Device and method for detecting leakage

Abstract

To provide means enabling the highest possible test gas sensitivity during control operation, and capable of evacuating a detector as quickly as possible in a case of test gas contamination.SOLUTION: At least one bypass 27, 28 is provided for test gas 21. The bypass leads from a bypass outlet 29 toward the outside of a turbopump region, which is located at the height of a test gas inlet 25 or upstream of the test gas inlet, directly to a detector 19 or to a bypass inlet 31 toward the inside of the turbopump region, which is located upstream of the bypass outlet, and at that time, the bypass bypasses at least some parts 17a, 18b, 18c of the turbopump region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus for detecting leaks according to the vacuum method using the countercurrent principle, comprising a vacuum pump unit having a turbomolecular vacuum pump with a turbopump region formed by one or more turbopump stages, which is connectable to a test object to be evacuated, a detector for detecting a test gas, in particular helium, in particular a mass spectrometer, wherein the turbomolecular vacuum pump is connected to the detector via at least one axial and / or radial intake port, has a test gas inlet downstream of the intake port, and at least a part of the turbopump region is located between the intake port and the test gas inlet in the pumping direction of the turbomolecular vacuum pump.

[0002] Furthermore, the present invention relates to a method for inspecting leaks according to the vacuum method using the countercurrent principle, using a leak inspection apparatus having a vacuum pump unit and a detector, the vacuum pump unit being connectable to a test object to be evacuated and having a turbomolecular vacuum pump with a turbopump region formed by one or more turbopump stages.

Background Art

[0003] A part of the term "turbo..." is used as a shortening for "turbo molecular..." for the sake of simplicity within the scope of the present disclosure, i.e., when, for example, a turbomolecular vacuum pump or a turbopump stage is mentioned, this is understood as a turbo molecular pump or a turbo molecular pump stage.

[0004] The concept of leak detection according to the vacuum method using the countercurrent principle is basically known in vacuum technology. The test object is the component itself, also referred to as the "test piece", which should actually be tested. This presupposes that this component can be evacuated to a certain vacuum pressure, or the test object is the vacuum chamber in which the component to be tested each time is located. In the latter case, it is not the component itself but the vacuum chamber that is evacuated. In both cases, the test gas located in the vacuum chamber is detected by a detector. Specifically stated, the test gas is measured and shown, for example, as a so-called leak rate.

[0005] Various leak detectors, especially helium detectors, are basically known to experts. The countercurrent principle mentioned here and the countercurrent leak detectors used therefor also belong to the specialized knowledge in the field of vacuum technology. In this regard, reference is made in particular to the 11th edition of "Wutz Handbuch Vakuumtechnik (Hrsg. Karl Jousten)", Springer Vieweg, and in particular to Chapter 14.4 "Leckdetektoren", Chapter 19 "Lecksuchtechniken" and Chapter 19.4 "Lecksuchverfahren mit Heliumleckdetektoren" therein.

[0006] In principle, an attempt is made to obtain the highest possible sensitivity of the leak detection device, that is, specifically stated, as much test gas as possible (per unit time) should be able to flow towards the detector. Therefore, the requirement for the type of leak detection device mentioned here is a large amount of test gas backflow through the part located upstream of the test gas inlet in the turbo pump area. Therefore, in the control operation, that is, during leak detection (here also referred to as the "test mode" of the leak detection device), basically, when it is guaranteed that the turbo vacuum pump can maintain the low pressure required in the detector in the test mode at that time, a relatively low compression and a relatively low exhaust speed of the test gas in the corresponding part of the turbo pump area are advantageous.

[0007] However, at the same time, it must be noted that in practice, especially when there is a relatively large leak in the object under test, so-called "test gas contamination" of the detector can occur. In this case, the detector must first be evacuated, i.e., the test gas must be discharged from the detector, and then the detector is newly prepared for operation for further leak detection. For this discharge process (also referred to here as the "vacuum evacuation mode" of the leak detection device), high compression in the turbopump region with respect to the test gas and the resulting high exhaust speed are aimed for.

[0008] Therefore, against this background, in practice, conflicting requirements arise between the leak detection device and especially the turbopump region of the turbomolecular pump. That is, the turbopump region, which is advantageous in the case of test gas contamination and optimized towards high exhaust speed and high compression, allows only relatively little test gas backflow, which thereby hinders the requirement for the highest possible test gas sensitivity of the detector during the test mode, i.e., during the control operation.

Prior Art Documents

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, the problem of the present invention is to provide means that enable the highest possible test gas sensitivity during the control operation and enable the detector to be evacuated as quickly as possible in the case of test gas contamination.

Means for Solving the Problems

[0011] This problem is solved by the features of the independent claims respectively.

