WO2013190417A1

WO2013190417A1 - An apparatus for circulating a cooling liquid

Info

Publication number: WO2013190417A1
Application number: PCT/IB2013/054602
Authority: WO
Inventors: Vincenzo Rossiello
Original assignee: Vincenzo Rossiello
Priority date: 2012-06-20
Filing date: 2013-06-04
Publication date: 2013-12-27
Also published as: ITMO20120162A1; EP2864605A1; EP2864605B1

Abstract

An apparatus comprises: - a pump impeller (2) for circulating a cooling liquid in an engine, - a driving device (4) for driving the pump impeller (2), - a conduit for conveying exhaust gases produced by the engine towards the driving device (4), so that the exhaust gases move a rotor (5) of the driving device (4); the driving device (4) comprises a plurality of vanes (7), each vane (7) of said plurality protruding from the rotor (5) by an amount which varies as the rotor (5) rotates.

Description

DESCRIPTION

AN APPARATUS FOR CIRCULATING A COOLING LIQUID

The invention relates to an apparatus for circulating a liquid in a cooling circuit, in particular for cooling an engine. The engine can be mounted onboard a motor car, another motor vehicle or an industrial or commercial vehicle. Alternatively, the engine can be destined for installation in a fixed station, for example for industrial uses.

The liquid which is circulated by the apparatus of the invention can be water, with possibly an additive of one or more additional substances. Previously it has been proposed to exploit the energy contained in the discharge gases emitted by an engine in order to circulate the cooling liquid destined for cooling the engine.

For example, the Japanese patent application no. JP 09-088595 describes a water-cooling apparatus comprising a pump for circulating the water internally of the engine and a gas turbine apt to actuate the pump. The gas turbine comprises an impeller which is activated in rotation by the exhaust gases, so as to rotate the pump impeller in turn.

Apparatus of the type described in JP 09-088595 have however the drawback that when the engine is rotating at a number of revolutions that is lower than a certain limit value, the exhaust gases are not able to move the impeller of the turbine and thus circulate the cooling liquid internally of the engine. When the rotation velocity of the motor is low, for example when the motor is functioning at minimum regime, the exhaust gases possess a relatively low kinetic energy, which is not sufficient to overcome the resistance that the turbine impeller produces when attempts are made to drive it in rotation. The exhaust gases thus exit through the escape channels defined between two consecutive vanes of the turbine impeller and leave the turbine without having moved the impeller thereof. Consequently the cooling liquid is not circulated and the temperature internally of the engine increases.

This can be dangerous for the functioning of the engine, especially during the summer season and in intense traffic conditions, when a vehicle might remain stationary in the sunlight with the engine running and in a traffic gridlock with other vehicles, even for relatively long times.

An aim of the invention is to improve the apparatuses for circulating a cooling liquid so as to cool an engine.

A further aim is to provide an apparatus which is able to circulate a cooling liquid in an engine, even when the engine functions at a relatively low number of revolutions.

A further aim is to reduce the risks that an engine can be damaged because excessive temperatures have been reached internally thereof. According to the invention, it is provided an apparatus comprising:

a pump impeller for circulating a cooling liquid in an engine, a driving device for driving the pump impeller,

a conduit for conveying exhaust gases produced by the engine towards the driving device, so that the exhaust gases move a rotor of the driving device,

characterized in that the driving device comprises a plurality of vanes, each vane of said plurality projecting from the rotor by an amount which varies as the rotor rotates.

In the invention, it is possible to effectively cool the engine even when it is rotating a relatively low rotation velocity. Thanks to the vanes projecting from the rotor by a quantity which varies while the rotor rotates, it is possible to ensure than a substantially closed chamber is defined between two consecutive vanes. This prevents the exhaust gases from finding escape routes and evacuating the chamber without driving the rotor in rotation.

The exhaust gases transfer kinetic energy to the vanes which drives the rotor in rotation, which consequently drives the pump impeller in rotation, which circulates the cooling liquid in the engine.

