To ensure that the particle separator functions well, it is of vital importance that the particle separation is as efficient as possible, which in turn imposes strict requirements concerning the properties of the filter which is used.

Mechanical filter arrangements with folded paper filters in the form of cylindrical filter cartridges are already known and provide satisfactory filtering.

However, it is desirable to be able to improve the properties of the filter still further and to be able to ensure that the good properties of the filter are maintained over a period of time in operation. As the filter is used, the degree of soiling of the filter increases, and in theory one would finally reach a stage where the filter is completely clogged and does not let any air through at all.

An advantageous way of avoiding clogging is therefore to frequently replace the filter. However, changing the filter has hitherto been a relatively complicated procedure since the fan unit has to be dismantled from the filter housing using tools in order to gain access to the filter cartridge and replace it. In addition, filter replacement has generally been carried out at irregular intervals, which has sometimes led to unnecessarily high filter costs as a result of filters

being replaced too frequently, and sometimes to impaired functioning if the filters have not been replaced often enough.

The object of the invention is therefore to make available a mechanical filter arrangement which does not have the disadvantages described above. This is possible with a particle separator comprising a mechanical filter arrangement with a conventional, folded paper filter in the form of a cylindrical filter cartridge, and having the characterizing features according to Patent Claim 1. Advantageous developments and refinements of the invention will be evident from the dependent patent claims and from the described embodiments.

The invention is described in more detail below with reference to the attached diagrammatic drawing. Fig. 1 shows a vertical view of a particle separator according to the invention. Fig. 2 shows the particle separator from Fig. 1 rotated 90° in the horizontal plane, Fig. 3 is a horizontal view of the particle separator from Fig. 1 seen from above, Fig. 4 is a perspective view which shows the particle separator with the outlet part resting on the top section of the filter housing, Fig.

5 is a view similar to Fig. 4 but with the outlet part lifted and pivoted outwards for filter replacement, Fig. 6 shows on a larger scale the arrangement for supporting the outlet part when it has been lifted and pivoted outwards, Fig. 7 shows a vertical view of an embodiment of the particle separator in a cross section showing the air paths through said particle separator, Fig. 8 is a horizontal view, from above, of the deflection arrangements in a centrifugal unit in the inlet part of the particle separator, Fig. 9 shows the centrifugal unit in a perspective view seen from below, and Fig. 10 shows the helical air flow through the filter housing brought about by the centrifugal unit.

The particle separator according to the invention is designated in general by reference number 1 and has a filter housing 2 which is formed by a wall arrangement 3 and has an inlet part 4 which is mounted in a bottom section of same, and an outlet part 8 which is mounted in a top section of same and which is provided with a fan unit 6. The filter housing has suspension consoles 9 for mounting it in position in the selected orientation. Arranged in the filter housing 2 there is a filter cartridge 10 which is designed as an elongate hollow cylinder 12 whose filtering surface has radial plates extending along the jacket surface of the hollow cylinder. The filter cartridge 10 is advantageously made of folded filter paper of conventional type and in addition has a first end wall 14 which is designed as an annular lid 14 provided with a central hole for the top section of the filter housing 2. The first end wall or lid 14 can be designed with a seal, for example an 0-ring, of conventional type (not shown here), so that the lid 14 tightly seals the top section of the filter housing and the fan unit 6 located in the outlet part 8. In its part directed towards the bottom section of the filter housing, the inside of the hollow cylinder 12 of the filter cartridge 10 is closed by means of a deflection arrangement 16 located in the inlet part 4 and acting as second end wall.

With the aid of the first end wall 14, the filter cartridge 10 is suspended and fixed in the filter housing 2 by means of the outlet part 8 mounted in the top section of the filter housing in such a way that on the inlet side the available air passage from the inlet part 4 on the one hand depends on the deflection arrangement 16 and on the other hand is located between the outside of the hollow cylinder 12 of the filter cartridge 10 and the wall arrangement 3 of the filter housing. Since the first end wall or lid 14 closes this air passage towards the outlet part 8, the only passage remaining is from the outside of the hollow cylinder 12

through the filtering surface thereof to its inside.

The available air passage to the outlet part 8 from the inside of the hollow cylinder is guided through the central hole and delimited by the annular lid 14 at the top section of the filter housing, which air passage finally leads to the suction side of the fan unit 6 located in the outlet part.

