EP3483448B1 - Vacuum pump with ballast gas valve - Google Patents

Description

The present invention relates to a vacuum pump with a pump body, the inside of which delimits a pump chamber and on the outside of which a valve for controlling the supply of a ballast gas into the pump chamber is arranged, the valve having an inlet opening and an outlet opening.

Vacuum pumps of the type mentioned are known in principle and are used in particular as backing pumps for generating a backing vacuum in an outlet region of a high vacuum pump. In operation, it is necessary under certain circumstances to introduce additional gas, generally referred to here as ballast gas, into the pump body as entraining gas, purge gas or sealing gas.

For example, when conveying corrosive gases, ballast gas in the form of an inert barrier gas is introduced into the pump body in order to protect sensitive components of the vacuum pump. The ballast gas can also be used for cooling, for example when the vacuum pump heats up due to a shift in the operating point. So-called trailing gas is introduced in order to be able to pump particularly light gases such as hydrogen or helium better. Trailing gas can also be used to transport undesired accumulations, eg condensation of liquids or deposits of solid substances within the pump system in the direction of a discharge of the vacuum pump. After the vacuum pump has been switched off, ballast gas can be introduced as the purge gas in order to prevent condensation of, in particular corrosive, gases in the pump chamber. For example, nitrogen can be used as ballast gas for this application.

Further areas of application relate to the dilution of a pumped gaseous medium (“passive addition”) in order to avoid, for example, an ignitable gas concentration which can arise from compression of the medium during the pumping process at various points in the pump system. In contrast, the pumped medium is changed to a more harmless type in the case of an “active addition”, it being possible, for example, to add and remove corrosive or otherwise harmful components of the pumped medium by adding suitable reactants or catalysts.

The supply of ballast gas into the pump body is usually controlled by a valve, the inlet opening of which is connected to a ballast gas container by means of a connecting hose and the outlet opening of which is connected to the pump body. Known ballast gas valves, however, have only two settings, namely "valve open" and "valve closed". A change in the amount of ballast gas supplied per unit of time is not possible with the known valves.

The DE 951 884 C. describes a vacuum pump which makes it possible to increase the supply of lubricant when ballast gas is admitted to the level which is desirable when operating with ballast gas. For this purpose, the vacuum pump has a valve with which both a channel for supplying ballast gas and a channel for supplying lubricant can be released or shut off at the same time. Furthermore, from the GB 2 196 696 A a vacuum pump with a pump body is known which has a plurality of channels for introducing a ballast gas into the pump body, but the amount of the ballast gas supplied per unit time cannot be changed.

The invention is therefore based on the object of creating a vacuum pump of the type mentioned at the outset, which makes it possible to change the amount of ballast gas supplied per unit of time in a simple and cost-effective manner.

The object is achieved by a vacuum pump with the features of claim 1 and in particular in that a first and a second channel are formed in the pump body, the inlet of each channel facing the valve and the outlet of each channel opening into the pump chamber Valve is adjustable between a first and a second opening position, the outlet opening in the first opening position is aligned with the entrance of the first channel and in the second opening position with the entrance of the second channel, and the first and second channels have different lengths and / or Outputs of the first and second channels have different cross-sectional areas.

Depending on the orientation of the outlet opening of the valve, ballast gas can be introduced into the pump chamber either through the first channel or through the second channel. With appropriate design of the channels, a multi-stage supply of ballast gas into the pump chamber is possible. In addition, a position of the valve is conceivable in which the outlet opening of the valve is aligned neither with the entrance of the first channel nor with the entrance of the second channel, but rather the entrances of both channels are closed, so that no ballast gas is introduced into the pump chamber .

The vacuum pump according to the invention is in particular a backing pump. For example, the vacuum pump according to the invention can be designed in the form of a one- or multi-stage scroll, diaphragm, rotary slide valve, rotary piston, reciprocating piston, screw, claw or also as a Roots pump. According to the invention, the first and second channels have different lengths in order to be able to introduce the ballast gas into different areas of the pump chamber. This makes it possible, for example, to introduce ballast gas optionally into a central area or an edge area of the pump chamber. In particular, it can be provided that the channels open into different pressure zones of the pump chamber, in particular into an inner region with a higher gas density and into a region further out with a lower gas density.

