EP2246573B1 - Safety system for high vacuum system - Google Patents

Description

The present invention relates to a protective device for high-vacuum pumps, in particular for turbomolecular pumps according to the preamble of claim 1, as well as a vacuum system with such a protective device.

Turbomolecular pumps have been used for several decades to create a high vacuum on all types of process equipment, especially those of the semiconductor industry. Turbomolecular pumps have the advantage that they have a high pumping speed, little susceptibility to contamination and are generally very durable. For the extraction of corrosive gases special turbomolecular pumps are used, whose bearings can be purged with an inert gas.

Selenium compounds are also used in the manufacture of modern photovoltaic cells. These compounds have the unpleasant property that they can deposit on cool surfaces. If turbomolecular pumps are used, the compounds are deposited on the rotors and stators of the turbomolecular pumps. This can lead to imbalances in a relatively short time, which can lead to the destruction of the turbomolecular pump. In order to solve this problem, sheets are often used in practice, which are arranged in the passage in front of the turbomolecular pump. By means of the plates harmful and also condensable gases and compounds can be deposited. The disadvantage, however, is that the sheets restrict the conductance, so that the suction power of the turbomolecular pump drops dramatically.

The U.S. Patent No. 6,368,371 discloses a collecting device for gases, which can be driven via a corrugated bellows in a collecting chamber, which is arranged in the suction line. The collecting device is arranged on a shaft, which can be moved in and out by means of an actuator in the collecting chamber. The collecting device consists of cooling plates, which have a straight and a curved portion and are held together by two terminal end plates. In operation, the gases flow along the curved passages formed between the individual cooling plates and are cooled on contact with the cooling plates. The cooling of the cooling plates takes place indirectly via the cooling of the shaft, on which the cooling plates are arranged. There is a relatively large gap between the cooling plates and the inner wall of the collecting chamber, so that harmful gas can either precipitate on the inner wall or pass through the gap into the pump.

The JP-A-56203682 shows a collecting device for gases, which is formed by a arranged in a collecting chamber liquid nitrogen cooling trap. The cold trap consists of a cylindrical container in which liquid nitrogen is introduced. To regenerate the cold trap, we separated the vacuum chamber and the pump by means of appropriate valves from the collecting chamber, removed the liquid nitrogen and heated the cold trap by means of radiant heat. The escaping from the cold trap gas is then withdrawn via a pump.

It is therefore an object of the present invention to propose a device with which turbomolecular pumps can be protected from harmful gases, in particular condensing compounds. One goal is to propose a device that is efficient. Another goal is to propose a device that is easy to clean. Another goal is to propose a device that allows a high conductance.

According to the invention the object is achieved by the characterizing features of claim 1.

The device according to the invention has the advantage that high-vacuum pumps and in particular turbomolecular pumps can be effectively protected by the protective device against undesirable, condensable vapors, in particular metal vapors. The fenders are accessible from the outside through the opening of the third connection flange. They can be inserted and removed through the opening of the third connection flange in the passage. This has the advantage that the fenders do not have to be permanently arranged in the passage, but - depending on the process - can be used or removed. By providing a separate connection flange to insert and remove the mudguards, the turbomolecular pump need not be removed to remove the mudguards. By providing an extended cross-sectional area, the conductance can still be relatively high because the fenders do not fill the entire cross-sectional area of the pipe section. The arrangement of the fenders on opposite sides of a corresponding to the shape of the pipe shell has the advantage that the inner wall of the pipe section through the shell, which is modeled on the inner walls of the pipe section, shielded and the vapors can condense on this. This makes it possible to protect the pipe section of the inventive connector from unwanted deposits.

Advantageously, there is sufficient clearance between the inner wall of the enlarged cross-sectional area and the baffles to keep the conductance high. Of importance, however, is that the fenders are arranged and arranged so that the passage between the first and second openings is optically blocked. This can ensure that the vapors to be pumped on their way to the pump on the fenders and can condense on this.

Conveniently, the fenders are designed such that the Leitwertverlust by the fenders arranged in the passage less than 40%, preferably less than 30% and most preferably less than 25% of the guide value without baffles.

