 can be rotated, as indicated by an arrow in fig 1 by means which are not further indicated in fig. 1, as this figure serves to show the function of the filter only.

In the continuous running of the filter the said medium is passed through the inlet 40 and forced by the differential pressure over the inlets and outlets through the filter element 26 and out through the outlet 41. Hereby particles floating in the medium in question are deposited in the filter element 26 on the side facing the inlet 40, whereby the filter element is gradually choked up by the deposited particles so that the purifying capacity of filter is constantly decreasing.

It should be mentioned that in this simple embodiment a part of the contaminated medium will pass unpurified through the annular gap between the radially outermost edge of the filter element and the inner side of the wall of the filter housing. This part will grow eventually as the filter element is choked up by deposited particles.

At appropriate intervals the filter element 26 is put into rotation around the axle 16.

Particles, which have been deposited on the radially outer side of the inner cone, will be loosened as a result of the centrifugal force, and the particles will sift down to the bottom of the filter housing 1 or be flung towards the radially inner side of the outer cone and from there fall down to the bottom of the filter housing 1, possibly after first having slid along this inner side to the area where the inner side adjoins the above mentioned edge of the filter element 26.

To collect the particles, which have fallen down from the inner side of outer cone, an annular canal is arranged a- long the inner side of the filter housing 1 by means of a wall 44 extending upwards from the bottom plate 3 of the filter housing, whereupon the separated particles can be removed according to requirements at a removal outlet 45 in the bottom 3 of the filter housing 1.

As mentioned above, the filter in this embodiment is not in a sufficiently tight way divided in a first and a se¬ cond part, since a part of the contaminated medium can pass through the above mentioned gap between the radially outermost edge of the filter element 26 and the inner side of the wall of the filter housing.

There is also the drawback that particles, which are part¬ ly deposited by the flow of the medium on the radially inner side of the outer cone and partly are being flung towards this side by the rotation, will not be released to a sufficient degree during the rotation of the filter ele¬ ment 26 so that they can fall down to the bottom of the filter housing 1. Some of the particles may even be able to pass through the outer cone.

With reference to fig. 2, a second embodiment or prototype of a filter for use in connection with the implementation of the method according -to the invention will be dis¬ cussed, which prototype is arranged with the possibility of adjusting the separate parts of the filter in relation to one another to obtain optimal efficiency of the filter, and in which the above mentioned drawbacks of the first embodiment have been avoided.

During the use of the filter the acceleration of gravity is utilized in a way actually known, and in the position of use the filter must therefore be placed with the bottom 3 of the housing 1 turned downwards. In the following the expressions of directions used, such as "upper", "lower", "horizontal, "vertical" and "height", refer to this posi- tion of use.

In a plane at approximately half the height of the housing 1 is placed an intermediate bottom 4, which divides the inner space of the housing 1 into an upper part 5 and a lower part 6, as the intermediate bottom 4 extends circum- ferentially along the inner wall of the housing and is tightly connected with this wall.

On the intermediate bottom 4 is placed a frame 7 consist¬ ing of at least one bar 8, which at its lower end 9 is connected to the intermediate bottom 4 in an adjustable way, whereby the bar 8 extends essentially vertically up¬ wards with the upper end 10 at a short distance below the top plate 2 of the housing 1.

This adjustability of height as shown in fig. 5 can be achieved by means of threaded bolts 50 which extend up¬ wards from the intermediate bottom and can cooperate with nuts 51 placed on each side of a plate 52, which is welded to or in some other way connected to the lower end 9 of the bar 8. By turning^' of the nuts 51 the said plate 52 and thereby also the the bar 8 can be adjusted upwards or downwards.

The importance of this adjustability of height will be further explained below.

From the upper end of the bar 8 a further bar 11 extends essentially horizontally towards the essentially vertical central axis 12 of the housing 1.