Alternatively or additionally, the vacuum pump according to the invention is designed such that the outputs of the first and second channels have different cross-sectional areas. Since the amount of ballast gas that can be introduced into the pump chamber per unit of time results from the cross-sectional area of the respective duct outlet and the prevailing pressure difference between the duct outlet and the outlet opening of the valve, different ballast gas quantities can be introduced into the pump chamber through the selection of the duct.

Advantageous embodiments of the invention can be found in the subclaims, the description and the drawing.

According to one embodiment, at least partial sections of the first and second channels have different cross-sectional areas. Since the amount of ballast gas that can be introduced into the pump chamber per unit of time results from the cross-sectional area and the section length of the respective channel and the prevailing pressure difference between the channel outlet and the outlet opening of the valve, different ballast gas quantities can be introduced into the pump chamber by selecting the channel.

According to a further embodiment, at least one first and second channel have at least one different in length and / or cross-sectional area Channel section and open into a common outlet opening, preferably with at least one shared channel section. Since the amount of ballast gas that can be introduced into the pump chamber per unit of time results from the cross-sectional area and the section length of the respective channel and the prevailing pressure difference between the channel outlet and the outlet opening of the valve, different ballast gas quantities can be introduced into the pump chamber by selecting the channel.

According to a further embodiment, more than two, preferably three or more channels and corresponding further positions of the valve are provided in order to allow a further gradation of the ballast gas quantity. By combining the aforementioned variants, for example, a first channel in an inner region of the pump chamber with a higher gas density and two further channels with different cross-sectional areas and / or channel lengths in a common outlet opening in a region of the pump chamber further away with a lower gas density lead to different ballast gas quantities can be introduced at different locations in the pump chamber.

Advantageously, a maximum dimension of the outlet of each channel is equal to or smaller than the width of a separating element that separates two areas of the pump chamber from one another and moves over the or each outlet during operation of the vacuum pump. This prevents ballast gas from undesirably flowing from one area to the other when the separating element moves over the outlet during operation of the vacuum pump. In other words, a "gas short circuit" is avoided.

To select the respective open position, the valve can in principle be designed to be displaceable on the pump body, i.e. the outlet port of the valve is aligned with the inputs of the channels by a linear movement. However, the valve preferably comprises a rotating body which is rotatably mounted on the pump body, a longitudinal axis of a valve bore and an axis of rotation of the rotating body being arranged offset parallel to one another.

The selection of the first or second channel for the supply of a ballast gas can be made particularly simple in that the valve can be adjusted between the first and the second open position by rotating the rotating body. In other words, the valve arranged in the rotating body offset from the axis of rotation describes a partial circular path which comprises the inputs of the first and second channels. In addition to the two opening positions, with a corresponding angle of rotation of the rotating body, a closure or zero position of the valve can also be provided, in which the inputs of both channels are closed at the same time and the supply of ballast gas to the pump chamber is prevented.

The entrances of the channels are advantageously each surrounded by a sealing element, in particular a sealing ring. The sealing elements prevent supplied ballast gas can escape in an uncontrolled manner and / or ambient air can flow into the pump chamber and contaminate the vacuum of the vacuum pump. The same also applies to the reverse flow path, because pumped gas can be contaminated and must not be released into this environment under any circumstances, even if the pumping chamber is overpressurized. In addition, the sealing elements serve as spacers between the underside of the rotating body and the pump body, as a result of which a friction-loaded contact preferably exists exclusively between the rotating body and the sealing elements, but not between the rotating body and the pump body. This reduces the friction between these components, which can be moved relative to one another, which reduces their wear, enables longer maintenance intervals and contributes to more economical operation of the vacuum pump.

