Vacuum Pump

Abstract

A vacuum pump, particularly a Roots pump, claw pump, or screw pump. The vacuum pump has at least one rotor as a pumping device, which rotor is disposed on a shaft. The vacuum pump has at least one bearing and/or drive region for the shaft and at least one suction chamber. During a pumping process, a medium is conveyed from an inlet of the suction chamber to an outlet of the suction chamber, by means of rotation of the rotor. At least one gas conveying device is configured for conveying the medium away from the bearing and/or drive region in the direction toward the rotor and/or toward the outlet of the suction chamber.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of German Patent Application No. 10 2010 035 620.4, filed Aug. 26, 2010, which application is incorporated herein by reference.

FIELD

The present disclosure relates to vacuum pumps, particularly Roots pumps, claw pumps, or screw pumps, having at least one shaft that has a rotor as the pumping device, at least one bearing and/or drive region for the shaft, and at least one suction chamber, where a medium is conveyed from an inlet of the suction chamber to an outlet of the suction chamber, during a pumping process, by means of rotation of the rotor. The pumping device serves for conveying the medium from the inlet of the suction chamber to the outlet of the suction chamber. In some examples, the disclosure relates to a dry-running vacuum pump that runs in oil-free and contact-free manner in the suction chamber, furthermore particularly having an end vacuum in the medium-vacuum range of 10² Pa to 10⁻² Pa.

BACKGROUND

Numerous processes in research and industry require a vacuum in the range of 10² Pa to 10⁻² Pa, for example, where frequently, condensing and/or aggressive vapors or gases also have to be conveyed. In order to generate a partial vacuum in this range, fluid-sealed or lubricated vacuum pumps, such as oil-sealed rotary vane pumps, are frequently used. The use of such pumps, in which the pumped medium comes into contact with oil or other fluids, has numerous disadvantages.

For this reason, so-called dry vacuum pumps are used in the state of the art to convey condensing and/or aggressive vapors or gases, in other words pumps in which the pumped media do not come into contact with any fluid.

Roots pumps represent a type of medium-vacuum pumps. Roots pumps can have two 8-shaped pistons, for example, which roll synchronously on one another, in contact-free manner, i.e. without seals that grind, in a suitably shaped housing. In this way, gas is conveyed from the inlet to the outlet. See for example U.S. Pat. No. 5,779,453.

With such an arrangement, it is possible to achieve compression ratios of about 10 to 30. Therefore a pre-pump or a multi-stage structure is required for producing a medium vacuum. Disadvantages of this type of construction are the complicated structure as well as the close mechanical tolerances that must be adhered to during production and in operation. Furthermore, Roots pumps react sensitively to condensates, aggressive media, or particles.

The same holds true for claw pumps, although these can reach a compression ratio of about 50, in other words make do with a smaller number of stages than Roots pumps. Claw pumps also have rotors that run synchronously on one another, in contact-free manner. For smaller suction capacities, however, the demands with regard to gap dimensions are too great for efficient implementation. See for example U.S. Pat. Nos. 5,846,062 and 7,338,266.

Another widespread type of construction of medium-vacuum pumps that run in oil-free manner is so-called screw pumps. In screw pumps, two screw-shaped rotors run on one another in contact-free manner, in a suitably shaped housing, where gas is conveyed from the inlet to the outlet. An advantage of screw pumps in comparison with Roots pumps or claw pumps is the great compression that is possible, since screw pumps can intrinsically be constructed with multiple stages, with each screw thread acting as a stage. As a result, screw pumps offer the possibility of achieving a deep end vacuum with only one pair of rotors. With only one rotor pair per shaft end, so-called cantilevered mounting of this rotor pair is also possible, i.e. the rotor pair is mounted on only one side. This allows simple disassembly, for example for maintenance and cleaning purposes. See for example U.S. Pat. No. 5,846,062. However, screw pumps in which two-sided mounting of the shafts with regard to the suction chamber is provided are also known from the state of the art. See for example U.S. Patent Application Publication No. 2009/0047142.

Drive of the rotors in the case of two-shaft pumps, such as Roots pumps, claw pumps, and screw pumps, can take place by means of two motors that run synchronously, or using a means for driving and synchronizing the rotors, proceeding from a single drive shaft, such as a gear mechanism, for example.

If the bearings and the drive of the vacuum pump are situated in a region touched by the gas, this can be disadvantageous for many applications, because gases having a certain dust or vapor component or actually corrosive gases or vapors frequently have to be conveyed. Pumping out containers that are filled with usual ambient air can also lead to condensation of moisture from the air in the pump. In the case of many other applications, the media to be conveyed also contain vapors. Even if these are not corrosive, they can lead to damage of the bearings, for example, in condensed form, in that the condensates wash out bearing greases and/or rust formation occurs in the bearings.

From the state of the art, it is known to use pumps in which the region(s) having bearings and drives are flushed with flushing gas in the direction toward the suction chamber, under elevated pressure, in order to convey gases having a dust and/or vapor component or to convey corrosive gases or vapors. This requires that the user connect flushing gas to the pump, at a specific elevated pressure. However, such compressed gas is frequently not available, particularly in the case of applications for smaller pumps, such as in the laboratory or in the case of mobile applications.

Alternatively, the drive region(s) can also be separated from the suction chamber by means of one or more shaft seals. However, such shaft seals must be dry-running at this location, since otherwise, the lubricant could contaminate the vacuum region. However, dry-running shaft seals have limited useful lifetimes.