[0012] The leak detection device according to the present invention is provided with at least one bypass for the test gas, and the bypass leads directly from a bypass outlet leading out of the turbo pump region, which is located at the height of the test gas inlet or upstream of the test gas inlet, to the detector or to a bypass inlet leading into the turbo pump region, which is located upstream of the bypass outlet, and in so doing bypasses at least a part of the turbo pump region.

[0013] Preferably, an adjusting device for changing the conductance of the bypass with respect to the test gas is provided, and the adjusting device is controllable by the control device of the device, whereby the conductance is changed between a relatively high value and a relatively low value according to the operating condition of the device.

[0014] The method for detecting a leak according to the present invention provides at least one bypass for the test gas generated in the object under test, reaching the turbo vacuum pump and flowing in the direction opposite to the pumping direction to the detector, and the bypass bypasses at least a part of the turbo pump region and leads directly to the detector or returns to the turbo pump region.

[0015] Preferably, during the operation of the leak inspection device, the conductance of the bypass with respect to the test gas is changed from a relatively high value in the test mode in which the test gas is detected by the detector to a relatively low value in the vacuum evacuation mode in which the detector is evacuated.

[0016] The bypass enables the test gas to bypass at least a part of the turbo pump region. Therefore, at least this part of the turbo pump region can be optimized for the highest possible compression and the highest possible exhaust speed, without this impairing the sensitivity of the detector to the test gas during the control operation. In this case, if test gas contamination occurs, the relatively high compression and the resulting high exhaust speed force advantageously act such that the test gas can be discharged from the detector relatively quickly.

[0017] For this operation, also referred to herein as the vacuum evacuation mode, it is possible, but not essential, to reduce the conductance of the bypass, i.e., to set it to a relatively low value.

[0018] It has been found that it is possible to realize a bypass for the test gas, and that the conductance of the bypass for the test gas need not be reduced for the vacuum evacuation mode. The conductance of the bypass can be maintained constant, and in so doing, an inconvenient "short - circuit effect" does not occur in the vacuum evacuation mode, i.e., the test gas discharged from the detector is not returned to the detector via the bypass to an inconvenient extent. Such a particularly passive bypass, i.e., a bypass whose conductance for the test gas cannot or does not change, may have, for example, a capillary or a selection device such as a selection diaphragm. Such a gas line in the form of a capillary has a higher conductance for a light gas, in particular helium, than for a heavy gas, in particular nitrogen or air, or such a selection diaphragm is permeable to the test gas, in particular helium, but impermeable to an external gas heavier than the test gas, in particular nitrogen.

[0019] Thus, the bypass concept according to the invention meets the contradictory requirements for the leak detection device mentioned at the beginning. At the same time, a high test gas sensitivity of the detector during the control operation and a rapid recovery of the detector's operational readiness in the case of test gas contamination of the detector are achieved.

[0020] Whether the test gas reaches the detector directly through the bypass during the control operation or first returns to the turbopump region again depends particularly on the specific form of the turbomolecular pump and / or the arrangement of the turbomolecular pump relative to the detector. This will be described in detail elsewhere in connection with the illustrated embodiments. When the turbomolecular pump has only one axial inlet with respect to the detector, for example, the radial bypass outlet is located between two turbopump stages, and the bypass may lead directly to the detector. When the vacuum pump is configured and arranged to have a plurality of radial inlets or one axial inlet and at least one radial inlet with respect to the detector, the bypass can return the test gas to the turbopump region after bypassing a part of the turbopump region, from where the test gas reaches the detector.

[0021] In both cases, the turbomolecular pump may be configured as a so-called split-flow vacuum pump, respectively. The radial inlets of the split-flow vacuum pump may be connected to the exhaust port of the valve unit of the vacuum pump unit, regardless of whether the split-flow vacuum pump is connected to the detector by one or more radial inlets or only by an axial inlet, as disclosed elsewhere.

[0022] In this specification, the terms "downstream side" and "upstream side", which are used particularly in relation to the positions of the test gas inlet, bypass outlet and bypass inlet, and the positions of the turbopump stages, refer to the pumping direction of the turbomolecular pump of the vacuum pump unit and thus the axis of rotation of the rotor of the turbomolecular pump within the scope of the present disclosure, unless otherwise specified.

[0023] The term "directly to the detector" applies to the bypass not being returned to the turbopump area. This means that in some possible embodiments, the bypass may extend through one or more other devices or lead into the chamber of the housing of a device placed in front of the detector, such as a leak detection device, before opening into the detector, and it is not excluded that the test gas then reaches the detector from there.

[0024] Yet another embodiment of the invention is also described in the dependent claims, the specification and the drawings.

[0025] At least two bypasses may be provided for the test gas. The bypasses may exit the turbopump area at different positions and / or lead directly to the detector at different positions or may first be returned to the turbopump area. The sensitivity of the detector can be further increased by one or more additional bypasses.

[0026] The plurality of bypasses may be designed such that portions of the turbopump area with different compression heights and / or different exhaust speeds are bypassed.

