SUCTION SYSTEM FOR EFFICIENTLY SUCKING UP THE DUST OF A ROTATING ELECTRIC MACHINE IN A POLLUTED ENVIRONMENT

Abstract

The invention relates to a suction system (10) intended to suck up dust generated by a brush (1) rubbing against a rotary element (3) of a rotating electric machine without sucking up the surrounding air. For this purpose, the suction system comprises a gas-ejection device (20) comprising at least one slot (21) opening out around at least a portion of the lower end (12a) of a through housing (12) receiving a brush (1) or a brush holder (2) and around at least a portion of the opening (15) of a dust suction chamber (14).

This slot is further configured to direct a gas flow exiting through the at least one slot in a direction away from the opening of the suction chamber, thus forming an air curtain isolating the latter from the surrounding air.

Claims

1. A suction system (10) intended to suck up dust generated by a brush (1) rubbing against a rotary element (3) of a rotating electric machine without sucking up the surrounding air, the system comprising: a through housing (12) extending in a guiding direction (D1) and capable of receiving a brush (1) or a brush holder (2) in said guiding direction, a suction chamber (14) having an opening (15) intended to face the rotary element (3), said opening (15) extending over at least a portion of the periphery of a lower end (12a) of the housing intended to be positioned facing the rotary element (3), a gas-ejection device (20) comprising at least one slot opening out from the side of the lower end of the housing, the at least one slot (21, 21a-21f) extending around the lower end (12a) of the housing over at least a portion of the periphery of the latter and around at least a portion of the opening of the suction chamber, characterised in that the at least one slot is oriented in a direction away from the opening of the suction chamber to direct a gas flow exiting through the at least one slot in a direction (D2) away from the opening of the suction chamber.

2. The suction system (10) according to claim 1, characterised in that the at least one slot extends over the entire periphery of the lower end of the housing.

3. The suction system (10) according to claim 1, characterised in that: the at least one slot is defined by an interior lateral surface (210) and an exterior lateral surface (211) disposed facing each other, the at least one slot is configured so that, over the entire length of the at least one slot, in each plane perpendicular to the interior and exterior lateral surfaces of the at least one slot and parallel to a radial direction of the rotary element (3) passing through a central point of a lower opening (13) of the housing when the suction system is mounted on the electric machine, an angle formed between a direction parallel to the radial direction and a median slot direction is from 0 to 90-phi, optionally from 1 to 50-phi, this median slot direction being defined as a median straight line of two segments formed by the intersection of said plane with the interior and exterior lateral surfaces of the slot, phi designating an angle less than or equal to the angle between the direction parallel to the radial direction and the median direction of the slot.

4. The suction system (10) according to claim 1, characterised in that: the at least one slot is defined by an interior lateral surface (210) and an exterior lateral surface (211) disposed facing each other, and, in each plane perpendicular to the interior and exterior lateral surfaces of the at least one slot and parallel to a radial direction of the rotary element (3) passing through a central point of a lower opening (13) of the housing when the suction system is mounted on the electric machine: a first angle i is formed between a direction parallel to the radial direction and the interior lateral surface (210) of the at least one slot, a second angle e is formed between a direction parallel to the radial direction and the exterior lateral surface (211) of the at least one slot, and each of the first and second angles is, independently, from 0 to 90-phi, optionally from 0 to 45-phi, phi designating an angle less than or equal to each of the first and second angles.

5. The suction system (10) according to claim 1, characterised in that the at least one slot has a width of 0.1 to 20 mm.

6. The suction system (10) according to claim 1, characterised in that it comprises at least one of the following features: the at least one slot has a variable width along its length, at least two distinct slots have different widths.

7. The suction system (10) according to claim 6, characterised in that it comprises at least one of the following features: a portion of the at least one slot closest to a gas admission orifice (201) supplying the at least one slot is narrower than the rest of the at least one slot and/or than an adjacent slot, a portion of the at least one slot closest to a gas suction orifice (16) of the suction chamber (14) is wider than the rest of the at least one slot and/or than an adjacent slot.

8. The suction system (10) according to claim 1, characterised in that the air ejection device comprises at least two slots disposed in the extension of one another and in that the sum of the distances separating two adjacent slots is 0.1 to 5% of the sum of the lengths of the slots.

9. The suction system (10) according to claim 1, characterised in that the gas-ejection device comprises at least one gas admission orifice (201) in fluid communication with the at least one slot.