SUMMARY

Through research and development, the present inventors have endeavored to make available a vacuum pump that works in dry and contact-free manner in the vacuum chamber, i.e. without seals that grind, is compact and, at the same time, can be economically produced and operated, for the range from atmospheric pressure to medium vacuum, with which pump even media that contain condensable vapors or aggressive substances can be conveyed, without damage to the pump occurring.

In examples disclosed herein, a gas conveying device serves to keep the gases and vapors conveyed by the pump, as well as the dust contained in them, away from the bearing and/or drive region. It should be differentiated from the actual pumping device or rotor, which provides compression within the suction chamber and conveys the medium from the inlet to the outlet of the suction chamber. The design differences between the actual pumping device or rotor and the gas conveying device provided according to certain examples lead to a different flow guidance behavior and/or to a different compression ratio during operation of the pump. The element of the vacuum pump that compresses the medium in the suction chamber, in other words the rotor, particularly configured as a screw, claw, rotary piston or Roots rotary piston, and the gas conveying device can be configured as separate components or in one piece. Preferably, the rotor and the gas conveying device are integrated into the shaft in one piece. Likewise, it is possible to configure the shaft, the rotor, and the gas conveying device as separate components or in one piece.

In some examples, a seal that grinds is not provided between the suction chamber and a bearing and/or drive region.

It is not necessary to feed a flushing gas to the bearing and/or drive region or to the region between the bearing and/or drive region and the suction chamber, under elevated pressure.

A gas conveying device can be provided adjacent to a bearing and/or drive region, on the atmospheric or pressure side of the suction chamber, and can be configured for conveying the medium counter to the conveying direction of the rotor and/or in the direction toward the outlet.

A gas conveying device can be disposed, supplementally or alternatively, also adjacent to a bearing and/or drive region, on the suction side of the suction chamber, and can be configured for conveying the medium in the conveying direction of the rotor and/or in the direction toward the outlet.

The gas conveying device can be configured in such a manner that the medium conveyed by the pumping device cannot get to the bearing and/or drive region, or can do so only in small amounts. Furthermore, the gas conveying device can be used in order to convey a medium that exits from the suction chamber during the pumping process of the vacuum pump and enters into a region between the suction chamber and an adjacent bearing and/or drive region back into the suction chamber and/or to the outlet.

The gas conveying device can be disposed in the region between a bearing and/or drive region for the shaft and the rotor. Furthermore, the gas conveying device can be disposed within a suction chamber housing that delimits the suction chamber. Fundamentally, the gas conveying device can also be disposed outside of the suction chamber, particularly in the region of an adjacent bearing and/or drive region for the shaft and a suction chamber housing.

In other examples, the vacuum pump can have at least one common bearing and drive region on an atmospheric side of the suction chamber or on its pressure side, respectively, for placement of bearing parts, shaft synchronization means, and shaft drive means. A corresponding bearing and drive region for the shaft can fundamentally be provided also on the suction side of the suction chamber. In other examples, no seals that grind are present between the suction chamber and the bearing and/or drive region.

In the case of a vacuum pump having shafts that have multiple rotors, which shafts are assigned to at least one bearing and/or drive region, at least one gas conveying device can be assigned to each bearing and/or drive region. Fundamentally, a common gas conveying device can also be provided for multiple shafts.

A vacuum pump having two shafts can have a double-pipe structure, in such a manner that the inlet is provided in the center of the suction cavity, and the gas is drawn in at the center of the suction cavity and conveyed toward both sides, so that atmospheric pressure can prevail at both ends of the suction chamber. A two-shaft vacuum pump having a double-pipe structure can have bearing parts and/or drive parts for the shafts and gas conveying devices provided according to the present disclosure, assigned to the corresponding bearing and/or drive regions, as well as devices for flushing gas feed, if necessary, at one or at both shaft ends.

In other examples, in a vacuum pump having two shafts, cantilevered rotors can be provided at least in a suction chamber, where the shafts are not mounted on the suction side of this suction chamber.

A vacuum pump having two shafts can be structured in the manner of a multi-stage pump, based on the Roots principle and/or the claw principle. In the case of these pump types, the “atmospheric side” refers to the stage of the multi-stage arrangement that compresses against atmosphere. In some examples, a vacuum pump having two shafts is a screw pump.

The gas conveying device provided in the vacuum pump can be structured or can work in the manner of an integrated fan having at least one fan blade, or in the manner of a blower compressor having at least one rotor, or in the manner of a molecular pump, such as a Holweck stage, for example. During the pumping process in the suction chamber, an elevated pressure level can be reached. The outlet of the vacuum pump can also be connected with a line or another device, such as a compressor or a gas washing bottle, to carry away pumped vapors and gases.

Depending on the media amount conveyed at the pump outlet, an elevated pressure on the order of 1 to 50 mbar can thereby occur at the pump outlet. An elevated pressure on the same order can also come about by means of drawing in media that have a high pressure level, for example if media are drawn in from a closed container in which an elevated pressure prevails.

The gas conveying device must be able to build up a sufficiently great pressure, accordingly, in order to overcome the counter-pressure and to ensure that the conveyed media cannot be pressed into the bearing and/or drive region. For example, specially shaped radial fans can be provided in order to generate a sufficiently high pressure level.

High speeds of rotation of vacuum pumps, in the range of 3,000 to 25,000 rpm, can advantageously be used. Alternatively, the gas conveying device can also be configured as a side-channel blower, where here again, high speeds of rotation are advantageous.

The rotating elements of the gas conveying device, for example fan wheels or other rotors, can be driven directly by the shaft of the vacuum pump, in the case of a vacuum pump having two shafts, by one or both shafts, or are mounted in this shaft or these shafts.

