WO2010045952A1

WO2010045952A1 - Road planer for milling road-surface

Info

Publication number: WO2010045952A1
Application number: PCT/EP2008/008893
Authority: WO
Inventors: Antonio Cipriani; Karl MÖTZ
Original assignee: Marini S.P.A.
Priority date: 2008-10-21
Filing date: 2008-10-21
Publication date: 2010-04-29
Also published as: EP2350390A1; EP2350390B1

Abstract

Self propelled road milling machine comprising: - a chassis (1) mobile on crawler-tracks/wheels (2), - a milling drum (3) supported by said chassis (1) and located inside a drum housing (7), - at least a first and a second conveying device (5, 6), supported by the machine chassis (1), receiving the material milled by the milling drum (3), and transporting it to a discharge point (36), - a suction-filtering unit (29) of the air polluted by dust and vapours produced by the milling process, characterised in that: - it comprises one or more tight hoses (27) connected to said suction- filtering unit (29) and maintained in depression by said suction- filtering unit (29), - said hoses (27) carry the polluted air from said first and second conveying device (5, 6) to the back of the road milling machine, - said suction-filtering unit (29) is mounted on the back of the road milling machine in cantilever abutment.

Description

ROAD PLANER FOR MILLING ROAD-SURFACE

DESCRIPTION

Technical Field

The present invention relates to suction of dust and vapours in a road planer or similar milling machines.

In particular the invention refers to a road planer improved with suction and disposal devices for dust, namely the invention refers to a self propelled road milling machine according to the pre-characterising part of claim 1.

Background Art A known road planer refers to a self propelled milling machine, generally used for removing a portion of asphalt road pavement in order to restore the road with re-deposition of renovated road-surface (repaving).

In the present invention the definitions "road planer" and "milling machine" are considered equivalent. The road planer or milling machine consists of a self propelled chassis, supported by crawler tracks, or wheels, generally equipped with hydraulic actuators, powered by a diesel engine and having a milling drum to mill the asphalt road surface for repaving.

A milling drum is supported by the chassis transversally to the direction of travel, being directly operated by the diesel engine through a mechanical transmission, or by a hydraulic transmission.

Said crawler tracks or wheels are connected to telescopic columns, which consent the chassis to achieve the correct height and attitude to get the requested milling profile. The material, milled by the drum, is removed by one or more conveyor belts, and finally discharged at the front section of the machine, or at its rear section.

In the first case the milled material is discharged into a transport vehicle, which precedes the milling machine, whilst in the second case the vehicle follows the milling machine, running backward.

During the milling operation dusts arise, caused by the partial crushing of the aggregates included in the road pavement; if the road pavement consists of an asphalt mixture also bitumen vapours are produced due to the high temperature caused by the friction of the cutting tools.

In an open-air milling machine dust and vapours escape from the drum housing and from the conveyor belts, being emitted into the surrounding environment generating pollution and particularly close to the driving platform with potential health risk for the operator. The health risk is enhanced during milling of a road pavement where aggregates contain silica and/or asbestos fibres. Scope of the invention

The main scope of the present invention is to improve functionality of the road planer or milling machine in order to reduce pollution and to recover fine dust and fibres for separate disposal in authorized centres. Closest prior art

Patent EP 0 971 075 A1 foresees to fit a suction hood over the collecting conveyor and to connect said hood with a cyclone followed by a suction ventilator: said cyclone being located in the rear part of the milling machine. This solution presents the following evident disadvantages: - the cyclone can knock down only the coarse dust particles, but it is not efficient at all in retaining fine dust and fibres which are spread around in the atmosphere close to the operator's platform and sometimes close to the engine cooling air intake. - the poor efficiency of the cyclone causes the ventilator to suck still dust- laden air which compromises the functionality of the unit in a short time.

Patent DE 102 23 819 A1 foresees the suction of the polluted air from the channel on the collecting conveyor and to convey it into the channel on the loading conveyor by means of the same suction-ventilator. This solution consents to exhaust the air, polluted by dust and vapours, into the atmosphere far away from the operator's platform. However the solution suffers the following disadvantages:

- the ventilator sucks dust-laden air which compromises the functionality of the unit in a short time.

- no filtering system is foreseen able to recover the dust and to limit its diffusion into the atmosphere.