To achieve the necessary rigidity of the frame 7, prefe¬ rably several, for example four bars 8, with uniform angu¬ lar distance, have been provided.

If, as indicated, preferably several vertical bars 8 have been provided, each of these is connected to a bar 11, said bars 11 being then united in a connection point 13 at said vertical central axis 12. Said vertical bars 8 and horizontal bars 11 may be hollow, massive or consist of profiles and may be mutually connected, for example being screwed together by bolts and nuts or by welding.

The connection point 13 is formed as a tube bearing con¬ sisting of a short tube 14 extending downwards, and is placed with its axis coinciding with the cental axis 12. The tube 14 is provided with bearings 15 at the top and bottom for rotatably supporting an axle 16 for a rotor 17, which will be described further below.

The axle 16 extends through the tube bearing 14 and the frame 13 and at the upper free end 42 is connected to drive means 43 placed preferably outside the housing, such as an electric motor or similar driving means, which can rotate the rotor 17.

The connection between the said free end 42 of the axle 16 and the drive means consists of an exchange, which may take the form of a cog wheel gear or a belt connection 53. The connection consists preferably of a toothed belt with such gear ratio that the rotor can be driven by a speed of about 700 r.p.m.

The rotor 17 consists, as shown more detailed in figs. 3 and 4, of a carrying frame 18, which is preferably formed by four bars 19 extending crosswise vertically from the lower end of the axle 16 when this is supported rota¬ tably in the above mentioned tube bearing 14. On the upper sides of the radially outer ends 21 of the bars 19 a cir¬ cumferential ring 22 is placed having a substantially U- shaped section, in which the two branches of the U extend upwards and each at their upper circumferential edges con¬ tinues in a horizontal flange 23, 24 in such a way that an upwards turned annular gap 25 is formed between the two flanges 23, 24, which are placed immediately below the in¬ termediate bottom 4.

At least one filter elememt is placed concentrically in- side the ring 22, preferably in the shape of a filter cy¬ linder 26, which has a circular or polygonal section and is built up in layers of stainless wire cloth of varying mask width, the size of which has to be adapted to the me¬ dium and the sizes of the particles in the medium which 'are to be filtered out in the filter.

Whether the filter cylinder 26 has a circular or a poly¬ gonal cross section, the cylinder can be divided by ver¬ tical and as well as horizontal dividing lines. The poly- gonal cross section is achieved when the filter cylinder is constructed of plane elements, which may be an advan¬ tage if only a small number of the filter cylinders 26 are to be produced. The circular cross section is to be preferred by production of a large number of filter cylin- ders.

It will be obvious to a person skilled in the art that even if it has been mentioned that the filter cylinder is made of stainless steel webbing, the material of the filter cylinder has to be adapted to the medium which is to be filtrated in the filter.

Concentrically between the filter cylinder and the circum¬ ferential ring 22 is placed a screening cylinder 27, which is fashioned of plate and impermeable to the medium in question, said cylinder usually, but not necessarily having a section corresponding to the section of the filter cylinder 26. The annular space 28 between the filter cylinder 26 and the screening cylinder 27 is closed at the top by an upper plate ring 29, which is tightly connected with the two cylinders 26, 27. The plane of the plate ring 29 is preferably horizontal. The spaces 30,31 between on one side the axle 16 and the filter cylinder 26, and on the other side the screening cylinder 27 and the circumferential ring 22, are sealed at the bottom by lower plate rings 32 and 33 respectively, the planes of which are also substantially horizontal.

To increase the area of the filter and thereby enhance its efficiency, additional filter and screening cylinders can be provided as shown in fig. 8, which cylinders are alii placed concentrically around the axle 16 and inside the circunferential ring 22. The diameter of the rotor 17 and the dimensions of the housing 1 and the intermediate bot¬ tom 4 will then have to be increased in relation to these additional cylinders.

The spaces produced by such additional cylinders will then have to be sealed- at the top and the bottom by plate rings corresponding to the above mentioned upper 29 and lower plate rings 32, 33.

