Radial impeller with a radially free basic rim

Abstract

An impeller designed to be mounted on a rotary shaft includes: a basic rim provided with blades protruding on one surface of the basic rim, and a hub capable of being coupled to the basic rim and to the rotary shaft. In certain embodiments, the impeller includes an annular plate and the hub, where the annular plate and the basic rim are configured to interact together so as to hold the basic rim axially and to maintain a freedom of radial deformation of the basic rim relative to the hub and to the annular plate.

Claims

1. An impeller designed to be mounted on a rotary shaft of a compressor, comprising: a basic rim provided with axial blades protruding on one radial face of the basic rim; an annular hub capable of being coupled to the basic rim and to the rotary shaft; and an annular plate, wherein the annular hub, the annular plate, and the basic rim are configured to interact together so as to hold the basic rim axially and to maintain a freedom of radial deformation of the basic rim relative to the annular hub and to the annular plate, the basic rim being held only by the annular plate and the annular hub, wherein the basic rim comprises a circular key on its inner perimeter capable of interacting with a first notch made in the annular hub and a second notch made in the annular plate, the first and second notches being placed opposite one another so that the circular key of the basic rim is held in the notches when the annular hub, the annular plate and the basic rim are assembled, and wherein the impeller further comprises radial guiding means capable of limiting friction between the basic rim and the annular hub, and between the basic rim and the annular plate during the radial deformation of the basic rim, the radial guiding means comprising, on each face of the basic rim, at least one circular groove placed in the circular key, the circular grooves each comprising an O-ring or a rolling means.

2. The impeller according to claim 1, in which the circular key comprises two outer O-rings respectively placed on either side of the basic rim on an outer radial surface of the circular key, and two inner O-rings respectively placed on either side of the basic rim on an inner radial surface of the circular key.

3. The impeller according to claim 1, in which the second notch made in the annular plate comprises an oblique outer radial contact surface, an outer radial surface of the circular key comprises a matching oblique portion opposite the oblique outer radial contact surface of the annular plate, and the annular plate is assembled to the annular hub so as to be able to be deformed and to separate from the annular hub over a distal portion during the radial deformation of the basic rim.

4. The impeller according to claim 1, in which the annular plate comprises centering means, and the annular hub comprises matching centering means capable of interacting with the centering means.

5. The impeller according to claim 4, in which the centering means comprise a centering ring fastened to the annular plate and comprising a tooth gear facing the annular hub, and the matching centering means comprise a matching centering ring fastened to the annular hub and comprising a matching tooth gear facing the annular plate capable of interacting with the tooth gear of the centering ring.

6. The impeller according to claim 4, in which the centering means comprise a conical, protruding proximal portion of the annular plate facing the annular hub and having as its axis the rotary shaft, and the matching centering means comprise, in the annular hub, a conical recess facing the annular plate having the rotary shaft as its axis, the conical protruding portion and the conical recess being capable of interacting during the assembly of the annular plate to the annular hub.

7. The impeller according to claim 1, in which the annular hub is placed on a first shaft portion and the annular plate is placed on a second shaft portion, the first shaft portion and the second shaft portion being secured by fastening means so as to secure the annular hub and the annular plate.

8. The impeller according to claim 1, further comprising a bolted fastening flange capable of securing the annular plate to the annular hub.

9. The impeller according to of claim 1, further comprising an end-piece coupled to the basic rim via the blades, the end-piece and the basic rim having an identical weight.

10. The impeller according to claim 1, in which the annular hub is shrink-fitted or incorporated over at least a portion of the rotary shaft of the compressor.

11. The impeller according to claim 1, in which the annular plate is shrink-fitted or incorporated over at least a portion of the rotary shaft of the compressor.

12. A compressor comprising at least one impeller according to claim 1.

13. The impeller according to claim 1, wherein radial dimensions of the notches are greater than a dimension of the circular key in a direction orthogonal to a rotation axis of the basic rim.

Description

(1) Other advantages and features of the invention will become evident on examination of the detailed description of embodiments that are in no way limiting, and of the appended drawings in which:

(2) FIG. 1 is a schematic view showing the general architecture of a motor-compressor unit furnished with impellers according to the invention;

(3) FIGS. 2a and 2b represent respectively an exploded view and an assembled view of an impeller according to a first embodiment;

(4) FIG. 3 represents an impeller according to a second embodiment;

(5) FIGS. 4a and 4b represent an impeller according to a third embodiment;

(6) FIG. 5 illustrates a variant of the embodiment of FIGS. 4a and 4b; and

(7) FIG. 6 illustrates an impeller according to another embodiment.