10. The suction system (10) according to claim 1, characterised in that the gas-ejection device (20) comprises a gas admission chamber (24) fluidly connected to the at least one slot and to at least one gas admission orifice (201).

11. The suction system (10) according to claim 10, wherein the admission chamber (24) is adjacent to the suction chamber (14) and extends, at least partly, along an exterior lateral wall (142) of the suction chamber and/or along an upper wall (144) of the suction chamber.

12. The suction system (10) according to claim 10, characterised in that the gas-ejection device (20) and the suction chamber (14) are separate parts assembled together.

13. The suction system (10) according to claim 1, characterised in that the gas-ejection device (20) is formed of at least two distinct portions assembled together, a portion defining an exterior lateral surface (211) of the at least one slot and the other portion defining an interior lateral surface of the at least one slot.

14. A method for sucking up dust generated by a brush rubbing against a rotary element of a rotating electric machine without sucking up the surrounding air by means of a suction system (10) according to claim 1, wherein, at least during the suction of gas through the suction chamber, the at least one slot of the suction system is supplied with a volume flow rate of gas sufficient to form a gas curtain isolating the opening of the suction chamber from the surrounding air.

15. The dust suction method according to claim 14, characterised in that said at least one slot is supplied with gas via a gas admission chamber connected to at least one gas admission orifice.

16. The dust suction method according to claim 15, characterised in that the gas pressure inside the admission chamber is greater than the gas pressure inside the suction chamber, optionally by at least 150 mbar.

17. The dust suction method according to claim 1, characterised in that the dust-laden gas contained in the suction chamber (14) is sucked up by means of a suction group (17) and at least a portion of the gas thus sucked up is used after passing through a filtration system (170) to supply the at least one slot (21, 21a-21f) of the suction system.

18. A rotating electric machine comprising at least one brush (1) rubbing against a rotary element (3) and equipped with at least one suction system (10) according to claim 1, said brush being received in the housing (12) of the suction system following the guiding direction (D1).

Description

DESCRIPTION OF THE FIGURES

[0052] The invention is now described with reference to the appended, non-limiting drawings, wherein:

[0053] FIG. 1 schematically shows in section in a plane (Ar, At) a suction system according to one embodiment of the invention.

[0054] FIG. 2 schematically shows the suction system of FIG. 1 in section in a plane (Ar, Aa) perpendicular to the plane (Ar, At).

[0055] FIG. 3 shows a bottom view of a suction system (in a plane (Aa, At)) according to another embodiment.

[0056] FIGS. 4A to 4C show sectional views of different slot configurations.

[0057] FIG. 5 shows a sectional view of another slot configuration.

[0058] FIGS. 6 to 9 show sectional views showing different relative positions of the suction and admission chambers.

[0059] FIG. 10 shows an exploded perspective view of a suction system according to one embodiment.

[0060] FIGS. 11 and 12 show the gas flows of a suction system according to one embodiment of the invention.

[0061] Substantially parallel means a direction parallel to or deviating by at most 20, or even by at most 10 or by at most 5 from a parallel direction.

Suction System

[0062] FIGS. 1-3 show a suction system 10 intended to suck up dust generated by a brush 1 intended to rub on a rotary element 3 of a rotating electric machine when it is mounted on the latter.

[0063] The rotary element 3 rotates in a direction of rotation represented by the arrow F1 in the figures. In the present description, the suction system being mounted on the rotating electric machine, upstream and downstream sides designate the sides of the suction system, in a plane perpendicular to the axis of rotation of the rotary element, through which a fixed point of the rotary element enters and exits, respectively, when it rotates. In the plane of FIGS. 1 to 3, the upstream and downstream sides therefore respectively designate the sides of the suction system located to the left and right of the brush 2.

[0064] The brush 1 is here held by a brush holder 2, generally called a brush holder cage. The brush 1 and its cage 2 are received in a through housing 12 of the suction system 10, this through housing 12 extending in a guiding direction D1. When the suction system 10 is mounted on a rotating machine, as shown in FIGS. 1 and 2, this guiding direction D1 can correspond to a radial direction Ar of the rotary element 3 passing through a central point C of the lower opening 13 of the housing. In the mounting position, the brush 1 is in contact with the rotary element 3 on the side of a lower end 12a of the housing. Typically, the brush 1 projects out of the housing 12 on the side of the lower opening 13 in the guiding direction D1.

[0065] In the figures, the axis Ar thus shows the radial direction of the rotary element of the rotating machine wherein the brush passing through the central point C is mounted, the axes Aa and At define a plane perpendicular to the axis Ar and correspond to perpendicular transverse directions, the axis Aa being parallel to the axis of rotation of the rotary element 3.

