EP3392509A1 - Vacuum system for generating at least one high vacuum in a recipient - Google Patents

Abstract

In order to operate a recipient in a high vacuum, a two-stage vacuum system with a final vacuum pump and a backing pump is generally used. In the event of a power failure, the vacuum pumps are slowly vented. It can disturbing back-diffusion, in particular of wet-running, especially oil-sealed backing pump, occur, in addition, the recipient is vented. Cleaning up and rebuilding the high vacuum are time and cost consuming. According to the invention, a first valve (09) is provided between the end vacuum pump (03) and backing pump (05), which is closed abruptly in the event of a power failure and secures the high vacuum (P vac) and the end vacuum pump (03) for hours. After power return, the first valve (03), which may be an electropneumatic solenoid valve (13), is opened again only after a time delay (T VZ1) which can be set at a delay device (10), so that reliable pump operation is ensured. prevents back-diffusion and ventilation. As a modification, a second valve (14) can be provided analogously to the backing pump (05). Such recipients (01) are used for example in mass spectrometry for material analysis in connection with climate research.

Description

The invention relates to a vacuum system for generating at least one high vacuum in a recipient with at least one final vacuum pump for generating at least the high vacuum and a backing pump for generating at least a fine vacuum and with an operation-dependent controlled valve device for pressure-tight sealing of the recipient in the event of a malfunction, wherein the recipient, final vacuum pump, backing pump and valve means are connected in series with each other via a pressure-tight connection line and wherein the operating-dependent controlled valve device has at least a first valve with a first delay device, to which a time constant is adjustable, to maintain the high vacuum in the recipient during a malfunction, which is arranged between the final vacuum pump and the backing pump.

In vacuum technology, the recipient is a vacuum-tight chamber made of glass or, as a rule, stainless steel, in which after evacuation of the gases contained there is a technical vacuum with the aid of vacuum pumps. In contrast to an ideal particle-free vacuum is a technical vacuum with residual particles with technical Means reachable. To generate extreme technical vacuums, the vacuum chamber can also be heated or deep-frozen. The fine vacuum FV (1 to 10 ^-3 hPa (mbar)) is followed by the high vacuum HV (10 ^-3 to 10 ^-7 hPa (mbar)). This is followed by ultrahigh vacuum UHV (10 ^-7 to 10 ^-12 hPa (mbar)) and extremely high vacuum XHV (<10 ^-12 hPa (mbar)). A common application for a high vacuum recipient is mass spectrometry, a method of mass determination of atoms or molecules for characterizing chemical compounds, such as those needed in biochemistry, geology, and climatology. The required for the operation of a mass spectrometer high vacuum is produced today usually by the series connection of a turbomolecular pump with a rotary vane pump. In this case, the turbomolecular pump generates the end vacuum in the recipient as the final vacuum pump on its suction side and the rotary vane pump as a backing pump on its suction side, the fine vacuum on the discharge side of the turbomolecular pump. On its discharge side, the rotary vane pump works against the atmospheric pressure.

In a high vacuum, there are only very few, namely 10 ¹³ to 10 ⁹ molecules in 1 cm ³ volume. Therefore, it is technically very complex and time-consuming to produce such a high-quality vacuum. The normal case of a malfunction of the vacuum system, in particular in a malfunction of the vacuum pumps by a power failure or by contamination or damage, consists in the resolution of the vacuum by slow complete or partial venting of the vacuum chamber. After the malfunction has been remedied, however, the time-consuming process to achieve a new vacuum in the vacuum chamber must be passed through. Optionally, the vacuum chamber and its periphery must first be cleaned when matter particles from the pump or the environment are backdiffused into the recipient. These are all extremely undesirable disturbances in a measuring operation. Accordingly, it is desirable and of great advantage to maintain a generated vacuum in a vacuum chamber even in a malfunction of the vacuum system. This will be in the state of Technique different solutions offered.

