Pumps – Motor driven – Electric or magnetic motor
Patent
1998-04-17
2000-02-29
Wolfe, Willis R.
Pumps
Motor driven
Electric or magnetic motor
417250, 415 90, F01D 136, F04D 2500
Patent
active
060301899
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a friction vacuum pump having the characteristics of patent claim 1.
A friction vacuum pump of this kind is known from DE-A-31 24 205. As to the design of the opening of the intermediate inlet into the pumping chamber of the friction pump, it is stated that it is advantageous to provide an annular channel.
It is the task of the present invention to design the opening of the intermediate inlet into the pumping chamber of the friction vacuum pump in a preferred manner while at the same time taking two aspects into account. On the one hand the stator forming components in the area of the annular channel shall be designed in such a manner that they obstruct the gases entering into the pumping chamber as little as possible. On the other hand simple production of the components in the area of the annular channel shall be ensured.
SUMMARY OF THE INVENTION
This task is solved through the present invention by the characteristic features of the claims. A stator of the kind according to the present invention differs only slightly from a stator for a friction pump without an intermediate inlet. It is only required to equip an annular spacer being present at the height of the annular channel with perforations--bore holes, milled openings or alike. Other differences do not exist, be they in respect to the way in which the stator is manufactured or the way in which it is fitted, so that the complexity of manufacturing a friction vacuum pump with an intermediate inlet is only insignificantly greater compared to a friction pump without an intermediate inlet. One annular spacer may be equipped with a multitude of perforations. It is particularly advantageous for the annular spacer to have several sections which are reduced in height. The total of these sections may amount to 20 to 80% of the circumference of the annular spacer, so that the conductance of the perforations can be designed to be very high without impairing the stability of the stator.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages and details of the present invention shall be explained by reference to the design examples of drawing FIGS. 1 to 4. Shown in
drawing FIG. 1 is a design example for a friction vacuum pump according to the present invention,
drawing FIG. 2 is a further design example,
drawing FIG. 3 is a top view on to an annular spacer of the stator for the design example according to drawing FIG. 2 and
drawing FIG. 4 is a section through the annular spacer according to drawing FIG. 3 along the line IV--IV.
DESCRIPTION OF THE INVENTION
In the design example according to drawing FIG. 1 the outer casing is designated as 1. It is equipped with a bearing bush 2 which extends inwards, supporting a shaft 3 by means of a spindle bearing arrangement 4. Coupled to the shaft 3 are the drive motor 5, the rotor 6 of a molecular pumping stage as well as the rotor 7 of a turbomolecular pumping stage. The rotor 7 is equipped with the rotor blades 8, which together with the stator blades 9 suspended within casing 1, form the turbomolecular pumping stage. By means of flange 11 the particular pump is connected to the vacuum chamber which is to be evacuated.
The molecular pump (or molecular pumping stage) comprises bell-shaped rotor 6 which embraces the bearing space 12, whereby said rotor is equipped on its outside with thread-like grooves 13, in which during operation of the pump the gas is conveyed from the high vacuum side to the forevacuum side. Assigned to the rotor 6 is a stator having approximately the same axial length. Located between the stator 14 and the rotor 6 is a slot 10. This slot needs to be as small as possible in order to attain a seal between the thread-like grooves which is as good as possible. The forevacuum port 20 is connected to the forevacuum chamber 19.
Stator blades 9 and annular spacers 22 to 24 belong to the stator 21 of the turbomolecular pump. The stator blades 9 are--in a manner which is basically known--part of the annular blades or blade segments 25 with outer
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patent: 5733104 (1998-03-01), Conrad et al.
Bohm Thomas
Hirche Ralf
Leybold Vakuum GmbH
Wolfe Willis R.
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