[0066] In a variant shown in FIG. 5, the guiding direction D1 of the brush (corresponding to the axis Z of FIG. 5) is inclined relative to the radial direction Ar in the plane (Ar, At) by an angle phi (), particularly downstream with respect to the rotation of the rotary element 3.

[0067] The suction system 10 also comprises a suction chamber 14 having an opening 15 located opposite the rotary element 3 in the mounting position of the suction system (FIG. 1, 2). This opening 15 extends over at least a portion of the periphery of the lower end 12a of the housing. In the example shown in FIGS. 1 and 2, the opening 15 extends over the entire periphery of the housing 12. In the example of FIG. 3, the opening 15, as well as the suction chamber 14, extend on a downstream side of the housing relative to the direction of rotation of the rotary element 3 (symbolized by the arrow F1 FIG. 3), and on the two adjacent lateral sides, thus forming a U shape (in the plane (Aa, At)) open upstream relative to the direction of rotation of the rotary element 3. The invention is however not limited by a particular shape of the suction chamber 14 and the opening 15, which could have not parallelepiped shapes as in the example, but rounded shapes (curved, oval or round) in the plane (Aa, At).

[0068] The housing 12 here has a parallelepiped shape corresponding to a typical shape of a brush or a brush-holder cage. The invention is however not limited to a particular shape of the housing provided that it can receive a brush or its cage, this shape being typically complementary to the shape of the brush or its cage. In an embodiment not shown, the housing 12 can be configured to receive more than one brush or more than one brush holder cage. The housing can then have as many guiding directions as there are brushes, these guiding directions being generally parallel to each other. It is also possible to provide several separate housings which are then surrounded at least partly by the opening of the suction chamber.

[0069] Generally, the suction chamber 14 is defined by at least one exterior lateral surface 140 and at least one interior lateral surface 141, which respectively form part of an exterior lateral wall 142 and an interior lateral wall 143. The interior lateral wall 143 is closest to the housing 12, the exterior lateral wall 142 is farthest from the housing 12. These lateral walls 142, 143 extend substantially parallel to the guiding direction D1 and are connected by an upper wall 144 on a side opposite the opening 15.

[0070] The interior lateral wall 143 can define the housing 12, as visible in FIGS. 1 and 2. As can also be seen in these figures, the exterior lateral wall 142, here its upstream and downstream sides visible in the view of the plane (Ar, At) (FIG. 2), can have a height, measured in the radial direction Ar, greater than the height of the interior lateral wall 143, in particular on the side of the lower end 12a of the housing, which allows to position it as close as possible to the rotary element 3. As shown in FIG. 5, the exterior lateral wall 142 (here its downstream side, visible in the view of the plane (Ar, At)) can further be inclined relative to the radial direction Ar so that the exterior lateral surface 140 forms an angle phi () with the radial direction Ar. Typically, this angle phi is from 0 to 25. In this case, the height of the exterior lateral wall 142 can be measured in the plane of the exterior lateral surface 140 in a direction defined by the intersection of the plane (Ar, At) with this exterior lateral surface 140. This inclination of an angle of the exterior lateral wall 140 allows to maintain the opening 15 of the suction chamber and the adjacent outlet orifice of the slot close to the rotary element 3, thus improving the efficiency of the gas curtain formed as well as the dust suction efficiency.

[0071] Generally speaking, the exterior lateral wall 142 can be inclined and/or its height can be increased on its upstream and/or downstream sides, in order to be positioned as close as possible to the rotary element 3 and to follow its curvature (see FIGS. 2 and 5).

[0072] The distance separating the rotary element 3 from the opening 15 of the suction chamber or from the outlet orifice of the slot(s) is typically 2 mm or more, for example 2 to 5 mm.

[0073] The invention is however not limited by a particular shape of the suction chamber 14 nor of its opening 15, provided that the latter allow evacuation of the gases sucked up through the opening 15, in particular via one or more suction orifices. In the example shown in FIG. 3, the opening 15 has a width (corresponding to the distance separating the interior 141 and exterior lateral surfaces 140 of the suction chamber 14) which varies on the periphery of the housing 12, with a width La on the downstream side of the opening larger on the side of the suction orifice 16 than the width la of the opening 15 on its lateral sides. For efficient dust evacuation, the opening 15 of the suction chamber is thus wider on the side where the wear dust of the brush is ejected when the rotary element rotates, that is to say on the side where the amount of dust ejected is the most significant.