State of the art

As an alternative to complete or partial ventilation of the recipient in the event of a malfunction, it is proposed in the prior art, inter alia, to aerate the vacuum pumps. If this ambient or atmospheric pressure is reached, then water or oil mist or vapors can not be drawn into the recipient in wet-running vacuum pumps and gases in the case of gas-ballast vacuum pumps. Without providing additional valves, the recipient is inevitably ventilated. Aeration of the recipient is avoided according to the DE 38 17 581 A1 , which discloses a special valve device with a solenoid valve and a spring valve with buffer volume between the recipient and the vacuum pump. In the event of a power failure, the vacuum pump is vented via the opening solenoid valve and at the same time the recipient is closed via the closing spring valve, so that the high vacuum in the recipient is maintained during malfunction. After the return of the current, the solenoid valve is first closed, so that the ventilation of the vacuum pump is stopped. Only when the vacuum pump has returned to its operating state, the spring valve for the recipient is opened again. Similar is from the DD 271 545 A1 known, which describes the arrangement of a special valve device with a spring valve and its own venting valve between recipient and rotary vane pump, the pressure-tight manner in a power failure, the recipient and the rotary vane pump is aerated as quickly as possible. After return of the flow, the ventilation of the rotary vane pump is closed and the recipient is only opened again when there is almost the same pressure between the recipient and the rotary vane pump. In both cases, there are special and relatively expensive technical designs of a vacuum safety valve with an electromechanical drive.

Furthermore, it is for example from the DE 100 48 210 B4 or the DE 199 29 519 A1 It is known to use a backing pump both as a precursor for a final vacuum pump behind a recipient as well as directly for a parallel pre-recipient in a common structure, as required for example for Schleusungsvorgänge in the recipient. For this purpose, a solenoid valve between the Endvakuumpumpe and the backing pump is arranged. This seals off the final vacuum pump and thus the recipient in a pressure-tight manner when the fore-vacuum pump is working for the pre-recipient.

Furthermore, it is from the publication. " New high vacuum for CCD camera 2 "by HR Schäfer (retrieved on the internet 22.04.2017 under the URL http://www.harpoint-observatory.com/english/publikationen/kameraevakuierung.pdf ) is known to evacuate the vacuum chamber of a CCD camera as a recipient again in a laboratory setup, when the factory-implemented high vacuum has subsided. The renewed high vacuum is generated in two stages by means of a turbomolecular pump as a final vacuum pump and an oil-lubricated rotary vane pump as a backing pump. In order to avoid fouling of the recipient in case of power failure or other malfunction of the two vacuum pumps, a simple high-vacuum solenoid valve is located directly behind the recipient, which is immediately closed in the event of a malfunction. Recipient, solenoid valve, final vacuum pump and backing pump are connected in series via a branchless pressure-tight connection line. The solenoid valve is electrically connected to the alarm output of the control electronics of the turbomolecular pump. Since the turbomolecular pump works almost frictionless in a high vacuum, it needs a certain amount of time in the event of a power failure until it loses its full speed and thus the high vacuum. Therefore, the closing time of the solenoid valve to prevent back diffusion into the recipient is quite sufficient. For renewed evacuation, the solenoid valve is first closed and the two vacuum pumps are started up. After approx. 20 min. Operating time, the solenoid valve is then opened and high vacuum generated in the recipient. Since in the prior art is a one-time process for permanently achieving the high vacuum in the CCD camera, such a long delay time to the opening the solenoid valve can be accepted. In addition, contaminants that could penetrate into the turbomolecular pump directly behind the recipient via the rotary vane pump until the solenoid valve opens, could enter the recipient when the solenoid valve opens, which can either increase the pumping time to reach the final vacuum or even lead to contamination ,