[0027] Furthermore, when an adjustment device is provided, it may be contemplated that the conductances of the bypasses can be changed independently of each other.

[0028] The turbopump area preferably has a plurality of turbopump stages arranged continuously in the pumping direction. Overall, the turbopump area has a plurality of moving blades and stationary blades arranged alternately, and the moving blades and stationary blades are arranged at a predetermined axial interval, where "axial" applies to the axis of rotation of the rotor coupled to the moving blades of the turbovacuum pump and thus to the pumping direction of the turbovacuum pump. Speaking of the individual turbopump stages, the individual turbopump stages can be defined relative to each other by the axial interval between two turbopump stages being greater than the axial interval between the moving blades or stationary blades within each turbopump stage.

[0029] Regarding the position of the test gas inlet, it can be contemplated that the test gas inlet is located at the height of one turbo pump stage or downstream of one turbo pump stage, particularly between two turbo pump stages. Alternatively, the test gas inlet can be contemplated to have an axial spacing such that the test gas inlet not only occupies the intermediate space between two turbo pump stages but also additionally occupies a part of one of the two turbo pump stages that define the intermediate space or a part of each of the two turbo pump stages that define the intermediate space.

[0030] Regarding the position of the bypass outlet, it can be contemplated that the bypass outlet is located at the height of one turbo pump stage or downstream of one turbo pump stage, particularly between two turbo pump stages. Thus, it is not essential for the bypass outlet to be arranged at the height of the axial intermediate space between two consecutive turbo pump stages. The bypass outlet may be located at the height of one of the turbo pump stages. Alternatively, the bypass outlet can be contemplated to have an axial dimension such that the bypass outlet not only occupies the intermediate space between two turbo pump stages but also additionally occupies a part of one of the two turbo pump stages that define the intermediate space or a part of each of the two turbo pump stages that define the intermediate space.

[0031] According to some embodiments, the test gas inlet and the bypass outlet are located axially, particularly between two turbo pump stages, at least substantially at the same height, such that it can be contemplated that there is no part of the turbo pump region between the axial height of the test gas inlet and the axial height of the bypass outlet. In this case, the test gas reaches the bypass without first flowing through a part of the turbo pump region. The bypass may, as described elsewhere in this specification, have here, in particular, a capillary and / or a selection device, particularly a selection diaphragm. In particular, the bypass may be passive if there is no adjustment device provided that changes the conductance of the bypass for the test gas, which can be achieved, for example, by a capillary or a selection device as described in this specification.

[0032] Regarding the position of the bypass inlet, i.e., when the bypass does not lead directly to the detector, the bypass inlet can be contemplated to be located at the height of one turbo pump stage or between two turbo pump stages. The bypass inlet can be contemplated to have an axial dimension such that it not only occupies the intermediate space between two turbo pump stages but also additionally occupies a part of one of the two turbo pump stages that define the intermediate space or a part of each of the two turbo pump stages that define the intermediate space.

[0033] Generally, it can be contemplated that the portion of the turbo pump region located between the bypass outlet and the bypass inlet is designed to obtain a higher compression and / or a higher exhaust velocity than the portion of the turbo pump region located upstream of the bypass inlet. This can be achieved by a larger number of turbo pump stages or by a larger number of interacting moving blades and stationary blades that perform a pumping action. The portion of the turbo pump region located between the bypass outlet and the bypass inlet is the portion bypassed by the bypass and, thus, is the portion through which the test gas does not have to flow during the control operation. At least a part of this portion of the turbo pump region can be optimized towards the highest possible compression and / or the highest possible exhaust velocity, and thus, thereby, in the vacuum exhaust mode, in the case of test gas contamination of the detector, the detector can be exhausted as quickly as possible.

[0034] According to some embodiments, the turbo vacuum pump is connected to the detector exclusively via an axial intake port, and it can be assumed that the bypass leads directly to the detector from a bypass outlet located at the height of a turbo pump stage or between two turbo pump stages. Thus, all portions of the turbo pump region located upstream of the bypass outlet are bypassed in this way.

[0035] In an alternative embodiment, the turbo vacuum pump is connected to the detector via a plurality of radial inlets located at a distance from each other in the pumping direction or via one axial inlet and one or more radial inlets located at a distance from each other in the pumping direction. In particular, it may be contemplated that the bypass inlet is located at the height of one turbo pump stage or between two turbo pump stages. In this case, a part of the turbo pump region located upstream of the bypass outlet is bypassed, i.e., the test gas returns to the turbo pump region before reaching the detector.

[0036] Alternatively or additionally, basically, even in the case of a turbo vacuum pump connected to the detector with one or more radial inlets, it may be contemplated that the bypass does not return to the turbo pump region but leads directly to the detector or to the housing connected to the detector above the turbo pump stage located furthest upstream. It is also conceivable that two or more bypasses are provided, in which case one or more bypasses return to the turbo pump region respectively and one or more other bypasses lead directly to the detector. In this case, the bypass outlets of the bypasses may be located at the same axial height, but this is not essential, and the bypass outlets may occupy the same circumferential position with respect to the axis of rotation of the rotor of the vacuum pump, but this is not essential.