Patents EP 1 507 925 B1 and US 7,219,964 B2 foresee to suck the polluted air from both the channel on the collecting conveyor and from the channel over the loading conveyor, where:

- the collecting conveyor is equipped with a sealing device, consisting of sets of flexible flaps, located close to its discharge head, which oppose to the entry of external air but do not oppose to the flow of the milled material; - the channel on the collecting conveyor is connected to the corresponding channel on the loading conveyor by means of hoses with air intakes located upstream of the above mentioned sealing device;

- sealing devices, consisting of sets of flexible flaps are provided for the loading conveyor such as for the collecting conveyor. On the loading conveyor the sealing devices are located downstream of the connection points of the above hoses with the loading conveyor channel and downstream of the suction-filtering unit;

- the discharge area of the collecting conveyor onto the loading conveyor is not involved in the suction of the polluted area; - the polluted air is forced to pass through a suction-filtering unit before being exhausted by the suction-ventilator into the atmosphere;

- the dust retained by the filter is discharged onto the loading conveyor with no chance to collect it for separate disposal. The disadvantages of the solution are the following:

- the bulk hoses connecting the channels of the two conveyors and the movements of said hoses caused by the slewing of the loading conveyor, compromise functionality; - the discharge area of the collecting conveyor onto the loading conveyor is not interested by the suction process. In said area dust and vapours are emitted and spread into the atmosphere in the vicinity of the operator's platform.

- the dangerous dust particles and fibres are partially emitted and spread into the atmosphere at the discharge point of the loading conveyor onto the truck.

Scope of the invention

The scope of the invention is to obviate the above disadvantages and to realize a more sure and simple milling machine, namely a road planer having improved performance to avoid pollution and damages on surroundings with possibility to recover the dangerous dust and fibres for final separate disposal.

Disclosure of the invention

The scope is reached with the features of claim 1.

Advantages With this solution a no-pollutant better performed road planer is realized.

The invention will be better understood with the following description.

Brief description of drawings

The features of the present invention are set forth in particulars in the appended claims. The invention itself, together with further features and attendant advantages, will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 discloses a side view of a planer of known type. Fig. 2 discloses a longitudinal view of a planer of known type. Fig. 3a -3b disclose longitudinal section views of the planer of the present invention. Fig. 4 discloses a rear view of the planer of the present invention. Fig. 5 discloses a section view of each conveyor belt. Fig. 6 discloses a section view of the loading conveyor belt with the sealing multi-layer rubber curtain.

Fig. 7 discloses a section view of the sealing devices in the discharge zone of the collecting conveyor onto the loading conveyor. Fig. 8 discloses a schematic view of the filtering group. Fig. 9 discloses a schematic view of the pre-separator.

Description of a known planer The machine of Fig.1 , Fig. 2 consists of a self propelled chassis (1 ), supported by crawler tracks (2), generally equipped with hydraulic actuators, powered by a diesel engine.

A milling drum (3) is supported by the chassis (1) transversally to the direction of travel, being directly operated by the diesel engine through a mechanical transmission, or by a hydraulic transmission.

The crawler tracks (2) are connected to telescopic columns (4), which consent the chassis to achieve the correct height and attitude to get the requested milling profile. The material, milled by the drum (3), is removed by one or more conveyor belts (5), (6) and is finally discharged at the front section of the machine (in an other solution this can be at its rear section). In the present case the milled material is discharged into a transport vehicle which precedes the milling machine, whilst in the opposed case the vehicle follows the milling machine, running backward. The milling drum (3) is located inside a drum housing (7). With reference to the work driving direction, said drum housing (7) is provided with a rear mobile moulder (8), fitted with scraping tools, and with two mobile side plates (9a), (9b), kept in contact with the road surface, and having a floating or a slightly downward forced action.

In the front section of the milling drum housing (7) an opening (10) is provided, which consents the milled material to be discharged onto a first conveyor belt (5) (collecting conveyor). Said collecting conveyor (5) is provided at its driven pulley section with a support device (11) (pressure bar), generally sliding over the road surface, in contact with the same. The driving pulley section of said collecting conveyor (5) slides over a support (12) which is part of the machine chassis (1 ). As a consequence the frame of the collecting conveyor (5) moves vertically and longitudinally, depending upon the working milling depth. The collecting conveyor (5) discharges the milled material onto a second conveyor belt (6) (loading conveyor) which can be slewed vertically and horizontally to adapt its discharge head (36) to the height and position of the transport vehicle.

