DE3438039A1 - CROSS-CURRENT FAN FOR CONVEYING GAS - Google Patents

Abstract

1. Axial-flow ventilator for conveying gas to be conveyed, making possible also the conveyance of hot and/or very cold gases for conveying, preferably air, and having a housing in which the impeller is arranged, the bearings serving to mount the impeller in a rotary manner being, for the purpose of heat insulation, at considerable axial distances from the conveying area of the impeller, this conveying area serving to convey, through a suction opening and a blow-off opening of the housing, the gas to be conveyed, and the housing at the side of the suction opening and the blow-off opening having pot-shaped bulges, characterized in that on both sides of the conveying area (52) of the impeller (46) there are extension areas (48, 48') of the impeller, these being situated within the pot-shaped bulges (45, 45') of the housing (41), the blades (50) of the impeller (46) extending totally or almost totally over the length of the impeller, and the drive shaft (60) of the impeller engaging at the outer axial end of the one impeller extension area (48) and a journal (64) of the rotary mounting of the impeller engaging at the axial outer end of the other impeller extension area (48'), which journal is connected, in a rotationally rigid manner, to the axial end in question of the impeller (46) ; or in that the journal is secured on the housing and a friction bearing or antifriction bearing is arranged on the neighbouring axial end of the impeller ; and in that the extension areas (48, 48') of the impeller are impeller areas which are ineffective at conveying the gas to be conveyed.

Description

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LTG Lufttechnische GmbH 7000 Stuttgart 40

Cross flow fan for conveying conveying gas

The invention relates to a cross-flow fan according to

the preamble of claim 1.

Under the impeller of the tangential fan is always the impeller without the drive shaft and without the bearing pin Understood. The gas is under the conveying gas

stood, for the promotion of which the cross-flow fan

each serves and none is only used for cooling / serving cooling air is. The diameter of the outer circle of rotation is also under impeller diameter understood the blades of the impeller in the conveying area serving to convey conveying gas.

A cross-flow fan 10 which is obviously sold by the applicant in the Federal Republic of Germany of the type mentioned in the preamble of claim 1

shown in Fig. 1 in a broken and partially longitudinal section. He has a metallic one Housing 11, which has a central region 12, in which the impeller 14 having blades 13 parallel to one another is located. This middle area 12

3438032

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has an approximately over the axial length of the end face plate 15 to the end face plate 1 5 'reaching impeller 14 extending Suction opening 16 and one is also on the axial Impeller length extending blowout opening 17 for the conveying gas. These metallic end rings 15,15 'des Impeller 14 are located at the level of the axial ends 19, 20, 21, 22 of the suction opening 16 and the exhaust opening 17. The metal drive shaft 23 of the impeller engaging the end face plate 15 is long and in two parts. It consists of a hollow shaft fastened directly to the end face plate 15 24 of relatively large diameter and inserted into the bore of this hollow shaft 24 Rotor shaft 25 of the electric drive motor 26.

This motor, which is used to drive the impeller 14 is attached to the outside of the housing 11 coaxially to the axis of rotation of the impeller 14. Also on his the other side, the impeller 14 is rotatably mounted by means of a long two-part shaft 27 which from a directly on the end face plate 15 ' fasten, thick shaft piece 27 'and a smaller diameter inserted into a bore of it Shaft piece 27 ″. These two-part shafts 23 and 27 make straightening processes when they are assembled required to establish good alignment. The camps for the drive shaft 23 are located in the motor bearings for the rotor shaft 25 and the Bearing point for the shaft 27 by means of metal disks and radial rubber spokes 31 elastically suspended and Plain bearing bushing located on the left end of the housing 11, lubricated by felt washers 29 impregnated with abrasives 30, which supports the shaft piece 27 '.