The closest to the invention prior art is in the DE 199 13 593 A1 described. From this, a vacuum system is known which serves to generate a high vacuum. The vacuum system comprises a recipient, a final vacuum pump for generating the final vacuum, a roughing pump for generating a fine vacuum and an operation-dependent controlled valve device for pressure-tight sealing of the recipient in the event of a malfunction. Here, recipient, Endvakuumpumpe, backing pump and valve means are connected via a pressure-tight connection line with each other in series. To maintain the high vacuum in the recipient during a malfunction, the operating-dependent controlled valve device has a valve with a delay device to which a time constant is adjustable. The valve is disposed between the final vacuum pump and the backing pump. The known vacuum system operates as an active system consistently pressure dependent. Pressure-changing malfunctions, such as a mechanical or contamination partial or full failure of the backing pump are detected by a capacitive pressure sensor, which is arranged in a branch in the connecting line between the Endvakuumpumpe and the valve, and processed in a control device. If an undesired increase in pressure occurs, the valve is already open. Upon reaching an error threshold value, the control device generates a control command which overrides the applied control command for opening the valve and actively closes the valve after the correspondingly adjusting time delay. If the pressure sensor detects a pressure value which is again below the error threshold value, the valve is evacuated after a time delay at which the backing pump evacuates the connection line to the valve, which is constantly set at the deceleration device again opened by a control command. The known vacuum system is thus an active system and always requires a power supply for its correct functioning. In the event of a power failure, it can not operate because control commands can not be generated for the valve. The vacuum system remains in its state in the event of a power failure.

task

Based on the above-mentioned closest prior art, the object of the present invention is to further develop the generic vacuum system described above so that it is suitable for a professional measurement setup with permanent measurement campaigns and the pressure-tight maintenance of a prevailing in the recipient high vacuum at a power failure as malfunction guaranteed with a failure of the vacuum pump safely. It should be used simple and commercially available means. The solution to this problem can be found in the main claim. Advantageous developments of the invention are set forth in the subclaims and explained in more detail below in connection with the invention.

The claimed vacuum system according to the invention is characterized in that the connecting line is unbranched, the valve is closed automatically in case of power failure as a malfunction automatically and after elimination of the power failure with the time delay adjustable at the first delay means time constant is opened automatically and that at least the Endvakuumpumpe no separate vent valve having.

In the case of the vacuum system according to the invention, the connecting line between the recipient, final vacuum pump, backing pump and valve device is designed without branches. In particular, no pressure sensors are provided which operate only under power supply and generate additional delays. That's why Although the claimed vacuum system does not react to malfunctions with pressure fluctuations caused, but faster to a power failure. The valve closes abruptly automatically, ie automatically without control command, and thus protects not only the recipient, but also the Endvakuumpumpe, which does not have its own ventilation valve in the invention. Both in the recipient and in the final vacuum pump, the prevailing high vacuum is reliably maintained for several hours or during the entire power failure. If the power failure is completed, recipient and final vacuum pump are not released immediately. This is done only after a predetermined time delay, so that it is ensured that the backing pump is already back in the operating state. The time delay is set on the first delay device on the first valve. This may be, for example, a commercially available timer. Thus, the safety system of the vacuum system according to the invention can be designed as a simple, cost-effective block, which consists only of the valve and a simple timer. Such a block is particularly well suited for retrofitting existing vacuum systems.

Ventilation of the final vacuum pump and / or the backing pump is not mandatory in the invention. For certain operating conditions independent of normal operation, such as maintenance with aeration of the recipient, it is preferred and advantageous according to a first development of the invention, if the first valve is also designed as a vent valve of Endvakuumpumpe, the ventilation function is suppressed in case of power failure. In such operating conditions, the backing pump is then taken out of operation first, so that no contamination from the backing pump can diffuse when venting the Endvakuumpumpe.

According to a next advantageous embodiment of the invention, it is provided that the operating-dependent controlled valve device has a second valve with a second delay device, which on the of the Endvakuumpumpe the opposite side of the backing pump is arranged and closed instantaneously in the event of a power failure and after the elimination of the power failure time-delayed with an adjustable time constant is opened, whereby the backing pump does not have its own vent valve. The time delay is set at the second delay device on the second valve. This may also be, for example, a commercially available timer. In this embodiment, it is ensured that in case of power failure in the backing pump, the pre-vacuum is maintained, so that after power return, the entire vacuum system is ready for use immediately. Ventilation of the backing pump is also not mandatory. However, in order to enable the ventilation of the backing pump for special operating conditions also in this variant, it is advantageous and preferred according to a next embodiment of the invention, if the second valve is also designed as a vent valve of the backing pump, wherein the ventilation function is suppressed in case of power failure. Aeration is thus - as with the Endvakuumpumpe - only outside a power failure, for example during a maintenance operation possible. During an unwanted power failure, however, the vacuum is kept safe and not ventilated.

