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  Vacuum pumpUSPTO Application #: 20070258836Title: Vacuum pump Abstract: A vacuum pump includes a housing, a rotor located in the housing and having a shaft and pump-active elements supported on the shaft, a stator having pump-active elements and located in a separate housing part of the housing, for driving the pump, bearings for rotatably supporting the rotor shaft, and at least one vacuum chamber located in the housing. (end of abstract)
Agent: Abelman, Frayne & Schwab - New York, NY, US Inventors: Bernd Hofmann, Tobias Stoll USPTO Applicaton #: 20070258836 - Class: 4174234 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070258836. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to a vacuum pump including a housing, a rotor located in the housing and having a shaft and pump-active elements supported on the shaft, a stator located in the housing and having pump-active elements, with the housing having a housing part for holding the pump-active elements of the stator, drive means for driving the pump and bearing means for rotatably supporting the rotor shaft. [0003]2. Description of the Prior Art [0004]Vacuum pumps form, together with vacuum chambers, vacuum systems with which numerous tasks can be performed. These tasks range from manufacturing monolithic layers through analyses of gases, and up to optical columns of high-resolution electronic microscopes. The technical developments put higher and higher requirements to the vacuum tightness and compactness of the vacuum systems. [0005]In some common applications, so-called differential pumps are used. With differential pumps, a system is formed of vacuum pumps connected with each other, with separate vacuum chambers being held at different gas pressures. [0006]A noticeable simplification of formation of a pump system for differential pumps is disclosed in German Patent DE-PS 43 31 589. Instead of a plurality of pumps, a single vacuum pump takes over evacuation of vacuum chambers. [0007]European Patent EP-PS 1 090 231 discloses a vacuum pump with a double housing. An inner housing combines a rotor/stator region and a drive/bearing region of the pump. The inner housing is then pushed into an outer housing that is adapted to a particular use. However, the latter solution has serious drawbacks, a double housing is expensive as more parts are used than with a single-part housing. This increases both expenses associated with manufacturing of the housing components and expenses associated with the assembly of numerous components. The contact surfaces of the two housings must be machined with a high precision. The danger of a virtual leak increases with an increase of number of components needed for the housing. Between the two separate housings, seals must be provided which, because of their large number, increase the risk of leakage. For a double housing, additional space should be provided, which makes gas feeding more expensive. These problems are independent of the number of vacuum chambers provided in the vacuum system. [0008]Accordingly, an object of the invention is a vacuum pump in which the problems, which are associated with a double housing, are eliminated. [0009]Another object of the invention is a vacuum pump having a compact construction and requiring a small number of parts. SUMMARY OF THE INVENTION [0010]These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a vacuum pump in which the housing part which serves for holding pump-active stator elements, has at least one vacuum chamber. This noticeably reduces the number of necessary parts. A smaller number of flanges and other housing transition elements becomes necessary, whereby vacuum tightness increases and expenses decreases. Generally, a very compact unit is provided. Because a flange connection between the vacuum chamber and vacuum pump, which is necessary in the existing state of the art, is eliminated, the vacuum tightness is noticeably increased. This permits to achieve lower end pressures with the inventive vacuum pump. [0011]A further reduction of the number of parts is achieved when the separate housing part further holds at least one component of bearing and drive means. [0012]According to the invention, the inventive vacuum pump has a plurality of pumping stages with each of which a vacuum chamber is connected, with the vacuum chambers being also connected with each other. Thereby, a single component, such as a housing, is necessary for all chambers in the vacuum pump, which reduces costs and increases tightness. With the gas pressure in the respective chambers being different, a plurality of differential pumps are provided in the vacuum pump. [0013]According to the invention the bearing means includes a permanent magnet bearing for supporting an end of the rotor shaft. This bearing does not require lubrication and is wear-free and, thus, can be used in the high-vacuum region of a vacuum pump. [0014]According to a further modification of the present invention, for production of the high vacuum, the pump-active rotor elements and the pump-active stator elements includes blades forming at least one high-vacuum pumping stage. This is particularly suitable for obtaining low pressures. [0015]According to a further development of the present invention, the at least one vacuum chamber has an opening, and the vacuum pump further includes a releasable cover for closing the opening, and at least two seals for sealing the opening. The opening provides for an easy access to the vacuum chamber so that, e.g., maintenance becomes possible, or the components located in the vacuum chamber, e.g., of some experiment, can be very easily replaced. The opening-sealing seals insure the vacuum tightness. [0016]The arrangement discussed above can be further improved by providing an annular channel between the two seals and in which vacuum is produced. Thereby, the pressure drop between the atmospheric pressure and vacuum takes place in stages, which reduces forces acting on the seals. Because the leakage rate of a leak depends on the pressure difference between the inner and outer sides, and the stagewise pressure drops means a smaller pressure difference across a seal, smaller leaks play a smaller role. By measuring the power consumption of a pump used for producing vacuum, leakage at the seals can be determined. [0017]According to further development of the present invention, there is provided a push-in or insertable module in which at least one of the vacuum chambers is located. The insertable module is pushed in a bore formed in the vacuum pump housing and is retained there. Thereby, it is possible to replace the vacuum chamber system of the inventive vacuum pump and adapt it to other requirements. In addition, it is possible to have the vacuum chambers and the vacuum pump produced by different manufactures. This reduces costs because manufacturing steps take place parallel with each other and respective professional skills and knowledge are optimally used. [0018]According to a further advantageous embodiment of the present invention, for producing vacuum in the annular channel, there is provided a connection conduit integrated in the housing between the annular channel and one of pumping stages and gas outlet channel. [0019]The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0020]The drawings show: [0021]FIG. 1 a cross-sectional view of a first embodiment of a vacuum pump according to the present invention; Continue reading... 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