The invention can be better understood and actuated with reference to the accompanying drawings, which illustrate an exemplifying and non-limiting embodiment thereof, in which:

figure 1 is an exploded view showing the components of an apparatus for circulating a cooling liquid internally of an engine;

figure 2 is a perspective view of the apparatus of figure 1 , in an assembled configuration;

figure 3 is a view as in figure 2, partially sectioned to show the internal components of the apparatus;

figure 4 is a perspective view showing a rotor of the apparatus of figure 1 ; figure 5 is a perspective view showing a housing element apt to house the rotor of figure 4;

figure 6 is a perspective view showing a vane apt to be mounted on the rotor of figure 4;

figure 7 is a perspective view showing a casing of the apparatus of figure 1 ;

figure 8 is a perspective view showing a closing element for closing the casing of figure 7;

figure 9 is a perspective view showing a rear portion of the apparatus of figure 1 .

Figure 1 shows the components of an apparatus 1 for circulating a cooling liquid, in particular water, in a cooling circuit apt to cool an engine, in particular an internal combustion engine.

The apparatus 1 comprises a pump, for example a centrifugal pump, provided with an impeller 2 for circulating the cooling liquid in the cooling circuit.

The apparatus 1 further comprises a driving device 4, shown in figure 3, for actuating the impeller 2 of the pump in rotation so as to circulate the cooling liquid in the cooling circuit.

The driving device 4 comprises a rotor 5, shown in figure 3, which can be driven in rotation by the exhaust gases of the engine to drive the pump impeller 2 in rotation.

In particular, the rotor 5 can be fixed with respect to a shaft 6, for example thanks to a tab that prevents the rotor 5 from rotating with respect to the shaft 6. The rotor 5 can also be manufactured solidly with the shaft 6. The pump impeller 2 can also be mounted on the shaft 6. In this way, when the rotor 5 rotates, the shaft 6 is driven in rotation, and the impeller 2 in turn. By doing this, the cooling liquid is circulated to cool the engine.

In an alternative version, not illustrated, the impeller 2 might not be mounted on the shaft of the rotor 5. In particular, the impeller 2 might be mounted on a coaxial shaft with respect to the shaft 6 of the rotor 5, but distinct therefrom. The impeller 2 might also be mounted on a shaft that is not coaxial with the shaft 6 of the rotor 5. In any case, the rotor 5 is coupled to the impeller 2 so that as the rotor 5 rotates the impeller 2 is also moved.

The rotor 5 has a body, which in the illustrated example is profiled substantially as a cylinder extending along a longitudinal axis Y, shown in figure 4. In the illustrated example, the longitudinal axis Y coincides with the axis of the shaft 6.

A plurality of grooves 8 is fashioned on the rotor 5 body, visible for example in figure 4. Each groove 8 extends parallel to the longitudinal axis Y. The grooves 8 can be angularly equidistanced about the longitudinal axis Y. In the illustrated example, six grooves 8 are included, arranged at reciprocal angles of 60° , but a number different tosix might be provided. The driving device 4 comprises a plurality of vanes 7, one of which is shown in figure 6. Each vane 7 engages in a groove 8 of the rotor 5, in particular is partially housed internally of a groove 8. Each vane 7 can have a head surface 9, delimited for example by a substantially straight profile. A portion of base 10 of each vane 7, opposite the head surface 9, apt to be received in the corresponding groove 8. The base portion 10 can be delimited by a curved profile.

Each vane 7 is received in the corresponding groove 8 without interposing intermediate coupling elements, in particular without interposing elastic elements. Each impeller 7 is received in the corresponding groove 8 with a small degree of play, so that the vane 7 can slide radially internally of the groove 8. The groove 8 guides the vane 7 while the vane 7 moves radially.

The rotor 5 is rotatably mounted internally of a housing element 1 1 , illustrated in detail in figure 5. A seat 12 is afforded internally of the housing element 1 1 , which seat 12 is apt to accommodate the rotor 5 and the vanes 7. The seat 12, which can be for example shaped as a cylindrical cavity, extends along a main axis Z.

The seat 12 can have a dimension along the main axis Z that is equal to the length of the vanes 7.

The housing element 1 1 is further provided with a through-hole 13, through which the shaft 6 passes.

The through-hole 13 can be afforded in a transversal wall of the housing element 1 1 , which extends transversally of the main axis Z. In the illustrated example, a bushing 14 is mounted in the through-hole 13, the shaft 6 being rotatably supported internally of the bushing 14. The through-hole 13 is coaxial to the longitudinal axis Y, i.e. to a geometric axis of the shaft 6 and the rotor 5.

