Rotary expansible chamber devices – Shaft or trunnion lubrication or sealing by diverted working...
Patent
1998-03-04
2000-09-26
Walberg, Teresa
Rotary expansible chamber devices
Shaft or trunnion lubrication or sealing by diverted working...
418 83, 418132, 418206, F04C 218
Patent
active
061235318
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of patent application Ser. No. 951 07 891.4 filed in the European Patent Office on May 24, 1995, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a bearing arrangement for a pump shaft for delivering newtonian or non-newtonian liquids of different viscosities, having a bearing for the shaft, a gear pump, and to a process for collecting and returning leakage liquid passing through a bearing during the pumping of liquids of different viscosities.
In the case of pumps, such as gear pumps, it cannot be prevented or it is not necessary to prevent that a small portion of the liquid medium to be delivered, which is relatively highly pressurized, is driven through a slide bearing, for example, along the drive shaft. As a rule, this leakage flow is used for lubricating the slide bearing. After passing through the slide bearing, the leakage liquid is collected in a collection groove or in a relief groove in order to be returned by way of the connection duct of the pump to its inlet side. Such sealing and returning arrangements are known, for example, from German Patent Documents DE-544 963 and 31 35 037. As long as liquids with largely constant viscosities are continuously delivered in a pump, the known return arrangements are perfectly sufficient. In contrast, during the discontinuous pumping of liquids having very different viscosities, the described arrangements are unsuitable.
Thus, for example, during the manufacturing of polyester, a discontinuous or batch-type polymerization can be carried out for process-related reasons. A gear pump can be used for this purpose. During the polymerization phase or circulation phase, very low-viscosity liquid first arrives in the pump causing an extremely low pressure difference in the pump. After the conclusion of the polymerization phase, that is, during the extrusion phase, the pump delivers high-viscosity to medium-viscosity molten mass against pressure consumers connected behind it, such as filters, extrusion tools and the like, causing the pump to have to deliver against a clearly higher pressure difference.
With respect to the pump, the following difficulty will arise:
During the delivery of the highly viscous product, that is, during the extrusion phase, the pressure difference above the pump is sufficiently high for causing a satisfactory lubricating flow or leakage flow through the bearings as well as through the return duct system of the suction side of the pump. After the change-over to the circulation operation, that is, during the pump operation in the polymerization phase, the differential pressure is very low although it is sufficient for the low-viscosity fluid medium. However, at the point in time of the change-over, high-viscosity liquid is still situated in the return system and after the change-over, because of the low differential pressure, can be replaced only very slowly by the new low-viscosity liquid. Because of a stagnation of the bearing leakage current, there is the potential danger of an undersupply of the bearing which may result in the risk of damage to the bearing.
It is therefore an object of the present invention to suggest a return arrangement on a pump shaft which ensures a sufficient leakage lubrication during the delivery of liquids of different viscosities. In particular, it is an object of the invention to ensure the leakage lubrication when a change-over takes place from the delivery of a high-viscosity medium to the delivery of a low-viscosity medium; that is, an extremely impaired flow or even a clogging of the return arrangement for the low-viscosity liquid is prevented.
The above object is achieved by means of a bearing arrangement or a return arrangement for a pump shaft of a pump for the delivery of liquids of very different viscosities having a bearing for the shaft wherein at least one collection or relief zone is arranged on a low-pressure side of the bearing for collecting leakage liquid padding
REFERENCES:
patent: 4090820 (1978-05-01), Teruyama
patent: 4160630 (1979-07-01), Wynn
patent: 4392798 (1983-07-01), Bowden
patent: 4486160 (1984-12-01), Lipscombe
patent: 4725211 (1988-02-01), Gray
patent: 4737087 (1988-04-01), Hertell
patent: 5324183 (1994-06-01), Capelle
patent: 5494425 (1996-02-01), Stehr
patent: 5641281 (1997-06-01), Russell et al.
patent: 5924854 (1999-07-01), Blume et al.
Blume Peter
Stehr Roger
Fastovsky Leonid
Maag Pump Systems Textron AG
Walberg Teresa
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