According to a further embodiment, at least three sealing elements are provided, which are distributed around the axis of rotation of the rotating body, in particular at least approximately symmetrically. The symmetrical arrangement counteracts a tilting of the rotating body and ensures that the underside of the rotating body and a plane of the pump body comprising the entrances of the channels are always aligned at least approximately parallel, which counteracts undesirable abrasion and contributes to an optimal sealing effect of the sealing elements. Not every sealing element has to enclose and seal a channel, at least one or more sealing elements can also be blind, i.e. without channel, be executed and arranged to produce sufficient symmetry with the other sealing elements.

According to a preferred embodiment, the rotating body is provided with a dry lubricant on its underside facing the pump body. For example, PTFE or MoS2 can be used as a dry lubricant. Dry lubricants of this type are not only particularly stable, they also produce also very little abrasion, which could get into the pump body and contaminate the fore vacuum, for example.

Alternatively or additionally, the sealing elements are each provided with a dry lubricant at least on their side facing the rotating body. In particular, the dry lubricant can be applied to the sealing elements as a lubricating varnish. For a completely dry design of the valve, the sealing elements can, for example, be enclosed by a PTFE lubricating lacquer and be connected to a PTFE-coated surface of the rotating body.

According to a further embodiment, the rotating body has a tensioning device in order to pre-tension the rotating body, in particular along its axis of rotation, against the pump body. The rotating body is pressed against the sealing rings and the pump body by means of the clamping device. The pretensioning force acting on the rotating body is selected so that it ensures maximum tightness of the valve and, on the other hand, a minimal effort is required to actuate the valve, i.e. select one of the open positions or the closed or zero position by rotating the rotating body. Excessive force would also cause increased abrasion and wear of the dry lubricant.

According to a further embodiment, the pump body forms a part-circular guide link. In particular, the guide link can have depressions at the positions corresponding to the first and second open positions. It is also conceivable that an additional depression is formed which corresponds to the position of the closed or zero position.

The rotary body is advantageously provided with a guide element which projects from the underside of the rotary body facing the pump body and is guided in the guide link of the pump body. By working together With the recesses formed in the guide link, the guide element simplifies the finding of the open positions or the closed or zero position when the rotating body is rotated. In addition, the guide element contributes to stabilizing the plane-parallel arrangement of the rotating body and the surface of the pump body.

The guide element preferably has a spring-loaded spherical body which engages in the guide link. The size of the spherical body is ideally adapted to the size of the recesses in the guide link. The spherical body is preferably designed to be vertically displaceable on the underside of the guide element facing the guide link, with the spherical body being displaced vertically in the direction of the rotating body against the restoring force of a spring element which is arranged in the guide element. At angles of rotation of the rotating body that do not correspond to an open position or the closed or zero position, the spherical body is pressed by the guide link in the direction of the rotating body and the spring element is tensioned. If the guide element moves during the rotational movement of the rotating body over a depression in the guide link, the restoring force of the spring element drives the spherical body into the depression, i.e. the spherical body snaps into the recess.

This not only makes it easier to find the correct angle of rotation of the rotating body for the open positions or the closed or zero position, but also helps to fix the valve in the selected open or closed position, thereby reducing the risk of undesired adjustment. Nevertheless, the snap connection can be released again due to the spherical design of the spherical body when the rotating body is rotated while overcoming a comparatively low resistance. In addition, the spherical shape of the spherical body contributes to a low-friction movement of the guide element in the guide link.

In order to make it easier to find a selected position of the rotating body and the valve, labels are advantageously attached to an outside of the pump body, which indicate the correct angle of rotation of the rotating body for the first opening position, the second opening position and / or the closed or zero position. Additionally or alternatively, the rotating body can have a non-circular cross-section, which can in particular be designed to indicate the direction. Roughly arrow-shaped designs are conceivable here, for example, in which the arrowhead indicates the current angle of rotation. Oval or other non-circular designs of the rotating body, which are particularly easy to grip and easy to operate manually, are also possible, additional markings on the top of the rotating body serving as a direction indicator.

Fig. 1

zeigt eine perspektivische Ansicht einer Ausführungsform eines Ballastgasventils einer erfindungsgemäßen Vakuumpumpe.