The outlet part 8 is suspended relative to the filter housing 2 by means of a control shaft 17 which is mounted movably on the filter housing 2 and which has a first control arm 18 at one end and a second control arm 20 at the other end, which first control arm 18 additionally constitutes a securing device for the outlet part. Each control arm is substantially at right angles to the control shaft, and the control arms are additionally rotated mutually in the horizontal plane almost at right angles. The control shaft 17 is mounted both rotatably and axially displaceably in a bracket 22 anchored on the filter housing 2. The control shaft 17 has a heel 24 shaped on it, and the bracket 22 has a recess 26 matching the heel and situated such that, in a first mutual position of the control shaft 17 and the bracket 22, the heel and the recess engage with one another so that a rotation catch 24,26 is activated which ensures that the outlet part is centred with the filter housing when the outlet part rests on the top section of the filter housing. The rotation catch 24, 26 can be released when the control shaft 17 and the bracket 22 have been brought, by means of one of the control arms 18,20, to assume an axially displaced second mutual position when the outlet part 8 is lifted from the top section of the filter housing 2. In this second mutual position, the control shaft 17 is freely rotatable, because the heel 24 and the recess 26 are rotationally moved out of engagement with one another.

The heel has a projection 28 which, when the heel 24 has been rotated from the position coinciding with the recess 26 in the bracket 22, can bear axially against a

support surface 30 of the bracket. As long as the heel 24 and the recess 26 are located in a rotation position separate from one another, the outlet part 8, by means of the first control arm 18, the control shaft 17 and its heel 24, is thus supported against the support surface 30 of the bracket with the aid of the projection 28 of the heel.

The deflection arrangement 16 of the inlet part 4 is arranged to deflect the inlet air in the direction towards the wall arrangement 3 of the filter housing 2 and is provided with at least one guide rail 32 for guiding the air in a helical movement through the filter housing 2, before passage through the filtering surface and out through the outlet part 8.

According to an advantageous embodiment, the deflection arrangement, which is shown in Figures 8 and 9, is designed as a centrifugal unit 34 which has four guide rails 32 evenly distributed and extending in an arc shape from an internal diameter (di) to an external diameter (dy). Trials have shown that a suitable value of the ratio between the external diameter dy and the radius of curvature r of the guide rails can be about 3: 4.

As polluted air is sucked in via the inlet part 4, it is forced to pass through the centrifugal unit 34 and is guided by the latter in the direction towards the wall arrangement 3 of the filter housing and is set in a helical rotating movement through the filter housing, as is illustrated in Fig. 10. As a result of this rotating movement, the polluted air is accelerated by the centrifugal force out towards the wall arrangement 3 of the filter housing, by which means an effective preliminary separation is obtained. In particular, relatively large particles are thrown out towards the wall arrangement and fall down to the bottom section of the filter housing 2. The centrifugal unit also

contributes to the speed of the air flow being reduced at the filter cartridge, see Fig. 7, which ensures a higher degree of separation and a longer useful life of the filter cartridge 10. Since the air flow is forced to follow a helical and longer route around the filter cartridge, a more even distribution is obtained across its filtering surface.

The particle separator 1 can also be equipped with a unit 36 for monitoring the operating status. The monitoring unit 36 is illustrated in Fig. 7 and comprises a manometer 38 which is attached to a first nozzle 40 and to a second nozzle 42, in each case via a hose 44 and 46, respectively. A hole is formed at the centre of the centrifugal unit 34, in which the first nozzle 40 is mounted, and the second nozzle 42 is mounted between the wall arrangement 3 of the filter housing and the outside of the filter cartridge 10 (overpressure side). When the filter cartridge is mounted in the filter housing 2 according to Fig. 7, the first nozzle 40 is situated on the inside of the filter cartridge (the underpressure side). The manometer 38 can then measure the differential pressure Ap between the nozzles and thus across the filter cartridge 10. In this way it is therefore possible to monitor the condition of the filter cartridge 10 so as to obtain a reliable indication of when a filter needs to be replaced.

The filter is replaced by means of the outlet part 8 with fan unit 6 being lifted either with the aid of the first control arm 18 or the second control arm 20 (Fig.

4) and being rotated in the desired direction, the heel 24 with its projection 28 being brought to bear against the support surface 30 of the bracket 22 and ensuring that the outlet part remains in the raised position (Figures 5 and 6). The filter cartridge 10 can now easily be changed. The whole procedure can be carried out without the aid of any tools. The particle

separator can be mounted in any desired positions, for example directly on a machine hood, a wall, a stand, or suspended from a ceiling. In the last three cases, the particle separator can be provided with a separate exhaust arm of any desired type, for example of a previously known type. By virtue of the fact that the first control arm 18 has a different position and a different orientation in relation to the second control arm 20, access is easily gained in order to manoeuvre the outlet part 8 from either side and also just as easily from the top as from the bottom.