VACUUM PUMP

Abstract

Vacuum pump having a housing which defines a pump chamber and a drive chamber. A rotor is arranged in the housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet. Therein, the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber. The shaft feedthrough has a connection, wherein the connection is connected to an underpressure, so that a barrier gas flows from the drive chamber at least partially through the shaft feedthrough to the connection.

Claims

1. A vacuum pump having: a housing which defines a pump chamber and a drive chamber, a rotor arranged in the housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet, wherein the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber, wherein the shaft feedthrough has a connection, wherein the connection is connected to an underpressure, so that a barrier gas flows from the drive chamber at least partially through the shaft feedthrough to the connection.

2. The vacuum pump according to claim 1, characterized in that a pressure P.sub.1 prevails in the drive chamber and the underpressure has a pressure P.sub.2, wherein P.sub.2<P.sub.1, wherein in particular P.sub.1 corresponds to atmospheric pressure.

3. The vacuum pump according to claim 1, characterized in that a pressure P.sub.3 prevails in the pump chamber at the shaft feedthrough and the underpressure has a pressure P.sub.2, wherein P.sub.2<P.sub.3, and in particular P.sub.3≥P.sub.1>P.sub.2 applies.

4. The vacuum pump according to claim 1, characterized in that the connection is connected to a further vacuum pump for generating the underpressure.

5. The vacuum pump according to claim 1, characterized in that the connection is connected to a vacuum portion of the pump chamber.

6. The vacuum pump according to claim 5, characterized in that the vacuum portion of the pump chamber corresponds to the inlet of the vacuum pump.

7. The vacuum pump according to claim 1, characterized in that a first throttle is arranged between the drive chamber and the connection.

8. The vacuum pump according to claim 7, wherein the first throttle is formed by a first portion of the shaft feedthrough, in particular designed as a contact-free shaft seal.

9. The vacuum pump according to claim 1, characterized in that a second throttle is arranged between the pump chamber and the connection.

10. The vacuum pump according to claim 9, wherein the second throttle is formed by a second portion of the shaft feedthrough, in particular designed as a contact-free shaft seal.

11. A vacuum pump system having a first vacuum pump and at least one second vacuum pump, wherein each vacuum pump has the following: a housing which defines a pump chamber and a drive chamber, a rotor arranged in the housing, wherein the rotor has at least one rotor element arranged in the pump chamber for conveying a gaseous medium from an inlet to an outlet, wherein the rotor extends from the pump chamber through a shaft feedthrough into the drive chamber, wherein the shaft feedthrough has a connection, wherein the connection is connected to a common inlet of the first vacuum pump and the at least second vacuum pump or to a common further vacuum pump, so that one barrier gas each flows from the respective drive chamber through the respective shaft feedthrough.

12. The vacuum pump system according to claim 11, characterized in that the outlet of the first vacuum pump is connected to the inlet of the second vacuum pump for the serial arrangement of the vacuum pumps.

13. The vacuum pump system according to claim 11, characterized in that the inlet of the first vacuum pump is connected to the inlet of the at least one second vacuum pump and the outlet of the first vacuum pump is also connected to the outlet of the at least one second vacuum pump for the parallel arrangement of the vacuum pumps.

14. The vacuum pump system according to claim 13, characterized in that a check valve, which closes when the pressure in the respective vacuum pump is higher than at the common inlet, is arranged between each vacuum pump and the common inlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the following, the invention will be described in more detail using preferred embodiments with reference to the accompanying drawings.

[0023] In the drawings:

[0024] FIG. 1 shows a vacuum pump having a shaft seal according to the prior art;

[0025] FIG. 2 shows a vacuum pump having a shaft seal according to the present invention in a first embodiment;

[0026] FIG. 3 shows a vacuum pump having a shaft seal according to the present invention according to a second embodiment;

[0027] FIG. 4 is a detailed view of the shaft feedthrough; and

[0028] FIG. 5 shows a vacuum pump system according to the present invention.