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The hollow shaft 24 and the shaft 27 penetrate pot-shaped, substantially circular cylindrical bulges 32,32 'des Housing 11 and in these are, as shown, two insulating washers 33 made of heat-insulating material fixed and immovable, the axial, central one Have passage openings for the hollow shaft 24 and the shaft piece 27 ', which of these with with little play. This cross-flow fan 10 can promote hot gases as well as very cold gases, but their temperatures for the bearing points of the impeller as well are too extreme for the drive motor, as these

! 5 temperatures the bearing points would overheat or become stiff and the drive motor could also suffer damage. In order to protect these bearings and the drive motor from such inadmissible temperatures, the drive shaft 23 is extended by the hollow shaft 24, as is the shaft piece 27 "by the shaft piece 27 'and, in addition, the heat-insulating discs 33 are immovably arranged in the housing bulges 32, 32'. these parts 24,27 'and 33 form here so heat stabilizers for the ¹ bearings and however the motor 26. the hollow shaft 24 as well as the shaft section 27 must' be carried out for reasons of good concentricity relatively thick and made of metal and therefore conduct the high or . Low temperatures of the conveyed gas still relatively well through the thermal insulation disks 33 to the bearings and to the drive motor 26. If you want to reduce the thermal conductivity of the hollow shaft 24 and shaft piece 27 'to improve the thermal protection, you would have to make them smaller in diameter

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train and extend it even more, which, however, raises problems in terms of concentricity and balancing

c and difficult straightening operations and extension the housing bulges 32, 32 'would make necessary. In some cases it is also necessary that the hollow shaft 24 between the associated thermal insulation disk 33 and the drive motor 26, for example for receiving coupling elements must be increased in diameter, which makes their assembly difficult and expensive because of the thermal insulation disk 33.

It is therefore an object of the invention to provide this transverse

,,. To improve current fan 10 so that the heat-Ib

Protection of the bearings and, if necessary, the drive motor or other drive, e.g. a belt drive, Serving measures do not raise any problems with regard to the concentricity and balancing of the impeller and also -_ do not require any additional straightening operations and particularly good thermal protection of the bearing points can be achieved without lengthening the cup-shaped bulges can.

According to the invention, this object is achieved by a cross-flow fan solved according to claim 1.

Since the impeller according to the invention is axially into the cup-shaped bulges of the pot-shaped bulges of the invention beyond its conveying area, which is used solely for conveying the conveying gas, to _{n both sides}

Housing is extended into it and the drive shaft and the bearing journal at the free ends of the extension

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Attacking and ending areas are not the cup-shaped ones There are more bulges over their full axial lengths penetrating shafts. It is therefore possible and advantageous, the rotatably mounted rotor shaft of the drive motor directly at the axial end of the relevant

jQ to attack the impeller extension area. Likewise for Rotary bearing of the face of the impeller facing away from the drive shaft only a one-piece, short, preferably circular cylindrical bearing journal required, that at the axial end of the impeller extension area in question attacks. As a result of the short drive shaft and the short bearing journal, there are no problems regarding the concentricity and balancing of the impeller and there are no additional ones Straightening operations required. Also is particularly good thermal protection without extending the pot-shaped Bulges of the bearing points reached. The bearing pin can expediently as on this impeller face fixed, short, relatively thin shaft be formed in one of the relevant Housing end wall arranged sliding bearing bush or is rotatably mounted by means of a roller bearing. It however, it is also often expedient to have a bearing pin fixed to the relevant end of the housing to be arranged and it in a plain bearing bushing or by means of a roller bearing that is attached to the relevant Front end of the impeller is arranged to be rotatable. The invention also makes it possible that the housing of the cross-flow fan according to the invention that of the cross-flow fan 10 shown in Fig. 1 or requires only minor changes

gg cause only low costs.

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The impeller extension areas located in the cup-shaped bulges of the housing, which at the conveyance of the gas to be conveyed through the conveying area of the impeller located between them do not participate, surprisingly give the bearings good thermal protection for themselves and the electric drive motor or other drive against high or low temperatures of the conveyed Gas when the blades of the impeller, as preferably provided, from end to end of the impeller and are made of metal, e.g. thin aluminum. The blades can be in some However, cases also end a short distance before the front ends of the impeller by placing these end washers For example, through cup-shaped end face disks or the like. Forms on which the blade ends are held. All other parts of the impeller can also be made of metal, in particular consist of aluminum, and yet there is very good thermal protection. So it turned out for one Cross-flow fan 40 according to FIG. 2, which is designed according to an exemplary embodiment of the invention and has been tested in trials, even if the conveying area of the impeller is good thermal insulation of its two extension areas not through gas-tight intermediate disks but through central ones Spacer washers with holes about 3cm in diameter was separated from aluminum by about 9 cm outer diameter. Despite the metallic conductivity of the extension areas of the impeller resulted in these extension areas of the impeller

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surprisingly good thermal insulation, which is due to the fact that the Extension areas do not serve to convey the conveying gas and also on the gas in the extension areas and the Arrangement of the drive shaft or the bearing journal directly on the in the cup-shaped Bulges located axial ends of the impeller extension regions, so that the drive shaft and the bearing journal had a correspondingly large distance from the impeller conveyor area, is due. Possibly also plays a role in the pot-shaped Gases located in bulges in the housing are set in circulation flows by the impeller extension areas. Even it is advantageous if the cup-shaped bulges of the housing are made of metal.