According to a preferred embodiment, the pipe section adjoining the first connection flange defines a first pipe section and the pipe section adjoining the second connection flange has a second pipe section, and the first and second pipe sections are arranged at an angle to each other, wherein the expanded cross-sectional area between the first and second pipe sections is provided. This is a convenient and space-saving embodiment. The first and second pipe sections may be arranged at an approximately right angle to each other. An expedient embodiment provides that the pipe section is designed as a T-connector, wherein the first and second connection flanges preferably have a smaller nominal diameter than the third connection flange.

Advantageously, the fenders angle profiles with a first and a second leg, which angle profiles in the space between the first and second, a bend defining pipe sections are arranged and their first leg in the axial direction of the first pipe section and the second leg in the preferred axial direction of the second Tube section are oriented. The shape of the fenders and their arrangement is thus such that on the one hand, the conductance is as high as possible and on the other hand, at least a single contact of the molecules to be pumped with the baffles is ensured. This is achieved in that the fenders are formed and arranged so that there is no optical passage between the first and second connection flange.

Advantageously, the fenders are arranged on a holder, which is arranged in the extended cross-sectional area of the pipe section. The holder can be supported on the inner wall of the pipe section or on a flange which can be screwed onto the third connecting flange. The latter embodiment has the advantage that the fenders unscrewed together with the flange resp. can be removed.

According to a preferred embodiment, the holder is formed by a tube, the ends of which are screwed through the tube piece or a screwed onto the third connection flange

Blind flange are guided. This has the advantage that the pipe and thus the fenders arranged on the pipe can be additionally cooled, since the fenders are in heat-conducting contact with the pipe. The tube can be made of copper or of a stainless steel. The fenders are located at a preferably short distance from the inner wall of the pipe section, i. they are thermally insulated from the pipe section.

Advantageously, the tube is arranged in turns on the jacket and with this in heat conductive contact. This allows not only the baffles but also the jacket to cool. By vacuum insulation of the jacket, the tube can also be used at low temperatures, e.g. with liquid nitrogen, to be cooled. For the vacuum insulation is required that the fender and optional jacket existing mounting part is spaced anywhere to the inner walls or is supported exclusively on thermal insulation elements on the pipe section.

Another aspect of the inventive device is the ability to remove the fenders from the passage. This has the advantage that the fenders can be cleaned or replaced without the pump would have to be unscrewed. Advantageously, the holder is arranged with the baffles on a flange which can be screwed to the third connection flange. This is a convenient design, in which no additional fasteners or supports on the pipe section are needed. It is conceivable spacers made of a material with a low coefficient of thermal conductivity, e.g. To use ceramic, plastic, etc., to keep the baffles, respectively the coat enclosing the fenders at a distance from the blank.

The present invention is also a vacuum system with a protective device according to one of claims 1 to 11 and a turbomolecular pump, which is connected to the second flange. Such systems have the advantage that the turbomolecular pump is well protected by the protection device.

Figur 1

Eine erste Ausführungsform einer erfindungsgemässen Vorrichtung umfassend ein einen geraden Durchgang definierendes Rohrstück mit 3 Anschlussflanschen und Umlenkblechen, welche im Durchgang angeordnet sind;

Figur 2

Ein zweites Ausführungsbeispiel einer erfindungsgemässen Schutzvorrichtung, bei welcher - im Unterschied zur Ausführungsform gemäss Fig. 1 - der Anschlussflansch für den Anschluss einer Hochvakuumpumpe senkrecht zum Anschlussflansch für den Anschluss des Rohrstücks an eine Prozessanlage steht;

Fig. 3

Ein drittes Ausführungsbeispiel einer erfindungsgemässen Schutzvorrichtung, bei welcher die Anzahl der im Durchgang angeordneten Schutzbleche reduziert ist; und

Fig. 4

Einen Schnitt durch das Ausführungsbeispiel gemäss Fig. 3.

The invention will be explained below by way of example with reference to the figures. In this case, the same parts are designated by the same reference numerals in the various embodiments. It shows:

FIG. 1

A first embodiment of a device according to the invention comprising a pipe section defining a straight passage with 3 connecting flanges and deflecting plates, which are arranged in the passage;

FIG. 2

A second embodiment of a protective device according to the invention, in which - in contrast to the embodiment according to Fig. 1 - the connection flange for connecting a high vacuum pump is perpendicular to the connection flange for connecting the pipe section to a process plant;

Fig. 3

A third embodiment of a protective device according to the invention, in which the number of fenders arranged in the passage is reduced; and

