EP2783115B1 - Liquid ring vacuum pump - Google Patents

Description

The invention relates to a liquid ring vacuum pump with a shaft which is mounted eccentrically in a pump housing. With the shaft, an impeller and a rotor of a drive motor are connected. Parallel to the impeller, a control disk is arranged.

Such pumps can be used to evacuate containers or other enclosed spaces. An inlet port of the pump is connected to the space to be evacuated, the gas contained in the space is drawn in through the inlet port, compressed in the pump and discharged through an exit port.

In liquid ring vacuum pumps, a fluid ring is held in motion by the impeller so that the chambers between the vanes' wings are closed by the fluid ring. Since the impeller is mounted eccentrically in the pump housing, the liquid ring penetrates different distances depending on the angular position of the impeller into the chamber and thereby acts as a piston which changes the volume of the chamber. All the force required for this is transmitted through the shaft and the impeller.

Liquid-ring vacuum pumps in monobloc design traditionally consist of a standard electric motor and the pump flanged to it. Pump and motor are hydraulically with Help of a mechanical seal separated. The pump does not have its own bearings, so that the bearings of the electric motor are used to absorb the process forces. These are usually reinforced. The process forces engage in the radial and axial direction on the overhanging impeller and load the shaft on pressure and especially on bending. This sag must be taken into account when designing the pump by providing sufficient tolerances. In particular, between the impeller and the control disk, a distance must be maintained, because a deflection of the shaft otherwise causes the impeller otherwise abuts the control disk. Tolerances between the impeller and the control disk but are associated with leakage, which reduce the efficiency of the pump.

The invention is based on the object to present a liquid ring vacuum pump, in which the leakage losses are reduced. Based on the above-mentioned prior art, the object is achieved with the features of claim 1. According to the invention, a first and a second main bearing for the shaft are provided. The first main bearing is disposed between the impeller and the rotor in the plane of the control disk. The impeller is disposed between the first main bearing and the second main bearing. Advantageous embodiments can be found in the subclaims.

First, some terms are explained. The impeller and the rotor of the drive motor lie on a common shaft. This is a monobloc pump with no shaft flange between the rotor and the impeller. The term main bearing refers to a pivot bearing in which the shaft is statically guided. Even if the shaft does not turn, it is held in a defined position by the main bearings. A hydrodynamic bearing that can only absorb bearing forces when the shaft rotates is not Main camp in this sense. As a main bearing, for example, plain bearings or bearings come into question. The main bearings are preferably lubricated by the operating fluid of the pump.

The pump housing refers to the part of the pump in which the impeller is housed. The eccentric bearing of the shaft thus relates to the impeller in the pump housing. In other sections of the pump, the shaft may be centrally located. In the adjacently arranged to the impeller control disk, the openings are formed, through which the gas to be conveyed enters the chambers of the impeller and exits again. It is not excluded that the control disc is incorporated directly into the housing. As a rule, the control disk but a separate component which is connected to the housing.

The invention has recognized that it is disadvantageous when the shaft bends in the central region between the drive motor and the impeller. It must then be maintained a greater tolerance between the impeller and the control disk, which is directly reflected in increased leakage. According to the invention, it is therefore proposed to arrange the first main bearing and the second main bearing adjacent to the impeller. The shaft is then mounted in the area in which a large part of the forces acting on the shaft, and it is possible to arrange the impeller at a shorter distance to the control disc, so that the leakage losses are reduced.

It makes sense to record the process forces as close as possible to the impeller. The first main bearing is therefore arranged in the plane of the control disk. For classic storage concepts (cf. GB 1 355 193 . DE 1 293 942 ) seals are possibly provided in the plane of the control disc.

The extent of the main bearing in the axial direction is regularly greater than the thickness of the control disk, so that the main bearing extends beyond the control disk in one or both directions. Preferably, the first main bearing is designed so that it can absorb axial forces from the shaft in addition to radial forces. The absorption of the axial forces can be done via the pointing in the direction of the impeller end face of the first main bearing. For this purpose, the main bearing can be arranged so that it protrudes in the axial direction over the control disk. The second main bearing may be configured to receive only radial forces and no axial forces from the shaft.