Fig. 2

zeigt eine vertikale Schnittansicht des Ballastgasventils von Fig. 1.

Fig. 3

zeigt eine Explosionsansicht des Ballastgasventils von Fig. 1.

Fig. 4

zeigt eine perspektivische und teilweise transparente Ansicht einer Oberfläche eines Pumpenkörpers der erfindungsgemäßen Vakuumpumpe.

The invention is described below purely by way of example using a possible embodiment with reference to the accompanying drawing.

Fig. 1

shows a perspective view of an embodiment of a ballast gas valve of a vacuum pump according to the invention.

Fig. 2

shows a vertical sectional view of the ballast gas valve of FIG Fig. 1 .

Fig. 3

shows an exploded view of the ballast gas valve of FIG Fig. 1 .

Fig. 4

shows a perspective and partially transparent view of a surface of a pump body of the vacuum pump according to the invention.

In Fig. 1 One embodiment of a ballast gas valve 12 of a vacuum pump 10 according to the invention, here in the form of a scroll pump, is shown. The ballast gas valve 12 is formed on a hood 14, which on a pump body 16 (see Fig. 2 ) is attached and has display elements 18 on its outside. The hood 14 can be formed from plastic and can be produced, for example, by means of an injection molding process. In the area of a ballast gas inlet, the hood 14 has a circular recess 20 for a rotating body 22 for controlling the ballast gas supply.

How Fig. 2 shows, the rotating body 22 is provided with a receiving bore 34 extending along an axis of rotation D of the rotating body 22 for receiving a tensioning device, which secures the rotating body 22 to the pump body 16 and prestresses along the axis of rotation D against a flat connection surface 17 of the pump body 16.

In the exemplary embodiment shown, the clamping device comprises a screw 28 which engages in a threaded bore 30 of the pump body 16 in order to secure the rotating body 22 to the pump body 16 so that it can rotate about the axis of rotation D. The screw 28 forms a shoulder 28a, which in the maximally screwed-in state of the screw 28 is seated on the connection surface 17 of the pump body 16 and thereby limits the pretensioning force which acts on the rotating body 22 which is held between the screw head 28b and the pump body 16. Alternatively or additionally, the tensioning device can also comprise a spring element which is arranged in the receiving bore 34 and acts along the axis of rotation D, and the screw 28 is tightened against the restoring force thereof.

How Fig. 2 and 3rd further show, the rotating body 22 is formed in two pieces. A first section facing away from the pump body 16 forms a head piece 24 and can be made from a plastic or metal material. A second section facing the pump body 16 is designed in the form of a sliding disk 26, which can also be made of a plastic or metal material. An underside of the sliding disk 26 facing the pump body 16 is coated with a sliding layer made of a dry lubricant, such as PTFE or MoS2.

The head piece 24 and the sliding disk 26 of the rotating body 22 are connected to one another with the aid of several, in the present exemplary embodiment three, connecting elements 32, which are guided through bores 36 in the head piece 24 and in the sliding disk 26 parallel to the axis of rotation D. Specifically, the connecting elements 32 are designed as Allen screws which extend through the head piece 24 and are screwed into threaded bores 30 of the sliding washer 26.

In the rotating body 22 there is also a bore 38 running parallel to the axis of rotation D for receiving a guide element 40 which extends through the sliding disc 26 and partially projects into the head piece 24. The guide element 40 is designed as a metal pin and has a spring-loaded ball 42 at its end facing the pump body 16. The ball 42 is displaceably mounted in the longitudinal direction of the guide element 40 and can at least partially be pushed into the guide element 40 against the restoring force of a spring element, not shown.

A valve bore 44, which defines an inlet opening 46 and an outlet opening 48, is formed in the rotating body 22 parallel to the axis of rotation D. In the area of the inlet opening 46, a connecting piece 50 is inserted into the valve bore 44, via which a ballast gas can be introduced into the valve bore 44. A sealing ring 52 is provided to seal the connecting piece 50 with respect to the rotating body 22.

