Turbomolecular pump with variable side inlet position for counterflow leak detection

Abstract

To provide a turbomolecular pump with variable intermediate gas inlet for a counterflow leak detector in a gas detection instrument. The turbomolecular pump (14) comprises a housing (abbreviation: H) (16), an internal structure including a pump stator (28) and a pump rotor within the H, a gas inlet (18) opening into the internal structure through the H, a gas outlet (20) opening to the outside of the internal structure through the H, and an intermediate gas inlet (22) opening into the internal structure through the H between the gas inlet and the outlet. The gas inlet is connected to a gas detector (12), and the intermediate gas inlet is connected to a test connection (24) for a test specimen or a test chamber containing the test specimen. The H has a longitudinally extending elongated slot (30) that can be partially covered by a movable cover such that the uncovered portion of the slot constitutes the intermediate gas inlet, and moving the cover changes the position and / or cross-sectional area of ​​the intermediate gas inlet.

Description

[Technical Field]

[0001] The present invention relates to a turbomolecular pump with a variable position of the side inlet for counterflow leak detection by a counterflow leak detector, the counterflow leak detector comprising a gas detector and the turbomolecular pump. [Background technology]

[0002] In a known counterflow leak detector, the gas inlet of a turbomolecular pump is connected to a gas detector, such as a mass spectrometer, the gas outlet of the turbomolecular pump is connected to the gas inlet of a pre-vacuum pump, and the intermediate gas inlet of the turbomolecular pump is connected to a test connection to a specimen under test or to a test chamber containing the specimen. Once an appropriate vacuum pressure is reached inside the gas detector, gas from the specimen or test chamber is introduced into the turbomolecular pump through the intermediate gas inlet and flows from there counter to the main flow of gas through the turbomolecular pump into the gas detector.

[0003] Conventionally, when exhaust gas is introduced into a turbomolecular pump, an intermediate gas inlet or introduction position is changed using a valve depending on the pressure generated at the inlet of the turbomolecular pump so that the number of compression stages of the turbomolecular pump leading to the mass spectrometer is kept small or the number of compression stages that must be passed through at low pressure is reduced. Each inlet location has different conditions such as compression, sensitivity, pumping speed, gas flow rate, heat generation, temperature sensitivity, etc. Summary of the Invention [Problem to be solved by the invention]

[0004] Because the pressure changes continuously during pumping of the test specimen by the turbomolecular pump, the selected intermediate gas inlet location is rarely optimal; rather, it is a compromise for the actual task. This compromise is based on the fact that the intermediate gas inlet of a multistage turbomolecular pump, which has multiple rotor stages between it and the gas detector, must be selected so that the total pressure of the gas detector is kept low enough while the pressure at the leak detector inlet is still high. On the other hand, the number of rotor stages between the inlet and the gas detector must be minimized to maximize sensitivity by keeping the path of the test gas molecules in the opposite direction to the pumping direction as short as possible. The goal is to measure the partial pressure of the test gas (typically helium or hydrogen) in the introduced gas with the highest sensitivity at the pumping speed for the fastest response time and the best detection limit. The pumping speed at the intermediate gas inlet of the turbomolecular pump is throttled by the valve used, adjusting its conductance.

[0005] In view of this background, the basic object of the present invention is to provide an improved counterflow leak detector comprising a gas detector and a turbomolecular pump, in which the position and / or opening cross-sectional area of ​​the intermediate gas inlet used can be changed. [Means for solving the problem]

[0006] The turbomolecular pump according to the present invention is defined by the features of claim 1.

[0007] The turbomolecular pump comprises a pump housing containing a structure, in particular a structure with a pump rotor and a pump stator. Preferably, the turbomolecular pump has several pump stages, each of which can be formed by a corresponding rotor stage. A gas inlet opens through the pump housing into the internal structure. A gas outlet opens from the internal structure through the pump housing. Between the gas inlet and the gas outlet, at least one intermediate gas inlet is provided, opening through the pump housing into the internal structure. The gas inlet is connected to the gas detector, and the intermediate gas inlet is connected to a test connection to a test object to be tested or to a test chamber containing the test object.

[0008] Particular features of the invention are that the pump housing has an elongated slot extending in the longitudinal direction of the pump housing, the internal structure has a plurality of inlet openings to the elongated slot, each of which can be assigned to one exhaust stage; and that within the internal structure, each stage of the turbomolecular pump has a stationary inlet opening (hereinafter referred to as a stator opening) to this elongated slot.

[0009] At least one cover is provided between the pump housing and the internal structure, configured to conceal the inlet openings from the elongated slots while exposing each of the inlet openings, thereby directly connecting each of the inlet openings to the elongated slots in a gas-communicating manner. The cover is movable relative to the elongated slots and the internal structure, and is configured to change the position and / or cross-sectional area of ​​the intermediate gas inlet by moving the cover. The intermediate gas inlet is a gas-communicating connection between the pump housing and the internal structure. Moving the cover changes the position of the intermediate gas inlet, specifically, establishing a gas-communicating connection to a specific exhaust stage. For this purpose, the internal structure may be provided with multiple stator openings, each assigned to a respective exhaust stage. The cover can be used to form a gas-communicating connection between the elongated slots and one of the stator openings. Additionally or alternatively, moving the cover can change the cross-sectional area of ​​the intermediate gas inlet.