The vacuum pump can have a housing that delimits the suction chamber, where the gas conveying device is disposed between the rotor and an outer wall of the suction chamber housing, in other words within the suction chamber, and the shaft is passed through the housing to the bearing and/or drive region. Fundamentally, the gas conveying device can also be disposed outside of the actual suction chamber housing, in the region between the suction chamber housing and the bearing and/or drive region.

In order to create a condensate drain, the suction chamber housing can have at least one drain slant that proceeds from an opening in the housing as a shaft pass-through for a shaft of the vacuum pump. The drain slant can extend, in collar-like manner, over the entire circumference of the shaft pass-through. If a fan wheel is provided as a further gas conveying device, the fan wheel can be adapted to the incline of the drain slant on the side that faces away from the rotor. The part of the gas conveying device or of the fan wheel that is close to the shaft and/or the part of the adjacent suction chamber housing that is close to the shaft can be disposed closer to the suction chamber, on the side facing away from the suction chamber, than the part of the gas conveying device and of the housing that is away from the shaft, so that condensates cannot exit in the suction chamber or can exit only with difficulty by way of the gap between the shaft and the suction chamber housing.

If the vacuum pump has two shafts having at least one rotor, in each instance, one gas conveying device can be assigned to each shaft, where the gas conveying devices can also work together as synchronous gear mechanisms for synchronization of the shafts. For example, synchronization of the two shafts can take place by way of fan wheels that work together as synchronous gear mechanisms. The fan wheels can have an outer gearing, in each instance, where the gearings stand in engagement and can bring about synchronization of the two shafts.

In other examples, a suction device connected with the outlet of the suction chamber, for drawing off the medium from the suction chamber, is provided to accomplish the task stated initially, in the case of a vacuum pump, particularly supplementally to the gas conveying device described above. The suction device can be disposed outside of the actual vacuum pump and connected with an outlet line, where the vapors and gases conveyed in the suction chamber are drawn off from the atmospheric-side region of the vacuum pump or via the outlet of the suction chamber, respectively. In particular, the suction device can be configured for sufficient pressure reduction at the outlet of the vacuum pump, so that exit of the medium out of the suction chamber into the bearing and/or drive region, by way of shaft pass-throughs, cannot come about.

If the suction device builds up sufficient conveying pressure so that a certain partial vacuum always prevails at the outlet of the vacuum pump, it is fundamentally also possible to make do without an integrated gas conveying device of the type described above, provided in addition to the actual pumping device, where protection of the bearing and/or drive region can take place by means of flushing gas drawn in from the outside.

The suction device can be driven by the shaft of the vacuum pump and/or mounted on it, where preferably the shaft for drive of the suction device is passed out of the bearing and/or drive region, preferably on the atmospheric side, on the side facing away from the suction chamber.

For example, an integrated side-channel blower that allows a pressure buildup of preferably more than 50 mbar can be provided as a suction device. This blower can also serve as a pre-compressor for the vacuum pump. For this purpose, the atmospheric-side region of the vacuum pump can be configured in such a manner that the blower simultaneously draws in and compresses gases or vapors from the bearing and/or drive region, and also pumped media from the suction chamber. The compressor can be provided on the outside on the vacuum pump, for example on a free shaft end, and/or can be driven separately. By means of the placement on the vacuum pump from the outside, the advantage is obtained, for example in the case of a side-channel compressor, that the diameter of a rotor of the compressor is not limited to the rotor diameter of the vacuum pump.

A shaft passed out of the bearing and/or drive region can also be used in the case of the examples described above, in order, for example, to make available a cooling air stream for cooling the vacuum pump with a set-on conventional fan.

In order to further improve the protection of the bearing and/or drive region, a flushing gas feed, particularly an air feed and/or nitrogen feed, from the surroundings into the region between the bearing and/or drive region and the suction chamber and/or directly into the bearing and/or drive region, can be provided. In this connection, the flushing gas is preferably not fed in at elevated pressure, but rather drawn in. If the gas let in from the outside is ambient air, no external flushing gas connection is required. In some examples, flushing gas can be let in from the outside adjacent to and/or directly into the bearing and/or drive region, which borders on a gas conveying device, toward the suction chamber, so that the flushing gas is conveyed in the direction of the suction chamber and/or outlet by the gas conveying device. If a suction device is provided for suction by way of the outlet of the suction chamber, the flushing gas can also be drawn into the suction chamber by way of a shaft pass-through, on the basis of the pressure decrease brought about by the suction device at the outlet.

On the suction side of the vacuum pump, it is not absolutely necessary, in this connection, to provide a gas conveying device, since a partial vacuum generally prevails on the suction side of the vacuum pump, so that flushing gas is generally drawn into the suction chamber from the outside, even without an additional gas conveying device, from the bearing and/or drive region or the region between the bearing and/or drive region and the suction chamber. However, entry of flushing gas into the suction chamber is ensured even at higher pressures on the suction side, by means of a gas conveying device on the suction side, where the volume stream of the flushing gas is preferably very slight, in order not to impair the end vacuum of the pump or to impair it only slightly.

The flushing gas stream can also be adjustable by a user by means of a valve, something that can apply for the pressure side and/or the suction side of the vacuum pump. For example, the flushing gas stream can be adjusted as a function of the amount of dust or vapor and the end vacuum requirements. Control of the valve can also take place automatically as a function of process parameters, such as the suction pressure, for example, or as a function of time. A motor-activated valve can simultaneously be used as a flushing gas valve after the end of operation; this will be discussed in greater detail below.