If both the final vacuum pump and the backing pump are provided with fast-closing valves and both vacuum pumps do not have their own ventilation valves, the invention can safely guarantee the high vacuum in the recipient in the event of a sudden power failure and thus the fastest possible start of operation after the end of the power failure. This achieves the shortest possible interruption in operation of a current measurement, for example in a mass spectrometer as a recipient, which saves time and costs for the operator of the vacuum system. It is conceivable that the operator of the power failure initially takes no notice. In order to automatically ensure after power return that no back diffusion into the forevacuum pump, the final vacuum pump and finally into the recipient can take place until the vacuum pumps are fully started again, is provided in the invention to open the valves after the return of the current delayed. In this case, according to a further embodiment of the invention, it is preferable and advantageous if the time constant for the time delay of the first delay device of the first valve and / or the second delay device of the second valve are set in a range between 8s and 12s, in particular 10 s. If only the final vacuum pump is sealed by the first valve, but the backing pump is vented in case of power failure, it makes sense if the two vacuum pumps first 8s to 12s, in particular 10 s run before the first valve is opened and releases the connection to Endvakumumpumpe , Pending contaminants in the backing pump or on the first valve can thus be sucked before opening the first valve before the Endvakuumpumpe first from the backing pump. If the backing pump has also been closed by the second valve in the event of a power failure, it will not be possible for any contaminants to enter and to be present before the second valve. So that they are not sucked into the backing pump during the restart, it makes sense here, too, that both vacuum pumps only run for 8 seconds to 12 seconds, in particular 10 seconds, before then both valves are opened. Other time constants for setting the delay time at the two valves are readily possible. These can be longer, but also shorter or even different on both valves. Furthermore, it is preferred and advantageous if both delay devices are integrated in a common control device. Then, for example, with a common timer as part of the valve device, the opening time of the first and the second valve is controlled.

From the state of the art, various valves with special constructions for implementing their special functions, for example, ventilating the vacuum pump and sealing the recipient, are known. In the invention, however, can be particularly advantageous and preferably simple solenoid valves are used, which are operated electropneumatically. Solenoid valves are commercially available valves without special designs. In an electropneumatic actuation, an electrical signal is converted into a pneumatic Signal converted. These valves have a directly operated valve which activates a pneumatic actuator upon receipt of an electrical signal. The big advantage of pneumatic actuation is the extremely short closing time of such valves. In the case of a power failure, it is preferred and advantageous in the invention if at least the first valve is electrically connected to an alarm output of the final vacuum pump and / or the backing pump. An occurring interference signal then automatically triggers the first valve. This is closed suddenly and ensures the high vacuum in the recipient. This also applies to the second valve, if this is also connected to the alarm output of the final vacuum pump and / or the backing pump. This and the pneumatic support a particularly rapid closure of the valves in a sudden power failure and thus a particularly good preservation of high vacuum in the recipient can be ensured. In operation, the solenoid valves are kept open by the current flow.