Fig. 4

A section through the embodiment according to Fig. 3 ,

The protective device 11 according to FIG. 1 comprises a pipe section 13 with a first connection flange 15 having a first opening 16 for connecting the pipe section 13 to a process installation (not shown in the figure), a second connection flange 17 having a second opening 18 for connecting a high-vacuum pump (not shown) to the first Pipe section 13 and a third opening 20 having third connection flange 19, which is provided between the first connection flange 15 and the second connection flange 17 on the pipe section 13. The space between the first connection flange 15 and the second connection flange 17 defines a passage 21 for the gas to be pumped out of a process chamber. In the passage 21 fenders 23 are arranged, which preferably completely obstruct the passage 21 optically. This means that the fenders are dimensioned so that in the suction direction 25 a view is optically blocked. In the embodiment shown corresponds to the diameter of the Fenders 23 substantially the clear widths of the passage at the narrowest points 27 and 29. An observer so the view through the pipe section from the first connection flange 15 to the second connection flange 17 is substantially completely blocked. Steam molecules that move <10-3 stochastically in the vacuum range (= molecular flow area) must hit the fenders on their way to the vacuum pump. They condense when the temperature of the mudguards is suitable. Between the spaced-apart fenders 23 in the form of roastssymmetrischen Cylindermänteln passage channels for the gas molecules are present. The mudguards 23 preferably have an angled structure which ensures that gas molecules once entered into the passageways - in the case where they do not adhere to the baffle plates - are deflected so that they penetrate the passageway.

It is important that the fenders 23 are easily accessible through the third connection flange 19. According to a preferred embodiment, the fenders are arranged directly on a blind flange 31. This has the advantage that the removal of the mudguards 23 by unscrewing the blind flange 31 is possible. Also, no additional fittings are needed to order the fenders 23 in the pipe section 13.

In order to impair the conductivity as little as possible by means of the protective plates 23 arranged in the passage 21, the tube piece has a pipe section 33 with an enlarged cross section 33. The extended cross-sectional area 33 is spherical in the embodiment shown. In the region of the largest cross section, the protective plates 23 are arranged. Due to the enlarged cross-section, a gap 35 between the baffles 23 and the inner wall of the pipe section 13 may be present, which ensures the maintenance of a good conductance.

So that all possible gas molecules collide at least once on a cooled protective surface when passing through the pipe section, the protective plates 23 are preferably surrounded by a jacket 37, respectively accommodated therein. The optional jacket 37 preferably has a shape adapted to the expanded pipe section 33, so that only a small gap 41 remains between the jacket 37 and the inner wall 39 of the pipe section 13.

So that light molecules with a low freezing point can be condensed on the mudguards, the mudguards 23 are in contact with a cooling circuit. This cooling circuit comprises a tube 43, which is guided through the blind flange 31 and in heat-conducting contact with the jacket 37 and preferably the mudguards 23. The protruding from the blind flange 31 pipe sections define connecting pieces 45,47 for connecting the pipe to a not shown in detail cooling unit. The connecting pieces 45, 47 are advantageously designed as vacuum-insulated passages for the lines transporting the cooling medium, so that there is no cold bridge to the connecting flange. Preferably, the cooling line at the same time forms the holder for the jacket and the shrouds arranged in the jacket 37.

According to the preferred embodiment, the connection flange 15 for the connection of the pipe section 13 to a vacuum system and the connection flange 17 for the connection of the high vacuum pump is not opposite each other as in the embodiment according to FIG. 1 but at an approximately right angle to each other. The first pipe section 49 adjoining the first connection flange 15 and the second pipe section 51 adjoining the second connection flange 17 are at right angles to one another. This embodiment has the advantage that the high-vacuum pump, which is normally a turbomolecular pump, can be arranged very close to the process plant. As a result, the space requirement of the turbomolecular pump to be protected by the protection device is not significantly increased.

