EA001345B1 - Underwater excavation apparatus - Google Patents

Abstract

1. An underwater excavation apparatus (300a; 300b; 300c) comprising a hollow body (370a; 370b; 370c) having at least one pair of inlets (371a; 371b; 371c) and at least one outlet (373a; 373b; 373c), at least one pair of impellers (335a; 335b; 335c, 340a; 340b; 340c) rotatably mounted in the hollow body and means for driving the impellers (310a; 310b; 310c), wherein the driving means cause the impellers to be driven in contrary rotating directions and wherein the at least one pair of inlets is inclined at an angle to an axis along which the at least one outlet is provided. 2. An underwater excavation apparatus as claimed in claim 1, wherein the at least one pair of inlets (371a; 371b; 371c) are substantially symmetrically disposed around an axis extending from the outlet (373a; 373b; 373c). 3. An underwater excavation apparatus as claimed in any of claim 1 or 2, wherein the apparatus comprises a pair of horizontally opposed inlets (371c) communicating with a single outlet (373c), the outlet being disposed vertically downwards substantially midway between the two inlets, in use, such that the excavation apparatus is substantially "Y" shaped in profile. 4. An underwater excavation apparatus as claimed in any of claims 1 to 3, wherein the apparatus comprises a pair of inlets (371c) communicating with a single outlet (373c), the inlets being substantially symmetrically disposed around an axis extending from the outlet, the outlet being disposed vertically downwards substantially midway between the two. 5. An underwater excavation apparatus as claimed in either of claims 3 or 4, wherein at least one impeller (335c, 340c) is provided within each inlet. 6. An underwater excavation apparatus as claimed in any preceding claim, wherein the means for driving the/each impellers (335a; 335b; 335c, 340a; 340b; 340c) includes at least one drilling motor (310a; 310b; 310c). 7. An underwater excavation apparatus as claimed in claim 6, wherein the at least one drilling motor (310a; 310b; 310c) comprises a stator (21, 51) and a rotor (23, 53) rotatably mounted in the stator, the stator being provided with a rod recess 75 and an exhaust port (33, 63) the rotor being provided with a rotor channel (27, 57) and at least one channel (28, 58) for conducting motive fluid from the rotor channel to a chamber between the rotor and the stator, the rod recess being provided with a rod (71) which, in use, forms a seal between the stator and the rotor. 8. An underwater excavation apparatus as claimed in claim 7, wherein the rotor is provided with a seal (76) for engagement with the stator. 9. An underwater excavation apparatus as claimed in claim 8, wherein the seal (76) is made from a material selected from the group consisting of plastics materials, polyethylethylketone, metal, copper alloys and stainless steel. 10. An underwater excavation apparatus as claimed in any of claims 7 to 9, wherein the rod (71) is made from a material selected from the group consisting of plastics materials, polyethylethylketone, metal, copper alloys and stainless steel. 11. An underwater excavation apparatus as claimed in any of claims 7 and 10, wherein the stator (21, 51) is provided with two rod recesses (75) which are disposed opposite one another, and two exhaust-ports (33, 63) which are disposed opposite one another, each of the rod recesses being provided with a respective rod, the rotor having two seals (76) which are disposed opposite one another. 12. An underwater excavation apparatus as claimed in claim 6, wherein the at least one drilling motor (310a; 310b; 310c) comprises two drilling motors (20, 50) arranged with their respective rotors (23, 53) connected together each motor comprising a stator (21, 51) and a rotor (23, 53) rotatably mounted in the stator, the stator being provided with a rod recess (75) and an exhaust port (33, 53) the rotor being provided with a rotor channel (27, 57) and at least one channel (28, 58) for conducting motive fluid from the rotor channel to a chamber between the rotor and the stator, the rod recess being provided with a rod (71) which, in use, forms a seal between the stator and the rotor. 13. An underwater excavation apparatus as claimed in claim 12, wherein the drilling motors (20, 50) are connected in parallel or in series. 14. An underwater excavation apparatus as claimed in claims 12 or 13, wherein the drilling motors (20, 50) are arranged so that, in use, one drilling motor operates out of phase with the other. 15. An underwater excavation apparatus as claimed in any preceding claim, wherein the impellers (335a; 335b; 335c; 340a; 340b; 340c) are driven by means of a gearbox or by exploitation of the opposing reactive torque on a drive body of the motor. 16. An underwater excavation apparatus as claimed in claim 15, wherein the reactive torque upon the motor body is utilised, at least one impeller is connected to an output shaft of said motor, while at least one other impeller may be connected to the motor body. 17. An underwater excavation apparatus as claimed in claim 1, wherein the impellers are driven by a pair of motors (20, 50) operating in opposite directions. 18. An underwater excavation apparatus as claimed in any preceding claim, wherein the underwater excavation apparatus further comprises an agitator device having mechanical disturbance means and fluid flow disturbance means. 19. An underwater excavation apparatus as claimed in any preceding claim, wherein in use the underwater excavation apparatus is suspended from a surface vessel or mounted upon a sled of the type currently known for use in subsea excavation operations. 20. An underwater excavation apparatus as claimed in claim 4, wherein the outlets (373a; 373b; 373c) are each inclined substantially 45 degree from the axis extending from the outlet. 21. An underwater excavation apparatus comprising a hollow body (310a; 310b; 310c) having a pair of inlets (371a; 371b; 371c) communicating with an outlet (373a; 373b; 373c), at least one pair of impellers (335a; 335b; 335c, 340a; 340b; 340c) rotatably mounted in the hollow body and means for driving the impellers, the inlets being substantially symmetrically disposed around an axis extending from the outlet, wherein the inlets are not horizontally opposed to one another.