The typical section view of the conveyor belts, of known technology, is schematically shown in Fig. 5. Each conveyor consists of a mobile rubber belt ring (13), supported in the transport section by "V" shaped rollers (14) and supported by other rollers (15) in the return section. The frame (16) of the conveyor is fitted with side walls (17a), (17b) and with a top sealing mean or cover (18). Said side walls (17a), (17b) support flexible skirts (19a), (19b) in positive contact with the upper surface of the mobile rubber belt ring (13). The milled material (20) is therefore transported inside a channel (21a, 21b) enclosed by said side walls (17a), (17b), by said flexible skirts (19a), (19b), by said cover (18) and by said mobile rubber belt ring (13).

During the milling operation dusts arise, caused by the partial crushing of the aggregates included in the road pavement.

If the road pavement consists of an asphalt mixture also bitumen vapours are produced, due to the high temperature caused by the friction of the cutting tools, so dust and vapours escape from the drum housing and from the conveyor belts and are emitted into the surrounding environment and particularly close to the driving platform (43) with potential health risk for the operator. The health risk is enhanced during milling of a road pavement where aggregates contain silica and/or asbestos fibres. Detailed description of the invention The description of the invention refers to a road planer improved with suction and disposal devices for dust and vapours as for Fig. 3a-3b and Fig. 4, where the milling drum (3) is located inside a drum housing (7) and where the suction- filtering unit (29) is preferably located at the back of the machine. Although in the illustrated embodiment the suction-filtering unit is represented as mounted on the back of the machine, it is evident that equivalent alterations and modifications will be obvious to one skilled in the art upon the reading and understanding of this specification and the annexed drawings. Thus, it should be understood that the invention is not limited by the description and the annexed drawings, but embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims. With reference to Fig..3a-6 the invention concerns the fitting of a suction- filtering unit (29) capable to maintain under negative pressure the areas where dusts are produced. Channels (21a) and (21b), respectively identifiable on conveyors (5) and (6), and the effective sealing of the discharge area (22) of the collecting conveyor (5) onto the loading conveyor (6), along with the drum housing (7) constitute one continuous channel or chamber (23). Said channel (23) is closed in its lower section by the walls of the milling drum housing (7), by the rear mouldboard (8) and by the side plates (9a), (9b), whilst its upper section is closed by sealing means, namely one or more sets of overlapped flexible flaps (24) which oppose the entry of external air but do not oppose the flow of the milled material (20). Said flexible flaps (24) slide over the milled material (20) in contact with it.

Said channel (23) and the drum housing (7) are kept in depression through one or more hoses (27) connecting it to the suction-filtering unit (29), said hoses (27) preferably being flexible. It will be apparent to the experts in the art that said hoses (27) could be a fixed duct or a fixed duct with flexible hoses on one or on both ends or in some intermediate positions to allow the movement of the adjustable devices of the machine.

With reference to Fig.4, the suction-filtering unit (29), of known technology, basically consists of a set of filtering elements (26) (pockets, hoses, cartridges), a suction fan (25), a filtering media cleaning system (35). Said fan (25) sucks the air polluted by dust and vapours from said channel (23) and drum housing (7) through the battery of filtering elements (26). Said filtering elements (26) are contained in an enclosed housing (28) fitted with a collecting hopper (30) in its lower section. In the drawings reference is made to a preferred solution consisting in a standard commercial suction-filtering unit, with the advantage to be a lower cost solution with respect to prior art solutions, requiring a specific non-commercial suction-filtering unit. Said suction-filtering unit comprises: a bottom dust collecting hopper (30), the set of filtering elements (26), the cleaned air outlet cowling (31), the suction fan (25), the compressed air contra-flow cleaning system (35).

The abrupt reduction of the polluted air speed at the enter into the collecting hopper causes the coarse dust particles to drop down without colliding against the filtering media thus reducing the risk of damage to a minimum. The filtering elements (26) oppose a resistance to the passing through air flow, which results in a pressure drop through the filtering media. This forces the dust to be retained on the external surface of the filtering elements (26), causing a slight compression of the dust and its agglomeration. The dust cake itself contributes to increase the pressure drop through the filtering elements, thus improving the dust agglomeration.

