EP2949938B1 - Vacuum pump - Google Patents

Description

The invention relates to a vacuum pump with a single or multi-piece shaft according to the preamble of claim 1.

Vacuum pumps, in particular Roots vacuum pumps, have become indispensable in many industrial applications. Examples of such applications include metallurgy, vacuum drying and chemical engineering.

The basic structure of these Roots vacuum pumps provides to operate two waves in opposite directions at the same speed. This is ensured for example by a mechanical synchromesh. On these waves are pistons which cooperate, include gas volumes and transfer from the pump inlet to the pump outlet.

The prior art ( DE 10 2008 060 540 A1 ) includes a Roots vacuum pump having a suction chamber with two mutually rotating pistons and two storage spaces in which bearings are provided for rotatably supporting at least one shaft.

The Roots vacuum pumps belonging to the prior art usually have two rotors whose shafts are mounted on both sides. The pump-effective pistons, which are part of the rotor, thereby rotate in the pump chamber and are spatially separated from the storage. The execution of the shaft passage and its seal between the pump chamber and storage space is of great importance for these pumps. Among other things, it determines the applied frictional heat and the resulting operating and oil temperature. Depending on the version, the achievable final pressure and the duration differ until the pump reaches it. Correct sealing protects the equipment from process gas, impurities conveyed and prevents the accumulation of condensate. Thus, these factors significantly determine the life of the pump and customer satisfaction.

From practice piston ring seals are known, which are arranged in the shaft passage. However, piston ring seals have the disadvantage that impurities in the gas to be conveyed, for example dust particles, damage the piston ring seals. In the medium to be pumped, which is located in the pump chamber, often contain gases that change lubricants and possibly carry dust particles with it. In addition, condensate is often contained in the media to be conveyed. Through these substances, the lubricants change chemically, so they must be replaced after a relatively short time, which in turn comes to a breakdown of the pump.

The prior art ( DE 195 44 994 A1 ) includes a multi-shaft vacuum pump, with which an effective seal between the gearbox, or storage rooms and storage spaces is to be achieved. This pump provides two lip seals so that the lips face one seal towards the suction chamber and the lips of the other seal towards the gearbox or storage space. This results in a number of advantages, for example, that contamination in the corners, undercuts and depressions in the immediate sealing region of the seals by accumulating substances from the pump chamber and from the transmission, or storage space can be avoided. This prior art seal assembly can be further improved.

Furthermore belongs to the state of the art ( EP 0 859 154 A1 ) a screw compressor with a shaft seal. The screw compressor also provides two lip seals. Between the lip seals a gas inlet is provided. On both sides next to the lip seals a spiral seal is arranged in each case. The two lip seals with the sealing gas inlet in between have the task of oil, which is used to lubricate a ball bearing on the one hand, and a fluid, such as water, which serves to lubricate the rotor on the other side, to separate so that the oil does not mixed with the water. This seal assembly has four sealing elements and is very expensive for this reason.

The technical problem underlying the invention is to provide a vacuum pump in which a seal of the shaft passage is provided, which is insensitive to gases that change lubricant, dust particles and / or condensate.

This technical problem is solved by a vacuum pump having the features according to claim 1.

The vacuum pump according to the invention with at least one single- or multi-piece shaft which is rotatably mounted with at least one bearing assembly, a pump chamber and a bearing or gear room for arranging the at least one bearing assembly with a seal assembly for performing the single or multi-piece shaft between pump chamber and bearing - Or gear chamber, wherein the seal assembly for carrying out the at least one single- or multi-piece shaft having a first seal, which is formed as a lip seal, wherein a second sealing arrangement is provided, characterized in that in the space between the first lip seal and the second sealing arrangement, a sealing gas inlet is provided and that the second sealing arrangement has at least one piston ring seal.

The vacuum pump according to the invention has the advantage that the lip seal has minimal gaps with high throttling effect for the sealing gas, that is, allows a small sealing gas flow despite a high pressure.