[0074] The suction chamber 14 typically includes at least one suction orifice 16, here only one, for connection to a suction group 17 via a flexible or rigid pipe. This suction group 17 can be equipped with a filtration system 170. In the example, the suction orifice 16 is extended by a duct 16a made in one piece with the suction chamber 14 (FIG. 2). The suction orifice(s) 16 are typically located on the upper wall 144 of the suction chamber.

[0075] According to the invention, the suction system 10 has a gas-ejection device 20, generally air, comprising at least one slot 21 opening out on the side of the lower end 12a of the housing and extending around the lower end 12a of the housing over at least a portion of its periphery and around at least a portion of the opening 15 of the suction chamber, preferably over the entire periphery of the housing, as shown in FIG. 3.

[0076] In the example of FIG. 3, a plurality of slots 21a, 21b, 21c, 21d, 21e, 21f extend in the extension of each other (end to end), over the entire periphery of the lower end 12a, separated from each other by thin separations 22a, 22b, 22c, 22d, 22e, 22f. The invention is not limited to a particular number of slots. When two or more slots are present, each separation, or discontinuity, between two slots may have a length of 0.05 to 2 mm, advantageously 0.1 to 1.5 mm. When several discontinuities are present, they can be of the same length. In particular, it will be possible to define a percentage of discontinuities corresponding to the ratio of the total length of the discontinuities to the sum of the lengths of all the slots, which could be from 0.1% to 5%, advantageously from 0.5% to 1.5% or in any interval defined by two of these limits. These separations or discontinuities can advantageously be located in the immediate vicinity of the outlet orifice of the slots, and extend over the entire height of a slot or over a portion of this height (according to the definition given below).

[0077] According to the invention, the slot(s) are configured, in particular oriented, to direct a gas flow exiting through this or these slot(s) in a direction D2 away from the opening 15 of the suction chamber 14. These slots are thus oriented in a direction deviating from the opening of the suction chamber 14, in other words in a direction opposite to this opening 15. By definition, a slot is a narrow and long opening, more or less deep, in other words having a greater or lesser height.

[0078] The use of slot(s) having an orientation as previously described relative to the opening of the suction chamber to eject gas allows to create a curtain of gas (typically air) along the suction chamber, preferably over the entire periphery of the housing 12, allowing to isolate the suction chamber 14 from the surrounding air and the pollutants it contains. The orientation of the slots in a direction away from the opening 15 of the suction chamber, and therefore from the housing 12, avoids, or at least limits, suction by the suction chamber 14 of the gas ejected by the slot(s). This arrangement allows to effectively protect the suction system from a polluted surrounding atmosphere, as shown in the simulations presented below in the examples.

[0079] Typically, the gas-ejection device 20 may comprise at least one gas admission orifice 201 in fluid communication with the at least one slot 21 for connection to a gas admission system 23, via a flexible or rigid pipe. In the example, the gas admission orifice 201 is extended by a duct 202. In the example, the gas admission system 23 further comprises a gas source, here the surrounding air, a device for regulating the pressure or flow of injected gas 230 and a filtration system 231 for the injected gas. It may also be possible to return a portion or all of the air sucked up by the suction group 17 into the gas admission system 23, after passing through a filtration system 170 allowing to rid it of dust, as shown in FIG. 1. For this purpose, the filtration system 170 can be connected by one or more appropriate pipes directly to the gas admission system 23 or to the pipes connecting the latter to the at least one slot of the gas-ejection device 20.

[0080] The suction system 10 according to the invention can be produced in a single part, for example by 3D printing, or in several parts, as shown in FIG. 10. In this figure, the suction system 10 is formed of three parts 101, 102, 103. The part 101 comprises the gas admission orifice 201, the duct 202 connecting this orifice to the gas admission chamber 24 and at least a portion of the admission chamber 24. The duct 202 here has a pyramidal shape. The portion of the part 101 corresponding to the admission chamber 24 has the shape of a frame. The part 102 comprises the suction chamber 14 (and its opening 15), the suction orifice 16 and the duct 16a, also pyramidal in shape. Furthermore, the lower portion of the exterior lateral wall 142 of the suction chamber 14 forms the interior lateral surface 210 of the slots 21 or 21a-21f and a portion of the admission chamber 24.

[0081] The part 102 fits inside the part 101, the exterior lateral wall 142 of the suction chamber being positioned in airtight support against the interior lateral wall 243 of the admission chamber 24.