Description

This invention relates to an improved excavation device and, in particular, to an improved underwater excavation device.

Underwater excavation devices are known, for example, from UK patent CB 2240568 (firms of the Consortium Resources and others). An underwater excavation device is disclosed and described therein, including a hollow body having an inlet for withdrawing water and an outlet for discharging water. A water jet is mounted in the hollow housing to rotate the water suction through the inlet and discharging the water through the outlet. Water jets through nozzles at the water jet edges provide rotation of the water jet when water is supplied to these nozzles.

This rotation causes water to be sucked into the housing through the inlet and expelled from the housing as a stream through the outlet. This stream can be used to move matter on the seabed.

The underwater excavation device of the prior art has a number of problems and disadvantages, for example (a) low energy efficiency due to, for example, hydrodynamic restrictions imposed on the liquid stream, and therefore requires the use of extremely large and high-power pumps for actuating the system;

(b) the desire of the device to rotate in response to the rotation of the water jet;

(c) the complexity of controlling the device and its positioning.

The purpose of at least some of the distinguishing features of the present invention is to achieve the elimination or mitigation of one or more of the above problems from the prior art.

In accordance with a first distinguishing feature of the present invention, there is provided an underwater excavation device comprising a hollow body having at least one inlet and at least one outlet, at least one pair of impellers mounted with the possibility of rotation in a hollow body, and a means of driving impeller wheels.

In a preferred embodiment, the drive means during operation causes the impellers to rotate in opposite directions.

At least one inlet may be inclined at an angle to the axis on which the at least one outlet is located.

In a preferred embodiment, at least one pair of inlets is provided.

In a preferred embodiment, at least one pair of inlets is arranged substantially symmetrically with respect to an axis extending from the outlet.

In one embodiment, the underwater excavation device includes a pair of inlet openings directed in opposite directions horizontally that communicate with one outlet, and during operation, the outlet is directed vertically downward and is located essentially halfway between the two inlet openings . Therefore, the excavation device in this embodiment has a substantially T-shaped cross section.

In an alternative embodiment, the underwater excavation device includes a pair of inlets communicating with one outlet, and in operation, the inlets are arranged substantially symmetrically with respect to an axis extending from the outlet, and the outlet is directed vertically downward and is located essentially half the distance between the two inlets. Therefore, the excavation device in this embodiment has a substantially Υ-shaped cross section.

In a preferred embodiment, each of the outlet openings is spaced / deflected substantially at an angle of 45 ° from an axis extending from the outlet.

Each inlet may have at least one impeller located in / near it.

The drive means of these impellers / each impeller may include at least one drilling motor.

At least one drilling motor may include a stator and a rotor rotatably mounted in the stator, the stator having a groove for the drill rod and an outlet channel, the rotor has a rotor channel and at least one channel for passing the working fluid from the rotor channel into the chamber between the rotor and the stator, and in the groove for the drill rod there is a drill rod, which during operation forms a seal between the stator and the rotor.

Although not required, it is highly desirable that the rotor has a seal that makes contact with the stator.