The control disk itself is generally a component that is not suitable for receiving large loads. In order to keep the control disk free from stresses by the main bearing, the main bearing may be held in a housing part, which is arranged adjacent to the control disk. The control disk is located between this housing part and the impeller. The rotor of the drive motor is preferably arranged beyond the housing part. The shaft thus extends through the housing part, so that the rotor is arranged on one side and the impeller on the other side of the housing part.

It is not excluded that the pump can have more than two main bearings. If additional bearings are provided, they are usually auxiliary bearings, which are smaller in size than the main bearings. The main bearings in this case are the two largest bearings of the shaft.

In an advantageous embodiment, exactly two main bearings are provided. Although there is a comparatively large mass on the shaft with the rotor of the drive motor, which is not arranged between the two main bearings. The rotor is but usually free of imbalances, so that there are no major forces acting on the shaft. In addition, the engine itself can absorb bearing forces to some extent. Namely, it forms by the operating fluid in which the rotor rotates, a hydrodynamic bearing when the gap between the rotor and the stator of the drive motor is sufficiently small.

If the shaft beyond the rotor is no longer supported (viewed from the impeller), damage to the rotor and the stator of the drive motor may result if the main bearings wear out. To reduce the risk of such damage, a stop ring may be provided beyond the rotor. In normal operation, no bearing forces occur in the thrust ring. The thrust ring can be designed so that the shaft has play in the thrust ring. The function of the thrust ring only becomes apparent when one of the main bearings has worn out. In this case, the stop ring prevents the rotor and the stator of the drive motor from touching each other. The thrust ring can also be used as a wear indicator in which it is concluded that any of the other bearings wear out when the bearing forces in the thrust ring exceed a predetermined threshold.

In order to keep the leakage low, the distance between the impeller and the control disc must be small. For this it is necessary to precisely adjust the axial position of the shaft. In an advantageous embodiment, the axial position of the shaft is defined by the fact that the impeller rests against an end face of the first main bearing. For this purpose, the first main bearing protrudes slightly beyond the plane of the control disk. When assembling the pump, the axial position of the first main bearing must be set exactly. In addition, however, no adjustments are required.

The impeller is preferably designed so that a force is generated in the direction of the first main bearing by the rotation, which takes place during operation of the pump. If the shaft has a slight play in the axial direction, the impeller is automatically pressed by this force against the end face of the main bearing.

At the end opposite the control disk, the chambers of the impeller are preferably closed by a flange, which projects into the liquid ring during operation of the pump. The leakage gap between the impeller and the control disk is then the only leakage gap of the pump. Beyond the flange, the working space of the pump can be closed by a housing cover.

Fig. 1:

eine schematische Querschnittsansicht einer erfindungsgemäßen Pumpe.

The invention will be described below by way of example with reference to the accompanying drawing with reference to an advantageous embodiment. It shows:

Fig. 1:

a schematic cross-sectional view of a pump according to the invention.

A liquid ring vacuum pump in Fig. 1 includes a housing 14 with a foot 15. In the housing 14, a shaft 19 is mounted, which extends transversely through the housing 14 from the left end to the right end. The shaft 19 carries on one side a rotor 20 of a drive motor of the pump and on the other side an impeller 21, with which the gas to be conveyed is transported.

The housing 14 is composed in the axial direction of three housing parts 16, 17, 18, wherein in the in Fig. 1 Housing part 18 shown on the left, the impeller 21 and in the housing part 16 shown on the right side of the drive motor is received. Of the The drive motor comprises the rotor 20 connected to the shaft 19 and a stator 24 connected to the housing part 16. Electrical energy is supplied to the drive motor via a power supply unit 25, so that the shaft 19 is rotated together with the impeller 21. By the rotation of the impeller 21, the medium to be transported is conveyed, as will be explained in more detail below.

The shaft 19 is mounted with a first main bearing 23 and a second main bearing 26, which are arranged on both sides of the impeller 21 at a small distance from the impeller 21. The first main bearing 23 is held in the central housing part 17 and extends from there just above the plane of the control disk 22 also. The second main bearing 26 is located in the end face of the housing part 18 and extends from the end of the shaft 19 to the impeller 21. The two main bearings 23, 26 are arranged in the region in which by the impeller 21, the strongest forces on the shaft 19th be transmitted.