[0037] Furthermore, it may be contemplated that the part of the turbo pump region located between the bypass outlet and the radial inlet located closest upstream of the bypass outlet is designed to obtain a higher compression and / or a higher exhaust speed than the respective parts of the turbo pump region located further upstream, which are located between the radial inlet located closest upstream of the bypass outlet and the bypass inlet or the upstream side of the bypass inlet.

[0038] For example, a turbo vacuum pump may have three turbo pump stages upstream of the test gas inlet. In this case, looking in the pumping direction, the intake port, the first turbo pump stage, the bypass inlet, the second turbo pump stage, another intake port, the third turbo pump stage, and the test gas inlet are arranged axially in succession. For example, the third and second turbo pump stages may be bypassed by a bypass. At least the third turbo pump stage located immediately upstream of the test gas inlet may be configured to obtain higher compression and / or higher exhaust speed than the first and second turbo pump stages.

[0039] This configuration, which will be described later based on one embodiment, is merely an example of a possible design of the vacuum pump unit according to the present invention. The specific configuration can be selected according to the requirements of each case.

[0040] The bypass itself and, if present, the adjustment device of the bypass can in principle be designed in various forms. If a change in conductance is assumed in each embodiment of the present invention, there are various possibilities for changing the conductance of the bypass for each test gas.

[0041] Generally, when an adjustment device is provided, it is possible but not essential to reduce the conductance of the bypass to zero for the vacuum evacuation mode in which the detector is to be evacuated when the test gas is contaminated. Thus, the conductance can be reduced to zero or be greater than zero during the vacuum evacuation mode.

[0042] In some embodiments, it can be contemplated that the bypass has at least one gas pipeline and the adjustment device has at least one bypass valve controllable by a control device. The bypass valve may be, for example, an electromagnetic valve. By the control device, the flow cross-sectional area of the bypass valve is variable, for example, steplessly or stepwise. The bypass valve may alternatively be a simple switching valve that can only switch between two positions, particularly between a fully open position and a fully closed position.

[0043] As an actuator for a valve configured in a normal form, for example, a rolling diaphragm may be used. Such a rolling diaphragm may also be used as an actuator for a throttle or slider that changes the flow cross-sectional area of the bypass gas pipeline.

[0044] The bypass valve may be disposed in the gas pipeline, in the turbo vacuum pump, particularly in contact with or within the pump housing, or within the valve unit assigned to the turbo vacuum pump. For example, the bypass valve may be disposed at the bypass outlet directly leading out from the turbo pump region. The valve unit mentioned in connection with one of these embodiments is a group of structures of leak detection devices generally known to those skilled in the art with respect to its structure and function. The valve unit, also referred to as a valve block, may be connected between the inlet of the test object to be evacuated and the test gas inlet of the turbo vacuum pump, and may further be connected to a forepump for the turbo vacuum pump. By the valve unit, in a manner known to those skilled in the art, the sensitivity of the leak detection device can be adjusted by taking out another compression of the turbo vacuum pump according to the switching of the individual valves of the valve unit.

[0045] In an alternative form, the bypass may particularly have a gas pipeline without a valve provided. The gas pipeline may particularly be a capillary. Such a gas pipeline has a higher conductance for light gases than for heavy gases. In particular, a gas pipeline having a higher conductance for helium than for nitrogen or air may be used for the bypass. According to a conceivable development of the present invention, in order to change the conductance of the gas pipeline for the test gas, a heating device controllable by a control device may be provided for the gas pipeline, and its heating output is changeable to change the conductance of the gas pipeline. Thereby, the situation where there is a gas-specific temperature dependence of the conductance can be utilized for the corresponding gas pipeline, particularly the capillary.

[0046] According to a further alternative form, the bypass may have a gas line that is not provided with a valve in particular, and is passable for the test gas, but is not passable for an external gas heavier than the test gas, in particular nitrogen. It may be contemplated that a selection device, in particular a so-called selection diaphragm, is provided. For example, if such a selection device is provided at the bypass outlet leading out from the turbopump region, the conductance of the gas line for the test gas is relatively high. In this case, during the test mode, i.e., during the control operation, the test gas can flow through the bypass, but the heavier gas cannot.

[0047] The selection device may be arranged in the gas line, in the turbomolecular pump, in particular in contact with or within the pump housing, or within a valve unit assigned to the turbomolecular pump.

[0048] In such an embodiment of the method according to the invention in which the conductance of the bypass is changed, in particular, after the evacuation of the detector, the conductance of the bypass is changed so as to newly return to a relatively high value, thereby enabling the leak detection device to operate in a new test mode.