The arrangement according to the invention has the advantage that the lip seal ensures a good seal against dust particles, condensate and gases. Piston ring seals, for example in a rectangular shape, operate relatively independently of the rotational speed and permit a pressure equalization which is faster compared to the lip seal (lower throttle effect). In addition, these ring seals have emergency running properties and work wear-resistant and they have less heat input and a lower power consumption.

The vacuum pump according to the invention has the advantage that over the prior art, a better seal is achieved by higher sealing gas pressures due to an increased throttle effect. By providing a barrier gas inlet between the first lip seal and the second seal assembly, this relatively small space can be filled with barrier gas. The sealing gas requirement is reduced compared with the prior art since, according to the prior art, the entire storage space has generally been filled with sealing gas.

Despite a minimal sealing gas flow in the direction of the suction chamber, an improved end pressure of the pumping station is obtained. In addition, only a minimal dilution or contamination of the process gas with sealing gas, especially when according to a preferred embodiment, the first lip seal is arranged on the pumping chamber side.

As already stated, the piston ring seals, for example rectangular rings, work relatively independently of the rotational speed and have runflat properties.

According to a further advantageous embodiment of the invention, the second sealing arrangement consists of two piston ring seals. Two piston ring seals have the advantage over a piston ring seal that the sealing effect is improved.

A further advantageous embodiment of the invention provides that the piston ring seals are arranged adjacent to each other at a distance from each other. By this embodiment, a sufficient sealing effect can be achieved.

As already stated, it is advantageous if the lip direction is arranged on the pump chamber side. This ensures that impurities in the medium to be pumped, which is located in the pump chamber, do not enter the seal chamber or in the direction of the bearing or gear compartment. As a result, lubricant in the bearing or gear chamber is not or not so quickly contaminated, so that the lubricant has a longer life.

The second sealing arrangement is advantageously arranged on the storage space side. This sealing arrangement serves primarily to form a relatively small gap with the sealing gas inlet, so that not the entire bearing or gear chamber must be filled with sealing gas. If the entire bearing or gear chamber to fill with sealing gas, as provided in the prior art, the consumption of sealing gas is very high.

The sealing gas arranged behind the lip seal builds up a pressure in the direction of the pumping chamber, so that less gas moves from the pumping chamber in the direction of the storage space. The lip seal is advantageously arranged such that the lip seal is pressed against the shaft or a bushing on the shaft by a higher pressure in the pump chamber.

According to an advantageous embodiment of the invention, a lip of the lip seal is arranged pointing in the direction of the suction chamber. This ensures that at a higher pressure in the pump chamber with respect to the space with the sealing gas, the lip seal is pressed against shaft or socket and thereby the throttle effect is increased.

A possible embodiment of the invention provides that the shaft or the bush is coated at least in the region of the system of the lip seal. This makes it possible to reduce the friction between the shaft or bushing and the lip seal, so that less heat is generated.

The lip seal has the advantage that it is process gas tight by the sealing gas. The barrier gas stream also cools the lip seal, which heats up during operation due to friction.

With the arrangement according to the invention, it is possible to reduce the amount of sealing gas to about one tenth compared to the prior art or even less.

A further advantageous embodiment of the invention provides that a mating surface of the lip seal has a twist. This will be a corresponding Gas flow achieved, so that the throttling effect of the lip seal is reinforced.

The vacuum pump according to the invention is advantageously designed as Roots piston pump. However, the invention can also be used with other pumps, for example turbomolecular pumps or the like. Fields of application are shaft feedthroughs through the pump chamber and storage room.

Fig. 1

einen Schnitt durch eine Wälzkolbenvakuumpumpe;

Fig. 2

einen Längsschnitt durch eine erfindungsgemäße Wellendurchführung.

Further features and advantages of the invention will become apparent from the accompanying drawings, in which several embodiments of a vacuum pump according to the invention with shaft passage are shown only by way of example. In the drawing show:

Fig. 1

a section through a Roots vacuum pump;

Fig. 2

a longitudinal section through a shaft passage according to the invention.

