GB2289801A

GB2289801A - Sleeved rotating machine

Info

Publication number: GB2289801A
Application number: GB9510530A
Authority: GB
Inventors: Herve Pommelet
Original assignee: Jeumont Industrie
Current assignee: Jeumont Industrie
Priority date: 1994-05-25
Filing date: 1995-05-24
Publication date: 1995-11-29
Anticipated expiration: 2015-05-24
Also published as: GB2289801B; FR2720562A1; GB9510530D0; FR2720562B1

Abstract

This invention relates to a rotating machine in which the stator bore (2) is intended to receive a sleeve (5), an elastic link being provided between said sleeve (5) and the frame (8), characterised in that said link, provided between at least one end flat face (20) of the sleeve (5) and the frame (8), is removable and sealed for any operating temperature of the machine while allowing axial and radial expansion of the sleeve. <IMAGE>

Description

This invention relates to rotating machines and more particularly to those comprising a sleeve in their stator bore.

It is known, in fact, that in all types of synchronous and asynchronous machines, the operating or environmental conditions may require the stator to be sleeved. This is particularly for motors working in difficult environments, in chemical or polluted surroundings, in a submerged environment, and in all cases where the windings must be insulated or protected from the fluid present in the. gap between stator and rotor.

The stator sleeve of an alternating current machine can be made from a metallic material, such as non-magnetic steel. However, the presence of such a metallic part gives rise to eddy-current losses, which reduce the efficiency of the machine.

This solution is only acceptable when the frequency is low (below 50 Hz) and when the sleeve can be easily cooled. However for machines operating at higher frequencies, the loss of efficiency becomes unacceptable.

It is therefore necessary in many cases to envisage sleeving the stator using a non-magnetic, non-conducting material so as to prevent generation of eddy-current losses. The materials normally used are composites and ceramics.

The sleeve is designed to insulate the stator and must therefore be connected to the frame to define a compartment known as the "stator compartment".

Conventionally, when the sleeve is metallic, it is welded directly onto the frame, and more particularly onto the support pieces provided for this purpose. The most popular technique used is the "thin lip" technique.

These pieces are generally called closure flanges and constitute link pieces between the sleeve and frame. This assembly presents no particular problem, due to the similitude of the expansion coefficients of the sheets of the frame and sleeve.

However, when the sleeve is made from a non-conducting metal, this assembly cannot be used since the materials of the sleeve and frame have different expansion coefficients.

The invention relates to a rotating machine comprising a link between the sleeve of the stator and the frame that ensures perfect sealing for any operating temperature of the machine, even if these pieces are made from materials having different thermal expansion coefficients.

While the invention is particularly adapted to machines comprising a non-metallic sleeve, it is also suitable for machines having a sleeve made from a metallic material.

The invention therefore relates to a rotating machine in which the stator bore is intended to receive a sleeve, an elastic link being provided between the sleeve and the frame, characterised in that said link, provided between at least one end flat face of the sleeve and the frame, is removable and sealed for all any operating temperature of the machine, while allowing axial and radial expansion of the sleeve.

Preferably, the link is made up of a sealing device located on the flat end face of the sleeve and elastic means fixed between said device and the frame.

According to one embodiment, said sealing device is made up of a seal pressed flat by tightening means against the flat end face of the sleeve, said seal behaving like a static seal.

The tightening means can particularly comprise a piece for supporting seal and tie rods, provided on the periphery of the sleeve or rods, fixed at one end, to the slots of the stator magnetic circuit.

According to a first modified embodiment, the elastic means are made up of a metal bellows element.

According to one embodiment, said elastic link is provided between the sleeve and a closure flange.

In this case and according to a second modified embodiment, the closure flange is flexible and constitutes said elastic means.

The flange therefore comprises, preferably, a compensation loop bend allowing radial expansion.

The rotating machine according to the invention comprises, in particular, a sleeve, made from a non-magnetic, non-conducting material, such as a composite or ceramic material. The sleeve can also be held elastically in the stator bore, as mentioned in French patent No.2 708 803.

The invention will be better understood and other objects, advantages and characteristics brought out from the following non-limiting description of a number of embodiments of the invention and which should be read in conjunction with the accompanying drawings. In these drawings - Figure 1 shows a partial section of a known rotating machine of the prior art, along the axis of the machine, - Figure 2 shows a partial half-section of an embodiment of a rotating machine according to the invention, along the axis of the machine, - Figure 3 shows the detail A of Figure 2.