(8) FIG. 1 shows an example of a compressor unit provided with impellers made according to the invention.

(9) It will be noted however that the application illustrated in FIG. 1 is in no way limiting, the invention relating, in general, to the mechanical compression of a gas such that there is no departure from the context of the invention when the impellers are mounted on other types of compressors.

(10) The motor-compressor unit illustrated in FIG. 1 comprises essentially a motor 1, consisting for example of a variable-speed electric motor rotating a rotor 2, itself driving at identical speed a rotary shaft 3 on which an impeller 4 is mounted.

(11) The motor-compressor unit in this instance comprises a single compression stage consisting of the radial impellers 4 which draw in a gas delivered from an inlet duct 5 in order to cause an increase in its pressure and deliver it at the outlet 5.

(12) In the exemplary embodiment shown, the rotor 2 is supported by two end bearings 6 and 7. This is also the case for the rotary shaft 3 which is also supported by two end bearings 8 and 9. Therefore, according to this arrangement, the rotor 2 and the rotary shaft 3 are connected via a flexible coupling 10. The rotor and the rotary shaft could equally be connected via a fixed coupling. In this case, one of the bearings, such as 7 and 8, could be omitted.

(13) Finally, the assembly, i.e. the motor 1 and the compression stage, is placed in a common casing 11 sealed against the gas handled by the compressor. In other words, the motor 1 is in this instance at the suction pressure of the motor-compressor unit.

(14) FIGS. 2a and 2b show respectively an exploded view and an assembled view of a first example of impellers, according to one embodiment of the invention that can be installed in the compressor unit of FIG. 1.

(15) The impeller 4 comprises three distinct portions: a basic rim 12, a hub 13, a plate 14.

(16) The basic rim 12 comprises a distal portion 12a and a proximal portion 12b relative to its rotation axis indistinguishable from the rotation axis of the rotary shaft 3. The basic rim 12 extends in a plane orthogonal to its rotation axis and comprises a first face 12f and an opposite face 12o. The basic rim 12 comprises, mainly on its distal portion 12a, blades 15 protruding on the first face 12f of the basic rim 12 facing an end-piece 16.

(17) The end-piece 16 comprises a distal portion 16a and a proximal portion 16b relative to its rotation axis indistinguishable from the rotation axis of the rotary shaft 3. The distal portion 16a of the end-piece 16 is placed parallel to the distal portion 12a of the basic rim 12 and is coupled to the blades 15 on a face 16f facing the basic rim 12.

(18) The end-piece 16 and the basic rim 12 have a similar weight so as to obtain a centrifugal force that is virtually symmetrical on either side of the connection with the blades 15. The stresses in the basic rim 12 are therefore reduced and a virtually radial deformation of the basic rim 12 is thus promoted.

(19) The basic rim 12 comprises, on its proximal portion 12b, a circular key 17. The circular key 17 is notably placed along the inner perimeter of the basic rim 12. The circular key 17 comprises, in this example, a section of generally square shape.

(20) The hub 13 has an annular shape of which the rotation axis is indistinguishable from the axis of the rotary shaft 3. The hub 13 has a bearing face 13f orthogonal to the axis of the rotary shaft 3 and designed to be facing the plate 14, a distal portion 13a and a proximal portion 13b relative to its rotation axis.

(21) The plate 14 also has an annular shape of which the rotation axis is indistinguishable from the axis of the rotary shaft 3. The plate comprises a bearing face 14f orthogonal to the axis of the rotary shaft 3 and designed to be facing the hub 13, a distal portion 14a and a proximal portion 14b relative to its rotation axis.

(22) The hub 13 comprises, on the distal portion 13a of its bearing face 13f, a first notch 18 capable of receiving in part the circular key 17. The plate comprises, on the distal portion 14a of its bearing face 14f, a second notch 19 capable of receiving in part the circular key 17. The first notch 18 and the second notch 19 are made so as to be facing one another with identical dimensions so that the second notch 19 is symmetrical with the first notch 18 relative to the axis defined by the bearing faces 13f and 14f when the hub and the plate are in contact.

