WO2013167370A1

WO2013167370A1 - High-vacuum system and evacuation method

Info

Publication number: WO2013167370A1
Application number: PCT/EP2013/058340
Authority: WO
Inventors: Johannes KRANTZ; René Marie LEFEBVRE; Gerard Loebig
Original assignee: Schmid Vacuum Technology Gmbh
Priority date: 2012-05-08
Filing date: 2013-04-23
Publication date: 2013-11-14
Also published as: DE102012104013A1; TW201408371A

Abstract

A high-vacuum system comprising a vacuum chamber (12) and a high-vacuum chamber (14) is defined, having at least one vacuum pump (16), which is preferably connected to the vacuum chamber (12), and at least one high-vacuum pump (24), which is preferably connected to the high-vacuum chamber (14), wherein a valve (30) is disposed between the vacuum chamber (12) and the high-vacuum chamber (14). Such a construction enables the vacuum chamber (12) and the high-vacuum chamber (14) to be jointly evacuated with the aid of the vacuum chamber (16) before the high-vacuum chamber (14), with the valve (30) closed, is evacuated to high vacuum by means of a high-vacuum pump (24).

Description

HIGH-VACUUM SYSTEM AND EVACUATION METHOD

[0001] The invention relates to a high-vacuum system comprising a vacuum chamber and a high-vacuum chamber, having at least one vacuum pump and having at least one high-vacuum pump.

[0002] The invention further relates to a method for evacuating a vacuum chamber and a high-vacuum chamber of a high-vacuum system.

[0003] High-vacuum systems have been known for decades and are used in the prior art for a variety of purposes. One possible purpose of use consists in the coating of parts by means of metals evaporated in the high-vacuum chamber in an evaporator. It is thus common, for instance, to coat foil packagings for the packing of crisps, peanuts and the like with a thin aluminum coating, which can be carried out in a high-vacuum system configured as a strip coating plant (vacuum web coater). In such strip coating plants, foils are generally coated with a coating width of several metres in a batch process. For this, two chambers are used, a winding chamber, in which the foil to be coated is located on a reel and in which the ready-coated foil is rewound onto a further reel, as well as a coating chamber, in which the coating of the foil is carried out under high vacuum by means of an evaporator. The coating chamber is kept during the coating process at high vacuum, that is to say at a pressure of around 10^"4 mbar, whilst the winding chamber is kept at a pressure of around 10^"2 mbar. The coating takes place at high speed (for example around 15 m/sec). The coating serves as a gas barrier and UV barrier, with the result that the goods which are packed herewith can be kept very fresh over a longer period. [0004] Vacuum pumps for generating the vacuum in the vacuum chamber or winding chamber and for generating the high vacuum in the high-vacuum chamber or coating chamber are arranged on the vacuum chamber, partially via pipelines and valves, in accordance with their functions. Moreover, the high-vacuum pumps are generally constituted by diffusion pumps, which can only be switched on once a sufficient forevacu- um is generated. In this case, in order to evacuate the high-vacuum chamber, an evacuation must therefore firstly be carried out with (mechanical) vacuum pumps before the high- vacuum pumps can be used.

[0005] US-A-5,228,838 discloses a high-vacuum system and a method for the evacuation thereof, in which two pump trains, respectively consisting of a vacuum pump unit and a forevacuum pump unit, are provided. The forevacuum pump unit of the pump train of the high-vacuum chamber can here be selectively connected upstream of the vacuum pump unit of the high-vacuum chamber or of a high-vacuum pump unit likewise connected to the high-vacuum chamber. The vacuum pump unit can suck either out of the high-vacuum chamber or out of the vacuum chamber and can deliver either to the forevacuum pump unit of the pump train connected to the vacuum chamber or to the forevacuum pump unit of the pump train connected to the high-vacuum chamber.

[0006] With such an arrangement, the investment costs are reduced, since for the high-vacuum pump of the high-vacuum chamber no separate forepump is necessary.

[0007] The pumps must nevertheless run for a long time until the desired vacuum can be obtained.

[0008] In order to improve accessibility to the roll chamber, it is further known from DE 10 2005 042 762 A1 to divide the interior of a vacuum chamber by a partition into the roll chamber and the coating chamber, wherein a fixed chamber portion and a movable chamber portion are provided and the vacuum chamber runs along a dividing plane running through lateral end portions of front and rear end walls of the vacuum chamber. By opening or closure of the movable chamber portion, split ends of the fixed chamber portion and of the movable chamber portion can be brought closer together or moved farther apart by a sealing element.