[0010] Moving the cover relative to the pump housing allows the size and / or location of the intermediate gas inlet along the pump housing to be adjusted depending on the current requirements such as compression, sensitivity, pumping speed, etc., without having to use multiple intermediate gas inlets in different positions and / or sizes and select the appropriate one one by one. It also eliminates the need to switch valves to change the position and / or size of the intermediate gas inlet.

[0011] The cover may be cylindrically arranged as a cover cylinder and rotatably disposed relative to the pump housing and the internal structure of the pump housing. Specifically, the cover cylinder may be disposed within the pump housing. The cover cylinder may have a plurality of cover openings disposed longitudinally and / or laterally offset from the longitudinal axis. Thus, when the cover cylinder is rotated relative to the pump housing, the position and / or size of the overlap between the cover openings and the elongated slots changes. This allows the position and / or cross-sectional area of ​​the intermediate gas inlet to be changed. The overlap between the cover openings and the elongated slots constitutes the opening of the intermediate gas inlet. The cover openings may be disposed along a line oblique to the elongated slots, preferably extending at least partially in a spiral pattern around the cover cylinder.

[0012] If the cover cylinder has a plurality of cover openings arranged in a spiral pattern around the cover cylinder, rotating the cover cylinder relative to the elongated slot can align certain cover openings with certain of the stator openings to define the intermediate gas inlets. Rotating the cover cylinder relative to the pump housing can change the position of the intermediate gas inlets along the elongated slot and / or the cross-sectional area of ​​the openings of the intermediate gas inlets.

[0013] The internal structure including the pump stator may have at least one stator opening constituting the intermediate gas inlet. Specifically, multiple stator openings may be arranged along a line extending in the longitudinal direction of the internal structure. By rotating the cover cylinder relative to the internal structure, one or more of the cover openings may overlap one or more of the stator openings. This allows for changing the cross-sectional area of ​​the intermediate gas inlet and for changing the position of the intermediate gas inlet along the longitudinal axis of the cover cylinder and the internal structure.

[0014] Advantageously, the cover and the internal structure or the pump stator are cylindrical, the cover forming a cover cylinder that is rotatable relative to the pump housing and relative to the pump stator and that provides a sufficient seal for the purpose.

[0015] An exemplary embodiment of the present invention will now be described in detail with reference to the drawings. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a block diagram of a turbomolecular pump. [Figure 2] FIG. 1 is a schematic diagram of a turbomolecular pump. DETAILED DESCRIPTION OF THE INVENTION

[0017] The counterflow leak detector 10 according to the present invention comprises a gas detector 12 in the form of a mass spectrometer and a turbomolecular pump 14. The turbomolecular pump 14 comprises a pump housing 16 having a gas inlet 18, a gas outlet 20, and an intermediate gas inlet 22 disposed between the gas inlet 18 and the gas outlet 20. As shown in FIG. 1, the gas inlet 18 is connected to the gas detector 12 via a gas conduit, while the intermediate gas inlet 22 is connected to a test connection 24 via another gas conduit. The test connection 24 may be connected to a specimen to be tested and / or a test chamber holding the specimen to be tested. The gas outlet 20 is adapted to be connected to a pre-vacuum pump (not shown) that generates a desired preliminary vacuum pressure at the outlet region of the turbomolecular pump 14.

[0018] 2 is a schematic perspective view of the turbomolecular pump 14, in which a cover cylinder 26 is disposed within the turbomolecular pump, an internal structure is disposed within the cover cylinder 26, and the internal structure includes a pump stator 28 and a pump rotor disposed within the pump stator 28. The pump rotor is composed of multiple rotor stages that respectively form each exhaust stage of the multi-stage turbomolecular pump 14. A stator opening 34 of the pump stator 28 is assigned to each of these exhaust stages.

[0019] The pump housing 16 is provided with an elongated slot 30 that forms an opening in the wall of the pump housing 16. The first cover cylinder 26 is sealingly guided within the pump housing 16 with its outer shell surface in sufficient airtight contact with the edge of the elongated slot 30, for example by a seal, a sufficiently low conductance, etc. The cover cylinder 26 is provided with a plurality of cover openings 32 that are arranged along a spiral line around a portion of its shell surface and each form an opening in the shell surface. The spiral line along which the cover openings 32 are arranged extends from the upper left to the lower right in FIG. 2 .