- Figure 4 shows a partial view of another embodiment of Figure 3, - Figure 5 shows a partial half-section of another embodiment of a rotating machine according to the invention, along the axis of the machine, and - Figure 6 shows a partial cross-sectional view along line VI-VI of Figure 5.

Elements common to the different figures are designated by the same references.

By reference to Figure 1, a conventional rotating machine comprises a stator 1 whose bore 2 is designed to receive the rotor 3 of the machine.

The magnetic circuit provided for in the stator is made up of windings 4.

The axis of the machine is identified by the reference 30.

A sleeve 5 is mounted in the bore by means of a sealing system 6 and flange 7, which is itself fixed to the frame 8 of the machine by conventional means.

Flange 7 comprises a protruding part 9 which is intended to engage with the outer face 10 of the sleeve.

The sealing system 6 essentially comprises an element 12 intended to engage with flange 7 and inner face 11 of the sleeve, a conical piece 13 for tightening element 12 against the sleeve and seals 14, 15 and 16.

Seal 16 is arranged between element 12 and flange 7. Seals 14 are located between the outer face 10 of the sleeve and the protruding part 9 of the flange, while seals 15 are arranged between inner face 11 of the sleeve and element 12.

Seals 14 and 15 are located on the cylindrical surface of the sleeve.

To ensure sealing, it is therefore necessary to locate seals both on outer face 10 and inner face 11 of the sleeve.

Flange 7 comprises a thinner portion 17 which provides it with a certain flexibility. This assembly could therefore be used to ensure a link between a sleeve and the frame of a machine, when these pieces are made from materials having different expansion coefficients.

This assembly, however, has many drawbacks.

Indeed, the seals are necessarily assembled with clearance and this can vary because of the different expansion coefficients of sleeve 5, flange 7 and element 12. These seals do not therefore ensure proper sealing. Moreover, if it is necessary to provide for seals on both faces of the sleeve, the resulting large number of seals further increases the risk of leakage.

It should further be noted that the seals may become damaged during their locating when protruding part 9 and element 1 which support seals 14 and 15 are fitted onto sleeve 5.

Furthermore, the pressure that prevails in stator compartment 19 is maintained substantially equal to that present in bore 2 thanks to an appropriate system (not shown). It can, however, be relatively high in relation to atmospheric pressure. Thus, at the time of assembly and after protruding part 9 and element 12 have been fitted onto the sleeve, a large pressure difference exists between the space corresponding to the initial clearance of the assembly and the face of the seal in contact with stator compartment 19 or bore 2. This involves the use of seals having antiextrusion rings.

Conical piece 13, which is necessary in order to tighten element 12 against sleeve 5, generates stresses in the sleeve itself. These can damage the sleeve if it is made from ceramic, this being a relatively fragile material.

Finally, this assembly is relatively costly, especially because of piece 13, and can only ensure sealing of the stator compartment within a relatively restricted temperature range.

Reference will now be made to Figure 2, in which the rotor is not shown. In the example shown, sleeve 5 is mounted in a rigid way at one end and in an elastic way at the other. The elastic assembly in accordance with the invention (detail A) will be described in detail with respect to Figure 3.

The rotating machine in accordance with the invention comprises at least one elastic link between the sleeve and frame. When such a link is provided at the two ends of the sleeve, a better distribution of expansion is obtained in addition to a reduction of strains.

As shown in Figure 3, in the rotating machine in accordance with the invention, the sealing elastic link between sleeve 5 and frame 8 is made between the flat end face 20 of the sleeve and the frame, and not between the cylindrical faces of the sleeve and frame as in the machine shown in Figure 1.

The link is made by means of a sealing device 28 comprising a piece 21, which comprises a groove in which a seal 22 is located. This seal is held in position flat against the flat end face 20 of the sleeve 5 by means of, on the one hand, a flange 23 which presses against a shoulder 24 of sleeve 5, and on the other hand, by tie rods 25 which are distributed on the periphery of the sleeve to ensure regular tightening.

Flange 23 can be made as a single part, or as several parts in the form of sectors if it cannot be introduced into bore 2. When the flange is made up of several sectors, the flange is reconstituted by assembling the sectors into a ring (particularly by bolting). A rigid complete flange is thus obtained for the tightening of seal 22.

Seal support piece 21 is preferably metallic and directly welded onto a bellows element 26 which is also preferably metallic. Bellows element 26 is itself welded onto the end flange 27 which is conventionally fixed to the frame by a bolted or welded link (shown in Figure 2).