[0082] Finally, the part 103, in the shape of a frame, comprises the lower lateral wall 245 of the admission chamber and includes a wall 104 forming the exterior lateral surface 211 of the slots 21 or 21a-21f. The part 103 thus partially closes the admission chamber 24 and ensures the fixing of the three parts, for example via fixing screws 105 assembling the part 103 to the part 101.

[0083] Alternatively, the exterior lateral wall 242 of the admission chamber 24 of the part 101 could form the exterior lateral surface 211 of the slots 21 or 21a-21f. The parts 101 and 103 could then be mounted on existing parts 102. Note that parts 101 and 103 could be integral or form a single part.

[0084] At least one brush wear detection sensor can be integrated into the suction chamber and/or the admission chamber. In particular, this sensor will be positioned as close as possible to the lower end of the housing or in an upper portion thereof.

[0085] FIGS. 1 and 2 show the directions of the circulating flows when the rotary element 3 of the electric machine rotates in the direction of arrow F1. During this suction, a suction flow generated by the suction group 17 and symbolised by the arrows F2 sucks up the air and dust located in the immediate vicinity of the end of the brush rubbing against the rotary element 3 and evacuates them via the suction chamber 14, the orifice 16 and its duct 16a. Simultaneously, an air flow generated by the air admission system 23 is routed to the slots 21 via the admission orifice 201 and its duct 202 and the admission chamber 24. These air flows are symbolised by the arrows F3. They are directed in a direction away from the opening 15 of the suction chamber 14 and in particular in the plane (Ar, At) are further deviated towards the outside by the presence of the rotary element 3. These air flows F3 allow to deflect the air flows from the environment (symbolised by the arrows F4) in a direction opposite to the suction system 10 protecting the latter from pollutants possibly present in the environment. As shown in the examples presented below, the air curtain thus formed allows to avoid suction of the surrounding air without itself being sucked up.

Management System

[0086] It will also be possible to provide a management system 28 of the suction group 17 and the gas admission system 23 configured to control the volume flow rates and/or the pressures delivered by the suction group and the gas admission system.

[0087] This management system 28 may comprise calculation and transmission means such as a processor, for example a microprocessor, a microcontroller or the like. The calculation and transmission means can be programmed for: [0088] calculating pressure and/or volume flow rate setpoint values for the gas flows sucked up and ejected, and [0089] transmitting these setpoint values to corresponding adjustment means of the suction group and the admission system.

[0090] These setpoint values can in particular be calculated in order to maintain a volume flow rate of gas sufficient to form a gas curtain isolating the opening of the suction chamber from the surrounding air, advantageously to maintain a gas pressure inside the admission chamber higher than the gas pressure inside the suction chamber, especially with a particular pressure difference.

[0091] These adjustment means can be devices for regulating the pressure or a gas flow rate.

[0092] The management system 28 can also comprise monitoring means, which are in particular automated: [0093] of the suction group 17 and the admission system 23, for example detection of filter clogging or a pressure sensor (verification that there is no deviation from the setpoint value), and/or [0094] of the rotating electric machine, for example to monitor via sensors the temperature of the air surrounding the rotary elements, the wear of the brushes, the current passing through the brushes, the starting or stopping of the machine.

[0095] The management system 28 can thus be configured to control the starting and stopping of the suction group 17 and the admission system 23, simultaneously or not (for example stopping the suction system 15 minutes after the stopping the rotating machine then stopping the admission system 5 minutes later).

Slot Configurations

[0096] Different slot configurations allow to direct a gas flow exiting through a slot in the direction D2 away from the opening 15 of the suction chamber 14.

[0097] A slot outlet orifice 212 corresponding to the orifice through which a slot opens onto the side of the rotary element 3 and a slot inlet orifice 213 through which the gas enters inside the slot will also be defined.

[0098] Examples of possible configurations are described with reference to FIGS. 4A to 4C and 5. These embodiments apply both to a configuration having a single slot and to a configuration having two or more slots. Different slots may have different configurations. In particular, the different embodiments described below can be combined.

[0099] Generally speaking, each slot 21 is defined by an interior lateral surface 210 and an exterior lateral surface 211 disposed facing each other. The interior lateral surface 210 is closest to the housing 12, the exterior lateral surface 211 is furthest from the housing 12. In FIGS. 4A-4C and 5, the direction Z is parallel to the exterior lateral surface 140 of the suction chamber. The reference frame (Z, X) is in FIG. 5, inclined by an angle relative to the reference frame (Ar, At), in the plane of (Ar, At). In FIGS. 4A-4C, the reference frame (Z, X) is coincident with the reference frame (Ar, At). In the plane (Ar, Aa), the angle phi is generally zero, in other words, on its lateral sides (substantially parallel to the direction At), the exterior lateral surface 140 of the suction chamber is parallel to the radial direction Ar (as shown in FIG. 1).