[0049] Therefore, in principle, by appropriately adapting the conductance of the bypass each time, it is possible to continuously operate the leak detection device even if test gas contamination occurs temporarily.

[0050] The test gas contamination in the detector can be recognized by appropriate pressure measurement in the detector. When the measured gas pressure in the detector exceeds a predetermined value, it can be automatically switched from the test mode to the evacuation mode by the control device.

[0051] In some embodiments, it may be contemplated that the conductance of the bypass is changed by changing the flow cross-sectional area of the bypass valve.

[0052] In a further alternative embodiment, the conductance of the bypass can be varied by heating and cooling the gas line for the test gas, in particular the capillary.

[0053] According to another aspect of the invention, which is claimed independently herein, the leak detection device has a test gas channel leading directly to the detector. Here, "leading directly to the detector" is understood to mean that no part of the pump region of the vacuum pump allows the test gas to flow in a direction opposite to the pumping direction. In particular, no reverse flow of the test gas through the turbopump region takes place. In this case, on the one hand, the evacuation of the detector by a vacuum pump of the normal type, in particular the turbomolecular vacuum pump disclosed herein, and on the other hand, the supply of the test gas to the detector, are carried out in somewhat separate flow paths. For example, the test gas can be led directly from the valve unit described herein to the detector. By suitable means, it can be ensured that an external gas such as nitrogen or air does not reach the detector, or that only a slight external gas component which is acceptable for each detector reaches the detector via the test gas channel. Suitable means may include, for example, capillaries and / or selection devices, such as selection diaphragms as disclosed elsewhere herein. The vacuum pump for evacuating the detector, in particular the turbomolecular vacuum pump disclosed herein, may in this case be configured without a test gas inlet or may be provided with a closable test gas inlet.

[0054] Hereinafter, the present invention will be illustratively described with reference to the drawings.

Brief Description of the Drawings

[0055]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0056] The leak detection devices shown in FIGS. 1 and 2 each include a vacuum pump unit 11. The vacuum pump unit 11 has a turbo molecular vacuum pump 15, a valve block 14, and a roughing pump 39. Only the pump housing 16 and the rotating components that perform the pumping action of the vacuum pump 15 are schematically shown together with the rotor 41. The differences between the two vacuum pumps 15 and the arrangement of the vacuum pumps within the device will be described in detail later.

[0057] The turbo vacuum pump according to FIG. 1 is a split flow vacuum pump and has an axial intake port 23 for connection to the detector 19. Three turbo pump stages 17a, 17b, 17c are connected to the axial intake port 23 in the pumping direction P. A Holweck pump stage 43 is connected to the last turbo pump stage 17c.

[0058] In the embodiment of FIG. 2, the turbo vacuum pump 15 is also a split flow pump and has an axial intake port 23 and a radial intake port 23 on its downstream side for connection to the detector 19. Between the two intake ports 23, a first turbo pump stage 18a and a second turbo pump stage 18b are located. Downstream of the radial intake port 23, the vacuum pump 15 has two further turbo pump stages 18c, 18d, and a Holweck pump stage 43 is connected to these turbo pump stages 18c, 18d.

[0059] The turbo vacuum pump 15 is respectively connected to a detector 19 which is in the form of a mass spectrometer and also belongs to the leak detection device. In the embodiment of FIG. 1, the detector 19 is connected to the axial intake port 23 via the opening 19a. In the embodiment of FIG. 2, the detector 19 is arranged laterally with respect to the vacuum pump 15. The pump housing 16 is here the outer housing, and the pump 15 is inserted into the outer housing together with the base housing, and the detector 19 is connected to the base housing via the opening 19a assigned to the intake port 23 respectively. The vacuum pump 15 inserted into the outer housing 16 may be, for example, a so-called cartridge vacuum pump.

[0060] The leak detection device according to FIGS. 1 and 2 further has a control device 35 for controlling the operation of the leak detection device respectively.

[0061] During the control operation (test mode), the test object 13 is connected to the vacuum pump unit 11. As described above, the test object 13 may be a component (test body) or a vacuum chamber to be tested for airtightness respectively, and the component to be tested exists in the vacuum chamber.

[0062] For the test mode, the detector 19 and the test object 13 are evacuated to a sufficiently low vacuum pressure by the vacuum pump unit 11. When the test body has a leak, the test gas 21 (usually helium) specifically shown by arrows in FIGS. 1 and 2 respectively reaches the test gas inlet 25 via the valve unit 14, and thus reaches the turbo pump region of the turbo vacuum pump 15 formed by the individual turbo pump stages 17a to 17c (FIG. 1) or 18a to 18d (FIG. 2).