Only slight forces act on the shaft 19 between the first main bearing 23 and the other end of the shaft 19. The drive motor 19 is formed by the thin gap between the rotor 20 and the stator 24, which is filled with operating fluid during operation of the pump own hydrodynamic bearing. In the provided at the other end of the shaft stop ring 27, the shaft 19 game. The stop ring 27 thus assumes no bearing forces in normal operation, but serves additional security if the main bearings 23, 26 wear out. By a suitable sensor on the stop ring 27 can be determined when bearing forces occur in the stop ring 27. The occurrence of bearing forces can be understood as an indication of incipient wear of the pump.

The impeller 21 is mounted eccentrically in the housing part 18, which forms the actual pump housing. When the impeller rotates, an operating fluid is set in motion, so that in the pump housing, a liquid ring is formed, which moves with the impeller. Depending on the angular position of the impeller, the liquid ring penetrates more or less deeply into the chambers of the impeller. The liquid ring thus acts like a piston which moves up and down in the chambers. The gas to be delivered is sucked in the area in which the volume of the chamber increases, and discharged again in the area in which the volume of the chamber is reduced.

For the supply and discharge of the gas 17 channels are provided in the central housing part, which in Fig. 1 are not shown. The channels open into a control disk 22, with in Fig. 1 is not visible openings. The openings are arranged so that the gas can enter the chamber in the correct area or exit from the chamber.

There must necessarily be a gap between the control disk 22 and the impeller 21, so that the impeller 21 can rotate freely. This gap also forms a leakage gap of the pump through which the gas to be delivered can escape from one chamber to the next chamber. On the opposite side of the impeller 21, the chambers are closed with a wall which projects into the liquid ring during operation of the pump.

In order to keep the leakage gap between the impeller 21 and the control disk 22 small, the impeller 21 must be accurately positioned in the longitudinal direction. In the pump according to the invention, the position of the impeller 21 is defined by the fact that the impeller rests against an end face of the first main bearing 23. The first main bearing 23 is held in the central housing part 17, so that the bearing forces there and not on the control disk 22nd be transferred. Starting from the central housing part 17, the first main bearing 23 protrudes slightly beyond the control disk 22 in the direction of the impeller 21. When the impeller 21 bears against the end face of the first main bearing 23, the impeller thus maintains a defined distance from the control disk 22. The impeller 21 is designed so that during operation of the pump, a force acting in the direction of the control disk 22 force arises. The impeller 21 thereby automatically assumes the desired position in the pump.

Claims (9)

1. Liquid-ring vacuum pump having a pump housing (18), having a shaft (19) which is mounted eccentrically in the pump housing (18), an impeller (21) and a rotor (20) of a drive motor (20, 24) being connected to the shaft (19), and having a control disk (22) which is arranged parallel to the impeller (21), a first main bearing (23) and a second main bearing (26) being provided for the shaft (19), the first main bearing (26) being arranged between the impeller (21) and the rotor (20), and the impeller (21) being arranged between the first main bearing (23) and the second main bearing (26), characterized in that the first main bearing (23) is arranged in the plane of the control disk (22).
2. Liquid-ring vacuum pump according to Claim 1, characterized in that the first main bearing (23) is held in a housing part (17) which is arranged adjacently with respect to the control disk (21).
3. Liquid-ring vacuum pump according to either of Claims 1 and 2, characterized in that the first main bearing (23) is designed to absorb radial forces and axial forces from the shaft (19).
4. Liquid-ring vacuum pump according to one of Claims 1 to 3, characterized in that the second main bearing (26) is designed to absorb radial forces from the shaft.
5. Liquid-ring vacuum pump according to one of Claims 1 to 4, characterized in that the rotor (20) and the stator (24) of the drive motor form a hydrodynamic bearing for the shaft (19).
6. Liquid-ring vacuum pump according to one of Claims 1 to 5, characterized in that a run-on ring (27) is provided on the other side of the rotor (20) of the drive motor (20, 24).
7. Liquid-ring vacuum pump according to Claim 6, characterized in that the run-on ring (27) serves at the same time as a wear indicator.
8. Liquid-ring vacuum pump according to one of Claims 1 to 7, characterized in that the axial position of the shaft (19) is defined by virtue of the fact that the impeller (21) bears against an end face of the first main bearing (23).
9. Liquid-ring vacuum pump according to one of Claims 1 to 8, characterized in that the impeller (21) is designed in such a way that a force is generated in the direction of the first main bearing (23) as a result of the rotation during operation of the pump.

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