In order not to endanger the (low) pressure level that can be reached during the pumping process, the volume stream of the flushing gas that is passed to the suction chamber can be limited. For the event that a flushing gas is conveyed or drawn in by means of a gas conveying device and/or a suction device connected with the outlet, from the bearing and/or drive region, in the direction of the suction space, the flushing gas volume stream can be adjusted by means of a suitable adaptation of flushing gas channels through which the flushing gas is passed, between the bearing and/or drive region and the suction chamber and/or the surroundings and/or by a suitable design configuration of the gas conveying device and/or by at least one adjustable valve, in such a manner that no pressure increase or only a slight pressure increase comes about in the suction chamber as the result of the flushing gas feed.

If the flushing gas flows through the bearing and/or drive region, cooling of a drive unit provided for drive of the shaft can be brought about by means of the flushing gas. This is particularly advantageous if the drive unit is disposed in a common bearing and drive chamber together with bearings of the shaft.

In another example, it is provided, in order to accomplish the task stated initially, that a medium and/or flushing gas is drawn off by way of at least one intermediate chamber disposed between a bearing and/or drive region and the adjacent suction chamber. For suction, the housing can have a suction channel, for example, which is connected with a suction device and empties into the intermediate chamber. It is understood that the embodiment described here can also be combined with one of the embodiments described above.

In the case of a vacuum pump having two rotors that can be rotated synchronously with one another, in opposite directions, synchronization of the shafts can take place by means of a magnetic gear mechanism, as in U.S. Patent Application Publication No. 2009/0047142 and U.S. Pat. Nos. 7,578,665 and 5,779,453. In this connection, synchronization takes place by means of disks that run past one another in contact-free manner, or the like, which are held in synchronization by means of magnetic forces on the basis of corresponding magnetization or applied magnets. Preferably, permanent magnets with alternate poles can be applied to the disks, distributed over the circumference in a mirror image. Since the two disks do not touch, the magnetic gear mechanism runs quietly, free of friction wear and therefore also free of lubricants.

If such a magnetic gear mechanism is surrounded with suitably disposed coils to generate magnetic fields, and if the coils have current applied to them in suitable manner, in accordance with the position of the magnetized disks, a synchronous two-shaft drive analogous to a brushless DC drive or synchronous motor is obtained, where the magnetized disks of the gear mechanism serve as motor rotors. For example, a motor stator that surrounds the disks merely in certain regions, particularly in the shape of a half to three-quarters circle, can be provided. In the end result, the drive is integrated into a magnetic gear mechanism in the form of a brushless two-shaft synchronous motor. See for example Japanese Patent JP 04-178143 A (Abstract).

Preferably, the combined drive and synchronization device is affixed in the vicinity of the shaft bearings, where drive parts for the shafts and bearing parts for mounting the shaft are disposed in a common bearing and drive region. In this manner, a compact and completely contact-free arrangement is obtained, where with the exception of the bearing grease, it is possible to provide no lubricants in the drive region. “Synchronous” in the sense of the present disclosure is to be interpreted broadly and relates, in this connection, not only to the rotation of the disks that run past each other in contact-free manner, with regard to the magnetic field applied from the outside, but also to the rotation of the disks relative to one another.

A two-shaft synchronous drive can be used if no seal that grinds is provided between the suction chamber and an adjacent bearing and/or drive region. The two-shaft synchronous drive can work in completely lubricant-free manner—similar to a drive based on two separate, electronically synchronized motors—but allows a clearly more compact structure than the latter. The use of a two-shaft synchronous drive in the case of the vacuum pump can thereby contribute to a small construction volume of the vacuum pump. The actual bearing region can be sealed off separately, where sealants integrated into the bearings prevent the exit of lubricants from the bearings. The gas conveying device provided in the vacuum pump furthermore can protect the bearing and/or drive region from the pumped media. Since lubricants therefore do not have to be prevented from exiting out of the drive region in the case of a two-shaft synchronous drive, and pumped media are prevented from entering the drive region by means of the effect of the gas conveying device, it is possible to structure the vacuum pump completely without seals that grind between the suction chamber and an adjacent bearing and/or drive region, even for applications with aggressive dusts, gases, and vapors. This is extraordinarily advantageous, since a completely contact-free and thus friction-wear-free and maintenance-free drive system is created in this way.

If synchronization of the shafts by means of a magnetic gear mechanism is provided, gear wheels of a gas conveying device provided that stand in engagement can interact as an emergency gear mechanism in the event of failure of the magnetic gear mechanism. For example, fan wheels of the gas conveying devices can have an outer gearing that extends over the circumference of the fan wheels. Preferably, however, such gear wheels of the gas conveying devices are configured in such a manner that contact of the gear wheels occurs only in the event of a failure of the magnetic gear mechanism. As a result, wear at the gear wheels and the occurrence of running noises are reduced or excluded in the normal operating state of the vacuum pump (in the case of synchronization merely by way of the magnetic gear mechanism). Fundamentally, emergency operation gear wheels can also be provided as separate components, which are disposed in the vicinity of the disks of the magnetic gear mechanism.