[0100] The angles , i and e described below as well as the median direction Dm are defined in each plane perpendicular to the interior 210 and exterior 211 lateral surfaces and which is parallel to the radial direction Ar passing through the central point C (visible in FIGS. 1-3) of the lower opening of the housing when the suction system is mounted on the electric machine. The angle values given are absolute values.

[0101] An angle alpha () can then be defined, when the angle phi is zero, as the angle formed between the exterior lateral surface 140 of the suction chamber 14 and a median slot direction Dm, defined as a median straight line of two segments formed by the intersection of the previously defined plane with the interior 210 and exterior 211 lateral surfaces of the slot. This median direction Dm corresponds, in particular substantially, to the second direction D2 wherein the gas is ejected at the outlet of a slot. This median direction thus corresponds to the orientation of the slot.

[0102] It is also possible to define, when the angle phi is zero, angles beta i (i) and beta e (e), formed between the exterior lateral surface 140 of the suction chamber and, respectively, the interior lateral surface 210 of slot and the exterior lateral surface 211 of the slot.

[0103] The angle is thus comprised between the angles i and e. The angle can be from 0 to 90, advantageously from 1 to 45 or in any interval defined by two of these limits.

[0104] These angles , i and e can be equal (interior 210 and exterior 211 lateral surfaces of the slot being parallel), as shown in FIG. 4A or 5. The median direction Dm is then parallel to the lateral surfaces of the slot. The value of the angle =i=e can be from 0 to 90, advantageously from 1 to 45 or else from 15 to 45, advantageously from 20 to 45, more preferably from 20 to 40, or in any interval defined by two of these limits, preferably greater than or equal to 1, in particular non-zero.

[0105] The angles i and e can be different as shown in FIGS. 4B and 4C.

[0106] In FIG. 4B, the interior 210 and exterior 211 lateral surfaces of the slot converge towards the outlet orifice 212 of the slot, in other words, i>e. This allows to increase the speed of ejection of the gas at the outlet of the slot (compared to the configuration of FIG. 4A with the same volume flow rate of gas and the same width of the outlet orifice of the slot) and to improve the precision of gas ejection direction.

[0107] In FIG. 4C, the interior 210 and exterior 211 lateral surfaces of the slot diverge towards the outlet orifice 212 of the slot, in other words, i<e. The gas is then ejected with a lower speed (compared to the configurations of FIGS. 4A and 4B with the same volume flow rate of gas and the same width of the outlet orifice of the slot) but in a cone. This embodiment can generate turbulence outside the slot, values of angles and width of the outlet orifice 212 allowing to limit this turbulence can then be chosen, for example by means of simulations and/or of tests. For example, i=18 and e=29 can be chosen.

[0108] In all cases, e is at most 90.

[0109] FIG. 5 represents a configuration similar to FIG. 4A, wherein the wall 140 is inclined at an angle phi relative to the radial direction. The angles , i and e are then defined with respect to the radial direction of the rotary element, the angle being defined between the radial direction Ar and the median direction Dm, the angles i and e being defined between the radial direction Ar and, respectively, the interior lateral surface 210 of the slot and the exterior lateral surface 211 of the slot respectively.

[0110] Regardless of the configuration (FIG. 4A-4C, 5), each of the angles i and e can indifferently and independently be from 0 to 90, advantageously from 0 to 45, preferably from 1 to 45, more preferably from 5 to 30 or in any other interval defined by two of these limits, preferably non-zero. In a particular embodiment, the angle i can be from 5 to 90, advantageously from 5 to 45, preferably from 5 to 30, or in any other interval defined by two of these limits, and the angle e is then from 0 to 90, advantageously from 5 to 45, preferably from 5 to 30, or in any other interval defined by two of these limits, preferably non-zero.

[0111] Regardless of the configuration, in absolute value, the difference between the angles i and e is from 0 to 90, advantageously from 0 to 45 or from 0 to 30, more preferably from 0 to 10, or is in any interval defined by two of these limits. This can allow to control the guiding and exit speed of the ejected gas in order to limit the formation of turbulence at the outlet of the slot.