The valve bore 44 extends through both the head piece 24 and the slide washer 26 of the rotating body 22 and is composed of several bore sections together. A first bore section extending from the inlet opening 46 and formed in the head piece 24 has a smaller cross-sectional area than an adjoining second bore section which is also located in the head piece 24. The second bore section communicates with a third bore section, which extends through the sliding disk 26 and opens into the outlet opening 48. Due to the different cross-sectional areas of the first and second bore sections, the valve bore 44 forms a valve seat 54 in the transition from the first bore section to the second bore section for a valve body 56 which is displaceably mounted in the second bore section and which is supported by a spring element 57, here in the form of a helical compression spring, is pressed against the valve seat 54. In this way, the valve seat 54 and the valve body 56 form a check valve 53, which prevents backflow both of the ballast gas introduced into the valve bore 44 through the connecting piece 50 and of the medium pumped through the vacuum pump.

To forward the ballast gas introduced into the valve bore 44 of the rotating body 22 into a pump space (not shown) inside the pump body 16, two channels 58 are formed in the pump body 16, each of which has a channel inlet 60 and a channel outlet (not shown). The channel outputs of the channels 58 open into different areas of the pump chamber, for example into areas of a scroll pump separated by a spiral wall.

In addition, the channel exits can have cross-sectional areas of different sizes, so that different amounts of ballast gas per unit time can be introduced into the pump chamber through the channels 58. In the present exemplary embodiment, a smaller amount of ballast gas per unit time can be fed into the pump chamber through the first channel 58 than through the second channel 58. In any case, the maximum dimensions of the channel outputs are the same or smaller than the width of a separating element, not shown, which separates two subregions of the pump chamber from one another and, during operation of the vacuum pump 10, moves over one or both channel outputs, for example a spiral wall of the scroll pump. The channels 58 can run both orthogonal to the connection surface 17 of the pump body 16 or at any oblique angle in order to reach a predetermined, remote outlet opening 48 or a channel starting with the outlet opening 48 in the pump body 16 and thus a connection between the channel inlet 60 and the outlet opening 48 create.

The cross-sectional area of the outlet opening 48 of the valve bore 44 is adapted to the cross-sectional area of the channel inlets 60 and is chosen to be at least similar or identical, preferably smaller than the cross-sectional areas of the channel inlets 60. In addition, the channel inlets 60 are surrounded by sealing rings 62, which are located in corresponding grooves 64 in the pump body 16 are included. The sealing rings 62 form a bearing surface for the rotating body 22, that is to say the sealing body 22 is in contact only with the sealing rings 62, but not with the surface of the pump body 16.

To reduce the friction between the rotating body 22 and the sealing rings 62, the sealing rings 62 are provided with a dry lubricant. For example, the sealing rings 62 can be coated with a PTFE lacquer. The exclusive use of dry lubricants such as PTFE or MoS2 reduces the contamination of the pump chamber with lubricant particles that could get into the pump chamber via the channels 58. In addition, dry lubricants have less wear than lubricants such as grease or oil and allow the vacuum pump 10 to be operated with less maintenance and at lower cost.

Furthermore, dry lubricants do not evaporate or creep as easily as liquid lubricants that can flow away, evaporate or evaporate. This primarily concerns the operation of the pump with high housing temperatures, which can reduce the viscosity of the liquid lubricant and allow components with low boiling points to evaporate. A combination of dry and liquid lubricants, for example PTFE and an oil, can advantageously lead to a further increase in service life and lubricity, and above all to increased emergency run safety in the event that one of the two components fails unexpectedly or unplanned use or evaporates.

In order to counteract a tilting of the rotating body 22 on the bearing surface formed from the sealing rings 62, at least one additional sealing ring 66 is provided, which forms a blind element without connection to a channel 58. An at least approximately symmetrical arrangement of the three sealing rings 62, 66 creates a contact surface which runs plane-parallel to the surface of the pump body 16 and holds the rotating body 22 in a corresponding plane-parallel position during rotation.