Furthermore, it is preferred and advantageous in the invention if the final vacuum pump is formed by a turbomolecular pump. In a molecular pump, the effect is exploited that particles impinging on a wall remain for a short time between adsorption and desorption on the wall. The turbomolecular pump is a dry-running gas transfer pump, which consists of a single or multi-stage alternating arrangement of inclined baffles as stators, between which run rotors with inclined rotor blades. The speed of the rotor blades is approximately on the order of the average thermal velocity of the gas molecules to be evacuated. The pumping action results from the fact that pulses of an axial component are added to the atoms and particles present while they are being maintained on the inclined surfaces. As a result, they are transported out through the pump room and thus out of the recipient. Furthermore, it is preferred and advantageous in the present invention, when the backing pump is designed as a wet-running rotary vane pump, in particular oil-sealed. This is wet running positive displacement pump, which consists of a hollow cylinder as a stator in which another cylinder rotates as a rotor, which is guided by an eccentric along the housing wall. The piston is connected to a hollow slide, which is pivotally mounted in the housing and divides the crescent-shaped working space into a suction side and a pressure side. The vacuum pump is filled with oil, which ensures its lubrication and serves to seal the pump chamber and the pressure valve. In the event of a power failure, however, oil mist may diffuse into the vacuum area and lead to undesirable contamination. Further explanations on the execution of the vacuum system and its components claimed with the invention can be found in the exemplary embodiments explained below.

embodiments

Fig. 1

den schematischen Aufbau eines zweistufigen Vakuumsystems mit einem Ventil,

Fig. 2

den schematischen Aufbau eines zweistufigen Vakuumsystems mit zwei Ventilen und

Fig. 3

den schematischen Aufbau eines zweistufigen Vakuumsystems mit zwei Ventilen, die gleichzeitig als Belüftungsventile fungieren.

Hereinafter, the vacuum system for generating at least one high vacuum in a recipient according to the invention and its advantageous modifications with reference to the schematic figures for a better understanding of the invention will be explained even further. It shows the

Fig. 1

the schematic structure of a two-stage vacuum system with a valve,

Fig. 2

the schematic structure of a two-stage vacuum system with two valves and

Fig. 3

the schematic structure of a two-stage vacuum system with two valves, which also act as ventilation valves.

In the Fig. 1 a two-stage vacuum system 01 is shown, which serves to generate a high vacuum P _vac in a recipient 02 . In the embodiment shown, the recipient 02 (vacuum chamber) is part of a mass spectrometer, not shown, with which the composition of ice cores is to be analyzed. To the recipient 02 a Endvakuumpumpe is 03 connected, for example, a turbomolecular pump 04. On its suction side, the Endvakuumpumpe 03 generates the high vacuum P _vac , which prevails in the interior of the recipient 02 . On its discharge side is a pressure P _before a fine vacuum (pre-vacuum), which is generated by an upstream roughing pump 05 . This is in the illustrated embodiment, an oil-sealed rotary vane pump 06. This works between the pressures P _before on its suction side and the ambient pressure P _a on its ejection side. Between the final vacuum pump 03 and the backing pump 05 , an operation-dependent controlled valve device 07 is arranged for the pressure-tight closing of the recipient 02 in the event of a power failure. All components Recipient 02 , Endvakuumpumpe 03 , backing pump 05 and valve device 07 are connected via a branchless pressure-tight connection line 08 with each other in series. The prevailing pressure gradient is indicated by the arrows (pumping direction). The linearity of the connection line 08 ensures that the high vacuum P _{vac is} reliably maintained in the event of a power failure and is not ventilated via branching connecting lines, for example to further pressure chambers with lock functions. Other vacuum systems 01 can also be configured in three or more stages, depending on the application and the performance of the vacuum pumps 03 , 05 used .

In the Fig. 1 is further shown schematically that to maintain the high vacuum in the recipient 02 during a power failure, the operation-dependent controlled valve device 07 has at least a first valve 09 with a first delay device 10 . This first valve 09 is arranged in the unbranched connection line 08 between the Endvakuumpumpe 03 and the backing pump 05 . This first valve 09 serves to protect the recipient 02 during a power failure by, for example, in a power failure, the recipient 02 is closed pressure-tight and thus prevents the high vacuum P _{vac is destroyed} in its interior. This is usually the case during a power failure and thus when the pumping operation ceases: the final vacuum pump 03 is slowly vented via a special venting valve to prevent oil mist from the backing pump 05 fight back. In the vacuum system 01 according to the invention, however, the Endvakuumpumpe 03 does not have its own vent valve. Existing ventilation valves can be easily replaced by blind plugs. The pressure-tight sealed first valve 09 ensures that no oil mist can penetrate into the final vacuum pump 03 .