(23) It is possible for notches 18 and 19 not to be symmetrical relative to the circular key 17 so long as the junction between the circular key 17 and the rest of the basic rim 12 is centred relative to the basic rim 12. The notches 18 and 19 may therefore comprise matching shapes so as to axially retain the circular key 17 and to define a passage for the junction between the circular key 17 and the rest of the basic rim 12, the junction being centred relative to the circular key 17 and the rest of the basic rim 12.

(24) In this embodiment, the notches 18 and 19 have dimensions so as to retain the circular key 17 axially, that is to say to be resting with the circular key 17 in a direction parallel to the rotation axis of the basic rim 12.

(25) The circular key 17 may comprise a section with a shape different from the square shape, such as for example a hexagonal, octagonal shape or any other shape capable of interacting with the first and second notches 18 and 19.

(26) On the other hand, the radial dimensions of the notches 18 and 19 are greater than the dimension of the circular key 17 in a direction orthogonal to the rotation axis of the basic rim 12. This is so as to maintain a freedom of radial movement of the circular key 17 notably when the basic rim 12 is deformed with the speed of rotation.

(27) The radial centering when cold of the basic rim 12, that is to say when the impeller 4 is stationary or at low speed, is achieved by virtue of the inner diameter of the circular key 17, while the centering of the basic rim 12 at full speed is achieved by virtue of the outer diameter of the circular key, after the basic rim has expanded.

(28) The circular key 17 comprises an inner radial surface 17i oriented towards the rotation axis of the basic rim and an outer radial surface 17e opposite to the inner radial surface 17i. The circular key 17 comprises, on its outer radial surface 17e, two outer O-rings 20. The two outer O-rings 20 are respectively placed on either side of the basic rim 12, that is to say one on the side of the first face 12f of the basic rim 12 and the other on the opposite side 12o.

(29) In the same way, the circular key 17 comprises, on its inner radial surface 17i, two inner O-rings 21 respectively placed on either side of the basic rim 12, that is to say symmetrically on either side of the plane in which the basic rim 12 extends.

(30) Thus, on start-up, the basic rim 12 is centred radially by virtue of the inner diameter of the circular key 17. In rotation, the basic rim 12 can be deformed more rapidly than the hub 13 and the plate 14 which constitute the fastening elements, this can be done with light retaining stresses due to the friction forces in the radial guiding between the circular key 17 and the hub, on the one hand, and between the circular key 17 and the plate 14, on the other hand. In this transitory phase, the centering is maintained by virtue of the two outer O-rings 20 and of the two inner O-rings 21 deforming naturally. When the operating speed is achieved, the maximum radial inflation of the basic rim 12 is achieved, the plate and the hub are configured to allow the basic rim to be centred by virtue of the outer diameter of the circular key 17.

(31) When the speed reduces, the basic rim 12 reproduces the opposite deformation until it is again centred at low speed.

(32) The hub 13 is incorporated into a first shaft portion 4a and the plate 14 is incorporated into a second shaft portion 3b. The hub 13 and the plate 14 could also be shrink-fitted respectively onto the first and the second shaft portions 3a and 3b. The assembly of the hub 13 with the plate 14 is carried out by screwing of the second shaft portion 3b into the first shaft portion 3a, the first shaft portion 3a comprising a threaded orifice along its rotation axis on an end-fitting facing the second shaft portion 3b, and the second shaft portion 3b comprising an end-fitting facing the first shaft portion 3a having a screw pitch matching the threading of the orifice in the first shaft portion 3a.

(33) As a variant, it would also be possible to use a bolted fastening flange in order to secure the plate to the hub, as will be described with reference to FIG. 3.

(34) The centering of the hub 13 with the plate 14 is carried out with the aid of an axial gear pair, for example with the aid of a Hirth tooth gear system. The plate 14 comprises a centering ring 22a fastened to the bearing face 14f of the plate 14. The hub 13 comprises a matching centering ring 22b fixed to the bearing face 13f of the hub 13. When the hub 13 and the plate 14 are assembled, the centering ring 21a interacts with the matching centering ring 21b for the radial centering, and thus making the first and second notches 18 and 19 match radially.

(35) FIG. 3 illustrates a second example of an impeller 4 according to one embodiment of the invention. The elements bearing the same references as in FIGS. 2a and 2b are identical.