It is evident that in the rotating machine of the invention, seal 22 can be pressed firmly against end face 20. The tightening of the seal therefore remains constant irrespective of any expansion of the sleeve. In this machine, static sealing is therefore provided at the level of the seal, this being effective for any operating temperature, and in particular up to 1500C. In the machine shown in Figure 1, sealing can only be ensured within a limited temperature range, particularly between 10 and 400C.

The rotating machine only requires one seal, which also contributes towards the sealing reliability of the link between the sleeve and frame.

Furthermore, elastic bellows element 26 ensures the elasticity of the link between sleeve 5 and flange 27, allowing the link to adapt to the axial and radial expansion of the sleeve. This also offers an advantage compared to the flexible flange shown in Figure 1 since the flange in Figure 1 can only take up axial expansion.

The rotating machine in accordance with the invention is not limited to the embodiment described in reference to Figures 2 and 3. Any other assembly allowing seal 22 to be tightened against a flat end face 20 of the sleeve may be used.

For example, Figure 4 shows another sealing assembly in which shoulder 24 is extended in such a manner that practically all of seal support part 21 comes to bear against it. It is therefore no longer necessary to provide for flange 23, tie rods 25 directly tightening piece 21 against shoulder 24.

Reference can also be made to Figure 5 which shows another embodiment of the rotating machine in accordance with the invention.

Figure 5 shows a sealed elastic link between sleeve 5 and the frame, by means of end flange 27. A similar link or even a rigid link can be provided at the other end of the sleeve.

This elastic link is made, as in the embodiment shown in Figure 3, between flat end face 20 of the sleeve and the frame.

It comprises a sealing device 30 comprising a seal support piece 31.

This piece has a hollow part 32 making a recess in which a seal 33 is located. Seal 33 is in the form of an L of which one part is located against the flat end face 20 and whose other part is located against the outer face 10 of sleeve 5. This other part of the seal is cylindrical. It allows to center seal 33 onto sleeve 5 and to avoid therefore withdrawal thereof from the recess if an overpressure appears from one side of the sleeve. The cylindrical part of seal 33 allows also to prevent any contact between piece 31 and sleeve 5 during assembly or if impacts are produced. Indeed the sleeve may particularly be made of composite or ceramic material. Thus it could be deteriorated during the contact with a metallic part, for example cracks or splits may appear.

This seal is maintained pressed against the flat end face 20 of sleeve 5 by means of rods 34 which are screwed into nuts 35.

As Figure 6 also shows, these nuts are housed in slots 36 of the magnetic circuit provided in the stator. The nuts are held in position in the axial direction by retaining lugs 37 welded onto the tightening fingers 38 of the sheets making up the stator. No modifications are required to the magnetic circuit of the stator. According to Figure 6, sleeve 5 is held elastically in the stator bore, thanks to elastic means 47 provided between the coils 48 of the stator and the wedges 49 closing slots 36 in which the coils are located. Such an assembly is described in French patent application 2.708.803.- This assembly, however, is not necessarily used within the scope of this invention.

The number of rods 34 is determined according to the force required to put the seal under pressure.

The rods are accessible after they have been mounted. Indeed, holes 41 are made in flange 27. They make it possible to slacken rods 34 and therefore release sleeve 5 from the seal tightening means, without having to unweld any parts. These holes 41 are obturated by threaded plugs which can be blocked if necessary. The elastic link described in relation to Figures 5 and 6 is therefore indeed removable, like the one shown in Figures 2 to 4.

Holes 41 provided in flange 27 can also be used, after assembly, to adjust the tension of tightening rods 34 and thus adjust the pressure exerted by seal 33 on sleeve 5.

Prestressed elastic washers 40 are located between the head 39 of each rod 34 and the seal support piece 31. These enable the prestressing force of seal 33 to be adjusted. These washers also compensate for the possible effects of differential expansion, due to the presence of different materials, and therefore enable seal 33 to be held tight against sleeve 5.

They also prevent tightening forces being directly applied onto sleeve 5.

The metal bellows element 26 is welded onto rings 43 and 44. Ring 43 is itself welded onto flange 27 while ring 44 is welded onto piece 31.

The metal bellows element allows free radial expansion of sleeve 5 and insulates it from deformations of flange 27, integral with the frame of the motor. These deformations can be caused by excessive pressure in the stator compartment or by elongations, due to the differences in expansion coefficients of the materials used. Finally, an insulating sheath 45 is, preferably, provided around each rod 34, at the seal support piece 31 level. It provides a means of electrically isolating the rods in order to avoid a cage being formed inside the electric field generated by the windings. Similarly, insulation 46 is, preferably, provided on the free part of each rod 34 in order to maintain sufficient distances to earth in relation to the adjacent winding.