Fig. 1 shows a Roots vacuum pump with a housing 1. In the housing 1 of the vacuum pump 100 is a pump chamber 2. The pump chamber 2 is penetrated by a first shaft 10 and a second shaft 14. Shaft axes of the pump chamber is limited by a first bearing plate 4 and a second bearing plate 5. In the region of the shafts 10, 14, which passes through the pump chamber 2, a first piston 12 with the first shaft 10 and a second piston 16 with the second shaft 14 are connected.

Both shafts 10, 14 are supported by bearing arrangements rotatably in the end shields 4, 5 from. In the first bearing plate 4 are a floating bearing 22 of the first shaft 10 and a floating bearing 26 of the second shaft 14. In the second bearing plate 5 are a fixed bearing 24 of the first shaft 10 and a bearing 28 of the second shaft 14th

On a side facing away from the pump chamber 2 of the first bearing plate 4, a gear chamber 3 is provided, in which the ends of the first and second shafts 10, 14 protrude. On the shaft ends sit a first and a second synchronous wheel 18, 20, which transmits the rotation of the first shaft 10 to the second shaft 14 so that it rotates at the same speed, but in opposite directions. A first centrifugal disc 30 dips into a lubricant reservoir and distributes the lubricant in the gear chamber 3.

On the side facing away from the pump chamber 2 of the second bearing plate 5 is a gap 8. This is penetrated by the first shaft 10, while the second shaft 14 terminates in it. On the end of the second shaft 14, a second centrifugal disc 32 is arranged, which also dips into a lubricant reservoir and causes a distribution of the lubricant in the intermediate space.

The intermediate space passing through the end of the first shaft 10 terminates in a motor housing 6. There are mounted on the shaft end inner magnets 44. The shaft end with the inner magnet 44 is surrounded by a split pot 40 which is mounted airtight by means of a split-top flange on the housing 6. A magnet carrier 48 carries outer magnets 46, which cooperate with the inner magnet 44 to transmit force and rotation. The magnet carrier 48 is arranged on a motor shaft 50, which is mounted in an engine mount 52. The motor magnets 54, which are likewise arranged on the motor shaft 50, interact with coils 56 in order to convert electrical energy into mechanical rotation. Coils and motor magnets form the drive of the Roots pump 100.

In the bearing plates 4, 5 shaft passages 34, 36, 38, 42 are provided, which in Fig. 1 are not shown in detail.

The shaft passages 34, 36, 38, 42 are of identical construction. The shaft passage 34 is in Fig. 2 shown.

On the shaft 14, a bush 58 is arranged. In the Fig. 2 The pump chamber is shown on the left and the gear compartment 3 on the right. It could be in the Fig. 2 also act around the shaft leadthrough 38 or 42. Then the pump chamber 2 would be on the left and the intermediate space 8 on the right.

The shaft leadthrough 34 has on the one side a lip seal 60 on the pump chamber side and two piston ring seals 62, 64 on the piston chamber or piston chamber side. The piston ring seals 62, 64 are designed as rectangular seals and are correspondingly arranged in rectangular grooves 66 of the shaft passage 34.

In addition, a barrier gas inlet 68 is provided to fill a space 70 between lip seal 60 and piston ring seal 62 with barrier gas.

The lip seal 60, which is arranged on the pump chamber side, is insensitive to dust particles and has a good throttling action with respect to condensate and gases, which form part of the medium to be pumped in the pump chamber 2.

The sealing gas has the advantage that it also prevents gas from the pumping chamber 2 from wandering in the direction of bearing or gear chamber 3.

The space 70 is relatively small compared to the transmission and storage space 3, so that the space 70, which is filled with sealing gas, has a smaller volume than the transmission or storage space 3. As a result, the consumption of sealing gas is significantly reduced.

The lip seal 60 has a very good throttle effect. Behind the lip seal 60 in the direction of bearing or gear chamber 3, the sealing gas is arranged, which builds up a pressure in the direction of the pump chamber, so that little gas migrates from the pump chamber in the direction of bearing or gear chamber 3.

The lip seal 60 is arranged such that the lip seal 60 is pressed against the bush 58 due to the higher pressure in the pump chamber 2.