[0009] The suitability for the execution of works, together with maintainability, is hereby intended to be improved.

[0010] In the light of the above, the object of the invention is to disclose a high- vacuum system comprising a vacuum chamber and a high-vacuum chamber and having at least one vacuum pump and at least one high-vacuum pump, which system can be evacuated with least possible effort up to a high vacuum. In addition, a simplified method for evacuating a high-vacuum system, which method operates as cost-effectively as possible, shall be disclosed.

[0011] The object of the invention is achieved in a high-vacuum system according to the aforementioned type by virtue of the fact that the vacuum chamber and the high- vacuum chamber can be connected to each other via at least one valve.

[0012] The object of the invention is in this way fully achieved.

[0013] According to the invention, the very fact that the vacuum chamber and the high-vacuum chamber can be connected to each other via a valve, means that a pump train can be connected directly to the vacuum chamber without an intermediate valve. It is sufficient to connect to the vacuum chamber a vacuum pump for generating the lesser vacuum of the vacuum chamber, and to the high-vacuum chamber a high-vacuum pump. For the evacuation of vacuum chamber and high-vacuum chamber, the valve between the two chambers is firstly opened and only the vacuum pump actuated until the pressure level is sufficiently low to allow the high-vacuum pump, connected to the high- vacuum chamber, to also be activated. To this end, the valve between the two chambers is then closed, so that the high-vacuum pump can evacuate the high-vacuum chamber to a lower pressure level (for example around 10^"4 mbar), whilst the ongoing vacuum pump maintains the pressure level in the vacuum chamber (for example around 10^"2 mbar). [0014] Such a construction of the high-vacuum system produces an improved vacuum generation or a faster evacuation facility.

[0015] Of course, the vacuum pump generally consists of at least two coupled- together mechanical pumps, for instance a forevacuum pump, to which is connected a main vacuum pump which can first generate the actual pressure level in the vacuum chamber. By contrast, the high-vacuum pump is generally constituted by a diffusion pump, which in any event can only be switched on once a sufficiently low preliminary pressure is in force. Otherwise, the diffusion pump would be damaged.

[0016] In a preferred embodiment of the invention, the vacuum pump is connected to the vacuum chamber and the high-vacuum pump is connected to the high-vacuum chamber.

[0017] According to another advantageous embodiment of the invention, the valve between the vacuum chamber and the high-vacuum chamber is configured as a slide valve.

[0018] This measure has the advantage that a very large valve cross section can in this way be achieved and that a simple installation and simple sealing are obtained.

[0019] The high-vacuum chamber is preferably located within the vacuum chamber and is separated from this only by a partition.

[0020] A simplified, compact construction is hereby obtained.

[0021] The valve preferably comprises a movable slide in a partition between the vacuum chamber and the high-vacuum chamber.

[0022] In this way, a particularly simple construction and high reliability are obtained. [0023] The slide of the valve here seals, preferably at the end face, against a hose seal.

[0024] At the side, additional seals can be arranged, where necessary.

[0025] A simple and cost-effective sealing of the movable slide is hereby obtained.

[0026] According to a further embodiment of the invention, the slide is guided in the vertical direction and is displaceable, preferably in a controlled manner, by means of a drive.

[0027] Such an arrangement produces a simple and cost-effective construction. By controlling the opening cross section, it is here possible to move the valve into intermediate settings between open setting and closing movement.

[0028] According to a further embodiment of the invention, the valve is controllable in dependence on a pressure difference between the vacuum chamber and the high-vacuum chamber.

[0029] If the high-vacuum system is used for foil coating, then during the coating process under high vacuum a sudden pressure increase can arise in the high- vacuum chamber, which can be caused, for example, by dirt contamination and, in particular, moisture.

[0030] In the event of a sudden pressure increase in the high-vacuum chamber, the valve can thus be wholly or partially opened in order to make additional use of the pumping capacity of the vacuum pump connected to the vacuum chamber, in order to more quickly relieve the increased pressure in the high-vacuum chamber until the pressure level in the high-vacuum chamber is again sufficiently low to allow the valve to be reclosed and the pressure level in the high-vacuum chamber to be reduced again to its set value. [0031] According to a further embodiment of the invention, at least one safety valve is provided between the vacuum chamber and the high-vacuum chamber, which safety valve, in the event of an overpressure in the high-vacuum chamber, opens in the direction of the vacuum chamber.