DETAILED DESCRIPTION

[0029] FIG. 1 shows the prior art with a vacuum pump 10 having an inlet 12 and an outlet 14. The vacuum pump 10 has a housing, wherein the housing defines a pump chamber and a drive chamber. A rotor rotatably mounted in the housing extends in this case from the pump chamber into the drive chamber through a shaft feedthrough 16. This is shown schematically in FIG. 1. In this case, a connecting point 19 is arranged in the pump chamber, whereas a connection point lies in the drive chamber 20. In the drive chamber 20, a pressure P.sub.1 usually prevails, which corresponds to atmospheric pressure due to the connection between the drive chamber 20 and the environment.

[0030] In this case, the shaft feedthrough 16 has a connection 18 via which the shaft feedthrough 16 is connected to a compressed air source 22 according to the prior art. The compressed air source 22 supplies compressed air at a pressure P.sub.2′. Furthermore, a pressure P.sub.3 prevails at the outlet 14 of the vacuum pump 10, which is usually higher than atmospheric pressure, so that the vacuum pump 10 can convey against the atmosphere. Due to the compressed air made available, P.sub.2′>P.sub.3>P.sub.1 applies. Therefore, compressed air flows as barrier gas from the connection 18 into the drive chamber 20 and to the outlet 14 of the vacuum pump 10, as indicated by the arrows in FIG. 1. Due to the flow of the flushing gas from the connection 18 to the outlet 14 of the vacuum pump 10, no process gas passes through the shaft feedthrough 16 into the drive chamber 20 in the direction opposite to the flow direction of the flushing gas. For this purpose, a first throttle 26 and a second throttle 24 are provided in the shaft feedthrough. A suitable design of the first throttle 26 and the second throttle 24 ensures that the barrier gas essentially reaches the connecting point 19, thus providing an adequate supply of the flushing gas. However, in the prior art, it is necessary to continuously supply the shaft feedthrough 16 with compressed air at the compressed air connection 22, so that P.sub.2′>P.sub.3 always applies. This leads to increased operating costs and such a solution is not possible unless compressed air is available.

[0031] FIG. 2 shows the solution of the present invention in a first embodiment. The same or similar components are denoted with the same reference signs.

[0032] According to the invention, a connection 18 of the shaft feedthrough 16 is connected to the inlet 12 of the vacuum pump 10. An underpressure P.sub.2 is therefore applied to the connection 18 of shaft feedthrough 16. In particular, P.sub.3≥P.sub.1>P.sub.2 applies. Process gas flowing through the shaft feedthrough 16 is thus suctioned off through the connection 18 due to the underpressure P.sub.2. At the same time, a barrier gas is suctioned from the drive chamber 20 to the connection 18 due to the underpressure P.sub.2, so that process gases cannot enter the drive chamber 20. The direction of the gas flow is indicated by the arrows in FIG. 2.

[0033] Furthermore, a first throttle is provided between the drive chamber 20 and the connection 18 of the shaft feedthrough. The first throttle 26 prevents leakage from being conveyed through the drive chamber 20 and through the vacuum pump 10 due to the restriction of the gas flow by the first throttle 26. Furthermore, a second throttle 24 is provided between the outlet 14 of the vacuum pump 10 and the connection 18 of the shaft feedthrough 16 for restricting the gas flow from the outlet 14 of the vacuum pump 10 to the inlet 12.

[0034] As can be seen from FIG. 2, the flow direction of the flushing gas is exactly reversed when compared to the prior art. This also prevents process gas from entering the drive chamber. However, this is achieved without an additional compressed air connection, resulting in a reduction in installation costs of the vacuum pump as well as in operating costs and a simultaneous improvement of the operational reliability of the vacuum pump.

[0035] FIG. 3 shows a further embodiment of the present invention. In this case, the outlet of the connection 18 of the shaft feedthrough 16 is connected to a further vacuum pump 28 which generates the underpressure P.sub.2 at the connection 18 of the shaft feedthrough 16 for generating the flushing gas flow in the shaft feedthrough. The further vacuum pump 28 can be designed to be significantly smaller than the vacuum pump 10. In this case, the further vacuum pump 28 can convey against the atmosphere. Alternatively, the outlet of the further vacuum pump 28 is connected to the outlet of the vacuum pump 10, so that process gases that are conveyed from the outlet 14 of the vacuum pump 10 through the shaft feedthrough 16 to the connection 18 and then through the further vacuum pump 28 cannot escape into the environment but can be fed back into the vacuum system.

