EP0834017B1 - Vacuum pump - Google Patents

Abstract

PCT No. PCT/EP96/02630 Sec. 371 Date Dec. 17, 1997 Sec. 102(e) Date Dec. 17, 1997 PCT Filed Jun. 18, 1996 PCT Pub. No. WO97/01037 PCT Pub. Date Jan. 9, 1997A vacuum pump contains two rotary displacement rotor (8) that engage each other, in particular in a convoluted manner, inside in expansion chamber through which flows a stream in the axial direction. The rotors are mounted in cantilever at the delivery side and are linked each to a driving motor (35, 36). Each rotor (8) forms together with its shaft (20), a stationary bearing body (7) and a bearing (21, 22) delimited by the shaft (20) and the bearing body (7) a module that may be removed as a single unit from the housing (3). The rotor (35) of the driving motor is preferably also part of said module.

Description

The invention relates to a vacuum pump with a pair within an axially flow Scooping space, in particular helically interlocking Displacement rotors, each of which is supported by a shaft mounted on the pressure side, each with the rotor of an outside of the housing that forms the scoop arranged motor is connected.

This design has the advantage that all the storage and drive of the rotors organs in question are arranged on the pressure side and outgassings originating from them therefore less easy to get to the suction side of the pump. Elaborate seals it becomes unnecessary. However, known pumps of this type (EP-A 472933 = US-A 5,197,861 and US-A 5,354 179; EP-A 558921 = US-A 5,393,201; USA 5,295,798; US-A 5,314,312; US-A 5,329,216; JP abstract 2283890) the disadvantage that the rotating parts are difficult to access and cannot be easily maintained because their assembly or disassembly presupposes that they or more receiving the storage Housing parts are separated from each other. Because the rotating parts and their storage particularly sensitive personnel are required for this, which is usually only available to the pump manufacturer.

The invention avoids these disadvantages in that each rotor with the associated one Shaft and a stationary bearing body that can be fixed to the housing and covers the entire Shaft bearing accommodates, forms a unit removable from the housing. In this The unit is the operationally sensitive Warehouse functions contracted. It can be used by the manufacturer for exchange purposes delivered pre-assembled, adjusted and balanced and as a whole sent to the manufacturer for maintenance while the rest of the maintenance including assembly and disassembly of the less specialized available to the user Personnel can be left.

It is expedient for each rotor assembly to be preassembled independently of the other a separate bearing body is assigned to each rotor. However, it likes use cases give in which a common bearing body is provided for both rotors can be.

The housing forming the scooping chamber is expediently on the pressure side of one Base plate limited, in or on which the bearing body can be centered and / or fixed. This Base plate can be connected in one piece to the scoop chamber. Conveniently however, it is a separate part. It can also be part of the motor housing. this is usually on the base plate on the side remote from the chamber is arranged.

As is known from the prior art mentioned at the outset, it is useful if at least one rotor bearing within the rotor in an open only to the pressure side Space arranged on a tubular part of the bearing body protruding into the rotor is. In this way it is achieved that the rotor shaft has only slight bending stresses is subject to and consequently the deformation-related changes the play of one rotor against the other and between the rotors and the housing can be kept low. This also allows a favorable dimensioning the rotor shaft, whereby the radial connected to the rotor inner bearing Space requirement is partially compensated.

It is known to provide the rotor shafts with interacting gears that the Synchronize the waves or in addition to electronic synchronization enable emergency synchronization. So that these gears are not affected by immediate Contact with the fluid to be contaminated and thus lubricated if necessary can, without the lubricant getting into the scoop, they are according to of the invention arranged on the motor side of a flange plate, the one for this purpose Sealing space limited space and to the removable unit with the rotor heard. Instead of the gears, it can also be a pulse encoder disk or the gears also serve as encoder disks.

The flange plate is expediently sealed off from the scooping space realized in that the flange plate opposite the base plate or the motor housing is sealed, while the base plate or the motor housing opposite the chamber housing is sealed. This gives the possibility to attach the flange plate Assemble and center the motor housing. The pump chamber (or its Jacket and cover) can be removed for maintenance of the scooping area and the rotor surfaces become. without this the tight closure of the synchronization discs receiving rooms impaired.