In a preferred embodiment, the seal is made of a material that is selected from the group consisting of plastics, polyethylene ethyl ketone, metals, copper alloys and stainless steel.

In a preferred embodiment, the drill rod is made of a material that is selected from the group consisting of plastics, polyethylene ethyl ketone, metals, copper alloys and stainless steel.

In a preferred embodiment, the stator is provided with two opposed to each other grooves for drill rods and two opposed to each other outlet channels, each of the grooves for drill rods provided with a corresponding drill rod, and the rotor is provided with two seals that are opposite each other.

In a preferred embodiment, the drill motor may include two drill motors mounted so that their respective rotors are connected together, and each engine includes a stator and a rotor mounted in the stator so that it can rotate, and the stator has a groove for the drill rod and the outlet channel, the rotor has a rotor channel and at least one channel for passing the working fluid from the rotor channel into the chamber between the rotor and the stator, and in the groove for the drill rod there is a drill rod, which when the bot forms a seal between the stator and the rotor.

In a preferred embodiment, the drill motors are connected in parallel, although if desired, they can be connected in series.

In a preferred embodiment, the drilling motors are arranged so that, during operation, one drilling motor is in antiphase with the other. Thus, in a preferred embodiment, each drill motor has two chambers, and the chambers in the first drill motor are 90 ° out of phase with respect to the chambers in the second drill motor. Similarly, in an embodiment in which each drill motor has four chambers, a preferred embodiment is when the chambers in the first drill motor have a 45 ° phase shift relative to the chambers in the second drill motor. This arrangement helps ensure uniform output power and prevents the engine from stopping.

Alternatively, the at least one drilling motor may be a Moyno (Mosheai) motor, a hydraulic or suitably adapted electric motor.

The impellers can be driven by means of a gearbox or by using a counter reactive torque on the motor drive housing.

When reactive torque is used on the motor housing, at least one impeller wheel may be connected to the output shaft of said engine, at least one other impeller wheel may be connected to the motor housing.

Alternatively, these impellers can be driven by a pair of motors operating in opposite directions. In this case, these motors and impellers are balanced and the same.

The underwater excavation device may further include a cultivator having a means of mechanical disturbing action and means of disturbing action on the fluid flow.

The underwater excavation device during operation can be suspended from a surface vessel or mounted on a skid of the currently known type used in excavation operations from the seabed.

In accordance with a second distinguishing feature of the present invention, there is provided an underwater device including a hollow body having two inlet openings communicating with the outlet, at least one pair of impellers rotatably mounted in the hollow body, and blade drive means wheels, the inlet openings being arranged substantially symmetrically with respect to an axis extending from the outlet in which the inlet openings are not directed in opposite directions horizontally Is relative to one another.

Embodiments of the present invention will now be described only by way of example with reference to the accompanying drawings.

In FIG. 1 is a side cross-sectional view of a first embodiment of a soil excavation device according to the present invention;

in FIG. 2 shows a longitudinal sectional view of one embodiment of a drilling device for use in the excavation device of FIG. 1 according to the present invention;

FIG. 3A-3G are cross-sections along line AA of FIG. 2, showing a rotor of an engine in four different positions; and FIG. 4A-4G are cross-sections along line BB (BB) of FIG. 2, showing a rotor of an engine in four different positions;

in FIG. 5 is a side cross-sectional view of a second embodiment of a soil excavation device according to the present invention;

in FIG. 6 is a cross-sectional side view of a third embodiment of a soil excavation device according to the present invention.

With reference to FIG. 1 shows a first embodiment of an underwater excavation device 300a in accordance with the present invention. The device 300a includes a hollow body 370a formed by two inlet pipes 371a and an exhaust pipe 373a directed horizontally in opposite directions, a drive motor 310a and two impellers 335a, 340a.

The device 300a is additionally provided with guide baffles 302a in the hollow body 370a, suspension brackets 306a to enable the device 300a to be suspended from a surface vessel, guiding devices 386a for regulating fluid flow through the impellers 335a, 340a and the safety grilles 385a in order to prevent the ingress of solid substances that can damage the impellers 335a, 340a.

In this first embodiment, the drive motor 310a is located along a common axis directed horizontally to opposite sides of the intake pipes 371a and the impellers 335a, 340a. The output shaft 330a of the engine 310a is connected to the first impeller 335a, while the second impeller 340a is fixed to the shaft 342a, which is connected to the outer casing of the drive motor 310a through a swivel 325a.