[0032] In addition, at least one ventilation opening can be provided between the vacuum chamber and the high-vacuum chamber, via which ventilation opening the vacuum chamber, in the event of an overpressure, can be ventilated in the direction of the high-vacuum chamber.

[0033] If the high-vacuum system, as already set out above, is used to coat strip-shaped material, then the vacuum chamber is configured as a winding chamber and the high-vacuum chamber as a coating chamber, wherein a reel for the take-up of the strip-shaped material to be coated is provided in the winding chamber, which material is guided via a vacuum seal, for instance in the form of a gap lock, into the high-vacuum chamber for coating and back into the winding chamber, and finally to a further reel for take-up after a coating.

[0034] To this end, an evaporator for the evaporation of a metal, in particular for the evaporation of aluminum, and for the metallization of the strip-shaped material is then preferably provided in the coating chamber.

[0035] With respect to the method, the object of the invention is further achieved by a method for evacuating a vacuum chamber and a high-vacuum chamber of a high-vacuum system, in which the vacuum chamber and the high-vacuum chamber are firstly coupled to each other via a valve, and the vacuum chamber and the high-vacuum chamber are jointly evacuated by means of one or more, parallel-connected vacuum pumps, and in which, when a certain underpressure is reached, the valve is closed in order to further evacuate the high-vacuum chamber by means of a high-vacuum pump.

[0036] In this way, too, the object of the invention is fully achieved, as has already been set out above. [0037] As the valve, a slide valve between the two chambers is preferably used, whereby a very large opening cross section and a cost-effective construction are obtained.

[0038] In a further advantageous embodiment of the invention, the valve between the two chambers is controlled in dependence on a pressure difference between the two chambers.

[0039] In this way, a sudden pressure increase in the high-vacuum chamber can be more quickly relieved by making additional use of the pumping capacity of a vacuum pump connected to the vacuum chamber.

[0040] In a method for vacuum coating a strip-shaped material, the raw material is firstly unwound from a reel in the vacuum chamber, is guided via a vacuum seal, for instance in the form of a gap lock, to an evaporator in the high-vacuum chamber, is coated there with a metal, in particular aluminum, and is finally rewound onto a further reel in the vacuum chamber.

[0041] Of course, those features of the invention which are stated above and which are yet to be stated below can be used not only in the respectively defined combination, but also in other combinations or in isolation, without departing from the scope of the invention.

[0042] Further features and advantages of the invention emerge from the following description of a preferred illustrative embodiment, with reference to the drawing, wherein:

Fig. 1 shows a heavily simplified cross section through a high-vacuum system which is configured as a strip coating plant for foil coating by means of aluminum, and Fig. 2 shows a perspective view of the slide valve according to Figure 1 in enlarged representation.

[0043] In Fig. 1 , a high-vacuum system, which is configured as a coating plant for the aluminum coating of strip-shaped foil material, is shown in simplified representation and is denoted in its entirety by the numeral 10.

[0044] The high-vacuum system 10 comprises a vacuum chamber 12 and a high-vacuum chamber 14, which latter is disposed within the vacuum chamber 12, is separated from this by a partition 28 and, jointly with the vacuum chamber 12, is enclosed by a housing 1 1 or recipient.

[0045] The vacuum chamber 12 is configured as a winding chamber, in which there is provided a reel 32 for the take-up of strip-shaped foil material 33 to be coated and a further reel 34 for the winding-on of the strip-shaped material 33 after the coating. The high-vacuum chamber 14 is located in a corner region of the vacuum chamber 12 and is separated from this by the partition 28. The high-vacuum chamber 14 serves as a coating chamber, within which the strip-shaped material 33 is provided with a thin aluminum coating by means of an evaporator 42.

[0046] To this end, in the upper partition between the vacuum chamber 12 and the high-vacuum chamber 14 is located a horizontally disposed coating cylinder 38, around which the strip-shaped material 33 is guided via a gap seal 40 into the high- vacuum chamber 14 and via the gap seal 40 back out into the vacuum chamber 12 and, via a multiplicity of deflection rollers 36, to the reel 34, onto which the strip-shaped material 33 is rewound after the coating.

