EP0669465B1 - Bearing arrangement for a viscous fluid pump - Google Patents

Abstract

The bearing acts on a pump shaft (1) within the pump. At least on side of the low pressure side of the bearing is arranged a collection or release zone for fluid which has leaked through the bearing. At least two channels (13,15) join the zone to the suction side of the pump. One at least of these channels can be shut off independently to one another. They can be of different diameters or cross-sectional areas, and the zone itself can consist of an annular chamber adjacent to the shaft. It can be contained at least partly in the plain bearing itself (9) or the pump cover.

Description

The present invention relates to a bearing arrangement for a pump shaft for conveying Newtonian or non-Newtonian liquids with different viscosities with a bearing for the shaft, a gear pump and a method for collecting and returning leakage liquid passing through a bearing when pumping liquids with different viscosities.

With pumps, such as gear pumps, it cannot be prevented or it is necessary for a small part of the liquid medium to be conveyed, which is under a relatively high pressure, to be driven along a slide bearing along the drive shaft, for example. This leakage flow is usually used to lubricate the plain bearing. After passing through the plain bearing, the leakage liquid is collected in a collecting channel or a relief channel in order to be returned to the inlet side of the pump via a connecting channel. Such sealing or return arrangements are known for example from DE-544 963 and 31 35 037. As long as liquids with largely constant viscosity are continuously pumped in a pump, the known return arrangements are quite sufficient. In contrast, the arrangements described are unsuitable for the discontinuous pumping of liquids with very different viscosities.

In the production of polyester, for example, a batchwise or batchwise polymerization can be carried out for process engineering reasons. For this can a gear pump are used. During the polymerization phase or circulation phase, very low-viscosity liquid first enters the pump, which means that there is an extremely low pressure difference in the pump. After the end of the polymerization phase, ie during the extrusion phase, the pump conveys high to medium-viscosity melt against downstream pressure consumers, such as filters, extrusion tools and the like, which means that the pump has to deliver against a significantly higher pressure difference.

From the pump's point of view, the following difficulty arises:

During the conveyance of the highly viscous product, i.e. during the extrusion phase, the differential pressure across the pump is sufficiently high to cause a sufficient lubrication flow or leakage flow through the bearings and through the return channel system to the suction side of the pump. After switching to circulation mode, i.e. during the pumping operation in the polymerization phase, the differential pressure is very low, albeit sufficient for the low-viscosity, fluid medium. However, at the time of the switchover there is still highly viscous liquid in the return system, which highly viscous medium can only be replaced very slowly by the new low-viscosity liquid after the switchover due to the low differential pressure. A stagnation of the bearing leakage current poses the potential risk of undersupply of the bearing, whereby there is a risk of damage to the bearing.

It is therefore an object of the present invention to propose a return arrangement on a pump shaft, by means of which a sufficient leak lubrication when pumping Liquids with different viscosities are guaranteed. In particular, the task is to ensure the leakage lubrication when switching from the conveyance of a highly viscous medium to the conveyance of a low-viscosity medium, that is to say that a strongly impeded flow or even a blockage of the return arrangement for the low-viscosity fluid is prevented.

The stated object is achieved by means of a bearing arrangement or return arrangement for a pump shaft of a pump for the conveyance of liquids with very different viscosities according to the wording according to claim 1.

> 5) weist mindestens eine entweder an jeder Lagerrückseite oder an beiden Pumpendeckeln angeordnete Auffang- oder Entlastungszone auf, für das Auffangen von entlang der Welle durch das Lager durchtretende Leckageflüssigkeit, welche gleichzeitig für das Schmieren des Lagers verantwortlich ist. Von den Auffang- bzw. Entlastungszonen weist das Rückführsystem mindestens je zwei Rückführkanäle oder Bohrungen auf, um die aufgefangene Leckageflüssigkeit an die Saugseite der Pumpe zurückzuführen.The return duct system of a pump proposed for the conveyance of liquids with different viscosities (eg $\frac{{\text{η}}_{\text{high}}}{\text{ηlow}}$

> 5) has at least one catchment or relief zone either on the rear of the bearing or on both pump covers, for collecting leakage fluid passing through the bearing along the shaft, which is also responsible for lubricating the bearing. The return system has at least two return channels or bores from each of the collecting or relief zones in order to return the collected leakage liquid to the suction side of the pump.