[0063] As described elsewhere, the sensitivity of the leak detection device can be adjusted by the valve unit 14. Since the individual valves of the valve unit 14 are connected to ports of the turbo vacuum pump 15 that are spaced apart from each other in the pumping direction P, depending on the switching state of the valves of the valve unit 14 selected according to the expected magnitude of the leak in the object 13 to be tested, the respective compression of the turbo molecular pump 15 is taken out. For example, if a relatively large leak is expected, only the lowermost of the three valves of the valve unit 14 is opened.

[0064] The leak detection devices each operate according to the so-called countercurrent principle, i.e., the test gas 21 reaches the detector 19 against the pumping direction P and is detected there. In this case, according to the present invention, the test gas 21 does not need to flow through all parts of the turbo pump region located upstream of the test gas inlet 25. This is because two bypasses 27a, 27b (FIG. 1) or one bypass 28 (FIG. 2) are provided, and the bypass allows a part of the turbo pump region located upstream of the test gas inlet 25 here to be bypassed. The differences between the two embodiments according to FIGS. 1 and 2 related thereto will be described in detail below.

[0065] In the embodiment of FIG. 1, two bypasses 27a, 27b are provided for the test gas 21 flowing countercurrently through the turbo pump region. In this case, alternatively, a single bypass 27 may be provided or three or more bypasses 27 may be provided.

[0066] The two bypasses 27a, 27b each have a gas pipeline 37 that leads directly from the bypass outlet 29 leading out of the turbo pump region to the detector 19. The bypass outlet 29 of the bypass 27a shown on the left side in FIG. 1 is located between the two turbo pump stages 17a and 17b that are most upstream in the axial direction. The bypass outlet 29 of the bypass 27b shown on the right side in FIG. 1 is located in the axial direction at the height of the turbo pump region 17a that is closest to the axial intake port 23.

[0067] Two gas pipelines 37 are each assigned an adjustment device 33 in the form of a bypass valve 33. The bypass valve 33 may be, for example, an electromagnetic valve that can be controlled by a control device 35. For example, the control device 35 can switch the valve 33 between an open state and a fully closed state respectively.

[0068] During the control operation for detecting the test gas 21 by the detector 19, the valves 33 are each open, that is, the conductance of the gas pipeline 37 with respect to the test gas 21 is at a relatively high value respectively. In this case, the test gas 21 can flow from the test gas inlet 25 in the reverse flow direction, that is, in the direction opposite to the pumping direction P, through the turbo pump region, and reach the bypass outlet 29 as specifically indicated by the arrow, and from there the test gas 21 is directly guided to the detector 19 via the gas pipeline 37. When the valve 33 is open, since the gas pipeline 37 has a relatively high conductance with respect to the test gas 21 respectively, the first turbo pump stage 17a closest to the intake port 23 is completely bypassed by the bypass 27a shown on the left side in FIG. 1, and this turbo pump stage 17a is partially bypassed by the bypass 27b shown on the right side in FIG. 1. Overall, this results in a significantly higher test gas flow in the detector 19 than when there are no bypasses 27a, 27b, thereby significantly increasing the sensitivity of the detector 19.

[0069] For example, if the pressure of the test gas 21 in the detector 19 is too high based on the relatively large leakage in the test object 13, this can be confirmed by pressure measurement in the corresponding detector 19, and then the bypass valve 33 is closed by the control device 35. This means a decrease in the conductance of the gas pipeline 37 with respect to the test gas 21, so the turbo vacuum pump 15 can evacuate the detector 19 to vacuum relatively quickly, and at this time, the discharged test gas 21 cannot return to the detector 19.

[0070] Thus, the turbo vacuum pump 15 can be designed such that it enables rapid evacuation of the detector 19 in the case of test gas contamination or in another situation with respect to evacuation speed and compression, and in this case, this characteristic of the turbo molecular pump 15 does not impair the test gas sensitivity of the detector 19, because during the control operation, a part of the turbo pump region is bypassed based on the bypasses 27a, 27b.

[0071] In the embodiment of FIG. 2, the bypass 28 likewise has a gas line 37, and in the gas line 37, a bypass valve 33 in the form of, for example, an electromagnetic valve is arranged. The bypass outlet 29 is arranged here axially at the height of the intermediate space between the two turbo pump stages 18c and 18d where the test gas inlet 25 opens. Since the pressure level at the test gas inlet 25 can be relatively high in certain situations, it can be advantageous in the control operation that at least essentially only the test gas 21 can flow through the bypass 28. In this case, the bypass 28 may have, for example, a capillary and / or a selection device, in particular a selection diaphragm, so that the test gas 21 can pass through, but heavier external gas cannot pass through, as described elsewhere.

[0072] The test gas 21 can bypass the two first turbo pump stages 18c and 18b located upstream of the test gas inlet 25 via the bypass 28 and return to the turbo pump region axially via the bypass inlet 31 between the first turbo pump stage 18a and the second turbo pump stage 18b. From there, the test gas 21 reaches the detector 19 and is detected there. Alternatively, the bypass inlet 31 may be positioned upstream of the first turbo pump stage 18a. Alternatively or additionally, the two first turbo pump stages 18a and 18b may be combined to form a single turbo pump stage. In this regard, the configuration of the vacuum pump 15 and the positioning of the bypass 28 shown in FIG. 2 are merely illustrative.