The piston rings 62, 64 delimit on the other side, that is, the storage and drive chamber side, the space which is filled with sealing gas. The piston ring seals 62, 64 produce the required throttle effect.

The piston rings 62, 64 also have emergency running properties. They also have the advantage that they are easy to assemble.

The barrier gas stream cools the lip seal 60, since by rotation of the shaft 14 frictional heat is generated.

By the arrangement according to the invention is effectively avoided that dust particles, gases or condensate from the pump chamber 2 in the transmission and storage room 3 reach, in which there are lubricants that change chemically by condensate and gases or can be contaminated by dust particles.

A lip 72 of the lip seal is arranged pointing in the direction of the suction chamber 2. This ensures that gas from the pump chamber 2, which would like to reach in the direction of the space 70 and thus in the direction of the transmission or storage space 3, the lip 72 of the lip seal 60 presses against the shaft 14 or bushing 58, whereby the throttling effect of the lip seal 60 is increased.

reference numerals

1

casing

2

pump room

3

gear compartment

4

end shield

5

end shield

6

motor housing

8th

gap

10

wave

12

piston

14

wave

16

piston

18

Synchronrad

20

Synchronrad

22

movable bearing

24

fixed bearing

26

movable bearing

28

fixed bearing

30

slinger

32

slinger

34

Shaft bushing

36

Shaft bushing

38

Shaft bushing

40

containment shell

42

Shaft bushing

44

inside magnets

46

outside magnets

48

magnet carrier

50

motor shaft

52

motor bearings

54

motor magnets

56

Do the washing up

58

Rifle

60

lip seal

62

Piston ring seal

64

Piston ring seal

66

groove

68

Sealing gas inlet

70

room

72

lip

100

pump

Claims (11)

1. A vacuum pump with at least one single- or multiple-part shaft (10), which is rotatably mounted by at least one bearing arrangement (22, 24, 26, 28), a pump chamber (2) and a bearing and/or gear chamber (3) for the arrangement of the at least one bearing arrangement (22, 24, 26, 28), with a sealing arrangement (60, 62, 64) for leading through the single- or multiple-part shaft (10) between pump chamber (2) and bearing or gear chamber (3), wherein the sealing arrangement (60, 62, 64) for leading through the single- or multiple-part shaft (10, 14) comprises a first seal, which is formed as a lip seal (60), wherein there is provided a second sealing arrangement (62, 64),
   characterised in that
   in a space (70) between the first lip seal (60) and the second sealing arrangement (62, 64) there is provided a sealing gas inlet and in that the second sealing arrangement (62, 64) comprises at least one piston ring seal (62, 64).
2. A vacuum pump according to claim 1, characterised in that the second sealing arrangement is formed of two piston ring seals (62, 64).
3. A vacuum pump according to either one of the preceding claims, characterised in that the piston ring seals (62, 64) are arranged mutually adjacent at a spacing from each other.
4. A vacuum pump according to any one of the preceding claims, characterised in that the lip seal (60) is arranged at the vacuum chamber side.
5. A vacuum pump according to any of the preceding claims, characterised in that the second sealing arrangement (62, 64) is arranged at the bearing or gear chamber side.
6. A vacuum pump according to any of the preceding claims, characterised in that the lip seal (60) is configured to abut the shaft (10, 14) or a bushing (58) arranged on the shaft (10, 14).
7. A vacuum pump according to any of the preceding claims, characterised in that a lip (72) of the lip seal (60) is arranged to be oriented in the direction of the vacuum chamber (2).
8. A vacuum pump according to any of the preceding claims, characterised in that the shaft (10, 14) is coated at least in the region of the abutting of the lip seal (60).
9. A vacuum pump according to claim 6, characterised in that the bushing (58) is coated at least in the region of the abutting of the lip seal (60).
10. A vacuum pump according to any of the preceding claims, characterised in that a counter face of the lip seal (60) comprises a twist.
11. A vacuum pump according to any of the preceding claims, characterised in that the vacuum pump (100) is formed as a Roots pump.

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