In the event of a power failure, the first valve 09 is automatically closed. For this purpose, it is for example electrically connected via an electrical line 11 to the alarm output 24 of the end vacuum pump 03 . If a warning signal is generated at the alarm output of the end-vacuum pump because the pump run slows down due to a power failure until the style level, this signal leads to the immediate closing of the first valve 09 . Furthermore, indicated by dashed lines by a second electrical line 12 that a triggering alarm signal can also come from the backing pump 05 . As a result, both vacuum pumps 03 , 05 are observed in their respective operating state. The first valve 09 can also receive its closing command directly from the power failure. In the exemplary embodiment shown, the first valve 09 is a first electro-pneumatically operated solenoid valve 13 which is open under power during operation. In the event of a power failure, an electromagnetically attracted circuit board automatically drops and generates a pneumatic pulse which causes the solenoid valve 13 to close immediately.

After removal of the malfunction, ie after return of the current, the delay device 10 comes into action. It is set with a delay time T _VZ1 and determines the time when the valve 09 may open again. In general, a period of 8s to 12s is sufficient to ensure that the vacuum pumps 03 , 05 work properly again. If the valve 09 thus opened again at T = _{V Z1} 10s, is reliably ensured that no oil mist from the backing pump 05 entering the Endvakuumpumpe 03 because the Vorkauumpumpe 05 oil mist already pumps off again towards ambient pressure P _a.

In the Fig. 2 an embodiment of the invention is shown, in which the operation-dependent controlled valve device 07 has a second valve 14 with a second delay means 15 , which is arranged on the side facing away from the final vacuum pump 03 side of the backing pump 05 . This second valve 14 can be seen in complete analogy to the first valve 09 described above, wherein now also the backing pump 05 does not have its own venting valve. Existing ventilation valves can be easily replaced by blind plugs. The second valve 14 fulfills the same function as the first valve 09 , but it is assigned to the backing pump 05 . In this embodiment, therefore, additionally prevents the fine vacuum P fails _before a power failure. After power return so also the backing pump 05 can go back into operation faster. Accordingly, the second valve 14 is then opened again via the second delay _device 15 after a delay time T _VZ2 . In this case, the second delay time T _{VZ2 is} again in a range of 10 s and is thus synchronous with the delay time T _{VZ1 of} the first valve 09 . But it can also be larger or smaller, as needed.

The second valve 14 is controlled via a third electrical line 16 , which is connected to the alarm output 25 of the backing pump 05 . Indicated is an (additional or alternative) activation via a fourth electrical line 17 , which in turn comes from the alarm output of Endvakuumpumpe 03 . Likewise, however, can be done again direct control. In the exemplary embodiment shown, the second valve 14 is a second electro-pneumatic solenoid valve 18 .

The Fig. 3 shows a further embodiment of the invention, in which the first valve 09 is formed as a first vent valve 19 for the Endvakuumpumpe 03 and the second valve 14 as a second vent valve 20 for the backing pump 05 . For this purpose, the first vent valve 19 is pressure-tightly connected via a first vent line 21 to the end vacuum pump 03 . Furthermore, that is second vent valve 20 via a second vent line 22 to the backing pump 05 pressure-tight manner. It is also possible that only first valve 09 is formed as a first vent valve 19 and the backing pump 05 has its own vent valve. The function of the ventilation is activated in the two valves 09 , 14 but only for purposes in which deliberately the fine vacuum or the pre-vacuum is to be abandoned, for example, for replacement purposes of the two vacuum pumps 03 , 05 or for opening purposes of the recipient 02.

Furthermore, in the Fig. 3 an operation-dependent controlled valve device 07 is shown, which comprises both the first and second valves 09 , 14 in the additional function as ventilation valves 19 , 20 and the two delay devices 10 , 15 . In particular, in a central control unit 23 , all signals can be detected and corresponding control commands can be generated easily, quickly and reliably.