As shown in figure 5, the longitudinal axis Y, i.e. the geometrical axis of the shaft 6 and the rotor 5, does not coincide with the main axis Z, i.e. with the axis of the seat 12. The longitudinal axis Y is located at a distance D from the main axis Z. The rotor 5 is therefore arranged in an offset position internally of the seat 12, as shown in figure 3.

The housing element 1 1 is delimited by an external lateral surface 15, shown in figure 5, which can be substantially cylindrical. In the illustrated example, the external lateral surface 15 is coaxial to the longitudinal axis Y.

The housing element 1 1 is received internally of a casing 3 shown in figure 7. A recess 1 6 is afforded in the casing 3 apt to house the housing element 1 1 and the components received internally of the housing element

1 1 . The recess 1 6, which can be substantially cylindrical in shape, has a geometrical axis coinciding with the longitudinal axis Y.

The recess 1 6 has a diameter that is substantially equal to the diameter of the external lateral surface 15 of the housing element 1 1 , so that the recess 1 6 can stably house the housing element 1 1 .

A positioning hole 18, shown in figure 7, can be afforded in the casing 3, which hole 18 is apt to receive a pin, not illustrated, which engages both with the casing 3 and with the housing element 1 1 . The pin acts as a positioning means for ensuring that the housing element 1 1 is mounted in a predefined angular position with respect to the casing 3.

The casing 3 is further provided with a flange 17, provided for example with a plurality of fastening holes 19. The apparatus 1 can be fastened to a desired support structure through the flange 17 and the fastening holes 19, for example to the cylinder block which is to be cooled. However, the apparatus 1 could also be fixed to a different structure from the engine block; for example it could be fixed to any desired point of the frame of the vehicle on which the engine is installed.

As shown in figures 1 and 8, the apparatus 1 further comprises a closing element 20 apt to close the casing 3 transversally on the opposite side of the impeller 2. The closing element 20 is provided with a plurality of holes 21 which is apt to receive respective fastening elements 22, for example screws, for fastening the closing element 20 to the casing 3. The screws 22 engage in corresponding threaded holes 23 afforded on the casing 3. The closing element 20 is provided with an opening 24, having for example a circular hole profile, in which a further bushing 25 can be accommodated, shown in figure 1 , apt to rotatably support the shaft 6.

The opening 24 has a geometrical axis coinciding with the longitudinal axis Y. The further bushing 25 extends about the longitudinal axis Y.

The shaft 6 thus has a first end that is rotatably supported by the housing element 1 1 , through the bushing 14. A second end of the shaft 6 is, instead, rotatably supported by the closing element 20, through the further bushing 25. Apart from partially closing the casing 3, the closing element 20 therefore also has the function of supporting the shaft 6 in a centred position with respect to the casing 3.

In a version that is not illustrated, in place of the bushing 14 and the further bushing 25, different support elements could be used, for example roller bearings.

The apparatus 1 can further comprise a cover 26, shown in figure 1 , apt to engage with the closing element 20 for closing the opening 24. The cover 26 can be removably fixed to the closing element 20 by threaded elements apt to engage in respective anchoring holes 27 provided in the closing element 20.

A greasing hole 28, shown in figure 7, can be afforded in the casing 3, through which a lubricating substance, especially grease, can be introduced internally of the casing 3 such as to lubricate the bushing 14. The greasing hole 28 is apt to be aligned with a further greasing hole 29, shown in figure 5, afforded in the housing element 1 1 . The further greasing hole 29 communicates with a greasing hole, not illustrated, made in the bushing 14, through which the lubricating substance can reach the shaft 6.

The greasing hole 28, the further greasing hole 29 and the greasing hole not illustrated afforded in the bushing 14 therefore make it possible to periodically send there-through a lubricating substance to the interface between the bushing 14 and the shaft 6, which enables minimizing the friction between the shaft 6 and the bushing 14.

The covering element 20 is similarly provided with a lubricating hole 30, shown in figure 8, through which a lubricating substance can be supplied, especially grease, towards the further bushing 25. The lubricating hole 30 communicates with a greasing hole provided in the further bushing 25 periodically to send the lubricating substance to the interface between the further bushing 25 and the shaft 6.

The rotor 5 is activated in rotation about the longitudinal axis Y thanks to the exhaust gases generated following the combustion taking place in the engine which the apparatus 1 is to cool.