Preferably, at least one of the channels or bores can be closed, which makes it possible, depending on the viscosity of the medium to be pumped, to close one of the bores, or to keep all bores or return channels open. If high-viscosity media are fed, the hole for the low-viscosity medium should be closed; if the low-viscosity medium or product is pumped, the hole for the low-viscosity medium must be open. In the latter case, the flow resistance ratio is such that the return hole for the high-viscosity product appears to the low-viscosity product to be closed.

Further preferred embodiment variants of the bearing arrangement defined according to the invention or of the return arrangement defined according to the invention are characterized in the dependent claims 2-6.

In the case of a gear pump, for example with two return channels, the return hole closer to the back of the bearing or the low-pressure side is preferably reserved for the return of the low-viscosity liquid. Thus, this closer return hole is opened after switching from the conveyance of a highly viscous medium to the conveyance of the low-viscosity medium, which return channel is not "blocked" by the highly viscous medium. In order to come back to the above example of a discontinuous production of polyester, this closer return channel is opened after switching to polymerization or circulation mode. The polymerization increases the viscosity in the polyester to be circulated, and after reaching a certain viscosity or after reaching a certain differential pressure or after switching back to extrusion operation, the nearer return duct is closed again so that no highly viscous material can enter it. This closer return hole can be closed and opened hydraulically, pneumatically or by electric motor, for example using a stepper motor. Whether the shorter return channel ultimately runs through the slide bearing or through the housing surrounding the slide bearing is, for example, of the geometrical type Conditions dependent. In any case, both versions are possible.

When using several slide bearings arranged next to one another, it is of course possible to combine return channels of the same type, at least along a common section, i.e. return channels for low-viscosity media can be combined and return channels for high-viscosity media.

Fig. 1

im Längsschnitt durch eine Gehäusewandung ein Gleitlager und eine erfindungsgemäss ausgebildete Rückführanordnung,

Fig. 2 und Fig.3

weitere Ausführungsvarianten einer erfindungsgemässen Lageranordnung bzw. einer Rückführanordnung im Längsschnitt, und

Fig. 4

im Querschnitt zwei nebeneinander angeordnete Gleitlager einer Zahnradpumpe.

The invention will now be explained in more detail, for example, and with reference to the accompanying figures.
It shows:

Fig. 1

in longitudinal section through a housing wall a plain bearing and a feedback arrangement designed according to the invention,

Fig. 2 and Fig. 3

further embodiment variants of a bearing arrangement according to the invention or a return arrangement in longitudinal section, and

Fig. 4

in cross section two slide bearings of a gear pump arranged side by side.

In Fig. 1, a bearing of a drive shaft 1 of a gear pump is shown schematically in longitudinal section, running through a housing wall 7. A gear 5 is arranged on the shaft 1 in the pump chamber 3 in order to convey a viscous liquid in the direction of arrow A. Through the housing wall 7, the shaft 1 is supported in a slide bearing 9, through which bearing, along the shaft 1, in the intermediate space 10 due to the high pressure in the pump chamber 3, the medium to be pumped is driven. This so-called Leakage liquid also serves to lubricate the slide bearing 9. A collecting or annular space 11 is arranged on the rear of the slide bearing 9 in order to collect the leakage liquid passing through the slide bearing 9. According to the invention, this collecting or annular space 11 is connected to the suction side of the pump space 3 via two return channels 13 and 15. In order to be able to close the return duct 13 guided closer to the rear of the bearing, a valve 17 is also provided, for example.

2 shows, analogously, in longitudinal section a further embodiment variant of a bearing according to the invention or a return arrangement, the collecting or annular space 11 now being arranged at least partially inside the rear of the sliding bearing 9. The two return channels 13 and 15 are again arranged peripherally from this annular space 11, running outwards, with the result that at least the branch 13a or 15a of each return channel, which runs perpendicular to the shaft 1, appears as lying one on top of the other. The two return duct sections 13a and 15a can also be guided independently of one another in this area, or they can be combined. This is because sections 13a and 15a can be very short. In contrast, the return holes 13 and 15, which are comparatively long, must be guided separately.