LIST OF REFERENCE NUMBERS

01

vacuum system

02

recipient

03

Endvakuumpumpe

04

Turbo molecular pump

05

backing pump

06

Rotary vane pump

07

valve means

08

connecting line

09

first valve

10

first delay device

11

first electrical line

12

second electrical line

13

first solenoid valve

14

second valve

15

second delay device

16

third electrical line

17

fourth electrical line

18

second solenoid valve

19

first ventilation valve

20

second ventilation valve

21

first ventilation line

22

second ventilation line

23

central control unit

24

Alarm output from 03

25

Alarm output from 05

P _vac

high vacuum

P _before

fine vacuum

P _a

atmospheric pressure

T _VZ1

Time constant of 10

T _VZ2

Time constant of 15

Claims (12)

Vacuum system (01) for generating at least one high vacuum (P _vac ) in a recipient (02) with at least one end vacuum pump (03) for generating at least the high vacuum (P _vac ) and a roughing pump (05) for generating at least one fine vacuum ( P _before) and with a function of operation controlled valve means (07) for pressure-tight closure of the recipient (01) at an operating fault, said recipient (01), Endvakuumpumpe (03), pre-vacuum pump (05) and valve means (07) (via a pressure-tight connection line 08 ) are connected to each other in series and wherein to maintain the high vacuum (P _vac ) in the recipient (02) during a malfunction the operation-dependent controlled valve means (07) at least a first valve (09) having a first delay means (10), at which a time constant (T _VZ1 ) is arranged between the end vacuum pump (03) and the backing pump (05),
characterized in that
the connecting line (08) is formed without a branch, that in case of power failure as a malfunction at least the first valve (09) automatically closed instantaneously and after the elimination of power failure time delay with the at the first delay means (10) adjustable time constant (T _VZ1 ) is opened automatically and that at least the final vacuum pump (03) does not have its own ventilation valve. Vacuum system (01) according to claim 1,
characterized in that
the first valve (09) is also designed as a ventilation valve (19) of the final vacuum pump (03), the ventilation function being suppressed in the event of a power failure. Vacuum system (01) according to claim 1 or 2,
characterized in that
the operation-dependent controlled valve device (07) with a second valve (14) a second delay means (15) arranged on the side of the backing pump (05) facing away from the end vacuum pump (03) and closed instantaneously in the event of a power failure and after the power failure has elapsed, with a time constant (T 1) adjustable at the second delay means (15) _VZ2 ) is opened, whereby the backing pump (05) does not have its own venting valve. Vacuum system (01) according to claim 3,
characterized in that
the second valve (09) is also designed as a ventilation valve (20) of the backing pump (05), the ventilation function being suppressed in the event of a power failure. Vacuum system (01) according to one of the preceding claims 1 to 4,
characterized in that
the time constant (T _VZ1 ) of the first delay means (10) of the first valve (09) is set in a range between 8s and 12s. Vacuum system (01) according to one of the preceding claims 3 to 5, characterized in that
the time constant (T _VZ2 ) of the second delay means (15) of the second valve (14) is set in a range between 8s and 12s. Vacuum system (01) according to one of the preceding claims 3 to 6,
characterized in that
the first delay device (10) and the second delay device (15) are combined in a common control device (23). Vacuum system (01) according to one of the preceding claims 1 to 7,
characterized in that
the at least first valve (09) is designed as a pneumatically controlled solenoid valve (13). Vacuum system (01) according to one of the preceding claims 1 to 8,
characterized in that
at least the first valve (09) is electrically connected to an alarm output (24) of the final vacuum pump (03) and / or to an alarm output (25) of the backing pump (05). Vacuum system (01) according to one of the preceding claims 1 to 9, characterized
characterized in that
the final vacuum pump (03) is designed as a dry-running turbomolecular pump (04). Vacuum system (01) according to one of the preceding claims 1 to 10,
characterized in that
the backing pump (05) is designed as a wet-running rotary vane pump (06). Vacuum system (01) according to claim 11,
characterized in that
the wet-running rotary vane pump (06) is sealed with oil.

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