[0036] FIG. 4 is a detailed view of the shaft feedthrough in the vacuum pump 10. The vacuum pump 10 has a housing 30, wherein a pump chamber 32 and a drive chamber 34 are defined by the housing 30. Furthermore, a rotor 36 is arranged in the housing 30 and is rotatably mounted by means of bearings 38. In this case, the rotor 36 has at least one rotor element in the pump chamber 32 for conveying a process gas from an inlet 12 (not depicted) to an outlet 14. For example, a transmission, an electric motor, a drive belt or the like is furthermore arranged in the drive chamber 34.

[0037] In addition, a shaft feedthrough 16 is provided which, in the example shown in FIG. 4, is designed as a piston ring seal. In this case, the shaft feedthrough 16 has a connection 18 which is connected to an underpressure. A first throttle is generated by a first part 42 of the shaft feedthrough 16 between the drive chamber 34 and the connection 18. A second throttle is formed by a second part 40 of the shaft feedthrough 16 between the pump chamber 32 and the connection 18. In this case, an underpressure P.sub.2 is applied to the connection 18. A pressure P.sub.1 prevails in the drive chamber 34, which usually corresponds to atmospheric pressure. In the pump chamber 32 in the region of the shaft feedthrough 16, a pressure P.sub.3 prevails which is usually higher than atmospheric pressure, so that the vacuum pump 10 can convey against the atmosphere. In this case, P.sub.2<P.sub.1≤P.sub.3 applies. Due to the underpressure P.sub.2 at the connection 18, a barrier gas is thus suctioned in from the drive chamber 34 through the first throttle, formed by the first part 42 of the shaft feedthrough 16, and thus prevents the process gas from escaping from the pump chamber 32 into the drive chamber 34. In particular, the shaft feedthrough 16 is designed to be contact-free and therefore requires little maintenance. Furthermore, an additional compressed air connection for the operation and prevention of process gas escaping into the environment is not required. This simplifies the structure.

[0038] In a further embodiment shown in FIG. 5, a vacuum pump system 50 is described. In this case, the vacuum pump system 50 in the example shown has three vacuum pumps 10, all of which having shaft feedthroughs according to FIG. 2-4. The vacuum pumps 10 are connected in parallel, so that the inlets 12 of the vacuum pumps 10 are connected to form a common inlet 52. The respective outlets 14 of the vacuum pumps 10 are also connected to one another to form a common outlet 54. The respective connections 18 of the shaft feedthroughs 16 of the respective vacuum pumps 10 are in this case connected to one another to form a common connection 56. The common connection 56 can in this case be connected to a further vacuum pump (not depicted) for generating an underpressure or, alternatively, as shown in FIG. 5, connected to the common inlet 52, so that the underpressure at the common inlet 52 is used to generate a flushing gas from the respective drive chamber of the respective vacuum pump 10 to the respective connections 18 of the shaft feedthroughs 16.

[0039] For this purpose, the respective inlets 12 of the vacuum pumps 10 are each connected to the common inlet 52 via a check valve 58. If the vacuum pump system is, for example, in an operating state in which one of the vacuum pumps is switched off, the pressure in the deactivated vacuum pump 10 rises and lies above the pressure of the common inlet 52, and the corresponding check valve 58 closes, so that a conveying through the deactivated vacuum pump is prevented.

[0040] The present invention provides a vacuum pump and a vacuum pump system in which process gases are reliably prevented from escaping into the environment. In particular, the underpressure generated by the vacuum pump itself or an underpressure generated by a further vacuum pump is used for this purpose. In this case, the flow direction of the barrier gas within the shaft seal is reversed when compared to known shaft seals from the prior art.

[0041] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0042] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.