For this purpose, a conduit (not illustrated) is provided to convey the exhaust fumes internally of the apparatus 1 . The conduit can be fastened to the apparatus 1 so as to open into an inlet hole 33, shown in figures 3 and 7, provided on the casing 3. The inlet hole 33 passes through the thickness of the casing 3.

A flat surface 36, shown in figure 5, is afforded on the external lateral surface 15 of the housing element 1 1 , which flat surface 36 is apt to be arranged in a position facing the inlet hole 33. An entry hole 35 opens on the flat surface 36, passing through the thickness of the housing element 1 1 .

When the housing element 1 1 is mounted internally of the casing 3, as shown in figure 3, the entry hole 35 is arranged in a position that is such as to communicate with the inlet hole 33, for example in a position about coaxial with the inlet hole 33.

A chamber 34 is defined between the flat surface 36 of the housing element 1 1 and the internal surface of the casing 3, shown in figure 3, which chamber 34 communicates with both the inlet hole 33 and with the entry hole 35. The exhaust gases pass from the chamber 34 to the seat 12 of the housing element 1 1 , through the entry hole 35, so as to rotate the rotor 5 about the longitudinal axis Y, as will be more fully described in the following.

One or more exit holes 37, shown in figure 5, are afforded in the housing element 1 1 , through which exit holes 37 the exhaust gases can exit the housing element 1 1 after having moved the rotor 5. The exit holes 37 can be aligned to one another along a line that is parallel to the longitudinal axis Y. In the illustrated example, three exit holes 37 are included, but the number of exit holes 37 can be freely selected or can be in a different number to three.

One or more further exit holes 41 , shown in figure 7, are afforded through the thickness of the casing 3, which exit holes 41 are apt to be set in communication with the exit holes 37 of the housing element 1 1 . For example, the further exit holes 41 can be operatively positioned at the exit holes 37. The exhaust gases in arrival from the housing element 1 1 can exit the casing 3 via the further exit holes 41 , after having moved the rotor 5.

An exhaust manifold 32 is connected to the casing 3, in particular in proximity of the further exit holes 41 , to convey the exiting exhaust gases from the apparatus 1 towards the external environment.

As already mentioned herein above, the impeller 2 is supported by an end of the shaft 6 opposite the further end of the shaft 6 supported by the closing element 20. The impeller 2 cooperates with a profiled surface 42 afforded in a portion of the casing 3 opposite a further portion of the casing 3 which houses the housing element 1 1 , transversally to the longitudinal axis Y. The profiled surface 42, shown in figure 9, partially defines the stator of the pump which circulates the cooling liquid in the engine.

In a case where the apparatus 1 is fastened to the engine cylinder block, the impeller 2 is housed internally of the engine cylinder block. The engine cylinder block, in this case, defines the stator of the pump, together with the profiled surface 42.

The impeller 2, which is of known type, receives the cooling liquid in a central region thereof via an inlet hole afforded for example in the engine cylinder block. The impeller 2 processes the cooling liquid and sends it tangentially towards an exit hole, also afforded for example in the engine block.

Seal means are interposed between the impeller 2 and the rotor 5, for preventing the cooling liquid from penetrating internally of the housing element 1 1 and mixing with the exhaust gases. The seal means can comprise a mechanical seal 31 , shown in figure 1 , which is apt to be supported by the shaft 6.

The mechanical seal 31 can be provided with a mobile part, which rotates solidly with the shaft 6, and a fixed part, mounted internally of the housing element 1 1 .

When the apparatus 1 is in an assembled configuration, the housing element 1 1 is mounted internally of the casing 3 in a fixed position with respect to the casing 3.

The rotor 5 is mounted internally of the housing element 1 1 , so as to be able to rotate with respect to the housing element 1 1 . In particular, the rotor 5 is arranged in an offset position internally of the seat 12. In fact, the longitudinal axis Y of the rotor 5 is arranged at a distance D from the main axis Z of the seat 12.