During operation, a working fluid is supplied to the engine 310a through the fluid inlet 308a, which in turn causes the output shaft 330a and the impeller 335a to rotate. The reactive torque from this rotation causes the outer casing of the drive motor 310a to rotate in a direction opposite to the rotation direction of the output shaft 330a. This, in turn, results in the rotation of the second impeller wheel 340a. The impellers 335a, 340a are so designed that, despite their rotation in opposite directions, each of them provides equal power to the water flow into the hollow body 370a. Thus, the water drawn into the hollow body 370a is guided through the guide walls 302a through the outlet pipe 373a towards the seabed 400a.

In an alternative embodiment, the shaft 342a and the swivel 325a may be replaced by a second engine that directly drives the impeller 340a, as described above with reference to FIG. 5.

The excavation device 300a may be suspended, for example, from the bow or from the stern of a surface vessel, or through the drill shaft of a specialized vessel for work on the seabed.

In an alternative embodiment, device 300a may be located on a slide (not shown) of the type currently used for seabed operations. The excavation device 300a may further be provided with a cultivator (not shown) having a means of mechanical perturbation and a means of perturbation of the liquid flow.

In an advantageous embodiment, the engine 310 includes a drill motor, for example, disclosed in AO 95/19488, the contents of which are incorporated herein by reference.

The drill engine 310 may include a first engine 20 and a second engine 50.

The first motor 20 includes a stator 21 and a rotor 23. The upper part 22 of the rotor 23 passes through the upper bearing assembly 24, which includes a thrust bearing 26 and seals 25.

The working fluid, for example, water, drilling fluid or gas under pressure, flows downward through the channel 1 2 of the central adapter into the central channel 27 of the rotor, and then flows out through the drain channels 28 from the rotor into the working chambers 31 and 32.

After the engine travels, the working fluid flows through the exhaust channels 33 in the stator 21 and then flows downward through the annular channel surrounding the stator 21 and the drain channels 35 in the lower bearing assembly 34. Part 36 of the rotor 23 passes through the lower bearing assembly 34, which includes thrust bearing 37 and seals 38.

The ends of the stator 21 have slots, the teeth of which are engaged with the grooves in the upper bearing assembly 24 and in the lower bearing assembly 34, respectively, preventing rotation of the stator 21. The upper bearing assembly 24 and the lower bearing assembly 34 are snug against the outer tubular element 1 4 and are held from rotation by joint compression of threaded couplings 1 6 and 84.

A splined coupling 39 connects the splined end of the rotor 23 to the splined end of the rotor 53 of the second engine 50. The second motor 50 has a stator 51.

The upper part 52 of the rotor 53 passes through the upper bearing assembly 54. Between the upper bearing assembly 54 and the outer side of the upper part 52 of the rotor 53 there are seals 55. The rotor 53 moves in the thrust bearings 56 relative to the upper bearing assembly 54.

The working fluid from the Central rotor channel 27 flows into the Central channel 57 of the rotor, and then flows out through the drain channels 58 from the rotor to the working chambers 61 and 62. After the engine has been running, the working fluid flows through the exhaust channels 63 in the stator 51, and then flows down through an annular channel surrounding the stator 51 and drain channels 65 in the lower bearing assembly 64. A portion 66 of the rotor 53 passes through the lower bearing assembly 64. The rotor 53 moves in the thrust bearings 67 relative to the lower bearing assembly 64, and the seals 68 There is a joint seal between the rotor and the bearing assembly. The working fluid that flowed through the drain channels 35 in the lower bearing assembly 34 also flows down through the channels 79 in the upper bearing assembly 54, bypassing the stator 51, and through the drain channels 65 in the lower bearing assembly 64.

The upper bearing assembly 54 and the lower bearing assembly 64 fit snugly against the outer tubular member 18 and are prevented from rotating by jointly compressing the threaded sleeve 84 and the lower threaded sleeve (not shown).

In FIG. 2A-2G and 3A-3G illustrate a typical duty cycle of the first and second engines, respectively 20 and 50, and show the position of two engines relative to each other at different points in time of the cycle. For example, in FIG. 2B shows the exhaust stroke for the first engine 20, while in FIG. 3B, corresponding to the same moment in time, the driving cycle for the second engine 50 is shown.