An automatic cleaning system (35), of known technology, periodically pulses blows of compressed air in contra-flow to detach the dust cake and makes it to drop into the bottom collecting hopper (30). It will be apparent to the ones skilled in the art that different but equivalent configurations can be used to clean said filtering elements (26), such, by way of example, vibrating devices shaking them, or a combination of different known cleaning systems. The negligible amount of dust, still remaining in the filtered air flow, does not affect in any way the efficiency of the system and the work continuity of the machine.

With reference to Fig.8 the bottom of said collecting hopper (30) is sealed by a replaceable dust container (32) consisting of a rigid barrel or of a bag, in the last case properly supported by an internal cage (37), which prevents the bag to be squeezed by the differential pressure between the outside and the inside of the suction-filtering unit.

In a preferred solution flexible bags are used with a capacity of about 30 kilos and fitted with braces to be easily handled by the operator. Flexible bags can be easily stored on board of the machine, have a low cost and can be economically disposed off along with the recovered dust. The mouth of the bag is forced around the outlet of the collecting hopper by a pneumatic clamping device (38) of known technology, widely used in the bagging machines. A level probe (39), located inside the bag support cage, warns the operator that the bag is full and must be replaced. Before the bag is released from the collecting hopper (30), it is preferably sealed by a sewing equipment (not shown in the drawings) and left on the road bank for the final collection, said sewing equipment being preferably portable . At the discharge head (36) of the loading conveyor (6) some dust is inevitably produced, which however spreads around in the atmosphere far away from the operator's platform (28).

Close to the discharge head (36) of the loading conveyor (6) a spray bar (40) is provided. Said spray bar (40), consists of a set of water atomizing nozzles, having the scope to further support the dust agglomeration and its fall. The suction efficiency depends upon the sealing degree of channel (23). In particular the sealing media of the critical discharge area (22) of the collecting conveyor (5) onto the loading conveyor (6) must be efficient enough so as to maintain the channel (23) depressurized at any position of conveyor (6) in respect of conveyor (5) and at any position of conveyor (5) in respect of the machine chassis (1 ).

The sealing means of the discharge area (22) of the collecting conveyor (5) onto the loading conveyor (6) are preferably made as schematically shown in Fig. 7, where:

- the sealing device (33a - 33b) compensates the vertical slew of the loading conveyor (6),

- the sealing device (34) compensates the horizontal slew of the loading conveyor (6).

Said sealing device (34) being preferably a ring of soft rubber conveniently centred on the vertical pivoting axis of the loading conveyor (6). The suction, supported by the ventilator (25), produces a depression inside the channel (23), which causes a continuous intake of external air and prevents the polluted air from escaping. Advantageously said sets of flexible sealing means (24) applied on the loading conveyor (6) are made of a plurality of closed vertical straps in which each strap overlaps with its border the adjacent one. In this way the advancing material on the continuous belt does not create openings between said straps deflected upwards by the variation in size of the continuous advancing material (20).

With reference to Fig. 3a-8 in a preferred solution the suction-filtering unit (29) is connected to the chassis (1) of the milling machine by means of movement means (41 , 42) which consent to move said suction-filtering unit (29) longitudinally and vertically so as to achieve the following positions: - transport position

- working position

- bag replacing position

- access to the road milling machine

Advantageously the vertical movement allows the suction-filtering unit (29) movement between transport and working position as well as the bag replacement. Advantageously the longitudinal movement allows an easy access to the machine as well as to the suction-filtering unit (29) itself. It will be apparent to the experts in the art that in a less preferable solution said suction-filtering unit (29) can be mounted in a fixed way. In the represented embodiment, being said suction-filtering unit (29) mounted on the back of the machine, the position of said access to the road milling machine is intended to allow the access to the engine radiator. In the preferred embodiment said movement means are two telescopic arms: one telescopic arm (41) performing a longitudinally movement and the other telescopic arm (42) performing a vertical movement.

Whenever the container (bag) (32) of the recovered dust is full the machine has to stop the milling operation to consent its replacement . Obviously it is of economical interest to reduce this dead time to a minimum. The gradation of the airborne dust also includes particles having a relatively coarse sizes, which do not represent a health risks. The removal and separate disposal of such particles from the dust laden air flow before entering the bag filter, takes to the following advantages: - protection of the filtering media from the collision of relatively high energy particles,

- increased autonomy of the dust container capacity with consequent reduction of the dead times.