For applications with non-corrosive gases and vapors, the media-touched parts of the vacuum pump can consist of aluminum, steel, or suitable plastics, for example. For applications with corrosive gases and vapors, the surfaces of the media-touched parts can be provided with correspondingly chemically resistant coatings, for example on the basis of fluoroplastics, such as ethylene tetrafluoroethylene polymers (ETFE), ethylene chlorotrifluoroethylene polymers (ECTFE), perfluoroalkoxy polymers (PFA), or similar materials, or can consist of chemically resistant solid materials, such as stainless steel or chemically resistant plastics, such as polyphenylene sulfides (PPS), ECTFE, or the like. In one example, the rotors of the vacuum pump consist of a plastic that is very much lighter than the steel materials usually used. This reduces imbalances that might be present, thereby reducing vibrations that can lead to vibration of the shafts and thereby collision of the rotors with one another or with the housing. Furthermore, plastics such as PPS or polyetheretherketones (PEEK) have great chemical resistance and demonstrate advantageous tribological properties, which can be further reinforced by means of additives, which properties can limit damage in the event of possible collisions of the rotors. Finally, rotors made of plastic can be applied to the rotor shafts, using the injection-molding process. In this connection, a fan vane of a gas conveying device, for example, can easily be molded on, as well, thereby allowing cost-advantageous production in one piece with the rotors.

If (slight) contamination of the bearing and/or drive region with conveyed corrosive media cannot be excluded, particularly during downtime of the vacuum pump, furthermore in particular if flushing after the end of operation is not provided, the bearing and/or drive region can also be designed to be corrosion-resistant. In this connection, ball bearings, for example, made from stainless steel or ceramics, for example, can be provided, particularly when using perfluoropolyether lubricants (PFPE lubricants) and PPS or PEEK ball cages, where the shafts can be coated with suitable media-resistant materials. If the drive is directly integrated into the bearing region, it should also be protected by means of corresponding coatings. In the case of a two-shaft synchronous motor having a magnetic gear mechanism, this can also take place by coating the magnetic disks as well as the stator sheets, or a thin, chemically resistant, gastight partition wall between the coated magnetic disks and the motor stator can be provided.

The suction chamber can be connected with a flushing gas line, where the flushing gas line can empty into the suction chamber in the region of the inlet of the suction chamber. Fundamentally, however, it is also possible that the flushing gas line is passed through the housing of the vacuum pump according to the invention at a different location, and empties into the suction chamber. For the remainder, a suction line can be connected with the inlet of the suction chamber, to draw in the medium to be compressed. At least one valve can be provided in the flushing gas line and/or in the suction line, where the valve control and the control of a drive unit for the shaft of the vacuum pump can take place by means of a common control device.

Some examples provide an inlet or suction line that empties into an inlet of the suction chamber and/or a flushing gas line connected with the suction chamber and/or the suction line, where the suction line has a suction valve and the flushing gas line has a flushing gas valve, and where a control unit for controlling the valves and for controlling a drive unit for the shaft is provided. For flushing the vacuum pump during a shutoff process, the control can be configured in such a manner that at the end of a pumping process, first the inlet valve closes, and the pumping process or the rotation of the rotor shaft(s) is continued for a limited period of time of 1 to 5 min, for example, in order to flush out gases and vapors that are contained in the suction chamber, while the flushing gas valve is open. In this connection, rotation of the rotor shaft(s) takes place at a reduced speed of rotation, if necessary. After a certain period of time, the pumping process or the rotation of the rotor shaft(s) is terminated, and the flushing gas valve is closed.

The inlet valve and/or the flushing gas valve can be motor-activated. Switching of the valves can take place manually by a user, or automatically as a function of process parameters, for example the suction pressure, or also as a function of time. In the event of an error state, such as a power failure, as well as at the end of a pumping process, the pump can shut off in vacuum-tight manner, by closing the inlet valve, where the inlet valve remains closed even after the end of the flushing process, when the pump drive is shut off.

Furthermore, a kickback valve can be disposed in an outlet line of the vacuum pump connected with an outlet of the suction chamber, in order to prevent periodic backflow of gases into the suction chamber during pump operation, and to guarantee quiet pump operation.

In detail, there are a large number of possibilities for configuring and further developing the vacuum pumps disclosed herein.

The characteristics described above and the characteristics described below, using the drawing, can be combined with one another, as needed, even if this is not explicitly described in detail. For the remainder, each of the characteristics described can have its own inventive significance.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing, the figures show:

FIG. 1 a schematic cross-section of a first embodiment of a vacuum pump;

FIG. 2a, 2b fan wheels of the gas conveying devices shown in FIG. 1,

FIG. 3 a second embodiment of a vacuum pump, in a schematic cross-sectional view,

FIG. 4 a third embodiment of a vacuum pump, in a schematic cross-sectional view, and

FIG. 5 a schematic representation of a vacuum pump, in which flushing of the pump with a flushing gas is possible.

In FIG. 1, a dry-running vacuum pump 1 having two rotors 2, 3 is shown. These rotors sit on shafts 4, 5. Furthermore, a suction chamber housing 6 is provided, which defines the suction chamber 7, together with the two rotors 2, 3. The rotors 2, 3 are merely shown schematically and can stand in meshing engagement with one another, for example in the case of a Roots, claw, or screw construction of the vacuum pump 1. The outer circumference of the rotors 2, 3 runs past the wall of the suction chamber 7 at a slight distance from it, but in contact-free manner. The rotors 2, 3 are guided in axis-parallel manner by the shafts 4, 5. The shafts 4, 5 are mounted in bearing and/or drive regions 8, 9 and are driven synchronously. The bearing and/or drive regions 8, 9 are disposed in housing parts 8a, 9a.

During synchronous rotation of the shafts 4, 5 and thus of the rotors 2, 3, a gaseous medium is conveyed from an inlet 10 to an outlet 11 of the suction chamber 7. The rotors 2, 3 form the actual pumping device of the vacuum pump 1 and serve to convey and/or compress the medium. The outlet 11 can lie at atmospheric pressure, for example, while a partial vacuum occurs at the inlet 10 in the case of driven shafts 4, 5, i.e. during rotation of the rotors 2, 3.