The motor housing is expediently sealed in a dust-tight manner from the atmosphere. It is therefore not necessary to seal the receiving the synchronization discs Spaces opposite the drive.

The motor rotor expediently also belongs to the one that can be pulled off the housing as a whole Rotor unit. The same applies to the synchronization gear or to the rotor assembly non-rotatable encoder disk, which is part of a device for measuring the angle of rotation of the rotor.

The invention makes it possible to considerably increase the cost of warehousing reduce the need for pumps with different delivery data belonging to the same series essentially only by the length of the rotors, the scoop housing and if necessary, distinguish the tubular parts of the bearing bodies. Instead or in addition They can also differ from the design of the displacement projections on the circumference of the rotors differentiate.

Fig.1

einen Längsschnitt in der Ebene beider Rotorachsen,

Fig.2

einen Längsschnitt quer dazu,

Fig.3

einen Horizontalschnitt gemäß Linie III-III der Fig.1 und

Fig.4

eine teilweise gemäß Linie IV der Fig.2 geschnittene Draufsicht.

The invention is explained in more detail below with reference to the drawing which illustrates an advantageous embodiment of the invention. In it show:

Fig. 1

a longitudinal section in the plane of both rotor axes,

Fig. 2

a longitudinal section across it,

Fig. 3

a horizontal section along line III-III of Fig.1 and

Fig. 4

a plan view partially sectioned along line IV of Figure 2.

The motor housing 2 rests on the foot part 1, with the flange-like base plate at the top 3 may be connected in one piece. on which the pump chamber 4 is built. This is closed at the top by a cover 5 which contains a suction opening 6.

On the base plate 3 are the flange plates 50 of the bearing body in a manner to be explained later 7 attached, each serve to support a rotor 8. its scope preferably two-helically arranged displacer projections 9 carries in the type of tooth engagement in the conveying cavities 10 between the displacer projections 9 of the adjacent rotor. The displacement projections also have an effect 9 together on the circumference with the inner surface of the scoop housing part 4. The Rotors 8 are connected to the suction chamber 11 at the top and to the pressure chamber 12 at the bottom.

The pressure chamber 12 communicates with the pressure outlet 17 through the channel 16 Parts are provided at the lower end of the vertical scoop housing.

Each rotor 8 is non-rotatably connected to a shaft 20 which passes through the bottom of the bearing body 7 a permanently lubricated roller bearing 21 is mounted. A second, also permanently lubricated Rolling bearing 22 is located at the upper end of a tubular part 23 of the Bearing body 7, in a downward, ie pressure side, open, concentric bore 24 of the rotor 8 protrudes. This bearing 22 is preferably located above the Center of the rotor 8. The tubular part 23 of the bearing body preferably extends by the greater part of the length of the rotor 8. The end of the tubular part 23 is in a vertical arrangement of the pump much higher than the pressure outlet 17. This is helpful for protecting the bearing and drive region from the ingress of liquid or other heavy impurities from the scooping area.

Cooling channels 25 are provided in the tubular part 23 of the bearing body, which channels 26 with a cooling water source and via corresponding channels shown in the drawing non-appearance. connected to a cooling water drain. The cooling channels 25 are preferably formed by helical recesses through a sleeve are tightly covered. The cooling of the rotor bearings extends the service life or the Maintenance intervals for these bearings. Furthermore, the circumferential surface is also due to the cooling of the tubular part 23 of the bearing body is kept at a low temperature. This Circumferential surface is the inner peripheral surface of the cavity 24 of the rotor with little Distance opposite. These surfaces are designed to ensure good heat exchange are capable and thus heat from the rotor indirectly via the tubular Part 23 of the bearing body and its cooling devices 25 can be removed. For Improvement of the heat exchange between the opposing surfaces of the tubular part 23 of the bearing body and the rotor cavity 24 can these can be designed in a suitable manner. For example, they can be treated or be browned that the radiation exchange is favored by high absorption coefficients becomes. The convective heat exchange mediates the gas layer in between can by small surface distance and suitable surface structure, the leads to an increase in the heat transfer coefficient. One area or both can be rough for this purpose or with heat exchange fins or threads or the like be trained. It is also possible to pass the rotor cavity 24 through the bearing body or to supply the shaft 20 with a sealing gas which flows from the Pressure chamber 12 is discharged. In addition to cordoning off the storage area, the serve additional cooling of the bearing, the bearing body and the rotor, it but expediently not through the camp or camp, so as not to pollute, but via a bypass channel 28.