In an alternative execution of the milling machine, a dust pre-separator (44) Fig.3b can be advantageously interposed between the suction point of the dust laden air and the bag filter (29).

The coarse dust particles, recovered by the pre-separator, are discharged by a auger (45) onto the loading conveyor (6), downstream the air sealing device (24), to be included into the milled material (20).

The pre-separator (44) Fig.9 consists of a box installed in the ductwork between an inlet (46) and an outlet (47) flange. The sudden expansion of size at the chamber inlet reduces the speed of the dust laden air stream (27a) and the heaviest particles settle down by gravity. A baffle plate (48) causes the air stream to make a sudden change of direction, forcing the intermediate size dust particles to hit the baffle, thus reducing their kinetic energy. The speed reduction also makes said dust particles to settle down.

The size of the baffle chamber does not consent a high separating efficiency and the lightest dust particles are carried by the partially cleaned air stream (27b) toward the bag filter inlet.

An auger (45) is fitted at the bottom of the pre-separator collecting hopper (49) to seal it and to discharge the recovered coarse dust onto the loading conveyor (6). Used nomenclature

With reference to the identification numbers reported in the enclosed figures, it has been used the following nomenclature:

I . Chassis 2. Crawler tracks

3. Drum

4. Telescopic columns

5. Collecting conveyor belt

6. Loading conveyor belt 7. Drum housing

8. Rear mould board 9a, 9b. Side plates 10. Opening

I 1. Support device or pressure bar 12. Support

13. Mobile rubber belt ring

14. "V" shaped rollers

15. Rollers

16. Frame 17a, 17b. Side walls

18. Top sealing mean or cover

19a, 19b. Flexible skirts

20. Milled material

21 Chamber or channel 21a. First chamber

21b. Second chamber

22. Discharge area

23. Continuous channel or chamber 24. Flexible flaps

25. Fan

26. Filtering elements

27. Flexible hose 27a. Dust laden air stream

27b. Partially cleaned air stream

28. Housing

29. Suction filtering unit

30. Collecting hopper 31. Outlet cowling

32. Replaceable dust container 33a, 33b. Sealing device

34. Sealing ring

35. Cleaning system 36. Discharge head

37. Internal cage

38. Clamping device

39. Level probe

40. Spray bar 41 , 42. movement means of telescopic arms

43. Driving platform

44. Pre-separator

45. Auger

46. Pre-separator inlet flange 47. Pre-separator outlet flange

48. Baffle plate

49. Pre-separator collecting hopper

Claims

Claims 1. Self propelled road milling machine comprising:

- a chassis (1 ) mobile on crawler-tracks/wheels (2),

- a milling drum (3) supported by said chassis (1 ) and located inside a drum housing (7),

- at least a first and a second conveying device (5, 6), supported by the machine chassis (1), receiving the material milled by the milling drum (3), and transporting it to a discharge point (36),

- a suction-filtering unit (29) of the air polluted by dust and vapours produced by the milling process, characterised in that:

- it comprises one or more tight hoses (27) connected to said suction- filtering unit (29) and maintained in depression by said suction- filtering unit (29), - said hoses (27) carry the polluted air from said first and second conveying device (5, 6) to the back of the road milling machine,

- said suction-filtering unit (29) is mounted on the back of the road milling machine in cantilever abutment.

2. Self propelled road milling machine according to claim 1 characterized in that said hoses (27) are flexible.

3. Self propelled road milling machine according to any of the previous claims characterized in that said suction-filtering unit (29) is mounted in a removable way.

4. Self propelled road milling machine according to any of the previous claims characterized in that it further comprises: - upper and side sealing means (18,17a, 17b,19a,19b) on said conveying devices (5,6), suitable to create on said conveying devices (5,6) a single channel (21a, 21b) by further providing

- sealing means (33a, 33b, 34) on the discharge area (22) of the first conveying device (5) onto the second conveying device (6),

- said sealing means (18, 17a, 17b, 19a, 19b, 24, 33a, 33b, 34) being able to realize one continuous chamber (23) above said conveying devices (5,6) and in the joint connections area between them,

- suction device (25) connected to said continuous chamber (23) by flexible hoses (27), able to realize a maintained depression inside said continuous chamber (23) in respect of the outside,

- said suction device (25) being conceived for sucking the polluted air from said continuous chamber (23) and being connected to,

- a suction-filtering unit (29) to filter the polluted air sucked from said suction device (25) consisting of a battery of filtering elements (26), functionally interposed between said continuous chamber (23) and said suction device (25).