On the outside of the housing is mounted a flow device 34 which through an opening 55 is connected to the upper part 5 of the housing in such a way that a medium contained in the upper part 5 can be removed from the housing 1.

The flow device 34 is connected by means of a pressure pipe 35 to a circumferential canal 36, which is tightly connected to the upper surface of the intermediate bottom 4 and extends concentrically around the rotor 17.

In the intermediate bottom are drilled an annular row of holes 37 in such a way that a connection is formed from the inside of the canal 36 to the circumferential gap 25 in the ring 22 on the rotor 17.

These holes 37 are on the under side of the intermediate bottom 4 connected with a ring 38, which can secure a circumferential ring-shaped packing of an elastic ma¬ terial, for example rubber or plastic. The inner and outer diameters of the ring 38 and the packing 39 correspond in such a way that the ring can be accomodated in the gap 25 between the horizontal flanges 23, 24 on the circumferen¬ tial ring 22 and in such a way that the packing 39 with its edges can bear against the ,flanges 23, 24, as the thickness of the packing 39 must be sligthly less than the distance between the flanges 23, 24 and the under side of the intermediate bottom.

The ring 38 can for example be secured to the intermediate bottom 4 by means of bushings, which are not shown in the drawing, placed in the holes 37. At the first end the bushings have a flange to bear against the ring 38 and at the other end they are provided with an outer thread to co-operate with a nut, which can be tightened against the inner surface of the canal 36.

The canal 36, the holes 37, the ring 38 and the packing 39 together with the ring 22, the flanges 23, 24 and the gap 25 form a connection 56, the function of which will be described further below.

The medium, which is to be filtered, is guided to the lower part 6 of the housing 1 through a first pipe 40 and is expelled through a second pipe 41, said first pipe 40 and and second pipe 41 being for example connected to side walls of the housing 1.

In normal use of the filter the rotor 17 is stationary, and during the the flow of said medium through the first pipe 40 and the second pipe 41 there will be a difference of pressure across the filter, which will force the pack¬ ing 39 against the flanges 23, 24 so that the above mentioned connection 56 is closed, whereby the rotor 17 is also held stationary by friction between the packing 39 and the flanges 23, 24.

If the rotor 17 comprises one single filter cylinder 26 with a single screening cylinder 27 only, the difference of pressure will force the said medium from the lower part 6 of the housing 1 up through the space 28 between the filter cylinder 26 and the screening cylinder 27, whereupon it will pass in a radially inwards direction through the filter cylinder and further through the ra¬ dially innermost space 30 between the axle 16 and the filter cylinder 26 up into the upper part 5 of the housing 1, from where the said medium is expelled in filtrated state through the second pipe 41 for renewed use.

If the rotor as shown in fig. 8 comprises several concen¬ tric filter cylinders 26 with connected screening cylin¬ ders 27, then the filtered medium, in addition to being able to pass through the above mentioned radially inner- most space 30 between the axle 16 and the innermost filter cylinder 26, will also be able to flow up through the spaces, which in the radial direction are limited towards the inner side by a screening cylinder 27 and towards the outer side by a filter cylinder 26.

In fig. 8 is furthermore shown an embodiment of the con¬ nection between the axle 16 and the carrying frame 18, which connection departs from the schematical embodiment shown in fig. 2-4.

During the passage through the filter cylinder or cylin¬ ders 26 the particles, which were contained in the said medium, will be expelled. When the deposit of particles in the filter cylinder or cylinders 26 increases, the diffe- rence of pressure across the filter will also increase, and when the difference of pressure has increased to a predetermined value, the cleaning process of the filter will be started.

Certain measuring and controlling means of actually well known kinds, which are not shown in the drawings, can be provided for starting the cleaning operation.

The cleaning operation is initiated by starting the flow device 34 which through the opening 55 in the housing 1 exhausts a part of the purified medium and forces it through the pressure pipe 35 down into the canal 36.