The position of the longitudinal axis Y and the main axis Z is such that the distance between the external lateral surface 15 of the rotor 5 and the internal lateral surface of the seat 12 is at a maximum in the zone of the housing element 1 1 in which the exit holes 37 are afforded. The distance between the external lateral surface 15 of the rotor 5 and the internal lateral surface of the seat 12 is, on the other hand, at a minimum thereof in a region of the housing element 1 1 about diametrically opposite to the zone in which the exit holes 37 are afforded. In this region, the rotor 5 can be in contact, or nearly so, with the internal lateral surface of the seat 12. While the rotor 5 rotates, the vanes 7 each housed in a corresponding seat 8 are also driven in rotation. The vanes 7 are pushed out of the respective seats 8 by centrifugal force. However, the vanes 7 cannot completely exit from the respective seats 8. The maximum quantity the vanes 7 can project from the respective seats 8 is determined, instant by instant, by the distance between the external lateral surface 15 of the rotor

5 and the internal lateral surface of the seat 12. The vanes 7 are in fact projected out of the respective seats 8 by effect of the centrifugal force, up to when the head surface 9 of each vane 7 contacts with the internal lateral surface of the seat 12. While the rotor 5 rotates about the longitudinal axis Y, the head surface 9 of each vane 7 therefore brushes against the internal surface of the seat 12. A chamber is defined between two adjacent vanes 7, a volume of which varies according to the position of the vanes 7 about the longitudinal axis Y, i.e. according to the angular position of the rotor 5.

In particular, in the position shown in figure 3, a thrust chamber 38 can be identified, directly facing the entry hole 33. The pushing chamber 38 is defined between a first vane 7a and a second vane 7b.

In the illustrated example, the rotor 5 rotates in an anticlockwise direction and the first blade 7a, arranged upstream of the entry hole 35 with respect to the rotation direction of the rotor 5, projects from the rotor 5 by a smaller quantity with respect to the second vane 7b, arranged downstream of the entry hole 35. In particular, the first vane 7a can be completely contained in the respective groove 8, as in the illustrated example.

An intermediate chamber 39 is identifiable downstream of the thrust chamber 38, defined between the second vane 7b and a third vane 7c, which projects from the rotor 5 by a greater quantity than the second vane 7b.

An exit chamber 40 is arranged downstream of the intermediate chamber 39, in which the exit holes 37 open.

Further chambers that do not have an active role in the driving in rotation of the rotor 5 are defined downstream of the exit chamber 40.

During functioning, the exhaust gases deriving from the combustion that has taken place internally of the engine enter the casing 3 through the entry hole 33. From here, the exhaust gases pass into the vane 34 and then, through the entry hole 35, enter the thrust chamber 38.

When the exhaust gases enter the thrust chamber 38, the exhaust gases possess a certain kinetic energy which is almost totally yielded to the second vane 7b, or in any case is yielded in a greater measure to the second vane 7b with respect to the first vane 7a. In fact, the first vane 7a does not project from the rotor 5, or in any case projects from the rotor 5 less than the second vane 7b, such that the second vane 7b provides, with respect to the first vane 7a, a greater surface on which the exhaust gases can exert a pressure. The resultant of the force applied to the first vane 7a and the second vane 7b by the exhaust gases in the thrust chamber 38 is thus facing towards the second vane 7b. This resultant generates a momentum that drives the rotor 5 in rotation in an anticlockwise direction, in the example of figure 3.

The first vane 7a and the second vane 7b are then rotated towards the exit holes 37 and the chamber defined between the first vane 7a and the second vane 7b progressively increases in volume. Consequently the pressure of the exhaust gases contained internally of the chamber defined between the first vane 7a and the second vane 7b progressively diminishes, while the rotor 5 rotates in an anticlockwise direction. This progressive diminishing of the exhaust gas pressure is such that the thrust the exhaust gases exert on the first vane 7a progressively diminishes, while the rotor 5 rotates. This however does not lead to drawbacks, as a new chamber has in the meantime reached a position facing the entry hole 35, and in this new chamber the thrust action exerted by the exhaust gases is at a maximum.

With the progressive diminishing of the exhaust gas pressures internally of a chamber which occurs progressively as the chamber is rotated towards the exit holes 37, it is ensured that the rotor 5 rotates always in the same rotation direction, i.e. in an anticlockwise direction in the illustrated example. Pressures cannot be generated in the intermediate chamber 39 which are such as to resist the pressure present in the thrust chamber 38, as the intermediate chamber 39 has a greater volume than the thrust chamber 38. The kinetic energy contained in the discharge gases can therefore be converted into mechanical energy which rotates the impeller 2 with a very high performance.

When the chamber defined between the first vane 7a and the second vane 7b reaches the exit holes 37, the exhaust gases pass into the exhaust manifold 32 and then exit the apparatus 1 . The exhaust gases naturally flow towards the external environment, where the pressure is lower with respect to the exit chamber 40. Consequently the exit chamber 40 empties and is ready to receive a new quantity of exhaust gases and thus recommence the operating cycle thereof.