[0073] By means of the bypass 28, in particular, the turbo pump stage 18c, which is located downstream of the radial intake port 23 of the vacuum pump 15 and immediately upstream of the test gas inlet 25, can be designed to obtain a higher compression and a higher exhaust velocity than the two turbo pump stages 18a and 18b located further upstream by means of a larger number of moving blades and stationary blades. The relatively high compression and relatively high exhaust velocity of the turbo pump stage 18c do not impair the test gas sensitivity of the detector 19 since this turbo pump stage 18c is bypassed by the bypass 28, but in the vacuum exhaust mode, for example, when the test gas of the detector 19 is contaminated, it serves to enable the detector 19 to be quickly evacuated.

[0074] For the vacuum exhaust mode, the valve 33 of the bypass 28 is closed by the control device 35, so that in this operating mode, the backflow of the test gas 21 through the gas pipeline 37 of the bypass 28 is prevented.

[0075] The foregoing embodiments each have an adjustment device in the form of a valve 33 for the bypass 28. As described at the beginning, in another possible embodiment of the invention, an adjustment device for changing the conductance to the test gas is not required for the bypass.

Explanation of reference numerals

[0076] 11 Vacuum pump unit 13 Object under test 14 Valve unit 15 Turbo vacuum pump 16 Pump housing 17, 18 Turbo pump stages 19 Detector 19a Opening 21 Test gas 23 Intake port 25 Test gas inlet 27, 28 Bypass 29 Bypass outlet 31 Bypass inlet 33 Adjustment device, bypass valve 35 Control device 37 Gas pipeline 39 Backup pump 41 Rotor 43 Holbeck pump stage P Pumping direction

Claims

1. A device for detecting leaks according to the vacuum method on the countercurrent principle, comprising: - a vacuum pump unit (11) connectable to a test object (13) to be evacuated and having a turbo vacuum pump (15) with a turbo pump area formed by one or more turbo pump stages (17, 18); a detector (19), in particular a mass spectrometer, for detecting a test gas (21), in particular helium; Equipped with the turbo vacuum pump (15) is connected to the detector (19) via at least one axial and / or radial inlet (23) and has a test gas inlet (25) downstream of the inlet (23); 2. An apparatus, comprising: at least a part of the turbo pump region located between the intake port (23) and the test gas inlet (25) in a pumping direction (P) of the turbo vacuum pump (15), 1. An apparatus comprising: at least one bypass (27, 28) for a test gas (21), which leads from a bypass outlet (29) towards the outside of the turbopump region, located at the level of the test gas inlet (25) or upstream of the test gas inlet (25), directly to the detector (19) or to a bypass inlet (31) towards the inside of the turbopump region, located upstream of the bypass outlet (29), thereby bypassing at least a part (17a, 18b, 18c) of the turbopump region.

2. 2. The apparatus of claim 1, further comprising an adjusting device (33) for varying the conductance of the bypass (27, 28) to the test gas (21), the adjusting device (33) being controllable by a control device (35) of the apparatus, whereby the conductance is varied between a relatively high value and a relatively low value depending on the operating conditions of the apparatus.

3. 3. The device according to claim 1 or 2, wherein at least two bypasses (27a, 27b) are provided for the test gas (21), the bypasses (27a, 27b) exiting the turbopump region at different positions and / or leading to the detector (19) or the turbopump region at different positions.

4. 4. The apparatus of claim 3, wherein the bypasses (27a, 27b) bypass portions of the turbopump region designed to obtain different heights of compression and / or pumping speeds, and / or the conductances of the bypasses (27a, 27b) are variable independently of each other.

5. the turbopump region comprises a number of turbopump stages arranged one after the other in the pumping direction (P), the test gas inlet (25) being located downstream of one turbopump stage, in particular between two turbopump stages; and / or 5. The arrangement according to claim 1, wherein the turbopump region comprises a number of turbopump stages arranged in succession in a pumping direction (P), and the bypass outlet (29) is located at the level of one turbopump stage or downstream of one turbopump stage, in particular between two turbopump stages.

6. 6. The apparatus according to claim 1, wherein the test gas inlet (25) and the bypass outlet (29) are located at at least substantially the same height in the axial direction, in particular between two turbopump stages (18c, 18d), so that no turbopump region is present between the axial height of the test gas inlet (25) and the axial height of the bypass outlet (29).

7. 7. The device according to claim 1, wherein the turbopump region comprises a number of turbopump stages arranged in succession in a pumping direction (P), and the bypass inlet (31) is located at the height of one turbopump stage or between two turbopump stages.