From here the purified medium flows through the holes 37 and the annular gap 25 into the ring 22 in the rotor 17. The pressure produced hereby in the ring exceeds the pressure outside the ring, and the packing 39 is there¬ fore lifted from the flanges 23, 24 to the effect that the rotor is now released for rotation. As long as the cleaning of the filter concinues there will be a pressure cushion consisting of purified medium in the connecting gap 56 between the flanges 23, 24 and the packing 39 in such a way that the latter will be kept floating above the flanges.

The above described adjustability of the bar or bars 8 by means of the bolts 50 with the nuts 51 serves to adjust the rotor 17 vertically so that the connecting gap 56 can be adjusted to the dimension most appropriate.

The rotor 17 will be practically frictionless hereby as the only friction preventing the rotation will be the friction in the bearings 15.

As the rotor 17 will be substantially frictionless, the drive means 43 may have a very low yield, for example 150 Watts.

With the above mentioned number of revolutions per minute the centrifugal force will be sufficiently great to ensure that the particles, which have been deposited on the fil¬ ter cylinder or cylinders and are essentially placed on the radially outer side of same, will be disengaged from the filter cylinder or cylinders and be flung across to¬ wards the inner side of the impermeable screening cylinder or cylinders 27.

The particles will collect here, and under the influence of gravity drift or slide downwards along the inner walls of the screening cylinder or cylinders 27, until the par¬ ticles at the lower edge of the wall or walls will fall down towards the bottom 3 of the housing 1, and from there the particles can be removed in any suitable way, which is not described in detail here.

As the particles are being flung towards the screening cy¬ linder or cylinders 27 during the rotation of the rotor 17, the difference of pressure across the filter cylinder or cylinders again declines.

When the measuring instruments then register that the difference of pressure across the filter has been lowered to a predetermined limit, which is lower than the difference of pressure starting the cleaning operation, the control means for stopping first the driving means 43, whereby the rotation of the rotor is arrested, and then the flow device 34, are activated so that the packing 39 again closes the connection between the intermediate bottom 4 and the flanges 23, whereby the filter is re¬ turned to its normal working condition.

If the medium to be filtered is gaseous, a ventilator is used for the flow device 34, and in the case of a liquid medium, a pump is used.

In fig. 9 is shown a preferred embodiment of the filter according to the invention, where the inner wall of the filter housing 1 is employed as the impermeable wall 27.

The filter here, under the assumption of the same outer diameter of the filter cylinder 26 or the outermost filter cylinder 26, has a smaller cross section than in the em¬ bodiment shown in figs. 2-8, as the filter has instead been made relatively higher by placing the canal 36 axi- ally in relation to the rotor 17.

This embodiment permits a rational construction of the connection 56 since this can now be built up of rings, which can be produced by turning, cf. fig. 10, illustrat¬ ing a section of the connection 56.

The connection 56 consists here of an upper ring 57, which is tightly connected with the intermediate bottom 4 and the canal 36, and a lower ring 58, which is tightly con¬ nected with the plate ring 33 on the rotor 17. On the un- der side of the upper ring 57 is provided an annular re¬ cess for the elastic packing 39, which can be kept in place here by a number of bolts 59 attached along the ring 57 and the packing 39 at identical intervals. The radially outer edge of the packing 39 can bear tightly against the surface of the lower ring 58 as a result of its elastici¬ ty, until such pressure is created in the canal 36 and the holes 37 by the starting of the flow device 34 that the packing 39 is lifted from its position against the lower ring 58.

It will be understood that in this embodiment the holes 37 shown do not necessarily have to be holes in the upper ring 57, but instead can consist of an annular groove in the upper ring 57, which would hereby consist of two con- centric rings kept in their mutual position by their connection to the canal 36. The vertical adjustment of the rotor 17 and thereby of the connecting gap 56 is achieved in a different way than in the embodiment shown in fig. 5, which will be explained in more detail with reference to fig. 11.