[0112] The values of the angles , i and e can be as described above at any point along the length of a slot. These angles may or may not be constant over the length of the slot(s), preferably constant. When a slot is not adjacent to the opening of the suction chamber, these angles can be defined in the reference frame (Ar, At) relative to a direction parallel to the radial direction Ar passing through the central point C of the opening 13 of the housing (the value of the angle is then subtracted from the values above).

[0113] The width of a slot, denoted If, can be defined as the distance separating its interior 210 and exterior 211 lateral surfaces at the outlet orifice 212 of the slot (it is therefore measured in a plane perpendicular to the median direction Dm). This width lf can be chosen depending on the gas pressure ejected by the slot and the gas ejection speed. Its value is typically from 0.1 to 20 mm, for example from 0.2 to 5 mm or in any interval comprised between two of these limits.

[0114] It may happen that a portion of the ejected gas is sucked up by the suction chamber, in particular if the distance between the outlet orifice 212 of the ejected gas and the opening 15 of the suction chamber is small and/or if the pressure difference between the volume formed by the suction chamber and the volume formed by the at least one slot is small. Furthermore, depending on the position of the gas admission orifice, the flow rate of ejected gas may not be sufficiently balanced over the entire length of the slot(s). In order to limit these effects, it is possible, in combination or not with each of the aforementioned angle values, to provide one or more of the following features: [0115] a variable slot width lf over the entire length of the slot and/or different adjacent slot widths, [0116] a minimum distance between the opening 15 of the suction chamber and the outlet orifice 212 of the slot.

[0117] The slot width lf can thus vary from one slot to another when several slots are present and/or along the length of one or more of the slots. This variation can be from 0% to 200% of a nominal slot width value, advantageously from 25% to 75%, advantageously from 40% to 60%, for example 50%. This nominal value of slot width can be from 0.1 to 20 mm and be chosen by simulations and/or tests. In particular, with reference to FIG. 3, the width lf of the downstream sides (parallel to the axis Aa) slots 21a and 21f located near a gas admission orifice in fluid communication with all the slots is less than the width lf of the slots 21c and 21d located near the gas suction orifice. When a slot has a variable width, this variation in width is preferably progressive over the entire length of the slot.

[0118] The width of the opening 15 of the suction chamber is typically 4 to 20 mm. The height H of a slot, measured along the median direction Dm defined above between the outlet orifice 212 of the slot and its inlet orifice 213, can advantageously be sufficiently large in order to orient the ejected gas in one main ejection direction corresponding to direction D2. For example, to properly guide the air, a minimum value of height of the slot can be 0.5 mm, a maximum value depending on the configuration of the system, in particular the position of the admission chamber when it is present. In the embodiments described, over its entire length, a slot extends in the direction Dm in a rectilinear direction between its inlet and outlet orifices. However, it could be considered that a slot extends in a slightly curved direction over at least a portion of its height and that it remains, for example, rectilinear in the immediate vicinity of its outlet orifice 212. The angles defined above are then relative to this rectilinear part. This rectilinear area in the immediate vicinity of the outlet orifice can extend over a height of at least 0.5 mm to ensure good guidance of the air.

[0119] The minimum distance between the opening 15 of the suction chamber and the outlet orifice 212 of the slot, in other words between the exterior lateral surface 140 of the suction chamber and the interior lateral surface 210 of the slot, at their opening/outlet orifice respectively, can be determined by means of simulations. For example, it could be from 0.1 to 10 mm, advantageously from 0.5 to 5 mm or in any interval defined by two of these limits.

[0120] In the embodiments shown, the opening of the at least one slot and the opening of the suction chamber are formed (in a plane perpendicular to the radial direction Ar) of rectilinear portions parallel to the sides of the housing and which extend over at least a portion of the periphery thereof. This configuration is simple to implement, however it could be possible to consider openings formed from non-rectilinear portions.

Admission Chamber

[0121] The slot(s) 21 of the gas-ejection device can be connected directly to the gas admission orifice 201. However, it is possible to advantageously provide an admission chamber 24 fluidly connected to the at least one slot and to one or more gas admission orifices. This admission chamber 24 can be fluidly connected directly to the inlet orifice 213 of the slot(s), as shown in FIGS. 8 and 9, or else be fluidly connected to the slot(s) 21 via a duct 26 (FIGS. 1-7).

[0122] Such an admission chamber 24 serves as a reservoir, which promotes maintaining a slight excess pressure relative to the pressure of the suction chamber 14. This excess pressure can be obtained by a suitable shape and dimension of the gas admission orifices 201. This overpressure is represented symbolically by the signs ++ in the figures.