The thermal protection can be further improved if it is provided that the conveying area of the impeller on at least one side, preferably on both sides by a complete or im essentially gas-impermeable intermediate disk or by completely or essentially gas-impermeable The intermediate washers are separated from the two impeller extension areas,

This enables the communication of the gas flowing through the conveying area of the impeller reduce even further with the gases in the cup-shaped bulges of the impeller, which additionally improves the thermal protection.

For this purpose it can also be provided that

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at least at a transition from the impeller conveying area to an impeller extension area on the circumferential side a labyrinth seal is arranged on the impeller. If the impeller conveyor area both by means of such Labyrinth seals, as well as by means of completely or essentially gas-impermeable intermediate discs is sealed against the interiors of the cup-shaped bulges of the housing, results particularly good thermal protection.

In many cases, this can also improve the thermal insulation even further in a simple manner that in at least one extension area of the impeller heat insulation means, preferably a heat insulating disk is arranged.

Other heat insulation means are also possible, for example. Insertion of heat-insulating cushions, for example. Made of glass fibers or the like, in at least one extension area of the impeller.

If the highest demands are placed on thermal protection, it can be provided that an end section at least one impeller extension area through an end chamber of the pot-shaped in question Housing bulge can promote cooling air through and that this end portion of the impeller extension area from the conveying area of the impeller through the remaining section of this impeller extension area is separated. This cooling air is therefore not a gas in the sense of the definition given above Conveying gas.

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The blades and disks of the impeller can be made of metal, preferably aluminum. However, it is also possible for the blades and / or one, several or all of the disks of the impeller to be made of material produce that is thermally insulated or has poor thermal conductivity, such as plastic or The same. By the latter measures, the thermal protection can also be improved even further.

It can preferably be provided that at least one of the two impeller extension areas is located over at least half, preferably over at least. 3/4 of the axial length of the cup-shaped Housing bulge extends.

In Figures 2 to 5 are exemplary embodiments of the invention shown. Show it:

Fig. 2 shows a cross-flow fan according to an embodiment the invention in broken and partly longitudinally sectioned representation,

3-5 each a section from a cross-flow fan in longitudinal section Representation according to further exemplary embodiments of the invention.

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The cross-flow fan 40 shown in FIG. 2 has a preferably metallic housing 41 similar to the housing 11 of the cross-flow fan 10 according to FIG. 1, which has a central region 44 with a suction opening 42 and a Blow-out opening 43 for the entire conveying gas and laterally adjoining this central area 44, pot-shaped, has substantially circular cylindrical bulges 45, 45 '. Notwithstanding the cross flow fan 10 according to Fig.1 However, the impeller 46 extends far into the cup-shaped bulges with extension regions 48, 48 'on both sides 45, 45 'in, so that its two axial ends 49, 49', as shown, only relatively small distances from the approximately flat end faces 47, 47 ″ of these cup-shaped bulges 45, 45 ′ have what distances here are somewhat smaller than 1/4 of the axial length of the respective bulge 45 or 45 '. The diameters of the extension areas 48, 48 'are only slightly smaller, preferably only about 2 to 6 mm smaller than the inside diameter of the

Bulges 45, 45 ', what causes or contributes that these extension areas 48, 48 'are not involved in the conveyance of the conveying gas flowing in through the inlet opening 44 take part.

The blades 50 of the impeller 46, which are preferably made of aluminum, extend in this embodiment expediently over the full length of the impeller 46, i.e. from the front end 49 to the front end 49 'of the impeller 46, where they are in thin end ring disks 51, 51' of the

Impeller 46, which can also be made of metal, are held. The only one pumping the conveying gas

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Conveying area 52 serving through the housing 41

of the impeller 46 extends in the axial direction from a metallic intermediate disk 53 to a metallic one Intermediate disk 53 ". These two intermediate disks 53, 53 'of the impeller through which the blades 50 penetrate 46 are located approximately at the level of the side 10

Ends 54, 55, 56, 57 of the only the inlet and outlet of the entire conveying gas serving two suction and exhaust openings 42, 43 of the housing 41. In these intermediate disks 53, 53 'it can be disks that have no air passage openings, or also annular disks, each with a small central opening of preferably have a maximum diameter of about 3 cm, which openings are used to open these disks during assembly to be able to center or clamp a mandrel.