As shown in FIG. 2A, the working fluid flowing through the channels 28 of the rotor drain enters the working chambers 31 and 32. As can be seen from FIG. 2B, due to the geometry of the chambers (which will be discussed below) and the action of the resulting forces, the working fluid moves the rotor in a clockwise direction. The working chamber 31 is sealed at one end by a rotating column of the drill rod 71, which abuts against the outer surface 72 of the rotor 23 and part 74 of the groove 75 for the drill rod.

At the other end of the working chamber 31, the seal 76 on the cam 77 of the rotor 23 is in contact with the inner surface of the stator 21, providing a seal.

As shown in FIG. 2B, rotor 23 has moved to a point close to the end of the propulsion stroke.

As shown in FIG. 2B, at this point in the engine’s duty cycle, the fluid begins to flow out through the exhaust channels 33.

As shown in FIG. 2G, rotary drill strings 71 and seals 76 isolated the working chambers, and the working fluids flowing into them rotate the rotor 23 until the seal 76 again passes past the outlet channels 33.

The second engine 50 functions in the same way as the first engine 20, but in the preferred embodiment shown in FIG. 3A-3G, these two engines have a phase shift of 90 ° so that at the moment when one engine releases the working fluid, the other provides power.

In one embodiment, the seals 76 are made of polyethylene ethyl ketone (PEEK) (PEEK). The rotary rods of 71 drill strings are also made of PEEK. In a preferred embodiment, the rotors (23, 25) and stators (21, 51) are made of corrosion-resistant materials, for example, stainless steel.

When the seal 76 in the first engine 20 rotates past the exhaust channel 33 during rotation, the working fluid that caused the rotation exits and then flows down through the channels 79 past the exhaust channels 63 and the drain channels 65.

It should be understood that although in the disclosed embodiment, the drill motor 310 includes two motors 20, 50, with appropriate development, the drill motor 310 may include only one engine 20 or 50.

Now, with reference to FIG. 5, a second embodiment of an underwater excavation device 300b is shown in accordance with the present invention. As in the device 300a, its nodes are indicated by numbers that were used to indicate the nodes of the device 300a of FIG. 1, with the exception of those that have a subscript b instead of a.

The device 300b differs from the device 300a in that the shaft 342a and the swivel 325a are replaced by a second motor 310'b and a T-shaped coupling 326b. Thus, in this embodiment, the impellers 335b, 340b are driven by respective engines 310b, 310'b. When operating on engines 310b, 310'b, the working fluid is supplied through the fluid inlet 308b and the T-shaped coupling 326b.

Now, with reference to FIG. 6, a second embodiment of an underwater excavation device 300b in accordance with the present invention is shown. As in the device 300b, its nodes are indicated by numbers that were used to refer to the nodes of the device 300b of FIG. 5, except for those that have a subscript in instead of b.

The device 300b has differences from the device 300b, in that while the inlet openings 371b are directed horizontally in opposite directions in the 300b device, the inlet openings 300 are arranged substantially symmetrically about an axis extending from the outlet 373b, such that the device 300b is substantially имеет-shaped. Therefore, this embodiment has a 326 shaped sleeve 326b.

The description of the above embodiments of the invention is given only through exemplary options, which does not imply any restrictions on the scope of patent claims for this invention. In particular, it should be understood that the drill motor 310 is suitable for use in any of the disclosed embodiments.

Claims (21)