8. 8. The device according to claim 1, wherein a portion (18b, 18c) of the turbopump region located between the bypass outlet (29) and the bypass inlet (31) is designed to obtain a higher compression and / or a higher pumping speed than a portion (18a) of the turbopump region located upstream of the bypass inlet (31).

9. 9. The device according to claim 1, wherein the turbo vacuum pump is connected to the detector (19) exclusively via an axial inlet (23) and the bypass (27) leads directly to the detector (19) through one bypass outlet (29), in particular the bypass outlet (29) being located at the height of one turbopump stage (17a) or between two turbopump stages (17a, 17b) or occupying an intermediate space between two turbopump stages in the axial direction and a part of at least one of the turbopump stages defining said intermediate space.

10. 9. The device according to claim 1, wherein the turbo vacuum pump (15) is connected to the detector (19) via a plurality of radial inlets (23) located at a distance from one another in the pumping direction (P) or via an axial inlet (23) and one or more radial inlets (23) located at a distance from one another in the pumping direction (P), and the bypass inlet (31) is located at the height of one turbopump stage or between two turbopump stages (18a, 18b) or occupies an intermediate space between two turbopump stages in the axial direction and a part of at least one of the turbopump stages defining the intermediate space.

11. 11. The apparatus according to claim 10, wherein a portion (18c) of the turbopump region between the bypass outlet (29) and the radial inlet (23) closest upstream to the bypass outlet (29) is designed for higher compression and / or higher pumping speed than further upstream portions (18a, 18b) of the turbopump region between the radial inlet (23) closest upstream to the bypass outlet (29) and the bypass inlet (31) or upstream of the bypass inlet (31).

12. 12. Apparatus according to claim 2, wherein the bypass (27, 28) comprises at least one gas line (37) and the regulating device comprises at least one bypass valve (33), in particular a solenoid valve, controllable by the control device (35), the flow cross-sectional area of ​​the bypass valve (33) being variable, in particular the flow cross-sectional area being reduceable to a value of zero for an evacuation mode.

13. 13. The arrangement according to claim 12, wherein the bypass valve (33) is arranged in the gas line (37), in the turbo vacuum pump (15), in particular on or in a pump housing (16) or in a valve unit (14) assigned to the turbo vacuum pump (15).

14. 14. The device according to claim 2, wherein the bypass (27, 28) comprises a gas line (37), in particular a capillary, without a valve, in particular provided with a regulating device, the regulating device comprising a heating device for the gas line (37) controllable by the control device (35), the heating power of the heating device being variable in order to vary the conductance of the gas line (37).

15. 15. The device according to claim 2, wherein the bypass (27, 28) has a gas line (37), in particular without a valve, and is provided with a selection device, in particular a selection diaphragm, which is permeable for the test gas but not for an external gas heavier than the test gas, in particular nitrogen.

16. 16. The arrangement according to claim 15, wherein the selection device is arranged in the gas line (37), in the turbo vacuum pump (15), in particular on or in a pump housing (16) or in a valve unit (14) assigned to the turbo vacuum pump (15).

17. 17. A method for testing for leaks according to a vacuum method in the counterflow principle using a leak test device, in particular a leak test device according to any one of claims 1 to 16, comprising a vacuum pump unit (11) and a detector (19), the vacuum pump unit (11) comprising a turbo vacuum pump (15) connectable to a test object (13) to be evacuated and having a turbo pump area, the turbo pump area being formed by one or more turbo pump stages (17, 18), 1. A method according to claim 1, further comprising providing at least one bypass (27, 28) for a test gas (21), in particular helium, which is generated in a test object (13), passes into the turbo vacuum pump (15) and flows against the pumping direction (P) to the detector (19), said bypass (27, 28) bypassing at least a part (17a, 18b, 18c) of the turbo pump region and leading directly to the detector (19) or back to the turbo pump region.

18. 18. The method according to claim 17, wherein during operation of the leak testing apparatus, the conductance of the bypass (27, 28) to the test gas (21) is changed from a relatively high value in a test mode, in which the test gas (21) is detected by the detector (19), to a relatively low value in an evacuation mode, in which the detector (19) is evacuated.

19. 19. A method according to claim 17 or 18, further comprising, after evacuating the detector (19), changing the conductance of the bypass (27, 28) back to a relatively high value again in order to operate the leak detection device in test mode again.

20. 20. The method according to any one of claims 17 to 19, wherein the method switches from a test mode to an evacuation mode when the gas pressure in the detector (19) exceeds a predetermined value.

21. 21. The method according to any one of claims 17 to 20, comprising varying the conductance of the bypass (27, 28) by varying the flow cross-sectional area of ​​the bypass valve (33), in particular by completely closing the bypass valve (33) for the evacuation mode.

22. 22. The method according to any one of claims 17 to 21, characterized in that the conductance of the bypass (27, 28) is changed by warming and cooling a gas line (37), in particular a capillary, for the test gas (21).

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