In a juittige opening of the right-hand end ring disc

53 is an elastic ring 58 made of steel, silicone rubber Or the like. Used, in which a rigid hub 59 is inserted into which the rotor shaft 60 of the on the outside the housing end wall 47 attached electrical terminals

drive motor 61 is firmly inserted, so that in the engine 61 located bearing points for the shaft 60 store the impeller 46 on the right-hand side. The shaft 60 ends, as shown, on the outer one formed by the hub 59

axial end of the impeller extension area 48. 30

The left-hand rotary bearing of the impeller 46 is shown in whose end ring disk 51 'has a hub 62 inserted into the a journal 64 is inserted in the form of a short cylindrical shaft in a rotationally fixed manner. The journal 64 ends thus, as shown, at the outer axial end of the impeller extension area formed by the hub 62 48 '. This journal 64 protrudes

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for its pivot bearing into a metallic plain bearing bushing 65, which is attached to the left end wall 47 'of the Housing 41 by means of metal disks 89 (see Fig. 3) and radial elastic spokes 63 or in their place is elastically suspended by means of an elastic disc. The elastic suspension of the impeller 46 by the links 58, 63 improve, among other things, its smoothness. The plain bearing bush 65 is still lubricant-soaked Felt rings 68 includes for their lubrication.

The left extension area 48 'of the impeller 46 is located extends completely within the cup-shaped bulge 45 'and extends almost over the axial one Length. It begins at the intermediate disk 53 'separating it from the conveying area 50 and extends to the left Front end 49 'of the impeller. The right extension area 48 of the impeller 46 is completely in the right-hand cup-shaped bulge 45 of the housing 41 and begins at the intermediate disk 53 and extends to the right-hand end 49 of the

Impeller 46.
25th

These two impeller extension areas 48, 48 'roll as a result of the blades 50, although the cup-shaped in these bulges 45, 45' located gases to where it normally is air, this ^ö gases but does not promote through the housing. It is here in the lateral cup-shaped bulges 45, 45 'located gases, which as a result of their

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poor thermal conductivity or nonexistent 5

which thermal conductivity have a very good thermal insulation effect. Preferably, the cross-flow fan can the Serve conveying air. Air is a good thermal insulator in the bulges 45, 45 '. The depth of the Bulges 45, 45 'can preferably be at least 0.5 times, particularly advantageously about 0.6 to 1.2 times the impeller diameter.

In a cross-flow fan investigated in an experiment,

which corresponded to that of Fig. 2, in which the depth each -15

that of the two bulges 45, 45 "was about 2/3 of the impeller diameter, it was determined that if the conveyed gas is air and is 300 C hot when flowing through the cross-flow fan, then the temperatures at the end ring disks 51, 51 '

η

were only about 90 C, so that the gases in the bulges 45, 45 "form good heat insulators, despite the metallic design of the blades 50 and the metallic washers 53,

53 · and the metallic end ring washers 25th

51, 51 'of the impeller. The hub was also 62

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metallic, but it can also advantageously consist of non-metal, for example ceramic. Included the intermediate disks 53, 53 'had a circular center with an outer diameter of approx. 9 cm openings of approx. 3 cm in diameter each, so that a communication between the Conveying area 52 flowing through hot gas ■ and the gases in the two cup-shaped Bulges to a certain extent

can take place, additionally 15

also through the narrow annular gaps between the two intermediate disks 53, 53 ' and the cup-shaped housing bulges 45, 45 'therethrough.

It is therefore easily possible to place the bulges on both sides of the conveying area 52 45, 45 'located heat protection areas in their heat protection effect even further

"_ Improve how it works on working examples 25th

is shown in Figs. 3 to 5 for the left heat protection area, which is not

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right-hand heat protection areas shown roughly correspond to the left-hand heat protection areas can be formed. The cross-flow fans according to these exemplary embodiments 3-5 can only apply to the heat protection means except for those explained below Differences between the cross-flow fan 40 according to FIG. correspond.