In order to obstruct the passage between the opening 16 of the first connecting flange 15 and the opening 18 of the second connecting flange 17, the protective plates are now preferably arranged diagonally in the passage 21. Analogous to the embodiment according to Fig. 1 a sheath 37 is provided with spaced-apart linear guards 23 therein. The jacket 37 has the shape of a preferably circular cylinder 53, which has an opening 55 on one end face and whose other end face is closed by a bottom 57. Diagonally in the cylinder and extending from the bottom 57 to the opening 55, a holder 59 is provided, on which the fenders 23 are arranged. The fenders 23 have the shape of an angle profile 61, wherein the one leg 63 of the angle profile 61 is oriented to the first opening 16 and the other leg 65 to the second opening 18. The cylinder 53 has a hole 69 in the cylinder jacket on the side oriented to the opening 16, which preferably the same or a similar dimension as the opening 16 has. The number of angle profiles is chosen so that the passage 21 between the opening 16 and the opening 18 is just blocked visually. Adjacent to the angle profiles 61 flat profiles 67 are still provided. However, these can also be omitted, as realized in the third embodiment ( 3 and 4 ).

The device of FIG. 2 can be inexpensively made of a pipe section of a certain diameter by the second flange inside and the third flange outside the tube is arranged. The first connection flange, which is preferably the same in diameter as the second connection flange, is attached to the jacket of the pipe section as a stub. In this way, one obtains a cost-producible connector for connecting a high-vacuum pump with a system to be evacuated. This connector has two connection flanges, which advantageously have the same nominal size as the connection flange of the high vacuum pump.

According to a preferred embodiment, the holder 59 is formed by a cooling line of a cooling circuit. Alternatively, the cooling line can also be soldered to the holder. This cooling line is guided through the blind flange 31 and extends in turns preferably also around the jacket of the cylinder 53. This has the advantage that both the cylinder jacket of the protection device and the mudguards 23 can be cooled. Like from the FIG. 2 can be seen, is located between the tubes 43 of the cooling pipe and the inner wall of the pipe section, a small gap, so that the pipe section 13 is thermally insulated from the protective device 11.

The embodiment according to the FIGS. 3 and 4 differs from that of the embodiment according to FIG. 2 only in that the flat profiles are omitted. Incidentally, it is common to the exemplary embodiments that the protective plates are arranged in a tube section with an enlarged cross-sectional area compared to the opening of the first connecting flange.

It is particularly advantageous if standard nominal sizes are used for the connection flanges. By way of example, the following nominal diameters can be used for a protective device: Nominal diameter of first connection flange: 250 mm (DIN250ISO-K / F) Nominal size of second connection flange: 250 mm (DIN250ISO-K / F) Nominal size of third connection flange: 320 mm (DIN320ISO-K / F) Mudguards and pipes Version in stainless steel

This results in a pipe section with an enlarged compared to the first flange cross-sectional area, which holds the pumping speed of the pump despite the additional internals to at least 60%, and preferably at least 70% of the pumping speed without internals. The internals, such as fenders, holder and shell are preferably made entirely of stainless steel.

The protection device 11 is used as follows: The protection device 11 is installed between the process plant and the high vacuum pump. During operation of the process plant and when high vacuum is reached in the plant, the mudguards are cooled before the actual processes run off. This can be done with water or other coolants, such as water, as required. Liquid nitrogen, done. Condensable molecules are deposited on the fenders or cladding as they pass through the protection device. After the process plant has been flooded, the blind flange 31 with the protective sheets arranged thereon can be removed and freed from the adhering molecules (eg by thermal (heating) or mechanical removal (eg sandblasting).) It is conceivable to provide a sliding valve between the protective device and the process plant. so that the fenders can be removed without having to flooded the process plant, and a sliding valve could be provided between the fender and the high vacuum pump.

In the production of photovoltaic cells, CuInSe compounds are used for certain cell types, inter alia, for the production of so-called CIGS solar cells or CIS cells, in which case S may be sulfur or selenium, depending on the cell type. When selenium compounds are used, selenium metal vapors also form in the reaction chamber. These vapors are deposited on the stators and rotors of turbomolecular pumps as they are drawn by the pump. If the turbomolecular pump for a long time in contact with these metal vapors, imbalances can arise, which lead to the destruction of the turbomolecular pump. With the aid of the device according to the invention it is possible To effectively protect turbomolecular pumps from harmful, condensable metal vapors.