[0123] In order to limit the size of the suction system and facilitate its assembly, the suction orifice 16 may be located on the side opposite the gas admission orifice 201.

[0124] The admission chamber 24 can be of any shape. It may have a section in the shape of a quadrilateral, for example with rounded corners, or of an oval or other shape. In particular, the shape of the admission chamber 24 can be variable on the periphery of the housing: the different shapes of the admission chambers 24 described with reference to the figures can thus be combined.

[0125] Generally, the admission chamber 24 is defined by at least one exterior lateral surface 240 and at least one interior lateral surface 241, which respectively form part of an exterior lateral wall 242 and an interior lateral wall 243. The interior lateral wall 243 is closest to the housing 12, the exterior lateral wall 242 is farthest from the housing 12. These lateral walls 242, 243 extend substantially parallel to the radial direction Ar and are connected by an upper wall 244 on a side opposite the slot and a lower wall 245 partially closes them in the lower portion. In the examples of FIGS. 1 to 3, the interior lateral wall 243 is formed by the exterior lateral wall 142 of the suction chamber 14, the upper walls 144 and 244 of the two chambers extending in the extension of one another (FIG. 1).

[0126] The admission chamber 24 can be positioned either laterally in relation to the suction chamber, as shown in FIGS. 1 to 3, the duct 26 can then be omitted, or else be disposed above the suction chamber (on the side opposite the opening of the suction chamber), as shown in FIGS. 6 and 7, requiring the presence of the duct 26. The duct 26 and the slot 21 can then either extend along the exterior lateral wall 142 of the suction chamber, over its entire height, as shown in FIG. 6, or else be formed in the thickness of this exterior lateral wall, as shown in FIG. 7. When the admission chamber 24 is positioned above the suction chamber 14 (in the radial direction Ar), it can partly define the housing 12, the other portion of the housing being defined by the suction chamber. The interior lateral walls 143 and 243 of the two chambers then extend in the extension of one another, in the radial direction Ar in the example of FIG. 6.

[0127] In yet another variant shown in FIG. 8, the admission chamber 24 can be integrated into the exterior lateral wall 142 of the suction chamber. The duct 26 may then be present or not, as shown.

[0128] In yet another variant shown in FIG. 9, the admission chamber 24 can be of oval or circular section and surround the suction chamber 14 in the manner of an air chamber. In this embodiment, the duct 26 is absent. This allows to further reduce the size of the gas-ejection device. The height of the admission chamber 24 can then be low.

[0129] The duct 26 thus connects the admission chamber 24 to the slot(s). It can have any shape in section along a plane containing the direction D1. It can thus be rectilinear, of constant section or not.

EXAMPLES

[0130] In the examples, the angle phi previously described and defined is zero.

Example 1

[0131] A suction system of the type shown in FIGS. 3 and 10 can have the dimensions collected in Table 1 (with reference to FIG. 3).

TABLE-US-00001 TABLE 1 Suction system Dimensions (mm) t: tangential dimension of the brush 12.5-50 a: axial dimension of the brush 10-40 T: tangential dimension of the cage .sup.t + 5 A: axial dimension of the cage a + 5 la: width of the opening of the suction chamber, 6-12 in the axial direction La: width of the opening of the suction chamber, 16-24 on the suction orifice side (approximately 2 la) La: width of the wall of the suction chamber, 0-La on the side opposite the suction orifice, ld: length of a discontinuity 0.05 to 2 n: number of discontinuities 2-10 % discontinuity = (ld n)/sum of slot lengths 0.1%-5%

Example 2Flow Simulations

[0132] Simulations were carried out on a suction system similar to that shown in FIGS. 3 and 10 using software developed by the company Ansys.

[0133] The simulations were implemented with a suction system having the following features: [0134] Brush of section 32 mm32 mm [0135] Slot height: 2 mm [0136] Slot: i=18.43; e=29.05, =23.74 [0137] Slot of constant width: 2 mm [0138] Vacuum in the suction chamber: 50 mbar [0139] Pressure in the admission chamber: 100 mbar

[0140] As shown by the flows in FIGS. 11 and 12, the air curtain generated pushes back the outside air so that the latter is not sucked up. Thus, any pollution present in the air surrounding the suction system is not sucked up. It is noted that a small portion of the air curtain generated is sucked up, but that this portion is too weak to destabilise the air curtain and take with it the surrounding air and its pollution.