In fact, the one shown in Fig. 3 differs.

! 5 set the left area of the cross-flow fan 40 from that according to FIG. 2 essentially in that the conveying area 52 of the cross-flow fan the left-hand intermediate disk 53 of the impeller 46 is a gas-impermeable disk, which therefore has no air passage openings. Furthermore, the circumference of the impeller 46 at the transition area from the conveying area 50 to the relevant extension area 48 'of the impeller comprehensive labyrinth seal 74 is provided which except through the outer peripheral area of the washer 53 'still through the outer circumferential area another arranged close to it, also designed as a gas-impermeable disk Intermediate disk 75 and formed by annular disks 76 arranged on the inner circumference of housing 41 is, with the one annular disk 7 6 in the space between the two intermediate disks 53 ', 75 engages and the other annular disk 76 is arranged on the left side of the intermediate disk 75 near her.

A corresponding labyrinth seal cannot be used

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In the manner shown, also at the other transition area between the conveying area 52 of the cross-flow fan and the right-hand cup-shaped bulge of the housing is provided accordingly be. In the extension area 48 'of the impeller 46 there is also another gas-impermeable Intermediate disk 77 used, namely at approximately the same axial distances from the intermediate disk 75 and the end ring washer 5d '. This additional washer '77 improves the thermal insulation effect of the gas located in this cup-shaped bulge 45 ″ by additional axial restraint even further. The left-hand end ring disk 51 'forms together with that in it inserted hub 62 and the bearing pin 64 firmly inserted into it an air-impermeable seal of the left front end 49 'of the impeller 46. Also the right-hand end of the impeller, not shown 46 can be sealed accordingly and in the right-hand extension area of the impeller can also have at least one washer like the washer 77 should be used.

FIG. 4 shows a variant of the section of a cross-flow fan shown in FIG. 3, which differs from the embodiment according to FIG. 3 in that by the space between the two intermediate disks located within the blade ring of the impeller 75,77 is filled by a thermal insulation material 79. It can be heat-insulating, high temperature resistant plastic, a fiberglass pillow

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5 or the like. Act. This will provide thermal protection improved even further. A corresponding measure can also be taken on the right-hand side, which is not shown Extension area of the impeller 46 can of course be provided. Otherwise, this cross-flow fan corresponds according to FIG. 4 that according to FIG. 3.

FIG. 5 shows a variant of the section of the cross-flow fan according to FIG. 4. Of the The difference is that the interior of the cup-shaped bulge 45 'by additional Sealing rings 80, 81 on the housing and on the impeller as shown, essentially in two against one another sealed, axially one behind the other arranged chambers 82, 83 is divided, of which the left, end Chamber 83 can be flowed through by cooling air, which is located in this chamber section 50 ' of the blade ring of the impeller 46 is conveyed by this section 50 'cooling air like a radial impeller sucks in and promotes radially outwards, thereby providing additional thermal protection to the one shown left-side plain bearing bushing 65 is effected. Appropriate air cooling can also be used in the other, right-hand cup-shaped housing bulge can be provided. The described cooling air is not a conveying gas in the context of the invention, since it only serves to cool the fan and not through it the fan is conveying gas to be conveyed from the suction opening 42 to the exhaust opening 43.

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The end regions protruding to the left beyond the sealing disk 81 serve to convey the cooling air of the blades 50 by having large segment-shaped air inlet openings in the left end ring disk 51 ' 87 are present, through which these blade end areas air through in the housing end wall suction provided cooling air inlet openings 85 through. This cooling air is radially through circumferential air outlet slots 86 of the chamber 83 of the housing 41 are blown through.

In the exemplary embodiments according to FIGS. 2 to 4, the cup-shaped bulges 45, 45 'do not need any Have ventilation holes, but can often be useful ventilation openings may also be provided, preferably in the end walls of the housing 41.

In the embodiment according to FIG. 2, the drive of the impeller 46 is formed by the motor 61. There come however, other drives are also possible, for example a belt "c drive or the like. In the case of a drive, the drive shaft of the shaft that is non-rotatably connected to the impeller 46 with the difference that they are not the rotor shaft, but a belt pulley of the belt drive supporting drive shaft for the impeller 46 is.