[0047] Within the high-vacuum chamber 14 is disposed the evaporator 42, which, during the coating process, is filled with liquid aluminum kept in the metal bath 44 at about 1 ,500°C. The strip-shaped material 33 is guided around the coating cylinder 38 above the metal bath 44, along this, and coated under high vacuum. [0048] In Fig. 1 can additionally be seen, above the metal bath 44, also an orifice plate 50, which serves to concentrate the metal vapours as far as possible onto the region of the coating cylinder 38 above the metal bath 44. Evaporated aluminum is replaced by feeding an aluminum wire 48 from an aluminum reel 46 into the metal bath 44.

[0049] In the vertical partition 28 between the vacuum chamber 12 and the high-vacuum chamber 14 is disposed a valve 30, which is constructed as a slide valve and can be moved in the vertical direction in order thus to open up or close off an opening cross section of greater or lesser dimension.

[0050] The high-vacuum chamber 14 is connected by a connecting branch 26 to a high-vacuum pump 24, which is constituted by a diffusion pump (represented schematically).

[0051] The vacuum chamber 12 is connected by a connecting branch 22 to a mechanical vacuum pump 16, which consists of a forepump 18 and a main pump 20 (represented schematically).

[0052] During the coating process, the vacuum chamber 12 is kept at a vacuum of around 10^"2 mbar, whilst the high-vacuum chamber 14 is kept at a vacuum of around 10^"4 mbar.

[0053] The pressure in the vacuum chamber 12 and in the high-vacuum chamber 14 is monitored by means of pressure sensors 54 and 55, which are coupled via lines 57, 58 to a central control system 53. The forevacuum pump 18, the main vacuum pump 20 and the high-vacuum pump 24 are also coupled via suitable lines to the central control system 53. Of course, a drive for the strip-shaped material 33 (not represented), as well as suitable sensors and control lines for the evaporator 42 or for the feeding of the aluminum wire 48, are also coupled to the central control system 53. As also explained in greater detail below with reference to Fig. 2, the slide valve 30 is controllable via linear drives 68, 70, which are coupled to the central control system 53 via suitable control lines 56.

[0054] Prior to the start-up of the coating process, the slide valve 30 is firstly moved into its open setting, so that the vacuum chamber 12 and the high-vacuum chamber 14 are coupled to each other via a wide opening cross section of the slide valve 30. Firstly, the vacuum pump 16 consisting of the forepump 18 and the main pump 20 is now activated in order to jointly evacuate the vacuum chamber 12 and the high-vacuum chamber 14 to a certain pressure, which process is monitored via the pressure sensors 54, 55. Once a certain switchover pressure of, for example, 10^"1 mbar, is reached, the valve 30 is fully closed, so that the vacuum chamber 12 is further evacuated by the vacuum pump 16, whilst the high-vacuum chamber 14 can now be evacuated by the high- vacuum pump 24.

[0055] As soon as the pressure in the high-vacuum chamber 44 is sufficiently low, for example has reached 10^"3, the evaporator 42 can be started up in order to heat the metal bath 44 to coating temperature to allow commencement of the process.

[0056] The actual coating operation is then carried out at a strip speed of around 15 m/sec at a bath temperature of around 1 ,500°C, with a set pressure of around 10^"2 mbar within the vacuum chamber 12 and a set pressure of around 10^"4 mbar within the high-vacuum chamber 14.

[0057] The valve 30 can be automatically controlled with the aid of the two linear drives 68, 70 in dependence on the pressure difference between the vacuum chamber 12 and the high-vacuum chamber 14 in order to partially or fully open the valve 30 in the event of an overpressure which suddenly arises within the high-vacuum chamber 14, this in order to briefly utilize the vacuum pump 16 for quicker pressure relief in the high- vacuum chamber 14.

[0058] The construction of the valve 30 can be seen in greater detail from Fig. 2. The valve 30, configured as a slide valve, has a slide 60, which on the partition 28 is guided in the vertical direction with the aid of two guides 64, 66 and is movable in the vertical direction with the aid of two linear drives 68, 70 (for example electromotively).

[0059] In the position shown in Fig. 2, the slide valve 30 is fully closed. The slide 60 rests with its bottom end face wholly on a seal 72, which can be in the form of a hose. At the side, the slide 60 can additionally be sealed off from the surround 62, which is part of the partition 28, by means of seals 74, via a gap seal or the like.