3 shows an arrangement similar to that in FIG. 2, but the return duct sections 13a and 15a are guided in the cover 8 of the pump. These return channel sections 13a and 15a can be formed, for example, by a so-called V-groove. This V-groove or V-grooves open into the two return bores 13 and 15, for example one behind the other, which is why they are not shown in the illustration according to FIG separately drilled holes appear. Finally, a sealing arrangement 16 is shown in the cover 8 in FIG. 3.

4 finally shows two slide bearings 9 ′ and 9 ″ arranged next to one another in the same housing wall 7, through which the shafts 1 ′ and 1 ″ run. Both bearings each have a collecting or annular space 11 'or 11 "on their rear side. The channels 13', 13", 15 'and 15 "leading away from this collecting ring 11' or 11" are each in a common return channel 19 and 21 guided, through which two latter channels the low-viscosity medium or high-viscosity medium are fed back into the pump on the suction side.

The return arrangements according to the invention shown in FIGS. 1-4 are of course only examples which can be modified, modified or supplemented in any manner. So it is of course possible to arrange further return channels and, in the case of several return channels, also to design more than one return channel to be closable. This can be useful, for example, if the viscosities of the different liquids to be pumped differ greatly. The sealability of the return channels can also be achieved in various ways, but this is know-how which is known per se and cannot be explained in more detail here. It is also in itself immaterial whether the return channels are partially passed through the bearings themselves or through the housing wall. Finally, it should be pointed out that the illustration of the sealing arrangement adjacent to the collecting or annular space has been omitted in the figures, since this is not part of the present invention.

Finally, it should be pointed out that the arrangement according to the invention was probably explained using a gear pump, but that the arrangement according to the invention can of course be used wherever leakage liquids have to be removed or returned.

It is essential to the invention that the discharge or return system has at least two return channels or bores, on each pump side.

Claims (11)

1. Bearing arrangement for a pump shaft (1) for transporting Newtonic or non-Newtonic fluids of different viscosities, with a bearing for the shaft, characterized by:

   - at least one capture or discharge zone (11) arranged on the low pressure side of the bearing for capturing the leakage fluid penetrating along the shaft through the bearing (9) and

   - at least two return channels or bores (13, 15) connecting the capture or discharge zone (11) with the suction side of the pump in order to return the captured leakage fluid.
2. Bearing arrangement according to claim 1, characterized in that at least one of the channels or bores can be closed.
3. Bearing arrangement according to claim 1 or 2, characterized in that the channels or bores are formed to be closeable independently of each other.
4. Bearing arrangement according to any of claims 1 to 3, characterized in that the channels or bores have different diameters or cross-sections.
5. Bearing arrangement according to any of claims 1 to 4, characterized in that the capture or discharge zone is formed by at least one annular chamber (11) adjacent to the shaft.
6. Bearing arrangement according to any of claims 1 to 5, characterized in that at least one annular chamber (11) is arranged on the back or low pressure side running at least partly in the plain bearing body (9) or on or in the pump cover (8) and at least one of the return channels or bores (13) is arranged running at least partly through or along the plain bearing housing(s).
7. Gear pump with one or more bearing arrangements according to any of claims 1 to 6.
8. Gear pump according to claim 7, characterized in that in each case each pair of similar return channels or bores (13', 13" and 15', 15") is composed at least partly of two bearings (9', 9") arranged next to each other in the pump housing wall or has a common section (19, 21).
9. Process for capturing leakage fluid penetrating through a bearing arrangement according to any of claims 1 to 6 in a pump plain bearing and return of the leakage fluid in pumps for fluids of different viscosities, characterized in that leakage fluid of a certain viscosity penetrating through the bearing along the shaft is captured at the bearing back or low pressure side in a capture or discharge zone and returned to the suction side of the pump via at least one of the return channels, while at least one of the further return channels remains closed when a preset pressure difference in the pump is reached or exceeded.
10. Process according to claim 9, characterized in that during transport of high viscosity media at least one of the return channels remains closed, and during transport of low viscosity media, i.e. below a preset pressure difference in the pump, at least one of the further closed return channels is opened in order to ensure the return of the low viscosity medium from the capture zone to the suction side of the pump.
11. Process according to claim 9 or 10, characterized in that low viscosity media are returned through the return channel (channels) closest to the bearing back or low pressure side, i.e. preferably the channel (channels) closest to the bearing back is (are) designed closable.

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