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Claims (15)

5654 claims 1. Cross flow fan for conveying conveying gas, which also conveying hot and / or very cold conveying gases, preferably air, and has a housing in which the impeller is arranged, wherein the bearing points serving for the rotary bearing of the impeller are in considerable axial distances from the conveying area of the impeller serving to convey the conveying gas and the housing has cup-shaped bulges at the side of the suction opening and the exhaust opening, characterized in that on both sides of the conveying area (52) of the impeller (46) extension areas (48, 48 ') of the Impeller are present, which are located within the cup-shaped bulges (45, 45 ') of the housing (41), the drive shaft (60) of the impeller at the outer axial end of the one impeller extension area (48) and a bearing pin (64) of the rotary bearing of the impeller on the axially outer Attack the end of the other impeller extension area (48 *) that the depth of the cup-shaped bulges (45, 45 ") is at least 0.3 times the impeller diameter, and that the extension areas (48, 48 ') of the impeller does not feed the conveying gas through this cross-flow fan serve through. - 2 - 2. Cross-flow fan according to claim 1, characterized in that the bearing pin (64) is rotatably connected to the relevant axial end of the impeller (46). 3. Cross-flow fan according to claim 1, characterized in that the bearing pin on the housing attached and at the adjacent axial end of the impeller one of the pivot bearing of the Impeller is arranged on this journal serving sliding or roller bearing. 4. Cross-flow fan according to one of the preceding claims, characterized in that the The blades (50) of the impeller (46) extend entirely or almost over its length, and preferably theirs Ends on end disks (51, TSl ') of the impeller extension areas (48, 48 ') are held. 5. Cross-flow fan according to one of the preceding claims, characterized in that the conveying area (52) of the impeller on at least one side, preferably on both sides by a completely or substantially gas-impermeable intermediate disk or by completely or substantially gas-impermeable intermediate disks (53; 53 ' _f Fig. 3-5) is separated from the two impeller extension areas (48, 48 '). - 3 - 6. Cross-flow fan according to one of the preceding claims, characterized in that a labyrinth IQ seal (74) is arranged on the circumferential side of the impeller at at least one transition from the impeller conveyor area (52) to an impeller extension area (48; 48 '). 7. Cross-flow fan according to one of the preceding claims, characterized in that at least in an extension region (48 ¹ I of the running "L5 rades (46) thermal insulation means, preferably a heat insulating disk (79) are arranged. 8. Cross-flow fan according to one of the preceding claims, characterized in that an end portion of at least one impeller extension region (48 ¹ ) through an end chamber (831 of the relevant cup-shaped housing bulge (45 ') can promote cooling air, which is not a conveying gas, and that this end portion of the impeller extension area is separated from the conveying area (52) of the impeller by the remaining portion of this impeller extension area. - 4 - 9. Cross-flow fan according to claim 8, characterized in that the remaining portion is of the impeller extension area in a its associated second chamber (821 of the pot-shaped bulge, the side of the final IQ chamber (83) by means disposed on the impeller (46) said washer (77) and preferably also through the peripheral side of the impeller and the sealing rings (80, 81) arranged on the housing are separated. 10. Cross-flow fan according to one of claims 1-4 or 6-9, characterized in that the two extension areas (48,48 ') of the Impeller from its conveying area (52) through two annular disks each having a central perforation (53, 53 ', Fig. 2) is separated. 11. Cross-flow fan according to one of the preceding Claims, characterized in that the blades (50) of the impeller (46) are made of metal exist. 12. Cross flow fan according to one of the preceding Claims, characterized in that the gO engages one end face (49) of the impeller The drive shaft is the rotor shaft (601 of an electric drive motor (61) of the impeller (46) arranged on the housing (41). - 5 - 13. Cross-flow fan according to one of the preceding claims, characterized in that at least one of the two impeller extension areas over at least half, preferably over at least 3/4 of the axial length of the cup-shaped housing bulge (45.45 * I extends. 14. Cross-flow fan according to one of the preceding claims,. Characterized in that the depth the cup-shaped housing bulges (45, 45 ') at least 0.5 times, preferably approximately 0.6 to 1.2 times the impeller diameter. 15. Cross-flow fan according to one of the preceding Claims, characterized in that the drive shaft (60) of the impeller and the bearing journal (64) end at the respective outer ends of the impeller extension regions (48, 48 ').