The suction chamber housing 6 has shaft pass-throughs 14 through which the shafts 4, 5 are passed into the bearing and/or drive regions 8, 9. No sealants that grind are provided between the suction chamber 7 and the bearing and/or drive regions 8, 9, so that the suction-side bearing and/or drive region 8 lies at a partial vacuum level during usual operating states of the vacuum pump 1, while the pressure in the region of the pressure-side bearing and/or drive region 9 corresponds to ambient pressure.

In the vacuum pump 1 shown, gas conveying devices 12, 13 are provided between the rotors 2, 3 and the bearing and/or drive regions 8, 9. These devices generate a gas conveying stream, in each instance, in the direction away from the bearing and/or drive regions 8, 9 and in the direction toward the rotors 2, 3 and/or toward the outlet 11 of the suction chamber 7. The gas conveying regions 12, 13 are disposed within the suction chamber housing 6, between the adjacent bearing and/or drive region 8, 9, on the one hand, and the rotors 2, 3, on the other hand, in each instance.

For the remainder, the gas conveying devices 12, 13 are disposed on the shafts 4, 5 and are driven by them. During operation of the vacuum pump 1, dusts, gases, and vapors are therefore conveyed back in the direction toward the rotors 2, 3 and/or to the outlet 11 by the gas conveying devices, so that the bearing and/or drive regions 8, 9 are protected from these dusts, gases, and vapors. The gas conveying devices 12, 13 prevent media conveyed in the suction chamber 7 and thus gases, dusts, vapors from being pressed through the shaft pass-throughs 14 toward the outside, in the surrounding region of the vacuum pump 1 and/or into an adjacent bearing and/or drive region 8, 9. The protection of the bearing and/or drive regions 8, 9 can be further reinforced if flushing gas, particularly ambient air, is fed in from the outside and conveyed into the suction chamber 7 and to the outlet 11 by the gas conveying devices 12.

Since a partial vacuum level forms in the suction-side region close to the inlet 10 and thus also in the adjacent bearing and/or drive region 8 during operation of the vacuum pump 1, optionally no feed or only a very slight feed of an external flushing gas is provided here. Aside from the possibility described above, of feeding a low-metered and possibly adjustable flushing gas stream to the bearing and/or drive region 8 and/or to a region 15 between the bearing and/or drive region 8 and the suction chamber 7, the housing part 8a for the bearing and/or drive region 8 is connected with the suction chamber housing 6 in essentially gastight manner on the suction side of the vacuum pump 1.

It is not shown that the gas conveying device 12 does not necessarily have to be provided on the suction side of the vacuum pump 1. Fundamentally, because of the prevailing partial vacuum, it can be possible to protect the suction-side bearing and/or drive region 8 from gases and vapors from the suction chamber 7 merely by means of a limited and possibly adjustable flushing gas stream that is supplied to the bearing and/or drive region 8 and/or to the region 15.

The pressure-side region of the vacuum pump 1 close to the outlet 11 and the adjacent bearing and/or drive region 9 stand under atmospheric pressure. Therefore it is not necessary that the housing part 9a for the bearing and/or drive region 9 is connected with the suction chamber housing 6 in gastight manner. Here, flushing gas, particularly ambient air, can be passed to the suction chamber 7 by way of channels 14a and the shaft pass-throughs 14, at ambient pressure. The channels 14a can be provided with a gas connector on the outside. Supplementally and/or alternatively, it is also possible to draw flushing gas in through the bearing and/or drive region 9 directly, where the housing part 9a must have a corresponding entry opening (not shown) for the flushing gas.

FIG. 1 shows a vacuum pump 1 having an inlet 10 on the one side of the suction chamber 7 and having an outlet 11 on the other side of the vacuum chamber 7. It is not shown that the vacuum pump 1 can also have a double-pipe structure in which the inlet is provided in the center region of the suction chamber 7, and an outlet is provided at both ends of the suction chamber 7, corresponding to the position of the inlet 10 and of the outlet 11 in the vacuum pump 1 shown in FIG. 1. In this case, atmospheric pressure prevails at both outlets.

In FIGS. 2a and 2b, exemplary embodiments of the gas conveying devices 12, 13 are shown as fans having fan wheels 16, 17. The fan wheels 16, 17 are disposed on the shafts 4, 5 and driven by them. According to FIG. 2a, the fan wheel 16 has straight vanes 18. As a result, the volume stream conveyed by the fan wheel 16 is independent of the direction of rotation. According to FIG. 2b, the fan wheel 17 can also have curved vanes 19, so that more efficient gas conveying is possible, but the conveying direction is defined by the predetermined direction of rotation of the fan wheel 17.

In FIG. 3, a vacuum pump 1 having cantilevered rotors 2, 3, in other words with merely one-sided mounting of the shafts 4, 5, is shown. Components that have the same design configuration and/or are functionally equivalent are provided with the same reference symbols.

According to the embodiment shown in FIG. 3, no bearing and/or drive region 8 is provided on the suction side, so that no bearing greases or the like can be released on the suction side.

Analogous to the construction shown in FIG. 3, with cantilevered rotors 2, 3, the vacuum pump 1 can also have shafts 4, 5 that have rotors 2, 3 on both shaft ends, in each instance. In this case, the shafts 4, 5 projects out downward out of FIG. 3 through the housing part 9a of the bearing and/or drive region 9. Then, rotors 2, 3 are also provided at the shaft ends that that project out downward, which rotors are disposed in a further suction chamber 7 (delimited by a further suction chamber housing 6). It is understood that gas conveying devices 13 can also be provided on the side of the further suction chamber 7, in order to protect the bearing and/or drive region 9 from the penetration of dusts, gases, and vapors out of the further suction chamber 7 on this side, as well. The two suction chambers 7 of the arrangement described above can be switched in series or in parallel with their rotor pairs, with a corresponding effect on the pressure conditions (vacuum or atmospheric pressure), and can also have effects on a possible flushing gas feed (flushing gas feed provided or none or only a very slight flushing gas feed).