The tube bearing 14 and thereby the bearings 15 and the axle 16 are immovably placed in the filter housing 1.

The rotor 17 is placed axially shiftable but cannot be turned on the axle 16 as the rotor 17 is provided with a bushing surrounding the axle 16 of the rotor. To the lower end of the axle is fastened a yoke 61 by means of an axial bolt 62 which is screwed into an axial threaded bore in the axle 16.

Into the plate 32. of the rotor 17, said plate being se¬ cured to the bushing 60, are screwed two threaded stay bolts 63, which are fastened securely to the plate with counter-nuts 64. The stay bolts 63 are of such length that they can extend through holes in the two branches or shoulders of the yoke 61 and co-operate with nuts 65 on each side of the branches of the yoke 61.

By turning the nuts 65 on the stay bolts 63, the rotor 17 can be displaced along the axle 16 so that the connecting gap 56 can achieve the most appropriate size.

In fig. 12 is schematically shown the construction of the rotor when according to the preferred embodiment of the filter according to the invention several concentric fil¬ ter cylinders are being employed.

In an embodiment, which is not shown, of the filter according to the invention the co-operation between the downwards turned radially outer edge of the rotor 17 and the intermediate bottom 4 can be suspended thereby that the entire rotor 17 is lowered from its position of rest, whereupon the rotor 17 can be rotated by the driving means 43 so that the particles are flung out from the filter cy¬ linder or cylinders 26.

In this embodiment it is possible to leave out the flow device 34, the pressure pipe 35, the canal 36, the circum¬ ferential ring 22 with the flanges 23, 24 and the packing 38, etc.

Claims

C L A I M S

1. Method of cleaning a filter comprising a filter housing (1) with an inlet (40) and an outlet (41) and at least one annular filter element (26) placed in the filter housing (1) for filtering a medium containing par¬ ticles, which medium is passed in a flow through the filter element (26) from the inlet (40) to the outlet (41), c h a r a c t e r i s e d in that the filter ele- ment (26) is placed rotatably around an axle (16) con¬ gruent with its axis of symmetri (12), that the filter element (26) is cleaned periodically, preferably during continuous running of the filter, of particles deposited on the influx side by rotating the filter element (26) a- round the axle (16), and that the particles separated by the rotation are collected from the filter housing (1).

2. Method according to claim 1, in which the said medium is passed radially inwards through the annular filter element (26), c h a r a c t e r i s e d in that a wall (4, 27, 29, 32, 33), which is impermeable to the said medium, is provided in the filter housing, which wall extends at least partly round the filter element (26) and divides the filter housing (1) in a first part (5) and a second part (6), and that the particles are collected from the wall (27) and/or from the second part (6) of the filter housing (1).

3. Method according to claims 1 and 2, c h a r a c t e - r i s e d in that the filter is placed in such a way that the axle (16) of the filter element (26) is substan¬ tially vertical, and so that the first part (5) and the second part (6) consists of an upper space (5) and a lower space (6) in the filter housing (1) .

4. Method according to claims 2 and 3, c h a r a c t e ¬ r i s e d in that the filter housing ( 1 ) is separated into the upper part (5) and the lower part (6) by an annu¬ lar intermediate bottom (4) which is tight-fittingly connected with the inner side of the wall of the filter housing (1), and a rotor (17) consisting of the axle (16), the filter element (26) and parts of the impermeable wall (27, 29, 32, 33), which rotor is made to co-operate tight¬ ly and releasably with the edge of the intermediate bottom (4), preferably by means of a pressure pad.