For additional guidance of the rotating body 22 during its rotation, a part-circular guide link 68 is formed on the surface of the pump body 16, into which the guide element 40 attached to the rotating body 22 engages, as is shown in the perspective view in FIG Fig. 4 is shown. The guide link 68 has three recesses 70, into which the spring-loaded ball 42 of the guide element 40 engages when the rotating body 22 is in a second opening position in a first opening position, in which the outlet opening 48 is aligned with the entrance of the first channel 58 , in which the outlet opening 48 is aligned with the entrance of the second channel 58, and is in a closed position in which the outlet opening 48 neither with the entrance of the first channel 58, nor with the entrance of the second Channel 58 is aligned. These locking positions make it easier to find and set the correct angle of rotation of the rotating body 22 for the open positions or for the closed position.

As a further adjustment aid, display elements 18 are attached to the hood 14, for example in the form of inscriptions, which indicate the correct angle of rotation to be set for the open positions and the closed position. To display the current angle of rotation, the rotating body 22 is not circular, in particular the head piece 24 of the rotating body 22 in the exemplary embodiment shown has a roughly arrow-shaped basic shape, the arrowhead pointing in the direction of the current angle of rotation. Alternatively, oval or other non-circular designs of the rotating body 22 are also possible, which are easy to grip and easy to operate manually. It is also conceivable that additional markings are attached to the rotating body 22, which indicate the current angle of rotation of the rotating body 22.

To introduce ballast gas into the pump chamber, the connecting piece 50 is connected to a ballast gas container, also not shown, by means of a connecting line, not shown, and the rotating body 22 is rotated into the desired open position until the guide element 40 engages in the corresponding recess 70 in the guide link 68. The valve body 56 is lifted off the valve seat 54 by the ballast gas flowing into the valve bore 44, so that the ballast gas can flow through the channel inlet 60 into the selected channel 58 and through the outlet of the respective channel 58 into the pump chamber of the vacuum pump 10.

By rotating the rotating body 22 from one open position to the other open position, the location of the introduction of the ballast gas into the pump chamber and also the amount of the ballast gas introduced into the pump chamber can be changed per unit of time. By arranging the check valve 53 within The rotary body 22 also has the advantage over known solutions that only one check valve 53 is required for any number of introduction points or channels 58.

It goes without saying that, although the invention has been described above with reference to a two-stage valve, embodiments are conceivable which, in addition to the two stages described, enable further stages of the ballast gas supply by forming additional channels in the pump body 16 with the inputs of which the outlet opening 48 of the rotating body 22 can be aligned.

Furthermore, it goes without saying that although the invention does not have such a seal above, a further sealing element can be arranged on the connection surface 17 in such a way that it tightly closes the outlet opening 48 in the closed or zero position of the ballast gas valve 12, so that in this Position with existing pressure differences, no ballast gas can escape into the environment through the gap formed between the sliding disk 26 and the channel inlet 60 or, conversely, ambient air can enter the ballast gas line.

Finally, it goes without saying that although the invention does not have such a guide link 68 above, it can also be carried out continuously without interruption or that the depressions 70 can also be arranged directly on the connection surface 17 on a connection concentric with the axis of rotation D without the guide link 68 can, so that the spring-loaded ball 42 can snap into it. Accordingly, the rotating body 22 can be rotated any number of times in any direction about the axis of rotation D, since there is no geometric limitation.

Reference numerals

10th

Vacuum pump

12

Ballast gas valve

14

Hood

16

Pump body

17th

Pad

18th

Display element

20th

deepening

22

Rotating body

24th

Headpiece

26

Sliding washer

28

screw

28a

shoulder

28b

Screw head

30th

Tapped hole

32

Fastener

34

Location hole

36

drilling

38

drilling

40

Guide element

42

spring-loaded ball

44

Valve bore

46

Inlet opening

48

Outlet opening

50

Connecting piece

52

Sealing ring

53

check valve

54

Valve seat

56

Valve body

57

Spring element

58

channel

60

Channel entrance

62

Sealing ring

64

Groove

66

Sealing ring

68

Leadership backdrop

70

deepening

Claims (13)