The elastic link just described provides a means of axially holding the sleeve in the bore and without stress while overcoming problems linked with deformations of the flange and differences in the expansion coefficients of the materials.

It guarantees the efficiency of the flat seal provided between the sleeve and the rings within a large temperature range.

The link can be removed or dismantled and is adjustable after assembly. Its assembly is very simple since it calls for no modification of the magnetic circuit of the stator.

In a general way, the seal can be tightened against a flat end face of the sleeve by any suitable means.

Regarding the bellows element, it can be replaced by any means ensuring the same function. In particular, if a flexible flange is used, such as the thin flange shown in Figure 1, it is preferable to provide for a compensation loop bend on the flange allowing radial expansion.

These elastic means (bellows, flexible flange or others) ensure an elastic link between the sleeve and frame and allow free expansion of the different parts of the rotating machine without generating stresses in the sleeve.

If, however, the flanges are intended to serve as a support for other equipment, it is preferable that the flanges be rigid.

It is also possible to envisage direct connection of the bellows element onto the frame without use of a closure flange, such as flange 27, if the frame is designed for this purpose.

As mentioned above, the invention is more particularly intended for rotating machines comprising a non-metallic sleeve which cannot be directly welded to the frame, or to a closure flange. The invention can however be advantageously used for rotating machines having a metallic sleeve. Indeed, since the link in accordance with the invention can be removed, it may be preferred for reasons of maintenance.

The invention is particularly adapted to the rotating machine described in French patent application No.2 708 803 whose contents is included here for reference. This machine comprises a sleeve which is held elastically in the stator bore, thanks to elastic means provided between the coils of the stator and the wedges closing the slots in which the coils are located. Such an assembly is well adapted to a sleeve made from a different material than the other parts of the machine, particularly from ceramic or a composite material. Indeed, thanks to this assembly, the sleeve is no longer subject to excessive stresses during operation of the machine due to the differential radial expansion of the materials used.

Any possible dimensional variations are compensated for thanks to the elastic assembly produced by the wedges-elastic means assembly.

On the other hand, the fixed assembly as shown in Figure 1 is unsuitable for a rotating machine in accordance with application FR-2 708 803 since it cannot compensate for dimensional variations occurring in this machine.

The reference signs inserted after the technical characteristics mentioned in the claims serve only to facilitate understanding of said claims and in no way limit their scope.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

1. Rotating machine in which the stator bore (2) is intended to receive a sleeve (5), an elastic link being provided between said sleeve (5) and the frame (8), characterised in that said link, provided between at least one end flat face (20) of the sleeve (5) and the frame (8), is removable and sealed for any operating temperature of the machine while allowing axial and radial expansion of the sleeve.

2. Rotating machine according to claim 1, characterised in that the link is made up of a sealing device (28, 30) located on the flat end face (20) of the sleeve and elastic means (26) fixed between said device and the frame (8).

3. Rotating machine according to claim 2, characterised in that said sealing device (28, 30) is made up of a seal (22, 33) pressed against the flat end face (20) of the sleeve (5) by tightening means (21, 23, 25; 21, 25; 31, 34), said seal behaving like a static seal.

4. Rotating machine according to claim 3, characterised in that said tightening means comprise a piece (21) for supporting seal (22) and tie rods (25), provided on the periphery of the sleeve.

5. Rotating machine according to claim 3, characterised in that said tightening means comprise a piece (31) for supporting seal (33) and rods (34) fixed, at one end, to slots (36) of the stator magnetic circuit.

6. Rotating machine according to any one of claims 2 to 5, characterised in that the elastic means are made up of a metallic bellows element (26).

7. Rotating machine according to any one of claims 1 to 6, characterised in that said elastic link is provided between the sleeve (5) and a closure flange (27).

8. Rotating machine according to claim 7, characterised in that said closure flange is flexible and constitutes said elastic means.

9.Rotating machine according to claim 8, characterised in that said flexible flange comprises a compensation loop bend allowing radial expansion.

10. Rotating machine according to any one of claims 1 to 9, characterised in that said sleeve (5) is made from a non-magnetic, nonconducting material, such as a composite or ceramic material.

11. Rotating machine according to any one of claims 1 to 10, characterised in that said sleeve (5) is held elastically in the stator bore (2).

12. Rotating machine substantially as hereinbefore described with reference to the accompanying drawings.