CLAIM 1. An underwater device (300a; 300b; 300c) for excavation, including a hollow body (370a; 370b; 370c) having at least one pair of inlets (371a; 371b; 371c) and at least one outlet (373a; 373b; 373c), at least one pair of impeller wheels (335a; 335b; 335v, 340a; 340b; 340c) mounted rotatably in the hollow body, and the means for driving the impellers (310a; 310b ; 310c), in which the drive means causes the impellers to rotate in opposite directions, and in which at least one pair of inlet openings tilts nen at an angle to the axis of at least one outlet. 2. The underwater excavation device according to claim 1, in which at least one pair of inlet openings (371a; 371b; 371c) is located substantially symmetrically with respect to the axis extending from the outlet (373a; 373b; 373c). 3. An underwater excavation device according to any one of claims 1 or 2, wherein the device includes two horizontally inlet openings (371c) that communicate with one outlet (373c), and this outlet is directed vertically down and located essentially halfway between the two inlet openings so that the excavation device has a substantially Υ-shape on the side. 4. An underwater excavation device according to any one of claims 1 to 3, in which the device includes two inlets (371c) that communicate with one outlet (373c), the inlets being arranged substantially symmetrically with respect to the axis, extending from the outlet, the outlet is directed vertically downward and is located substantially halfway between the two openings. 5. Underwater excavation device according to any one of claims 3 or 4, in which at least one impeller is located in each inlet (335v, 340v). 6. An underwater excavation device according to any one of the preceding paragraphs, wherein the impeller drive means (335a; 335b; 335v, 340a; 340b; 340c) includes at least one drilling motor (310a; 310b; 310c). 7. The underwater excavation device according to claim 6, in which at least one drilling motor (310a; 310b; 310c) includes a stator (21, 51) and a rotor (23, 53) installed in the stator with the possibility of rotation, the stator has a groove 75 for the drill rod and the exhaust channel (33, 63), the rotor has a channel (27, 57) the rotor and at least one channel (28, 58) to pass the working fluid from the rotor channel into the chamber between the rotor and the stator, in the groove for the drill rod there is a drill rod (71), which during operation forms a seal between the stator and the rotor. 8. Underwater excavation device according to claim 7, in which the rotor has a seal (76) to ensure contact with the stator. 9. An underwater excavation device according to claim 8, in which the seal (76) is made of a material selected from the group including plastics, polyethylene ethyl ketone, metals, copper alloys and stainless steel. 1 0. Underwater excavation device according to any one of claims 7 to 9, in which the drill rod (71) is made of a material selected from the group including plastics, polyethylene ethyl ketone, metals, copper alloys and stainless steel. 11. Underwater excavation device according to any one of paragraphs.7 and 10, in which the stator (21, 51) has two grooves (75) for drill rods, which are located opposite each other, and two outlet channels (33, 63), which are located opposite each other, and in each of these grooves for drill rods there is a corresponding drill rod, and the rotor has two seals (76), which are located opposite each other. 1 2. An underwater excavation device according to claim 6, in which this at least one drilling engine (310a; 310b; 310c) includes two drilling engines (20, 50) installed so that their respective rotors (23 , 53) are connected together, and each motor includes a stator (21, 51) and a rotor (23, 53) mounted rotatably in the stator, the stator having a groove (75) for the drill rod and an exhaust channel (33, 53 ), the rotor has a channel (27, 57) of the rotor and at least one channel (28, 58) for passing the working fluid from the channel of the rotor into the chamber between the rotor and the stator, in the groove for the drill rod there is a drill rod (71), which during operation forms a seal between the stator and the rotor. 1 3. Underwater excavation device according to claim 12, in which the drilling motors (20, 50) are connected in parallel or in series. 1 4. An underwater excavation device according to claim 1 2 or 1 3, in which the drilling engines (20, 50) are arranged so that during operation one drilling engine operates in antiphase with the other. 1 5. Underwater excavation device according to any one of the preceding paragraphs, in which the impellers (335a; 335b; 335v, 340a; 340b; 340c) are driven by a gearbox or by using a counter reactive torque on the motor drive housing. 16. The underwater excavation device according to clause 15, which uses reactive torque on the engine housing, at least one impeller wheel is connected to the output shaft of the specified engine, while at least one other impeller wheel can be connected with engine housing. 17. The underwater excavation device according to claim 1, in which the impellers are driven by two engines (20, 50) operating in opposite directions. 18. Underwater excavation device according to any one of the preceding paragraphs, in which the underwater excavation device further includes a cultivator having means of mechanical disturbing action and means of disturbing influence on the fluid flow. 19. Underwater excavation device according to any one of the preceding paragraphs, in which during operation the underwater excavation device is suspended from a surface vessel or mounted on a slide of a known type used in excavation operations from the seabed. 20. The underwater excavation device according to claim 4, in which each of the outlet openings (373 a; 373b; 373c) is inclined substantially 45 ° with respect to an axis extending from the outlet. 21. An underwater excavation device including a hollow body (310a; 310b; 31 0c) having two inlet openings (371a; 371b; 371c) in communication with the outlet (373a; 373b; 373c), at least one pair of blade wheels (335a; 335b; 335v, 340a; 340b; 340c) mounted rotatably in the hollow body, and impeller drive means, the inlet openings being arranged substantially symmetrically with respect to an axis extending from the outlet in which the inlet openings not directed in opposite directions horizontally relative about each other.