5. Filter for use in connection with the implementation of the method according to claim 1 comprising a filter housing (1) with an inlet (40) and an outlet (41) and at least one annular filter element (26) placed in the filter housing (1) for filtering a medium containing par- tides, which medium can be passed in a flow through the filter elememt (26) from the inlet (40) to the outlet (41), c h a r a c t e r i s e d in that the filter ele¬ ment (26) is connected to a rotatable axle (16), which is congruent with the axis of symmetri (12) of the filter element (26), in means for periodically rotating said axle (16), preferably during continuous use of the filter, and in that the filter has means for collecting particles separated from the filter housing (1) by the rotation.

6. Filter according to claim 5, in which the said medium is passed radially inwards through the annular filter ele¬ ment (26), c h a r a c t e r i s e d in that the filter housing (1) has a wall (4, 27, 29, 32, 33), which extends at least partly around the filter elememt (26) and divides the filter housing (1) in a first part (5) and a second part (6), and that the means for collecting the se¬ parated particles are arranged to collect them from the wall (27) and/or from the second part (6) of the filter housing (1) .

7. Filter according to claims 5 and 6, c h a r a c t e ¬ r i s e d in that the axle (16) is placed substantially vertical while the filter is in use, and that the said first and said second parts consist of an upper space (5) and a lower space (6) in the filter housing (1).

8. Filter according to claims 5-7, c h a r a c t e ¬ r i s e d in that the filter housing (1) is divided into the upper space (5) and the lower space (6) by an annular intermediate bottom (4), which is tightly connected to the inner side of the wall of the filter housing (1), and a rotor (17) consisting of the axle (16), the filter element (26) and parts of the impermeable wall (27, 29, 32, 33), which rotor is made to co-operate tightly and releasably with the edge of the intermediate bottom (4), preferably by means of a pressure pad.

9. Filter according to claims 5-8, c h a r a c t e ¬ i s e d in that the annular filter element (26) con¬ sists of a filter wall (26), preferably of a circular cy- lindric or polygonal cross section, that at least a part of the wall (27) is placed radially outside the filter wall (26) and has a corresponding cross section, an annu¬ lar ring (22) surrounding the wall (27), whereby the spaces (30) between on one side the axle (16) of the ro¬ tor (17) and the filter wall (26) and between the wall (27) and the circumferential ring (22) at their lower ends or edges and on the other side the space (31) between the filter wall (26) and the wall (27) at their upper edges are tightened by a plane disk (29), respectively plane rings (32, 33), said disk (29) and rings (32, 33) consti- tuting the remaining parts of the wall (27, 29, 32, 33).

10. Filter according to claims 5-9, c h a r a c t e ¬ r i s e d in that the seal between the rotor (17) and the intermediate bottom (4) during the cleaning of the filter is provided by a connection (56) between the rotor (17) and the intermediate bottom (4) which connection is designed to as a pressure pad to become tightened by the filtrated medium.

11. Filter according to claims 5-10, c h a r a c t e ¬ r i s e d in that the connection consists of a canal (36) surrounding the rotor (17), the bottom of which con¬ sists of the intermediate bottom (4), an upwards turned gap (25) formed in the circumferential ring (22, 58), which gap is enclosed on each side by plane flanges (23, 24), an annular elastical seal (39) secured to the under side of the intermediate bottom (4) and with downturned circumferential edges which are shaped to bear against at least one of the plane flanges (23, 24), whereby the thickness of the seal (39) is slightlaey less than the distance between the flanges (23, 24) and the intermediate bottom (4), and a circular row of holes (37) placed out¬ side of the gap (25) through the seal (39) and the inter¬ mediate bottom (4).

12. Filter according to claims 5-11, c h a r a c t e - r i s e d in that the filter has a flow device (34) con¬ structed to remove parts of the filtrated medium from the upper space (5) and to conduct these under pressure to the canal (36).

13. Filter according to any of the preceding claims, c h a r a c t e r i s e d in that the rotor (17) is con¬ structed to be lowered at the periodical cleaning of the filter to cancel the co-operation between the intermediate bottom (4) and the upwards turned radially outermost edge of the rotor (17).