The schematic sectional representation in FIG. 4 shows a preferred embodiment of the vacuum pump 1, in which the rotors 2, 3 are mounted in cantilevered manner. The shafts 4, 5 are synchronized by means of a magnetic gear mechanism 20, where the drive of the shafts 4, 5 is configured as an integrated two-shaft synchronous motor.

The bearing and drive region 9 has bearing parts 22, 23 for mounting the shafts 4, 5, where the bearing parts 22, 23 can be configured as ball bearings. Disks 24, 25 having permanent magnets on the outer circumference are affixed between the bearing parts 22, 23, where the permanent magnets are disposed over the circumference in a mirror image, with alternating poles. Because of the reciprocal forces of the permanent magnets, the disks 24, 25 and thus the shafts 4, 5 are synchronized. The disks 24, 25 run at a slight distance from one another, so that a contact-free magnetic gear mechanism 20 is formed. The disks 24, 25 are surrounded, radially on the outside, by a motor stator 26 that consists of sheet-metal packets having windings to which current is suitably applied by means of control electronics, not shown, in order to put the magnetized disks 24, 25 into synchronous rotation. The arrangement shown therefore forms a two-shaft synchronous motor. In this connection, the term “synchronous” relates not only to the rotation of the disks 24, 25 with regard to the magnetic field applied from the outside, but also to the rotation of the disks 24, 25 relative to one another.

It is not shown that the gas conveying devices 13 have a gearing that lies on the outside, and can stand in reciprocal contact-free engagement, in order to serve as emergency gear mechanisms in the event of failure of the magnetic gear mechanism 20 formed by the disks 24, 25.

In this example, the suction chamber housing 6 is in a flow connection with the housing part 9a that delimits the bearing and drive region 9.

During operation of the vacuum pump 1, it is ensured, by means of the effect of the gas conveying device 13, that no dusts, gases, and vapors from the suction chamber 7, i.e. from the region of the vacuum pump 1 in which the rotors 2, 3 are disposed, can flow into the bearing and drive region 9. In order to support this effect, a flushing gas stream supplied from the outside can be conveyed out of the bearing and drive region 9 in the direction toward the suction chamber 7 by the gas conveying devices 13. For this purpose, the housing part 9a has channels 27, 28, where the channels 28 are connected with the shaft pass-throughs 14 in flow-conducting manner. The bearing and drive region 9 is very effectively protected from dusts, gases, and vapors from the suction chamber 7, by means of the flushing gas, where the flushing gas stream 21 additionally contributes to cooling of the drive of the shafts 4, 5, formed by the disks 24, 25 and the stator 26. At the inlet of the flushing gas channel 27, a gas connector can preferably be provided, so that an inert gas or other flushing gas can be supplied, if the feed of ambient air as a flushing gas is not desired.

Fundamentally, it is also possible, supplementally and/or alternatively, that flushing gas is drawn in directly from the outside and enters into the suction chamber 7 by way of the shaft pass-throughs 14. This particularly applies if the flushing gas is not supposed to flow through the bearing and drive region 9. In this case, flushing gas channels can directly connect the outside region or the surroundings of the vacuum pump 1 with the shaft pass-throughs 14. Furthermore, a gas connector that lies on the outside can be provided for supplying an inert gas. Furthermore, filters that lie on the outside can be provided in order to prevent the entry of dusts or the like with the flushing gas.

As is furthermore evident from FIG. 4, the part of the vacuum pump 1 that forms the suction chamber housing 6 can have drain slants 29 that proceed from the shaft pass-throughs 14, which slants serve as a condensate drain. In this connection, the sides of the gas conveying devices 13 that face away from the suction chamber 7 as well as the adjacent part of the suction chamber housing 6 are shaped in such a manner that the part close to the shaft, in each instance, lies closer to the suction chamber 7 than the part away from the shaft. In this way, it is prevented that liquid condensates can flow out of the suction chamber 7 into the bearing and drive region 9, specifically independent of the installation position of the vacuum pump 1.

For all the alternative embodiments described above, it holds true that the gas conveying devices 12, 13 can also be disposed outside of the suction chamber 7, i.e. outside of the suction chamber housing 6 that delimits the suction chamber 7, namely between the suction chamber housing 6 and an adjacent bearing and/or drive region 8, 9.

According to FIG. 5, flushing of the vacuum pump 1 with a flushing gas can be provided at the end of operation. For this purpose, a suction line 30 that empties into the inlet 10 of the suction chamber 7 and a flushing gas line 31 that is connected with the suction chamber 7 are provided, where the suction line 30 has a suction valve 32 and the flushing gas line 31 has a flushing gas valve 33, and where a control device 34 is provided for activating the valves 32, 33, and optionally also controls the drive of the shafts 4, 5, the control device 34 having a microprocessor and being programmable and configured to control operation of the valves 32, 33 and optionally control operation of the shafts 4, 5. The valves 32, 33 are driven by motors or electromagnets. In the embodiment shown, the flushing gas line 31 empties into the suction line 30 between the suction valve 32 and the inlet 10 in the suction chamber 7. Fundamentally, the flushing gas line 31 can also empty directly into the suction chamber 7.