To protect the bearing and drive area from penetration from the scooping area Suitable sealing and / or locking devices are provided. Especially The equipment of the opposing surfaces of the bearing body is advantageous 23 and the inner surfaces of the rotor cavity 24 on one side or on both Sides with a feed thread, not shown, that have a feed effect from the rotor cavity 24 exercises towards the pressure chamber 12. This promotional effect works because of it higher density primarily on solid or liquid particles and thereby prevents their penetration into the bearing and drive area. The conveyor thread is expedient designed so that this effect even at significantly reduced speed is effective.

The conveying effect can also be brought about by the gap between the rotor and bearing body widens conically towards the pressure chamber. The gap width (distance of the Surface of the bearing body from the surface of the rotor) remains essentially constant. In addition, the surfaces facing each other can also be used in this case be provided with a conveyor thread on one or both sides; required but it is not.

Because the gap between the rotor and bearing body is equipped with a conveyor thread or a tapering effect very effective against the penetration of liquid or seals solid particles, additional sealing devices can often be dispensed with become; however, they can be provided, preferably in a non-contact manner or low-contact design, e.g. Labyrinth seals or piston ring type Seals.

Because of the sealing effect of the conveying thread or the taper of the gap, this is the invention Pump insensitive to the presence of liquid in the pumping chamber, as long as the rotors are rotating. This insensitivity also exists in steady state thanks to the high bearing arrangement in the rotor, as long as the liquid in the Bucket does not reach the storage level. It is not only important when the medium is being pumped carries a liquid surge, but can also be used for cleaning and / or cooling of the pump can be used by liquid injection. For example can cleaning or cooling liquid through nozzles, one of which is indicated at 27 be sprayed. The same or separate nozzles 27 can be sprayed the cleaning liquid and the cooling liquid.

If very heavy pollution has to be expected, there is the possibility. constantly spray cleaning liquid during operation. When operating a Vacuum pump should the cleaning liquid, as far as they get into the suction space can have a vapor pressure below the suction pressure. If the pump is multi-stage is and the pollution (depending on pressure, for example) mainly in the second and / or subsequent stages, there is the possibility of injection limit the cleaning liquid to the second or subsequent level and thereby to separate from the suction side.

In most cases, however, the cleaning operation is not carried out continuously, but periodically when cleaning is required (e.g. due to an increase in drive torque) is detected. Thanks to the pump's insensitivity to liquids relatively large amounts of liquid can then also be used. If the operating speed due to the amount or type of cleaning fluid used cannot be maintained, the speed can be reduced accordingly. Are for suitable control devices are provided. For example, the speed can be dependent are controlled by the drive torque. what with increased power requirements automatically to a corresponding reduction in speed compared to the operating speed leads. The continuous rotation of the rotors even during the cleaning phase not only serves to seal the rotor bearing, but also promotes the action the cleaning liquid on the soiled surfaces.

The promotional effect in the gap between the rotor and bearing body can also be used to promote Seal gas can be used independently of an external compressed gas source. In general but is the effect of such a pressurized gas source to promote the sealing gas prefer to be independent of the rotor speed in the sealing gas supply.

The scoop chamber 4 can contain a chamber 30 (Fig. 2), the whole or over Much of the circumference revolves and circulates through the cooling water to the housing to keep at a predetermined temperature. Cooling of the housing jacket is not required in all cases. However, it is in the context of the invention advantageously possible because the rotors 8 are cooled and their thermal expansion is therefore limited. There is no need to fear that the rotors are only there tarnish on the case because they stretch while the case on less Temperature is maintained.