1. A vacuum pump (10) comprising a pump body (16) whose inner side bounds a pump space and at whose outer side a valve (12) for controlling the supply of a ballast gas into the pump space is arranged, with the valve (12) having an inlet opening (46) and an outlet opening (48), characterized in that

   a first and a second channel (58) are formed in the pump body (16), with the inlet (60) of each channel (58) facing the valve (12) and the outlet of each channel (58) opening into the pump space;

   in that the valve (12) is adjustable between a first open position and a second open position, with the outlet opening (48) being aligned with the inlet (60) of the first channel (58) in the first open position and being aligned with the inlet (60) of the second channel (58) in the second open position; and

   in that the first and second channels (58) have different lengths and/or the outlets of the first and second channels (58) have different cross-sectional surfaces.
2. A vacuum pump (10) in accordance with claim 1,
   characterized in that
   the valve (12) has at least one further position in which the outlet opening (48) is not aligned with any of the channel inlets (60).
3. A vacuum pump (10) in accordance with claim 1 or claim 2, characterized in that
   the valve (12) has a check valve (53) which prevents a backflow of gases from the outlet opening (48) to the inlet opening (46).
4. A vacuum pump (10) in accordance with at least one of the preceding claims,
   characterized in that
   a maximum dimension of the outlet of a or each channel (58) is equal to or less than a width of a separation element which separates two regions of the pump space from one another and which moves via the or each outlet in the operation of the vacuum pump (10).
5. A vacuum pump (10) in accordance with at least one of the preceding claims,
   characterized in that
   the valve (12) comprises a rotary body (22) which is rotatably supported at the pump body (16), in particular with an axis of rotation D of the rotary body (22) being arranged orthogonally to a planar connection surface (17) at the pump body (16), with the channel inlets (60) being arranged in the connection surface (17).
6. A vacuum pump (10) in accordance with claim 5,
   characterized in that
   the valve (12) is at least adjustable between the first and second open positions by rotation of the rotary body (22).
7. A vacuum pump (10) in accordance with claim 5 or claim 6, characterized in that
   the inlets (60) of the channels are each surrounded by a sealing element (62), in particular by a sealing ring.
8. A vacuum pump (10) in accordance with at least one of the claims 5 to 7, characterized in that
   at least three sealing elements (62, 66) are provided which are arranged distributed around an axis of rotation D of the rotary body (22), in particular in an at least approximately symmetrical arrangement as three sealing rings 62, 66 which provide a support surface which extends in a planoparallel manner with respect to the surface of the pump body 16.
9. A vacuum pump (10) in accordance with at least one of the claims 5 to 8, characterized in that
   the rotary body (22) is provided with a dry lubricant at its lower side facing the pump body (16) and/or the sealing elements (62, 66) are provided with a dry lubricant at least at their side facing the rotary body (22).
10. A vacuum pump (10) in accordance with at least one of the claims 5 to 9, characterized in that
    the rotary body (22) has a tensioning apparatus (28) to preload the rotary body (22), in particular along its axis of rotation D, toward the pump body (16).
11. A vacuum pump (10) in accordance with at least one of the claims 5 to 10, characterized in that
    the pump body (16) forms a guide slot (68) of part-circle shape and the rotary body (22) is provided with a guide element (40) which projects from the lower side of the rotary body (22) facing the pump body (16) and which is guided in the guide slot (68) of the pump body (16).
12. A vacuum pump (10) in accordance with claim 11,
    characterized in that
    the guide element (40) has a spring-loaded spherical body (42) which engages into the guide slot (68), with the guide slot (68) having recesses (70) at the positions corresponding to the at least first and second open positions.
13. A vacuum pump (10) in accordance with at least one of the claims 5 to 12, characterized in that
    letterings (18) are applied to an outer side of the pump body (16) and indicate the correct angle of rotation of the rotary body (22) for the at least first or second open position; and/or in that the rotary body (22) has a non-circular cross-section, in particular a cross-section indicating the direction.

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