- the suction-filtering unit (29) being equipped with a dust collecting hopper (30) discharging the collected dust into replaceable containers (32) connected in a sealed way to said collecting hopper

(30).

- the replaceable dust containers (32) suitable to be sealed when full of dust before their final disposal. elf propelled road milling machine according to any of the previous claims characterized in that it comprises movement means (41 , 42) changing the position of said suction-filtering unit (29).

6. Self propelled road milling machine according to the previous claim characterized in that said movement means are means for the lifting and lowering of said suction-filtering unit (29).

S 7. Self propelled road milling machine according to any of the claims 6 to 7 characterized in that said movement means are means to approach and move away said suction-filtering unit (29) to/from said self propelled road milling machine. 0 8. Self propelled road milling machine according to any of the previous claims 5 to 7 characterized in that said movement means (41 , 42) moving said suction-filtering unit (29) between the following positions:

- transport position

- working position 5 - bag replacing position

- access to the road milling machine.

9. Self propelled road milling machine according to the previous claims 5 to 8 characterized in that said movement means are two telescopic arms, one0 telescopic arm (41 ) performing a longitudinally movement and the other telescopic arm (42) performing a vertical movement.

10. Self propelled road milling machine according to any of the previous claims 4 to 9 characterized in that said replaceable dust containers (32) are bags,5 supported by an internal cage (37).

11. Self propelled road milling machine according to any of the previous claims 4 to 10 characterized in that said suction-filtering unit (29) includes a level probe (39) warning the operator that the replaceable dust container (32) is full.

12. Self propelled road milling machine according to any of the claims 4 to 11, characterised in that said continuous chamber (23) extends continuously from the milling drum area up to the discharge head (36), said continuous chamber (23) being formed by:

- sidewalls of the milling drum housing (7),

- rear mouldboard (8), - side plates (9a, 9b),

- a first chamber (21a) enclosing the first conveying device (5), said first chamber (21a) being formed by said side sealing means (17a, 17b),said flexible means (19a, 19b), top sealing mean (18) above the conveyor belt, and said first chamber (21a) being closed and sealed on its lower part by said conveyor belt, being further provided sealing junction flexible means (19a, 19b) on sliding contact with the upper part of the mobile rubber belt ring (13) of said conveying device, said junction being elastic.

- one or more secondary chambers (21b) enclosing secondary conveying device (6), each secondary chamber (21b) being formed by said side sealing means (17a, 17b), said flexible means (19a, 19b), said top sealing mean (18) above the conveyor belt and said secondary chamber (21b) being closed and sealed on its lower part by said conveyor belt, being further provided sealing junction flexible means (19a, 19b) on sliding contact with the upper part of the mobile rubber belt ring (13) of said conveying device, said junction being elastic

- at least sealing means (33a, 33b) and at least one sealing means (34) enclosing an intermediate area (22) being this area the discharge area of the first conveying device (5) and the charge area of the second conveying device (6), - two or more sets of sealing means (24) on the top end of the continuous chamber (23), said continuous chamber (23) being free from external air-channellings between said first chamber (21a) and said second chamber/s (21b), said sealing means (24) being flexible and overlapped one with the other, said sets of flexible sealing means (24) being kept in contact one with the other and with the flow (20) of the milled material by the depression induced by said suction device (25), said contact being elastic and sealing said chamber (23) to maintain it in depression on its whole by said suction device (25).

13. Self propelled road milling machine according to any of previous claims 4 to 12, characterised in that the joint between said first chamber (21a) and said secondary chamber/s (21 b) is an articulated sealed joint.

14. Self propelled road milling machine according to any of the previous claims 4 to 13, characterised in that said sealing means (24) are flexible flaps.

15. Self propelled road milling machine according to any of the previous claims 4 to 14, characterised in that a coarse dust pre-separator (44) is interposed between the suction point of the dust laden air and the inlet of the bag filter (29).

16. Self propelled road milling machine according to any of the previous claims 4 to 15, characterised in that the coarse dust pre-separator (44) is located over the loading conveyor (6) downstream the sealing device (24) to discharge the recovered dust onto the flow (20) of the milled material.