The pump according to the invention can be equipped with pre-inlet. It means that Channels 31 in the areas of high, possibly even medium compression in the housing are provided, through which gas of higher pressure than it reaches the compression stage corresponds to this area of the scooping space, is let in to effect cooling and / or noise reduction according to known principles. According to an advantageous feature of the invention, the pre-inlet gas can be directly the Pressure side of the pump can be removed by placing it in the cooler pockets 30 of the scoop jacket 4 is cooled. For this purpose, it can be passed through heat exchanger tubes become.

The roller bearings 21, 22 in the example shown are angular contact ball bearings, which are set against each other by a spring 29. Each shaft 20 carries below the Bearing 21 preferably immediately, i.e. without an intermediate clutch, the rotor 35 of the drive motor, the stator 36 is arranged in the motor housing 2. The Motor housing can be equipped with cooling channels 38.

The flange plates 50, which in the example shown with the bearing bodies 7 from one Pieces are, with their outer edges 51, which is essentially the scope follow the scoop chamber 4, and their abutting inner edges 52 the top of the base plate 3 placed. The flange plates 50 are opposite Base plate 3 sealed. Also the end faces following a secant in radial section 53, on which they lie against each other, are equipped with a sealing insert.

A recess is provided under the flange plates 50, between the edges 51, 52, which includes a space 39 with the top of the base plate 3, which is for receiving of synchronization gears 40, which rotates with known means on the Shafts 20 are arranged between the bearings 21 and the motor rotors. So that they Area of the inner edges 52 of the flange plates 50 can comb with each other the inner edges at a corresponding point on a cutout through which the gears reach through. Below this section there is a bridge on each side 1 the reference line of the reference number 52, which generally designates the inner edge points. This web is not only advantageous for reasons of stability, but also because it is a circumferential seal on the one hand against the base plate 3 and on the other hand allows between the flattened secant surfaces of the flange plates 50.

The recesses 39 in the flange plates 50 have a diameter that is larger than the diameter of the synchronization gears 40. They are in relation to the Inner edges 52 arranged a little eccentrically so that the synchronization gears 40 when assembling the rotor assemblies despite the presence of the sealing web can be used at 52.

Since the space 39 containing the synchronization gears 40 from the scoop space is completely separated, there is a risk of contamination for the synchronization gears Not. They are only used for emergency synchronization of the rotors. her teeth do not normally come into contact with each other. Lubrication is therefore in usually not required. It can be used if desired, but it can be run dry The synchronization gears simplify the design because of a seal between the room 39 and the drive motors is not required.

The synchronization gears 40 can also serve as pulse generator disks or be supplemented by additional pulse generator disks, which are sensed by sensors 42 1, of which one is shown. These sensors 42 are with a control device in connection, which the respective rotational position of the rotors relative to one Setpoint is monitored and corrected via the drive. It is a synchronization of the rotors electronically, which is known as such and therefore no further explanation is required here. The game between the teeth of the synchronization gears 40 is slightly less than the backlash between the projections 9 of the rotors 8. However, it is larger than the synchronization tolerance of the electronic ones Synchronization device. If the latter works properly thus come neither the flanks of the displacement projections 9 nor the teeth of the Synchronization gears 40 in contact with each other. In the event that the latter But should they ever come into contact with one another, they are wear-resistant and if necessary provide a low-friction coating.

The performance data of the pump are determined by the drive power and speed by the displacement or delivery volume formed on the rotors and thus by the Length of the rotors determined. The funding data can therefore be changed in that the length of the pump part containing the rotors is changed. A range of Pumps with different performance data are therefore characterized by this from that the individual pumps of this series differ by grading the length distinguish between these parts, the scoop chamber, the rotors and possibly the include tubular parts of the bearing body protruding into the rotors.