Legend:

11

guard

13

pipe section

15

first connection flange

16

a first opening of the first connection flange

17

second connection flange

18

a second opening of the second connection flange

19

third connection flange

20

a third opening of the third connection flange

21

passage

23

baffles

25

suction direction

27.29

Clear widths of passage at points 27 and 29

31

blind flange

33

Pipe section with an extended cross-section

35

gap

37

coat

39

Inner wall of the pipe section 13

41

Gap between inner wall and jacket

43

pipe

45.47

spigot

49

First pipe section

51

Second pipe section

53

cylinder

55

opening

57

ground

59

holder

61

angle section

63, 65

Leg of the angle profile

67

flat profiles

Claims (14)

1. Protection device for high vacuum pumps, in particular turbomolecular pumps, against harmful vapors, in particular condensable vapors, in particular metal vapors with a pipe piece (13) with

   - a first connecting flange (15) which has a first opening (16) and

   - a second connecting flange (15) which has a second opening (18), which connecting flanges (15, 17) are connected with each other by a pipe section defining a passageway (21),

   - a third connecting flange (20) which has a third opening (20) which is provided between the first and the second connecting flange (15, 17) at the passageway (21) and

   - an arrangement of a plurality of guide plates (23) placed spaced from each other which can be placed in the passageway (21) at a distance from the third connecting flange (19) and which can be put in and removed through this passageway,

   characterized in that the pipe section constituting a passageway (21) has an enlarged section area (33) for receiving the guide plates and the guide plates (23) are placed on opposed sides on a shell corresponding to the configuration of the pipe section so that the inner wall of the pipe section is protected by the shell which imitates the inner walls of the pipe section.
2. Device according to claim 1, characterized in that the protection plates (23) fill only one part of the enlarged cross-section area (33) and are placed preferably to such an extent and in such a manner that the passageway (21) between the first and the second opening (16, 18) is visually obstructed.
3. Device according to one of the claims 1 to 2, characterized in that the pipe section annexed to the first connecting flange (15) defines a first pipe section (49) and the pipe section annexedto the second connecting flange (17) and that the first and second pipe sections (49, 51) are placed at an angle to each other, whereby the enlarged cross-section (33) is provided between the first and second pipe sections (49, 51).
4. Device according to one of the claims 1 to 3, characterized in that the pipe section (13) is configured as a T-connector, whereby the first and second connecting flanges (15, 17) preferably have a smaller nominal width than the third connecting flange (19).
5. Device according to claims 3 or 4, characterized in that the protection plates (23) are corner steels (61) with a first and a second leg (63, 65), which corner steels (61) are placed in the space between the first and second pipe sections (49, 51) which define a curvature and the first legs (63) of which are orientated in preferably axial direction of the first pipe section (49) and the second legs (65) of which are orientated in preferably axial direction of the second pipe section (51).
6. Device according to one of the claims 1 to 5, characterized in that the protection plates (23) are placed on a support that is placed in the enlarged cross-section area (33) of the pipe section.
7. Device according to one of the claims 1 to 6, characterized in that the support is formed by a pipe (43) or is in heat conducting contact with a pipe (43), the ends of which are guided preferably through the pipe piece (13) or through a blind flange (31) which can be screwed to the third connecting flange (19).
8. Device according to one of the claims 1 to 7, characterized in that the protection plates (23) are placed at a short distance from the inner wall of the pipe section.
9. Device according to one of the claims 7 or 8, characterized in that the pipe is guide in windings around the shell (37) and is in heat conducting contact therewith.
10. Device according to one of the claims 1 to 9, characterized in that the support is placed with the guide plates on a flange (31) which can be screwed to the third connecting flange (19).
11. Vacuum installation with a protection device according to one of the claims 1 to 10 and with a high vacuum pump that is connected to the second connecting flange (17).
12. Vacuum installation according to claim 11, characterized in that the high vacuum pump is a turbomolecular pump.
13. Method for protecting high vacuum pumps, in particular turbomolecular pumps, against harmful, in particular condensable metal vapors,
    characterized in that the gas flow is guided before entering the high vacuum pump through a pipe piece (13) with an enlarged cross-section area (33), in which enlarged cross-section area (33) protection plates (23) are placed in such a manner that a marginal area remains free, whereby however a contact of the gaseous molecules when passing through the pipe piece with the guide plates (23) is ensured and that moreover the protection plates are placed on opposite sides on a shell (37) corresponding to the configuration of the pipe piece so that the inner wall of the pipe section is protected by the shell which imitates the inner walls of the pipe section and that the protection plates (23) are cooled.
14. Method according to claim 14, characterized in that it is used as a protection of a turbomolecular pump against metal vapors, in particular against selenium molecules.

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