[0020] The pump stator 28 is guided within the cover cylinder 26 such that the outer surface of the pump stator 28 is in sealing contact with the inner surface in the edge region of the cover opening 32, for example by a seal, a sealing ring, etc. The pump stator 28, like the cover cylinder 26, is provided with a plurality of stator openings 34 on its shell surface that correspond in size and shape to the cover openings 32 and are arranged along straight lines extending parallel to the longitudinal central axis of the pump stator 28. Each stator opening 34 penetrates the shell surface of the pump stator 28 to form an opening for the pump stator 28. Each of these openings is assigned as an inlet to one exhaust stage.

[0021] That is, the stator openings 34 are aligned along a straight line parallel to the longitudinal axis, and the cover openings are aligned along a helical line. When the cover cylinder 26 is rotated relative to the pump stator 28, one or more adjacent cover openings 32 overlap one or more adjacent stator openings 34, thereby defining and changing the size and shape of an opening 36 for the intermediate gas inlet 22 in the region of the elongated slot 30. The pump stator is oriented relative to the pump housing 16 so that the stator openings 34 are located within the elongated slots 30, and the overlapping stator openings 34 with the cover openings 34 provide a passageway through the pump housing 16, cover cylinder 26, and pump stator 28 to the interior of the pump stator.

[0022] Gas from the test connection 24 flows through the opening 36 into the interior of the turbomolecular pump 14, and thus into the interior of the pump stator 28. From there, under the appropriate pressure conditions, the gas flows through the gas inlet 18 to the gas detector 12 for detection.

[0023] Rotating the cover cylinder 26 relative to the pump stator 28 and relative to the pump housing 16 changes the position of the opening 36 along the elongated slot 30 and the size of the opening 36 (ie, the cross-sectional area of ​​the opening 36).

[0024] This changes the position of the intermediate gas inlet 22 in the longitudinal direction of the pump housing 16, so that the distance from the intermediate gas inlet 22 to the gas inlet 18 can be easily increased or decreased depending on requirements. The size of the cross-sectional area of ​​the opening 36 also changes accordingly, making it possible to increase or decrease the gas flow rate depending on requirements.

[0025] The movement and rotational position of the cover cylinder 26 and pump stator 28 may be manually or electronically controlled.

Claims

1. A turbomolecular pump (14) with a variable intermediate gas inlet for a counterflow leak detector (10) equipped with a gas detector (12), comprising: a pump housing (16); an internal structure contained within said pump housing (16) comprising a pump stator (28) and a pump rotor; a gas inlet (18) opening through the pump housing (16) into the internal structure; a gas outlet (20) opening from the internal structure through the pump housing (16); at least one intermediate gas inlet (22) opening through the pump housing (16) into the internal structure between the gas inlet (18) and the gas outlet (20); wherein the gas inlet (18) is configured to be connected to the gas detector (12) and the intermediate gas inlet (22) is configured to be connected to a test connection (24) to a test object to be tested or to a test chamber containing the test object, 1. A turbomolecular pump (14) comprising: a pump housing (16) having an elongated slot (30) extending in the longitudinal direction of the pump housing (16); the elongated slot (30) being capable of being partially covered by at least one cover movable relative to the elongated slot (30) such that an uncovered portion of the elongated slot (30) constitutes the intermediate gas inlet (22); and movement of the cover changes the position and / or opening cross-sectional area of ​​the intermediate gas inlet (22).

2. 2. The turbomolecular pump (14) according to claim 1, wherein the cover is cylindrical as a cover cylinder (26) and is arranged rotatably relative to the pump housing (16) and the internal structure within the pump housing (16).

3. 3. The turbomolecular pump (14) according to claim 1 or 2, characterized in that the cover has a plurality of cover openings (32) arranged offset in the longitudinal direction and / or laterally of the longitudinal direction.

4. 4. The turbomolecular pump (14) of claim 3, wherein the cover openings (32) are arranged in a row that is inclined relative to the elongated slots (30) and preferably extend at least partially helically around the cover cylinder (26).

5. 5. The turbomolecular pump (14) according to claim 1, wherein the pump stator (28) has at least one stator opening (34) that defines the intermediate gas inlet (22).

6. 6. The turbomolecular pump (14) of claim 5, wherein a plurality of stator openings (34) are arranged along a line extending in the longitudinal direction of the pump stator (28).

7. 7. The turbomolecular pump (14) according to claim 1, wherein the cover and the pump stator (28) are cylindrical, and the cover forms a cover cylinder (26) rotatably and sealingly arranged relative to the pump housing (16) and relative to the pump stator (28).

8. 8. The turbomolecular pump (14) according to claim 7, wherein the cover cylinder (26) has a plurality of cover openings (32) that are spirally distributed around the cover cylinder (26) such that, by rotating the cover cylinder (26), certain cover openings align with certain of the stator openings (34) within the elongated slot (30), thereby forming the intermediate gas inlet (22).

9. 9. The turbomolecular pump (14) according to claim 8, characterized in that the position of the intermediate gas inlet (22) along the elongated slot (30) and / or the opening cross-sectional area of ​​the intermediate gas inlet (22) can be changed by rotating the cover cylinder (26) relative to the pump housing (16).

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