While the chamber defined between the first vane 7a and the second vane 7b displaces about the longitudinal axis Y, a further chamber, defined between two other vanes 7, is brought in front of the entry hole 35. The new chamber located in front of the entry hole 35 acts as a thrust chamber, receiving energy from the exhaust gases.

The rotor 5 is thus driven in rotation about the longitudinal axis Y. The shaft 6 rotates solidly with the rotor 5, like the impeller 2, which is fixed with respect to the shaft 6. The impeller 2 consequently sends the cooling liquid internally of the engine.

Thanks to the vanes 7 which exit from the seats 8 by a variable quantity according to the angular position of the rotor 5, the head surface 9 can, in any angular position of the rotor 7, be in contact with the internal lateral surface of the seat 12. Consequently, a substantially closed chamber is defined between two consecutive vanes 7. When the exhaust gases enter the thrust chamber 38, the exhaust gases accumulate in the thrust chamber 38 up to reaching a sufficient pressure to overcome the resistance that the rotor 5 opposes to rotation. The exhaust gases thus succeed in driving the rotor 5 in rotation even when the velocity of the engine is relatively low, especially when the engine rotates at minimum regime. Consequently the cooling liquid can correctly circulate internally of the engine even when the engine is turning at a low number of revolutions. In this way the risk of malfunctioning is avoided, due to an excessive temperature reached internally of the engine.

In the illustrated embodiment, the offset positions of the rotor 5 and the seat 12 was obtained by mounting the rotor 5 coaxially to the casing 3 and providing an offset seat 12 with respect to the casing 3. In a further embodiment that is not illustrated, the seat 12 can also be arranged in a coaxial position with respect to the casing 3 and the rotor 5 can be mounted in an offset position with respect to the casing 3.

Claims

1 . An apparatus comprising:

a pump impeller (2) for circulating a cooling fluid in an engine, a driving device (4) for driving the pump impeller (2),

- a conduit for conveying exhaust gases produced by the engine towards the driving device (4), so that the exhaust gases move a rotor (5) of the driving device (4),

characterized in that the driving device (4) comprises a plurality of vanes (7), each vane (7) of said plurality protruding from the rotor (5) by an amount which varies as the rotor (5) rotates.

2. An apparatus according to claim 1 , wherein the rotor (5) is provided with a plurality of grooves (8), each groove (8) housing a vane (7), so that the vane (7) exits at least partially from the groove (8) due to centrifugal force as the rotor (5) rotates.

3. An apparatus according to claim 2, wherein each vane (7) is received in the corresponding groove (8) without any interposed elastic element.

4. An apparatus according to any preceding claim, and further comprising a housing element (1 1 ) provided with a seat (12), the rotor (5) being mounted eccentrically within the seat (12).

5. An apparatus according to claim 4, wherein two consecutive vanes (7) define, between the housing element (1 1 ) and the rotor (5), at least one chamber (38, 39, 40) which is substantially closed.

6. An apparatus according to claim 5, wherein the housing element (1 1 ) is provided with an entry hole (35) and an exit hole (37) for the exhaust gases, a longitudinal axis (Y) of the rotor (5) being at a distance from an axis (Z) of the seat (12) so that the volume of said at least one chamber (38, 39, 40) increases from the entry hole (35) towards the exit hole (37).

7. An apparatus according to any of claims 4 to 6, and further comprising a casing (3) provided with a recess (1 6), the housing element (1 1 ) being mounted inside the casing (3) in a position fixed relative to the casing (3), the recess (1 6) being preferably coaxial with the rotor (5).

8. An apparatus according to claim 7, wherein the casing (3) is provided with a flange (17) having a plurality of fastening holes (19) for fastening the casing (3) to a support, particularly a cylinder block of an engine.

9. An apparatus according to claim 7 or 8, wherein the casing (3) is delimited, at a side opposite the rotor (5), by a shaped surface (42) which defines, at least partially, a stator of the pump.

10. An apparatus according to any preceding claim, wherein the rotor (5) is fixed relative to a shaft (6) which supports the pump impeller (2), so that the shaft (6) is rotated when the rotor (5) rotates, the shaft (6) in turn rotatingly driving the pump impeller (2).