It can be seen that each rotor with the associated bearing and drive devices forms an independently mountable unit which, in addition to the rotor, consists of the bearings 21, 22, the bearing body 7, the cooling devices provided therein, the shaft 20, the synchronization gear 40, the associated sensor 42 and the motor rotor 35. These units are completely pre-assembled in the pump. You can go after the removal of the pumping chamber housing is easily removed from the base plate 3 or be used. Your replacement can therefore be left to the user. while the manufacturer takes care of the maintenance of the sensitive units as such.

Fig. 2 and Fig. 4 illustrate that the suction chamber 11 through the scoop a cover plate 14 is separated, which allows an immediate passage of the sucked medium prevented from the suction opening 6 in the scoop. Instead, it arrives first through one or the other of two openings 61 into the head space 62 one of two settling rooms 63, which act as special containers 68 on the broad sides of the pumping chamber housing 4 are scheduled. The head space 62 is down towards the settling space 63 open and laterally delimited by partitions 64 from two side spaces 65 which are also open to the settling space 63 and through an opening 66 on both sides the opening 61 are arranged, are connected to the pumping chamber of the pump. The medium drawn in passes from the suction opening 6 through the suction chamber 11 into a middle head space 62, is deflected downward into the settling space 63, is therein deflected upwards to one of the side head spaces 65 and passes through from here the opening 66 into the scoop. The openings 61, 62 through which the medium in the Settling space 63 flows in, are thus spatially offset from the openings 65, 66, through which it flows back into the scoop. The one thereby forced on the gas flow Redirection has the result that liquid or solid particles carried by him are thrown down into the settling chamber 63 due to the inertia effect. In particular, this also applies to any liquid surge. If often with Liquid slug must be expected, the settling rooms with discharge devices be provided for the liquid contained therein. Regardless of or a fill level meter 67 may also be functionally connected therewith.

The pump is preferably of an isochoric design to handle larger quantities of liquid to be able to support without harm.

Claims (9)

1. Vacuum pump having a pair of displacement rotors (8) which rotate inside an axial-flow pump chamber, intermesh in particular in a helical manner and are carried in a floating manner by one shaft (20) each mounted on the pressure side, of which each is connected to the armature (35) of a motor arranged outside the housing (4) forming the pump chamber, characterized in that each rotor (8), with the associated shaft (20) and a special stationary bearing body (7) which can be fixed to the housing and accommodates the entire shaft bearing arrangement, forms a unit which is removable from the housing.
2. Vacuum pump according to Claim 1, characterized in that a separate bearing body (7) is allocated to each rotor (8).
3. Vacuum pump according to Claim 1 or 2, characterized in that the housing (4) forming the pump chamber adjoins a base plate (3) on the pressure side, to which base plate (3) the bearing body (7) can be fixed.
4. Vacuum pump according to one of Claims 1 to 3, characterized in that a flange plate (50) which can be removed together with the rotor construction unit defines a space which is sealed off from the pump chamber and in which a synchronization gear wheel (40) and/or a pulse generator disc is provided.
5. Vacuum pump according to Claim 3 or 4, characterized in that a motor housing (37) accommodating the motors is arranged on the base plate (3) on the side remote from the pump-chamber housing (4).
6. Vacuum pump according to one of Claims 1 to 5, characterized in that at least one rotor bearing (22) is arranged inside the rotor (8) in a space (24), open only towards the pressure side (12), of the rotor at a tubular part (23), projecting into the rotor (8), of the bearing body (7).
7. Vacuum pump according to one of Claims 1 to 6, characterized in that the motor armature (35) also belongs to the rotor construction units removable in their entirety.
8. Vacuum pump according to one of Claims 1 to 7, characterized in that the synchronization gear wheel or the pulse generator disc belongs to the rotor construction unit removable in its entirety.
9. Series of vacuum pumps according to one of Claims 1 to 8, characterized in that pumps having different delivery data, apart from the drive, differ essentially only in the length of the rotors, the pump-chamber housing and if need be the tubular parts of the bearing bodies as well as if need the style of the displacement projections at the periphery of the rotors (8).

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