(36) In this embodiment, the circular key 17 comprises radial guiding means making it possible to prevent the friction between the circular key 17 and the hub 13 on the one hand, and between the circular key 17 and the plate 14 on the other hand. The radial guiding means, comprise, on the first face 12f and the opposite face 12o of the basic rim 12 at least one circular groove 23 placed in the circular key 17. Each circular groove 23 comprises rolling balls 24 making it possible to separate the circular key 17 from the hub 13 on the one hand, and the circular key 17 from the plate 14 on the other hand.

(37) This embodiment also differs from that shown in FIGS. 2a and 2b by virtue of the centering means and the means for fastening the hub 13 to the plate 14.

(38) The impeller 4 illustrated in FIG. 3 comprises, as fastening means, a bolted fastening flange 24 capable of securing the plate 14 to the hub 13. The fastening flange 24 comprises a blind threaded hole 25 in the hub 13, the opening of the threaded hole 25 being placed on the bearing face 13f of the hub 13. The fastening flange 24 also comprises a through-orifice 26 made in the plate 14 facing the threaded hole 25. The through-orifice 26 comprises an abutment 27 so that a screw 28 resting on the abutment 27 can keep the plate 14 tight on the hub 13.

(39) In order to centre the plate 14 and the hub 13, the plate 14 comprises a protruding portion 29 on its proximal portion 14b. The protruding portion extends towards the hub 13 with a conical shape with a decreasing section. The hub 13 comprises a matching recess 13 made in its proximal portion 13b with a conical shape capable of interacting with the protruding portion 29 of the plate 14.

(40) With such centering means, it would be possible for the impeller 4 to comprise no bolted fastening flange 24, the transmission of the torque between the hub 13 and the plate 14 being able to be carried out by friction between the protruding portion 29 and the surfaces of the hub 13 delimiting the recess 30, or else by fitting a pin or a key between the hub 13 and the plate 14.

(41) FIGS. 4a and 4b show a third example of an impeller 4 according to one embodiment of the invention. The elements bearing the same references as in FIGS. 2a and 2b are identical. FIG. 4a shows the third example of an impeller 4 when stationary or at low rotation speed, while FIG. 4b shows the third example of an impeller 4 at high rotation speed.

(42) In this embodiment, the second notch 19 made in the plate 14 comprises an oblique outer radial contact surface 31 so as to form an obtuse angle with the face of the notch 32 facing the hub 13.

(43) Correspondingly, the outer radial surface 17e of the circular key 17 comprises an oblique portion facing and parallel to the oblique outer radial contact surface 31 of the plate 14. As a variant, the circular key 17 may comprise a section of hexagonal shape, one of the faces of the circular key 17 being parallel to and facing the outer radial contact surface 17e.

(44) The plate 14 is secured to the hub 13 with the aid of a fastening flange 24. The fastening flange 24 is mounted on the plate 14 in the proximal portion 14b so that the plate 14 can be deformed and separate from the hub 13 over a distal portion 14a during the radial deformation of the basic rim 12.

(45) In one embodiment, it would also be possible to provide another oblique surface made in the hub, in the location of the angle formed by the notch 18 and an oblique matching surface 31 in radial contact in the circular key 17 (FIG. 5).

(46) As illustrated in FIG. 4b, when the impeller 4 is set to rotate in order to achieve its maximum speed, the basic rim 12 may thus be deformed radially, the circular key 17 moving slightly away radially from its rotation axis by virtue of the deformation of the plate 14, and more precisely from the distal portion 14a of the plate, the oblique portion of the outer radial surface 17e of the circular key 17 sliding along the oblique outer radial contact surface 31.

(47) The invention is not limited to these three various embodiments. It also comprises all the possible combinations between these embodiments.

(48) The invention thus makes it possible to provide an impeller with a basic rim having a freedom of radial deformation, and a possibility of using materials for the basic rim which cannot be used for the fastening parts.

(49) Finally, referring now to FIG. 6, in which elements identical to the elements of FIGS. 2a and 2b bear the same reference numbers, according to another exemplary embodiment, the plate 14 can be attached by bolting to the hub 13 and thus constitute an element that is distinct from the rotary shaft 3.

(50) In this FIG. 6, the bolting system used to fasten the plate 14 to the hub 13 has not been shown. It will be noted however that it would be possible, with advantage, to use a bolted fastening flange similar to that described with reference to FIG. 3.

(51) Note furthermore that, in this embodiment, the circular key 17 is furnished with a set of radial contact surfaces interacting with matching oblique surfaces made on the hub, on the one hand, and on the plate, on the other hand.