[0060] In Fig. 2, it is further indicated that the drives 68, 70 are coupled via control lines 56 to the central control system 53. In the partition 28 between the vacuum chamber 12 and the high-vacuum chamber 14 is also disposed a safety valve 76, which allows a short-term overpressure to escape from the high-vacuum chamber 14 to the vacuum chamber 12. In the partition 28 between the vacuum chamber 12 and the high- vacuum chamber 14 are also located two ventilation openings 78, 80, by which an overpressure can escape from the vacuum chamber 12 into the high-vacuum chamber 14.

[0061] The gap seal 40 for sealing between the vacuum chamber 12 and the high-vacuum chamber 14 in the region of the coating cylinder 38 is constituted by a seal having a gap of about 2 mm, which is fully sufficient for sealing in the vacuum.

Claims

1 . High-vacuum system comprising a vacuum chamber (12) and a high-vacuum

chamber (14), comprising at least one vacuum pump (16) and further comprising at least one high-vacuum pump (24), characterized by at least one valve (30) arranged between the vacuum chamber (12) and the high-vacuum chamber (14).

2. High-vacuum system according to Claim 1 , characterized in that the vacuum pump (16) is connected to the vacuum chamber (12) and the high-vacuum pump (24) is connected to the high-vacuum chamber (14).

3. High-vacuum system according to Claim 1 or 2, characterized in that the valve (30) between the vacuum chamber (12) and the high-vacuum chamber (14) is configured as a slide valve.

4. High-vacuum system according to Claim 3, characterized in that the valve (30) comprises a movable slide (60) in a partition (28) between the vacuum chamber (12) and the high-vacuum chamber (14).

5. High-vacuum system according to any of Claims 3 or 4, characterized in that the slide (60) seals at the end face against a hose seal (72).

6. High-vacuum system according to any of Claims 3 to 5, characterized in that the slide (60) is guided in the vertical direction and is displaceable, preferably in a controlled manner, by means of a drive (68, 70).

7. High-vacuum system according to one of the preceding claims, characterized in that the valve (30) is controllable in dependence on a pressure difference between the vacuum chamber (12) and the high-vacuum chamber (14).

8. High-vacuum system according to one of Claims 3 to 7, characterized in that at least one safety valve (76) is provided between the vacuum chamber (12) and the high-vacuum chamber (14), which safety valve, in the event of overpressure in the high-vacuum chamber (14), opens in the direction of the vacuum chamber (12).

9. High-vacuum system according to one of the preceding claims, characterized in that the vacuum chamber (12) is configured as a winding chamber and the high- vacuum chamber (14) as a coating chamber, and in that a reel (32) for the take-up of a strip-shaped material (33) to be coated is provided in the winding chamber, which material is guided via a vacuum seal (40) into the high-vacuum chamber (14) for coating and back into the winding chamber, and finally to a further reel (34) for take-up after its coating.

10. High-vacuum system according to one of Claims 3 to 9, characterized in that at least one ventilation opening (78, 80) is provided between the vacuum chamber (12) and the high-vacuum chamber (14), via which ventilation opening the vacuum chamber (12), in the event of an overpressure, can be ventilated in the direction of the high-vacuum chamber (14).

1 1 . High-vacuum system according to Claim 10, characterized in that an evaporator (42) for the evaporation of a metal, in particular for the evaporation of aluminum, and for the metallization of the strip-shaped material (33) is provided in the high- vacuum chamber (14).

12. Method for evacuating a vacuum chamber (12) and a high-vacuum chamber (14) of a high-vacuum system (10), in which the vacuum chamber (12) and the high- vacuum chamber (14) are firstly coupled to each other via a valve (30), and the vacuum chamber (12) and the high-vacuum chamber (14) are jointly evacuated by means of a vacuum pump (16), and in which, when a certain underpressure is reached, the valve (30) is closed in order to further evacuate the high-vacuum chamber (14) by means of a high-vacuum pump (24).

13. Method according to Claim 12, in which, as the valve (30), a slide valve between the two chambers (12, 14) is used.

14. Method according to Claim 12 or 13, in which the valve (30) between the two chambers (12, 14) is controlled in dependence on a pressure difference between the two chambers (12, 14).

15. Method for vacuum coating a strip-shaped material (33) according to one of Claims 12 to 14, in which raw material (33) is unwound from a reel (32) in the vacuum chamber (12), is guided via a vacuum seal (40), for instance in the form of a gap lock, to an evaporator (42) in the high-vacuum chamber (14), is coated there with a metal, in particular aluminum, and is rewound onto a further reel (34) in the vacuum chamber (12).