The control device 34 is configured in such a manner that first, the suction valve 32 is closed at the end of a pumping process. Subsequently, the flushing gas valve 33 is opened, thereby leading to entry of flushing gas into the suction chamber 7. During this flushing process, the shafts 4, 5 continue to be driven, possibly at a lowered speed of rotation. After a certain period of time, the rotation of the shafts 4, 5 is stopped and the flushing gas valve 33 is also closed.

Furthermore, a kickback valve 35 can be disposed in an outlet line 36 that empties into the outlet 11 of the vacuum pump. In this way, noise reduction can be achieved during pump operation. Furthermore, mufflers or gas deflectors can be provided in order to further reduce the occurrence of noise during pump operation.

All of the characteristics of the embodiments shown can be combined with one another as desired, even if this is not described in detail.

Claims

1. A vacuum pump comprising:

at least one shaft that has a rotor as a pumping device;

at least one of a bearing and a drive region for the shaft;

at least one suction chamber, where a medium is conveyed from an inlet of the suction chamber to an outlet of the suction chamber, during a pumping process, by rotation of the rotor; and

at least one gas conveying device configured for conveying the medium away from at least one of the bearing and drive region, in a direction toward at least one of the rotor and the outlet of the suction chamber.

2. A vacuum pump according to claim 1, wherein the gas conveying device is disposed between at least one of the bearing and drive region for the shaft and the rotor, and wherein the gas conveying device is disposed within a suction chamber housing that delimits the suction chamber.

3. A vacuum pump according to claim 1, wherein the gas conveying device is provided only on the side of the vacuum pump that faces the outlet of the suction chamber, and wherein a flushing gas stream is supplied only on the side of the vacuum pump that faces the inlet of the suction chamber.

4. A vacuum pump according to claim 1, wherein the gas conveying device comprises a fan having at least one fan wheel.

5. A vacuum pump according to claim 1, wherein the gas conveying device is driven by the shaft of the vacuum pump.

6. A vacuum pump according to claim 1, wherein the gas conveying device is mounted on the shaft of the vacuum pump.

7. A vacuum pump according to claim 2, wherein the gas conveying device is disposed between the rotor and an outer wall of the suction chamber housing, and the shaft is passed through the suction chamber housing.

8. A vacuum pump according to claim 7, wherein the suction chamber housing comprises at least one drain slant for a condensate drain, proceeding from a shaft pass-through.

9. A vacuum pump according to claim 8, wherein sides of the gas conveying device that face away from the suction chamber as well as adjacent part of the suction chamber housing are shaped in such a manner that a part close to the shaft, in each instance, lies closer to the suction chamber than a part away from the shaft.

10. A vacuum pump according to claim 1, comprising two shafts, each having at least one rotor, wherein at least one gas conveying device is assigned to each shaft.

11. A vacuum pump according to claim 10, wherein the gas conveying devices work together for synchronization of the shafts, as synchronous gear mechanisms.

12. A vacuum pump according to claim 10, comprising two shafts having rotors that can be rotated in opposite directions, synchronous to one another, and a two-shaft synchronous motor configured for magnetic drive and for magnetic synchronization of the shafts.

13. A vacuum pump according to claim 12, wherein the two-shaft synchronous motor and bearing parts for shaft mounting of the two shafts are disposed in a common bearing and drive region.

14. A vacuum pump according to claim 1, wherein a suction line that empties into the inlet of the suction chamber is provided with at least one of a suction valve and a flushing gas line connected with the suction line, which is provided with a flushing gas valve.

15. A vacuum pump according to claim 14, comprising a control device controlling the suction valve and flushing gas valve.

16. A vacuum pump according to claim 15, wherein the control device is coupled with a further control device for the drive unit of the shafts.

17. A vacuum pump according to claim 1, wherein the vacuum pump is at least one of a Roots pump, a claw pump, and a screw pump.

18. A vacuum pump according to claim 1, comprising a flushing gas feed.

19. A vacuum pump according to claim 18, wherein the flushing gas feed is provided into at least one of a region between at least one of the bearing and drive region and the suction chamber, and directly into at least one of the bearing and drive region.

20. A vacuum pump comprising:

at least one shaft that has a rotor as a pumping device;

at least one of a bearing and drive region for the shaft; and

at least one suction chamber;

wherein a medium is conveyed from an inlet of the suction chamber to an outlet of the suction chamber, during a pumping process, by means of rotation of the rotor; and

wherein at least one of the medium and a flushing gas can be drawn off, by way of an intermediate chamber disposed between at least one of the bearing and drive region and the suction chamber, using a suction device connected with the intermediate chamber.

21. A vacuum pump according to claim 20, comprising two shafts, each having rotors that can be rotated in opposite directions, synchronous to one another, and a two-shaft synchronous motor configured for magnetic drive and for magnetic synchronization of the shafts.

22. A vacuum pump according to claim 21, wherein the two-shaft synchronous motor and bearing parts for shaft mounting of the two shafts are disposed in a common bearing and drive region.

23. A vacuum pump according to claim 20, wherein a suction line that empties into the inlet of the suction chamber is provided with at least one of a suction valve and a flushing gas line connected with the suction line, which is provided with a flushing gas valve.

24. A vacuum pump according to claim 23, comprising a control device controlling the suction valve and flushing gas valve.

25. A vacuum pump according to claim 24, wherein the control device is coupled with a further control device for the drive unit of the shafts.

26. A vacuum pump according to claim 20, wherein the vacuum pump is at least one of a Roots pump, a claw pump, and a screw pump.